Diabetes mellitus and subjects' ageing: A study on the ATP content and ATP-related enzyme activities in human erythrocytes

Na⁺/K⁺- and Ca²⁺-ATPase are the major ATP-dependent membrane-bound enzymes that regulate the cation transmembrane gradient which is altered both in red blood cell (RBC) senescence and in RBCs of diabetic patients. In an attempt to clarify the possible connection between diabetes mellitus and ageing, we investigated the relationship between RBC ATP content, Na⁺/K⁺-ATPase, Ca²⁺-ATPase activities and ageing in healthy, insulin-dependent (IDDM) and non-insulin-dependent (NIDDM) subjects. A significant correlation was found (r = -0.82; P <0.001) between RBC ATP content and subject's age only in the control group. A significant reduction in Na⁺/K⁺-ATPase activity was observed in the older group (C₂) Of control subjects, in comparison with the younger (C₁) one. In both IDDM and NIDDM subjects, the enzymatic activity was significantly decreased when compared with healthy subjects of similar age (P <0.001). A significant negative correlation was found between age and enzymatic activity in healthy subjects (r = -0.60; P <0.001). No difference was observed in the RBC membrane Ca²⁺-ATPase activity between younger (C₁) and older (C₂) healthy subjects. Ca²⁺-ATPase activity was significantly increased both in IDDM patients compared with C₁ (P <0.001) and in NIDDM patients compared with C₂ (P <0.001). The present data indicate that ageing causes a reduction in the erythrocyte ATP content in both healthy and diabetic subjects. In diabetic patients Na⁺/K⁺-ATPase activity decreases independently of age.