Erythrocyte Na⁺-K⁺-ATPase Activity, Metabolic Control, and Neuropathy in IDDM Patients

To study the relationship among red blood cell Na⁺-K⁺-ATPase activity, metabolic control, and diabetic neuropathy.

Na⁺-K⁺-ATPase activity has been measured in the red cell membrane of 43 long-standing IDDM patients (duration of diabetes 17.5 ± 2 years, mean ± SE), with 20 of the patients presenting with peripheral neuropathy. There were 23 healthy subjects serving as the control group.

Na⁺-K⁺-ATPase activity was significantly lower in diabetic patients than in healthy subjects (236.5 ± 7.5 vs. 294 ± 10 nmol P₁ · mg protein⁻¹ · h⁻¹, P < 0.05). Among diabetic patients, Na⁺/K⁺-ATPase activity was not dependent on the degree of diabetic control, nor was it correlated with either fasting blood glucose (r = 0.16, NS) or HbA_1c (r = 0.01, NS). Na⁺-K⁺-ATPase activity was lower in patients with neuropathy than in those without it (212 ± 8.5 vs. 261 ± 6.6, P < 0.05). Furthermore, in a subgroup of 20 patients, a positive correlation was observed between erythrocyte Na⁺-K⁺-ATPase activity and nerve conduction velocity in the peroneal (r = 0.558, P < 0.02) and tibial nerve (r = 0.528, P < 0.05).

These results suggest that diabetes-induced Na⁺-K⁺-ATPase activity dysfunction could be implicated in the pathogenesis of human diabetic neuropathy and the electrophysiological abnormalities observed in these patients.