Protein Kinase C (Pkc)-δ Mediates Arginine-Induced Glucagon Secretion in Pancreatic α-Cells.

The pathophysiology of type 2 diabetes involves insulin and glucagon. Protein kinase C (Pkc)-δ, a serine-threonine kinase, is ubiquitously expressed and involved in regulating cell death and proliferation. However, the role of Pkcδ in regulating glucagon secretion in pancreatic α-cells remains unclear. Therefore, this study aimed to elucidate the physiological role of Pkcδ in glucagon secretion from pancreatic α-cells. Glucagon secretions were investigated in Pkcδ-knockdown InR1G9 cells and pancreatic α-cell-specific Pkcδ-knockout (αPkcδKO) mice. Knockdown of Pkcδ in the glucagon-secreting cell line InR1G9 cells reduced glucagon secretion. The basic amino acid arginine enhances glucagon secretion via voltage-dependent calcium channels (VDCC). Furthermore, we showed that arginine increased Pkcδ phosphorylation at Thr505, which is critical for Pkcδ activation. Interestingly, the knockdown of Pkcδ in InR1G9 cells reduced arginine-induced glucagon secretion. Moreover, arginine-induced glucagon secretions were decreased in αPkcδKO mice and islets from αPkcδKO mice. Pkcδ is essential for arginine-induced glucagon secretion in pancreatic α-cells. Therefore, this study may contribute to the elucidation of the molecular mechanism of amino acid-induced glucagon secretion and the development of novel antidiabetic drugs targeting Pkcδ and glucagon.

Leukotriene A4 hydrolase deficiency protects mice from diet-induced obesity by increasing energy expenditure through neuroendocrine axis.

Obesity is a health problem worldwide, and brown adipose tissue (BAT) is important for energy expenditure. Here, we explored the role of leukotriene A4 hydrolase (LTA4 H), a key enzyme in the synthesis of the lipid mediator leukotriene B4 (LTB4 ), in diet-induced obesity. LTA4 H-deficient (LTA4 H-KO) mice fed a high-fat diet (HFD) showed a lean phenotype, and bone-marrow transplantation studies revealed that LTA4 H-deficiency in non-hematopoietic cells was responsible for this lean phenotype. LTA4 H-KO mice exhibited greater energy expenditure, but similar food intake and fecal energy loss. LTA4 H-KO BAT showed higher expression of thermogenesis-related genes. In addition, the plasma thyroid-stimulating hormone and thyroid hormone concentrations, as well as HFD-induced catecholamine secretion, were higher in LTA4 H-KO mice. In contrast, LTB4 receptor (BLT1)-deficient mice did not show a lean phenotype, implying that the phenotype of LTA4 H-KO mice is independent of the LTB4 /BLT1 axis. These results indicate that LTA4 H mediates the diet-induced obesity by reducing catecholamine and thyroid hormone secretion.

Anagliptin suppresses diet-induced obesity through enhancing leptin sensitivity and ameliorating hyperphagia in high-fat high-sucrose diet fed mice.

Obesity is a major risk factors for type 2 diabetes, and weight loss is beneficial to diabetic patients who are obese or overweight. Dipeptidyl peptidase-4 (DPP-4) inhibitors are anti-diabetic drugs. Although it has been known that the effect of most of the DPP-4 inhibitors on body weight is neutral, several studies suggested that some DPP-4 inhibitors suppressed body weight. Nonetheless, the mechanisms underlying DPP-4 inhibitor-induced weight loss are not fully understood. In this study, the mice fed high-fat high sucrose diet (HFHSD) containing a DPP4 inhibitor, anagliptin, showed reduced food intake and body weight compared to the mice fed non-treated HFHSD, but oxygen consumption and respiratory exchange ratio (RER) were not altered. Sequential administration of leptin suppressed food intake and body weight more apparently in anagliptin treated HFHSD fed mice than non-treated HFHSD fed mice. Oxygen consumption and RER were comparable between anagliptin treated and non-treated mice after leptin administration. The number of phospho STAT3 expressed cells in the arcuate nucleus after leptin administration was increased in anagliptin treated mice compared to non-treated mice. These data suggested that anagliptin ameliorated leptin resistance induced by HFHSD and thereby decreased food intake and body weight. These effects of anagliptin could be beneficial to the treatment of obese diabetic patients.

