Vitamin E ameliorates renal injury in an experimental model of immunoglobulin A nephropathy

Causal relationships between vitamin E and multiple kidney diseases: evidence from trans-ethnic Mendelian randomization study

PURPOSE

The association between vitamin E and the risk of kidney disease is well documented in observational studies, but the role of vitamin E in kidney disease remain inconclusive. Here, we evaluated the causal effect of vitamin E on the risk of multiple kidney diseases, including chronic kidney disease, membranous nephropathy, diabetic nephropathy, IgA nephropathy, and dialysis.

METHODS

We conducted a two-sample Mendelian randomization analysis from large-scale trans-ancestry genome-wide association studies to determine whether there was a significant causal relationship between vitamin E and multiple kidney diseases in European, American, and Asian ancestry. Instrumental genetic variants associated with vitamin E were selected, and summary statistic-based methods of inverse variance weighted, MR Egger, weighted median, simple mode, and weighted mode methods were conducted. Pleiotropy and sensitivity were assessed.

RESULTS

We obtained 87 instrumental genetic variants in European ancestry and found no causal relationship between vitamin E and chronic kidney disease, membranous nephropathy, diabetic nephropathy, IgA nephropathy, and dialysis with no heterogeneity and pleiotropy. We obtained 18 instrumental genetic variants in Asian ancestry and vitamin E had no causal relationship with membranous nephropathy, diabetic nephropathy, and IgA nephropathy with no heterogeneity and pleiotropy. In African ancestry, 25 instrumental genetic variants were obtained and no causal relationship was identified with no heterogeneity and pleiotropy.

CONCLUSION

Our study first suggested plausible non-causal associations between vitamin E and multiple kidney diseases among different ancestry.

Beneficial and adverse effects of vitamin E on the kidney

This article reviews the beneficial and adverse effects of high-dose vitamin E supplementation on the vitamin E status and renal function in human and rodent studies. The high doses of vitamin E, which can cause renal effects, were compared to upper limits of toxicity (UL) as established by various authorities worldwide. In recent mice studies with higher doses of vitamin E, several biomarkers of tissue toxicity and inflammation were found to be significantly elevated. In these biomarker studies, the severity of inflammation and the increased levels of the biomarkers are discussed together with the need to re-evaluate ULs, given the toxic effects of vitamin E on the kidney and emphasizing oxidative stress and inflammation. The controversy in the literature about vitamin E effects on the kidney is mainly caused by the dose-effects relations that do not give a clear view, neither in human nor animals studies. In addition, more recent studies on rodents with new biomarkers of oxidative stress and inflammation give new insights into possible mechanisms. In this review, the controversy is shown and an advice given on the vitamin E supplementation for renal health.

Liposoluble vitamins A and E in kidney disease

Kidney disease (KD) is characterized by the presence of elevated oxidative stress, and this is postulated as contributing to the high cardiovascular morbidity and mortality in these individuals. Chronic KD (CKD) is related to high grade inflammatory condition and pro-oxidative state that aggravates the progression of the disease by damaging primary podocytes. Liposoluble vitamins (vitamin A and E) are potent dietary antioxidants that have also anti-inflammatory and antiapoptotic functions. Vitamin deficits in CKD patients are a common issue, and multiple causes are related to them: Anorexia, dietary restrictions, food cooking methods, dialysis losses, gastrointestinal malabsorption, etc. The potential benefit of retinoic acid (RA) and α-tocopherol have been described in animal models and in some human clinical trials. This review provides an overview of RA and α tocopherol in KD.

Steroid-sensitive nephrotic syndrome candidate gene CLVS1 regulates podocyte oxidative stress and endocytosis

We performed next-generation sequencing in patients with familial steroid-sensitive nephrotic syndrome (SSNS) and identified a homozygous segregating variant (p.H310Y) in the gene encoding clavesin-1 (CLVS1) in a consanguineous family with 3 affected individuals. Knockdown of the clavesin gene in zebrafish (clvs2) produced edema phenotypes due to disruption of podocyte structure and loss of glomerular filtration barrier integrity that could be rescued by WT CLVS1 but not the p.H310Y variant. Analysis of cultured human podocytes with CRISPR/Cas9-mediated CLVS1 knockout or homozygous H310Y knockin revealed deficits in clathrin-mediated endocytosis and increased susceptibility to apoptosis that could be rescued with corticosteroid treatment, mimicking the steroid responsiveness observed in patients with SSNS. The p.H310Y variant also disrupted binding of clavesin-1 to α-tocopherol transfer protein, resulting in increased reactive oxygen species (ROS) accumulation in CLVS1-deficient podocytes. Treatment of CLVS1-knockout or homozygous H310Y-knockin podocytes with pharmacological ROS inhibitors restored viability to control levels. Taken together, these data identify CLVS1 as a candidate gene for SSNS, provide insight into therapeutic effects of corticosteroids on podocyte cellular dynamics, and add to the growing evidence of the importance of endocytosis and oxidative stress regulation to podocyte function.

