Association between plasma leptin levels and diabetes mellitus.

BACKGROUND

Leptin is an important adipose tissue-derived hormone that has been shown to be involved in pathophysiological mechanisms related to cardiovascular disease and diabetes. However, few studies have examined the association between plasma leptin and diabetes mellitus in humans. Also, it is not clear if this association is present among women as well as in men. Therefore, we examined the association between plasma leptin levels and diabetes mellitus in a representative multiethnic sample of U.S. adults.

METHODS

We examined the 1988-1994 third National Health and Nutrition Examination Survey (NHANES III) participants >20 years of age (n = 5,599, 54.7% women). Plasma leptin levels were categorized into quartiles (women, <7.68 fg/L, 7.68-13.18 fg/L, 13.19-21.70 fg/L, >21.70 fg/L; men, <2.64 fg/L, 2.64-4.36 fg/L, 4.37-7.12 fg/L, >7.12 fg/L). Diabetes mellitus was defined as fasting glucose ≥126 mg/dL, non-fasting glucose ≥200 mg/dL or use of oral hypoglycemic medication or insulin (n = 395).

RESULTS

Higher plasma leptin levels were initially found to be associated with diabetes mellitus after adjusting for age, sex, race/ethnicity, education, smoking, alcohol intake, hypertension, serum cholesterol and C-reactive protein [odds ratio (OR), 3.79; confidence interval (CI), 2.05-7.00; P trend <0.0001). However, when we additionally adjusted for body mass index (BMI), the association between plasma leptin levels and diabetes mellitus disappeared in both men (OR, 1.07; CI, 0.59-1.94; P trend = 0.5004) and women (OR, 0.86; CI, 0.49-1.51; P trend = 0.2819).

CONCLUSION

Higher plasma leptin levels are not independently associated with diabetes mellitus after adjustment for BMI. The null association was evident both in women as well as in men.