Food-restricted Animals Research Articles

Alterations in hypothalamic gene expression following Roux-en-Y gastric bypass.

ObjectiveThe role of the central nervous system in mediating metabolic effects of Roux-en-Y gastric bypass (RYGB) surgery is poorly understood. Using a rat model of RYGB, we aimed to identify changes in gene expression of key hypothalamic neuropeptides known to be involved in the regulation of energy balance.MethodsLean male Sprague-Dawley rats underwent either RYGB or sham surgery. Body weight and food intake were monitored bi-weekly for 60 days post-surgery. In situ hybridization mRNA analysis of hypothalamic AgRP, NPY, CART, POMC and MCH was applied to RYGB and sham animals and compared with ad libitum fed and food-restricted rats. Furthermore, in situ hybridization mRNA analysis of dopaminergic transmission markers (TH and DAT) was applied in the midbrain.ResultsRYGB surgery significantly reduced body weight and intake of a highly palatable diet but increased chow consumption compared with sham operated controls. In the arcuate nucleus, RYGB surgery increased mRNA levels of orexigenic AgRP and NPY, whereas no change was observed in anorexigenic CART and POMC mRNA levels. A similar pattern was seen in food-restricted versus ad libitum fed rats. In contrast to a significant increase of orexigenic MCH mRNA levels in food-restricted animals, RYGB did not change MCH expression in the lateral hypothalamus. In the VTA, RYGB surgery induced a reduction in mRNA levels of TH and DAT, whereas no changes were observed in the substantia nigra relative to sham surgery.ConclusionRYGB surgery increases the mRNA levels of hunger-associated signaling markers in the rat arcuate nucleus without concomitantly increasing downstream MCH expression in the lateral hypothalamus, suggesting that RYGB surgery puts a brake on orexigenic hypothalamic output signals. In addition, down-regulation of midbrain TH and DAT expression suggests that altered dopaminergic activity also contributes to the reduced intake of palatable food in RYGB rats.

Sex and estrogens alter the action of glucagon-like peptide-1 on reward.

BackgroundFeeding behavior is regulated through an intricate array of anorexic and orexigenic hormones acting on the central nervous system (CNS). Some of these hormones may have differential effects in males and females, effects potentially attributed to actions of gonadal steroids, especially estrogens. Central stimulation of the glucagon-like peptide-1 (GLP-1) receptors reduces feeding and food-reward behavior by acting on CNS regions important for the anorexic actions of estrogens. Thus, we propose that the action of GLP-1 on food intake and reward may differ between sexes.MethodsMale and female rats were centrally injected with the GLP-1 analog exendin-4 (Ex4) in a non-deprived or food-restricted state; reward behavior was measured in a progressive ratio operant conditioning task. Intake of chow and palatable food were also measured. To determine if sex differences in the actions of Ex4 are due to interactions with estrogens, Ex4 treatment was preceded by treatment with a nonselective estrogen receptor-α (ERα) and ERβ or ERα-selective antagonist.ResultsCentral injection of Ex4 revealed increased reward behavior suppression in females, compared to males, in the operant conditioning task. This increase was present in both non-deprived and food-restricted animals with larger differences in the fed state. Intake of chow and palatable food, after Ex4, were similar in males and females. Food reward, but not food intake, effect of Ex4 was attenuated by pretreatment with ER antagonist in both sexes, suggesting that estrogens may modulate effects of Ex4 in both sexes. Furthermore, central pretreatment with ERα-selective antagonist was sufficient to attenuate effects of Ex4 on reward.ConclusionsCollectively, these data reveal that females display much higher sensitivity to the food reward impact of central GLP-1 receptor activation. Surprisingly, they also demonstrate that central ERα signaling is necessary for the actions of GLP-1 on food-reward behavior in both sexes.

