Association of baseline plasma des-acyl ghrelin level with the response to rikkunshito in patients with functional dyspepsia.

BACKGROUND AND AIM: We recently conducted a randomized placebo-controlled trial on the efficacy and safety of rikkunshito, a standardized Japanese herbal medicine, for the treatment of functional dyspepsia (FD). The present post-hoc study aimed to evaluate the differences in clinical characteristics between responders and non-responders among FD patients who received rikkunshito for 8 weeks. METHODS: Rikkunshito responders were defined by using a global patient assessment. Candidate predictors included age, gender, smoking, alcohol consumption, body mass index, comorbidity, Helicobacter pylori infection, plasma levels of acyl ghrelin and des-acyl ghrelin, severity of dyspeptic symptoms, FD subgroup, previous medication, and the type of recruiting institution (clinic or hospital). We calculated hazard ratios (HRs) by using Cox regression analysis with the factors that were indicated to be associated with responders. RESULTS: We assigned 83 and 42 patients to responder and non-responder categories, respectively. Lack of alcohol consumption (HR, 2.04; 95% confidence interval, 1.08-3.88) and low plasma des-acyl ghrelin levels (< 177 fmol/mL; HR, 2.42; 95% confidence interval, 1.24-4.73) were significantly associated with the efficacy of rikkunshito. Lack of alcohol consumption was associated with the efficacy of rikkunshito especially among H. pylori-infected participants. On the other hand, the low plasma des-acyl ghrelin was associated with the efficacy of rikkunshito especially among H. pylori-negative participants. CONCLUSIONS: A low baseline level of plasma des-acyl ghrelin was associated with an increased treatment efficacy of rikkunshito against FD. Lack of alcohol consumption was also clinically useful for predicting the response to rikkunshito.

C-type natriuretic peptide attenuates lipopolysaccharide-induced acute lung injury in mice.

BACKGROUND: C-type natriuretic peptide (CNP), secreted by vascular endothelial cells, belongs to a family of peptides that includes atrial and brain natriuretic peptides. CNP exhibits many vasoprotective effects against pulmonary hypertension and pulmonary fibrosis. The objective of this study was to investigate the prophylactic effects of CNP in a mouse model of lipopolysaccharide (LPS)-induced acute lung injury (ALI). MATERIALS AND METHODS: C57BL/6 mice were divided into three groups as follows: normal control mice (n = 13), LPS mice treated with vehicle (n = 12), and LPS mice treated with CNP (n = 12). Twenty-four hours after tail vein injection of LPS, histopathologic, gene expression, and bronchoalveolar lavage fluid (BALF) assessments were performed on the lungs. To examine the neutrophils in the lungs, cells positive for myeloperoxidase staining were detected by immunohistochemistry. BALF cytokine levels were analyzed by enzyme-linked immunosorbent assays. Gene expression in lung tissue was analyzed by real-time polymerase chain reaction. RESULTS: CNP significantly attenuated the elevation of leukocyte cell counts and levels of tumor necrosis factor-alpha, macrophage inflammatory protein-2, monocyte chemoattractant protein-1, interleukin-6, and keratinocyte-derived chemokine in the BALF after LPS injection. Furthermore, there were significantly fewer myeloperoxidase-positive cells in lungs treated with CNP after LPS injection. In lungs of CNP-treated mice, expression of the monocyte chemoattractant protein-1, S100A8, and E-selectin genes was significantly lower than that in vehicle-treated mice. CONCLUSIONS: CNP had a protective effect on ALI induced by LPS by reducing inflammatory cell infiltration. CNP may hold promise in therapeutic strategies for ALI after pulmonary resection surgery.

Effect of rikkunshito, a Japanese herbal medicine, on gastrointestinal symptoms and ghrelin levels in gastric cancer patients after gastrectomy.

