Effect of chronic treatment with losartan on streptozotocin induced diabetic nephropathy

Inhibition of (pro)renin Receptor Contributes to Renoprotective Effects of Angiotensin II Type 1 Receptor Blockade in Diabetic Nephropathy

Aims: Renal renin-angiotensin system (RAS) plays a pivotal role in the development of diabetic nephropathy (DN). Angiotensin II (Ang II) type 1 receptor (AT₁R) blockade elevates (pro)renin, which may bind to (pro)renin receptor (PRR) and exert receptor-mediated, angiotensin-independent profibrotic effects. We therefore investigated whether PRR activation leads to the limited anti-fibrotic effects of AT₁R blockade on DN, and whether PRR inhibition might ameliorate progression of DN.

Methods: To address the issue, the expression of RAS components was tested in different stages of streptozotocin (STZ)-induced diabetic rats (6, 12, and 24 weeks) and 6-week AT₁R blockade (losartan) treated diabetic rats. Using the blocker for PRR, the handle region peptide (HRP) of prorenin, the effects of PRR on high glucose or Ang II-induced proliferative and profibrotic actions were evaluated by measurement of cell proliferation, matrix metalloproteinase-2 (MMP-2) activity, activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and transforming growth factor-β1 (TGF-β1) expression in rat mesangial cells (MCs).

Results: PRR was downregulated in the kidneys of different stages of diabetic rats (6, 12, and 24 weeks). Moreover, 6-week losartan treatment further suppressed PRR expression via upregulating AT₂R, and ameliorated diabetic renal injury. HRP inhibited high glucose and Ang II-induced proliferative and profibrotic effects in MCs through suppressing TGF-β1 expression and activating MMP-2. Meanwhile, HRP enhanced losartan's anti-fibrotic effects through further inhibiting phosphorylation of ERK1/2 and TGF-β1 expression. Moreover, the inhibitive effect of HRP on Ang II-induced TGF-β1 expression depended on the regulation of PRR expression by AT₂R.

Conclusions: Our findings suggest that inhibition of PRR contributes to renoprotection against diabetic nephropathy by AT₁R blockade.

Combination of melatonin and certain drugs for treatment of diabetic nephropathy in streptozotocin-induced diabetes in rats

Diabetic nephropathy is a major complication of diabetes and a leading cause of end-stage renal failure in many developed countries. The study aimed to evaluate the efficiency of certain drugs and melatonin in the treatment of nephropathy secondary to diabetes. Diabetes was induced in rats by a single intraperitoneal injection of streptozotocin (50 mg/kg body weight). Three days after induction of diabetes (460-500 mg/dl), rats were treated daily for 60 days with Rowatinex, melatonin, Rowatinex + melatonin, Amosar (Losartan Potassium) (LSP) and LSP + melatonin. The evaluations were made by measuring blood urea nitrogen (BUN), serum uric acid, serum creatinine, urine creatinine, creatinine clearance, nitric oxide, malondialdehyde, superoxide dismutase, glutathione, total antioxidant capacity, kidney injury molecule-1, heat shock protein-70, caspase-3, transforming growth factor β1, and DNA degradation by comet assay and total protein contents. The histopathological picture of the kidneys and pancreases was confirmed in our results. Diabetic rats showed drastic changes in all the measured parameters. Treatment with melatonin and the selected drugs revealed amelioration levels with variable degrees. In conclusion, the combination of LSP and melatonin had the most potent effect on treating the deleterious action of diabetes on rat kidney.

Comparison of the effects of levocetirizine and losartan on diabetic nephropathy and vascular dysfunction in streptozotocin-induced diabetic rats

