Pathogenesis of diabetic nephropathy: the role of oxidative stress and protein kinase C

Targeting the transcription factor Nrf2 to ameliorate oxidative stress and inflammation in chronic kidney disease

Oxidative stress and inflammation are mediators in the development and progression of chronic kidney disease (CKD) and its complications, and they are inseparably linked as each begets and amplifies the other. CKD-associated oxidative stress is due to increased production of reactive oxygen species (ROS) and diminished antioxidant capacity. The latter is largely caused by impaired activation of Nrf2, the transcription factor that regulates genes encoding antioxidant and detoxifying molecules. Protective effects of Nrf2 are evidenced by amelioration of oxidative stress, inflammation, and kidney disease in response to natural Nrf2 activators in animal models, while Nrf2 deletion amplifies these pathogenic pathways and leads to autoimmune nephritis. Given the role of impaired Nrf2 activity in CKD-induced oxidative stress and inflammation, interventions aimed at restoring Nrf2 may be effective in retarding CKD progression. Clinical trials of the potent Nrf2 activator bardoxolone methyl showed significant improvement in renal function in CKD patients with type 2 diabetes. However, due to unforeseen complications the BEACON trial, which was designed to investigate the effect of this drug on time to end-stage renal disease or cardiovascular death in patients with advanced CKD, was prematurely terminated. This article provides an overview of the role of impaired Nrf2 activity in the pathogenesis of CKD-associated oxidative stress and inflammation and the potential utility of targeting Nrf2 in the treatment of CKD.

The effect of pioglitazone on antioxidant levels and renal histopathology in streptozotocin-induced diabetic rats

Objective. Diabetic nephropathy is the most commonly seen cause of chronic renal failure, and oxidative stress is important in etiology. In the present study, favorable effects (if any) of the treatment with a thiazolidinedione group drug, pioglitazone, on antioxidant enzyme levels in the renal tissue, renal histopathology, and inflammatory cytokine levels have been investigated. Method. Forty male Wistar rats were divided into 4 groups as the control, diabetic control, and 10 and 30 mg pioglitazone-administered diabetic groups. After 4 weeks, antioxidant enzyme levels in renal tissues and inflammatory markers were investigated. Results. Blood glucose levels did not differ between the diabetic control and drug-administered groups. In pioglitazone-administered rats, histopathological findings such as tubular dilation, necrotic tubular epithelium, glomerular focal necrosis, and vascular consolidation were observed at a lesser extent than the diabetic control group. Any difference was not detected between the diabetic groups with respect to the levels of malondialdehyde, superoxide dismutase, catalase, glutathione, nitric oxide, interleukin-6, and tumor necrosis factor-alpha. Conclusion. Pioglitazone regressed development of histopathological lesions such as glomerular focal necrosis, tubular epithelial necrosis, tubular dilation, and vascular wall consolidation. However, any favorable effect on antioxidant enzyme levels in renal tissues and inflammation markers was not detected.

Potential efficacy of broccoli sprouts as a unique supplement for management of type 2 diabetes and its complications

Functional foods and their nutraceutical components are now considered as supplementary treatments in type 2 diabetes and prevention of its long-term complications. Young broccoli sprouts as a functional food contain many bioactive compounds specially sulforaphane. In hyperglycemic and oxidative conditions, sulforaphane has the potential to activate the NF-E2-related factor-2 (Nrf2)-dependent antioxidant response-signaling pathway, induces phase 2 enzymes, attenuates oxidative stress, and inactivates nuclear factor kappa-B (NF-κB), a key modulator of inflammatory pathways. Interestingly, sulforaphane induces some peroxisome proliferator-activated receptors, which contribute to lipid metabolism and glucose homeostasis. In animal and in vitro models, sulforaphane also shows antihypertensive, anticancer, cardioprotective, and hypocholesterolemic capacity, and has bactericidal properties against Helicobacter pylori. Supplementation of type 2 diabetics with high sulforaphane content broccoli sprouts resulted in increased total antioxidant capacity of plasma and in decreased oxidative stress index, lipid peroxidation, serum triglycerides, oxidized low-density lipoprotein (LDL)/LDL-cholesterol ratio, serum insulin, insulin resistance, and serum high-sensitive C-reactive protein. Sulforaphane could prevent nephropathy, diabetes-induced fibrosis, and vascular complications. Potential efficacy of sulforaphane and probably other bioactive components of young broccoli sprouts makes it as an excellent choice for supplementary treatment in type 2 diabetes.

The protective effects of α-lipoic acid on kidneys in type 2 diabetic Goto-Kakisaki rats via reducing oxidative stress

To evaluate the protective effects of α-lipoic acid on the kidneys of Goto-Kakisaki (GK) diabetic rats, ten GK diabetic rats were randomly divided into a diabetic control group and a lipoic acid-treated diabetic group with α-lipoic acid 35 mg·Kg-1 intraperitoneal injections. Four healthy Wistar rats served as normal controls. Malonaldehyde (MDA), ascorbic acid (vitamin C), vitamin E, glutathione (GSH) and superoxide dismutase (SOD) levels in renal homogenate, and urine protein excretion were measured. The expression of mRNA for NF-κB, NADPH oxidase subunits p22phox and p47phox in renal tissue was examined by realtime PCR. Pathological changes in renal tissue were evaluated by light and electron microscopy. There were significant increases in urine protein excretion, MDA levels and the expression of mRNA of NF-κB, p22phox and p47phox, and significant decreases in GSH, SOD, vitamin C and vitamin E levels in the diabetic control group compared with the normal control group. Pathological changes of renal tissue were more progressive in the diabetic control group than in the normal control group. All the parameters above were improved in the α-lipoic acid-treated diabetic group. Oxidative stress is increased in the kidney of type 2 diabetic GK rats. It is associated with the progression of diabetic nephropathy. α-lipoic acid can protect renal function in diabetic rats via its antioxidant activity.

Chronic Administration of Oil Palm (Elaeis guineensis) Leaves Extract Attenuates Hyperglycaemic-Induced Oxidative Stress and Improves Renal Histopathology and Function in Experimental Diabetes

Oil palm (Elaeis guineensis) leaves extract (OPLE) has antioxidant properties and because oxidative stress contributes to the pathogenesis of diabetic nephropathy (DN), we tested the hypothesis that OPLE prevents diabetes renal oxidative stress, attenuating injury. Sprague-Dawley rats received OPLE (200 and 500 mg kg(-1)) for 4 and 12 weeks after diabetes induction (streptozotocin 60 mg kg(-1)). Blood glucose level, body and kidney weights, urine flow rate (UFR), glomerular filtration rate (GFR), and proteinuria were assessed. Oxidative stress variables such as 8-hydroxy-2'-deoxyguanosine (8-OHdG), glutathione (GSH), and lipid peroxides (LPO) were quantified. Renal morphology was analysed, and plasma transforming growth factor-beta1 (TGF-β1) was measured. Diabetic rats demonstrated increase in blood glucose and decreased body and increased kidney weights. Renal dysfunction (proteinuria, elevations in UFR and GFR) was observed in association with increases in LPO, 8-OHdG, and TGF-β1 and a decrease in GSH. Histological evaluation of diabetic kidney demonstrated glomerulosclerosis and tubulointerstitial fibrosis. OPLE attenuated renal dysfunction, improved oxidative stress markers, and reduced renal pathology in diabetic animals. These results suggest OPLE improves renal dysfunction and pathology in diabetes by reducing oxidative stress; furthermore, the protective effect of OPLE against renal damage in diabetes depends on the dose of OPLE as well as progression of DN.

