Unit 3 - Lecture 23/24

Question 1

Reactive Oxygen Species (ROS) are/are not naturally produced in the body.

Answer 1

Are

Question 2

What is oxidative stress?

Answer 2

It is a balance between and pro-oxidants and anti-oxidants.

Question 3

Tissue response to ROS:

Answer 3

Question 4

Markers of Reactive Oxygen Species (ROS)

Answer 4

1. Protein Oxidation
2. DNA Damage
3. Lipid Peroxidation

Question 5

Markers of Reactive Oxygen Species (ROS)

Answer 5

1. Basal
2. Signaling
3. Damage

Question 6

Effects on Muscle Contraction from Reactive Oxygen Species (ROS):

Answer 6

• At rest, there is not much effect on muscle contraction at basal levels.
• As for exercise increases (volume/intensity/frequency), there is an increase in signaling.
• As exercise increases, potential overtraining has a damaging effect on muscle contraction.

Question 7

What does the tissue responses to reactive oxygen species (ROS) suggest?

Answer 7

• ROS, in balance, plays an important role in adaptation.
• Exercise (muscle contraction) can help increase ROS for adaptation and increase antioxidant capacity.

Question 8

Exercise attenuates:

Answer 8

1. DNA Damage
2. Lipid Peroxidation
3. Protein Oxidation

Question 9

How does exercise increase ROS, yet protect against ROS-induced mechanisms of disease?

Answer 9

There are four factors affecting the magnitude of exercise ROS onset:

1. Age
   
   1. Older individuals have a greater magnitude of a response than younger individuals.
2. Training Status
   
   1. The higher trained you are, the lower magnitude of the oxidative stress response.
3. Dietary Intake
   
   1. Fat, especially saturated fat, produces the most oxidative stress of any macronutrient.
4. Degree of Antioxidants Present
   
   1. Individuals who have more antioxidants than others are more protected.

Practically, sedentary older adults with poor diets favor oxidative stress onset.

Question 10

How do we prevent excess ROS?

Answer 10

1. Exercise
   
   1. ROS is critical for muscle homeostasis.
   2. ROS increases cell antioxidants.
   3. ROS increases cell cytoprotective enzymes that prevent damage.

Question 11

What is nuclear factor-kB (NF-kB)?

Answer 11

1. NF-kB is a transcriptional factor that regulates multiple aspects of innate and adaptive immune functions and serves as a pivotal mediator of inflammatory responses.
   
   1. NF-kB induces the expression of various pro-inflammatory genes, including those encoding cytokines and chemokines, and also participates in inflammasome regulation.
   2. NF-kB plays a critical role in regulating the survival, activation, and differentiation of innate immune cells and inflammatory T cells.
2. Deregulated NF-kB activation contributes to pathogenic processes of various inflammatory diseases.

Question 12

Reactive Oxygen Species (ROS) stimulates the activation of NF-kB.

Answer 12

• In the cytosol, increased levels of ROS can phosphorylate IkB proteins.
• Phosphorylated IkB initiates ubiquitination and subsequent IkB degradation via the proteasome.
• Degradation of IkB proteins removes the inhibition and releases NF-kB complexes so that nuclear translocation will occur.
• NF-kB is a transcriptional factor that regulates pro-inflammatory genes. It also has a role in cell stress and apoptosis.
• Oxidative stress can promote NF-kB.

Question 13

NF-kB also regulates __________.

Answer 13

• Antioxidants
  
  • There are specific enzymes that are key to this process.
    
    • SOD = Superoxide Dismutase
    • NOS = Nitric Oxide Synthase
      
      • eNOS = Endothelial Nitric Oxide Dismutase
        
        • Found in endothelial cells.
      • iNOS = Inducible Nitric Oxide Dismutase
        
        • Found in myocytes.
• Both SOD and NOS have specific promoter regions for NF-kB.

Question 14

What happens during intermittent NF-kB?

Answer 14

• Adaptation
  
  • Improve fuel provisions and increase antioxidants.
  • Tissue regeneration.
  • Benefit physiology.

Question 15

What happens to chronic activation of NF-kB?

