Effect of Omega-3 Fatty Acid on the Fatty Acid Content of the Erythrocyte Membrane and Proteinuria in Patients with Diabetic Nephropathy

Role of omega-3 fatty acids in reducing proteinuria: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Proteinuria, a hallmark of renal and systemic disorders, is associated with adverse outcomes, especially in chronic kidney disease and cardiovascular disease. Omega-3 fatty acids have garnered attention for their cardiovascular benefits and potential therapeutic effects on proteinuria. This systematic review and meta-analysis aimed to evaluate the impact of omega-3 fatty acid supplementation on proteinuria levels across various kidney-related conditions.

METHODS AND STUDY DESIGN

Studies published from 1989 to 2023 were systematically identified, including randomized controlled trials, cohort, case-control, and cross-sectional studies. Nine studies involving a total of 347 participants were included in the analysis.

RESULTS

The meta-analysis revealed a neutral overall effect size of omega-3 fatty acid supplementation on proteinuria levels, assessed under both common and random effect models. Despite the lack of statistically significant evidence supporting the efficacy of omega-3 fatty acids in reducing proteinuria, the variability in interventions and patient populations suggests potential individual responses.

CONCLUSIONS

The find-ings highlight the heterogeneity in responses to omega-3 fatty acid supplementation and emphasize the need for cautious interpretation. While no definitive conclusion can be drawn, the results underscore the importance of targeted research focusing on specific subgroups or conditions that may benefit from omega-3 supplementation. These findings contribute to the evolving understanding of personalized kidney health strategies and pave the way for further exploration and optimization of omega-3 fatty acids' therapeutic applications.

Omega-3 world map: 2024 update

In 2016, the first worldwide n3 PUFA status map was published using the Omega-3 Index (O3I) as standard biomarker. The O3I is defined as the percentage of EPA + DHA in red blood cell (RBC) membrane FAs. The purpose of the present study was to update the 2016 map with new data. In order to be included, studies had to report O3I and/or blood EPA + DHA levels in metrics convertible into an estimated O3I, in samples drawn after 1999. To convert the non-RBC-based EPA + DHA metrics into RBC we used newly developed equations. Baseline data from clinical trials and observational studies were acceptable. A literature search identified 328 studies meeting inclusion criteria encompassing 342,864 subjects from 48 countries/regions. Weighted mean country O3I levels were categorized into very low ≤4%, low >4-6%, moderate >6-8%, and desirable >8%. We found that the O3I in most countries was low to very low. Notable differences between the current and 2016 map were 1) USA, Canada, Italy, Turkey, UK, Ireland and Greece (moving from the very low to low category); 2) France, Spain and New Zealand (low to moderate); and 3) Finland and Iceland (moderate to desirable). Countries such as Iran, Egypt, and India exhibited particularly poor O3I levels.

Omega-3 Fatty Acids and Their Interaction with the Gut Microbiome in the Prevention and Amelioration of Type-2 Diabetes

Type-2 diabetes mellitus (T2DM) is often linked with hyperglycemia, disturbed lipid profiles, inflammation, and gut dysbiosis. Omega-3 fatty acid supplementation has a vital role in the management of T2DM. As a result, a better understanding of the potential role of omega-3 fatty acids in the development and progression of T2DM by influencing the intestinal microflora will help to improve the therapeutic intervention for T2DM and related complications. Focusing on the molecular mechanisms and signaling pathways induced by omega-3 fatty acids, this paper attempts to comprehensively review and discuss the putative associations between omega-3 fatty acids, gut dysbiosis, and the pathophysiology of T2DM and its related comorbidities. In addition, we contemplate the importance of gut microbiota in T2DM prevention and treatment and ponder the role of omega-3 fatty acids in T2DM by positively modulating gut microbiota, which may lead to discovery of novel targets and therapeutic strategies thereby paving way for further comprehensive, mechanistic, and clinical studies.

Effect of pravastatin on erythrocyte membrane fatty acid contents in patients with chronic kidney disease

Background

Statin treatment has decreased the risk of cardiovascular events in patients with chronic kidney disease (CKD). Erythrocyte membrane oleic acid level is higher in patients with acute coronary syndrome. This study aimed to evaluate the effect of pravastatin on the erythrocyte membrane fatty acid (FA) contents in patients with CKD.

