Information

Food Choice - Biology


Food Choice

Diet choice: The two-factor host acceptance system of silkworm larvae

Affiliations Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo, Japan, Department of Integrated Bioscience, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan

Roles Investigation, Visualization

Affiliation Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo, Japan

Roles Methodology, Resources, Supervision, Writing – review & editing

Affiliation Graduate School of Agriculture, Tamagawa University, Machida, Tokyo, Japan

Roles Methodology, Resources, Supervision, Writing – review & editing

Affiliation Department of Integrated Bioscience, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan

Roles Conceptualization, Funding acquisition, Project administration, Resources, Supervision, Writing – review & editing

Affiliation Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo, Japan


Brain region tracking food preferences could steer our food choices

Researchers discovered that a specific brain region monitors food preferences as they change across thirsty and quenched states. By targeting neurons in that part of the brain, they were able to shift food choice preferences from a more desired reward (think: chocolate cake) to a less tasty one (think: stale bread).

Their findings, published in the journal Science Advances, built upon the same team's discovery two years ago that neural activity in this brain region called the ventral pallidum is related to the preference for different food options.

Working with rats, the researchers were able to demonstrate that this same area of the brain is tracking and updating food preferences in ways that shifted as physiological states progressed from extremely thirsty to happily quenched.

"Your brain has to weigh different possible outcomes or options in order to make good decisions that are necessary for survival," said Patricia Janak, senior author and Bloomberg Distinguished Professor of Psychological and Brain Sciences and Neuroscience at Johns Hopkins. "We knew the ventral pallidum is involved in that process. Exactly how the neurons there do that was still a bit of a mystery, especially in real time when the best decision for you to make right now can change based on your state."

David Ottenheimer, lead author and a former Johns Hopkins doctoral student who is now at the University of Washington, said he devised the research to determine how the neurons in the ventral pallidum related to the food decisions subjects made as their preference shifted due to changes in physiological state.

To study the question, researchers gave thirsty rats two options to choose from by selecting one of two levers. One lever provided plain water, the other a well-liked sugar water.

"At the beginning they picked the water when they were thirsty," Ottenheimer said. "At the end of the test when they were no longer thirsty they picked the sugar water, which tastes sweeter."

At the same time the team was monitoring the brain activity and found that the neurons reflected the rats' choices for each reward.

"We saw that the neural activity when tasting the sucrose gradually increased over time while the neural activity when tasting the water decreased, which gave us evidence that the brain signal is closely related to the change in preference as the subjects became less thirsty and were less interested in the water," Ottenheimer said.

Remarkably, in a separate test, the researchers were able to artificially manipulate the ventral pallidum neurons to force a shift in preference from the more desired sugar water to a less desirable flavor.

"We hypothesize that the ventral pallidum neurons that are tracking our preferences may actually be involved in forming the choices we make when faced with food decisions," Ottenheimer said. "In the future, ventral pallidum may be a good therapeutic target to change our decision-making processes."

"These same circuits are responsible for choices made in addiction," Janak said. "So the knowledge we gain here can help in understanding how we prioritize drugs over other rewards"


Results

Selective deletion of the GG circuitry

The conflicting environmental olfactory messages carried by odorants emitted by familiar food and by olfactory danger cues need to be continuously evaluated for risk taking and final food decision-making. To address the functional relevance of the GG in this last process in mice, we first surgically disconnected it by nerve axotomy 9 (axo Fig. 1a). Thanks to the expression of the olfactory marker protein (OMP Fig. 1b, c), a neuronal marker for both the GG and the MOE, we then verified that the axotomy induced specific loss of the GG in axotomized (Axo) but not in control sham-operated mice (Ctrl) (Fig. 1b) without affecting the MOE (Fig. 1c). We next demonstrated that the GC-D neurons were still present in the MOE after GG axotomy (Fig. 1c) thanks to the expression of the enzyme phosphodiesterase 2 A (PDE2A Fig. 1b and c) which is shared by GG and GC-D circuities 19 . We then used transgenic guanylyl cyclase-G (GCG, a marker of GG circuitry)–Cre–green fluorescent protein (GFP) mice 19 to selectively trace the GG connections into their olfactory bulb target (OB Fig. 1a), the necklace glomerular complex (NG Fig. 1a). Thereby, we distinctly differentiated, in the NG, the parallel connections between GG and GC-D circuitries and we found that the GC-D circuitry and, in particular its associated necklace glomeruli (NG), were still intact in GCG–Cre–GFP Axo mice (Fig. 1d and Supplementary Fig. 1 Ctrl, Nmouse = 3 Axo, Nmouse = 5). Moreover, this GC-D circuitry was still active in the presence of CS2, independently from the GG axotomy procedure, as verified by immediate-early gene c-Fos expression 15 (Fig. 1e, f Ctrl, Nglomeruli = 6 Axo, Nglomeruli = 7 two-tailed t-test: p = 0.544, ns). We have then systematically used the selective deletion of this olfactory subsystem to functionally dissect the relevance of the GG circuitry in odor-driven food selection when mice were exposed to chemical danger cues.

a Schematic representation of a mouse head and its olfactory subsystems. GG: Grueneberg ganglion (red) GC-D: guanylyl cyclase type D (blue) MOE: main olfactory epithelium SO septal organ VNO: vomeronasal organ NG: necklace glomeruli (red and blue) OB: olfactory bulb. Localization of the GG axotomy procedure is represented by a black dashed line (axo). b, c Maximum-intensity projection of a double immunostaining (anti-OMP, OMP, in green anti-PDE2A, PDE2A, in red colocalization, in yellow) of the GG (b) and MOE/GC-D (c) region in Ctrl and Axo mice. Slice views of detailed regions of dashed white rectangles highlight the presence of MOE (OMP + | PDE2A-) and GC-D (OMP- | PDE2A+) but absence of GG (OMP + | PDE2A+) neurons in Axo mice. NC: nasal cavity BV: blood vessel. d GG axotomy leads to the deletion of gg glomeruli without affecting the gcd glomeruli. e Representative c-Fos (anti-c-Fos, c-Fos, in white) activity of GC-D glomeruli observed in Ctrl and Axo mice after conditioning either with water (NG + Water, basal activity) or with 10 ppm of CS2 (NG + CS2, stimulated activity). f Quantification of c-Fos activity observed in GC-D glomeruli for Ctrl (black) and Axo (gray) mice. Data are represented as mean ± SEM with aligned dot plots for individual mice values. For comparisons between conditions and between Ctrl vs. Axo mice, two-tailed Student’s t-tests or Wilcoxon w-tests are used, **p < 0.01. A minimum of 5 glomeruli were used per condition. Scale bars are 25 μm (b, c), 20 μm (d) and 10 μm (e). DAPI counterstains are shown in blue. Glomeruli are delimited with dashed white lines.

