Ghrelin does not influence gastric emptying in obese subjects.

OBJECTIVE

To evaluate the relationship between fasting plasma concentrations of ghrelin and gastric emptying in obese individuals compared with lean subjects.

RESEARCH METHODS AND PROCEDURES

We included 20 obese patients (9 men and 11 women, BMI > 30 kg/m2) and 16 nonobese control subjects (7 men and 9 women, BMI < or = 25 kg/m2). Gastric emptying of solids (egg sandwich labeled with radionuclide) was measured at 120 minutes with (99m)Tc-single photon emission computed tomography imaging. Ghrelin and leptin were analyzed by radioimmunoassay and ELISA methods, respectively.

RESULTS

The gastric half-emptying time was similar in obese men and women (67.8 +/- 14.79 vs. 66.6 +/- 13.56 minutes) but significantly shorter (p < 0.001) than in the control population (men: 88.09 +/- 11.72 minutes; women: 97.25 +/- 10.31 minutes). Ghrelin levels were significantly lower in obese subjects (131.37 +/- 47.67 vs. 306.3 +/- 45.52 pg/mL; p < 0.0001 in men and 162.13 +/- 32.95 vs. 272.8 +/- 47.77 pg/mL; p < 0.0001 in women). A negative correlation between gastric emptying and fasting ghrelin levels was observed only in lean subjects (y = -0.2391x + 157.9; R2 = 0.95). Also, in the lean group, ghrelin was the only significant independent determinant of gastric emptying, explaining 98% of the variance (adjusted R2) in a multiple regression analysis.

DISCUSSION

This report shows that, in humans, gastric emptying is faster in obese subjects than in lean controls and that, whereas ghrelin is the best determinant of gastric kinetics in healthy controls, this action is lost in obesity.