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Background: Inwardly Rectifying Potassium Channel 2.1 (Kir2.1) a ubiquitously expressed K+ channel with the main functions of the maintenance of membrane potential and K+ homeostasis is known to be strongly suppressed by the elevation of membrane cholesterol and diet-induced hypercholesterolemia. To determine the role of cholesterol-induced suppression of Kir2.1 channels in overall health under high fat diet (HFD) conditions, we generated a CRISPR mouse expressing a cholesterol-insensitive Kir 2.1 mutant, Kir2.1L222I. Our recent study showed that this mutation has a strong protective effect against the impairment of flow-induced vasodilation, a hallmark of endothelial function. Objective: In this study, we demonstrate that cholesterol insensitive Kir2.1 has a protective effect against diet induced obesity. Methods: C57/BL6J (WT) male mice with the Kir2.1L222I mutation were fed HFD and weighed weekly for 25 weeks until the mice were 6 months of age. Mouse feeding behavior was assessed under BioDaq monitoring and nuclear magnetic resonance spectroscopy (NMR) was used to determine body composition. Fat mass and serum were analyzed postmortem in these mice. Results: Initially, WT (n=4) and Kir2.1L222I (n=5) male mice weighed the same. After 14 weeks on HFD Kir2.1L222I mice weighed 28±0.60 less than WT mice 36±2.78 grams(p=0.01). After 25 weeks, the protection against weight gain persisted with animals weighing 31±3 compared to 40.5±1.5 grams for WT mice(p=0.053, n=2). Kir2.1L222I mice have decreased fat mass 8.29±1.56 compared to WT mice with 24.75±3.20 percent(p=0.0018, n=4). Kir2.1L222I mice have more lean mass 76.67±1.54 than WT mice with 62.92±2.18 percent(p=0.0011). The lean-to-fat mass ratio for Kir2.1L222I mice was greater 10.47±2.25 than WT 2.77±0.59(p=0.0081). There was no difference in water weight. Kir2.1L222I mice have less brown, visceral white, and subcutaneous adipose than WT mice (n=4). Additionally, Kir2.1L222I mice have a decreased ratio of visceral to subcutaneous adipose 1.39±0.11 compared to WT 2.07±0.21(p=0.015). Kir2.1L222I mice have an increase in brown relative to white adipose 0.71±0.09 compared to WT 0.38±0.06(p=0.011). Total cholesterol, HDL, and LDL were decreased in Kir2.1L222I male mice compared to WT(n=4, p≤0.02). There was also a decrease in serum glucose in Kir2.1L222I 117.50±22.04 compared to WT 230.25±16.42 mg/dL(p=0.003). Liver markers including ALK phosphate, ALT, creatinine, and direct bilirubin(p≤0.03) were decreased. Preliminary data show no difference in mouse feeding behavior. Conclusions: The Kir2.1L222I mutation is protective against weight gain in male mice up to 6 months of age. Kir2.1L222I mice on HFD have reduced fat, increased lean-to-total body mass, and altered fat distribution compared to WT mice. Kir2.1L222I mice had improved lipid profiles and liver markers compared to WT. These findings along with previous cardiovascular protective effects suggest the role of Kir2.1 in improved healthspan. UIC-T32HL144909 to KMB, R01HL073965 to IL This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Long-term ad libitum dietary restrictions, such as low-protein diets (LPDs), improve metabolic health and extend the life span of mice and humans. However, most studies conducted thus far have focused on the preventive effects of LPDs on metabolic syndromes. To test the therapeutic potential of LPD, we treated a lipodystrophy mouse model IRFKO (adipose-specific insulin receptor knockout) in this study. We have previously shown that IRFKO mice have profound insulin resistance, hyperglycemia, and whitenng of interscapular brown adipose tissue (BAT), closely mimicking the phenotypes in lipoatrophic diabetic patients. Here, we demonstrate that 14-day of LPD (5.1% kcal from protein) feeding is sufficient to reduce postprandial blood glucose, improve insulin resistance, and normalize glucose tolerance in the IRFKO mice. This profound metabolic improvement is associated with BAT activation and increase in whole body energy expenditure. To confirm, we showed that surgical denervation of BAT attenuated the beneficial metabolic effects of LPD feeding in IRFKO mice, including the ‘browning’ effects on BAT and the glucose-ameliorating results. However, BAT denervation failed to affect the body weight-lowering effects of LPD. Together, our results imply a therapeutic potential to use LPD for the treatment of lipoatrophic diabetes.

Asprosin, a recently identified adipokine, activates agouti-related peptide (AgRP) neurons in the arcuate nucleus of the hypothalamus (ARH) via binding to protein tyrosine phosphatase receptor δ (Ptprd) to increase food intake. However, the intracellular mechanisms responsible for asprosin/Ptprd-mediated activation of AgRP ARH neurons remain unknown. Here, we demonstrate that the small-conductance calcium-activated potassium (SK) channel is required for the stimulatory effects of asprosin/Ptprd on AgRP ARH neurons. Specifically, we found that deficiency or elevation of circulating asprosin increased or decreased the SK current in AgRP ARH neurons, respectively. AgRP ARH -specific deletion of SK3 (an SK channel subtype highly expressed in AgRP ARH neurons) blocked asprosin-induced AgRP ARH activation and overeating. Furthermore, pharmacological blockade, genetic knockdown, or knockout of Ptprd abolished asprosin’s effects on the SK current and AgRP ARH neuronal activity. Therefore, our results demonstrated an essential asprosin-Ptprd-SK3 mechanism in asprosin-induced AgRP ARH activation and hyperphagia, which is a potential therapeutic target for the treatment of obesity.