GG encodes threatening scents and dominates over MOE-transmitted odor signals

Mice naturally disregard unfamiliar food based on the unknown odorants it releases, moreover familiar food soiled with danger cues is likewise avoided 2 . As a first physiological assay, we, therefore, tested odorants commonly used to odorize food such as non-synthetic spices 13 and we found that these odorants were not directly detected by GG neurons. Indeed, we revealed with calcium imaging experiments performed on acute Fura-2 acetoxymethyl ester (Fura Fig. 2a) loaded GG slice preparations from transgenic OMP-GFP mice 9 that, in a total of 54 living GFP tagged GG neurons (Nmouse = 4 nslice = 6), Cinnamon, Cocoa, Anise, Oregano, Thyme, Basil, Nutmeg, Ginger as well as the standard mice food and CS2 did not generate any GG neuronal activity (Fig. 2b). On the other hand, the predator-derived cues 2-propylthietane (2PT) from the stoat anal glands, the mouse alarm pheromone 2-sec-butyl-4,5-dihydrothiazole (SBT) as well as mountain lion (Mt.Lion) urine 15,20 initiated reversible calcium responses in respectively 83, 57 and 100% of the GG neurons. Thus, this first approach not only suggests that the unfamiliarity of a food encoded by its emitted odorants could not be directly deciphered by the GG but also confirmed the ability of the GG to identify danger cues potentially emitted by soiled food.

a Representative GG calcium imaging from an OMP-GFP mouse loaded with Fura-2AM (Fura), observed here at 380 nm in color-encoded map for unbound Fura. NC: nasal cavity BV: blood vessel. Scale bar, 20 μm. b Representative continuous recording of a responding GFP+ GG neuron (dashed white rectangle in (a)) performed with Fura-2 ratio (340 nm/380 nm, in arbitrary units a.u.). Control pulse of KCl (25 mM) determines the cellular viability. Tested solutions are listed Spices and Food (1:100), CS2 (10 ppm), 2PT and SBT (1:5000), Mt.Lion (1:500). c Two choices assay, illustrated here with an infrared snapshot and a procedure time-table. Odorants were placed around food resources (odor #1, yellow odor #2, red). d, e Quantification of food Preference ratio for Ctrl (black) and Axo (gray) mice, calculated as the ratio of food consumption [(odor #1)/(odor #1 + odor #2)] - 0.5. Positive scores display a preference for the food odor #1 negative scores for the food odor #2. Tested odor #1 (10%, or pure for Mt.Lion) are indicated and are opposed to odor #2 (Water, in (d) and BA (10 %), in (e)). Data are represented as mean ± SEM with aligned dot plots for individual mice values. Calculation of statistical significances of the preference ratio is performed with Z tests, #p < 0.05 (yellow or red # for a preference respectively for odor #1 or odor #2) non-significant if not mentioned. For comparisons between Ctrl vs. Axo mice, two-tailed Student’s t-tests or Wilcoxon w-tests are used, *p < 0.05 **p < 0.01. 6 to 16 animals are used per condition.

We next verified, in an integrative context of food choice, the implication of the GG in decoding food unfamiliarity based on the odorants emitted. Ctrl and Axo mice were challenged to select, between familiar and unfamiliar food in a two choices assay (Fig. 2c and Supplementary Fig. 2a). To that purpose, two familiar powdered foods were proposed to mice, odorized either with a series of never-encountered before odorants (odor #1 as unfamiliar food) or with the odorless water (odor #2 as familiar food). We placed all the tested odorants around the powdered foods to exclude any toxicity potentially displayed by synthetic cues. Subsequently, the preference for an odorized food was calculated as the ratio between the consumption of food odor #1 versus the total food consumed (food odor #1 + odor #2) in which the 0.5 value, corresponding to the non-preference threshold was subtracted. Values were thus expressed between 0.5 and −0.5 where positive scores corresponded to a preference for the food odor #1 negative scores for the food odor #2 and zero corresponded to no preference displayed. Hence we showed that rodents indeed prefer familiar food 2 as non-synthetic spices such as the unfamiliar Cinnamon or Cocoa 13 as odor #1 were not preferred by mice. Moreover, we observed that this innate choice was also performed by Axo mice (Fig. 2d), confirming that this avoidance behavior was indeed not directly dependent of the GG detection (Fig. 2a, b) but also pointed out to the conserved MOE functionality in the GG Axo mouse model. Then we found that the GC-D-related ligand CS2, without any social context 10 , did not influence diet selection in both Ctrl and Axo mice (Fig. 2d). We next tested butyric acid (BA) a known aversive odorant that smells rancid and has no alerting relevance 15 and found that it indeed generated food avoidance both in Ctrl and Axo mice confirming its previously reported GG-independent detection 15 (Fig. 2d). Food odorized with predator scents were also aversive (Fig. 2d) as observed with the pyrazine analogues (Pyrazines), found for example in Mt.Lion urine 20 , 2-PT, 2,4,5-trimethylthiazoline (TMT) from the red fox feces as well as the mouse alarm pheromone SBT. Nevertheless, in Axo mice, this dislike was reduced indicating and confirming (Fig. 2b) that the GG was indeed implicated in the perception of these chemical danger cues 15 . Finally, we used Mt.Lion urine as a natural source of predator scents 20 and found that its aversive effect on food choice was exclusively dependent on a functional GG (Fig. 2d). Thus, confirming our GG calcium imaging investigations (Fig. 2a, b) that show that mice do not recognize odor signals emitted by unfamiliar food via GG detection as demonstrated by exposing them to familiar versus unfamiliar foods (Fig. 2d).

We next highlighted that this olfactory subsystem was fundamental for mice to decipher the threatening quality of an unfamiliar food (Fig. 2e). Indeed, on sets of naive mice, when we used the pungent and unfamiliar BA as odor #2 (Fig. 2e) in the previous two choices assay (Fig. 2c), Ctrl and Axo mice now preferred Cinnamon, Cocoa and CS2 as sources of unfamiliar odorized food (Fig. 2e) confirming the previously observed aversity of the BA (Fig. 2c). Interestingly, in the presence of danger cues such as the Pyrazines, 2PT, TMT, SBT and Mt.Lion urine, Ctrl mice now systematically preferred the aversive and unfamiliar BA (Fig. 2e). TMT and SBT were particularly efficient as they were still able to generate this innate reaction in serial dilutions (Supplementary Fig. 2b, c). Remarkably, this observed preference for BA disappeared in the absence of a functional GG, without affecting the total food consumption (Supplementary Fig. 2d, e). Thus, mice decode the threatening quality of unfamiliar food by GG detection.

Taken together, our results show that, the GG acts as an immediate sensor, which deciphers the threatening quality of odorants emitted by food. Mice will take their final consumption decision about the safety of the resource thanks to its smell and to its GG perception.

Threatening scents activate GG-dependent corticosterone responses

In the wild, food resources are often limited and could be located in a dangerous setting such as impending predation. Nevertheless, the motivational state is modified under hunger context 3 . To evaluate trade-offs displayed by fasting mice when confronted to actively searching a food resource in a danger context, we next challenged Ctrl and Axo mice with unreachable food resources moistened with SBT and with Mt.Lion urine, as sources of respectively intra- and inter-species conditioning stimuli (+C.S) mimicking environmental evidence of olfactory threats (Fig. 3a). Remarkably, we observed the absence of a fear-like response such as freezing (Fig. 3b) and the display of a risk assessment behavior (Fig. 3c) in both Ctrl and Axo mice 15 , indicating that, in a context of food scarceness, the opportunity to eat indeed overrules fear (Fig. 3a–c). These observed behavioral adaptations also highlight that odorants emitted by food were sufficient to initiate this motivational-related behavioral process independently from GG detection (Fig. 3c). We then followed the systemic integration of these stressful situations with the expression of the immediate-early gene c-Fos 21 . We focused on the amygdalopiriform transition area (APir Fig. 3d) which is the brain region implicated in the increase of stress-related hormone level in the blood when mice smell volatile predator scents 15,22 . We found that this brain region was significantly activated by both SBT and the predator urine (Fig. 3e, f). We next confirmed this result by measuring an increase of the systemic corticosterone level (Fig. 3g), implying that intra- and inter-species danger cues were both processed in this specific APir nucleus. In a dilution series of intraperitoneal corticosterone injections (Cort. i.p. Fig. 3h), we were further able to mimic the observed stress-related hormonal elevation with an amount of Cort. i.p. of 5.0 mg kg −1 , therefore bypassing APir activation in absence of conditioning stimuli (−C.S Fig. 3h and Supplementary Fig. 3). Moreover, we found that, in Axo mice, the activation of the APir region, as well as the elevation of the systemic corticosterone, were significantly impaired in this threatening context (Fig. 3e–g), demonstrating that, although the GG was not involved in odor-driven foraging, it was essential for the hormonal and physiological adaptation to danger sensing.

