PLP Concentrations Research Articles

A proteomic approach identifies plasma proteins correlated with vitamin B6 in Nepalese children (804.14)

Vitamin B6 is a coenzyme for >140 distinct enzymes involved in amino acid metabolism. In the plains of Nepal, we have reported 43% of children age 6‐8 years of age to be B6 deficient (pyridoxal‐5’‐phosphate, PLP <20nmol/L), revealing a public health problem. This study identified differentially abundant plasma proteins in relation to B6 status in 500 6‐8 yr old Nepalese children that represent possible B6 biomarkers with the potential to predict B6 status. Plasma PLP concentration was analyzed by HPLC, and relative abundance of plasma proteins by isobaric tags for relative and absolute quantification (iTRAQ) tandem mass spectrometry. A total of 87 proteins were associated with PLP (for all, q<0.1, p<0.008), defining a plasma B6 proteome: 39 and 48 were positively and negatively correlated (r from 0.51 to 0.29 and ‐0.56 to ‐0.21) with PLP, respectively. Identified proteins are involved in numerous metabolic pathways, including cell proliferation, proteolysis, adhesion, acute phase reaction, coagulation and transport. Linear mixed effects analysis estimated ~60% of the variance (R²) in plasma PLP could be estimated by the relative abundance of 5 proteins (complement 9, cyclin D‐type binding‐protein 1, dynein, axonemal, heavy chain 10, leucine rich repeat containing 47, and NOP2/Sun domain family, member 6). A predictive plasma PLP proteome may exist for assessing population B6 status.Grant Funding Source: Supported by Bill and Melinda Gates Foundation Grants 614 and 5241

Smokeless Tobacco Use: A Risk Factor for Hyperhomocysteinemia in a Pakistani Population

BackgroundSmokeless tobacco (ST) use is highly prevalent in the South Asian populations. While there have been a number of reports on association of ST consumption with cancer, very few studies have been conducted to investigate its relationship with cardiovascular disease. Hyperhomocysteinemia is a well-recognized risk factor for cardiovascular disease; however, its association with ST use has never been investigated. The objective of this study was to evaluate the relationship of ST use with hyperhomocysteinemia in an urban Pakistani population.Methodology/Principal FindingsIn a cross-sectional study for assessment of risks of hyperhomocysteinemia, 872 healthy adults (355 males and 517 females of age range 18–60 years) were recruited from a low-income population in Karachi, Pakistan. A detailed questionnaire was administered which included information about smoking, non-smoking, use of ST alone (chewing as well as sniffing) and use of ST with betel nuts. Fasting serum/plasma levels of homocysteine, folate, vitamin B12 and pyridoxal phosphate (PLP; a coenzymic form of vitamin B6) were analyzed. In this population, 43.4% males and 15.5% females were found to be regular users of ST products. Laborers and vendors were the major ST consumers. Smoking was not found to be associated with plasma/serum concentrations of homocysteine, folate, vitamin B12 and PLP. However, homocysteine concentrations in the group which consumed ST alone and the group which consumed ST along with betel nut were significantly higher compared to the non-user group (17.7±7.5 µmol/L, 25.48 µmol/L vs. 11.95 µmol/L, respectively; p<0.01). Odds ratio for the association of hyperhomocysteinemia (>15 µmol/L) was 11-fold higher in the ST-consumer group compared to the non-user group, [OR (95%CI) = 11.34 (7.58–16.96); p<0.001], when the model was adjusted for age, gender, folate and vitamin B12 status.ConclusionThis study shows a positive association between ST consumption and hyperhomocysteinemia in a low-income urban Pakistani population.

Dietary Vitamin B6 intake modulates colonic inflammation in the IL10−/− model of Inflammatory Bowel Disease

Pyridoxal‐5‐phosphate, the biologically active form of vitamin B6, serves as a cofactor for over 140 distinct biochemical reactions. Although severe vitamin B6 deficiency is rare, mild inadequacy (plasma PLP &lt; 20 nmol/L) is observed in 19–27% of the US population, depending on age and sex. Plasma PLP concentrations are inversely related to markers of systemic inflammation such as CRP. Furthermore, plasma PLP is depleted in those with inflammatory conditions and, in the case of inflammatory bowel disease (IBD), more so in those with active versus quiescent disease. Restricting B6 intake has been shown to attenuate IBD pathology in mice; however the effects of supplementation are unclear. Thus, we tested the effect of mild inadequacy and moderate supplementation of vitamin B6 on the severity of colonic inflammation in the IL10−/− mouse model of IBD. We observed a bell‐shaped relationship between histologic inflammation and expression of inflammatory mediators (TNFalpha, IL‐6, IFN‐gamma, COX‐2, iNOS), whereby both low and high plasma PLP was associated with a suppression of inflammation. These results raise the possibility that vitamin B6 supplementation might be used to complement existing therapies for the treatment of IBD. Studies to reproduce these results and uncover mechanisms are underway.

