Longitudinal semen parameter assessments and live birth: variability and implications for treatment strategies.

OBJECTIVE: To examine whether semen parameters are associated with live birth among couples seeking infertility treatment after accounting for semen parameter variability. DESIGN: Folic Acid and Zinc Supplementation Trial (FAZST) prospective cohort. SETTING: Four US reproductive endocrinology and infertility care study centers, 2013-2017. PATIENT(S): Couples (n = 2,369) seeking fertility consultations at 4 US infertility care study centers. INTERVENTION(S): Semen volume, pH, sperm viability, morphology, progressive and total motility, concentration, count, and total and progressive motile count assessed at baseline and at 2, 4, and 6 months after enrollment. MAIN OUTCOME MEASURE(S): Log-binomial models stratified by fertility treatment received (in vitro fertilization [IVF], intrauterine insemination [IUI], ovulation induction [OI], or no treatment) estimated risk differences (RDs) between semen parameter quartiles and live birth and accounted for multiple semen assessments per person. We accounted for abstinence time, the biological interdependence of semen parameters, and potential selection bias because of loss to follow-up. RESULT(S): Among couples using OI only or no treatment, 39% had a live birth, and relative to the highest quartile, the lowest quartiles of morphology (RD, -19 [95% CI, -23 to -15] per 100 couples), motility (RD, -13 [95% CI, -17 to -9]), concentration (RD, -22 [95% CI, -26 to -19]), and total motile count (RD, -18 [95% CI, -22 to -14]) were associated with fewer live births. For IUI, 26% had a live birth, and the lowest quartiles of volume (RD, -6 [95% CI, -11 to -0.4]), concentration (RD, -6 [95% CI, -11 to -0.1]), count (RD, -10 [95% CI, -15 to -4]), and total motile count (RD, -7 [95% CI, -13 to -1]) were associated with fewer live births. For IVF, 61% had a live birth, and only morphology (Q1 RD, -7 [95% CI, -14 to 0.2]; Q2 RD, -10 [95% CI, -17 to -2.2]) was associated with live birth. CONCLUSION(S): Semen parameters are critical in couples undergoing OI/IUI. Only low morphology was important for live birth after IVF. Although data supporting the use of semen parameters are fragmented across differing populations, current findings are generalizable across the range of male fertility and couple fertility treatments, providing evidence about which semen parameters are most relevant in which settings. CLINICAL TRIAL REGISTRATION NUMBER: NCT#01857310.

The impact of zinc and folic acid supplementation on sperm DNA methylation: results from the folic acid and zinc supplementation randomized clinical trial (FAZST).

OBJECTIVE: To determine if 6-month folic acid (5 mg) and zinc (30 mg) supplementation impacts sperm DNA methylation patterns. DESIGN: A multicenter, double-blind, block randomized, placebo-controlled trial titled "The Folic Acid and Zinc Supplementation Trial (FAZST)." SETTING: Infertility care centers. PATIENT(S): Male partners (18 years and older) from heterosexual couples (female partners aged 18-45 years) seeking fertility treatment were recruited. INTERVENTION(S): Men were randomized 1:1 to receive folic acid (5 mg) and elemental zinc (30 mg) (n = 713) or a matching placebo (n = 757) daily for 6 months. MAIN OUTCOME MEASURE(S): Sperm DNA methylation was analyzed using the EPIC methylation array (Illumina) at 6 months. Differential sperm DNA methylation was assessed at multiple levels (regional, single cytosine phosphate guanine, etc.). We additionally assessed the impact of supplementation on epigenetic age. RESULT(S): No significant differences were identified between the treatment and placebo groups although some trends appeared to be present. To determine if these trends were noteworthy, we implemented various permutations and found that the patterns we identified were no more than would be expected by random chance. CONCLUSION(S): The data presented here strongly suggest that this supplementation regimen is not effective at altering sperm DNA methylation. These data comport well with previous findings from the FAZST study that found no impact of supplementation on basic semen analysis parameters or live birth. CLINICAL TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Identifier: NCT01857310.

