n-3 fatty acids and renal diseases

Allicin and Omega-3 fatty acids attenuates acetaminophen mediated renal toxicity and modulates oxidative stress, and cell apoptosis in rats

Acetaminophen (APAP), a widely used medication known for its pain-relieving and fever-reducing effects, can cause kidney failure if taken in excess. To investigate the potential protective effects of allicin (ALC) and/or omega-3 fatty acids (O3FA) against acetaminophen-induced kidney damage, a study was conducted using 49 rats divided into seven groups. The control group was given saline, while the other groups received ALC, O3FA, APAP, ALC + APAP, O3FA + APAP, or ALC + O3FA + APAP. After administering APAP, the rats showed decreased levels of total protein and albumin in their blood, along with increased levels of creatinine and urea. The concentration of reduced glutathione (GSH), as well as the activity of superoxide dismutase (SOD) and catalase (CAT), decreased, while the level of malondialdehyde (MDA) in the renal tissues increased. The activation of caspase-3 and HSP70 also suggested an impact on kidney histopathology. Overall, the study found that ALC and/or O3FA may have a protective impact against acetaminophen-induced kidney damage through their anti-inflammatory, anti-apoptotic, and antioxidant defense systems.

Polyunsaturated fatty acid deficiency affects sulfatides and other sulfated glycans in lysosomes through autophagy-mediated degradation

Metabolic changes in sulfatides and other sulfated glycans have been related to various diseases, including Alzheimer's disease (AD). However, the importance of polyunsaturated fatty acids (PUFA) in sulfated lysosomal substrate metabolism and its related disorders is currently unknown. We investigated the effects of deficiency or supplementation of PUFA on the metabolism of sulfatides and sulfated glycosaminoglycans (sGAGs) in sulfatide-rich organs (brain and kidney) of mice. A PUFA-deficient diet for over 5 weeks significantly reduced the sulfatide expression by increasing the sulfatide degradative enzymes arylsulfatase A and galactosylceramidase in brain and kidney. This sulfatide degradation was clearly associated with the activation of autophagy and lysosomal hyperfunction, the former of which was induced by suppression of the Erk/mTOR pathway. A PUFA-deficient diet also activated the degradation of sGAGs in the brain and kidney and that of amyloid precursor proteins in the brain, indicating an involvement in general lysosomal function and the early developmental process of AD. PUFA supplementation prevented all of the above abnormalities. Taken together, a PUFA deficiency might lead to sulfatide and sGAG degradation associated with autophagy activation and general lysosomal hyperfunction and play a role in many types of disease development, suggesting a possible benefit of prophylactic PUFA supplementation.

Heart Rate Variability: A Potential Tool for Monitoring Immunomodulatory Effects of Parenteral Fish Oil Feeding in Patients With Sepsis

Fish oil, rich in the very-long chain omega (ω)-3 polyunsaturated fatty acids (PUFAs), has been found to have immunomodulatory effects in different groups of critically ill patients. In addition, its parenteral administration seems to attenuate the inflammatory response within 2 to 3 days. The activation of the cholinergic anti-inflammatory pathway has been suggested to mediate such immunoregulatory effects. As different experimental studies have convincingly illustrated that enhanced vagal tone can decrease pro-inflammatory cytokine secretion, novel monitoring tools of its activity at the bedside could be developed, to evaluate nutritional manipulation of immune response in the critically ill. Heart rate variability (HRV) is the variability of R-R series in the electrocardiogram and could be a promising surrogate marker of immune response and its modulation during fish oil feeding, rich in ω-3 PUFAs. Heart rate variability is an indirect measure of autonomic nervous system (ANS) output, reflecting mainly fluctuations in ANS activity. Through HRV analysis, different "physiomarkers" can be estimated that could be used as early and more accurate "smart alarms" because they are based on high-frequency measurements and are much more easy to get at the bedside. On the contrary, various "biomarkers" such as cytokines exhibit marked interdependence, pleiotropy, and their plasma concentrations fluctuate from day to day in patients with sepsis. In this respect, an inverse relation between different HRV components and inflammatory biomarkers has been observed in patients with severe sepsis and septic shock, whereas a beneficial effect of ω-3 PUFAs on HRV has been demonstrated in patients with cardiovascular diseases. Consequently, in this article, we suggest that a beneficial effect of ω-3 PUFAs on HRV and clinical outcome in patients with sepsis merits further investigation and could be tested in future clinical trials as a real-time monitoring tool of nutritional manipulation of the inflammatory response in the critically ill.

Omega-3 Polyunsaturated Fatty Acids Attenuate Fibroblast Activation and Kidney Fibrosis Involving MTORC2 Signaling Suppression

Epidemiologic studies showed the correlation between the deficiency of omega-3 polyunsaturated fatty acids (n-3 PUFAs) and the progression of chronic kidney diseases (CKD), however, the role and mechanisms for n-3 PUFAs in protecting against kidney fibrosis remain obscure. In this study, NRK-49F cells, a rat kidney interstitial fibroblast cell line, were stimulated with TGFβ1. A Caenorhabditis elegans fat-1 transgenic mouse model in which n-3 PUFAs are endogenously produced from n-6 PUFAs owing to the expression of n-3 fatty acid desaturase were deployed. Docosahexaenoic acid (DHA), one member of n-3 PUFAs family, could suppress TGFβ1-induced fibroblast activation at a dose and time dependent manner. Additionally, DHA could largely inhibit TGFβ1-stimulated Akt but not S6 or Smad3 phosphorylation at a time dependent manner. To decipher the role for n-3 PUFAs in protecting against kidney fibrosis, fat-1 transgenic mice were operated with unilateral ureter obstruction (UUO). Compared to the wild types, fat-1 transgenics developed much less kidney fibrosis and inflammatory cell accumulation accompanied by less p-Akt (Ser473), p-Akt (Thr308), p-S6 and p-Smad3 in kidney tissues at day 7 after UUO. Thus, n-3 PUFAs can attenuate fibroblast activation and kidney fibrosis, which may be associated with the inhibition of mTORC2 signaling.

