W6 - Biochemistry Basis of Dietary Supplements Flashcards
What do plasma NO biomarkers do?
What type of individuals have higher NO?
- Lowered with ageing and several diseases
– Increased in individuals with high aerobic fitness
What does NO signalling result in?
- vasodilation
- calcium handling
- neuro-transmission
- glucose uptake
- mitochondrial respiration
- muscle force production
what does nitric oxide do?
- Makes mitochondria more efficient, less mitochondria to create the same energy production
- NO is a free radicle, they have a very short half-life - gone within a few seconds
- When NO reacts with RBC’s becomes NO3
- Plasma NO biomarkers are lowered with ageing and several diseases
- Increased in individuals with high aerobic fitness
Describe oral L-arginine supplementation
- Low doses (< 20 g) of L-arginine are well tolerated with no side effects(alkaline, 20g is more than enough, does not cause any GI problems)
- Plasma [L-arginine] peaks 60-120 min post oral ingestion of 6 g L-arginine
- Usually give 60-90 mins pre-exercise test
What affect does L-arginine have on exercise performance?
- 6 g of L-arginine or placebo for 3 days
- No effect of L-arginine on peak or mean power output during 13 repetitions of 20 s all-out cycling, 15 s recovery
- No effect(significant difference) of L-arginine on time-to-exhaustion during severe-intensity cycling exercise
- No effect of L-arginine on end-sprint performance during severe-intensity cycling exercise
- Criticised that exercise-to-exhaustion does not represent real life scenario
What are the positive effects of L-arginine?
- Most studies that have found positive effects of L-arginine supplementation have
– Assessed power/strength based exercise
– Administered L-arginine with L-glycine - These effects may be NO independent and linked to enhanced creatine synthesis
- Increases creatine production
- Supplement blends causes nutrient interactions which complicate how it works to produce creatine
Why is L-arginine ingestion ineffective?
- Approximately 40% of ingested oral ARG is metabolised by intestinal bacteria and arginases (enzymes that break down arginine for excretion)
- In the blood stream approximately 10-15% of the circulating ARG is extracted by the liver and catabolised by intra-hepatocyte arginases
- ARG(a charged amino acid, so needs a transporter) also competes with ADMA for transport into the muscle
Why is L-citrulline more effective in producing NO?
L-citrulline (product of nitric oxide) - tasteless
1. CIT undergoes degradation in intestines
2. Limited uptake of CIT by liver
3. Majority of an oral CIT bolus enters the systemic circulation - better bioavailability
4. CIT is converted into ARG in the kidneys, increases amount of ARG into the site of interest than ingested ARG (less degradation of citrulline)
5. Increase plasma and muscle [ARG] to a greater extent than oral ARG ingestion
6. CIT inhibits arginase = limiting ARG catabolism
7. Increased muscle ARG delivery after CIT ingested, can increase ARG uptake
8. CIT does not compete for cellular uptake in muscle
Describe the oral L-citrulline supplementation
- Low doses (< 20 g) of L-citrulline are well tolerated with no side effects
- Plasma [L-arginine] peaks ~ 90 min post oral ingestion of 6 g L-citrulline
Describe L-citrulline as an ergogenic aid
- Some studies suggest that L-citrulline is more effective than L-arginine supplementation at increasing circulating plasma [L-arginine]
- L-citrulline improves end-sprint performance during severe-intensity cycling exercise
- L-citrulline might increase performance through enhanced creatine synthesis
What role does L-Citrulline play in the urea cycle?
- L-citrulline is an intermediate in the urea cycle
- L-citrulline has been shown to lower ammonia accumulation during exercise (detoxifying ammonia better)
- Important in repeated sprint activities
Name some enzymes that reduce NO2 to NO?
Deoxyhemoglobin
Deoxymyoglobin
Nitric Oxide Synthase
Xanthine Oxidase
Aldehyde Oxidase
Carbonic Anhydrase
Mitochondrial Respiratory Complexes
NO2
What is the most common food source of Nitrate?
Describe how it is broken down by the body
Beetroot is common food source for nitrate
And leafy green - a balanced diet give you the amount of nitrate you need
- Nitrate is not broken down in the gut
- Oral microbiome(bacteria on the tongue) reduce nitrate into nitrite - effectively breakdowns nitrate
- Symbiotic relationship - bacteria lives in our mouth to breakdown nitrate
Some of nitrite is reduced into the gut into nitric oxide - this then enters the blood
How do we improve exercise economy with Nitrate?
- To reduce the O2 cost of exercise at the same WR, dietary nitrate supplementation may have:
1) Increased the mitochondrial P/O ratio (i.e., reduced the O2 cost of ATP resynthesis);
2) Inhibited mitochondrial ATP synthesis- resulting in a compensatory increase in anaerobic energy liberation;
3) Reduced the ATP cost of force production- Costing less ATP for exercise means we do not need to resynthesise as much ATP
What does nitrate supplementation appear to be ergogenic for?
- Endurance exercise performance
– High-intensity intermittent exercise
– All-out sprint exercise