This work was designed to investigate the effects of levocetirizine, a histamine H1 receptor antagonist, on diabetes-induced nephropathy and vascular disorder, in comparison to an angiotensin II receptor antagonist, losartan. Diabetes was induced in male Sprague Dawley rats by a single intraperitoneal injection of streptozotocin (50mg/kg). Diabetic rats were divided into three groups; diabetic, diabetic-levocetirizine (0.5mg/kg/day) and diabetic-losartan (25mg/kg/day). Treatments were started two weeks following diabetes induction and continued for additional eight weeks. At the end of the experiment, urine was collected and serum was separated for biochemical measurements. Tissue homogenates of kidney and aorta were prepared for measuring oxidative stress, nitric oxide (NO), transforming growth factor-β1 (TGF-β1) and tumor necrosis factor-α (TNF-α). Moreover, histological analyses were conducted and aortic vascular reactivity was investigated. Levocetirizine improved renal function in diabetic rats (evidenced by mitigation of diabetes-induced changes in kidney to body weight ratio, serum albumin, urinary proteins and creatinine clearance). Moreover, levocetirizine attenuated the elevated renal levels of TNF-α and TGF-β1, ameliorated renal oxidative stress and restored NO bioavailability in diabetic kidney. These effects were comparable to or surpassed those produced by losartan. Moreover, levocetirizine, similar to losartan, reduced the enhanced responsiveness of diabetic aorta to phenylephrine. Histological evaluation of renal and aortic tissues further confirmed the beneficial effects of levocetirizine on diabetic nephropathy and revealed a greater attenuation of diabetes-induced vascular hypertrophy by levocetirizine than by losartan. In conclusion, levocetirizine may offer comparable renoprotective effect to, and possibly superior vasculoprotective effects than, losartan in streptozotocin-diabetic rats.

Combined effect of hydrogen sulphide donor and losartan in experimental diabetic nephropathy in rats

Background

Diabetic nephropathy (DN) is one of the complex complications of Diabetes Mellitus (DM). The present study has been designed to examine protective role of hydrogen Sulphide (H₂S) donor against streptozotocin (STZ) -induced behavioral, oxidative abnormalities and its DN like symptoms in rats.

Methods

For the induction of DN single intraperitoneal administration of STZ (45 mg/kg) was given till third week. Behavioral parameters were measured on 1st, 7th, 21st and 42nd days and biochemical parameters were performed on 42nd day. All the drug treatments [NaHS (10 & 30 μmol/kg i.p), DL-propargylglycine (10 mg/kg i.p), standard drug- Losartan (5 mg/kg p.o)] were given for 3 weeks staring from 21st day after the STZ injection.

Results

Three weeks treatment with sodium hydrosulphide (NaHS) (10 and 30 μmol/kg i.p,) significantly attenuated the behavioral and biochemical abnormalities in STZ-treated animals. DL-propargylglycine (10 mg/kg i.p) pretreatment with sub-effective dose of NaHS (30 μmol/kg i.p) significantly reversed the protective effect of NaHS. However, combination of both NaHS (30 μmol/kg i.p) and standard drug losartan (5 mg/kg p.o) potentiated their effects as compared to their effect alone.

Conclusion

The results of the present study suggest that H₂S treatment showed significant improvement in behavioral and biochemical abnormalities induced by STZ administration. Thus H₂S represents a target of treatment to prevent the progression of complications by DN.

Long-term dietary antioxidant cocktail supplementation effectively reduces renal inflammation in diabetic mice

Diabetic nephropathy is a serious complication for diabetic patients, yet the precise mechanism that underlies the development of diabetic complications remains unknown. We hypothesised that dietary antioxidant supplementation with single N-acetylcysteine (NAC) or vitamin C combined with either vitamin E or vitamin E and NAC improves diabetic renal inflammation through the modulation of blood glucose levels, oxidative stress and inflammatory response. Experimental animals were treated with alloxan monohydrate to induce diabetes. Mice were divided into five groups and supplemented with single or a combination of antioxidants. Body weights and blood glucose levels were measured once a week. After 8 weeks of dietary antioxidant supplementation, mice were killed and blood urea N (BUN) and plasma creatinine levels were measured to evaluate renal function. NF-κB protein was indirectly demonstrated by the phosphorylated IκBα (pIκBα) level, and the expressions of oxidative stress- and inflammatory response-related proteins were also determined. We demonstrated that dietary antioxidant supplementation decreased lipid peroxidation levels demonstrated by thiobarbituric acid-reacting substances, BUN and plasma creatinine levels in diabetic kidneys. Moreover, dietary antioxidant cocktail supplementation improved blood glucose levels and selectively regulated the expressions of Cu-Zn superoxide dismutase, haeme oxygenase-1, pIκBα, inducible NO synthase, cyclo-oxygenase-2 and C-reactive protein in diabetic kidneys effectively. These findings demonstrated that diabetic renal failure was associated with inflammatory responses induced by hyperglycaemia. In addition, results in the study suggest that antioxidant cocktail supplementation may have beneficial effects on diabetic nephropathy through selective reduction of blood glucose levels and inflammatory response.

