Dietary flax oil reduces renal injury, oxidized LDL content, and tissue n-6/n-3 FA ratio in experimental polycystic kidney disease

A Review of the Potential Benefits of Herbal Medicines, Small Molecules of Natural Sources, and Supplements for Health Promotion in Lupus Conditions

The Latin word lupus, meaning wolf, was in the medical literature prior to the 1200s to describe skin lesions that devour flesh, and the resources available to physicians to help people were limited. The present text reviews the ethnobotanical and pharmacological aspects of medicinal plants and purified molecules from natural sources with efficacy against lupus conditions. Among these molecules are artemisinin and its derivatives, antroquinonol, baicalin, curcumin, emodin, mangiferin, salvianolic acid A, triptolide, the total glycosides of paeony (TGP), and other supplements such as fatty acids and vitamins. In addition, medicinal plants, herbal remedies, mushrooms, and fungi that have been investigated for their effects on different lupus conditions through clinical trials, in vivo, in vitro, or in silico studies are reviewed. A special emphasis was placed on clinical trials, active phytochemicals, and their mechanisms of action. This review can be helpful for researchers in designing new goal-oriented studies. It can also help practitioners gain insight into recent updates on supplements that might help patients suffering from lupus conditions.

Diet and Polycystic Kidney Disease: Nutrients, Foods, Dietary Patterns, and Implications for Practice

Polycystic kidney disease (PKD) is a chronic, progressive hereditary condition characterized by abnormal development and growth of cysts in the kidneys and other organs. There is increasing interest in exploring whether dietary modifications may prevent or slow the disease course in people with PKD. Although vasopressin-receptor agonists have emerged as a novel drug treatment in advancing care for people with PKD, several recent landmark trials and clinical discoveries also have provided new insights into potential dietary-related therapeutic strategies. In this review, we summarize the current evidence pertaining to nutrients, foods, dietary patterns, cyst growth, and progression of PKD. We also describe existing evidence-based dietary care for people with PKD and outline the potential implications for advancing evidence-based dietary interventions. Semin Nephrol 43:x-xx © 2023 Elsevier Inc. All rights reserved.

Dietary Interventions in Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the progressive growth of renal cysts, leading to the loss of functional nephrons. Recommendations for individuals with ADPKD to maintain a healthy diet and lifestyle are largely similar to those for the general population. However, recent evidence from preclinical models suggests that more tightly specified dietary regimens, including caloric restriction, intermittent fasting, and ketogenic diets, hold promise to slow disease progression, and the results of ongoing human clinical trials are eagerly awaited. These dietary interventions directly influence nutrient signaling and substrate availability in the cystic kidney, while also conferring systemic metabolic benefits. The present review focuses on the importance of local and systemic metabolism in ADPKD and summarizes current evidence for dietary interventions to slow disease progression and improve quality of life.

Effect of flaxseed on systemic inflammation and oxidative stress in diabetic rats with or without chronic kidney disease

Background

Diabetes mellitus (DM) and chronic kidney disease (CKD) are common causes of morbidity and mortality. Flaxseed contains several bioactive compounds that have been shown to possess anti-inflammatory and antioxidative properties. The aim of the present study was to investigate the possible effect of flaxseed in diabetic rats with adenine–induced CKD.

Methods

Male Wister rats (n = 48) were randomly divided into seven equal groups and treated for 33 consecutive days as follows: G1: control. G2 adenine, G3: streptozotocin (STZ), G4: flaxseed, G5: adenine+flaxseed, G6: STZ+flaxseed, G7: adenine+STZ+flaxseed). DM or CKD were experimentally induced by a single intraperitoneal injection of streptozotocin (STZ) or by adenine via oral gavage, respectively.

Results

Rats fed adenine alone exhibited several changes including decreased body weight, increased food and water intake and urine output, increased urinary albumin/creatinine ratio. They also showed an increase in plasma urea and, creatinine, indoxyl sulfate, neutrophil gelatinase-associated lipocalin and cystatin C, and a decrease in renalase activity. These were associated with significant changes in inflammatory and oxidative biomarkers, e.g., increase in 8-isoprostane, 8 -hydroxy -2-deoxy guanosine and decrease in antioxidant enzymes, as well as increase in interleukins 1β and 6, and NF-κB, and a decrease in interlukin-10. Histopathologically, there was increased tubular necrosis and fibrosis. Concomitant administration of adenine and STZ further worsened the renal damage induced by adenine alone. Flaxseed significantly ameliorated the changes caused by adenine and STZ, given either singly or in combination.

Conclusion

These findings suggest that flaxseed is a potential therapeutic agent in attenuating the progression of CKD in diabetes.