The influence of food quantity on carbon and nitrogen stable isotope values in southern African spiny mice (Acomys spinosissimus)

Stable isotope analysis is frequently applied as a tool to examine dietary patterns in animals. However, some of the underlying assumptions associated with using this approach are increasingly being questioned. We carried out a controlled diet experiment on the southern African spiny mouse (Acomys spinosissimus Peters, 1852) to test a number of aspects relating to these assumptions and also examine the hypothesis that stable isotopes, especially δ15N, can be used to provide evidence of nutritional stress. We compared the δ13C and δ15N values of livers and blood from animals that were fed ad libitum with animals undergoing a 10% reduction in food supply. Food-restricted animals showed no significant difference in δ15N; however, δ13C values of both liver and blood were depleted. Restricted animals also had a significantly lower C:N ratio. We examined the role of lipids and found following lipid extraction that both livers and lipids still showed the same separation in carbon values. Tissue–diet discrimination values were also calculated and found to be higher for both Δ13C and Δ15N compared with other mice species. Empirical values for discrimination rates were then compared with values calculated using an alternative method based on employing generic values and were found to be dissimilar, suggesting the use of generic values are not always appropriate. Our results highlight the need for greater understanding of the assumptions associated with using stable isotope analysis to examine diet and we suggest that studying a single species under captive conditions presents an ideal method to begin to test these hypotheses.

Body mass affects seasonal variation in sickness intensity in a seasonally breeding rodent.

Species that display seasonal variation in sickness intensity show the most intense response in the season during which they have the highest body mass, suggesting that sickness intensity may be limited by an animal's energy stores. Siberian hamsters (Phodopus sungorus) display lower body masses and less intense sickness when housed in short, winter-like days as opposed to long, summer-like days. To determine whether reduced sickness intensity displayed by short-day hamsters is a product of seasonal changes in body mass, we food restricted long-day hamsters so that they exhibited body mass loss that mimicked the natural photoperiod-induced loss of body mass in short-day hamsters. We then experimentally induced sickness with lipopolysaccharide (LPS) and compared sickness responses among long-day food-restricted and long- and short-day ad libitum fed groups, predicting that long-day food-restricted hamsters would show sickness responses comparable to those of short-day ad libitum fed hamsters and attenuated in comparison to long-day ad libitum fed hamsters. We found that long-day food-restricted hamsters showed attenuated LPS-induced anorexia, loss of body mass and hypothermia compared with long-day ad libitum fed animals; however, anorexia remained elevated in long-day food-restricted animals compared with short-day ad libitum fed animals. Additionally, LPS-induced anhedonia and decreases in nest building were not influenced by body mass. Results of hormone assays suggest that cortisol levels could play a role in the attenuation of sickness in long-day food-restricted hamsters, indicating that future research should target the roles of glucocorticoids and natural variation in energy stores in seasonal sickness variation.

Behavioural Effects of Short-term Total Food Restriction in Rats

Abstract Reducing food intake can decrease anxiety indices in rats. Th e aim of this study was to evaluate the influence of short-term (48 hours) total food restriction on the behavioural characteristics, the motor coordination and balance, of rats. Th ree-month-old male Wistar albino rats (n=20) weighing 350-400 g were divided into a control group (food and water intake ad libitum) and an experimental group (total food restriction 48 hours before testing). Behavioural studies were performed using the open field, elevated plus maze, Barnes maze, beam walking, evoked beam walking and linear locomotor tests. Th e total distance moved, the velocity, the movement and the frequency in the centre zone of the open field were significantly higher in the treated group. Th e cumulative duration in the centre zone of the open field did not significantly increase in the treated group. Th e number of entries into the open arms, the total time spent in the open arms and the total distance moved in the elevated plus maze significantly increased with no change in the velocity in the food-restricted animals. Th e 48 hours of total food restriction did not affect the Barnes maze test parameters or the parameters of the linear locomotor test. Th e velocity recorded during the beam walking test was not affected by the food restriction, but the velocity recorded during the evoked beam walking test significantly decreased in the treated group. In summary, short-term total food restriction did not produce significant changes in the physical performance of rats but did result in anxiolytic- like behaviour accompanied by food-seeking behaviour due to enhanced motivation to forage for food.

