Body composition changes after laparoscopic adjustable gastric banding: what is the role of -174G>C interleukin-6 promoter gene polymorphism in the therapeutic strategy?

Background: There is growing evidence that interleukin-6 (IL-6) is linked to the regulation of fat mass (FM). Our previous data define the common -174G>C IL-6 polymorphism as a marker for 'vulnerable' individuals at risk of age-and obesity-related diseases. An association between -174G>C IL-6 polymorphism and weight loss after bariatric surgery has been demonstrated. Objective: We investigated the impact of -174G>C IL-6 polymorphism on weight loss, body composition, fluid distribution and cardiometabolic changes in obese subjects, after laparoscopic adjustable gastric banding (LAGB) surgery. Design and Outcome measures: A total of 40 obese subjects were studied at baseline and at 6 months follow-up after LAGB surgery. Cardiometabolic and genetic assessment of -174G>C IL-6 polymorphism, anthropometric, body composition and fluid distribution analysis were performed. Results: After LAGB surgery, significant reductions in weight (Delta% -11.66 +/- 7.78, P<0.001), body mass index (P<0.001), total and trunk FM (kg, %) (Delta% of total FM -22.22 +/- 12.15, P<0.01), bone mineral density (T-score) (P<0.001), resting metabolic rate (RMR) (P<0.01), and total body water and intracellular water (TBW, ICW) (P<0.05) were observed. At baseline, C(-) carriers of IL-6 polymorphism had a significantly higher RMR (P<0.05), free FM (kg), but less total and trunk FM (%), higher body cell mass (BCM), content of TBW (L) and ECW (extracellular water)/ICW ratio compared with C(+) carriers (P<0.001). After LAGB, C(+) carriers had a significantly stronger reduction of total FM (kg), but lower bone density, compared with C(-) carriers (P<0.05). Conclusions: Beyond the relationship between -174G>C IL-6 polymorphism and body composition, this study provides first evidence about the association of IL-6 variant with fluid distribution, at baseline, and FM and bone density loss in obese subjects at 6 months follow-up after LAGB surgery. LAGB was less effective if the subjects were carrying risk genotypes, C(-) carriers, for obesity, suggesting a role of genetic variations on bariatric surgery outcomes. International Journal of Obesity (2012) 36, 369-378; doi:10.1038/ijo.2011.132; published online 5 July 2011