Insulin (Hormone Action 2) Flashcards
Insulin Classification
Peptide hormone (51 a.a.), hydrophilic, binds to cell surface, tyrosine kinase receptor (signal transduction via phosphorylation)
Insulin Natural Outline
Produced in pancreas. Allows glucose entry from blood to tissue (eg muscle and adipose). Nourishes cell and removes glucose from blood
Type 1 Diabetes
Inability to synthesize insulin due to loss of beta cells. Hyperglycemia
Type 2 Diabetes
Impairment/ Inability to respond to insulin and dysregulation of beta cells. Poor glycemic control
5 endocrine cells of isles of langerhans
Acinar, Pancreatic acini, Alpha, Beta and Delta
Alpha Cell Outline
Produces glucagon. Stimulates beta cells release of insulin. Inhibited by somatostatin and insulin (at certain level)
Beta Cell Outline
Produces insulin. Acts on Delta cells to regulate stomatison release. Stimulated by glucagon, inhibited by somatostatin
Delta Cell Outline
Produces somatosatin. Acts as regulatory feedback mechanism. Inhibits glucagon and insulin
Insulin Synthesis Stages
Pre-proinsulin, proinsulin, maturation and insulin finalisation
Pre-proinsulin Def.
IN endoplasmic recticulum. Produced as a single polypeptide
Proinsulin
Single peptide is removed from pre-postinsulin peptide chain
Maturation
Golgi Apparatus, proinsulin folds to form disulfide bonds and packaged into secretory granules
Insulin Finalisation
In granules proinsulin is divided into insulin and C-peptide
Insulin Secretion
High blood glucose conc. triggers granules fuse with membrane and excrete (exocytosis) insulin and c-peptides into blood (in equal amopunts)
GLUT2 Definition
Transfer protein for glucose through membrane
How Glucose crosses membrane
Increase in glycolysis in respiration, increases ATP. ATP sensitive K+ channels close and voltage gated Ca^2+ open (depolarisation). Causes vesticles fuse to membrane
Insulin Receptor Compoaition
2 Subuints (alpha and beta) linked by disulfide bonds. Alpha is extracellular (insulin binds to it) and beta penetrates membrane (phosphorylates activating catalytic site)
Insulin Receptor Type
Tyrosine Kinase
Signal Propagation By Phosphorylation
Receptor Substrate-1 is stimulated by phosphorylated. This propagates signals
Rapid Insulin Effects
Glucose uptake, amino acid and K+ iontransport
Intermediate Insulin Effect
Protein synthesis stimulation, glycosis and glycogenesis, inhibition of glycogenlysis + gluconeogenesis and inhibition of proteolysis
Delayed Insulin Effects
Transcription of Lipogenic Genes
Factors Regulating Insulin Release
Blood glucose conc., amino and fatty acids, glucagon (stimulant), somatostatin (inhibits), automatic nervous system and incretins (GIP and GLP)
Characteristic of Type 2 Diabetes
High blood glucose >7 mmol/L while fasting (and also high insulin)
Hyperglycemia Def.
Elevated blood glucose due to poor regulation
Polyuria
Glucose in urine, resulting in increased urination
Polydispa
Excessive thirst as result of polyuria
2 Types of Diabetes Tests
HbA1c and Glucose Tolerance Tests
HbA1c Def.
Measures glycosylated haemoglobin. Average blood glucose over 8-12 weeks. Normal (<5.7%), Prediabetic (5.7-6.4%) and diabetic (>6.5%)
Glucose Tolerance Tests
75g of blood taken and glucose meaured over 2 hrs. 7.8-11 mmol/L (impaired glucose tolerance) and .11.1 mmol/L (diabetes)