Methods

Sixty-two patients were enrolled from January 2017 to March 2019 (NCT02992548). Pravastatin was initially administered at a dose of 20 mg for 24 weeks. The pravastatin dose was increased to 40 mg after 12 weeks if it was necessary to control dyslipidemia. The primary outcome was change in erythrocyte membrane FA, including oleic acid, after pravastatin treatment for 24 weeks.

Results

Forty-five patients finished this study, and there was no adverse effect related to pravastatin. Compared with baseline, total cholesterol and low-density lipoprotein cholesterol levels were significantly decreased after pravastatin treatment. Compared with baseline, saturated FA, oleic acid, and arachidonic acid levels were significantly increased and polyunsaturated FA and linoleic acid (LA) levels were significantly decreased after pravastatin treatment. There was also a decrease in eicosapentaenoic acid after pravastatin treatment in CKD patients with estimated glomerular filtration rate < 60 mL/min/1.73 m².

Conclusion

Administration of pravastatin in patients with CKD leads to a decrease in FA known to be protective against the risk of CVD. Omega-3 FA or LA supplementation might be necessary to recover changes in erythrocyte membrane FA contents when pravastatin is used for treating dyslipidemia in patients with CKD.

The effects of omega-3 fatty acids on diabetic nephropathy: A meta-analysis of randomized controlled trials

OBJECTIVE

To evaluate the effects of omega-3 long-chain polyunsaturated fatty acids on proteinuria, estimated glomerular filtration rate (eGFR) and metabolic biomarkers among patients with diabetes.

STUDY DESIGN

Meta-analysis of randomized controlled clinical trials (RCTs).

SETTING & SUBJECTS

Patients with diabetes.

SELECTION CRITERIA FOR STUDIES

We conducted electronic searches in PubMed, Embase and Cochrane Central Register of Controlled Trials from January 1960 to April 2019 to identify RCTs, which examined the effects of omega-3 fatty acids on proteinuria, eGFR and metabolic biomarkers among diabetic patients.

RESULTS

Ten RCTs with 344 participants were included in our meta-analysis. Omega-3 fatty acids reduced the amount of proteinuria among type 2 diabetes mellitus (type 2 DM) and type 1 diabetes mellitus (type 1 DM). This association was only significant among type 2 DM (SMD = -0.29 (95% CI: -0.54, -0.03; p = 0.03). Only studies with duration of intervention of 24 weeks or longer demonstrated a significant lower proteinuria among omega-3 fatty acids compared to control group (SMD = -0.30 (95% CI: -0.58, -0.02; p = 0.04). There was a higher eGFR for both type 1 and type 2 DM groups among omega-3 fatty acids compared to control group, however, the effect was not statistically significant. Regarding serum total cholesterol, LDL-cholesterol and HbA1C, there was no significant difference comparing omega-3 fatty acids to control group. There was a non-significant systolic blood pressure reduction in the omega-3 fatty acids supplementation group compared to control.

CONCLUSION

Omega-3 fatty acids could help ameliorate proteinuria among type 2 DM who received omega-3 supplementation for at least 24 weeks without adverse effects on HbA1C, total serum cholesterol and LDL-cholesterol.

Impact of Blood or Erythrocyte Membrane Fatty Acids for Disease Risk Prediction: Focusing on Cardiovascular Disease and Chronic Kidney Disease

Fatty acids (FAs) are essential nutrients and main constituents of cell membranes that are involved in the signaling pathway and associated with health conditions. We investigated if blood or erythrocyte membrane FAs can predict the risk of cardiovascular disease (CVD), chronic kidney disease (CKD), and related complications. Omega-3 (n-3) FAs are important predictors for metabolic syndrome, diabetes, CVD, and CKD risks, and the n-3 index is also a good biomarker for sudden cardiac death in coronary artery disease. Linoleic acid, which is one of the major n-6 FAs reflecting recent dietary FA intake, may predict CVD risk and mortality in the general population and patients with CKD. Monounsaturated FAs (MUFAs) are also related to diabetes or diabetic nephropathy. Oleic acid, a major MUFA, is an emerging marker that is related to acute coronary syndrome, low glomerular filtration rate, and vascular calcification in patients with CKD, and can be modified by n-3 FA supplementation. Saturated FAs, trans-FAs, and FA desaturation/elongation are associated with CVD risk; however, few studies have been conducted on patients with CKD. In summary, blood or erythrocyte membrane FA measurements are important for CVD and CKD risk prediction and management. Further studies are needed to elucidate the FAs for their risk predictions.

