Folate status and homocysteine response to folic acid doses and withdrawal among young Chinese women in a large-scale randomized double-blind trial.

BACKGROUND: There are no large randomized trials of the effect of folic acid dosing regimens on blood folate and homocysteine concentrations. OBJECTIVE: We aimed to evaluate the changes in folate and homocysteine concentrations in response to different folic acid doses and to withdrawal in young women not exposed to other sources of folic acid. DESIGN: Women (n = 1108) were randomly assigned to 1 of 6 intervention groups for which daily intakes of folic acid for 6 mo were 100 microg 1 time/d, 25 microg 4 times/d, 400 microg 1 time/d, 100 microg 4 times/d, 4000 microg 1 time/d, or 4000 microg 1 time/wk. Plasma and red blood cell folate and homocysteine concentrations were measured at baseline; at 1, 3, and 6 mo; and 3 mo after the discontinuation of folic acid. RESULTS: Folate and homocysteine concentrations were not different at baseline between the groups who had the same daily intake of folic acid as a single dose or multiple doses (P = 0.058). Plasma folate concentrations plateaued at 3 mo with 108% (95% CI: 97.7%, 120%), 259% (95% CI: 240%, 279%), 460% (95% CI: 417%, 503%), and 142% (95% CI: 123%, 162%) observed increases for the folic acid groups receiving 100, 400, and 4000 microg/d and 4000 microg/wk, respectively. The rate of reduction in folate concentrations during the 3 mo after cessation of folic acid was dose-dependent-higher intakes were associated with faster reductions. CONCLUSIONS: Changes in folate and homocysteine concentrations were unaffected by different dosing schedules. After folic acid cessation, blood folate declined rapidly, which indicated that the intervention-enhanced folate status was rapidly diminished.

[Study on the association between transforming growth factor alpha gene TaqI variant and cleft lip with or without cleft palate].

OBJECTIVE: To study the association between transforming growth factor alpha gene (TGFalpha) TaqI variant and nonsyndromic cleft lip with or without cleft palate (nsCL/P) in Chinese population. METHODS: TGFalpha TaqI variant was detected using polymerase chain reaction-restriction fragment length polymorphism for DNA samples of the 149 triads with nsCL/P affected child. We performed the Transmission/disequilibrium test and the family-based association study (FBAT) to identify the associations between this variant and risk of nsCL/P. RESULTS: Significant distortion of C2 allele at TGFalpha TaqI locus in nsCL/P groups (P > 0.05) was not found. In the family-based association test, C2 allele and offspring C2C1 genotype was not found to be significantly associated with an increase risk of nsCL/P (P > 0.05). CONCLUSION: Our findings did not suggest an association between offspring TGFalpha TaqI variant and the increased risk of nsCL/P in Chinese population.

[Association between parental transforming growth factor alpha gene TaqI variant, paternal smoking and the cleft lip with or without cleft palate].

OBJECTIVE: To study the association between transforming growth factor alpha gene (TGFalpha) TaqI variant and nonsyndromic cleft lip with or without cleft palate (nsCL/P) in Chinese population, and the interaction with parental smoking. METHODS: TGFalpha TaqI variant was detected using RFLP-PCR for DNA samples of the 170 triads with nsCL/P affected child. We performed the transmission/disequilibrium test (TDT) and the family-based association study (FBAT) to test the associations between this variant and risk of nsCL/P. RESULTS: It was not found significant distortion of C2 allele at TGFalpha TaqI locus in nsCL/P groups (P > 0.05), however, by stratified analysis, we found that the rate of C2 allele transmission among nuclear families whose fathers were smoking was 1/5 (0.062 - 0.711) as compared with that among nuclear families whose fathers were not smoking, and the OR of interaction between TGFalpha variant and parental smoking is 0.102 (0.017 - 0.619). CONCLUSION: The parental smoking may interact with TGFalpha variants of Chinese populations in occurrence of nsCL/P, but it remains to have more investigations.

[Study on reduced folate carrier gene (RFC1) polymorphism in the southern and northern Chinese population].

