A common genetic variant of a mitochondrial RNA processing enzyme predisposes to insulin resistance.

Mitochondrial energy metabolism plays an important role in the pathophysiology of insulin resistance. Recently, a missense N437S variant was identified in the gene, which encodes a mitochondrial RNA processing enzyme within the RNase P complex, with predicted impact on metabolism. We used CRISPR-Cas9 genome editing to introduce this variant into the mouse gene and show that the variant causes insulin resistance on a high-fat diet. The variant did not influence mitochondrial gene expression markedly, but instead, it reduced mitochondrial calcium that lowered insulin release from the pancreatic islet β cells of the variant mice. Reduced insulin secretion resulted in lower insulin levels that contributed to imbalanced metabolism and liver steatosis in the variant mice on a high-fat diet. Our findings reveal that the MRPP3 variant may be a predisposing factor to insulin resistance and metabolic disease in the human population.