Integration of Metabolism Flashcards
What is the body’s primary energy store?
TAGs in Adipose Tissue
Why are proteins used as fuel during the fed state?
Normal Protein Turnover is happening, as old proteins are degraded their amino acids are recycled
Even when you are staving glycogen still sits in the muscle untouched. How is this glycogen maintained while liver glycogen is broken down?
- Muscle glycogen is only responsive to epinephrine, not glucagon
- High Levels of Glucagon indicating absence of glucose doesn’t affect glycogen breakdown enzymes
- These glycogen stores will be present as long as you don’t have to sprint or release epinephrine for some other reason
How does the brain save muscle from breaking down?
- Gluconeogenesis starts at about 12 hrs no food and ceases for the most part after around 3 days
- from 12-72 hours this process is largely running off of protein breakdown products which come from the muscle
- After 72hrs the brain starts to run on ketone bodies and the only thing left that needs to use gluconeogensis are RBCs.
What is the main fuel source for the brain?
- Glucose
- Ketone Bodies ( after 3d)
What are they only organs in the body that can export molecules that can be processed and used for energy?
-What are the exports?
- Skeletal muscle:
- Lactate (ONLY DURING HARD EXCERCISE)
- Amino Acids (only during fasting) - Adipose tissue - FA and glycerol
- Liver - TAGs, Glucose, Ketones
What tissues prefer to use fatty acids in their resting states?
Skeletal muscle, Cardiac muscle, Adipose tissue, Liver
Note: this does not refer to fed state in which everything prefers glucose
What are the major substrates for gluconeogenesis?
-Where do these come from?
- Lactate - remaking NAD+ (lact. dehydr.)
- Alanine - protein breakdown
- Glycerol - LPL or Hormone Sensitive Lipase
What enzyme is required to enter glycerol to gluconeogenesis?
Glycerol Kinase
Why are fatty acids not used for gluconeogenesis?
- Because there is no net gains of carbons during the TCA cycle (none are available for biosynth)
- AcCoA cannot be turned to FAs
What substrates are required to make fats?
Acetyl CoA, Glucose, Glycerol
What starting material is needed for the PPP?
Glc-6-P
When is all glucose depleted by fed state?
~2hrs at this point you enter the post-prandial state
When does the postabsorptive state begin and end, what processes are supplying the body with energy?
~6-8 hours (ends after 12 hrs)
- Glycogenolysis from the liver keeps the body supplied
When does the Basal state begin and end, what processes are supplying the body with energy?
~12 hrs (ends after 24hrs)
- Gluconeogensis - Brain, RBCs
- Ketone body Synth - skeletal muscle
In what state will Chylomicrons and VLDLs be broken down?
Fed state only
- In any other state chylomicrons and VLDLs have already been been extracted by fat cells
What is the endogenous fat transporting particle?
-VLDLs
When would you expect urea levels to be the highest and why?
- Urea will be the highest in the basal and fasting state when gluconeogenesis is still ramped up
- High urea results from lots of proteins being broken down.
- In times before and after this (fed and starving states) there is relatively little protein breakdown
What is the cori cycle?
- Uses lactate to remake glucose for the RBCs
You find a camper that has been lost for 5 days, you feed him 3 packs of ramen noodles and he dies. Why did he die?
- His body is not used to using glucose, a high fat meal would have been a better choice
Why:
- GLUT2 is hardly expressed at all so liver and pancreas don’t even realize there is glucose in the body
- Most glucose will bypass the kidney and get taken up by muscle since it has GLUT1
- Muscle glycolysis overloads TCA and pyruvate gets converted to lactate which can be converted to more glucose because GLUCONEOGENESIS enzymes are high
- Ultimately the lactate builds up and the guy dies from lactic acidosis.
When is the only time the body is using exogenous glucose?
- Fed state (~0-4 hrs)
What state is defined as glycogenolysis being greater energy contributor than gluconeogenesis?
Post-absorptive state (between fed and basal states)
In what state would you expect lactate levels to be the highest?
During the Fed State
What hormone is responsible for maintaining blood glucose levels during fasting?
Glucagon
