1.
Skeletal muscle fatty acid handling in insulin resistant men.
van Hees, AM, Jans, A, Hul, GB, Roche, HM, Saris, WH, Blaak, EE
Obesity (Silver Spring, Md.). 2011;(7):1350-9
Abstract
Disturbances in skeletal muscle lipid metabolism may precede or contribute to the development of whole body insulin resistance. In this study, we examined fasting and postprandial skeletal muscle fatty acid (FA) handling in insulin resistant (IR) men. Thirty men with the metabolic syndrome (MetS) (National Cholesterol Education Program-Adult Treatment Panel III) were included in this sub-study to the LIPGENE study, and divided in two groups (IR and control) based on the median of insulin sensitivity (S(I) = 2.06 (mU/l(-1))·min(-1)·10(-4)). Fasting and postprandial skeletal muscle FA handling were examined by combining the forearm balance technique with stable isotopes of palmitate. [(2)H(2)]-palmitate was infused intravenously to label endogenous triacylglycerol (TAG) and free FAs (FFAs) in the circulation and [U-(13)C]-palmitate was incorporated in a high-fat mixed meal (2.6 MJ, 61 E% fat) to label chylomicron-TAG. Muscle biopsies were taken to determine muscle TAG, diacylglycerol (DAG), FFA, and phospholipid (PL) content, their fractional synthetic rates (FSRs) and degree of saturation, as well as messenger RNA (mRNA) expression of genes involved in lipid metabolism. In the first 2 h after meal consumption, forearm muscle [(2)H(2)]-labeled TAG extraction was higher in IR vs. control (P = 0.05). Fasting percentage saturation of muscle DAG was higher in IR vs. control (P = 0.016). No differences were observed for intramuscular TAG, DAG, FFA, and PL content, FSR, and muscle mRNA expression. In conclusion, increased muscle (hepatically derived) TAG extraction during postprandial conditions and increased saturation of intramuscular DAG are associated with insulin resistance, suggesting that disturbances in skeletal muscle FA handling could play a role in the development of whole body insulin resistance and type 2 diabetes.
2.
Potential of phosphorus nuclear magnetic resonance spectroscopy in studies of the energy metabolism of skeletal muscles.
Ternovoi, SK, Veselova, TN, Sinitsin, VE
Neuroscience and behavioral physiology. 2003;(7):723-7
Abstract
The aim of the present study was to investigate the possibility of phosphorus magnetic resonance spectroscopy (MR spectroscopy) in the diagnosis of metabolic lesions of skeletal musculature in patients with intermittent claudication syndrome, chronic cardiac failure, and varicose diseases of the lower limbs. Studies included 50 males: 20 patients with intermittent claudication, 10 patients with chronic cardiac failure, and 10 patients with varicose veins. The control group consisted of 10 healthy volunteers. The following measures were determined: the phosphocreatinine index, the intracellular pH in the gastrocnemius muscle, and the half-recovery time for the phosphocreatinine index. The phosphocreatinine index and the pH at rest did not differ between study groups. Isotonic exercise produced no change in the phosphocreatinine index in the control group; patients with intermittent claudication showed a 26.1% decrease, patients with chronic cardiac failure showed an 8% decrease, and patients with varicose veins showed a 25.6% decrease. The only group showing a significant decrease in pH during exercise was the group of patients with intermittent claudication. This group also showed an inverse correlation between the pressure index and the extent of the decrease in the phosphocreatinine index. Thus, MR spectroscopy provides a non-invasive diagnostic method for lesions of energy metabolism in skeletal musculature in patients with deranged peripheral hemodynamics.
3.
Maximal exercise and muscle energy metabolism after recovery from exercise hyperthermia syndrome.
Vanuxem, P, Vanuxem, D, Raharison, L, Aubert, M, Pouliquen, G, Deslangles, O
Muscle & nerve. 2001;(8):1071-7
Abstract
Muscle energy metabolism was studied in 30 subjects after recovery from exercise hyperthermia syndrome (EHTS subjects) and 15 healthy men with identical physical activities. Blood lactate, free fatty acid (FFA), serum creatine kinase activity (CK), and glycerol and the temperature in the auditory duct (T(c)) and on the thumb pad (T(sk)) were measured at rest and during and after maximal exercise on a cycloergometer. The EHTS subjects had a limitation of physical performance, with lowered values for maximal oxygen uptake (VO(2max), P < 0.0005), maximal workload (P < 0.05), and ventilatory threshold (V(t), P < 0.0005). The discrepancy between high plasma concentrations of FFA and the lack of decrease in respiratory ratio (RR) suggests that, in EHTS subjects, a very active release of FFA was not balanced by a proportional increase in catabolism. The increased skin temperature was smaller in EHTS subjects (P < 0.05 at 180 and 200 W). At the end of exercise, auditory duct temperature increase was higher in EHTS subjects than in control subjects (P < 0.05). This study thus showed an impairment of muscle metabolism and an abnormality of thermoregulatory mechanisms. These results may provide insight into the underlying physiopathological disturbance.