Muscle glucose oxidation

Antidiabetic Drugs other than Insulin. Figure 3 The antihyperglycaemic effect of metformin involves enhanced insulin-mediated suppression of hepatic glucose production and muscle glucose uptake. Metformin also exerts non-insulin-dependent effects on these tissues, including reduced fatty acid oxidation and increased anaerobic glucose metabolism by the intestine. FA, fatty acid f, increase i decrease. 

The rate of mitochondrial oxidations and ATP synthesis is continually adjusted to the needs of the cell (see reviews by Brand and Murphy 1987 Brown, 1992). Physical activity and the nutritional and endocrine states determine which substrates are oxidized by skeletal muscle. Insulin increases the utilization of glucose by promoting its uptake by muscle and by decreasing the availability of free long-chain fatty acids, and of acetoacetate and 3-hydroxybutyrate formed by fatty acid oxidation in the liver, secondary to decreased lipolysis in adipose tissue. Product inhibition of pyruvate dehydrogenase by NADH and acetyl-CoA formed by fatty acid oxidation decreases glucose oxidation in muscle. 

Insufficient thiamine significantly impairs glucose oxidation, causing highly aerobic tissues, such as brain and cardiac muscle, to fail first. In addition, branched-chain amino acids are sources of energy in brain and muscle. 

When there is an increase in demand for ATP generation that cannot be met by an increase in glucose oxidation, e.g. skeletal and cardiac muscle during sustained physical activity. 

Dnring starvation there is a decrease in the resting energy expenditnre which is due to reduced metabolic activity in most tissnes including, perhaps surprisingly, the brain. The decrease in muscle protein breakdown may, therefore, be a simple consequence of a decrease in the rate of glucose oxidation, so that gluconeogenesis from the amino acids is decreased. 

Lactate consumption The direction of the lactate dehydrogenase reaction depends on the relative intracellular concentrations of pyruvate and lactate, and on the ratio of NADH/NAD+ in the cell. For example, in liver and heart, the ratio of NADH/NAD+ is lower than in exercising muscle. These tissues oxidize lactate (obtained from the blood) to pyruvate. In the liver, pyruvate is either converted to glucose by gluconeogenesis or oxidized in the TCA cycle. Heart muscle exclusively oxidizes lactate to CO2 and H20 via the citric acid cycle. 

Orally administered L-carnitine and propionyl-L-carnitine may have metabolic benefits by providing an additional source of carnitine to buffer the cellular acyl CoA pool. In this way, carnitine may enhance glucose oxidation under ischemic conditions and improve energy metabolism in the ischemic skeletal muscle. Propionyl-CoA generated from propionyl-L-carnitine may also improve oxidative metabolism through its anaphoretic actions in priming the Kreb s cycle, secondary to succinyl-CoA production. 

Tomas, E., Tsao, T. S., Saha, A. K., Murrey, H. E., Zhang, C. C., Itani, S. I., Lodish, H. F., and Ruderman, N. B. 2002. Enhanced muscle fat oxidation and glucose transport by ACRP30 globular domain acetyl-CoA carboxylase inhibition and AMP-activated protein kinase activation. Proc Natl Acad Sci USA 99 16309-16313. 

Increased glucose uptake, glucose oxidation, and glucose conversion to fatty acids in adipose tissue, adipocytes and muscle. 

Similarly, Coriandrum sativum (coriander) has also been used as a traditional treatment of diabetes. The coriander incorporated into the diet and drinking water could reduce the hyperglycaemia of the streptozotocin-diabetic mice. Administration of the aqueous extract of coriander increased the 2-deoxyglucose transport (1.6-fold), glucose oxidation (1.4-fold) and incorporation of glucose into glycogen (1.7-fold) of the isolated murine abdominal muscle, more efficiently than insulin. In acute 20 min tests, the aqueous... 

Reviews by Ruderman (19) and Adibi (20,21) indicate that the branched-chain amino acids, particularly leucine, have an important role along with alanine in gluconeogenesis. Leucine and the other two branched-chain amino acids are catabolized in skeletal muscle. The nitrogen that is removed from the branched-chain amino acids in skeletal muscle is combined with pyruvate and returned to the liver as alanine. In the liver the nitrogen is removed for urea production and the carbon chain is utilized as substrate for synthesis of glucose. Adibi et al. (22) reported that during the catabolic conditions of starvation, oxidation of leucine and fatty acids increases in skeletal muscles. While glucose oxidation is reduced, the capacity for oxidation of the fatty acid palmltate more than doubled, and leucine oxidation increased by a factor of six. 

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