Hypermethylation of hepatic mitochondrial ND6 provokes systemic insulin resistance

Purpose: To reveal the mechanism of mitochondrial DNA methylation in the progression of fatty liver and insulin resistance. Methods: Liver mitochondrial DNA bisulfite-sequencing of high-fat diet (HFD) and db/db diabetic mice were using Illumina 4000. Western blot, real-time PCR and confocal microscopy were used for further biochemical validation. Results: In the present study, we found increased mitochondrial localization of DNA methyltransferase 1 (DNMT1) in the liver of high-fat diet (HFD) and db/db diabetic mice. Whole genome bisulfite sequencing of mouse liver mtDNA revealed significant increase of cytosine methylation frequencies including CG, CHG and CHH on both L and H-strand in the diabetic mice comparing with normal control, and ND6 showed the most dramatic increase on the L-strand. Conclusions: Our present study suggests an epigenetic regulatory of mitochondrial homeostasis and insulin sensitivity by DNMT1, providing novel therapeutic targets for the prevention and treatment of fatty liver and type 2 diabetes. Liver mitochondrial DNA bisulfite-sequencing of male C57BL/6J mice fed a normal diet (NFD, n=8), male C57BL/6J mice fed a high-fat diet (HFD, n=4), and male db/db mice fed a normal diet (NFD, n=4), using Illumina 4000.