Impact of common polymorphisms in candidate genes for insulin resistance and obesity on weight loss of morbidly obese subjects after laparoscopic adjustable gastric banding and hypocaloric diet

Context: It is unknown whether genetic factors that play an important role in body weight homeostasis influence the response to laparoscopic adjustable gastric banding ( LAGB). Objective: We investigated the impact of common polymorphisms in four candidate genes for insulin resistance on weight loss after LAGB. Design: The design was a 6-month follow-up study. Setting: The study setting was hospitalized care. Patients: A total of 167 unrelated morbidly obese subjects were recruited according to the following criteria: age, 18 - 66 yr inclusive; and body mass index greater than 40 kg/m(2) or greater than 35.0 kg/m(2) in the presence of comorbidities. Intervention: LAGB was used as an intervention. Main Outcome Measure: Measure of correlation between weight loss and common polymorphisms in candidate genes for insulin resistance and obesity was the main outcome measure. Results: The following single nucleotide polymorphisms were detected by digestion of PCR products with appropriate restriction enzymes: Gly972Arg of the insulin receptor substrate-1 gene, Pro12Ala of the proliferator-activated receptor-gamma gene, C-174G in the promoter of IL-6 gene, and G-866A in the promoter of uncoupling protein 2 gene. Baseline characteristics including body mass index did not differ between the genotypes. At the 6-month follow-up after LAGB, carriers of G-174G IL-6 genotype had lost more weight than G-174C or C-174C genotype (P = 0.037), and carriers of A-866A uncoupling protein 2 genotype had lost more weight as compared with G-866G (P = 0.018) and G-866A (P = 0.035) genotype, respectively. Weight loss was lower in carriers of Gly972Arg insulin receptor substrate- 1 genotype than Gly972Gly carriers, but not statistically significant (P = 0.06). No difference between carriers of Pro12Ala and Pro12Pro proliferatoractivated receptor-gamma genotype was observed. Conclusions: These data demonstrate that genetic factors, which play an important role in the regulation of body weight, may account for differences in the therapeutic response to LAGB.