Fasting ghrelin is related to skeletal muscle mass in healthy adults

The determinants of plasma ghrelin concentrations including the effects of aging, gender, and body composition, are unclear. Appetite and energy intake decrease with advancing age, and there is a corresponding decline in total body lean tissue, and an increase in fat mass. We measured fasting plasma ghrelin and insulin concentrations in 52 healthy subjects aged 22-82 years, and assessed body composition by dual energy X-ray absorptiometry. Energy intake was estimated from diet diaries. Fasting ghrelin concentrations were not significantly correlated with age and energy intake (R = 0.07, P = 0.62; and R = -0.14, P = 0.34 respectively) on univariate regression analysis, and ghrelin concentrations were higher in females than males (2886.8 +/- A 182.1 pg/ml vs 2082.5 +/- A 121.2 pg/ml; P = 0.001). Ghrelin was inversely related to body mass index (R = -0.328, P = 0.018), fat-free body mass (R = -0.428, P = 0.002), and total skeletal muscle mass (R = -0.439, P = 0.001), but not related to body fat mass (R = 0.177, P = 0.208). On multiple regression analysis, total skeletal muscle mass (corrected for height) was the only significant negative predictor (P < 0.0001) of fasting ghrelin concentrations. In conclusion, in healthy adults, plasma ghrelin concentrations are not significantly influenced by age or energy intake per se, but relate to skeletal muscle mass.