Ghrelin: integrative neuroendocrine peptide in health and disease

Ghrelin hyporesponsiveness contributes to age-related hyperinflammation in septic shock

OBJECTIVE

To test the hypothesis that hyporesponsiveness to ghrelin due to reduced growth hormone (GH) contributes to the aging-related hyperinflammatory state in sepsis.

SUMMARY BACKGROUND DATA

Sepsis and septic shock are a serious problem, particularly in the geriatric population. Ghrelin is an endogenous ligand for the GH secretagogue receptor 1a (GHSR1a, ie, ghrelin receptor). The decline in GH with age is directly associated with many adverse changes that occur with aging. However, the role of GH, ghrelin, and GHSR1a in the age-associated vulnerability to sepsis remains unknown.

METHODS

Male Fischer 344 rats (young: 3 months; aged: 24 months) were used. Plasma GH levels, ghrelin receptor expression, and neuronal activity in the parasympathostimulatory nuclei of the brain stem in normal young and aged animals were measured. Endotoxemia was induced by intravenous injection of lipopolysaccharide (LPS, 15 mg/kg BW).

RESULTS

While LPS-induced release of proinflammatory cytokines from macrophages isolated from aged rats decreased, LPS injection resulted in an in vivo hyperinflammatory state. GH levels were lower in aged rats, which was associated with lower expression of GHSR1a in the dorsal vagal complex and a decrease in parasympathostimulatory neuronal activity. GHSR1a antagonist elevated LPS-induced cytokine release in young rats. GH increased GHSR-1a expression in the dorsal vagal complex in aged rats. Coadministration of ghrelin and GH, but not ghrelin alone or GH alone, markedly reduced cytokine levels and organ injury after endotoxemia in aged rats, which was associated with significantly elevated parasympathostimulatory neuronal activity.

CONCLUSIONS

These findings suggest that the reduced central (brain) responsiveness to ghrelin due to the decreased GH, plays a major role in producing the hyperinflammatory state, resulting in severe organ injuries and high mortality after endotoxemia in aged animals. Ghrelin and GH can be developed as a novel therapy for sepsis in the geriatric population.

Orexigenic hormone ghrelin attenuates local and remote organ injury after intestinal ischemia-reperfusion

BACKGROUND

Gut ischemia/reperfusion (I/R) injury is a serious condition in intensive care patients. Activation of immune cells adjacent to the huge endothelial cell surface area of the intestinal microvasculature produces initially local and then systemic inflammatory responses. Stimulation of the vagus nerve can rapidly attenuate systemic inflammatory responses through inhibiting the activation of macrophages and endothelial cells. Ghrelin, a novel orexigenic hormone, is produced predominately in the gastrointestinal system. Ghrelin receptors are expressed at a high density in the dorsal vagal complex of the brain stem. In this study, we investigated the regulation of the cholinergic anti-inflammatory pathway by the novel gastrointestinal hormone, ghrelin, after gut I/R.

METHODS AND FINDINGS

Gut ischemia was induced by placing a microvascular clip across the superior mesenteric artery for 90 min in male adult rats. Our results showed that ghrelin levels were significantly reduced after gut I/R and that ghrelin administration inhibited pro-inflammatory cytokine release, reduced neutrophil infiltration, ameliorated intestinal barrier dysfunction, attenuated organ injury, and improved survival after gut I/R. Administration of a specific ghrelin receptor antagonist worsened gut I/R-induced organ injury and mortality. To determine whether ghrelin's beneficial effects after gut I/R require the intact vagus nerve, vagotomy was performed in sham and gut I/R animals immediately prior to the induction of gut ischemia. Our result showed that vagotomy completely eliminated ghrelin's beneficial effect after gut I/R. To further confirm that ghrelin's beneficial effects after gut I/R are mediated through the central nervous system, intracerebroventricular administration of ghrelin was performed at the beginning of reperfusion after 90-min gut ischemia. Our result showed that intracerebroventricular injection of ghrelin also protected the rats from gut I/R injury.

