Glucagon directly interacts with vagal afferent nodose ganglion neurons to induce Ca(2+) signaling via glucagon receptors.

Glucagon is released from the pancreatic islets postprandially and under hypoglycemic and cold conditions, and regulates glucose metabolism, feeding, energy expenditure and heat production, the functions partly controlled by the brain. Peripheral glucagon could signal to the brain via passing through the blood-brain barrier and/or acting on the vagal afferent. However, the latter remains to be determined. The present study aimed to clarify whether glucagon directly interacts with the nodose ganglion (NG) neurons of vagal afferent nerves in mice. In vivo study showed that intraperitoneal injection of glucagon induced phosphorylation of extracellular signal regulated kinase 1 and 2 (ERK1/2), cellular activation makers, in NG neurons. In fura-2 microfluorometric studies, glucagon increased cytosolic Ca(2+) concentration ([Ca(2+)]i) in single NG neurons. The glucagon-induced [Ca(2+)]i increases were suppressed by a glucagon receptor antagonist, des-His(1)-[Glu(9)]-Glucagon (1-29) amide, and the glucagon receptor mRNA was expressed in NG neurons. The majority of glucagon-responsive NG neurons exhibited [Ca(2+)]i responses to insulin and cholecystokinin-8, the hormones that are secreted postprandially and implicated in satiety. These results demonstrate that glucagon, by interacting with the glucagon receptor, directly activates vagal afferent nerves, possibly being relayed to the signaling to the brain and formation of satiety.

The genetic analysis of eight families with hemophilia B in Mongolia: Identification of two novel mutation.

BACKGROUND: This study aimed to conduct molecular diagnostics among individuals with hemophilia B (HB) and carriers of hemophilia in Mongolia. METHODS: Eight patients (six severe, two mild) with HB and their 12 female relatives were enrolled from eight families. Sanger sequence was performed for mutation identification. The questionnaire survey was conducted to evaluate carrier symptoms in female relatives. RESULTS: Two families had a history of HB. A total of five different variants (c.223C > T; c.344A > G; c.464G > C; c.187_188del; and c.1314_1314delA) were identified in six patients with severe HB. Of these, two (c.187_188del and c.1314_1314delA) were novel. No variant in the entire F9 was found in two patients with mild HB. Nonsense c.223C > T (p.Arg75*) mutation was detected in two unrelated patients. Carrier testing identified five mothers as carriers, while one younger sister was a non-carrier. The carrier status of six female relatives of the two mild patients remained undetermined. By questionnaire survey, only one of the five genetically identified carriers displayed noticeable symptoms of being a carrier. CONCLUSION: The novel variants c.187_188del and c.1314_1314delA can cause severe hemophilia B. This study did not observe a significant association between symptoms and carrier status in the five carriers.

Neuropeptide Y and α-melanocyte-stimulating hormone reciprocally regulate nesfatin-1 neurons in the paraventricular nucleus of the hypothalamus.

Nesfatin-1 is an 82 amino acids peptide processed from its precursor nucleobindin-2 (NUCB2). Accumulating evidences have shown that the nesfatin-1/NUCB2 localized in the paraventricular nucleus (PVN) of the hypothalamus regulates food intake and energy metabolism. However, the factors that regulate nesfatin-1/NUCB2 neurons in PVN are less defined. In the hypothalamic feeding center, the second-order neurons in PVN are extensively projected by the first-order neurons in the arcuate nucleus (ARC), the representatives of which are orexigenic neuropeptide Y (NPY) and anorexigenic α-melanocyte-stimulating hormone (α-MSH) neurons. The present study explored whether NPY and α-MSH regulate the PVN nesfatin-1/NUCB2 neurons. This was achieved by cytosolic Ca ([Ca]i) imaging, followed by nesfatin-1/NUCB2 immunostaining in single neurons isolated from PVN. The moderate increase in [Ca]i with 5 mM glucose was suppressed by NPY, but further increased by α-MSH in the PVN neurons that were shown to be immunoreactive to nesfatin-1/NUCB2. The majority (60%) of nesfatin-1/NUCB2 neurons in PVN responded to NPY and/or α-MSH. Confocal immunohistochemical images showed that both NPY and α-MSH neuronal terminals contacted nesfatin-1/NUCB2 neurons in PVN. These data show that NPY inhibits and α-MSH activates PVN nesfatin-1/NUCB2 neurons, presenting dual and reciprocal neuro-circuits from ARC to PVN, possibly contributing toward the balanced regulation of feeding.

