Rates of skeletal muscle and adipose tissue glycerol release in nonobese and obese subjects.

Abstract

Skeletal muscle and adipose tissue lipolysis rates were quantitatively compared in 12 healthy nonobese and 14 insulin-resistant obese subjects for 3.5 h after an oral glucose load using microdialysis measurements of interstitial glycerol concentrations and determinations of local blood flow with 133 Xe clearance in the gastrocnemius muscle and in abdominal subcutaneous adipose tissue. Together with measurements of arterialized venous plasma glycerol, the absolute rates of glycerol mobilization were estimated. In the basal state, skeletal muscle and adipose tissue glycerol levels were 50% higher (P < 0.05-0.01) and adipose tissue blood flow (ATBF) and muscle blood flow (MBF) rates were 30-40% lower (P < 0.02-0.05) in obese versus nonobese subjects. After glucose ingestion, adipose tissue glycerol levels were rapidly and transiently reduced, whereas in muscle, a progressive and less pronounced fall in glycerol levels was evident. MBF remained unchanged in both study groups, whereas ATBF increased more markedly (P < 0.01) in the nonobese versus obese subjects after the oral glucose load. The fasting rates of glycerol release per unit of tissue weight from skeletal muscle were between 20 and 25% of that from adipose tissue in both groups. After glucose ingestion, the rates of glycerol release from skeletal muscle and from adipose tissue were almost identical in nonobese and obese subjects. However, the kinetic patterns differed markedly between tissues; in adipose tissue, the rate of glycerol mobilization was suppressed by 25-30% (P < 0.05) after glucose ingestion, whereas no significant reduction was registered in skeletal muscle. We conclude that significant amounts of glycerol are released from skeletal muscle, which suggests that muscle lipolysis provides an important endogenous energy source in humans. In response to glucose ingestion, the regulation of skeletal muscle glycerol release differs from that in adipose tissue; although the rate of glycerol release from adipose tissue is clearly suppressed, the rate of glycerol mobilization from skeletal muscle remains unaltered. In quantitative terms, the rate of glycerol release per unit of tissue weight in adipose tissue and in skeletal muscle is similar in nonobese and obese subjects in both the postabsorptive state and after glucose ingestion. Diabetes 49:797-802, 2000 S keletal muscle insulin resistance, as reflected by attenuated insulin-mediated glucose disposal, is a key finding of the various clinical components of the metabolic syndrome (e.g., obesity, dyslipidemia, hypertension, and type 2 diabetes) and thus is a predisposing factor in the pathogenesis of premature atherosclerotic cardiovascular disease (1). Among the putative mechanisms underlying insulin resistance, increased attention has been paid to elevated circulating concentrations of free fatty acids (FFAs). We have known for many years that an inverse relationship exists regarding the use of lipids and carbohydrates as metabolic fuels and that inappropriate elevation of FFA levels mediates an i...

Heterogeneity in limb fatty acid kinetics in type 2 diabetes

“…Furthermore, heterogeneity in adipose tissue [39] and skeletal muscle [16] lipolysis has been reported. In addition, skeletal muscle and adipose tissue lipolysis can respond differently to insulin [40][41][42][43], also in relation to the insulin level [44,45]. Taken together, these factors hamper a clear interpretation of palmitate release in the arm and leg of healthy individuals and diabetic patients.…”

Major differences in noradrenaline action on lipolysis and blood flow rates in skeletal muscle and adipose tissue in vivo

“…Lipolysis in skeletal muscle appears to be regulated differently. Several studies have demonstrated that insulin does not suppress muscle lipolysis [6][7][8], which may be due to different phosphodiesterase subtypes in the two tissues [9]. With regard to the catecholamine regulation of skeletal muscle lipolysis, disparate findings have been reported.…”

Changes in abdominal subcutaneous fat water content with rapid weight loss and long-term weight maintenance in abdominally obese men and women

“…[7][8][9] In obesity, the insulin-stimulated increase in skeletal muscle and adipose tissue blood flow 2,4 also appears to be blunted. 2 These findings suggest that the decrease in basal and postprandial adipose and skeletal muscle blood flow 9 is because of insulin resistance. Decreased adipose tissue blood flow affects metabolism by decreasing delivery of glucose, fatty acids and hormones to adipose tissue, and by decreasing release of lipolysis products and peptides from fat tissue into the general circulation.…”