Obese adolescents show impaired meal responses of the appetite-regulating hormones ghrelin and PYY

Abstract

Ghrelin and peptide YY (PYY) stimulate hunger and satiety, respectively. The physiology of these hormones during normal meal intake remains unclear. This study was designed to compare the responses of these two hormones to meal intake between lean and obese Hispanic adolescents. A total of 10 obese and 7 lean Hispanic youth, aged 11-14 years, consumed two mixed meals, one small and one large, during which plasma measurements of active and total ghrelin and total PYY were obtained. Obese subjects tended to consume more calories during the small meal than lean subjects, although this did not reach statistical significance. Intake of the small meal significantly suppressed active ghrelin and stimulated PYY levels in the lean subjects, and these changes were further accentuated by the large meals. In obese subjects, the suppression of active ghrelin and stimulation of PYY by caloric intake were blunted. Interestingly, a paradoxical stimulation of active ghrelin levels was noted during the small meals in both lean and obese subjects. This stimulation was not seen during the larger meals in lean subjects, but remained present in the obese subjects. Thus, meal-related changes in active ghrelin and PYY are blunted in obese as compared to lean Hispanic subjects. This blunting could contribute to the development or worsening of obesity.

Figure 1

Glucose and Insulin levels during the small (top) and large meals (bottom). Meals were given at t=0, and food removed at t=30 min. Lean subjects = open squares with dashed line; obese subjects = closed circles with solid line.

Figure 2

Total plasma ghrelin levels (left two panels) during the small (top) and large meals (bottom). Only large meals suppressed total ghrelin levels significantly in either obese or lean subjects (^†p<0.005), and mixed model analysis showed a significant effect of meal type on these levels (p<0.001). However, there were no significant effects of obesity or interactions between obesity and meal type (p=n.s.). Active (acylated) ghrelin levels (right two panels) were suppressed in the lean subjects after intake of either meal (p<0.01 for both meal types), while in the obese subjects, only the large meal suppressed these levels (p=n.s. for small, p<0.05 for large). Symbols are defined in Figure 1

Figure 3

Total plasma PYY levels were increased in both lean and obese subjects during either meal type (p<0.05 for all comparisons). Symbols are defined in Figure 1.

Figure 4

Dose response of active ghrelin and total PYY (expressed as percentage of basal levels) vs. calories consumed during small and large meals. Symbols are defined in Figure 1.