Relationships Between Acylated Ghrelin with Growth Hormone, Insulin Resistance, Lipid Profile, and Cardio Respiratory Function in Lean and Obese Men

Background: Acylated ghrelin, biologically active form of ghrelin, activates growth hormone (GH) secretagogue receptor 1a and play a role in regulating of energy balance. The purpose of this study was to survey relationships between acylated ghrelin with GH, insulin resistance, lipid profile, and cardio respiratory function in lean and obese men.

Methods: Nineteen obese men (body mass index 31.0 ± 3.5 kg/m(2), aged 27.5 ± 5.8 year) and the same number of lean men (body mass index = 18.47 ± 2.1 kg/m(2), aged 26.9 ± 5.6 year) were selected if they had no experience of regular physical activity during six month ago. After 12 hour fasting, blood samples were collected and blood parameters as well as maximal oxygen uptake (as indicator of cardiorespiratory function) was assessed.

Results: Insulin levels and HOMA-IR (homeostasis model assessment of insulin resistance) were higher, and GH, acylated ghrelin and maximal oxygen uptake levels were lower, in obese versus lean men (p < 0.01). No significant differences were observed in systolic and diastolic blood pressure, fasting blood glucose, and lipid profiles between the two groups (p > 0.01). Plasma acylated ghrelin concentrations in obese and lean men were negatively correlated to body weight (r= -0.50, r= -0.43, respectively), body fat percent (r = -0.53, r = -0.44, respectively), body mass index (r = -0.53, r = -0.49, respectively), insulin (r = -0.42, r = -0.40, respectively) and HOMA-IR (r = -0.48, r = -0.45, respectively), and positively correlated to GH levels (r = 0.37, r = 0.31, respectively) and maximal oxygen uptake (r = 0.33, r = 0.31, respectively) (p < 0.01). No significant correlations were observed between plasma acylated ghrelin concentrations and systolic and diastolic blood pressure, fasting blood glucose, and lipid profiles in both groups (p > 0.01).

Conclusions: Obese and lean inactive young men had different levels of acylated ghrelin, GH, insulin, insulin resistance index, cardiorespiratory function and body fat percent. Body fat percent, insulin, and GH levels appear to be best determinant factors of acylated ghrelin levels. Also, in both obese and lean young men, higher levels of cardiovascular function were associated with higher levels of acylated ghrelin.