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The hypothalamic arcuate–median eminence (Arc-ME) complex is rich with functionally distinct cell types, a fraction of which have been characterized. The authors profile 20,921 individual cells by single-cell RNA-seq, identifying 50 Arc-ME cell types and their markers, determining each's response to energy status and implicating two neuron populations in the genetic control of obesity. The hypothalamic arcuate–median eminence complex (Arc-ME) controls energy balance, fertility and growth through molecularly distinct cell types, many of which remain unknown. To catalog cell types in an unbiased way, we profiled gene expression in 20,921 individual cells in and around the adult mouse Arc-ME using Drop-seq. We identify 50 transcriptionally distinct Arc-ME cell populations, including a rare tanycyte population at the Arc-ME diffusion barrier, a new leptin-sensing neuron population, multiple agouti-related peptide (AgRP) and pro-opiomelanocortin (POMC) subtypes, and an orexigenic somatostatin neuron population. We extended Drop-seq to detect dynamic expression changes across relevant physiological perturbations, revealing cell type–specific responses to energy status, including distinct responses in AgRP and POMC neuron subtypes. Finally, integrating our data with human genome-wide association study data implicates two previously unknown neuron populations in the genetic control of obesity. This resource will accelerate biological discovery by providing insights into molecular and cell type diversity from which function can be inferred.

Hypothalamic pro-opiomelanocortin (POMC) neurons promote satiety. Cannabinoid receptor 1 (CB 1 R) is critical for the central regulation of food intake. Here we test whether CB 1 R-controlled feeding in sated mice is paralleled by decreased activity of POMC neurons. We show that chemical promotion of CB 1 R activity increases feeding, and notably, CB 1 R activation also promotes neuronal activity of POMC cells. This paradoxical increase in POMC activity was crucial for CB 1 R-induced feeding, because designer-receptors-exclusively-activated-by-designer-drugs (DREADD)-mediated inhibition of POMC neurons diminishes, whereas DREADD-mediated activation of POMC neurons enhances CB 1 R-driven feeding. The Pomc gene encodes both the anorexigenic peptide α-melanocyte-stimulating hormone, and the opioid peptide β-endorphin. CB 1 R activation selectively increases β-endorphin but not α-melanocyte-stimulating hormone release in the hypothalamus, and systemic or hypothalamic administration of the opioid receptor antagonist naloxone blocks acute CB 1 R-induced feeding. These processes involve mitochondrial adaptations that, when blocked, abolish CB 1 R-induced cellular responses and feeding. Together, these results uncover a previously unsuspected role of POMC neurons in the promotion of feeding by cannabinoids. Cannabinoid-induced feeding signals are shown to enhance pro-opiomelanocortin (POMC) neuronal activity in mice, causing an enhancement of β-endorphin release, which is crucial in causing this cannabinoid-induced response; these results uncover an overlooked role of hypothalamic POMC neurons in the promotion of feeding by cannabinoids. Complex effects of cannabinoids on feeding Previous work has established a role for hypothalamic pro-opiomelanocortin (POMC) neurones in reducing feeding due to satiety, suggesting that signals promoting feeding may reduce POMC neuronal activity. Tamas Horvath and colleagues have tested this idea and find that, surprisingly, cannabinoid feeding signals enhance POMC neuronal activity. This paradoxical POMC neuronal activation is indispensable for appropriate promotion of feeding triggered by cannabinoid receptor 1 activation in the state of satiety. The authors conclude that the overall effect of cannabinoids on feeding may be driven by both pre- and post-synaptic effects — possibly independently from one another — and that it is their temporal synchrony that brings about the overall behavioural changes.

Excessive adiposity raises blood pressure and accounts for 65–75% of primary hypertension, which is a major driver of cardiovascular and kidney diseases. In obesity, abnormal kidney function and associated increases in tubular sodium reabsorption initiate hypertension, which is often mild before the development of target organ injury. Factors that contribute to increased sodium reabsorption in obesity include kidney compression by visceral, perirenal and renal sinus fat; increased renal sympathetic nerve activity (RSNA); increased levels of anti-natriuretic hormones, such as angiotensin II and aldosterone; and adipokines, particularly leptin. The renal and neurohormonal pathways of obesity and hypertension are intertwined. For example, leptin increases RSNA by stimulating the central nervous system proopiomelanocortin–melanocortin 4 receptor pathway, and kidney compression and RSNA contribute to renin–angiotensin–aldosterone system activation. Glucocorticoids and/or oxidative stress may also contribute to mineralocorticoid receptor activation in obesity. Prolonged obesity and progressive renal injury often lead to the development of treatment-resistant hypertension. Patient management therefore often requires multiple antihypertensive drugs and concurrent treatment of dyslipidaemia, insulin resistance, diabetes and inflammation. If more effective strategies for the prevention and control of obesity are not developed, cardiorenal, metabolic and other obesity-associated diseases could overwhelm health-care systems in the future.Hypertension is one of the most common comorbid conditions that is associated with obesity. Here, the authors discuss the complex interactions between renal, hormonal and nervous system factors that link excess adiposity with elevated blood pressure.

