Effects of energy status and diet on Bdnf expression in the ventromedial hypothalamus of male and female rats.
ABSTRACT: Sex differences exist in the regulation of energy homeostasis in response to calorie scarcity or excess. Brain-derived neurotrophic factor (BDNF) is one of the anorexigenic neuropeptides regulating energy homeostasis. Expression of Bdnf mRNA in the ventromedial nucleus of the hypothalamus (VMH) is closely associated with energy and reproductive status. We hypothesized that Bdnf expression in the VMH was differentially regulated by altered energy balance in male and female rats. Using dietary intervention, including fasting-induced negative energy status and high-fat diet (HFD) feeding-induced positive energy status, along with low-fat diet (LFD) feeding and HFD pair-feeding (HFD-PF), effects of diets and changes in energy status on VMH Bdnf expression were compared between male and female rats. Fasted males but not females had lower VMH Bdnf expression than their fed counterparts following 24-hour fasting, suggesting that fasted males reduced Bdnf expression to drive hyperphagia and body weight gain. Male HFD obese and HFD-PF non-obese rats had similarly reduced expression of Bdnf compared with LFD males, indicating that dampened Bdnf expression was associated with feeding a diet high in fat instead of increased adiposity. Decreased BDNF signaling during HFD feeding would increase a drive to eat and may contribute to diet-induced obesity in males. In contrast, VMH Bdnf expression was stably maintained in females when energy homeostasis was disturbed. These results suggest sex-distinct regulation of central Bdnf expression by diet and energy status.
Project description:Metabolic sensing neurons in the ventromedial hypothalamus (VMH) alter their activity when ambient levels of metabolic substrates, such as glucose and fatty acids (FA), change. To assess the relationship between a high-fat diet (HFD; 60%) intake on feeding and serum and VMH FA levels, rats were trained to eat a low-fat diet (LFD; 13.5%) or an HFD in 3 h/day and were monitored with VMH FA microdialysis. Despite having higher serum levels, HFD rats had lower VMH FA levels but ate less from 3 to 6 h of refeeding than did LFD rats. However, VMH ?-hydroxybutyrate (?-OHB) and VMH-to-serum ?-OHB ratio levels were higher in HFD rats during the first 1 h of refeeding, suggesting that VMH astrocyte ketone production mediated their reduced intake. In fact, using calcium imaging in dissociated VMH neurons showed that ketone bodies overrode normal FA sensing, primarily by exciting neurons that were activated or inhibited by oleic acid. Importantly, bilateral inhibition of VMH ketone production with a 3-hydroxy-3-methylglutaryl-CoA synthase inhibitor reversed the 3- to 6-h HFD-induced inhibition of intake but had no effect in LFD-fed rats. These data suggest that a restricted HFD intake regimen inhibits caloric intake as a consequence of FA-induced VMH ketone body production by astrocytes.
Project description:Using standardized, semipurified diets is a crucial factor for reproducibility of experimental nutritional studies. For the purpose of comparability and integration of research, two European consortia, Mitofood and BIOCLAIMS, proposed an AIN-93-based standard reference diet, the standardized BIOCLAIMS low-fat diet (LFD) as well as a high-fat diet (HFD). In order to evaluate the BIOCLAIMS LFD and HFD, we performed short-term (5 days) and long-term (12 weeks) feeding experiments using male C57BL/6 mice. The HFD has the same composition as the LFD except the fat content is increased to 40% energy in exchange for carbohydrates. Both diets were accepted by the animals and proof of principle was given that the BIOCLAIMS HFD increases body weight and body fat and affects glucose homeostasis. Short-term feeding trials (5 days) were performed in order to identify metabolic and molecular parameters which can serve as acute predictors for metabolic disorders due to high-fat diet-induced obesity. We analyzed gene expression in gonadal white adipose tissue of short- and long-term fed animals with whole genome microarrays. The BIOCLAIMS HFD strongly influenced gene expression in white adipose tissue after short- and long-term intervention. A total number of 973 and 4678 transcripts were significantly different between both diets after 5 days feeding and 12 weeks feeding, respectively. A total number of 764 transcripts encoding 549 genes were significantly differentially regulated between LF and HF animals after 12 weeks feeding as well as after 5 days feeding. Of these 549 overlapping genes, a substantial number (434 genes) were expressed at a lower level and 115 genes were expressed at a higher level in the HF mice compared to the LF mice. Without exception, all genes were regulated equally. Pathway analysis revealed a prominent role for genes involved in lipid metabolism, carbohydrate metabolism and oxidative phosphorylation. This was confirmed by quantitative real-time reverse transcription PCR. The high predictive value of gene expression changes in our short-term study compared to long-term high fat feeding is a promising step to get well-defined, early biomarkers that could shorten animal trials considerably and allow a more rapid and efficient screening of different compounds. C57BL/6J wildtype male mice, aged 12 weeks, received a low-fat diet or a high-fat diet for 5 days or 12 weeks. After sacrification, white adipose tissue depots were dissected, and immediately snap frozen in liquid nitrogen. Total RNA was isolated, quantified and qualified, and subsequently used for global gene expression profiling using Agilent 4x44K microarrays.
