Novel functions of vitamin B6

Role of micronutrients in inflammatory bowel disease

Inflammatory bowel disease (IBD) is an autoimmune intestinal disease that includes ulcerative colitis, Crohn's disease, and indeterminate colitis. Patients with IBD are often at risk for malnutrition, including micronutrient deficiencies, due to dietary restrictions and poor intestinal absorption. Micronutrients, including vitamins and minerals, play an important role in the human body's metabolism and maintenance of tissue functions. This article reviews the role of micronutrients in IBD. Micronutrients can affect the occurrence and progression of IBD by regulating immunity, intestinal flora, oxidative stress, intestinal barrier function, and other aspects. Monitoring and timely supplementation of micronutrients are important to delay progression and improve clinical symptoms in IBD patients.

Effectiveness of homocysteine lowering vitamins in prevention of thrombotic tendency at high altitude area: A randomized field trial

INTRODUCTION

A higher risk of thrombosis has been reported on prolonged stay at high altitude (HAA). Lowering of homocysteine (Hcy) has been found to reduce the risk of venous thrombosis. A randomized field trial was conducted with primary question whether Hcy lowering agents have any effect on the incidence of thrombosis at HAA amongst Indian soldiers as compared to existing interventions.

METHODS

All units freshly inducted to HAA were randomized into intervention (Vit B12 1000 microgram/day, B6 3mg/day & folic acid 5mg/day) and control arms, with a sample size of 12,000 person-years in each arm.

RESULTS

At the end of one year stay at HAA, Folate and B 12 levels decreased significantly in control arm. The levels of Hcy, fibrinogen and plasminogen activator inhibitor (PAI 1) were lower and nitric oxide higher in intervention arm as compared to control arm (p<0.05). At the end of 2years, 5 thrombotic episodes occurred in the intervention arm and 17 in control arm with RR of 0.29 (95% CI 0.11-0.80), attributable fraction % (AFe) 70.59%, Population attributable risk percent 54.55% and Protective Fraction 240%.

CONCLUSION

Intervention with B12 and folic acid is effective in reducing Hcy, PAI 1, fibrinogen levels and increasing NO levels at 1yr as compared to control arm and reducing the incidence of thrombosis at 2years of stay at HAA. Thus, vitamin B 12, B6 and folic acid intervention is safe and effective method of reducing morbidity and mortality caused by HAA induced coagulopathy.

Modulation of gene expression by vitamin B6

The physiologically active form of vitamin B6, pyridoxal 5'-phosphate (PLP), is known to function as a cofactor in many enzymic reactions in amino acid metabolism. Recent studies have shown that, apart from its role as a coenzyme, PLP acts as a modulator of steroid hormone receptor-mediated gene expression. Specifically, elevation of intracellular PLP leads to a decreased transcriptional response to glucocorticoid hormones, progesterone, androgens, and oestrogens. For example, the induction of cytosolic aspartate aminotransferase (cAspAT) in rat liver by hydrocortisone is suppressed by the administration of pyridoxine. The suppression of the cAspAT induction by pyridoxine is caused by a decrease in the expression of the cAspAT gene, which is brought about by inactivation of the binding activity of the glucocorticoid receptor to the glucocorticoid-responsive element in the regulatory region of the cAspAT gene. Vitamin B6 has recently been found to modulate gene expression not only for steroid hormone-responsive or PLP-dependent enzymes but also for steroid- and PLP-unrelated proteins such as serum albumin. Albumin gene expression was found to be modulated by vitamin B6 through a novel mechanism that involves inactivation of tissue-specific transcription factors, such as HNF-1 or C/EBP, by direct interaction with PLP in a similar manner to glucocorticoid receptor. Enhancement of albumin gene expression in the liver by an increased supply of amino acids can be explained by elevated binding of HNF-1 and C/EBP to their DNA-binding sites which, in turn, is caused by a decrease in the intracellular level of PLP by the increased amino acid supply. These findings that vitamin B6 acts as a physiological modulator of gene expression add a new dimension to the hitherto recognized function of vitamin B6 as a cofactor of enzyme action.