SUMMARYA potential therapeutic target to curb the obesity and diabetes epidemic is thermogenic beige adipocytes. However, beige adipocytes quickly transition into white adipocytes upon removing stimuli. Here, we define the critical role ofCdkn2aas a molecular pedal for the beige-to-white transition. Beige adipocytes lackingCdkn2aexhibit prolonged lifespan, and mice are more resistant to diet-induced obesity, along with enhanced energy expenditure and improved glucose tolerance. Mechanistic studies demonstrate thatCdkn2apromotes the expression and activity of BECN1 by directly binding to its mRNA and its negative regulator BCL2L1, activating autophagy and accelerating the beige-to-white transition. Notably, reactivating autophagy by pharmacological or genetic methods abolishes beige adipocyte maintenance induced byCdkn2a-ablation. Furthermore, hyperactive BECN1 alone significantly accelerates the beige-to-white transition. Collectively, these findings show thatCdkn2a-mediated autophagy serves as a brake system for beige adipocyte maintenance and is a highly promising target for anti-obesity and anti-diabetes therapy.HighlightsCdkn2aablation promotes beige fat maintenance and ameliorates diet-induced obesityLoss ofCdkn2aretains beige adipocytes by inhibiting BECN1-mediated autophagyCdkn2amodulates BECN1 by binding to its mRNA and its inhibitor BCL2L1, respectivelyHyperactive BECN1 is sufficient to accelerate the beige-to-white transition

Obesity is primarily a consequence of consuming calories beyond energetic requirements, but underpinning drivers have not been fully defined. 5-Hydroxytryptamine (5-HT) neurons in the dorsal Raphe nucleus (5-HTDRN) regulate different types of feeding behavior, such as eating to cope with hunger or for pleasure. Here, we observed that activation of 5-HTDRN to hypothalamic arcuate nucleus (5-HTDRN → ARH) projections inhibits food intake driven by hunger via actions at ARH 5-HT2C and 5-HT1B receptors, whereas activation of 5-HTDRN to ventral tegmental area (5-HTDRN → VTA) projections inhibits non-hunger-driven feeding via actions at 5-HT2C receptors. Further, hunger-driven feeding gradually activates ARH-projecting 5-HTDRN neurons via inhibiting their responsiveness to inhibitory GABAergic inputs; non-hunger-driven feeding activates VTA-projecting 5-HTDRN neurons through reducing a potassium outward current. Thus, our results support a model whereby parallel circuits modulate feeding behavior either in response to hunger or to hunger-independent cues.

The central nervous system (CNS) circuits that regulate binge eating remain to be identified, and effective treatments for binge eating are limited. Here, we provide evidence to support the vital role of asprosin, a novel fasting-induced glucogenic and orexigenic hormone, in the development of binge eating. We found that heterozygous deletion of fibrillin 1, the gene encoding asprosin protein, led to a 50% decrease in asprosin production and reduced binge-like eating behavior in mice. Consistently, systemic treatment of asprosin promoted, while an asprosin-neutralizing antibody inhibited, binge-like eating behavior. These behavioral changes were associated with increased or decreased activity of gamma-aminobutyric acid (GABA) producing neurons in the zona incerta (ZI) brain region, respectively. Mechanistically, we further demonstrate that asprosin stimulates ZI GABA neurons by decreasing small-conductance, calcium-activated potassium (SK) currents. Conversely, the asprosin-neutralizing antibody inhibits ZI GABA neurons by increasing SK currents. Our results support a model that asprosin decreases SK currents to stimulate ZI GABA neurons, further promoting binge-like eating behavior and causing obesity in mice. Our findings also provided preclinical evidence that asprosin-neutralizing antibodies could be used to treat binge eating. Keywords: Asprosin, neutralizing antibody, binge eating, obesity, GABA neurons Disclosure P. Xu: None. Y. He: None. Funding National Institutes of Health (P30 DK072476)

Oxysterols are metabolites of cholesterol produced in peripheral tissues as a means to eliminate cholesterol. 27-hydroxycholesterol (27HC) is the most abundant oxysterols and can cross the blood-brain barrier. Interestingly, 27HC has recently been identified as an endogenous selective estrogen receptor modulator (SERM) for both estrogen receptor α and β (ERα/β) . Considering the regulatory effects of brain estrogen/ERα signaling on energy metabolism, we hypothesize that the endogenous SERM 27HC binds with ERα in the arcuate nucleus of hypothalamus (ARH) of brain to modulate energy homeostasis.In supporting this point of view, we found that a single acute intracerebroventricular (ICV) injection of 27HC inhibited food intake in both male and female mice. The reduced food intake was attributed to decreased meal size and increased intermeal intervals. This anorexigenic effect was also associated with the increased c-fos expression in the pro-opiomelanocortin neurons in ARH (POMCARH) . Using brain slice patch-clamp recording, we consistently showed that 27HC dose-dependently actives POMCARH in an ERα-dependent manner, suggesting a mediating role of ERα expressed by POMCARH neurons. Notably, we further revealed that the inhibitory effects of 27HC on food intake were blocked by antagonists for ERα or POMC downstream melanocortin 3/4 receptors. In addition, chemogenetic inhibition of POMCARH neurons also blunted the anorexigenic effects of 27HC in mice. Collectively, these results support a model that 27HC acutely inhibits food intake by acting on ERα to stimulate POMCARH neuronal activity. This 27HC/ERα/POMC signaling pathway may serve as a critical defending mechanism against high-fat diet-induced obesity. Disclosure H. Ye: None. B. Feng: None. D. Dixit: None. Y. He: None. P. Xu: None.