Immunoglobulin A Nephropathy and Immunoglobulin A Vasculitis

Henoch-Schönlein purpura nephritis and immunoglobulin A nephropathy are common glomerulopathies in the pediatric population that deserve special attention. In some cases the primary care provider can follow the patient but others need more intensive management. Delaying this treatment can lead to worse morbidity. This article provides information on the pathogenesis, outcomes, and follow-up strategies that will aid in the diagnosis and referral of patients at risk for kidney disease.

Toll-like Receptor 4 Signaling Pathway in the Protective Effect of Pioglitazone on Experimental Immunoglobulin A Nephropathy

Background:

In vitro experiments have revealed that toll-like receptor 4 (TLR4) pathway is involved in the progression of immunoglobulin A nephropathy (IgAN) by induction of proinflammatory cytokines. Evidence showed that, in other disease models, peroxisome proliferator-activated receptor-γ (PPAR-γ) agonists have been shown to exert anti-inflammatory effects through suppression of the expression and activity of TLR4. However, the interaction between PPAR-γ and TLR4 in IgAN has not been fully studied both in vitro and in vivo. In this study, we explored whether TLR4 pathway attributed to the progression of IgAN in experimental rats.

Methods:

Bovine gamma globulin was used to establish IgAN model. Fifty-four Lewis rats were randomly divided into six groups: Control_TAK242, IgAN_TAK242, toll-like receptor 4 inhibitor (TAK242) groups (rats were administrated with TLR4 inhibitor, TAK242) and Control_Pio, IgAN_Pio, Pio groups (rats were administrated with PPAR-γ agonist, pioglitazone). Urinary albumin-to-creatinine ratio (ACR), serum creatinine, and blood urea nitrogen were detected by automatic biochemical analyzer. Renal histopathological changes were observed after hematoxylin-eosin staining, and the IgA deposition in glomeruli was measured by immunofluorescence staining. Real-time polymerase chain reaction and Western blotting were used to detect TLR4 and interleukin-1 beta (IL-1β) message ribonucleic acid (mRNA) and protein expression in renal tissues. Results were presented as mean ± standard deviation. Differences between groups were analyzed by one-way analysis of variance.

Results:

Compared to normal rats, experimental rats showed higher ACR (4.45 ± 1.33 mg/mmol vs. 2.89 ± 0.96 mg/mmol, P < 0.05), obvious IgA deposition with mesangial hypercellularity, hyperplasia of mesangial matrix accompanied by increased serum IL-1β (48.28 ± 13.49 pg/ml vs. 35.56 ± 7.41pg/ml, P < 0.05), and renal expression of IL-1β and TLR4. The biochemical parameters and renal pathological injury were relieved in both TAK242 group and Pio group. The expressions of renal tissue TLR4, IL-1β, and serum IL-1β were decreased in rats treated with TAK242, and the expression of TLR4 mRNA and protein was significantly reduced in Pio group compared to IgAN_Pio group (1.22 ± 0.28 vs. 1.72 ± 0.45, P < 0.01, and 0.12 ± 0.03 vs. 0.21 ± 0.05, P < 0.01).

Conclusions:

Our study proves that inflammation mediated by TLR4 signaling pathway is involved in the progression of IgAN in rat models. Moreover, pioglitazone can inhibit the expression of TLR4 in IgAN.