Application of in vitro bioaccessibility and bioavailability methods for calcium, carotenoids, folate, iron, magnesium, polyphenols, zinc, and vitamins B(6), B(12), D, and E

A review of in vitro bioaccessibility and bioavailability methods for polyphenols and selected nutrients is presented. The review focuses on in vitro solubility, dialyzability, the dynamic gastrointestinal model (TIM)™, and Caco-2 cell models, the latter primarily for uptake and transport, and a discussion of how these methods have been applied to generate data for a range of nutrients, carotenoids, and polyphenols. Recommendations are given regarding which methods are most justified for answering bioaccessibility or bioavailability related questions for specific nutrients. The need for more validation studies in which in vivo results are compared to in vitro results is also discussed.

Vitamin B-6 intake is inversely related to, and the requirement is affected by, inflammation status

Low circulating pyridoxal 5'-phosphate (PLP) concentrations have been linked to inflammatory markers and the occurrence of inflammatory diseases. However, the implications of these findings are unclear. The measurement of PLP and C-reactive protein (CRP) in blood samples collected from participants in the 2003-2004 NHANES afforded us the opportunity to investigate this relationship in the general U.S. population. Dietary and laboratory data were available for 3864 of 5041 interviewed adults, 2686 of whom were eligible (i.e. provided reliable dietary data and were not diabetic, pregnant, lactating, or taking hormones or steroidal antiinflammatory drugs). Vitamin B-6 intake was assessed using 2 24-h diet recalls and supplement use data. After multivariate adjustment for demographics, smoking, BMI, alcohol use, antioxidant vitamin status, intakes of protein and energy, and serum concentrations of creatinine and albumin, high vitamin B-6 intake was associated with protection against serum CRP concentrations >10 mg/L compared with < or =3 mg/L. However, plasma PLP > or =20 nmol/L compared with <20 nmol/L was inversely related to serum CRP independently of vitamin B-6 intake (P < 0.001). Among participants with vitamin B-6 intakes from 2 to 3 mg/d, the multivariate-adjusted prevalence of vitamin B-6 inadequacy was <10% in participants with serum CRP < or =3 mg/L but close to 50% in those with serum CRP > 10 mg/L (P < 0.001). In conclusion, higher vitamin B-6 intakes were linked to protection against inflammation and the vitamin B-6 intake associated with maximum protection against vitamin B-6 inadequacy was increased in the presence compared to absence of inflammation.

Genome-wide significant predictors of metabolites in the one-carbon metabolism pathway

Low plasma B-vitamin levels and elevated homocysteine have been associated with cancer, cardiovascular disease and neurodegenerative disorders. Common variants in FUT2 on chromosome 19q13 were associated with plasma vitamin B12 levels among women in a genome-wide association study in the Nurses' Health Study (NHS) NCI-Cancer Genetic Markers of Susceptibility (CGEMS) project. To identify additional loci associated with plasma vitamin B12, homocysteine, folate and vitamin B6 (active form pyridoxal 5'-phosphate, PLP), we conducted a meta-analysis of three GWA scans (total n = 4763, consisting of 1658 women in NHS-CGEMS, 1647 women in Framingham-SNP-Health Association Resource (SHARe) and 1458 men in SHARe). On chromosome 19q13, we confirm the association of plasma vitamin B12 with rs602662 and rs492602 (P-value = 1.83 x 10(-15) and 1.30 x 10(-14), respectively) in strong linkage disequilibrium (LD) with rs601338 (P = 6.92 x 10(-15)), the FUT2 W143X nonsense mutation. We identified additional genome-wide significant loci for plasma vitamin B12 on chromosomes 6p21 (P = 4.05 x 10(-08)), 10p12 (P-value=2.87 x 10(-9)) and 11q11 (P-value=2.25 x 10(-10)) in genes with biological relevance. We confirm the association of the well-studied functional candidate SNP 5,10-methylene tetrahydrofolate reductase (MTHFR) Ala222Val (dbSNP ID: rs1801133; P-value=1.27 x 10(-8)), on chromosome 1p36 with plasma homocysteine and identify an additional genome-wide significant locus on chromosome 9q22 (P-value=2.06 x 10(-8)) associated with plasma homocysteine. We also identified genome-wide associations with variants on chromosome 1p36 with plasma PLP (P-value=1.40 x 10(-15)). Genome-wide significant loci were not identified for plasma folate. These data reveal new biological candidates and confirm prior candidate genes for plasma homocysteine, plasma vitamin B12 and plasma PLP.

