Relationship between single nucleotide polymorphisms in leptin, IL6 and adiponectin genes and their circulating product in morbidly obese subjects before and after gastric banding surgery

Background: Certain adipose-produced signals are secreted in proportion to body fat mass and are involved in regulation of the energy metabolism of the whole body. Leptin, IL6 and adiponectin can be considered as adiposity signals. Several Single Nucleotide Polymorphisms (SNPs) in genes encoding for these molecules are known to influence their concentration in situations of stable weight. We hypothesized that polymorphism effects could be better detected in a situation of negative energy balance and that modified concentrations of adiposity signal genes could change the dynamics of weight gain in obese subjects. Methods: 65 obese patients undergoing gastric banding surgery were genotyped for LEP+19A-->G, LEP-2548G-->C, IL6-174G-->C, APM1-11377C-->G and APM1-11391G-->A common SNPs. BMI and concentrations of leptin, IL6 and adiponectin were measured before surgery and after 1 year. Results: All SNPs except IL6-174G-->C SNP were associated with modifications of the circulating concentrations of signals produced by adipose tissue at baseline. During weight loss, variant genotype carriers of LEP-2548 and +19 SNPs were characterized by a trend towards less decrease in circulating leptin. Weight loss was associated with an increase in IL6 concentration (16.9%+/-12.2) in the IL6-174 C/C genotype carriers, whereas the C/G or G/G genotypes carriers showed a decrease in IL6 (19.9%+/-5.2, P=0.001). Conclusion: We observed that the SNPs studied could modulate the concentration of adiposity signals not only at baseline but also during weight loss. Such variations may be sensed by the homeostatic feedback system that controls energy balance and may in turn contribute to some disturbances in weight regulation.