Background: N,N,N-trimethyl-5-aminovaleric acid (TMAVA), a lysine-derived metabolite generated by gut microbiota, has been associated with metabolic disorders. However, its role in cardiovascular disease remains unclear. This study aimed to investigate whether TMAVA promotes atherosclerosis progression by disrupting mitochondrial metabolism through inhibition of γ-butyrobetaine hydroxylase (BBOX), a key enzyme in carnitine biosynthesis.

Methods: In vivo, ApoE⁻/⁻ mice were fed a high-fat diet and treated with TMAVA, with or without concurrent BBOX overexpression, for eight weeks. In vitro, human umbilical vein endothelial cells (HUVECs) were exposed to TMAVA, with or without BBOX overexpression, or left untreated. Molecular, metabolic, and functional assays were conducted to evaluate lipid metabolism, mitochondrial function, inflammation, and endothelial function.

Results: TMAVA accumulated in the aortic tissue of ApoE⁻/⁻ mice (p < 0.05) and was associated with aggravated lipid profiles (p < 0.05), increased inflammatory cytokine expression (p < 0.05), and impaired mitochondrial function (p < 0.05). In HUVECs, TMAVA further exacerbated ox-LDL-induced mitochondrial damage, oxidative stress, and inflammation (p < 0.05), accompanied by significant reductions in carnitine levels, ATP production, and fatty acid oxidation markers (AMPK, CPT1α) (p < 0.05). BBOX overexpression restored mitochondrial function and reversed TMAVA-induced metabolic and inflammatory abnormalities in both models (p < 0.05).

Conclusion: TMAVA accelerates atherosclerosis by suppressing BBOX expression, impairing carnitine biosynthesis, and disrupting mitochondrial fatty acid oxidation, ultimately leading to endothelial dysfunction and vascular inflammation. Targeting the TMAVA-BBOX-carnitine pathway may represent a promising therapeutic strategy for cardiovascular disease.