Vitamin B1 Deficiency Does not Affect the Liver Concentrations of the Other Seven Kinds of B-Group Vitamins in Rats

We aimed to determine the effects of vitamin B1 deficiency on vitamin contents of urine, liver, and blood. In the current study, rats were divided into 3 groups (n = 5, each group): the first was freely fed a complete diet (ad lib-fed control group); the second freely fed a vitamin B1-free diet (vitamin B1 deficient group); and the third pair-fed a complete diet with the same amounts of the vitamin B1 deficient group (pair-fed control group). The experimental period was for 15 days. The blood concentrations of vitamin B2, PLP, vitamin B12, folic acid, and biotin were lower in the pair-fed control than in the ad lib-fed control and those of nicotinamide and pantothenic acid were the same. We conclude that Vitamin B1 deficiency did not affect concentrations of the other B-group vitamins.

Gender and age influence blood folate, vitamin B12, vitamin B6, and homocysteine levels in European adolescents: the Helena Study

It is important to be able to evaluate vitamin status correctly at any age, but this is especially vital during adolescence since there are higher requirements for healthy growth and development. However, there are no currently available B-vitamin reference values for healthy adolescents. The aim of the present study is to assess the vitamin B status in European adolescents in order to contribute to the development of reference values for selected B-vitamins and total homocysteine (tHcy). Within the HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) cross-sectional study, a sub sample of 1051 (499 males, 552 females) adolescents from ten European cities aged 12.5 to 17.49 were analyzed for fasting plasma folate (PF), red blood cell (RBC) folate, serum cobalamin (Cbl), holo-transcobalamin (Holo-TC), Vitamin B6 (PLP), and tHcy. The level of significance was set at P < .05. Following the current cut-off for adults, 2% had low Cbl and 5% had low holo-TC concentrations. Low concentrations of both PF and RBC folate were identified in 10%. Five percent had PLP concentrations <20 nmol/L and 20% <30 nmol/L. Moreover, 5% had high tHcy; median values for the whole sample were: PF 16.0 nmol/L, RBC folate 721.9 nmol/L, Cbl 319 pmol/L, Holo-TC 57.8 pmol/L, and tHcy 6.7 μmol/L. Females had significantly higher median Cbl but lower PLP and tHcy concentrations (P < .01). THcy increased (P < .001) and PF (P < .001) concentrations decreased across age categories. Subjects showed significantly higher tHcy values at the fifth percentile of PF, corresponding with 7.5 nmol/L. Sex and age had an influence on most of the studied biomarkers and should be taken into account. The HELENA percentile distribution is consistent with data from smaller studies and could be used as reference value to characterize B-vitamin status of European adolescents.

Abstract 34: Relationships between biomarkers of diet, one-carbon metabolism, and inflammation within the Women's Health Initiative observational study.

