Decreased circulating levels of active ghrelin are associated with increased oxidative stress in obese subjects

Objective: To investigate the relationship between active ghrelin and oxidative stress in obese subjects. Design: We measured the plasma levels of free 8-epi-prostaglandin F-2 alpha (8-epi-PGF(2 alpha), a reliable and systemic marker of oxidative stress) and the active form of ghrelin in 17 obese and 17 normal subjects. The biologically active forms of ghrelin were measured-using a commercially available radio-immunoassay kit and free 8-epi-PGF(2 alpha) was measured using an enzyme immunoassay kit. Results: The circulating level of active ghrelin was significantly decreased (20.4+/-2.6 vs 40.9 +/- 3.9 fmol/ml, P < 0.01) while that of 8-epi-PGF(2 alpha) was significantly increased (61.5 +/- 9.6 vs 17.3 +/- 3.4 pg/ml, P < 0.01) in obese subjects compared with normal subjects. The plasma levels of active ghrelin and 8-epi-PGF(2 alpha) were significantly correlated in obese (r = -0.507, P < 0.05) and in all (r = 0.577, P < 0.01) subjects. Multivariate analysis showed that the plasma levels of active ghrelin and 8-epi-PGF(2 alpha) were significantly and independently correlated in all subjects (F = 7.888, P < 0.01). Conclusions: There is an inverse correlation between circulating levels of active ghrelin and oxidative stress in obesity. Low circulating levels of active ghrelin may enhance oxidative stress and the process of atherosclerosis in obese subjects.