Decreased propionyl-CoA metabolism facilitates metabolic reprogramming and promotes hepatocellular carcinoma

Abstract

Alterations of multiple metabolites characterize distinct features of metabolic reprograming in hepatocellular carcinoma (HCC). However, most metabolites including propionyl-CoA (Pro-CoA) are illusive for their functions in metabolic reprograming and hepatocarcinogenesis. This study aims to dissect how Pro-CoA metabolism affects these processes. TCGA data and HCC samples were used to analyze the ALDH6A1-mediated Pro-CoA metabolism and its correlation with HCC. Multiple metabolites were assayed by targeted mass spectrometry. The function of ALDH6A1-generated Pro-CoA was evaluated by HCC proliferation, migration, xenograft nude mouse model and primary liver cancer mouse models. Nontargeted metabolomic and targeted energy metabolomic analyses followed by multiple biochemical assays were performed to dissect the underlying mechanisms. Decreases in Pro-CoA and its derivative propionyl-L-carnitine (PLC) due to ALDH6A1 downregulation were tightly associated with HCC. Functionally, ALDH6A1-mediated Pro-CoA metabolism suppressed HCC proliferation and impaired hepatocarcinogenesis in mice. The aldehyde dehydrogenase activity was indispensable for the ALDH6A1 function while Pro-CoA carboxylases antagonized ALDH6A1 function by eliminating Pro-CoA. Mechanistically, ALDH6A1 caused a signature enrichment of central carbon metabolism in cancer and impaired energy metabolism: ALDH6A1-generated Pro-CoA suppressed citrate synthase (CS) activity that subsequently reduced TCA cycle flux, impaired mitochondrial respiration and membrane potential, and decreased ATP production. Moreover, Pro-CoA metabolism generated 2-methylcitric acid (MCA), which mimicked the inhibitory effect of Pro-CoA on CS and dampened mitochondrial respiration and HCC proliferation. Our study unveils novel features that the decline of ALDH6A1-mediated Pro-CoA metabolism contributes to metabolic remodeling and facilitates hepatocarcinogenesis. Pro-CoA, PLC and MCA may serve as novel metabolic biomarkers for diagnosis and therapy of HCC. Pro-CoA metabolism may provide potential targets for development of novel strategies against HCC. Our study presents new insights on metabolic reprogramming and hepatocarcinogenesis attribute to the decline of ALDH6A1-mediated propionyl-CoA. These findings may enrich molecular and metabolic indicators for physicians to improve clinical practice. These biomarkers may potentially be used for diagnosis and serve as targets for the development of therapeutic strategies against HCC.