Peroral Glucose Tolerance Test

Skeletal muscle magnesium content is correlated with plasma glucose concentration in patients with essential hypertension treated with lisinopril or bendrofluazide

The association between change in glucose metabolism and change in skeletal muscle magnesium (Mg) concentration induced by antihypertensive treatment was evaluated in 37 patients with essential hypertension randomly treated with either lisinopril or bendrofluazide. Before and after 6 months of treatment, skeletal muscle biopsies were performed, glucose tolerance was determined by oral (OGTT) and intravenous glucose tolerance tests (IVGTT), and insulin sensitivity was assessed by the hyperinsulinemic euglycemic clamp technique. An inverse relationship was found between the treatment-induced change in fasting plasma glucose concentration and change in skeletal muscle Mg concentration (r = -0.39, P < .05). However, there was no significant correlation between skeletal muscle Mg content and either insulin sensitivity measured by the hyperinsulinemic euglycemic clamp test or glucose tolerance evaluated by IVGTT and OGTT. In conclusion, an increased circulating glucose concentration was correlated with a decreased Mg concentration in skeletal muscle during antihypertensive treatment. However, the Mg concentration in skeletal muscle did not significantly predict the insulin sensitivity or glucose tolerance.

Increased skeletal muscle Na/K-ratio in obese men, but not in women, with glucose intolerance

Obesity is associated with glucose intolerance. Glucose is to a large extent disposed in the skeletal muscle. Peripheral insulin resistance, as well as decreased enzymatic activity in the skeletal muscle, has been suggested in type II diabetes. Potassium is essential for such enzymatic reactions. In this study, obese men, but not women, with glucose intolerance tended to have a lower total body potassium per kg body weight, indicating a smaller muscle mass, than weight-matched normoglycaemic men. They also had a lower skeletal muscle potassium content per 100 g dry weight (P less than 0.05) and a higher muscle Na/K-ratio (P less than 0.05) compared with obese men with normal glucose tolerance. Muscle fat and muscle sodium content were higher in obese men than in women with the same body mass index (P less than 0.01). The muscle electrolyte changes can be explained by a decrease in the insulin mediated Na/k-pump activity across the cell membrane or a smaller number of insulin receptors on the skeletal muscle cell in patients with glucose intolerance.