Effects of Omega-3 Fatty Acid Supplementation on Diabetic Nephropathy Progression in Patients with Diabetes and Hypertriglyceridemia

Beneficial effects of omega-3 fatty acid (O3FA) supplementation in a wide range of disease condition have been well studied. However, there is limited information regarding the effects of O3FAs on chronic kidney disease (CKD), especially in diabetic nephropathy (DN) with hypertriglyceridemia. We investigate whether O3FA supplementation could help maintain renal function in patients with diabetes and hypertriglyceridemia. Total 344 type 2 diabetic patients with a history of O3FA supplementation for managing hypertriglyceridemia were included. Reduction in urine albumin to creatinine ratio (ACR) and glomerular filtrate rate (GFR) were examined. Subgroup analyses were stratified according to the daily O3FA doses. Serum total cholesterol, triglyceride, and urine ACR significantly reduced after O3FA supplementation. Overall, 172 (50.0%) patients did not experience renal function loss, and 125 (36.3%) patients had a GFR with a positive slope. The patients treated with O3FAs at 4g/day showed greater maintenance in renal function than those treated with lower dosages (p < 0.001). This dose dependent effect remains significant after adjustment for multiple variables. O3FA supplementation in diabetic patients with hypertriglyceridemia shows benefits of reducing albuminuria and maintaining renal function. The effects are dependent on the dose of daily O3FA supplementation.

IgA nephropathy

Globally, IgA nephropathy (IgAN) is the most common primary glomerulonephritis that can progress to renal failure. The exact pathogenesis of IgAN is not well defined, but current biochemical and genetic data implicate overproduction of aberrantly glycosylated IgA1. These aberrant immunoglobulins are characterized by galactose deficiency of some hinge-region O-linked glycans. However, aberrant glycosylation alone is insufficient to induce renal injury: the participation of glycan-specific IgA and IgG autoantibodies that recognize the undergalactosylated IgA1 molecule is required. Glomerular deposits of immune complexes containing undergalactosylated IgA1 activate mesangial cells, leading to the local overproduction of cytokines, chemokines and complement. Emerging data indicate that mesangial-derived mediators that are released following mesangial deposition of IgA1 lead to podocyte and tubulointerstitial injury via humoral crosstalk. Patients can present with a range of signs and symptoms, from asymptomatic microscopic haematuria to macroscopic haematuria. The clinical progression varies, with 30-40% of patients reaching end-stage renal disease 20-30 years after the first clinical presentation. Currently, no IgAN-specific therapies are available and patients are managed with the aim of controlling blood pressure and maintaining renal function. However, new therapeutic approaches are being developed, building upon our ever-improving understanding of disease pathogenesis.

Endogenous synthesis of n-3 PUFA modifies fatty acid composition of kidney phospholipids and eicosanoid levels in the fat-1 mouse

The goal of the present study was to determine whether endogenous synthesis of n-3 polyunsaturated fatty acids (PUFA) in the fat-1 mouse is comparable to fish oil feeding with respect to kidney n-3 PUFA composition and eicosanoid levels. Wild-type and heterozygous fat-1 mice, capable of synthesizing n-3 PUFA endogenously, were given diets enriched in either n-3 or n-6 PUFA in a 2×2 factorial design and terminated after 12 weeks. Kidney phospholipid fatty acids were analysed by gas chromatography. Kidney eicosanoids were analysed by liquid chromatography tandem mass spectrometry. Relative to control mice fed n-6 PUFA, n-3 PUFA fed and fat-1 mice had higher levels of kidney phospholipid n-3 PUFA, and lower levels of n-6 PUFA and eicosanoids. However, mice fed n-3 PUFA mice had higher levels of n-3 PUFA and lower levels of eicosanoids as compared to fat-1 mice. In conclusion, diet feeding had a greater impact on kidney fatty acid composition and eicosanoid levels than the genetic effect of the fat-1 gene. However, the fat-1 mouse remains a close approximation that can be used as a complementary model to study the role of n-3 PUFA in the kidney.

Protective effect of ω-3 polyunsaturated fatty acids (PUFAs) on sodium nitroprusside-induced nephrotoxicity and oxidative damage in rat kidney

Sodium nitroprusside (SNP) a nitric oxide (NO) donor has proven toxic effects. Dietary ω-3 polyunsaturated fatty acid (PUFA) has been shown to reduce the severity of numerous ailments. Present study examined whether intake of fish oil (FO)/flaxseed oil (FXO, Omega Nutrition, St Vancouver, Canada) would have protective effect against SNP-induced toxicity. Male Wistar rats (150 ± 10 g) were used in this study. Initially animals were divided into two groups: one fed on normal diet and the other on 15% FO/FXO for 15 days. On the 16th day, SNP (1.5 mg/kg body weight) was administered intraperitoneally for 7 days daily. After 7 days animals were killed, kidneys were harvested for further analysis. SNP induced nephrotoxicity by increasing serum creatinine and blood urea nitrogen, SNP significantly decreased malate dehydrogenase, glucose-6-phosphatase, fructose-1,6-bisphosphatase and malic enzyme but increased lactate dehydrogenase and glucose-6-phosphate dehydrogenase. Brush border membrane enzymes such as alkaline phosphatase, γ-glutamyl transpeptidase and leucine amino peptidase were also decreased. The activity of catalase and glutathione peroxidase decreased concomitantly with increased lipid peroxidation, indicating that the significant kidney damage has been inflicted by SNP. Feeding of FO and FXO with SNP ameliorated the changes in various parameters caused by SNP. The results of the present study suggest that ω-3 PUFA-enriched FO and FXO from seafoods and plant sources, respectively, are similarly effective in reducing SNP-induced nephrotoxicity and oxidative damage. Thus, vegetarians who cannot consume FO can have similar health benefits from plant-derived ω-3 PUFA.

The effects of fish oil supplementation on markers of inflammation in chronic kidney disease patients

OBJECTIVE

One prevalent characteristic of all stages of chronic kidney disease (CKD) is excessive production of proinflammatory cytokines. Fish oil (FO) supplementation has been reported to lower levels of proinflammatory cytokines. The benefits of FO for an extensive range of populations and a variety of health concerns are apparent, yet the anti-inflammatory benefits for nondialysis CKD patients are not as well documented. Therefore, the purpose of this study was to investigate the effects of the daily consumption of FO (1,400 mg eicosapentaenoic acid + 1,000 mg docosahexaenoic acid) on interleukin 1β (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor α (TNF-α) for 8 weeks in nondialysis CKD patients.

