n-3 Fatty acids and their role in nephrologic practice

Effects of Immunosuppressive Drugs on Serum Fatty Acids of Phospholipids Fraction in Renal Transplant Recipients

BACKGROUND

Immunosuppressive medications often cause posttransplant hyperlipidemia. The effects of cyclosporine (CsA) and tacrolimus (Tac) on lipid profile is well-known; however, there are very few studies related to the effect of these immunosuppressants on fatty acids (FA) of phosholipids fraction (PL) in renal transplant recipients (RTR). We sought to analyze the FA profile in PL fraction of RTR treated with Tac or CsA.

METHODS

The study included 65 renal transplant patients on CsA (n = 24, group I) or Tac (n = 41, group II), and 14 healthy controls. Individual serum FA concentrations were measured by gas chromatography. Chemstation software was used to analyze the data.

RESULTS

No differences between studied groups and controls were noted for monounsaturated FA, polyunsaturated n-3 FA (PUFA n-3), PUFA n-6, or the ratio of PUFA n-6 to PUFA n-3. The following mean values of FA were significantly higher in the CsA-RTR and Tac-RTR as compared with controls: total FA (P < .01 in both cases), saturated FA (SFA; P < .02 in both cases), C12 (P < .003 in both cases), C18 (P < .003 in both cases), and C18:2 (P < .01 for CsA RTR; P < .02 for Tac RTR). No differences between the measurements in patients on CsA and in patients on Tac were noticed. Significant correlation between SFA and eGFR was observed only in the CsA RTR group (P < .05). A negative relationship between PUFA n-6 and the estimated glomerular filtration rate was seen, but the correlation was not significant.

CONCLUSIONS

Immunosuppressive drugs may affect FA metabolism, but the FA profile does not depend on the type of immunosuppressive drug administered.

The effect of n-3 polyunsaturated fatty acids on leukotriene B₄ and leukotriene B₅ production from stimulated neutrophil granulocytes in patients with chronic kidney disease

The proinflammatory leukotriene B₄ (LTB₄) may be of importance in the progression of chronic kidney disease (CKD). We investigated whether n-3 polyunsaturated fatty acids (PUFA) decrease LTB₄ and increase the formation of the less inflammatory leukotriene B₅ (LTB₅) in patients with CKD. Fifty-six patients with CKD stage 2-5 were randomised to 2.4 g n-3 PUFA or olive oil for 8 weeks. Compared to controls, n-3 PUFA significantly decreased release of LTB₄ (p<0.001) and 5-hydroxyeicosatetraenoic acid (5-HETE) (p<0.01) and significantly increased release of LTB₅ (p<0.001) and 5-hydroxyeicosapentaenoic acid (5-HEPE) (p<0.001) from stimulated neutrophil granulocytes. Kidney function evaluated by creatinine clearance and proteinuria did not improve. In conclusion, n-3 PUFA supplementation for 8 weeks in patients with CKD stage 2-5 significantly decreased LTB₄ and 5-HETE and significantly increased LTB₅ and 5-HEPE. No effect was seen on kidney function.

Omega-3 and renal function in older adults

Chronic kidney disease (CKD) is a major public health problem and can result in end-stage renal disease with need for dialysis or transplantation. In Europe up to 12% of the adult population had some renal impairment, while in the United States the end stage of CKD has increased dramatically from 209.000 in 1991 to 472.000 in 2004. Diabetes and hypertension are major causes of kidney pathology. Infection, particularly ascending infection, is more common with increasing age, as both immune function declines and associated pathology predisposing to infection, such as obstructive uropathy, becomes more common. Most pathological changes in the kidney appear to be initiated by oxidative stress, followed by an inflammatory reaction. Oxidative stress results from an imbalance between free radicals and their detoxification by endogenous and exogenous scavengers, including polyunsaturated fatty acids (PUFA). Recent studies showed that PUFA supplementation slowed the rate of loss of renal function in patients with IgA nephropathy. Then, studies of omega-3 supplementation in dialysis patients describe salutary effects on triglyceride levels and dialysis access patency. We examined the relationship between total plasma PUFA levels and change in creatinine clearance over a three-year follow-up in the older persons enrolled in the InCHIANTI study, a population-based epidemiology study conducted in Tuscany, Italy. This study showed that older adults with low total plasma PUFA levels have a greater decline in creatinine clearance over three years of follow-up. These findings suggest that a higher dietary intake of PUFA may be protective against progression to chronic kidney disease.