Project description:Adolescence represents a crucial period for maturation of brain structures involved in cognition. Early in life unhealthy dietary patterns are associated with inferior cognitive outcomes at later ages; conversely, healthy diet is associated with better cognitive results. In this study we analyzed the effects of a short period of hypercaloric diet on newborn hippocampal doublecortin+ (DCX) immature neurons in adolescent mice. Male mice received high fat diet (HFD) or control low fat diet (LFD) from the 5th week of age for 1 or 2 weeks, or 1 week HFD followed by 1 week LFD. After diet supply, mice were either perfused for immunohistochemical (IHC) analysis or their hippocampi were dissected for biochemical assays. Detailed morphometric analysis was performed in DCX+ cells that displayed features of immature neurons. We report that 1 week-HFD was sufficient to dramatically reduce dendritic tree complexity of DCX+ cells. This effect occurred specifically in dorsal and not ventral hippocampus and correlated with reduced BDNF expression levels in dorsal hippocampus. Both structural and biochemical changes were reversed by a return to LFD. Altogether these studies increase our current knowledge on potential consequences of hypercaloric diet on brain and in particular on dorsal hippocampal neuroplasticity.
Project description:Studies were designed to examine the effects of dietary fats on metabolic effects of 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy). These effects included hyperthermia, expression of uncoupling protein (UCP1 and 3) in brown adipose tissue or skeletal muscle and plasma free fatty acid (FFA) levels.Male Sprague-Dawley rats were fed either a high-fat diet (HFD, 60% kcal) or a lower fat isocaloric controlled diet (LFD, 10% kcal) for 28 days before MDMA challenge.No significant differences were observed between LFD and HFD groups in terms of body weight, plasma thyroxine (T4) levels and expression of brown fat UCP1 or skeletal muscle UCP3 protein. HFD significantly raised levels of circulating FFA and potentiated the thermogenesis induced by MDMA (10 mg kg(-1), s.c.), compared to the effects of the LFD. Moreover, 30 and 60 min after MDMA administration, plasma FFA levels decreased in HFD animals, but were markedly elevated in the LFD group.These results indicate that high-fat feeding regulates MDMA-induced thermogenesis by augmenting the activation of UCP rather than its expression.
Project description:Background. Naturally occurring substances from the flavanol and anthocyanin family of polyphenols have been proposed to exert beneficial effects in the course of obesity. We hypothesized that their effects on attenuating obesity-induced dyslipidemia as well as the associated inflammatory sequelae especially have health-promoting potential. Methods. Male C57BL/6J mice (n = 52) received a control low-fat diet (LFD; 10?kcal% fat) for 6 weeks followed by 24 weeks of either LFD (n = 13) or high-fat diet (HFD; 45?kcal% fat; n = 13) or HFD supplemented with 0.1% w/w of the flavanol compound epicatechin (HFD+E; n = 13) or an anthocyanin-rich bilberry extract (HFD+B; n = 13). Energy substrate utilization was determined by indirect calorimetry in a subset of mice following the dietary switch and at the end of the experiment. Blood samples were collected at baseline and at 3 days and 4, 12, and 20 weeks after dietary switch and analyzed for systemic lipids and proinflammatory cytokines. Adipose tissue (AT) histopathology and inflammatory gene expression as well as hepatic lipid content were analyzed after sacrifice. Results. The switch from a LFD to a HFD lowered the respiratory exchange ratio and increased plasma cholesterol and hepatic lipid content. These changes were not attenuated by HFD+E or HFD+B. Furthermore, the polyphenol compounds could not prevent HFD-induced systemic rise of TNF-? levels. Interestingly, a significant reduction in Tnf gene expression in HFD+B mice was observed in the AT. Furthermore, HFD+B, but not HFD+E, significantly prevented the early upregulation of circulating neutrophil chemoattractant mKC. However, no differences in AT histopathology were observed between the HFD types. Conclusion. Supplementation of HFD with an anthocyanin-rich bilberry extract but not with the flavanol epicatechin may exert beneficial effects on the systemic early inflammatory response associated with diet-induced obesity. These systemic effects were transient and not observed after prolongation of HFD-feeding (24 weeks). On the tissue level, long-term treatment with bilberry attenuated TNF-? expression in adipose tissue.