a Infrared snapshot and procedure time-table illustrating mice in contact with an unreachable food resource (food, gray), moistened with conditioning stimuli (+C.S, purple). Here, Ctrl mice displayed a typical risk assessment behavior in the presence of + Mt.Lion. bc Quantification of the absence of freezing response expressed as a percentage of time (b) and of the risk assessment mean occurrence per minute (c) displayed by mice during the behavioral assay (a). d Serial coronal brain sections corresponding to Bregma (−3.28 to −3.80) used for the c-Fos investigation of the amygdalopiriform (APir, red) and the ventral subiculum (VS, blue) areas. e Representative c-Fos stainings (dark spots) in Ctrl and Axo mice in APir (dashed red lines) obtained after + Water, + SBT (1:500) or + Mt.Lion (pure urine) conditioning. Scale bars, 50 μm. f Quantification of the density of c-Fos+ cells observed in APir. g Plasma corticosterone analysis after + C.S stimulation. h Procedure time-table illustrating the plasma corticosterone analysis in absence of conditioning stimulus (− C.S) and after intraperitoneally injection of corticosterone (Cort. i.p., 10.0, 5.0, 2.5, 0.5, 0.0 mg kg −1 ). (b, c and fh) Values obtained from Ctrl (black) and Axo (gray) mice are represented as mean ± SEM with aligned dot plots. For comparisons between conditions and between Ctrl vs. Axo mice, two-tailed Student’s t-tests or Wilcoxon w-tests are used, *p < 0.05 **p < 0.01 ***p < 0.001. A minimum of four animals were used per condition.

Elevation of corticosterone optimizes learned-food selection

In the search of food resources, knowledge of familiar food obtained by STFP support the food decision-making by a recall memory process that requires the activation of a specific part of the hippocampus, the ventral subiculum 13,23 (VS Fig. 3d). In this study, we found that the presence of danger cues enhanced this learned food-odorant preference when we performed a two choices assay under threatening conditions. For that, we first trained mice to develop a food-odorant preference. In brief, a demonstrator mouse ate an odorized demonstrating food (de.food standard powdered food odorized for example with Cinnamon as a spice #1 Phase 1 Fig. 4a). Then it returned with its observer littermates to allow the STFP learning process to happen (Phase 2 Fig. 4a). Finally, after 24 h of fasting, the observer mice were individually confronted to a two choices assay between two odorized foods, the demonstrating food and a novel food (new.food standard powdered food odorized for example with Cocoa as spice #2 Phase 3 Fig. 4b), both surrounded with the same conditioning stimulus (+C.S Fig. 4b). To avoid any individual innate preference, spices were used in a counterbalanced mode 13 (Supplementary Fig. 4a to c). We observed in both Ctrl and Axo mice that STFP was, indeed, required to develop a food preference (STFP+ | + Water Fig. 4c) that was, remarkably, not impacted by a chemical confusion generated by the pungent BA (STFP+ | + BA Fig. 4c). These first effects not only confirmed the conserved functionality of the GC-D circuitry in Axo mice (Fig. 1c, e, f) but also pointed out that, under aversive distraction, mice still olfactively decipher food preferences. Surprisingly, we obtained, with the danger cue SBT (STFP+ | + SBT) and with Mt.Lion urine (STFP+ | + Mt.Lion) an enhancement of the food-odorant preference (Fig. 4c). Indeed, the observed mean food preferences were amplified by around 60 % compared to STFP under standard environmental (STFP+ | + Water) or under pungent conditions (STFP+ | + BA). This enhancement was observed in Ctrl but not in Axo mice. It was found to be both independent from food consumption (Supplementary Fig. 5a) and from an improvement of the recall memory process as no significant increase in c-Fos activity was observed in the VS brain area under these conditions (Fig. 4d, e). Interestingly, we found that injection of Cort. i.p. 5.0 mg kg −1 under neutral context (STFP+ | Cort. i.p.) was sufficient to mimic this behavioral improvement both in Ctrl and Axo mice (Fig. 4c) without affecting the memory-retrieval activity of the VS (Supplementary Fig. 5b, c). We thus demonstrated here that, when danger cues are sensed by the GG, the increase in the systemic corticosterone level that occurs (Fig. 3e) leads to an enhancement of the food preference previously acquired by STFP.

a Acquisition of a food preference performed by STFP assay is illustrated by infrared snapshots and a procedure time-table. In phase 1, a demonstrating food (de.food, yellow) is presented to a demonstrator mouse (de). In phase 2, observer mice (ob) are in contact with the de for social interactions and acquisition of a preference for the de.food. b In phase 3, each ob mouse is individually tested in a two choices assay with two sources of food (de.food, yellow new.food, red) surrounded with the same conditioning stimulus (+C.S, purple). c Quantification of the food preference ratio in Ctrl and Axo mice without or with STFP procedure and under the indicated environmental conditioning (STFP− or + | + C.S) or after intraperitoneal injection of 5.0 mg kg −1 corticosterone (Cort. i.p.). Statistical significances of preference ratio are performed with Z tests, #p < 0.05 (yellow, for a preference for de.food) non-significant if not mentioned. 12 to 36 animals were used per condition. The following pairs of spices were used: cinnamon 1% vs. cocoa 2% anise 1% vs. oregano 2.4% thyme 2% vs. basil 1.4%. d Representative c-Fos staining (dark spots) in Ctrl and Axo mice under the indicated conditioning in VS (blue dashed line). Scale bars, 50 μm. The following pair of spices were used: nutmeg 1% vs. ginger 1%. e Quantification of the density of c-Fos+ cells in VS from (d). A minimum of 4 animals were used per condition. c, e Values obtained from Ctrl (black) and Axo (gray) mice are represented as mean ± SEM with aligned dot plots. For comparisons between conditions and between Ctrl vs. Axo mice, two-tailed Student’s t-tests or Wilcoxon w-tests are used, *p < 0.05 ***p < 0.001.

