Ghrelin and peptide YY in youth: are there race-related differences?

Obesity prevalence is higher in African-American (AA) vs. American white (AW) youth. Ghrelin is a "hunger" peptide that is high preprandially and decreases postprandially, and peptide YY (PYY) is a "satiety" hormone increasing after meals. Impaired regulation of ghrelin/PYY may be conducive to obesity. We hypothesized that racial differences in childhood obesity could partly be explained by differences in ghrelin/PYY dynamics.

We investigated: 1) ghrelin suppression/PYY elevation in response to an oral glucose tolerance test (OGTT) in AA vs. AW, and 2) the relationship of ghrelin and PYY dynamics to insulin sensitivity. Thirty-three AA and 54 AW prepubertal children underwent an OGTT measuring ghrelin, PYY, glucose, and insulin. Fasting glucose to insulin ratio (G(F)/I(F)) was used to assess the relationship of insulin sensitivity to fasting and post-OGTT ghrelin and PYY levels.

OGTT-induced suppression in ghrelin (Delta ghrelin) was lower in AA youth. Delta ghrelin correlated with G(F)/I(F) (r = 0.47, P < 0.001) and Delta insulin at 30 min (r = -0.47, P < 0.001). In multiple regression analysis, race (P = 0.013) and G(F)/I(F) (P = 0.004) contributed independently to the variance in Delta ghrelin (R(2) = 0.28, P < 0.001). Fasting and post-OGTT PYY levels were lower in AAs and were not related to insulin sensitivity.

The lower suppression of ghrelin in AA, but not the lower PYY levels, correlates with insulinemia and insulin resistance. Less ghrelin suppression and PYY elevation after a meal in black youth could be a potential mechanism of race-related differences in hunger/satiety predisposing to risk of obesity.