Growth, development, and nutritional physiology of grasshoppers from subarctic and temperate regions

Despite the importance of developmental rate, growth rate, and size at maturity in the life history of poikliotherms, the trade-offs among these traits and selection pressures involved in the evolution of these traits are not well understood. This study compared these traits in a grasshopper, Melanoplus sanguinipes F. (Orthoptera: Acrididae), from two contrasting geographical regions, subarctic Alaska and temperate Idaho. The growing season in the interior of Alaska is about 80 d shorter than at low-elevation sites in Idaho. We hypothesized that the Alaskan grasshoppers would show more rapid growth and development than grasshoppers from Idaho, at the cost of greater sensitivity to food quality. On a diet of lettuce and wheat bran, grasshoppers from Alaska developed from egg hatch to adult more rapidly than those from Idaho at each of three different temperature regimes. Averaged over all temperature treatments, the weight of the Alaskan grasshoppers was about 5% less than that of the Idaho grasshoppers at the adult molt. Feeding and digestive efficiencies were determined for the final two instars using two meridic diets: one with a high concentration of nutrients and the other with the same formulation but diluted with cellulose. Alaskan grasshoppers again developed more rapidly, weighed less, and had faster growth rates than those from Idaho. Alaskan grasshoppers supported their more rapid growth by increasing postingestive efficiencies; that is, they had higher conversion rates of digested matter to biomass on the high-quality diet, greater assimilation of food on the low-quality diet, and greater efficiency of nitrogen assimilation or retention on both diets. There was no evidence that performance of Alaskan grasshoppers suffered any more than that of the Idaho grasshoppers on the low-quality diet.     

Interactions among morphotype,nutrition, and temperature impact fitness of an invasive fly

Invasive animals depend on finding a balanced nutritional intake to colonize, survive, and reproduce in new environments. This can be especially challenging during situations of fluctuating cold temperatures and food scarcity, but phenotypic plasticity may offer an adaptive advantage during these periods. We examined how lifespan, fecundity, pre‐oviposition periods, and body nutrient contents were affected by dietary protein and carbohydrate (P:C) ratios at variable low temperatures in two morphs (winter morphs WM and summer morphs SM) of an invasive fly, Drosophila suzukii. The experimental conditions simulated early spring after overwintering and autumn, crucial periods for survival. At lower temperatures, post‐overwintering WM lived longer on carbohydrate‐only diets and had higher fecundity on low‐protein diets, but there was no difference in lifespan or fecundity among diets for SM. As temperatures increased, low‐protein diets resulted in higher fecundity without compromising lifespan, while high‐protein diets reduced lifespan and fecundity for both WM and SM. Both SM and WM receiving high‐protein diets had lower sugar, lipid, and glycogen (but similar protein) body contents compared to flies receiving low‐protein and carbohydrate‐only diets. This suggests that flies spend energy excreting excess dietary protein, thereby affecting lifespan and fecundity. Despite having to recover from nutrient depletion after an overwintering period, WM exhibited longer lifespan and higher fecundity than SM in favorable diets and temperatures. WM exposed to favorable low‐protein diet had higher body sugar, lipid, and protein body contents than SM, which is possibly linked to better performance. Although protein is essential for oogenesis, WM and SM flies receiving low‐protein diets did not have shorter pre‐oviposition periods compared to flies on carbohydrate‐only diets. Finding adequate carbohydrate sources to compensate protein intake is essential for the successful persistence of D. suzukii WM and SM populations during suboptimal temperatures.     

Protein-leverage in mice: the geometry of macronutrient balancing and consequences for fat deposition

