Leptin is associated with insulin resistance in Japanese migrants

Leptin and insulin are both influenced by body adiposity. Insulin plays an important role in the context of the metabolic syndrome (MS). We evaluated whether leptin was associated with insulin resistance and MS after adjusting for confounders in Japanese-Brazilian women.

A total of 717 Japanese-Brazilian women aged >/=30 years were investigated for the presence of MS. They were submitted to clinical examination and laboratory measurements, including oral GTT, lipid profile, uric acid, C-reactive protein (CRP), insulin, and leptin levels. Insulin sensitivity was assessed by HOMA. Diagnosis of MS was based on the National Cholesterol Education Program criteria modified for Asians. Pearson correlation coefficient and logistic regression analysis were used.

MS was diagnosed in 56% (95% CI 52-59); these subjects were older and had higher body mass index (BMI) and fat mass, and worse metabolic profile. Leptin and CRP levels were statistically greater in women with MS when compared to those without the syndrome (8.6 +/- 8.0 vs. 7.2 +/- 5.9 ng/mL and 0.219 +/- 0.848 vs. 0.360 +/- 0.852 mg/dL, p < 0.05). Leptin was significantly correlated to BMI, fat mass, waist circumference, HOMA-IR, and insulin but not to other components of MS, such as fasting plasma glucose, blood pressure, HDL-cholesterol, triglyceride, and CRP levels. Correlation between leptin and HOMA-IR or fasting insulinemia was maintained after adjustments for body adiposity. However, in logistic regression model, age, BMI, 2-h glucose, and uric acid were independently associated with MS, but not leptin.

Adiposity-adjusted correlation of leptin with HOMA-IR and fasting insulinemia suggested that the former is associated with insulin resistance, despite the lack of independent association with the definition of the MS according to NCEP-ATP III. These findings in such Japanese-Brazilian population of high prevalence of MS need to be confirmed in other populations.