The effect of dehydroepiandrosterone (DHEA) on renal function and metabolism in diabetic rats

Dehydroepiandrosterone (DHEA) is an endogenous steroid hormone involved in a number of biological actions in humans and rodents, but its effects on renal tissue have not yet been fully understood. The aim of this study is to assess the effect of DHEA treatment on diabetic rats, mainly in relation to renal function and metabolism. Diabetic rats were treated with subcutaneous injections of a 10mg/kg dose of DHEA diluted in oil. Plasma glucose and creatinine, in addition to urine creatinine, were quantified espectophotometrically. Glucose uptake and oxidation were quantified using radioactive glucose, the urinary Transforming Growth Factor β(1) (TGF-β(1)) was assessed by enzyme immunoassay, and the total glutathione in the renal tissue was also measured. The diabetic rats displayed higher levels of glycemia, and DHEA treatment reduced hyperglycemia. Plasmatic creatinine levels were higher in the diabetic rats treated with DHEA, while creatinine clearance was lower. Glucose uptake and oxidation were lower in the renal medulla of the diabetic rats treated with DHEA, and urinary TGF-β(1), as well as total gluthatione levels, were higher in the diabetic rats treated with DHEA. DHEA treatment was not beneficial to renal tissue, since it reduced the glomerular filtration rate and renal medulla metabolism, while increasing the urinary excretion of TGF-β(1) and the compensatory response by the glutathione system, probably due to a mechanism involving a pro-oxidant action or a pro-fibrotic effect of this androgen or its derivatives. In conclusion, this study reports that DHEA treatment may be harmful to renal tissue, but the mechanisms of this action have not yet been fully understood.

The effects of captopril and losartan on erythrocyte membrane Na+/K(+)-ATPase activity in experimental diabetes mellitus

Diabetes mellitus induces a decrease in sodium potassium-adenosine triphosphatase (Na+/K(+)-ATPase) activity in several tissues in the rat and red blood cells (RBC) and nervous tissue in human patients. This decrease in Na+/K(+)-ATPase activity is thought to play a role in the development of long-term complications of the disease. Angiotensin enzyme inhibitors (ACEi) and angiotensin-II receptor antagonists (ARBs) reduce proteinuria and retard the progression of renal failure in patients with IDDM and diabetic rats. We investigated the effects of captopril and losartan, which are used in the treatment of diabetic nephropathy, on Na+/K(+)-ATPase activity. Captopril had an inhibitory effect on red cell plasma membrane Na+/K+ ATPase activity, but losartan did not. Our study draws attention to the inhibitory effect of captopril on Na+/K+ ATPase activity. Micro and macro vascular complications are preceeding mortality and morbidity causes in diabetes mellitus. There is a strong relationship between the decrease in Na+/K+ ATPase activity and hypertension. The non-sulphydryl containing ACEi and ARBs must be the choice of treatment in hypertensive diabetic patients and 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.

Resveratrol, a Polyphenolic Phytoalexin, Attenuates Diabetic Nephropathy in Rats

Diabetic nephropathy is a serious microvascular complication and one of the main causes of end-stage renal disease. Various studies have revealed that increased oxidative stress is a major pathophysiological mechanism which is involved in the etiology of diabetic nephropathy. Resveratrol, a polyphenolic phytoalexin present in red wine, is known to possess potent antioxidant properties and thus we aimed to examine its effect 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. After 4 weeks of STZ injection, rats were divided into four groups: the control rats, diabetic rats and diabetic rats treated with resveratrol (5 and 10 mg/kg, orally) respectively from week 4 up till week 6. At the termination of the experiments, urine albumin excretion, urine output, serum creatinine, blood urea nitrogen, creatinine and urea clearance were measured. The levels of the renal oxidative stress markers malonaldehyde and glutathione and the antioxidant enzymes superoxide dismutase and catalase were measured in kidney homogenate. STZ-injected rats showed significant increases in blood glucose, polyuria, proteinuria and a decrease in body weight compared with age-matched control rats. After 6 weeks, diabetic rats 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 antioxidant enzymes. Treatment with resveratrol significantly attenuated renal dysfunction and oxidative stress in diabetic rats. The present study reinforces the important role of oxidative stress in diabetic kidney and points towards the possible antioxidative mechanism being responsible for the renoprotective action of resveratrol.