Dnmt3a in Sim1 neurons is necessary for normal energy homeostasis.

Obesity rates continue to rise throughout the world. Recent evidence has suggested that environmental factors contribute to altered energy balance regulation. However, the role of epigenetic modifications to the central control of energy homeostasis remains unknown. To investigate the role of DNA methylation in the regulation of energy balance, we investigated the role of the de novo DNA methyltransferase, Dnmt3a, in Single-minded 1 (Sim1) cells, including neurons in the paraventricular nucleus of the hypothalamus (PVH). Dnmt3a expression levels were decreased in the PVH of high-fat-fed mice. Mice lacking Dnmt3a specifically in the Sim1 neurons, which are expressed in the forebrain, including PVH, became obese with increased amounts of abdominal and subcutaneous fat. The mice were also found to have hyperphagia, decreased energy expenditure, and glucose intolerance with increased serum insulin and leptin. Furthermore, these mice developed hyper-LDL cholesterolemia when fed a high-fat diet. Gene expression profiling and DNA methylation analysis revealed that the expression of tyrosine hydroxylase and galanin were highly upregulated in the PVH of Sim1-specific Dnmt3a deletion mice. DNA methylation levels of the tyrosine hydroxylase promoter were decreased in the PVH of the deletion mice. These results suggest that Dnmt3a in the PVH is necessary for the normal control of body weight and energy homeostasis and that tyrosine hydroxylase is a putative target of Dnmt3a in the PVH. These results provide evidence for a role for Dnmt3a in the PVH to link environmental conditions to altered energy homeostasis.

Steroidogenic factor 1 directs programs regulating diet-induced thermogenesis and leptin action in the ventral medial hypothalamic nucleus.

The transcription factor steroidogenic factor 1 (SF-1) is exclusively expressed in the brain in the ventral medial hypothalamic nucleus (VMH) and is required for the development of this nucleus. However, the physiological importance of transcriptional programs regulated by SF-1 in the VMH is not well defined. To delineate the functional significance of SF-1 itself in the brain, we generated pre- and postnatal VMH-specific SF-1 KO mice. Both models of VMH-specific SF-1 KO were susceptible to high fat diet-induced obesity and displayed impaired thermogenesis after acute exposure to high fat diet. Furthermore, VMH-specific SF-1 KO mice showed significantly decreased LepR expression specifically in the VMH, leading to leptin resistance. Collectively, these results indicate that SF-1 directs transcriptional programs in the hypothalamus relevant to coordinated control of energy homeostasis, especially after excess caloric intake.

DNA Methylation in the Hypothalamic Feeding Center and Obesity.

Obesity rates have been increasing worldwide for decades, mainly due to environmental factors, such as diet, nutrition, and exercise. However, the molecular mechanisms through which environmental factors induce obesity remain unclear. Several mechanisms underlie the body's response to environmental factors, and one of the main mechanisms involves epigenetic modifications, such as DNA methylation. The pattern of DNA methylation is influenced by environmental factors, and altered DNA methylation patterns can affect gene expression profiles and phenotypes. DNA methylation may mediate the development of obesity caused by environmental factors. Similar to the factors governing obesity, DNA methylation is influenced by nutrients and metabolites. Notably, DNA methylation is associated with body size and weight programming. The DNA methylation levels of proopiomelanocortin (Pomc) and neuropeptide Y (Npy) in the hypothalamic feeding center, a key region controlling systemic energy balance, are affected by diet. Conditional knockout mouse studies of epigenetic enzymes have shown that DNA methylation in the hypothalamic feeding center plays an indispensable role in energy homeostasis. In this review, we discuss the role of DNA methylation in the hypothalamic feeding center as a potential mechanism underlying the development of obesity induced by environmental factors.

The Hypothalamic Paraventricular Nucleus Is the Center of the Hypothalamic-Pituitary-Thyroid Axis for Regulating Thyroid Hormone Levels.