Objective: The Protein‐Leverage Hypothesis proposes that humans regulate their intake of macronutrients and that protein intake is prioritized over fat and carbohydrate intake, causing excess energy ingestion when diets contain low %protein. Here we test in a model animal, the mouse: (i) the extent to which intakes of protein and carbohydrate are regulated; (ii) if protein intake has priority over carbohydrates so that unbalanced foods low in %protein leads to increased energy intake; and (iii) how such variations in energy intake are converted into growth and storage. Methods and Procedures: We fed mice one of five isocaloric foods having different protein to carbohydrate composition, or a combination of two of these foods (N = 15). Nutrient intake and corresponding growth in lean body mass and lipid mass were measured. Data were analyzed using a geometric approach for analyzing intake of multiple nutrients. Results: (i) Mice fed different combinations of complementary foods regulated their intake of protein and carbohydrate toward a relatively well‐defined intake target. (ii) When mice were offered diets with fixed protein to carbohydrate ratio, they regulated the intake of protein more strongly than carbohydrate. This protein‐leverage resulted in higher energy consumption when diets had lower %protein and led to increased lipid storage in mice fed the diet containing the lowest %protein. Discussion: Although the protein‐leverage in mice was less than what has been proposed for humans, energy intakes were clearly higher on diets containing low %protein. This result indicates that tight protein regulation can be responsible for excess energy ingestion and higher fat deposition when the diet contains low %protein.     

Dietary self‐selection and rules of compromise by fifth‐instar Vanessa cardui

We examined dietary self‐selection and rules of compromise for protein (P) and digestible carbohydrate (C) intake by fifth‐instar Vanessa cardui L. (Lepidoptera: Nymphalidae: Nymphalini). We presented six fat‐free diet pairs to larvae in a choice trial to determine the ‘intake target’. In addition, we fed larvae seven fat‐free single diets differing in dietary nutrient ratio in no‐choice trials to determine the rules of compromise they exhibit when constrained to a singular, sub‐optimal dietary source. In choice trials, caterpillars regulated nutrient intake to a ratio of 1 protein to 1.09 carbohydrate (1P:1.09C), exhibiting tighter regulation of protein than of carbohydrate. Furthermore, larvae from different diet pair treatments did not differ in pupal mass or stadium duration. In no‐choice experiments, larvae reduced consumption on increasingly protein‐biased diets and increased consumption on increasingly carbohydrate‐biased diets, relative to a 1P:1C ratio diet. Differences in carbohydrate consumption were much greater between no‐choice treatments than differences in protein consumption. Dietary nutrient ratio affected pupal mass when accounting for initial larval mass. Pupal mass decreased as nutrient ratio was shifted off of 1P:1C, but to a greater extent when the ratio was skewed toward carbohydrate. Stadium duration increased as nutrient ratio diverged from 1P:1C, being more pronounced when shifted toward carbohydrate than toward protein. Regulation to near 1P:1C is consistent with results found for other Lepidoptera, and the rule of compromise exhibited by V. cardui is consistent with that expected for a generalist herbivore.     

A comparison of dietary selection behaviour in larval Locusta migratoria and Spodoptera littoralis

ABSTRACT. . Final instar nymphs of the oligophagous acridid Locusta migratoria (L.) and larvae of the polyphagous noctuid Spodoptera littoralis (Boisduval) were fed for 4, 8 or 12 h, the conditioning period, on one of four artificial diets. Of these, diet PC contained 20% protein and 10% digestible carbohydrate; another, P, contained 20% protein but with the digestible carbohydrate component replaced by cellulose; a third, C, had the protein component substituted by cellulose, and the fourth, O, had both protein and digestible carbohydrate replaced. After this conditioning period, insects were given a choice of two diets, P and C, and hence an opportunity to select for the nutrients, if any, which were lacking in their previous food. Amounts eaten and selection behaviour were then recorded in detail for a total of 9 h. This paper deals with total amounts of diet eaten during the conditioning and choice periods. Spodoptera larvae were more sensitive than the locusts to being fed a nutritionally inadequate conditioning diet, and ate only small quantities of the P, C and O diets as compared with the PC diet, irrespective of the duration of conditioning. Locusts, on the other hand, when restricted to the P diet continued to eat relatively large amounts of it throughout a 12 h conditioning period. Those nymphs fed the C diet ingested large quantities (more than of the PC diet) up until 8 h, after which intake fell. When offered a choice, both species selected for the nutrients missing from the conditioning diet, even if the conditioning period had been as short as 4 h. During the first hour of choice locusts selected the P diet if they had been previously fed C and the C diet if previously fed P. Those deprived of both nutrients increased consumption of both P and C diets. Spodoptera larvae were more sensitive to prior deprivation of digestible carbohydrate than of protein. During the first hour of choice they selected the C diet if previously fed P or O but did not choose the P diet if previously fed C. In the subsequent 8 h of choice, however, a strong selection for the P diet after previous deprivation became apparent. In the locust, the selection for nutrients missing from the conditioning diet continued for the following 8 h of choice but became masked by a tendency, shown by all nymphs, to select C over P. The functional significance and possible physiological basis of all these responses is discussed.     