Plasma pyridoxal 5'-phosphate in the US population: the National Health and Nutrition Examination Survey, 2003-2004

BACKGROUND

No large-scale, population-based study has considered the descriptive epidemiology of vitamin B-6 status with use of plasma pyridoxal 5'-phosphate (PLP), the indicator of vitamin B-6 adequacy used to set the current Recommended Dietary Allowance, which is < or = 2 mg/d for all subgroups.

OBJECTIVES

We sought to examine the epidemiology of vitamin B-6 status in the US population.

METHODS

In > 6000 participants aged > or = 1 y in the National Health and Nutrition Examination Survey (2003-2004), we considered relations between plasma PLP and various subject characteristics and examined trends in plasma PLP and homocysteine with vitamin B-6 intake, both overall and in selected subgroups.

RESULTS

In males, plasma PLP decreased with age after adolescence only in nonusers of supplemental vitamin B-6. Regardless of supplement use, plasma PLP concentrations of women of childbearing age were significantly lower than those of comparably aged men, and most oral contraceptive users had plasma PLP < 20 nmol/L. The prevalence of low plasma PLP was significantly > 3% at vitamin B-6 intakes from 2 to 2.9 mg/d in all subgroups and at intakes from 3 to 4.9 mg/d in smokers, the elderly, non-Hispanic blacks, and current and former oral contraceptive users. Intakes from 3 to 4.9 mg/d compared with < 2 mg/d were associated with significant protection from low plasma PLP in most subgroups and from hyperhomocysteinemia in the elderly.

CONCLUSIONS

Vitamin B-6 intakes of 3 to 4.9 mg/d appear consistent with the definition of a Recommended Dietary Allowance for most Americans. However, at that intake level, substantial proportions of some population subgroups may not meet accepted criteria for adequate vitamin B-6 status.

Dietary factors of one-carbon metabolism and prostate cancer risk

BACKGROUND

Folate is hypothesized to be inversely associated with the risk of several cancers, but such a potential association has not been well studied for prostate cancer. Vitamin B-6, vitamin B-12, methionine, and alcohol can influence folate-related metabolism.

OBJECTIVE

The objective was to investigate the associations between dietary factors of one-carbon metabolism and prostate cancer risk within the alpha-Tocopherol, beta-Carotene Cancer Prevention Study.

DESIGN

Of the cohort's 27 111 Finnish male smokers aged 50-69 y who had complete dietary data, 1270 had a diagnosis of incident prostate cancer between 1985 and 2002. Folate, vitamin B-6, vitamin B-12, methionine, and alcohol intakes were estimated from a 276-item modified dietary history questionnaire. Cox proportional hazard models, adjusted for age and vitamin supplement use, estimated relative risks (RR) and 95% CIs.

RESULTS

Vitamin B-6 intake was inversely associated with prostate cancer risk (RR for highest versus lowest quintile: 0.88; 95% CI: 0.72, 1.07; P for trend = 0.045), whereas vitamin B-12 intake was associated with significantly increased risk (RR = 1.36; 95% CI: 1.14, 1.96; P for trend = 0.01). No association between folate or alcohol intake and prostate cancer risk was observed. No differences were found in the above associations according to stage of disease or subgroups of several potential effect modifiers.

CONCLUSIONS

We found no convincing evidence for a protective role of one-carbon metabolism against prostate cancer, although these observations can be generalized only to smokers. The possible modest protective association with vitamin B-6 and the significantly elevated risk with vitamin B-12 intake warrant further investigation.