Saskatoon berry supplementation prevents cardiac remodeling without improving renal disease in an animal model of reno-cardiac syndrome

Saskatoon berry (SKB) may have the potential to counter reno-cardiac syndrome owing to its antioxidant capacity. Here, we investigated the renal and cardiovascular effects of SKB-enriched diet in a rat model of reno-cardiac disease. Two groups of wild-type rats (+/+) and two groups of Hannover Sprague-Dawley (Han:SPRD-Cy/+) rats were given either regular diet or SKB diet (10% w/w total diet) for 8 weeks. Body weight, kidney weight, kidney water content, and left ventricle (LV) weight were measured. Blood pressure (BP) was measured by the tail-cuff method. Echocardiography was performed to assess cardiac structure and function. Serum creatinine and malondialdehyde (MDA) were also measured. Han:SPRD-Cy/+ rats had significantly higher kidney weight, kidney water content, LV weight, BP, and creatinine compared with wild-type rats (+/+). The SKB diet supplementation did not reduce kidney weight, kidney water content, BP, and LV weight in Han:SPRD-Cy/+ rats. The SKB diet also resulted in higher systolic BP in Han:SPRD-Cy/+rats. Han:SPRD-Cy/+rats showed cardiac structural remodeling (higher LV wall thickness) without any cardiac functional abnormalities. Han:SPRD-Cy/+ rats also had significantly higher creatinine whereas the concentration of MDA was not different. The SKB diet supplementation reduced cardiac remodeling and the concentration of MDA without altering the concentration of creatinine in Han:SPRD-Cy/+ rats. In conclusion, Han:SPRD-Cy/+ rats developed significant renal disease, high BP, and cardiac remodeling by 8 weeks without cardiac functional impairment. The SKB diet may be useful in preventing cardiac remodeling and oxidative stress in Han:SPRD-Cy/+rats. PRACTICAL APPLICATIONS: Saskatoon berry (SKB) is widely consumed as fresh fruit or processed fruit items and has significant commercial value. It may offer health benefits due to the presence of bioactives such as anthocyanins. SKB has very good culinary flavors, and it is an economically viable fruit crop in many parts of the world. The disease-modifying benefits of SKB are mainly ascribed to the antioxidant nature of its bioactive content. Polycystic kidney disease is a serious condition that can lead to renal and cardiac abnormalities. Here, we showed that SKB supplementation was able to mitigate cardiac remodeling and lower the level of a marker of oxidative stress in an animal model of reno-cardiac syndrome. Our study suggests that SKB possesses beneficial cardioprotective properties. Further evidence from human studies may help in increasing the consumption of SKB as a functional food.

Linseed oil: Characterization and study of its oxidative degradation

This paper proposes to characterize and monitor the degradation of linseed oil under two oxidation conditions using some traditional oxidative and quality parameters. The experimental section of this study was divided into 2 stages. In the first one, three commercial linseed oil samples (OL1, OL2, and OL3) were characterized according to oxidative stability (90 °C) and fatty acid composition. In the second stage, the OL1 sample, selected due to its availability, was subjected to the following oxidation procedures: storage at room temperature conditions with exposure to light and air (temperature ranging from 7 to 35 °C) for 140 days and accelerated oxidation at 100 °C for 7h. Samples were collected at different time intervals and analyzed for oxidative stability (90 °C), peroxide value, and acid value. The results showed that all the samples presented a similar fatty acid profile and that the OL3 sample showed a higher induction period (p < 0.05). Regarding the oxidative degradation, the induction period of the OL1 sample reduced from 9.7 to 5.7 and 9.7 to 6.3 during 140 days of storage under room temperature and 7 h of accelerated oxidation, respectively. The end of induction period of the OL1 sample is expected to occur within 229 days according to an exponential mathematical model fitted to the induction period values at different temperatures. In addition, the OL1 sample met the limits proposed by Codex and Brazilian regulations for peroxide and acid values during the oxidation time intervals.

Lack of Benefit of Early Intervention with Dietary Flax and Fish Oil and Soy Protein in Orthologous Rodent Models of Human Hereditary Polycystic Kidney Disease

Rationale for dietary advice in polycystic kidney disease (PKD) is based in part on animal studies that have examined non-orthologous models with progressive development of cystic disease. Since no model completely mimics human PKD, the purpose of the current studies was to examine the effects of dietary soy protein (compared to casein) or oils enriched in omega-3 fatty acids (fish or flax oil compared to soy oil) on early disease progression in two orthologous models of PKD. The models studied were Pkd2^WS25/- mice as a model of autosomal dominant PKD, and PCK rats as a model of autosomal recessive PKD. After 13 weeks of feeding, dietary fish (but not flax) oil resulted in larger kidneys and greater kidney water content in female Pkd2^WS25/- compared to control mice. After 12 weeks of feeding male PCK compared to control rats, both fish and flax compared to soy oil resulted in enlarged kidneys and livers, greater kidney water content and higher kidney cyst area in diseased rats. Dietary soy protein compared to casein had no effects in Pkd2^WS25/- compared to control mice. In PCK rats, kidney and liver histology were not improved, but lower proteinuria and higher urine pH suggest that soy protein could be beneficial in the long term. Therefore, in contrast to studies in non-orthologous models during the progressive development phase, these studies in orthologous PKD models do not support dietary advice to increase soy protein or oils enriched in omega-3 oils in early PKD.

