Abstract
BACKGROUND: Ghrelin, a 28-amino-acid gastric peptide hormone, has an appetite-stimulating effect and controls the energy balance. Serum ghrelin levels inversely correlate with body mass index. Recently, several papers reported the ethnic difference in the ghrelin levels. To our knowledge, however, no studies have compared the serum ghrelin levels between Caucasians in the USA and the Japanese in Japan. METHODS: We conducted a cross-sectional study of 189 men 40-49 years of age (91 US Caucasians in the U.S. and 98 Japanese in Japan) to examine serum ghrelin levels and metabolic and other factors. RESULTS: Serum ghrelin levels correlated with waist circumferences and lipid profiles among Caucasian Americans and the Japanese. Serum ghrelin levels were significantly higher among Caucasian Americans than among the Japanese (904.5 (632.0, 1132.0) pg/mL, 508.0 (399.0, 1378.3) pg/mL (median and 95% confidence interval), respectively, P < 0.01), although Caucasian Americans were much more obese (BMI: 26.9 +/- 3.3 kg/m(2) versus 23.3 +/- 3.1 kg/m(2) respectively, P < 0.01). The ethnic difference remained after adjusting for metabolic factors, smoking status, and other factors (P < 0.01). CONCLUSIONS: We have shown in our population-based study that serum ghrelin levels among men aged 40-49 are significantly higher in Caucasian Americans than in the Japanese in Japan. Reasons for the ethnic difference in the ghrelin levels are largely unknown and warrant further investigation.