Obesity is a consequence of chronic disruption in energy homeostasis. This phenomenon is controlled by systemic and local signals such as leptin, a nutrient-sensitive signal secreted primarily by the white adipose tissue (WAT) . In contrast, interscapular brown adipose tissue (iBAT) has been shown to express undetectable or very low levels of leptin. In this study, unexpectedly, we observed overnight fasting decreased leptin expression in iBAT, and 2-hour refeeding was able to restore the iBAT leptin levels. This nutritional status-dependent fluctuation suggests a vital role of iBAT leptin in the acute regulation of energy homeostasis. Consistently, we found that mice with leptin selectively overexpressed in the UCP1-positive cells of iBAT (LEP-OEiBAT/UCP1) showed reduced fast-induced food intake. This hypophagia phenotype was associated with increased satiation as reflected by decreased meal numbers and increase postmeal interval. Notably, LEP-OEiBAT/UCP1 selectively increased the mRNA expression of leptin in the iBAT without affecting circulating leptin levels, indicating a possible paracrine role of iBAT leptin. In supporting this point of view, we showed that chemical ablation of sensory nerves (SS) in iBAT significantly increased fast-induced food intake, associated with altered meal frequency. Additionally, we also found that iBAT-specific infusion of leptin increased Stat3 phosphorylation (pStat3) in the upstream iBAT-innervating sensory neurons, suggesting leptin-mediated sensory detection. Notably, the increased pStat3 was associated with neural activation in the arcuate nucleus of the hypothalamus in the brain, and chemical ablation of iBAT SS blunted this stimulation. Our results support a model that feeding-induced iBAT leptin modulates iBAT-specific sensory inputs to the brain to regulate food intake and feeding patterns. Disclosure M.D.Munoz: None. V.C.Torres irizarry: None. P.Xu: None. C.Liew: None. Funding RDK109015A1

The preoptic anterior hypothalamus (POAH) , known as a thermointegrative center, modulates metabolic adaptation in response to temperature change, thus making it relevant for body weight homeostasis. Forkhead transcription factor O1 (FoxO1) plays an important role in mediating effects of leptin and insulin on metabolic homeostasis in the hypothalamus. However, the homeostatic role of FoxO1 in POAH has not been investigated. We found that FoxO1 specific deletion in the POAH neurons (FoxO1POAH-KO) prevented high fat diet-induced obesity (DIO) in female but not male mice. This female-specific protection was associated with increased lean mass, decreased fat mass, and upregulated thermogenesis in adipose tissues. The female FoxO1POAH-KO mice also showed improved insulin sensitivity and increased energy expenditure when exposed at room temperature (22 °C) or cold (6 °C) . Moreover, the FoxO1POAH-KO-induced protection against DIO in females was blunted by ovariectomy (OVX) , while 17β-estradiol supplementation after OVX failed to restore this protection, suggesting an estrogen-independent mechanism. Finally, mice with FoxO1 constitutively activated in the POAH neurons (FoxO1POAH-CA) significantly increased DIO in both sexes, further supporting an essential metabolic role of FoxO1POAH. Together, these findings indicate that FoxO1POAH is a crucial transcription factor that directs and coordinates control of energy balance, thermogenesis, and glucose homeostasis in female mice. Key words: FoxO1, POAH, sex difference. Disclosure P. Luo: None. H. Ye: None. T. Unterman: None. P. Xu: None. Funding P. Xu is supported by National Institutes of Health (R00DK1070 and R01DK123098) , Department of Defense (Innovative Grant W81XWH-19-PRMRP-DA) , and The University of Chicago Diabetes Research and Training Center (The Pilot and Feasibility Award DK020595) .

Systemic insulin sensitivity shows a diurnal rhythm with a peak upon waking. The GABAergic (γ-aminobutyric acid-producing) neurons in the suprachiasmatic nucleus (SCN) (SCNGABA neurons) were reported to control the diurnal rhythm of insulin-mediated suppression of hepatic glucose production in mice in earlier work1. SCNGABA neural firing activity displays a diurnal rhythm, with the intrinsic ionic mechanism underlying this temporal pattern not completely understood. Here we provided evidence supporting a role of the T type voltage-gated calcium ion channel subunit 3.2 (Cav3.2) in SCNGABA neurons in regulating rhythmic neural firing and glucose homeostasis. We found that Cav3.2 global knockout (Cav3.2KO) mice displayed disrupted diurnal rhythm of blood glucose levels. Selective deletion of Cav3.2 in the SCNGABA neurons abolished the oscillatory firing activity of SCNGABA neurons and led to glucose intolerance. Furthermore, our real-time calcium imaging data in freely moving mice showed that SCN GABA neuronal activity displayed a circadian rhythm pattern in WT control mice but not Cav3.2KO mice or mice with Cav3.2 selectively deleted in the SCNGABA neurons. These findings provide insights into how the calcium ion channel regulates the central circadian clock and glucose metabolism, with implications in the extended dawn phenomenon in type 2 diabetes. Keywords: Type 2 diabetes, calcium channel, Cav3.2, GABA neurons, circadian rhythm Reference: 1 Ding, G. et al. REV-ERB in GABAergic neurons controls diurnal hepatic insulin sensitivity. Nature 592, 763-767, doi:10.1038/s41586-021-03358-w (2021) . Disclosure P. Xu: None. W. Zhou: None. Z. Sun: None. Y. He: None. Funding NIH (P20 GM135002)

