Branched-Chain Amino Acids Contribute to Diabetic Kidney Disease Progression via PKM2-Mediated Podocyte Metabolic Reprogramming and Apoptosis

Approximately 30-40% of people living with diabetes develop diabetic kidney disease (DKD). It is of great importance to identify the “decisive factors” for DKD initiation. Recently, high levels of plasma and urinary branched-chain animo acid (BCAA) metabolites were shown to predict the future risk of DKD. Here, we observed that glomerular podocytes in male and female patients with DKD and db/db mice specifically displayed BCAA catabolic defects. Podocyte-specific knockout of PP2Cm, a key enzyme involved in BCAA catabolism, or exogenous supplementation of BCAAs induced DKD phenotypes in high-fat (HF) diet-fed male mice as manifested by podocyte dysfunction and apoptosis, glomerular pathological changes, and proteinuria. Mechanistically, BCAAs promoted PKM2 depolymerization and inactivation in podocytes. Depolymerized PKM2 suppressed glucose oxidative phosphorylation (OXPHOS) and promoted a shift in glucose metabolism to serine and folate biosynthesis. Depolymerized PKM2 is also cotransported to the nucleus with DDIT3, acting as a novel cotranscriptional factor to increase DDIT3 transcriptional activity, which promotes Chac1 and Trib3 expression and directly induces podocyte apoptosis. We concluded that BCAA catabolic defects may be one of the missing factors that determine DKD initiation. Targeting BCAA catabolism or PKM2 activation is a promising strategy for preventing DKD progression.