GG circuitry activation selectively erases safety food memory

Conspecific interactions are useful for mice to get food familiarity. We found here that mice can also benefit from threatening chemical information present in their environment to reset this previously acquired food-odorant familiarity when associated with a danger context. We indeed tested the impact of olfactory threats on the acquisition of a new food-odorant preference as we challenged mice 1 h after an STFP procedure (Phase 1 Fig. 5a) with a surrogate display that contained the unreachable demonstrating food moistened with an associated conditioning stimulus (Phase 2 +C.S Fig. 5a), a procedure that allows food investigation (Fig. 3a–c). After 24 h of fasting, the observer mice were then tested in a two choices assay (Phase 3 Fig. 5b). Unexpectedly, we found that in association with the danger cues SBT (STFP+/+ SBT) or with Mt.Lion urine (STFP+/+ Mt.Lion), Ctrl mice did not display food-odorant preferences while they were still observed in Axo mice (Fig. 5c). As a control, we verified that GG-related ligands directly associated with a demonstrating food could not act as conditioning stimuli promoting a food preference or avoidance (Supplementary Fig. 6a–c), confirming our previous observations that avoidance towards an unfamiliar odorized food is innately coded (Fig. 2d). Besides, we also observed that this apparent and selective amnesia was independent from food consumption (Supplementary Fig. 7a) or corticosterone elevation. Indeed, mice injected with Cort. i.p. 5.0 mg kg −1 instead of the associated conditioning stimuli (STFP+/Cort. i.p.) still displayed a food-odorant preference (Fig. 5c). Moreover, we observed a striking resetting of the VS brain area (c-Fos stainings Fig. 5d, e), that suggests an impairment in the recall memory for a food preference or for its consolidation. Remarkably, as this process was independent from the systemic corticosterone level (Supplementary Fig. 7b, c) and not observed in Axo mice, this cerebral adaptation was thus directly related with the activation of the GG neuronal circuitry itself (Fig. 5d, e).

a Acquisition of a food preference performed by STFP assay followed by an associated conditioning stimulus (+C.S, purple) is illustrated by infrared snapshots and a procedure time-table. In phase 1, acquisition of a food preference. A demonstrating food (de.food, yellow) is presented to observer mice (ob) with a surrogate display, moistened with CS2, mimicking social interactions. In phase 2, de.food is again presented to ob mice but associated with a +C.S. b In phase 3, each ob mouse is individually tested in a two choices assay with two sources of food (de.food, yellow new.food, red). c Quantification of the food preference ratio in Ctrl and Axo mice without or with STFP procedure followed by the indicated associated stimulus (STFP− or +/+C.S) or after intraperitoneal injection of 5.0 mg/kg corticosterone (Cort. i.p.). Statistical significances of preference ratio are performed with Z tests, # p < 0.05 (yellow, for a preference for de.food) non-significant if not mentioned. 10–18 animals were used per condition. The following pairs of spices were used: cinnamon 1% vs. cocoa 2% anise 1% vs. oregano 2.4% thyme 2% vs. basil 1.4%. d Representative c-Fos staining (dark spots) in Ctrl and Axo mice under the indicated conditioning in VS (blue dashed line). Scale bars, 50 μm. The following pair of spices was used: nutmeg 1% vs. ginger 1%. e Quantification of the density of c-Fos+ cells in VS from (d). Four animals were used per condition. c, e Values obtained from Ctrl (black) and Axo (gray) mice are represented as mean ± SEM with aligned dot plots. For comparisons between conditions and between Ctrl vs. Axo mice, two-tailed Student’s t-tests or Wilcoxon w-tests are used, *p < 0.05 **p < 0.01 ***p < 0.001.


Why Do We Eat?

The answer to the question “Why do we eat?” seems an obvious one—to obtain the energy we need to support our everyday activities and, ultimately, promote our survival. However, many of our modern day food choices suggest another answer—one that actually stands to threaten our health and well being.

Many times, the reason we eat has less to do with sustenance and more to do with taste. Moreover, our daily food choices are influenced by a variety of other factors including the social situations we find ourselves in, our budgets, sleep schedules, and stress levels, as well as the amount of time we have to prepare and eat a meal.

A quick comparison between the food landscape of our ancestors and the current environment shows dramatic changes on both sides of the energy balance equation (energy expended vs. energy consumed). In more primitive times, hunters and gatherers foraged for vegetation and hunted animals to eat. They worked hard and expended energy to obtain foods that were not typically calorically dense. As a result, their energy expenditure was more closely balanced with their energy intake.

Advances in agriculture and modern farming techniques have provided the opportunity to grow massive quantities of food with far less effort than before. On the other side of the equation, there has also been a dramatic change in our food sources. Today, many food items are highly processed combinations of several palatable ingredients and chemicals. The food industry creates and markets food and beverage products that are engineered to be both desirable and inexpensive. For instance, foods such as corn and wheat are transformed from their original form and combined with salt, fat, sugars, and other ingredients to produce the low cost, high energy food and beverage items that line our grocery store shelves.

Even though food is essential for survival, not all foods are created equal. Eating certain foods, especially in excess, can produce the opposite effect of sustaining life by compromising our health. Overeating and obesity are on the rise in both the United States and around the world.

Despite warnings of the physical health risks associated with increased body weight, the plethora of diet books and programs available, and the stigma associated with excess weight, many people find it difficult to achieve and maintain a healthy body weight. Thus, it is important to consider what other factors are driving weight gain or sabotaging weight loss efforts. It is impossible to avoid the fact that the pleasurable aspects of foods are powerful motivators of our choices.

The basic biology underlying food intake is closely linked to pleasure. Since food is necessary for survival, eating, especially when hungry, is inherently reinforcing. However, eating can be reinforcing even when it is not driven by a caloric deficit. This is why we continue to eat past the point of satiation and eat highly palatable foods like cupcakes and candy bars that aren’t filling. Unfortunately, our natural inclination to consume these types of foods collides with the many influences in our modern food environment—such as convenience, cost, and social influences—to ultimately encourage the overconsumption of highly palatable foods.

In my new book, Hedonic Eating, I examine the various behavioral, biological, and social factors associated with highly palatable food consumption in an effort to offer greater insight into what promotes this behavior and shed light on the different factors that may be involved in perpetuating current obesity epidemic.


Our research programs are designed to expand understanding of the biological/microbiological, chemical, physical, sensory, nutritional and engineering properties of foods and beverages. Our extension and outreach programs transfer research-based information and technology to consumers, food and beverage companies, and government agencies with the goal of enhancing the availability, quality, and safety of our food supply.

We work together to provide new answers and discover new questions across the food science sectors.

We offer comprehensive undergraduate and graduate programs that prepare students for leadership positions in the food industry, academia and government.

Our research programs are designed to expand understanding of the biological/microbiological, chemical, physical, sensory, nutritional and engineering properties of foods and beverages.

Our extension and outreach programs transfer research-based information and technology to consumers, food and beverage companies and government agencies with the goal of enhancing the availability, quality and safety of our food supply.


6. Changing food behaviour: successful interventions

Dietary change is not easy because it requires alterations in habits that have been built up over a life-time. Various settings such as schools, workplaces, supermarkets, primary care and community based studies have been used in order to identify what works for particular groups of people. Although results from such trials are difficult to extrapolate to other settings or the general public, such targeted interventions have been reasonably successful, illustrating that different approaches are required for different groups of people or different aspects of the diet.

Interventions in supermarket settings are popular given this is where the majority of the people buy most of their food. Screening, shop tours and point-of-purchase interventions are ways in which information can be provided. Such interventions are successful at raising awareness and nutrition knowledge but their effectiveness of any real and long-term behaviour change is unclear at present.

Schools are another obvious intervention setting because they can reach the students, their parents and the school staff. Fruit and vegetable intake in children has been increased through the use of tuck shops, multimedia and the internet and when children get involved in growing, preparing and cooking the food they eat 1,6,35 . Moreover, covert changes to dishes to lower fat, sodium and energy content improved the nutritional profile of school dinners without losing student participation in the school lunch programme 44 .