Background: Thyrotropin-releasing hormone (TRH) was the first hypothalamic hormone isolated that stimulates pituitary thyrotropin (TSH) secretion. TRH was also later found to be a stimulator of pituitary prolactin and distributed throughout the brain, gastrointestinal tract, and pancreatic ß cells. We previously reported the development of TRH null mice (conventional TRHKO), which exhibit characteristic tertiary hypothyroidism and impaired glucose tolerance due to insufficient insulin secretion. Although in the past five decades many investigators, us included, have attempted to determine the hypothalamic nucleus responsible for the hypothalamic-pituitary-thyroid (HPT) axis, it remained obscure because of the broad expression of TRH. Methods: To determine the hypothalamic region functionally responsible for the HPT axis, we established paraventricular nucleus (PVN)-specific TRH knockout (PVN-TRHKO) mice by mating Trh floxed mice and single-minded homolog 1 (Sim1)-Cre transgenic mice. We originally confirmed that most Sim1 was expressed in the PVN using Sim1-Cre/tdTomato mice. Results: These PVN-TRHKO mice exhibited tertiary hypothyroidism similar to conventional TRHKO mice; however, they did not show the impaired glucose tolerance observed in the latter, suggesting that TRH from non-PVN sources is essential for glucose regulation. In addition, a severe reduction in prolactin expression was observed in the pituitary of PVN-TRHKO mice compared with that in TRHKO mice. Conclusions: These findings are conclusive evidence that the PVN is the center of the HPT axis for regulation of serum levels of thyroid hormones and that the serum TSH levels are not decreased in tertiary hypothyroidism. We also noted that TRH from the PVN regulated prolactin, whereas TRH from non-PVN sources regulated glucose metabolism.

Utility of O-arm navigation for atlantoaxial fusion with Bow Hunter's syndrome.

BACKGROUND: In spinal instrumentation surgery, safe and accurate placement of implants such as lateral mass screws and pedicle screws should be a top priority. In particular, C2 stabilization can be challenging due to the complex anatomy of the upper cervical spine. Here, we present a case of Bow Hunter's syndrome (BHS) successfully treated by an O-arm-navigated atlantoaxial fusion. CASE DESCRIPTION: A 53-year-old male presented with a 10-year history of repeated episodes of transient loss of consciousness following neck rotation to the right. Although the unenhanced magnetic resonance imaging showed no pathological findings, the MR angiogram with dynamic digital subtraction angiography revealed a dominant left vertebral artery (VA) and hypoplasia of the right VA. The latter study further demonstrated significant flow reduction in the left VA at the C1-C2 level when the head was rotated toward the right. With these findings of BHS, a C1-C2 decompression/posterior fusion using the Goel-Harms technique with O-arm navigation was performed. The postoperative cervical X-rays showed adequate decompression/fixation, and symptoms resolved without sequelae. CONCLUSION: C1-C2 posterior decompression/fusion effectively treats BHS, and is more safely/effectively performed utilizing O-arm navigation for C1-C2 screw placement.

Role of PDK1 in skeletal muscle hypertrophy induced by mechanical load.

Phosphatidylinositol 3-kinase (PI3K) plays an important role in protein metabolism and cell growth. We here show that mice (M-PDK1KO mice) with skeletal muscle-specific deficiency of 3'-phosphoinositide-dependent kinase 1 (PDK1), a key component of PI3K signaling pathway, manifest a reduced skeletal muscle mass under the static condition as well as impairment of mechanical load-induced muscle hypertrophy. Whereas mechanical load-induced changes in gene expression were not affected, the phosphorylation of ribosomal protein S6 kinase (S6K) and S6 induced by mechanical load was attenuated in skeletal muscle of M-PDK1KO mice, suggesting that PDK1 regulates muscle hypertrophy not through changes in gene expression but through stimulation of kinase cascades such as the S6K-S6 axis, which plays a key role in protein synthesis. Administration of the ß2-adrenergic receptor (AR) agonist clenbuterol activated the S6K-S6 axis in skeletal muscle and induced muscle hypertrophy in mice. These effects of clenbuterol were attenuated in M-PDK1KO mice, and mechanical load-induced activation of the S6K-S6 axis and muscle hypertrophy were inhibited in mice with skeletal muscle-specific deficiency of ß2-AR. Our results suggest that PDK1 regulates skeletal muscle mass under the static condition and that it contributes to mechanical load-induced muscle hypertrophy, at least in part by mediating signaling from ß2-AR.

