Control of Glucose Homeostasis by Incretin Hormones

Abstract

In humans as well as in other animal species, the ingestion of food provides the fundamental source of energy for various cellular activities. The intake of food and the ability of controlling the plasma levels of substrates for energy production involve complex mechanisms that ensure a constantly adequate supply of metabolites both in the fasting and in the fed state. A number of hormonal peptides released from the gastrointestinal (GI) tract in response to the ingestion of food have been shown to play a critical role in the postprandial control of glucose homeostasis. They are known to act through three main mechanisms of action. These include; (1) stimulation of insulin secretion of pancreatic islet (beta) cells; (2) inhibition of hepatic gluconeogenesis by suppression of glucagon secretion; and (3) inhibition of GI motility. While for some of these hormones all three mechanisms of action are utilized under physiological conditions, others preferentially use one or a combination of two mechanisms for lowering postprandial hyperglycemia. Although the term glucoincretins (or incretins, or insulinotropic hormones) etymologically only describes factors capable of inducing insulin secretion, it is more frequently used to identify a larger class of peptides that, rather than manifesting a specific mechanism of action (i.e., insulin secretion), share the ability of controlling glucose excursion in the fed state (with or without a direct insulinotropic effect). The latter more inclusive meaning, incretins, is used in this article. This review summarizes recent advances on synthesis, secretion, blood plasma patterns, and metabolism of some of the major GI regulatory peptides acting in the postprandial state.

Almonds vs complex carbohydrates in a weight reduction program

“…Also, the high oleic acid content in the almonds may have contributed to improved b-cell efficiency through enhanced intestinal secretion of glucagon-like-peptide-1 (GLP-1). 46 Enhancing the b-cell secretory response by dietary measures will improve the regulation of postprandial glucose disposal and insulin sensitivity, 47 which has the potential for improving the cluster of abnormalities linked to the metabolic syndrome. 48 Further, among subjects with type 2 diabetes, diabetes medication reductions were sustained or further reduced in a greater proportion of almond-LCD as compared to CHO-LCD subjects (96 vs 50%, respectively).…”

Effects ofCinnamomum zeylanicum(Ceylon cinnamon) on blood glucose and lipids in a diabetic and healthy rat model

“…The fact that cinnamon lowers blood glucose usually within physiological levels without hypoglycemia and increases satiety leads to the hypothesis that it may act by potentiating the effects of incretin hormones. [19]…”

Targeting postprandial hyperglycemia

“…This effect is called the incretin effect and is estimated to be responsible for 50% to 70% of the insulin response to glucose. It is caused mainly by the 2 intestinal insulin stimulating hormones, glucagon-like peptide 1 (GLP-1) and glucosedependent insulinotropic polypeptide (GIP) [33][34][35]. These peptides not only stimulate pancreatic insulin secretion, but also inhibit glucagon secretion and reduce gastric emptying [36].…”