The influence of gut bacteria on host energy homeostasis is increasingly recognized, but mechanistic links are lacking. The gut microbiota digests and ferments nutrients, which result in short-chain fatty acids (SCFAs) . The body senses these nutrients in large part through free fatty acid receptors 2 (FFA2) and 3 (FFA3) . Accumulating evidence indicates that the gut microbiota/SCFAs interact with the central nervous system (CNS) to regulate brain metabolic function. Consistently, we found that a single acute intracerebroventricular (ICV) injection of acetate (ACE) , propionate (PRO) , or butyrate (BUT) dose-dependently inhibited food intake in an FFA2/3-dependent manner. The reduced food intake induced by ACE, PRO, or BUT was attributed to decreased meal size or increased intermeal interval. These regulatory effects on meal patterns were blunted in FFA2 and FFA3 double-receptor knockout mice, suggesting a mediating role of brain FFA2/3. Interestingly, RNAscope analysis showed that FFA3 but not FFA2 highly expressed in the cerebellar granule neurons. Using brain slice patch-clamp, we consistently showed that PRO or FFA3-selective agonists inhibited these granule neurons. Notably, the hyperpolarization effects of PRO on cerebellar granule neurons were blocked by pertussis toxin (PTX) , a G-protein coupled receptor subunit Gi/o blocker, further supporting an FFA3-Gi/o-mediated inhibition on granule neurons. These results suggest a model that SCFAs inhibit food intake through FFA3 expressed by the cerebellar granule neurons. Key words: SCFA; Brain; FFA3 Disclosure P. Luo: None. P. Xu: None. H. Ye: None. B.T. Layden: None. Y. He: None. V.C. Torres Irizarry: None.

Previously, we found that α-ketoglutaric acid (AKG) stimulates muscle hypertrophy and fat loss through 2-oxoglutarate receptor 1 (OXGR1). Here, we demonstrated the beneficial effects of AKG on glucose homeostasis in a diet-induced obesity (DIO) mouse model, which are independent of OXGR1. We also showed that AKG effectively decreased blood glucose and hepatic gluconeogenesis in DIO mice. By using transcriptomic and liver-specific serpina1e deletion mouse model, we further demonstrated that liver serpina1e is required for the inhibitory effects of AKG on hepatic gluconeogenesis. Mechanistically, we supported that extracellular AKG binds with a purinergic receptor, P2RX4, to initiate the solute carrier family 25 member 11 (SLC25A11)–dependent nucleus translocation of intracellular AKG and subsequently induces demethylation of lysine 27 on histone 3 (H3K27) in the seprina1e promoter region to decrease hepatic gluconeogenesis. Collectively, these findings reveal an unexpected mechanism for control of hepatic gluconeogenesis using circulating AKG as a signal molecule.

Elevations in estrogen (17β-estradiol, E2) are associated with increased alcohol drinking by women and experimentally in rodents. E2 alters the activity of the dopamine system, including the VTA and its projection targets, which plays an important role in binge drinking. A previous study demonstrated that, during high E2 states, VTA neurons in female mice are more sensitive to ethanol excitation. However, the mechanisms responsible for the ability of E2 to enhance ethanol sensitivity of VTA neurons have not been investigated. In this study, we used selective agonists and antagonists to examine the role of ER subtypes (ERα and ERβ) in regulating the ethanol sensitivity of VTA neurons in female mice and found that ERα promotes the enhanced ethanol response of VTA neurons. We also demonstrated that enhancement of ethanol excitation requires the activity of the metabotropic glutamate receptor, mGluR1, which is known to couple with ERα at the plasma membrane. To investigate the behavioral relevance of these findings, we administered lentivirus-expressing short hairpin RNAs targeting either ERα or ERβ into the VTA and found that knockdown of each receptor in the VTA reduced binge-like ethanol drinking in female, but not male, mice. Reducing ERα in the VTA had a more dramatic effect on binge-like drinking than reducing ERβ, consistent with the ability of ERα to alter ethanol sensitivity of VTA neurons. These results provide important insight into sex-specific mechanisms that drive excessive alcohol drinking. SIGNIFICANCE STATEMENT Estrogen has potent effects on the dopamine system and increases the vulnerability of females to develop addiction to substances, such as alcohol. We investigated the mechanisms by which estrogen increases the response of neurons in the VTA to ethanol. We found that activation of the ERα increased the ethanol-induced excitation of VTA neurons. 17β-Estradiol-mediated enhancement of ethanol-induced excitation required the metabotropic glutamate receptor mGluR1. We also demonstrated that ERs in the VTA regulate binge-like alcohol drinking by female, but not male, mice. The influence of ERs on binge drinking in female mice suggests that treatments for alcohol use disorder in women may need to account for this sex difference.

