Weeks Of Streptozotocin Injection Research Articles

Berberine Improves Glucose Homeostasis in Streptozotocin-Induced Diabetic Rats in Association with Multiple Factors of Insulin Resistance

The present study was carried out to determine the effect of berberine on glucose homeostasis and several biomarkers associated with insulin sensitivity in male Wistar rats with intraperitoneal injection of streptozotocin (STZ)-induced diabetes. Rats with fasting blood glucose 16.7 mmol/L after 2 weeks of STZ injection were divided into two groups. One group was used as the diabetic control and another treated by gavage feeding with 100 mg/kg/d of berberine in water containing 0.5% carboxymethyl cellulose. A group of rats without receiving STZ was used as the normal control. After 7 weeks, berberine supplementation moderately but significantly lowered fasting blood glucose levels and improved oral glucose tolerance. Berberine lowered plasma free fatty acids and C-reactive protein levels without affecting plasma insulin levels. Diabetic rats treated with berberine showed significantly lower plasma triacylglycerol and cholesterol levels. Furthermore, berberine inhibited dipeptidyl peptidase-4 and protein tyrosine phosphatase-1B activities. In conclusion, berberine showed a dramatic effect of lowering blood cholesterol and triacylglycerols and improved moderately glucose homeostasis in STZ-induced diabetic rats in association with multiple factors related to insulin resistance.

Comparative hypoglycemic and nephroprotective effects of tocotrienol rich fraction (TRF) from palm oil and rice bran oil against hyperglycemia induced nephropathy in type 1 diabetic rats

Diabetic nephropathy (DN) is a serious complication confronted by patients with diabetes. Available data indicate that the development of DN is linked to hyperglycemia. Tocotrienol rich fraction (TRF) from palm oil (PO) and rice bran oil (RBO) has been shown to lower the blood glucose level in patients and preclinical animal models. This study was designed to investigate if TRF from PO and RBO could improve the renal function in DN by the virtue of their hypoglycemic and antioxidant activities. Male Wistar rats having an average body weight (bw) 250 g were divided into four groups of six each .The first group served as diabetic control [injected with 55 mg/kg bw of streptozotocin (STZ), intraperitoneally], while the second and third group received PO-TRF and RBO-TRF, respectively, by gavage at a dose of 200 mg/kg bw/day, over a period of 8 weeks post-induction of diabetes. The fourth group comprised of age-matched male Wistar rats that received single intraperitoneal injection of normal saline only and served as control. After 8 weeks of STZ injection and TRF treatment, 24 h urine was collected and animals were sacrificed. Fasting blood glucose, glycosylated hemoglobin, biochemical markers of renal function and oxidative stress were evaluated in serum, urine and kidney tissue. The results show that treatment with PO-TRF as well as RBO-TRF significantly improved the glycemic status and renal function in type 1 diabetic rats but PO-TRF afforded greater efficiency at similar dose as compared to RBO-TRF. In conclusion, PO-TRF was found to be more effective hypoglycemic and nephroprotective agent in DN than RBO-TRF.

Association of gastric emptying with ghrelin, obestatin and receptor (GHSR, GPR-39) in hypothalamus of diabetic rats

