Effects of dietary lutein and zeaxanthin on skin pigmentation, hepatic lipid metabolism, and oxidative stress under hypoxic conditions in yellow catfish (Pelteobagrus fulvidraco)

Skin pigmentation is a critical determinant of quality and market value in farmed fish, while environmental stressors such as hypoxia can induce oxidative stress and metabolic disorders, thereby threatening fish health and aquaculture sustainability. The present study investigated the effects of dietary lutein and zeaxanthin on skin pigmentation, hepatic lipid metabolism, and oxidative stress responses in yellow catfish ( Pelteobagrus fulvidraco ) through a 50-day feeding trial followed by an acute hypoxia challenge. Fish (initial body weight: 25.98 ± 0.03 g) were randomly assigned to three experimental diets: a basal control diet (Con), or the basal diet supplemented with 0.2% lutein (Lut) or 0.2% zeaxanthin (Zea). Although no significant differences in growth performance were observed among dietary groups, skin yellowness and total carotenoid deposition in both skin and liver were significantly elevated in the Lut group ( P < 0.05), followed by the Zea group. Lipidomic profiling revealed that both lutein and zeaxanthin supplementation modulated multiple lipid classes, including glycerophospholipids (GP), glycerolipids (GL), sphingolipids (SP), sterols (ST), and fatty acids (FA) in liver and skin tissues ( P < 0.05). Skin lutein content exhibited strong positive correlations with phosphatidylcholine (PC) levels (R=0.978, P < 0.01) and the expression of lipid transport-related genes cd36 (R=0.978) and scarb1 (R=0.977, P < 0.01). Under acute hypoxic stress, fish fed Lut or Zea diets displayed significantly higher plasma SOD activity and lower levels of glucose, lactic acid, and MDA compared to the control group ( P < 0.05). Moreover, lutein supplementation specifically upregulated the expression of antioxidant and anti-apoptotic genes ( nrf2 , sod , gpx , bcl2 ) while downregulating pro-apoptotic genes ( p53 , casp3 ) in the liver ( P < 0.05). In conclusion, dietary lutein plays a more prominent role than zeaxanthin in enhancing skin pigmentation and antioxidant defense in yellow catfish, and its functional efficacy is closely associated with lipid metabolism and carotenoid transport mechanisms.