Estrogen receptor–α (ERα) expressed by neurons in the ventrolateral subdivision of the ventromedial hypothalamic nucleus (ERαvlVMH) regulates body weight in females, but the downstream neural circuits mediating this biology remain largely unknown. Here we identified a neural circuit mediating the metabolic effects of ERαvlVMH neurons. We found that selective activation of ERαvlVMH neurons stimulated brown adipose tissue (BAT) thermogenesis, physical activity, and core temperature and that ERαvlVMH neurons provide monosynaptic glutamatergic inputs to 5-hydroxytryptamine (5-HT) neurons in the dorsal raphe nucleus (DRN). Notably, the ERαvlVMH → DRN circuit responds to changes in ambient temperature and nutritional states. We further showed that 5-HTDRN neurons mediate the stimulatory effects of ERαvlVMH neurons on BAT thermogenesis and physical activity and that ERα expressed by DRN-projecting ERαvlVMH neurons is required for the maintenance of energy balance. Together, these findings support a model that ERαvlVMH neurons activate BAT thermogenesis and physical activity through stimulating 5-HTDRN neurons., Description, An estrogen-sensitive neural circuit mediating beneficial metabolic effects of estrogen has been identified.

The human gut microbiota influences obesity, insulin resistance, and the subsequent development of type 2 diabetes (T2D). The gut microbiota digests and ferments nutrients resulting in the production of short-chain fatty acids (SCFAs), which generate various beneficial metabolic effects on energy and glucose homeostasis. However, their roles in the central nervous system (CNS)-mediated outputs on the metabolism have only been minimally studied. Here, we explore what is known and future directions that may be worth exploring in this emerging area. Specifically, we searched studies or data in English by using PubMed, Google Scholar, and the Human Metabolome Database. Studies were filtered by time from 1978 to March 2022. As a result, 195 studies, 53 reviews, 1 website, and 1 book were included. One hundred and sixty-five of 195 studies describe the production and metabolism of SCFAs or the effects of SCFAs on energy homeostasis, glucose balance, and mental diseases through the gut-brain axis or directly by a central pathway. Thirty of 195 studies show that inappropriate metabolism and excessive of SCFAs are metabolically detrimental. Most studies suggest that SCFAs exert beneficial metabolic effects by acting as the energy substrate in the TCA cycle, regulating the hormones related to satiety regulation and insulin secretion, and modulating immune cells and microglia. These functions have been linked with AMPK signaling, GPCRs-dependent pathways, and inhibition of histone deacetylases (HDACs). However, the studies focusing on the central effects of SCFAs are still limited. The mechanisms by which central SCFAs regulate appetite, energy expenditure, and blood glucose during different physiological conditions warrant further investigation.

Objective Cav3.2, a T-type low voltage-activated calcium channel widely expressed throughout the central nervous system, plays a vital role in neuronal excitability and various physiological functions. However, the effects of Cav3.2 on energy homeostasis remain unclear. Here we examined the role of Cav3.2 expressed by hypothalamic GABAergic neurons in the regulation of food intake and body weight in mice and explored the underlying mechanisms. Methods Male congenital Cana1h (the gene coding for Cav3.2) global knockout (Cav3.2KO) mice and their wild type (WT) littermates were first used for metabolic phenotyping studies. Subsequently, with the help of the CRISPR-Cas9 technique, Cav3.2 was selectively deleted from GABAergic neurons in the arcuate nucleus of the hypothalamus (ARH) by specifically overexpressing Cas9 protein and Cav3.2-targeting sgRNAs in ARH Vgat (VgatARH) neurons. These male mutants (Cav3.2KO-VgatARH) were used to determine whether Cav3.2 expressed by VgatARH neurons is required for the proper regulation of energy balance. Finally, we employed electrophysiological patch-clamp recording in ex vivo brain slices to explore the impact of Cav3.2KO on the cellular excitability of VgatARH neurons. Results Male Cav3.2KO mice had significantly lower food intake than their WT littermate controls when fed with either a normal chow diet (NCD) or a high-fat diet (HFD). This hypophagia phenotype was associated with increased energy expenditure and decreased fat mass, lean mass, and total body weight. Additionally, selective deletion of Cav3.2 in VgatARH neurons resulted in similar feeding inhibition and lean phenotype without changing energy expenditure. This data provides an intrinsic mechanism to support the previous finding on ARH non-AgRP GABA neurons in regulating diet-induced obesity. Lastly, we found that naringenin extract, a predominant flavanone found in various fruits and herbs and known to act on Cav3.2, decreased the firing activity of VgatARH neurons and reduced food intake and body weight. These naringenin-induced inhibitions were fully blocked in Cav3.2KO-VgatARH mice. Conclusion Our results identified Cav3.2 expressed by VgatARH neurons as an important intrinsic modulator for food intake and energy homeostasis, which is a potential therapeutic target in the treatment of obesity.

Chronic stress causes dysregulations of mood and energy homeostasis, but the neurocircuitry underlying these alterations remain to be fully elucidated. Here we demonstrate that chronic restraint stress in mice results in hyperactivity of pro-opiomelanocortin neurons in the arcuate nucleus of the hypothalamus (POMCARH neurons) associated with decreased neural activities of dopamine neurons in the ventral tegmental area (DAVTA neurons). We further revealed that POMCARH neurons project to the VTA and provide an inhibitory tone to DAVTA neurons via both direct and indirect neurotransmissions. Finally, we show that photoinhibition of the POMCARH→VTA circuit in mice increases body weight and food intake, and reduces depression-like behaviors and anhedonia in mice exposed to chronic restraint stress. Thus, our results identified a novel neurocircuitry regulating feeding and mood in response to stress.