Abstract Background: Folate-mediated one-carbon metabolism is essential for DNA synthesis, repair, and methylation. Perturbations in associated biomarkers have been implicated in increased risk of colorectal cancer. Inflammation, especially related to inflammatory bowel disease, is also implicated as a risk factor for colorectal cancer, and one-carbon nutrients, particularly vitamins B6 and B12, may directly affect inflammatory processes. A concurrent investigation of these two interrelated pathways could yield new information regarding relationships between inflammatory processes and one-carbon metabolism. Objective: To investigate correlations between nutritional, inflammatory, and one-carbon metabolism biomarkers. Methods: A cross-sectional study design was used to explore correlations between biomarkers of nutrition, inflammation and one-carbon metabolism in 1,976 women selected from the 93,676 participants in the Women's Health Initiative Observational Study. Nutritional biomarkers included vitamin B6 (pyridoxal-5'-phosphate [PLP]), vitamin B12, plasma folate, and red blood cell (RBC) folate. C-reactive protein (CRP) and serum amyloid A (SAA) were used as biomarkers of inflammation. Homocysteine and cysteine levels were measured as integrated biomarkers of one-carbon metabolism. All biomarkers were measured using established methods from samples obtained at baseline. SAS 9.2 was used to perform Student's t, Chi-squared, and Spearman rank correlation tests, along with multivariate linear regressions adjusted for age and body mass index (BMI), to explore the relationships between the biomarkers, with statistical significance at p&amp;lt;0.05. Results: Plasma PLP was the only nutritional one-carbon metabolism biomarker to show significant inverse correlations with both CRP and SAA (r=-0.22, -0.12 respectively; p&amp;lt;0.0001). A similar result was also observed when PLP [nmol/L] was regressed on CRP [mg/L] and SAA [mg/L] (adjusted regression coefficient [β]=-1.41, -0.89 respectively; p&amp;lt;0.0001). While cysteine [μmol/L] was significantly correlated with PLP and plasma folate, and showed a significant association with CRP (β=-2.19, p&amp;lt;0.0001), homocysteine [μmol/L] showed significant inverse correlations with all nutritional biomarkers, and was significantly associated with both CRP (β=19.86, p=0.003) and SAA (β=25.62, p&amp;lt;0.0001). Conclusions: Biomarkers of inflammation are associated with concentrations of PLP, cysteine and homocysteine. While these associations between the biomarkers of inflammation, diet, and one-carbon metabolism are promising, determining causality is an important next step. Citation Format: Michael J. Paskow, Clare Abbenhardt, Joshua W. Miller, Xiaoling Song, Elissa C. Brown, Ting-Yuan David Cheng, Mark H. Wener, Yingye Zheng, Adetunji T. Toriola, Marian L. Neuhouser, Shirley A. A. Beresford, Karen Makar, Lynn B. Bailey, David R. Maneval, Ralph Green, JoAnn Manson, Linda Van Horn, Cornelia Ulrich. Relationships between biomarkers of diet, one-carbon metabolism, and inflammation within the Women's Health Initiative observational study. [abstract]. In: Proceedings of the AACR Special Conference on Post-GWAS Horizons in Molecular Epidemiology: Digging Deeper into the Environment; 2012 Nov 11-14; Hollywood, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(11 Suppl):Abstract nr 34.

Highlights of This Issue

Using cases from several Australian pediatric oncology centers, Milne and colleagues investigated the protective effects of maternal folic acid against childhood brain tumors. Their work represents the largest study of its kind and provides evidence of an inverse association between childhood brain tumors and folic acid use before pregnancy. These findings are intriguing given that the folic acid/brain cancer connection is biologically plausible through established mechanisms.Previous studies have suggested that vitamin B6 may reduce the risk of breast cancer. Lurie and colleagues examined the association of plasma concentrations of PLP (an active form of vitamin B6) with postmenopausal breast cancer risk. They report that women with high plasma PLP concentrations had a 30% reduced risk of invasive breast cancer compared with women with lower PLP levels. This association appeared to be limited to cases with hormone receptor–positive tumors. These results suggest a role for vitamin B6 in the prevention of postmenopausal breast cancer and indicate a potential heterogeneity of the association by tumor hormone receptor status.Although cervical infection with high-risk human papillomavirus (HPV) is considered a cause of cervical cancer, smoking has also been associated with cervical cancer. Jensen and colleagues used structured interviews, HPV DNA analysis, and up to 13 years of cervical lesion follow-up to explore the relationships among smoking, HPV, and cervical cancer. The authors report that among woman with persistent, high-risk HPV infection, the risk for future high-grade cervical lesions was associated with both long- term and heavy smoking. This work strengthens the role of smoking in the natural history of HPV and cervical carcinogenesis.In the United States, prostate cancer incidence rates are dramatically low in Latino and Japanese men. To explore the reasons for this, Cheng and colleagues conducted genomewide association studies, tested prostate cancer risk variants, and developed genetic risk models in U.S. Japanese and Latino populations. Although no new genome-wide significant prostate cancer loci were uncovered, the authors report that known risk variants contribute to prostate cancer susceptibility in both populations. This important study helps define the risk alleles that contribute to prostate cancer in Japanese and Latino men.

Oral clefts and maternal biomarkers of folate‐dependent one‐carbon metabolism in utah

