Restriction In Rats Research Articles

Maternal food restriction in rats of the F0 generation increases retroperitoneal fat, the number and size of adipocytes and induces periventricular astrogliosis in female F1 and male F2 generations.

The present study investigated whether male offspring (F2 generation) from female rats (F1 generation) whose mothers (F0 generation) were food restricted during gestation inherit a phenotypic transgenerational tendency towards being overweight and obese in the juvenile period, in the absence of food restriction in the F1/F2 generations. Dams of the F0 generation were 40% food restricted during pregnancy. Bodyweight, the number and size of larger and small hypodermal adipocytes (HAs), total retroperitoneal fat (RPF) weight and the expression of glial fibrillary acidic protein (GFAP) in periventricular hypothalamic astrocytes (PHAs), as determined by immunohistochemistry, were evaluated in both generations. In the female F1 generation, there was low bodyweight gain only during the juvenile period (30-65 days of age), a decrease in the size of small adipocytes, an increase in the number of small adipocytes, an increase in RPF weight and an increase in GFAP expression in PHAs at 90-95 days of age. In males of the F2 generation at 50 days of age, there was increased bodyweight and RPF weight, and a small number of adipocytes and GFAP expression in PHAs. These data indicate that the phenotypic transgenerational tendency towards being overweight and obese was observed in females (F1) from mothers (F0) that were prenatally food restricted was transmitted to their male offspring.

Effect of L-carnitine and Hoodia gordonii Supplementation on Metabolic Markers and Physical Performance under Short Term Calorie Restriction in Rats

<p>Calorie restriction can occur as a consequence of food shortage due to natural calamities, war like situations or voluntarily for health benefits. This state of negative energy balance leads to decrease in performance and increase in feeling of hunger. A normal individual can sustain himself on stored energy in form of body fat for a period of time. It was hypothesised that use of an appetite suppressant like Hoodia gordonii along with L-carnintine, which helps in fat oxidation can be used as strategy for coping adverse situation without compromising physical performance. The aim of the study was to evaluate the combined effect of H. gordonii and L-carnitine supplementation on metabolic changes and appetite regulatory peptides during calorie restriction. Male albino rats were divided into two groups (n=12 in each) i.e. control (without treatment) and treated (H. gordonii organic solvent extract and L-carnitine, orally for 5 days at a dose of 100 mg/kg under 25 per cent calorie restriction). Biochemical variables including regulatory peptides were estimated along with physical efficiency tests. Significant changes in ghrelin, leptin, corticosterone and thyroid hormones were observed in comparison to control. While blood glucose, AMP kinase decreased significantly in the treated group, an increase in CPT-1 activity was observed compared with controls. It is concluded that approach could be practically suitable and effective in emergency situations of combat or food shortage.</p><p><strong>Defence Science Journal, Vol. 66, No. 1, January 2016, pp. 11-18, DOI: http://dx.doi.org/10.14429/dsj.66.9178</strong></p>

Nuclear Magnetic Resonance-Based Blood Metabolic Profiles of Rats Exposed to Short-Term Caloric Restriction

Caloric restriction increases the life-span of a number of organisms. The relationship between the increase in life-span and the extent of caloric restriction, however, varies among species. The underlying mechanisms are yet unknown, but appear to be related to changes in metabolism. In order to investigate the metabolic response of caloric restriction of rats, here is presented the first nuclear magnetic resonance (NMR) spectroscopy-based study of how blood metabolite profiles are influenced by graded levels of caloric restriction. The study involved three groups of obese rats exposed to 0, 20, and 40 percent caloric restriction for five days. Blood serum from each individual was analyzed by 1H NMR and the resulting spectra were subjected to multivariate analysis by unsupervised principal component analysis and supervised orthogonal-partial least square discriminant analysis. The analyses revealed that a response to caloric restriction was present at 20 percent caloric restriction. The metabolites that distinguished the profiles at 20 percent restriction deviated from those at 40 percent restriction. The changes induced by caloric restriction were most clearly observed as an increased level of 3-hydroxybutyrate, and decreased levels of lipids and pyruvate. The metabolic responses of rats exposed to caloric restriction are in good agreement with a switch in metabolism from anabolic pathways towards fatty acid catabolism and gluconeogenesis, which is consistent with previous observations for mice.

