Glucose uptake by muscle

The promotion by insulin of glucose uptake by muscle and fat cells (adipocytes), of glycogen deposition in liver and muscle, and its stimulation of growth soon emerged as the purified hormone became available for study. Although insulin was crystallized by Abel in 1926, its primary structure established by Sanger in 1953 (see Chapter 10),... 

Figure 3.23 A sequence of processes explaining the role of glucokinase in the liver and fi-cells in regulation of the blood glucose concentration. The increase in the plasma insulin increases glucose uptake by muscle and decreases fatty acid mobilisation from adipose tissue which lowers the plasma fatty acid level which also increases glucose uptake (Chapter 12).

Changes in the blood levels of these hormones all contribute to regulation of blood glncose level in several conditions. After a meal glucose utilisation is increased, since insulin stimulates glucose uptake by muscle and inhibits release of fatty acids from adipose tissue. Physical activity... 

Figure 16.3 Effects of insulin on the glucose/fatty acid cycle. Insulin enhances glucose metabolism by stimulating glucose uptake by muscle and adipose tissue and by inhibiting lipolysis in adipose tissue (see Chapter 12 for the mechanism of these effects). The effect of glucose metabolism on lipolysis is via stimulation of fatty acid esterification via glycerol 3-phosphate.

Insulin stimulates glucose uptake by muscle and adipose tissue (Table 23-3), where the glucose is converted to glucose 6-phosphate. In the liver, insulin also activates... 

Insulin resistance is the decreased ability of target tissues, such as liver, adipose, and muscle, to respond properly to normal circulating concentrations of insulin. For example, insulin resistance is characterized by uncontrolled hepatic glucose production, and decreased glucose uptake by muscle and adipose tissue. 

The reduction of carbohydrate absorption from the intestine of rats with a saccharide supplemented by EGCG or green tea is based upon suppression of the activity of intestinal a-amylase, sucrase, or a-glucosidase. Also, green tea enhances insulin sensitivity of normal and fructose-fed rats as demonstrated by increased glucose uptake by muscle cells. ... 

The lipolytic effects of GH increase free fatty acid levels in the blood bathing muscle. These fatty acids are preferentially used as fuel, indirectly suppressing glucose uptake by muscle cells. Through the effects on glucose uptake, the rate of glycolysis is proportionately reduced. 

In physiologic concentrations, Tj increases glucose uptake by muscle cells. It also stimulates protein synthesis, and, therefore, growth of muscle, through its stimulatory actions on gene expression. 

Type 2 diabetes meUitus is a complex chronic metabohc disorder, which results from defects in both insulin secretion and insuhn action. An elevated rate of basal hepatic glucose production in the presence of hyperin-suhnemia is the primary cause of fasting hypergly-caemia. After a meal, impaired suppression of hepatic glucose production by insulin and decreased insulin-mediated glucose uptake by muscle contribute almost equally to postprandial hyperglycaemia. 

IV. Factors That Regulate Uptake of Glucose by Muscle A. Mitochondrial Regulation of Glucose Uptake by Muscle... 

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