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This Article Full Text Full Text (PDF) All Versions of this Article: 90/5/1151    most recent ajcn.2009.28338v1 Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Mushtaq, S. Articles by Powers, H. J PubMed PubMed Citation Articles by Mushtaq, S. Articles by Powers, H. J Agricola Articles by Mushtaq, S. Articles by Powers, H. J

Erythrocyte pyridoxamine phosphate oxidase activity: a potential biomarker of riboflavin status?^1,2,3

¹ From the Human Nutrition Unit, School of Medicine and Biomedical Sciences, University of Sheffield, Sheffield, United Kingdom.

² Supported in part by the UK Food Standards Agency (N05061).

³ Address correspondence to HJ Powers, Human Nutrition Unit, Faculty of Medicine, Dentistry and Health, University of Sheffield, Beech Hill Road, Sheffield S10 2RX, United Kingdom. E-mail: h.j.powers{at}sheffield.ac.uk.

Background: Riboflavin status is commonly measured by the in vitro stimulation of erythrocyte glutathione reductase with flavin adenine dinucleotide and expressed as an erythrocyte glutathione reductase activation coefficient (EGRAC). However, this assay is insensitive to poor riboflavin status in subjects with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Because G6PD deficiency is common in parts of the world where ariboflavinosis is endemic, it is important to have a measure of riboflavin status that is unaffected by differences in G6PD status.

Objective: The objective was to further develop and validate a fluorometric assay for pyridoxamine phosphate oxidase (PPO) activity as a measure of riboflavin status.

Design: A fluorometric assay was optimized for the flavin-dependent enzyme PPO in erythrocytes. Hemolysates from a previous riboflavin intervention study (2- and 4-mg riboflavin supplements) were used to investigate the responsiveness of the method to changes in riboflavin intake.

Results: PPO activity and the PPO activation coefficient (PPOAC) were used to assess riboflavin status. Both PPO activity and PPOAC responded to riboflavin supplements (P < 0.01), but only PPO showed a dose response (P < 0.001). The change from baseline to after the intervention in PPOAC and PPO enzyme activity was significantly inversely correlated (P < 0.001). Both PPO activity and PPOAC were strongly correlated with EGRAC (P < 0.001). Additionally, both PPOAC and EGRAC showed a significant inverse correlation with dietary riboflavin intake (P < 0.01); PPO activity was positively correlated with riboflavin intake (P < 0.01).

Conclusion: PPO activity could be used as a biomarker for measuring riboflavin status, especially in populations with a high prevalence of G6PD deficiency. This trial is registered at www.isrctn.org as ISRCTN35811298.