Maternal Protein Restriction Increases Respiratory and Sympathetic Activities and Sensitizes Peripheral Chemoreflex in Male Rat Offspring1–3

Background: Maternal protein restriction in rats increases the risk of adult offspring arterial hypertension through unknown mechanisms.Objectives: The aims of the study were to evaluate the effects of a low-protein (LP) diet during pregnancy and lactation on baseline sympathetic and respiratory activities and peripheral chemoreflex sensitivity in the rat offspring.Methods: Wistar rat dams were fed a control [normal-protein (NP); 17% protein] or an LP (8% protein) diet during pregnancy and lactation, and their male offspring were studied at 30 d of age. Direct measurements of baseline arterial blood pressure (ABP), heart rate (HR), and respiratory frequency (Rf) as well as peripheral chemoreflex activation (potassium cyanide: 0.04%) were recorded in pups while they were awake. In addition, recordings of the phrenic nerve (PN) and thoracic sympathetic nerve (tSN) activities were obtained from the in situ preparations. Hypoxia-inducible factor 1α (HIF-1α) expression was also evaluated in carotid bifurcation through a Western blotting assay.Results: At 30 d of age, unanesthetized LP rats exhibited enhanced resting Rf (P = 0.001) and similar ABP and HR compared with the NP rats. Despite their similar baseline ABP values, LP rats exhibited augmented low-frequency variability (∼91%;P = 0.01). In addition, the unanesthetized LP rats showed enhanced pressor (P = 0.01) and tachypnoeic (P = 0.03) responses to peripheral chemoreflex activation. The LP rats displayed elevated baseline tSN activity (∼86%;P = 0.02) and PN burst frequency (45%;P = 0.01) and amplitude (53%;P = 0.001) as well as augmented sympathetic (P = 0.01) and phrenic (P = 0.04) excitatory responses to peripheral chemoreflex activation compared with the NP group. Furthermore, LP rats showed an increase of ∼100% in HIF-1α protein density in carotid bifurcation compared with NP rats.Conclusion: Sympathetic-respiratory overactivity and amplified peripheral chemoreceptor responses, potentially through HIF-1α–dependent mechanisms, precede the onset of hypertension in juvenile rats exposed to protein undernutrition during gestation and lactation.

Psychomotor Vigilance Task Performance During and Following Chronic Sleep Restriction in Rats

Chronic sleep restriction (CSR) impairs sustained attention in humans, as commonly assessed with the psychomotor vigilance task (PVT). To further investigate the mechanisms underlying performance deficits during CSR, we examined the effect of CSR on performance on a rat version of PVT (rPVT). Adult male rats were trained on a rPVT that required them to press a bar when they detected irregularly presented, brief light stimuli, and were then tested during CSR. CSR consisted of 100 or 148 h of continuous cycles of 3-h sleep deprivation (using slowly rotating wheels) alternating with a 1-h sleep opportunity (3/1 protocol). After 28 h of CSR, the latency of correct responses and the percentages of lapses and omissions increased, whereas the percentage of correct responses decreased. Over 52-148 h of CSR, all performance measures showed partial or nearly complete recovery, and were at baseline levels on the first or second day after CSR. There were large interindividual differences in the magnitude of performance impairment during CSR, suggesting differential vulnerability to the effects of sleep loss. Wheel-running controls showed no changes in performance. A 28-h period of the 3/1 chronic sleep restriction (CSR) protocol disrupted performance on a sustained attention task in rats, as sleep deprivation does in humans. Performance improved after longer periods of CSR, suggesting allostatic adaptation, contrary to some reports of progressive deterioration in psychomotor vigilance task performance during CSR in humans. However, as observed in humans, there were individual differences among rats in the vulnerability of their attention performance to CSR.

Impaired alveolarization and intra-uterine growth restriction in rats: a postnatal genome-wide analysis.