Vitamin E supplementation ameliorates aflatoxin B1-induced nephrotoxicity in rats

Fungal toxins in nutrition can cause organ dysfunction or even failure. Aflatoxin B1 (AFB1)-induced renal impairment is not sufficiently studied regarding its extent and prevention. The aim of this experiment was to study the effect of AFB1 on renal cortical tissue and whether its possible harmful effect could be prevented by the conventional economical antioxidant, vitamin E. Forty rats were divided into four groups; I-IV. Group I represented the control while the others received vitamin E (Vit E), AFB1 and AFB1+Vit E, respectively. Renal cortex specimens were taken from each group after 25 days. Then, specimens were prepared for histological study by hematoxlyin and eosin (H&E), Masson's trichrome, caspase-3 as well as for ultrastructural examination and oxidative stress parameters evaluation. Data were morphometrically and statistically analyzed. In AFB1-treated group, focal tubulo-interstitial affection in the form of tubular cytoplasmic vacuolation, mitochondrial disruption, numerous lysosomes, marked increase in collagen deposition and in caspase-3 expression were observed. Glomerular impairment in the form of fusion of podocytes enlarged foot processes and thickening of the glomerular basement membrane (GBM) with loss of its trilaminar appearance were detected. In the group treated by AFB1+Vit E, there were minimal affection of the histological structure of the renal cortex as well as significant increase in the anti-oxidative parameters which were significantly decreased in the AFB1-treated group. Therefore, Vit E could be considered in wide experimental studies to be a first choice antioxidant of high cost-effectiveness in prevention of fungal toxins pro-oxidant-induced renal impairment.

Rapamycin slows IgA nephropathy progression in the rat

BACKGROUND

IgA nephropathy (IgAN) is the most frequent glomerulonephritis worldwide. Different therapeutic approaches have been tested against IgAN. The present study was designed to explore the renoprotective potential of low-dose mammalian target of rapamycin (mTOR) inhibitor rapamycin in an IgAN rat model and the possible mechanism of action.

METHODS

After establishing an IgAN model, the rats were randomly divided into four groups: control, control with rapamycin treatment, IgAN model, and IgAN model with rapamycin treatment. Coomassie Brilliant Blue was utilized to measure 24-hour urinary protein levels. Hepatic and renal function was determined with an autoanalyzer. Proliferation was assayed via 5-bromo-2'-deoxyuridine incorporation. Real-time PCR and immunohistochemistry were utilized to detect the expression of α-SMA, collagen I, collagen III, TGF-β1 and platelet-derived growth factor. Western blotting and immunohistochemistry were performed to determine p-S6 protein levels.

RESULTS

Low-dose mTOR inhibitor rapamycin prevented an additional increase in proteinuria and protected kidney function in a model of IgAN. Rapamycin directly or indirectly interfered with multiple key pathways in the progression of IgAN to end-stage renal disease: (1) reduced the deposition of IgA and inhibited cell proliferation; (2) decreased the expression of fibrosis markers α-SMA and type III collagen, and (3) downregulated the expression of the profibrotic growth factors platelet-derived growth factor and TGF-β1. The expression of p-S6 was significantly elevated in IgAN rats.

CONCLUSIONS

The mTOR pathway was activated in IgAN rats and the early application of low-dose mTOR inhibitor rapamycin may slow the renal injury of IgAN in rats.

High serum thioredoxin levels are reduced after tonsillectomy in patients with IgA nephropathy

OBJECTIVE

The role of oxidative stress in IgA nephropathy (IgAN), the most common type of primary glomerulonephritis, is unknown. We evaluated the clinical significance of serum levels of oxidative stress markers, thioredoxin (TRX) and manganese superoxide dismutase (MnSOD), in patients with IgAN.

METHODS

Forty-eight patients with histologically confirmed IgAN and 14 healthy subjects were enrolled in this study. Serum samples from 14 IgAN patients were obtained after tonsillectomy, a procedure hypothesized to be an effective treatment for IgAN.

RESULTS

Serum TRX levels were significantly higher in patients with IgAN than in healthy subjects (mean [ng/mL]; 49.5 vs.14.4, p<0.001). Serum TRX levels are positively correlated with blood urea nitrogen, serum uric acid and proteinuria, and negatively with estimated glomerular filtration rate (eGFR). In addition, serum TRX levels gradually increased as the severity of renal histology increased. High levels of serum TRX were significantly decreased after tonsillectomy in patients with IgAN (mean [ng/mL]; 55.5 to 41.1, p=0.02). In contrast, serum MnSOD levels did not differ between IgAN patients and healthy subjects, and these levels did not change after tonsillectomy in IgAN patients.

CONCLUSION

Serum TRX is associated with IgAN, and tonsillectomy may decrease oxidative stress in IgAN patients, leading to clinical improvement.

