Deficiency in Mitochondrial Complex I Activity Due to Ndufs6 Gene Trap Insertion Induces Renal Disease

Aims: Defects in the activity of enzyme complexes of the mitochondrial respiratory chain are thought to be responsible for several disorders, including renal impairment. Gene mutations that result in complex I deficiency are the most common oxidative phosphorylation disorders in humans. To determine whether an abnormality in mitochondrial complex I per se is associated with development of renal disease, mice with a knockdown of the complex I gene, Ndufs6 were studied. Results: Ndufs6 mice had a partial renal cortical complex I deficiency; Ndufs6(gt/gt), 32% activity and Ndufs6(gt/+), 83% activity compared with wild-type mice. Both Ndufs6(gt/+) and Ndufs6(gt/gt) mice exhibited hallmarks of renal disease, including albuminuria, urinary excretion of kidney injury molecule-1 (Kim-1), renal fibrosis, and changes in glomerular volume, with decreased capacity to generate mitochondrial ATP and superoxide from substrates oxidized via complex I. However, more advanced renal defects in Ndufs6(gt/gt) mice were observed in the context of a disruption in the inner mitochondrial electrochemical potential, 3-nitrotyrosine-modified mitochondrial proteins, increased urinary excretion of 15-isoprostane F-2t, and up-regulation of antioxidant defence. Juvenile Ndufs6(gt/gt) mice also exhibited signs of early renal impairment with increased urinary Kim-1 excretion and elevated circulating cystatin C. Innovation: We have identified renal impairment in a mouse model of partial complex I deficiency, suggesting that even modest deficits in mitochondrial respiratory chain function may act as risk factors for chronic kidney disease. Conclusion: These studies identify for the first time that complex I deficiency as the result of interruption of Ndufs6 is an independent cause of renal impairment.