Disordered branched chain amino acid catabolism in pancreatic islets is associated with postprandial hypersecretion of glucagon in diabetic mice.

Dysregulation of glucagon is associated with the pathophysiology of type 2 diabetes. We previously reported that postprandial hyperglucagonemia is more obvious than fasting hyperglucagonemia in type 2 diabetes patients. However, which nutrient stimulates glucagon secretion in the diabetic state and the underlying mechanism after nutrient intake are unclear. To answer these questions, we measured plasma glucagon levels in diabetic mice after oral administration of various nutrients. The effects of nutrients on glucagon secretion were assessed using islets isolated from diabetic mice and palmitate-treated islets. In addition, we analyzed the expression levels of branched chain amino acid (BCAA) catabolism-related enzymes and their metabolites in diabetic islets. We found that protein, but not carbohydrate or lipid, increased plasma glucagon levels in diabetic mice. Among amino acids, BCAAs, but not the other essential or nonessential amino acids, increased plasma glucagon levels. BCAAs also directly increased the intracellular calcium concentration in α cells. When BCAAs transport was suppressed by an inhibitor of system L-amino acid transporters, glucagon secretion was reduced even in the presence of BCAAs. We also found that the expression levels of BCAA catabolism-related enzymes and their metabolite contents were altered in diabetic islets and palmitate-treated islets compared to control islets, indicating disordered BCAA catabolism in diabetic islets. Furthermore, BCKDK inhibitor BT2 suppressed BCAA-induced hypersecretion of glucagon in diabetic islets and palmitate-treated islets. Taken together, postprandial hypersecretion of glucagon in the diabetic state is attributable to disordered BCAA catabolism in pancreatic islet cells.

A rare case of spinal dural arteriovenous fistula mimicking malignant glioma of the medulla oblongata: Significance of cerebral angiography for accurate diagnosis of brain stem region.

BACKGROUND: The findings of a hyperintense sign on T2-weighted imaging (T2-WI) and gadolinium (Gd) contrast enhancement on magnetic resonance imaging (MRI) of the brain stem suggest malignant glioma. However, this pathological condition is probably uncommon, and it may be unknown that a dural arteriovenous fistula (DAVF) can imitate this radiological pattern. In addition, it is extremely rare to be caused by a spinal DAVF. Here, a rare case of spinal DAVF that mimicked malignant glioma of the medulla oblongata is presented. CASE DESCRIPTION: A 56-year-old woman was admitted with a progressive gait disturbance, vertigo, and dysphasia. MRI showed a hyperintense signal in the medulla oblongata on fluid-attenuated inversion recovery (FLAIR) and moderate contrast enhancement on Gd-enhanced MRI. Interestingly, Gd-enhanced MRI demonstrated abnormal dilated veins around the brain stem and cervical spinal cord. Cerebral angiography showed spinal DAVF at the left C4/C5 vertebral foramen fed by the C5 radicular artery. The fistula drained into spinal perimedullary veins and flowed out retrograde at the cortical vein of the posterior cranial fossa. Therefore, surgical disconnection of the spinal DAVF was performed by a posterior approach. The patient's postoperative course was uneventful. Cerebral angiography showed complete disappearance of the DAVF, with marked reductions of the hyperintense sign of the medulla oblongata on FLAIR. CONCLUSION: This important case illustrates MRI findings mimicking brain stem glioma. In cases with the hyperintense sign-on T2-WI associated with contrast enhancement suspicious of brainstem glioma, careful checking for perimedullary abnormal vessels and additional cerebral angiography should be performed.

Epithelioid glioblastoma presenting as multicentric glioma: A case report and review of the literature.

