Search

Objective: To investigate associations between nonsyndromic oral clefts and biochemical measures of folate status and the MTHFR C677T variant in the United Kingdom, where there has been no folic acid fortification program.Method: Dietary details were obtained from the mothers of 112 cases of cleft lip with or without cleft palate (CL±P), 78 cleft palate only (CP) cases, and 248 unaffected infants. Infant and parental MTHFR C677T genotype was determined. Red blood cell (RBC) and serum folate and homocysteine levels were assessed in 12-month postpartum blood samples from a subset of mothers. The data were analyzed by logistic and log-linear regression methods.Results: There was an inverse association between CL±P and maternal MTHFR CT (odds ratio [OR] ?=? 0.5, 95% confidence interval [CI] ?=? 0.31–0.95) and TT (OR ?=? 0.6, 95% CI ?=? 0.21–1.50) genotypes, with similar risk estimates for CP. There was no clear association with infant MTHFR genotype. Higher levels of maternal postpartum RBC and serum folate were associated with a lower risk for CL±P and an increased risk for CP. Higher levels of serum homocysteine were associated with a slightly increased risk for both CL±P and CP.Conclusion: While the inverse relation between the mother's having the MTHFR C677T variant and both CL±P and CP suggests perturbation of maternal folate metabolism is of etiological importance, contrasting relations between maternal postpartum levels of RBC and serum folate by type of cleft are difficult to explain.

Folic acid is essential for the synthesis and repair of DNA. We report the effects of folate depletion on DNA stability in normal human lymphocytes in vitro. DNA strand breakage, uracil misincorporation, oxidative DNA base damage, and DNA repair capability were determined using variants of the comet assay (single cell gel electrophoresis). Lymphocyte proliferation was measured as an indicator of normal replication. Lymphocytes isolated from human venous blood were stimulated to grow in either complete medium containing folic acid (1 ng/ml–2 µg/ml) or medium deficient in folic acid for up to 10 days. Cells prepared for comet analysis were treated either with the bacterial DNA repair enzyme endonuclease III to determine the level of oxidized pyrimidines in lymphocyte DNA or with uracil DNA glycosylase, which detects misincorporated uracil. Cell number and viability were measured. Normal human lymphocyte DNA contained detectable amounts of misincorporated uracil (estimated as approximately 1000 per cell). DNA strand breakage and uracil misincorporation increased in a time‐ and concentration‐dependent manner after lymphocytes were cultured with decreasing amounts of folic acid. DNA damage was induced at folic acid concentrations routinely observed in plasma from the human population (1–10 ng/ml). Lymphocytes cultured under folate‐deficient conditions failed to grow normally compared with control cells. However, all lymphocytes remained viable as measured by Trypan blue exclusion. Cells deprived of folate were unable to efficiently repair oxidative DNA damage induced by hydrogen peroxide. Inhibition of repair was maximal after 8 days in culture. Folate supply had no effect on the level of oxidized pyrimidines in lymphocyte DNA, even after 10 days in culture, suggesting that folate deficiency increases uracil misincorporation relatively specifically. These in vitroresults help to determine the mechanism(s) through which folic acid maintains DNA stability.—Duthie, S. J., Hawdon, A. DNA instability (strand breakage, uracil misincorporation, and defective repair) is increased by folic acid depletion in human lymphocytes in vitro. FASEB J.12, 1491–1497 (1998)

The effect of increasing dietary intakes of polyunsaturated fatty acids (PUFAs) and vitamin E on indices of oxidative DNA damage was investigated. Twenty‐one healthy male, nonsmokers aged 28.9 ± 1.3 years participated in a free‐living, split plot/change over trial in which half the volunteers consumed diets containing 5% PUFA as food energy for 4 wk and, after a 10 wk washout period, consumed a 15% PUFA diet for another 4 wk. The other volunteers followed an identical protocol, except that they consumed the 15% PUFA diet first. The diets were provided to volunteers either with or without an additional 80 mg dα‐tocopherol acetate/ day; otherwise total fat, carbohydrates, protein, and basal vitamin E contents remained unchanged. DNA damage induced by 200 µMH2O2in lymphocytes from volunteers as well as endogenous DNA damage in the form of oxidized pyrimidines, measured by alkaline single‐cell gel electrophoresis (the comet assay), significantly decreased after consumption of the 5% PUFA diet (P<0.001 and P=0.01, respectively), but significantly increased after consumption of the 15% PUFA diet when α‐tocopherol levels were in the range of 5–7 mg/day (P = 0.008 and P= 0.03, respectively). These changes were abolished by an additional 80 mg dα‐tocopherol/day. This study indicates that increasing dietary levels of PUFA to 15% may adversely affect some indices of DNA stability. However, increasing the dietary intake of vitamin E by 80 mg/day ameliorates the damaging effects of PUFA.—Jenkinson, A. McE., Collins, A. R., Duthie, S. J., Wahle, K. W. J., Duthie, G. G. The effect of increased intakes of polyunsaturated fatty acids and vitamin E on DNA damage in human lymphocytes. FASEB J.13, 2138–2142 (1999)

Folic acid deficiency in humans has been linked with megaloblastic anaemia, neural tube defects in the neonate, and heart disease. Folate has also been implicated in the development of cancer, especially cancer of the colorectum. There appear to be two principal mechanisms through which low folate status may increase the risk of malignancy. Folate deficiency, by reducing intracellular S-adenosylmethionine (SAM), can alter cytosine methylation in DNA, leading to inappropriate activation of proto-oncogenes and induction of malignant transformation. Alternatively, folic acid is crucial for normal DNA synthesis and repair. Folate deficiency may cause an imbalance in DNA precursors, uracil misincorporation into DNA, and chromosome breakage. This chapter briefly describes the epidemiological data supporting the involvement of folic acid in the aetiology of cancer. It also assesses the evidence from cellular, animal and human studies that folic acid can modulate DNA by such mechanisms.

