Blood sugar regulation
The body's hormonal control of blood glucose levels.
Blood sugar regulation is the process by which the body maintains the concentration of glucose in blood plasma within a narrow range, a state known as glucose homeostasis. The pancreas secretes two primary hormones, insulin and glucagon, that are chiefly responsible for this regulation. More recently discovered glucoregulatory hormones have further expanded understanding of this system.
Quick Facts
- Primary hormones
- Insulin and glucagon
- Insulin effect
- Lowers blood sugar
- Glucagon effect
- Raises blood sugar
- Glucose transporter involved
- GLUT4
Facts from the source article.
Mechanisms
Blood sugar levels are regulated through negative feedback to maintain bodily balance. Glucose levels are monitored by many tissues, with pancreatic islet cells being among the most important. When blood glucose falls dangerously low, such as during heavy exercise or prolonged lack of food, alpha cells in the pancreas release glucagon. This peptide hormone travels to the liver, binds to glucagon receptors on liver cells, and stimulates glycogenolysis—the breakdown of stored glycogen into glucose—which is then released into the bloodstream, raising blood sugar. Hypoglycemia, or low blood sugar, is treated by restoring glucose levels through ingestion of dextrose or carbohydrate foods, often self-managed with balanced meals; severe cases may require injection or infusion of glucagon. When blood sugar rises, whether from glycogen conversion or meal digestion, beta cells in the pancreatic islets of Langerhans release insulin. Insulin causes the liver to convert more glucose into glycogen (glycogenesis) and prompts about two-thirds of body cells, mainly muscle and fat tissue, to take up glucose via the GLUT4 transporter. Insulin binding to cell surface receptors triggers vesicles containing GLUT4 to fuse with the plasma membrane through endocytosis, enabling facilitated diffusion of glucose into the cell. Once inside, glucose is phosphorylated to glucose-6-phosphate to maintain the concentration gradient. Insulin also signals other body systems and is the chief regulator of metabolic control in humans. Additional causes of increased blood sugar include stress hormones such as epinephrine, several steroids, infections, trauma, and food ingestion. Granule docking, a glucose-dependent step in human insulin secretion, does not function properly in type 2 diabetes.
Carbohydrate control in invertebrates
Insects possess two types of blood sugar: the monosaccharide glucose and the disaccharide trehalose, with trehalose being the major carbohydrate used for flight. Concentrations of trehalose and glucose in insect hemolymph are tightly regulated by multiple enzymes and hormones, including trehalase, insulin-like peptides (ILPs and DILPs), adipokinetic hormone (AKH), leucokinin (LK), octopamine, and other mediators, maintaining carbohydrate homeostasis through endocrine and metabolic feedback mechanisms.
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