Intra-uterine growth restriction (IUGR) dramatically increases the risk of bronchopulmonary dysplasia in preterm babies, a disease characterized by arrested alveolarization and abnormal microvascular angiogenesis. We have previously described a rodent low protein diet (LPD) model of IUGR inducing impaired alveolarization, but failed to demonstrate any modification of the classical factors involved in lung development. We performed a genome-wide microarray analysis in 120 rat pups with LPD-induced IUGR and their controls, at three key time points of the alveolarization process: postnatal day 4 (P4): start of alveolarization; P10: peak of the alveolarization process and P21: end of the alveolarization process. Results were analysed using Arraymining, DAVID and KEGG software and validated by qRT-PCR and western blots. Considering a cut-off of 2:1 as significant, 67 transcripts at P4, 102 transcripts at P10 and 451 transcripts at P21 were up-regulated, and 89 transcripts at P4, 25 transcripts at P10 and 585 transcripts at P21 were down-regulated. Automatic functional classification identified three main modified pathways, 'cell adhesion molecules', 'cardiac muscle contraction' and 'peroxisome proliferator-activated receptor' (PPAR). Protein analysis confirmed involvement of the PPAR pathway, with an increase of FABP4, an activator of this pathway, at P4 and an increase of adiponectin at P21. Other data also suggest involvement of the PPAR pathway in impaired alveolarization. Our results show that deregulation of the PPAR pathway may be an important component of the mechanism inducing impaired alveolarization observed in IUGR. The complete dataset is available as GEO profiles on the Gene Expression Omnibus (GEO) database ( www.ncbi.nih.gov/geo/, GEO Accession No. GSE56956).

Developmental programming of cardiovascular disease following intrauterine growth restriction: findings utilising a rat model of maternal protein restriction.

Over recent years, studies have demonstrated links between risk of cardiovascular disease in adulthood and adverse events that occurred very early in life during fetal development. The concept that there are embryonic and fetal adaptive responses to a sub-optimal intrauterine environment often brought about by poor maternal diet that result in permanent adverse consequences to life-long health is consistent with the definition of “programming”. The purpose of this review is to provide an overview of the current knowledge of the effects of intrauterine growth restriction (IUGR) on long-term cardiac structure and function, with particular emphasis on the effects of maternal protein restriction. Much of our recent knowledge has been derived from animal models. We review the current literature of one of the most commonly used models of IUGR (maternal protein restriction in rats), in relation to birth weight and postnatal growth, blood pressure and cardiac structure and function. In doing so, we highlight the complexity of developmental programming, with regards to timing, degree of severity of the insult, genotype and the subsequent postnatal phenotype.

Regulation of postnatal pancreatic Pdx1 and downstream target genes after gestational exposure to protein restriction in rats.

The study carried out in our laboratory demonstrated that protein restriction (low protein, LP) during fetal and neonatal life alters pancreatic development and impairs glucose tolerance later in life. In this study, we examined the role of the transcription factor Pdx1, a master regulator of β-cell differentiation and function along with its downstream target genes insulin, Glut2 and glucokinase (GK). The role(s) of these genes and protein products on the pancreata of male offspring from mothers exposed to LP diets were assessed during gestation, weaning, and adult life. Pregnant rats were allocated to two dietary treatments: control (C) 20% protein diet or LP, 8% protein diet. At birth, offspring were divided into four groups: C received control diet all life, LP1 received LP diet all life, LP2 changed the LP diet to C at weaning, and LP3 switched to C after being exposed to LP during gestation only. Body weights (bw) were significantly (P<0.001) decreased in all LP groups at birth. At weaning, only the LP3 offspring had their body weight restored to control levels. Pdx1 or any of the Pdx1-target genes were similar in all diets at day 21. However, at d130 Pdx1 mRNA expression and protein abundance were significantly decreased (P<0.05) in all LP groups. In addition, insulin mRNA and protein were decreased in LP1 and LP3 groups compared with C, Glut2 mRNA and GLUT2 protein levels were decreased in LP3 and GK did not change between groups. Intraperitoneal glucose tolerance test revealed impaired glucose tolerance in LP3 males, concomitant with decreased β-cell mass, islet area, and PDX1 nuclear protein localization. Collectively, this study suggests that restoring proteins in the diet after birth in LP offspring dramatically impairs glucose homeostasis in early adulthood, by altering Pdx1 expression and downstream-target genes increasing the risk to develop type 2 diabetes.