DESIGN, SETTING, AND SUBJECTS

In this double-blind, randomized, placebo-controlled intervention, the effect of 8 weeks of FO administration on IL-1β, IL-6, and TNF-α levels in nondialysis CKD patients were evaluated.

INTERVENTION

Thirty-one nondialysis CKD patients (17 = FO; 14 = placebo) randomly received either FO dietary supplementation 2.4 g/day (1,400 mg eicosapentaenoic acid + 1,000 mg docosahexaenoic acid) or placebo (safflower oil) for 8 weeks.

MAIN OUTCOME MEASURES

IL-1β, IL-6, and TNF-α were all measured as markers of inflammation.

RESULTS

One-way analysis of variance revealed no significant differences in IL-6 (P = .06), IL-1β (P = .18), and TNF-α (P = .20) between groups in pretest values. Additionally, no pretest differences existed between groups for age (P = .549), weight (P = .324), waist circumference (P = .086), gender (P = .591), and ethnicity (P = .875). Covariance was calculated using compliance, age, gender, ethnicity, body weight, and waist circumference as covariates. No significant differences were discovered between groups after FO supplementation for IL-6 (P = .453) and TNF-α (P = .242). A significant difference was discovered for IL-1β (P = .050) with lower levels in the FO group.

CONCLUSIONS

The results of this study are in agreement with some previous studies that suggest that FO supplementation has no effect on plasma proinflammatory cytokines TNF-α or IL-6, but does have an effect on IL-1β in nondialysis CKD patients.

LC/ESR/MS study of pH-dependent radical generation from 15-LOX-catalyzed DPA peroxidation

Docosapentaenoic acid (DPA) is a unique fatty acid that exists in two isomeric forms (n-3 and n-6), which differ in their physiological behaviors. DPA can undergo free radical-mediated peroxidation via lipoxygenase (LOX). 15-LOX, one of the LOX isomers, has received much attention in cancer research because of its very different expression level in normal tissues compared to tumors and some bioactive fatty acid metabolites modulating the tumorigenic pathways in cancer. However, the mechanism linking 15-LOX, DPA metabolites, and their bioactivities is still unclear, and the free radicals generated in DPA peroxidation have never been characterized. In this study, we have studied radicals formed from both soybean and human cellular (PC3-15LOS cells) 15-LOX-catalyzed peroxidation of DPAs at various pH's using a combination of LC/ESR/MS with the spin trapping technique. We observed a total of three carbon-centered radicals formed in 15-LOX-DPA (n-3) stemming from its 7-, 17-, and 20-hydroperoxides, whereas only one formed from 17-hydroperoxide in DPA (n-6). A change in the reaction pH from 8.5 (15-LOX enzyme optimum) to 7.4 (physiological) and to 6.5 (tumor, acidic) not only decreased the total radical formation but also altered the preferred site of oxygenation. This pH-dependent alteration of radical formation and oxygenation pattern may have significant implications and provide a basis for our ongoing investigations of LOXs as well as fatty acids in cancer biology.

Omega-3 fatty acids and metabolic syndrome: effects and emerging mechanisms of action

Epidemiological, human, animal, and cell culture studies show that n-3 fatty acids, especially α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), reduce the risk factors of cardiovascular diseases. EPA and DHA, rather than ALA, have been the focus of research on the n-3 fatty acids, probably due to the relatively inefficient conversion of ALA to EPA and DHA in rodents and humans. This review will assess our current understanding of the effects and potential mechanisms of actions of individual n-3 fatty acids on multiple risk factors of metabolic syndrome. Evidence for pharmacological responses and the mechanism of action of each of the n-3 fatty acid trio will be discussed for the major risk factors of metabolic syndrome, especially adiposity, dyslipidemia, insulin resistance and diabetes, hypertension, oxidative stress, and inflammation. Metabolism of n-3 and n-6 fatty acids as well as the interactions of n-3 fatty acids with nutrients, gene expression, and disease states will be addressed to provide a rationale for the use of n-3 fatty acids to reduce the risk factors of metabolic syndrome.

Cardiovascular effects of edible oils: a comparison between four popular edible oils

Edible oils form an essential part of the modern diet. These oils play a role as an energy source, and provide the diet with many beneficial micronutrients. Although a popular conception may be that fat should be avoided, certain edible oils as a dietary supplement may play an important role in the improvement of cardiovascular health. CVD has become one of the leading causes of death worldwide. Dietary supplementation with different oils may have beneficial effects on cardiovascular health. While olive oil and sunflower-seed oil are known to reduce serum cholesterol, fish oil has become well known for reducing potentially fatal cardiac arrhythmias. Recently, red palm oil research has shown beneficial effects on cardiac recovery from ischaemia-reperfusion injury. It is clear that dietary supplementation with edible oils may play a vital role in reducing the mortality rate due to heart disease. The specific benefits and disadvantages of these oils should, however, be explored in greater depth. The present review will attempt to identify the benefits and shortcomings of four popular edible oils, namely olive oil, sunflower-seed oil, fish oil and palm oil. Additionally the present review will aim to reveal potential areas of research which could further enhance our understanding of the effects of edible oils on cardiovascular health.

Evaluation of phosphorus, protein, and n-3 fatty-acid content in 15 marine fish species identifies the species most beneficial to renal patients

OBJECTIVE

Among 15 marine fish species, we sought to identify those most beneficial to renal patients by evaluating their phosphorus (P), protein (PC), and n-3 fatty-acid (n-3 PUFA) content.

DESIGN

These 15 species are all edible. They were obtained and sampled randomly, and were filleted to obtain 100g, enabling us to perform the analysis in triplicate. Crude protein was analyzed with a Kjeltec, and minerals were analyzed using atomic absorption spectrophotometry.

