Studies of the synergistic effect of the Trp/Arg ⁶⁴ polymorphism of the β ₃-adrenergic receptor gene and the -3826 A→G variant of the uncoupling protein-1 gene on features of obesity and insulin resistance in a population-based sample of 379 young Danish subjects

This study examined whether the simultaneous presence of the previously identified Trp/Arg ⁶⁴ polymorphism of the β ₃-adrenergic receptor (BAR) gene and the -3826 A→G nucleotide variant of the uncoupling protein-1 (UCP1) gene are associated with obesity, insulin resistance, or alterations in size at birth in a Danish study population comprising 379 unrelated young Caucasian subjects. All study participants underwent an iv glucose tolerance test with addition of tolbutamide after 20 min. In addition, a number of biochemical and anthropometric measures were performed on each subject. The subjects were genotyped for the 2 polymorphisms by applying PCR-restriction fragment length polymorphism. The subjects were divided into 4 groups according to their BAR and UCP1 genotype: wild-type carriers (n = 184), only Trp/Arg ⁶⁴ carriers (n = 29), only A→G UCP1 carriers (n = 146), and carriers of both genetic variants (n = 20). There were no differences across the genotype groups with respect to body mass index, fat mass, waist to hip ratio, birth weight or length, ponderal index, or weight gain during childhood or adolescence, nor was the combined genotype related to alterations in fasting serum levels of lipids, insulin, or C peptide or the insulin sensitivity index. In conclusion, the present study failed to demonstrate an additive or synergistic effect of the Trp/Arg ⁶⁴ variant of the BAR gene and the -3826 A→G variant of the UCP1 gene on the development of obesity and insulin resistance among randomly recruited Danish Caucasian subjects.