Insulin cellular actions

In recent years, tremendous progress has been achieved in the elucidation of the cellular and molecular mechanisms of insulin action. Tire acute cellular action of insulin is initiated by rapid clustering of occupied receptors on the cell surface. Within three minutes, a redistribution of glucose transporters from the cytoplasm to the plasma membrane can be measured lipolysis is also increased. 

Electrochemical phenomena are by no means confined to reactions involving the synthesis of ATP within transducing membranes. In recent years electrical changes within cells have been observed in processes as diverse as differentiation and exocrine secretion. It is now appreciated that so-called non-excitable cells respond to certain stimuli, often hormonal in nature, with a transient alteration in the polarity of their plasma membrane. This event invariably precedes any measurable chemical change. Indeed for both the catecholamines and for insulin a case has been made that an alteration of membrane polarity is an initial and essential step in their cellular action. ... 

Bradykinin stimulates natriuresis and, through stimulation of prostaglandin synthesis, inhibits the actions of antidiuretic hormone (ADH), thereby inhibiting water retention. Bradykinin further improves insulin sensitivity and cellular glucose utilization of skeletal muscle cells in experimental models. This, however, appears not to be relevant in the clinical context. 

The predominant cell type in the pancreatic islets of Langerhans. The main secretory product of the (3 -cell is the peptide hormone insulin which has vital actions for the control of nutrient homeostasis and cellular differentiation. 

TNF is a pleiotropic cytokine exerting a wide range of cellular responses, that affect biological processes such as lipid metabolism, coagulation, and insulin resistance and the function of endothelial cells. As a major proinflammatory cytokine TNF is also involved in progression of diseases like cancer, Alzheimer, Diabetes type II, cardiovascular, pulmonary or neurological disorders, and many autoimmune diseases. Blocking the action of TNF clearly reduces its inflammatory potential on various autoimmune disorders like Crohn s disease, rheumatoid arthritis (RA), and psoriasis. 

Table 11.2 Selected genes whose rate of transcription is altered by binding of insulin to its receptor. In virtually all instances, the ultimate effect is to promote anabolic events characteristic of insulin action. Two-dimensional gel electrophoresis has also pinpointed dozens of proteins of unknown function whose cellular level is altered by insulin...

Il.f.l.1. Insulins. Insulin is the most effective of diabetes medications. Insulin has profound effects on carbohydrate, protein, fat metabolism and electrolytes. It has anabolic and anticatabolic actions. In a state of insulin deficiency, glycogenesis, glucose transport, protein synthesis, triglyceride synthesis, LPL activity in adipose tissue, cellular potassium uptake all decrease on the other hand, gluconeogene-sis, glycogenolysis, protein degradation, ketogene-sis, lipolysis increase. 

Hormones, such as glucagon and insulin, override the normal cellular controls, a Whatever the cells were doing before they received their hormonal instruction, their activities are redirected. Usually the action triggered by the hormone brings no immediate gain to the cells acted on, but since it is beneficial for the organism, it ultimately benefits all cells of the organism. 

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