Frequency and significance of the A -> G (-3826) polymorphism in the promoter of the gene for uncoupling protein-I with regard to metabolic parameters and adipocyte transcription factor binding in a large population-based Caucasian cohort

Background: The recently described A-->G (-3826) point mutation within the distal region of the UCP-1 promoter is possibly involved in the development of obesity, diabetes and related metabolic disorders. It was the aim of th is study to examine the allelic frequency and the prevalence of the three U CP-1 genotypes in a broad caucasian cohort and to investigate the significa nce of this polymorphism for obesity and diabetes. Methods: 1020 subjects were randomly chosen from 6450 participants in the D iabetomobile Study. The UCP-1 genotype was determined by genomic PCR and Bc l-I-RFLP analysis in 1020 subjects and tested for association with a variet y of metabolic parameters. In addition, the influence of this mutation on a dipocyte nuclear factor binding was investigated by electrophoretic mobilit y shift assays (EMSA). Results: The genotype frequencies in 1020 subjects were: AA genotype, 57.0% ; AG genotype, 35.4%; GG genotype, 7.6%; with allelic frequencies of 0.75 f or allele A and 0.25 for allele G. No significant differences between the g enotypes and age, gender, BMI, leptin, glucose, fasting insulin, C-peptide, HbA1(c), diabetes manifestation, total cholesterol, and HDL cholesterol we re found. Analysis of the Trp64Arg polymorphism of the beta(3)-adrenergic r eceptor in a subgroup of 343 subjects revealed no additive effect to the UC P-1 polymorphism. An yet unknown adipocyte-specific factor of nuclear extra cts from 3T3-L1 adipocytes during differentiation is able to bind specifica lly to the distal UCP-1 promoter region and this binding ability can not be abolished by the mutation. Conclusions: We determined the genotype and allelic frequency of the UCP-1 promoter polymorphism in the largest known population-based study. The resu lts from genotyping demonstrate clearly that this polymorphism does not pla y a major role in the pathogenesis obesity and diabetes. A yet unknown adip ocyte derived and differentiation-dependent regulated transcription factor is able to bind to the distal UCP-1 promoter surrounding -3826 bp. This bin ding is not affected by presence of the mutation.