A diet containing n-3 and n-6 fatty acids favorably alters the renal phospholipids, eicosanoid synthesis and plasma lipids in nephrotic rats

Nutritional interventions based on dietary restriction and nutrient reductions for the prevention of doxorubicin chemotherapy side effects

BACKGROUND: Doxorubicin (DOX) is one of most used chemotherapeutic drugs, but it has important adverse effects. Nutrition has a critical role to prevent or minimize chemotherapy side effects. Caloric and nutrient restriction has been widely studied in different health fields showing extensive beneficial effects. Given the importance of these interventions, it is expected that some of them have benefits in patients under DOX chemotherapy. OBJECTIVE: This review aimed to compile published studies evaluating the effects of different dietary intetrventions based on restriction of calories or certain nutrients against DOX-induced damage and toxicity. RESULTS: Caloric restriction and partial reduction of fat have shown to reduce DOX cardiotoxicity correlating with a reduction of oxidative stress. Reduction of dietary fat was proved to act in the same sense at liver and kidney. Studies in relation to protein reduction is more elevated has focused only on kidneys and bone, and under certain circumstances, these interventions could increase susceptibility to DOX toxicity. CONCLUSIONS: The promising effects of restriction of dietary fat, protein and sodium on differerent organs have been supported by a greater number of studies among all the dietary interventions evaluated. Still, clinical studies are necessary to confirm the potential usefulness of these interventions.

AMP-activated protein kinase activation ameliorates eicosanoid dysregulation in high-fat-induced kidney disease in mice

High-fat diet (HFD) causes renal lipotoxicity that is ameliorated with AMP-activated protein kinase (AMPK) activation. Although bioactive eicosanoids increase with HFD and are essential in regulation of renal disease, their role in the inflammatory response to HFD-induced kidney disease and their modulation by AMPK activation remain unexplored. In a mouse model, we explored the effects of HFD on eicosanoid synthesis and the role of AMPK activation in ameliorating these changes. We used targeted lipidomic profiling with quantitative MS to determine PUFA and eicosanoid content in kidneys, urine, and renal arterial and venous circulation. HFD increased phospholipase expression as well as the total and free pro-inflammatory arachidonic acid (AA) and anti-inflammatory DHA in kidneys. Consistent with the parent PUFA levels, the AA- and DHA-derived lipoxygenase (LOX), cytochrome P450, and nonenzymatic degradation (NE) metabolites increased in kidneys with HFD, while EPA-derived LOX and NE metabolites decreased. Conversely, treatment with 5-aminoimidazole-4-carboxamide-1-β-D-furanosyl 5'-monophosphate (AICAR), an AMPK activator, reduced the free AA and DHA content and the DHA-derived metabolites in kidney. Interestingly, kidney and circulating AA, AA metabolites, EPA-derived LOX, and NE metabolites are increased with HFD; whereas, DHA metabolites are increased in kidney in contrast to their decreased circulating levels with HFD. Together, these changes showcase HFD-induced pro- and anti-inflammatory eicosanoid dysregulation and highlight the role of AMPK in correcting HFD-induced dysregulated eicosanoid pathways.

Effects of dietary lipids on daunomycin-induced nephropathy in mice: comparison between cod liver oil and soybean oil