Insulin Activates Vagal Afferent Neurons Including those Innervating Pancreas via Insulin Cascade and Ca(2+) Influx: Its Dysfunction in IRS2-KO Mice with Hyperphagic Obesity.

Some of insulin's functions, including glucose/lipid metabolism, satiety and neuroprotection, involve the alteration of brain activities. Insulin could signal to the brain via penetrating through the blood-brain barrier and acting on the vagal afferents, while the latter remains unproved. This study aimed to clarify whether insulin directly regulates the nodose ganglion neurons (NGNs) of vagal afferents in mice. NGs expressed insulin receptor (IR) and insulin receptor substrate-2 (IRS2) mRNA, and some of NGNs were immunoreactive to IR. In patch-clamp and fura-2 microfluorometric studies, insulin (10(-12)∼10(-6) M) depolarized and increased cytosolic Ca(2+) concentration ([Ca(2+)]i) in single NGNs. The insulin-induced [Ca(2+)]i increases were attenuated by L- and N-type Ca(2+) channel blockers, by phosphatidylinositol 3 kinase (PI3K) inhibitor, and in NGNs from IRS2 knockout mice. Half of the insulin-responsive NGNs contained cocaine- and amphetamine-regulated transcript. Neuronal fibers expressing IRs were distributed in/around pancreatic islets. The NGNs innervating the pancreas, identified by injecting retrograde tracer into the pancreas, responded to insulin with much greater incidence than unlabeled NGNs. Insulin concentrations measured in pancreatic vein was 64-fold higher than that in circulation. Elevation of insulin to 10(-7) M recruited a remarkably greater population of NGNs to [Ca(2+)]i increases. Systemic injection of glibenclamide rapidly released insulin and phosphorylated AKT in NGs. Furthermore, in IRS2 knockout mice, insulin action to suppress [Ca(2+)]i in orexigenic ghrelin-responsive neurons in hypothalamic arcuate nucleus was intact while insulin action on NGN was markedly attenuated, suggesting a possible link between impaired insulin sensing by NGNs and hyperphagic obese phenotype in IRS2 knockout mice These data demonstrate that insulin directly activates NGNs via IR-IRS2-PI3K-AKT-cascade and depolarization-gated Ca(2+) influx. Pancreas-innervating NGNs may effectively sense dynamic changes of insulin released in response to nutritional states. These interactions could serve to convey the changes in pancreatic and systemic insulin to the brain.

Pancreatic polypeptide and peptide YY3-36 induce Ca2+ signaling in nodose ganglion neurons.

Peripheral injection of pancreatic polypeptide (PP) and peptide YY(3-36) (PYY(3-36)), the hormones released in response to meals, reduce food intake, in which the rank order of the potency is PP>PYY(3-36). These anorectic effects are abolished in abdominal vagotomized rats, suggesting that PP and PYY(3-36) induce anorexia via vagal afferent nerves. However, it is not clear whether PP and PYY(3-36) directly act on vagal afferent neurons. In this study, we examined the effects of PP and PYY(3-36) on cytosolic Ca(2+) concentration ([Ca(2+)](i)) in isolated nodose ganglion neurons of the mouse vagal afferent nerves. At 10(-11)M, PP but not PYY(3-36) recruited a significant population of nodose ganglion neurons into [Ca(2+)](i) increases. PP at 10(-11) to 10(-7) and PYY(3-36) at 10(-10) to 10(-7)M increased [Ca(2+)](i) in a concentration-dependent manner. At submaximal to maximal concentrations of 10(-10) and 10(-8)M, PP increased [Ca(2+)](i) in approximately twice greater population of nodose ganglion neurons than PYY(3-36). Furthermore, the majority of PP-responsive neurons also exhibited [Ca(2+)](i) responses to cholecystokinin-8, a hormone known to induce satiety through activating nodose ganglion neurons. The results demonstrate that PP and PYY(3-36) directly activate nodose ganglion neurons and suggest that the marked effect of PP on cholecystokinin-8-responsive nodose ganglion neurons could be linked to the regulation of feeding.