Part 3

Question 1

Content of parenteral/intravenous nutrition regimens

Answer 1

1 L bag of water soluble nutrients (glucose, crystalline AA, vitamins and minerals)
- Separate lipid infusion

Question 2

Issues with designing parenteral AA composition

Answer 2

Bypass of splanchnic control - difficult to determine AA requirements without the liver

1) Tyr insolubility

2) Glutamine and cysteine are unstable in solution (soluble but oxidizes to cysteine and precipitate out)

3) Transient hyperphenylalaninemia and hypertyrosinemia - especially in babies can cause toxicity
- formulas can be very low in these AA
- Solution: can give a more soluble Phe precursor to avoid hypertyrosinemia (since Phe –> Tyr via hydroxylation)

Question 3

Baby formula nitrogen retention results

Answer 3

Vamin - egg protein based, ↑ Phe content - 80% N retention

Vaminolact - no added Phe or Tyr - 70% N retention

Vaminolact + Phe - 90% N retention (best)

Vaminolact + N-acetyltyrosine - 75% N retention

Vaminolact + Glysyltyrosine - 85% N retention (not approved in north America but very good, expensive)

Question 4

Growth curve in infants

Result of baby pig experiment on protein deficient diet

Answer 4

Weight in lbs by months of age
Above 97th percentile baby is on track to become obese

Protein deficient baby pigs don’t gain weight as fast

Question 5

DRI based on old N balance studies

Answer 5

EAR: .66 g/kg/day
RDA: .8 g/kg/day

Roughly 56g per day

Question 6

Collection of studies which demonstrated new breakpoint in N balance studies

Answer 6

Because of miscellaneous losses, “0” N balance line is actually at 120mg of N, old value was 100mg of N

Actual data said:
New adjusted breakpoint is at 145 mg/kg/day of N or .91 g/kg/day of protein (EAR)
RDA: .99g/kg/day

Question 7

When all AA are at requirement VS.

When there is a limiting AA

Breakpoint in C(13)O2 breath collection study

Answer 7

When all AA are at requirement there are no excess AA

When there is a limiting AA the rest are in excess

Use IAAO Phe indicator to track oxidation levels as other AA intake is increasedBreakpoint = .93g/kg/day (EAR)
Upper 95% = 1.24g/kg/day (RDA)

Question 8

Old DRI, re-analyzed DRI
IAAO DRI recommendations

Answer 8

Old: EAR = .66 g/kg/day, RDA = .8 g/kg/day
Adjusted: EAR = .91 g/kg/day, RDA = 1.0 g/kg/day
IAAO: EAR = .93 g/kg/day, RDA = 1.2 g/kg/day

Question 9

Protein recommendation in endurance trained young men

Between male and females post-exercise

Answer 9

EAR = 2.1g/kg/day, RDA = 2.6 g/kg/day (IAAO and N balance studies)
Additional study showed 1.5g/1.7g breakpoint instead

Similar protein recommendations for males and females post-exercise recovery

Question 10

Lower protein intakes (.6g or .75g/kg/day) compared to 1g/kg/day

Decreasein:

Increase in:

Takeaway from data

Answer 10

Decrease in:
Protein turnover
Glutathione synthesis: ↓ antioxidant capacity and increased vulnerability to oxidative stress
Albumin synthesis: negative acute phase protein

Increase in: fibrinogen synthesis (positive acute phase protein)

Moderate protein intake results in minor stress response

Question 11

Overall athlete protein recommendations

Answer 11

Athletes require not much more than everyone else based on new RDA recommendations (because athletes consume more calories in general)

Timing is more important than increased quantity

Consume 3-4 isonitrogenous meals including breakfast and post-exercise

ACSM recommends 1.2 to 2g of protein
Stew Phillips at McMasters 1.3-1.8g/kg/day

Experienced athletes require less protein than athletes in high frequency/intensity training (building phases)

Question 12

Protein recommendation to prevent lean mass losses during periods of energy restriction for fat loss

Answer 12

1.8-2.0g/kg/day

Question 13

Protein requirement during critical illness

Answer 13

Critically ill infants: 4g/kg/day
Critically ill adults: 2.5 g/kg/day

Difficult to study critically ill patients for obvious reasons and especially long term

IV feeding supplementation lacks limiting AA and doesn’t help much

Question 14

Why use indirect calorimetry in hospitals ?

Answer 14

Accurate BMR measurement

Thermal effect of feeding

Gauge of hypermetabolism

Gauge substrate utilization (respiratory quotient and RER)

Question 15

Role of the different organs in metabolism of AA

Answer 15

1) Pepsin in stomach - activated by low pH

2) Pancreatic proteases in SI - luminal digestion of peptide bonds

3) Peptidases on brush border of SI epithelium

4) Active transporters for absorption

Question 16

Percent of body weight and BMR of the liver and muscle

Percent body’s protein synthesis liver vs muscle

Turnover

Overall takeaway is

Answer 16

Body weight and BMR:
Liver: 3% BW, 21% BMR
Muscle: 40% BW, 21% BMR

Protein synthesis: liver and muscle each do 30% of protein synthesis

Turnover:
50% proteins synthesized in liver newly every day
3% of proteins newly synthesized every day

Takeaway: the liver is highly metabolically active and flexible compared to muscle which takes up much more mass of the body

Question 17

Metabolic turnover of proteins in liver and muscle

Answer 17

Half life of muscle structural proteins maybe 1 month

There are proteins in the urea cycle with half life of 11 minutes

Metabolic flexibility allows for quick response to external conditions
- Proteins can be produced quickly and modified by post-translational modification

Question 18

Anabolic and catabolic protein roles in the liver

Answer 18

Anabolic:
1) constitutive protein synthesis
2) plasma protein synthesis
- albumin (most abundant), fibrinogen (blood clotting)
3) gluconeogenesis
4) lipogenesis

Catabolic: AA catabolism, urea cycle