Polymorphism of the leptin gene promoter in pedigrees of type 2 diabetes mellitus in Chongqing, China

BACKGROUND: It has been shown that the presence of leptin is associated with deabefes, glucose wefabolism and insulin metablism. In this research, we evaluated the presence of the leptin C-2549-A polymorphism in the Chinese population in Chongqing and verified its association with plasma leptin levels and anthropometric, metabolic, and clinical parameters. METHODS: Two hundred and sixty-nine patients with diabetes, 135 non-diabetic first-degree relatives of the patients, and 85 healthy controls were screened for the presence of C-2549-A polymorphism using a PCR-RFLP assay. Body mass index, fasting leptin, fasting insulin, fasting glucose and homeostatic model assessment for insulin resistance (HOMA)-IR were also determined. RESULTS: In the type 2 diabetes group, AA genotype frequency (6.32%) and A allele frequency (34.94%) was higher than in normal controls (1.18% and 25.29%, respectively). Diabetic patients with the AA genotype had lower fasting leptin and insulin levels than those with other genotypes. Carriers with the AC genotype had decreased fasting leptin and insulin levels and longer duration of disease as compared with those with CC genotype. The HOMA-IR of patients with AA or AC genotypes was lower than those with the CC genotype. In non-diabetic relatives group, individuals with the AA genotype had a lower fasting leptin level than those with the AC genotype. The fasting insulin and HOMA-IR level of carriers of the AA or AC genotype were lower than those of the CC genotype. CONCLUSION: The C-2549-A polymorphism in the leptin gene is associated with fasting leptin in patients with type 2 diabetes. The distribution of the genotypes in diabetic subjects from diabetic pedigrees differs from those in normal controls. The A allele frequency in diabetic patients is higher than that in normal controls. The haplotypes defined by genotypes are different in the familial subjects.