A study in Scientific Reports examined how reintroducing an ancient ancestral enzymatic gene into human liver cells alters cellular metabolism. Humans – and other apes – lost functional uricase millions of years ago, a change that contributes to higher uric acid levels and influences disorders such as gout, kidney disease, and fatty liver. By restoring this enzyme in vitro, the study explores how human hepatocytes behave when uricase is present once again.
Using CRISPR–Cas9 editing, the team inserted a reconstructed ancestral uricase (AncUOX) into the AAVS1 safe-harbor locus of Huh-7 liver cells. PCR and DNA sequencing confirmed correct insertion, and Western blotting and immunofluorescence showed that the protein was expressed and localized to cell structures called peroxisomes.
The central question was whether these engineered hepatocytes could oxidize uric acid – and if doing so would alter downstream metabolic pathways. In both standard 2D cultures and 3D spheroid models, AncUOX-expressing cells oxidized urate efficiently across a wide concentration range. Control cells, lacking uricase, showed no measurable activity. Oxidation was somewhat reduced in spheroids, likely because of limited diffusion, but remained functionally detectable.
The study also evaluated responses to fructose exposure. In control cells, fructose exposure raised urate levels and stimulated triglyceride accumulation. In AncUOX-expressing cells, these increases were absent, indicating that uricase prevented the fructose-linked metabolic shift. The pattern was consistent in both monolayer and spheroid cultures.
Under starvation conditions, uricase-positive spheroids maintained lower urate, higher ATP levels, and different triglyceride responses compared with controls. These findings suggest that uricase affects not only urate disposal but also broader pathways related to cellular energy and lipid regulation.
This study provides mechanistic insight into how urate metabolism interacts with lipid synthesis and cellular energy pathways. Although these findings were generated in vitro, they highlight metabolic features relevant to hyperuricemia, fatty liver disease, and other urate-associated disorders.
The work also demonstrates a gene-editing approach that may be useful for future research on urate metabolism or for evaluating potential therapeutic strategies involving uricase restoration.
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