While earlier studies reported reduced GLP-1 secretion and enhanced GIP secretion in Caucasian T2DM [65, 66•, 67], later studies failed to confirm this [68•, 69•, 70], which strongly suggests that incretin secretion per se is not involved in the pathogenesis of T2DM in Caucasian. This evidence concerns the gene GCG and type 2 diabetes mellitus.