Blood Fatty Acid Status and Clinical Outcomes in Dialysis Patients: A Systematic Review

Fatty Acid Composition of a Maternal Diet and Erythrocyte Phospholipid Status in Latvian Pregnant Women

BACKGROUND AND OBJECTIVES

Dietary fats are essential for maternal and fetal health. Fatty acids (FAs) in erythrocytes characterize the FA profile, which is influenced by diet and other factors. The aim of this study was to evaluate the association between the main FAs in erythrocyte membrane phospholipids and their influencing factors-dietary fat and supplement intake and lifestyle factors-in Latvian pregnant women.

MATERIALS AND METHODS

This cross-sectional study included 236 pregnant and postpartum women. The data were collected from medical documentation, a food frequency questionnaire, and a questionnaire on demographic, lifestyle, health status, and nutritional habits in outpatient clinics and maternity departments. FAs in erythrocyte membrane phospholipids were determined using gas chromatography.

RESULTS

Correlations were found between dietary SFAs and erythrocyte SFAs (r = -0.140, p = 0.032) and PUFAs (r = 0.167, p = 0.01) and between dietary PUFAs and erythrocyte MUFAs (r = -0.143, p = 0.028). Dietary SFAs, MUFAs, and PUFAs positively correlated with the studied n-3 and n-6 FAs in erythrocytes. Vitamin D correlated positively with MUFA and negatively with total PUFA and AA in erythrocytes. There was a negative correlation between dietary vitamin A and linoleic acid in erythrocytes. Physical activity negatively correlated with erythrocyte MUFAs and positively with erythrocyte PUFAs. Alcohol consumption positively correlated with erythrocyte SFAs and negatively with erythrocyte PUFAs.

CONCLUSIONS

There are indications that some dietary FAs may be correlated with erythrocyte FAs. Possible influencing factors for this association are alcohol, physical activity, vitamin D, and vitamin A.

Effect of nutritional supplementation on mortality in peritoneal dialysis patients: A meta-analysis

BACKGROUND

Malnutrition is a common clinical problem in peritoneal dialysis (PD) patients and is a predictor of mortality. This work analyzes the effect of nutritional supplementation for PD patients on all-cause and cardiovascular disease (CVD)-related deaths by meta-analysis.

METHODS

A study about nutritional interventions for PD patients on all-cause or CVD-related mortality is included.

RESULTS

Eight studies were included. The results showed that nutritional intervention can reduce all-cause mortality in PD patients (HR, 0.71; 95% confidence interval (CI), 0.64-0.79; p < 0.01). In CVD-related mortality, the results also showed that nutritional interventions significantly reduce CVD-related mortality (HR, 0.75; 95% CI, 0.64-0.87; p < 0.01). In exploratory analysis, vitamin D, folic acid, and high-plant-protein ratio intake have relative advantages.

CONCLUSION

Appropriate nutritional supplementation to PD patients can effectively reduce all-cause and CVD- related mortality in clinical practice, especially for vitamin D, folic acid, sodium supplements, and a high proportion of plant protein.

Causal associations between polyunsaturated fatty acids and kidney function: A bidirectional Mendelian randomization study

BACKGROUND

PUFAs were suggested to be beneficial for kidney function in observational studies. However, whether these associations are causal remains unclear.

OBJECTIVES

This study explores the causality between PUFAs and chronic kidney disease (CKD) or estimated glomerular filtration rate (eGFR) using bidirectional 2-sample Mendelian randomization (MR).

METHODS

Single nucleotide polymorphisms associated with PUFAs and kidney function were obtained from the largest and most recent genome-wide association studies with sample sizes of 13,544, 13,506, 13,499, 13,527, and 13,549 for omega-3 fatty acids, omega-6 fatty acids, DHA, LA, and other PUFAs than 18:2 (otPUFA), and 480,698 and 1,201,909 for CKD and eGFR, respectively. MR inverse-variance weighted (IVW) and pleiotropy residual sum and outlier test (MR-PRESSO) were used for data analysis, supplemented with a weighted median estimator, MR-Egger regression, and multivariable MR, giving β or OR and their 95% CIs.

RESULTS

There was suggestive evidence that higher omega-6 fatty acids were associated with increased eGFR using MR-PRESSO [β: 0.005 log(mL/min/1.73 m²) per SD increase in omega-6 fatty acids; 95% CI: 0.002, 0.008; P = 0.008]. Higher LA level was also associated with higher eGFR [β: 0.005 log(mL/min/1.73 m²) per SD increase in LA; 95% CI: 0.003, 0.007; P = 0.0007] using MR-PRESSO. Neither association of the other PUFAs, i.e., omega-3 fatty acids, DHA, and otPUFA, with CKD or eGFR nor the association of CKD and eGFR with PUFAs was found. Similar results were found in sensitivity analyses.