Flax Fiber Hydrophobic Extract Inhibits Human Skin Cells Inflammation and Causes Remodeling of Extracellular Matrix and Wound Closure Activation

Inflammation is the basis of many diseases, with chronic wounds amongst them, limiting cell proliferation and tissue regeneration. Our previous preclinical study of flax fiber applied as a wound dressing and analysis of its components impact on the fibroblast transcriptome suggested flax fiber hydrophobic extract use as an anti-inflammatory and wound healing preparation. The extract contains cannabidiol (CBD), phytosterols, and unsaturated fatty acids, showing great promise in wound healing. In in vitro proliferation and wound closure tests the extract activated cell migration and proliferation. The activity of matrix metalloproteinases in skin cells was increased, suggesting activation of extracellular components remodeling. The expression of cytokines was diminished by the extract in a cannabidiol-dependent manner, but β-sitosterol can act synergistically with CBD in inflammation inhibition. Extracellular matrix related genes were also analyzed, considering their importance in further stages of wound healing. The extract activated skin cell matrix remodeling, but the changes were only partially cannabidiol- and β-sitosterol-dependent. The possible role of fatty acids also present in the extract is suggested. The study shows the hydrophobic flax fiber components as wound healing activators, with anti-inflammatory cannabidiol acting in synergy with sterols, and migration and proliferation promoting agents, some of which still require experimental identification.

Dietary flax oil rich in α-linolenic acid reduces renal disease and oxylipin abnormalities, including formation of docosahexaenoic acid derived oxylipins in the CD1-pcy/pcy mouse model of nephronophthisis

The CD1-pcy/pcy mouse model of nephronophthisis displays reduced renal docosahexaenoic acid (DHA) levels and alterations in renal cyclooxygenase and lipoxygenase oxylipins derived from n-6 fatty acids. Since dietary flax oil ameliorates disease progression, its effect on renal fatty acids and oxylipins was examined. Sixteen weeks of feeding resulted in reduced disease progression and enrichment of renal phospholipid α-linolenic acid (ALA) and eicosapentaenoic acid, reduction in arachidonic acid (AA), but no change in linoleic acid (LA) or DHA. In diseased kidneys, flax oil feeding mitigated the elevated levels of renal cyclooxygenase derived oxylipins formed from AA and the lowered lipoxygenase and cytochrome P450 derived oxylipins formed from ALA and DHA. Increased DHA oxylipins occurred with flax feeding despite not altering DHA levels. Dietary flax oil may therefore reduce disease progression via mitigation of oxylipin abnormalities. This study also provides evidence of in vivo ALA conversion to DHA in amounts necessary to restore DHA oxylipin levels.

Flax and flaxseed oil: an ancient medicine & modern functional food

Flaxseed is emerging as an important functional food ingredient because of its rich contents of α-linolenic acid (ALA, omega-3 fatty acid), lignans, and fiber. Flaxseed oil, fibers and flax lignans have potential health benefits such as in reduction of cardiovascular disease, atherosclerosis, diabetes, cancer, arthritis, osteoporosis, autoimmune and neurological disorders. Flax protein helps in the prevention and treatment of heart disease and in supporting the immune system. As a functional food ingredient, flax or flaxseed oil has been incorporated into baked foods, juices, milk and dairy products, muffins, dry pasta products, macaroni and meat products. The present review focuses on the evidences of the potential health benefits of flaxseed through human and animals' recent studies and commercial use in various food products.

Evidence for the use of glomerulomegaly as a surrogate marker of glomerular damage and for alpha-linolenic acid-rich oils in the treatment of early obesity-related glomerulopathy in a diet-induced rodent model of obesity