To investigate the association of gastric emptying with ghrelin, obestatin and GHSR, GPR-39 in hypothalamus of diabetic rats. Sixty Wistar rats were randomly divided into three groups: a normal control group (NC, n = 20), a diabetes mellitus group (DM, n = 20) induced by intraperitoneal injection of streptozotocin (STZ) and an insulin treated group (INS, n = 20). After two and six weeks of STZ injection, gastric emptying was measured by intragastric administration of phenol red, ghrelin and obestatin in hypothalamus measured by ELISA (enzyme-linked immunosorbent assay) and GHSR and GPR-39 by RT-PCR (reverse transcription-polymerase chain reaction). After two weeks of STZ injection, gastric emptying (%) (74 +/- 8, 40 +/- 5), ghrelin level(ng/g) (52 +/- 9, 51 +/- 7) and ratio of ghrelin/obestatin (3.8 +/- 1.0, 2.8 +/- 1.0) increased significantly in DM and INS groups compared to those in NC group [32% +/- 7%, (39 +/- 11) ng/g, 2.1 +/- 0.8, all P < 0.05]. Obestatin level(ng/g) (14.2 +/- 2.0) of hypothesis decreased significantly in DM group as compared to those in NC group (21.7 +/- 4.7) while GHSR/beta-actin increased significantly (1.26 +/- 0.46 vs 0.77 +/- 0.21, P < 0.05). Gastric emptying was positively correlated with ghrelin, ghrelin/obestatin and GHSR/beta-actin of hypothalamus (r = 0.49; r = 0.63; r = 0.73; P < 0.01). But there was a negative correlation with obestatin of hypothalamus (r = -0.74, P < 0.01). After six weeks of STZ injection, gastric emptying (78.97% +/- 8.13% vs 44.06% +/- 5.06%) increased significantly in DM and INS groups as compared to those in NC group (35.06% +/- 3.91%, P < 0.01). Gastric emptying was positively correlated with ghrelin/obestatin of hypothalamus (r = 0.40, P < 0.05). There was no detection of GPR-39 in hypothalamus. The rapid gastric emptying may be due to the rising levels of ghrelin and GHSR in hypothalamus during early hyperglycemia. And the duration of hyperglycemia is affected by the rising ratio of ghrelin/obestatin.

DHEA improves impaired activation of Akt and PKC ζ/λ‐GLUT4 pathway in skeletal muscle and improves hyperglycaemia in streptozotocin‐induced diabetes rats

Addition of dehydroepiandrosterone (DHEA) to a cultured skeletal muscle locally synthesizes 5alpha-dihydrotestosterone (DHT). It induced activation of glucose metabolism-related signalling pathway via protein kinase B (Akt) and protein kinase C zeta/lambda (PKC zeta/lambda)-glucose transporter-4 (GLUT4) proteins. However, such an effect of DHEA in vivo remains unclear. Using streptozotocin (STZ)-induced rats with type 1 diabetes mellitus, we tested the hypothesis that a single bout of DHEA injection in the rats improves hyperglycaemia and muscle GLUT4-regulated signalling pathway. After 1 week of STZ injection (55 mg kg(-1)) with male Wistar rats, fasting glucose concentrations were determined in a blood sample taken from the tail vein. Blood glucose levels were then monitored for 180 min after DHEA or sesame oil (control) was injected (n = 10 for each group). Blood glucose levels decreased significantly for 30-150 min after 2 mg DHEA injection in the STZ rats. In the skeletal muscle, expression and translocation of GLUT4 protein, phosphorylation of Akt and PKC zeta/lambda, and phosphofructokinase and hexokinase enzyme activities increased significantly by DHEA injection. However, DHEA-induced improvements in Akt and PKC zeta/lambda-GLUT4 pathways were blocked by a DHT inhibitor. These results suggest that a single bout of DHEA injection can improve hyperglycaemia and activate the glucose metabolism-related signalling pathway via Akt and PKC zeta/lambda-GLUT4 proteins of skeletal muscles in rats. Moreover, these results show that a DHEA-induced increase in muscle glucose uptake and utilization might contribute to improvement in hyperglycaemia in type 1 diabetes mellitus.

Attenuation of Renoinflammatory Cascade in Experimental Model of Diabetic Nephropathy by Sesamol

Diabetes has become the most common single cause of end-stage renal disease (ESRD) in the United States and Europe. Approximately 30-40% of patients with type I and 15% with type II diabetes mellitus develop end ESRD. The study was designed to evaluate the impact of sesamol on renal function and renoinflammatory cascade in streptozotocin (STZ)-induced diabetes. STZ-induced diabetic rats were treated with sesamol (2, 4, and 8 mg/kg/day; po) or with vehicle from the fifth to eighth weeks. After 8 weeks, urine albumin excretion, urine output, serum creatinine, blood urea nitrogen, creatinine, and urea clearance were measured. Cytoplasmic and nuclear fractions of kidney were prepared for the quantification of oxidative-nitrosative stress (lipid peroxidation, superoxide dismutase, catalase, nonprotein thiols, total nitric oxide), tumor necrosis factor-alpha (TNF-alpha), tissue growth factor-1 beta (TGF-beta1), p65 subunit of NFkappabeta, and caspase-3. After 8 weeks of STZ injection, the rats produced significant alteration in renal function, increased oxidative-nitrosative stress, TNF-alpha, TGF-beta1, caspase-3 activity in cytoplasmic lysate, and active p65 subunit of NFkappabeta in nuclear lysate of kidney of diabetic rats. Interestingly, co-administration of sesamol significantly and dose-dependently prevented biochemical and molecular changes associated with diabetes. Moreover, diabetic rats treated with insulin-sesamol combination produced more pronounced effect on molecular parameters as compared to their respective groups. The data reveal that sesamol modulates the release of profibrotic cytokines, oxidative stress, ongoing chronic inflammation, and apoptosis and thus exerts a marked renoprotective effect.