Diet quality mitigates intraspecific larval competition in Drosophila suzukii

The invasive frugivore Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) utilizes a wide range of host plants and damages important fruit crops, including blueberries, cherries, blackberries, raspberries, and strawberries. Field infestations of D. suzukii often exceed one larva per berry, suggesting that intraspecific competition may frequently occur. Because dietary resources are also likely to vary across the host range of D. suzukii, we designed a laboratory assay to measure larval performance across diets of varying quality: a standard artificial diet, a fruit‐based medium, a low‐protein, and a low‐carbohydrate diet. We manipulated egg density across these diets to provide increasing levels of competition and measured larval performance by observing survival to pupation and adulthood, and development times for both life stages. Although increasing density generally negatively impacted D. suzukii performance across diets, the magnitude of these impacts varied by diet type. Drosophila suzukii performance was generally similar in fruit and standard diets, although larval development was more rapid in fruit diets at lower densities. Even at low densities (5 or 10 eggs per arena), survival was reduced and development time increased in low‐protein diets relative to standard and fruit diets. At the two highest larval densities (20 or 40 eggs per arena), survivorship was reduced in low‐carbohydrate diets as compared to standard and fruit diets. There is evidence that larvae compensated in both low‐quality diets by extending development time, which could have consequences for population dynamics. Population models for use in D. suzukii management may need to account for both host nutritional quality and relative competition to accurately predict turnover and geographic expansion.     

Cost‐Effectiveness of a Low‐Carbohydrate Diet and a Standard Diet in Severe Obesity

Objective: Low‐carbohydrate diets have become a popular alternative to standard diets for weight loss. Our aim was to compare the cost‐effectiveness of these two diets. Research Methods and Procedures: The patient population included 129 severely obese subjects (BMI = 42.9) from a randomized trial; participants had a high prevalence of diabetes or metabolic syndrome. We compared within‐trial costs, quality‐adjusted life years (QALYs), and the incremental cost‐effectiveness ratio (CER) for the two study groups. We imputed missing values for QALYs. The CER was bootstrapped to derive 95% confidence intervals and to define acceptability cut‐offs. We took a societal perspective for our analysis. Results: Total costs during the one year of the trial were $6742 ± 6675 and $6249 ± 5100 for the low‐carbohydrate and standard groups, respectively (p = 0.78). Participants experienced 0.64 ± 0.02 and 0.61 ± 0.02 QALYs during the one year of the study, respectively (p = 0.17 for difference). The point estimate of the incremental CER was $?1225/QALY (i.e., the low‐carbohydrate diet dominated the standard diet). However, in the bootstrap analysis, the wide spread of CERs caused the 95% confidence interval to be undefined. The probabilities that the low‐carbohydrate diet was acceptable, using cut‐offs of $50, 000/QALY, $100, 000/QALY, and $150, 000/QALY, were 72.4% 78.6%, and 79.8%, respectively. Discussion: The low‐carbohydrate diet was not more cost‐effective for weight loss than the standard diet in the patient population studied. Larger studies are needed to better assess the cost‐effectiveness of dietary therapies for weight loss.     