CONCLUSIONS

These findings suggest that ghrelin attenuates excessive inflammation and reduces organ injury after gut I/R through activation of the cholinergic anti-inflammatory pathway.

Laparoscopic sleeve gastrectomy for morbid obesity

The incidence of obesity is steadily rising, and it has been estimated that 40% of the US population will be obese by the year 2025 if the current trend continues. In recent years there has been renewed interest in the surgical treatment of morbid obesity in concomitance with the epidemic of obesity. Bariatric surgery proved effective in providing weight loss of large magnitude, correction of comorbidities and excellent short-term and long-term outcomes, decreasing overall mortality and providing a marked survival advantage. The Laparoscopic Sleeve Gastrectomy (LSG) has increased in popularity and is currently very “trendy” among laparoscopic surgeons involved in bariatric surgery. As LSG proved to be effective in achieving considerable weight loss in the short-term, it has been proposed by some as a sole bariatric procedure. This editorial focuses on the particular advantages of LSG in the treatment of morbid obesity.

Oxidant stress and B vitamins status in patients with non-small cell lung cancer

In this study, we examined oxidative stress and B vitamins status in non-small cell lung cancer (NSCLC) patients at different stages. NSCLC patients were divided into 2 groups, stage III (IIIA + IIIB, n = 27) and stage IV (n = 23). A total of 16 healthy control subjects were included for comparison. Plasma levels of alpha-tocopherol, beta-carotene, vitamin C, Se, Cu, Zn, reduced glutathione (GSH), oxidized glutathione (GSSG), lipid oxidation and the activities of glutathione peroxidase (GPX), superoxide dismutase (SOD), catalase, and xanthine oxidase (XO) were determined for evaluating oxidative status in these subjects. B vitamins (B(1), B(2), B(6), B(12), folate) in blood and plasma ghrelin level in these subjects were analyzed. Results showed that plasma level of ghrelin and lipid oxidation in NSCLC patients were significantly greater than control groups (P < 0.05). The activity of GPX, SOD, or catalase was significantly reduced, but XO activity was significantly elevated in NSCLC patients (P < 0.05). Plasma level of GSH was significantly lower, but GSSG level was significantly increased in NSCLC patients (P < 0.05). Vitamins B(2) and B(6) levels in red blood cells (RBC) from NSCLC patients were significantly lower (P < 0.05), and both were negatively correlated with plasma ghrelin. The correlation coefficients were -0.788 and -0.752, respectively. These data suggest that plasma GSH level may be a proper biomarker for evaluating oxidation status for NSCLC patients. RBC levels of vitamins B2 and B6 were reduced in NSCLC patients; thus, the importance of vitamins B(2) and B(6) for NSCLC patients could not be ignored.

Ghrelin, leptin, IGF-1, IGFBP-3, and insulin concentrations at birth: is there a relationship with fetal growth and neonatal anthropometry?

BACKGROUND

Insulin, growth hormone (GH), and growth factors (insulin-like growth factors [IGFs] and their binding proteins [IGFBPs]) are known to influence fetal growth and also the synthesis/secretion of the recently discovered hormones leptin and ghrelin.

METHODS

In 153 delivering mothers and their offspring at birth, we prospectively investigated the association between mothers' and babies' serum concentrations of ghrelin, leptin, insulin, IGF-1, and IGFBP-3 and neonatal anthropometric characteristics and the growth of the fetus. We also tried to put babies' serum glucose and GH measurements in this context.

RESULTS

Birth weight (BW), birth length, head circumference, and ponderal index (PI) were positively associated with cord IGF-1, IGFBP-3, and leptin and negatively associated with GH. BW was independently associated with maternal stature and prepartum weight, birth length with maternal stature, PI with maternal insulin and prepartum weight, and head circumference with maternal ghrelin. Compared with preterm infants whose development was appropriate for gestational age (AGA), preterm growth-restricted babies displayed alteration in GH-IGF axis (increased GH and low IGF-1 and IGFBP-3 concentrations), low leptin and glucose concentrations, and increased ghrelin concentrations. In large-for-gestational-age (LGA) babies, leptin, IGFBP-3, insulin, and glucose concentrations were significantly higher in asymmetric LGA newborns than in symmetric LGA and AGA newborns.

