Antioxidants

Chapter 9 Study Guide

Investigating individual special needs for antioxidant vitamins

Become proficient in choosing appropriate tests and interpreting the laboratory results.

Recognize patterns that show priorities and dosage aggressiveness.

Textbook Reading Assignments
Textbook Chapter 9 – Oxidant Stress

Evaluating and treating insufficiencies of antioxidant nutrients, including glutathione and its precursors, vitamins A, C, E (tocopherols), -carrotene, riboflavin, ubiquinones, polyphenols (esp. isoflavones), and trace elements copper, manganese, and zinc.

Apply knowledge to real life situations for choosing tests to assess patient status of each nutrient.

Supplementary Material

Download the report named “2011_Gutier_ Liver iron overload is associated with elevated SHBG.”

Your study of this report can help to bridge the material of Chapter 9 with that to come next in Chapter 10. What measure of iron loading did the researchers use? How does that measure compare with those discussed in Chapter 3 for routine clinical application? Familiarize yourself with the term “hypogonadotrophic hypogonadism” used in the left-hand column of p. 165 in the report.  What does this report say about long-term effects of oxidant stress due to iron overload?

Points to Ponder

(Fig. 9.2) What essential trace elements are involved in protecting against oxidative stress?

(Fig. 9.2) Se, Zn, Cu, Mn

(Fig. 9.4) Note the central roles of glutathione in multiple mechanisms for responding to oxidative stress and the micronutrients needed to maintain cellular status of reduced and oxidized agents.

(Fig. 9.4) Glutathione directly participates in clearance of hydrogen peroxide and other oxygen radicals, and its restoration requires the presence of lipoic acid (LipSH).

(pp. 523-531) Note the array of biomarkers that can reveal the status of specific aspects of oxidative damage to guide clinical decisions about aggressiveness of antioxidant therapy and about needs for special interventions to reduce the origins of oxidative stress.

(pp. 523-531) Profiles of fat-soluble vitamins (specific compounds shown of p. 525), Malondialdehyde (lipid peroxides), Isoprostanes, 4-Hydroxy-2-nonenal, OxLDL, 3-Nitrotyrosine, MetO, 8-OhHdG, DNA strand breakage, p-Hydroxyphenyllactate, Homogentisate,

(p. 533) a. Consider the range of supplemental antioxidant interventions that may be applied to achieve balanced (and therefore safe) antioxidant status in each patient when data is available about the nature of oxidative stress and the status of individual antioxidant systems. How may herbal products such as Ginko biloba, Panax ginseng and dietary polyphenols help to achieve such balance?

              b. What factor released during sleep adds strong protection against oxidative stress?

-Previous studies – Integrate the nutrient and biomarker evaluations studied in previous chapters with the information in Chapter 9 to expand your insight about how patients may be evaluated for oxidative stress and stress on specific antioxidant systems.

(p. 533) a. Numerous dietary phenolics (bioflavinoinds and polyphenols) contribute to offset oxidative stress; b. Melatonin

Case Illustration (CI) Questions

(CI 2.1) Return to this case in Chapter 2 after reading Chapter 9 and reconsider why it is unusual to find elevated lipid peroxides when fat-soluble vitamins in serum are in their upper ranges, and what such a finding tells you about other nutrients that need evaluation?

(CI 2.1) The pattern is unusual because abundant levels of fat-soluble vitamins usually confer adequate protection against oxidative stress episodes. An additional factor frequently found to cause such patterns is the presence of one or more elevated PUFAs.

(CI 9.1) What specific factor not mentioned in the conclusions on p. 537 is very likely contributing to oxidative stress? How does the 2011_Gautier article connect this factor to another strong abnormality in this case? What interventions might help to rectify that factor? Identify multiple other abnormalities that help to form the clinical picture of uncontrolled oxidative stress as a major health factor in this patient. What aggressive interventions might be implemented and what plan for management might be formulated?

 (CI 9.1) A relevant factor not mentioned on p. 537 is the elevated ferritin level that indicates contribution to persistent oxidative stress by iron. The coincident elevation of SHBG may be confirmative for iron excess that may be reduced by a series of phlebotomies or therapeutic desferrioxamine. Amino acids and organic acids that show aspects of glutathione status may be investigated, and, when  abnormalities are found, glutathione or its precursor amino acids may be used in therapeutic doses.

By integrating knowledge from prior course work on actions of the vitamins, recognize patterns of vitamin interactions and co-dependencies.

Design appropriate repletion or maintenance dosing according to patient history, presentations and laboratory results.

