Project description:Autophagy represents a key regulator of aging and metabolism upon cell autonomous sensing of energy deprivation. We find that fasting in mice activates autophagy in liver paralleled by activation of hypothalamic AgRP neurons. Optogenetic and chemogenetic activation of AgRP neurons induces autophagy, alters phosphorylation of autophagy regulators and promotes ß-oxidation in the liver. AgRP neuron dependent induction of liver autophagy relies on NPY expression in these neurons. AgRP neuron projections in the paraventricular nucleus of the hypothalamus (PVH) and the lateral hypothalamus (LHA) mediate AgRP neuron-dependent control of liver autophagy. Conversely, inhibiting AgRP neurons during energy deprivation abrogates induction of hepatic autophagy and re-wiring of metabolism. Finally, AgRP neuron activation increases circulating corticosterone concentrations, and reduction of hepatic glucocorticoid receptor expression attenuates AgRP neuron-dependent activation of hepatic autophagy. Collectively, our study reveals a fundamental regulatory principle of non-cell autonomous control of liver autophagy in control of metabolic adaptation during nutrient deprivation.
Project description:The hypothalamic arcuate nucleus contains multiple types of neurons controlling critical physiological processes. However, the gene regulatory network directing their development remains rudimentary. Here we report that two transcription factors Otp and Dlx1 segregate the identity of orexigenic/anti-thermogenic NPY/AgRP- and growth-promoting GHRH-neurons in the developing arcuate nucleus. Otp-null and Dlx1-null mice lose NPY/AgRP and GHRH expression, respectively. Dlx1-null mice also show enhanced expression of Otp/NPY/AgRP, which is normalized in Dlx1;Otp-double mutant mice. Correspondingly, Dlx1-null mice exhibit decreased growth, lower body temperature and increased feeding. Furthermore, our genome-wide studies identify Otp as a negative target gene of Dlx1. Therefore, Otp is critical for NPY/AgRP-neuronal development, while Dlx1 promotes GHRH-neuronal development and antagonizes NPY/AgRP-neuronal development. These results identify a mechanism for segregating the identity of two functionally related neurons, and the Dlx1-Otp axis likely contributes to coordinating energy balance and growth by maintaining a proper ratio of NPY/AgRP- to GHRH-neurons.
Project description:Pre- and postnatal calorie restriction is associated with postnatal growth restriction, reduced circulating leptin concentrations and perturbed energy balance. Hypothalamic regulation of energy balance demonstrates enhanced orexigenic (NPY, AgRP) and diminished anorexigenic (POMC, CART) neuropeptide expression (PN21) setting the stage for subsequent development of obesity. Leptin replenishment during the early postnatal period (PN2-PN8) led to reversing the hypothalamic orexigenic:anorexigenic neuropeptide ratio at PN21 by only reducing the orexigenic (NPY, AgRP) without affecting the anorexigenic (POMC, CART) neuropeptide expression. This hypothalamic effect was mediated via enhanced leptin receptor (ObRb) signaling that involved increased pSTAT3 but reduced PTP1B. This was further confirmed by an increase in body weight at PN21 in response to intracerebroventricular administration of antisense ObRb oligonucleotides (PN2-PN8). The change in the hypothalamic neuropeptide balance in response to leptin administration caused increased oxygen consumption, carbon dioxide production and physical activity which resulted in increased milk intake (PN14) with no change in body weight. This is in contrast to the reduction in milk intake with no effect on energy expenditure and physical activity observed in controls. We conclude that pre- and postnatal calorie restriction perturbs hypothalamic neuropeptide regulation of energy balance setting the stage for hyperphagia and reduced energy expenditure, hallmarks of obesity. Leptin in turn reverses this phenotype by increasing hypothalamic ObRb signaling (sensitivity) and affecting only the orexigenic arm of the neuropeptide balance.
Project description:Despite their opposing actions on food intake, POMC and NPY/AgRP neurons in the arcuate nucleus of the hypothalamus (ARH) are derived from the same progenitors that give rise to ARH neurons. However, the mechanism whereby common neuronal precursors subsequently adopt either the anorexigenic (POMC) or the orexigenic (NPY/AgRP) identity remains elusive.We hypothesize that POMC and NPY/AgRP cell fates are specified and maintained by distinct intrinsic factors. In search of them, we profiled the transcriptomes of developing POMC and NPY/AgRP neurons in E15.5 mice embryos. Moreover, cell-type-specific transcriptomic analyses revealed transcription regulators that are selectively enriched in either population, but whose developmental functions are unknown in these neurons.Among them, we found the expression of the PR domain-containing factor 12 (Prdm12) was enriched in POMC neurons but absent in NPY/AgRP neurons. To study the role of Prdm12 in vivo, we developed and characterized a floxed Prdm12 allele. Selective ablation of Prdm12 in embryonic POMC neurons led to significantly reduced Pomc expression as well as early-onset obesity in mice of either sex that recapitulates symptoms of human POMC deficiency. Interestingly, however, specific deletion of Prdm12 in adult POMC neurons showed that it is no longer required for Pomc expression nor energy balance. Collectively, these findings establish a critical role for Prdm12 in the anorexigenic neuron identity and suggest that it acts developmentally to program body weight homeostasis. Finally, the combination of cell-type-specific genomic and genetic analyses provides a means to dissect cellular and functional diversity in the hypothalamus whose neurodevelopment remains poorly studied.
