Lactic acid as a systemic product and biomarker of physical load

Abstract

This paper presents an up-to-date review of research data on the specific features of lactic acid metabolism and its role as an effector of vital regulatory mechanisms. Lactic acid is an alpha-hydroxy monocarboxylic acid. Physical loads of submaximal intensity and some diseases can cause dramatic increase of lactic acid content in the body fluids. The excessive lactate is removed from the working muscle and either metabolized by other tissues or excreted from the human body. Alteration of the lactate-pyruvate balance is one of the main markers of the development of cardiac hypertrophy and failure. The redistribution of lactate between the cells producing it and the cells that metabolize it is vital to maintain a stable pH level in tissues and hold lactate in the body since this compound is an important energy source as well as an effector of important regulatory mechanisms. The quantification of lactate is used to assess general physical capabilities of the human body, the intensity of physical load and the rate of recovery in physical rehabilitation. Specialized proteins, which refer to the group of monocarboxylate transporters, are involved in lactate excretion and absorption by cells. The presence of various types of transporters in cell membranes that differ in affinity to lactate and the direction of transport ensures a rapid redistribution of lactic acid throughout the body and regulates the intensity and direction of its metabolism according to the physiological needs. Efficient transfer and redistribution of lactate between different tissues of the body is essential, given the participation of lactate in several important regulatory mechanisms. As an effector, lactate is involved in the regulation of angiogenesis, differentiation of myosatellitocytes, regeneration of muscle fibers, polarization of macrophages and the course of inflammatory processes. Besides, lactate participates in epigenetic mechanisms of muscle tissue metabolism regulation. Therefore, lactate is one of the key metabolites in the human body.

Anaerobic glycolysis and oxidative stress interrelation in erythrocytes under administration of Cornus mas L. fruit extracts to rats with streptozotocin-induced diabetes mellitus

“…According to the results of our experiments, the content of pyruvate increases 1.3-fold in erythrocytes under diabetes (Table 1). Pyruvate, the end product of glycolysis, is converted into lactate in erythrocytes with the enzyme LDH 2 (Boretsky et al, 2023). We detected a 2.9fold increase in lactate concentration in rats' erythrocytes in diabetes mellitus (Table 1).…”

“…Acetyl-CoA formed from β-hydroxybutyrate or acetoacetate is an allosteric inhibitor of the pyruvate dehydrogenase and provokes the accumulation of pyruvate (Kolb et al, 2021;Gray et al, 2014). In addition, under diabetes, erythrocytes are also an important source of pyruvate, transporting it into the plasma by monocarboxylate transporters (MCT) (Boretsky et al, 2023;Halestrap, 2012).…”

“…The imbalance of metabolites of carbohydrate metabolism was definitely reflected in the ratio between these acids, which led to an increase in the L/P ratio in the plasma of rats with diabetes. One of the main markers of the development of myocardial hypertrophy and heart failure is the violation of the lactate-to-pyruvate balance, which is accompanied by a decrease in the intensity of pyruvate oxidation in the mitochondria of cardiomyocytes and an increase in lactate export (Boretsky et al, 2023).…”

“…If this does not happen, glycolysis will stop due to a deficiency of oxidized NAD + . Accumulation of lactate affects the glucose breakdown, as it slows the overall rate of glycolysis, reduces the affinity of phosphofructokinase enzyme (EC 2.7.1.11) for ATP and fructose-6-phosphate and causes the dissociation of the active tetrameric form of phosphofructokinase into less active dimers (Boretsky et al, 2023).…”