Aim: To determine whether different glycemic index (GI) diets have different effects on the acute secretion of motilin, orexin and neuropeptide Y (NPY), regulators of food intake, energy homeostasis and glucose metabolism.
Methods: Fifty healthy volunteers were randomly assigned to two groups and were fed an isocaloric breakfast (464 kcal) containing high GI (HGI; GI=90) or low GI (LGI; GI=47) components. Serum motilin, orexin, and NPY concentrations were measured before (0 h) and 2h after the meal.
Results: The concentrations of motilin, orexin-A, NPY, C-peptide, and blood glucose at 0 h were similar in both groups of subjects. However, 2 h after breakfast, the serum motilin, NPY, C-peptide, and blood glucose concentrations were increased and orexin-A concentrations were decreased in both groups. The percentage changes from 0 to 2 h [(2-h value-0-h value)/baseline×100)] in motilin (27.72±2.46% vs. 20.95±2.06%, p=0.04) and orexin-A (9.15±2.06% vs. 3.49±1.67%, p=0.038) concentrations were significantly higher in the LGI group than in the HGI group. By contrast, the percentage changes in NPY (53.7±9.73% vs. 28.1±5.2%, p=0.026) and blood glucose (12.3±3.78% vs. 1.77±2.52%, p=0.025) concentrations were significantly greater in the HGI group than in the LGI group. Although C-peptide concentrations increased significantly after breakfast in both groups, the magnitude of the increase was similar (132.69±25.15% vs. 139.98±27.29%, p=0.845). Motilin and NPY concentrations were moderately positive correlated (r=0.410, p=0.042), while orexin-A and NPY concentrations were negatively correlated (r=-0.429, p=0.033) at 2h in the LGI group.
Conclusions: A breakfast with a LGI reduced the secretion of orexin-A but significantly stimulated motilin secretion, without marked effects on the secretion of NPY. Therefore, consumption of a LGI diet may help to regulate food intake and energy expenditure in healthy individuals based on the changes in these hormones.
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