Oxidative modifications impair albumin quantification |
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Authors: | Regina Michelis Batya Kristal Shifra Sela |
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Institution: | a Eliachar Research Laboratory, Western Galilee Hospital, Nahariya, Israel b Nephrology Department, Western Galilee Hospital, Nahariya, Israel c Biochemistry Laboratory, Western Galilee Hospital, Nahariya, Israel |
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Abstract: | BackgroundHypoalbuminemia is a measure of malnutrition, inflammation and a predictor of mortality in uremia. It is controversial whether albumin levels per se are associated with the clinical outcomes in uremic patients. The co-occurrence of hypoalbuminemia and oxidative stress in hemodialysis (HD) patients led us to hypothesize that oxidative modifications of albumin decrease its detection and influence albumin quantification.MethodsAlbumin levels are determined in clinical laboratories mainly by the bromocresol green (BCG) spectrophotometric assay. The detection of serum albumin was investigated in HD patients and in healthy controls using an “albumin-detection index”, defined as the ratio between BCG read-out (albumin-specific) to total albumin. The detection efficacy of albumin was also investigated in vitro, after glycoxidation, HOCl-mediated-oxidation, and metal-catalyzed-oxidation. Oncotic pressure was measured to assess albumin function.ResultsThe albumin-detection index of patients was significantly lower compared with controls, correlating negatively with oxidative stress markers (serum advanced oxidation protein products-AOPP and glycoxidized serum albumin) and positively with serum albumin levels. The albumin-detection index was also decreased after in vitro oxidation.ConclusionsThe study shows, both in vivo and in vitro, decreased detection of oxidized albumin by a commonly-used clinical assay, thus providing the molecular link between oxidative stress and hypoalbuminemia. Oxidative stress as reflected by hypoalbuminemia, rather than actual albumin levels, may be related to cardiovascular morbidity outcomes in HD patient. |
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Keywords: | AGE advanced glycoxidation end products AGE-HSA glycoxidized human serum albumin AOPP advanced oxidation protein products BCG bromocresol green CML carboxy-methyllysine CO-HSA carbonylated human serum albumin DNPH 2 4-dinitrophenylhydrazine HC healthy control subjects HD hemodialysis HSA human serum albumin IMA ischemia modified albumin MIA malnutrition-inflammation-atherosclerosis syndrome MS mass spectroscopy PBS phosphate-buffered saline SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis |
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