Long-Term Caloric Restriction in Rats may Prevent Age Related Impairment of In Vitro Bladder Function

Bladder function is often impaired with aging. In other organs caloric restriction has had a prophylactic effect on the biological changes associated with aging. We tested the hypothesis that long-term caloric restriction can prevent age related impaired bladder function in the rat. Fisher 344 male rats were divided into 3 groups, including 16 young rats at age 6 months with free access to normal food, 15 old rats at age 25 to 28 months with free access to normal food and 16 old rats at age 25 to 28 months fed with normal food 3 days per week since age 6 weeks (caloric restriction). We performed frequency volume measurements, in vitro organ bath functional studies using full-thickness longitudinal detrusor strips, evaluation of muscarinic and purinergic receptor mRNA expression, and histological examination with Masson trichrome staining of bladder tissue. Frequency volume changes did not significantly differ among the 3 groups. The old group fed normal food showed weaker contractile responses to carbachol and electrical field stimulation (especially in the cholinergic component), lower M3 receptor mRNA expression and higher collagen deposition compared to the young group. These age related bladder changes were milder in the old group with caloric restriction than in the old group fed normal food. This study suggests that in the rat long-term caloric restriction has a preventive effect against age related functional and morphological bladder changes. These changes include impaired detrusor contractility that may be related to decreased expression of M3 receptors and to bladder wall fibrosis.

Transgenerational left ventricular hypertrophy and hypertension in offspring after uteroplacental insufficiency in male rats.

Epidemiological studies have shown an association between low birthweight and adult disease development with transmission to subsequent generations. The aim of the present study was to examine the effect of intrauterine growth restriction in rats, induced by uteroplacental insufficiency, on cardiac structure, number, size, nuclearity, and adult blood pressure in first (F1) and second (F2) generation male offspring. Uteroplacental insufficiency or sham surgery was induced in F0 Wistar-Kyoto pregnant rats in late gestation giving rise to F1 restricted and control offspring, respectively. F1 control and restricted females were mated with normal males, resulting in F2 control and restricted offspring, respectively. F1 restricted male offspring were significantly lighter at birth (P < 0.05), but there were no differences in birthweight of F2 offspring. Left ventricular weights and volumes were significantly increased (P < 0.05) in F1 and F2 restricted offspring at day 35. Left ventricular cardiomyocyte number was not different in F1 and F2 restricted offspring. At 6 months-of-age, F1 and F2 restricted offspring had elevated blood pressure (8-15 mmHg, P < 0.05). Our findings demonstrate the emergence of left ventricular hypertrophy and hypertension, with no change in cardiomyocyte number, in F1 restricted male offspring, and this was transmitted to the F2 offspring. The findings support transgenerational programming effects.

Zinc deficiency in rats is associated with up-regulation of hippocampal NMDA receptor.

Data indicated that zinc deficiency may contribute to the development of depression; however changes induced by zinc deficiency are not fully described. In the present paper we tested whether the dietary zinc restriction in rats causes alterations in N-methyl-D-aspartate receptor (NMDAR) subunits in brain regions that are relevant to depression. Male Sprague Dawley rats were fed a zinc adequate diet (ZnA, 50 mg Zn/kg) or a zinc deficient diet (ZnD, 3 mg Zn/kg) for 4 or 6weeks. Then, the behavior of the rats was examined in the forced swim test, sucrose intake test and social interaction test. Western blot assays were used to study the alterations in NMDAR subunits GluN2A and GluN2B and proteins associated with NMDAR signaling in the hippocampus (Hp) and prefrontal cortex (PFC). Following 4 or 6 weeks of zinc restriction, behavioral despair, anhedonia and a reduction of social behavior occurred in rats with concomitant increased expression of GluN2A and GluN2B and decreased expression of the PSD-95, p-CREB and BDNF protein levels in the Hp. The up-regulation of GluN2A protein was also found in the PFC, but only after prolonged (6 weeks) zinc deprivation. The procedure of zinc restriction in rats causes behavioral changes that share some similarities to the pathophysiology of depression. Obtained data indicated that depressive-like behavior induced by zinc deficiency is associated with the changes in NMDAR signaling pathway.

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.

When early life growth restriction in rats is followed by attenuated postnatal growth: effects on cardiac function in adulthood.