Oxidative stress and inflammation: Implications in uremia and hemodialysis

Oxidative response and inflammation constitute a major defense against infections, but if not properly regulated they could also lead to a number of deleterious effects. Patients affected by different stages of acute and chronic kidney disease, particularly patients on hemodialysis, present a marked activation of oxidative and inflammatory processes. This condition exposes these patients to an elevated risk of morbidity and mortality. This Review is up to date and it analyses the newest notions about pathophysiological mechanisms of oxidative stress and inflammation in patients with renal diseases, also considering the different strategies studied to counterbalance this high risk state.

Vitamin E in renal therapeutic regiments

Administration of vitamin E in children with immunoglobulin A (IgA) nephropathy, focal segmental glomerulosclerosis (FSGS) and type I diabetes demonstrated potential towards ameliorating progression. Oral vitamin E therapy reduced endothelial dysfunction, lipid peroxidation and oxidative stress in patients with chronic kidney failure (CKF). Moreover, the use of vitamin E-bonded hemodialyzers reduced atherosclerotic changes, erythropoietin dosage and muscular cramps in patients on hemodialysis (HD). However, several controlled clinical trials failed to document beneficial effects on the study subjects' cardiovascular and renal outcomes. A recent report of increased all-cause mortality in adult patients receiving high dose vitamin E therapy has caused considerable concern and debate. These issues regarding the efficacy and safety of vitamin E in renal therapeutic regimens will be reviewed in this article.

Modulating the Progression in IgA Nephropathy

IgA nephropathy affects almost 1% of the population and yet the diagnosis is often missed. This significant kidney disease is often progressive with 25% of the patients going on to end-stage kidney disease over the course of 25 years. This minireview describes the clinical presentations in children and young adults. Therapeutic options are discussed including angiotensin-converting enzyme blockade, steroids, cytotoxics, tonsillectomy, fish oil, vitamin E, singly or in combination, in order to modulate the rate of progression.

Oxidative stress and damage induced by abnormal free radical reactions and IgA nephropathy

OBJECTIVE

To estimate the oxidative stress and oxidative damage induced by abnormal free radical reactions in IgA nephropathy (IgAN) patients' bodies.

METHODS

Seventy-two IgA N patients (IgANP) and 72 healthy adult volunteers (HAV) were enrolled in a random control study design, in which the levels of nitric oxide (NO) in plasma, lipoperoxide (LPO) in plasma and in erythrocytes, and vitamin C (VC), vitamin E (VE) and beta-carotene (beta-CAR) in plasma as well as the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) in erythrocytes were determined with spectrophotometric methods.

RESULTS

Compared with the HAV group, the averages of NO in plasma, and LPO in plasma and in erythrocytes in the IgANP group were significantly increased (P<0.0001), while those of VC, VE and beta-CAR in plasma as well as those of SOD, CAT and GPX in erythrocytes in the IgANP group were significantly decreased (P<0.0001). Linear correlation analysis showed that with the increase of the values of NO, and LPO in plasma and in erythrocytes, and with the decrease of those of VC, VE, beta-CAR, SOD, CAT and GPX in the IgAN patients, the degree of histological damage of tubulointerstitial regions was increased gradually (P<0.0001); and that with the prolongation of the duration of disease the values of NO, and LPO in plasma and erythrocytes were increased gradually, while those of VC, VE, beta-CAR, SOD, CAT and GPX were decreased gradually (P<0.005). The discriminatory correct rates of the above biochemical parameters reflecting oxidative damage of the IgAN patients were 73.8%-92.5%, and the correct rates for the HAV were 70.0%-91.3% when independent discriminant analysis was used; and the correct rate for the IgAN patients was increased to 98.8%, the correct rate for the HAV was increased to 100% when stepwise discriminant analysis was used. The above biochemical parameters' reliability coefficient (alpha) were used to estimate the oxidative damage of the IgAN patients as 0.8145, the standardized item alpha=0.9730, F=53273.5681, P<0.0001.

CONCLUSIONS

A series of free radical chain reactions caused serious pathological aggravation in the IgANP' bodies, thus resulting in oxidative damage in their bodies. In treating IgANP, therefore, it is necessary that suitable dose antioxidants should be supplemented to them so as to alleviate the oxidative damage in their bodies.