Comparison of Fat Storage between Fischer 344 and Obesity‐Resistant Lou/C Rats Fed Different Diets**

Objective: We aimed to characterize further the Lou/C (LOU) and Fischer 344 (F344) rat strains for nutritional traits to validate their use as contrasting strains for molecular genetic studies. Research Methods and Procedures: Five batches of LOU and F344 rats were used to measure caloric intake, weight gain, and body composition when fed a chow diet, a self‐selection diet (together with the study of preferences for macronutrients), hypercaloric diets, and a chow diet in a cold environment. Results: Despite a higher caloric intake when fed a chow diet, LOU rats showed a lower weight gain, final body weight, and percentage of fat tissue, together with a higher percentage of carcass weight, than F344 rats. When fed a self‐selection diet, LOU males ingested less protein and more fat than F344 males, and the reverse was observed for females. In this condition, feed efficiency was reduced in LOU but increased in F344 rats compared with the chow diet. Diet‐induced obesity was observed in F344 rats but not in LOU rats fed hypercaloric diets. In a cold environment, both LOU and F344 rats displayed an increased percentage of brown adipose tissue compared with control groups, together with a higher caloric intake. Discussion: The study shows robust nutritional differences between the LOU rat, a lean strain with a low feed efficiency and resistant to diet‐induced obesity, and the contrasting F344 rat strain. It also shows the interest in these strains for studying the genetic components of resistance to obesity.     

Effects of dietary protein and carbohydrate on life‐history traits and body protein and fat contents of the black soldier fly Hermetia illucens

We investigate how the black soldier fly Hermetia illucens L. (Diptera: Stratiomyidae) responds to dietary protein (P) and carbohydrate (C) contents and the P:C ratio in terms of both immature and adult life‐history traits, as well as effects on larval body composition. Nine chicken‐feed based diets varying in their P:C ratio are formulated. We test three protein concentrations (10%, 17% and 24%) and three carbohydrate concentrations (35%, 45% and 55%) and their combinations. All nine diets support the complete development and reproduction of this species. Survival is high on all diets. Development time, larval yield, larval crude fat and egg yield are more influenced by P and C contents than by the P:C ratio. Low contents result in a shorter development time. Larval yield is higher on diets with higher C‐contents. Pupal development is faster on a low dietary P‐content for all three C‐contents. Egg yield only increases when P‐content increases, although it also varies with the P:C ratio. Larval crude protein content is similar on all nine diets but increases when C‐content is low (10%) in P10 and P17. Larval crude fat content is high at P24‐diets irrespective of C‐content. We conclude that a high macronutrient content combined with a low P:C ratio positively affects H. illucens performance. The diet P17:C55 supports the highest larval and adult performance and results in a high larval body protein content and an intermediate crude fat content.     

Effects of diet quality on performance and nutrient regulation in an omnivorous katydid

1. Omnivores by definition eat both plants and animals. However, little is known about how diet macronutrient content affects omnivore performance, or the extent to which they can regulate macronutrient intake. We assessed these questions using the salt marsh katydid, Conocephalus spartinae Fox (Tettigoniidae). 2. In our first experiment we used artificial diets with different protein–carbohydrate ratios to assess the effects of diet quality on survival, growth, and lipid accumulation. We found that diets with a high protein–carbohydrate ratio negatively affected Conocephalus survival. Among surviving individuals growth was not significantly different across the treatments, but lipid content decreased significantly as the protein–carbohydrate ratio of diets increased. 3. In a second experiment we explored the ability of Conocephalus to regulate their protein–carbohydrate intake. Results revealed that Conocephalus did not feed randomly when presented with two nutritionally complementary foods. A detailed analysis of their protein–carbohydrate intake revealed selection for a protein‐biased diet, but a lack of tight regulate of protein–carbohydrate intake. 4. We discuss how key macronutrients can limit omnivores, and how nutritional flexibility may enable omnivores to persist in nutritionally heterogeneous environments.     

Adaptive contraction of diet breadth affects sexual maturation and specific nutrient consumption in an extreme generalist omnivore