Epidemiological and experimental studies demonstrate that intrauterine growth restriction (IUGR) followed by accelerated postnatal growth leads to increased risk of developing cardiac disease in adulthood. The aim of this study was to examine the effect of early life growth restriction on cardiac structure and function in young adult rats. IUGR was induced in Wistar Kyoto dams through administration of a low protein diet (LPD; 8.7% casein) during pregnancy and lactation; controls received a normal protein diet (NPD; 20% casein). Cardiac function and structure were assessed in female NPD (n = 7) and LPD (n = 7) offspring at 18 weeks of age by echocardiography and pressure-volume techniques, and systolic blood pressure by tail-cuff sphygmomanometry. LPD offspring remained significantly smaller throughout life compared to controls. There were no differences in the levels of systolic blood pressure, left ventricular cardiac dimensions, heart rate, ejection fraction and fractional shortening of the cardiac muscle between the investigated groups. Aortic peak systolic velocity was significantly reduced in the LPD group (P = 0.02). Our findings support the idea that the programming of adult cardiovascular disease can be prevented or delayed in IUGR offspring when postnatal growth trajectory resembles that of in utero.

Increases in mature brain-derived neurotrophic factor protein in the frontal cortex and basal forebrain during chronic sleep restriction in rats: Possible role in initiating allostatic adaptation

Chronic sleep restriction (CSR) has various negative consequences on cognitive performance and health. Using a rat model of CSR that uses alternating cycles of 3h of sleep deprivation (using slowly rotating activity wheels) and 1h of sleep opportunity continuously for 4days (‘3/1’ protocol), we previously observed not only homeostatic but also allostatic (adaptive) sleep responses to CSR. In particular, non-rapid eye movement sleep (NREMS) electroencephalogram (EEG) delta power, an index of sleep intensity, increased initially and then declined gradually during CSR, with no rebound during a 2-day recovery period. To study underlying mechanisms of these allostatic responses, we examined the levels of brain-derived neurotrophic factor (BDNF), which is known to regulate NREMS EEG delta activity, during the same CSR protocol. Mature BDNF protein levels were measured in the frontal cortex and basal forebrain, two brain regions involved in sleep and EEG regulation, and the hippocampus, using Western blot analysis. Adult male Wistar rats were housed in motorized activity wheels, and underwent the 3/1 CSR protocol for 27h, for 99h, or for 99h followed by 24h of recovery. Additional rats were housed in either locked wheels (locked wheel controls [LWCs]) or unlocked wheels that rats could rotate freely (wheel-running controls [WRCs]). BDNF levels did not differ between WRC and LWC groups. BDNF levels were increased, compared to the control levels, in all three brain regions after 27h, and were increased less strongly after 99h, of CSR. After 24h of recovery, BDNF levels were at the control levels. This time course of BDNF levels parallels the previously reported changes in NREMS delta power during the same CSR protocol. Changes in BDNF protein levels in the cortex and basal forebrain may be part of the molecular mechanisms underlying allostatic sleep responses to CSR.

Inflammation-induced fetal growth restriction in rats is associated with altered placental morphometrics

IntroductionEvidence links alterations in placental shape and size to fetal growth restriction (FGR). Here we determined whether alterations in placental morphometrics are linked to FGR induced by abnormal maternal inflammation. MethodsWe used an inflammation-induced model of FGR in which pregnant rats receive lipopolysaccharide (LPS) on gestational days (GD) 13.5–16.5. Fetal weights were matched to various parameters of placental morphometrics including weight, area, minor and major axes lengths and thickness. ResultsCompared with saline administration, LPS administration was associated with altered placental morphometrics, including reduced placental weight, decreased placental area and a trend towards reduced placental thickness. When data were dichotomized as FGR or normal-sized fetuses within treatment groups, a significant increase in the placental-weight-to-fetal-weight ratio and placental thickness was observed only in the saline-associated FGR subgroup. Multivariable linear regression revealed that the lengths of the major and minor placental axes were predictors of fetal weight, regardless of treatment modality. Subgroup regression analysis by treatment revealed that the lengths of the major and minor placental axes were predictors of fetal weight in the saline-treatment group while only the minor placental axis was a predictor of fetal weight in the LPS cohort. Finally, placental area and the length of the minor placental axis were correlated with implantation site location only in the saline-treatment group. Discussion/conclusionThese findings indicate that inflammation-induced FGR is associated with alterations in placental morphometrics. Our data reveal that the mechanisms leading to inflammation-induced FGR may be different from the mechanisms leading to idiopathic FGR.