BACKGROUND: Epithelioid glioblastoma is a rare aggressive variant of glioblastoma multiforme (GBM), which was formally recognized by the World Health Organization classification of the central nervous system in 2016. Clinically, epithelioid GBMs are characterized by aggressive features, such as metastases and cerebrospinal fluid dissemination, and an extremely poor prognosis. A rare case of epithelioid GBM that was discovered as a multicentric glioma with different histopathology is reported. CASE DESCRIPTION: A 78-year-old man was admitted to our hospital with mild motor weakness of the right leg. Neuroimaging showed small masses in the left frontal and parietal lobes on magnetic resonance imaging. The abnormal lesion had been increasing rapidly for 3 weeks, and a new lesion appeared in the frontal lobe. 11C-methionine positron emission tomography (PET) showed abnormal uptake corresponding to the lesion. To reach a definitive diagnosis, surgical excision of the right frontal mass lesion was performed. Histological findings showed diffuse astrocytoma. Only radiotherapy was planned, but the left frontal and parietal tumors progressed further within a short period. Therefore, it was thought that these tumors were GBM, and a biopsy of the left parietal tumor was performed. The histological diagnosis was epithelioid GBM. Immunohistochemistry showed that most tumor cells were negatively stained for p53 and isocitrate dehydrogenase 1. BRAF V600E mutations were not identified, but TERT promoter mutations were identified. Immediately after surgery, the patient was given chemotherapy using temozolomide, extended local radiotherapy and then bevacizumab. After 6 months, he showed no signs of recurrence. CONCLUSION: Epithelioid GBM is one of the rarest morphologic subtypes of GBM and has a strongly infiltrative and aggressive nature. Therefore, careful identification of preoperative imaging studies and detailed evaluation of genetic studies are necessary to select the appropriate treatment for epithelioid GBM.

P110ß in the ventromedial hypothalamus regulates glucose and energy metabolism.

Phosphoinositide 3-kinase (PI3K) signaling in hypothalamic neurons integrates peripheral metabolic cues, including leptin and insulin, to coordinate systemic glucose and energy homeostasis. PI3K is composed of different subunits, each of which has several unique isoforms. However, the role of the PI3K subunits and isoforms in the ventromedial hypothalamus (VMH), a prominent site for the regulation of glucose and energy homeostasis, is unclear. Here we investigated the role of subunit p110ß in steroidogenic factor-1 (SF-1) neurons of the VMH in the regulation of metabolism. Our data demonstrate that the deletion of p110ß in SF-1 neurons disrupts glucose metabolism, rendering the mice insulin resistant. In addition, the deletion of p110ß in SF-1 neurons leads to the whitening of brown adipose tissues and increased susceptibility to diet-induced obesity due to blunted energy expenditure. These results highlight a critical role for p110ß in the regulation of glucose and energy homeostasis via VMH neurons.

SGLT1 in pancreatic α cells regulates glucagon secretion in mice, possibly explaining the distinct effects of SGLT2 inhibitors on plasma glucagon levels.

OBJECTIVES: It is controversial whether sodium glucose transporter (SGLT) 2 inhibitors increase glucagon secretion via direct inhibition of SGLT2 in pancreatic α cells. The role of SGLT1 in α cells is also unclear. We aimed to elucidate these points that are important not only for basic research but also for clinical insight. METHODS: Plasma glucagon levels were assessed in the high-fat, high-sucrose diet (HFHSD) fed C57BL/6J mice treated with dapagliflozin or canagliflozin. RT-PCR, RNA sequence, and immunohistochemistry were conducted to test the expression of SGLT1 and SGLT2 in α cells. We also used αTC1 cells and mouse islets to investigate the molecular mechanism by which SGLT1 modulates glucagon secretion. RESULTS: Dapagliflozin, but not canagliflozin, increased plasma glucagon levels in HFHSD fed mice. SGLT1 and glucose transporter 1 (GLUT1), but not SGLT2, were expressed in αTC1 cells, mouse islets and human islets. A glucose clamp study revealed that the plasma glucagon increase associated with dapagliflozin could be explained as a response to acute declines in blood glucose. Canagliflozin suppressed glucagon secretion by inhibiting SGLT1 in α cells; consequently, plasma glucagon did not increase with canagliflozin, even though blood glucose declined. SGLT1 effect on glucagon secretion depended on glucose transport, but not glucose metabolism. Islets from HFHSD and db/db mice displayed higher SGLT1 mRNA levels and lower GLUT1 mRNA levels than the islets from control mice. These expression levels were associated with higher glucagon secretion. Furthermore, SGLT1 inhibitor and siRNA against SGLT1 suppressed glucagon secretion in isolated islets. CONCLUSIONS: These data suggested that a novel mechanism regulated glucagon secretion through SGLT1 in α cells. This finding possibly explained the distinct effects of dapagliflozin and canagliflozin on plasma glucagon levels in mice.