Workplace interventions can also reach large numbers of people and can target those at risk. Increasing availability and appeal of fruit and vegetables proved successful in worksite canteens 34 and price reductions for healthier snacks in vending machines increased sales 24 . Thus, the combination of nutrition education with changes in the workplace are more likely to succeed particularly if interactive activities are employed and if such activities are sustained for long periods 41 .

Tackling several dietary factors simultaneously such as reducing dietary fat and increasing fruit and vegetables, has proved effective in the primary care setting 48 . Behavioural counselling in conjunction with nutrition counselling seems most effective in such settings although the cost implications of training primary care professionals in behaviour counselling are unclear at this time. Educational and behavioural strategies have also been used in public health/ community settings, which have been shown to increase fruit and vegetable intake 2,3,12 .


It’s Not Just About The Food

Sustainable food isn’t only about the food itself. It’s a combination of factors including how the food is produced, how it’s distributed, how it’s packaged and how it’s consumed.

Food miles, or how far a food has traveled, plays a large role. But it’s a whole lot more complicated than that.

When considering the sustainability of food there are many other factors at play.

Resource usage, environmental impact and animal agriculture all affect sustainability. As do health considerations and social and economic impact.


Food Choice - Biology

The sense of taste is stimulated when nutrients or other chemical compounds activate specialized receptor cells within the oral cavity. Taste helps us decide what to eat and influences how efficiently we digest these foods. Human taste abilities have been shaped, in large part, by the ecological niches our evolutionary ancestors occupied and by the nutrients they sought. Early hominoids sought nutrition within a closed tropical forest environment, probably eating mostly fruit and leaves, and early hominids left this environment for the savannah and greatly expanded their dietary repertoire. They would have used their sense of taste to identify nutritious food items. The risks of making poor food selections when foraging not only entail wasted energy and metabolic harm from eating foods of low nutrient and energy content, but also the harmful and potentially lethal ingestion of toxins. The learned consequences of ingested foods may subsequently guide our future food choices. The evolved taste abilities of humans are still useful for the one billion humans living with very low food security by helping them identify nutrients. But for those who have easy access to tasty, energy-dense foods our sensitivities for sugary, salty and fatty foods have also helped cause over nutrition-related diseases, such as obesity and diabetes.


Contents

Genetic engineering is a process that alters the genetic structure of an organism by either removing or introducing DNA. Unlike traditional animal and plant breeding, which involves doing multiple crosses and then selecting for the organism with the desired phenotype, genetic engineering takes the gene directly from one organism and delivers it to the other. This is much faster, can be used to insert any genes from any organism (even ones from different domains) and prevents other undesirable genes from also being added. [4]

Genetic engineering could potentially fix severe genetic disorders in humans by replacing the defective gene with a functioning one. [5] It is an important tool in research that allows the function of specific genes to be studied. [6] Drugs, vaccines and other products have been harvested from organisms engineered to produce them. [7] Crops have been developed that aid food security by increasing yield, nutritional value and tolerance to environmental stresses. [8]

The DNA can be introduced directly into the host organism or into a cell that is then fused or hybridised with the host. [9] This relies on recombinant nucleic acid techniques to form new combinations of heritable genetic material followed by the incorporation of that material either indirectly through a vector system or directly through micro-injection, macro-injection or micro-encapsulation. [10]

Genetic engineering does not normally include traditional breeding, in vitro fertilisation, induction of polyploidy, mutagenesis and cell fusion techniques that do not use recombinant nucleic acids or a genetically modified organism in the process. [9] However, some broad definitions of genetic engineering include selective breeding. [10] Cloning and stem cell research, although not considered genetic engineering, [11] are closely related and genetic engineering can be used within them. [12] Synthetic biology is an emerging discipline that takes genetic engineering a step further by introducing artificially synthesised material into an organism. [13] Such synthetic DNA as Artificially Expanded Genetic Information System and Hachimoji DNA is made in this new field.

Plants, animals or microorganisms that have been changed through genetic engineering are termed genetically modified organisms or GMOs. [14] If genetic material from another species is added to the host, the resulting organism is called transgenic. If genetic material from the same species or a species that can naturally breed with the host is used the resulting organism is called cisgenic. [15] If genetic engineering is used to remove genetic material from the target organism the resulting organism is termed a knockout organism. [16] In Europe genetic modification is synonymous with genetic engineering while within the United States of America and Canada genetic modification can also be used to refer to more conventional breeding methods. [17] [18] [19]

Humans have altered the genomes of species for thousands of years through selective breeding, or artificial selection [20] : 1 [21] : 1 as contrasted with natural selection. More recently, mutation breeding has used exposure to chemicals or radiation to produce a high frequency of random mutations, for selective breeding purposes. Genetic engineering as the direct manipulation of DNA by humans outside breeding and mutations has only existed since the 1970s. The term "genetic engineering" was first coined by Jack Williamson in his science fiction novel Dragon's Island, published in 1951 [22] – one year before DNA's role in heredity was confirmed by Alfred Hershey and Martha Chase, [23] and two years before James Watson and Francis Crick showed that the DNA molecule has a double-helix structure – though the general concept of direct genetic manipulation was explored in rudimentary form in Stanley G. Weinbaum's 1936 science fiction story Proteus Island. [24] [25]

In 1972, Paul Berg created the first recombinant DNA molecules by combining DNA from the monkey virus SV40 with that of the lambda virus. [26] In 1973 Herbert Boyer and Stanley Cohen created the first transgenic organism by inserting antibiotic resistance genes into the plasmid of an Escherichia coli bacterium. [27] [28] A year later Rudolf Jaenisch created a transgenic mouse by introducing foreign DNA into its embryo, making it the world's first transgenic animal [29] These achievements led to concerns in the scientific community about potential risks from genetic engineering, which were first discussed in depth at the Asilomar Conference in 1975. One of the main recommendations from this meeting was that government oversight of recombinant DNA research should be established until the technology was deemed safe. [30] [31]

In 1976 Genentech, the first genetic engineering company, was founded by Herbert Boyer and Robert Swanson and a year later the company produced a human protein (somatostatin) in E.coli. Genentech announced the production of genetically engineered human insulin in 1978. [32] In 1980, the U.S. Supreme Court in the Diamond v. Chakrabarty case ruled that genetically altered life could be patented. [33] The insulin produced by bacteria was approved for release by the Food and Drug Administration (FDA) in 1982. [34]

In 1983, a biotech company, Advanced Genetic Sciences (AGS) applied for U.S. government authorisation to perform field tests with the ice-minus strain of Pseudomonas syringae to protect crops from frost, but environmental groups and protestors delayed the field tests for four years with legal challenges. [35] In 1987, the ice-minus strain of P. syringae became the first genetically modified organism (GMO) to be released into the environment [36] when a strawberry field and a potato field in California were sprayed with it. [37] Both test fields were attacked by activist groups the night before the tests occurred: "The world's first trial site attracted the world's first field trasher". [36]

