LECTURE 2

Blood Glucose Control

The process of regulating blood glucose concentrations to maintain health, involving mechanisms like glycogen storage, glycogenolysis, and gluconeogenesis.

Islets of Langerhans

Clusters of endocrine cells in the pancreas responsible for producing hormones like insulin and glucagon to regulate blood glucose levels.

Glucose Homeostasis

The balance of blood glucose levels in the body, controlled by insulin and glucagon to ensure normal concentrations for proper bodily functions.

Hypoglycemia

A condition where blood glucose levels drop below normal range, typically defined as below 3 millimoles per liter, leading to potential health risks.

Hyperglycemia

A condition characterized by high blood glucose concentrations, usually above 10 millimoles per liter, often associated with diabetes and its complications.

Insulin and Glucagon

Two major hormones involved in blood glucose regulation, with insulin lowering blood glucose levels and glucagon raising them as needed.

Gluconeogenesis

The process in the liver where new glucose molecules are produced from non-carbohydrate sources, helping to maintain blood glucose levels during fasting or low glucose conditions.

Glucagon-Like Peptide 1 (GLP-1)

A hormone released from gut cells in response to meals, stimulating insulin secretion from pancreatic beta cells to regulate blood glucose levels.

Diabetes Mellitus

A metabolic disorder characterized by hyperglycemia due to either autoimmune destruction of pancreatic beta cells (Type 1) or defects in insulin release or sensing (Type 2).

Lack of Insulin Action

Common to both types of diabetes mellitus, leading to the inability to return to normal blood glucose levels.

Hypoglycemia

Low blood glucose levels, which can result from excess insulin or glucagon secretion, leading to serious complications like coma or death.

Islets of Langerhans

Clusters of endocrine cells in the pancreas responsible for producing hormones like insulin, glucagon, and somatostatin.

Pancreatic Beta Cells

Cells in the islets of Langerhans that produce insulin, a hormone crucial for regulating blood glucose levels.

Pancreatic Alpha Cells

Cells in the islets of Langerhans that produce glucagon, a hormone that raises blood glucose levels.

Pancreatic Delta Cells

Cells in the islets of Langerhans that produce somatostatin, a hormone involved in regulating insulin and glucagon release.

Epsilon Cells

Islet cells that secrete ghrelin, and PP Cells:Cells that secrete pancreatic polypeptide, both playing minor roles in glucose homeostasis.

Vascularization of Islets

Highly vascularized to respond to changes in blood glucose levels and facilitate hormone release.

Nervous System Innervation

Islets are richly innervated by sympathetic, parasympathetic, and enteric nerve fibers, influencing hormone secretion.

Autocrine and Paracrine Signaling

Mechanisms within the islets where hormones like insulin, glucagon, and somatostatin regulate each other's secretion.

Human vs

Human islets have fewer beta cells and more alpha cells compared to rodent islets, suggesting a different mechanism to avoid hypoglycemia.

Insulin

Hormone produced by pancreatic beta cells that increases glycogen production and lowers blood glucose levels.

Glucagon

Hormone produced by pancreatic alpha cells that breaks down glycogen to increase blood glucose levels.

C-peptide

23 amino acid peptide linked to insulin in proinsulin, used as a marker for insulin production.

Insulin Receptor

Large multi-domain tyrosine kinase receptor activated by insulin binding, leading to glucose uptake.

Glucose Homeostasis

Maintenance of stable blood glucose levels through insulin and glucagon actions.

Glucagon Receptor

GPCR linked to adenylate cyclase, activated by glucagon to increase cAMP levels.

Glucagon Secretion

Stimulated by low glucose levels and inhibited by factors like high glucose, insulin, and somatostatin.

Glucagon Function

Increases endogenous glucose production through glycogenolysis and gluconeogenesis in the liver.

Somatostatin

Hormone produced by pancreatic delta cells, dampens insulin and glucagon secretion in response to high glucose levels.

Counter Regulatory Response

Body's response to hypoglycemia, involving glucagon to increase blood glucose levels.

Glucagon

Hormone released by alpha cells in response to high blood glucose levels, stimulates the release of insulin from beta cells.

Insulin

Hormone released by beta cells in response to high blood glucose levels, helps lower blood glucose levels by promoting glucose uptake.

Somatostatin

Hormone secreted by delta cells, inhibits the release of both glucagon and insulin to maintain glucose homeostasis.

Glucose homeostasis

The balance of blood glucose levels maintained by the actions of insulin, glucagon, and other hormones in the body.

Hyperinsulinism

Condition characterized by excess insulin secretion, leading to low blood glucose levels and potential brain damage.

Diabetes mellitus

Condition characterized by insufficient insulin production or action, resulting in high blood glucose levels and impaired glucagon control.