Investigating Genetic Determinants of Plasma Inositol Status in Adult Humans.

BACKGROUND: Myo-inositol (MI) is incorporated into numerous biomolecules, including phosphoinositides and inositol phosphates. Disturbance of inositol availability or metabolism is associated with various disorders, including neurological conditions and cancers, whereas supplemental MI has therapeutic potential in conditions such as depression, polycystic ovary syndrome, and congenital anomalies. Inositol status can be influenced by diet, synthesis, transport, utilization, and catabolism. OBJECTIVES: We aimed to investigate potential genetic regulation of circulating MI status and to evaluate correlation of MI concentration with other metabolites. METHODS: GC-MS was used to determine plasma MI concentration of >2000 healthy, young adults (aged 18-28 y) from the Trinity Student Study. Genotyping data were used to test association of plasma MI with single nucleotide polymorphisms (SNPs) in candidate genes, encoding inositol transporters and synthesizing enzymes, and test for genome-wide association. We evaluated potential correlation of plasma MI with d-chiro-inositol (DCI), glucose, and other metabolites by Spearman rank correlation. RESULTS: Mean plasma MI showed a small but significant difference between males and females (28.5 and 26.9 µM, respectively). Candidate gene analysis revealed several nominally significant associations with plasma MI, most notably for SLC5A11 (solute carrier family 5 member 11), encoding a sodium-coupled inositol transporter, also known as SMIT2 (sodium-dependent myo-inositol transporter 2). However, these did not survive correction for multiple testing. Subsequent testing for genome-wide association with plasma MI did not identify associations of genome-wide significance (P < 5 × 10-8). However, 8 SNPs exceeded the threshold for suggestive significant association with plasma MI concentration (P < 1 × 10-5), 3 of which were located within or close to genes: MTDH (metadherin), LAPTM4B (lysosomal protein transmembrane 4 ß), and ZP2 (zona pellucida 2). We found significant positive correlation of plasma MI concentration with concentration of dci and several other biochemicals including glucose, methionine, betaine, sarcosine, and tryptophan. CONCLUSIONS: Our findings suggest potential for modulation of plasma MI in young adults by variation in SLC5A11, which is worthy of further investigation.

Requirement of FAT and DCHS protocadherins during hypothalamic-pituitary development.

Pituitary developmental defects lead to partial or complete hormone deficiency and significant health problems. The majority of cases are sporadic and of unknown cause. We screened 28 patients with pituitary stalk interruption syndrome (PSIS) for mutations in the FAT/DCHS family of protocadherins that have high functional redundancy. We identified seven variants, four of which putatively damaging, in FAT2 and DCHS2 in six patients with pituitary developmental defects recruited through a cohort of patients with mostly ectopic posterior pituitary gland and/or pituitary stalk interruption. All patients had growth hormone deficiency and two presented with multiple hormone deficiencies and small glands. FAT2 and DCHS2 were strongly expressed in the mesenchyme surrounding the normal developing human pituitary. We analyzed Dchs2-/- mouse mutants and identified anterior pituitary hypoplasia and partially penetrant infundibular defects. Overlapping infundibular abnormalities and distinct anterior pituitary morphogenesis defects were observed in Fat4-/- and Dchs1-/- mouse mutants but all animal models displayed normal commitment to the anterior pituitary cell type. Together our data implicate FAT/DCHS protocadherins in normal hypothalamic-pituitary development and identify FAT2 and DCHS2 as candidates underlying pituitary gland developmental defects such as ectopic pituitary gland and/or pituitary stalk interruption.

Perspective: Time to Resolve Confusion on Folate Amounts, Units, and Forms in Prenatal Supplements.

Folate-containing prenatal supplements are commonly consumed in the United States, but inconsistencies in units of measure and chemical forms pose challenges for providing authoritative advice on recommended amounts. New regulations require folate to be declared as micrograms of dietary folate equivalents (DFE) on product labels, whereas intake recommendations for reducing the risk of neural tube defects (NTDs) and the Tolerable Upper Intake Level are expressed as micrograms of folic acid. Today, >25% of prenatal supplements contain folate as synthetic salts of L-5-methyltetrahydrofolate (L-5-MTHF), but recommendations do not include this form of the vitamin. Harmonizing units of measure and addressing newer forms of folate salts in intake recommendations and in the prevention of NTDs would resolve the confusion.