Sodium-glucose cotransporter inhibition prevents oxidative stress in the kidney of diabetic rats

The hyperglycemia triggers several chronic diabetic complications mediated by increased oxidative stress that eventually causes diabetic nephropathy. The aim of this study was to examine if the sodium-glucose cotransporter (SGLT2) inhibition prevents the oxidative stress in the kidney of diabetic rats. Methods. The diabetic rat model was established by intraperitoneal injection of streptozotocin (50 mg/kg). The inhibition of SGLT2 was induced by daily subcutaneous administration of phlorizin (0.4 g/kg). Oxidative stress was assessed by catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) activities and by immunohistochemical analysis of 3-nitrotyrosine (3-NT). Results. Streptozotocin-induced diabetes caused hyperglycemia and lower body weight. The CAT activity decreased in cortex and medulla from diabetic rats; in contrast, the GPx activity increased. Furthermore the 3-NT staining of kidney from diabetic rats increased compared to control rats. The inhibition of SGLT2 decreased hyperglycemia. However, significant diuresis and glucosuria remain in diabetic rats. The phlorizin treatment restores the CAT and GPX activities and decreases 3-NT staining. Conclusion. The inhibition of SGLT2 by phlorizin prevents the hyperglycemia and oxidative stress in kidney of diabetic rats, suggesting a prooxidative mechanism related to SGLT2 activity.

Deletion of p47phox attenuates the progression of diabetic nephropathy and reduces the severity of diabetes in the Akita mouse

AIMS/HYPOTHESIS

Reactive oxygen species (ROS) contribute to diabetes-induced glomerular injury and endoplasmic reticulum (ER) stress-induced beta cell dysfunction, but the source of ROS has not been fully elucidated. Our aim was to determine whether p47(phox)-dependent activation of NADPH oxidase is responsible for hyperglycaemia-induced glomerular injury in the Akita mouse, a model of type 1 diabetes mellitus resulting from ER stress-induced beta cell dysfunction.

METHODS

We examined the effect of deleting p47 (phox) (also known as Ncf1), the gene for the NADPH oxidase subunit, on diabetic nephropathy in the Akita mouse (Ins2 (WT/C96Y)) by studying four groups of mice: (1) non-diabetic mice (Ins2 (WT/WT)/p47 (phox+/+)); (2) non-diabetic p47 (phox)-null mice (Ins2 (WT/WT)/p47 (phox-/-)); (3) diabetic mice: (Ins2 (WT/C96Y)/p47 (phox+/+)); and (4) diabetic p47 (phox)-null mice (Ins2 (WT/C96Y)/p47 (phox-/-)). We measured the urinary albumin excretion rate, oxidative stress, mesangial matrix expansion, and plasma and pancreatic insulin concentrations in 16-week-old mice; we also measured glucose tolerance and insulin sensitivity, islet and glomerular NADPH oxidase activity and subunit expression, and pro-fibrotic gene expression in 8-week-old mice. In addition, we measured NADPH oxidase activity, subunit expression and pro-fibrotic gene expression in high glucose-treated murine mesangial cells.

RESULTS

Deletion of p47 (phox) reduced kidney hypertrophy, oxidative stress and mesangial matrix expansion, and also reduced hyperglycaemia by increasing pancreatic and circulating insulin concentrations. p47 (phox-/-) mice exhibited improved glucose tolerance, but modestly decreased insulin sensitivity. Deletion of p47 (phox) attenuated high glucose-induced activation of NADPH oxidase and pro-fibrotic gene expression in glomeruli and mesangial cells.

CONCLUSIONS/INTERPRETATION

Deletion of p47 (phox) attenuates diabetes-induced glomerular injury and beta cell dysfunction in the Akita mouse.

Ursodeoxycholic acid decreases sodium-glucose cotransporter (SGLT2) expression and oxidative stress in the kidney of diabetic rats

Oxidative stress has been associated with diabetic complications like nephropathies. Recent studies indicate that ursodeoxycholic acid (UDCA) may be beneficial preventing diabetes-induced oxidative stress and secondary complications. Thus, we study if the UDCA-treatment decreases the expression of sodium-glucose cotransporter (SGLT2) and the oxidative stress in the kidney of diabetic rats.

METHODS

The diabetes model was established by intraperitoneal injection of streptozotocin (50mg/kg). SGLT2 expression was evaluated by western blot and RT-PCR. Oxidative stress was assessed by catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase activities (SOD) and immunohistochemical analysis of 3-nitrotyrosine (3-NT).

RESULTS

Streptozotocin-induced diabetes caused hyperglycemia and lower body weight. The SGLT2 expression and mRNA levels increased in cortex of kidney from diabetic rats. The CAT activity decreased in cortex and medulla from diabetic rats, otherwise the GPx activity increased. Furthermore the 3-NT staining of kidney from diabetic rats increased compared to control rats. The UDCA treatment was able to decrease hyperglycemia and prevents the SGLT2 over-expression, restores the CAT and GPX activities and decreases 3-NT staining.

CONCLUSION

The UDCA treatment prevents the over-expression of SGLT2 and oxidative stress in kidney of diabetic rats.

Green Tea Polyphenols for the Protection against Renal Damage Caused by Oxidative Stress

Green tea, prepared from the leaves of Camellia sinensis L., is a beverage that is popular worldwide. Polyphenols in green tea have been receiving much attention as potential compounds for the maintenance of human health due to their varied biological activity and low toxicity. In particular, the contribution of antioxidant activity to the prevention of diseases caused by oxidative stress has been focused upon. Therefore, in this study, we investigated the effects of (−)-epigallocatechin 3-O-gallate and (−)-epigallocatechin 3-O-gallate, which account for a large fraction of the components of green tea polyphenol, on oxidative stress-related renal disease. Our observations suggest that green tea polyphenols have a beneficial effect on pathological states related to oxidative stress of the kidney.

Preventive effects of North American ginseng (Panax quinquefolium) on diabetic nephropathy

PURPOSE

Ginseng has been used as an herbal medicine and nutritional supplement in East Asia for thousands of years and gained popularity in the west because of its various pharmacological properties. Panax ginseng (Asian ginseng) and Panax quinquefolium (North American ginseng) both are reported to possess antihyperglycemic properties. The aim of the present study is to evaluate the preventive effects of North American ginseng on diabetic nephropathy (DN) and the underlying mechanisms of such effects.

METHODS

Models of both type 1 (C57BL/6 mice with STZ-induced diabetes) and type 2 diabetes (db/db mice) and age- and sex-matched controls were examined. Alcoholic ginseng root (200mg/kgbodywt, daily oral gavage) extract was administered to the diabetic mice (type 1 and type 2) for two or four months in order to evaluate its effects on DN.