A novel open-source drug-delivery system that allows for first-of-kind simulation of nonadherence to pharmacological interventions in animal disease models.

Nonadherence to a physician-prescribed therapeutic intervention is a costly, dangerous, and sometimes fatal concern in healthcare. To date, the study of nonadherence has been constrained to clinical studies. The novel approach described herein allows for the preclinical study of nonadherence in etiologically relevant disease animal model systems. The method herein describes a novel computer-automated pellet delivery system which allows for the study of nonadherence in animals. This system described herein allows for tight experimenter control of treatment using a drug-in-food protocol. Food-restricted animals receive either medicated or unmedicated pellets, designed to mimic either "taking" or "missing" a drug. The system described permits the distribution of medicated or unmedicated food pellets on an experimenter-defined feeding schedule. The flexibility of this system permits the delivery of drug according to the known pharmacokinetics of investigational drugs. Current clinical adherence research relies on medication-event monitoring system (MEMS) tracking caps, which allows clinicians to directly monitor patient adherence. However, correlating the effects of nonadherence to efficacy still relies on the accuracy of patient journals. This system allows for the design of studies to address the impact of nonadherence in an etiologically relevant animal model. Given methodological and ethical concerns of designing clinical studies of nonadherence, animal studies are critical to better understand medication adherence. While the system described was designed to measure the impact of nonadherence on seizure control, it is clear that the utility of this system extends beyond epilepsy to include other disease states.

86. The relation between body weight, brain inflammation, cognitive and emotional changes in response to an immune challenge

Obesity is clearly a risk factor for increased basal inflammation and increased inflammatory responses to immune challenge. However, even weight variation within the normal range or in food-restricted animals is correlated with the immune response to a pathogen challenge and changes in behavior. We discovered that mice’s adverse responses to mold exposure were strongly correlated with body weight. In fact, small variations in body weight were better predictors of inflammation and/or cognitive effects than spore dose. Male C57Bl/6 mice were randomly assigned to treatment groups according to a stratified block design controlling for initial weight. Mice were nasally instilled with (1) intact Stachybotrys spores, (2) extracted spores that had their toxins removed and proteins denatured, or (3) saline vehicle three times per week. Their behavior was tested after three weeks of treatment, and the animals sacrificed and hippocampal tissue analyzed after six weeks. Weight did not differ across groups at any point in the experiment. However, the more the animals weighed, the higher the numbers of amoeboid microglia in the hippocampus, the greater the memory deficits on a contextual fear task, the higher the anxiety as measured on the elevated plus maze and the more fearful the animals were of the auditory cue that had been paired with one mild footshock. Clearly, weight within the normal range is a crucial variable in inflammatory responses leading to cognitive changes.

Behavioural effects of short-term total food restriction in rats

Reducing food intake can decrease anxiety indices in rats. Th e aim of this study was to evaluate the influence of short-term (48 hours) total food restriction on the behavioural characteristics, the motor coordination and balance, of rats. Th ree-month-old male Wistar albino rats (n=20) weighing 350-400 g were divided into a control group (food and water intake ad libitum) and an experimental group (total food restriction 48 hours before testing). Behavioural studies were performed using the open field, elevated plus maze, Barnes maze, beam walking, evoked beam walking and linear locomotor tests. Th e total distance moved, the velocity, the movement and the frequency in the centre zone of the open field were significantly higher in the treated group. Th e cumulative duration in the centre zone of the open field did not significantly increase in the treated group. Th e number of entries into the open arms, the total time spent in the open arms and the total distance moved in the elevated plus maze significantly increased with no change in the velocity in the food-restricted animals. Th e 48 hours of total food restriction did not affect the Barnes maze test parameters or the parameters of

Sustained Liver Glucose Release in Response to Adrenaline Can Improve Hypoglycaemic Episodes in Rats under Food Restriction Subjected to Acute Exercise