Project description:The ventromedial hypothalamus (VMH) plays chief roles regulating energy and glucose homeostasis and is sexually dimorphic. We discovered that expression of metabotropic glutamate receptor subtype 5 (mGluR5) in the VMH is regulated by caloric status in normal mice and reduced in brain-derived neurotrophic factor (BDNF) mutants, which are severely obese and have diminished glucose balance control. These findings led us to investigate whether mGluR5 might act downstream of BDNF to critically regulate VMH neuronal activity and metabolic function. We found that mGluR5 depletion in VMH SF1 neurons did not affect energy balance regulation. However, it significantly impaired insulin sensitivity, glycemic control, lipid metabolism, and sympathetic output in females but not in males. These sex-specific deficits are linked to reductions in intrinsic excitability and firing rate of SF1 neurons. Abnormal excitatory and inhibitory synapse assembly and elevated expression of the GABAergic synthetic enzyme GAD67 also cooperate to decrease and potentiate the synaptic excitatory and inhibitory tone onto mutant SF1 neurons, respectively. Notably, these alterations arise from disrupted functional interactions of mGluR5 with estrogen receptors that switch the normally positive effects of estrogen on SF1 neuronal activity and glucose balance control to paradoxical and detrimental. The collective data inform an essential central mechanism regulating metabolic function in females and underlying the protective effects of estrogen against metabolic disease.
Project description:Gene expression for genes differentially expressed between early vs. late tumor onset and high fat diet (HFD) vs. low fat diet (LFD) in P53 -/- mice. 4 HFD early tumor onset, 7 HFD late tumor onset, 4 HFD to LFD switch with early tumor onset, 6 HFD to LFD switch with late tumor onset, 4 LFD early tumor onset, 7 LFD late tumor onset, 5 LFD to HFD switch with early tumor onset, 4 LFD to HFD switch with late tumor onset
Project description:To investigate the variations in body weight, food intake, and body composition of both male and female C57BL/6J mice during a diet-induced obesity model with high-fat diet (HFD) feeding.Mice were individually housed and fed ad libitum either a low-fat diet (LFD, 10% calories from fat; n?=?15 male, n?=?15 female) or HFD (45% calories from fat; n?=?277 male, n?=?278 female) from 8 to 43 weeks of age. Body weight, food intake, and body composition were routinely measured.Body weight was significantly increased with HFD (vs. LFD) in males from week 14 (P?=?0.0221) and in females from week 27 (P?=?0.0076). Fat mass and fat-free mass of all groups were significantly increased over time (all P?<?0.0001), with a large variation observed in fat mass. Baseline fat mass, fat-free mass, and daily energy intake were significant predictors of future body weight for both sexes (P?<?0.0001). Baseline fat mass was a significant predictor of future body fat (P?<?0.0001).Both males and females have large variations in fat mass, and this variability increases over time, while that of fat-free mass remains relatively stable. Sex differences exist in HFD responses and multivariate predicting models of body weight.
Project description:The hypothalamus plays a central role in the integrated regulation of feeding and energy homeostasis. The hypothalamic arcuate nucleus (ARC) contains a population of neurons that express orexigenic and anorexigenic factors and is thought to control feeding behavior via several neuronal circuits. In this study, a comparative proteomic analysis of low-fat control diet- (LFD-) and high-fat diet- (HFD-) induced hypothalamic ARC was performed to identify differentially expressed proteins (DEPs) related to changes in body weight. In the ARC in the hypothalamus, 6621 proteins (FDR < 0.01) were detected, and 178 proteins were categorized as DEPs (89 upregulated and 89 downregulated in the HFD group). Among the Gene Ontology molecular function terms associated with the DEPs, protein binding was the most significant. Fibroblast growth factor receptor substrate 2 (Frs2) and SHC adaptor protein 3 (Shc3) were related to protein binding and involved in the neurotrophin signaling pathway according to Kyoto Encyclopedia of Genes and Genomes analysis. Furthermore, high-precision quantitative proteomic analysis revealed that the protein profile of the ARC in mice with HFD-induced obesity differed from that in LFD mice, thereby offering insight into the molecular basis of feeding regulation and suggesting Frs2 and Shc3 as novel treatment targets for central anorexigenic signal induction.
Project description:This study aims to investigate the effect of feeding low-fat diet (LFD) to diet-induced obesity (DIO) mice lacking TLR5 (TLR5(-/-)), which have a tendency to develop glucose intolerance with increased adiposity, compared to that in C57BL/6 mice.TLR5(-/-) and C57BL/6 male mice were divided into three subgroups: (1) control, mice were fed a standard AIN-76A (fat: 11.5 kcal%) diet for 12 weeks; (2) DIO, mice were fed a 58 kcal% high-fat diet (HFD) for 12 weeks; and (3) diet, mice were fed a HFD for 8 weeks to induce obesity and then switched to a 10.5 kcal% LFD for 4 weeks. The glucose intolerance in DIO TLR5(-/-) mice was more significant than that in DIO C57BL/6 mice and was not attenuated by a switch to the LFD. Weight-reduction with LFD had significantly decreased the epididymal fat mass in C57BL/6 mice but not in TLR5(-/-) mice. In addition, the LFD-fed TLR5(-/-) mice showed significantly higher expression of ghrelin in the serum and resistin in the epididymal fat than that in C57BL/6 mice.This study demonstrated that TLR5 gene knockout impairs some effects of weight-reduction in DIO.