RESUMO
Mitochondrial gene mutation plays a role in the development of diabetes mellitus. An A to G substitution at base pair 3243 in the mitochondrial tRNAleu[UUR] gene [mt3243] is commonly associated with maternally inherited diabetes and deafness and other diseases. The aim of this study is to detect A to G substitution at base pair 3243 in mitochondrial RNAleu[UUR] in the plasma of patients with type 2 diabetes mellitus, and to evaluate insulin sensitivity in all cases. This study, included 41 patients [Group I, 31 cases with type 2 diabetes mellitus and maternal history of diabetes mellitus-and Group II, 10 cases with type 2 diabetes mellitus, bilateral SNHL, maternal history of diabetes mellitus with or without SNHL. Other10 healthy control group was included. Patients and controls were subjected to full medical history and clinical examination. Serum measurements for liver and kidney function tests, fasting and postprandial blood glucose as well as C-peptide levels, in addition to lipid profile were collected. Audiological evaluation for all patients with SNHL was also done. Genetic investigation, for mDNA analysis, done by polymerase chain reaction restriction fragment length polymorphism [PCR-RFLP], to determine the mutation in the mitochondrial gene at position 3243. Results of the study showed that glycemic indices [FPG, 2hPPG and HbA1c], liver enzymes and blood urea were significantly higher among patient group compared to control group [P<0.05]. There was no significant difference for values of creatinine and uric acid between cases and controls. Lipid profile was significantly higher among patient group compared to controls [P<0.05], except for HDL-C which was higher in controls however, it did not reach statistical significance. C-peptide values were not significantly different between studied groups. Age at onset of diabetes was relatively earlier in group II than group I. mDNA was present in all plasma samples of patients and controls. mDNA 3243 mutation was detected in the plasma of three patients with diabetes and SNHL with a rate of 7.3% of all diabetic patients and 30% of diabetic patients associated with deafness. The presence of mDNA mutation allowed 294 bp product to be cleaved into 180 and 114 bp fragments and were seen as two bands. The A 3243 G mutation is present in Egyptian population and is considered as a cause of maternally inherited diabetes and deafness at a rate of 7.3% of all diabetic subjects and a rate of 30% of diabetics associated with deafness. mDNA mutation is present and detectable in plasma. Maternally inherited diabetes and deafness differs pathophysiologically from the more common forms of type 2 diabetes in that, insulin resistance does not seem to be a major factor