Coronary artery disease, HDL cholesterol, and insulin-gene flanking sequences

The relationship between coronary artery disease, HDL cholesterol, and the hypervariable region flanking the human insulin gene was studied in Saudi Arabian non-diabetic subjects (n = 68) and in patients with Type 2 diabetes (n = 35). A locus of insulin-gene-linked DNA polymorphism with three average size classes of alleles was found: a small class 1, a rare medium size class 2, and a large class 3 allele. In the total group of subjects (n = 103), those with the class 3 allele had a lower plasma HDL cholesterol concentration than those without the class 3 allele (0.93 +/- 0.26 vs 1.12 +/- 0.30 mmol l-1, 2p less than 0.003). No difference in genotype and allelic frequency was found between patients with and without coronary artery disease in the combined group of subjects, with and without diabetes. Similarly the genotype distribution was not different between non-diabetic subjects and patients with Type 2 diabetes in the combined group of subjects, both with and without coronary artery disease. In conclusion, the study did not confirm a previous study showing an association between the class 3 allele and atherosclerosis in a Caucasian population. However, the class 3 allele was associated with a low plasma HDL cholesterol concentration.