CONCLUSIONS

Our results suggest that higher omega-6 fatty acids and LA may increase eGFR levels. Although the estimated effects were relatively small, the results provide public health and research relevance, indicating the need for further longitudinal cohorts or randomized controlled trials on omega-6 fatty acids in improving kidney function.

Dietary habits in Australian, New Zealand and Malaysian patients with end stage kidney failure: A pre-specified cross-sectional study of the FAVOURED trial participants

BACKGROUND

Dietary management plays an important role in patients with kidney failure. Current dietary habits of Australians and New Zealanders (ANZ) and Malaysians with chronic kidney disease (CKD Stage 4-5) have not been adequately investigated. We report the dietary habits of people with advanced CKD and their adherence to country-specific dietary guidelines.

METHODS

Participants with CKD Stage 4-5, enrolled in the Omega-3 Fatty Acids (Fish oils) and Aspirin in Vascular access Outcomes in Renal Disease (FAVOURED) trial, completed a lifestyle questionnaire at baseline on their dietary intake.

RESULTS

Of 567 participants, 538 (ANZ, n = 386; Malaysian, n = 152; mean ± SD age 54.8 ± 14.3 years, 64% male) completed the questionnaire. Dietary fruit and vegetable intakes were higher in ANZ participants; 49% (n = 189) consumed ≥2 serves day^-1 of fruit and 61% (n = 235) ate ≥2 serves day^-1 of vegetables compared to 24% (n = 36) and 34% (n = 52) of Malaysians, respectively (p < 0.0001). Only 4% (n = 15) of ANZ participants met Australian Dietary recommendations of two fruit and five vegetable serves day^-1 . Fish consumption was higher in Malaysians with 83% (n = 126) consuming ≥2 serves week^-1 compared to 21% (n = 81) of ANZ participants (p < 0.001). Red meat intake was higher in ANZ participants; however, chicken consumption was similar; 48% (n = 185) consumed >2 chicken serves week^-1 and 65% (n = 251) ate >2 serves week^-1 of red meat compared to 43% (n = 65) and 15% (n = 23) of Malaysians, respectively.

CONCLUSIONS

Significant regional variation in dietary intake for fruit, vegetables and animal protein is described that likely reflects cultural and economic differences. Barriers to meeting recommended dietary intakes require further investigation.

Bioaccumulation of Blood Long-Chain Fatty Acids during Hemodialysis

Long-chain fatty acids (LCFAs) serve as energy sources, components of cell membranes, and precursors for signaling molecules. Uremia alters LCFA metabolism so that the risk of cardiovascular events in chronic kidney disease (CKD) is increased. End-stage renal disease (ESRD) patients undergoing dialysis are particularly affected and their hemodialysis (HD) treatment could influence blood LCFA bioaccumulation and transformation. We investigated blood LCFA in HD patients and studied LCFA profiles in vivo by analyzing arterio–venous (A–V) LFCA differences in upper limbs. We collected arterial and venous blood samples from 12 ESRD patients, before and after HD, and analyzed total LCFA levels in red blood cells (RBCs) and plasma by LC–MS/MS tandem mass spectrometry. We observed that differences in arterial and venous LFCA contents within RBCs (RBC LCFA A–V differences) were affected by HD treatment. Numerous saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) n-6 showed negative A–V differences, accumulated during peripheral tissue perfusion of the upper limbs, in RBCs before HD. HD reduced these differences. The omega-3 quotient in the erythrocyte membranes was not affected by HD in either arterial or venous blood. Our data demonstrate that A–V differences in fatty acids status of LCFA are present and active in mature erythrocytes and their bioaccumulation is sensitive to single HD treatment.

Lipoproteins and fatty acids in chronic kidney disease: molecular and metabolic alterations

Chronic kidney disease (CKD) induces modifications in lipid and lipoprotein metabolism and homeostasis. These modifications can promote, modulate and/or accelerate CKD and secondary cardiovascular disease (CVD). Lipid and lipoprotein abnormalities - involving triglyceride-rich lipoproteins, LDL and/or HDL - not only involve changes in concentration but also changes in molecular structure, including protein composition, incorporation of small molecules and post-translational modifications. These alterations modify the function of lipoproteins and can trigger pro-inflammatory and pro-atherogenic processes, as well as oxidative stress. Serum fatty acid levels are also often altered in patients with CKD and lead to changes in fatty acid metabolism - a key process in intracellular energy production - that induce mitochondrial dysfunction and cellular damage. These fatty acid changes might not only have a negative impact on the heart, but also contribute to the progression of kidney damage. The presence of these lipoprotein alterations within a biological environment characterized by increased inflammation and oxidative stress, as well as the competing risk of non-atherosclerotic cardiovascular death as kidney function declines, has important therapeutic implications. Additional research is needed to clarify the pathophysiological link between lipid and lipoprotein modifications, and kidney dysfunction, as well as the genesis and/or progression of CVD in patients with kidney disease.

