OBJECTIVETo understand the role of insulin-receptor gene in the development of insulin resistance on a population-based study in China.

METHODSPolymerase chain reaction (PCR) was used to amplify the EXON2 of the insulin-receptor gene and all amplified products were analyzed by direct sequencing.

RESULTSThree genotypes of single nucleotide at the site of 2257 in EXON2 of the insulin-receptor gene were identified. In 237 of the 345 cases (68.7%), homozygote genotype of CC phenotype was found with a gene frequency of 0.825; 13 cases (3.77%) showed homozygote genotype of TT phenotype with a gene frequency of 0.175 and the rest 95 cases (27.54%) showed heterozygote genotype of CT phenotype. Data were in agreement with the test of Hardy-Weinberg balance (chi(2) = 0.2898, upsilon = 3 - 2 = 1, 0.5 < P < 0.75). The serum level of triglyceride and the HOMA-IR index, the status of insulin resistance assessed by homeostasis model assessment (HOMA), were lower in the TT or CT genotype group than that in the CC genotype group (P < 0.05). Comparing with CC genotype, the proportion of CT genotype (18.4%) in the insulin resistance group (large than 75th percentile of HOMA-IR) was significantly lower than that in the control group (30.6%) (P = 0.022, OR = 0.493). The proportion of TT genotype (2.3%) in insulin resistance group was lower than that in the control group (4.3%, P = 0.297). logistic analysis revealed that after adjusting possible confounding factors such as taking anti-hypertensive and anti-diabetic medications, serum triglyceride and high density lipoprotein cholesterol (HDL-C), hypertension, BMI, smoking history, the OR value of people in the insulin resistance group with CT genotype was 0.448 (95% CI: 0.214 to 0.940) compared to the group with CC genotype.

CONCLUSIONThe hybridization CT genotype at the site of 2257 in EXON2 of insulin-receptor gene might have a candidate gene to serve as a protective factor for insulin resistance.