Background. As the liver is important for blood glucose regulation, this study aimed at relating liver glucose release stimulated by glucagon and adrenaline to in vivo episodes of hypoglycaemia. Methods. The blood glucose profile during an episode of insulin-induced hypoglycaemia in exercised and nonexercised male Wistar control (GC) and food-restricted (GR, 50%) rats and liver glucose release stimulated by glucagon and adrenaline were investigated. Results. In the GR, the hypoglycaemic episodes showed severe decreases in blood glucose, persistent hypoglycaemia, and less complete glycaemic recovery. An exercise session prior to the episode of hypoglycaemia raised the basal blood glucose, reduced the magnitude of the hypoglycaemia, and improved the recovery of blood glucose. In fed animals of both groups, liver glucose release was activated by glucagon and adrenaline. In fasted GR rats, liver glycogenolysis activated by glucagon was impaired, despite a significant basal glycogenolysis, while an adrenaline-stimulated liver glucose release was recorded. Conclusions. The lack of liver response to glucagon in the GR rats could be partially responsible for the more severe episodes of hypoglycaemia observed in vivo in nonexercised animals. The preserved liver response to adrenaline can partially account for the less severe hypoglycaemia in the food-restricted animals after acute exercise.

Conditioned place preference or aversion as animal welfare assessment tools: Limitations in their application

Conditioned place preference (CPP) or aversion (CPA) methods are potentially useful tools in animal welfare assessment because they permit measurement of the reinforcing properties of a stimulus in the absence of the stimulus itself. We used CPP/CPA techniques in a series of experiments to assess the preference of food restricted broiler breeders for increased food quantities or avoidance of aversive stimuli. In all experiments, 6–10 week old Ross308 pairs of broiler breeders were housed in pens divided in half. Pen sides were visually differentiated and birds were trained with different stimuli on each pen side, correcting for possible side biases, either different food amounts for CPP or aversive stimuli on one pen side and none, or ‘neutral’, on the other, for CPA. To test if a preference for a pen side had been formed, the pen divider was removed when no stimulus was present and the amount of time birds spent on each pen side was recorded. Each experiment had a factorial treatment structure (n=10 replicate pens per treatment combination) and the proportions of time spent by birds on the ‘positive’ pen side (i.e. increased food amount for CPP or ‘neutral’ for CPA) were analysed. In experiment 1 on CPP (180 birds forming 90 pairs), three different training regimes in combination with three different testing methods were trialled: whilst during training of all birds, on one pen side the birds received the commercially recommended, restricted amount of food (R) and on the other pen side they received twice that amount (2R) (no food was present during testing). In experiment 2 (110 birds forming 40 pairs and 10 individually housed) and 3 (80 birds forming 40 pairs), further refinements were made to the experimental methods and birds were allocated to CPP treatments with food amounts 2R or 3R (vs. R) or to CPA treatments, ‘social isolation’ or ‘unpredictable wind’. Overall, there was no evidence of aversion at testing to the pen sides with aversive stimuli during training and little evidence of preference at testing for the pen sides with increased food amounts during training. Furthermore, where statistical significance was achieved for CPP the preferences shown were very small. The most consistent result was a strong preference for the pen side birds were not previously housed on immediately before each test (P<0.001 in all experiments). It appeared that birds were motivated to explore a location where they had not just been housed in an attempt to find food and this motivation seemed to overshadow other effects. This series of experiments demonstrates some limitations of CPP/CPA techniques for welfare assessment and the learning problems experienced by chronically food restricted animals.

Ghrelin-Induced Orexigenic Effect in Rats Depends on the Metabolic Status and Is Counteracted by Peripheral CB1 Receptor Antagonism

