Search PubMed⌕ Search

Biomedical subjects

Reiko Hanada

Publications and source records attributed to Reiko Hanada.

7 recordsLinked to original sources

Deletion of neurosecretory proteins GL and GM drives dual anti-obesity effects via appetite suppression and enhanced energy expenditure.

Obesity results from an imbalance between energy intake and expenditure and is regulated by hypothalamic neuropeptide systems. The neurosecretory proteins GL (NPGL) and GM (NPGM) are expressed in the hypothalamus and promote feeding in gain-of-function studies; however, their endogenous physiological roles remain unclear. Here, we show that mice lacking both NPGL and NPGM display a lean phenotype driven by reduced food intake and increased energy expenditure. This anti-obesity phenotype is associated with increased expression of anorexigenic pro-opiomelanocortin in the hypothalamus and enhanced thermogenic activity in brown adipose tissue, marked by elevated uncoupling protein 1. Consistent with these findings, suppression of NPGL/NPGM signaling reduces feeding and alters sympathetic nerve activity. In addition, genome-wide association analysis identifies an obesity-associated variant near the human NPGM locus, suggesting relevance to human energy balance. Together, these findings identify NPGL and NPGM as endogenous regulators of energy homeostasis with potential relevance to obesity.

Animals↗

Regulation of gonadotropin secretion and puberty onset by neuromedin U.

Neuromedin U (NMU), an anorexigenic peptide, was originally isolated from porcine spinal cord in 1985. As NMU is abundant in the anterior pituitary gland, we investigated the effects of NMU on gonadotropin secretion. Both NMU and its receptors, NMUR1 and NMUR2, were expressed in the pituitary gland. NMU suppressed LH and FSH releases from rat anterior pituitary cells. Moreover, NMU-deficient mice exhibit an early onset of vaginal opening. The LHbeta/FSHbeta ratio, which is an index of puberty onset, is high in young NMU-deficient mice. These results indicate that NMU suppresses gonadotropin secretion and regulates the onset of puberty.

Animals↗

Ghrelin directly regulates bone formation.

UNLABELLED: To clarify the role of ghrelin in bone metabolism, we examined the effect of ghrelin in vitro and in vivo. Ghrelin and its receptor, GHS-R1a, were identified in osteoblasts, and ghrelin promoted both proliferation and differentiation. Furthermore, ghrelin increased BMD in rats. Our results show that ghrelin directly affects bone formation. INTRODUCTION: Ghrelin is a gut peptide involved in growth hormone (GH) secretion and energy homeostasis. Recently, it has been reported that the adipocyte-derived hormone leptin, which also regulates energy homeostasis and opposes ghrelin's actions in energy homeostasis, plays a significant role in bone metabolism. This evidence implies that ghrelin may modulate bone metabolism; however, it has not been clarified. To study the role of ghrelin in skeletal integrity, we examined its effects on bone metabolism both in vitro and in vivo. MATERIALS AND METHODS: We measured the expression of ghrelin and growth hormone secretagogue receptor 1a (GHS-R1a) in rat osteoblasts using RT-PCR and immunohistochemistry (IHC). The effect of ghrelin on primary osteoblast-like cell proliferation was examined by recording changes in cell number and the level of DNA synthesis. Osteoblast differentiation markers (Runx2, collagen alpha1 type I [COLI], alkaline phosphatase [ALP], osteocalcin [OCN]) were analyzed using quantitative RT-PCR. We also examined calcium accumulation and ALP activity in osteoblast-like cells induced by ghrelin. Finally, to address the in vivo effects of ghrelin on bone metabolism, we examined the BMD of Sprague-Dawley (SD) rats and genetically GH-deficient, spontaneous dwarf rats (SDR). RESULTS: Ghrelin and GHS-R1a were identified in osteoblast-like cells. Ghrelin significantly increased osteoblast-like cell numbers and DNA synthesis in a dose-dependent manner. The proliferative effects of ghrelin were suppressed by [D-Lys(3)]-GHRP-6, an antagonist of GHS-R1a, in a dose-dependent manner. Furthermore, ghrelin increased the expression of osteoblast differentiation markers, ALP activity, and calcium accumulation in the matrix. Finally, ghrelin definitely increased BMD of both SD rats and SDRs. CONCLUSIONS: These observations show that ghrelin directly stimulates bone formation.

Adipocytes↗

Neuromedin U is involved in nociceptive reflexes and adaptation to environmental stimuli in mice.