Nutrient excess, a major driver of obesity, diminishes hypothalamic responses to exogenously administered leptin, a critical hormone of energy balance. Here, we aimed to identify a physiological signal that arises from excess caloric intake and negatively controls hypothalamic leptin action. We found that deficiency of the gastric inhibitory polypeptide receptor (Gipr) for the gut-derived incretin hormone GIP protected against diet-induced neural leptin resistance. Furthermore, a centrally administered antibody that neutralizes GIPR had remarkable antiobesity effects in diet-induced obese mice, including reduced body weight and adiposity, and a decreased hypothalamic level of SOCS3, an inhibitor of leptin actions. In contrast, centrally administered GIP diminished hypothalamic sensitivity to leptin and increased hypothalamic levels of Socs3. Finally, we show that GIP increased the active form of the small GTPase Rap1 in the brain and that its activation was required for the central actions of GIP. Altogether, our results identify GIPR/Rap1 signaling in the brain as a molecular pathway linking overnutrition to the control of neural leptin actions.

Aim Heparin, a widely used antithrombotic drug has many other anticoagulant‐independent physiological functions. Here, we elucidate a novel role of heparin in glucose homeostasis, suggesting an approach for developing heparin‐targeted therapies for diabetes. Methods For serum heparin levels and correlation analysis, 122 volunteer’s plasma, DIO (4 weeks HFD) and db/db mice serums were collected and used for spectrophotometric determination. OGTT, ITT, 2‐NBDG uptake and muscle GLUT4 immunofluorescence were detected in chronic intraperitoneal injection of heparin or heparinase (16 days) and muscle‐specific loss‐of‐function mice. In 293T cells, the binding of insulin to its receptor was detected by fluorescence resonance energy transfer (FRET), Myc‐GLUT4‐mCherry plasmid was used in GLUT4 translocation. In vitro, C2C12 cells as mouse myoblast cells were further verified the effects of heparin on glucose homeostasis through 2‐NBDG uptake, Western blot and co‐immunoprecipitation. Results Serum concentrations of heparin are positively associated with blood glucose levels in humans and are significantly increased in diet‐induced and db/db obesity mouse models. Consistently, a chronic intraperitoneal injection of heparin results in hyperglycaemia, glucose intolerance and insulin resistance. These effects are independent of heparin’s anticoagulant function and associated with decreases in glucose uptake and translocation of glucose transporter type 4 (GLUT4) in skeletal muscle. By using a muscle‐specific loss‐of‐function mouse model, we further demonstrated that muscle GLUT4 is required for the detrimental effects of heparin on glucose homeostasis. Conclusions Heparin reduced insulin binding to its receptor by interacting with insulin and inhibited insulin‐mediated activation of the PI3K/Akt signalling pathway in skeletal muscle, which leads to impaired glucose uptake and hyperglycaemia., Circulating heparin is positively correlated with blood glucose level in humans and increases in diet‐induced obese and type 2 diabetic db/db mice. Chronic intraperitoneal injection of heparin results in hyperglycemia, glucose intolerance, and insulin resistance. Heparin interacts with insulin to inhibit insulin and insulin receptor binding in skeletal muscle, and by doing so, impairs skeletal muscle GLUT4 translocation and glucose uptake.

Sufficient feeding is essential for animals’ survival, which requires a cognitive capability to facilitate food seeking, but the neurobiological processes regulating food seeking are not fully understood. Here we show that stimulation of agouti-related peptide-expressing (AgRP) neurons triggers a long-term depression (LTD) of spontaneous excitatory post-synaptic current (sEPSC) in adjacent pro-opiomelanocortin (POMC) neurons and in most of their distant synaptic targets, including neurons in the paraventricular nucleus of the thalamus (PVT). The AgRP-induced sEPCS LTD can be enhanced by fasting but blunted by satiety signals, e.g. leptin and insulin. Mice subjected to food-seeking tasks develop similar neural plasticity in AgRP-innervated PVT neurons. Further, ablation of the majority of AgRP neurons, or only a subset of AgRP neurons that project to the PVT, impairs animals’ ability to associate spatial and contextual cues with food availability during food seeking. A similar impairment can be also induced by optogenetic inhibition of the AgRP→PVT projections. Together, these results indicate that the AgRP→PVT circuit is necessary for food seeking.

Objective Estrogen protects animals from obesity through estrogen receptor α (ERα), partially by inhibiting overeating in animals fed ad libitum. However, the effects of estrogen on feeding behavior in hungry animals remain unclear. In this study, we examined the roles of 17β-estradiol (E2) and ERα in the regulation of feeding in hungry female animals and explored the underlying mechanisms. Methods Wild-type female mice with surgical depletion of endogenous estrogens were used to examine the effects of E2 supplementation on acute refeeding behavior after starvation. ERα-C451A mutant mice deficient in membrane-bound ERα activity and ERα-AF20 mutant mice lacking ERα transcriptional activity were used to further examine mechanisms underlying acute feeding triggered by either fasting or central glucopenia (induced by intracerebroventricular injections of 2-deoxy-D-glucose). We also used electrophysiology to explore the impact of these ERα mutations on the neural activities of ERα neurons in the hypothalamus. Results In the wild-type female mice, ovariectomy reduced fasting-induced refeeding, which was restored by E2 supplementation. The ERα-C451A mutation, but not the ERα-AF20 mutation, attenuated acute feeding induced by either fasting or central glucopenia. The ERα-C451A mutation consistently impaired the neural responses of hypothalamic ERα neurons to hypoglycemia. Conclusion In addition to previous evidence that estrogen reduces deviations in energy balance by inhibiting eating at a satiated state, our findings demonstrate the unexpected role of E2 that promotes eating in hungry mice, also contributing to the stability of energy homeostasis. This latter effect specifically requires membrane-bound ERα activity., Highlights • Endogenous E2 is required to maintain acute refeeding in hungry female mice after starvation. • Membrane-bound ERα activity in female mice is required for efficient refeeding after starvation. • Membrane-bound ERα activity is required for hypothalamic ERα neurons to respond to hypoglycemia.

