Factors associated with fasting plasma ghrelin levels in children and adolescents

Abstract

INTRODUCTIONGhrelin, recently isolated from rat and human stomachs, is an endogenous ligand for growth hormone secretagogue receptor (GHSR) type 1a [1,2] . Recent studies have shown that ghrelin is secreted from hypothalamus, pituitary, endocrine pancreas islets, bowel, kidney, heart and testis [1,2] . Besides stimulating GH secretion, ghrelin has been reported to have other endocrine and nonendocrine actions, including stimulation of lactotroph and corticotroph secretion, effects on the gonadal axis, cardiovascular activity, influence on behavior and sleep, modulation of cell proliferation, repression of apoptosis, and orexigenic effects [3][4][5][6][7] . However, most of these studies used animal models and there were some discrepancies in the results. Thus, the regulation of ghrelin secretion and its specific role in endocrinology in humans, including the gonadal axis, insulin resistance, energy balance and obesity, are not completely understood.In this study, we measured plasma ghrelin levels in Chinese children and adolescents, analyzed their associated factors, and investigated the role of ghrelin in obesity, insulin resistance and reproductive physiology. MATERIALS AND METHODS Materials METHODS:A total of 283 subjects aged 4.8-15.8 year were enrolled. Fasting blood samples were collected and plasma ghrelin levels were measured by radioimmunoassay. Fasting glucose (FG), fasting insulin (FI), baseline testosterone (T), estradiol (E2), prolactin (PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH), serum total cholesterol (TC), triglyceride (TG), alanine aminotransferase (ALT) and uric acid (UA) were measured. Body mass index (BMI), insulin resistance by homeostasis model (HOMA-IR) and beta cell function by homeostasis model (HOMA-β) were calculated. RESULTS:The median ghrelin level was 290 ng/L (15.0-1325.0 ng/L). Bivariate correlation analysis showed that ghrelin levels were inversely correlated with BMI, ALT, TG, UA, LH, FI and HOMA-IR (all P < 0.05). No other significant correlation was found between ghrelin levels and age, gender, TC, E2, FSH, PRL, FG and HOMA-β. Stepwise multiple regression analysis showed that only BMI and FI were independent determinants of plasma ghrelin levels in these children and adolescents (P = 0.018 and P = 0.046, respectively), which explained 25.4% of the variance. CONCLUSION:These data suggest that the lower ghrelin levels in obese subjects may be the result of obesity and hyperinsulinemia, which is very common in obese subjects. Moreover, ghrelin may regulate human

A preprandial and postprandial plasma levels of ghrelin hormone in lean, overweight and obese Saudi females

“…Ghrelin has been considered as a cause of obesity in some studies, on account of the fact that ghrelin has orexigenic effects in both rats and humans (Haqq et al, 2003;Tang-Christensen et al, 2004). However, the results of most studies in humans, similar to ours, have demonstrated that ghrelin levels are negatively correlated with BMI (Tritos et al, 2003;Baldelli et al, 2006;Zou et al, 2008).…”

“…Stimulatory factors appear to be fasting and a low protein diet These factors may explain why ghrelin is suppressed in obese subjects but do not explain the dynamic response of ghrelin to eating, why concentration of peptide that stimulates gastric emptying (Vicennati et al, 2007) fall after food ingestion or why these responses are altered in obese individuals. Zou et al (2008) speculate that the lower ghrelin levels in obesity are part of negative feedback to inhibit appetite and body weight, but not the primary cause of obesity (McLaughlin et al, 2004). This is also supported by the fact that circulating ghrelin levels increase in anorexia and cachexia (Misra et al, 2005;Janas-Kozik et al, 2007).…”

“…However, animals without ghrelin do not have significantly altered body weight or food intake when compared with their wildtype littermates (Sun et al, 2003;Wortley et al, 2004). This suggests that it is a part of a reversible feedback mechanism, but not a determinant factor (Zou et al, 2008).…”

Study of Ghrelinand LeptinHormones Changes in Obese Postmenopausal Patients

“…ghrelin levels were negatively associated with BMI.Castaneda et al [38] suggested that ghrelin itself is not the key cause of obesity and stated whether potentially low levels of ghrelin in obesity represent an adaptation to the positive energy balance or an increased sensitivity to ghrelin remains an open question.Zou et al [39]speculated that the lower ghrelin levels in obesity were part of negative feedback to inhibit appetite and body weight, but not the primary cause of obesity.Ghrelin plays an important role in the regulation of food intake. Therapeutic intervention with ghrelin in catabolic situation may induce a combination of enhanced food intake, increased gastric emptying and nutrient storage, so ghrelin agonists might address cachexia Constance et al [40].…”

Hyperghrelinemia in the patients presenting with Prader-Willi syndrome

“…Гипергрелинемия может быть частично объяс-нена менее выраженной инсулинорезистентностью и более низкой секрецией инсулина при СПВ [12,39,40], так как известно, что внутривенное введение инсулина приводит к снижению уровня грелина [41], а при низком содержании глюкозы и инсулина секреция грелина повышается [42].…”