Aponte et al . show that optogenetic activation of a population of hypothalamic neurons expressing agouti-related peptide (AGRP) is sufficient to evoke voracious feeding behavior in mice. This feeding was not dependent on suppressing the activity of anorexigenic pro-opiomelanocortin–expressing neurons, suggesting that AGRP neurons directly engage feeding circuits. Two intermingled hypothalamic neuron populations specified by expression of agouti-related peptide (AGRP) or pro-opiomelanocortin (POMC) positively and negatively influence feeding behavior, respectively, possibly by reciprocally regulating downstream melanocortin receptors. However, the sufficiency of these neurons to control behavior and the relationship of their activity to the magnitude and dynamics of feeding are unknown. To measure this, we used channelrhodopsin-2 for cell type–specific photostimulation. Activation of only 800 AGRP neurons in mice evoked voracious feeding within minutes. The behavioral response increased with photoexcitable neuron number, photostimulation frequency and stimulus duration. Conversely, POMC neuron stimulation reduced food intake and body weight, which required melanocortin receptor signaling. However, AGRP neuron–mediated feeding was not dependent on suppressing this melanocortin pathway, indicating that AGRP neurons directly engage feeding circuits. Furthermore, feeding was evoked selectively over drinking without training or prior photostimulus exposure, which suggests that AGRP neurons serve a dedicated role coordinating this complex behavior.

Hunger-promoting AgRP neurons and satiety-promoting POMC neurons in the arcuate nucleus mediate homeostatic regulation of hunger. Yet a rapidly acting satiety component analogous to rapidly hunger-promoting AgRP neurons has been missing. The authors identify this missing satiety signal and show that it is carried by a novel subset of arcuate glutamatergic neurons. Arcuate nucleus (ARC) neurons sense the fed or fasted state and regulate hunger. Agouti-related protein (AgRP) neurons in the ARC (ARC AgRP neurons) are stimulated by fasting and, once activated, they rapidly (within minutes) drive hunger. Pro-opiomelanocortin (ARC POMC ) neurons are viewed as the counterpoint to ARC AgRP neurons. They are regulated in an opposite fashion and decrease hunger. However, unlike ARC AgRP neurons, ARC POMC neurons are extremely slow in affecting hunger (many hours). Thus, a temporally analogous, rapid ARC satiety pathway does not exist or is presently unidentified. Here we show that glutamate-releasing ARC neurons expressing oxytocin receptor, unlike ARC POMC neurons, rapidly cause satiety when chemo- or optogenetically manipulated. These glutamatergic ARC projections synaptically converge with GABAergic ARC AgRP projections on melanocortin-4 receptor (MC4R)-expressing satiety neurons in the paraventricular hypothalamus (PVH MC4R neurons). Transmission across the ARC Glutamatergic →PVH MC4R synapse is potentiated by the ARC POMC neuron-derived MC4R agonist, α-melanocyte stimulating hormone (α-MSH). This excitatory ARC→PVH satiety circuit, and its modulation by α-MSH, provides insight into regulation of hunger and satiety.

Mutations in the leptin gene ( ob ) result in a metabolic disorder that includes severe obesity 1 , and defects in thermogenesis 2 and lipolysis 3 , both of which are adipose tissue functions regulated by the sympathetic nervous system. However, the basis of these sympathetic-associated abnormalities remains unclear. Furthermore, chronic leptin administration reverses these abnormalities in adipose tissue, but the underlying mechanism remains to be discovered. Here we report that ob/ob mice, as well as leptin-resistant diet-induced obese mice, show significant reductions of sympathetic innervation of subcutaneous white and brown adipose tissue. Chronic leptin treatment of ob/ob mice restores adipose tissue sympathetic innervation, which in turn is necessary to correct the associated functional defects. The effects of leptin on innervation are mediated via agouti-related peptide and pro-opiomelanocortin neurons in the hypothalamic arcuate nucleus. Deletion of the gene encoding the leptin receptor in either population leads to reduced innervation in fat. These agouti-related peptide and pro-opiomelanocortin neurons act via brain-derived neurotropic factor-expressing neurons in the paraventricular nucleus of the hypothalamus (BDNF PVH ). Deletion of BDNF PVH blunts the effects of leptin on innervation. These data show that leptin signalling regulates the plasticity of sympathetic architecture of adipose tissue via a top-down neural pathway that is crucial for energy homeostasis. The authors show that leptin signalling regulates the plasticity of sympathetic architecture of adipose tissue via a top-down neural pathway that is crucial for energy homeostasis.