Animals balance their intake of specific nutrients, but little is known about how they do so when foraging in an environment with toxic resources and whether toxic foods promote adaptations that affect life history traits. In German cockroach (Blattella germanica) populations, glucose aversion has evolved in response to glucose‐containing insecticidal baits. We restricted newly eclosed glucose‐averse (GA) and wild‐type (WT) female cockroaches to nutritionally defined diets varying in protein‐to‐carbohydrate (P : C) ratio (3 : 1, 1 : 1, or 1 : 3) or gave them free choice of the 3 : 1 and 1 : 3 diets, with either glucose or fructose as the sole carbohydrate source. We measured consumption of each diet over 6 days and then dissected the females to measure the length of basal oocytes in their ovaries. Our results showed significantly lower consumption by GA compared to WT cockroaches when restricted to glucose‐containing diets, but also lower fructose intake by GA compared to WT cockroaches when restricted to high fructose diets or given choice of fructose‐containing diets. Protein intake was regulated tightly regardless of carbohydrate intake, except by GA cockroaches restricted to glucose‐containing diets. Oocyte growth was completely suppressed in GA females restricted to glucose‐containing diets, but also significantly slower in GA than in WT females restricted to fructose‐containing diets. Our findings suggest that GA cockroaches have adapted to reduced diet breadth through endocrine adjustments which reduce requirements for energetic fuels. Our study illustrates how an evolutionary change in the chemosensory system may affect the evolution of other traits that govern animal life histories.     

Functional macronutritional generalism in a large omnivore,the brown bear

We combine a recently developed framework for describing dietary generalism with compositional data analysis to examine patterns of omnivory in a large widely distributed mammal. Using the brown bear (Ursus arctos) as a model species, we collected and analyzed data from the literature to estimate the proportions of macronutrients (protein, carbohydrate, and lipid) in the diets of bear populations. Across their range, bears consumed a diversity of foods that resulted in annual population diets that varied in macronutrient proportions, suggesting a wide fundamental macronutrient niche. The variance matrix of pairwise macronutrient log‐ratios indicated that the most variable macronutrient among diets was carbohydrate, while protein and lipid were more proportional or codependent (i.e., relatively more constant log‐ratios). Populations that consumed anthropogenic foods, such agricultural crops and supplementary feed (e.g., corn), had a higher geometric mean proportion of carbohydrate, and lower proportion of protein, in annual diets. Seasonally, mean diets were lower in protein and higher in carbohydrate, during autumn compared to spring. Populations with anthropogenic subsidies, however, had higher mean proportions of carbohydrate and lower protein, across seasons compared to populations with natural diets. Proportions of macronutrients similar to those selected in experiments by captive brown bears, and which optimized primarily fat mass gain, were observed among hyperphagic prehibernation autumn diets. However, the majority of these were from populations consuming anthropogenic foods, while diets of natural populations were more variable and typically higher in protein. Some anthropogenic diets were close to the proportions selected by captive bears during summer. Our results suggest that omnivory in brown bears is a functional adaptation enabling them to occupy a diverse range of habitats and tolerate variation in the nutritional composition and availability of food resources. Furthermore, we show that populations consuming human‐sourced foods have different dietary macronutrient proportions relative to populations with natural diets.     

Design and use of 16S ribosomal DNA-directed primers in competitive PCRs to enumerate proteolytic bacteria in the rumen

Competitive Polymerase Chain Reaction primers were designed for Streptococcus, B. fibrisolvens, P. bryantii, Eubacterium sp., Prevotella, and a universal primer for the eubacteria. DNA was extracted from rumen contents collected from eight dairy cows fed four diets: adequate nitrogen, adequate nitrogen plus carbohydrate, low nitrogen, and low nitrogen plus carbohydrate. B. fibrisolvens was significantly higher on the adequate nitrogen plus carbohydrate and the low nitrogen plus carbohydrate diets compared with the other diets, while P. bryantii was significantly higher on the low nitrogen plus carbohydrate diet compared with the adequate nitrogen diet. The population of Eubacterium sp. was significantly lower on both the adequate nitrogen plus carbohydrate and low nitrogen plus carbohydrate diets. Streptococcus populations were significantly lower on the low nitrogen plus carbohydrate diet compared with all three other diets, whereas there were no significant differences in populations of Prevotella or total eubacteria on any of the diets.     

