Estrogen receptor–α (ERα) expressed by neurons in the ventrolateral subdivision of the ventromedial hypothalamic nucleus (ERα ^vlVMH ) 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 ERα ^vlVMH neurons. We found that selective activation of ERα ^vlVMH neurons stimulated brown adipose tissue (BAT) thermogenesis, physical activity, and core temperature and that ERα ^vlVMH neurons provide monosynaptic glutamatergic inputs to 5-hydroxytryptamine (5-HT) neurons in the dorsal raphe nucleus (DRN). Notably, the ERα ^vlVMH → DRN circuit responds to changes in ambient temperature and nutritional states. We further showed that 5-HT ^DRN neurons mediate the stimulatory effects of ERα ^vlVMH neurons on BAT thermogenesis and physical activity and that ERα expressed by DRN-projecting ERα ^vlVMH neurons is required for the maintenance of energy balance. Together, these findings support a model that ERα ^vlVMH neurons activate BAT thermogenesis and physical activity through stimulating 5-HT ^DRN neurons.

Thymol is a major component of thyme, and it has been reported that thymol administration reduces body weight, plasma insulin and blood glucose in type-2 diabetes. Skeletal muscle is the most important metabolism organs in the body; however, to date, there is no report on the effect of thymol on skeletal muscle. Our goal was to determine whether thymol has an effect on the different types of skeletal muscle fibers and their metabolism characteristics. Hence, we performed in vivo and in vitro experiments. In vivo, SD rats (4 weeks old) were fed with different concentrations of thymol for 4 weeks, and in vitro C2C12 myotubes were directly treated with thymol for 2 days. The rats fed with 0.025% thymol showed a significantly lower body weight, subcutaneous white adipose tissue index and gastrocnemius muscle index (P < 0.05), while their proportion of brown adipose tissue significantly increased (P < 0.05). The protein and mRNA expression of MyHC I and MyHC IIa in the gastrocnemius muscle of the rats significantly increased (P < 0.05), while the protein level of MyHC II and mRNA expression of MyHC IIb decreased (P < 0.05). Furthermore, 0.025% thymol supplement significantly reduced (P < 0.05) the activity of lactate dehydrogenase (LDH) in the gastrocnemius muscle of the rats, but their succinate dehydrogenase (SDH) and hexokinase (HK) activities increased (P < 0.05). Also, the expression of the fatty acid oxidation-related genes in the gastrocnemius muscle of the rats decreased with the thymol supplement (P < 0.05). In vitro, similar results were obtained. Furthermore, the Ca²⁺-calcineurin-NFAT pathway, which is an important pathway to regulate the transformation of skeletal muscle fiber type, was studied. We found that the effects of thymol on the myosin heavy chain isoforms, genes related to metabolism and the activation of the Ca²⁺-calcineurin-NFAT pathway were all reversed by a Ca²⁺ chelator (P < 0.05). Thus, thymol can promote the oxidative metabolism and fiber type switch in skeletal muscle, and the Ca²⁺-calcineurin-NFAT pathway plays an important role in it.

Oxysterols are metabolites of cholesterol that regulate cholesterol homeostasis. Among these, the most abundant oxysterol is 27-hydroxycholesterol (27HC), which can cross the blood-brain barrier. Because 27HC functions as an endogenous selective estrogen receptor modulator, we hypothesize that 27HC binds to the estrogen receptor α (ERα) in the brain to regulate energy balance. Supporting this view, we found that delivering 27HC to the brain reduced food intake and activated proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (POMC^ARH) in an ERα-dependent manner. In addition, we observed that inhibiting brain ERα, deleting ERα in POMC neurons, or chemogenetic inhibition of POMC^ARHneurons blocked the anorexigenic effects of 27HC. Mechanistically, we further revealed that 27HC stimulates POMC^ARHneurons by inhibiting the small conductance of the calcium-activated potassium (SK) channel. Together, our findings suggest that 27HC, through its interaction with ERα and modulation of the SK channel, inhibits food intake as a negative feedback mechanism against a surge in circulating cholesterol.

Introduction: Ginseng polysaccharide (GPS, same as Panax polysaccharide) is a kind of polysaccharide extracted from ginseng. It has been reported that GPS has the ability to activate innate immunity, regulates blood sugar balance, and improves antioxidant capacity, but the effect on feeding behavior and its mechanism remains unclear.Method: To investigate the possible effect of GPS on feeding behavior of animals, mice were supplied with GPS in water, and food intake, hedonic feeding behavior, anxiety‐like behavior, expression of appetite‐regulation peptides in the central nervous system and glucose‐related hormone levels in the serum of mice were measured.Results: Ginseng polysaccharide significantly increased the average daily food intake in mice and promoted hedonic eating behavior. Meanwhile, the levels of serum glucose and glucagon were significantly reduced by GPS, and GPS promoted hypothalamic neuropeptide Y expression, inhibited proopiomelanocortin (POMC) expression, and reduced dopamine D1 receptor (DRD1) levels in the midbrain. We also found that the anxiety level of mice was significantly lower after GPS intake. In conclusion, oral supplementation with GPS promoted food intake in mice, most likely through the regulation of circulating glucose levels.

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. 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. By using 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 (Vgat^ARH) neurons. These male mutants (Cav3.2KO-Vgat^ARH) were used to determine whether Cav3.2 expressed by Vgat^ARH neurons is required for the proper regulation of energy balance. Subsequently, we used an electrophysiological patch-clamp recording in ex vivo brain slices to explore the impact of Cav3.2KO on the cellular excitability of Vgat^ARH neurons. 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. Selective deletion of Cav3.2 in Vgat^ARH neurons resulted in similar feeding inhibition and lean phenotype without changing energy expenditure. These 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 Vgat^ARH neurons and reduced food intake and body weight. These naringenin-induced inhibitions were fully blocked in Cav3.2KO-Vgat^ARH mice. Our results identified Cav3.2 expressed by Vgat^ARH neurons as an essential intrinsic modulator for food intake and energy homeostasis, which is a potential therapeutic target in the treatment of obesity.