Obesity-related glomerulopathy (ORG) is a unique and emerging condition that can lead to renal failure. Early detection, aided by an earlier diagnostic marker, would improve patient outcomes; this could be facilitated by an accurate model. Such a model would be useful to examine interventions like dietary fatty acids, which are known to influence renal diseases in later stages. In this study, obese-prone rats were provided high-fat (55% of energy) diets for 12 weeks to generate a model of diet-induced obesity. The rats were subsequently provided dietary oils with various levels of alpha-linolenic acid (ALA) and linoleic acid (LA) for 8 weeks, as follows: (g ALA:LA per 100 g oil): canola/flax (20:18), canola (8:18), soy (9:53), high-oleic canola/canola (5:16), high-oleic canola (2:15), lard/soy (1:8), and safflower (0.2:73). The model developed obesity, glomerulomegaly, proteinuria, and scarce glomerular damage with an indolent course. Morphometry and histology revealed glomerulomegaly as the first renal structural alteration. The utility of this marker as a predictor for the presence of ORG and renal injury was evidenced by its correlation to visceral adiposity (p < 0.0001, r = 0.44), proteinuria (p < 0.0001, ρ = 0.55), change in proteinuria (p = 0.0092, ρ = 0.42), and glomerular damage (p < 0.0001, ρ = 0.48). Renal triglyceride ALA:LA was strongly correlated with dietary ALA:LA (p < 0.0005, ρ = 0.96), and inversely associated with mean glomerular volume (p = 0.02, ρ = -0.82). The diet-induced obese model accurately represents early ORG, and implicates glomerulomegaly as an early surrogate diagnostic marker. Early intervention with ALA-rich dietary oils slowed glomerular enlargement; these findings warrant further clinical investigation to promote optimal patient outcomes.

Renal cyclooxygenase and lipoxygenase products are altered in polycystic kidneys and by dietary soy protein and fish oil treatment in the Han:SPRD-Cy rat

SCOPE

Dietary fish oil (FO) and soy protein (SP) are two interventions that slow disease progression in the Han:SPRD-Cy rat model of polycystic kidney disease (PKD). Inhibition of cyclooxygenase (COX)-derived eicosanoids also reduces disease progression, but the role of lipoxygenase (LOX) products in this disease is not known.

METHODS AND RESULTS

Since dietary FO and SP have been shown to alter eicosanoid formation via differing mechanisms, Han:SPRD-Cy rats were given diets containing either casein protein (CP) or SP, and soy oil (SO) or FO. Analysis of eicosanoids revealed that renal COX products were higher and LOX products were lower in diseased kidneys. SP feeding resulted in lower COX products, activity and COX1 protein and higher LOX products in the diseased kidneys in parallel with reduced renal cyst growth and fibrosis. By comparison, FO reduced both COX and LOX products produced from n-6 fatty acids and increased 3-series prostanoids in both normal and diseased cortex and medulla, but these differences did not parallel effects on disease.

CONCLUSION

Renal COX-derived eicosanoids are elevated and LOX products are reduced in this model of kidney disease. The effects of dietary SP, but not FO, on renal eicosanoids parallel the effects on disease.

Dietary Flaxseed Oil Protects against Bleomycin-Induced Pulmonary Fibrosis in Rats

Bleomycin, a widely used antineoplastic agent, has been associated with severe pulmonary toxicity, primarily fibrosis. Previous work has shown a reduction in bleomycin-induced lung pathology by long-chain omega-3 fatty acids. Treatment by short-chain omega-3 fatty acids, α-linolenic acid, found in dietary flaxseed oil may also reduce lung fibrosis, as previously evidenced in the kidney. To test this hypothesis, 72 rats were divided between diets receiving either 15% (w/w) flaxseed oil or 15% (w/w) corn oil (control). These groups were further divided to receive either bleomycin or vehicle (saline) via an oropharyngeal delivery, rather than the traditional intratracheal instillation. Lungs were harvested at 2, 7, and 21 days after bleomycin or saline treatment. Animals receiving flaxseed oil showed a delay in edema formation (P = 0.025) and a decrease in inflammatory cell infiltrate and vasculitis (P = 0.04 and 0.007, resp.). At days 7 and 21, bleomycin produced a reduction in pulmonary arterial lumen patency (P = 0.01), but not in rats that were treated with flaxseed oil. Bleomycin-treated rats receiving flaxseed oil had reduced pulmonary septal thickness (P = 0.01), signifying decreased fibrosis. Dietary flaxseed oil may prove beneficial against the side effects of this highly effective chemotherapeutic agent and its known toxic effects on the lung.

A 1H NMR study of the fatty acid distribution in developing flax bolls before and after a cooking treatment

Flax is an important Canadian crop that contains a large percentage of fatty acids (FAs) by seed weight. Gas chromatography (GC) methods have traditionally been used to study FA distributions in oil seed crops. These methods, however, require sample preparation involving saponification and methyl ester formation. Recently, 1H NMR has been shown to be an excellent way to directly measure FA distributions in edible oils using a nondestructive and experimentally faster methodology. As such, we have examined the FA profiles in developing bolls of flax cultivar AC McDuff using 1H NMR and assessed the effect of cooking on FA stability and distribution. The data confirmed the high percentage of linolenic acid in mature AC McDuff flax seed compared to early stages of development and showed that FAs at early stages of boll development are more prone to thermal degradation. Triacylglycerol was found to be important to FA stability to heat. It was also observed that the FAs did not convert from cis to trans under the cooking process used herein. The usefulness of 1H NMR spectroscopy in oils chemistry is highlighted.

