Fatty acid oxidation-induced HIF-1α activation facilitates hepatic urate synthesis through upregulating NT5C2 and XDH

Abstract

Abstract Dyslipidemia affects approximately half of all people with gout, and prior Mendelian randomization analysis suggested a causal role for elevated triglycerides in hyperuricemia (HU), but the underlying mechanisms remain elusive. We hypothesize that dyslipidemia promotes hepatic urate biosynthesis in HU and gout and fatty acid (FA) oxidation (FAO) drives this process. Here we developed a targeted metabolomics to quantify major metabolites in purine metabolic pathway in the sera of a human cohort with HU, gout, and normaluricemic controls. We found that the levels of major purine metabolites and multiple FAs were significantly elevated in HU and gout groups compared to normouricemic controls, whereas hypoxathine showed opposite trend. Furthermore, the levels of multiple serum FAs were positively correlated with urate, xanthine, and inosine but negatively with hypoxanthine, which was also observed in a murine model of high-fat diet-induced HU. Using a stable isotope-labeled metabolic flux assay, we discovered that exogenous hypoxanthine plays a key role in urate synthesis. Moreover, FAO-induced hypoxia-inducible factor 1 alpha (HIF-1α) activation upregulated 5ʹ-nucleotidase II (NT5C2) and xanthine dehydrogenase (XDH) levels to facilitate hypoxanthine uptake from the blood to the liver and activation of urate biosynthesis. Our findings were further supported by data in human hepatocytes and 50 paired serum and liver tissues from liver transplant donors. Together, this study uncovers a mechanism by which FAO promotes hepatic urate synthesis by activating HIF-1α-NT5C2/XDH pathways, directly linking lipid metabolism to HU.