RESULTS

Dysmetabolic state in the diabetic mice was significantly improved by ginseng treatment. In the kidneys of diabetic animals, ginseng significantly prevented oxidative stress and reduced the NF-κB (p65) levels. Diabetes-induced up-regulations of ECM proteins and vasoactive factors in the kidneys were significantly diminished by ginseng administration. Furthermore, albuminuria and mesangial expansion in the diabetic mice were prevented by ginseng therapy.

CONCLUSION

North American ginseng has preventive effects on DN and it works through a combination of mechanisms such as antihyperglycemic and antioxidant activities.

The role of oxidative stress and antioxidants in diabetic complications

Diabetes is considered to be one of the most common chronic diseases worldwide. There is a growing scientific and public interest in connecting oxidative stress with a variety of pathological conditions including diabetes mellitus (DM) as well as other human diseases. Previous experimental and clinical studies report that oxidative stress plays a major role in the pathogenesis and development of complications of both types of DM. However, the exact mechanism by which oxidative stress could contribute to and accelerate the development of complications in diabetic mellitus is only partly known and remains to be clarified. On the one hand, hyperglycemia induces free radicals; on the other hand, it impairs the endogenous antioxidant defense system in patients with diabetes. Endogenous antioxidant defense mechanisms include both enzymatic and non-enzymatic pathways. Their functions in human cells are to counterbalance toxic reactive oxygen species (ROS). Common antioxidants include the vitamins A, C, and E, glutathione (GSH), and the enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GRx). This review describes the importance of endogenous antioxidant defense systems, their relationship to several pathophysiological processes and their possible therapeutic implications in vivo.

Renoprotective potential of Macrothelypteris torresiana via ameliorating oxidative stress and proinflammatory cytokines

ETHNOPHARMACOLOGICAL RELEVANCE

Macrothelypteris torresiana is traditionally used in Chinese folk medicine for the treatment of edema for patients suffering from kidney/bladder problems due to its satisfactory therapeutic effectiveness.

AIM OF THE STUDY

The aim of this study was to investigate the renoprotective nature of the total polyphenols fraction from Macrothelypteris torresiana (PMT).

MATERIALS AND METHODS

The biochemical criterions of plasma and kidney tissues were evaluated to study the effects of PMT on puromycin aminonucleoside-induced chronic nephrotic syndrome (NS) in hyperlipidemic mice.

RESULTS

In this study, the NS and hyperlipidemia were ameliorated after 9 weeks administration of PMT. Besides, PMT was able to modulate the level of renal oxidative stress and vascular endothelial growth factor-nitric oxide (VEGF-NO) pathway.

CONCLUSIONS

It represented a potential resource of PMT for the treatment of NS involved in metabolic syndrome.

Antidiabetic effect of flax and pumpkin seed mixture powder: effect on hyperlipidemia and antioxidant status in alloxan diabetic rats

Reactive oxygen species play a crucial role in the pathogenesis of diabetes and its complications. This study aims to examine the effects of flax and pumpkin powder seed mixture on alloxan induced diabetes in Wistar rats. Animals were allocated into three groups of six rats each: a control group (CD), diabetic group (DD) and diabetic rats fed with flax and pumpkin seed mixture (DMS) group. The diabetic rats (DD) presented a significant increase in glycemia, plasma and liver lipid parameters such as total lipid, total cholesterol and triglycerides compared to the control group (CD). In addition, plasma and liver malonaldialdehyde levels (MDA, an index of lipid peroxidation) significantly increased compared to (CD). Antioxidant enzymes activities such as catalase, superoxide dismutase, and reduced glutathione (GSH) levels significantly decreased in the plasma and liver of diabetic rats compared to controls. Diet supplemented with flax and pumpkin seed mixture in the DMS group ameliorated antioxidant enzymes activities and level of GSH in diabetic rats and significantly decreased MDA levels. The present study revealed a significant increase in the activities of aspartate aminotransferase and alanine aminotransferase on diabetic status, indicating considerable hepatocellular injury. The administration of flax and pumpkin seed mixture attenuated the increased levels of the plasma enzymes produced by the induction of diabetes and caused a subsequent recovery towards normalization comparable to the control group animals. Our results thus suggest that flax and pumpkin seed mixture supplemented to diet may be helpful in preventing diabetic complications in adult rats.

Dietary polyunsaturated fatty acid prevents hyperlipidemia and hepatic oxidant status in pregnant diabetic rats and their macrosomic offspring

A considerable amount of clinical and experimental evidence now exists and suggests the involvement of fatty acids and free radical-mediated oxidative processes in the pathogenesis of diabetic complications. Fetuses from diabetic mothers are at increased risk of developing neonatal macrosomia and oxidative stress. We investigated the modulation of antioxidant status and liver biochemical parameters in normal and diabetic pregnant rats and their offspring. Animals were randomly allocated into three groups of six rats each: a control group, a diabetic group and diabetic rats fed with flax and sesame seeds mixture group. The time course of changes in lipid metabolism and antioxidant status by dietary rich in ω3- and ω6-polyunsaturated fatty acids in alloxan-induced diabetic pregnant rats and their macrosomic offspring was studied. Glucose and insulin levels were also assessed in order to characterize the diabetic state of dams and their offspring. The diabetic rats presented a significant increase in glycemia, plasma and liver lipid parameters compared with those of control group. In addition, liver malonaldialdehyde levels significantly increased. Antioxidant enzyme activities such as catalase and superoxide dismutase and reduced glutathione levels significantly decreased in the liver of diabetic rats when compared with controls. Diet supplemented with flax and sesame seeds mixture in pregnant diabetic rats ameliorated lipid parameters, antioxidant enzyme activities, level of reduced glutathione and significantly decreased malonaldialdehyde levels. These ameliorations were also observed in pups whose pregnant diabetic mothers were fed seeds mixture. Our results suggested that flax and sesame seeds mixture supplemented to diet of pregnant diabetic rats might be helpful in preventing diabetic complications in adult dams and their offspring.

Vascular protective potential of the total flavanol glycosides from Abacopteris penangiana via modulating nuclear transcription factor-κB signaling pathway and oxidative stress

ETHNOPHARMACOLOGICAL RELEVANCE

"Sanxuelian", the rhizome of Abacopteris penangiana (AP), is traditionally used in Chinese medicine for the treatment of blood circulation stasis, hemorheology barriers, edema and inflammation for patients of metabolic syndrome. This study was to investigate the protective effect of the total flavanol glycosides from AP (FAP) on diabetic vascular impairments by measuring the extents of oxidative stress and inflammatory response in mice.

MATERIALS AND METHODS

The experimental aortic pathology in diabetic mice was induced by fed on high-fat diet and injected with streptozotocin. The activities of FAP on attenuating aortas injuries, hypoglycemic, hypolipidemic, inhibiting oxidative stress and anti-inflammation were investigated. Additionally, the aortic expressions of nuclear transcription factor-κB (NFκB) were determined by western blot and immunohistochemistry analysis. Furthermore, the effects of FAP on human umbilical vein endothelia cells (HUVECs) were studied.

