Reverse Erythroblastosis Virus α Antagonism Promotes Homocysteine Catabolism and Ammonia Clearance

Metabolic homeostasis of amino acids is essential for human health. Here, we aimed to investigate a potential role for the clock component reverse erythroblastosis virus alpha (Rev-erb alpha) in circadian regulation of amino acid metabolism. RNA-seq with Rev-erb alpha(-/-) mice showed expression changes in genes involved in amino acid metabolism, particularly, the urea cycle and methionine metabolism. Rev-erb alpha ablation increased hepatic mRNA, protein, and enzymatic activity of betaine homocysteine methyltransferase (Bhmt), cystathionine beta-synthase (Cbs), and cystathionine gamma-lyase (Cth) and decreased the levels of plasma and liver homocysteine in mice. Cell-based assays confirmed negative regulation of these three genes by Rev-erb alpha. Combined luciferase reporter, mobility-shift, and chromatin immunoprecipitation assays identified Rev-erb alpha as a transcriptional repressor of Bhmt, Cbs, and Cth. Rev-erb alpha ablation or antagonism alleviated chemical-induced hyperhomocysteinemia in mice. This was accompanied by elevated expressions of Bhmt, Cbs, and Cth. Moreover, Rev-erb alpha ablation or antagonism promoted urea production and ammonia clearance. Of urea cycle-related genes, arginase 1 (Arg1), ornithine transcarbamylase (Otc), and carbamoyl-phosphate synthase 1 (Cps1) expressions were up-regulated in Rev-erb alpha(-/-) mice. Negative regulation of these urea cycle genes by Rev-erb alpha was validated using cell-based experiments. Mechanistic studies revealed that Rev-erb alpha inhibited CCAAT-enhancer-binding protein alpha transactivation to repress the transcription of Arg1, Cps1, and Otc. Conclusion: Rev-erb alpha antagonism alleviates hyperhomocysteinemia and promotes ammonia clearance. Targeting Rev-erb alpha represents an approach for the management of homocysteine- and ammonia-related diseases.