Abstract:
Type 2 diabetes mellitus is a heterogeneous disease characterized by chronic hyperglycemia owing to a combination of insulin resistance and changed insulin secretion. Several pathogenic processes are involved in the development of diabetes. The genetic defect is the one of causes of diabetes especially in diabetes shown family transmission. Earlier studies have found mutation of the mitochondrial gene at position A3243G in tRNALeu gene of diabetic family in many ethnic populations of the world. Previous studies have shown that several mutations in mitochondrial DNA (mtDNA) contribute to the development of this disease. In this study those mutations were studied in type 2 diabetic patients in Thailand. No pathogenic mutation was found to be associated with diabetes, although the family histories of some of the diabetic patients show maternal inheritance. In order to search the other point mutation in these patients, the whole mitochondrial genome of 19 type 2 diabetic patients with suspected maternally inherited were analyzed in comparison with those of 50 normal healthy control subjects. This study found 22 potential mutations associated with diabetes located on rRNA, tRNA, cytochrome c oxidase and NADH dehydrogenase gene. The effect of 2-deoxy-D-glucose uptake was also studied in a group of skin fibroblast cultures from patients with A3243G and A8344G mutation in mtDNA, and from a healthy control group without these mutations using survival of these fibroblasts in galactose medium. The results show that the proportion of mutant mtDNA decreases from 7.7% to 10.1% in 3 patient fibroblast cultures whereas 2-deoxy-D-glucose uptake increased significantly (p<0.01) by 1.8-2.1-fold at the basal state, 1.9-2.3-fold (p<0.05-p <0.001) at 60 ng/ml, and 1.8-2.1-fold (p<0.01) at 100 ng/ml insulin stimulation state. This study indicated that alteration of mutant mtDNA content may relate to the impaired glucose uptake of fibroblast cells