RESULTS

In animal study, the results showed that FAP enhanced the activities of antioxidant enzymes and attenuated the levels of proinflammatory cytokines. The plasma lipid profiles and glucose level in FAP treated groups were significantly decreased along with the vascular impairments were alleviated. Moreover, the aortic expression of NFκB was decreased. In cellular experiment, FAP could inhibit the apoptosis of HUVECs induced by H(2)O(2).

CONCLUSIONS

The results indicated that FAP had hypolipidemic, hypoglycemic and vascular protective activities and represented a potential herb for the treatment of aortic pathology involved with metabolic syndrome.

Beneficial effect of the leaves of Murraya koenigii (Linn.) Spreng (Rutaceae) on diabetes-induced renal damage in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Murraya koenigii (Linn.) Spreng (curry leaf) is widely used as a nephroprotective agent in kidney's infirmities among diabetics by the traditional practitioners in Malaysia. However, the latter role of curry leaf has been grossly under reported and is yet to receive proper scientific evaluation.

AIM OF THE STUDY

The present study was designed to investigate the beneficial effect of the leaves of Murraya koenigii (Linn.) on diabetes-induced renal damage in vivo with regard to prove its efficacy by local traditional practitioners in the treatment of kidney frailties in diabetics.

MATERIALS AND METHODS

Aqueous (AQ) extract of the leaves of Murraya koenigii (Linn.) was administered to both normal and streptozotocin (STZ) induced diabetic male rats (Sprague-Dawley strain). Animals were divided into six groups (n=6) and treated with variable dose levels of AQ extract (200 and 400mg/kg body weight/day) for 30 days. At the end of 30 days, animals were sacrificed, blood was collected, processed and stored at -70°C for the zestimation of serum urea and creatinine, changes in plasma antioxidant capacity by FRAP assay, and glutathione peroxidase levels, in the normal and STZ-induced diabetic rats. Histological changes of the kidneys of these animals were also evaluated by light microscopy to determine the beneficial effect of the leaves.

RESULTS

Daily oral administration of variable dose levels of the AQ extract for 30 days, produced significant dose dependant decrease in serum urea and creatinine levels (p<0.001), and marked increase in the levels of plasma antioxidant capacity (p<0.01) in diabetic treated rats, compared to the control (non-diabetic) subjects. However, the normal treated rats showed minimal variation in these parameters in comparison to normal controls. Histological studies of the kidneys of these animals showed comparable tissue regeneration by the AQ extract.

CONCLUSION

The results of our study scientifically support the traditional belief for using the leaves of Murraya koenigii (Linn.) as adjuvant, in the treatment of pain disorders related to renal impairments among diabetics.

Biochemical evaluation of the protective effect of Aegle marmelos (L.), Corr. leaf extract on tissue antioxidant defense system and histological changes of pancreatic beta-cells in streptozotocin-induced diabetic rats

Oxidative stress is produced under diabetic conditions and is likely involved in the progression of pancreatic damage found in diabetes. This study was undertaken to evaluate the protective effect of Aegle marmelos leaf extract, a medicinal plant, on the tissue antioxidant defense system and lipid peroxidative status in streptozotocin-induced diabetic rats. Ethanol extract of A. marmelos was administered orally for 30 days (150 mg/kg body weight/day) to diabetic rats. Activity of the three primary scavenger enzymes (superoxide dismutase, catalase, and glutathione peroxidase), levels of glutathione, and lipid peroxidation were estimated in plasma and pancreas of diabetic rats and compared to the reference drug, glibenclamide (600 microg/kg body weight/day). A significant increase in the levels of plasma glucose, vitamin E, ceruloplasmin, lipid peroxides, and a concomitant decrease in the levels of vitamin C and reduced glutathione were observed in diabetic rats. The activities of antioxidant enzymes were altered in diabetic rats. These alterations were reverted back to near normal levels after treatment with A. marmelos and glibenclamide. Histopathological studies also revealed the protective effect of A. marmelos on pancreatic beta-cells. The present study indicates that extract of A. marmelos modulates the activity of enzymic and nonenzymic antioxidants and enhances the defense against reactive oxygen species-generated damage in diabetic rats.

PKC-dependent superoxide production by the renal medullary thick ascending limb from diabetic rats

Type 1 diabetes (T1D) is a state of oxidative stress accompanied by PKC activation in many tissues. The primary site of O2*- production by the normal rat kidney is the medullary thick ascending limb (mTAL). We hypothesized that T1D increases O2*- production by the mTAL through a PKC-dependent mechanism involving increased expression and translocation of one or more PKC isoforms. mTAL suspensions were prepared from rats with streptozotocin-induced T1D (STZ mTALs) and from normal or sham rats (normal/sham mTALs). O2*- production by STZ mTALs was fivefold higher than normal/sham mTALs (P < 0.05). PMA (30 min) mimicked the effect of T1D on O2*- production. Exposure to calphostin C or chelerythrine (PKC inhibitors), Gö6976 (PKCalpha/beta inhibitor), or rottlerin (PKCdelta inhibitor) decreased O2*- production to <20% of untreated baseline in both normal/sham and STZ mTALs. PKCbeta inhibitors had no effect. PKC activity was increased in STZ mTALs (P < 0.05 vs. normal/sham mTALs) and was unaltered by antioxidant exposure (tempol). PKCalpha protein levels were increased by 70% in STZ mTALs, with a approximately 30% increase in the fraction associated with the membrane (both P < 0.05 vs. sham). PKCbeta protein levels were elevated by 29% in STZ mTALs (P < 0.05 vs. sham) with no change in the membrane-bound fraction. Neither PKCdelta protein levels nor its membrane-bound fraction differed between groups. Thus STZ mTALs display PKC activation, upregulation of PKCalpha and PKCbeta protein levels, increased PKCalpha translocation to the membrane, and accelerated O2*- production that is eradicated by inhibition of PKCalpha or PKCdelta (but not PKCbeta). We conclude that increased PKCalpha expression and activity are primarily responsible for PKC-dependent O2*- production by the mTAL during T1D.

Urinary Excretion of Creatol, an In Vivo Biomarker of Hydroxyl Radical, in Patients with Chronic Renal Failure

Creatol (CTL) is a hydroxyl radical adduct of creatinine (Cr). The serum methylguanidine (MG) level and the MG/Cr molar ratio are reported to be biomarkers for oxidative stress. The aim of this study was to examine whether urinary excretion of CTL, another oxidative stress-related marker, is increased in patients with chronic renal failure (CRF). One hundred twenty-four non-dialyzed patients with chronic renal failure (serum Cr level, 1.3-10.0 mg/dL) were recruited from our hospitals. Urine and serum levels of CTL and MG were determined by high-performance liquid chromatography with the use of 9, 10- phenanthrenequinone as a fluorogenic reagent. The CTL/Cr and (CTL+MG)/Cr molar ratios in spot urine samples were also compared with those in 24-h urine samples. The urinary CTL/Cr and (CTL+MG)/Cr molar ratios increased with decreases in Cr clearance in patients with CRF. Correlations between serum and spot urine (CTL+MG)/Cr and between serum and spot urine CTL/Cr were quite similar to those in 24-h urine samples. CTL/Cr and (CTL+MG)/Cr molar ratios in both 24-h urine and spot urine samples appear to be useful indices of the severity of CRF.