Effects of omega-3 fatty acid supplementation on vascular access thrombosis in polytetrafluorethylene grafts

OBJECTIVE

The purpose of this study was to investigate the effects of orally administered over-the-counter omega-3 (n-3) fatty acid supplements on primary patency of polytetrafluoroethylene (PTFE) grafts.

DESIGN

This study was conducted with a triple-blind, permuted-block, randomized, placebo-controlled experimental design.

SETTING

Dialysis clinics with patients who, in accordance with physician diagnosis, needed a new PTFE graft.

PATIENTS AND OTHER PARTICIPANTS

Patients on long-term hemodialysis with newly placed PTFE grafts who were unable to receive a native arteriovenous fistula.

INTERVENTION

Patients were followed prospectively for 8 months after they had been placed into an n-3 fatty acid or control group and were monitored for primary patency.

MAIN OUTCOME VARIABLE

Primary patency of the PTFE graft.

RESULTS

The n-3 fatty acid group had a mean PTFE graft primary patency rate of 254.2 days (SEM = 51.8), and the control group had a mean PTFE graft primary patency rate of 254.1 days (SEM = 34.6), revealing no significant difference in survival time between groups.

CONCLUSIONS

No significant differences in primary patency rates were noted in the experimental and control groups.

Fatty acid intake and incident nephrolithiasis

BACKGROUND

Elevated levels of arachidonic acid in cell membranes may promote the hypercalciuria and hyperoxaluria that are characteristic of idiopathic calcium nephrolithiasis. The intake of n-3 fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may decrease the arachidonic acid content of cell membranes and reduce urinary excretion of calcium and oxalate. It has been proposed that greater intake of EPA and DHA (through dietary sources or fish oil supplementation) may reduce the risk for kidney stone formation.

METHODS

After excluding subjects with a prior history of kidney stones, we prospectively examined the relation between fatty acid intake (including fish oil supplements) and incident symptomatic kidney stones in 3 large cohorts: the Health Professionals Follow-Up Study (N = 46,043), the Nurses' Health Study I (NHS I; N = 92,079), and the Nurses' Health Study II (N = 96,304). Self-administered food-frequency questionnaires were used to assess fatty acid intake every 4 years. Cox proportional hazards regression was used to adjust simultaneously for a variety of risk factors.

RESULTS

We documented 3,956 incident kidney stones during a combined 36 years of follow-up. After adjustment for intake of other dietary factors, no association was detected between the intake of arachidonic acid or linoleic acid (a metabolic precursor to arachidonic acid) and the risk for incident kidney stones. Older women (NHS I) in the highest quintile of EPA and DHA intake had a multivariate relative risk of 1.28 (95% confidence interval, 1.04 to 1.56; P for trend = 0.04) of stone formation compared with women in the lowest quintile. However, this relation was not observed in the other 2 cohorts.

CONCLUSION

Fatty acid intake is not consistently associated with the development of kidney stones. Greater levels of arachidonic and linoleic acid intake do not increase the risk for developing a kidney stone, and greater intake of n-3 fatty acids does not reduce the risk.

Effect of chronic fish oil supplementation on renal function of normal and cachectic rats

In the present study we determined the effect of chronic diet supplementation with n-3 PUFA on renal function of healthy and cachectic subjects by providing fish oil (1 g/kg body weight) to female rats throughout pregnancy and lactation and then to their offspring post-weaning and examined its effect on renal function parameters during their adulthood. The animals were divided into four groups of 5-10 rats in each group: control, control supplemented with fish oil (P), cachectic Walker 256 tumor-bearing (W), and W supplemented with fish oil (WP). Food intake was significantly lower in the W group compared to control (12.66 +/- 4.24 vs 25.30 +/- 1.07 g/day). Treatment with fish oil significantly reversed this reduction (22.70 +/- 2.94 g/day). Tumor growth rate was markedly reduced in the P group (16.41 +/- 2.09 for WP vs 24.06 +/- 2.64 g for W). WP group showed a significant increase in mean glomerular filtration rate compared to P and control (1.520 +/- 0.214 ml min-1 kg body weight-1; P < 0.05). Tumor-bearing groups had low urine osmolality compared to control rats. The fractional sodium excretion decreased in the W group compared to control (0.43 +/- 0.16 vs 2.99 +/- 0.87%; P < 0.05), and partially recovered in the WP group (0.90 +/- 0.20%). In summary, the chronic supplementation with fish oil used in this study increased the amount of fat in the diet by only 0.1%, but caused remarkable changes in tumor growth rate and cachexia, also showing a renoprotective function.

