The role of Glucagon-like peptide -1 (GLP-1) in blood sugar regulation and type II diabetes: a systematic review

Glucagon-like peptide-1 (GLP-1) is one of the incretin hormones secreted from the intestine upon ingestion of food to increase insulin secretion and regulate blood sugar. In addition to that, GLP-1 can inhibit apoptosis of pancreatic beta cells and enhances their proliferation. The aim of this study is to review the present evidences about GLP-1 effects in regulation of blood sugar, insulin secretion and type 2 diabetes.

The Case-control, cohort, observational and review studies were considered and evaluated using the search engines PubMed, the period between the years 1987 to December 2012. The study was performed by the key words; glucagon-like pepetide-1, GLP-1, "type 2 diabetes", "type II diabetes" and NIDDM. Articles that contained sufficient data and information in relation to GLP-1 in the treatment of type 2 diabetes and its function were used.

From among of the 216 articles that analyzed to evaluate the effects of GLP-1on diabetes, the146 articles were belong to type 2 diabetes and GLP-1. From which only the 25 articles contained sufficient information related to the effects of GLP-1 in the treatment of type 2 diabetes and its role in the regulation of blood glucose and insulin secretion. They were considered and evaluated.

The GLP-1 has effects on lowering blood sugar and increasing insulin levels in two ways, direct and indirect. In direct way, it can increase insulin gene expression and synthesis through pancreatic beta cell receptors. In addition to that, via indirect pathway, by signaling on its receptors on the β-cell surface via hepatic portal vein and vagus nerve could cause an increase in insulin secretion and release. The recent studies show that in Type II diabetes, GLP-1 secretion is impaired, thus its improving can cause an increase in insulin and blood glucose regulation. Nowadays, two types of GLP1-enhancing drugs are administrated orally or subcutaneous injection.