Role of protein kinase C and oxidative stress in interleukin-1beta-induced human proximal tubule cell injury and fibrogenesis

BACKGROUND

Interleukin (IL)-1beta, a pro-inflammatory macrophage-derived cytokine, is implicated as a key mediator of interstitial fibrosis and tubular loss or injury in progressive renal insufficiency. This study investigates some of the mechanisms of action of IL-1beta on the proximal tubule.

METHODS

Confluent cultures of primary human proximal tubule cells (PTC) were incubated in serum-free media supplemented with either IL-1beta (0-4 ng/mL), phorbol-12-myristate 13-acetate (PMA, protein kinase C activator) (6.25-100 nmol/L), or vehicle (control), together with a non-specific protein kinase C inhibitor (H7), a specific protein kinase C inhibitor (BIM-1), an anti-oxidant (NAC) or a NADPH oxidase inhibitor (AEBSF).

RESULTS

Interleukin-1beta-treated PTC exhibited time-dependent increases in fibronectin secretion (ELISA), cell injury (LDH release) and reactive nitrogen species (RNS) release (Griess assay). Proximal tubule cell DNA synthesis (thymidine incorporation) was also significantly suppressed. The effects of IL-1beta, which were reproduced by incubation of PTC with PMA (6.25-100 nmol/L), were blocked by H7 but not by BIM-1. The anti-oxidant (4 mmol/L) partially blocked IL-1beta-induced fibronectin secretion by PTC, but did not affect IL-1beta-induced LDH release, RNS release or growth inhibition. The NADPH oxidase inhibitor (AEBSF) significantly attenuated all observed deleterious effects of IL-1beta on PTC.

CONCLUSION

Interleukin-1beta directly induces proximal tubule injury, extracellular matrix production and impaired growth. The anti-oxidant, NAC, appears to ameliorate part of the fibrogenic effect of IL-1beta on PTC through mechanisms that do not significantly involve protein kinase C activation or nitric oxide release.

Toluene diisocyanate exposure induces laryngo-tracheal eosinophilia, which can be ameliorated by supplementation with antioxidant vitamins in guinea pigs

OBJECTIVE

Toluene diisocyanate (TDI)-induced asthma is a common cause of occupational lung disease. In addition, a sore throat is one of the complaints of TDI-exposed workers. The aim of the present study was to determine whether TDI exposure induces laryngeal and/or tracheal lesions in experimental animals.

MATERIAL AND METHODS

Guinea pigs underwent naris application of TDI three times, and their respiratory tracts were then examined using light and electron microscopy. Some animals simultaneously received vitamins C and E. which function as antioxidant agents.

RESULTS

When TDI-treated animals showed the clinical sign of labored breathing, many eosinophils had appeared in the lamina propria and mucosa of both the larynx and trachea, which finally infiltrated the tract lumen through the ruptured epithelium. Laryngo-tracheal inflammation was more severe than that observed in the lungs. However, supplementation with antioxidant vitamins in TDI-treated animals ameliorated the respiratory eosinophilia.

CONCLUSION

Naris application of TDI induced laryngotracheitis. which was significantly suppressed by the antioxidant vitamins, This implies a preventive effect of the vitamins on this occupational disease.

Effects of antioxidants on kidney disease

Kidney mesangial cells (MCs) and vascular smooth muscle cells (VSMCs) are closely related in terms of origin, microscopic anatomy, histochemistry, and contractility. This relationship suggests a similarity between kidney glomerular sclerosis and atherosclerosis. Vitamin E appears beneficial in the prevention and treatment of coronary disease and also inhibits the proliferation of VSMCs in vitro. We used vitamin E and probucol to treat glomerular sclerosis and MC-proliferative glomerulonephritis (GN) in two animal models of glomerular disease. Using rats, a remnant kidney model accelerated with hyperlipidemia was employed to reflect progressive glomerular sclerosis leading to chronic renal failure, and an anti-thymocyte serum treatment was used to model acute MC-proliferative GN. Supplemental dietary antioxidants suppress MC proliferation and glomerular sclerosis in models of glomerular disease in rats. These results suggest that treatment with antioxidants may be a promising intervention to prevent progression of kidney disease.

