To investigate the effects of supplementation of Antarctic krill oil (KO) on muscle plasma membrane injury and functional recovery in mice after exhaustive exercise, and to explore the possible mechanism by which KO supplementation promotes muscle plasma membrane injury repair.

Sixty male C57 mice aged eight weeks were randomly divided into a soybean oil control group (BOC), a soybean oil plus exercise group (BOE), a krill oil control group (KOC) and a krill oil plus exercise group (KOE). The mice in the KO groups were intragastrically adminsitered with 200 mg/(kg m_b·d) of KO for four weeks, and those in the BO groups were given an equal amount of soybean oil. Thereafter, the mice in the exercise groups were subjected to one-time exhaustive treadmill exercise. Six mice in each group were tested for grasping force immediately (0 h), 6, 24, 48 and 72 h after exhaustive exercise, and the rest were sacrificed 2 h after exhaustive exercise. The activities of serum creatine kinase (CK) and lactate dehydrogenase (LDH) were measuredby colorimetric assays. The integrity of mouse quadriceps muscle plasma membrane was detected by Evan’s blue dye (EBD) staining. The fatty acid composition of mouse quadriceps muscle plasma membrane was detected by liquid chromatography-mass spectrometry (LC-MS). The fluorescence polarization degree, microviscosity and fluidity of mouse quadriceps muscle plasma membrane were measured by fluorescence polarization method.

1) After four and three weeks of intervention, the body mass of mice in the KO groups was significantly lower than that of mice in the BO groups (P < 0.05). 2) The exhaustive exercise time of mice in the KOE group was significantly longer than that in the BOE group (P < 0.01), and the grasping force of limbs in mice in the KOE group was significantly higher than that in BOE group at 2, 6, 24 and 48 h after exhaustive exercise (P < 0.05). 3) The serum activity of CK and LDH in mice in the KOE group was significantly lower than that in the BOE group (P < 0.01 and 0.05, respectively). 4) The area of EBD positive muscle fibers in mic from the KOE group was significantly smaller than that in mice from the BOE group (P < 0.05). 5). Compared with the BOC group, the concentration of the unsaturated fatty acid C_18:3 in skeletal muscle plasma membrane was significantly decreased in the BOE group (P < 0.05). Compared with the KOC group, the concentrations of the saturated fatty acids C_9:0, C_10:0, C_12:0, C_18:0 and C_20:0 and the concnentration of the unsaturated fatty acid C_20:2 in skeletal muscle plasma membrane were significantly decreased in the KOE group (P < 0.05). The concentrations of the unsaturated fatty acids C_22:5, C_22:6 (DHA) and C_24:5 in skeletal muscle plasma membrane were significantly higher in the KOE group than in the BOE group (P < 0.05). 6) Compared with the BOC group, the fluidity of skeletal muscle plasma membrane in the BOE group was significantly increased (P < 0.05), while the fluidity of skeletal muscle plasma membrane in the KOE group was significantly higher than that in the BOE group (P < 0.01).

KO supplementation for four weeks can improve exhaustive exercise performance in mice, enhance the fluidity of skeletal muscle plasma membrane, accelerate the repair of skeletal muscle plasma membrane after exhaustive exercise, and promote the recovery of skeletal muscle function during delayed onset muscle soreness.