Ketogenic diet-induced changes in hepatic drug metabolism with potential implications for ozanimod pharmacokinetics in mice.

Ketogenic diet (KD) is increasingly considered as an adjunctive therapeutic approach across a range of diseases, but its effects on the pharmacokinetics of concomitantly administered drugs remain unclear. Such interactions may be particularly relevant in multiple sclerosis, where KD is being explored as a complementary strategy alongside disease-modifying therapies, such as ozanimod. We therefore investigated whether KD affects ozanimod metabolism and pharmacokinetics and explored potential factors that may contribute to such effects. Specific pathogen-free female C57BL/6 mice were fed either a control diet containing 10% of calories from fat or a ketogenic diet containing 90% of calories from fat for 4 weeks. Metabolic, inflammatory, and hormonal parameters were determined in plasma. Gut microbiota composition was analyzed by whole-metagenome shotgun sequencing. In parallel, hepatic cytochrome P450 (CYP) enzymes were evaluated by mRNA expression and activity together with ozanimod pharmacokinetics. KD induced the expected metabolic adaptation to ketosis and led to a significant increase in plasma cholesterol accompanied by changes in gut microbiota composition. Other metabolic and inflammatory parameters showed only modest changes. In addition, KD altered the expression and activity of hepatic CYP enzymes, including enzymes involved in ozanimod metabolism: CYP1A activity and mRNA expression were significantly increased in KD-fed mice, whereas lower CYP2C activity was observed in pooled samples and CYP3A activity showed a non-significant trend toward lower values. Ozanimod exposure tended to be higher in KD-fed mice, resulting in an approximately 17% increase in area under the concentration-time curve, although this effect did not reach statistical significance. In conclusion, our findings demonstrate that KD altered the expression and activity of hepatic CYP enzymes and revealed a non-significant trend toward increased ozanimod exposure. These observations highlight the potential importance of considering dietary interventions as a factor contributing to variability in drug response.