Tocotrienol attenuates oxidative–nitrosative stress and inflammatory cascade in experimental model of diabetic neuropathy

Diabetic neuropathic pain, an important microvascular complication in diabetes mellitus, is recognised as one of the most difficult types of pain to treat. The development of tolerance, inadequate relief and potential toxicity of classical antinociceptives warrant the investigation of the newer agents to relieve this pain. Reactive oxygen/nitrogen species, cytokines and apoptosis are implicated in the pathogenesis of diabetic neuropathy. The aim of the present study was to explore the effect of tocotrienol on thermal and mechanical hyperalgesia, allodynia, oxidative–nitrosative stress, inflammation and apoptosis in streptozotocin-induced experimental diabetes. Diabetic rats developed neuropathy which was evident from a marked hyperalgesia and allodynia associated with enhanced nitrosative stress, release of inflammatory mediators (TNF-α, IL-1β, TGF-1β) and caspase-3. Chronic treatment with tocotrienol (25, 50 and 100 mg/kg body weight; p.o.) for 4 weeks starting from the 4th week of streptozotocin injection significantly attenuated behavioral, biochemical and molecular changes associated with diabetic neuropathy. Moreover, diabetic rats treated with insulin–tocotrienol combination produced more pronounced beneficial effect as compared to their per se groups. The major finding of the study is that insulin alone corrected the hyperglycemia and partially reversed the pain response in diabetic rats. However, combination with tocotrienol not only attenuated the diabetic condition but also reversed neuropathic pain through modulation of oxidative–nitrosative stress, inflammatory cytokine release and caspase-3 in the diabetic rats and thus it may find clinical application to treat neuropathic pain in the diabetic patients.

Attenuation of diabetic nephropathy by tocotrienol: Involvement of NFkB signaling pathway

Aim Diabetic nephropathy is a serious complication for patients with diabetes mellitus. Approximately 30–40% of patients with type I and 15% with type II diabetes mellitus develop end stage renal disease. The study was designed to evaluate the impact of tocotrienol on renal function and reno-inflammatory cascade in streptozotocin-induced diabetes. Main methods Streptozotocin (STZ)-induced diabetic rats were treated with tocotrienol (25, 50 and 100 mg/kg), α-tocopherol (100 mg/kg) or with vehicle form 5th to 8th weeks. After 8 weeks, urine albumin excretion, urine output, serum creatinine, blood urea nitrogen, creatinine and urea clearance were measured. Cytoplasmic and nuclear fractions of kidney was prepared for the quantification of oxidative–nitrosative stress (lipid peroxidation, superoxide dismutase, catalase, non protein thiols, total nitric oxide), tumor necrosis factor-alpha (TNF-α), tissue growth factor-1beta (TGF-β1), p65 subunit of NFκβ and caspase-3. Key findings After 8 weeks of STZ injection, the rats produced significant alteration in renal function, increased oxidative–nitrosative stress, TNF-α, TGF-β1, caspase-3 activity in cytoplasmic lysate and active p65 subunit of NFκβ in nuclear lysate of kidney of diabetic rats. Interestingly, co-administration of tocotrienol significantly and dose-dependently prevented biochemical and molecular changes associated with diabetes. Tocotrienol (100 mg/kg) was demonstrated to be more effective than α-tocopherol (100 mg/kg). Moreover, diabetic rats treated with insulin-tocotrienol combination produced more pronounced effect on molecular parameters as compared to their respective groups. Significance Taken together, the data reveal that tocotrienol modulates the release of profibrotic cytokines, oxidative stress, ongoing chronic inflammation and apoptosis and thus exerts a marked renoprotective effect.

