Relationships between baseline serum leptin levels and 2-year changes in body mass index, blood pressure and metabolic parameters in Japanese male adolescents and middle-aged men.

We and others have reported that serum leptin levels are positively correlated with body mass index (BMI), blood pressure and heart rate (HR) in cross-sectional clinical studies. However, only a few longitudinal studies have focused on the relationships between leptin, BMI and blood pressure. The present study was performed to elucidate the relationships between baseline serum leptin levels and 2-year changes in BMI, blood pressure, HR and metabolic parameters in 314 Japanese male adolescents aged 16-17 years and in 225 Japanese men aged 30-63 years. Height, weight, systolic blood pressure (SBP), diastolic blood pressure (DBP), HR, fasting plasma glucose (FPG), serum lipids [total cholesterol (TC), triacylglycerols (TG), high-density-lipoprotein cholesterol (HDL-C) and low-density-lipoprotein cholesterol (LDL-C)], uric acid (UA), insulin and leptin levels were measured in the morning after an overnight fast. In the male adolescents, serum leptin levels in 1996 (log[leptin'96]) were significantly correlated with BMI, SBP, mean blood pressure and HR in 1998 (r=0.40, 0.13, 0.11 and 0.14, respectively). The percentage change in BMI per year (DeltaBMI) was negatively correlated with log[leptin'96], even after adjustment for baseline BMI (r=-0.12, P=0.030). In men aged 30-63 years, log[leptin'96] was also positively correlated with BMI'98, SBP'98, DBP'98, FPG'98, TC'98, log[TG'98], LDL-C'98 and UA'98 (all P<0.05), and negatively correlated with HDL-C'98, DeltaBMI, DeltaFPG, DeltaTC and DeltaLDL-C. The relationship between log[leptin'96] and DeltaTC was significant, even after adjustment for initial BMI (r=-0.15, P=0.023). These findings therefore suggest that serum leptin levels are correlated with subsequent decreases in BMI and TC in Japanese men.