Dietary fish oil suppresses experimental immunoglobulin a nephropathy in mice

Dietary fish oil (FO) supplementation reportedly retards the progression of renal disease in patients with immunoglobulin (Ig)A nephropathy (IgAN), the most common glomerulonephritis worldwide. Using an experimental mouse model in which early immunopathological hallmarks of IgAN are induced by the mycotoxin vomitoxin (VT), the ameliorative effects of FO ingestion on this disease were evaluated in two studies. In Study 1, the capacity of VT to induce IgAN was evaluated in mice fed for 12 wk AIN-76A diets containing 50 g/kg corn oil (CO), 50 g/kg CO plus 9 mg/kg tert butylhydroquinone (TBHQ), or 5 g/kg CO plus 45 g/kg menhaden FO that contained 200 mg/kg TBHQ. Serum IgA, serum IgA immune complexes and kidney mesangial IgA deposition were greater in mice fed VT + CO compared with the CO control group, whereas all three variables were significantly attenuated in mice fed VT + FO. Although TBHQ also had attenuating effects, these were significantly less than those for the VT + FO group. In Study 2, the effects of feeding modified AIN 93G diets containing either 70 g/kg CO or 10 g/kg CO plus 60 g/kg FO for 20 wk on VT-induced IgAN were compared. Again, consumption of FO attenuated all three immunopathological variables. In addition, spleen cell cultures from the VT + FO group produced markedly less IgA than those cultures from mice fed VT + CO. Taken together, the results suggested that diets containing FO may impair early immunopathogenesis in VT-induced IgAN and that this was not totally dependent on the presence of the antioxidant TBHQ.

mRNA expression for insulin-like growth factor 1, receptors of growth hormone and IGF-1 and transforming growth factor-beta in the kidney and liver of Zucker rats

Kidney dysfunction and mesangial enlargement are consequences of obesity found in Zucker rats. This study examines some of the early mechanisms by which the kidneys of Zucker rats undergo these changes. Our study shows that the glomerular planar area in the genetically obese Zucker rat undergo enlargement as early as 12 weeks of life, compared to the lean controls. This suggests mesangial proliferation is already occurring at this time, earlier than previously shown. The mRNA expression for IGF-I, and GHR in the kidney and liver of the obese Zucker rats were significantly reduced compared to the lean controls. However, the mRNA of the IGF-IR was significantly elevated in the kidney of the obese Zucker rats. The increase in kidney IGF-1R mRNA in the obese Zucker rat may suggest an increase in IGF-1 binding leading to the kidney hypertrophy observed in these rats.

Vitamin E treatment of experimental glomerular disease in rats

BACKGROUND

Kidney mesangial cells (MCs) and vascular smooth muscle cells (VSMCs) are closely related in terms of origin, microscopic anatomy, histochemistry, and contractility. This relationship suggests a similarity between kidney glomerular sclerosis and atherosclerosis. Vitamin E appears beneficial in the prevention and treatment of coronary heart disease and it also inhibits the proliferation of VSMCs in vitro. Thus, we investigated the effect of vitamin E on glomerular sclerosis and MC-proliferative glomerulonephritis (GN) in two rat models of glomerular disease.

METHODS

A remnant kidney rat model accelerated with hyperlipidemia was used to examine progressive glomerular sclerosis leading to chronic renal failure. A rat model of MC-proliferative GN was induced by the intravenous administration of absorbed rabbit anti-rat thymocyte serum (ATS).

RESULTS

In the remnant kidney rat model, dietary supplementation with vitamin E (500 IU dl-alpha-tocopheryl acetate/kg) and cholesterol (2%) significantly inhibited glomerular sclerosis and macrophage infiltration in glomeruli relative to controls receiving basal and cholesterol-supplemented diets. In the ATS-induced GN model, glomerular cell proliferation (principally MCs) was lower in rats fed diets supplemented with vitamin E (1000 IU dl-alpha-tocopheryl acetate/kg) compared with controls fed the basal diet only. Although the degree of glomerular macrophage infiltration was similar in both groups, fewer proliferative cell nuclear antigen (PCNA)-positive cells were observed in the vitamin E group, suggesting that MC proliferation was suppressed via the inhibition of intracellular transduction.

CONCLUSIONS

Supplemental dietary vitamin E suppresses MC proliferation and glomerular sclerosis in models of glomerular disease in rats. This action of vitamin E in experimental nephritis suggests the value of clinical trials testing the potential benefit of vitamin E in chronic GN patients.