Maternal folate intake and related biomarkers have been inconsistently associated with a risk of oral clefts. Maternal concentrations of plasma folate (PF) and erythrocyte folate (EF), plasma pyridoxal-5'-phosphate (PLP; active vitamin B(6) ) and total plasma homocysteine (tHcy) were measured in a Utah study with 347 cases and 469 controls. Risk of all clefts combined, including cleft lip with or without cleft palate (CL/P) and cleft palate only (CP), was 65% lower in the highest versus lowest PF quartile (odds ratio [OR], 0.35; 95% confidence interval [CI], 0.23-0.53; p-trend < 0.001). Results remained significant in the subgroups with isolated CL/P and CP (p-trend < 0.001 in each). EF results were similar. In the highest versus lowest PLP quartile, risk of CP with other malformations was lower (OR, 0.25; 95% CI, 0.07-0.95); however, no other associations were significant for PLP or tHcy. Differences in mean biomarker levels between cases and controls widened with an increasing interval between delivery and maternal blood collection. Decreased cleft risk with increasing quartiles of PF, EF, and PLP and decreasing tHcy was more apparent in mothers with a longer versus shorter interval between the index child delivery and blood collection. Low maternal blood folate concentration was associated with an increased risk of clefts, and the differences in mean case and control PF, EF, PLP, and tHcy concentrations widened over time. Additional mechanistic studies are warranted to elucidate whether an acquired or inherited disorder of folate metabolism plays a role in the etiology of clefts.

Plasma Vitamins, Amino Acids, and Renal Function in Postexercise Hyperhomocysteinemia

Several studies have assessed the effect of the physical activity on plasma homocysteine (Hcy) concentrations, although the findings have been contradictory, and the exact mechanism by which plasma Hcy concentrations varied after an acute intense exercise remains unknown. We studied the effect of different acute aerobic intense exercises on plasma, reduced, and total Hcy (rHcy, tHcy) and cysteine (rCys, tCys) and on its metabolically related vitamins and amino acids. Parallel effects on renal function were assessed by plasma creatinine. Fifteen cyclists and 14 kayakers were examined before and 30 +/- 5 min after a specific test to exhaustion during a low-intensity training period. After a bout of specific exercise, the concentrations of aminothiols were increased regardless of the group considered. Plasma concentrations were higher than baseline values in tHcy (17.7 +/- 1.5%; P < 0.001), rHcy (10.6 +/- 1.6%; P < 0.001), tCys (9.9 +/- 1.6%; P < 0.001), and rCys (7.6 +/- 2.2%; P < 0.01). Both groups showed significant elevations of pyridoxal-5'-phosphate (PLP; P < 0.01), vitamin B12 (P < 0.001), and creatinine concentrations (P < 0.001) after acute exercises, but no changes were seen in folate. Changes in plasma aminothiols after exercise did not reach significant correlation with changes in free amino acids or baseline vitamins, but significant and positive correlations were observed with changes in plasma PLP, vitamin B12, and creatinine concentrations, when the pooled data were considered. Our results show that higher plasma concentrations of tHcy after an acute intense exercise are associated to higher concentrations of rHcy, and this effect is independent of the type of exercise, vitamin status, or amino acid metabolic stress but could be related to potential changes in the renal function.

Moderate Dietary Vitamin B-6 Restriction Raises Plasma Glycine and Cystathionine Concentrations While Minimally Affecting the Rates of Glycine Turnover and Glycine Cleavage in Healthy Men and Women

Glycine is a precursor of purines, protein, glutathione, and 1-carbon units as 5,10-methylenetetrahydrofolate. Glycine decarboxylation through the glycine cleavage system (GCS) and glycine-serine transformation by serine hydroxymethyltransferase (SHMT) require pyridoxal 5′-phosphate (PLP; active form of vitamin B-6) as a coenzyme. The intake of vitamin B-6 is frequently low in humans. Therefore, we determined the effects of vitamin B-6 restriction on whole-body glycine flux, the rate of glycine decarboxylation, glycine-to-serine conversion, use of glycine carbons in nucleoside synthesis, and other aspects of 1-carbon metabolism. We used a primed, constant infusion of [1,2-13C2]glycine and [5,5,5-2H3]leucine to quantify in vivo kinetics in healthy adults (7 males, 6 females; 20–39 y) of normal vitamin B-6 status or marginal vitamin B-6 deficiency. Vitamin B-6 restriction lowered the plasma PLP concentration from 55 ± 4 nmol/L (mean ± SEM) to 23 ± 1 nmol/L (P < 0.0001), which is consistent with marginal deficiency, whereas the plasma glycine concentration increased (P < 0.01). SHMT-mediated conversion of glycine to serine increased from 182 ± 7 to 205 ± 9 μmol·kg−1·h−1 (P < 0.05), but serine production using a GCS-derived 1-carbon unit (93 ± 9 vs. 91 ± 6 μmol·kg−1·h−1) and glycine cleavage (163 ± 11 vs. 151 ± 8 μmol·kg−1·h−1) were not changed by vitamin B-6 restriction. The GCS produced 1-carbon units at a rate (∼140–170 μmol·kg−1·h−1) that greatly exceeds the demand for remethylation and transmethylation processes (∼4–7 μmol·kg−1·h−1). We conclude that the in vivo GCS and SHMT reactions are quite resilient to the effects of marginal vitamin B-6 deficiency, presumably through a compensatory effect of increasing substrate concentration.