Effect of Folic Acid and Zinc Supplementation in Men on Semen Quality and Live Birth Among Couples Undergoing Infertility Treatment: A Randomized Clinical Trial.

Importance: Dietary supplements marketed for male fertility commonly contain folic acid and zinc based on limited prior evidence for improving semen quality. However, no large-scale trial has examined the efficacy of this therapy for improving semen quality or live birth. Objective: To determine the effect of daily folic acid and zinc supplementation on semen quality and live birth. Design, Setting, and Participants: The Folic Acid and Zinc Supplementation Trial was a multicenter randomized clinical trial. Couples (n = 2370; men aged ≥18 years and women aged 18-45 years) planning infertility treatment were enrolled at 4 US reproductive endocrinology and infertility care study centers between June 2013 and December 2017. The last 6-month study visit for semen collection occurred during August 2018, with chart abstraction of live birth and pregnancy information completed during April 2019. Interventions: Men were block randomized by study center and planned infertility treatment (in vitro fertilization, other treatment at a study site, and other treatment at an outside clinic) to receive either 5 mg of folic acid and 30 mg of elemental zinc (n = 1185) or placebo (n = 1185) daily for 6 months. Main Outcomes and Measures: The co-primary outcomes were live birth (resulting from pregnancies occurring within 9 months of randomization) and semen quality parameters (sperm concentration, motility, morphology, volume, DNA fragmentation, and total motile sperm count) at 6 months after randomization. Results: Among 2370 men who were randomized (mean age, 33 years), 1773 (75%) attended the final 6-month study visit. Live birth outcomes were available for all couples, and 1629 men (69%) had semen available for analysis at 6 months after randomization. Live birth was not significantly different between treatment groups (404 [34%] in the folic acid and zinc group and 416 [35%] in the placebo group; risk difference, -0.9% [95% CI, -4.7% to 2.8%]). Most of the semen quality parameters (sperm concentration, motility, morphology, volume, and total motile sperm count) were not significantly different between treatment groups at 6 months after randomization. A statistically significant increase in DNA fragmentation was observed with folic acid and zinc supplementation (mean of 29.7% for percentage of DNA fragmentation in the folic acid and zinc group and 27.2% in the placebo group; mean difference, 2.4% [95% CI, 0.5% to 4.4%]). Gastrointestinal symptoms were more common with folic acid and zinc supplementation compared with placebo (abdominal discomfort or pain: 66 [6%] vs 40 [3%], respectively; nausea: 50 [4%] vs 24 [2%]; and vomiting: 32 [3%] vs 17 [1%]). Conclusions and Relevance: Among a general population of couples seeking infertility treatment, the use of folic acid and zinc supplementation by male partners, compared with placebo, did not significantly improve semen quality or couples' live birth rates. These findings do not support the use of folic acid and zinc supplementation by male partners in the treatment of infertility. Trial Registration: ClinicalTrials.gov Identifier: NCT01857310.

A Randomized Trial to Evaluate the Effects of Folic Acid and Zinc Supplementation on Male Fertility and Livebirth: Design and Baseline Characteristics.

The Folic Acid and Zinc Supplementation Trial (FAZST) was a multicenter, double-blind, block-randomized, placebo-controlled trial to determine whether folic acid and zinc supplementation in men improves semen quality and increases livebirth rate among couples seeking infertility treatment (2013-2017). Eligible men were aged 18 years or older with female partners aged 18-45 years, seeking infertility treatment. Men were randomized (1:1) to 5 mg folic acid and 30 mg elemental zinc daily or matching placebo for 6 months. Randomization was stratified by site and intended infertility treatment (in vitro fertilization (IVF), non-IVF/study site, and non-IVF/outside clinic). Follow-up of men continued for 6 months, and female partners were passively followed for a minimum of 9 months. Women who conceived were followed throughout pregnancy. Overall, 2,370 men were randomized during 2013-2017 (1,185 folic acid and zinc, 1,185 placebo); they had a mean age of 33 years and body mass index (weight (kg)/height (m)2) of 29.8. Most participants were white (82%), well educated (83% with some college), and employed (72%). Participant characteristics were balanced across intervention arms. Study visits were completed by 89%, 77%, and 75% of men at months 2, 4, and 6, respectively. Here we describe the study design, recruitment, data collection, lessons learned, and baseline participant characteristics.

