PROJECT SUMMARY (ABSTRACT) The morbidity and mortality of diabetes mellitus occurs largely from its major complications, which include diabetic kidney disease (DKD). Although extensive data exist on disease mechanisms in experimental models, the pathogenesis of human DKD remains unclear except that hyperglycemia is a major risk factor for DKD. Our studies have led to an emerging paradigm that altered nutrient utilization and flux in the diabetic kidney is a key feature of DKD. Utilizing BKS db/db diabetic mouse model, we investigated changes in carbohydrate and lipid metabolism in kidney cortex. A systems approach using transcriptomics, metabolomics, and metabolic flux analysis identified increased glucose and fatty acid metabolism in the kidney. The increased nutrient utilization did not result in an increased ATP/ADP ratio, and was accompanied by mitochondrial dysfunction. Furthermore, we observed decreased lysine-malonylation of proteins (a process that can alter enzyme activity) in diabetic kidney associated with increased Sirtuin 5 (SIRT 5) activity, a known mediator of demalonylation. These observations form the basis of this proposal that seeks to test the role of SIRT5 in mediating altered metabolic flux in the diabetic kidney. We hypothesize that the decreased malonylation, which is regulated by SIRT 5, observed in the db/db diabetic kidney contributes to the increased nutrient flux. Using SIRT 5 knock- out mice made diabetic with high-fat diet and streptozotocin treatments, our plan is to: 1) investigate the effect of SIRT 5 deficiency in glucose and fatty-acid metabolic flux in kidney cortex in diabetic mice, 2) identify targets of differential malonylation with SIRT 5 deficiency in kidney and assess for the effect of malonylation on target metabolic enzyme activity in diabetic kidney cortex, and 3) evaluate effect of lysine malonylation of SIRT 5 target metabolic enzymes under diabetic conditions. These studies will be pivotal in clarifying the role of SIRT5 in nutrient utilization in the kidney in diabetic states.