W8 - Anti-oxidant Supplements Flashcards
What are free radicals?
A type of reactive species
Environmental sources of oxidants
UV radiation
Pollution
Smoking
Burnt food
Cellular sources of oxidants
Oxidase enzymes
Mitochondrial respiration
What happens when reactive species exposure exceeds anti-oxidant defences?
Damage to lipids
Damage to body proteins
DNA damage
Triggers inflammation
When reactive species exposure exceeds antioxidant defences
What comes under damage to lipids?
Peroxidation
Damage to cell membranes –> Dysfunctional cells
Red NO bioavailability –> Impaired bv function
When reactive species exposure exceeds antioxidant defences
What comes under damage to body proteins?
Oxidative modification
Altered function –> ageing
What are the anti-oxidant systems available to combat the effects of reactive species
Endogenous antioxidants (enzymatic + non-enzymatic i.e uric acid)
Nutritional (VC,E+ carotene, minerals i.e copper + zinc, polyphenols i.e flavonoids)
What are polyphenols?
A nutritional source of potential antioxidants
What comes under polyphenols
Flavonoids
Lignans
Phenolic Acids
Stilbenes
What is the direct antioxidant property?
Radical scavengers
What is the challenge faced by polyphenols acting as radical scavengers?
Their bioavailability is poor
Develop of the poor bioavailability of polyphenols
i.e if a cherry reaches the intestines
Only ~5-10% of the polyphenols consumed will actually make it into circulation.
Reminder will continue down GI tract to colon due to not being able to be broken down to be absorbed.
Once in colon, broken down + exposed to the microbiome which can help break down more polyphenols to become bioavailable.
Uric acid in plasma
Uric acid is present in high levels within plasma (150-450μM)
Uric acid in plasma and radical scavenging capacity
Confers ~60% of the radical scavenging capacity of the plasma.
Peak plasma phenolic conc
<10μM.
What is it thought polyphenols are converted to?
Into a stable radical i.e pro-oxidants
What are pro-oxidant compounds called?
Semiquinones
Quinones
What do pro-oxidants semiquinones and quinones do?
Trigger increased synthesis of endogenous antioxidants
= Triggering cells to prod more of the enzymatic antioxidant systems
What does evidence suggest about phenolic compounds absorbed from polyphenols?
That they are able to inhibit the prod of ROS
- Meaning they can inhibit enzymes such as NADPH oxidase
When is there an increased generation of ROS + NOS
During exercise
Half-life of reactive species
VERY SHORT
Indirect markers of reactive species
Looking at compounds that are indicative or are markers of oxidative damage.
i.e Protein carbonyls and nitrotyrosine or MDA.
Direct markers of reactive species
e- paramagnetic spin resonance which are like spin traps for specific radicals whereby it fixes them in time, preventing them from changing
What is meant by oxidative stress?
When the generation of reactive species overwhelms the antioxidant defences
ROS + NOS exposure contributes to fatigue development in various ways causing issue to…
Ionic gradients
E-C coupling
Central drive
Substrate depletion
By-product accumulation
Muscle perfusion
—— Their relative contribution will depend on the intensity and duration of the exercise.
What does ROS exposure trigger?
Incr prod of antioxidant enzymes due to particular signalling mechanisms involving the nuclear transcription factor nrf2 which is normally bound to another protein called KEAP1.
Can the nrf2 and KEAP1 complex enter the nucleus?
NO
Why does the nrf2 and KEAP1 complex need to enter the nucleus?
To incr prod of antioxidant enzymes
What happens when the nrf2 and KEAP1 complex is exposed to ROS + NOS
It dissociates
= Allows nrf2 to become small enough to enter the nucleus where it triggers a cascade of signalling through a whole series of proteins incl. a system called the antioxidant response element.
What happens when the antioxidant response element is activated?
Triggers prod of incr level os some of our key antioxidant enzymes.
Levels of what are sig higher in trained individuals than in sedentary individuals
Dismutase
Catalase
Peroxiredoxin
What is N-acetylcysteine
A direct oxidant scavenger
What can the thiol containing compound in the N-acetylcysteine do?
Donate a cysteine to support the function of 1 of our antioxidant systems glutathione.
What is suggested about supplementing N-acetylcysteine?
That it can reduce exposure to reactive species
+
Reduce the inflammatory response post-exercise.
N-acetylcysteine (NAC) supplementation and cycling sprint performance
Improved
Better tolerance of increased training intensity
NAC supplementation for endurance and sprint performance
Some studies suggest NAC is better for endurance rather than sprint performance.
Purported properties of quercetin
Anti-oxidant
Anticarcinogenic
Cardioprotective
Ergogenic
500-1000mg quercetin a day…
Provided a 2.8% increase in endurance perf.
7 days cherry supplementation and cycling TT perf
Cycling TT perf was enhanced
– Possibly via improved muscle perfusion.
Plausible mechanisms for a favourable influence on cognitive function or decision making during exercise.
Rationale as to why we think its worth exploring antioxidants in regards to ergogenic effects
Seen that oxidative stress + inflammation are contributing factors to the process of muscle damage, so can antioxidants protect against muscle damage +/or improve recovery from muscle damage?
- Benefit for athletes during intensive training +/or intense competition.
Antioxidant vitamin supplementation on recovery from intensive exercise
NO sig effects
Functional recovery from intensive exercise after 7 days pre-loading with Montmorency cherry concentrate (~550mg anthocyanin/d)
Enhanced functional recovery
