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

ABSTRACT: 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.

ORGANISM(S): Mus musculus

PROVIDER: GSE283568 | GEO | 2025/06/13

REPOSITORIES: GEO

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Project description:Diabetic kidney disease, a major microvascular complication of diabetes, is the primary cause of end-stage renal disease globally 1. Current treatments mainly target glycemic, blood pressure, and lipid control but often fail to prevent renal impairment. Early DKD is characterized by tubular damage, glomerular hypertrophy, thickening of the glomerular basement membrane, and loss of podocytes. Podocyte damage and loss are potentially significant in the pathogenesis of DKD. Hyperglycemia, a critical factor in podocyte injury, can contribute to the progression of DKD. Therefore, mitigating podocyte injury may be a crucial factor in the future management and alleviation of DKD. Chronic hyperglycemia leads to podocyte dysfunction through inflammation, oxidative stress, autophagy, and apoptosis. As is well known, the non-enzymatic glycation of proteins, leading to the formation of advanced glycation end-products (AGEs), constitutes a significant contributing factor to DKD. Notably, recent studies underscore the crucial role of O-linked-N-acetylglucosamine (O-GlcNAc) modification (also known as O-GlcNAcylation) in DKD progression. The hexosamine biosynthesis pathway (HBP) converts glucose to UDP-N -acetylglucosamine (UDP-GlcNAc), a substrate for O-GlcNAcylation, which is catalyzed by O-GlcNAc transferase (OGT) and removed by O-GlcNAcase (OGA). Aberrant O-GlcNAcylation is linked to renal fibrosis, inflammation, and apoptosis, which worsen diabetic kidney function. Elevated levels of O-GlcNAcylation have been observed in renal tissues of diabetic patients, indicating a potential link between hyperglycemia and dysregulated O-GlcNAc signaling. However, the exact molecular mechanisms of O-GlcNAcylation in DKD are not well understood. This study explores the changes in protein and glycosylated protein in podocytes after OGT knockdown to learn the molecular mechanisms of podocyte injury induced by high glucose (HG). A total of 128 up-regulated proteins and 45 down-regulated proteins in OGT knockdown group than in the control group were identified. Furthermore, 55 significantly changed glycosylation modification sites on 43 proteins were identified. To the best of our knowledge, this is the first study to conduct a global analysis of O-GlcNAcylation in podocytes.

Project description:Glomerular podocytes are highly differentiated cells that are key components of the kidney filtration units. The podocyte cytoskeleton builds the basis for the dynamic podocyte cytoarchitecture and plays a central role for proper podocyte function. Recent studies implicate that immunosuppressive agents including the mTOR-inhibitor everolimus have a protective role directly on the stability of the podocyte cytoskeleton. To elucidate mechanisms underlying mTOR-inhibitor mediated cytoskeletal rearrangements, we carried out microarray gene expression studies to identify target genes and corresponding pathways in response to everolimus. We analyzed the effect of everolimus in a puromycin aminonucleoside experimental in vitro model of podocyte injury. Upon treatment with puromycin aminonucleoside, microarray analysis revealed gene clusters involving cytoskeletal-associated pathways, adhesion, migration and extracellular matrix composition to be affected. Everolimus is capable of protecting podocytes from injury, both on the transcriptome and protein level. Rescued genes included TUBB2B and DCDC2, both involved in microtubule structure formation in neuronal cells but not identified in podocytes so far. Confirming gene expression data, Western-blot analysis in cultured podocytes showed an increase of TUBB2B and DCDC2 protein after everolimus treatment, and immunohistochemistry in healthy control kidneys confirmed a podocyte-specific expression. Microtubule-inhibitor experiments led to a maldistribution of TUBB2B and DCDC2 as well as an aberrant reorganization of the actin cytoskeleton. Tubb2bbrdp/brdp mice showed a delay in glomerular podocyte and capillary development. Taken together, our study suggests that off-target, non-immune mediated effects of the mTOR-inhibitor everolimus on the podocyte cytoskeleton might involve regulation of microtubules, revealing a potential novel role of TUBB2B and DCDC2 in glomerular podocyte development We analyzed the effect of everolimus on gene expression in a puromycin aminonucleoside experimental in vitro model of podocyte injury using microarrays

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

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