Oral administration of Eucalyptus globulus extract reduces the alloxan-induced oxidative stress in rats

In light of evidence that some complications of diabetes mellitus may be caused or exacerbated by an oxidative stress, the putative protective effect of Eucalyptus globulus, a medicinal plant, was investigated in alloxan-diabetic rats. E. globulus extract was given in drinking water for 15 days at a daily dose equivalent to 130 mg dry leaves/kg of body weight. Lipids peroxidation level and activities of catalase, superoxide-dismutase and glutathione peroxidase were then measured in liver and kidney. Under our experimental conditions, eucalyptus extract was found to significantly reduce the blood glucose level in diabetic animals but failed to restore the liver glycogen level, whereas insulin lowered blood glucose and restored liver glycogen to high concentration. Our results suggest that the antihyperglycemic action of eucalyptus extract is not exerted via the stimulation of insulin secretion but rather unveil a proper effect of the extract involving the enhancement of peripheral glucose uptake. In addition, eucalyptus extract appears to exert an antioxidative activity demonstrated (1) by the increase of catalase, superoxide-dismutase and gluthatione-peroxidase activities in liver and kidney, and (2) a lowering of lipids peroxidation level in these organs. In conclusion, the present study indicates that extract of E. globulus, administered per os, could be used with some profit in diabetic patients.

Effects of alpha-lipoic acid on transforming growth factor beta1-p38 mitogen-activated protein kinase-fibronectin pathway in diabetic nephropathy

In diabetic nephropathy, transforming growth factor beta1 (TGFbeta1) is related to p38 mitogen-activated protein kinase (MAPK) that induces production of fibronectin in mesangial cells. We investigated the effects of alpha-lipoic acid (ALA), a potent antioxidant, on proteinuria and TGFbeta1-p38 MAPK-fibronectin pathway in diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. After ALA treatment for 5 weeks in OLETF rats at 30 weeks of age, plasma malondialdehyde, urinary protein excretion, renal cortical TGFbeta1, and fibronectin protein levels were decreased; and urinary protein excretion was positively correlated with renal cortical TGFbeta1 and fibronectin protein levels. Phospho-form but not total-form levels as well as fold activations of each protein consisting of p38 MAPK pathway were also attenuated. These results suggest that ALA ameliorates proteinuria by attenuating expressions of TGFbeta1 and fibronectin proteins, and these favorable effects are related to inhibition of phosphorylating activation of p38 MAPK pathway in renal cortex of OLETF rats.

Evaluation of the effect of oxidative stress and vitamin E supplementation on renal function in rats with streptozotocin-induced Type 1 diabetes

We investigated the possible role of reactive oxygen species (ROS) on renal function in experimental diabetes.

MATERIALS AND METHODS

Seven groups of male rats were studied. Group I consisted of control animals. Diabetes was induced (by streptozotocin) in the animals in the other groups and they received either insulin or vitamin E (300 or 600 mg/kg), both insulin and vitamin E, or no treatment for 4 weeks. At the end of the study, blood pressure was measured and parameters of kidney function and oxidative stress were evaluated in serum and kidney tissue samples.

RESULTS

Diabetic animals had higher blood pressures; increased serum glucose, urea, creatinine, cyclic guanosine monophosphate (cGMP); increased kidney tissue levels of malondialdehyde and inducible nitric oxide synthetase (iNOS); and reduced serum glutathione peroxidase when compared with control animals. Blood glucose levels in diabetic animals were controlled by insulin and not by any dose of vitamin E alone. However, all other measured parameters improved towards control levels with either insulin or vitamin E in either dose. An additive beneficial effect was observed on the levels of iNOS and cGMP when both forms of treatment were used in diabetic animals.

CONCLUSIONS

We conclude that ROS may play an important role in diabetes-induced nephropathy in this rat model. Vitamin E supplementation in addition to insulin can have additive protective effects against deterioration of renal function in this model.

The renoprotective effects of RAS inhibition: focus on prevention and treatment of chronic kidney disease

Chronic kidney disease (CKD) shares major risk factors with cardiovascular disease(CVD), including hypertension and diabetes mellitus. In patients with hypertensive kidney disease and diabetic nephropathy, inhibitors of the renin-angiotensin system (RAS) significantly reduce the risk of renal and cardiovascular endpoints. Whether the renoprotective effects of RAS inhibitors can be fully accounted for by blood pressure reductions or whether other mechanisms are involved has not been clearly established. Because RAS inhibitors reduce albuminuria and slow progression of kidney disease, they are recommended as fi rst-line antihypertensive agents in patients with CKD, who often require aggressive treatment with > or = 2 drugs to reach the goal blood pressure (< 130/80 mm Hg). Greater RAS inhibition with higher-than-usual doses of a single agent or dual RAS inhibition with an angiotensin-converting enzyme inhibitor and an angiotensin receptor blocker may be necessary for maximum renoprotective effects. Ongoing clinical trials assessing treatment and prevention of CKD may resolve unanswered questions about RAS inhibition in patients with hypertension and/or diabetes.

Bacopa monnieri modulates antioxidant responses in brain and kidney of diabetic rats

Role of oxidative stress has been reported in various diabetic complications including neuropathy, nephropathy and cardiopathy. This study was undertaken to evaluate the protective effect of Bacopa monnieri, a medicinal plant, on tissue antioxidant defense system and lipid peroxidative status in streptozotocin-induced diabetic rats. Extract of B. monnieri was administered orally, once a day for 15 days (at doses 50, 125 and 250mg/(kgbw)) to diabetic rats. Activity of antioxidant enzymes (SOD, Catalase, and GPx), levels of GSH and lipid peroxidation were estimated in kidney, cerebrum, cerebellum and midbrain of diabetic rats and compared to reference drug, Glibenclamide. Administration of plant extract to diabetic rats showed significant reversal of disturbed antioxidant status and peroxidative damage. Significant increase in SOD, CAT, GPx activity and levels of GSH was observed in extract treated diabetic rats. The present study indicates that extract of B. monnieri modulates antioxidant activity, and enhances the defense against ROS generated damage in diabetic rats.

Impaired immune responses in streptozotocin-induced type I diabetes in mice. Involvement of high glucose

Diabetes is widely believed to predispose to serious infections. However, the mechanisms linking diabetes and immunosuppression are not well defined. One potential mediator of the altered defence mechanisms is hyperglycaemia. It has been identified as the main factor contributing to the development of diseases associated with diabetes mellitus. In this study we analyse the immune response in diabetes and the direct effect of hyperglycaemia on T and B lymphocyte reactivity. Diabetes induced an early decrease in IgG levels in the secondary response. However, both primary responses against a T-cell-dependent or independent antigen were affected after 6 months of diabetes induction. T- and B- cell proliferation was only decreased at this time. To gain insight into the potential mechanisms involved, we evaluated the influence of hyperglycaemia over the immune response. Pre-incubation of lymph node and spleen cells in a high glucose (HG) containing medium led to a significant time- and dose-dependent decrease in T- and B-cell proliferation. This effect was associated with the presence of HG-derived supernatants. Still viable cells after HG exposition were able to improve their proliferative response when cultured with the mitogen in a fresh standard medium. HG diminished cell viability, increased apoptosis and induced oxidative stress in lymphocytes. These results indicate that HG concentrations can directly affect lymphoid cell growth. An increase in oxidative stress would be implicated in this deleterious effect. The possibility that prolonged exposure to pathologically HG concentrations would result in the immunosuppressive state observed in diabetes is also discussed.

