Lifelong caloric restriction reshapes age-related hepatic oxylipin profiles and is associated with a CYB5R3-linked epoxide–diol signature

Caloric restriction (CR) is among the most effective non-genetic strategies to extend lifespan and delay age-related metabolic decline. Yet, the molecular mediators linking CR to hepatic protection remain incompletely understood. Here, we performed age-stratified targeted oxylipin (lipid mediator) profiling of livers from ad libitum (AL) and CR mice across adulthood and aging. In AL-fed mice, ~9 months emerged as an inflection point where oxylipin networks shifted toward a pro-inflammatory state, marked by transient elevations in PGE₂, 11-keto-TXB₂, 20-HETE, and 5-oxo-ETE, with concomitant loss of pro-resolving/hydroxy-dihydroxylated mediators. Later life was characterized by depletion of CYP-derived epoxides and accumulation of soluble epoxide hydrolase (sEH)-generated diols, indicating impaired epoxide-to-diol coupling and resolution capacity. Lifelong CR dynamically reprogrammed these trajectories, blunting mid-life inflammatory surges, preserving EPA-derived epoxy-fatty acids (eg., EpETEs), and inducing the redox enzyme CYB5R3, which may sustain CYP epoxygenase activity (and epoxide output) despite reduced enzyme abundance. These oxylipin changes coincided with reduced hepatic lipid accumulation and a more favorable systemic metabolic profile in CR mice. Collectively, these findings identify age- and diet-associated remodeling of the hepatic COX/LOX/CYP oxylipin network, particularly the epoxide-diol profile, and nominate CYB5R3-associated redox regulation as a hypothesis for future mechanistic investigation.