Dissertation/Thesis Abstract

There are observable metabolic signature patterns in C. elegans: Specifically for different life stages grown with and without the added antioxidants vitamin C and vitamin E?
by Sudama, Gita, Ph.D., George Mason University, 2008, 228; 3313520
Abstract (Summary)

Aging, a complex phenomenon, experienced by all living organisms, continues to intrigue mankind. Characteristics of aging in animals include a decline in motility and strength, reduction of memory retention, weakening of the immune system, decrease or cease of the ability to reproduce, pigmentation, and decrease in skin, ligament and muscle elasticity. The most common theories on aging are: the Gene Regulation theory, the Free Radical theory, the Oxygen Stress-Mitochondrial Mutation theory, Programmed Cell Death theory, Evolution Theory and Neuroendocrine and Immune (System-Based) theory.

This research investigates oxidative stress using Vitamin C and/or E at each life stage of the laboratory-cultured axenic nematode C. elegans . Size and response to cold temperature stress (functions of age) were used to separate the C. elegans into pre-reproductive, reproductive and post-reproductive life stages. Redox responses for electrogenic compounds in the C. elegans, separated using reverse phase high performance liquid chromatography (CEAS-HLPC), and sixteen electrodes set between 0 and 900 mv at 60 mv intervals, were measured and saved as chromatographs for each life stage/treatment. Within these chromatographs one can identify and acquire quantitative data for the electrogenic analytes. Tryptophan, tyrosine, serotonin, norepinephrine, epinephrine, 8-Hydroxyguanine and the purine catabolites (guanosine, guanine, hypoxanthine, xanthosine, xanthine and uric acid) were identified and measured.

Tryptophan and tyrosine are small molecules that are conserved throughout evolution. Products of their metabolism include the neurotransmitters and hormones serotonin, norepinephrine and epinephrine that are involved in the aging process. Epinephrine and norepinephrine control responses to stress and increase heart rate. Serotonin is associated with behavioral responses. 8-Hydroxyguanine is a marker of DNA damage. The purine catabolites are formed from the breakdown of nucleotides and reflect alterations in nucleotide synthesis and salvage. The analysis of this set of metabolites provides one means of investigating effects of antioxidants on levels of cellular homeostasis dependent upon these ligands and their end products.

The population distributions are altered in C. elegans, cultured for 10 days in response to doses of Vitamin C and/or E at levels of 0.1, 0.5 and 1.0 mg/ml of media. The cultures with the Vitamin treatment had observable differences in population profiles, life stage distributions and analyte profiles at the end of their incubation period when compared to the untreated population. An increase of pre-reproductive C. elegans in all Vitamin treated populations was observed. This effect is likely due the antioxidant properties of the Vitamins, resulting in a delay of the aging process.

A marker of DNA damage repair, 8-Hydroxyguanine was not found in any of the populations treated with Vitamin E and C in combination, but was found in all post-reproductive stages in populations derived from controls, or those treated with Vitamin C or Vitamin E alone. All of the purine metabolites were found in greater concentrations in the pre-reproductive worms treated with the Vitamin C and E combinations, compared to the Vitamin C, Vitamin E or untreated pre-reproductive worms. This implies that these antioxidants are capable of affecting purine metabolism, possibly through a reduction of oxidative damage to DNA and RNA.

There are substantial observed alterations in the trp/tyr ratios, that can affect the production of a host of key metabolites derived from these amino acids, that serve as important factors, ligands, neurotransmitters and hormones, that are key to the establishment and maintenance of cellular and physiologic homeostasis, in these, and other organisms. Serotonin was found in the post-reproductive C. elegans, where the concentrations in the Vitamin C & E combination experiments were the least. Epinephrine existed in measurable quantities in the pre-reproductive life stage, with the smallest concentration in the Vitamin C & E combination experiments. These are all indication that homeostasis is better maintained in the Vitamin C & E treatments, since there is minimal damage to the control systems due to ROS.

In summary the biochemical patterns from CEAS-HPLC are altered in the respective age groups where C. elegans is grown in the presence of the known oxidative suppressors, Vitamin C and E. Higher concentrations of added Vitamin C and E do not seem to have negative effects on the biochemistry of the nematode, as measured with this analytic system but the combination of Vitamin C and E treatment produces the most dramatic effect. This study provides data that is supportive of the current theories of aging that involve ROS such as the Free Radical theory. However, the effects of the Vitamins on the organism can be explained by the neuroendocrine theory since the neurotransmitters concentrations changed with the addition of Vitamin C & E. It also implies Vitamin C and/or E increases longevity, with their antioxidant properties.

Indexing (document details)
Advisor: Willett, James D.
Commitee:
School: George Mason University
School Location: United States -- Virginia
Source: DAI-B 69/06, Dissertation Abstracts International
Source Type: DISSERTATION
Subjects: Molecular biology
Keywords: Aging, Antioxidants, Oxidative stress, Vitamin C, Vitamin E
Publication Number: 3313520
ISBN: 9780549646778
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