Ghrelin is an endogenous regulator of energy homeostasis synthesized by the stomach to stimulate appetite and positive energy balance. Similarly, the endocannabinoid system is part of our internal machinery controlling food intake and energy expenditure. Both peripheral and central mechanisms regulate CB1-mediated control of food intake and a functional relationship between hypothalamic ghrelin and cannabinoid CB1 receptor has been proposed. First of all, we investigated brain ghrelin actions on food intake in rats with different metabolic status (negative or equilibrate energy balance). Secondly, we tested a sub-anxiogenic ultra-low dose of the CB1 antagonist SR141716A (Rimonabant) and the peripheral-acting CB1 antagonist LH-21 on ghrelin orexigenic actions. We found that: 1) central administration of ghrelin promotes food intake in free feeding animals but not in 24 h food-deprived or chronically food-restricted animals; 2) an ultra-low dose of SR141716A (a subthreshold dose 75 folds lower than the EC50 for induction of anxiety) completely counteracts the orexigenic actions of central ghrelin in free feeding animals; 3) the peripheral-restricted CB1 antagonist LH-21 blocks ghrelin-induced hyperphagia in free feeding animals. Our study highlights the importance of the animaĺs metabolic status for the effectiveness of ghrelin in promoting feeding, and suggests that the peripheral endocannabinoid system may interact with ghrelińs signal in the control of food intake under equilibrate energy balance conditions.

Effect of food restriction on cocaine locomotor sensitization in Sprague–Dawley rats

The interaction between repeated cocaine exposure and food restriction on sensitization to the stimulatory effects of cocaine has not been characterized. To compare cocaine sensitization in rats free fed and food restricted, and begin to explore the role of the stress-responsive dynorphin/kappa opioid system. Male rats were maintained for 10 days on two feeding conditions: free fed or food restricted (85 % of free fed weight). Test 1 of locomotor reactivity to cocaine (3, 9, or 15 mg/kg, IP) was followed by a sensitizing regimen of cocaine exposure (0 or 30 mg/kg/day × 5 days, IP), by a 10-day drug-free period, and by Test 2 of reactivity to the same cocaine dose. In a second experiment, rats received an injection of norbinaltorphimine (nor-BNI; 0, 5 or 20 mg/kg, SC) 10 days prior to each locomotion test, and plasma corticosterone (CORT) was assessed after Test 2. On Test 1, it was found that food restriction enhanced locomotor responses to all doses of cocaine. On Test 2, it was found that free fed and food restricted animals displayed similar sensitized responses to cocaine. This, however, was not observed in nor-BNI-treated rats. Furthermore, 20 mg/kg nor-BNI reduced both the locomotor response to cocaine on Test 2 and the effect of cocaine and food restriction on CORT plasma levels. These results indicate that the interaction between cocaine sensitization and food restriction is not synergistic, and that it involves activation of kappa-opioid receptors.

Different Levels of Food Restriction Reveal Genotype-Specific Differences in Learning a Visual Discrimination Task

In behavioural experiments, motivation to learn can be achieved using food rewards as positive reinforcement in food-restricted animals. Previous studies reduce animal weights to 80–90% of free-feeding body weight as the criterion for food restriction. However, effects of different degrees of food restriction on task performance have not been assessed. We compared learning task performance in mice food-restricted to 80 or 90% body weight (BW). We used adult wildtype (WT; C57Bl/6j) and knockout (ephrin-A2−/−) mice, previously shown to have a reverse learning deficit. Mice were trained in a two-choice visual discrimination task with food reward as positive reinforcement. When mice reached criterion for one visual stimulus (80% correct in three consecutive 10 trial sets) they began the reverse learning phase, where the rewarded stimulus was switched to the previously incorrect stimulus. For the initial learning and reverse phase of the task, mice at 90%BW took almost twice as many trials to reach criterion as mice at 80%BW. Furthermore, WT 80 and 90%BW groups significantly differed in percentage correct responses and learning strategy in the reverse learning phase, whereas no differences between weight restriction groups were observed in ephrin-A2−/− mice. Most importantly, genotype-specific differences in reverse learning strategy were only detected in the 80%BW groups. Our results indicate that increased food restriction not only results in better performance and a shorter training period, but may also be necessary for revealing behavioural differences between experimental groups. This has important ethical and animal welfare implications when deciding extent of diet restriction in behavioural studies.

Time to pay attention: attentional performance time-stamped prefrontal cholinergic activation, diurnality, and performance.

