183-OR: Pyruvate Kinase M2 (PKM2) Enzymatic Activity Is Necessary to Improve Podocyte Mitochondrial Function and Glomerular Fuel Metabolism and Diabetic Nephropathy

Diabetic nephropathy (DN) is the result of abnormal systemic and local changes in metabolism and hemodynamics. We have reported that many glycolytic enzymes, such as pyruvate kinase M2 (PKM2), were elevated in the renal glomeruli of type 1 and type 2 diabetic patients who were protected from DN. TEPP46, a small-molecule which activates PKM2 by inducing oligomerization, reversed glomerular pathology in diabetic mice. After 7 months of STZ induced diabetes, mice with PKM2 specific overexpression in podocytes (PPKM2Tg) with podocin promoter, exhibited lower albumin-creatinine ratio (ACR), kidney-body weight ratio, mesangial expansion, basement membrane thickness and podocyte foot process effacement vs. WT diabetic littermates. PPKM2Tg mice exhibited lower expression of fibrotic (FN, TGFβ1 and Col4a) and oxidative stress (p47phox, NOX2 and NOX4) genes and improvement in endothelial function with increased eNOS and VEGF expressions in the glomeruli, compared to diabetic WT mice. Glycolytic and mitochondrial metabolisms as measured by oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) using Seahorse showed striking improvement of impaired mitochondrial maximal respiration capacity and glycolytic rate in isolated glomeruli of diabetic PPKM2Tg mice, in concordance with elevated expressions of mitochondrial related-genes, such as PGC1α. Knocking-down PKM by shRNA in podocyte cell line (pPKMKD) replicated metabolic findings induced by diabetes with dramatic decline of both OCR and glycolytic rate. Re-expressing human PKM1 or PKM2 in pPKMKD cell line reversed impaired mitochondrial function and glycolysis, which were not improved in pPKMKD cells re-expressing with enzymatically inactive human PKM2 gene. These results indicate that PKM2 and its enzymatical function are both necessary in podocytes to improve glomerular mitochondrial abnormalities and delay the progression of DN.