The first field trials of genetically engineered plants occurred in France and the US in 1986, tobacco plants were engineered to be resistant to herbicides. [38] The People's Republic of China was the first country to commercialise transgenic plants, introducing a virus-resistant tobacco in 1992. [39] In 1994 Calgene attained approval to commercially release the first genetically modified food, the Flavr Savr, a tomato engineered to have a longer shelf life. [40] In 1994, the European Union approved tobacco engineered to be resistant to the herbicide bromoxynil, making it the first genetically engineered crop commercialised in Europe. [41] In 1995, Bt Potato was approved safe by the Environmental Protection Agency, after having been approved by the FDA, making it the first pesticide producing crop to be approved in the US. [42] In 2009 11 transgenic crops were grown commercially in 25 countries, the largest of which by area grown were the US, Brazil, Argentina, India, Canada, China, Paraguay and South Africa. [43]

In 2010, scientists at the J. Craig Venter Institute created the first synthetic genome and inserted it into an empty bacterial cell. The resulting bacterium, named Mycoplasma laboratorium, could replicate and produce proteins. [44] [45] Four years later this was taken a step further when a bacterium was developed that replicated a plasmid containing a unique base pair, creating the first organism engineered to use an expanded genetic alphabet. [46] [47] In 2012, Jennifer Doudna and Emmanuelle Charpentier collaborated to develop the CRISPR/Cas9 system, [48] [49] a technique which can be used to easily and specifically alter the genome of almost any organism. [50]

Creating a GMO is a multi-step process. Genetic engineers must first choose what gene they wish to insert into the organism. This is driven by what the aim is for the resultant organism and is built on earlier research. Genetic screens can be carried out to determine potential genes and further tests then used to identify the best candidates. The development of microarrays, transcriptomics and genome sequencing has made it much easier to find suitable genes. [51] Luck also plays its part the round-up ready gene was discovered after scientists noticed a bacterium thriving in the presence of the herbicide. [52]

Gene isolation and cloning Edit

The next step is to isolate the candidate gene. The cell containing the gene is opened and the DNA is purified. [53] The gene is separated by using restriction enzymes to cut the DNA into fragments [54] or polymerase chain reaction (PCR) to amplify up the gene segment. [55] These segments can then be extracted through gel electrophoresis. If the chosen gene or the donor organism's genome has been well studied it may already be accessible from a genetic library. If the DNA sequence is known, but no copies of the gene are available, it can also be artificially synthesised. [56] Once isolated the gene is ligated into a plasmid that is then inserted into a bacterium. The plasmid is replicated when the bacteria divide, ensuring unlimited copies of the gene are available. [57]

Before the gene is inserted into the target organism it must be combined with other genetic elements. These include a promoter and terminator region, which initiate and end transcription. A selectable marker gene is added, which in most cases confers antibiotic resistance, so researchers can easily determine which cells have been successfully transformed. The gene can also be modified at this stage for better expression or effectiveness. These manipulations are carried out using recombinant DNA techniques, such as restriction digests, ligations and molecular cloning. [58]

Inserting DNA into the host genome Edit

There are a number of techniques used to insert genetic material into the host genome. Some bacteria can naturally take up foreign DNA. This ability can be induced in other bacteria via stress (e.g. thermal or electric shock), which increases the cell membrane's permeability to DNA up-taken DNA can either integrate with the genome or exist as extrachromosomal DNA. DNA is generally inserted into animal cells using microinjection, where it can be injected through the cell's nuclear envelope directly into the nucleus, or through the use of viral vectors. [59]

Plant genomes can be engineered by physical methods or by use of Agrobacterium for the delivery of sequences hosted in T-DNA binary vectors. In plants the DNA is often inserted using Agrobacterium-mediated transformation, [60] taking advantage of the Agrobacteriums T-DNA sequence that allows natural insertion of genetic material into plant cells. [61] Other methods include biolistics, where particles of gold or tungsten are coated with DNA and then shot into young plant cells, [62] and electroporation, which involves using an electric shock to make the cell membrane permeable to plasmid DNA.

As only a single cell is transformed with genetic material, the organism must be regenerated from that single cell. In plants this is accomplished through the use of tissue culture. [63] [64] In animals it is necessary to ensure that the inserted DNA is present in the embryonic stem cells. [65] Bacteria consist of a single cell and reproduce clonally so regeneration is not necessary. Selectable markers are used to easily differentiate transformed from untransformed cells. These markers are usually present in the transgenic organism, although a number of strategies have been developed that can remove the selectable marker from the mature transgenic plant. [66]

Further testing using PCR, Southern hybridization, and DNA sequencing is conducted to confirm that an organism contains the new gene. [67] These tests can also confirm the chromosomal location and copy number of the inserted gene. The presence of the gene does not guarantee it will be expressed at appropriate levels in the target tissue so methods that look for and measure the gene products (RNA and protein) are also used. These include northern hybridisation, quantitative RT-PCR, Western blot, immunofluorescence, ELISA and phenotypic analysis. [68]

The new genetic material can be inserted randomly within the host genome or targeted to a specific location. The technique of gene targeting uses homologous recombination to make desired changes to a specific endogenous gene. This tends to occur at a relatively low frequency in plants and animals and generally requires the use of selectable markers. The frequency of gene targeting can be greatly enhanced through genome editing. Genome editing uses artificially engineered nucleases that create specific double-stranded breaks at desired locations in the genome, and use the cell's endogenous mechanisms to repair the induced break by the natural processes of homologous recombination and nonhomologous end-joining. There are four families of engineered nucleases: meganucleases, [69] [70] zinc finger nucleases, [71] [72] transcription activator-like effector nucleases (TALENs), [73] [74] and the Cas9-guideRNA system (adapted from CRISPR). [75] [76] TALEN and CRISPR are the two most commonly used and each has its own advantages. [77] TALENs have greater target specificity, while CRISPR is easier to design and more efficient. [77] In addition to enhancing gene targeting, engineered nucleases can be used to introduce mutations at endogenous genes that generate a gene knockout. [78] [79]

Genetic engineering has applications in medicine, research, industry and agriculture and can be used on a wide range of plants, animals and microorganisms. Bacteria, the first organisms to be genetically modified, can have plasmid DNA inserted containing new genes that code for medicines or enzymes that process food and other substrates. [80] [81] Plants have been modified for insect protection, herbicide resistance, virus resistance, enhanced nutrition, tolerance to environmental pressures and the production of edible vaccines. [82] Most commercialised GMOs are insect resistant or herbicide tolerant crop plants. [83] Genetically modified animals have been used for research, model animals and the production of agricultural or pharmaceutical products. The genetically modified animals include animals with genes knocked out, increased susceptibility to disease, hormones for extra growth and the ability to express proteins in their milk. [84]

Medicine Edit

Genetic engineering has many applications to medicine that include the manufacturing of drugs, creation of model animals that mimic human conditions and gene therapy. One of the earliest uses of genetic engineering was to mass-produce human insulin in bacteria. [32] This application has now been applied to human growth hormones, follicle stimulating hormones (for treating infertility), human albumin, monoclonal antibodies, antihemophilic factors, vaccines and many other drugs. [85] [86] Mouse hybridomas, cells fused together to create monoclonal antibodies, have been adapted through genetic engineering to create human monoclonal antibodies. [87] In 2017, genetic engineering of chimeric antigen receptors on a patient's own T-cells was approved by the U.S. FDA as a treatment for the cancer acute lymphoblastic leukemia. Genetically engineered viruses are being developed that can still confer immunity, but lack the infectious sequences. [88]