Distinctive effects of plant protein sources on renal disease progression and associated cardiac hypertrophy in experimental kidney disease

SCOPE

Dietary soy protein reduces renal disease progression in a number of renal diseases, suggesting that plant compared with animal proteins may be renoprotective. The inclusion of other plant protein sources could enhance compliance of intervention diets, but the effects of other plant protein sources are not known.

METHODS AND RESULTS

Weanling Han:SPRD-cy rats with experimental polycystic kidney disease were given hemp-, pea- and soy protein-based diets compared with the standard AIN 93G diet with casein as the protein source. Kidneys from diseased rats given diets which contained soy or hemp protein compared with casein-based diets were less enlarged, had lower fluid content, smaller cyst volumes, less fibrosis, lower chemokine receptor 2 (CCR2) levels and normalized serum creatinine levels. Soy and hemp protein diets also normalized heart size, which was enlarged in diseased compared with normal rats consuming casein. Kidneys from diseased rats given pea protein compared with casein were more enlarged and had higher fluid content and cyst volumes, despite growing better and having lower serum creatinine and renal chemokine receptor 2 levels, and similar levels of renal fibrosis.

CONCLUSION

Not all plant proteins are equally protective in experimental kidney disease and associated cardiac hypertrophy.

Relative efficacy of casein or soya protein combined with palm or safflower-seed oil on hyperuricaemia in rats

Diets that ameliorate the adverse effects of uric acid (UA) on renal damage deserve attention. The effects of casein or soya protein combined with palm or safflower-seed oil on various serum parameters and renal histology were investigated on hyperuricaemic rats. Male Wistar rats administered with oxonic acid and UA to induce hyperuricaemia were fed with casein or soya protein plus palm- or safflower-seed oil-supplemented diets. Normal rats and hyperuricaemic rats with or without allopurinol treatment (150 mg/l in drinking water) were fed with casein plus maize oil-supplemented diets. After 8 weeks, allopurinol treatment and soya protein plus safflower-seed oil-supplemented diet significantly decreased serum UA in hyperuricaemic rats (one-way ANOVA; P < 0.05). In addition, soya protein and casein attenuated hyperuricaemia-induced decreases in serum albumin and insulin, respectively (two-way ANOVA; P < 0.05). Safflower-seed oil significantly decreased serum TAG and UA, whereas palm oil significantly increased serum cholesterol, TAG, blood urea N and creatinine. However, soya protein significantly decreased renal NO and nitrotyrosine and palm oil significantly decreased renal nitrotyrosine, TNF-alpha and interferon-gamma and increased renal transforming growth factor-beta. Casein with safflower-seed oil significantly attenuated renal tubulointerstitial nephritis, crystals and fibrosis. Comparing casein v. soya protein combined with palm or safflower-seed oil, the results support that casein with safflower-seed oil may be effective in attenuating hyperuricaemia-associated renal damage, while soya protein with safflower-seed oil may be beneficial in lowering serum UA and TAG.

Antioxidative and anti-inflammatory actions of docosahexaenoic acid and eicosapentaenoic acid in renal epithelial cells and macrophages

Oxidative stress due to excessive reactive species (RS) and weakened antioxidant defenses is causally associated with inflammation and inflammatory mediators. To investigate the effects of the major fish oil ingredients, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), on oxidative stress-related inflammatory status, we conducted in vitro experiments utilizing rat renal epithelial cells (NRK-52E) and murine macrophages (RAW 264.7) by assessing their effects on the generation of cyclooxygenase (COX)-2-derived and xanthine oxidase (XOD)-derived RS, reduced glutathione (GSH) levels, and antioxidative enzyme activities. Additionally, 6-keto-prostaglandin (PG) F1alpha, PGE2, and nitrite levels were measured in lipopolysaccharide-stimulated RAW 264.7 macrophages. Results showed that the generation of RS from arachidonic acid through the COX-2 and XOD pathways was effectively suppressed by DHA and EPA, while GSH levels and antioxidative enzyme activities were significantly enhanced by DHA and EPA. Furthermore, levels of inflammatory mediators (thromboxane B2, PGE2, and 6-keto-PGF1alpha) and nitrite were effectively down-regulated by DHA and EPA. These results strongly indicate that DHA and EPA exert antioxidative and anti-inflammatory actions by reducing the cellular levels of RS, pro-inflammatory mediators, and nitrite levels and by maintaining higher GSH levels and antioxidative enzyme activities.