Risk factors for IgA nephropathy: a case-control study in Japan

To disclose the risk factors for immunoglobulin A nephropathy (IgAN), we conducted a case-control study in the Tokai area of central Japan. The subjects were 94 patients, aged 20 years or older at diagnosis, who had histologically confirmed IgAN. Two sex-, age-, and residence-matched controls were randomly selected for each case from the general population. Information on medical history and lifestyle was collected using a self-administered questionnaire. The strength of association between IgAN and a potential risk factor was assessed by calculating an odds ratio. A family history of chronic nephritis, susceptibility to the common cold, preference for salty foods, frequent consumption of raw eggs, and a high intake of carbohydrates, including rice, were significantly associated with an increased risk for IgAN. Alcohol consumption, use of antioxidant vitamin supplements, and a high intake of protein, fat, monounsaturated fatty acids, and all/n-3 polyunsaturated fatty acids were somewhat protective against IgAN. Episodes of tonsillitis and exposure to organic solvents were found not to be associated with the risk in the present study. Our findings may provide some clues to the cause of IgAN.

Effects of fish oil and alpha-tocopherol in immunoglobulin A nephropathy in the rat

Alpha-tocopherol and fish oil have been reported to modulate the progression of IgA nephropathy in animals and humans. Because fish oil has been reported to exacerbate renal disease in subtotal nephrectomized rats, we investigated the effects of fish oil, with and without alpha-tocopherol, on the course of IgA nephropathy. Experimental IgA nephropathy was induced in male Sprague-Dawley rats, weighing 170-200 g, by oral and i.v. immunization with bovine gamma-globulin for 8 wk. IgA nephropathy was evidenced by hematuria, proteinuria, and IgA deposition in the mesangium. Standard rodent chow, containing 30 IU of alpha-tocopherol/kg of diet, was given to the control and IgA nephropathy rats. Fish oil (20% wt/wt), stripped of alpha-tocopherol preservative, was given to control and a second group of IgA nephropathy rats. Alternatively, corn oil or fish oil was supplemented with alpha-tocopherol at 100 IU/kg of diet and given to the third and fourth groups of IgA nephropathy rats. All animals were killed at 8 wk. Urinary protein excretion, plasma and kidney alpha-tocopherol concentrations, as well as glomerular planar area, and kidney transforming growth factor-beta1 mRNA were analyzed. As determined by reductions in proteinuria, glomerular planar area, and TGF-beta1 mRNA, fish oil with alpha-tocopherol ameliorated the renal injury induced by bovine gamma-globulin, whereas fish oil without alpha-tocopherol did not. Our findings support the importance of alpha-tocopherol, more so than fish oil, in mitigating the injury and promoting repair in experimental IgA nephropathy.

alpha-Tocopherol reduces proteinuria, oxidative stress, and expression of transforming growth factor beta 1 in IgA nephropathy in the rat

Oxidative stress and the fibrogenic cytokine transforming growth factor beta 1 (TGF beta 1) have been implicated in the pathogenesis and progression of IgA nephropathy. In the present study, we used alpha-tocopherol as a dietary supplement to test the hypothesis that the proteinuria, oxidative stress, and TGF beta mRNA can be more effectively lowered with higher doses of alpha-tocopherol. Hematuria, proteinuria, and mesangial IgA deposition are parameters which characterize IgA nephropathy. IgA nephropathy was induced by bovine gamma globulin oral immunization in rats during an 8-week course, and all hallmarks of IgA nephropathy were produced in this 8-week animal model. The elevation in renal malondialdehyde content and TGF beta 1 mRNA, as well as the severity of proteinuria, was blunted by alpha-tocopherol. Our data suggested that conventional dosage of alpha-tocopherol at 100 IU/kg chow lowered kidney TGF beta 1 to control values and increasing the dose by 2 1/2-fold or even 5-fold resulted in no further reduction in TGF beta 1 mRNA. Significant reduction of proteinuria was achieved better with a dose of 250 IU/kg chow of alpha-tocopherol supplementation than with the 100 IU/kg chow. We conclude that alpha-tocopherol at this dose is efficacious in controlling proteinuria, downregulating TGF beta 1, and reducing oxidative stress in experimental IgA nephropathy. Doubling this dose achieved no further benefits.

Vitamin E may slow kidney failure owing to oxidative stress

Progression to kidney failure in a number of major renal diseases is now thought to be significantly worsened by oxidative stress at the biochemical level. Evidence is accumulating that the rate of deterioration could, in many cases, be slowed down to a more acceptable level by the simple expedient of dietary supplementation with the antioxidant, vitamin E. Evidence for the potential use of vitamin E as an adjunctive therapy to help prolong kidney function in conditions that are accelerated by oxidative stress is discussed.