Effect of vitamin B6 deficiency on glyoxylate metabolism in rats with or without glyoxylate overload

We examined the effect of vitamin B6 deficiency on glyoxylate metabolism and hepatic alanine: glyoxylate aminotransferase (AGT) activity in rats with normal or high glyoxylate intake. Male rats were divided into four groups: a control group, a vitamin B6-free diet group, a glyoxylate water group, and a vitamin B6-free diet + glyoxylate water group. Each group was given special diet (control or vitamin B6-deficient diet) and drinking water (plain or 0.5% glyoxylate water) for 4 weeks, after which biochemical parameters and hepatic AGT mRNA level were measured. Compared with control rats, the urinary oxalate/creatinine ratio was higher in each of the other 3 groups. The urinary glycolate/creatinine ratio was also higher in the vitamin B6-free diet group and the vitamin B6-free diet + glyoxylate water group than the control group, while the urinary glycine/creatinine and citrate/creatinine ratio was lower in both groups. The hepatic AGT mRNA level was reduced in the vitamin B6-free diet group, but was increased in the glyoxylate water group than the control group. These results suggest that vitamin B6 is necessary for glyoxylate metabolism as a coenzyme of AGT. Especially in the presence of a high glyoxylate intake, vitamin B6 deficiency leads to severe hyperoxaluria and hypocituria.

Simultaneous Spectrofluorometric Determination of Piroxicam and Pyridoxine Using Generalized Rank Annihilation Method

The application of generalized rank annihilation method (GRAM) to the analysis of fluorescence excitation-emission matrices of mixtures of piroxicam and pyridoxine is described. The input of GRAM consists of two bilinear data matrices, i.e. one for unknown and one for the calibration sample. The excitation wavelength range was from 290 to 340 nm and the emission was recorded from 370 to 560 nm. Piroxicam and pyridoxine were determined in the concentration ranges 0.33 - 4.00 microg ml(-1) and 0.66 - 8.00 microg ml(-1), respectively. To check the accuracy of the proposed method, several binary synthetic mixtures and one real sample were analyzed successfully. No matrix effect was observed in mixture analysis, so a single external calibration sample was used for each analyte. The ability of GRAM to quantify the studied compounds and the comparability of GRAM results were evaluated by comparing them with those of PLS regression as a standard first-order calibration.

Red cell aspartate aminotransferase saturation with oral pyridoxine intake

CONTEXT AND OBJECTIVE

The coenzyme of aspartate aminotransferase is pyridoxal phosphate, generated from fresh vegetables containing pyridoxine. Vitamin B6-responsive sideroblastic anemia, myelofibrosis and Peyronies syndrome respond to high pyridoxine doses. The objective was to investigate the oral pyridoxine oral dose that would lead to maximized pyridoxal phosphate saturation of red cell aspartate aminotransferase.

DESIGN AND SETTING

Controlled trial, in Hematology Division of Instituto Adolfo Lutz.

METHODS

Red cell aspartate aminotransferase activity was assayed (before and after) in normal volunteers who were given oral pyridoxine for 15-18 days (30 mg, 100 mg and 200 mg daily). In vitro study of blood from seven normal volunteers was also performed, with before and after assaying of aspartate aminotransferase activity.

RESULTS

The in vivo study showed increasing aspartate aminotransferase saturation with increasing pyridoxine doses. 83% saturation was reached with 30 mg daily, 88% with 100 mg, and 93% with 200 mg after 20 days of oral supplementation. The in vitro study did not reach 100% saturation.

CONCLUSIONS

Neither in vivo nor in vitro study demonstrated thorough aspartate aminotransferase saturation with its coenzyme pyridoxal phosphate in red cells, from increasing pyridoxine supplementation. However, the 200-mg dose could be employed safely in vitamin B6-responsive sideroblastic anemia, myelofibrosis and Peyronies syndrome treatment. Although maximum saturation in circulating red cells is not achieved, erythroblasts and other nucleated and cytoplasmic organelles containing cells certainly will reach thorough saturation, which possibly explains the results obtained in these diseases.