Midbrain dopamine (DA) and serotonin (5-HT) neurons regulate motivated behaviors, including feeding, but less is known about how these circuits may interact. In this study, we found that DA neurons in the mouse ventral tegmental area bidirectionally regulate the activity of 5-HT neurons in the dorsal raphe nucleus (DRN), with weaker stimulation causing DRD2-dependent inhibition and overeating, while stronger stimulation causing DRD1-dependent activation and anorexia. Furthermore, in the activity-based anorexia (ABA) paradigm, which is a mouse model mimicking some clinical features of human anorexia nervosa (AN), we observed a DRD2 to DRD1 shift of DA neurotransmission on 5-HT(DRN) neurons, which causes constant activation of these neurons and contributes to AN-like behaviors. Finally, we found that systemic administration of a DRD1 antagonist can prevent anorexia and weight loss in ABA. Our results revealed regulation of feeding behavior by stimulation strength-dependent interactions between DA and 5-HT neurons, which may contribute to the pathophysiology of AN.

While resistance exercise effectively improves overall health in diabetic patients, the underlying biological mechanism by which resistance exercise improves metabolic function and glucose homeostasis remain mostly unknown. Previously, we identified a myometabolite-mediated metabolic pathway that is essential for the beneficial effects of resistance exercise on metabolic function. We found that resistance exercise-induced α-ketoglutaric acid (AKG) stimulates muscle hypertrophy and fat loss through 2-oxoglutarate receptor 1 (OXGR1)-dependent adrenal activation. Here, we provided evidence for the beneficial effects of AKG on glucose homeostasis in a diet-induced obesity (DIO) mouse model, which are independent of OXGR1. We showed that circulating AKG levels are negatively correlated with the fraction of blood glycated hemoglobin (HbA1c) in both humans and mice and significantly decreased in DIO mice. Consistently, pharmacological elevation of AKG effectively decreased body weight, blood glucose, and hepatic gluconeogenesis without changing insulin sensitivity and glucose tolerance in DIO mice. Notably, OXGR1KO blocked the inhibitory effects of AKG on body weight but failed to affect AKG’s suppression on blood glucose and hepatic gluconeogenesis, indicating distinct mechanisms for AKG’s regulation on energy balance and glucose homeostasis. In supporting this view, we showed that serpina1e, a member of protease inhibitor serpins superfamily, mediates the direct inhibitory effects of AKG on gluconeogenesis in both in vitro hepatocytes and liver slice. By using a liver-specific serpina1e deletion mouse model, we further demonstrated that liver serpina1e is required for the inhibitory effects of AKG on hepatic gluconeogenesis and hyperglycemia in DIO mice. Finally, we provided in vitro evidence to support a model in which AKG decreases hepatic gluconeogenesis by targeting trimethylation of lysine 27 on histone 3 (H3K27me3) in seprina1e promoter region. Our studies established an important role of AKG in glucose homeostasis, and identified the AKG-serpina1e pathway as potential therapeutic targets to attenuate hyperglycemia.

Obesity and diabetes have already become the second largest risk factor for cardiovascular disease. During the last decade, remarkable advances have been made in understanding the human genome’s contribution to glucose homeostasis disorders and obesity. A few studies on rare mutations of candidate genes provide potential genetic targets for the treatment of diabetes and obesity. In this review, we discussed the detailed findings of these studies and the possible causalities between specific genetic variations and dysfunctions in energy or glucose homeostasis. We are optimistic that novel therapeutic strategies targeting these specific mutants for treating and preventing diabetes and obesity will be developed in the near future. Studies on rare genetic mutation-caused obesity or diabetes have identified potential genetic targets to decrease body weight or reduce the risk of diabetes. Rare mutations observed in lipodystrophy, obese, or diabetic human patients are promising targets in the treatment of diabetes and obesity.

SUMMARY The neuroendocrine system coordinates metabolic and behavioral adaptations to fasting, including reducing energy expenditure, promoting counterregulation, and suppressing satiation and anxiety to engage refeeding. Here, we show that steroid receptor coactivator-2 (SRC-2) in pro-opiomelanocortin (POMC) neurons is a key regulator of all these responses to fasting. POMC-specific deletion of SRC-2 enhances the basal excitability of POMC neurons; mutant mice fail to efficiently suppress energy expenditure during food deprivation. SRC-2 deficiency blunts electric responses of POMC neurons to glucose fluctuations, causing impaired counterregulation. When food becomes available, these mutant mice show insufficient refeeding associated with enhanced satiation and discoordination of anxiety and food-seeking behavior. SRC-2 coactivates Forkhead box protein O1 (FoxO1) to suppress POMC gene expression. POMC-specific deletion of SRC-2 protects mice from weight gain induced by an obesogenic diet feeding and/or FoxO1 overexpression. Collectively, we identify SRC-2 as a key molecule that coordinates multifaceted adaptive responses to food shortage., In brief Yang et al. demonstrate that SRC-2 in POMC neurons coordinates multifaceted adaptive responses to food shortage, including reducing energy expenditure, promoting counterregulation and suppressing satiation and anxiety to engage refeeding. These effects are mediated by SRC-2 functions to regulate POMC gene expression and modulate POMC neuron activities., Graphical Abstract