Plasma folate, vitamin B-6, vitamin B-12, and risk of breast cancer in women

Background: B vitamins such as folate, vitamin B-6, and vitamin B-12 are coenzymes that are important for DNA integrity and stability. Deficiency in these B vitamins may promote tumor carcinogenesis.Objective: We prospectively evaluated plasma concentrations of folate, pyridoxal 5-phosphate (PLP; the principal active form of vitamin B-6), and vitamin B-12 in relation to breast cancer risk.Design: We included 848 incident cases of invasive breast cancer identified as of 31 March 2004, and 848 individually matched control subjects from 28 345 women in the Women's Health Study aged ≥45 y who provided blood samples and had no history of cancer and cardiovascular disease at baseline in 1993. Logistic regression controlling for matching factors and other risk factors for breast cancer was used to estimate relative risks (RRs) and 95% CIs. All statistical tests were 2 sided.Results: Plasma concentrations of folate, PLP, and vitamin B-12 were not associated with overall risk of breast cancer. Women in the highest quintile group relative to those in the lowest quintile had multivariate RRs of 1.42 (95% CI: 1.00, 2.02) for plasma folate (P for trend = 0.21), 0.91 (95% CI: 0.63, 1.30) for plasma PLP (P for trend = 0.48), and 1.29 (95% CI: 0.92, 1.82) for plasma vitamin B-12 (P for trend = 0.18). However, higher plasma folate concentrations were moderately associated with an increased risk of developing premenopausal breast cancer (P for trend = 0.04) and for developing estrogen receptor (ER)–positive or progesterone receptor (PR)–positive breast tumors (P for trend ≤ 0.06). Conversely, an inverse association was seen between plasma PLP and postmenopausal breast cancer (P for trend = 0.04).Conclusions: Data from this study suggest that B vitamins, including folate, vitamin B-6, and vitamin B-12, may confer little or no reduction in overall risk of developing breast cancer. The observed positive associations of folate status with risk of developing premenopausal breast cancer and ER-positive or PR-positive tumors are unexpected. Additional research is needed to elucidate the role of folate in breast cancer development.

Plasma pyridoxal 5′-phosphate is a significant indicator of immune responses in the mechanically ventilated critically ill

Objectives This study assessed the effect of vitamin B6 status on immune responses in mechanically ventilated, critically ill patients and compared the results with those of healthy controls. Methods This was designed as a cross-sectional observational study. Forty patients in the intensive care unit successfully completed this study. Vitamin B6 intake was recorded for 8 d. Severity of illness (Second Acute Physiology and Chronic Health Evaluation score) was recorded. Thirty-eighty healthy controls were recruited from the physical check unit of Taichung Veterans General Hospital (Taichung, Taiwan). All control subjects were given instruction on how to complete a 24-d diet recall. Vitamin B6 status was assessed by direct measures (plasma pyridoxal 5′-phosphate [PLP] and 4-pyridoxic acid) and indirect measures (erythrocyte alanine and aspartate aminotransferase activity coefficients). Levels of serum albumin, hemoglobin, hematocrit, high-sensitivity C-reactive protein, and immune responses (white blood cell, neutrophil, total lymphocytes, T lymphocytes [CD3], B lymphocytes [CD19], T-helper cells [CD4], and suppressor cells [CD8]) were determined. Results Critically ill patients had sufficient vitamin B6 intake but showed marginal PLP deficiency (20.9 ± 1.5 nmol/L). In addition, critically ill patients had significantly lower and abnormal immune responses than did healthy controls. There was no significant correlation of vitamin B6 intake and erythrocyte alanine and aspartate aminotransaminase activity coefficients with immune indices. Plasma PLP concentration was strongly negatively correlated with high-sensitivity C-reactive protein level. However, plasma PLP was significantly associated with immune responses after adjustment for age, sex, high-sensitivity C-reactive protein, and the other four vitamin B6 indicators. Conclusions Plasma PLP is a significant indicator of immune responses in human subjects. Further research is warranted to study whether vitamin B6 supplementation in critically ill patients improves their immune responses.