Liraglutide is a glucagon-like peptide-1 (GLP-1) analog marketed for the treatment of type 2 diabetes. Besides lowering blood glucose, liraglutide also reduces body weight. It is not fully understood how liraglutide induces weight loss or to what degree liraglutide acts directly in the brain. Here, we determined that liraglutide does not activate GLP-1-producing neurons in the hindbrain, and liraglutide-dependent body weight reduction in rats was independent of GLP-1 receptors (GLP-1Rs) in the vagus nerve, area postrema, and paraventricular nucleus. Peripheral injection of fluorescently labeled liraglutide in mice revealed the presence of the drug in the circumventricular organs. Moreover, labeled liraglutide bound neurons within the arcuate nucleus (ARC) and other discrete sites in the hypothalamus. GLP-1R was necessary for liraglutide uptake in the brain, as liraglutide binding was not seen in Glp1r(-/-) mice. In the ARC, liraglutide was internalized in neurons expressing proopiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART). Electrophysiological measurements of murine brain slices revealed that GLP-1 directly stimulates POMC/CART neurons and indirectly inhibits neurotransmission in neurons expressing neuropeptide Y (NPY) and agouti-related peptide (AgRP) via GABA-dependent signaling. Collectively, our findings indicate that the GLP-1R on POMC/CART-expressing ARC neurons likely mediates liraglutide-induced weight loss.

Parabens are preservatives widely used in consumer products including cosmetics and food. Whether low-dose paraben exposure may cause adverse health effects has been discussed controversially in recent years. Here we investigate the effect of prenatal paraben exposure on childhood overweight by combining epidemiological data from a mother–child cohort with experimental approaches. Mothers reporting the use of paraben-containing cosmetic products have elevated urinary paraben concentrations. For butyl paraben (BuP) a positive association is observed to overweight within the first eight years of life with a stronger trend in girls. Consistently, maternal BuP exposure of mice induces a higher food intake and weight gain in female offspring. The effect is accompanied by an epigenetic modification in the neuronal Pro-opiomelanocortin (POMC) enhancer 1 leading to a reduced hypothalamic POMC expression. Here we report that maternal paraben exposure may contribute to childhood overweight development by altered POMC-mediated neuronal appetite regulation. Parabens are preservatives widely used in consumer products including cosmetics and food. Here the authors demonstrate that maternal paraben exposure may contribute to childhood overweight development by an altered neuronal appetite regulation.

Insulin-independent glucose disposal (referred to as glucose effectiveness [GE]) is crucial for glucose homeostasis and, until recently, was thought to be invariable. However, GE is reduced in type 2 diabetes and markedly decreased in leptin-deficient ob/ob mice. Strategies aimed at increasing GE should therefore be capable of improving glucose tolerance in these animals. The gut-derived hormone FGF19 has previously been shown to exert potent antidiabetic effects in ob/ob mice. In ob/ob mice, we found that systemic FGF19 administration improved glucose tolerance through its action in the brain and that a single, low-dose i.c.v. injection of FGF19 dramatically improved glucose intolerance within 2 hours. Minimal model analysis of glucose and insulin data obtained during a frequently sampled i.v. glucose tolerance test showed that the antidiabetic effect of i.c.v. FGF19 was solely due to increased GE and not to changes of either insulin secretion or insulin sensitivity. The mechanism underlying this effect appears to involve increased metabolism of glucose to lactate. Together, these findings implicate the brain in the antidiabetic action of systemic FGF19 and establish the brain’s capacity to rapidly, potently, and selectively increase insulin-independent glucose disposal.

Glycolysis-derived lactate was identified as substrate for histone lactylation, which has been regarded as a significant role in transcriptional regulation in many tissues. However, the role of histone lactylation in the metabolic center, the hypothalamus, is still unknown. Here, we show that hypothalamic pro-opiomelanocortin (POMC) neuron-specific deletion of family with sequence similarity 172, member A (Fam172a) can increase histone lactylation and protect mice against diet-induced obesity (DIO) and related metabolic disorders. Conversely, overexpression of Fam172a in POMC neurons led to an obesity-like phenotype. Using RNA-seq and CUT&Tag chromatin profiling analyzes, we find that knockdown of Fam172a activates the glycolytic process and increases peptidylglycine α-amidating monooxygenase (PAM), which affects the synthesis of α-MSH, via H4K12la (histone lactylation). In addition, pharmacological inhibition of lactate production clearly abrogates the anti-obesity effect of PFKO ( POMC-Cre, Fam172a loxP/loxP , POMC neurons Fam172a knockout). These findings highlight the importance of Fam172a and lactate in the development of obesity and our results mainly concern male mice. Glycolysis-derived lactate was identified as substrate for histone lactylation which has been reported to play a significant role in transcriptional regulation. However, it’s role in the hypothalamus is still unknown. Here, the authors show the importance of Fam172a and lactate in the development of obesity and related metabolic disorders