Building Competency in Diabetes Education THE ESSENTIALS

PATHOPHYSIOLOGY| 3-5

PHYSIOLOGY AND REGULATION OF GLUCOSE HOMEOSTASIS

A basic understanding of metabolism in the non-diabetes state is essential to understanding the many forms of diabetes treatment. This includes the biological functions of insulin and glucagon, the role of the liver in glucose homeostasis, the incretin effect, the endocannabinoid system and metabolic responses to nutrient intake and exercise. Illustrations and text that are used to explain these complex physiological processes to individuals with prediabetes and diabetes should be simple and culturally appropriate, but at the same time accurate and detailed enough to make treatment recommendations clear. Glucose homeostasis represents the balance between glucose production, utilization and storage. This metabolic equilibrium is achieved by neural mechanisms, metabolic signals, and hormones (e.g. insulin, glucagon) between various organs involved in glucose supply and utilization. The metabolic process The mechanical and chemical breakdown of various types of food results in the absorption of food particles for ongoing energy requirements, tissue repair and growth. Protein, fat and carbohydrate foods are broken down in the digestive tract to their respective absorbable components. Once digested, each nutrient provides available glucose to body cells; carbohydrates convert 90 to 100% to glucose, protein 58% and fat <10% (4). In the fasting state, insulin levels are low, but glucagon levels increase and stimulate glucose production through hepatic gluconeogenesis (new synthesis of glucose) and glycogenolysis (glycogen breakdown). Low insulin and high glucagon levels also lead to reduced glucose uptake in insulin-sensitive organs, such as fat and skeletal muscles, and mobilization of stored amino acids and free fatty acids (FFAs) (5). In the fed state, glucose from ingested food stimulates a rise in insulin and a fall in glucagon levels which leads to a reversal of the above processes (5). During the first few hours after a carbohydrate meal, glucose from that meal provides needed fuel directly, and any excess energy is stored. The two principal circulating fuels — glucose and FFAs — are stored intracellularly as glycogen and triglycerides, respectively (6). Postprandial glucose is used mainly by skeletal muscles through insulin-stimulated glucose uptake (5). Approximately 75 g of carbohydrate may be stored as glycogen in the liver and 300 to 500 g in muscle (6). The