RESULTS

The PC values (g/100g) ranged from 14.3 (blue runner; BR) to 22.8 (California butterfly ray). The fish with the highest P (mg/100g) content were spotted sea trout (ST), gafftopsail fish (CF) (289), and BR (274), followed by smalltail shark (272). The species with the lowest ratio of P:n-3 PUFA was dollar fish (DF) (0.28), followed by BR, ST, and vermilion snapper (range, 0.28 to 0.67). The highest ratio of P:n-3 PUFA was found in the small-tail shark (11.6). Fish with a high n-3 PUFA/g PC content were DF (41.7), BR (38.05), ST (34.8), and CF (22.5). There was a tendency of P to increase as muscle fat increased (mg P/100g), i.e., lean fish (194), semifatty fish (239), and fatty fish (262).

CONCLUSIONS

The regular inclusion in the diet, at least three times a week, of the species DF, BR, CF, ST, caitipa mojarra, vermillion snapper, and pot snapper can be considered beneficial to the general health status of renal patients.

The effects of [omega]3 fatty acids and coenzyme Q10 on blood pressure and heart rate in chronic kidney disease: a randomized controlled trial

BACKGROUND AND OBJECTIVE

Chronic kidney disease (CKD) associates with increased cardiovascular disease (CVD) risk. Hypertension is a major determinant of progression of CKD. Omega-3 fatty acids (omger3FA) protect against CVD via improvements in blood pressure, heart rate, vascular reactivity and serum lipids. Coenzyme Q(10) (CoQ) may improve blood pressure and vascular function. This study determined whether omega3FA and CoQ have independent or additive effects in improving the cardiovascular profile, particularly blood pressure and heart rate, in nondiabetic patients with CKD stages 3-4.

METHODS

In a double-blind, placebo-controlled intervention, patients were randomized to either omega3FA (4 g), CoQ (200 mg), both supplements or control (4 g), daily for 8 weeks.

RESULTS

Eighty-five patients aged 56.5 +/- 1.4 years; BMI 27.3 +/- 0.5 kg/m(2); supine blood pressure 125.0/72.3mmHg; and glomerular filtration rate 35.8 +/- 1.2 ml/min/1.73m(2), were randomized. Seventy-four completed the study. omega3FA, but not CoQ, reduced 24-h ambulatory heart rate (P<0.0001) and blood pressure (P<0.0001). Main effects for omega3FA on 24-h measurements were -3.3 +/- 0.7/ -2.9 +/- 0.5mmHg and -4.0 +/- 0.5 bpm. Postintervention blood pressure showed significant interactions between treatments. omega3FA reduced triglycerides 24% (P<0.001). There were no changes in glomerular filtration rate, urinary albumin or total protein excretion, cholesterol, HDL-cholesterol (C), LDL-C, glucose, insulin, or high-sensitivity C-reactive protein.

CONCLUSION

This study has shown that omega3FA reduce blood pressure, heart rate and triglycerides in patients with CKD. CoQ had no independent effect on blood pressure but increased heart rate. These results show that omega3FA lower blood pressure and may reduce cardiovascular risk in nondiabetic patients with moderate-to-severe CKD.

Studies on the protective effect of dietary fish oil on gentamicin-induced nephrotoxicity and oxidative damage in rat kidney

Gentamicin (GM)-induced nephrotoxicity limits its long-term clinical use. Several agents/strategies were attempted to prevent GM nephrotoxicity but were not found suitable for clinical practice. Dietary fish oil (FO) retard the progression of certain types of cancers, cardiovascular and renal disorders. We aimed to evaluate protective effect of FO on GM-induced renal proximal tubular damage. The rats were pre-fed experimental diets for 10 days and then received GM (80 mg/kg body weight/day) treatment for 10 days while still on diet. Serum/urine parameters, enzymes of carbohydrate metabolism, brush border membrane (BBM), oxidative stress and phosphate transport in rat kidney were analyzed. GM nephrotoxicity was recorded by increased serum creatinine and blood urea nitrogen. GM increased the activities of lactate and glucose-6-phosphate dehydrogenases whereas decreased malate, isocitrate dehydrogenases; glucose-6 and fructose-1,6-bisphosphatases; superoxide dismutase, catalase, glutathione peroxidase and BBM enzymes. In contrast, FO alone increased enzyme activities of carbohydrate metabolism, BBM and oxidative stress. FO feeding to GM treated rats markedly enhanced resistance to GM elicited deleterious effects and prevented GM-induced decrease in 32Pi uptake across BBM. Dietary FO supplementation ameliorated GM-induced specific metabolic alterations and oxidative damage due to its intrinsic biochemical/antioxidant properties.

Effect of n-3 fatty acids on nutritional status and inflammatory markers in haemodialysis patients

AIMS

Nutrition as an aetiological factor participates a great deal in premature atherosclerosis in haemodialysis (HD) patients. The basic mechanisms of end-stage renal disease and premature atherosclerosis are connected with changes in cell functions at the membrane level. We investigated the red cell membrane fatty acids and the effects of fish oil supplements on nutritional status and inflammatory markers in HD patients.

METHODS

We examined 42 HD patients (mean age 55 +/- 8 years). The control group consisted of 16 healthy subjects of similar age and sex to the tested group. HD patients were administered supplements with 2.4 g of n-3 polyunsaturated fatty acids per day for 2 months. Before and after supplementation, we examined plasma lipids, cell membrane erythrocyte phospholipids content, serum albumin, haemoglobin, interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF-alpha).

RESULTS

Baseline values in the tested group confirmed the presence of essential fatty acids deficiency. A statistically significant negative correlation between TNF-alpha and eicosapentaenoic acid (EPA) (r = -0.497; P < 0.05) and IL-6 and EPA (r = -468; P = 0.03) was found in HD patients before supplementation. There was a significant increase in docosahexaenoic acids, high density lipoprotein cholesterol, plasma albumin, haemoglobin levels in HD patients after supplementation (P = 0.0001). There was a significant increase in EPA (P = 0.01) after treatment, and there was a significant decrease in inflammatory markers (IL-6 and TNF-alpha, P = 0.0001) after supplementation in the tested group.

