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DNA strand break accumulation, thymidylate synthesis and NAD levels in lymphocytes from methyl donor-deficient rats
S J James1, L Yin, M E Swendseid
1Division of Nutritional Sciences, School of Public Health, University of California, Los Angeles.
Abstract:
Although tumor development with methyl donor-deficient diets has been well established, the biochemical and molecular mechanisms which predispose to tumor development are not yet understood. In the present study, DNA damage and nucleotide metabolism associated with DNA synthesis and repair were evaluated in splenic lymphocytes from rats fed a basal diet low in methionine and lacking in choline and folate or a supplemented control diet for a period of 3 wk. The accumulation of DNA strand breaks, as assessed by DNA unwinding in alkali, was found to be significantly elevated in lymphocytes from rats fed the methyl donor-deficient diet and was associated with an increase in mitogen-stimulated incorporation of [3H]-thymidine via the salvage pathway for thymidylate synthesis. In addition, a significant decrease in the DNA repair-associated pyridine nucleotide, NAD, was observed in lymphocytes from the deficient group and was associated with a decrease in total spleen cell numbers. These results suggest that alterations in nucleotide metabolism and DNA damage are induced when methyl donor pools are stressed by dietary deficiency.
Insights
Methyl donor deficiency in rats causes DNA damage and alters nucleotide metabolism in lymphocytes. This suggests dietary factors significantly impact DNA integrity and cellular repair mechanisms.
Area of Science:
- Biochemistry
- Molecular Biology
- Nutritional Science
Background:
- Tumor development is linked to methyl donor-deficient diets.
- The underlying biochemical and molecular mechanisms remain unclear.
Purpose of the Study:
- To investigate DNA damage and nucleotide metabolism in splenic lymphocytes.
- To understand the effects of methyl donor deficiency on DNA synthesis and repair.
Main Methods:
- Rats were fed either a methyl donor-deficient diet (low methionine, no choline/folate) or a control diet for 3 weeks.
- DNA strand breaks were assessed using DNA unwinding in alkali.
- Nucleotide metabolism, including [3H]-thymidine incorporation, was evaluated.
- Nicotinamide adenine dinucleotide (NAD) levels were measured.
Main Results:
- Elevated DNA strand breaks were observed in lymphocytes from rats on the deficient diet.
- Increased mitogen-stimulated [3H]-thymidine incorporation via the salvage pathway was noted.
- A significant decrease in NAD levels and total spleen cell numbers was found in the deficient group.
Conclusions:
- Dietary methyl donor deficiency induces alterations in nucleotide metabolism.
- This deficiency leads to increased DNA damage in lymphocytes.
- These findings highlight the link between diet, DNA integrity, and cellular mechanisms.