Adipocytes arise from distinct progenitor populations during developmental and adult stages but little is known about how developmental progenitors differ from adult progenitors. Here, we investigate the role of platelet-derived growth factor receptor alpha (PDGFRα) in the divergent regulation of the two different adipose progenitor cells (APCs). Using in vivo adipose lineage tracking and deletion mouse models, we found that developmental PDGFRα+ cells are adipogenic and differentiated into mature adipocytes, and the deletion of Pdgfra in developmental adipose lineage disrupted white adipose tissue (WAT) formation. Interestingly, adult PDGFRα+ cells do not significantly contribute to adult adipogenesis, and deleting Pdgfra in adult adipose lineage did not affect WAT homeostasis. Mechanistically, embryonic APCs require PDGFRα for fate maintenance, and without PDGFRα, they underwent fate change from adipogenic to fibrotic lineage. Collectively, our findings indicate that PDGFRα+ cells and Pdgfra gene itself are differentially required for WAT development and adult WAT homeostasis.

Compelling evidence has demonstrated that estradiol and estrogen receptor α/β (ERα/β) play key roles in the central regulation of energy balance and glucose homeostasis. Our previous research showed that ERα in the medial amygdala (ERαMeA) mediates estrogenic actions to stimulate physical activity, therefore promotes energy expenditure and prevents diet-induced obesity (DIO). Interestingly, another estrogen receptor, ERβ, is also highly expressed in the MeA. To test the metabolic functions of ERβMeA, we generated a mouse model with ERβ selectively deleted in the MeA (ERβKOMeA) during adulthood using AAV virus-mediated Cre-Lox site-specific recombination. We found that, when fed on a high-fat diet but not on a normal chow diet, compared to the control mice, both male and female ERβKOMeA mice showed decreased body weight gain and fat deposition, which were associated with increased energy expenditure. We further showed that half of the ERαMeA neurons co-express ERβ. In these ERα&β co-expressing MeA neurons, ERα agonist propyl pyrazole trio (PPT) induced ERα-dependent depolarization, while ERβ agonist diarypropionitrile (DPN) induced ERβ-dependent hyperpolarization. Finally, we showed that chemogenetic activation of ERαMeA or ERβMeA neurons induces a similar increase in energy expenditure. Collectively, our results support a model that, estrogen acts on ERα/βMeA neurons to provide bidirectional regulation of body weight and resistance to DIO, whereas activating ERαMeA decreases and activating ERβMeA increases body weight. Disclosure H. Ye: None. Y. He: None. L. Ibrahimi: None. S. Schaul: None. P. Luo: None. L. Carrillo-Sáenz: None. P. Lai: None. N. Patel: None. M. Kota: None. D. Dixit: None. P. Xu: None. Funding National Institutes of Health (5R00DK107008-04)

The conversion of skeletal muscle fiber from fast twitch to slow‐twitch is important for sustained and tonic contractile events, maintenance of energy homeostasis, and the alleviation of fatigue. Skeletal muscle remodeling is effectively induced by endurance or aerobic exercise, which also generates several tricarboxylic acid (TCA) cycle intermediates, including succinate. However, whether succinate regulates muscle fiber‐type transitions remains unclear. Here, we found that dietary succinate supplementation increased endurance exercise ability, myosin heavy chain I expression, aerobic enzyme activity, oxygen consumption, and mitochondrial biogenesis in mouse skeletal muscle. By contrast, succinate decreased lactate dehydrogenase activity, lactate production, and myosin heavy chain IIb expression. Further, by using pharmacological or genetic loss‐of‐function models generated by phospholipase Cβ antagonists, SUNCR1 global knockout, or SUNCR1 gastrocnemius‐specific knockdown, we found that the effects of succinate on skeletal muscle fiber‐type remodeling are mediated by SUNCR1 and its downstream calcium/NFAT signaling pathway. In summary, our results demonstrate succinate induces transition of skeletal muscle fiber via SUNCR1 signaling pathway. These findings suggest the potential beneficial use of succinate‐based compounds in both athletic and sedentary populations.

Brain glucose-sensing neurons detect glucose fluctuations and prevent severe hypoglycemia, but mechanisms mediating functions of these glucose-sensing neurons are unclear. Here we report that estrogen receptor-α (ERα)-expressing neurons in the ventrolateral subdivision of the ventromedial hypothalamic nucleus (vlVMH) can sense glucose fluctuations, being glucose-inhibited neurons (GI-ERαvlVMH) or glucose-excited neurons (GE-ERαvlVMH). Hypoglycemia activates GI-ERαvlVMH neurons via the anoctamin 4 channel, and inhibits GE-ERαvlVMH neurons through opening the ATP-sensitive potassium channel. Further, we show that GI-ERαvlVMH neurons preferentially project to the medioposterior arcuate nucleus of the hypothalamus (mpARH) and GE-ERαvlVMH neurons preferentially project to the dorsal Raphe nuclei (DRN). Activation of ERαvlVMH to mpARH circuit and inhibition of ERαvlVMH to DRN circuit both increase blood glucose. Thus, our results indicate that ERαvlVMH neurons detect glucose fluctuations and prevent severe hypoglycemia in mice., Glucose-sensing neurons are found in the ventromedial hypothalamic nucleus (VMH). Here the authors identify the role of estrogen receptor-α expressing neurons in the ventrolateral subdivision of the VMH in sensing hypoglycemia.