GLP-1 inhibits glucagon secretion (32,33). In type 2 diabetes, excessive glucagon secretion in relation to the plasma glucose aggravates fasting hyperglycemia by stimulating hepatic glucose output (34). Exogenous administration of GLP-1 in type 2 diabetic patients leads to a significant suppression of glucagon secretion together with a normalization in fasting plasma glucose (29). The counterregulatory response of glucagon secretion in hypoglycemia is unaffected by GLP-1 administration (35). GLP-1-based therapies will therefore not bear an intrinsic risk for hypoglycemia (36).
Concerning gastrointestinal functions, GLP-1 slows gastric emptying and inhibits gastric acid secretion (18). In the central nervous system, GLP-1 acts as a neurotransmitter in the hypothalamus and stimulates satiety directly (37). Continuous GLP-1 application over 6 weeks in type 2 diabetic patients produced significant weight loss due to reduced food intake and increased satiety (37,38). Whether the effects of GLP-1 on satiety in humans are mainly mediated by the retardation of gastric emptying through a feedback loop or are centrally mediated is not completely clear yet (39,40).
In animal studies as well as in vitro studies including studies with human islets GLP-1 causes an increase of beta cell mass. This increase is explained by a stimulation of islet cell neogenesis (41-43) from precursor cells as well as an inhibition of apoptosis of beta cells (42,44). In man, the effect of GLP-1 on the beta cell mass cannot easily be quantified, but indirect measures of beta cell function have shown an improvement after GLP-1 application (45). in vitro, in isolated human islets, GLP-1 improves insulin secretion and islet cell morphology (46).
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All you need is a proper diet of fresh fruits and vegetables and get plenty of exercise and you'll be fine. Ever heard those words from your doctor? If that's all heshe recommends then you're missing out an important ingredient for health that he's not telling you. Fact is that you can adhere to the strictest diet, watch everything you eat and get the exercise of amarathon runner and still come down with diabetic complications. Diet, exercise and standard drug treatments simply aren't enough to help keep your diabetes under control.