The features of metabolic transformations of homocysteine and cysteine in rats’ hepatocytes under the nutritional imbalance

Abstract

The work is devoted to the study of the homocysteine concentration in blood plasma and the activity of the enzymes of cysteine catabolic transformations γ-glutamate-cysteine ligase and cysteine dioxygenase in rats’ hepatocytes under the conditions of consumption of excessive sucrose content on the background of alimentary protein deprivation. It was found, that the consumption of a high-sucrose diet in animals is accompanied by the increase of homocysteine concentration in plasma by 57% compared to control, whereas the excess of sucrose under the conditions of protein deficiency leads to hypohomocysteinemia (the content of homocysteine decreased by 43% compared to control). The increased plasma homocysteine levels in excess-consuming sucrose can be considered as a prognostic marker of functional disorders of the transsulfuration pathway in the liver and used in the diagnosis of hepatopathologies. Since, the cysteine content in liver cells increased under the conditions of high-sucrose diet consumption, the increasing γ-GCS, a key enzyme of glutathione synthesis, is probably associated with the maintenance of intercellular glutathione stores. Our data of the occurrence hypohomocysteinemia under the conditions of the consumption of excessive amounts of sucrose on the background of dietary protein deficiency highlight gaps in the understanding of the correlation between the metabolic processes of methionine, homocysteine and cysteine in the liver. Under the excessive consumption of sucrose on the background of protein deficiency, the exogenous protein deficiency can be considered as a key factor in reducing the γ-GCS activity (36%) and the cysteine content, because not only the amount of this amino acid is reduced but also its synthesis is disrupted. At the same time, the maximum increase in cysteine dioxygenase activity in rats’ hepatocytes under the conditions of high-sucrose/low-protein diet consumption on the background of decreased γ-GCS activity indicates the utilization of excess cysteine with the formation of taurine and sulfates.