TGF-β1 is a regulator of the pyruvate dehydrogenase complex in fibroblasts

TGF-beta 1 reprograms metabolism in renal fibroblasts, inducing a switch from oxidative phosphorylation to aerobic glycolysis. However, molecular events underpinning this are unknown. Here we identify that TGF-beta 1 downregulates acetyl-CoA biosynthesis via regulation of the pyruvate dehydrogenase complex (PDC). Flow cytometry showed that TGF-beta 1 reduced the PDC subunit PDH-E1 alpha in fibroblasts derived from injured, but not normal kidneys. An increase in expression of PDH kinase 1 (PDK1), and reduction in the phosphatase PDP1, were commensurate with net phosphorylation and inactivation of PDC. Over-expression of mutant PDH-E1 alpha, resistant to phosphorylation, ameliorated effects of TGF-beta 1, while inhibition of PDC activity with CPI-613 was sufficient to induce alpha SMA and pro-collagen I expression, markers of myofibroblast differentiation and fibroblast activation. The effect of TGF-beta 1 on PDC activity, acetyl-CoA, alpha SMA and pro-collagen I was also ameliorated by sodium dichloroacetate, a small molecule inhibitor of PDK. A reduction in acetyl-CoA, and therefore acetylation substrate, also resulted in a generalised loss of protein acetylation with TGF-beta 1. In conclusion, TGF-beta 1 in part regulates fibroblast activation via effects on PDC activity.