The effect of n-3 fatty acids on plasma lipids and lipoproteins and blood pressure in patients with CRF

BACKGROUND

Patients with chronic renal failure (CRF) have a high incidence of cardiovascular disease and increased premature mortality. n-3 Polyunsaturated fatty acids (PUFAs) are known to decrease plasma triglyceride levels, reduce blood pressure (BP), and have a cardioprotective effect in subjects with normal renal function. The aim of this study is to examine the effect of n-3 PUFAs on plasma lipid and lipoprotein levels and 24-hour ambulatory BP in patients with CRF.

METHODS

Sixty-four patients with CRF, defined as a plasma creatinine level between 1.70 and 4.52 mg/dL (150 and 400 micromol/L), were included and randomly assigned to treatment with 2.4 g of n-3 PUFAs or control treatment (olive oil) for 8 weeks. Patients were evaluated by measurement of fasting plasma lipid and lipoprotein levels and 24-hour ambulatory BP recordings before and after the supplements. n-3 PUFA content was determined in cell membranes of granulocytes and adipose tissue samples to evaluate n-3 PUFA intake.

RESULTS

There was a significant 8% increase in high-density lipoprotein cholesterol levels (P < 0.01) and a significant 21% decrease in serum triglyceride levels (P < 0.02) in the group administered n-3 PUFA supplements. There were no changes in total cholesterol or low-density lipoprotein cholesterol levels in any group, and n-3 PUFAs had no effect on 24-hour ambulatory BP.

CONCLUSION

Supplementation with n-3 PUFAs had a favorable effect on lipoprotein profile in patients with CRF, whereas no effect on 24-hour ambulatory BP was observed.

Docosahexaenoic acid and eicosapentaenoic acid, but not alpha-linolenic acid, suppress deoxynivalenol-induced experimental IgA nephropathy in mice

Diets enriched in the (n-3) PUFAs, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and their precursor alpha-linolenic acid (ALA), were evaluated for efficacy in ameliorating the development of IgA nephropathy (IgAN) induced in mice by the mycotoxin deoxynivalenol (DON). The effects of DON were compared in mice that were fed for 18 wk with AIN-93G diets containing 1) 10 g/kg corn oil plus 60 g/kg oleic acid (control); 2) 10 g/kg corn oil plus 35 g/kg oleic acid and 25 g/kg DHA-enriched fish oil (DHA); 3) 10 g/kg corn oil plus 33 g/kg oleic acid and 27 g/kg EPA-enriched fish oil (EPA); and 4) 10 g/kg corn oil plus 37 g/kg oleic acid and 23 g/kg DHA + EPA (1:1) enriched fish oil (DHA + EPA). The DHA, EPA and DHA + EPA diets attenuated induction by dietary DON (10 mg/kg) of serum IgA and IgA immune complexes, kidney mesangial IgA deposition, and ex vivo IgA secretion by spleen cells. Consumption of the DHA + EPA diet for 8 wk significantly abrogated the DON-induced gene expression of interleukin (IL)-6, a requisite cytokine for DON-induced IgA nephropathy, in spleen and Peyer's patches. Finally, incorporation of ALA-containing flaxseed oil up to 60 g/kg in the AIN-93G diet did not affect DON-induced IgA dysregulation in mice. Taken together, both DHA and EPA, but not ALA, ameliorated the early stages of IgAN, and these effects might be related to a reduced capacity for IL-6 production.

Benefits of fish oil supplementation for hemodialysis patients

A literature review on fish oil supplementation in the population undergoing chronic hemodialysis therapy suggests that supplementation may be beneficial for various challenges to health and well-being prevalent in this population. One study indicated that pruritus symptoms improved with fish oil supplementation, but not with supplementation with two other oils. In a study designed to determine whether fish oils could prevent vascular access graft thrombosis, graft patency rates were approximately 76% in the fish oil and approximately 15% in the placebo group (P>.03). In a pilot study, subjects given fish oil required 16% less erythropoietin and experienced a 3.6% increase in serum albumin levels. Some studies suggest that fish oil supplementation in hemodialysis patients is cardioprotective, with one study finding that "fish eaters" are half as likely to die as "non-fish eaters." Potential risks of supplementation include gastrointestinal distress, prolonged bleeding, and vitamin A toxicity, although the likelihood of serious side effects is probably low. Dietitians are in a position to advise physicians and/or patients regarding appropriate dosages and ways to minimize risks when supplementation seems warranted. Future research could compare the benefits of fish consumption with those of fish oil supplementation and explore the benefits of other n-3 fatty acid sources, such as flaxseed.

