Glucose homeostasis and the pancreas- go over the leture as not all info is in here Flashcards
Glucose balance
Insulin decreases plasma
glucose
amino acids
FFAs
“anabolic”
Glucagon increases plasma
glucose
ketones
“catabolic”
Hormone secretion from the Islets
beta-cells produce and release insulin
stimulates glucose utilization and uptake
alpha-cells produce and release glucagon
increases breakdown of glycogen and glucose release
sigma-cells produce and release somatostatin
suppresses GI motility, and release of insulin and glucagon
Structure of insulin
Biologically active
C-peptide is inactive
Degraded by insulinase in liver and kidneys
t1/2 ~ 6 min
Highly conserved structure across many species
Insulin is secreted in response to changes in
glucose/ATP
Insulin secretion occurs via calcium- dependent exocytosis
The insulin receptor
Insulin binding:
dimerization
“receptor tyrosine kinase” autophosphorylation
effects on intracellular kinases/phosphatases
effects on key enzymes
receptor tyrosine kinase
Receptor tyrosine kinase is a type of cell surface receptor protein that, upon activation by binding to specific ligands, initiates intracellular signaling pathways by phosphorylating tyrosine residues, regulating various cellular processes such as cell growth, differentiation, and survival.
Actions of insulin
Carbohydrate metabolism
Facilitates glucose entry into muscle, adipose (GLUT)
Stimulates the liver to store glucose as glycogen
Decreases concentration of glucose in the blood
Lipid metabolism
Promotes synthesis of fatty acids in the liver (when glycogen saturated) leading to increase in lipoproteins in circulation to release FAs (triglyceride synthesis in adipocytes)
Inhibits breakdown of fat in adipose tissue
Promotes glycerol synthesis from glucose and increase triglyceride synthesis
Insulin stimulates muscle glucose
uptake
Glucagon
-cells of islets synthesize and release glucagon
A peptide hormone (29 amino acids)
Released when blood glucose falls
the “counter-regulatory” hormone to insulin
stimulates glycogenolysis
promotes gluconeogenesis
increases breakdown of fats
Hypoglycaemia
Blood glucose < 3 mM (normal 4-6 mmol/L)
Uptake of glucose by glucose-dependent tissue not adequate to maintain tissue function
CNS very sensitive
impaired vision
slurred speech
staggered walk
mood change
confusion
coma
death
Overactivity of the ANS-
palpitations
sweats
shakiness
hunger
gestational diabetes
associated with pregnancy- transient
serious risk to mother and child
increased risk of developing type 2 diabetes
type 2 diabetes
risk factors: body weight, inactivity, family history age
can go undiagnosed for years
can be changed by diet and lifestyle changes and medication
type 1 diabetes
risk factors: family history, genetics, infection
it appears suddenly
its incurable, insulin dependent
