Mitochondrial Diabetes is Associated with tRNA^Leu(UUR) A3243G and ND6 T14502C Mutations

Abstract

Background

Mutations in mitochondrial DNA (mtDNA) are associated with type 2 diabetes mellitus (T2DM). In particular, m.A3243G is the most common T2DM-related mtDNA mutation in many families worldwide. However, the clinical features and pathophysiology of m.A3243G-induced T2DM are largely undefined.

Methods

Two pedigrees with maternally inherited T2DM were underwent clinical, molecular and biochemical assessments. The mtDNA genes were PCR amplified and sequenced. Mitochondrial adenosine triphosphate (ATP) and reactive oxygen species (ROS) were measured in polymononuclear leukocytes derived from three patients with both the m.A3243G and m.T14502C mutations, three patients with only the m.A3243G mutation and three controls without these mutations. Moreover, GJB2, GJB3 and GJB6 mutations were screened by PCR-Sanger sequencing.

Results

Members of the two pedigrees manifestated variable clinical phenotypes including diabetes and hearing and vision impairments. The age at onset of T2DM varied from 31 to 66 years, with an average of 41 years. Mutational analysis of mitochondrial genomes indicated the presence of the m.A3243G mutation in both pedigrees. Matrilineal relatives in one of the pedigrees harbored the coexisting of m.A3243G and m.T14502C mutations. Remarkably, the m.T14502C mutation, which causes the substitution of a conserved isoleucine for valine at position 58 in ND6 mRNA, may affect the mitochondrial respiratory chain functions. Biochemical analysis revealed that cell lines bearing both the m.A3243G and m.T14502C mutations exhibited greater reductions in ATP levels and increased ROS production compared with those carrying only the m.A3243G mutation. However, we did not find any mutations in the GJB2, GJB3 and GJB6 genes.

Conclusion

Our study indicated that mitochondrial diabetes is associated with the tRNA^Leu(UUR) A3243G and ND6 T14502C mutations.

Keywords:

• T2DM
• mt-tRNA
• ND6
• m.A3243G
• m.T14502C
• mutations

Abbreviations

mtDNA, mitochondrial DNA; T2DM, type 2 diabetes mellitus; PMNs, polymononuclear leukocytes; mt-tRNA, mitochondrial tRNA; ATP, adenosine triphosphate; ROS, reactive oxygen species; OXPHOS, oxidative phosphorylation; nDNA, nuclear DNA; IR, insulin resistance; MELAS, mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes; MERRF, myoclonic epilepsy and ragged-red fiber disease; ND6, NADH-dehydrogenase 6; OGTT, oral glucose tolerance test; HbA1c, hemoglobin A1c; BMI, body mass index; BP, blood pressure; HOMA-IR, homeostasis model assessment of IR; PTA, pure tone audiometry; DPOAE, distortion product otoacoustic emissions; rCRS, revised Cambridge sequence; CI, conservation index; FBS, fetal bovine serum; LHON, Leber’s hereditary optic neuropathy.

Data Sharing Statement

The datasets used and analysed during the current study are available from corresponding author (Yu Ding, E-mail: [email protected]) on reasonable request.

Acknowledgments

We thank Catherine Perfect, MA (Cantab), from Liwen Bianji (Edanz) (www.liwenbianji.cn), for editing the English text of a draft of this manuscript.

Disclosure

The authors report no conflicts of interest in this work.

Additional information

Funding

This work was supported by the grants from Health Commission of Zhejiang Province (No.2021RC022), Hangzhou Science and Technology Bureau (No. 20201203B210), Hangzhou Municipal Health Commission (No. ZD20220010).