Suppression of NF-κβ signaling pathway by tocotrienol can prevent diabetes associated cognitive deficits

Objective The etiology of diabetes associated cognitive decline is multifactorial and involves insulin receptor down regulation, neuronal apoptosis and glutamatergic neurotransmission. The study was designed to evaluate the impact of tocotrienol on cognitive function and neuroinflammatory cascade in streptozotocin-induced diabetes. Research design and method Streptozotocin-induced diabetic rats were treated with tocotrienol for 10 weeks. Morris water maze was used for behavioral assessment of memory. Cytoplasmic and nuclear fractions of cerebral cortex and hippocampus were prepared for the quantification of acetylcholinesterase activity, oxidative–nitrosative stress, tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β), NFκβ and caspase-3. Results After 10 weeks of streptozotocin injection, the rats produced significant increase in transfer latency which was coupled with enhanced acetylcholinesterase activity, increased oxidative–nitrosative stress, TNF-α, IL-1β, caspase-3 activity and active p65 subunit of NFκβ in different regions of diabetic rat brain. Interestingly, co-administration of tocotrienol significantly and dose-dependently prevented behavioral, biochemical and molecular changes associated with diabetes. Moreover, diabetic rats treated with insulin–tocotrienol combination produced more pronounced effect on molecular parameters as compared to their per se groups. Conclusions Collectively, the data reveal that activation of NFκβ signaling pathway is associated with diabetes induced cognitive impairment and point towards the therapeutic potential of tocotrienol in diabetic encephalopathy.

Effect of insulin and its combination with resveratrol or curcumin in attenuation of diabetic neuropathic pain: participation of nitric oxide and TNF‐alpha

Diabetic neuropathic pain, an important microvascular complication in diabetes mellitus, is recognized as one of the most difficult types of pain to treat. The underlying mechanisms of painful symptoms may be closely associated with hyperglycaemia but a lack of the understanding of its proper aetiology, inadequate relief, development of tolerance and potential toxicity of classical antinociceptives warrant the investigation of newer agents to relieve this pain. The aim of the present study was to explore the antinociceptive effect of insulin and its combinations with resveratrol and curcumin in attenuating diabetic neuropathic pain. The study also aimed to examine the effect of these combinations on tumour necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) levels in streptozotocin (STZ) induced diabetic mice. Four weeks after a single intraperitoneal injection of streptozotocin (200 mg/kg), mice were tested in the tail immersion and hot-plate assays. Diabetic mice exhibited significant hyperalgesia along with increased plasma glucose and decreased body weights compared with control mice. Chronic treatment with insulin (10 IU/kg/day, s.c.) and its combinations with antioxidants (resveratrol 20 mg/kg or curcumin 60 mg/kg, p.o.) for 4 weeks starting from the 4th week of STZ injection significantly attenuated thermal hyperalgesia and the hot-plate latencies. There was a significant inhibition of TNF-alpha and NO levels when these drugs were given in combination compared with their effects per se. These results indicate an antinociceptive activity of resveratrol and curcumin and point towards the beneficial effect of these combinations with insulin in attenuating diabetic neuropathic pain, possibly through the participation of NO and TNF-alpha.

The effects of quercetin on bone minerals, biomechanical behavior, and structure in streptozotocin‐induced diabetic rats

This study was designed to investigate the effect of quercetin (QE) on bone minerals and biomechanics in insulin-dependent diabetic rats. Diabetes was induced by 50 mg kg(-1) intraperitoneal streptozotocin (STZ) in a single dose. The rats were randomly allotted into four experimental groups: A (control), B (non-diabetic + QE), C (diabetic), and D (diabetic + QE) each containing 10 animals. The diabetic rats received QE (15 mg kg(-1) day(-1)) for 4 weeks following 8 weeks of STZ injection. Blood samples were taken to determine glucose, insulin, calcium, and magnesium levels. The rats' femora were assessed biomechanically at femoral mid-diaphysis and neck. It was found that QE treatment increased insulin, calcium, and magnesium levels. Three-point bending of the femoral mid-diaphysis and necks showed significantly lower maximum load values (F max) in animals in the STZ group than the QE + STZ or control groups (p < 0.05). The results support the conclusion that QE treatment may decrease blood glucose and increase plasma insulin, calcium, and magnesium. QE treatment may also be effective in bone mineral metabolism, biomechanical strength, and bone structure in STZ-induced diabetic rats.