Short-term dietary magnesium restriction lowers spleen iron concentrations in growing rats fed a high-fat diet

Lipotoxicity and dietary inadequacies have been associated with dysregulation of Fe homeostasis in obesity. In this study, we tested the hypothesis that dietary Mg restriction in rats fed a high-fat diet affects Fe concentrations in liver and spleen, tissues related with Fe storage and recycling, respectively. Weanling male Wistar rats (n = 48) were fed either control (ad libitum or pair-fed) or high-fat (Mg-adequate or Mg-restricted; 500 and 150 mg Mg/kg, respectively) diets for 4 weeks. Epididymal and retroperitoneal fat pad weights were used to determine the adiposity index. Serum (colorimetry) and tissue Fe (atomic absorption spectrophotometry) were analyzed. Liver hepcidin was determined by qPCR and ferroportin-1 in liver and spleen was measured by immunoblotting. Dietary fat overload increased adiposity irrespective of dietary Mg levels. Rats fed the high-fat diet, but not those fed the high-fat Mg-restricted diet, had higher spleen Fe concentrations than controls. Weak but significant associations between body adiposity and serum (r = −0.31, P = 0.04) and spleen Fe (r = 0.29, P = 0.04) concentrations were obtained. The unaltered ferroportin-1 expression with low Fe levels suggests increased Fe recycling from spleen to bone marrow due to dietary Mg restriction. A longer study could clarify the consequences of these findings on erythropoiesis and other conditions related to diet-induced obesity.

Changes of gene expressions in zinc deficiency and diet restriction in rats (1043.8)

We previously reported that both zinc deficiency and diet restriction affect total RNA concentration and expression of Gapdh and Actb in kidney. In this study, we have examined whether zinc deficiency and diet restriction affect Crebbp and Taf5l in kidney. Thirty 3‐week‐old male Sprague‐Dawley rats were assigned into 3 dietary treatment groups of 10 for the four‐week study: Control group (AIN‐93G), Zn‐deficient group (4.5 mg Zn/kg) and pair‐fed group (AIN‐93G). Kidney was separated into cortex and medulla for RNA isolation. Quantitative real time RT‐PCR using TaqMan proves was performed for mRNAs of Crebbp and Taf5l. Difference between groups was statistically analyzed by Fisher's PLSD. P value less than 0.05 was considered significant. Kidney cortex Crebbp per total RNA was not changed by the treatments. Kidney medulla Crebbp per total RNA was significantly increased by zinc deficiency and diet restriction, respectively. Kidney cortex Taf5l per total RNA was significantly increased by zinc deficiency and diet restriction, respectively. Kidney medulla Taf5l per gram tissue was significantly decreased by zinc deficiency and diet restriction, respectively. These results suggest that zinc deficiency and diet restriction differently affect expression of Crebbp and Taf5l in kidney cortex and medulla. This work was supported by KAKENHI grant‐in‐aid for Young Scientists (B) (23700928).

Involvement of the Cannabinoid CB1 Receptor in Modulation of Dopamine Output in the Prefrontal Cortex Associated with Food Restriction in Rats

