Endocrine Control of Metabolism and Digestion PDF

Endocrine Control of Metabolism and Digestion Endocrine Control of Metabolism Insulin and Glucagon Beyond Insulin Beyond the Pancreas The role of gut hormones in metabolically important organs. Gut hormones are implicated in the regulation in glucose homeostasis through their differential actions on...

Endocrine Control of Metabolism and Digestion Endocrine Control of Metabolism Insulin and Glucagon Beyond Insulin Beyond the Pancreas The role of gut hormones in metabolically important organs. Gut hormones are implicated in the regulation in glucose homeostasis through their differential actions on the liver and endocrine pancreas. They also play important roles in maintaining energy balance by modulating nutrient absorption, mobilization of fat stores from adipose tissue and appetite regulation. 5-HT, serotonin; CCK, cholecystokinin; GIP, glucose-dependent insulinotropic peptide; GLP-1, glucagon-like peptide 1; INSL5, insulin-like peptide 5; PYY, peptide YY; OXM, oxyntomodulin; BAT, brown adipose tissue; WAT, white adipose tissue. Prader–Willi syndrome - a rare genetic disorder that results in a number of physical, mental and behavioral problems. A key feature is a constant sense of hunger from about age 2 BloodGlucose So What? Metabolism - Fed state Nutrient Rich Glucose, Amino acids -> transport from intestine to blood Dietary lipids transported -> lymphatic system -> blood Predominant Hormone - Insulin Stimulates storage of fuels and synthesis of proteins 9 Fed State Early Fasting State Metabolism Blood-glucose level drops after several hours after the meal Pancreatic Hormone Predominating - Glucagon Glucagon: Mobilizes and Spares Fuel Early Fasting State Prolonged Starvation Well-fed 70 kg human -> fuel reserves about 161,000 kcal -> energy needed for a 24 h period -> 1600 kcal - 6000 kcal -> sufficient reserves for starvation up to 1 – 3 months -> however glucose reserves are exhausted < 1 day Even under starvation -> blood-glucose level must be above 40 mg/100 ml 13 Prolonged Starvation o First priority Sufficient glucose for brain, Nervous Tissue, RBC o Second priority Preserve Protein - Lipolysis and Gluconeogenesis o Three days starvation Brain and heart start to use ketones as fuel o Several weeks of starvation Ketone bodies major fuel of brain o TAG stores used Increased Protein degraded Decreased heart, liver, kidney function Prolonged Starvation 15 Endocrine Pancreas and Control of Blood Glucose Concentration Pancreas  Exocrine Pancreas ⚫ 99% of Gland  Acini ⚫ Digestion  Endocrine Pancreas ⚫ 1% of Gland  Islets of Langerhans ⚫ Control of Blood Glucose Endocrine Pancreas  Islets of Langerhans ⚫ ⚫  - Cells - cells Somatostatin PP cells Pancreatic polypeptides Insulin - Cells Maintenance of Optimal Blood Glucose Concentration Glucagon Normal Fasting Level ≈ 90-100mg/100mls ≈ 5mM Insulin the Only Hypoglycemic Hormone? Preproinsulin (11500) Highly conserved AA sequence Interspecies activity Bovine, Porcine Proinsulin (9000) Insulin (5800) Control of Insulin Secretion Major Stimulus - Increased Blood Glucose Glucose →Insulin → Glucose →Insulin Islets are richly vascularized 1-2% of of pancreas, 10 to 15% of pancreatic blood flow Monitor Blood Constituents, Release Products Control of Insulin Secretion Also Influenced By  Plasma AAs  FFA  Glucagon  GH, GIT hormones → → → →  Insulin Insulin Insulin Insulin ANS innervates Islets so modulates insulin & glucagon secretion Insulin Secretion By Beta Cells Glucose Transporters  In recent years developments in genetics have shed new light on the types and physiology of various glucose transporters  There are two main types  Sodium–glucose linked transporters (SGLTs) Facilitated diffusion glucose transporters (GLUTs)  Sodium Glucose Linked Transporters Glucose Transporters Glucose Transporters