Curcumin attenuates thermal hyperalgesia in a diabetic mouse model of neuropathic pain

Diabetic neuropathic pain, an important microvascular complication in diabetes mellitus is recognised as one of the most difficult types of pain to treat. A lack of the understanding of its aetiology, inadequate relief, development of tolerance and potential toxicity of classical antinociceptives warrant the investigation of the newer agents to relieve this pain. The aim of the present study was to explore the antinociceptive effect of curcumin and its effect on tumour necrosis factor-α (TNF-α) and nitric oxide (NO) release in streptozotocin induced diabetic mice. Four weeks after a single intraperitoneal injection of streptozotocin (200 mg/kg), mice were tested in the tail immersion and hot-plate assays. Diabetic mice exhibited significant hyperalgesia along with increased plasma glucose and decreased body weights as compared with control mice. Chronic treatment with curcumin (15, 30 and 60 mg/kg body weight; p.o.) for 4 weeks starting from the 4th week of streptozotocin injection significantly attenuated thermal hyperalgesia and the hot-plate latencies. Curcumin also inhibited the TNF-α and NO release in a dose dependent manner. These results indicate an antinociceptive activity of curcumin possibly through its inhibitory action on NO and TNF-α release and point towards its potential to attenuate diabetic neuropathic pain.

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.

Gas6 induces Akt/mTOR-mediated mesangial hypertrophy in diabetic nephropathy

We have already reported Gas6 is involved in glomerular hypertrophy observed in diabetic nephropathy. However, the molecular mechanisms involved in glomerular hypertrophy are still unknown, especially in vivo. In vivo, diabetes was induced in rats and mice by streptozotocin (STZ) and the activation of the Akt/mTOR pathway in glomeruli was examined. In vitro, mesangial hypertrophy was assessed by [(3)H]leucine incorporation and measuring cell areas. Akt, p70 S6 kinase, and 4E-BP-1 were induced and phosphorylated in rat glomerular lysates after 12 weeks of STZ injection when mesangial and glomerular hypertrophy was observed. We then examined the role of Gas6 by treating STZ-rats with warfarin, and found that warfarin treatment inhibited the phosphorylation of these molecules as well as the hypertrophy. We next examined whether high glucose stimulation can induce the expression of Gas6/Axl in mesangial cells. Stimulation of the cells with 25 mmol/L of glucose increased the expression of Gas6/Axl and mesangial cell size compared with that with 5.6 mmol/L of glucose. This hypertrophic effect was abolished in mesangial cells derived from Gas6 knockout mice. We also found that LY294002 and rapamycin blocked Gas6-induced activation of the Akt/mTOR pathway and mesangial hypertrophy. Furthermore, less phosphorylated Akt-positive or 4E-BP-1-positive areas were found in STZ-treated Gas6 knockout mice than in STZ-treated wild-type mice. Our study indicates that the Akt/mTOR pathway is a key signaling cascade in Gas6-mediated mesangial and glomerular hypertrophy and revealed a crucial role of Gas6/Axl and the Akt/mTOR pathway in the development of diabetic nephropathy.

Oxysterols increase in diabetic rats

To address whether diabetes enhances lipid peroxidation and attenuates nitric oxide (NO) generation resulting in tissue complications, we measured oxysterols and NO metabolites (NOx) in the tissues of diabetic Wistar rats. After 4 weeks of streptozotocin injection (STZ, 80 mg/kg, i.p.), we measured 7α- and 7β-hydroperoxycholest-5-en-3β-ol (7α-OOH and 7β-OOH), 7α- and 7β-hydroxycholesterol (7α-OH and 7β-OH) and 7-ketocholesterol (7-keto) by HPLC in the kidneys, heart, and liver. All the oxysterols were much higher in the diabetic than in sham rats, while the extent of the increase was higher in the order of the kidney, heart, and liver. Together with high blood urea nitrogen, the data indicate that the kidney is the predominant target of early diabetic complications. Plasma NOx were decreased by 20% in the STZ rats. The enhanced oxidative stress in diabetes would increase oxysterols by peroxidation, while superoxide is known to reduce NO by reaction to form another potent oxidant peroxynitrite.