Although it is well known that dietary lipids affect the course of glomerulonephritis in rats and humans, the precise mechanisms involved have not been fully elucidated. The aim of this study was to investigate the effects of different types of dietary lipids (fish oil and vegetable oil) on daunomycin (DM)-induced nephropathy in mice fed on soybean oil (SO) or cod liver oil (CLO). Urinary protein excretion, serum albumin, creatinine, total cholesterol, and TG were measured, and glomerular histological changes were evaluated. Antioxidant enzymes were also measured, along with the levels of lipid peroxide, GSH, thromboxane (Tx) B2, and 6-keto prostaglandin F1alpha in renal cortical tissue. Dietary CLO significantly reduced urinary albumin excretion and ameliorated the histological changes induced by DM. The increase of tissue lipid peroxide levels seen in SO-fed mice was suppressed in CLO-fed mice, whereas CLO-fed mice showed higher GSH levels than SO-fed mice throughout the experiment. In addition, renal tissue GSH peroxidase activity was significantly higher at 72 h after DM injection in CLO-DM mice than in SO-DM mice. Both renal cortical TxB2 and 6-keto PGF1alpha levels were significantly lower in CLO-DM mice than in SO-DM mice. These results suggest that inhibition of oxidative damage by dietary CLO played an important role in the prevention of DM nephropathy in this mouse model. The effect of CLO was closely associated with the inhibition of Tx synthesis.

Update on solid-phase extraction for the analysis of lipid classes and related compounds

This article provides information on the different procedures and methodologies developed when solid-phase extraction (SPE) is used for lipid component separation. The analytical systematics, established by different authors and designed to separate groups of compounds and also specific components by using a combination of chromatographic supports and solvents are presented. The review has been divided into three parts, which we consider well defined: edible fats and oils, fatty foods and biological samples. Separations of non-polar and polar lipids is the most extensive systematic, although many other published methods have been established to isolate specific components or a reduced number of components from edible fats and oils, fatty foods or biological samples susceptible to further analysis by other quantitative techniques.

Dietary effect of a symmetrical triacylglycerol, 1,3-biseicosapentaenoyl-2-gamma-linolenoyl glycerol, on fatty acid composition of guinea pigs

The dietary effect of 1,3-biseicosapentaenoyl-2-gamma-linolenoyl glycerol (STG) on the fatty acid composition of guinea pigs was examined and compared with that of an eicosapentaenoic acid ethyl ester (EPA-E) and of a soybean oil (SBO) diet. In terms of content of plasma lipid, EPA-E had a greater hypolipidemic effect than STG. On the other hand, in terms of EPA incorporation, contents of EPA in liver lipid were almost the same in the STG and EPA-E groups. Considering that the amount of EPA administered in the EPA-E group was almost 1.5 times that of the STG group, EPA may be absorbed more effectively as the glycerol ester than as the ethyl ester in guinea pigs. In all the tissue lipids, the STG group had a higher unsaturation index (UI) than the EPA-E group even though there is a lower UI in the STG diet than the EPA-E diet. These results suggest that greater amounts of desaturase products as a whole were synthesized in the STG group than in the other two groups. The dihomo-gamma-linolenic acid/arachidonic acid (DGLA/AA) ratio in plasma total lipids in the STG group was 3.5 times that of SBO group, and the DGLA/AA ratio in the EPA-E group was half that of the SBO group. In liver lipid, the ratios of DGLA/AA and EPA/AA in the STG group were 0.687 and 0.488 (phosphatidylcholine fraction) and 0.237 and 0.752 (phosphatidylethanolamine fraction), respectively. The ratio of DGLA/AA as well as the high EPA/AA ratio obtained in the present study with the STG diet may lead to physiological alterations, including enhanced synthesis of 1- and 3-series eicosanoids.

Synergistic effects of fish oil diet and dimethylthiourea in acute adriamycin nephrosis