Late dietary intervention limits benefits of soy protein or flax oil in experimental polycystic kidney disease

BACKGROUND/AIMS

Dietary soy protein and flax oil retard kidney disease progression when initiated in the early stages of disease in several experimental models, including the Han:SPRD-cy rat. However, individuals with kidney disease often do not become aware of their condition until injury to the kidney is extensive. The objective of this study was to determine whether initiating these interventions in established disease would alter further progression of renal injury.

METHODS

Two-month-old adult male Han:SPRD-cy rats were given either a flax oil diet (7% flax oil), a soy protein diet (20% soy protein) or a control diet (7% corn oil, 20% casein) for 4 months. Renal disease progression was assessed by examining morphological, immunohistochemical and biochemical parameters.

RESULTS

Compared to controls, there was 21-24% less staining of proliferating cells, 21-24% less oxidative damage and 13-15% less renal inflammation in kidneys from rats given dietary soy protein and flax oil. Renal cystic growth and fibrosis and serum creatinine levels were not altered by these dietary treatments.

CONCLUSIONS

Late intervention with dietary soy protein and flax oil reduces some disease-associated pathologies in established renal disease in Han:SPRD-cy rats. The potential benefits of the antioxidant and anti-inflammatory effects on ultimate renal disease outcome in the long term remains to be determined.

Selective COX-2 inhibition markedly slows disease progression and attenuates altered prostanoid production in Han:SPRD-cy rats with inherited kidney disease

Selective cyclooxygenase-2 (COX-2) inhibitors appear to have beneficial renoprotective effects in most, but not all, renal disease conditions. The objective of our study was to examine the effects of COX-2 inhibition in a rat model of polycystic kidney disease. Four-week-old Han:SPRD-cy rats were given a standard rodent diet containing NS-398 (3 mg.kg body wt(-1).day(-1)) or a control diet without NS-398 for 7 wk. In diseased rats, selective COX-2 inhibition resulted in 18% and 67% reduction in cystic expansion and interstitial fibrosis, respectively, but no change in renal function. NS-398 also ameliorated disease-associated pathologies, such as renal inflammation, cell proliferation, and oxidant injury (by 33, 38, and 59%, respectively). Kidney disease was associated with elevated renal COX-1 and COX-2 enzyme activities, and NS-398 blunted the increase in COX-2 enzyme activity (as indicated by 21 and 28% lower renal thromboxane B2 and PGE2 levels, respectively). NS-398 reduced urinary excretion of prostanoid metabolites in diseased rats. In summary, COX-2 inhibition attenuated renal injury, reduced the elevated renal COX-2 activity, and ameliorated disease-related alterations in prostanoid production in this rat model of chronic renal disease.

Dietary flax oil during pregnancy and lactation retards disease progression in rat offspring with inherited kidney disease

Dietary flax oil (FO) retards disease progression in growing or adult animal models of kidney disease. To determine whether dietary flax oil during the perinatal period would alter renal disease progression in offspring, Han-SPRD-cy rats with inherited cystic kidney disease were given diets with either 7% FO or corn oil (CO), throughout pregnancy and lactation. At 3 wk of age, offspring were then given either the same or the alternate diet for 7 wk. Rats given FO during the maternal period had 15% less renal cyst growth compared with rats given FO only in the postweaning period. Dietary FO, compared with CO, in the maternal period also resulted in 12% lower cell proliferation and 15% less oxidant injury in diseased kidneys of offspring. Including FO in both the maternal and postweaning period resulted in 29-34% less renal interstitial fibrosis and 22-23% lower glomerular hypertrophy. Along with improved histology, these rats exhibited 13% less proteinuria and 30% lower creatinine clearance when dietary FO was given in the maternal period. The potential for dietary FO during pregnancy and lactation to positively modulate adult renal disease has significant implications for the 1 in 1000 individuals with congenital cystic kidney disease.

Effects of flaxseed derivatives in experimental polycystic kidney disease vary with animal gender

Flaxseed derivatives, including both oil and flax lignan, modify progression of renal injury in animal models, including Han:SPRD-cy polycystic kidney disease (PKD). Gender is a significant factor in the rates of progression of many forms of human renal disease, but the role of gender in the response to nutrition intervention in renal disease is unexplored. In this study, male and female Han:SPRD-cy rats or normal littermates were fed either corn oil (CO) or flax oil (FO) diets, with or without 20 mg/kg of the diet flax lignan secoisolaricinoresinol dyglycoside (SDG). Renal injury was assessed morphometrically and biochemically. Renal and hepatic PUFA composition was assessed by GC and renal PGE2 release by ELISA. FO preserved body weight in PKD males, with no effect in females. SDG reduced weight in both normal and PKD females. FO reduced proteinuria in both male and female PKD. FO reduced cystic change and renal inflammation in PKD males but reduced cystic change, fibrosis, renal inflammation, tissue lipid peroxides, and epithelial proliferation in PKD females. SDG reduced renal inflammation in all animals and lipid peroxides in PKD females. A strong interaction between SDG and FO was observed in renal FA composition of female kidneys only, suggesting increased conversion of C18 PUFA to C20 PUFA. FO reduced renal release of PGE2 in both genders. Gender influences the effects of flaxseed derivatives in Han:SPRD-cy rats. Gender-based responses to environmental factors, such as dietary lipid sources and micronutrients, may contribute to gender-based differences in disease progression rates.