Amelioration of tacrolimus-induced nephrotoxicity in rats using juniper oil

BACKGROUND

Calcineurin-inhibitor nephrotoxicity plays a role in the pathogenesis of chronic allograft nephropathy by causing renal ischemia mediated by vasoconstrictive metabolites of the prostanoid pathway. The purpose of our study was to evaluate whether altering the prostanoid profile using juniper oil (JO) would afford renoprotection in rats treated with tacrolimus.

METHODS

Diets supplemented with biologic oils (no supplementation, JO, fish oil [FO], safflower oil [SO], and arachidonic acid [AA]) were fed to five groups of rats for 5 weeks; during the last 2 weeks, tacrolimus was administered to all groups except for a control group of animals. At week 5, urinary prostaglandin (PG)F(2-alpha) and inulin clearances were measured. The rat kidneys were harvested to determine the renal cell membrane composition for arachidonic, eicosatrienoic, and eicosapentaenoic acids.

RESULTS

Both JO and FO completely reversed the decrease in inulin clearance seen with tacrolimus, the greatest effect being with JO (inulin clearance 15.1+/-3 vs. 6.0+/-1.1 ml/min in the nonsupplemented group; P<0.001); urinary PGF(2-alpha) excretion was also highest in the JO group (328+/-23 pg/mL, P<0.001 vs. the nonsupplemented group). Fatty acid membrane analysis showed greatest incorporation of eicosapentaenoic and eicosatrienoic acids in the JO- (5.7+/-0.6% and 3.1+/-0.4%, respectively) and FO- (8.1+/-0.7% and 2.8+/-0.6%, respectively) treated animals.

CONCLUSIONS

JO supplementation in tacrolimus-treated rats was associated with incorporation of vasodilatory prostanoids in the renal-cell membrane and elevated urinary PGF(2-alpha) excretion, and the precipitous fall in inulin clearance induced by tacrolimus was completely prevented. Whether this benefit will translate into a reduction in chronic allograft nephropathy remains to be determined. However, our preliminary data point towards the need for human trials.

Efficiency of conversion of alpha-linolenic acid to long chain n-3 fatty acids in man

Alpha-linolenic acid (18:3n-3) is the major n-3 (omega 3) fatty acid in the human diet. It is derived mainly from terrestrial plant consumption and it has long been thought that its major biochemical role is as the principal precursor for long chain polyunsaturated fatty acids, of which eicosapentaenoic (20:5n-3) and docosahexaenoic acid (22:6n-3) are the most prevalent. For infants, n-3 long chain polyunsaturated fatty acids are required for rapid growth of neural tissue in the perinatal period and a nutritional supply is particularly important for development of premature infants. For adults, n-3 long chain polyunsaturated fatty acid supplementation is implicated in improving a wide range of clinical pathologies involving cardiac, kidney, and neural tissues. Studies generally agree that whole body conversion of 18:3n-3 to 22:6n-3 is below 5% in humans, and depends on the concentration of n-6 fatty acids and long chain polyunsaturated fatty acids in the diet. Complete oxidation of dietary 18:3n-3 to CO2 accounts for about 25% of 18:3n-3 in the first 24 h, reaching 60% by 7 days. Much of the remaining 18:3n-3 serves as a source of acetate for synthesis of saturates and monounsaturates, with very little stored as 18:3n-3. In term and preterm infants, studies show wide variability in the plasma kinetics of 13C n-3 long chain polyunsaturated fatty acids after 13C-18:3n-3 dosing, suggesting wide variability among human infants in the development of biosynthetic capability to convert 18:3n-3 to 22:6n3. Tracer studies show that humans of all ages can perform the conversion of 18:3n-3 to 22:6n3. Further studies are required to establish quantitatively the partitioning of dietary 18:3n-3 among metabolic pathways and the influence of other dietary components and of physiological states on these processes.