Podocyte specific knock out of selenoproteins does not enhance nephropathy in streptozotocin diabetic C57BL/6 mice

Background

Selenoproteins contain selenocysteine (Sec), commonly considered the 21^st genetically encoded amino acid. Many selenoproteins, such as the glutathione peroxidases and thioredoxin reductases, protect cells against oxidative stress by functioning as antioxidants and/or through their roles in the maintenance of intracellular redox balance. Since oxidative stress has been implicated in the pathogenesis of diabetic nephropathy, we hypothesized that selenoproteins protect against this complication of diabetes.

Methods

C57BL/6 mice that have a podocyte-specific inability to incorporate Sec into proteins (denoted in this paper as PodoTrsp^-/-) and control mice were made diabetic by intraperitoneal injection of streptozotocin, or were injected with vehicle. Blood glucose, body weight, microalbuminuria, glomerular mesangial matrix expansion, and immunohistochemical markers of oxidative stress were assessed.

Results

After 3 and 6 months of diabetes, control and PodoTrsp^-/- mice had similar levels of blood glucose. There were no differences in urinary albumin/creatinine ratios. Periodic acid-Schiff staining to examine mesangial matrix expansion also demonstrated no difference between control and PodoTrsp^-/- mice after 6 months of diabetes, and there were no differences in immunohistochemical stainings for nitrotyrosine or NAD(P)H dehydrogenase, quinone 1.

Conclusion

Loss of podocyte selenoproteins in streptozotocin diabetic C57BL/6 mice does not lead to increased oxidative stress as assessed by nitrotyrosine and NAD(P)H dehydrogenase, quinone 1 immunostaining, nor does it lead to worsening nephropathy.

Albuminuria and dementia in the elderly: a community study

BACKGROUND

Dementia is associated with microvascular disease of the retina. In this study, we examine whether cognitive status (normal cognition, mild cognitive impairment, and dementia) is associated with albuminuria, a microvascular disorder of the kidney.

STUDY DESIGN

Cross-sectional analysis.

SETTING & PARTICIPANTS

2,316 participants from the Cardiovascular Health Cognition Study who underwent brain magnetic resonance imaging and testing for albuminuria.

PREDICTOR

Doubling of albuminuria.

OUTCOME

Dementia defined according to neuropsychological and clinical evaluation.

MEASUREMENTS

Multinomial logistic modeling was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) of dementia and mild cognitive impairment with doubling of albuminuria compared with the odds with normal cognition.

RESULTS

283 participants (12.2%) had dementia, 344 (14.9%) had mild cognitive impairment, and 1,689 (72.9%) had normal cognition. Compared with participants with normal cognition, doubling of albuminuria was associated with increased odds of dementia (OR, 1.22; 95% CI, 1.15 to 1.29). Adjustment for prevalent cardiovascular disease and cardiovascular risk factors, lipid levels, C-reactive protein level, estimated glomerular filtration rate, and apolipoprotein E-4 genotype attenuated this association, but it remained statistically significant (OR, 1.12; 95% CI, 1.03 to 1.22). Mild cognitive impairment was associated with albuminuria on unadjusted analysis, but not with adjustment for other factors.

LIMITATIONS

Results are cross-sectional; causality cannot be imputed.

CONCLUSIONS

The odds of dementia increased in the presence of albuminuria. These findings suggest a role of shared susceptibility for microvascular disease in the brain and kidney in older adults.

Oxidative stress and diabetic retinopathy

Oxygen metabolism is essential for sustaining aerobic life, and normal cellular homeostasis works on a fine balance between the formation and elimination of reactive oxygen species (ROS). Oxidative stress, a cytopathic consequence of excessive production of ROS and the suppression of ROS removal by antioxidant defense system, is implicated in the development of many diseases, including Alzheimer's disease, and diabetes and its complications. Retinopathy, a debilitating microvascular complication of diabetes, is the leading cause of acquired blindness in developed countries. Many diabetes-induced metabolic abnormalities are implicated in its development, and appear to be influenced by elevated oxidative stress; however the exact mechanism of its development remains elusive. Increased superoxide concentration is considered as a causal link between elevated glucose and the other metabolic abnormalities important in the pathogenesis of diabetic complications. Animal studies have shown that antioxidants have beneficial effects on the development of retinopathy, but the results from very limited clinical trials are somewhat ambiguous. Although antioxidants are being used for other chronic diseases, controlled clinical trials are warranted to investigate potential beneficial effects of antioxidants in the development of retinopathy in diabetic patients.

Does garlic have a role as an antidiabetic agent?

Diabetes affects a large segment of the population worldwide, and the prevalence of this disease is rapidly increasing. Despite the availability of medication for diabetes, traditional remedies are desirable and are currently being investigated. Garlic (Allium sativum), which is a common cooking spice and has a long history as a folk remedy, has been reported to have antidiabetic activity. However, there is no general agreement on the use of garlic for antidiabetic purposes, primarily because of a lack of scientific evidence from human studies and inconsistent data from animal studies. The validity of data from previous studies of the hypoglycemic effect of garlic in diabetic animals and the preventive effects of garlic on diabetes complications are discussed in this review. The role of garlic as both an insulin secretagogue and as an insulin sensitizer is reviewed. Evidence suggests that garlic's antioxidative, antiinflammatory, and antiglycative properties are responsible for garlic's role in preventing diabetes progression and the development of diabetes-related complications. Large-scale clinical studies with diabetic patients are warranted to confirm the usefulness of garlic in the treatment and prevention of diabetes.

Antioxidative effects of azelnidipine on mesangial cell proliferation induced by highly concentrated insulin

Insulin resistance combined with hyperinsulinemia is involved in the generation of oxidative stress. There is known to be a relationship between increased production of reactive oxygen species and the diverse pathogenic mechanisms involved in diabetic vascular complications including nephropathy. The present study found that high doses of insulin affect mesangial cell proliferation through the generation of intracellular reactive oxygen species and the activation of cell signaling pathways. We also examined whether azelnidipine, a dihydropyridine-based calcium antagonist with established antioxidant activity, has the potential to inhibit mesangial cell proliferation. Cell proliferation was increased in a dose-dependent manner by high doses of insulin (0.1-10 microM), but was inhibited by 0.1 microM azelnidipine. Phosphorylation of extracellular signal-regulated kinase (ERK)-1/2 was found to be increased by insulin in a dose-dependent manner (0.1-10 microM). This increased phosphorylation of ERK-1/2 was inhibited by treatment with 0.1 microM azelnidipine. Intracellular oxidative stress was also increased by insulin stimulation in a dose-dependent manner (0.01-10 microM), and 0.1 microM azelnidipine was found to block intracellular reactive oxygen species production more effectively than 0.1 microM nifedipine. The NAD(P)H oxidase inhibitor, apocynin (0.01-0.1 microM), prevented insulin-induced mesangial cell proliferation. Taken together, these results suggest that azelnidipine inhibits insulin-induced mesangial cell proliferation by inhibiting the production of reactive oxygen species. Given these pharmacological characteristics, azelnidipine may have the potential to protect against the onset of diabetic nephropathy and slow its progression.