Prepregnancy Habitual Intakes of Total, Supplemental, and Food Folate and Risk of Gestational Diabetes Mellitus: A Prospective Cohort Study.

OBJECTIVE: To identify novel modifiable risk factors of gestational diabetes mellitus (GDM) by examining the association between prepregnancy habitual folate intake and GDM risk. RESEARCH DESIGN AND METHODS: The study included 14,553 women in the Nurses' Health Study II who reported at least one singleton pregnancy between the 1991 and 2001 questionnaires. Prepregnancy intakes of total folate, supplemental folate, and food folate were assessed using a food frequency questionnaire administered every 4 years. Incident GDM was ascertained from a self-reported physician diagnosis. Relative risks (RRs) of GDM were estimated using log-binomial models, with adjustment for demographic, lifestyle, and dietary factors. RESULTS: Over the study follow-up, 824 incident GDM cases were reported among 20,199 pregnancies. Women with adequate total folate intake (≥400 µg/day) had an RR of GDM of 0.83 (95% CI 0.72, 0,95, P = 0.007) compared with women with inadequate intake (<400 µg/day). This association was entirely driven by supplemental folate intake. The RRs of GDM for 1-399, 400-599, and ≥600 µg/day of supplemental folate intake were 0.83, 0.77, and 0.70, respectively, compared with no supplemental folate intake (P trend = 0.002). The association between supplemental folate intake and GDM risk largely persisted after additional adjustment for intake of multivitamins and other micronutrients, as well as among women who likely planned for the pregnancy. CONCLUSIONS: Higher habitual intakes of supplemental folate before pregnancy were significantly associated with lower GDM risk. If confirmed, these findings indicate that prepregnancy folic acid supplementation could offer a novel and low-cost avenue to reduce GDM risk.

Lifestyle, metabolite, and genetic determinants of formate concentrations in a cross-sectional study in young, healthy adults.

Background: Formate is an important metabolite that serves as a donor of one-carbon groups to the intracellular tetrahydrofolate pool. However, little is known of its circulating concentrations or of their determinants. Objective: This study aimed to define formate concentrations and their determinants in a healthy young population. Design: Serum formate was measured in 1701 participants from the Trinity Student Study. The participants were men and women, aged 18 to 28 y, enrolled at Trinity College, Dublin. Formate concentrations were compared with other one-carbon metabolites, vitamin status, potential formate precursors, genetic polymorphisms, and lifestyle factors. Results: Serum formate concentrations ranged from 8.7 to 96.5 µM, with a mean of 25.9 µM. Formate concentrations were significantly higher in women than in men; oral contraceptive use did not further affect them. There was no effect of smoking or of alcohol ingestion, but the TT genotype of the methylenetetrahydrofolate reductase (MTHFR) 677C→T (rs1801133) polymorphism was associated with a significantly decreased formate concentration. Formate was positively associated with potential metabolic precursors (serine, methionine, tryptophan, choline) but not with glycine. Formate concentrations were positively related to serum folate and negatively related to serum vitamin B-12. Conclusions: Formate concentrations were sensitive to the concentrations of metabolic precursors. In view of the increased susceptibility of women with the TT genotype of MTHFR to give birth to infants with neural tube defects as well as the effectiveness of formate supplementation in decreasing the incidence of folate-resistant neural tube defects in susceptible mice, it will be important to understand how this genotype decreases the serum formate concentration. This trial was registered at www.clinicaltrials.gov as NCT03305900.

