Regulation of Blood Glucose Flashcards
blood glucose must be closely maintained at what concentration?
60-100 mg/dL
4.5-5.5 mM
liver
- insulin dependent or independent?
- has capacities for what metabolic capacities?
- relies predominantly on what fuel sources?
- insulin dependent
- capable of
- gluconeogenesis - unique to liver*. using substrates from elsewhere
- glycogen storage - for other tissues: using glucose-6-phosphotase
- TAG synthesis
- ketone body synthesis
- relies on: mostly FAs
- glucose (in first 4 hrs post meal) + FA oxidation
muscle/heart
- insulin dependent or independent?
- capacities?
- relies on what fuel?
- insulin dependent
- capacities:
- glycogen synthesis - for self (does not have glycogen-6 phosphorylase)
- produces gluconeogenic substrates: alanine, lactate - does not itself do gluconeogenesis
- reslies on: glucose, FAs
- active muscle: aerobic + anaerobic glycolysis
- resting muscle: fatty acids*
adipose tissue
- insulin dependent or independent?
- has what capacities?
- insulin dependent
- capacities:
- produces:
- FAs - TAG synthesis in liver
- glycerol-3-P - TAG synthesis in liver
- as a gluconeogenic substrate (through DHAP)
- stores: FAs
- produces:
brain
- insulin dependent or independent?
- capacities?
- relies on what fuels?
- insulin independent
- relies on: glucose, ketone bodies
-
glucose: the brain relies on glucose in all states
- HEAVILY in most states
- ketone bodies: are utilized in in severe fasting state, though never exclusively
-
glucose: the brain relies on glucose in all states
erythrocytes
- insulin dependent or independent?
- has what capacities?
- relies on what fuels?
- insulin independent
- capacities:
- produces gluconeogenic substrate - lactate
- uses 2,3- BPG to
- modulate HbO2 affinity
- reflect blood glucose levels
- relies on: anaerobic glycolysis excusively - has no mitochondria
phase 1: 0-4 hrs. only time liver uses glucose as fuel
phase 2: 4-16 hrs. exogenous source depleted, glycogen > gluconeogenesis
phase 3: 16-32 hrs: gluconeogenesis > glycogen
phase 4: > 32 hrs: brain starts using ketone bodies
what two tissues can take up glucose inependent of insulin?
- brain
- RBCs
glucocorticoids
- secreted by what tissue?
- have what effects on blood glucose?
- by adrenal cortex (zone fasculata) in when blood glucose low
- effects:
- inreases gluconeogenesis
- inhibits glucose uptake in tissues
growth hormone
- secreted by what tissue?
- has what effects on blood glucose?
- by somatrophes (ant pit) during low BP
- decreases glucose uptake by muscle
mature granules in beta cells contain what?
what stimulates their degranulation & how?
- contain equal parts INSULIN + C-PEPTIDE
- release contents in response:
- hyperglycemia:
- via GLUT-2 receptors that detect
- glucose
- glucokinase
- via GLUT-2 receptors that detect
- ACh / arginine / FAs
- hyperglycemia:
how is insulin synthesized?
- as preproinsulin on RER
- preprosinulin –> proinsulin
- proinsulin –> insulin by two protelytic activities (removing each side of the C-peptide)
describe the structure of the insulin receptor
- two paired subunits
- alpha - extracellular
- beta - transmembrane
- associated with Tyr residues w/ tyrosine kinase activity
discuss the phosphorylation of Tyr residues on the insulin receptor.
how do different stimuli effect Tyr phosphorylation, and how does this modulate its activity?
- insulin binding: causes autophosphorylation of Tyr residues –> activing their tyorine kinase activity and cascade
- cAMP activity: PKA phosphoryolates Ser/Thr tresidues –> which inhibits tyrosine kinase acitivity
summarize the effects of insulin on glucose metabolism
overall effect: decreases blood glucose
- stimulates:
- glycolysis
- ex:
- + glucokinase in the liver
- + F, 26-BP
- ex:
- glycogenesis - in liver, muscle
- glucose transport - into muscle, adipose tissue by promoting addition of GLUT-4 into their membranes
- glycolysis
- inhibits:
- gluconeogenesis in the liver
other than glucose, insulin also stimulates transport of?
aas / nucleosides / Ca++ / PO4 / K+
summarize the effects of inuslin on lipid metabolism
- stimulates:
- lipogenesis - in liver, adipose
-
fatty acid uptake from serum (blood)
- for lipogenesis
- inhibits:
- lipolyis
insulin effects on protein / nucleic acid synthesis
- promotes protein synthesis
- promotes nucleic acid (DNA, RNA) synthesis
glucagon
- synthesized by what cells & how?
- in response to?
- acts on what targets?
- and has what effects?
- how?
- by a-cells in pancreas as a prepropeptide
- in respone hypoglycemia
- effects:
- stimulates
- glycogenolysis - liver, adipose
- gluconeogenesis - liver
- inhibits
- glycolysis
- stimulates
- via Gs (GCRP) -adenylate cyclas/cAMP
(cannot act on muscle)
epinephrine
- synthesized by what cells?
- in response to?
- acts on what tissues?
- has what effects?
- how?
- by adrenal medulla cells
- in response to hypogycemia & fear / excitement
- in liver
- stimulates
- gluconeogenesis
- glycogenolysis
- inhibits
- glycolysis - 1. can’t go on at the same time as gluconeogenesis & 2. want to mobilize glucose to other tissues
- stimulates
- in muscle
- stimulates
- glycogenolysis
- glycolysis - muscle uses glucose from glycogen breakdown for itself
- inhibits
- glucose uptake into muscle - muscle will use glucose from glycogen/the liver instead, to get blood glucose back up
- stimulates
- in liver
- via cAMP (like glucagon)
summarize the key differences between glucose metabolism under regulation in insulin vs glucagon predominant state
insulin
- syntheis of protein, fat, glycogen (liver, muscle)
- fat stored in adipose tissue
glucagon
- breakdown of glyogen (liver, muscle)
- mobilization of alanine, lactate for gluconeogenesis
what can an excesss of insulin administration lead to?
hypoglycemia
what is glucosuria and at what blood glucose level does it present?
- when glucose is present in the urine
- seen when r_enal threshold is exceded:_ > 150 mg/ 100 mL