Quercetin, an anti-oxidant bioflavonoid, attenuates diabetic nephropathy in rats

1. Diabetic nephropathy is an important microvascular complication and one of the main causes of end-stage renal disease. Many in vivo and in vitro studies have indicated that oxidative stress is one of the major pathophysiological mechanisms involved in the development of diabetic nephropathy. In the present study, we examined the effect of an anti-oxidant bioflavonoid quercetin on renal function and oxidative stress in streptozotocin (STZ)-induced diabetic rats. 2. Diabetes was induced in Sprague-Dawley rats with a single intravenous injection of STZ (45 mg/kg). Four weeks after STZ injection, quercetin (10 mg/kg per day) was given orally for 4 weeks in both control and diabetic rats. Plasma glucose levels and bodyweights were measured at 4 and 8 weeks after the STZ injection. At the termination of the experiments, urine albumin excretion, urine output, serum creatinine, blood urea nitrogen, creatinine and urea clearance were measured. The renal oxidative stress marker malonaldehyde, glutathione levels and the anti-oxidant enzymes superoxide dismutase and catalase were measured in kidney homogenate. 3. Streptozotocin-injected rats showed significant increases in blood glucose, polyuria, proteinuria and a decrease in bodyweight compared with age-matched control rats. After 8 weeks, diabetic rats 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. Treatment with quercetin significantly attenuated renal dysfunction and oxidative stress in diabetic rats. 4. These results confirm the role of oxidative stress in the development of diabetic nephropathy and point to the possible anti-oxidative mechanism being responsible for the nephroprotective action of quercetin.

Effect of irbesartan on the antioxidant defence system and nitric oxide release in diabetic rat kidney

BACKGROUND/AIMS

Increased oxidative stress is involved in the aetiology of diabetic nephropathy, and angiotensin II is reported to play a considerable role in the development of renal damage in diabetic kidney. Angiotensin antagonism can slow the progression of renal impairment in diabetes. The present study was thus designed to examine the effect of an angiotensin II type 1 (AT1) receptor antagonist, irbesartan on renal function, oxidative stress and nitric oxide (NO) release in streptozotocin (STZ)-induced diabetic rats.

METHODS

Diabetes was induced by a single intraperitoneal injection of streptozotocin (65 mg/kg) in rats. After 4 weeks of STZ injection, rats were divided into four groups: the control rats, diabetic rats and diabetic rats treated with irbesartan (25 and 50 mg/kg, orally) respectively till 8 weeks starting from 4 weeks after STZ injection. Renal function was assessed by creatinine, blood urea nitrogen, creatinine clearance and urea clearance. Oxidative stress was measured by renal malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD) and catalase. We also measured renal nitrite levels.

RESULTS

At the end of the 8th week, diabetic rats exhibited renal dysfunction as evidenced by reduced creatinine and urea clearance along with enhanced albumin excretion rate as compared with control rats. Biochemical analysis of kidneys revealed a marked increase in oxidative stress demonstrated by increased lipid peroxidation and decreased activities of key antioxidant enzymes, GSH, SOD and catalase in diabetic rats. NO release was also significantly higher in diabetic rats than controls. Chronic treatment with irbesartan in diabetic rats significantly attenuated both renal dysfunction and oxidative stress along with increased NO levels as compared with untreated diabetic rats. The kidneys of diabetic rats showed morphological changes such as hyaline casts, glomerular thickening and moderate interstitial fibrosis and arteriolopathy, whereas irbesartan administration markedly prevented diabetic-induced renal morphological alterations.

CONCLUSIONS

The present study suggests that oxidative stress/nitrosative stress is increased in the diabetic kidney and AT1 receptor blockade can prevent these changes. The results also suggest that in STZ-induced diabetic rats, the protective action of irbesartan might be mediated, at least in part, by its effect on tissue oxidant/antioxidant status.

Effect of feeding Murraya koeingii and Brassica juncea diet on [correction] kidney functions and glucose levels in streptozotocin diabetic mice

Purpose of the study was to investigate the effects of daily oral feeding 15% of powdered leaves of Murraya koeingii (MK) (commonly called as Curry patta) and 10% powder of seeds of Brassica juncea (BJ) (commonly called as Rai) for 60 days on serum glucose concentrations and kidney functions in streptozotocin (STZ; 100mg/kg) diabetic rats. Serum glucose levels, body weight, urine volume, serum creatinine, and urinary albumin (UAE) levels were monitored on day 0, 10, 25, 40, and 70 of the experiment. After 60 days of STZ administration, urine volume per day and UAE levels were significantly higher (P<0.0005) in diabetic controls (DC) as compared to normal controls (NC). Although feeding of the MK/BJ showed a trend towards improvement in most of the parameters, results were not statistically different from the DC except in serum creatinine values in BJ-fed rats on day 70. Thus, these plants can be best utilized by promoting them as preferable food adjuvants for diabetic patients.