CONCLUSION

A dietary regime with fish oil could be used in dialysis patients to slow down the development of atherosclerosis and improve nutritional parameters.

Omega-3 fatty acids and inflammation

Dietary omega-3 (n-3) fatty acids have a variety of anti-inflammatory and immune-modulating effects that may be of relevance to atherosclerosis and its clinical manifestations of myocardial infarction, sudden death, and stroke. The n-3 fatty acids that appear to be most potent in this respect are the long-chain polyunsaturates derived from marine oils, namely eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and this review is restricted to these substances. A variety of biologic effects of EPA and DHA have been demonstrated from feeding studies with fish or fish oil supplements in humans and animals. These include effects on triglycerides, high-density lipoprotein cholesterol, platelet function, endothelial and vascular function, blood pressure, cardiac excitability, measures of oxidative stress, pro- and anti-inflammatory cytokines, and immune function. Epidemiologic studies provide evidence for a beneficial effect of n-3 fatty acids on manifestations of coronary heart disease and ischemic stroke, whereas randomized, controlled, clinical feeding trials support this, particularly with respect to sudden cardiac death in patients with established disease. Clinically important anti-inflammatory effects in man are further suggested by trials demonstrating benefits of n-3 fatty acids in rheumatoid arthritis, psoriasis, asthma, and inflammatory bowel disorders. Given the evidence relating progression of atherosclerosis to chronic inflammation, the n-3 fatty acids may play an important role via modulation of the inflammatory processes.

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.

Detrimental effects of a high fat diet in early renal injury are ameliorated by fish oil in Han:SPRD-cy rats

Dietary fish oils containing (n-3) fatty acids can modulate renal inflammatory injury. We previously demonstrated that a high fat (HF) diet worsens early renal disease progression in the Han:SPRD-cy rat model of polycystic kidney disease (PKD). Therefore, using HF (20 g/100 g diet) and low fat (LF; 5 g/100 g diet) diets, we compared the effects of menhaden oil (MO), soybean oil (SO) and cottonseed oil (CO) on renal function and histology in male Han:SPRD-cy rats fed the diets for 6 wk in the early stages of renal disease. Overall, rats fed HF compared with those fed LF diets had larger kidneys, more renal fibrosis and lower creatinine clearance (main effects of fat level). Rats fed MO rather than CO and SO diets had significantly lower kidney weights, kidney water content, cyst volumes and serum cholesterol and triglyceride concentrations (main effects of fat type). Rats fed MO diets also had less renal fibrosis than those fed CO diets, but the least fibrosis was in rats fed SO diets. Analysis of simple effects (due to interactions between fat level and type) revealed that HF diets increased renal inflammation in rats fed CO diets, but reduced inflammation was present in those fed SO and MO diets; HF diets also increased compared with LF diets serum urea nitrogen concentrations in rats fed the MO and CO diets, but not the SO diet. These results confirm that high dietary fat worsens early disease progression in this model of renal disease, and further demonstrate that diets with oils containing (n-3) fatty acids ameliorate some of the detrimental effects of a high fat diet.

Developments in the Immunotherapy of Glomerular Disease

Glomerular diseases span a broad spectrum of clinical syndromes, with varied clinical manifestations, underlying etiologies, and pathogenic mechanisms. They can be secondary to underlying infectious, toxic, environmental, or drug exposures, or present as “primary entities.” In the latter case, most glomerular diseases are thought to be due to autoimmune dysregulation, and their treatment is primarily immunosuppressive. The armamentarium for immunomodulation includes corticosteroids, alkylating agents, anti-metabolites, calcineurin inhibitors, and new biological agents designed to block specific inflammatory pathways. The choice of therapy for an individual patient must be based on the specific character of the glomerular disease and its acuity and severity, as well as the patient’s comorbidities, history of prior exposure to immunosuppressive drugs, and risk factors for developing complications of the disease or its treatment. The complexities of such therapy can best be addressed by an experienced team of care givers in which the clinical pharmacist can help minimize, if not eliminate, potential sources of drug induced toxicities and adverse effects. This article will describe the major agents and modalities used in the management of the most common glomerular diseases.

Prophylaxis of hemodialysis graft thrombosis with fish oil: double-blind, randomized, prospective trial

Diets enriched with fish oil may favorably affect the vascular perturbations underlying synthetic graft thrombosis. Therefore, these studies were designed to test the hypothesis that diets enriched with fish oil would decrease the incidence of thrombosis in newly constructed polytetrafluorethylene grafts. A double-blind, randomized trial was conducted. Twenty-four patients were randomized to receive 4000 mg of fish oil or 4000 mg of control oil. Both preparations were enriched with antioxidants and deodorized with peppermint. Patients began therapy within 2 wk after graft placement and were monitored for 12 mo or until thrombosis developed. With a permuted-block randomization schedule, 12 patients received fish oil and 12 patients received control oil. The primary patency rates at 365 d were 14.9% for the control group and 75.6% for the fish oil-treated group. Survival analysis revealed a significant difference between fish oil-treated and untreated patients (P < 0.03, Mantel-Cox test), with a power of 90%. Moreover, analysis of covariables, including age of > or =50 yr, gender, race, body weight, diabetes mellitus, bleeding times, and lipid profiles, indicated that this effect occurred principally as a result of fish oil administration. Importantly, fish oil treatment also decreased venous outflow resistance and systemic BP, compared with control values. Fish oils possess unique biologic properties that favorably affect the incidence of polytetrafluorethylene graft thrombosis, and they thus represent a potential treatment strategy for the prevention of access thrombosis.

The emerging role of omega-3 polyunsaturated fatty acids in the management of patients with IgA nephropathy

Immunoglobulin A nephropathy (IgAN), the most common primary glomerulonephritis in the world, affects mostly young adults, and shows a widely variable clinical course with many patients developing progressive renal disease, culminating in terminal renal failure in 20% to 40% of those afflicted. Until recently, no treatment options have been available for IgAN. Although a cure for the disease remains elusive, drugs that slow disease progression are becoming available, including omega-3 (n-3) fatty acids. The largest long-term clinical trial evaluating n-3 fatty acids in high-risk patients with IgAN showed that early and prolonged treatment with n-3 fatty acids retards renal progression. The rationale for using these fats involves potential mechanisms that reduce renal inflammation and glomerulosclerosis, hallmarks of progressive disease.