The synergistic effects of combining fish oil (FO) diet, which reduces thromboxane A production, with the free radical scavenger, dimethylthiourea (DMTU), were evaluated in acute adriamycin nephrosis, because proteinuria in adriamycin nephrosis is mediated by increased renal thromboxane A and free radical production. The effects of combined evening primrose oil (EPO) and DMTU were compared with the DMTU + FO combination because EPO increases prostaglandin E but not thromboxane A. After 7, 14, and 21 days, proteinuria was significantly (p < 0.05) reduced in rats receiving either DMTU + corn oil (CO) or DMTU + FO compared with untreated control rats. However, after 21 days, rats receiving DMTU + FO had significantly reduced urine protein excretion compared with those receiving DMTU + CO (103.9 +/- 20 mg daily vs 351.8 +/- 29.8 mg daily; P < 0.05). In contrast to FO, rats receiving EPO + DMTU had similar urine protein excretion to rats receiving DMTU + CO after 21 days (170.2 +/- 20.34 mg daily vs 179.45 +/- 26.38 mg daily). The mean serum cholesterol concentration was significantly (P < 0.01) reduced in rats receiving DMTU + FO (195.2 +/- 23.8 mg/dL) compared with DMTU + CO (377.9 +/- 28.5 mg/dL). Serum triglyceride levels also were significantly (P < 0.01) reduced in rats receiving DMTU + FO (52.5 +/- 26.4 mg/dL) compared with DMTU + CO (100.5 +/- 36.9 mg/dL). No significant differences in serum cholesterol concentrations or triglycerides occurred between rats receiving DMTU + CO and DMTU + EPO. Renal glutathione content was significantly (P < 0.05) increased by 23% in normal rats receiving FO diet and by 34% in rats receiving combined DMTU + FO compared with CO alone.(ABSTRACT TRUNCATED AT 250 WORDS)

n-3 fatty acids and renal diseases

There are numerous biologic rationales for the use of n-3 fatty acids in renal diseases, including a possible increase in the renal vasodilatory capacity by a rearrangement of renal prostanoid production, a reduction in the production of proinflammatory leukotrienes, a reduction in the transcapillary escape rate of albumin, and actions limiting cyclosporine-related nephrotoxicity. Studies of animal models of renal disease, mostly of immune-renal disease, support the idea of the possible usefulness of these compounds. The most promising areas of clinical investigation include the reduction of proteinuria in some chronic glomerular diseases, the treatment of immunoglobulin A nephropathy, and the prevention of cyclosporine-induced nephrotoxicity. However, the results of larger clinical studies, some of which are ongoing, are necessary to support the use of n-3 fatty acids in human renal diseases.

Interaction of dietary fatty acids and cyclosporine A in the borderline hypertensive rat: tissue fatty acids

In this study we examined (i) the effects of cyclosporine A (CS) on tissue lipid composition and (ii) the effect of changes in dietary n-6 fatty acids on tissue responses to CS. Fatty acid composition of liver, kidney, heart and brain were determined after 4 wk of treatment with CS (10 mg/kg.d p.o.) in male borderline hypertensive rats (BHR, n = 4/group), whose diet was supplemented with either safflower oil or evening primrose oil (EPO). Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine/phosphatidylinositol, triglyceride and cholesteryl ester fatty acids were measured in kidney, heart, brain and liver. The same parameters were also measured in safflower-fed BHR (n = 4) receiving placebo. The effects of CS on liver microsomal delta 9, delta 6 and delta 5 desaturases in vitro were also followed. CS affected the fatty acid composition of all tissues examined, with the greatest changes seen in the renal phosphatidylcholine and phosphatidylserine/phosphatidylinositol fractions. All CS-induced changes that occurred in the liver, brain and renal fatty acids were reversed by EPO. CS elevated delta 9 desaturase but had no effect on delta 6 and delta 5 desaturase. In light of (i) the observation that EPO normalizes renal function and blood pressure in CS-treated BHR, and (ii) the importance of the kidney in blood pressure regulation, the data suggest that the beneficial effects of EPO on CS toxicity may involve changes in renal phospholipid fatty acid profiles.

