Fuel Homeostasis Flashcards
What organs are involved in fuel homeostasis?
Liver: major glycogen store and fuel convertor
Adipose: TAG store
Muscle: most of body mass, major consumer of fuel and some glycogen storage
CNS: needs constant supply of glucose
In the absorptive state what happens to glucose?
liver - glycogen for storage - short term store
alpha-glycerol phosphate and fatty acids transported to adipose to form TAG - long term store
muscle stores some glucose as glycogen
uses glucose for energy
adipose - converted TAG in adipocytes
In the absorptive state what happens to amino acids?
liver - converted to keto acids, enter TCA cycle or converted to fatty acids for storage
muscle - used to replace proteins lost by catabolism
In the absorptive state what happens to fats?
adipose - FA converted to TAG by combing alpha-GP from glucose
other organs - some fat oxidised to provide energy
What happens in the post-absorptive state?
no glucose absorbed from GI tract
plasma glucose must be maintained for CNS by gluconeogenesis (generating glucose from stored fuels) or glucose sparing (fat utilisation)
How do you generate glucose in the post-absorptive state?
glycogenolysis - liver/muscle: hepatic glycogenolysis is first response to plasma glucose levels but short lived
protein - skeletal muscle catabolised, amino acids converted to glucose in liver
lipolysis - adipose tissue, TAG generates FA and glycerol, liver converts glycerol to glucose
How do organs spare glucose for the CNS?
by using FA as main use of energy
liver FAs are mainly converted to ketones and released into blood for use by many tissues
How does endocrine system control body in absorptive and post-absorptive states?
Insulin and glucagon are most important hormones and are made in pancreatic islets of langerhans
insulin stimulated by ↑blood glucose and glucagon inhibited
What specific anabolic effects does insulin have on the body?
↑glucose uptake by increasing transporters
↑glucokinase activity
activates glycogen synthetase to promote glycogen production
↑amino acid uptake and protein synthesis
promotes syntheis of TAG parts
induces expression of lipoprotein lipase to generate triglycerides
What specific catabolic effects does insulin have on the body?
↓glycogen phosphorylase to reduce glycogenolysis
↓gluconeogenesis
↓ketone production
↓adipocyte lipolysis be reducing lipase activity
What part does cortisol play?
maintains liver and adipose enzymes required for gluconeogenesis and lipolysis
cortisol deficiency prevents ‘glucagon’ responses (addison’s disease)
↑conc. of cortisol cause post absorptive changes and oppose effects of insulin (cushing’s syndrome)
What part does growth hormone play?
makes adipose ↑sensitive to lipolytic stimuli
↑gluconeogenesis in liver
↑V increase due to in vivo effect (laboratory)
↓effects of insulin to promote glucose uptake in peripheral tissues
opposes effects of insulin
What part do thyroid hormones play?
set ‘basal metabolic rate’ in most tissues
↑mitochondrial metabolism
regulate expression of many enzymes involved in metabolic processes
What part does the SNS play?
adrenaline and sympa. innervation of islets inhibit insulin release and ↑glucagon release
both affect liver directly to ↑glycogenolysis and gluconeogenesis so ↑plasma glucose
↑lipolysis in adipose
adrenaline ↑glycogenolysis in skeletal muscle