CONCLUSIONS

We found relationships between metabolic factors, fetal growth, and anthropometry. Intrauterine growth restriction involved alteration in the fetal GH-IGF axis, with relatively low leptin and glucose concentrations and increased ghrelin concentrations. Leptin, insulin, and IGFBP-3 delineated subtypes of fetal overgrowth.

Exogenous ghrelin modulates release of pro-inflammatory and anti-inflammatory cytokines in LPS-stimulated macrophages through distinct signaling pathways

BACKGROUND

Ghrelin, an orexigenic 28-amino-acid peptide, has been studied primarily in relation to the control of appetite and fat metabolism. In addition to these well-known functions, ghrelin, and its target receptors, growth hormone secretagogue receptors (GHS-Rs), have been localized to neutrophils, lymphocytes, and macrophages, which suggests that ghrelin may be involved in immune modulation.

METHODS

To assess the therapeutic role of ghrelin in production of pro-inflammatory and anti-inflammatory cytokines, the effects of exogenous ghrelin administration on the regulation of cytokine release in lipopolysaccharide (LPS)-activated murine RAW 264.7 macrophages were analyzed.

RESULTS

Ghrelin and GHS-Rs are expressed in murine macrophages. In addition, exogenous ghrelin inhibited the production of pro-inflammatory cytokines IL-1beta and TNF-alpha in LPS-stimulated murine macrophages in a dose dependent and time-dependent fashion. Exogenous ghrelin pretreatment resulted in a decrease in LPS-induced NFkappaB activation and was presumably the reason for this ghrelin-mediated effect. In contrast to these findings, exogenous ghrelin significantly augmented the release of the anti-inflammatory cytokine IL-10 in a dose-dependent and time-dependent fashion from LPS-stimulated murine macrophages. Ghrelin administration enhanced activation of p38 MAPK, which is known to control the release of IL-10 in macrophages independent of the NFkappaB pathway. These effects of ghrelin on both pro-inflammatory and anti-inflammatory cytokines were offset when a specific GHS-R receptor antagonist was added to the culture media.

CONCLUSIONS

These data suggest that ghrelin has potent anti-inflammatory properties through modulation of secretion of both pro-inflammatory and anti-inflammatory cytokines from LPS-stimulated macrophages through distinct signaling cascades. Therapeutic utility of ghrelin to control, modulate, or treat pathologic inflammatory conditions like endotoxemic shock and ulcerative colitis requires additional investigation.

Ghrelin inhibits sympathetic nervous activity in sepsis

Our previous studies have shown that norepinephrine (NE) upregulates proinflammatory cytokines by activating alpha(2)-adrenoceptor. Therefore, modulation of the sympathetic nervous system represents a novel treatment for sepsis. We have also shown that a novel stomach-derived peptide, ghrelin, is downregulated in sepsis and that its intravenous administration decreases proinflammatory cytokines and mitigates organ injury. However, it remains unknown whether ghrelin inhibits sympathetic activity through central ghrelin receptors [i.e., growth hormone secretagogue receptor 1a (GHSR-la)] in sepsis. To study this, sepsis was induced in male rats by cecal ligation and puncture (CLP). Ghrelin was administered through intravenous or intracerebroventricular injection 30 min before CLP. Our results showed that intravenous administration of ghrelin significantly reduced the elevated NE and TNF-alpha levels at 2 h after CLP. NE administration partially blocked the inhibitory effect of ghrelin on TNF-alpha in sepsis. GHSR-la inhibition by the administration of a GHSR-la antagonist, [d-Arg(1),d-Phe(5), d-Trp(7,9),Leu(11)]substance P, significantly increased both NE and TNF-alpha levels even in normal animals. Markedly elevated circulating levels of NE 2 h after CLP were also significantly decreased by intracerebroventricular administration of ghrelin. Ghrelin's inhibitory effect on NE release was completely blocked by intracerebroventricular injection of the GHSR-1a antagonist or a neuropeptide Y (NPY)/Y(1) receptor antagonist. However, ghrelin's downregulatory effect on TNF-alpha release was only partially diminished by these agents. Thus ghrelin has sympathoinhibitory properties that are mediated by central ghrelin receptors involving a NPY/Y1 receptor-dependent pathway. Ghrelin's inhibitory effect on TNF-alpha production in sepsis is partially because of its modulation of the overstimulated sympathetic nerve activation.