Answer 15

• Exhaustion
  
  • Metabolic and oxidative perturbations.
  • Tissue degradation
  • Pathology

Question 16

How does fuel provisions/selection fit here?

Answer 16

1. ROS stimulates AMPK, leading to PGC1-alpha stimulation, which increases mitochondrial biogenesis.
   
   1. ROS, through a series of steps, can support greater oxidative capacity.
   2. It can promote increased mitochondria, which can favor fuels like fat or carbohydrate.
   3. Ultimately, ROS contributes to metabolic adaptations.
      
      1. AMPK has promoter regions that ROS can activate.
2. Of interest, PGC1-alpha has NF-kB regions.
   
   1. NF-kB can stimulate PGC1-alpha.
      
      1. Mitochondria can be stimulated through inflammatory pathways.

Question 17

What do you think happens with antioxidant supplementation and exercise?

Answer 17

• Blunted adaptation to exercise (Riston, PNAS, 2008).
  
  • Outcomes:
    
    • Insulin Sensitivity, PGC1-alpha, Adiponectin
    • Control, Vitamin C/Vitamin E
• Other data:
  
  • SOD + NOS are blunted with supplementation.
  • Flow-mediated dilation (FMD) has been reported to be blunted.
  • Some evidence supports no effect on VO_2max and GLUT4.
    
    • Blunting one aspect doesn’t mean that you are blunting every response.
    • Diet is not rigorously controlled in these studies.

Question 18

Hormesis (54:19)

Answer 18

• We have seemingly dose-response systems in place with supplementation and exercise.
  
  • Adequate stimuli = “Good Effect”
  • Too many stimuli = “Bad Effect”
• Minimal effective dose.

Question 19

Fatigue

Answer 19

• Exercise can produce oxidative stress that yields molecules like hydrogen peroxide.
  
  • Hydrogen peroxide inhibits myosin heavy chains.
    
    • Inhibited myosin heavy chains impair muscle contraction.

Question 20

Pharmacology in regards to antioxidants and hormesis.

What happens when we combine exercise and Metformin?

Does Drug + Exercise = 1+1 = 2?

Answer 20

• Exercise increases AMPK.
• Metformin increases AMPK.
  
  • Studies indicate that drugs and exercise are not compounding.
    
    • This is indicative of insulin sensitivity and muscle AMPK activity.

Metformin is believed to inhibit complex I in the electron transport chain on the inner membrane of the mitochondria.

People on Metform had blunted responses in exercise fat oxidation and VO_2peak.

Question 21

There is a wide range of diseases that is associated with oxidative stress.

Answer 21

• Diabetes
• Alcohol-induced Liver Disease
• Mitochondrial DNA disorders
• Aging
• Etc…

Question 22

Can you reduce oxidative stress?

Answer 22

• There are a lot of opportunities from our foods to mitigate oxidative stress in the body.
  
  • Fruits and Vegetables (Blueberries, Pomegranate
  • Teas (Green Tea)
  • Wine (Resveratrol)
  • Cacao

Question 23

Free Radicals

Answer 23

A molecule that contains 1 or more unpaired electrons and is capable of independent existence.

Question 24

Reactive Oxygen Species (ROS)

Answer 24

Refers to both oxygen-centered free radicals and non-radical derivatives of oxygen (H₂O₂).

Question 25

Reactive Oxygen and Nitrogen Species (RONS)

Answer 25

Refers to both nitrogen and oxygen species. (ONOO)

Question 26

__________ is often discussed as the primary site of ROS/RONS production.

Answer 26

Mitochondria

Question 27

Which type of muscle fibers is more prolific in the production of ROS and RONS?

Answer 27

Type II Muscle Fiber

Makes sense given that the metabolic scenario that raises oxygen consumption leads to ROS/RONS.

Question 28

Basal energy production is related to oxidative stress.

Answer 28

Question 29

Newer data suggest that more ROS production occurs in the ______ state than ______ _______ states.

Answer 29

• Rested
• ADP stimulated
• Example: inactivity vs. exercise = “ROS paradox”
  
  • Inactivity = Mitochondria produce ROS
  • Exercise = Cytosol produce ROS

Question 30

Other sources of O₂·^-, H₂O₂, ·OH, ONOO^- in skeletal muscle.

