משתמש:בנצי/ארגז חול ??: פפטיד דמוי-גלוקגון 1

Glucagon-like peptide-1 (GLP-1) is derived from the transcription product of the proglucagon gene. The major source of GLP-1 in the body is the intestinal L cell that secretes GLP-1 as a gut hormone. The biologically active forms of GLP-1 are: GLP-1-(7-37) and GLP-1-(7-36)NH2. Those peptides result from selective cleavage of the proglucagon molecule.

GLP-1 secretion by ileal L cells is dependent on the presence of nutrients in the lumen of the small intestine. The secretagogues (agents that cause or stimulate secretion) of this hormone include major nutrients like carbohydrate, protein and lipid. Once in the circulation, GLP-1 has a half-life of less than 2 minutes, due to rapid degradation by the enzyme dipeptidyl peptidase-4. It is a potent antihyperglycemic hormone, inducing glucose-dependent stimulation of insulin secretion while suppressing glucagon secretion. Such glucose-dependent action is particularly attractive because, when the plasma glucose concentration is in the normal fasting range, GLP-1 no longer stimulates insulin to cause hypoglycemia. GLP-1 appears to restore the glucose sensitivity of pancreatic β-cells, with the mechanism possibly involving the increased expression of GLUT2 and glucokinase. GLP-1 is also known to inhibit pancreatic β-cell apoptosis and stimulate the proliferation and differentiation of insulin-secreting β-cells. In addition, GLP-1 inhibits gastric secretion and motility. This delays and protracts carbohydrate absorption and contributes to a satiating effect.

Physiological functions עריכה

GLP-1 possesses several physiological properties that make it (and its analogs) a subject of intensive investigation as a potential treatment of diabetes mellitus.^[1]^[2]^[3] The known physiological functions of GLP-1 include:

increases insulin secretion from the pancreas in a glucose-dependent manner.
decreases glucagon secretion from the pancreas by engagement of a specific G protein-coupled receptor.
increases insulin-sensitivity in both alpha cells and beta cells
increases beta cells mass and insulin gene expression, post-translational processing and incretion.
inhibits acid secretion and gastric emptying in the stomach.
decreases food intake by increasing satiety in brain.
promotes insulin sensitivity.

As evidence of the physiological role of GLP-1 in post-prandial insulin secretion, it has been shown that an oral dose of glucose triggers a much higher peak in plasma insulin concentration compared to an intravenous dose.

References עריכה

^ "Diabetes and Intestinal Incretin Hormones: A New Therapeutic Paradigm" at medscape.com (slide 36)
^ Toft-Nielsen M, Madsbad S, Holst J (2001). "Determinants of the effectiveness of glucagon-like peptide-1 in type 2 diabetes". J Clin Endocrinol Metab. 86 (8): 3853–60. doi:10.1210/jc.86.8.3853. PMID 11502823.{{cite journal}}: תחזוקה - ציטוט: multiple names: authors list (link)
^ Meier J, Weyhe D, Michaely M, Senkal M, Zumtobel V, Nauck M, Holst J, Schmidt W, Gallwitz B (2004). "Intravenous glucagon-like peptide 1 normalizes blood glucose after major surgery in patients with type 2 diabetes". Crit Care Med. 32 (3): 848–51. doi:10.1097/01.CCM.0000114811.60629.B5. PMID 15090972.{{cite journal}}: תחזוקה - ציטוט: multiple names: authors list (link)