Self‐Grooming Response of Meadow Voles to the Odor of Opposite‐Sex Conspecifics in Relation to the Dietary Protein Content of Both Sexes

Many animals self‐groom when they encounter the scent marks of opposite‐sex conspecifics. Self‐grooming transmits odiferous substances that contain information about the groomer’s condition, which is affected by its nutritional state. We tested the hypothesis that the amount of time that individuals self‐groom to opposite‐sex conspecifics is affected by the amount of protein in their diet and that of the scent donor. We did so by feeding meadow voles (Microtus pennsylvanicus) a diet containing 9%, 13%, or 22% dietary protein for 30 d and observing their self‐grooming behavior when they were exposed to bedding scented by an opposite‐sex conspecific (odor donor) fed one of the three diets, or fresh cotton bedding (control). The hypothesis was partially supported. We found that the protein content of the diet of male and female groomers did not affect the amount of time they self‐groomed. However, the protein content of the diet of male odor donors affected the amount of time that female voles spent self‐grooming. Female voles self‐groomed more in response to male odor donors fed a 22% protein‐content diet than to those produced by male odor donors fed either a 9% or a 13% protein‐content diet. Interestingly, the amount of time males self‐groomed was not affected by the protein content of the diet of the female odor donor. These results may, in part, be explained by the natural history of free‐living meadow voles, sex differences in costs associated with mate attraction and reproduction, and the direct or indirect benefits that females receive from males fed a diet high in protein content.     

Nutrient balance in medfly, Ceratitis capitata, larval diets affects the ability of the developing insect to incorporate lipid and protein reserves

The Mediterranean fruit fly [Ceratitis capitata Wiedemann (Diptera: Tephritidae)], or medfly, is mass produced in many facilities throughout the world to supply sterile flies for sterile insect technique programs. Production of sterile males requires large amounts of larval and adult diets. Larval diets comprise the largest economic burdens in the mass production of sterile flies, and are one of the main areas where production costs could be reduced without affecting quality and efficacy. The present study investigated the effect of manipulating diet constituents on larval development and performance. Medfly larvae were reared on diets differing in the proportions of brewer's yeast and sucrose. We studied the effect of such diets on the ability of pupating larvae to accumulate protein and lipids, and on other developmental indicators. Except for diets with a very low proportion of brewer's yeast (e.g., 4%), pupation and adult emergence rates were in general high and satisfactory. The ability of pupating larvae to accumulate lipid reserves and proteins was significantly affected by the sucrose and yeast in the diet, and by the proportion of protein to carbohydrates (P/C). In contrast to previous nutritional studies conducted with other insects, low P/C in medfly larval diets (with excess dietary carbohydrates) resulted in pupating medfly larvae having a relatively reduced load of lipids; medfly larvae protein contents in these diets were, as expected, relatively low. Similarly, high P/C ratios in the diet produced larvae with high protein and lipid contents. Differences with other insects may be due to differential post‐ingestion regulation where a high dietary carbohydrate diet reduces the lipogenic activity of the larvae, and induces a shift from lipid to glucose oxidation. Larvae reared on low P/C diets spent more time foraging in the diet than larvae maintained on a high P/C diet, suggesting a compensatory mechanism to complement nutrient intake. The results suggest that the content of brewer's yeast, the most expensive diet component, could be fine‐tuned without apparently affecting fly quality.     

Effects of dietary protein to carbohydrate balance on energy intake,fat storage,and heat production in mice

Objective:

Protein leverage plays a role in driving increased energy intakes that may promote weight gain. The influence of the protein to carbohydrate ratio (P:C) in diets of C57BL/6J mice on total energy intake, fat storage, and thermogenesis was investigated.

Design and Methods:

Male mice (9 weeks old) were provided ad libitum access to one of five isocaloric diets that differed in P:C. Food intake was recorded for 12 weeks. After 16 weeks, white adipose tissue (WAT) and brown adipose tissue (BAT) deposits were dissected, weighed, and the expression levels of key metabolic regulators were determined in BAT. In a separate cohort, body surface temperature was measured in response to 25 diets differing in protein, fat, and carbohydrate content.

Results:

Mice on low P:C diets (9:72 and 17:64) had greater total energy intake and increased WAT and BAT stores. Body surface temperature increased with total energy intake and with protein, fat, and carbohydrate, making similar contributions per kJ ingested. Expression of three key regulators of thermogenesis were downregulated in BAT in mice on the lowest P:C diet.