Alpha-melanocyte stimulating hormone and ghrelin: central interaction in feeding control

Alpha-melanocyte stimulating hormone (alpha-MSH) and ghrelin play significant yet opposite roles in the regulation of feeding: alpha-MSH inhibits, whereas ghrelin stimulates consumption. The two peptidergic systems may interact in the process of food intake control. A single report published thus far has shown that a synthetic agonist of the melanocortin receptors, MTII, injected in the hypothalamic paraventricular nucleus (PVN) decreases feeding generated by ghrelin. We found that very low doses of alpha-MSH and MTII administered ICV significantly reduced ghrelin-dependent hyperphagia. However, an endogenous molecule, alpha-MSH, infused in the PVN did not exert an inhibitory effect on ghrelin-induced consumption, whereas the effective dose of PVN MTII exceeded that necessary to decrease short-term deprivation-induced feeding. We conclude that it is likely that in feeding regulation alpha-MSH and ghrelin "interact" at the central nervous system level, but the involvement of the PVN in this interaction appears questionable.

Ghrelin attenuates sepsis-induced acute lung injury and mortality in rats

RATIONALE

Our study has shown that plasma levels of ghrelin, a stomach-derived peptide, are significantly reduced in sepsis, and that ghrelin administration improves organ blood flow via a nuclear factor (NF)-kappaB-dependent pathway. However, it remains unknown whether ghrelin has any protective effects on severe sepsis-induced acute lung injury (ALI) and, if so, whether inhibition of NF-kappaB plays any role in it.

OBJECTIVES

To test the hypothesis that ghrelin reduces severe sepsis-induced ALI and mortality through inhibition of NF-kappaB.

METHODS

Sepsis was induced in rats by cecal ligation and puncture (CLP). Five hours after CLP, a bolus intravenous injection of 2 nmol of ghrelin was followed by continuous infusion of 12 nmol of ghrelin via a minipump for 15 hours. Samples were harvested 20 hours post-CLP (i.e., severe sepsis). Pulmonary levels of ghrelin and proinflammatory cytokines were measured by ELISA. NF-kappaB p65 and IkappaBalpha expression and NF-kappaB activity were measured by Western blot analysis and ELISA, respectively. Pulmonary blood flow was measured with radioactive microspheres. In additional animals, the necrotic cecum was excised 20 hours post-CLP and 10-day survival was recorded.

MEASUREMENTS AND MAIN RESULTS

Pulmonary levels of ghrelin decreased significantly 20 hours post-CLP. Ghrelin administration restored pulmonary levels of ghrelin, reduced lung injury, increased pulmonary blood flow, down-regulated proinflammatory cytokines, inhibited NF-kappaB activation, and improved survival in sepsis. Administration of a specific ghrelin receptor antagonist worsened the survival rate after CLP and cecal excision.

CONCLUSIONS

Ghrelin can be developed as a novel treatment for severe sepsis-induced ALI. The protective effect of ghrelin is mediated through inhibition of NF-kappaB.

