To evaluate the significance of a longevity-associated mitochondrial genotype (Mt5178A) derived from a C --> A transversion at nucleotide position 5178 of mitochondrial DNA, which causes a Leu-to-Met substitution within the NADH dehydrogenase subunit 2 gene, in type 2 diabetic subjects.
Mt5178 typing was done by polymerase chain reaction-restriction fragment-length polymorphism with the restriction enzyme AluI in 1,148 type 2 diabetic Japanese subjects, and the results were compared with the clinical characteristics. Then, the association of Mt5178 type with early atherosclerotic changes of the bilateral carotid arteries on ultrasonography was assessed in 412 diabetic subjects randomly selected from the original 1,148 type 2 diabetic subjects, while maintaining the same frequency of Mt5178A and Mt5178C.
The frequency of Mt5178A in the type 2 diabetic subjects (454 of 1,148; 40%) was not different from that previously found in healthy blood donors (114 of 252; 45%). Clinical characteristics regarding diabetes were not significantly different between the Mt5178A group (n = 454) and the Mt5178C group (n = 694). However, the mean intima-media thickness (IMT) at six sites in the bilateral carotid arteries was significantly smaller in the Mrt5178A group than in the Mt5178C group (0.906 +/- 0.018 vs. 0.995 +/- 0.021 mm, mean +/- SEM, P = 0.022), and the Mt5178 type was significantly correlated with both the mean IMT and the presence of plaque on multiple regression analysis and discriminant analysis.
The Mt5178A genotype may be unrelated to the etiology of type 2 diabetes. However, Mt5178A seems to have an antiatherogenic effect, at least in type 2 diabetic individuals.