G-2548A Leptin Promoter and Q223R Leptin Receptor Polymorphisms in Obese Mexican Subjects

Leptin interaction with its receptor in the hypothalamus stimulates a specific signaling cascade that results in the synthesis of anorexigenic and orexigenic peptides in order to regulate food intake and energy expenditure. Many polymorphisms in leptin (lep) and leptin receptor (lepr) genes have been associated with body weight. In particular, G-2548A in the lep promoter and Q223R in lepr variants have been associated with obesity in several populations, although no linkage has been evidenced in others. Here, we examined the genetic associations of these polymorphisms with Body Mass Index (BMI) and serum leptin levels in adult Mexican people. A set of 160 subjects was recruited at the Acupuncture Clinic of the National School of Medicine and Homeopathy of the National Polytechnic Institute (Mexico) and classified according to BMI, gender and age. Blood samples were obtained to extract genomic DNA and determine genetic variants by PCR-RFLP. Leptin was quantified by ELISA assays. Analysis of association and determination of Odd Ratio (OR) were performed using SPSS software. G-2548A in lep gene promoter and Q223R in lepr gene polymorphisms were not found associated with BMI in the whole study population. However, GG genotype in lep gene promoter was related to an increased leptin concentration (p≤0.05) and suggested as a protective factor for obesity in Mexican women. Leptin levels were higher in postmenopausal women, confirming the link between the hormonal system and body weight control. In contrast, no association was found between lepr gene polymorphism and serum leptin level. Our results suggest a possible association between G-2548A polymorphism in lep gene promoter, BMI and leptin levels in Mexican women. Further analysis of a larger population is required to confirm the biological relevance of this polymorphism for obesity in the Mexican population.