Although the impairments in cognitive performance that result from shifting or disrupting daily rhythms have been demonstrated, the neuronal mechanisms that optimize fixed-time daily performance are poorly understood. We previously demonstrated that daily practice of a sustained attention task (SAT) evokes a diurnal activity pattern in rats. Here, we report that SAT practice at a fixed time produced practice time-stamped increases in prefrontal cholinergic neurotransmission that persisted after SAT practice was terminated and in a different environment. SAT time-stamped cholinergic activation occurred regardless of whether the SAT was practiced during the light or dark phase or in constant-light conditions. In contrast, prior daily practice of an operant schedule of reinforcement, albeit generating more rewards and lever presses per session than the SAT, neither activated the cholinergic system nor affected the animals' nocturnal activity pattern. Likewise, food-restricted animals exhibited strong food anticipatory activity (FAA) and attenuated activity during the dark phase but FAA was not associated with increases in prefrontal cholinergic activity. Removal of cholinergic neurons impaired SAT performance and facilitated the reemergence of nocturnality. Shifting SAT practice away from a fixed time resulted in significantly lower performance. In conclusion, these experiments demonstrated that fixed-time, daily practice of a task assessing attention generates a precisely practice time-stamped activation of the cortical cholinergic input system. Time-stamped cholinergic activation benefits fixed-time performance and, if practiced during the light phase, contributes to a diurnal activity pattern.

Food-Restricted and Dehydrated-Induced Anorexic Rats Present Differential TRH Expression in Anterior and Caudal PVN. Role of Type 2 Deiodinase and Pyroglutamyl Aminopeptidase II

TRH synthesized in hypothalamic paraventricular nucleus (PVN) regulates thyroid axis function and is also implicated in anorexigenic effects. Under energy deficit, animals present decreased PVN TRH expression and release, low TSH levels, and increased appetite. Dehydration-induced anorexia (DIA) model allows insight into underlying mechanisms of feeding regulation. Animals drinking a 2.5% NaCl solution for 7 d present body weight reduction; despite their negative energy balance, they avoid food and have increased PVN TRH expression and TSH serum levels. These findings support an inhibiting role of PVN TRH in feeding control. We compared TRH expression by in situ hybridization in PVN subdivisions of 7-d dehydrated male rats to those of a pair-fed group (forced food-restricted) with similar metabolic changes than DIA, but motivated to eat, and to controls. We measured peripheral deiodinase activities, and expression and activity of medial basal hypothalamic type 2 deiodinase and pyroglutamyl-aminopeptidase II, to understand their regulating role in PVN TRH changes between food restriction and anorexia. TRH mRNA levels increased in anterior (aPVN) and medial-caudal subdivisions in DIA rats, whereas it decreased in medial PVN in both experimental groups. We confirmed the nonhypophysiotropic nature of aPVN TRHergic cells by injecting ip fluorogold tracer. Findings support a subspecialization of TRHergic hypophysiotrophic cells that responded differently between anorexic and food-restricted animals; also, that aPVN TRH participates in food intake regulation. Increased type 2 deiodinase activity seemed responsible for low medial PVN TRH synthesis, whereas increased medial basal hypothalamic pyroglutamyl-aminopeptidase II activity in DIA rats might counteract their high TRH release.

Influence of food restriction on lipid profile and spontaneous glucose levels in male rats subjected to paradoxical sleep deprivation

OBJECTIVES:The purpose of this study was to determine the paired consequences of food restriction and paradoxical sleep deprivation on lipid profile and spontaneous glucose levels in male rats.METHOD:Food restriction began at weaning, with 6 g of food being provided per day, which was subsequently increased by 1 g per week until reaching 15 g per day by the eighth week. At adulthood, both rats subjected to food restriction and those fed ad libitum were exposed to paradoxical sleep deprivation for 96 h or were maintained in their home-cage groups.RESULTS:Animals subjected to food restriction exhibited a significant increase in high-density lipoprotein levels compared to animals that were given free access to food. After the paradoxical sleep deprivation period, the food-restricted animals demonstrated reduced concentrations of high-density lipoprotein relative to their respective controls, although the values for the food-restricted animals after sleep deprivation were still higher than those for the ad libitum group. The concentration of low-density lipoproteins was significantly increased in sleep-deprived animals fed the ad libitum diet. The levels of triglycerides, very low-density lipoproteins, and glucose in food-restricted animals were each decreased compared to both ad libitum groups.CONCLUSION:These results may help to illustrate the mechanisms underlying the relationship between sleep curtailment and metabolism and may suggest that, regardless of sleep deprivation, dietary restriction can minimize alterations in parameters related to cardiovascular risk.