n-3 fatty acids reduce proteinuria in patients with chronic glomerular disease

Dietary supplementation with n-3 polyunsaturated fatty acids (n-3 PUFA) has been shown to reduce proteinuria in experimental models of renal diseases, but their potential role in the treatment of human renal disease is unknown. We administered n-3 PUFA in the form of triglycerides [with eicosapentaenoic (EPA)+docosahexaenoic (DHA) = 3 g/day into 4 patients] and of ethyl esters (EPA+DHA = 7.7 g/day) into 10 patients (one patient twice) with chronic glomerular disease (membranous glomerulonephritis and focal glomerular sclerosis), all diagnosed histologically. Serum albumin was > 2.4 g/dl and serum creatinine < 2.5 mg/dl in all patients. Treatment was given for periods of six weeks, followed by a prolonged follow-up for 27 weeks in 10 cases. Dietary supplementation with n-3 PUFA caused the expected reduction in platelet generation of thromboxane B2 (mean +/- SEM, from 490 +/- 70 ng/ml at baseline, to 342 +/- 147 ng/ml at 6 weeks, P < 0.05) of serum triglycerides (from 236 +/- 60 to 170 +/- 43, P < 0.01), and a prolongation of the bleeding time (from 5.8 +/- 0.4 min to 7.7 +/- 0.4 min, P < 0.01) in patients treated with ethyl esters. A modest but significant reduction in serum total cholesterol was noticed (from 275 +/- 27 to 252 +/- 24 mg/dl).(ABSTRACT TRUNCATED AT 250 WORDS)

Fish oil has protective and therapeutic effects on proteinuria in passive Heymann nephritis

Passive Heymann nephritis (PHN) is a rat model of membranous nephropathy induced by injecting anti-Fx1A. The onset of proteinuria in PHN is caused by complement-mediated injury to glomerular epithelial cells (GEC) accompanied by enhanced glomerular eicosanoid production. In addition, sublethal injury by complement of rat GECs in culture leads to phospholipase activation, phospholipid hydrolysis and release of arachidonic acid and dienoic prostanoids. Based on these findings, we undertook to determine if substituting arachidonic acid (omega-6) in GEC membrane phospholipids with omega-3 fatty acids derived from fish oil would alter the development and course of proteinuria in PHN. We found that rats fed a diet containing 10% fish oil for four weeks prior to antibody injection developed 50 to 60% less proteinuria between two and six weeks after anti-Fx1A than rats fed an equivalent diet containing 10% safflower oil, and had substantial enrichment of glomerular phospholipids with omega-3 fatty acids and displacement of arachidonic acid. This outcome was associated with a 50% reduction in release of glomerular thromboxane B2 (stable metabolite of thromboxane A2) in the fish oil group. More importantly, when PHN rats with well established proteinuria while on regular chow were randomized to three dietary groups, those fed fish oil had a 25 to 50% decline in proteinuria as compared to those fed lard or safflower oil. This difference was evident within two weeks of randomization and persisted until the end of the study after eight weeks. In neither study could the differences in urine protein excretion be accounted for by protein or calorie deprivation, or by differences in blood pressure, renal function, immune response to sheep IgG, or glomerular deposition of IgG or complement. Thus, our results indicate that dietary fish oil has protective and therapeutic effects with regard to proteinuria in PHN. These benefits may relate to alterations in membrane phospholipid composition in favor of omega-3 fatty acids and release of less reactive trienoic eicosanoids.

Effect of n-3 and n-6 fatty acids on hepatic microsomal lipid metabolism: a time course study

The present study examines the time dependent effects of n-6 and n-3 polyunsaturated fatty acids on liver microsomal lipid metabolism in FVB mice fed a diet supplemented with a mixture of free fatty acids (mainly 18:3n-6 and 20:5n-3) at 25 mg/g diet. Significant changes in the fatty acid composition of total liver and microsomal lipids were observed after 7 days on the diets. Thereafter, some animals remained on the same diet while others were fed a diet supplemented with hydrogenated coconut oil (HCO). With the exception of 20:5n-3 which showed a slower recovery, establishment of the HCO pattern was rapid indicating that the diet-induced changes could be easily reversed. The unsaturation index, the cholesterol/phospholipid ratio and the microviscosity of the microsomal membranes were not affected by these dietary manipulations. Unsaturated fatty acid supplementation reduced the activity of delta 9 desaturase by 50%. Feeding the HCO diet to mice previously fed the EPA/GLA diet led to a progressive increase in delta 9 desaturase activity, reaching 80% of the day zero values after 14 days. The monoene content of hepatic total lipids reflected, in most cases, the changes in enzyme activity. This study shows that a low dose of a n-3 and n-6 free fatty acid mixture increases the quantities of members of the n-3 family, without loss of n-6 fatty acids in microsomal membranes and modifies the activity of delta 9 desaturase without altering the microsome physicochemical parameters.

