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Urinary malondialdehyde as an indicator of lipid peroxidation in the diet and in the tissues
Abstract:
Although malondialdehyde (MDA) is extensively metabolized to CO2, small amounts are nevertheless excreted in an acid-hydrolyzable form in rat urine. In this study, urinary MDA was evaluated as an indicator of lipid peroxidation in the diet and in the tissues. MDA was released from its bound form(s) in urine by acid treatment and determined as the TBA-MA derivative by HPLC. MDA excretion by the rat was found to be responsive to oral administration of the Na enol salt and to peroxidation of dietary lipids. Urinary MDA also increased in response to the increased lipid peroxidation in vivo produced by vitamin E deficiency and by administration of iron nitrilotriacetate. Chronic feeding of a diet containing cod liver oil led to increases in MDA excretion which were not completely eliminated by fasting or feeding a peroxide-free diet, indicating that there was increased lipid peroxidation in vivo. MDA excretion was not responsive to Se deficiency or CCl4 administration. DPPD, a biologically active antioxidant, but not BHA, a non-biologically active antioxidant, prevented the increase in MDA excretion in vitamin E deficient animals. The results indicate that MDA excretion can serve as an indicator of the extent of lipid peroxidation in the diet and, under conditions which preclude a dietary effect, as an index of lipid peroxidation in vivo.
Insights
Urinary malondialdehyde (MDA) excretion indicates dietary lipid peroxidation and, when diet is controlled, reflects tissue lipid peroxidation. This marker is sensitive to vitamin E deficiency and certain pro-oxidants, with antioxidants affecting its levels.
Area of Science:
- Biochemistry
- Toxicology
- Nutritional Science
Background:
- Malondialdehyde (MDA) is a byproduct of lipid peroxidation.
- Urinary MDA is typically metabolized to CO2, but a small fraction is excreted in an acid-hydrolyzable form.
- Assessing urinary MDA offers a potential method to evaluate lipid peroxidation.
Purpose of the Study:
- To investigate urinary MDA as a biomarker for dietary and in vivo lipid peroxidation in rats.
- To determine factors influencing MDA excretion, including diet composition and oxidative stress.
- To evaluate the efficacy of antioxidants in modulating MDA levels.
Main Methods:
- Urine samples were treated with acid to release bound MDA.
- MDA was quantified using High-Performance Liquid Chromatography (HPLC) after derivatization to TBA-MA.
- Rats were subjected to dietary manipulations (e.g., cod liver oil, vitamin E deficiency) and chemical treatments (e.g., iron nitrilotriacetate).
Main Results:
- Urinary MDA excretion increased in response to dietary lipid peroxidation and in vivo lipid peroxidation induced by vitamin E deficiency or iron nitrilotriacetate.
- Chronic cod liver oil feeding led to sustained increases in MDA excretion, suggesting persistent in vivo peroxidation.
- The antioxidant DPPD, but not BHA, prevented MDA excretion increases in vitamin E deficient rats.
Conclusions:
- Urinary MDA is a responsive indicator of lipid peroxidation in both diet and tissues.
- MDA excretion can serve as a valuable biomarker for assessing oxidative stress in vivo.
- The study highlights the utility of urinary MDA in nutritional and toxicological research.
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