Abstract
BackgroundHaemodialysis (HD) patients tend to have higher levels of oxidative stress (OS), associated with increased morbidity and premature mortality, compared to the general population. Levels of malondialdehyde (MDA), a biomarker of OS, are reduced by the antioxidant properties of vitamin E (VE) but outcomes from randomised control trials of VE supplementation on MDA in HD patients have been inconsistent.MethodsWe undertook a systematic review and meta-analysis of adult HD patients from VE supplementation studies with measures of MDA. The following search criteria of MEDLINE and EMBASE were considered from inception to January 2020: ‘dialysis’ AND ‘Vitamin E OR tocopherol’ AND ‘malondialdehyde OR MDA’. Two reviewers independently extracted study data and assessed risk of bias. Mean MDA levels and standard deviation were determined before and after VE supplementation. Standardised mean difference (SMD) and standard error were calculated as the within person difference and units of measure were not consistently recorded across all studies. The SMD were pooled using random effects meta-analysis.ResultsThe SMD of MDA levels from 18 comparisons was significantly lower in HD patients following VE supplementation (− 1.55; confidence interval: − 2.17 to − 0.94, P < 0.00001). There were significant levels of heterogeneity between studies (I2 value = 91%; P < 0.00001) with evidence of potential publication bias toward smaller studies.ConclusionsOur findings support the use of VE to reduce the effects of OS in HD patients although high levels of heterogeneity and variation in the methodological approaches used by some studies highlight the need for further investigation.
Highlights
Haemodialysis (HD) patients tend to have higher levels of oxidative stress (OS), associated with increased morbidity and premature mortality, compared to the general population
Uraemic toxin accumulation has been associated with OS that is associated with cardiovascular disease (CVD) progression in end-stage renal disease (ESRD) patients [4]
One randomised controlled trial (RCT) of HD patients consisted of a treatment arm with Alpha tocopherol (AT) as a monotherapy (Asemia et al) or AT and omega 3 fatty acids co-supplementation (Asemib et al) [43]
Summary
Haemodialysis (HD) patients tend to have higher levels of oxidative stress (OS), associated with increased morbidity and premature mortality, compared to the general population. Oxidative stress (OS) is defined as “an imbalance between oxidants and antioxidants in favour of the oxidants that leads to a disruption of redox signalling and control and/or molecular damage” [1]. Endogenous oxidants such as reactive oxygen species (ROS), generally manifest from unstable superoxides and hydroxyl free radical by-products of intracellular metabolic reactions. Patients with end-stage renal disease (ESRD) accumulate uraemic toxins with progressive loss of renal function Some uraemic toxins, such as homocysteine and advanced glycation end-products (AGEs), are difficult to remove during haemodialysis because significant proportions are protein bound. Uraemic toxin accumulation has been associated with OS that is associated with cardiovascular disease (CVD) progression in ESRD patients [4]
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