Project description:Associated with numerous metabolic and behavioral abnormalities, obesity is classified by metrics reliant on body weight (such as body mass index). However, overnutrition is the common cause of obesity, and may independently contribute to these obesity-related abnormalities. The goal of this study is to isolate ‘diet/energy balance’ effects independent from ‘body weight’ effects on various metabolic and behavioral parameters using the Diet Switch feeding paradigm in mice. [We conducted] unbiased gene expression analysis of the nutrient-sensing circumventricular hypothalamus [using RNA-seq]. Remarkably, only two genes responded to diet/energy balance (neuropeptide y [npy] and agouti-related peptide [agrp]), while others were related only to body weight. Furthermore, linear regression models revealed that npy and agrp showed similar modifiability by diet/energy balance and body weight compared to electroencephalographic-measured sleep/wake behavior.
Project description:Anorexia is a common symptom among cancer patients and contributes to malnutrition and insufficient food intake. In cancer-induced anorexia, food intake regulation in the hypothalamus appears to be impaired. A negative energy balance persists and accelerates muscle wasting and malnutrition. Moreover, it strongly affects mortality and survival in these patients. Here, we show that the neuropeptide Y system (NPY) appears to fail to respond adequately to changes in energy balance during cancer cachexia. In addition, we investigate the connection between serotonin and NPY release in hypothalamic cell lines. Hypothalamic neuronal cells mHypoE-46 (serotonin sensitive cells) and mHypoA-2/12 (serotonin unresponsive cells) were used to study the effect of serotonin on messenger NPY expression and NPY excretion.
Project description:Obesity, a worldwide epidemic, leads to various metabolic disorders threatening human health. In response to stress or fasting, glucocorticoid (GC) levels are elevated to promote food intake. This involves GC-induced expression of the orexigenic neuropeptides in agouti-related protein (AgRP) neurons of the hypothalamic arcuate nucleus (ARC) via the GC receptor (GR). Here, we report a selective GR modulator (SGRM) that suppresses GR-induced transcription of genes with non-classical glucocorticoid response elements (GREs) such as Agrp-GRE, but not with classical GREs, and via this way may serve as a novel anti-obesity agent. We have identified a novel SGRM, 2-O-trans-p-coumaroylalphitolic acid (Zj7), a triterpenoid extracted from the Ziziphus jujube plant, that selectively suppresses GR transcriptional activity in Agrp-GRE without affecting classical GREs. Zj7 reduces the expression of orexigenic genes in the ARC and exerts a significant anorexigenic effect with weight loss and increased energy expenditure in both high-fat diet-induced obese and genetically obese db/db mouse models. Transcriptome analysis showed that Zj7 represses the expression of a group of orexigenic genes including Agrp and Npy induced by the synthetic GR ligand dexamethasone (Dex) in the hypothalamus. Overall, our studies demonstrate that selectively targeting the orexigenic action of GR in AgRP neurons is a promising approach for the treatment of metabolic disorders with fewer side effects.
Project description:Hypothalamic neurons expressing Agouti-related peptide (AgRP) are critical for initiating food intake, but druggable biochemical pathways that control this response remain elusive. Thus, genetic ablation of insulin or leptin signaling in AgRP neurons is predicted to reduce satiety but fails to do so. FoxO1 is a shared mediator of both pathways, and its inhibition is required to induce satiety. Accordingly, FoxO1 ablation in AgRP neurons of mice results in reduced food intake, leanness, improved glucose homeostasis, and increased sensitivity to insulin and leptin. Expression profiling of flow-sorted FoxO1-deficient AgRP neurons identifies G-protein-coupled receptor Gpr17 as a FoxO1 target whose expression is regulated by nutritional status. Intracerebroventricular injection of Gpr17 agonists induces food intake, whereas Gpr17 antagonist cangrelor curtails it. These effects are absent in Agrp-Foxo1 knockouts, suggesting that pharmacological modulation of this pathway has therapeutic potential to treat obesity. We used microarrays to detail the change of gene expression in AgRP neurons after knocking out FoxO1. AgRP neurons from control and KO mice were collected by FACS. Gene expression was analyzed by microarray.
Project description:Microarrays were used to examine gene expression changes between two hypothalamic cell lines derived from adult and embryonic tissues. Both cell lines endogenously express the protein Npy (neuropeptide y) which is involved in feeding and reproductive processes. Results identify novel gene candidates that are implicated in the development of hypothalamic sub-poplulations. Immortalized hypothalamic cell lines were created by overexpression of SV40 T-antigen from tissue sources derived from both embryonic and adult mice. Triplicate plates of each cell line were grown to 70% confluence and RNA was harvested for microarray analysis.