Anti-inflammatory effect of omega-3 in haemodialysis patients
The World Health Organisation (WHO) defines terminal kidney disease (TKD) as kidney disease requiring renal replacement therapy (RRT, dialysis or kidney transplantation) to safeguard the patient’s life. Based on 2008 data, the WHO estimated that over 1.4 million people a year required RRT wordwide, and that this amount would increase by 8% each year.
In 2015, over 2 million people received RRT worldwide, but it is estimated that this figure represents only 10% of those who need it to live. Chronic kidney disease (CKD) is considered a world health crisis.
Haemodialysis (HD) patients have a mortality rate three to four times higher than their reference group without CKD, and cardiovascular (CV) disease is the main cause of death. Chronic systemic low-grade inflammation (an important pathogenic factor in atherosclerosis) is reported in 30-50% of these patients, in whom high levels of anti-inflammatory markers such as C-reactive protein (CRP) and interleukin (IL) 6 are predictors for CV and overall mortality. Furthermore, inflammation contributes to the development of comorbidities, such as protein energy wasting, vascular calcification, endocrine disorders and depression, which affect the quality of life of haemodialysis patients. CKD has a very negative effect on quality of life, due to these comorbidities and the limitations to daily life experienced by patients.
Inflammation in patients on HD can be triggered by exogenous and endogenous factors. The HD procedure itself can be the cause of inflammation: infections at the access point/catheter; bioincompatible dialysis membrane; and exposure to endotoxins, among others. Endogenous factors included fluid overload, persistent infections, periodontal disease (a prevalence of 63% in HD patients has been reported in the literature), increased oxidative stress and alterations to gut microbiota whose effects reach the bloodstream.
Thus, it is thought that treating inflammation could improve results in haemodialysis patients. Potentially useful drugs in this respect include statins, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers and anticytokine treatments. From a non-pharmacological perspective, there is also growing interest in dietary elements with immune-modulating properties, which could reduce inflammation markers, such as CRP, IL-6 and tumour necrosis factor-α (TNF-α) In this context, an international research group (Malaysia, United States and Italy) carried out a systemic review of published controlled, randomised trials in HD patients who had received some form of nutritional intervention (food rich in polyphenols, omega-3 fatty acids (FA), antioxidants, vitamin D, fibre or probiotics) for a minimum of four weeks, with the aim of assessing the effects of these interventions on inflammation markers.
Two previous systemic reviews that assessed the potential of omega-3 FAs for the same purpose concluded that: 1) the association of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) could reduce levels of CRP, but not those of IL-6 and TNF-α; and 2) supplementation with EPA, DHA and α-linoleic acid (ALA) reduce CRP levels in a mixed population of HD patients on peritoneal dialysis and in stage 5 of non-dialysis dependent CKD.
The results of the authors from the current study indicate that both omega-3 FAs (ALA, EPA and DHA) and vitamin E, alone, are significantly effective in reducing CRP in patients on HD, while the available evidence does not support this view for other nutritional interventions (polyphenols, antioxidant, fibre and probiotics).
Khor BH, Narayanan SS, Sahathevan S, Gafor AHA, Daud ZAM, Khosla P, et al. Efficacy of Nutritional Interventions on Inflammatory Markers in Haemodialysis Patients: A Systematic Review and Limited Meta-Analysis. Nutrients. 2018 Mar 23;10(4).
Heidari B. C-reactive protein and other markers of inflammation in hemodialysis patients. Caspian J Intern Med. 2013; 4(1):611-6.
National Kidney Foundation. Global facts: about kidney disease. March, 2015.
World Health Organization. How can we achieve global equity in provision of renal replacement therapy? Bulletin of the World Health Organization. 2008;86(3):161-240.