Effect on Glucose Uptake

The effect is a nerve-mediated increased insulin secretion, particularly increased first phase activity [41-43], but the effect on glucose uptake is more pronounced. It appears that the neural response can increase the translocation of GLUT4 much like the effect of exercise and without concomitant changes in insulin concentration [44]. 

In the past, the main focus has been on insulin s effect on glucose uptake and hepatic glucose production. It now appears that there are many more players. The fate of glucose - or G6P - after uptake appears to be even more important for glucose metabolism, both in healthy persons and in patients with diabetes. There is an intimate interplay between the nutrient stores and between the different organs. This interplay appears well controlled, but the control is dynamic, so the detailed setup of the control system varies with the amount and type of nutrients. In this way the system can cope with almost any eating habit. 

Loimaranta, V., Tenovuo, J., Virtanen, S., Marnila, P., Syvaoja, E., Tupasela, T., and Korhonen, H. 1997. Generation of bovine immune colostrum against Streptococcus mutans and Streptococcus sobrinus and its effect on glucose uptake and extracellullar polysaccharide formation by mutans streptococci. Vaccine 15, 1261-1268. 

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. 

The liver is the first organ to receive blood that contains glucose absorbed from the intestine. The portal vein drains from the small intestine into the hepatic sinuses that are surrounded in a neat columnar fashion by hepatocytes. The arrival of glucose in the blood is detected by the p-cells in the pancreas, and they respond by secreting the peptide hormone insulin. Insulin facilitates glucose uptake by many cell types, from skeletal muscle to white blood cells (Fig. 11-4), but it has no effect on glucose uptake by the brain or red blood cells that rely on GLUT-1. 

Saperstein R, Vicario PP, Strout HV, Brady E, Slater EE, Greenlee WJ, Ondeyka DL, Patchett AA, Hangauer DG (1989) Design of a selective insulin receptor tyrosine kinase inhibitor and its effect on glucose uptake and metabolism in intact cells. Biochemistry 28 5694-5701... 

Although insulin probably affects glucose transport in muscle (see below), in liver a primary effect of insulin on hexokinase could not be excluded. Studies performed on dogs with complete end-to-side portocaval shunt, on dog liver perfused in situ, and on liver slices suggested that insulin had no effect on glucose uptake in liver. 

In view of more recent data that have been accumulated on the effects of alloxan and insulin on gluconeogenic and glycolytic enzymes, these long-range effects appear to result from modification of the pattern of enzyme synthesis. Despite the fact that growth hormones and cortisone had no effect on glucose uptake in vitro, injection of the hormones into hypophysecto-mized and adrenalectomized diabetic rats restored the inhibitory properties in the serum. 

Kim M. High-methoxyl pectin has greater enhancing effect on glucose uptake in intestinal perfused rats. Nutrition. 2005 21(3) 372—377. 

Rask-Madsen C, Dominguez H, Dilemann N, et al. Tumor necrosis factor-alpha inhibits insulin s stimulating effect on glucose uptake and endothelium-dependent vasodilation in humans. Circulation 2003 108 1815-1821. 

The second question concerns the fact that insulin action involves not only effects on glucose uptake, but other effects such as changes in phosphate turnover (Stadie, 1954) and the cellular accumulation of potassium (Verzdr, 1952), as well as effects on protein synthesis (Bouckaert and de Duve, 1947). Are these changes simply the secondary consequence of a primary insulin action upon cell permeability to glucose We do not know. Despite the appeal of a single unitary mechanism for insulin action, the possibility of direct effects of insulin on events other than glucose transfer cannot be ruled out. 

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