DACH-LIGA homocystein (german, austrian and swiss homocysteine society): consensus paper on the rational clinical use of homocysteine, folic acid and B-vitamins in cardiovascular and thrombotic diseases: guidelines and recommendations

About half of all deaths are due to cardiovascular disease and its complications. The economic burden on society and the healthcare system from cardiovascular disability, complications, and treatments is huge and getting larger in the rapidly aging populations of developed countries. As conventional risk factors fail to account for part of the cases, homocysteine, a "new" risk factor, is being viewed with mounting interest. Homocysteine is a sulfur-containing intermediate product in the normal metabolism of methionine, an essential amino acid. Folic acid, vitamin B12, and vitamin B6 deficiencies and reduced enzyme activities inhibit the breakdown of homocysteine, thus increasing the intracellular homocysteine concentration. Numerous retrospective and prospective studies have consistently found an independent relationship between mild hyperhomocysteinemia and cardiovascular disease or all-cause mortality. Starting at a plasma homocysteine concentration of approximately 10 micromol/l, the risk increase follows a linear dose-response relationship with no specific threshold level. Hyperhomocysteinemia as an independent risk factor for cardiovascular disease is thought to be responsible for about 10% of total risk. Elevated plasma homocysteine levels (>12 micromol/l; moderate hyperhomocysteinemia) are considered cytotoxic and are found in 5 to 10% of the general population and in up to 40% of patients with vascular disease. Additional risk factors (smoking, arterial hypertension, diabetes, and hyperlipidemia) may additively or, by interacting with homocysteine, synergistically (and hence over-proportionally) increase overall risk. Hyperhomocysteinemia is associated with alterations in vascular morphology, loss of endothelial anti-thrombotic function, and induction of a procoagulant environment. Most known forms of damage or injury are due to homocysteine-mediated oxidative stress. Especially when acting as direct or indirect antagonists of cofactors and enzyme activities, numerous agents, drugs, diseases, and lifestyle factors have an impact on homocysteine metabolism. Folic acid deficiency is considered the most common cause of hyperhomocysteinemia. An adequate intake of at least 400 microg of folate per day is difficult to maintain even with a balanced diet, and high-risk groups often find it impossible to meet these folate requirements. Based on the available evidence, there is an increasing call for the diagnosis and treatment of elevated homocysteine levels in high-risk individuals in general and patients with manifest vascular disease in particular. Subjects of both populations should first have a baseline homocysteine assay. Except where manifestations are already present, intervention, if any, should be guided by the severity of hyperhomocysteinemia. Consistent with other working parties and consensus groups, we recommend a target plasma homocysteine level of <10 micromol/l. Based on various calculation models, reduction of elevated plasma homocysteine concentrations may theoretically prevent up to 25% of cardiovascular events. Supplementation is inexpensive, potentially effective, and devoid of adverse effects and, therefore, has an exceptionally favorable benefit/risk ratio. The results of ongoing randomized controlled intervention trials must be available before screening for, and treatment of, hyperhomocysteinemia can be recommended for the apparently healthy general population.

Low vitamin B(6) plasma levels, a risk factor for thrombosis, in inflammatory bowel disease: role of inflammation and correlation with acute phase reactants

OBJECTIVES

Individuals with inflammatory bowel disease (IBD) are at increased risk for thrombosis and vitamin deficiencies. Low plasma levels of vitamin B(6) are an independent risk factor for thrombosis and may cause hyperhomocysteinemia, another recognized risk factor for thrombosis. The aim of this study was to evaluate vitamin B(6) plasma levels in IBD patients.

METHODS

We studied 61 IBD patients: 32 with Crohn's disease and 29 with ulcerative colitis. For each patient, three sex- and age-matched healthy control subjects were studied.

RESULTS

Median vitamin B(6) levels were significantly lower in IBD patients (22.0 pmol/L, range 3.6-231.0) than in controls (31.1 pmol/L, 3.7-363.4; p < 0.01). In all, 13.1% IBD patients and 5.5% controls had plasma vitamin B(6) levels lower than the 5th percentile of distribution in normal controls (p < 0.05). Low vitamin B(6) levels were significantly more frequent in patients with active disease than in patients with quiescent disease (seven of 26, 26.9%, vs one of 35, 2.9%; p < 0.001). Moreover, patients with active disease had significantly lower median vitamin B(6) levels (13.4 pmol/L, range 3.6-124.0) than patients in a quiescent phase (27.0 pmol/L, 7.8-231.0; p < 0.001). Low vitamin B(6) levels were significantly correlated with serum concentrations of C-reactive protein (r = -0.36, 95% CI = -0.59 to -0.09, p < 0.01) and alpha(1)-acid-glycoprotein (r = -0.37, 95% CI = -0.59 to -0.10, p < 0.01). Hyperhomocysteinemia was more frequent in patients with low vitamin B(6) levels (three of eight, 37.5%) than in patients with normal levels (nine of 53, 17.0%; p = 0.18). There was no statistically significant correlation between vitamin B(6) and homocysteine plasma levels (r = -0.13, 95% CI = -0.37 to +0.14, p = 0.33).

