L32 - fuel homeostasis Flashcards
why is fuel homeostasis needed?
tissues constantly require nutrients but food consumption isnt constant
where is glycogen stored
liver mainly
muscles in small amounts
define absorptive state
food in gut
when nutrients are entering blood from GI tract
define post-absorptive state
empty GI tract
energy supplied by body stores
eg sleeping
(in absorptive state) how is absorbed glucose stored short term by the liver
converted to glycogen for storage
(in absorptive state) how is absorbed glucose stored long term by the liver when glycogen stores full
converted to glycerol and FAs and transported to adipose to form TGs (when glycogen stores full)
(in absorptive state) what happens to glucose in muscles
used for energy
some stored as glycogen
(in absorptive state) what happens to absorbed AAs in liver
converted to keto acids which either:
enter TCA cycle
get converted into FAs then TGs
(in absorptive state) what happens to absorbed AAs in muscle
used to replace proteins lost by catabolism
(in absorptive state) what happens to absorbed fats in adipose tissue
converted to TGs (with glycerol from glucose) and stored in adipose tissue
(in absorptive state) how are absorbed fats utilised by other organs
oxidised to provide energy
in absorptive state what happens to excess
sugars
fat
AAs
sugars - stored as glycogen / converted to
FA&glycerol and stored as TGs in adipose
tissue
Fat - oxidised for energy / stored in adipose as TGs
AAs - used for protein synthesis/ converted to
ketoacids and oxidised or converted to FA and
stored as TGs in adipose
how is plasma [glucose] maintained in post-absorptive state
- gylcogenolysis
- gluconeogenesis (converting protein/fat to glucose)
- glucose sparing ( using FA / KA as fuel) to spare glucose for CNS
short term glucose store
glycogen (liver and muscles)
long term glucose store
breakdown of TGs in adipose tissue
(postabsorptive state) how is glucose generated from protein
skeletal muscle protein catabolised to AAs
AAs converted to glucose in liver
(post-absorptive state) how is glucose generated from adipose tissue)
TG converted to Glycerol and FAs
liver then converts glycerol to glucose
how are states controlled
SNS
endocrine - pancreatic H’s and thyroid H’s
what cells secrete insulin
pancreatic B cells
what cells secrete glucagon
pancreatic a cells
is insulin anabolic or catabolic?
anabolic
is glucagon anabolic or catabolic
catabolic
how does insulin increase glucose uptake in muscles and adipose
- increases glucose uptake in muscles and adipose by moving transporters to membrane
- increases glucokinase activity (involved in glycolysis1 so more glucose uptake to produce energy)
- promotes synthesis of FA and glycerol from glucose which can then be stored as TG in adipose
how does insulin increase glycogen production in liver and muscle
activates glygogen synthase
how does insulin increase AA uptake in muscle
by increasing transporter activity and protein synthesis
list ways insulin stimulates anabolism (5 ways)
- increases glucose uptake in muscles and adipose by moving transporters to membrane
- increases glucokinase activity (involved in glycolysis 1 so more glucose uptake)
- activates glycogen synthase increasing glycogen production in liver and muscle
- increases AA uptake in muscle by increasing transporter activity and protein synthesis
- promotes synthesis of FA and glycerol which can then be stored as TG in adipose
how does insulin reduce glycogenolysis in muscle and liver
inhibits glycogen phosphorylase
how does insulin inhibit adipocyte lipolysis
by inhibiting lipoprotein lipase
in what ways does insulin inhibit catabolic activity
- inhibits glycogen phosphorylase - reducing glycogenolysis in muscle and liver
- inhibits gluconeogenesis in liver
- inhibits keto-acid production in liver
- inhibits adipocyte lipolysis by inhibiting lipoprotein lipase
what are the actions of glucagon
targets liver to generate glucose by
- glycogenolysis
- gluconeogenesis
what influence do the thyroid hormones have on fuel homeostasis (3 things)
- they set the basal metabolic rate
- increase mitochondrial metabolism
- regulate expression of many enzymes involved in metabolic processes)
what effect does NA and adrenaline have on insulin and glucagon
inhibit insulin
stimulate glucagon
(stimulate breakdown of stores)
what organs involved in fuel homeostasis are affected by NA
liver and adipose tissue as they are under autonomic control, skeletal muscle isnt so only affected by Adrenaline
how does an insulin deficiency affect catabolism
- increased catabolism (glycogenolysis/gluconeogenesis/lipolysis/protein breakdown)
- cant stop breaking down stores leads to weight loss
in an insulin deficiency, what energy source does the body try to replace glucose with and what does this lead to
ketoacids
diabetic ketoacidosis
how does insulin deficiency affect anabolism
- anabolism decrease
- leads to hyperglycaemia ( high plasma [glucose] that cant be utilised as no insulin)
- glucose lost in urine
- osmotic diuresis (water retention in urine due to high [glucose])
- water & ssalt loss & polydipsia (thirst)
