08 September, 2010

Physiological Effects Of Insulin!!

Insulin binds to its receptor, which in turn starts many protein activation cascades.

These include-

Translocation of Glut-4 transporter to the plasma membrane and influx of glucose, glycogen synthesis, glycolysis and fatty acid synthesis.

The actions of insulin on the human metabolism level include:

Control of cellular intake of certain substances, most prominently glucose in muscle and adipose tissue (about ⅔ of body cells).
Increase of DNA replication and protein synthesis via control of amino acid uptake.
Modification of the activity of numerous enzymes.

The actions of insulin on cells include:

Increased glycogen synthesis
– insulin forces storage of glucose in liver (and muscle) cells in the form of glycogen; lowered levels of insulin cause liver cells to convert glycogen to glucose and excrete it into the blood. This is the clinical action of insulin, which is directly useful in reducing high blood glucose levels as in diabetes.
Increased fatty acid synthesis – insulin forces fat cells to take in blood lipids, which are converted to triglycerides; lack of insulin causes the reverse.
Increased esterification of fatty acids – forces adipose tissue to make fats (i.e., triglycerides) from fatty acid esters; lack of insulin causes the reverse.
Decreased proteolysis – decreasing the breakdown of protein.
Decreased lipolysis – forces reduction in conversion of fat cell lipid stores into blood fatty acids; lack of insulin causes the reverse.
Decreased gluconeogenesis – decreases production of glucose from non-sugar substrates, primarily in the liver (remember, the vast majority of endogenous insulin arriving at the liver never leaves the liver); lack of insulin causes glucose production from assorted substrates in the liver and elsewhere.
Decreased autophagy - decreased level of degradation of damaged organelles. Postprandial levels inhibit autophagy completely.
Increased amino acid uptake – forces cells to absorb circulating amino acids; lack of insulin inhibits absorption.
Increased potassium uptake – forces cells to absorb serum potassium; lack of insulin inhibits absorption. Insulin's increase in cellular potassium uptake lowers potassium levels in blood.
Arterial muscle tone – forces arterial wall muscle to relax, increasing blood flow, especially in micro arteries; lack of insulin reduces flow by allowing these muscles to contract.
Increase in the secretion of hydrochloric acid by Parietal cells in the stomach.

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