Nesfatin-1 neurons in paraventricular and supraoptic nuclei of the rat hypothalamus coexpress oxytocin and vasopressin and are activated by refeeding.

Nesfatin-1, a newly discovered satiety molecule, is located in the hypothalamic nuclei, including the paraventricular nucleus (PVN) and supraoptic nucleus (SON). In this study, fine localization and regulation of nesfatin-1 neurons in the PVN and SON were investigated by immunohistochemistry of neuropeptides and c-Fos. In the PVN, 24% of nesfatin-1 neurons overlapped with oxytocin, 18% with vasopressin, 13% with CRH, and 12% with TRH neurons. In the SON, 35% of nesfatin-1 neurons overlapped with oxytocin and 28% with vasopressin. After a 48-h fast, refeeding for 2 h dramatically increased the number of nesfatin-1 neurons expressing c-Fos immunoreactivity by approximately 10 times in the PVN and 30 times in the SON, compared with the fasting controls. In the SON, refeeding also significantly increased the number of nesfatin-1-immunoreactive neurons and NUCB2 mRNA expression, compared with fasting. These results indicate that nesfatin-1 neurons in the PVN and SON highly overlap with oxytocin and vasopressin neurons and that they are activated markedly by refeeding. Feeding-activated nesfatin-1 neurons in the PVN and SON could play a role in the postprandial regulation of feeding behavior and energy homeostasis.

Ghrelin raises [Ca2+]i via AMPK in hypothalamic arcuate nucleus NPY neurons.

Ghrelin, an orexigenic hormone, directly activates neuropeptide (NPY) neurons in the hypothalamic arcuate nucleus (ARC), and thereby stimulates food intake. The hypothalamic level of AMP-activated protein kinase (AMPK), an intracellular energy sensor, is activated by peripheral and central administration of ghrelin. We examined whether ghrelin regulates AMPK activity in NPY neurons of the ARC. Single neurons were isolated from the ARC and cytosolic Ca(2+) concentration ([Ca(2+)](i)) was measured by fura-2 microfluorometry, followed by immunocytochemical identification of NPY, phospho-AMPK, and phospho-acetyl-CoA carboxylase (ACC). Ghrelin and AICAR, an AMPK activator, increased [Ca(2+)](i) in neurons isolated from the ARC. The ghrelin-responsive neurons highly overlapped with AICAR-responsive neurons. The neurons that responded to both ghrelin and AICAR were primarily NPY-immunoreactive neurons. Treatment with ghrelin increased phosphorylation of AMPK and ACC. An AMPK inhibitor, compound C, suppressed ghrelin-induced [Ca(2+)](i) increases. These results demonstrate that ghrelin increases [Ca(2+)](i) via AMPK-mediated signaling in the ARC NPY neurons.

Synaptic interaction between ghrelin- and ghrelin-containing neurons in the rat hypothalamus.

Synaptic relationships between ghrelin-like immunoreactive axon terminals and other neurons in the hypothalamic arcuate nucleus (ARC) were studied using immunostaining methods at the light and electron microscope levels. Many ghrelin-like immunoreactive axon terminals were found to be in apposition to ghrelin-like immunoreactive neurons at the light microscopic level. At the electron microscopic level, ghrelin-like immunoreactive axon terminals were found to make synapses on ghrelin-like immunoreactive cell bodies and dendrites in the ARC. While the axo-dendritic synapses between ghrelin- and ghrelin-like immunoreactive neurons were mostly the asymmetric type, the axo-somatic synapses were both asymmetric and symmetric type of synapses. Ghrelin at 10(-10) M increased cytosolic Ca(2+) concentration ([Ca(2+)](i)) in the neurons isolated from the ARC, some of which were immunocytochemically identified as ghrelin-positive. Ghrelin at 10(-10) M also increased [Ca(2+)](i) in 12% of ghrelin-like immunoreactive neurons in the ARC. These findings suggest that ghrelin serves as a transmitter and/or modulator that stimulates [Ca(2+)](i) signaling in ghrelin neurons of the ARC, which may participate in the orexigenic action of ghrelin. Our data suggests a possibility of existing a novel circuit implicating regulation of feeding and/or energy metabolism.

