Plasma Pyridoxal 5′-Phosphate Is Not Associated with Inflammatory and Immune Responses after Adjusting for Serum Albumin in Patients with Rheumatoid Arthritis: A Preliminary Study

Abstract

Background/Aims: Plasma pyridoxal 5′-phosphate (PLP) has been shown to be associated with inflammatory and immune responses.Rheumatoid arthritis (RA) is an autoimmune and chronic systemic inflammatory disease and patients with RA have lower plasma PLP levels. We studied the relationship between plasma PLP and inflammatory or immune responses in patients with RA. Methods: This study was designed as an observational cross-sectional study. Forty-three patients with RA were allocated to the adequate (PLP ≥20 nmol/l) (n = 30) or deficient vitamin B₆ (PLP <20 nmol/l) (n = 13) group according to their fasting plasma PLP concentration on the day blood was taken. Plasma PLP, inflammatory parameters [i.e. high-sensitivity CRP (hs-CRP), erythrocyte sedimentation rate, interleukin-6, tumor necrosis factor-α] and immune parameters (i.e. white blood cells, total lymphocytes, neutrophils, T lymphocytes, B lymphocytes, T helper cells and T suppressor cells) were measured. Results: Patients with deficient plasma PLP concentration were mostly considered to have a systemic inflammatory status (hs-CRP >3 mg/l) and apparently had significantly higher mean hs-CRP levels and immune parameters than patients with adequate plasma PLP concentration. There was no significant association between plasma PLP levels and inflammatory parameters. The significantly inverse correlation of plasma PLP with the numbers of white blood cells, neutrophils, total lymphocytes, T lymphocytes and T helper cells remained after adjusting for serum hemoglobin concentration, but the significant correlation disappeared after serum albumin concentration was also considered. Conclusions: RA patients with deficient plasma PLP concentration had more severe inflammatory and immune responses than patients with adequate plasma PLP concentration. However, there was a lack of association of low plasma PLP concentration with inflammatory and immune parameters after serum albumin concentration was considered in patients with RA.

Direct and Functional Biomarkers of Vitamin B6 Status

“…Liver is the organ responsible for the formation of PLP in plasma (83, 129), which in addition to PLP (about 70–90%) also contains PL (8–30%) and 4-pyridoxic acid (PA), a vitamin B6 catabolite that is excreted into the urine (110, 213). The concentration of plasma PLP in an individual is increased with increasing vitamin B6 intake over a broad range (75, 76).…”

“…The concentration of plasma PLP in an individual is increased with increasing vitamin B6 intake over a broad range (75, 76). In plasma, PLP is strongly bound to albumin (83, 129), and free PLP can be dephosphorylated to PL in a reaction catalyzed by tissue non-specific alkaline phosphatase (ALP). This is an ectoenzyme located on the outer membrane of cells, including erythrocytes (26).…”

“…Low PLP in RA patients with moderate inflammation (83) and in critically ill patients (85) has actually been attributed to reduced binding of PLP to albumin. Because of high protein binding of PLP in plasma, measurement of PLP in undeproteinized serum/plasma gives false low PLP concentrations (179).…”

Is there a Link between Vitamin B and Multiple Sclerosis?

“…In infants fed with autoclaved formula, where pyridoxine is destroyed, hyper-irritability and epileptic-type seizures were reported; administration of the vitamin reversed symptoms [45]. In addition, clinically low pyridoxine levels (< 20 nmol/L) are not uncommon in autoimmune disorders, as noted in rheumatoid arthritis [46] and type I diabetes [47]. In fact, in an observational cross-sectional study of 43 patients with rheumatoid arthritis, patients were put into 2 groups, (i) < 20 nmol/L (n=30, deficient levels) or (ii) > 20 nmol/L (n=13, adequate levels) pyridoxine levels.…”

“…In fact, in an observational cross-sectional study of 43 patients with rheumatoid arthritis, patients were put into 2 groups, (i) < 20 nmol/L (n=30, deficient levels) or (ii) > 20 nmol/L (n=13, adequate levels) pyridoxine levels. Those in the deficient pyridoxine group were reported to have high inflammation as measured by Creactive protein and higher immune cell numbers (T cells) [46]. In addition, in 32 type I diabetic patients and 27 matched healthy controls it was noted that type I diabetes altered the metabolism of pyridoxine leading to increased risk of pyridoxine deficiency and diabetic complications [48].…”