Prepregnancy habitual intake of vitamin D from diet and supplements in relation to risk of gestational diabetes mellitus: A prospective cohort study.

BACKGROUND: Vitamin D may play a pivotal role in regulating insulin secretion and insulin sensitivity. However, the effect of vitamin D intake, either from the diet or from supplements, on the development of gestational diabetes mellitus (GDM) remains unclear. We prospectively examined the association of prepregnancy habitual intake of vitamin D from diet and supplements with the risk of incident GDM in a well-established cohort. METHODS: The present study was performed on 21 356 singleton pregnancies from 15 225 women in the Nurses' Health Study II cohort. Diet information, including vitamin D intake from food sources and supplements, was assessed in 1991 and every 4 years thereafter by validated food frequency questionnaires. Log-binomial models with generalized estimating equations were used to estimate relative risks (RRs) and 95% confidence intervals (CIs). RESULTS: During 10 years of follow-up, 865 incident GDM cases were documented. After adjustment for age, parity, race/ethnicity, family history of diabetes, dietary and lifestyle factors, and body mass index, the RRs (95% CIs) of GDM risk associated with supplemental vitamin D intake of 0, 1-399, and ≥400 IU/day were 1.00 (reference), 0.80 (0.67-0.96), and 0.71 (0.56-0.90), respectively (Ptrend = 0.002). Dietary and total vitamin D intakes were also inversely associated with GDM risk, but the associations were not statistically significant. CONCLUSIONS: Prepregnancy supplemental vitamin D intake was significantly and inversely associated with risk of GDM. This study indicates potential benefits of increasing vitamin D intake from supplements in the prevention of GDM in women of reproductive age.

Folate, homocysteine and the ovarian cycle among healthy regularly menstruating women.

STUDY QUESTION: How are concentrations of plasma homocysteine and serum folate associated with reproductive hormones and anovulation in regularly menstruating women? SUMMARY ANSWER: Higher homocysteine was associated with sporadic anovulation and hormonal changes that may be indicative of impaired ovulatory function, but higher serum folate was associated only with higher luteal phase progesterone. WHAT IS KNOWN ALREADY: Higher folate levels as well as some variants in genes relevant to one-carbon metabolism, are associated with improved reproductive outcomes and responses to fertility treatment, but only a few small studies have explored the relationship between markers of one-carbon metabolism and menstrual cycle characteristics. STUDY DESIGN, SIZE, DURATION: The BioCycle Study (2005-2007) is a prospective, longitudinal cohort of 259 regularly menstruating women not using hormonal contraceptives or dietary supplements who were followed for up to two menstrual cycles. PARTICIPANTS/MATERIALS, SETTING, METHODS: Serum folate and reproductive hormones were measured up to eight times per cycle and plasma homocysteine up to three times. Linear mixed models were used to estimate associations between serum folate or plasma homocysteine and log-transformed reproductive hormone levels while accounting for multiple observations and cycles per woman. Generalized estimating equations were used to examine risk of sporadic anovulation. All models were adjusted for age, race, body mass index, cigarette and alcohol use, and energy and fiber intake. MAIN RESULTS AND THE ROLE OF CHANCE: Higher plasma homocysteine concentrations were associated with lower total estradiol across the cycle (adjusted percent change per unit increase in homocysteine [aPC] -2.3%, 95% CI: -4.2, -0.03), higher follicle stimulating hormone around the time of expected ovulation (aPC 2.4%, 95% CI: 0.2, 4.7) and lower luteal phase progesterone (aPC -6.5%, 95% CI: -11.1, -1.8). Higher serum folate concentrations were associated with higher luteal phase progesterone (aPC per unit increase in folate 1.0%, 95% CI: 0.4, 1.6). Higher homocysteine concentrations at expected ovulation were associated with a 33% increased risk of sporadic anovulation. We observed no risk associated with decreased folate concentrations, but a higher ratio of folate to homocysteine at ovulation was associated with a 10% decreased risk of anovulation. LIMITATIONS, REASONS FOR CAUTION: Our results are generalizable to healthy women with adequate serum folate levels. The independent influence of homocysteine should be confirmed in larger cohorts and among women with folate deficiency or increased risks of anovulation. WIDER IMPLICATIONS OF THE FINDINGS: If these findings are confirmed, it is possible that lowering homocysteine with B-vitamins through diet or supplementation could improve ovulatory function in some women. Study FUNDING/COMPETING INTEREST(S): This work was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (Contract numbers: HHSN275200403394C, HHSN275201100002I and Task one HHSN27500001). None of the authors has any conflicts of interest to disclose.