Genetic engineering is also used to create animal models of human diseases. Genetically modified mice are the most common genetically engineered animal model. [89] They have been used to study and model cancer (the oncomouse), obesity, heart disease, diabetes, arthritis, substance abuse, anxiety, aging and Parkinson disease. [90] Potential cures can be tested against these mouse models. Also genetically modified pigs have been bred with the aim of increasing the success of pig to human organ transplantation. [91]

Gene therapy is the genetic engineering of humans, generally by replacing defective genes with effective ones. Clinical research using somatic gene therapy has been conducted with several diseases, including X-linked SCID, [92] chronic lymphocytic leukemia (CLL), [93] [94] and Parkinson's disease. [95] In 2012, Alipogene tiparvovec became the first gene therapy treatment to be approved for clinical use. [96] [97] In 2015 a virus was used to insert a healthy gene into the skin cells of a boy suffering from a rare skin disease, epidermolysis bullosa, in order to grow, and then graft healthy skin onto 80 percent of the boy's body which was affected by the illness. [98]

Germline gene therapy would result in any change being inheritable, which has raised concerns within the scientific community. [99] [100] In 2015, CRISPR was used to edit the DNA of non-viable human embryos, [101] [102] leading scientists of major world academies to call for a moratorium on inheritable human genome edits. [103] There are also concerns that the technology could be used not just for treatment, but for enhancement, modification or alteration of a human beings' appearance, adaptability, intelligence, character or behavior. [104] The distinction between cure and enhancement can also be difficult to establish. [105] In November 2018, He Jiankui announced that he had edited the genomes of two human embryos, to attempt to disable the CCR5 gene, which codes for a receptor that HIV uses to enter cells. He said that twin girls, Lulu and Nana, had been born a few weeks earlier. He said that the girls still carried functional copies of CCR5 along with disabled CCR5 (mosaicism) and were still vulnerable to HIV. The work was widely condemned as unethical, dangerous, and premature. [106] Currently, germline modification is banned in 40 countries. Scientists that do this type of research will often let embryos grow for a few days without allowing it to develop into a baby. [107]

Researchers are altering the genome of pigs to induce the growth of human organs to be used in transplants. Scientists are creating "gene drives", changing the genomes of mosquitoes to make them immune to malaria, and then looking to spread the genetically altered mosquitoes throughout the mosquito population in the hopes of eliminating the disease. [108]

Research Edit

Genetic engineering is an important tool for natural scientists, with the creation of transgenic organisms one of the most important tools for analysis of gene function. [109] Genes and other genetic information from a wide range of organisms can be inserted into bacteria for storage and modification, creating genetically modified bacteria in the process. Bacteria are cheap, easy to grow, clonal, multiply quickly, relatively easy to transform and can be stored at -80 °C almost indefinitely. Once a gene is isolated it can be stored inside the bacteria providing an unlimited supply for research. [110] Organisms are genetically engineered to discover the functions of certain genes. This could be the effect on the phenotype of the organism, where the gene is expressed or what other genes it interacts with. These experiments generally involve loss of function, gain of function, tracking and expression.

  • Loss of function experiments, such as in a gene knockout experiment, in which an organism is engineered to lack the activity of one or more genes. In a simple knockout a copy of the desired gene has been altered to make it non-functional. Embryonic stem cells incorporate the altered gene, which replaces the already present functional copy. These stem cells are injected into blastocysts, which are implanted into surrogate mothers. This allows the experimenter to analyse the defects caused by this mutation and thereby determine the role of particular genes. It is used especially frequently in developmental biology. [111] When this is done by creating a library of genes with point mutations at every position in the area of interest, or even every position in the whole gene, this is called "scanning mutagenesis". The simplest method, and the first to be used, is "alanine scanning", where every position in turn is mutated to the unreactive amino acid alanine. [112]
  • Gain of function experiments, the logical counterpart of knockouts. These are sometimes performed in conjunction with knockout experiments to more finely establish the function of the desired gene. The process is much the same as that in knockout engineering, except that the construct is designed to increase the function of the gene, usually by providing extra copies of the gene or inducing synthesis of the protein more frequently. Gain of function is used to tell whether or not a protein is sufficient for a function, but does not always mean it's required, especially when dealing with genetic or functional redundancy. [111]
  • Tracking experiments, which seek to gain information about the localisation and interaction of the desired protein. One way to do this is to replace the wild-type gene with a 'fusion' gene, which is a juxtaposition of the wild-type gene with a reporting element such as green fluorescent protein (GFP) that will allow easy visualisation of the products of the genetic modification. While this is a useful technique, the manipulation can destroy the function of the gene, creating secondary effects and possibly calling into question the results of the experiment. More sophisticated techniques are now in development that can track protein products without mitigating their function, such as the addition of small sequences that will serve as binding motifs to monoclonal antibodies. [111]
  • Expression studies aim to discover where and when specific proteins are produced. In these experiments, the DNA sequence before the DNA that codes for a protein, known as a gene's promoter, is reintroduced into an organism with the protein coding region replaced by a reporter gene such as GFP or an enzyme that catalyses the production of a dye. Thus the time and place where a particular protein is produced can be observed. Expression studies can be taken a step further by altering the promoter to find which pieces are crucial for the proper expression of the gene and are actually bound by transcription factor proteins this process is known as promoter bashing. [113]

Industrial Edit

Organisms can have their cells transformed with a gene coding for a useful protein, such as an enzyme, so that they will overexpress the desired protein. Mass quantities of the protein can then be manufactured by growing the transformed organism in bioreactor equipment using industrial fermentation, and then purifying the protein. [114] Some genes do not work well in bacteria, so yeast, insect cells or mammalians cells can also be used. [115] These techniques are used to produce medicines such as insulin, human growth hormone, and vaccines, supplements such as tryptophan, aid in the production of food (chymosin in cheese making) and fuels. [116] Other applications with genetically engineered bacteria could involve making them perform tasks outside their natural cycle, such as making biofuels, [117] cleaning up oil spills, carbon and other toxic waste [118] and detecting arsenic in drinking water. [119] Certain genetically modified microbes can also be used in biomining and bioremediation, due to their ability to extract heavy metals from their environment and incorporate them into compounds that are more easily recoverable. [120]

In materials science, a genetically modified virus has been used in a research laboratory as a scaffold for assembling a more environmentally friendly lithium-ion battery. [121] [122] Bacteria have also been engineered to function as sensors by expressing a fluorescent protein under certain environmental conditions. [123]

Agriculture Edit

One of the best-known and controversial applications of genetic engineering is the creation and use of genetically modified crops or genetically modified livestock to produce genetically modified food. Crops have been developed to increase production, increase tolerance to abiotic stresses, alter the composition of the food, or to produce novel products. [125]

The first crops to be released commercially on a large scale provided protection from insect pests or tolerance to herbicides. Fungal and virus resistant crops have also been developed or are in development. [126] [127] This makes the insect and weed management of crops easier and can indirectly increase crop yield. [128] [129] GM crops that directly improve yield by accelerating growth or making the plant more hardy (by improving salt, cold or drought tolerance) are also under development. [130] In 2016 Salmon have been genetically modified with growth hormones to reach normal adult size much faster. [131]

GMOs have been developed that modify the quality of produce by increasing the nutritional value or providing more industrially useful qualities or quantities. [130] The Amflora potato produces a more industrially useful blend of starches. Soybeans and canola have been genetically modified to produce more healthy oils. [132] [133] The first commercialised GM food was a tomato that had delayed ripening, increasing its shelf life. [134]

Plants and animals have been engineered to produce materials they do not normally make. Pharming uses crops and animals as bioreactors to produce vaccines, drug intermediates, or the drugs themselves the useful product is purified from the harvest and then used in the standard pharmaceutical production process. [135] Cows and goats have been engineered to express drugs and other proteins in their milk, and in 2009 the FDA approved a drug produced in goat milk. [136] [137]

Other applications Edit

Genetic engineering has potential applications in conservation and natural area management. Gene transfer through viral vectors has been proposed as a means of controlling invasive species as well as vaccinating threatened fauna from disease. [138] Transgenic trees have been suggested as a way to confer resistance to pathogens in wild populations. [139] With the increasing risks of maladaptation in organisms as a result of climate change and other perturbations, facilitated adaptation through gene tweaking could be one solution to reducing extinction risks. [140] Applications of genetic engineering in conservation are thus far mostly theoretical and have yet to be put into practice.