Immunomodulatory actions of central ghrelin in diet-induced energy imbalance

We investigated the effects of centrally administered orexigenic hormone ghrelin on energy imbalance-induced inflammation. Rats were subjected for four weeks to three different dietary regimes: normal (standard food), high-fat (standard food with 30% lard) or food-restricted (70%, 50%, 40% and 40% of the expected food intake in 1st, 2nd, 3rd and 4th week, respectively). Compared to normal-weight controls, starved, but not obese rats had significantly higher levels of proinflammatory cytokines (TNF, IL-1β, IFN-γ) in the blood. When compared to normally fed animals, the hearts of starved and obese animals expressed higher levels of mRNAs encoding proinflammatory mediators (TNF, IL-1β, IL-6, IFN-γ, IL-17, IL-12, iNOS), while mRNA levels of the anti-inflammatory TGF-β remained unchanged. Intracerebroventricular (ICV) injection of ghrelin (1 μg/day) for five consecutive days significantly reduced TNF, IL-1β and IFN-γ levels in the blood of starved rats, as well as TNF, IL-17 and IL-12p40 mRNA expression in the hearts of obese rats. Conversely, ICV ghrelin increased the levels of IFN-γ, IL-17, IL-12p35 and IL-12p40 mRNA in the heart tissue of food-restricted animals. This was associated with an increase of immunosuppressive ACTH/corticosterone production in starved animals and a decrease of the immunostimulatory adipokine leptin both in food-restricted and high-fat groups. Ghrelin activated the energy sensor AMP-activated protein kinase (AMPK) in the hypothalamus and inhibited extracellular signal-regulated kinase (ERK) in the hearts of obese, but not starved rats. Therefore, central ghrelin may play a complex role in energy imbalance-induced inflammation by modulating HPA axis, leptin and AMPK/ERK signaling pathways.

Characterizing an Animal Model of Anorexia Nervosa

Anorexia Nervosa is a condition of severe under-nutrition characterized by alterations in multiple neuroendocrine axes. PURPOSE: To investigate the temporal changes in body composition and neuroendocrine hormones in food restricted rats, with and without access to running wheels, over a four week period. METHODS: Sixteen, 12 wk old, female Wistar rats were randomly divided into four groups: Control (C), Control/Wheel-Running (C/WR), Starved (S), and Starved/Wheel-Running (SWR). C animals were fed ad libitum, while S were food restricted with the goal of achieving 75% of body mass within the first two weeks with a maintenance phase for the final two weeks. Wheel running activity and food intake were measured constantly through-out the study, and IGF-1, leptin (ELISA) and body composition (DXA, GE Lunar Prodigy) were measured at baseline (B) and once a week ending at 4 weeks (T4). RESULTS: SWR animals demonstrated a rapid loss of body fat (BF) (B = 43.4±5.3g, T4 = 6.6±5.0g) tracked by significant decreases in both leptin (B = 12.5±1.48ng/mL, T4 = 1.8±0.12ng/mL) and IGF-1 (B = 184±13.2ng/mL, T4 = 44±5.8ng/mL). S animals demonstrated similar reductions in BF (B = 37.8g±3.8, T4 = 5.9g±2.4), leptin (B = 7.5±1.3ng/mL, T4 = 2.0±0.3ng/mL) and IGF-1 (B = 196±20.3ng/mL, T4 = 67±7.9ng/mL). C and CWR animals grew to roughly 110%-115% of their original body mass over the study and demonstrated similar increases in IGF-1 (C: B = 181.5±22.9ng/mL, T4 = 244±14.4ng/mL; CWR: B = 180±13.2ng/mL, T4 = 246±21.6ng/mL). However, despite an increase in body mass, wheel running resulted in a reduction in BF (CWR: B = 42.4±6.6g, T4 = 33.3±3.9g) while C animals gained BF (B = 38.2±9.83g, T4 = 46.9±10.1g). In both cases, leptin changed in parallel with BF (CWR: B = 16.4±1.6ng/mL±, T4 = 10.3±0.9ng/mL; C: B = 5.37±0.3ng/mL, T4 = 14.3±3.2ng/mL. CONCLUSION: These data demonstrate that changes in leptin occur rapidly upon initiation of food restriction tracking losses in BF, while adaptations in IGF-1 parallel changes in lean tissue. Wheel running did not prohibit weight gain in ad lib fed animals and resulted in modest reductions in body fat suggesting that investigation of a refeeding program for the food restricted animals that includes exercise is warranted and might not be counter-productive as previously thought.