Biomarkers of Nutrition for Development-Folate Review.

The Biomarkers of Nutrition for Development (BOND) project is designed to provide evidence-based advice to anyone with an interest in the role of nutrition in health. Specifically, the BOND program provides state-of-the-art information and service with regard to selection, use, and interpretation of biomarkers of nutrient exposure, status, function, and effect. To accomplish this objective, expert panels are recruited to evaluate the literature and to draft comprehensive reports on the current state of the art with regard to specific nutrient biology and available biomarkers for assessing nutrients in body tissues at the individual and population level. Phase I of the BOND project includes the evaluation of biomarkers for 6 nutrients: iodine, iron, zinc, folate, vitamin A, and vitamin B-12. This review represents the second in the series of reviews and covers all relevant aspects of folate biology and biomarkers. The article is organized to provide the reader with a full appreciation of folate's history as a public health issue, its biology, and an overview of available biomarkers (serum folate, RBC folate, and plasma homocysteine concentrations) and their interpretation across a range of clinical and population-based uses. The article also includes a list of priority research needs for advancing the area of folate biomarkers related to nutritional health status and development.

The Dihydrofolate Reductase 19 bp Polymorphism Is Not Associated with Biomarkers of Folate Status in Healthy Young Adults, Irrespective of Folic Acid Intake.

BACKGROUND: Dihydrofolate reductase (DHFR) is essential for the conversion of folic acid to active folate needed for one-carbon metabolism. Common genetic variation within DHFR is restricted to the noncoding regions, and previous studies have focused on a 19 bp deletion/insertion polymorphism (rs70991108) within intron 1. Reports of an association between this polymorphism and blood folate biomarker concentrations are conflicting. OBJECTIVE: In this study, we evaluated whether the DHFR 19 bp deletion/insertion polymorphism affects circulating folate biomarkers in, to our knowledge, the largest cohort to address this question to date. METHODS: Healthy young Irish individuals (n = 2507) between 19 and 36 y of age were recruited between February 2003 and February 2004. Folic acid intake from supplements and fortified foods was assessed with the use of a customized food intake questionnaire. Concentrations of serum folate and vitamin B-12, red blood cell (RBC) folate, and plasma total homocysteine (tHcy) were measured. Data were analyzed with the use of linear regression models. RESULTS: Folic acid intake was positively associated with serum (P < 0.0001) and RBC (P = 0.0005) folate concentration and was inversely associated with plasma tHcy (P = 0.001) as expected. The DHFR 19 bp polymorphism was not significantly associated with either serum (P = 0.82) or RBC (P = 0.21) folate, or plasma tHcy (P = 0.20), even in those within the highest quintile of folic acid intake (>326 µg folic acid/d; P = 0.96). A nonsignificant trend toward lower RBC folate by genotype (P = 0.09) was observed in the lowest folic acid intake quintile (0-51 µg/d). CONCLUSION: In this cohort of healthy young individuals, the DHFR 19 bp deletion allele did not significantly affect circulating folate status, irrespective of folic acid intake. Our data rule out a strong functional effect from this polymorphism on blood folate concentrations.

B-vitamin status and bone mineral density and risk of lumbar osteoporosis in older females in the United States.