CONCLUSIONS

Low vitamin B(6) plasma levels, an independent risk factor for thrombosis, are frequent in patients with IBD, especially those with active disease.

Low plasma levels of vitamin B(6) are independently associated with a heightened risk of deep-vein thrombosis

BACKGROUND

Elevated plasma levels of total homocysteine (tHcy) before and after an oral methionine load (PML) are associated with an elevated risk of deep-vein thrombosis (DVT). We investigated whether plasma levels of B vitamins that are involved in Hcy metabolism are associated with an elevated risk of DVT.

METHODS AND RESULTS

We compared 397 cases with previous DVT with 585 matched healthy controls. The plasma levels of folate, vitamin B(12), vitamin B(6,), and fasting and PML tHcy were measured. The ORs for DVT associated with high (>95th percentile) fasting levels and PML increases of tHcy were 2.1 (95% CI, 1.2 to 3.4) and 2.4 (95% CI, 1.5 to 3.9) after adjustment for established risk factors for DVT. Fasting plasma levels and PML increases in tHcy correlated negatively with vitamin levels. The crude OR for folate levels in the lowest quartile compared with the highest was 1.5 (95% CI, 1.1 to 2.1), and that for B(6) levels in the lowest and second quartiles compared with the highest was 1.5 (95% CI, 1.0 to 2.1). However, after adjustment for established risk factors and fasting and PML tHcy, the ORs for B(6) levels in the lowest and second quartiles only remained statistically significant (lowest quartile: OR, 1.8; 95% CI, 1.2 to 2.8; second quartile, OR, 1.9; 95% CI, 1.3 to 2.9).

CONCLUSIONS

High fasting and PML tHcy and low vitamin B(6) plasma levels are associated with an elevated risk for DVT independently of established risk factors for DVT. The association of low vitamin B(6) levels with the risk for DVT is independent of fasting and PML tHcy levels.

A case-control study of diet and prostate cancer

We interviewed 328 men diagnosed with prostate cancer before the age of 75 years and 328 age-matched population controls. The principal hypotheses were that risk would increase with a high intake of total or saturated fat and would decrease with a high intake of carotene (beta-carotene equivalents) or lycopene. We also examined the associations of other nutrients and foods with risk. There was no evidence for an association between fat intake and risk, although the average fat intake was high and the range of fat intakes was narrow (medians of lower and upper thirds of percentage of energy from fat among controls were 34.3% and 42.9% respectively). Risk was lower in subjects with higher carotene intake: odds ratios 0.65 (95% CI 0.45-0.94) and 0.76 (0.53-1.10) in the middle and upper thirds of carotene intake respectively (P for trend = 0.150). Lycopene was not associated with risk. Among 13 other nutrients examined, the odds ratios in the top third of intake were below 0.8 for: potassium, 0.74 (0.51-1.09; P for trend = 0.054); zinc, 0.73 (0.49-1.08; P for trend = 0.126); iodine, 0.75 (0.51-1.11; P for trend = 0.077); vitamin B6 food only, 0.77 (0.53-1.12; P for trend = 0.077); and vitamin B6 including supplements, 0.70 (0.48-1.03; P for trend = 0.029). Among 18 foods examined, statistically significant associations were observed for: garlic as food, > or = 2/week vs never, 0.56 (0.33-0.93); garlic including supplements, > or = 2/week vs never, 0.60 (0.37-0.96); baked beans, > or = 2/week vs < 1/month, 0.57 (0.34-0.95); and garden peas, > or = 5/week vs < or = 3/month, 0.35 (0.13-0.91). This study does not support the hypothesis that fat increases risk and is equivocal in relation to carotene. The possible relationships of vitamin B6, garlic, beans and peas with risk for prostate cancer should be further investigated.