Discuss how recommendations of individual patient interventions with graded doses of specific antioxidant nutrients based on laboratory evaluation should be differentiated from scientific studies where high doses of single antioxidants may have been found to increase the risk of certain diseases. (pp. 524-525)

OXIDATIVE STRESS

ORIGINS and EFFECTS of OXIDATIVE STRESS


FREE RADICAL DAMAGE and PROTECTION


ANTIOXIDANTS

Antioxidant Activities of Metabolic Products

• Uric Acid
• Serum Albumin
• Glutathione

Anti-Oxidant Nutrients

• Vitamin A, C, E, B-carotene
• Isoflavones
• Copper, Manganese, Selenium, Zinc, Riboflavin
• Antioxidant supplements

MARKERS of OXIDATIVE DAMAGE

Total Antioxidant Capacity

Lipid Oxidation

• Malondialdehyde (MDA, LIPID PERSOXIDES)
• Isoprostanes
• 4-Hydroxy-2-Nonenal
• Oxidized Low-Density Lipoprotein

Protein Oxidation
The surface of proteins tend to contain abundant amino acid side chains that can undergo oxidation.

2 of the most well-known products of protein oxidation arise from reactions of nitric oxide and ROS with tyrosine and methionine.

These protein modifications signal CATHEPSINS to degrage modified proteins.

Retina especially needs anti-oxidant protection due to UV radiation.

• 3-Nitrotyrosine (3NT)
• Nitric oxide present with oxidative stress results in PEROXYNITRITE, a reactive nitrogen species (RNS)
• PEROXYNITRITE formed by combination of superoxide and NO radicals
• Tyrosin residues in proteins (usually endothelium) are nitrated by peroxynitrite forming 3NT
• Once protein degraded, 3NT is released into blood stream
• Increased 3NT suggests increased tissue NO and SOD
• Arginine is contraindicated
• Polyphenols offer protection against peroxynitrites 
• Methione Sulfoxide (MetO)
• Marker of cellular oxidative stress, specifically the enzymes and structural proteins because it is formed from methionine residues that are exposed on protein surfaces
• Elevated MetO levels indicate inadequate overall oxidative protection
• MetO can be reversed to Met by methionine sulfoxide reductase enzyme - these are peptide methionine sulfoxide reductases (PMSR).
• MetO causes inactivation of the enzyme
• Lipoic acid may help stimulate the enzyme

Nucleotide Oxidation

• 8-Hydroxy-2'-Deoxyguanosine (8-OHdG)
• Rate of oxidative DNA damage may be estimated by 8-OHdG
• 8-OHdG is a repair product of the highly mutagenic oxidation of guanine in DNA
• Intracellular antioxidants glutathione and ascorbate can protect human lymphocytes against oxidative DNA damage
• High fat diet increase levels
• DNA Strand Breakage (Comet Assay)
• Breaks in DNA by single-cell (WBC) gel electrophoresis

Oxygen-Radical Absorption Capacity
Lack of sensitivity

Endogenous Oxidative Stress Modulators

• p-Hydroxyphenyllactate (HPLA)
• On urinary organic acid profiles, a carcinogenic tyrosine metabolite
• HPLA reveals how much challenge is being generated within tissues
• Increased HPLA suggests decreased ascorbic acid in liver, adrenals, blood
• Homogentisate (HGA)
• Elevation of HGA associated with Plasma Soluble Melanins (PSM)
• PSM formed by copolymerizaiton of dopa, catecholamines, HGA, and other polyhydroxy compounds
• Antioxidants delay the formation of pSM that contribute to the yellow color of plasma and urine.
• PSM found in:
• Pheochromocytoma
• Parkinson's disease
• Alkaptonuria
• In presence of Cu, HGA causes DNA damage (and increases 8OHdG)

Pathogen Invasion

• Neutrophil-mediated oxidative burst
• Rapid generation and release of reactive oxygen intermediates by the NADPH-oxidase complex
• Increased oxidative stress with infection:
• H. pylori
• Prevotella intermedia
• Brucella Melitersis
• Benefit to host is apoptosis of infected cells
• Cryptosporidium parvum able to survive oxidative bursts and may persist in machrophage phagosomes for weeks
• Improved infection management with supplements

TREATMENT OPTIONS
In patients with elevated oxidative damage markers, there is a 2-fold approach:

1. Reducing exposure to free radical-generating agents
2. Increasing antioxidant levels in the body

Reducing Pro-Oxidants

• Environmental agents increase free radical activity
• Examples: cadmium, pesticides, ionizing radiation, cigarette smoke
• Lifestyle factors such as stress, heavy exercise, smoking, excess alcohol, infections tend to raise lipid peroxide levels

Increase Anti-Oxidants

• Supplementation
• Vitamin A, C, E, beta-carotene, selenium, co-enzyme Q10, taurine, B2, B3, certain bioflavinoids
• Balanced intake preferable
• Magnesium deficiency can increase oxidant loads by increasing stress responses

Other Lifestyle Factors

• Sleep disorders
• Pineal hormone melatonin is a free radical scavenger (antioxidant)
•