Muscle sodium, potassium, and [H-3]Ouabain binding in identical twins, discordant for type 2 diabetes

A reduced functional capacity of the sodium (Na), potassium (K) pump might reduce energy expenditure, inducing obesity and type 2 diabetes. Consequent ly, the Na and K content and [H-3]ouabain binding capacity of skeletal musc le were measured in 10 monozygotic twin pairs discordant for type 2 diabete s and in 10 obese controls. Muscle [H-3]ouabain binding capacity was reduce d by approximately 20% in type 2 diabetes. Removing the genetic component b y looking at differences within twin pairs, the difference in waist/hip rat io was associated with the difference in [H-3]ouabain binding (r = -0.85; P < 0.002). Except for the type 2 diabetic twins in the basal state, both ba sal and insulin-stimulated energy expenditure were associated with the musc le K/Na ratio in the twins. In controls, the 2-h plasma glucose concentrati on during an oral glucose tolerance test was associated with the change in both muscle and plasma K induced by a euglycemic, hyperinsulinemic clamp. I n conclusion, environmental factors related to the waist/hip ratio reduce t he muscle [H-3]ouabain binding capacity in type 2 diabetes. Without proving causality, the muscle K/Na ratio is associated with energy expenditure in individuals genetically predisposed to the development of type 2 diabetes.