Exogenous Lactate Intake Can Induce Muscle Synthesis in Rats

Abstract

PurposeLactate had been recognized as fatigue substance during high intensity exercise. However, the lactate paradigm has changed in the last decades, and it was reconsidered as a potential factors of energy resource and muscle adaptation. Nevertheless, the effect of administration of exogenous lactate on muscle has not been elucidated, and it has been no molecular signaling study of the muscle synthesis over time after ingestion. Therefore, we aimed to investigate the effect of lactate on muscle synthesis on skeletal muscle, according to the different time intervals within 2 hours.MethodsMale rats were randomly assigned into one of following four timings that were sacrificed time after oral administration of sodium lactate (2 g/kg); 0 min (n = 8), 30 min (n = 8), 60 min (n = 8) and 120 min (n = 8). After administration lactate, rats were sacrificed and immediately obtained blood and skeletal muscle (plantaris). To determine the effect of lactate on muscle synthesis (Akt, mTOR) and degradation (MuRF1, atrogin‐1), we measured mRNA expression in plantaris by RT‐PCR, and analyzed blood parameters of lactate, insulin, IGF1, glycerol and glucose.ResultsThe results showed that, despite no significant differences in the hormone receptors for androgen and IGF1 associated with synthesis, Akt remained 1.5~2 fold higher after 30minutes, and mTOR was lower than the 30‐minute expression level but showed a high trend at 60 and 120 minutes. In muscle degradation factors, MuRF1 remained elevated after 30 minutes, but atrogin‐1 had no change. Lactate intake increased plasma lactate by about 3.2 mmol / L at 60 minutes and decreased insulin and IGF 1 after 30 minutes. Furthermore, plasma glycerol was increased at 120 min, but glucose has not changed within 2 hours.ConclusionIt is demonstrated in the present study that lactate administration contributes to increase muscle synthesis factors at 30 minutes, and it remained at high levels within 2 hours. Moreover, the reduction of insulin and IGF1, and the upregulation lactate confirmed that the administration of lactate might be similar to the blood response of the human body during low or moderate exercise. Therefore, our results suggest that lactate intake as a supplement has the potential to increase muscle synthesis and have a positive effect on muscle injury and recovery after exercise. Despite these results, because our study is acute intake and synergies with exercise are not identified, further research is required to investigate the long‐term administration of lactate and the effects of exercise on muscle synthesis.Support or Funding InformationThis work was supported by the Ministry of Education of the Republic of Korea and the National Research Foundation of Korea(NRF‐2019S1A5A8033825)