• Journal of Nutrition and Health
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• v.28 no.5
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• pp.426-434
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• 1995

The purpose of this study were to investigate the effect of fasting and vitamin B6 repletion on tissue concentration of pyridoxal 5-phosphate and urinary excreteion of 4-pyridoxic acid in vitamin B6 deficient rats. Sixty six rats(6 per group) were fed either a vitamin B6 deficient diet (-B6) or a control diet (+B6) for 6 weeks and then rats were repleted with +B6 diet for 2 weeks. Rats were fasted for 1 and 3 days and for 3 days after repletion. Pyridoxal 5-phosphate (PLP) concentration in plasma, liver, skeletal muscle, and heart muscle and urinary 4-pyridoxic acid (4-PA) excretion were compared. Fasting resulted in a significant increase in PLP concentration in the plasma, liver and heart muscle of rats fed the -B6 diet. Skeletal muscle PLP concentration was significantly decreased in +B6 rats but not in -B6 rats. Following vitamin B6 repletion, PLP concentration in the plasma, liver and heart muscle in previously -B6 rats was similar to the respective concentration in +B6 rats while PLP concentration in the skeletal muscle of previously -B6 rats increased, but it was not reached to that of +B6 rats. At day 1 and 2 of the fast, urinary 4-PT excretion increased in both +B6 and -B6 rats although there was no supply of vitamin B6 due to fasting. These results suggest that vitami B6 is redistributed as PLP when there is a caloric deficit and PLP is supplied by an endogenous source, possibly PLP bound to skeletal muscle glycogen phosphorylase.

• Journal of Nutrition and Health
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• v.43 no.3
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• pp.315-323
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• 2010

The purpose of this study was to establish the selection of indicators for estimating and factors affecting the requirement of vitamin B6. There has been a need to establish the human requirements of vitamin $B_6$ since vitamin $B_6$ is thought to be involved in more than one hundred biochemical reactions as a coenzyme in the metabolism of amino acids, glucose, and lipid, and the synthesis of neurotransmitters. For the review of the literature, this study included from early findings of the sixties to studies of 2009. This study suggests that plasma pyridoxal 5' phosphate (PLP) is the best single indicator of vitamin $B_6$ status for the healthy but not for the non-healthy. Erythrocyte aspartate aminotransferase and alanine aminotransferase activation by PLP as an indirect measure and urinary 4-pyridoxic acid excretion as a direct measure are useful as supporting indicators. Bioavailability, nutrient interaction, physiological need, and chronic diseases may increase the requirement for vitamin $B_6$. However, these effects can not be quantified due to insufficient evidences.