Polymorphisms in the interleukin-6 receptor gene are associated with body mass index and with characteristics of the metabolic syndrome

Summary Objective Low‐grade inflammation has been related to obesity, insulin resistance and the metabolic syndrome. The Asp358Ala variant and the CA‐repeat polymorphism in the interleukin‐6 receptor (IL‐6R) gene have been reported to be associated with obesity in Pima Indians and Spanish women, respectively. The aim of this study was to investigate the association between these polymorphisms and obesity in a Mediterranean‐Caucasian population, and to determine whether this polymorphism was related to the metabolic syndrome as defined by the National Cholesterol Education Program – Adult Treatment Panel III (NCEP/ATP‐III) criteria. Design Cross‐sectional. Patients Three hundred and ninety subjects from the general population. Methods The Asp358Ala and CA‐repeat polymorphisms were analysed by polymerase chain reaction (PCR) amplification, followed by restriction fragment length polymorphism or capillary electrophoresis, respectively. Results Both polymorphisms were in strong linkage disequilibrium, Asp358 alleles being associated with 149 CA‐repeat alleles (χ2 = 76·275, P