Active clinical trials for "Vitamin B 6 Deficiency"

Chronically inadequate B6 nutritional status is associated with aberrant one-carbon (1C) metabolism and health. Plasma pyridoxal phosphate (PLP) >30 nmol/L often has been considered to be the cutoff indicative of nutritional adequacy, with 20-30 nmol/L considered marginal deficiency; however, the current Recommended Dietary Allowance (RDA) value was based on a more conservative cutoff of 20 nmol/L plasma PLP. As shown by in the investigators preliminary data, biochemical perturbations occur when humans have marginal B6 deficiency consistent with plasma PLP of 20-30 nmol/L. A prospective study also showed that plasma PLP <23.3 nmol/L is associated with 1.8-times higher risk of recurrent venous thromboembolism than those with PLP >23.3 nmol/L. The mechanism by which low B6 intake is associated with risk of vascular disease is not known. Since B6-deficiency has little tendency to raise fasting plasma total homocysteine (tHcy) but yields an elevated tHcy response following a methionine load, low B6 nutriture may lead to repeated transient mild hyperhomocysteinemia following meal consumption. Several reports of associations between elevated plasma C-reactive protein (CRP) and low B6 status have raised the hypothesis that systemic inflammation is prone to occur during B6 deficiency or contributes to low B6 status. The investigators previously found that healthy humans in low B6 status caused by dietary restriction exhibited normal plasma CRP levels. The investigators also postulate that oxidative stress associated with low B6 status, coupled with impaired glutathione synthesis, contributes to such risk. These questions indicate the need for a more thorough understanding of the metabolic changes occurring in low B6 status from marginal B6 intake and from drug interactions such as in women using oral contraceptives.

Marginal vitamin B6 deficiency, which occurs commonly worldwide, leads to a cellular deficiency of the coenzyme pyridoxal phosphate (PLP). PLP is a coenzyme in several phases of one carbon (1C) metabolism, which is the array of reactions in which one carbon units are acquired and used in reactions including nucleotide synthesis, regeneration of methionine (Met) from homocysteine (Hcy), and methylation of many biological compounds. 1C metabolism is linked to the transsulfuration pathway in which Hcy undergoes PLP-dependent catabolism leading to cysteine, whose availability governs the formation of the antioxidant glutathione. Nutritional or genetic conditions that impair 1C metabolism are associated with elevation in plasma Hcy concentration and increased risk of vascular disease. It is believed that the metabolic effects of vitamin B6 deficiency will be most pronounced following protein intake when the vitamin B6-dependent pathways of amino acid metabolism experience the greatest substrate load. The human subjects protocols of this study consist of two distinct phases intended to extend our understanding of basic human 1C metabolism and the effects of marginal vitamin B6 deficiency under postprandial conditions. Phase 1 will investigate the effects of vitamin B6 nutrition on the PLP-dependent generation of 1C units by the glycine cleavage system and on the synthesis of glutathione. Phase 2 will investigate the dependence of methionine metabolism on vitamin B6 nutritional status, with particular emphasis on the recycling of Hcy to Met. Each phase of this study will involve 14 healthy, nutritionally adequate, young adults (7 male, 7 female) who will undergo metabolite profiling and kinetic analysis using intravenously infused stable isotopic tracers performed both before and after a ~4-week period of dietary vitamin B6 restriction. Subjects will be assigned to either Phase 1 or Phase 2, which will be identical in design except for the tracers and analytical methods used. We hypothesize that vitamin B6 deficiency will yield reduction in postprandial rates of homocysteine remethylation, generation of 1C units from glycine, and synthesis of glutathione. The results of this study will aid in assessing the consequences of nutritional and genetic variables affecting human metabolism and will further our understanding of the relationships between vitamin B6 nutrition and disease.

In a cross-over study the investigators evaluate the effects of natural (Panmol-B-Complex) (Pan [Greek] = all; moles [Latin] = molecules/particles - brand name) versus synthetic vitamin B complexes to identify the bioavailability of distinct vitamins as well as long-term effects. The primary hypothesis for this study: "Natural Vitamin B-complexes are as effective as synthetic Vitamin B-complexes or better." For this reason 30 subjects (18 to 65y; BMI >19 to <29) were recruited for this study. The study population was divided into 2 groups of each 15 subjects in a cross-over trial. Vitamin supplementation consisted of Thiamine (2.93 mg), Riboflavin (3.98 mg), Niacin (29.85 mg), Pantothenic acid (10.95 mg), Pyridoxine (3.38 mg), Biotin (0.108 mg), Folic acid (0.69 mg) and Cobalamin (8.85 µg) per day in both groups. Blood samples are taken at baseline - 1.5h after vitamin supplementation - 4h - 7h - 6 weeks - wash out phase I (2 weeks); start cross-over: baseline - 1.5h after vitamin supplementation - 4h - 7h - 6 weeks - washout phase II (6 weeks). In case of main target criteria Thiamin, Riboflavin, Pyridoxine, Folic acid and Cobalamin were measured in serum as well as total peroxides (µmol/L), peroxidase-activity (U/L), total antioxidant status (mmol/L) and polyphenols (mmol/L).

The objective of this study was to evaluate vitamin B deficiency (particularly vitamin B6 deficiency) in diabetic patients in Germany in relation to the presence or absence of proteinuria, and global vascular risk.