The polyunsaturated fatty acid balance in kidney health and disease: A review

Epidemiological studies show that circulating polyunsaturated fatty acids contribute to preserve renal function. In renal disease states there is generally a lack of omega-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) as measured in biological samples, but despite intense research for more than 30 years, it is still unclear how and to what extent their supplementation would benefit kidney disorders. Studies evaluating the n-6 series and the kidney are less frequent. The last compilation of clinical trials with n-3 LCPUFA supplements focusing on renal function and damage dates back to 2012. We here discuss n-3 and n-6 fatty acids in relation to the kidney summarizing single- and double blind randomized controlled trials performed between 2012 and 2016. Nine were sub-studies/post-hoc analyses of previous parent trials. Twelve out of the twenty trials reported on fatty acid profile or fatty acid species. Factors that may explain inconsistent results obtained after supplementation with the n-3 LCPUFA EPA and DHA in kidney disease are discussed such as baseline levels determining response, drug interaction. The need of evaluating fatty acid status before and after intervention is emphasized, to match changes in outcome measure with changes of any fatty acid potentially involved.

Bioavailability of Dietary Omega-3 Fatty Acids Added to a Variety of Sausages in Healthy Individuals

A low Omega-3 Index (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in erythrocytes) is associated with cardiac, cerebral, and other health issues. Intake of EPA and DHA, but not of alpha-linolenic acid (ALA), increases the Omega-3 Index. We investigated bioavailability, safety, palatability and tolerability of EPA and DHA in a novel source: a variety of sausages. We screened 96 healthy volunteers, and recruited 44 with an Omega-3 Index <5%. Participants were randomly assigned to receive a variety of sausages enriched with approximately 250 mg EPA and DHA per 80 g (n = 22) daily for 8 weeks, or matching placebo sausages (n = 22). All sausages contained approximately 250 mg ALA/80 g. In the verum group, the mean Omega-3 Index increased from 4.18 ± 0.54 to 5.72 ± 0.66% (p < 0.001), while it remained unchanged in the placebo group. While ALA levels increased only in the placebo group, DPA levels increased in both groups. Inter-individual variability in the response was large. The mean increase of the Omega-3 Index per intake of EPA and DHA we observed was higher than for other sources previously studied, indicating superior bioavailability. As increasing production of EPA and DHA is difficult, improvements of bioavailability can facilitate reaching the target range for the Omega-3 Index (8-11%).

Stirring the Pot: Can Dietary Modification Alleviate the Burden of CKD?

Diet is one of the largest modifiable risk factors for chronic kidney disease (CKD)-related death and disability. CKD is largely a progressive disease; however, it is increasingly appreciated that hallmarks of chronic kidney disease such as albuminuria can regress over time. The factors driving albuminuria resolution remain elusive. Since albuminuria is a strong risk factor for GFR loss, modifiable lifestyle factors that lead to an improvement in albuminuria would likely reduce the burden of CKD in high-risk individuals, such as patients with diabetes. Dietary therapy such as protein and sodium restriction has historically been used in the management of CKD. Evidence is emerging to indicate that other nutrients may influence kidney health, either through metabolic or haemodynamic pathways or via the modification of gut homeostasis. This review focuses on the role of diet in the pathogenesis and progression of CKD and discusses the latest findings related to the mechanisms of diet-induced kidney disease. It is possible that optimizing diet quality or restricting dietary intake could be harnessed as an adjunct therapy for CKD prevention or progression in susceptible individuals, thereby reducing the burden of CKD.