Higher intakes of fish protein are related to a lower risk of microalbuminuria in young Swedish type 1 diabetic patients

OBJECTIVE

To examine the influence of dietary intake from various protein and fat sources on the occurrence of microalbuminuria in type 1 diabetic patients.

RESEARCH DESIGN AND METHODS

In this nested case control study, 1,150 patients with diabetes duration >5 years reported dietary habits for the previous 12 months and submitted urinary samples for the analysis of albumin excretion rate (AER). A total of 75 cases of albuminuria (overnight AER > or = 15 microg/min) were identified and compared with 225 duration-matched control subjects.

RESULTS

Neither mean protein, fat intake, average fish protein intake (control subjects 4.56 +/- 3.83 g/day and cases 3.82 +/- 2.87 g/day; P = 0.12), nor intake of meat and vegetable protein differed between the cases of albuminuria and the control subjects. High consumers of fish protein (greater than the 75th percentile) (12 cases and 63 control subjects, mean intake 9.35 g fish protein/day, i.e., approximately 53 g fish/day) had lower odds ratios (ORs) for microalbuminuria than individuals consuming less fish protein (mean 2.72 g/day) (crude OR 0.49 and 95% CI 0.25-0.97). When adjusted for known confounding factors, such as HbA1c, mean arterial pressure, diabetes duration, age, sex, smoking, BMI, country region, and total energy, individuals with a high intake of fish protein and fish fat showed a reduction in the risk for microalbuminuria (OR 0.22 and 0.31, respectively; 95% CI 0.09-0.56 and 0.13-0.76, respectively). When fish protein and fat were adjusted for each other, a high intake of fish protein but not of fish fat was still significantly associated with a decrease in the risk for microalbuminuria.

CONCLUSIONS

Total protein and fat intake were not associated with the presence of microalbuminuria, but a diet including a high amount of fish protein seemed to lessen the risk.

Dietary docosahexaenoic acid affects stearic acid desaturation in spontaneously hypertensive rats

Docosahexaenoic acid (DHA, 22:6n-3) is an n-3 polyunsaturated fatty acid which attenuates the development of hypertension in spontaneously hypertensive rats (SHR). The effects of DHA on delta-9-desaturase activity in hepatic microsomes and fatty acid composition were examined in young SHR. Two groups of SHR were fed either a DHA-enriched diet or a control diet for 6 wk. Desaturase activity and fatty acid composition were determined in hepatic microsomes following the dietary treatments. Delta-9-desaturase activity was decreased by 53% in DHA-fed SHR and was accompanied by an increase in 16:0 and a reduction in 16:1n-7 content in hepatic microsomes. The DHA diet also increased the levels of eicosapentaenoic acid (20:5n-3) and DHA. The n-6 fatty acid content was also affected in DHA-fed SHR as reflected by a decrease in gamma-linolenic acid (18:3n-6), arachidonic acid (20:4n-6), adrenic acid (22:4n-6), and docosapentaenoic acid (22:5n-6). A higher proportion of dihomo-gamma-linolenic acid (20:3n-6) and a lower proportion of 20:4n-6 is indicative of impaired delta-5-desaturase activity. The alterations in fatty acid composition and metabolism may contribute to the antihypertensive effect of DHA previously reported.

Modulation of hypersensitivity reaction by lipids given orally

The effect of lipids administration by gavage (0.4% body weight) given daily during four weeks on the hypersensitivity reaction in trachea, upper and lower bronchi, liver, kidney, mesentery, and pancreas was investigated in male rats. The plasma exudation was assessed by using Evans blue (EB) dye extravasation method. There was a significant difference in the permeability of the organs in nonimmunized rats. The immunization increased the vascular permeability and the response with the organs varied greatly. The effect of lipids on anaphylactic reaction was compared to those of untreated rats (control group). The EB extravasation was significantly increased in the trachea obtained from rats treated with cocoa butter and soybean oil. In the upper bronchi of rats treated with soybean oil, the EB extravasation was increased. However, in the lower bronchi, none of the treatments with lipids changed the extravasation of EB. The same was observed in the liver and kidney. The animals treated with lipids by gavage did not present differences in EB extravasation in the mesentery. However, in the pancreas and duodenum, the treatment with fish and soybean oils and cocoa butter markedly lowered EB extravasation.

Gene expression of 5-lipoxygenase and LTA4 hydrolase in renal tissue of nephrotic syndrome patients

Leukotrienes (LT) of the 5-lipoxygenase pathway constitute a class of potent biological lipid mediators of inflammation implicated in the pathogenesis of different models of experimental glomerulonephritis. The key enzyme, 5-lipoxygenase (5-LO), catalyses oxygenation of arachidonic acid to generate the primary leukotriene LTA4. This LT, in turn, serves as a substrate for either LTA4 hydrolase, to form the potent chemoattractant LTB4, or LTC4 synthase, to produce the powerful vasoconstrictor LTC4. To investigate the potential role of LT in the pathogenesis of human glomerulonephritis with nephrotic syndrome, we examined the gene expression of 5-LO and LTA4 hydrolase in renal tissue of 21 adult patients with nephrotic syndrome and 11 controls. The patients consisted of 11 cases of membranous nephropathy (MN), seven focal and segmental glomerulosclerosis (FSGS), two non-IgA mesangial glomerulonephritis and one minimal change disease. Total RNA purified from renal tissue was reverse transcribed into cDNA and amplified with specific primers in a polymerase chain reaction (RT-PCR). Eight patients' renal tissue, four MN and four FSGS, co-expressed 5-LO and LTA4 hydrolase. In situ hybridization analysis revealed 5-LO expression and distribution limited to the interstitial cells surrounding the peritubular capillaries. Comparative clinical and immunohistological data showed that these eight patients had impaired renal function and interstitial changes that significantly correlated with 5-LO expression. These findings suggest that leukotrienes may play an important role in the pathogenesis of MN and FSGS. These results are also relevant to elucidating the pathophysiologic mechanisms which underlie progression to renal failure in these diseases.