An immunohistochemical study of the localization and developmental expression of ghrelin and its functional receptor in the ovine placenta

BACKGROUND

Ghrelin is an orexigenic hormone principally produced by the stomach, but also by numerous peripheral tissues including the placenta. Ghrelin acts via growth hormone secretagogue receptors (GHSR-1a) to alter food intake, fat utilization, and cellular proliferation, and has been suggested to play a role in the developmental growth of the fetoplacental unit. The placental expression of ghrelin and its role in ruminant species is not known. We tested the hypotheses that ghrelin and its functional receptor, GHSR-1a, are present in tissues of the ovine placenta, and that their expression is linked to the stage of development.

METHODS

Antibodies raised against ghrelin and GHSR-1a were used in standard immunohistochemical protocols on placental tissues collected from pregnant ewes (n = 6 per gestational time point) at days 50, 80, 100, 128 and 135 of gestation (term approximately day 145). Immunostaining for ghrelin and GHSR-1a was quantified using computer-aided image analysis. Image analysis data were subjected to one-way ANOVA, with differences in immunostaining between time-points determined by Fisher's least significant difference.

RESULTS

Positive immunostaining for ghrelin was detected in ovine placentae at all gestational time points, with staining localized to the maternal epithelium, caruncle and trophectoderm. There was a significant effect of gestational age (p < 0.001) on the placental expression of ghrelin, with maximal levels at gestational day 80. GHSR-1a immunostaining was detected in the fetal trophectoderm at all time points. In contrast to the gestational pattern of ghrelin expression, there was no effect of gestational age on placental GHSR-1a immunoexpression.

CONCLUSION

Ghrelin and GHSR-1a are both present in the ovine placenta, and ghrelin displays a developmentally-related pattern of expression. Therefore, these data strongly suggest that the ghrelin system may have a role in feto-placental development in sheep.

B vitamins deficiency and decreased anti-oxidative state in patients with liver cancer

BACKGROUND

This study examined the status of oxidative stress and B vitamins in hepatocellular carcinoma (HCC) patients in different tumor-node-metastasis stages. Patients were divided into two groups as I + II (n = 21) and III + IV (n = 19).

METHODS

Plasma levels of lipid oxidation, alpha-tocopherol, beta-carotene, vitamin C, glutathione and the activity of antioxidant enzymes (glutathione peroxidase, superoxide dismutase, catalase, and xanthine oxidase) were determined for evaluating oxidative status. Blood B vitamins (B(1), B(2), B(6), B(12), and folate) and serum ghrelin were analyzed, and the relationship between serum ghrelin and vitamins B(2) (or B(6)) was evaluated.

RESULTS

HCC patients at III + IV stage showed significantly lower ghrelin, higher cholesterol, triglyceride, and uric acid than patients at I + II stage and healthy subjects (P < 0.05). Plasma lipid oxidation level in HCC patients was significantly greater than healthy subjects (P < 0.05). The activity of glutathione peroxidase, superoxide dismutase or catalase was significantly decreased, but xanthine oxidase activity was significantly elevated in HCC patients (P < 0.05). Plasma level of glutathione and vitamin C, not alpha-tocopherol and beta-carotene, in HCC patients was significantly lower (P < 0.05). Vitamins B(2) and B(6) levels in red blood cells from these HCC patients were significantly lower (P < 0.05).

CONCLUSION

This study provided novel clinical findings regarding the status of oxidative stress and B vitamins in HCC patients. Plasma glutathione level may be a proper biomarker for evaluating oxidative status for HCC patients. Our data indicate that HCC patients might need B vitamins supplementation. The increased serum level of triglyceride and cholesterol might be a consequence of an impaired hepatic fat metabolism, and might be improved by a lower fat administration to these patients.

An Investigation of Hormone and Lipid Associations after Weight Loss in Women

OBJECTIVE

The objectives of this study were to determine 1) whether the extent of weight loss is predictive of the degree of changes in hormone and lipid levels; 2) the interactions between energy regulating hormones after weight loss through an energy deficit/exercise protocol diet and exercise; 3) whether initial metabolic parameters are indicative of the extent of weight loss.

