Genetic regulator of mitochondrial metabolism and insulin resistance [ncRNA-Seq]

Mitochondrial energy metabolism and function are key processes underlying the pathophysiology of insulin resistance and predisposition to type 2 diabetes. This is because mitochondria produce most of the energy required by the cell. Impaired energy production, use of energy stores and mitochondrial dysfunction are major features in metabolic diseases. Nevertheless, it remains uncertain how mitochondrial dysfunction can cause, contribute to, or result in insulin resistance and metabolic diseases. Furthermore there is growing evidence from genetic and genome wide-association studies that genetic variation in mtDNA contributes to these common metabolic diseases (Wallace, 2005), however there has been essentially no in vivo functional validation for these findings. Therefore we generated a mouse model homozygous for a polymorphism in the Mrpp3 gene identified in the French Canadian population responsible for 22% of mitochondrial epitranscriptome variation, with likely consequences on metabolism. We investigated the in vivo effects of the polymorphism on mitochondrial function and metabolism in mice fed normal and high fat diet. We identify that the polymorphism reduces the efficiency of mitochondrial RNA processing and this is most pronounced in the pancreas that results in insulin resistance. The MRPP3 protein containing the Asn434Ser polymorphism associates specifically with the calcium antiporter LETM1 preventing effective release of calcium from mitochondria and consequently impairs insulin release from the pancreatic islet cells of these mice. Reduction in insulin secretion and enlarged pancreatic islet size results in lower circulating levels of insulin that causes insulin resistance and liver steatosis. Our findings reveal for the first time the link between mitochondrial gene regulation and insulin resistance via calcium signaling. Small RNA coverage and analysis of tRNA position 9 mismatch rates of pancreatic RNA isolated from three Mrpp3WT and three Mrpp3N434S mice fed on a high-fat diet.