Dietary fish oil interferes with renal arachidonic acid metabolism in rats: correlations with renal physiology

Dietary fish oil has been reported to have both beneficial and deleterious effects in animal models of renal disease, which may be related to alterations in renal eicosanoid metabolism. The influence of dietary fish oil on glomerular and renal tubular responses that are linked to arachidonic acid metabolism was examined. Dietary fish oil had antidiuretic and antinatriuretic effects, which correlated with reduced renal cortical endogenous prostaglandin E2 (PGE2). Fish oil altered the renal balance of dienoic prostacyclin (PGI2) to thromboxane (TXA2) in favor of vasodilation, which may explain the observed exaggerated compensatory increases in glomerular function in response to uninephrectomy. Intact rats fed fish oil for 6 months developed proteinuria and impaired glomerular filtration rates (GFR). These deleterious effects were associated with evidence of increased renal lipid peroxidation. These results suggest that dietary fish oil modifies glomerular and renal tubular function in rats, and worsens age-associated proteinuria and declines in GFR. These effects may reflect the impact of dietary fish oil on renal fatty acid composition and arachidonic acid metabolism.

Effect of dietary alpha-linolenate/linoleate balance on crescent type-anti-glomerular basement membrane nephritis in rats

Rats were fed diets with three different ratios of alpha-linolenate (18:3 n-3) and linoleate (18:2 n-6), and then crescentic-type anti-glomerular basement membrane (GBM) nephritis was induced. The urinary protein levels and the plasma urea nitrogen levels were significantly higher, and histological abnormalities of glomeruli were seen more frequently in the high-alpha-linolenate group than in the high-linoleate group. The differences in dietary alpha-linolenate/linoleate balances were reflected in the proportions of arachidonate and eicosapentaenoate in glomerular phospholipids. Our results indicate that dietary enrichment with alpha-linolenate causes unfavorable effects in this anti-GBM nephritis model.

Effects of dietary n - 3 fatty acids on mass changes and [3H]glycerol incorporation in various glycerolipid classes of rat kidney in vivo

The effects of dietary fish oil containing n - 3 polyunsaturated fatty acids on triacylglycerol synthesis and phospholipid metabolism (including the alkylacyl subclass of choline glycerophospholipids (CGP)) was studied in rat kidney in vivo. After a 3 week feeding period, the triacylglycerol content (in mumol/g kidney) was 47% lower in the fish oil group relative to animals given sunflower oil. This alteration was accompanied by a substantially lower amount of arachidonic acid (20:4(n - 6)) and higher level (mumol/g tissue) of eicosapentaenoic acid (20:5(n - 3)) plus docosahexaenoic acid (22:6(n - 3)) in the triacylglycerol, CGP, and ethanolamine glycerophospholipids (EGP) of the fish oil group. The labelling of triacylglycerol relative to phospholipid from [3H]glycerol following i.p. administration was 49% lower in the fish oil as compared to the sunflower oil group, indicating a suppression of renal triacylglycerol synthesis relative to phospholipid synthesis. Modest differences in the labelling of CGP and EGP were found. A moderate and significantly lower proportional labelling (by 35%) of the alkylacyl subclass of CGP was observed in the fish oil as compared to the sunflower oil animals. These findings may have relevance to eicosanoid and platelet activating factor (PAF) biosyntheses as well as renal function and pathophysiology.