METHODS

Thirty-five hyperlipidemic females (BMI 28-39 kg/m2) 35-60 years old participated in a six month weight loss trial. Weight loss resulted from a diet and exercise program that when combined produced a 30% energy deficit. Fasting plasma taken during 2 wk stabilization periods at the beginning and end of the study was analysed for lipids, hormone and glucose levels.

RESULTS

Average weight loss was 11.7 +/- 2.5 kg (p < 0.0001). TC, LDL-C, and triacylglycerols decreased 9.3 +/- 9.5% (p < 0.0001), 7.4 +/- 12.2% (p < 0.001), and 26.8 +/- 19.6% (p < 0.05), respectively, while HDL-C increased (p < 0.05) by 8.2 +/- 16.3%. Leptin levels declined (p < 0.001) 48.9 +/- 16.0% and ghrelin levels rose (p < 0.001) 21.2 +/- 26.7%. While overall levels of adiponectin did not differ, individual values changed such that weight loss predicted increases in adiponectin levels. Though initial weight did not predict weight loss, baseline lipid and insulin levels positively predicted weight loss.

CONCLUSION

Initial metabolic parameters may be predictors of weight loss. Beneficial effects of weight loss as achieved through diet and exercise on measured parameters indicate moderate weight loss reduces key risk factors of cardiovascular disease in overweight individuals.

Ghrelin down-regulates proinflammatory cytokines in sepsis through activation of the vagus nerve

OBJECTIVE

To test the hypothesis that administration of ghrelin attenuates inflammatory responses in sepsis through vagal nerve stimulation.

SUMMARY BACKGROUND DATA

Ghrelin has been demonstrated to possess multiple functions, including stimulation of the vagus nerve. Our recent study has shown that plasma levels of ghrelin were significantly reduced in sepsis; and ghrelin administration improved organ perfusion and function. However, it remained unknown whether ghrelin also decreases proinflammatory cytokines in sepsis and, if so, whether the down-regulatory effect of ghrelin is mediated by activation of the vagus nerve.

METHODS

Male rats were subjected to sepsis by cecal ligation and puncture (CLP). At 5 hours after CLP, a bolus intravenous injection of 2 nmol ghrelin was followed by a continuous infusion of 12 nmol ghrelin via a primed 200-microL Alzet mini-pump for 15 hours. At 20 hours after CLP, plasma and peritoneal fluid levels of TNF-alpha and IL-6 were determined. The direct effect of ghrelin on cytokine production was studied using cultured normal rat Kupffer cells or peritoneal macrophages stimulated by lipopolysaccharide (LPS). In additional animals, vagotomy or sham vagotomy was performed in sham and septic animals immediately prior to ghrelin administration and cytokine levels were then measured.

RESULTS

Ghrelin significantly reduced TNF-alpha and IL-6 levels in sepsis. In contrast, ghrelin did not inhibit TNF-alpha and IL-6 release from LPS-stimulated Kupffer cells or peritoneal macrophages. However, vagotomy, but not sham vagotomy, prevented ghrelin's down-regulatory effect on TNF-alpha and IL-6 production.

CONCLUSIONS

Ghrelin down-regulates proinflammatory cytokines in sepsis through activation of the vagus nerve. Pharmacologic stimulation of the vagus nerve may offer a novel approach of anti-sepsis therapy.

Total ghrelin plasma level in patients with the restrictive type of anorexia nervosa

Ghrelin is produced mainly in the stomach and is an essential link of the brain-gut axis. Ghrelin stimulates hunger centers in hypothalamus controlling food intake and body mass gain. The aim of the study is to analyze the total ghrelin plasma level in patients suffering from restrictive type of anorexia nervosa (AN-R). According to DSM-IV classification a group of 30 AN-R patients was investigated before and after 3 and 6 months of therapy. Therapy included normocaloric diet and cognitive-behavioral psychotherapy (CBT). The control group consisted of 20 girls without any eating disorders. Before the therapy the total ghrelin plasma level in AN-R patients was significantly higher than in the control group. After 3 and 6 months of treatment the total ghrelin plasma level in AN-R patients was significantly lower than in the control group. In AN-R patients, the total ghrelin plasma level is connected with the pathological feeding behavior.

