3 – Metabolism and Energetics Flashcards
Why is glucose important? How is it regulated?
- Must be tightly regulated
o Important source of energy
o Brain cannot synthesize glucose=are dependent on blood glucose - Regulated by insulin and glucagon
Insulin is anabolic what does it do?
- Increases glucose and AA uptake by cells
- Stimulates synthesis of
o Glycogen in liver and muscles
o Protein in muscle tissue
o TAGs in adipose tissue
After a meal
- Excess CHO broken down and metabolized
o Used for energy directly
o Or excess stored as glycogen
o If even more excess=stored as lipids - *sharper spike in glucose (exogenous source)
Short fast (few hours)
- Glucose from meal is digested, absorbed and disposed of
- Body may need to generate glucose to maintain glucose levels
o Deplete glycogen stores from liver (and other sources)
o Gluconeogenesis - *all tissues in body consuming it, but liver/muscle
Energy sources during LONG fast (16+ hours)
- Gluconeogenesis: burning FAs
- *brain is consuming glucose
Starvation ‘energy’ sources
- No glucose source
- *Ketone bodies
Acetyl Co-A usage
- Make ATP via Kreb’s cycle and ETC
- If longer fast=beta-oxidation and ketone bodies produced
“2 types of AA”
- Glucogenic
- Ketogenic: Lysine and Leucine
a. Can only go to pyruvate - BOTH
Glycemic index: does it work for all species?
- *measures post prandial response to blood glucose with a meal, but if it is not just from the meal=does NOT work
Measuring glycemic index: graph (straight glucose vs. pea flower)
- Y-axis: Serum glucose concentration
- X-axis: time
- *if straight glucose source=rise and fall
o Greater peak and sooner on
o Could be gone within 1 hr - *if pea flower (more starchy): takes longer to digestion, so blood glucose rises later on
o Peak later on and NOT as high
o More sustained blood glucose (can lasts hours)
o *will feel more full
o Smaller AUC
What is your equation for glycemic index?
- (SAMPLE AUC divided by standard AUC) *100
- *if lower than 100=slower to digest
Steps following consumption of a high glycemic load meal: who would you want to feed this to?
- High serum glucose and insulin
- Rapid uptake of serum glucose and AA
- *high fat and protein deposition=GOOD PRODUCTION QUALITY
Steps following a low glycemic load meal
- Low serum glucose and insulin
- Slow uptake of serum glucose and AA
- *low fat and protein deposition
What have carnivores evolved to consume? What is their response?
- High protein, low CHO
o High rates of gluconeogenesis, even after a meal
o Some AA (particularly arginine), can stimulate insulin release
Important as you wouldn’t want to have to rely on CHO for insulin release if they are not eating much CHO - *why glycemic index does not work well for them
- *domestic dogs do you have more CHO digesting enzymes then they used to (domestic cats, have NOT evolved)
What can carnivores appear as if fed a high CHO diet?
- ‘glucose intolerant’
- Postprandial hyperglycemia due to continued gluconeogenesis AND glucose surge from meal
- *tend to have very prolonged postprandial hyperglycemia (ex. cats)
- We feed them it because protein is expensive
Diet formulations fed to pigs: digestible energy, starch and glycemic index
- *glycemic index works well
- Digestible energy and starch are the same between corn, high glycemic index barley and low glycemic index barley
- Glycemic index is highest for corn and lowest for low glycemic index barley
Diet formulations fed to pigs: retained N and N utilization %
- *low glycemic starch sources REDUCE protein deposition in pigs
- *want high glycemic index to get anabolic effect
What are some high GI foods?
- Glucose syrup
- Potato
- Corn
- Rice
- Wheat
Why is the GI of milk chocolate only 49?
- Would think it would be higher
- Has FAT in it
o Slows gastric emptying=only little bits of digesta get to intestine
o Slows SPIKE in glucose - *GI gets harder with a more complex meal