Maternal Supplementation with Cow's Milk Naturally Enriched with PUFA Alters the Metabolism of Sows and the Fatty Acid Profile of the Offspring

The study aimed to evaluate the supplementation of gilts with cow's milk naturally enriched with n-3 and n-6 polyunsaturated fatty acids (PUFA) on reproductive outcomes, and the serum biochemical and FA profile of swine females and their offspring. During 316 days, 30 gilts were distributed into three groups: (1) Control, fed a basal diet + milk from cows without oil; (2) n-3, fed a basal diet + milk from cows fed a diet enriched with linseed oil; (3) n-6, fed a basal diet + milk from cows fed a diet enriched with soybean oil. The gilts receiving the diets containing PUFA had higher serum urea and very-low-density lipoprotein levels and lower serum total protein and low-density lipoprotein levels compared to the Control group. Females supplemented with n-3 presented higher serum palmitic acid and γ-linolenic acid levels than those fed n-6. Piglets from the Control group were heavier at birth than those from females supplemented with enriched milk. The piglets from females receiving enriched milk had 140 g higher body weight from 1 to 21 days old compared to the Control group, and greater average daily weight gain from 7 to 14 days old. The serum eicosapentaenoic acid level of piglets fed n-3 was 69% higher than those fed n-6, which reduced the AA/EPA ratio. Gilts supplemented with PUFA-enriched cow's milk showed changes in their serum palmitic and γ-linolenic acid levels, in addition to improved performance, EPA concentration and consequently reduced AA/EPA ratio in their piglets, demonstrating beneficial results for their progeny.

Plasma fatty acids and kidney function decline in post-myocardial infarction patients of the Alpha Omega Cohort

BACKGROUND AND AIMS

Age-related kidney function decline is accelerated in patients with coronary heart disease (CHD). CHD and chronic kidney disease may share common etiologies. We examined plasma fatty acids (FAs) as novel biomarkers of kidney function decline after myocardial infarction (MI).

METHODS AND RESULTS

The analysis included 2329 Dutch post-MI patients aged 60-80y (Alpha Omega Cohort) most receiving state-of-the-art medications. Plasma FAs (% total FAs) in cholesteryl esters were assessed at baseline (2002-2006), and ∼40 months change in creatinine-cystatin C based glomerular filtration rate was estimated (eGFR, in ml/min per 1.73 m²). Beta coefficients for annual eGFR change in relation to plasma linoleic acid (LA; 50.1% of total FAs in CE), omega-3 FAs (EPA + DHA; 1.7%), odd-chain FAs (C15:0 and C17:0; 0.2%), and C14:0 (0.7%) were obtained from linear regression analyses adjusted for age, sex, smoking, and alcohol intake. Mean baseline eGFR ±SD was 78.5 ± 18.7, which declined by 4.7 ± 13.1 during follow-up, or 1.4 ± 3.9 per year. The annual decline in eGFR was less in patients with higher plasma LA (adjusted beta: 0.40 for LA >47 vs ≤ 47%, 95% CI: 0.01; 0.78; p = 0.046). Associations of plasma LA with annual eGFR decline were stronger in 437 patients with diabetes (1.21, 0.24; 2.19) and in 402 patients with CKD (eGFR<60; 0.90, -0.09; 1.89). Weaker, non-significant associations with kidney function decline were observed for the other plasma FAs.

CONCLUSION

Higher plasma LA may be a good predictor of less kidney function decline after MI, particularly in patients with diabetes. The Alpha Omega Cohort is registered with clinicaltrials.gov, NCT03192410.

