Body Weight, Skeletal Muscle Morphology, and Enzyme Activities in Relation to Fasting Serum Insulin Concentration and Glucose Tolerance in 48-year-old Men

Abstract

Tissue samples were taken from the gastrocnemius muscle of 26 randomly selected, glucose-tolerant, 48-yr-old men. Hexokinase, phosphorylase, lactate dehydrogenase (LDH), succinate dehydrogenase, and lipoprotein lipase activity (LPLA), as well as the area per fiber type and capillary density, were determined. Mean fiber area correlated positively with relative body weight (r equals 0.53, P less than 0.01), but capillary density did not. The result is that, in cases of high body weight, each capillary supplies a larger muscle fiber area. Serum insulin concentration in the fasting state correlated positively with body weight (r equals 0.77, P less than 0.001) and with mean fiber area per capillary (r equals 0.87; P less than 0.001). Only during the latter part of an oral glucose tolerance test (OGTT) did blood glucose concentrations correlate with relative body weight and mean fiber area per capillary (r equals 0.42, r equals 0.51, P less than 0.05). A stepwise multiple regression analysis showed that the different muscle morphology measurements could account for 3/4 of the variation in the fasting serum insulin concentration, the fasting insulin/glucose ratio, and the blood glucose concentration at 120 min in the OGTT. Of the intracellular enzymes, only LDH (r equals -0.71, P less than 0.001) correlated with the mean fiber area per capillary. LPLA correlated with capillary density (r equals 0.66, P less than 0.001), and, long with the muscle morphology measurements, could account for 3/4 of the variation in serum triglyceride concentrations. The results show that a large mean muscle fiber area/capillary ratio indicates a morphologic imbalance, which is related to both glucose tolerance and various degrees of insulin sensitivity.

Altered Fiber Distribution and Fiber-Specific Glycolytic and Oxidative Enzyme Activity in Skeletal Muscle of Patients With Type 2 Diabetes

“…CONCLUSIONS -In the present study, we extend previous findings that glycolytic capacity is higher and oxidative capacity is reduced in skeletal muscle of patients with type 2 diabetes (5,6,13,14) by demonstrating that metabolic alterations in skeletal muscle of type 2 diabetic patients are a consequence of both changes in fiber composition and in fiberspecific metabolism. Moreover, chronic hyperglycemia and insulin resistance were identified as significant determinants of diminished contractility of skeletal muscle in type 2 diabetes.…”

“…Insulin resistance correlates with skeletal muscle fiber type distribution (3), a reduced percentage of slow oxidative type I fibers (4), and reduced oxidative enzyme capacity (5)(6)(7). Aging and physical inactivity, which are both associated with insulin resistance, also lead to diminished oxidative capacity of skeletal muscle (6).…”

Insulin resistance syndrome: possible key role of blood flow in resting muscle

“…Moreover, capillary density correlates with the percentage of oxidative fibres in the muscles [44] and both these variables correlate with insulin resistance, blood pressure and degree of obesity [44][45][46][47] (Fig. 2).…”

Insulin sensitivity measured by the euglycaemic insulin clamp and proinsulin levels as predictors of stroke in elderly men

“…Third, insulin resistance is related to an increased pressor response to angiotensin II [19] and has been found to increase the stimulating effects of angiotensin II on cellular hypertrophy and collagen production [20] in individuals with hypertension. Fourth, a deranged microcirculation with vascular hypertrophy and rarefaction has been proposed as a central pathological feature in insulin resistance [21].…”