Hypertension aggravates glomerular dysfunction with oxidative stress in a rat model of diabetic nephropathy

Oxidative stress may contribute to the pathogenesis of diabetic nephropathy (DN), although the detailed mechanism of reactive oxygen species (ROS) regulation is still unclear. This study examined the effect of high-salt diet on ROS production and expression of antioxidant enzymes in control and experimentally diabetic rats. Wistar fatty rats (WFR) as a type 2 diabetes mellitus model and Wistar lean rats (WLR) as a control were fed a normal-salt diet (NS) and high-salt diet (HS) from the age of 6 to 14 weeks. We then examined the blood pressure, urinary albumin excretion (UAE), and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels. The expression of antioxidant enzymes including alpha-catalase (CAT), Cu-Zn superoxide dismutase (SOD), Mn SOD, and glutathione peroxidase (GPx) were analyzed in the glomeruli of the rats using Western blotting. The expression of NAD(P)H oxidase p47(phox) and NFkappaB p65 was evaluated using immunohistochemical staining. By 14 weeks of age, the WFR-HS group exhibited hypertension and markedly increased UAE. The level of 8-OHdG, a marker of oxidative damage, in the WFR-HS group was also higher than that in the WLR groups or WFR-NS group. The expression of alpha-CAT and Mn SOD proteins was significantly decreased in isolated glomeruli in the WFR-HS group. GPx and Cu-Zn SOD expression did not differ between the WFR and WLR groups. High expression of ROS and decreases in antioxidants were seen in the glomeruli of diabetic rats with hypertension, suggesting that oxidative stress may be involved in the development of DN.

Dysregulated intracellular signaling impairs CTGF-stimulated responses in human mesangial cells exposed to high extracellular glucose

High ambient glucose activates intracellular signaling pathways to induce the expression of extracellular matrix and cytokines such as connective tissue growth factor (CTGF). Cell responses to CTGF in already glucose-stressed cells may act to transform the mesangial cell phenotype leading to the development of glomerulosclerosis. We analyzed cell signaling downstream of CTGF in high glucose-stressed mesangial cells to model signaling in the diabetic milieu. The addition of CTGF to primary human mesangial cells activates cell migration which is associated with a PKC-zeta-GSK3beta signaling axis. In high ambient glucose basal PKC-zeta and GSK3beta phosphorylation levels are selectively increased and CTGF-stimulated PKC-zeta and GSK3beta phosphorylation was impaired. These effects were not induced by osmotic changes. CTGF-driven profibrotic cell signaling as determined by p42/44 MAPK and Akt phosphorylation was unaffected by high glucose. Nonresponsiveness of the PKC-zeta-GSK3beta signaling axis suppressed effective remodeling of the microtubule network necessary to support cell migration. However, interestingly the cells remain plastic: modulation of glucose-induced PKC-beta activity in human mesangial cells reversed some of the pathological effects of glucose damage in these cells. We show that inhibition of PKC-beta with LY379196 and PKC-beta siRNA reduced basal PKC-zeta and GSK3beta phosphorylation in human mesangial cells exposed to high glucose. CTGF stimulation under these conditions again resulted in PKC-zeta phosphorylation and human mesangial cell migration. Regulation of PKC-zeta by PKC-beta in this instance may establish PKC-zeta as a target for constraining the progression of mesangial cell dysfunction in the pathogenesis of diabetic nephropathy.

Curcumin, the active principle of turmeric (Curcuma longa), ameliorates diabetic nephropathy in rats

Chronic hyperglycaemia in diabetes leads to the overproduction of free radicals and evidence is increasing that these contribute to the development of diabetic nephropathy. Among the spices, turmeric (Curcuma longa) is used as a flavouring and colouring agent in the indian diet every day and is known to possess anti-oxidant properties. The present study was designed to examine the effect of curcumin, a yellow pigment of turmeric, on renal function and oxidative stress in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced by a single intraperitoneal injection of STZ (65 mg/kg) in rats. Four weeks after STZ injection, rats were divided into four groups, namely control rats, diabetic rats and diabetic rats treated with curcumin (15 and 30 mg/kg, p.o.) for 2 weeks. Renal function was assessed by creatinine, blood urea nitrogen, creatinine and urea clearance and urine albumin excretion. Oxidative stress was measured by renal malonaldehyde, reduced glutathione and the anti-oxidant enzymes superoxide dismutase and catalase. Streptozotocin-injected rats showed significant increases in blood glucose, polyuria and a decrease in bodyweight compared with age-matched control rats. After 6 weeks, diabetic rats also exhibited renal dysfunction, as evidenced by reduced creatinine and urea clearance and proteinuria, along with a marked increase in oxidative stress, as determined by lipid peroxidation and activities of key anti-oxidant enzymes. Chronic treatment with curcumin significantly attenuated both renal dysfunction and oxidative stress in diabetic rats. These results provide confirmatory evidence of oxidative stress in diabetic nephropathy and point towards the possible anti-oxidative mechanism being responsible for the nephroprotective action of curcumin.

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.

Protective effect of Lycium barbarum polysaccharides on streptozotocin-induced oxidative stress in rats

Fruit from Lycium barbarum L. in the family Solanaceae is well-known in traditional Chinese herbal medicine. Lycium barbarum polysaccharides (LBP) have been identified as one of the active ingredients responsible for its biological activities. We isolated polysaccharides from dried Lycium barbarum fruits by boiling water extraction. In the study, 50 animals were divided into two groups: a nondiabetic control (n=10) and a diabetic group (n=40). Diabetes was induced by a single injection of streptozotocin (50mg/kg BW; Sigma, USA) freshly dissolved in a 0.1 mol/L citrate buffer (pH 4.5) into the intraperitonium. The normal control rats and the untreated diabetic control rats were only injected with the citrate buffer. Treated diabetic rats were administrated with LBP in drinking water through oral gavage for 30 days. At the end of experiment, oxidative indice in blood, liver and kidney of all groups were examined. The results show that administration of LBP can restore abnormal oxidative indice near normal levels. Therefore, we may assume that LBP is effective in the protection of liver and kidney tissue from the damage of STZ-induced diabetic rats and that the LBP may be of use as a antihyperglycemia agent.