Following our recent observations of inactivity and slowed movement in neuromedin U knockout (NMU KO) mice, we compared nociceptive reflexes and environmental adaptation in NMU KO and wild-type mice. Hot plate and formalin tests revealed that reflexes to heat and pain were significantly decreased in NMU KO mice. Conversely, intracerebroventricular injection of NMU into wild-type mice stimulated nociceptive reflexes in a dose-dependent manner. After NMU injection, increased c-Fos expression was observed in a wide range of locations in hypothalamus, brainstem, and spinal cord. NMU mRNA expression increased in the spinal cord, but not in the hypothalamus, 2 and 4 h after formalin injection. When their light-dark cycle was advanced or retarded by 5 h, NMU KO mice required a longer time to re-entrain into the new light-dark cycle than did wild-type mice. Wild-type mice displayed increased blood pressure after their environmental temperature was changed from 23 to 37 degrees C, whereas no such increase was observed in NMU KO mice. Blood corticosterone levels were significantly increased after 10 min of immobilization stress in wild-type mice, but not in NMU KO mice. These results suggest that endogenous NMU may be involved in reflexes and adaptation to environmental stimuli.

Adaptation, Physiological↗

Neuromedin U has a novel anorexigenic effect independent of the leptin signaling pathway.

Neuromedin U (NMU) is a hypothalamic neuropeptide that regulates body weight and composition. Here we show that mice lacking the gene encoding NMU (Nmu(-/-) mice) develop obesity. Nmu(-/-) mice showed increased body weight and adiposity, hyperphagia, and decreased locomotor activity and energy expenditure. Obese Nmu(-/-) mice developed hyperleptinemia, hyperinsulinemia, late-onset hyperglycemia and hyperlipidemia. Notably, however, treatment with exogenous leptin was effective in reducing body weight in obese Nmu(-/-) mice. In addition, central leptin administration did not affect NMU gene expression in the hypothalamus of rats. These results indicate that NMU plays an important role in the regulation of feeding behavior and energy metabolism independent of the leptin signaling pathway. These characteristic functions of NMU may provide new insight for understanding the pathophysiological basis of obesity.

Adipose Tissue↗

Socs3 deficiency in the brain elevates leptin sensitivity and confers resistance to diet-induced obesity.

Leptin is an adipocyte-derived hormone that plays a key role in energy homeostasis, yet resistance to leptin is a feature of most cases of obesity in humans and rodents. In vitro analysis suggested that the suppressor of cytokine signaling-3 (Socs3) is a negative-feedback regulator of leptin signaling involved in leptin resistance. To determine the functional significance of Socs3 in vivo, we generated neural cell-specific SOCS3 conditional knockout mice using the Cre-loxP system. Compared to their wild-type littermates, Socs3-deficient mice showed enhanced leptin-induced hypothalamic Stat3 tyrosine phosphorylation as well as pro-opiomelanocortin (POMC) induction, and this resulted in a greater body weight loss and suppression of food intake. Moreover, the Socs3-deficient mice were resistant to high fat diet-induced weight gain and hyperleptinemia, and insulin-sensitivity was retained. These data indicate that Socs3 is a key regulator of diet-induced leptin as well as insulin resistance. Our study demonstrates the negative regulatory role of Socs3 in leptin signaling in vivo, and thus suppression of Socs3 in the brain is a potential therapy for leptin-resistance in obesity.

Animals↗

The gut-brain peptide neuromedin U is involved in the mammalian circadian oscillator system.

Immunohistochemical analysis revealed the presence of a gut-brain peptide, neuromedin U (NMU), in the suprachiasmatic nucleus (SCN), which is the site of the master circadian oscillator. The expression of NMU mRNA exhibited a circadian rhythm, with the peak expression in the SCN occurring at CT4-8h. The two NMU-binding receptors (NMU-R1 and NMU-R2) were also expressed in the SCN, but their phase angles were different. Intracerebroventricular injection (ICV) of NMU induced the expression of Fos protein in the SCN cells and caused a phase-dependent phase shift of the circadian locomotor activity rhythm. The magnitude of the phase shift was dose dependent. This NMU-induced phase shift was of the nonphotic type. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed increases in the expression in the SCN of immediate early genes, such as c-fos, NGFI-A, NGFI-B, and JunB. Furthermore, ICV injection of NMU increased the expression of Per1, but not Per2, in the SCN. These results indicate that NMU may play some important role in the circadian oscillator by exerting an autocrine or paracrine action in the SCN.

Animals↗