Hormonal, hypothalamic and striatal responses to reduced body weight gain are attenuated in anorectic rats bearing small tumors

Lack of compensatory or even reduced food intake is frequently observed in weight-losing cancer patients and contributes to increased morbidity and mortality. Our previous work has shown increased transcription factor expression in the hypothalamus and ventral striatum of anorectic rats bearing small tumors. mRNA expression of molecules known to be involved in pathways regulating appetite in these structures was therefore assessed in this study. Given that pain, pro-inflammatory cytokines and metabolic hormones can modify food intake, spinal cord cellular activation patterns and plasma concentrations of cytokines and hormones were also studied. Morris hepatoma 7777 cells injected subcutaneously in Buffalo rats provoked a 10% lower body weight and 15% reduction in food intake compared to free-feeding tumor-free animals 4weeks later when the tumor represented 1–2% of body mass. No differences in spinal cord activation patterns or plasma concentration of pro-inflammatory cytokines were observed between groups. However, the changes in plasma ghrelin and leptin concentrations found in food-restricted weight-matched rats in comparison to ad libitum-fed animals did not occur in anorectic tumor-bearing animals. Real-time PCR showed that tumor-bearing rats did not display the increase in hypothalamic agouti-related peptide mRNA observed in food-restricted weight-matched animals. In addition, microarray analysis and real-time PCR revealed increased ventral striatal prostaglandin D synthase expression in food-restricted animals compared to anorectic tumor-bearing rats. These findings indicate that blunted hypothalamic AgRP mRNA expression, probably as a consequence of relatively high leptin and low ghrelin concentrations, and reduced ventral striatal prostaglandin D synthesis play a role in maintaining cancer-associated anorexia.

Changes of behavioral parameters during long-term food restriction in middle-aged Wistar rats

Food restriction (FR) has a beneficial effect on aging process and exerts a significant effect on the responses of rodents to standard behavioral tasks. The aim of this study was to assess the cumulative influence of FR on the behavioral and biochemical parameters in Wistar rats. Six-month-old rats were subjected to restrictive feeding (50% of the daily food intake, every-other-day feeding regimen) for one month or for six months until ages of 7 and 12 months, respectively. We examined the habituation of exploratory movement, amphetamine (AMPH)-induced motor activity, as well as changes in serum corticosterone (CORT) and glucose levels. The results obtained from FR animals were compared with ad libitum (AL)-fed age-matched control rats. Habituation of motor activity was only affected by six months of restrictive feeding. The sensitization of the motor response to AMPH that was observed in animals exposed to FR for one month was not observed in animals that were exposed to the same feeding regimen for six months. Serum CORT was increased and serum glucose was decreased in both FR groups. These results clearly show that despite the similarity of the biochemical changes that were induced by one and six months of FR, the nature of the changes in motor activities in these two groups of animals during habituation and after AMPH treatment was different. Our findings indicate that long-term FR has complex behavioral consequences that need to be carefully evaluated with respect to animal age, duration of FR and severity of the diet.