Carotenoids are thought to act as antioxidants in vivo, decreasing oxidative damage to biomolecules and thus protecting against coronary heart disease and cancer. However, human intervention studies with beta-carotene have given equivocal results in terms of cancer incidence. In an alternative molecular epidemiological approach, we have employed the 'comet assay' (single cell alkaline gel electrophoresis) to measure strand breaks, oxidized pyrimidines and altered purines in the DNA of lymphocytes from volunteers supplemented with alpha/beta-carotene, lutein, lycopene or placebo. In addition, we measured concentrations of the main serum carotenoids, and vitamins E and C, by HPLC. We report a significant negative correlation between basal concentrations of total serum carotenoids and oxidized pyrimidines. A similar correlation was seen between individual carotenoids (notably lutein and beta-carotene) and oxidized pyrimidines. However, carotenoid supplementation did not have a significant effect on endogenous oxidative damage. This suggests that there are some factors in the basal diet, probably found in fruit and vegetables, that decrease oxidative damage to DNA. In this case, basal serum carotenoids may simply be markers of consumption of fruit and vegetables, they themselves having little or no protective value.

Poor folate status may be important in the aetiology of several epithelial cell malignancies including cancer of the uterine cervix. Folic acid is essential in the synthesis of purine nucleotides and the pyrimidine nucleoside thymidine and it is probable that imbalances in these DNA precursors negatively effect DNA stability and may ultimately lead to malignant transformation. The development of a modified 'comet assay' using the bacterial DNA repair enzyme uracil DNA glycosylase, to detect misincorporated uracil in human DNA is reported here. The effect of perturbing folic acid and deoxyuridine levels on uracil misincorporation in normal human lymphocytes and cultured human tumour cells was investigated using this assay. HeLa cells and peripheral human lymphocytes incubated as agarose-embedded nucleoids, with 1 unit of uracil DNA glycosylase per microg of DNA, contained low levels of uracil in their DNA. Both HeLa cells and stimulated human lymphocytes cultured in folate-deficient medium were growth arrested. Incubating human lymphocytes in folate-deficient medium significantly increased the level of uracil detected compared with control cells. HeLa cells showed an increase in non-specific DNA damage (strand breaks). Deoxyuridine (100 microM) significantly increased the level of uracil detected in the DNA of both folate-deficient and control HeLa cells. It appears that this modified comet assay specifically detects misincorporated uracil in single human cells. It should, therefore, prove valuable in determining the role of folic acid status in DNA instability and cancer.

Objectives: To determine the prevalence of abnormal carbohydrate metabolism in Chinese pregnant women. To study the inter‐relationship between maternal body habitus, maternal serum glucose and birth weight of the baby.

The outcome of termination of pregnancy was observed in relation to the preoperative clinical and microbiological findings in 167 women attending a day care abortion unit in Liverpool. Before termination, Chlamydia trachomatis was isolated from the cervix of 19 (11%) of the patients and high counts (greater than 10(4) colour changing units (ccu) per ml of specimen) of mycoplasmas were found in 30 (18%). Coexistent infections with chlamydiae and high counts of mycoplasmas occurred in only seven (4%) women. Trichomonas vaginalis, yeasts, or pathogenic bacteria were found in vaginal swabs from 30 (18%) women. After undergoing termination, seven (4%) women developed pelvic inflammatory disease (PID), five (71%) of whom had yielded C trachomatis before undergoing termination. A further 13 (8%) patients developed minor morbidity of the upper genital tract; high count mycoplasmal infection had been found in seven (54%) and chlamydial infection in three (23%) of these women before termination. In contrast, C trachomatis had been isolated from only 11 (8%) and high counts of mycoplasmas from 23 (16%) of the 147 women who had uneventful recoveries after undergoing termination. No correlation was apparent between the presence of vaginal pathogens before termination and the development of untoward sequelae postoperatively. Neither the history nor clinical examination before termination would have indicated that chlamydial or mycoplasmal infections were present, or that postoperative complications were likely to occur. Abnormal cervical cytology, however, was found in 86 (52%) of women overall, including 15 (79%) of the 19 women with chlamydial infection. [ABSTRACT FROM PUBLISHER]

In a prospective study the prevalence of syphilis amongst a group of pregnant Vietnamese refugees in Hong Kong was found to be 3.4%. No cases of gonorrhoea, genital warts or genital ulcers were found in the same group of patients. The implications of these results are discussed and the importance of adequate screening, treatment, contact tracing and health education amongst this group are emphasised. [ABSTRACT FROM PUBLISHER]