BACKGROUND: Gastric cancer patients who undergo gastrectomy suffer from a post-gastrectomy syndrome that includes weight loss, dumping syndrome, reflux esophagitis, alkaline gastritis, and finally malnutrition. It is important to ameliorate the post-gastrectomy symptoms to restore postoperative quality of life (QoL). The aim of this study was to investigate the effect of rikkunshito, a Japanese herbal medicine, on postoperative symptoms and ghrelin levels in gastric cancer patients after gastrectomy. METHODS: Twenty-five patients who had undergone gastrectomy received 2.5 g of rikkunshito before every meal for 4 weeks, and a drug withdrawal period was established for the next 4 weeks. Changes in gastrointestinal hormones, including ghrelin, and appetite visual analog scale scores were measured, and QoL was estimated by using the European Organization for Research and Treatment of Cancer core questionnaire QLQ-C30. The Dysfunction After Upper Gastrointestinal Surgery for Cancer (DAUGS) scoring system was used to evaluate gastrointestinal symptoms after gastrectomy. RESULTS: Sixteen men and nine women (mean age 61.9 years) were enrolled in the study. All patients had either stage I (n = 24) or II (n = 1) disease and had undergone either distal gastrectomy (n = 17) or total gastrectomy (n = 8) by a laparoscopy-assisted approach. The mean ratio of the acyl-/total ghrelin concentration increased significantly after rikkunshito administration (Pre: 7.8 ± 2.1, 4 weeks: 10.5 ± 1.7 %, p = 0.0026). The total DAUGS score, as well as the scores reflecting limited activity due to decreased food consumption, reflux symptoms, dumping symptoms, and nausea and vomiting significantly improved after rikkunshito administration. CONCLUSIONS: The present study demonstrated a significant attenuation of gastrointestinal symptoms after gastrectomy by treatment with rikkunshito. Rikkunshito is potentially useful to minimize gastrointestinal symptoms after gastrectomy.

Determination of nonmammalian ghrelin.

Ghrelin is a peptide with a unique molecular modification by a fatty acid such as n-octanoic acid. The acyl modification is necessary for ghrelin to bind to its receptor (growth hormone secretagogue-receptor 1a, GHS-R1a) and to induce subsequent intracellular Ca(2+) signaling. Ghrelin is widely expressed in mammals as well as in nonmammalian vertebrates. In our laboratory, a method for efficient purification of ghrelin from a small amount of tissues has been established. Here, we introduce the identification process of ghrelin in nonmammalian vertebrates.

Regional distribution and the dynamics of n-decanoyl ghrelin, another acyl-form of ghrelin, upon fasting in rodents.

n-Decanoyl ghrelin (D-ghrelin), a member of ghrelin-derived peptides, is found in plasma and the stomach; however, there have so far been no studies describing its dynamics. A D-ghrelin-specific radioimmunoassay was established to examine the tissue distribution and the kinetics of D-ghrelin in mice. The effect of D-ghrelin on food intake was also examined and compared to n-octanoyl ghrelin (O-ghrelin). D-ghrelin was detected throughout the gastrointestinal tissue and plasma with highest level in the stomach. An immunofluorescent study revealed the co-localization of D- and O-ghrelin in the same stomach cells. Upon fasting, the levels of D-ghrelin in the stomach and plasma significantly increased, while that of O-ghrelin in the stomach declined. D-ghrelin increased the 2 h food consumption in mice as O-ghrelin does. These findings indicate that D-ghrelin is mainly produced in the stomach to work in concert with O-ghrelin. The different kinetics of D- and O-ghrelin in the stomach upon fasting implies the possibility of D-ghrelin-specific bioregulation.

Exogenous ghrelin attenuates the progression of chronic hypoxia-induced pulmonary hypertension in conscious rats.

Chronic exposure to hypoxia, a common adverse consequence of most pulmonary disorders, can lead to a sustained increase in pulmonary arterial pressure (PAP), right ventricular hypertrophy, and is, therefore, closely associated with heart failure and increased mortality. Ghrelin, originally identified as an endogenous GH secretagogue, has recently been shown to possess potent vasodilator properties, likely involving modulation of the vascular endothelium and its associated vasoactive peptides. In this study we hypothesized that ghrelin would impede the pathogenesis of pulmonary arterial hypertension during chronic hypoxia (CH). PAP was continuously measured using radiotelemetry, in conscious male Sprague Dawley rats, in normoxia and during 2-wk CH (10% O(2)). During this hypoxic period, rats received a daily sc injection of either saline or ghrelin (150 microg/kg). Subsequently, heart and lung samples were collected for morphological, histological, and molecular analyses. CH significantly elevated PAP in saline-treated rats, increased wall thickness of peripheral pulmonary arteries, and, consequently, induced right ventricular hypertrophy. In these rats, CH also led to the overexpression of endothelial nitric oxide synthase mRNA and protein, as well as endothelin-1 mRNA within the lung. Exogenous ghrelin administration attenuated the CH-induced overexpression of endothelial nitric oxide synthase mRNA and protein, as well as endothelin-1 mRNA. Consequently, ghrelin significantly attenuated the development of pulmonary arterial hypertension, pulmonary vascular remodeling, and right ventricular hypertrophy. These results demonstrate the therapeutic benefits of ghrelin for impeding the pathogenesis of pulmonary hypertension and right ventricular hypertrophy, particularly in subjects prone to CH (e.g. pulmonary disorders).

