Probes for INS

Neuropeptide FF (NPFF) group peptides belong to the evolutionary conserved RF-amide peptide family. While they have been assigned a role as pain modulators, their roles in other aspects of physiology have received much less attention. NPFF peptides and their receptor NPFFR2 have strong and localized expression within the dorsal vagal complex that has emerged as the key centre for regulating glucose homeostasis. Therefore, we investigated the role of the NPFF system in the control of glucose metabolism and the histochemical and molecular identities of NPFF and NPFFR2 neurons.We examined glucose metabolism in Npff-/- and wild type (WT) mice using intraperitoneal (i.p.) glucose tolerance and insulin tolerance tests. Body composition and glucose tolerance was further examined in mice after 1-week and 3-week of high-fat diet (HFD). Using RNAScope double ISH, we investigated the neurochemical identity of NPFF and NPFFR2 neurons in the caudal brainstem, and the expression of receptors for peripheral factors in NPFF neurons.Lack of NPFF signalling in mice leads to improved glucose tolerance without significant impact on insulin excursion after the i.p. glucose challenge. In response to an i.p. bolus of insulin, Npff-/- mice have lower glucose excursions than WT mice, indicating an enhanced insulin action. Moreover, while HFD has rapid and potent detrimental effects on glucose tolerance, this diet-induced glucose intolerance is ameliorated in mice lacking NPFF signalling. This occurs in the absence of any significant impact of NPFF deletion on lean or fat masses, suggesting a direct effect of NPFF signalling on glucose metabolism. We further reveal that NPFF neurons in the subpostrema area (SubP) co-express receptors for peripheral factors involved in glucose homeostasis regulation such as insulin and GLP1. Furthermore, Npffr2 is expressed in the glutamatergic NPFF neurons in the SubP, and in cholinergic neurons of the dorsal motor nucleus of the vagus (DMV), indicating that central NPFF signalling is likely modulating vagal output to innervated peripheral tissues including those important for glucose metabolic control.NPFF signalling plays an important role in the regulation of glucose metabolism. NPFF neurons in the SubP are likely to receive peripheral signals and mediate the control of whole-body glucose homeostasis via centrally vagal pathways. Targeting NPFF and NPFFR2 signalling may provide a new avenue for treating type 2 diabetes and obesity.

Sarcopenia and frailty are urgent socio-economic problems worldwide. Here we demonstrate a functional connection between the lateral hypothalamus (LH) and skeletal muscle through Slc12a8, a recently identified nicotinamide mononucleotide transporter, and its relationship to sarcopenia and frailty. Slc12a8-expressing cells are mainly localized in the LH. LH-specific knockdown of Slc12a8 in young mice decreases activity-dependent energy and carbohydrate expenditure and skeletal muscle functions, including muscle mass, muscle force, intramuscular glycolysis, and protein synthesis. LH-specific Slc12a8 knockdown also decreases sympathetic nerve signals at neuromuscular junctions and β2-adrenergic receptors in skeletal muscle, indicating the importance of the LH-sympathetic nerve-β2-adrenergic receptor axis. LH-specific overexpression of Slc12a8 in aged mice significantly ameliorates age-associated decreases in energy expenditure and skeletal muscle functions. Our results highlight an important role of Slc12a8 in the LH for regulation of whole-body metabolism and skeletal muscle functions and provide insights into the pathogenesis of sarcopenia and frailty during aging.

Homeostatic thermogenesis is an essential protective feature of endotherms. However, the specific neuronal types involved in cold-induced thermogenesis remain largely unknown. Using functional magnetic resonance imaging and in situ hybridization, we screened for cold-sensitive neurons and found preprodynorphin (PDYN)-expressing cells in the dorsal medial region of the ventromedial hypothalamus (dmVMH) to be a candidate. Subsequent in vivo calcium recording showed that cold temperature activates dmVMHPdyn neurons, whereas hot temperature suppresses them. In addition, optogenetic activation of dmVMHPdyn neurons increases the brown adipose tissue and core body temperature, heart rate, and blood pressure, whereas optogenetic inhibition shows opposite effects, supporting their role in homeostatic thermogenesis. Furthermore, we found that dmVMHPdyn neurons are linked to known thermoregulatory circuits. Importantly, dmVMHPdyn neurons also show activation during mouse social interaction, and optogenetic inhibition suppresses social interaction and associated hyperthermia. Together, our study describes dual functions of dmVMHPdyn neurons that allow coordinated regulation of body temperature and social behaviors.

Calorie-rich diets induce hyperphagia and promote obesity, although the underlying mechanisms remain poorly defined. We find that short-term high-fat-diet (HFD) feeding of mice activates prepronociceptin (PNOC)-expressing neurons in the arcuate nucleus of the hypothalamus (ARC). PNOCARC neurons represent a previously unrecognized GABAergic population of ARC neurons distinct from well-defined feeding regulatory AgRP or POMC neurons. PNOCARC neurons arborize densely in the ARC and provide inhibitory synaptic input to nearby anorexigenic POMC neurons. Optogenetic activation of PNOCARC neurons in the ARC and their projections to the bed nucleus of the stria terminalis promotes feeding. Selective ablation of these cells promotes the activation of POMC neurons upon HFD exposure, reduces feeding, and protects from obesity, but it does not affect food intake or body weight under normal chow consumption. We characterize PNOCARC neurons as a novel ARC neuron population activated upon palatable food consumption to promote hyperphagia

Metabolic health depends on the brain's ability to control food intake and nutrient use versus storage, processes that require peripheral signals such as the adipocyte-derived hormone, leptin, to cross brain barriers and mobilize regulatory circuits. We have previously shown that hypothalamic tanycytes shuttle leptin into the brain to reach target neurons. Here, using multiple complementary models, we show that tanycytes express functional leptin receptor (LepR), respond to leptin by triggering Ca2+ waves and target protein phosphorylation, and that their transcytotic transport of leptin requires the activation of a LepR-EGFR complex by leptin and EGF sequentially. Selective deletion of LepR in tanycytes blocks leptin entry into the brain, inducing not only increased food intake and lipogenesis but also glucose intolerance through attenuated insulin secretion by pancreatic β-cells, possibly via altered sympathetic nervous tone. Tanycytic LepRb-EGFR-mediated transport of leptin could thus be crucial to the pathophysiology of diabetes in addition to obesity, with therapeutic implications.