TMAO promotes disorders of lipid metabolism in psoriasis

Psoriasis is associated with lipid metabolism disorders, but the underlying mechanisms remain unclear. This study aims to investigate the role of trimethylamine N-oxide (TMAO) in lipid metabolism dysregulation in psoriasis.

An imiquimod (IMQ)-induced psoriasis-like mouse model was used to assess lipid metabolism parameters, TMAO levels, and liver flavin monooxygenase 3 (FMO3) mRNA expression. Blood samples from healthy individuals and psoriatic patients were collected to measure serum TMAO levels and lipid profiles. To clarify the role of TMAO in the lipid metabolism disorder of mice with psoriasis model, exogenous TMAO, choline, or 3,3-dimethyl-1-butanol (DMB) were administered via intraperitoneal injections or diet in IMQ-treated mice. Liver tissues from the mouse models were subjected to RNA sequencing to identify TMAO-regulated signaling pathways.

IMQ-induced psoriatic mice exhibited abnormal glucose, insulin, and lipid levels. IMQ treatment also downregulated the hepatic mRNA expression of glucose transporter 2 (Glut2) and silence information regulator 1 (Sirt1), while upregulating glucose transporter 4 (Glut4) and peroxisome proliferator-activated receptor gamma (PPARγ). Elevated serum TMAO levels were observed in both psoriatic patients and IMQ-treated mice. Additionally, liver FMO3 mRNA expression was increased in the psoriatic mouse model. In patients, TMAO levels positively correlated with Psoriasis Area and Severity Index (PASI) scores, serum triglyceride (TG), and total cholesterol (TC) levels. The intraperitoneal injection of TMAO exacerbated lipid dysregulation in IMQ-treated mice. A choline-rich diet further aggravated lipid abnormalities and liver injury in psoriatic mice, whereas DMB treatment alleviated these effects. RNA-Seq analysis demonstrated that TMAO upregulated hepatic microRNA-122 (miR-122), which may suppress the expression of gremlin 2 (GREM2), thus contributing to lipid metabolism disorder.

TMAO may promote lipid metabolism dysregulation in psoriasis by modulating the hepatic miR-122/GREM2 pathway.