Dietary modulation of p-nonylphenol-induced polycystic kidneys in male Sprague-Dawley rats

We had previously found that p-nonylphenol (NP) at 1000-2000 ppm in a soy- and alfalfa-free diet induced severe polycystic kidney disease (PKD) in both male and female pups exposed from gestation day 7 through postnatal day (PND) 50 and hypothesized that differences in dietary components contributed to the severity of lesions relative to those reported in other studies using similar doses of NP. The present study investigated the dietary modulation of NP-induced PKD using the same exposure regimen with 2000 ppm NP in four different diets: the natural ingredient soy- and alfalfa-free diet that had been used in the earlier study, Purina 5K96; two defined diets AIN-93G, designated AIN-CAS, and a modified AIN-93G with soy protein isolate replacing casein as the protein source (AIN-SPI); and the commonly used natural ingredient diet Purina 5001 (P5001). Serum isoflavone levels were negligible in animals fed the soy-free AIN-CAS and 5K96 diets and were 2- to 18-fold higher in animals fed P5001 than in those fed AIN-SPI. Consumption of P5001 was significantly greater than consumption of the other diets, and those animals fed P5001 were generally significantly heavier than animals receiving the other diets. NP significantly reduced body weight gain in male pups regardless of the diet fed. There was no evidence of NP-induced kidney toxicity in male pups at PND 2, 14, or 21 or in the dams. In PND 50 male pups, serum blood urea nitrogen was significantly elevated by NP in all diet groups. Urine volume and urinary N-acetyl beta-glucuronidase were significantly increased by NP in the soy-free 5K96 and AIN-CAS diet groups. Relative kidney weights were increased by NP in all diet groups except P5001, with the greatest increase in AIN-CAS and 5K96 diet groups. Microscopic evaluation of kidneys from the PND 50 males showed that NP induced PKD in all diet groups but with marked variation in the severity depending on the diet. PKD was severe in 100% of the NP-treated animals in the AIN-CAS and 5K96 groups, moderate in 88% of the AIN-SPI diet group, and mild in only 40% of the P5001 diet group. Thus, diet can significantly modulate the development of PKD induced by dietary NP in rats. Soy components, as well as other complex dietary factors, may account for the level of protection afforded by the P5001 diet.

Exotic mammal renal disease: diagnosis and treatment

Knowledge of the renal anatomy and clinical pathology associated with renal disease can help the practitioner with interpretation of imaging procedures and urine, blood, and serum biochemical values. This article discusses specimen collection techniques, along with species variables in several clinical pathology parameters. Diagnostic tools and interpretations are discussed for the more common renal maladies affecting exotic mammals. Treatment guidelines are offered for general as well as specific exotic mammal renal diseases.

Anti-inflammatory action of dietary fish oil and calorie restriction

Inflammation, inflammatory mediators, cyclooxygenase (COX)-2, and inducible nitric oxide (iNOS) are all influenced by age-related oxidative status. To investigate the effect of dietary fish oil (FO) and calorie restriction (CR) on oxidative stress-related inflammatory status with age, (NZB/NZW) F1 (B/W) mice were fed for 4 and 9 months either ad libitum or calorie-restricted (60% of ad libitum intake) diets containing 5% corn oil or 5% FO. We measured several key oxidative and inflammatory markers: TBARS, xanthine oxidase (XOD)-derived superoxide generation, and PGE2 and LTB4 production. Expressions of renal COX-1, COX-2, and iNOS mRNA were analyzed by RT-PCR; additionally, COX-2 protein was estimated by Western-blot method. Results show that FO intake and CR individually and together suppressed age-related increases in lipid peroxidation and superoxide generation. The inhibitory effects of dietary FO and CR were also found for iNOS expression, COX-2 expression, which subsequently led to the suppression of PGE2 and LTB4. We conclude that the beneficial effects of FO feeding and CR are synergistic in ameliorating the age-related nephritis of B/W mice by suppressing COX-2 and iNOS, reactive species generation, and pro-inflammatory mediators.

