Author(s): KIM, T., KIM, J., Institution: KONKUK UNIVERSITY - SEOUL CAMPUS, Country: KOREA, SOUTH, Abstract-ID: 534

INTRODUCTION:
A recently published study described lactate function in three keywords : lactate as an energy source, as a precursor of gluconeogenesis, and a signaling molecule, especially during exercise, when lactate moves into or out of the cell (1). A previous study showed potential that lactate upregulates the expression level of catalytic enzymes in the process of glucose production (2). However, it is difficult to conclude that lactate alone was responsible for these effects, as most previous studies used combined treatments, such as lactate and glucose. Therefore, this study aimed to examine the effects of exogenous lactate intake immediately after exercise on glycogen synthesis at 1, 3, and 5 h post-administration, and on energy metabolism at rest.
METHODS:
Eight-week-old male Institute of Cancer Research mouse were randomly grouped in standard laboratory animal cages: post-exercise group with oral administration of lactate or saline immediately after exercise (LAC, SAL; n = 24 per group), Lactate or saline (3 g/kg) were orally administered to the LAC and SAL groups immediately after the treadmill exercise (speed: 25 m/min, slope: 15 º, duration: 50min). Mice were sacrificed at different times (1, 3, and 5 hours). Glycogen concentration was measured using plantaris muscle. Additionally mRNA of four main enzymes that are relevant to the glycogen synthesis in the plantaris muscle (hexokinase 2, glycogen synthase 1, phosphoglucomutase 1, pyruvate dehydrogenase E1 alpha 1), and lactate transporter (monocarboxylate transpoter-1,4), was measured by qPCR method. Moreover, energy metabolism was measured after exercise for 5hours.
RESULTS:
As a result of mRNA analysis of four main enzymes relevant to the glycogen synthesis process in skeletal muscle, significantly higher levels of hk-2 and gs-1 were found in the LAC group at 5 hours. In addition, we observed that pgm-1 and pdh-a1 were significantly higher in the LAC group at 3 hours. And mct-1 was significantly higher in the LAC group at 5 hours, and mct-4 analysis results showed that it remained high in the LAC group for up to 3 hours. In the results of measuring resting metabolic rate for 5 hours after lactate ingestion after exercise, we observed that the LAC group had lower respiratory exchange rate up to 1 hour. The amount of carbohydrate oxidation was observed to be lower in the LAC group until the 30 minutes.
CONCLUSION:
We observed that lactate intake after exercise increased glycogen synthase in skeletal muscle for up to 5 hours. Additionally, exogenous lactate intake after exercise increased glycogen resynthesis and decreased carbohydrate utilization. Overall, these results suggest that lactate supplementation post-exercise can improve glycogen synthesis and recovery in skeletal muscles, and can be developed as a novel supplements to enhance energy recovery after exercise.