Absorption and Metabolism of Pyridoxamine in Mice. I.Pyridoxal as the Only Form of Transport in Blood.

Sakurai, Takahiro; Asakura, Tadashi; Mizuno, A; Matsuda, Makoto

doi:10.3177/jnsv.37.341

Cited by 20 publications

(20 citation statements)

References 15 publications

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“…In contrast with these findings are the results of in vivo studies on vitamin B6 metabolism in mice [18], [19], [20]. Trace amounts of [ 3 H]-PN and [ 3 H]-PM were found to be rapidly absorbed by the intestine.…”

Section: Introductionmentioning

confidence: 64%

The Intestine Plays a Substantial Role in Human Vitamin B6 Metabolism: A Caco-2 Cell Model

et al. 2013

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BackgroundVitamin B6 is present in various forms (vitamers) in the diet that need to be metabolized to pyridoxal phosphate (PLP), the active cofactor form of vitamin B6. In literature, the liver has been reported to be the major site for this conversion, whereas the exact role of the intestine remains to be elucidated.ObjectiveTo gain insight into the role of the intestine in human vitamin B6 metabolism.Materials and MethodsExpression of the enzymes pyridoxal kinase (PK), pyridox(am)ine phosphate oxidase (PNPO) and PLP-phosphatase was determined in Caco-2 cells and in lysates of human intestine. Vitamin B6 uptake, conversion and excretion were studied in polarized Caco-2 cell monolayers. B6 vitamer concentrations (pyridoxine (PN), pyridoxal (PL), PLP, pyridoxamine (PM), pyridoxamine phosphate (PMP)) and pyridoxic acid (PA) were quantified by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) using stable isotope-labeled internal standards.ResultsThe enzymatic system involved in vitamin B6 metabolism (PK, PNPO and PLP-phosphatase) is fully expressed in Caco-2 cells as well as in human intestine. We show uptake of PN, PM and PL by Caco-2 cells, conversion of PN and PM into PL and excretion of all three unphosphorylated B6 vitamers.ConclusionWe demonstrate, in a Caco-2 cell model, that the intestine plays a substantial role in human vitamin B6 metabolism.

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Section: Introductionmentioning

confidence: 64%

The Intestine Plays a Substantial Role in Human Vitamin B6 Metabolism: A Caco-2 Cell Model

et al. 2013

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“…B6 vitamers contained in the diet are known to appear in the plasma mainly as PL (15) and are incorporated into various tissues according to need. Based on the finding of a high content of glycogen phosphorylase in muscle, Krebs and Fischer proposed that muscle phosphorylase acts as a repository of B6 (16) .…”

Section: Discussionmentioning

confidence: 99%

Dietary Protein as a Factor Affecting Vitamin B6 Requirement.

Okada

Shibuya

Akazawa

et al. 1998

Journal of Nutritional Science and Vitaminology, J Nutr Sci Vit

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SummaryRats were fed 20 or 70% casein diets with varying amounts of vitamin B6 (B6), and the B6 content and B6-dependent enzymatic activity in their tissues were examined to determine the minimum re quirement of B6 for animals subjected to different levels of dietary protein (i.e., 20%: 0, 1.45, 2.90, 5.80mg pyridoxine (PN)/kg diet; 70%: 0, 2.90, 5.80, 8.70mg PN/kg diet). B6 requirements for the rats were almost met in the 1.45mg PN/kg 20% casein diet and the 2.90mg PN/kg 70% casein diet when judged from the hepatic B6 content. However, almost twice the PN was required in both 20 and 70% casein diets when judged from PLP-enzymatic activity. The content of B6 vitamers in plasma appeared to be most sensitive to B6 status, though the satisfactory level is not known. It was confirmed that, in any case tested, a high-protein diet increased the requirement of B6. Key Words vitamin B6 requirement, vitamin B6 content, aspartate aminotransferase, glycogen phosphorylase Vitamin B6 (B6) is found in biological tissues and fluids as pyridoxine (PN), pyridoxal (PL), pyridoxamine (PM) and their phosphorylated derivatives. The vitamers function as coenzymes of glycogen phosphorylase and many amino acid metabolic enzymes. A high-protein diet increases the requirement for B6 as follows: First, a high-protein diet containing a low B6 content increases the urinary excre tion of xanthrenic acid (an abnormal metabolite of tryptophan) and some other tryptophan metabolites such as kynurenine and hydroxykynurenine (1); second, in animals fed a B6-free, high-protein diet, growth is retarded and is accompanied by a severe decrease in the activity of pyridoxal enzymes compared to animals fed a B6-free, low-protein diet (2, 3); and third, an increase in B6 intake increases phosphorylated pyridoxal (PLP) concentration, whereas increased protein intake decreases plasma PLP concentration (4).The accurate determination of B6 in biological samples is essential for assessing nutritional and metabolic requirements. There have been many attempts to analyze