Dietary soy protein attenuates renal disease progression after 1 and 3 weeks in Han:SPRD-cy weanling rats

Compared with casein, dietary soy protein slows disease progression in animal models of chronic renal injury. To determine whether dietary soy protein feeding can alter early disease progression, male Han:SPRD-cy rats (n = 87) in a very early stage of chronic kidney disease were fed soy protein compared with casein-based diets for 1 or 3 wk. Kidneys were assessed for fibrosis, cyst growth, fatty acid composition and prostaglandin E(2) (PGE(2)) production. Soy protein feeding significantly reduced renal fibrosis by 22% (P = 0.0347) and 38% (P = 0.0102) after 1 and 3 wk of diet, and cyst growth was 34% lower after 3 wk (P < 0.0001). Kidney 18:2(n-6) levels were reduced in normal and diseased rats after as little as 1 wk of consuming the soy protein diet. Dietary soy protein also partially ameliorated the suppression of PGE(2) production observed in diseased kidneys. Compared with diseased kidneys from casein-fed rats, ex vivo PGE(2) release was 31-32% higher after 1 (P = 0.0281) and 3 (P = 0.0189) wk of dietary soy protein consumption. Hence, the first signs of a beneficial soy protein effect were observed after 1 wk of feeding, with further improvements evident after 3 wk. These data demonstrate that dietary soy protein compared with casein delays disease progression in an early stage of chronic kidney disease.

Modulation of renal injury in pcy mice by dietary fat containing n−3 fatty acids depends on the level and type of fat

Low-fat diets and diets containing n-3 fatty acids (FA) slow the progression of renal injury in the male Han:Sprague-Dawley (SPRD)-cy rat model of polycystic kidney disease. To determine whether these dietary fat effects are similar in females and in another model of renal cystic disease, in this study we used both male and female pcy mice to examine the effects of fat level and type on disease progression. Adult pcy mice were fed 4, 10, or 20 g soybean oil/100 g diet for 130 d in study 1. In study 2, weanling pcy mice were fed high or low levels of fat rich in 18:2n-6 (corn oil, CO), 18:3n-3 (flaxseed oil/CO 4:1 g/g, FO), or 22:6n-3 (algal oil/CO 4:1 g/g, DO) for 8 wk. In adult pcy mice, low- compared with high-fat diets lowered kidney weights (2.4 +/- 0.2 vs. 3.1 +/- 0.2 g/100 g body weight, P = 0.006) and serum urea nitrogen (SUN) (9.6 +/- 0.6 vs. 11.9 +/- 0.6 mmol/L, P = 0.009), whereas in young pcy mice it reduced renal fibrosis volumes (0.44 +/- 0.04 vs. 0.62 +/- 0.04 mL/kg body weight, P < 0.0001). FO feeding in young pcy mice mitigated the detrimental effects of high fat on fibrosis while not altering kidney size, function, and oxidative damage when compared with the CO-fed mice. In contrast, DO- compared with CO-fed mice had higher kidney weights (2.64 +/- 0.07 vs. 2.24 +/- 0.08 g/100 g body weight, P = 0.005), SUN (9.4 +/- 0.57 vs. 7.0 +/- 0.62 mmol/L, P < 0.0001), and cyst volumes (7.9 +/- 0.28 vs. 6.2 +/- 0.30 mL/kg body weight, P < 0.0001) and similar levels of oxidative damage and fibrosis. The FA compositions of the diets were reflected in the kidneys: 18:2n-6, 18:3n-3, and 22:6n-3 were the highest in the CO, FO, and DO diets, respectively. Dietary effects on kidney disease progression were similar in males and females. A low-fat diet slows progression of renal injury in male and female pcy mice, consistent with findings in the male Han:SPRD-cy rat. Dietary fat type also influenced renal injury, with flaxseed oil diets rich in 18:3n-3 slowing early fibrosis progression compared with diets rich in 18:2n-6 or in 22:6n-3.

Omega-3 fatty acids and cardiovascular disease

PURPOSE OF REVIEW

Omega-3 fatty acids are gaining acceptance in the cardiovascular field. The present review describes the most recent studies and developments in the field.

RECENT FINDINGS

Marine omega-3 fatty acids, that is eicosapentaenoic and docosahexaenoic acids, prevent fatal myocardial infarction and sudden cardiac death by their antiarrhythmic effects and presumably also by their effect on infarct size, the latter mediated by plaque stabilization, improvements in endothelial function and other mechanisms. In contrast, a cardioprotective effect of alpha-linolenic acid, a plant-derived omega-3 fatty acid, remains to be clearly demonstrated in adequate intervention trials. Other forms of applications, like parenteral use or other indications, like in the psychiatric field, are currently being actively investigated.

SUMMARY

Eicosapentaenoic and docosahexaenoic acids, but not alpha-linolenic acid, prevent sudden death and other cardiovascular catastrophies, and have therefore been recently incorporated into the pertinent guidelines of European and American cardiologic societies.