OBJECTIVE: To describe the distribution of reduced folate carrier gene (RFC1)genotype and allele frequency between southern and northern, female and male Chinese population. METHOD: RFC1 (A80G) genotype was detected, using polymerase chain reaction-restriction fragment length polymorphism (RFLP-PCR) on 720 blood spot DNA from the normal subjects. RESULTS: The frequencies of the northern population with AA, GG and GA genotypes were 22.28%, 31.09% and 46.63%, and the frequencies of the southern population were 18.56%, 22.75% and 58.68%, respectively. Findings showed that there were significant differences between southerners and northerners in RFC1 (A80G) genotype (P < 0.01). There was no significant difference between G allele frequency of the northern (52.10%) and southern population (54.40%). The frequencies of male with RFC1 (A80G) AA, GG and GA genotype were 24.88%, 25.85% and 49.27%, and among female were 18.83%, 27.77% and 53.40%, respectively. There were no significant differences between male and female in RFC1 genotype (P > 0.05), or between G allele frequency in female (50.49%) and that in male (54.47%). CONCLUSIONS: The distribution of RFC1 genotype seemed to be consistent with neural tube defects (NTDs) while its prevalence among the northerners was higher than that of southerners, with female having a higher NTDs prevalence. This study provided genetic epidemiological data for etiological hypothesis between RFC1 and diseases relative to folate metabolism.

[Study on the association between reduced folate carrier gene polymorphism and congenital heart defects and cleft lip with or without cleft palate].

OBJECTIVE: To study the association between reduced folate carrier gene (RFC1) polymorphism and congenital heart defects (CHD) as well as cleft lip with or without cleft palate (CLP) and to provide epidemiological evidence on genetic markers of CHD and CLP. METHODS: RFC1 (A80G) genotype was detected using RFLP-PCR for blood DNA of the 67 triads with nonsyndromic CHD-affected child, the 82 triads with child-affected cleft lip with or without CLP and the 100 control families without child-affected birth defects. We performed a family-based association test and analyzed the interaction between RFC1 A80G genotype and maternal periconceptional supplementation of folic acid. RESULTS: Offspring of mothers who did not take folic acid had an elevated risk for CHD when comparing with offspring of mothers who did (OR = 2.68, 95% CI: 1.14 - 6.41). There was a statistical association between the risk of CHD and maternal periconceptional folic acid supplementation (chi(2) = 6.213, P < 0.05). In the family-based association test, G allele was positively associated with an increased risk for children CHD (Z = 2.140, P < 0.05) while G allele of RFC1 (A80G) polymorphism might increase the risk for CHD. Elevated risks for either CLP group were not observed between RFC1 genotype using or not using folic acid. CONCLUSION: Our findings suggested that the G allele was likely to be a genetically susceptible allele for CHD. There was possible association between offspring with GG, GA genotype and maternal periconceptional folicacid deficiency.

[The epidemiology of neural tube defects in high-prevalence and low-prevalence areas of China].

OBJECTIVE: To describe the epidemiology of neural tube defects (NTDs) in high- and low-prevalence areas of China. METHODS: Birth defects surveillance data, collected from 1992 through 1994 was analyzed. These data were collected as part of the Sino-American cooperative project on NTDs prevention. We classified NTDs as anencephaly, encephalocele, high-level and low-level spina bifida (SB) according to location of the lesion (high vs low) and whether the defect was isolated or occurred in association with other birth defects. Rates were compared in the high-prevalence (North) region and the low-prevalence (South) region, after adjusted for classification, urban and rural, season and sex, and calculated the adjusted rate of NTDs. RESULTS: Among seven hundred and eighty-four NTDs cases in 326 874 recorded births (include in livebirth, stillbirth and fetal death with a gestational age of at least 20 weeks), the overall NTDs prevalence in the North was 5.57/1,000 births, and in the South was 0.88/1 000. There were also significant differences in the prevalence of anencephaly, encephalocele, high-level and low-level SB between North (0.97, 0.49, 2.75 and 1.11/1,000 birth) and South (0.36, 0.15, 0.21 and 0.14/1,000 birth) (P < 0.01), with adjusted prevalences in the North 3 - 7 times higher than those in the South. There were significant difference between urban (2.04) and rural areas (6.57/1,000 birth) in the North (P < 0.01), urban (0.52) and rural areas (0.95/1,000 birth) in the South (P < 0.05). Adjusted prevalence rates in the rural were 3 - 4 times higher than those of urban in the North and 1.6 - 1.9 times higher than in the South; The seasonal rate of high-level SB increased between September and November in the North (3.44/1,000 birth), while the seasonal rate of anencephaly decreased between September and November (0.18/1,000 birth) in the South. However there were no seasonal changes in other classified NTDs both in the South and North. CONCLUSIONS: The birth prevalence of NTDs in the North of China was the highest in the world. There were significant differences between the North and the South, urban and rural. There was seasonal change in high-level SB in the North, which was in accordance to the phenotype of NTDs. It was suggested that there might exist etiological heterogeneity among anecephalus, low- and high-level SB.