A role of the histaminergic system for the control of feeding by orexigenic peptides.

A considerable number of neuropeptides are involved in the hypothalamic regulation of feeding behavior. We previously reported that leptin, the ob gene product, expressed its anorectic effect though the histaminergic system via histamine H(1) receptors. However, the interactions among the orexigenic neuropeptides, such as orexin-A, neuropeptide Y (NPY), and ghrelin, and the histaminergic system have not yet been clarified. In this study, we investigated the effect of the neuropeptides on the hypothalamic histamine release in rats, and on food intake and locomotor activity in H(1)-receptor knockout (H1R-KO) mice. Orexin-A increased the histamine release and locomotor activity, but not food intake, suggesting that the histaminergic system participates in arousal rather than feeding by orexin-A. NPY also increased histamine release, but its effect was not immediate. NPY-injected H1R-KO mice consumed more food than the wild-type mice; thus, the histaminergic system may act as a feedback factor downstream of NPY. Ghrelin did not affect histamine release, and it increased food intake, even in H1R-KO mice. Thus, ghrelin expresses its action in a histamine-independent manner.

Different effects of peripheral and central ghrelin on regulation of food intake in the Japanese quail.

When rat or human ghrelin is administered to chickens or rats it stimulates the release of growth hormone, however, its effects on food intake differ between the two species. To investigate this discrepancy, we measured plasma ghrelin concentrations before and after food intake, and determined the effects of central (intracerebroventricular, icv) and peripheral (intraperitoneal, ip) injections of various ghrelin doses on food intake and body temperature in the Japanese quail. In control quails, plasma ghrelin levels were significantly increased in the fasting state; subsequent feeding produced a reduction, suggesting that ghrelin may act as an orexigenic signal in Japanese quails as well as mammals. Food intake was stimulated by ip, but not icv, injections of small doses of ghrelin, whereas both ip and icv injections of larger doses inhibited feeding. A large dose of ghrelin also increased body temperature. These results suggest that an increase in peripheral ghrelin may act as a hunger signal to induce food intake through stimulation of the afferent vagal nerve in the Japanese quail, as in rats, whereas central ghrelin may inhibit feeding in different ways in the two species.

Analysis of rat insulin II promoter-ghrelin transgenic mice and rat glucagon promoter-ghrelin transgenic mice.

We developed and analyzed two types of transgenic mice: rat insulin II promoter-ghrelin transgenic (RIP-G Tg) and rat glucagon promoter-ghrelin transgenic mice (RGP-G Tg). The pancreatic tissue ghrelin concentration measured by C-terminal radioimmunoassay (RIA) and plasma desacyl ghrelin concentration of RIP-G Tg were about 1000 and 3.4 times higher than those of nontransgenic littermates, respectively. The pancreatic tissue n-octanoylated ghrelin concentration measured by N-terminal RIA and plasma n-octanoylated ghrelin concentration of RIP-G Tg were not distinguishable from those of nontransgenic littermates. RIP-G Tg showed suppression of glucose-stimulated insulin secretion. Arginine-stimulated insulin secretion, pancreatic insulin mRNA and peptide levels, beta cell mass, islet architecture, and GLUT2 and PDX-1 immunoreactivity in RIP-G Tg pancreas were not significantly different from those of nontransgenic littermates. Islet batch incubation study did not show suppression of insulin secretion of RIP-G Tg in vitro. The insulin tolerance test showed lower tendency of blood glucose levels in RIP-G Tg. Taking lower tendency of triglyceride level of RIP-G Tg into consideration, these results may indicate that the suppression of insulin secretion is likely due to the effect of desacyl ghrelin on insulin sensitivity. RGP-G Tg, in which the pancreatic tissue ghrelin concentration measured by C-RIA was about 50 times higher than that of nontransgenic littermates, showed no significant changes in insulin secretion, glucose metabolism, islet mass, and islet architecture. The present study raises the possibility that desacyl ghrelin may have influence on glucose metabolism.