BACKGROUND: Previous data suggest that elevated serum total homocysteine (tHcy) may be a risk factor for bone fracture and osteoporosis. Nutritional causes of elevated tHcy are suboptimal B-vitamin status. To our knowledge, this is the first nationally representative report on the relation of B vitamins and bone health from a population with folic acid fortification. OBJECTIVE: The purpose of this analysis was to examine the relation between B-vitamin status biomarkers and bone mineral density (BMD), risk of osteoporosis, and biomarkers of bone turnover. DESIGN: We examined the relation of tHcy, methylmalonic acid (MMA), and serum/red blood cell folate and total-body and lumbar spine BMD in women aged ≥50 y participating in the NHANES 1999-2004 (n = 2806), a nationally representative cross-sectional survey. These are the only years with concurrent measurement of tHcy and whole-body dual-energy X-ray absorptiometry. We also examined B-vitamin biomarkers relative to bone turnover markers, bone alkaline phosphatase, and urinary N-terminal cross-linked telopeptide of type I collagen in a 1999-2002 subset with available data (n = 1813). RESULTS: In comparison with optimal concentrations, women with elevated tHcy were older with lower serum vitamin B-12, red blood cell folate, and dietary micronutrient intakes and had significantly higher mean ± SE markers of bone turnover (bone alkaline phosphatase: 15.8 ± 0.59 compared with 14.0 ± 0.25 µg/L; urinary N-terminal cross-linked telopeptide of type I collagen: 48.2 ± 2.9 compared with 38.9 ± 0.90 nmol bone collagen equivalents per mmol creatinine/L). Elevated MMA (OR: 1.88; 95% CI: 1.10, 3.18) and tHcy (OR: 2.17; 95% CI: 1.14, 4.15) were related to increased risk of lumbar osteoporosis. When examined as a continuous variable, tHcy was negatively associated, serum folates were positively associated, and MMA and vitamin B-12 were not significantly associated with lumbar and total-body BMD. CONCLUSION: In this nationally representative population of older US women with high exposure to B vitamins through food fortification and dietary supplements, only elevated tHcy and MMA were independently associated with risk of lumbar spine osteoporosis.

Common Variants at Putative Regulatory Sites of the Tissue Nonspecific Alkaline Phosphatase Gene Influence Circulating Pyridoxal 5'-Phosphate Concentration in Healthy Adults.

BACKGROUND: Vitamin B-6 interconversion enzymes are important for supplying pyridoxal 5'-phosphate (PLP), the co-enzyme form, to tissues. Variants in the genes for these enzymes [tissue nonspecific alkaline phosphatase (ALPL), pyridoxamine 5'-phosphate oxidase, pyridoxal kinase, and pyridoxal phosphatase] could affect enzyme function and vitamin B-6 status. OBJECTIVES: We tested whether single-nucleotide polymorphisms (SNPs) in these genes influence vitamin B-6 status markers [plasma PLP, pyridoxal (PL), and 4-pyridoxic acid (PA)], and explored potential functional effects of the SNPs. METHODS: Study subjects were young, healthy adults from Ireland (n = 2345). We measured plasma PLP, PL, and PA with liquid chromatography-tandem mass spectrometry and genotyped 66 tag SNPs in the 4 genes. We tested for associations with single SNPs in candidate genes and also performed genome-wide association study (GWAS) and gene-based analyses. RESULTS: Seventeen SNPs in ALPL were associated with altered plasma PLP in candidate gene analyses (P < 1.89 × 10(-4)). In the GWAS, 5 additional ALPL SNPs were associated with altered plasma PLP (P < 5.0 × 10(-8)). Gene-based analyses that used the functional linear model ß-spline (P = 4.04 × 10(-15)) and Fourier spline (P = 5.87 × 10(-15)) methods also showed associations between ALPL and altered plasma PLP. No SNPs in other genes were associated with plasma PLP. The association of the minor CC genotype of 1 ALPL SNP, rs1256341, with reduced ALPL expression in the HapMap Northern European ancestry population is consistent with the positive association between the CC genotype and plasma PLP in our study (P = 0.008). No SNP was associated with altered plasma PL or PA. CONCLUSIONS: In healthy adults, common variants in ALPL influence plasma PLP concentration, the most frequently used biomarker for vitamin B-6 status. Whether these associations are indicative of functional changes in vitamin B-6 status requires more investigation.