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Elevated plasma 4-pyridoxic acid in renal insufficiency
Stephen P Coburn1, Robert D Reynolds, J Dennis Mahuren
1Department of Biochemistry, Fort Wayne State Developmental Center, Fort Wayne, IN 46835, USA. coburn@ipfw.edu
The American Journal of Clinical Nutrition
|January 5, 2002
Summary
Renal insufficiency significantly elevates 4-pyridoxic acid levels, a key vitamin B-6 metabolite. The ratio of 4-pyridoxic acid to pyridoxal (PA:PL) in plasma can differentiate between dietary vitamin B-6 changes and kidney dysfunction.
Area of Science:
- Biochemistry
- Nephrology
- Nutritional Science
Background:
- Renal insufficiency is linked to disrupted vitamin B-6 metabolism.
- Elevated plasma 4-pyridoxic acid, a major vitamin B-6 catabolite, is observed in patients with kidney dysfunction.
Purpose of the Study:
- To investigate the renal handling of 4-pyridoxic acid.
- To determine the impact of renal dysfunction on vitamin B-6 metabolism.
Main Methods:
- Measured renal clearance of 4-pyridoxic acid and creatinine in pregnant, nonpregnant, and lactating women.
- Assessed the influence of vitamin B-6 intake and alkaline phosphatase activity on plasma PA:PL in various subject groups, including those with differing serum creatinine levels.
Main Results:
- Renal clearance of 4-pyridoxic acid was significantly higher than creatinine clearance, suggesting tubular secretion.
- Elevated plasma creatinine correlated with marked increases in 4-pyridoxic acid and the PA:PL ratio.
- Plasma PA:PL was unaffected by vitamin B-6 intake variations or pyridoxal-P levels.
Conclusions:
- Plasma 4-pyridoxic acid concentrations are substantially elevated in renal insufficiency.
- The plasma PA:PL ratio serves as a valuable biomarker to distinguish elevated 4-pyridoxic acid caused by dietary intake versus renal impairment.