Leptin transiently antagonizes ghrelin and long-lastingly orexin in regulation of Ca2+ signaling in neuropeptide Y neurons of the arcuate nucleus.

AIM: To explore the mechanism for interactions of leptin with ghrelin and orexin in the arcuate nucleus (ARC) activating neuropeptide Y (NPY) neurons during physiological regulation of feeding. METHODS: Single neurons from ARC of adult rats with matured feeding function were isolated. [Ca2+]i was measured to monitor their activities. The time course of leptin effects on ghrelin-induced versus orexin-induced [Ca2+]i increases in NPY neurons was studied. RESULTS: Administration of ghrelin or orexin-A at 10(-10) mol/L increased cytosolic Ca2+ concentration ([Ca2+]i) in NPY neurons isolated from the ARC of adult rats. Upon administration of leptin at 10(-14)-10(-12) mol/L, ghrelin-induced [Ca2+]i increases were initially (<10 min) inhibited but later restored, exhibiting a transient pattern of inhibition. In contrast, orexin-induced [Ca2+]i increases were inhibited by leptin in a long-lasting manner. Furthermore, a prior administration of leptin inhibited orexin action but not ghrelin action to increase [Ca2+]i. CONCLUSION: Leptin counteracted ghrelin effects transiently and orexin effects long-lastingly in NPY neurons. The transient property with which leptin counteracts ghrelin action in NPY neurons may allow the fasting-associated increase in ghrelin levels to activate NPY neurons in the presence of physiological leptin and to stimulate feeding.

Aberrant DNA methylation of hypothalamic angiotensin receptor in prenatal programmed hypertension.

Maternal malnutrition, which causes prenatal exposure to excessive glucocorticoid, induces adverse metabolic programming, leading to hypertension in offspring. In offspring of pregnant rats receiving a low-protein diet or dexamethasone, a synthetic glucocorticoid, mRNA expression of angiotensin receptor type 1a (Agtr1a) in the paraventricular nucleus (PVN) of the hypothalamus was upregulated, concurrent with reduced expression of DNA methyltransferase 3a (Dnmt3a), reduced binding of DNMT3a to the Agtr1a gene, and DNA demethylation. Salt loading increased BP in both types of offspring, suggesting that elevated hypothalamic Agtr1a expression is epigenetically modulated by excessive glucocorticoid and leads to adult-onset salt-sensitive hypertension. Consistent with this, dexamethasone treatment of PVN cells upregulated Agtr1a, while downregulating Dnmt3a, and decreased DNMT3a binding and DNA demethylation at the Agtr1a locus. In addition, Dnmt3a knockdown upregulated Agtr1a independently of dexamethasone. Hypothalamic neuron-specific Dnmt3a-deficient mice exhibited upregulation of Agtr1a in the PVN and salt-induced BP elevation without dexamethasone treatment. By contrast, dexamethasone-treated Agtr1a-deficient mice failed to show salt-induced BP elevation, despite reduced expression of Dnmt3a. Thus, epigenetic modulation of hypothalamic angiotensin signaling contributes to salt-sensitive hypertension induced by prenatal glucocorticoid excess in offspring of mothers that are malnourished during pregnancy.

Neuronal SIRT1 regulates macronutrient-based diet selection through FGF21 and oxytocin signalling in mice.

Diet affects health through ingested calories and macronutrients, and macronutrient balance affects health span. The mechanisms regulating macronutrient-based diet choices are poorly understood. Previous studies had shown that NAD-dependent deacetylase sirtuin-1 (SIRT1) in part influences the health-promoting effects of caloric restriction by boosting fat use in peripheral tissues. Here, we show that neuronal SIRT1 shifts diet choice from sucrose to fat in mice, matching the peripheral metabolic shift. SIRT1-mediated suppression of simple sugar preference requires oxytocin signalling, and SIRT1 in oxytocin neurons drives this effect. The hepatokine FGF21 acts as an endocrine signal to oxytocin neurons, promoting neuronal activation and Oxt transcription and suppressing the simple sugar preference. SIRT1 promotes FGF21 signalling in oxytocin neurons and stimulates Oxt transcription through NRF2. Thus, neuronal SIRT1 contributes to the homeostatic regulation of macronutrient-based diet selection in mice.