Abstract: Objective: To investigate the protective effects of different dosage of L. meyennii on hypoglycemia of rats induced by exhaustive exercise.Methods: The exercise-induced hypoglycemia animal model was established using the increasing load to exhaustion swimming training. Fifty-five male Wistar rats aged six-week were randomly divided into five groups:①control group (C group), ②exercise control group (M group), ③~⑤exercise+ low dose or medium dose or high dose L. meyennii group (LM I, LM Ⅱ, LM Ⅲ group), 10 rats in each group (5 rats were excluded). L. meyennii was given to LM groups once a day, the dosage was 0.2,0.4,1.2 g/kg body weight respectively, the volume was 5 ml/kg body weight, C and M group were given the same volume of normal saline intragastrically. The exercise rats were drilled in an exhaustive swimming training for 42 d with an increasing load. After 42 d exhaustive training, the body weight, exhaustive swimming time were determined, and related biochemical indicators were detected from samples of plasma, liver and deep strands of quadriceps.Results: The body weight, the level of blood glucose, muscle glycogen, hepatic glycogen, expression of PEPCK in hepatocytes and hepatocyte positive staining accumulated absorbance of M group were lower than those of C group (P<0.05 or P<0.01), there was no obvious difference between C and M groups in the time of exhaustive swimming. Compared with the C group, the content of blood lactate of M group was increased significantly (P<0.01). Compared with M group, body weight, the level of blood glucose, muscle glycogen, hepatic glycogen, expression of PEPCK in hepatocytes and hepatocyte positive staining accumulated absorbance of LM groups were obviously increased (P<0.05 or P<0.01), the time of exhaustive swimming was prolonged (P<0.01), and the content of blood lactate was decreased significantly(P<0.01). There was no difference between LM Ⅰ and LM Ⅲ group in body weight. Compared with LM I group, the level of blood glucose, muscle glycogen, hepatic glycogen, expression of PEPCK in hepatocytes and hepatocyte positive staining accumulated absorbance of LM Ⅲ group was obviously increased (P<0.05), the time of exhaustive swimming of LM Ⅲ group was prolonged, and the content of blood lactate of LM Ⅲ group decreased significantly (P<0.05).Conclusion: High dosage of L. meyennii may effectively suppress and delay the occurrence and development of exercise-induced hypoglycemia and fatigue induced by the long-time and intensive training, and the mechanism may be related to optimize of muscle glycogen and hepatic glycogen reserve in one hand. It is also related to up-regulates the limited enzyme of PEPCK expression and activity in the other hand. Finally it promotes the impact of gluconeogenesis.

Key words: Lepidium meyennii, exhaustive exercise, exercise-induced hypoglycemia, rate-limiting enzyme, phosphoenolpyruvate carboxykinase, rat