Role of vitamins B6, B12 and folic acid on hyperhomocysteinemia in a Pakistani population of patients with acute myocardial infarction

Pakistani people belong to an ethnic group which has the highest rate of coronary artery disease (CAD). We investigated the possible correlation between deficiency of vitamins B6, B12 or folic acid and hyperhomocysteinemia in Pakistani patients with acute myocardial infarction (AMI). A case-control study was carried out involving 224 AMI patients (age 30-70 years; 55 females and 169 males) and 126 normal healthy subjects (age 31-70 years; 35 females and 91 males). Fasting venous blood was obtained from cases and controls. Serum was analyzed for folic acid and B12 using radioassays. Plasma was analyzed for pyridoxal phosphate (PLP; coenzymic form of B6) using a radioenzymatic assay and for total homocysteine using a fluorescence polarization immunoassay. Mean serum B12 concentration in AMI patients was found to be significantly lower than the mean for controls (241+/-185 pg/ml vs 608+/-341 pg/ml; p < 0.001). Mean serum folate level in patients was also found to be lower than controls (3.35+/-3.78 ng/ml vs 4.93+/-2.93 ng/ml), however, the differences were not statistically significant. Similarly, mean PLP concentration in plasma of cases (19.4+/-24.4 nmol/l) was lower than the concentration in controls (23.2+/-17.6 nmol/l), but the difference was not statistically significant. Mean plasma homocysteine level in AMI cases (18+/-8.36 micromol/l) was higher than the mean level in controls (16.4+/-4.9 micromol/l), but not to a significant extent. However, this mean homocysteine concentration in normal healthy subjects was among the highest reported in the literature and was significantly more than mean values reported in most Eastern and Western studies. Compared to controls, there was significantly greater deficiency of folate (32.5% vs 67.1%), B12 (3.2% vs 63.4%) and PLP (49.2% vs 74.1%) in AMI patients. Deficiencies of folate, B12 and PLP were defined as serum folate levels less than 3.5 ng/ml, serum levels of B12 less than 200 pg/ml and plasma PLP levels less than 20 nmol/l. Mean plasma homocysteine levels in smokers were found to be significantly higher in both cases and controls. Similarly, mean serum folate levels in smokers (compared to nonsmokers) were significantly lower in both cases and controls. Substantial nutritional deficiencies of these three vitamins along with mild hyperhomocysteinemia, perhaps through an interplay with the classical cardiovascular risk factors (highly prevalent in this population), could be further aggravating the risk of CAD in the Pakistani population.

Coronary heart disease mortality, plasma homocysteine, and B-vitamins: a prospective study

The results of prospective studies on the relations between the plasma concentration of total homocysteine (tHcy) and B-vitamins, on the one hand, and coronary heart disease (CHD) mortality, on the other hand, are inconclusive and scarce considering the relation with B-vitamins. We prospectively determined these relations in a case-cohort study. The full-cohort existed in ∼36,000 Dutch adults aged 20–59 years at baseline. The statistical analyses were done with a random sample from the cohort ( n=630) complemented with all subjects who died of CHD ( n=102) during a mean follow-up of 10.3 years. All subjects reported the absence of cardiovascular diseases (CVDs) at baseline. The plasma concentrations of tHcy, folate, PLP, and vitamin B12 were determined in samples obtained at baseline. Men with a tHcy concentration in the highest tertile (T3) compared with men in the lowest tertile (T1) had a relative risk (RR) of 1.14 for CHD (95% confidence interval (CI): 0.50, 2.61) after adjusting for age, study center, hypertension, HDL and total cholesterol, smoking, and creatinine. For women, this RR was 2.04 (95% CI: 0.48, 8.62). For each 5 μmol/l increase in tHcy, the RR of CHD was 1.03 (95% CI: 0.83–1.29) for men and women combined. In women only, high folate levels were associated with a statistically significant protection of fatal CHD (T3 versus T1; RR: 0.22, 95% CI: 0.06, 0.87). Plasma PLP (B6) and vitamin B12 concentrations were not associated with CHD risk. We conclude that elevated tHcy concentrations do not seem to be a risk factor for CHD mortality in these relatively young healthy Dutch subjects free of baseline CVD. Higher folate concentrations may be protective of CHD, but this needs confirmation.

