Altered Erythrocyte Glycolytic Enzyme Activities in Type-II Diabetes

[Expression levels and activity of rat liver lactate dehydrogenase isoenzymes in alloxan diabetes]

A significant decrease in the activity of lactate dehydrogenase (LDH, EC 1.1.1.27) in liver cells of rats with alloxan diabetes was found due to a decrease in the expression of the corresponding genes. The decrease in the activity of the enzyme under study in experimental type I diabetes was associated with inactivation of the cytoplasmic isoform of LDH. It was found that the level of ldha and ldhb gene transcripts in the liver of healthy rats was higher than in animals with alloxan diabetes. The ldha gene expression demonstrated almost 9-fold decrease, while a decrease in the ldhb gene expression was less pronounced (just 1.25-fold). Probably, the decrease in the rate of functioning of the enzyme under study is associated with a decrease in the intensity of glucose uptake by cells, which leads to inhibition of glycolysis and intensification of all stages of gluconeogenesis, particularly, reversed glycolysis reactions. Thus, the data obtained by us indicate an important role of LDH in the adaptive response of cellular metabolism in the development of type I diabetes mellitus.

The Relationship between Erythrocytes and Diabetes Mellitus

High blood glucose level (hyperglycemia) is a leading indicator of diabetes mellitus (DM). Erythrocytes are the most abundant cells in the circulation and the first to perceive changes in plasma composition. Long-lasting hyperglycemia affects the structure and function of erythrocytes. The detection of erythrocyte-related indicators can provide a valuable reference for the prevention, diagnosis, and treatment of DM and its complications. This paper reviews the normal structure and function of erythrocytes, the changes in erythrocytes in patients with diabetes, and the role of erythrocytes in the development of diabetic complications to provide more indicators for the early prevention of DM complications and to monitor the therapeutic effect of DM.

Type 2 diabetes differentially affects the substrate saturation kinetic attributes of erythrocyte hexokinase and phosphofructokinase

The substrate kinetic parameters of hexokinase (HK) and phosphofructokinase (PFK)-the key irreversible enzymes of glycolysis-in erythrocytes from type 2 diabetic subjects were examined in comparison with control subjects. It was observed that the kinetic parameters such as K_m , V_max , Apparent K_cat , K_cat /K_m , and substrate (ATP) inhibition kinetic and substrate binding characteristics are significantly altered in the diabetic group. The observed changes are suggestive of compositional changes in the subunit makeup of HK and PFK. The implication of these findings in relation to energy status of the diabetic erythrocyte and its interrelationship with loss of cell deformability are discussed here.

Altered Kinetics Properties of Erythrocyte Lactate Dehydrogenase in Type II Diabetic Patients and Its Implications for Lactic Acidosis

Recent studies have been noted that the erythrocytes from Type II diabetic patients show significantly altered structural and functional characteristics along with the changed intracellular concentrations of glycolytic intermediates. More recent studies from our laboratory have shown that the activities of enzymes of glycolytic pathway changed significantly in RBCs from Type II diabetic patients. In particular the levels of lactate dehydrogenase (LDH) increased significantly. Lactic acidosis is an established feature of diabetes and LDH plays a crucial role in conversion of pyruvate to lactate and reportedly, the levels of lactate are significantly high which is consistent with our observation on increased levels of LDH. Owing to this background, we examined the role of erythrocyte LDH in lactic acidosis by studying its kinetics properties in Type II diabetic patients. Km, Vmax and apparent catalytic efficiency were determined using pyruvate and NADH as the substrates. With pyruvate as the substrate the Km values were comparable but Vmax increased significantly in the diabetic group. With NADH as the substrate the enzyme activity of the diabetic group resolved in two components as against a single component in the controls. The Apparent Kcat and Kcat/Km values for pyruvate increased in the diabetic group. The Ki for pyruvate increased by two fold for the enzyme from diabetic group with a marginal decrease in Ki for NADH. The observed changes in catalytic attributes are conducive to enable the enzyme to carry the reaction in forward direction towards conversion of pyruvate to lactate leading to lactic acidosis.