Acute Effects of Insulin Deficiency
Insulin acts to create energy reserves. It promotes the uptake of amino acids and glucose, especially in the muscle and fat cells. In hepatic, muscle, and fat cells (among others) insulin stimulates protein synthesis and inhibitis protein breakdown; in the liver and muscles it promotes glycogen synthesis, inhibits its breakdown, stimulates glycolysis, and inhibits gluconeogenesis from amino acids. Also in the liver, insulin promotes the formation of triglycerides and lipoproteins as well as the hepatic release ofVLDL. At the same time it stimulates lipoprotein lipase and thus accelerates the splitting of triglycerides into lipoproteins in blood (especially chylomicrons). The free fatty acids and glycerol are then taken up by the fat cells and stored again as triglycerides. Insulin stimulates lipogenesis and inhibits lipolysis in the fat cells. Lastly, it promotes cell growth, increases renal tubular absorption of Na+, and cardiac contractility. Part of insulin action is mediated by cell swelling (especially antiproteolysis) and intracellular alkalosis (stimulation of glycolysis, increased cardiac contractility). Insulin achieves this effect by activating the Na +/H+exchanger (cell swelling and alkalinization), the Na+-K+-2 Cl– cotransporter (cell swelling), and Na+-K+-ATPase. This results in K + uptake by the cell and hypokalemia. As glucose is coupled to phosphate in the cell, insulin also reduces plasma phosphate concentration. It further stimulates the cellular uptake of Mg2+. Insulin also paracrinally in hibits the release of glucagon and thus diminishes its stimulating action on glycogenolysis, gluconeogenesis, lipolysis, and ketogenesis.
ผลเฉียบพลันของการขาดอินซูลินInsulin acts to create energy reserves. It promotes the uptake of amino acids and glucose, especially in the muscle and fat cells. In hepatic, muscle, and fat cells (among others) insulin stimulates protein synthesis and inhibitis protein breakdown; in the liver and muscles it promotes glycogen synthesis, inhibits its breakdown, stimulates glycolysis, and inhibits gluconeogenesis from amino acids. Also in the liver, insulin promotes the formation of triglycerides and lipoproteins as well as the hepatic release ofVLDL. At the same time it stimulates lipoprotein lipase and thus accelerates the splitting of triglycerides into lipoproteins in blood (especially chylomicrons). The free fatty acids and glycerol are then taken up by the fat cells and stored again as triglycerides. Insulin stimulates lipogenesis and inhibits lipolysis in the fat cells. Lastly, it promotes cell growth, increases renal tubular absorption of Na+, and cardiac contractility. Part of insulin action is mediated by cell swelling (especially antiproteolysis) and intracellular alkalosis (stimulation of glycolysis, increased cardiac contractility). Insulin achieves this effect by activating the Na +/H+exchanger (cell swelling and alkalinization), the Na+-K+-2 Cl– cotransporter (cell swelling), and Na+-K+-ATPase. This results in K + uptake by the cell and hypokalemia. As glucose is coupled to phosphate in the cell, insulin also reduces plasma phosphate concentration. It further stimulates the cellular uptake of Mg2+. Insulin also paracrinally in hibits the release of glucagon and thus diminishes its stimulating action on glycogenolysis, gluconeogenesis, lipolysis, and ketogenesis.
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