Effect of smoking on serum concentrations of total homocysteine and B vitamins in mid-pregnancy

There are conflicting findings in the literature on the effect of smoking on total homocysteine (tHcy) concentrations in non-pregnant subjects. We evaluated the effect of smoking on serum concentrations of tHcy, folate, vitamin B-12 pyridoxal 5′-phosphate (PLP, a coenzyme form of vitamin B-6) in 196 women at 18 and 30 weeks' gestation. The smokers were defined as those who self-reported cigarette smoking and had serum concentrations of thiocyanate, a biomaker of smoking, in the highest quartiles of the population. Mid-pregnancy serum tHcy concentrations were not significantly different between smokers and non-smokers. Folate, vitamin B-12 and PLP concentrations were generally lower in smokers than non-smokers. In smokers, tHcy concentrations had significant negative correlations with folate at both time points. The multiple regression analyses indicated that serum folate concentration was the most significant factor associated with tHcy concentrations among smokers, whereas thiocyanate concentrations showed no such effect. We conclude that serum tHcy concentrations were most strongly associated with the nutritional status of folate among the B vitamins tested during mid-pregnancy in our subjects. We suggest that it is essential to consider the nutritional status of folate, vitamin B-12 and vitamin B-6 in evaluating the effect of smoking on homocysteine metabolism.

Homocysteine, folate, vitamin B-12 and vitamin B-6 in patients receiving antiepileptic drug monotherapy

We hypothesized that elevated plasma homocysteine concentrations (hyperhomocysteinemia) exist in patients receiving antiepileptic drugs (AED), and a long-term administration of AED may result in an increased risk of occlusive vascular disease in these patients. A total of 62 patients who received AED monotherapy (phenytoin, lamotrigine, carbamazepine or valproate) participated in this study. Blood concentrations of homocysteine, folate, vitamin B-12 and pyridoxal-5′-phosphate (PLP, a coenzyme form of vitamin B-6) were measured, and thermolabile genotypes of 5,10-methylenetetrahydrofolate reductase (MTHFR) were also determined. Of 62 patients, only seven (11.4%) had hyperhomocysteinemia. Of 20 patients who received phenytoin, three (15.0%) had hyperhomocysteinemia, whereas 85% of these had plasma folate concentrations below the normal range. However, erythrocyte folate concentrations were abnormally low in only 25% of the patients who received phenytoin. Valproate administration increased serum vitamin B-12 concentrations. Over 55% of the entire patients had PLP concentrations below the normal range, although the reason is unknown. Only three patients had the homozygous thermolabile genotype of MTHFR; therefore, meaningful statistical analysis was not possible in this study. However, one patient with homozygous genotype who received phenytoin therapy had hyperhomocysteinemia with poor folate nutritional status, and the other two had normal homocysteine concentrations with normal folate status. Our data suggest that hyperhomocysteinemia is not a serious clinical concern in epileptic patients when folate nutriture is adequate.

Homocysteine, B vitamins, and vascular-access thrombosis in patients treated with hemodialysis

To evaluate whether increased plasma homocysteine concentrations (hyperhomocysteinemia) are associated with thrombosis of arteriovenous (AV) grafts, we determined plasma homocysteine, plasma and erythrocyte folate, plasma vitamin B12, and vitamin B6 (pyridoxal-5'-phosphate [PLP]) in 48 patients (45 black patients and three white patients) with end-stage renal disease who received hemodialysis. 5,10- Methylenetetrahydrofolate reductase (MTHFR) genotypes were also analyzed. The patients were divided into two groups, including a thrombosis-prone group with frequent graft loss (n = 24) and a control group with prolonged graft survival who were matched by age and duration of dialysis (n = 24). Hyperhomocysteinemia (>15 micromol/L) was found in 42 patients. There were no significant differences in all values, including the concentrations of homocysteine and vitamins between the two groups. Based on plasma folate and PLP concentrations, over 70% of patients appeared to have inadequate folate and/or vitamin B6 nutriture. Plasma homocysteine concentrations showed significant negative correlations with plasma and erythrocyte folate, and plasma vitamin B12 in all patients combined, whereas no significant correlation was found between plasma PLP and homocysteine concentrations. Among 48 patients, the heterozygous mutation (Val/Ala) of MTHFR was found only in three patients, two of whom belonged to the thrombosis-prone group and one to the control group, and there were no individuals with homozygous thermolabile mutation (Val/Val). All three white patients had Ala/Ala genotype, and 3 in 45 black patients (6.7%) were heterozygotes (Val/Ala). (Am J Kidney Dis 1998 Sep;32(3):475-81)

Vitamin B6, vitamin C, and carpal tunnel syndrome. A cross-sectional study of 441 adults.