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“…Kanouchi et al (30) showed that when RAW264.7 cells were cultured in a culture medium treated with the B6 vitamers PL, PM, PN or PLP, only PL interacted with the cell surface. PL is known as a primary form of transport in blood and is capable of freely passing through the cell membrane, while PLP cannot easily cross the cell membrane and must be hydrolyzed by alkaline phosphatase into PL (31)(32)(33). Therefore, PL appears to affect IGFBP1 expression in HepG2 cells as PL crosses cell membranes from a cultured medium.…”

Section: Discussionmentioning

confidence: 99%

High concentrations of pyridoxal stimulate the expression of IGFBP1 in HepG2 cells through upregulation of the ERK/c-Jun pathway

Zhang

Suidasari

Hasegawa

et al. 2013

Molecular Medicine Reports

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Abstract. Increasing evidence suggests that dietary vitamin B6 is linked to the prevention of cancer and cardiovascular disease. However, the molecular mechanisms involved in this process are not yet understood. Preliminary results in the current study indicated, following DNA microarray analysis and quantitative PCR, that insulin-like growth factor-binding protein 1 (IGFBP1) mRNA is upregulated in HT29 colon carcinoma cells exposed to pyridoxal (PL, 500 µM). IGFBP1 is secreted from the liver and is hypothesized to exert a protective role in the development of cancer and cardiovascular disease. Thus, further experiments were performed to investigate the effect of PL on the expression of IGFBP1 in HepG2 hepatocellular carcinoma cells. The addition of PL (500 µM) markedly increased the expression of IGFBP1 mRNA in HepG2 cells at 6, 12 and 24 h (P<0.01), whereas other vitamers (500 µM), including pyridoxal 5'-phosphate (PLP), pyridoxine (PN) and pyridoxamine (PM), caused no such effect. The expression of the IGFBP1 protein in the cell lysate and culture medium was elevated in the presence of PL. PL elevated expression of the active form of ERK1 protein, p-ERK1, and the p-c-Jun protein, a downstream factor of ERK. Furthermore, IGFBP1 expression, elevated by PL, was suppressed by PD98059, an ERK inhibitor. Higher expression of IGFBP1 protein by PL was suppressed by cycloheximide. These results suggest that PL may induce the expression of IGFBP1 in hepatoma cells via a mechanism involving the ERK/c-Jun pathway.

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Absorption and Metabolism of Pyridoxamine in Mice. I.Pyridoxal as the Only Form of Transport in Blood.

Cited by 20 publications

References 15 publications

The Intestine Plays a Substantial Role in Human Vitamin B6 Metabolism: A Caco-2 Cell Model

The Intestine Plays a Substantial Role in Human Vitamin B6 Metabolism: A Caco-2 Cell Model

Dietary Protein as a Factor Affecting Vitamin B6 Requirement.

High concentrations of pyridoxal stimulate the expression of IGFBP1 in HepG2 cells through upregulation of the ERK/c-Jun pathway

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