The entero-insular axis and adipose tissue-related factors in the prediction of weight gain in humans

Obesity has now reached epidemic proportions. Epidemiological studies in the past decades have shown that adults gain weight and adiposity from the early twenties until their sixties. In the paediatric population, growing numbers of children and adolescents put on unhealthy weight. Many environmental, socio-economical and biological determinants that predispose to weight gain have been identified thus far. The aim of the present review is to summarize the current knowledge on the role of the circulating levels of adipokines and other entero-insular hormones and biological markers of obesity to predict weight gain in humans. The review focuses on relationship between hormonal and biochemical markers (insulin, insulin-like growth factors, gastrointestinal hormones, leptin, adiponectin, resistin, inflammatory proteins and cytokines) and weight gain in prospective studies. The complex relationships displayed by these hormonal factors with future weight gain in humans are critically reviewed and integrative models are proposed. Overall, most of the studies reported to date made adjustments for baseline body mass index but failed to consider dietary intake and physical activity as confounding factors. Outstanding questions are raised and new directions for future prospective studies are proposed in order to improve our understanding of the role of biological determinants of energy balance and development of obesity in humans.

Electroacupuncture suppresses expression of gastric ghrelin and hypothalamic NPY in chronic food restricted rats

Electroacupuncture (EA) has been reported to reduce body weight in overweight subjects in clinical practice, as well as in rats and mice with diet-induced obesity. In the present study, this effect of EA was tested in lean rats subjected to long-term food restriction (FR, food was offered only 1 h/day). Two hertz EA administered once every other day produced a further reduction in body weight in FR rats. Exploration of the mechanism involved revealed significant downregulation of the orexigenic peptides: ghrelin in the stomach, and neuropeptide Y (NPY) but not Agouti-related peptide (AgRP) in the hypothalamus, which was in line with the reduction in food intake in rats receiving EA stimulation as compared with those receiving restraint only. Uncoupling protein 3 (UCP3), involved in accelerating energy expenditure, was not significantly altered. These results suggest that the EA-induced body weight reduction was due mainly to a decrease in food intake rather than an increase in energy expenditure. A reduction in the orexigenic peptides ghrelin and NPY may be involved in the underlying mechanism.

Serum ghrelin, IGF-I and IGFBP-3 levels in children with normal variant short stature

This study is planned to investigate the role of ghrelin in normal variant short stature. Serum ghrelin, IGF-I and IGFBP-3 levels were measured in 17 children with constitutional delay of growth, 19 children with familial short stature and 11 age matched healthy children. Mean bone age of the constitutional delay of growth group was lower compared to other groups. Constitutional delay of growth group had lower mean weight compared to the controls. Serum IGF-I values were lower in the constitutional delay of growth group compared to the familial short stature and control groups. IGFBP-3 levels of the groups were similar. Ghrelin levels were higher in the short stature groups compared to the controls. In the multiple regression analyses, weight (beta = -.54, p < 0.0001) and height SDS (beta = -.33, p = 0.01) were the independent determinants of ghrelin. The results of this study, the first one in which ghrelin levels are investigated in normal variant short stature, suggest that ghrelin does not play a role as a cause, but as a consequence in these patients because it is negatively correlated with weight and height standard deviation score. These negative correlations can be attributed to the compensatory response of ghrelin, which deserves further attention in future studies.