Genetic engineering is also being used to create microbial art. [141] Some bacteria have been genetically engineered to create black and white photographs. [142] Novelty items such as lavender-colored carnations, [143] blue roses, [144] and glowing fish [145] [146] have also been produced through genetic engineering.

The regulation of genetic engineering concerns the approaches taken by governments to assess and manage the risks associated with the development and release of GMOs. The development of a regulatory framework began in 1975, at Asilomar, California. [147] The Asilomar meeting recommended a set of voluntary guidelines regarding the use of recombinant technology. [30] As the technology improved the US established a committee at the Office of Science and Technology, [148] which assigned regulatory approval of GM food to the USDA, FDA and EPA. [149] The Cartagena Protocol on Biosafety, an international treaty that governs the transfer, handling, and use of GMOs, [150] was adopted on 29 January 2000. [151] One hundred and fifty-seven countries are members of the Protocol and many use it as a reference point for their own regulations. [152]

The legal and regulatory status of GM foods varies by country, with some nations banning or restricting them, and others permitting them with widely differing degrees of regulation. [153] [154] [155] [156] Some countries allow the import of GM food with authorisation, but either do not allow its cultivation (Russia, Norway, Israel) or have provisions for cultivation even though no GM products are yet produced (Japan, South Korea). Most countries that do not allow GMO cultivation do permit research. [157] Some of the most marked differences occurring between the US and Europe. The US policy focuses on the product (not the process), only looks at verifiable scientific risks and uses the concept of substantial equivalence. [158] The European Union by contrast has possibly the most stringent GMO regulations in the world. [159] All GMOs, along with irradiated food, are considered "new food" and subject to extensive, case-by-case, science-based food evaluation by the European Food Safety Authority. The criteria for authorisation fall in four broad categories: "safety", "freedom of choice", "labelling", and "traceability". [160] The level of regulation in other countries that cultivate GMOs lie in between Europe and the United States.

Regulatory agencies by geographical region
Region Regulators Notes
US USDA, FDA and EPA [149]
Europe European Food Safety Authority [160]
Canada Health Canada and the Canadian Food Inspection Agency [161] [162] Regulated products with novel features regardless of method of origin [163] [164]
Africa Common Market for Eastern and Southern Africa [165] Final decision lies with each individual country. [165]
China Office of Agricultural Genetic Engineering Biosafety Administration [166]
India Institutional Biosafety Committee, Review Committee on Genetic Manipulation and Genetic Engineering Approval Committee [167]
Argentina National Agricultural Biotechnology Advisory Committee (environmental impact), the National Service of Health and Agrifood Quality (food safety) and the National Agribusiness Direction (effect on trade) [168] Final decision made by the Secretariat of Agriculture, Livestock, Fishery and Food. [168]
Brazil National Biosafety Technical Commission (environmental and food safety) and the Council of Ministers (commercial and economical issues) [168]
Australia Office of the Gene Technology Regulator (oversees all GM products), Therapeutic Goods Administration (GM medicines) and Food Standards Australia New Zealand (GM food). [169] [170] The individual state governments can then assess the impact of release on markets and trade and apply further legislation to control approved genetically modified products. [170]

One of the key issues concerning regulators is whether GM products should be labeled. The European Commission says that mandatory labeling and traceability are needed to allow for informed choice, avoid potential false advertising [171] and facilitate the withdrawal of products if adverse effects on health or the environment are discovered. [172] The American Medical Association [173] and the American Association for the Advancement of Science [174] say that absent scientific evidence of harm even voluntary labeling is misleading and will falsely alarm consumers. Labeling of GMO products in the marketplace is required in 64 countries. [175] Labeling can be mandatory up to a threshold GM content level (which varies between countries) or voluntary. In Canada and the US labeling of GM food is voluntary, [176] while in Europe all food (including processed food) or feed which contains greater than 0.9% of approved GMOs must be labelled. [159]

Critics have objected to the use of genetic engineering on several grounds, including ethical, ecological and economic concerns. Many of these concerns involve GM crops and whether food produced from them is safe and what impact growing them will have on the environment. These controversies have led to litigation, international trade disputes, and protests, and to restrictive regulation of commercial products in some countries. [177]

Accusations that scientists are "playing God" and other religious issues have been ascribed to the technology from the beginning. [178] Other ethical issues raised include the patenting of life, [179] the use of intellectual property rights, [180] the level of labeling on products, [181] [182] control of the food supply [183] and the objectivity of the regulatory process. [184] Although doubts have been raised, [185] economically most studies have found growing GM crops to be beneficial to farmers. [186] [187] [188]

Gene flow between GM crops and compatible plants, along with increased use of selective herbicides, can increase the risk of "superweeds" developing. [189] Other environmental concerns involve potential impacts on non-target organisms, including soil microbes, [190] and an increase in secondary and resistant insect pests. [191] [192] Many of the environmental impacts regarding GM crops may take many years to be understood and are also evident in conventional agriculture practices. [190] [193] With the commercialisation of genetically modified fish there are concerns over what the environmental consequences will be if they escape. [194]

There are three main concerns over the safety of genetically modified food: whether they may provoke an allergic reaction whether the genes could transfer from the food into human cells and whether the genes not approved for human consumption could outcross to other crops. [195] There is a scientific consensus [196] [197] [198] [199] that currently available food derived from GM crops poses no greater risk to human health than conventional food, [200] [201] [202] [203] [204] but that each GM food needs to be tested on a case-by-case basis before introduction. [205] [206] [207] Nonetheless, members of the public are less likely than scientists to perceive GM foods as safe. [208] [209] [210] [211]

Genetic engineering features in many science fiction stories. [212] Frank Herbert's novel The White Plague described the deliberate use of genetic engineering to create a pathogen which specifically killed women. [212] Another of Herbert's creations, the Dune series of novels, uses genetic engineering to create the powerful but despised Tleilaxu. [213] Films such as The Island and Blade Runner bring the engineered creature to confront the person who created it or the being it was cloned from. Few films have informed audiences about genetic engineering, with the exception of the 1978 The Boys from Brazil and the 1993 Jurassic Park, both of which made use of a lesson, a demonstration, and a clip of scientific film. [214] [215] Genetic engineering methods are weakly represented in film Michael Clark, writing for The Wellcome Trust, calls the portrayal of genetic engineering and biotechnology "seriously distorted" [215] in films such as The 6th Day. In Clark's view, the biotechnology is typically "given fantastic but visually arresting forms" while the science is either relegated to the background or fictionalised to suit a young audience. [215]


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