A small protein, Mitoregulin (Mtln), localizes in mitochondria and contributes to oxidative phosphorylation and fatty acid metabolism. knockout mice develop obesity on a high-fat diet, demonstrating elevated cardiolipin damage and suboptimal creatine kinase oligomerization in muscle tissue. Kidneys heavily depend on the oxidative phosphorylation in mitochondria. Here we report kidney-related phenotypes in aged knockout mice. Similar to knockout mice muscle mitochondria, those of the kidney demonstrate a decreased respiratory complex I activity and excessive cardiolipin damage. Aged male mice carrying knockout demonstrated an increased frequency of renal proximal tubules' degeneration. At the same time, a decreased glomerular filtration rate has been more frequently detected in aged female mice devoid of Mtln. An amount of Mtln partner protein, Cyb5r3, is drastically decreased in the kidneys of knockout mice.