Answer 30

• Superoxide (O₂·^-); Sarcoplasmic Reticulum, Sarcolemma
• eNOS; Extracellular Matrix
  
  • Produces nitric oxide (NO), which can combine with O₂·^- to form peroxynitrite (ONOO^-).
    
    • This can occur within the cell and outside the cell.
• Xanthine Oxidase (XO); An enzyme within the Sarcolemma that produces O₂·^-.

Question 31

Antioxidant Defense System

Answer 31

• Superoxide Dismutase (SOD)
  
  • Keep superoxide radicals in check.
    
    • O2·^- + e^- > H₂O₂
    • Highest in Type I Fibers
  • Location:
    
    • 15-35% in the Mitochondria
    • 65-85% in the Cytosol
    • Also found in locations outside the plasma membrane (extracellular matrix).
• Glutathione Peroxidase (GPX)
  
  • Converts H₂O₂ to H₂O
  • 2 GSH + H₂O₂ > GSSG + 2 H₂O
  • Reduced GSH donates H⁺ to H₂O₂
• Catalase
  
  • Also converts H₂O_{2 to} H₂O
  • Lower affinity for H₂O₂ than GPX
• Minor or less understood antioxidants
  
  • Thioredoxin, Glutaredoxin, Peroxiredoxin, Metalothionine

Question 32

Dietary Antioxidants

Answer 32

1. Vitamin C
   
   1. “Chain breaking” Antioxidant
2. Vitamin E
   
   1. Plays a role in recycling Vitamin E.
   2. Can also sequester superoxide, hydroxyl, lipid hydroperoxide radicals independently.

• Observational findings regarding the antioxidant supplements selenium, beta-carotene, and vitamins A, C, and E and total mortality have been inconsistent.
  
  • Some studies report that there is a raised risk with the consumption of antioxidants and the incidence of cancer at standard dosages.

Question 34

The balance between pro-oxidants and antioxidants.

Answer 34

• Lean Individuals @ Rest
  
  • In Balance
• Obese Individuals @ Rest
  
  • Increased oxidation.
• Lean Individuals @ Exercise
  
  • Even more increased oxidation than the obese individuals at rest.

Question 35

Exercise helps balance the equation from energy coming in and energy going out.

Answer 35

Question 36

Possible functions of UCP-3; protective role?

Answer 36

• Uncoupling proteins may move hydrogen peroxide away from pathways that are being promoted towards manipulating glutathione and helping hydrogen peroxide move towards steps of uncoupling that utilize hydrogens.
  
  • Creating a proton leak helps manage oxidative stress.

1. Byproducts of ROS production induce UCP-3.
2. Create proton leak.
3. Decrease membrane potential.
4. Decrease ROS production.

Question 37

Consequences of Oxidative Stress

Answer 37

1. Protein Oxidation
   
   1. Proteins scavenge the majority of RONS (50-75%).
   2. Protein damage is irreparable and can lead to loss of enzymatic, contractile function.
   3. Damaged proteins are subject to degradation.
2. DNA Damange
   
   1. RONS results in forming a variety of base and sugar modification products, ultimately leading to cell growth arrest and apoptosis.
3. Lipid Peroxidation
   
   1. Free radical steals an H+ from a lipid side chain.
   2. Carbon reaction with oxygen creates another free radical.
   3. This radical attacks another lipid side chain, generating another radical and lipid peroxide.

Question 38

Biomarkers of oxidative stress

Answer 38

• Lipid Peroxidation
• DNA Damage
• Protein Oxidation
• Antioxidant Capacity

The order below is most sensitive to least sensitive.

Question 39

What metabolic scenarios cause oxidative stress?

Answer 39

• Exercise - Link.
• Diet - Link to caloric intake.
• Medications/Supplements - Alter substrate availability or mitochondria function.
• Disease - Excess substrate availability.

All are linked to energy metabolism.

Question 40

Reactive oxygen species connected to fatigue.

Answer 40

• As ROS is produced at different stages, there are different locations that produce ROS.
  
  • ROS can inhibit the myosin heavy chain and/or impact the sarcoplasmic reticulum.