The effects of dietary lipids on gene expression and apoptosis

The beneficial effects of dietary FO with respect to autoimmune disease, CVD and some types of cancer are well established. Studies conducted over the last 10-15 years have established the potent effects of FO on gene expression in the previously mentioned diseases. The effects of dietary FO appear to be selective in nature, with the expression of individual genes simultaneously being increased, decreased or completely unaffected. In order to elucidate the molecular mechanism(s) involved, recent studies have focused on analysing the effects of the long-chain polyunsaturated n-3 fatty acids EPA and DHA which are highly enriched in FO and thought to be the primary mediators of its biological activity. Indeed, it has been found that EPA and DHA appear to both directly and indirectly modulate gene expression in vivo, depending on the gene examined. The direct effects of EPA and DHA are most probably mediated by their ability to bind to positive and/or negative regulatory transcription factors, while the indirect effects appear to be mediated through alterations in the generation of intracellular lipid second messengers (e.g. diacylglycerol and ceramide). Future studies need to be focused on further elucidation of the inter- and intracellular signalling events mediated by dietary n-3 fatty acids. Understanding the molecular mechanism(s) modified by dietary FO will ultimately lead to improved dietary strategies to aid in the prevention of autoimmune disease, CVD and/or certain types of cancer.

Effects of polyunsaturated fatty acids on rat glomerulosclerosis induced by hypercholesterolaemic diet

Association between lipids and renal disease has been reported recently. Its pathogenic mechanisms remain unknown. The aims of this study were to establish: (1) if a cholesterol-rich diet, alone or associated with nephrectomy, produces nephropathy; and (2) if a treatment with omega-3 polyunsaturated fatty acids (PUFA) reduces glomerulosclerotic lesions. Sixty Sprague-Dawley rats were randomized in two different groups: (A) sham operated rats and (B) uninephrectomized rats. Rats in both groups were divided into three subgroups (A1-3, B1-3) according to the diet they were fed: normal chow diet, cholesterol-rich diet (4.5%) or cholesterol-rich diet supplemented with omega-3 PUFA. Twenty weeks later, serum creatinine, creatinine clearance, serum cholesterol, triglycerides, albumin, proteinuria, mesangial cell score and focal glomerulosclerosis were assessed. Results showed that a cholesterol-rich diet significantly increased serum cholesterol, proteinuria and glomerular lesions and decreased creatinine clearance, especially in nephrectomized rats. Glomerular lesions, serum cholesterol and proteinuria ameliorated when cholesterol-rich diet was supplemented with PUFA. Hypertension was noticed only in nephrectomized rats following a normal chow diet. Simple correlation analysis showed that glomerulosclerosis correlated with renal weight, blood creatinine, cholesterol and proteinuria. In spite of some significant differences in urinary prostaglandins, no correlation with glomerular lesions was found. Multiple logistic regression analysis showed that cholesterol and proteinuria were independent risk factors for induction of glomerular sclerosis. In conclusion, a diet rich in cholesterol induces glomerulosclerosis, especially if it is associated with unilateral nephrectomy. Omega-3 PUFA administration reduces serum cholesterol, proteinuria and glomerular injury.

Membrane fluidity and fatty acid metabolism in kidney cells from rats fed purified eicosapentaenoic acid or purified docosahexaenoic acid

Rats were given a supplement (1.5 ml/day) of purified eicosapentaenoic acid (EPA, 20:5,n-3), purified docosahexaenoic acid (DHA, 22:6,n-3)), or corn oil for 10 days. Membrane fluidity, measured as the steady-state fluorescence polarization of diphenylhexatriene (DPH), was approximately 20% lower in kidney cells from rats fed purified EPA than in cells from the DHA-fed or corn-oil fed animals. The level of 20:5(n-3) in kidney phospholipids was 18 times higher in rats fed EPA, and four times higher in those fed DHA as compared to the corn-oil group. The level of arachidonic acid (20:4,n-6) was concomitantly decreased, while linoleic acid (18:2,n-6) was increased in kidney-phospholipids in the n-3 fatty acid fed rats. The proportion of 22:6(n-3) in kidney phospholipids was not affected by EPA supplementation, while the DHA diet slightly increased the level of this fatty acid. The distribution of phospholipid subclasses was significantly altered in that phosphatidylcholine was increased and phosphatidylethanolamine was concomitantly decreased. It is suggested that the decrease in 20:4(n-6) is relatively more important in the regulation of fluidity than a concomitant increase in 20:5(n-3). It is also suggested that the compensatory modifications of the phospholipid subclass distribution as a response to decreased 20:4(n-6)/20:5(n-3) ratio was not sufficient to maintain fluidity when the ratio was as low as in the present study. The incorporation of labelled linolenic acid (18:3,n-3) in phospholipids was decreased in cells from the n-3 supplemented rats. Since endogenous 22:5(n-3) in phospholipids was only increased in the EPA group, 22:6(n-3) only in the DHA group, and 20:5(n-3) in both, it is suggested that the decreased incorporation of labelled 18:3(n-3) into phospholipids of the DHA-fed rats in particular is correlated to the increased level of 22:6(n-3) in the membrane phospholipids. The incorporation of fatty acids into phopholipids may thus show substrate specificity, in that 22:6(n-3) is less exchangable with labelled 18:3(n-3) than is 20:5(n-3). These results demonstrate that increasing levels of n-3 fatty acids in membranes affect the uptake and intracellular metabolism of fatty acids as well as membrane fluidity in the kidney.