Circulating fatty acid profiles are associated with protein energy wasting in maintenance hemodialysis patients: a cross-sectional study

The metabolic impact of circulating fatty acids (FAs) in patients requiring hemodialysis (HD) is unknown. We investigated the associations between plasma triglyceride (TG) FAs and markers of inflammation, insulin resistance, nutritional status and body composition. Plasma TG-FAs were measured using gas chromatography in 341 patients on HD (age = 55.2 ± 14.0 years and 54.3% males). Cross-sectional associations of TG-FAs with 13 markers were examined using multivariate linear regression adjusted for potential confounders. Higher levels of TG saturated fatty acids were associated with greater body mass index (BMI, r = 0.230), waist circumference (r = 0.203), triceps skinfold (r = 0.197), fat tissue index (r = 0.150), serum insulin (r = 0.280), and homeostatic model assessment of insulin resistance (r = 0.276), but lower malnutrition inflammation score (MIS, r =  − 0.160). Greater TG monounsaturated fatty acid levels were associated with lower lean tissue index (r =  − 0.197) and serum albumin (r =  − 0.188), but higher MIS (r = 0.176). Higher levels of TG n-3 polyunsaturated fatty acids (PUFAs) were associated with lower MIS (r =  − 0.168) and interleukin-6 concentrations (r =  − 0.115). Higher levels of TG n-6 PUFAs were associated with lower BMI (r =  − 0.149) but greater serum albumin (r = 0.112). In conclusion, TG monounsaturated fatty acids were associated with poor nutritional status, while TG n-3 PUFAs were associated with good nutritional status. On the other hand, TG saturated fatty acids and TG n-6 PUFAs had both favorable and unfavorable associations with nutritional parameters.

Effects of hemodialysis on blood fatty acids

Omega‐3 (n‐3) fatty acids have beneficial cardiovascular effects, perhaps also in chronic kidney disease (CKD) patients. A low omega‐3 index is an independent cardiovascular risk factor in end‐stage renal disease (ESRD) dialysis patients. However, the plasma measurements invariably ignore circulating blood cells, including the preponderant erythrocytes (RBCs). We measured fatty acids (HPLC‐MS lipidomics) in all components of the circulating blood, since RBC n‐3 fatty acid status has been linked to cardiovascular disease and mortality. We studied 15 healthy persons and 15 CKD patients undergoing regular hemodialysis treatments. While total fatty acid levels differed significantly in RBCs from healthy controls and CKD patients, the hemodialysis treatment had no effect on plasma or RBC fatty acid levels. No changes occurred in the percentage of eicosapentaenoic acid (C20:5 n‐3, EPA) and docosahexaenoic acid (C22:6 n‐3; DHA) (omega‐3 quotient) in RBC membrane fatty acids. Nonetheless, hemodialysis treatments increased plasma levels of various total fatty acids, namely C12:0, C14:0, C16:0, C20:2 n‐6, C20:4 n‐6, and C22:6 n‐3 (DHA), while plasma levels of free fatty acids were unchanged. These data suggest that despite significant changes in fatty acids signatures between healthy persons and CKD patients, hemodialysis does not alter RBC n‐3 fatty acid status, including the omega‐3 quotient. The dialysis treatment per se does not appear to be responsible for a lower omega‐3 index in CKD patients.

Dietary fatty acid intake in hemodialysis patients and associations with circulating fatty acid profiles: A cross-sectional study

OBJECTIVES

The aims of this study were threefold: first, to assess the dietary fatty acid (FA) intake and blood FA status in Malaysian patients on hemodialysis (HD); second, to examine the association between dietary FA intakes and blood FA profiles in patients on HD; and third, to determine whether blood FAs could serve as a biomarker of dietary fat intake quality in these patients.

METHODS

Using 3 d of dietary records, FA intakes of 333 recruited patients were calculated using a food database built from laboratory analyses of commonly consumed Malaysian foods. Plasma triacylglycerol (TG) and erythrocyte FAs were determined by gas chromatography.

RESULTS

High dietary saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA) consumption trends were observed. Patients on HD also reported low dietary ω-3 and ω-6 polyunsaturated fatty acid (PUFA) consumptions and low levels of TG and erythrocyte FAs. TG and dietary FAs were significantly associated respective to total PUFA, total ω-6 PUFA, 18:2 ω-6, total ω-3 PUFA, 18:3 ω-3, 22:6 ω-3, and trans 18:2 isomers (P < 0.05). Contrarily, only dietary total ω-3 PUFA and 22:6 ω-3 were significantly associated with erythrocyte FAs (P < 0.01). The highest tertile of fish and shellfish consumption reflected a significantly higher proportion of TG 22:6 ω-3. Dietary SFAs were directly associated with TG and erythrocyte MUFA, whereas dietary PUFAs were not.

CONCLUSION

TG and erythrocyte FAs serve as biomarkers of dietary PUFA intake in patients on HD. Elevation of circulating MUFA may be attributed to inadequate intake of PUFAs.