Mitochondrial tRNAGlu 14687A>G May Be A Novel Mutation for Type 2 Diabetes Mellitus.

Background: Sequence alternations in mitochondrial genomes, especially in mitochondrial tRNA (mt-tRNA), are closely related to type 2 diabetes mellitus (T2DM); however, the detailed molecular mechanism is still largely undetermined.

Methods: Herein, we reported a T2DM Chinese family by using molecular and biochemical analyses. The mtDNA mutations in this pedigree were detected by PCR and Sanger sequencing. Moreover, phylogenetic analysis was used to assess the pathogenic mitochondrial DNA (mtDNA) mutation. We further evaluated mt-tRNA stability levels and mitochondrial functions in cybrids with and without the m.14687A>G mutation.

Results: Members of this family expressed variable clinical phenotypes. Screening for the entire mitochondrial genomes revealed the occurrence of a novel m.14687A>G mutation, which was located at position 60 in the TψC loop of tRNA^Glu, and that position was important for tRNA structure and function. By establishing cybrids derived from three diabetic patients carrying the m.14687A>G mutation and three healthy individuals without this mutation, we noticed that this mutation caused approximately 52% reduction in tRNA^Glu stability level (p < 0.0001). The 14687G cybrid showed more severely impaired mitochondrial functions than the 14687A cybrid: mtDNA content, ATP, and mitochondrial membrane potential (MMP) and OXPHOS enzyme activities were markedly decreased. But the levels of reactive oxygen species (ROS) were significantly increased.

Conclusion: Our finding revealed that the novel m.14687A>G mutation resulted in aberrant mt-tRNA metabolism and mitochondrial dysfunctions, which should be regarded as a pathogenic mutation for T2DM.