Intermedin/Adrenomedullin-2 inhibits growth hormone release from cultured, primary anterior pituitary cells

Intermedin (IMD), a novel member of the adrenomedullin (AM), calcitonin gene-related peptide (CGRP), amylin (AMY) peptide family, has been reported to act promiscuously at all the known receptors for these peptides. Like AM and CGRP, IMD acts in the circulation to decrease blood pressure and in the brain to inhibit food intake, effects that could be explained by activation of the known CGRP, AM, or AMY receptors. Because AM, CGRP, and AMY have been reported to affect hormone secretion from the anterior pituitary gland, we examined the effects of IMD on GH, ACTH, and prolactin secretion from dispersed anterior pituitary cells harvested from adult male rats. IMD, in log molar concentrations ranging from 1.0 pm to 100 nm, failed to significantly alter basal release of the three hormones. Similarly, IMD failed to significantly alter CRH-stimulated ACTH or TRH-stimulated prolactin secretion in vitro. However, IMD concentration-dependently inhibited GHRH-stimulated GH release from these cell cultures. The effects of IMD, although requiring higher concentrations, were as efficacious as those of somatostatin and, like somatostatin, may be mediated, at least in part, by decreasing cAMP accumulation. These actions of IMD were not shared by other members of the AM-CGRP-AMY family of peptides, suggesting the presence of a novel, unique IMD receptor in the anterior pituitary gland and a potential neuroendocrine action of IMD to interact with the hypothalamic mechanisms controlling growth and metabolism.

Postprandial acylated ghrelin status following fat and protein manipulation of meals in healthy young women

The aim of the present study was to investigate the postprandial effect of diet composition on circulating acylated ghrelin levels in healthy women. A randomized cross-over study of three experimental treatments was performed. A total of 11 healthy young women of normal body weight completed the study. All 11 subjects consumed three iso-energetic meals of different macronutrient composition, a balanced meal (50% carbohydrates, 30% fat and 20% protein), a high-fat meal (45% carbohydrates, 45% fat and 10% protein) and a high-protein meal (45% carbohydrates, 20% fat and 35% protein), for breakfast on separate days. The test meals were administered 1 month apart. Blood samples were withdrawn immediately before and at 15, 30, 60, 120 and 180 min after the test meal for measurement of plasma acylated ghrelin, as well as serum glucose, insulin and triacylglycerol (triglyceride) levels. Acylated ghrelin fell significantly after ingestion of both the balanced and high-protein meals. Ghrelin persisted at significantly lower levels than baseline for a longer duration following the high-protein meal (P<0.05 at 15, 30, 60 and 120 min) compared with the balanced meal (P<0.05 at 30 and 60 min). Moreover, acylated ghrelin levels correlated negatively with the postprandial insulin levels. In conclusion, postprandial changes in acylated plasma ghrelin depend on the macronutrient composition of the meal and are possibly influenced by insulin.

Endocrine regulation of energy metabolism: review of pathobiochemical and clinical chemical aspects of leptin, ghrelin, adiponectin, and resistin

BACKGROUND

Recent studies point to the adipose tissue as a highly active endocrine organ secreting a range of hormones. Leptin, ghrelin, adiponectin, and resistin are considered to take part in the regulation of energy metabolism.

APPROACH

This review summarizes recent knowledge on leptin and its receptor and on ghrelin, adiponectin, and resistin, and emphasizes their roles in pathobiochemistry and clinical chemistry.

CONTENT

Leptin, adiponectin, and resistin are produced by the adipose tissue. The protein leptin, a satiety hormone, regulates appetite and energy balance of the body. Adiponectin could suppress the development of atherosclerosis and liver fibrosis and might play a role as an antiinflammatory hormone. Increased resistin concentrations might cause insulin resistance and thus could link obesity with type II diabetes. Ghrelin is produced in the stomach. In addition to its role in long-term regulation of energy metabolism, it is involved in the short-term regulation of feeding. These hormones have important roles in energy homeostasis, glucose and lipid metabolism, reproduction, cardiovascular function, and immunity. They directly influence other organ systems, including the brain, liver, and skeletal muscle, and are significantly regulated by nutritional status. This newly discovered secretory function has extended the biological relevance of adipose tissue, which is no longer considered as only an energy storage site.

SUMMARY

The functional roles, structures, synthesis, analytical aspects, and clinical significance of leptin, ghrelin, adiponectin, and resistin are summarized.