Inhibition of phosphorylation of p38 MAPK involved in the protection of nephropathy by emodin in diabetic rats

To explore the protection of emodin on renal dysfunction in the streptozotocin-induced diabetic rats with nephropathy and the role of p38 mitogen-activated protein kinase (p38 MAPK) signal transduction pathway in this protection. 30 male Spraque-Dawley rats were randomly divided into control group, model group and emodin group. The rats in the model group and emodin group were administered with streptozotocin (60 mg/kg) to induce diabetes. 40 mg/kg/day of emodin were orally given to the rats in emodin group. The rats in other groups were only given solvent. Biochemical index were analysed by oxidase and oxidase dynamical enzyme method. Glomerular area and volume were determined quantitatively by using Image Analysis System. Western blotting and immunohistochemical staining was used to detect the total p38 MAPK, phosphorylated p38 MAPK, phosphorylated cAMP response element binding protein (CREB) and fibronectin. The average kidney weight/body weight, glomerular area, glomerular volume and all biochemical indexes significantly increased in model group as compared to the control group (P<0.05), while the average body weight decreased. The expressions of phosphorylaed p38 MAPK, phosphorylated CREB and fibronectin increased by 1.98-fold, 1.94-fold and 1.96-fold respectively in model group compared with those in the control group (P<0.05). Emodin markedly decreased the average kidney weight/body weight, glomerular area, glomerular volume and all biochemical indexes (P<0.05), having a weak action on the level of blood glucose. The expressions of phosphorylated p38 MAPK, phosphorylated CREB and fibronectin also significantly downregulated in emodin group compared with those in model group (P<0.05). Emodin was efficient to ameliorate renal dysfunction in diabetic nephropathy rats probably by its inhibition of the activation of p38 MAPK pathway and downregulation of the expression of fibronectin.

Antidiabetic effect of garlic oil but not diallyl disulfide in rats with streptozotocin-induced diabetes

We investigated the effects of garlic oil and diallyl disulfide (DADS) on glycemic control and renal function in rats with streptozotocin-induced diabetes. Rats received by gavage garlic oil (100 mg/kg body wt) or DADS (40 or 80 mg/kg body wt) every other day until 16 weeks after the induction of diabetes. The control rats were treated with corn oil only. Neither garlic oil nor DADS significantly affected fasting blood glucose concentrations throughout the investigation period. Garlic oil did not affect oral glucose tolerance in diabetes acutely but significantly improved oral glucose tolerance at 4, 8, 12, and 16 weeks and significantly ameliorated proteinuria at the end of 16 weeks. DADS did not significantly affect oral glucose tolerance or renal function. Diabetic rats fed 80 mg DADS/kg body wt had a significantly lower rate of body weight gain and a significantly lower ratio of muscle weight to body weight than did vehicle-treated diabetic rats. In conclusion, long-term treatment of diabetes with garlic oil can improve oral glucose tolerance and renal function in diabetes but not through the action of DADS. High doses of DADS may further complicate the metabolic disturbances in diabetes.

Silent information regulator 2 (SIRT1) attenuates oxidative stress-induced mesangial cell apoptosis via p53 deacetylation

Oxidative stress-induced apoptosis of renal glomerular cells is an important factor for the development of various kidney diseases. Identification of molecules that modulate this process could lead to the development of new strategies for preventing kidney diseases. In this study, we evaluated whether mammalian silent information regulator 2 (SIRT1), which has been recently identified as a cell survival factor countering various stressors, is a key regulator of oxidative stress-induced mesangial cell apoptosis. Morphological features of apoptotic cell death (nuclear condensation) and the expression of biochemical proapoptotic markers [cleavages of caspase-3 and poly (ADP-ribose) polymerase (PARP)] were assessed in murine mesangial cells (MMCs) exposed to hydrogen peroxide (H(2)O(2)). H(2)O(2) increased mesangial cell apoptosis, predominantly through p53 activation by acetylation, which is a posttranscriptional modification for p53 activation. H(2)O(2)-induced apoptosis was significantly attenuated in SIRT1-overexpressing MMCs, but enhanced in SIRT1-knockdown MMCs. Although SIRT1 did not affect H(2)O(2)-mediated phosphorylation of mitogen-activated protein (MAP) kinase, it interacted with p53 and inhibited H(2)O(2)-mediated p53 acetylation but not phosphorylation in MMCs. Our results indicate that SIRT1 can prevent oxidative stress-induced apoptosis through p53 deacetylation in mesangial cells. Upregulation of SIRT1 may provide a new strategy for preventing kidney glomerular diseases.

Chronic inhibition of nitric oxide production aggravates diabetic nephropathy in Otsuka Long-Evans Tokushima Fatty rats

BACKGROUND

Nitric oxide (NO) is known to play a role in diabetic nephropathy, but the molecular basis for this effect remains unclear.

METHOD

Otsuka Long-Evans Tokushima Fatty spontaneous diabetic rat models were used along with Long-Evans Tokushima Otuska rat models as age-matched controls. Either L-arginine (a NO precursor) or L-NAME (a nitric oxide synthase inhibitor) was administered from the age of 22 weeks. Clinical parameters and serum and urinary NO2+NO3 levels were measured, in addition to renal histological findings and ED-1-positive cell counts in glomeruli.

RESULTS

There were no significant differences in creatinine clearance between any of the groups at any point. The levels of urinary NO2+NO3 in the diabetic group were significantly lower than those in the control groups after 40 weeks; that in the L-NAME diabetic group was significantly lower than in the other diabetic groups at 52 weeks. Compared with the other diabetic groups, the L-NAME diabetic group had significantly higher urinary protein excretion levels, histological scores, and numbers of ED-1-positive cells in glomeruli. Diabetic rats administered L-arginine excreted more urinary protein than the diabetic controls.

CONCLUSION

Diabetic nephropathy was exacerbated drastically by a nitric oxide synthase inhibitor and mildly by a NO precursor. These data suggested that NO may modify type 2 diabetic nephropathy in Otuska Long-Evans Tokushima Fatty rats through factors other than hemodynamics.

Role of altered renal lipid metabolism and the sterol regulatory element binding proteins in the pathogenesis of age-related renal disease

BACKGROUND

There are well-known changes in age-related renal function and structure, including glomerulosclerosis and decline in glomerular filtration rate (GFR). The purpose of this study was to identify a potential role for lipids in mediating age-related renal disease.

METHODS

Mice of five different age groups (3, 6, 12, 19, and 23 months old) were studied.

RESULTS

We have found that in C57BL/6 mice there was a progressive increase in age-related glomerulosclerosis [increase in periodic acid-Schiff (PAS) staining and accumulation of extracellular matrix proteins including type IV collagen and fibronectin], increased glomerular basement thickness and podocyte width and effacement, and increased proteinuria. These changes were associated with age-related increase in lipid accumulation as determined by increased Oil Red O staining in kidney sections. Biochemical analysis indicated that these lipid deposits corresponded to significant increases in renal triglyceride and cholesterol content. We have also found significant age-related increases in the nuclear transcription factors, sterol regulatory element-binding proteins (SREBP-1 and SREBP-2), protein abundance and increased expression or activity of their target enzymes that play an important role in lipid synthesis.

CONCLUSION

Our results indicated that there was an age-related increase in renal expression of SREBP-1 and SREBP-2 with resultant increases in lipid synthesis and triglyceride and cholesterol accumulation in the kidney. Because we have previously shown that increased expression of SREBPs in the kidney per se results in glomerulosclerosis and proteinuria, our data suggested that increased SREBPs' expression resulting in increased renal lipid accumulation may play an important role in age-related nephropathy.