A central role for protein kinase C overactivity in diabetic glomerulosclerosis: implications for prevention with antioxidants, fish oil, and ACE inhibitors

The primary etiologic factor in diabetic glomerulosclerosis appears to be an overproduction of transforming growth factor-beta by mesangial cells, which in turn reflects a hyperglycemically mediated overactivation of protein kinase C (PKC) throughout the glomerulus. Membrane-active antioxidants, fish oil, and angiotensin-converting enzyme inhibitors can act to down-regulate glomerular PKC activity, via a variety of mechanisms that may include activation of diacylglycerol kinase and suppression of phosphatidate phosphohydrolase, support of endothelial nitric oxide and heparan sulfate production, inhibition of thromboxane and angiotensin synthesis/activity, and correction of glomerular hypertension. The beneficial impact of these measures on vascular endothelial function may be of more general utility in the prevention of diabetic complications such as retinopathy, neuropathy, and atherosclerosis. Adjunctive use of gamma-linolenic acid is indicated for prevention of neuropathy, and it is conceivable that bioactive chromium will have protective activity not solely attributable to improved glycemic control. Re-establishing euglycemia must clearly remain the core strategy for preventing diabetic complications, but when glycemic control remains suboptimal, practical, safe measures are at hand for decreasing risk.

Pharmacology of immunosuppressive medications used in renal diseases and transplantation

As understanding of the molecular basis for the immune response has expanded rapidly, so have the possibilities for designing therapeutic interventions that are more effective, more specific, and safer than current treatment options. The promise of therapeutic advances in the future is based on the rapidly expanding insights into the pathogenesis of abnormal immunologic reactions. Nowhere is the understanding of molecular mechanisms, pathophysiology, and targeted therapy more relevant than in the field of renal transplantation, which makes up much of the clinical database for the use of immunosuppressive therapy for renal disease. Despite the recent advances in basic immunology, clinical validation of new agents and approaches is lacking for most drugs at present. This review will focus in the pharmacology of agents used in the therapy of immunologic renal disease and in renal transplantation. It should be recognized that clinical pharmacology and experience with newer agents is limited, and potential utility is based largely on experimental data.

Dietary fish oil prevents the development of renal damage in salt-loaded stroke-prone spontaneously hypertensive rats

1. Stroke-prone spontaneously hypertensive rats (SHRSP) fed a high salt diet rapidly develop proteinuria, a marker of renal damage. We have recently shown that supplementing the diet of these rats with pure omega-3 fatty acids can inhibit the development of proteinuria. The aim of the present study was to examine the underlying renal pathology and to see whether a similar benefit could be obtained with fish oil or canola oil. 2. Diets containing sodium (2% by weight) and 5% fish oil, canola oil, olive oil or safflower oil (the latter two serving as controls) were fed to groups of eight young SHRSP and the development of hypertension and proteinuria was monitored. After 9 weeks, rats were killed and their kidneys were taken for histological examination and fatty acid analysis. Urinary protein was characterized electrophoretically. 3. Patterns of protein excretion were consistent with the appearance of pathological changes in both glomeruli and tubules. Fish oil inhibited the elevation of blood pressure, prevented the development of proteinuria and minimized histological lesions. However, in rats fed canola oil, hypertension and renal damage were equally severe as in rats fed olive or safflower oil. 4. The prevention of hypertensive renal damage by dietary fish oil may be attributable to the increased incorporation of long-chain omega-3 fatty acids in the kidney.

The cardiovascular protective role of docosahexaenoic acid

Dietary fish oils rich in n-3 polyunsaturated fatty acids can modulate a diverse range of factors contributing to cardiovascular disease. This study examined the relative roles of eicosapentaenoic acid (20:5 n-3; EPA) and docosahexaenoic acid (22:6 n-3; DHA) which are the principal n-3 polyunsaturated fatty acids regarded as candidates for cardioprotective actions. At low dietary intakes (0.4-1.1% of energy (%en)), docosahexaenoic acid but not eicosapentaenoic acid inhibited ischaemia-induced cardiac arrhythmias. At intakes of 3.9-10.0%en, docosahexaenoic acid was more effective than eicosapentaenoic acid at retarding hypertension development in spontaneously hypertensive rats (SHR) and inhibiting thromboxane-like vasoconstrictor responses in aortas from SHR. In stroke-prone SHR with established hypertension, docosahexaenoic acid (3.9-10.0%en) retarded the development of salt-loading induced proteinuria but eicosapentaenoic acid alone was ineffective. The results demonstrate that purified n-3 polyunsaturated fatty acids mimic the cardiovascular actions of fish oils and imply that docosahexaenoic acid may be the principal active component conferring cardiovascular protection.

Omega-3 fatty acids attenuate glomerular capillary hydraulic pressure in rats with renal ablation

To clarify the emerging role of omega-3 fatty acids (FAs) in the regulation of the renal microcirculation, we recently performed micropuncture studies in normal rats maintained on diets enriched with omega-3 FAs. Although those studies suggested that omega-3 FAs alter the renal microcirculation in normal rats, it was not apparent whether this dietary maneuver could modulate intrarenal hemodynamics in the setting of renal disease. Therefore, the present renal micropuncture studies were performed in nephrectomized rats maintained on control diets or diets enriched with omega-3 FAs. Omega-3 FAs abrogated glomerular capillary (56.2 +/- 0.8 vs. 63.9 +/- 2.0 mm Hg) and transcapillary hydraulic pressure (40.9 +/- 1.4 vs. 50.6 +/- 1.3 mm Hg) compared to untreated rats. This effect was attributable to (1) a reduction in mean arterial pressure (138 +/- 3 vs. 163 +/- 2 mm Hg) and (2) a decrease in efferent arteriolar resistance (0.43 +/- 0.06 vs 0.98 +/- 0.19 dyn x seconds x cm-5 x 10(10)). Sclerosis index and albuminuria were also lessened by this dietary maneuver. To further characterize the mechanism of altered renal arteriolar resistance, we then explored the effects of omega-3 FAs on renal prostaglandin synthesis and angiotensin II-stimulated phospholipid turnover. A significant decrease in the urinary excretion of the renal vasoconstrictor, TXA2 (12.8 +/- 2.3 vs. 35.1 +/- 14.0 ng/24 hr), was induced by treatment with omega-3 FAs. Moreover, angiotensin II-stimulated phospholipid turnover was attenuated in intact glomeruli pretreated with omega-3 FAs. We conclude that omega-3 FAs exert favorable effects on experimental renal injury by eliciting a salutary effect on the renal microcirculation of rats subjected to subtotal renal ablation. Moreover, the similarities between these findings and those obtained with sustained inhibition of angiotensin II converting-enzyme suggest that these compounds act through parallel pathways of inhibition.