Vascular Smooth Muscle Cell-Specific BCAT2 Deficiency Attenuates Diabetic Atherosclerotic Calcification via Histone Propionylation

Background: Vascular calcification is a major cause of adverse outcomes of acute cardiovascular events in diabetic patients. However, the effective therapeutic target for diabetic atherosclerotic calcification remains unclear. Branched-chain amino acid transaminase 2 (BCAT2), a key rate-limiting enzyme of branched-chain amino acid (BCAA) catabolism, may play a potential role in the development of diabetic complications. This study aimed to elucidate the role of BCAT2 in diabetic atherosclerotic calcification. Methods: Airflow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI) was employed to investigate the spatial distribution of metabolites in frozen arterial sections obtained from diabetic foot amputations. Single-cell RNA sequencing datasets from arteries of diabetic foot amputations were used to identify the expression of metabolic enzymes in the BCAA catabolism. ApoE knockout mice with specific deletion of BCAT2 in vascular smooth muscle cells (VSMCs) were generated, and a diabetic atherosclerotic calcification model was established to evaluate the impact of BCAT2 in diabetic atherosclerotic calcification. Further, the gene regulatory mechanisms of BCAT2 in diabetic atherosclerotic calcification were investigated. Results: BCAA catabolism was enhanced in the calcified anterior tibial arteries from diabetic foot amputation revealed by spatial metabolomics. Furthermore, BCAT2 was found to be up-regulated in VSMCs of calcified anterior tibial arteries from diabetic foot amputation by single-cell transcriptomics. Notably, VSMC-specific BCAT2 deficiency attenuated diabetic atherosclerotic calcification without sex bias. Further experiments revealed that branched-chain α-ketoacids (BCKA) supplement, especially α-keto-β-methylvaleric acid (KMV) and α-ketoisovaleric acid (KIV), promoted osteogenic differentiation of VSMCs and diabetic atherosclerotic calcification. Mechanistically, VSMC-specific BCAT2 deficiency suppressed the generation of BCKA-derived propionyl-CoA, mitigating histone propionylation at the promoter of RUNX2, and thereby osteogenic differentiation of VSMCs and diabetic atherosclerotic calcification. Conclusions: Our study demonstrates a previously unrecognized role of BCAA catabolism in diabetic atherosclerotic calcification and further delineates that the BCAT2-BCKA axis contributes to the osteoblastic differentiation of VSMCs by epigenetically modulating RUNX2 expression via histone propionylation.