Transgenic mice overexpressing des-acyl ghrelin show small phenotype.

Ghrelin, a 28-amino acid acylated peptide, displays strong GH-releasing activity in concert with GHRH. The fatty acid modification of ghrelin is essential for the actions, and des-acyl ghrelin, which lacks the modification, has been assumed to be devoid of biological effects. Some recent reports, however, indicate that des-acyl ghrelin has effects on cell proliferation and survival. In the present study, we generated two lines of transgenic mice bearing the preproghrelin gene under the control of chicken beta-actin promoter. Transgenic mice overexpressed des-acyl ghrelin in a wide variety of tissues, and plasma des-acyl ghrelin levels reached 10- and 44-fold of those in control mice. They exhibited lower body weights and shorter nose-to-anus lengths, compared with control mice. The serum GH levels tended to be lower, and the serum IGF-I levels were significantly lower in both male and female transgenic mice than control mice. The responses of GH to administered GHRH were normal, whereas those to administered ghrelin were reduced, especially in female transgenic mice, compared with control mice. These data suggest that overexpressed des-acyl ghrelin may modulate the GH-IGF-I axis and result in small phenotype in transgenic mice.

Clinical endocrinology and metabolism. Ghrelin, a novel growth-hormone-releasing and appetite-stimulating peptide from stomach.

Recent identification of novel appetite-regulating hormones has revealed the complex interactions of these humoral factors in the regulation of feeding behavior in mammals. One of these hormones, ghrelin, a natural ligand of the orphan receptor GHS-R, purified from stomach, is able to stimulate growth hormone release from pituitary cells. Ghrelin is a 28 amino acid peptide containing an n-octanoylated serine 3 residue that is essential for its activity. Ghrelin stimulates appetite by acting on the hypothalamic arcuate nucleus, the region known to control food intake. As an orexigenic peptide, ghrelin is therefore an endogenous regulator of feeding behavior from the peripheral tissues to the central nervous system.

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.

Regulation of ghrelin secretion during pregnancy and lactation in the rat: possible involvement of hypothalamus.

We investigated the plasma concentration of ghrelin peptide during pregnancy and lactation in rats. Plasma ghrelin levels on days 10 and 15 of pregnancy were significantly lower than those of the non-pregnant rats. Thereafter, the plasma ghrelin levels on day 20 of pregnancy sharply increased to levels comparable with those in non-pregnant rats. Ghrelin peptide concentrations in the stomach did not change significantly during pregnancy. In the hypothalamus, ghrelin mRNA levels were significantly lower on day 15 of pregnancy than in the non-pregnant rats. Also, plasma ghrelin levels were significantly lower in lactating dams than non-lactating controls on days 3 and 8 of lactation. We examined the possible involvement of prolactin and oxytocin in the regulation of plasma ghrelin concentrations during lactation. Although plasma prolactin levels were decreased by the administration of bromocriptine, plasma ghrelin levels did not differ significantly between vehicle- and drug-treated lactating rats. Administration of haloperidol produced a marked increase in plasma prolactin levels as compared with the non-lactating controls. However, plasma ghrelin levels were not significantly different between vehicle- and drug-treated rats. Administration of an oxytocin antagonist into the lateral ventricle significantly inhibited the increase in the plasma oxytocin level induced by acute suckling. However, plasma ghrelin levels did not significantly between the groups. These observations indicated that the decrease in serum ghrelin is caused by a loss of the contribution of hypothalamic ghrelin. Furthermore, the present results suggested that the suckling stimulus itself, but the release of prolactin or oxytocin, is the factor most likely to be responsible for the suppression of ghrelin secretion during lactation.

Ghrelin and the regulation of food intake and energy balance.

Ghrelin, an endogenous ligand for the growth hormone secretagogue receptor, is synthesized principally in the stomach and is released in response to acute and chronic changes in nutritional state. In addition to having a powerful effect on the secretion of growth hormone, ghrelin stimulates food intake and transduces signals to hypothalamic regulatory nuclei that control energy homeostasis. Thus, it is interesting to note that the stomach may play an important role in not only digestion but also pituitary growth hormone release and central feeding regulation. We summarize recent findings on the integration of ghrelin into neuroendocrine networks that regulate food intake and energy balance.