Abstract: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… Show more
“…Vitamin B 6 kinetic studies The results of our in vivo kinetic studies in three probands are in accordance with observations in rodents and in vitro cell models (Sakurai et al 1987;Albersen et al 2013) showing that PL and PA are the most abundant plasma vitamin B 6 vitamers following PN intake. PN was rapidly cleared from plasma while PLP showed a slow but steady increase.…”
PM concentrations and the PM/PA ratio clearly separated PNPO-deficient patients from the other cohorts. The plasma PM/PA ratio thus represents a robust biomarker for the selective screening of PNPO deficiency.
“…Vitamin B 6 kinetic studies The results of our in vivo kinetic studies in three probands are in accordance with observations in rodents and in vitro cell models (Sakurai et al 1987;Albersen et al 2013) showing that PL and PA are the most abundant plasma vitamin B 6 vitamers following PN intake. PN was rapidly cleared from plasma while PLP showed a slow but steady increase.…”
PM concentrations and the PM/PA ratio clearly separated PNPO-deficient patients from the other cohorts. The plasma PM/PA ratio thus represents a robust biomarker for the selective screening of PNPO deficiency.
“…Although liver is a major site of vitamin B-6 metabolism, small doses of pyridoxine and pyridoxamine can be converted to pyridoxal in the intestine prior to release into the portal circulation in the mouse (Sakurai et al 1987(Sakurai et al , 1988. Similar results were reported with cultured Caco-2 cells (Albersen et al 2013). The main transport forms of vitamin B-6 in blood are pyridoxal and pyridoxal phosphate, which is released from the liver associated primarily with albumin .…”
Section: Absorption and Transport Of Vitamin B-6supporting
“…However, in vivo it is likely that PAP is hydrolysed and subsequently excreted as pyridoxic acid in urine . It is known that the B6 vitamers are mostly absorbed in their non‐phosphorylated form and do not cross the gastro‐intestinal wall in appreciable amounts before hydrolysis . In addition, upon measurement of the B6 vitamer blood levels of patients on PLP supplementation, PAP is not detected in significant amounts (Unpublished data Laboratory of Mills P, 2016).…”
Pyridoxal 5'-phosphate tablets from Solgar were found to be the most reliable product for the preparation of extemporaneous PLP liquids. This work highlighted the difference between the marketed PLP dietary supplements quality and the importance of proper storage of aqueous PLP. There is a need to develop pharmaceutical forms of PLP that ensure dose accuracy and avoid potentially unsafe impurities with the aim of enhancing safety and compliance.
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