Conclusions:

Low‐protein diets induced sustained hyperphagia and a generalized expansion of fat stores. Increased body surface temperature on low P:C diets was consistent with diet‐induced thermogenesis (DIT) as a means to dissipate excess ingested energy on such diets, although this was not sufficient to prevent development of increased adiposity. Whether BAT was involved in DIT is not clear. Increased BAT mass on low P:C diets might suggest so, but patterns of thermogenic gene expression do not support a role for BAT in DIT, although they might reflect failure of thermogenic function with prolonged exposure to a low P:C diet.     

Change of the Gluconeogenic Capacity of Rat Kidney Cortex Slices with Dietary Components

Substituting protein for carbohydrate in diets significantly enhanced the rates of glucose formation from pyruvate, glutamate, or glycerol in rat kidney cortex slices. The tissue, however, increased slightly its gluconeogenic capacity in response to low carbohydrate, high fat diet. The rates of glucose taken up per unit weight of kidney cortex of rats fed a high carbohydrate diet was higher than those of rats fed diets high in protein or fat. Kidney weight in g per 100 g body weight (relative kidney size) of rats fed diets high in protein was significantly higher than that of rats fed diets high in carbohydrate or fat.     

Haemolymph amino acid and sugar levels in locusts fed nutritionally unbalanced diets

Aspects of pre- and post-ingestive compensation were investigated in locusts (Locusta migratoria) fed nutritionally unbalanced artificial diets containing 7% protein and 21% digestible carbohydrate (7:21) or 21% protein and 7% digestible carbohydrate (21:7). Feeding behaviour and haemolymph levels of amino acids and sugars were measured in locusts fed ad libitum on these diets. Locusts fed the high-protein diet had chronically elevated haemolymph levels of 15 out of 19 amino acids measured compared to locusts fed the low protein diet. However, haemolymph levels of lysine, alanine, aspartic acid and glutamic acid did not differ between diets, suggesting some specific regulatory mechanism for these amino acids. Haemolymph glucose and trehalose reflected levels of carbohydrate in the diets, being high in insects fed diet 7:21 relative to those given diet 21:7. These data are discussed in relation to the physiological and behavioural bases of nutritional homeostasis.Abbreviations AA amino acid(s) - PRO protein - CHO carbohydrate - PBS phosphate-buffered saline - MW molecular weight     

Effect of Dietary Carbohydrate Source on the Development of Obesity in Agouti Transgenic Mice**

Objectives: Our objective was to evaluate the effects of a qualitative change in dietary carbohydrate source on body weight and adiposity in a rodent model of diet‐induced obesity. Research Methods and Procedures: We evaluated the effects of high‐fat diets (basal) varying in carbohydrate source in aP2‐agouti transgenic mice. In the ad libitum study, animals were given free access to the basal diet or one of four test diets for 6 weeks. In two of the diets, dietary carbohydrate was derived from a single source: mung bean noodles (MUNG) or rolled oats (ROLL). The remaining diets were designed to mimic commercially available instant oatmeal with added sugar (IO‐S) or flavored instant oatmeal (IO‐F). In the energy‐restricted study, animals were given ad libitum access to the basal diet for 6 weeks. Subsequently, animals were assigned to one of six treatment groups for 6 weeks. One group was continued on the basal diet ad libitum. The remaining groups were maintained with energy restriction (70% ad libitum) on either the basal, MUNG, ROLL, IO‐S, or IO‐F diet. Results: Subcutaneous fat pad mass was significantly higher (p < 0.05) in the energy‐restricted basal and IO‐S groups compared with the energy‐restricted ROLL diet. Similarly, visceral fat pad mass was significantly lower with ROLL and MUNG diets (p < 0.05 for both) compared with basal and IO‐S diets, and the insulin:glucose ratio was reduced (by 23% to 34%, p < 0.05) in these two diets compared with all others. In ad libitum‐fed animals, liver fatty acid synthase expression was 43% to 62% lower (p < 0.05) with ROLL and MUNG diets compared with all others. Discussion: These data suggest that a qualitative change in dietary carbohydrate source modulates body weight and adiposity.