Elevated plasma levels of alpha-melanocyte stimulating hormone (alpha-MSH) are correlated with insulin resistance in obese men

OBJECTIVE: The role of alpha-melanocyte stimulating hormone (MSH) in obesity has been well-documented. However, circulating alpha-MSH concentrations in obese men and their relationship with clinical indicators of obesity and glucose metabolism have not as yet been evaluated. METHODS: We measured the plasma concentrations of alpha-MSH in 15 obese and 15 non-obese male subjects. The relationship of the plasma concentrations of alpha-MSH with body mass index (BMI), body fat mass (measured by bioelectric impedance), body fat distribution (measured by computed tomography), insulin levels, insulin resistance (assessed by the glucose infusion rate (GIR) during an euglycemic hyperinsulinemic clamp study) and with the serum concentrations of leptin and TNF-alpha were also evaluated. RESULTS: In obese men, the plasma alpha-MSH concentrations were significantly increased compared with those in non-obese men (P< 0.02). The plasma levels of alpha-MSH were positively correlated with BMI (r= 0.560, P< 0.05), fasting insulin levels (r=0.528, P< 0.05) and with visceral fat area (r=0.716, P<0.01), but negatively correlated with GIR (r= -0.625, P< 0.02) in obese male subjects. There were significant correlations between plasma concentrations of alpha-MSH and visceral fat area (r=0.631, P< 0.02), and GIR (r = -0.549, P< 0.05) in non-obese male subjects. Circulating concentrations of alpha-MSH were not significantly correlated with the serum concentrations of leptin and TNF-alpha in both obese and non-obese men. CONCLUSION: Circulating concentrations of alpha-MSH are significantly increased and correlated with insulin resistance in obese men.