Increase in dopamine output on corticolimbic structures, such as medial prefrontal cortex (mPFC) and nucleus accumbens, has been related to reward effects associated with palatable food or food presentation after a fasting period. The endocannabinoid system regulates feeding behavior through a modulatory action on different neurotransmitter systems, including the dopaminergic system. To elucidate the involvement of type 1 cannabinoid receptors in the regulation of dopamine output in the mPFC associated with feeding in hungry rats, we restricted the food availability to a 2-h period daily for 3 weeks. In food-restricted rats the extracellular dopamine concentration in the mPFC increased starting 80 min before food presentation and returned to baseline after food removal. These changes were attenuated in animals treated with the CB1 receptor antagonist SR141716. To better understand how food restriction can change the response of mesocortical dopaminergic neurons, we studied several components of the neuronal circuit that regulates dopamine output in the mPFC. Patch-clamp experiments revealed that the inhibitory effect of the CB1 receptor agonist WIN 55,212-2 on GABAergic sIPSC frequency was diminished in mPFC neurons of FR compared to fed ad libitum rats. The basal sIPSC frequency resulted reduced in mPFC neurons of food-restricted rats, suggestive of an altered regulation of presynaptic GABA release; these changes were accompanied by an enhanced excitability of mPFC and ventral tegmental area neurons. Finally, type 1 cannabinoid receptor expression in the mPFC was reduced in food-restricted rats. Together, our data support an involvement of the endocannabinoid system in regulation of dopamine release in the mPFC through changes in GABA inhibitory synapses and suggest that the emphasized feeding-associated increase in dopamine output in the mPFC of food-restricted rats might be correlated with an altered expression and function of type 1 cannabinoid receptor in this brain region.

A systems biology analysis of the unique and overlapping transcriptional responses to caloric restriction and dietary methionine restriction in rats

Dietary methionine restriction (MR) and calorie restriction (CR) each improve metabolic health and extend life span. We used comprehensive transcriptome profiling and systems biology analysis to interrogate the unique and overlapping molecular responses in rats provided these dietary regimens for 20 mo after weaning. Microarray analysis was conducted on inguinal white adipose (IWAT), brown adipose tissue (BAT), liver, and skeletal muscle. Compared to controls, CR-induced transcriptomic responses (absolute fold change ≥1.5 and P≤0.05) were comparable in IWAT, BAT, and liver (~800 genes). MR-induced effects were largely restricted to IWAT and liver (~2400 genes). Pathway enrichment and gene-coexpression analyses showed that induction of fatty acid synthesis in IWAT was common to CR and MR, whereas immunity and proinflammatory signaling pathways were specifically down-regulated in MR-treated IWAT and liver (FDR≤0.07-0.3). BAT demonstrated consistent down-regulation of PPAR-signaling under CR and MR, whereas muscle was largely unaffected. Interactome analysis identified CR-specific down-regulation of cytoskeletal matrix components in IWAT and MR-specific up-regulation of ribosomal genes in liver (FDR≤0.001). Transcriptomic down-regulation of inflammation genes by MR in IWAT was consistent with upstream inhibition of STAT3. Together, these results provide an integrated picture of the breadth of transcriptional responses to MR and CR among key metabolic tissues.

Piromelatine, a novel melatonin receptor agonist, stabilizes metabolic profiles and ameliorates insulin resistance in chronic sleep restricted rats

Chronic sleep deprivation may speed the onset or increase the severity of age-related conditions such as Type 2 diabetes, high blood pressure and obesity. Piromelatine (Neu-P11) is a novel melatonin agonist, which has been developed for the treatment of insomnia. Animal studies have suggested possible efficacy of piromelatine in sleep maintenance, anxiety and depression. In addition, piromelatine has been shown to inhibit weight gain and improve insulin sensitivity in high-fat/high-sucrose-fed (HFSD) rats. The objective of this study was to investigate the effects of piromelatine on insulin sensitivity in sleep restricted rats. Sleep restriction was established by rotating cages intermittently for 20h thereby sleeping time of rats was limited to 4h per day. During 8 days of sleep restriction, rats were injected intraperitoneally with piromelatine (20mg/kg), melatonin (5mg/kg) or a vehicle. The results showed that sleep restriction increased plasma glucose, fasting insulin, total cholesterol (TC), triglycerides (TG) and oxidative stress markers while HDL-cholesterol (HDL-C) level and glucose tolerance were decreased. However, under piromelatine or melatonin treatment, the levels of plasma glucose, TG, TC decreased and HDL-C, glucose tolerance and antioxidative potency increased when compared with the vehicle-treated group. These data suggest that chronic sleep restriction in rats induce metabolic dysfunction, oxidative stress and insulin resistance, and these symptoms were improved by treatment with piromelatine or melatonin. We conclude that piromelatine could regulate metabolic profiles and insulin sensitivity, and attenuate insulin resistance induced by sleep restriction.