Mutations in mitochondrial DNA (mtDNA) are important causes for type 2 diabetes mellitus (T2DM). To investigate the association between mtDNA mutations/variants and diabetes, we reported here clinical, genetic and biochemical characterization of a Chinese pedigree with maternally transmitted T2DM. Using PCR and direct sequencing analysis of mitochondrial genomes from the matrilineal relatives, we identified two potential pathogenic mutations, m.T4216C (p.Y304H) and m.C5178A (p.L237M) in the ND1 and ND2 genes, respectively, together with a set of genetic polymorphisms belonging to the human mitochondrial haplogroup D4b. Moreover, by isolating and analyzing polymononuclear leukocytes generated from the T2DM patients and controls, we identified lower levels of mitochondrial membrane potential and ATP production in T2DM patients than in the controls, in contrast, a significantly higher level of reactive oxygen species was observed in the T2DM patients carrying both of the m.T4216C and m.C5178A mutations (p < 0.05 for all). In addition, the plasma levels of malondialdehyde and 8-hydroxydeoxyguanosine in the T2DM patients markedly increased, while the level of superoxide dismutase decreased (p < 0.05 for all). Taken together, our data indicated that the ND1 T4216C and ND2 C5178A mutations may lead to oxidative stress and impair the mitochondrial function, and this, in turn, might have been involved in the pathogenesis and progression of T2DM in this pedigree. Thus, our study provides novel insight into the pathophysiology of T2DM that is manifested by mitochondrial dysfunction.
Keywords: C5178A; T2DM; T4216C; mitochondrial dysfunction; oxidative stress.