Lecture 34: Absorptive and Postabsorptive Nutrient Utilization-2 Flashcards
What happens to glucose and glucagon during the postabsorptive phase
Blood glucose decreases, stimulates glucagon and inhibits insulin secretion
Describe the liver transition from absorptive to postabsorptive phase
Liver switches from glucose utilization to glucose production by glycogen and gluconeogenesis
What tissues are using glucose during postabsorptive phase
All tissues, including brain. Muscle and adipose tissue at a diminished rate
How does the liver mobilize its stores during postabsorptive phase
Decrease glucose stimulates glucagon secretion
Glucagon stimulated glycogenolysis and gluconeogenesis
How long does glycogen depot last during rest/moderate ecercise
8-12 hrs
How long does glycogen depot last during high demand/severe exercise
30 minutes
How does glucagon act on adipose tissues
Stimulates lipolysis
__ and ___ stimulate lipolysis and FA release through B-adrenoreceptors
Epi and NE
___ peptide from the heart stimulate lipolysis during exercise
Natriuretic
__ and ___ reinforce increased lipolysis during and after prolonged exercise
Growth hormone and cortisol
How are FA mobilized and released from adipose tissue
- Epi or Glucagon bind B-adrenergic receptor
- Activate hormone sensitive lipase
- NEFA are transported out as free FA, bound to albumin or VLDL
- Taken up by liver and skeletal muscle
NEFA’s are used for synthesis of ___ and ___
Ketones and VLDL
Why are there multiple transport mechanisms for NEFA’s
Albumin decreases during long phases of nutrient deficiency. VLDL’s are independent of AA availability
What transporters FA into cells
CD36
Describe the steps in transportation of FA into cells—> kreb cycle
- NEFA’s bind albumin and are transported
- CD36 transporters NEFA’s into cell
- After absorption enter B-oxidation in Krebs cycle
How does the absorption of fatty acids and glucose in the absorptive phase vs postabsorptive (what receptors are used)
Absorptive: GLUT4
Post-absorptive: CD36
How are muscle stores/proteins utilized during postabsorptive phase
- Decrease AA entry into AA pool
- Degrade and use AA pool for energy
During the postabsorptive phase what enzymes does glucagon activate and deactivate
Deactivate: glycogensynthase and phosphofructokinase
Activate: fructose-1,6 biphosphate and glycogenophosphorylase
Without food for 24 hrs or more the body forms ___
Ketone bodies
After 24 hours without food all glycogen stores are exhausted and the body utilized ___ for energy
FA (which get converted to ketones)
Brain can’t use __ too large so for first 48hrs without food the brain uses ___
FA, glucose
> 48hrs without food the liver metabolizes FA to ___ which can be used by the brain
Ketone bodies
How does the fuel oxidation shift in prolonged energy deficiency
Carbs to mainly lipids as oxidative source
During prolonged energy deficiency what happens to lipolysis
Increases to provide body with FA—> TG and ketone bodies