Diltiazem Attenuates Oxidative Stress in Diabetic Rats

Diabetic nephropathy is the main cause of end stage renal damage. Oxidative stress is involved in the etiology of diabetic nephropathy and intracellular calcium is reported to play a considerable role in the development of renal damage in the diabetic kidney. Calcium antagonism can slow the progression of renal impairment in diabetes. The present study was thus designed to examine the effect of a nondihydropyridine calcium channel blocker, diltiazem, on renal function, oxidative stress, and nitric oxide (NO) release 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, the rats were divided in to four groups: control rats, diabetic rats treated with saline, and two groups of diabetic rats treated with diltiazem (5 and 10 mg/kg, i.p, respectively) for 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. At the end of the 8 weeks, 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. Release of NO also significantly higher in diabetic rats than controls. Chronic treatment with diltiazem 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 diltiazem administration markedly prevented diabetic-induced renal morphological alterations. The present study suggests that oxidative stress/nitrosative stress is increased in the diabetic kidney and calcium channel blockage can prevent these changes. The results also suggest that in STZ-induced diabetic rats, the protective action of diltiazem might be mediated, at least in part, by its effect on tissue oxidant/antioxidant status.

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.

Growth Arrest-specific Gene 6 Is Involved in Glomerular Hypertrophy in the Early Stage of Diabetic Nephropathy

Nephropathy is one of the most common complications of diabetes mellitus. Glomerular hypertrophy is a hallmark in the early phase of the nephropathy. The mechanism of glomerular hypertrophy, however, remains incompletely understood. We have reported that Gas6 (growth arrest-specific gene 6) and its receptor, Axl, play a key role in the development of glomerulonephritis. Here we show the important role of Gas6/Axl in the pathogenesis of diabetic glomerular hypertrophy. In streptozotocin (STZ)-induced diabetic rats, mesangial and glomerular hypertrophy and an increase in the glomerular filtration rate (GFR) and albuminuria were observed after 12 weeks of STZ injection. The glomerular expression of Gas6 and Axl was increased in those rats. Administration of warfarin inhibited mesangial and glomerular hypertrophy and the increase in GFR and albuminuria in STZ rats. Moreover, we found less mesangial hypertrophy in STZ-treated Gas6 knockout mice than control mice. In vitro we found that stimulation of mesangial cells with Gas6 resulted in mesangial cell hypertrophy. Thus we have found a novel mechanism of glomerular hypertrophy through the Gas6/Axl-mediated pathway in the development of diabetic nephropathy. Inhibition of the Gas6/Axl pathway in diabetic patients might be beneficial to slow down the progression of diabetic nephropathy.

Effects of rhg-csf on neutrophil functions and survival in sepsis induced diabetic rats

Diabetic patients are more prone to infection and evidence for an immunologic defect superimposed upon the metabolic abnormalities of diabetes is convincing. Neutrophils play a critical role in the host defense mechanism against various bacterial infections, and it is suggested that impaired neutrophil functions cause susceptibility to infections in diabetic patients. To explore the possibility that Granulocyte colony-stimulating factor (G-CSF) may be useful to prevent the morbidity and mortality caused by infections in diabetics. We studied the effect of G-CSF against septicemia in diabetic rats.Forty eight rats were divided into seven equal groups. The IInd. IVth-VIIth groups were made diabetic by single intraperitoneal injection of streptozotocin. Fourth, Vtth and Vllth groups were made sepricemic by cecal ligation and perforation at the end of the second week of streptozotocin injection. G-CSF was subcutaneously injected into IIIrd, Vth and VIth groups. White blood cell count, neutrophil counts and function were determined. Rats in all groups were also observed for seven days for survival.