As part of an ongoing study of carpal tunnel syndrome (CTS) in industry, we measured plasma concentrations of pyridoxal 5'-phosphate (PLP, a measure of vitamin B6 status) and total ascorbate (ASC, a measure of vitamin C status) in 441 adult volunteers from six industries and a university exercise study. In the entire study group and in non-vitamin users (n = 218), there were no significant differences in mean plasma PLP or ASC concentrations between controls (neither symptoms nor slowing), subjects with symptoms only, subjects with median nerve slowing only, or subjects with CTS (symptoms + slowing). In male non-vitamin users (n = 137), there were significant inverse univariate associations between plasma PLP concentration and the prevalence of pain, the frequency of tingling and nocturnal awakening, and the Phalen test result. In this same subgroup, the ASC/PLP ratio was directly associated with the prevalence of pain and nocturnal awakening, and with the frequency of pain, tingling, and nocturnal awakening. In multivariate analyses, plasma ASC concentration predicted more median nerve slowing and confirmed CTS, and vitamin or vitamin interaction variables were independent predictors of 20 CTS-related outcomes. These multivariate relationships often occurred only after adjustment for age, gender, body mass index, serum alkaline phosphatase activity, or tobacco use. We conclude that there are significant relationships between plasma vitamin levels and both components of CTS (specific symptoms and median nerve slowing). The interaction between plasma PLP and ASC appears to be particularly important with respect to symptoms.

Enzymatic transesterification of palm olein with nonspecific and 1,3‐specific lipases

AbstractThe enzymatic transesterification of palm olein was conducted in a low‐moisture medium with nonspecific and 1,3‐specific lipases from microbial sources. The enzymes were first immobilized on Celite, lyophilized for 4 h and then added to a reaction medium that consisted of 10% (wt/vol) palm olein in water‐saturated hexane. The catalytic performance of the enzymes was evaluated by determining the changes in triglyceride (TG) composition and concentrations by reverse‐phase high‐performance liquid chromatography (HPLC) and the formation of free fatty acids by titration. Studies with lipase fromCandida rugosa showed that the degree of hydrolysis was reduced by drying the immobilized preparation and that the best drying time was 4 h. In all cases, the transesterification process resulted in the formation of PPP, a TG initially undetected in the oil, and increases in the concentrations of OOO (1.3–2.1‐fold), OOL (1.7–4.5‐fold), and OLL (1.7–4.3‐fold), where P, O, and L are palmitic, oleic, and linoleic acids, respectively. SOS (where S is stearic acid), another TG not detected in the oil, was synthesized byRhizomucor miehei andPseudomonas lipases, with the latter producing more of this TG. There was a corresponding decrease in the concentrations of POP, PLP, POO, and POL. PPP concentration ranged from 1.9% (w/w) forMucor javanicus lipase to 6.2% (w/w) forPseudomonas lipase after 24 h. The greatest degree and fastest rate of change were caused byPseudomonas lipase, followed by the enzymes fromR. miehei andAspergillus niger. The effects of transesterification and hydrolysis of palm olein by the various lipases resulted in changes in the overall degree of saturation of the triglyceride components. There seems to be no clear correlation between the enzyme positional specificity and the products formed. Possible mechanisms for the formation of PPP, OOL, OLL, OOO, and SOS are discussed.

Alkaline phosphatase: placental and tissue-nonspecific isoenzymes hydrolyze phosphoethanolamine, inorganic pyrophosphate, and pyridoxal 5'-phosphate. Substrate accumulation in carriers of hypophosphatasia corrects during pregnancy.

Hypophosphatasia features selective deficiency of activity of the tissue-nonspecific (liver/bone/kidney) alkaline phosphatase (ALP) isoenzyme (TNSALP); placental and intestinal ALP isoenzyme (PALP and IALP, respectively) activity is not reduced. Three phosphocompounds (phosphoethanolamine [PEA], inorganic pyrophosphate [PPi], and pyridoxal 5'-phosphate [PLP]) accumulate endogenously and appear, therefore, to be natural substrates for TNSALP. Carriers for hypophosphatasia may have decreased serum ALP activity and elevated substrate levels. To test whether human PALP and TNSALP are physiologically active toward the same substrates, we studied PEA, PPi, and PLP levels during and after pregnancy in three women who are carriers for hypophosphatasia. Hypophosphatasemia corrected during the third trimester because of PALP in maternal blood. Blood or urine concentrations of PEA, PPi, and PLP diminished substantially during that time. After childbirth, maternal circulating levels of PALP decreased, and PEA, PPi, and PLP levels abruptly increased. In serum, unremarkable concentrations of IALP and low levels of TNSALP did not change during the study period. We conclude that PALP, like TNSALP, is physiologically active toward PEA, PPi, and PLP in humans. We speculate from molecular/crystallographic information, indicating significant similarity of structure of the substrate-binding site of ALPs throughout nature, that all ALP isoenzymes recognize these same three phosphocompound substrates.