Vehicle-treated Diabetic Rats Research Articles

Tocotrienol-rich fraction reduces retinal inflammation and angiogenesis in rats with streptozotocin-induced diabetes

BackgroundDiabetic retinopathy (DR) is the second commonest microvascular complication of diabetes mellitus. It is characterized by chronic inflammation and angiogenesis. Palm oil-derived tocotrienol-rich fraction (TRF), a substance with anti-inflammatory and anti-angiogenic properties, may provide protection against DR development. Therefore, in this study, we investigated the effect of TRF on retinal vascular and morphological changes in diabetic rats. The effects of TRF on the retinal expression of inflammatory and angiogenic markers were also studied in the streptozotocin (STZ)-induced diabetic rats.MethodsMale Sprague Dawley rats weighing 200–250 g were grouped into normal rats (N) and diabetic rats. Diabetes was induced by intraperitoneal injection of streptozotocin (55 mg/kg body weight) whereas N similarly received citrate buffer. STZ-injected rats with blood glucose of more than 20 mmol/L were considered diabetic and were divided into vehicle-treated (DV) and TRF-treated (DT) groups. N and DV received vehicle, whereas DT received TRF (100 mg/kg body weight) via oral gavage once daily for 12 weeks. Fundus images were captured at week 0 (baseline), week 6 and week 12 post-STZ induction to estimate vascular diameters. At the end of experimental period, rats were euthanized, and retinal tissues were collected for morphometric analysis and measurement of NFκB, phospho-NFκB (Ser536), HIF-1α using immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA). Retinal inflammatory and angiogenic cytokines expression were measured by ELISA and real-time quantitative PCR.ResultsTRF preserved the retinal layer thickness (GCL, IPL, INL and OR; p < 0.05) and retinal venous diameter (p < 0.001). TRF also lowered the retinal NFκB activation (p < 0.05) as well as expressions of IL-1β, IL-6, TNF-α, IFN-γ, iNOS and MCP-1 (p < 0.05) compared to vehicle-treated diabetic rats. Moreover, TRF also reduced retinal expression of VEGF (p < 0.001), IGF-1 (p < 0.001) and HIF-1α (p < 0.05) compared to vehicle-treated rats with diabetes.ConclusionOral TRF provided protection against retinal inflammation and angiogenesis in rats with STZ-induced diabetes by suppressing the expression of the markers of retinal inflammation and angiogenesis.

Oral Spirulina Platensis Attenuates Hyperglycemia and Exhibits Antinociceptive Effect in Streptozotocin-Induced Diabetic Neuropathy Rat Model.

IntroductionDiabetic neuropathy is a common consequence of diabetes. Hyperalgesia is one of the main symptoms of diabetic neuropathy. In response to noxious stimuli, streptozotocin (STZ)-induced diabetic rats show exaggerated hyperalgesic behavior, while Spirulina platensis has anti-inflammatory, antioxidant, and insulin-like effects. To assess the antinociceptive effect of oral Spirulina platensis (SP) powder on formalin-induced nociceptive responses in STZ-induced diabetic rats.MethodsSixty mature male albino rats were randomly allocated into six equal groups (10 in each group). Group 1 (control non-diabetic group) received 0.9% saline; group 2 was given oral pure SP powder-treated as a non-diabetic control group, group 3 was sodium salicylate-treated rats and used as a positive non-diabetic control group, group 4 managed as vehicle-treated diabetic rats, group 5 considered as SP-treated-diabetic group, and sodium salicylate-treated-diabetic rats used as a diabetic positive control group (group 6). STZ-diabetic rats were orally given SP in a dose of 500 mg kg/day for 1 month. The formalin test was implemented in two phases: the early phase in the first 10-min post-formalin injection, and the late phase was considered in the 15–60 min post-formalin injection time interval.ResultsPain scores were increased in the diabetic groups during both phases of the experiment. Blood glucose was significantly reduced in diabetic rats that received oral SP, P < 0.01. Besides, SP-treated rats had lower pain scores during both phases of the experiment than untreated diabetic ones. However, in the sodium salicylate group, the pain score was reduced only during the second phase. An exaggerated nociceptive response occurred in diabetic rats after the formalin test. A significant antinociceptive effect appeared in SP-treated control and diabetic rats.DiscussionThe findings suggest that oral Spirulina platensis could have a potential therapeutic role for managing induced painful diabetic neuropathy in rats.

Klotho ameliorates the onset and progression of cataract via suppressing oxidative stress and inflammation in the lens in streptozotocin-induced diabetic rats

Increased oxidative stress and inflammation play an important role in the pathogenesis of diabetic cataract. Klotho, known as an anti-ageing protein, has antioxidative and anti-inflammatory properties. Klotho is expressed in limited tissues including the lens. Here we examined whether klotho expression is decreased in diabetic lens and, if so, whether klotho treatment can prevent diabetic cataract formation. Streptozotocin (STZ)-induced diabetic rats and age-matched control rats were treated with vehicle or klotho protein, starting at 1 week after STZ injection. Twelve weeks after treatment, cataract formation was observed in diabetic rats but not control rats. Cataract formation and scores were significantly less in klotho-treated diabetic rats than vehicle-treated diabetic rats. Levels of klotho in plasma, aqueous humor and lens were significantly decreased in vehicle-treated diabetic rats, compared with control rats, but were restored in klotho-treated diabetic rats. Additionally, vehicle-treated diabetic rats had increased oxidative stress and inflammation in the lens, which were associated with decreased antioxidant transcriptional master regulator Nrf2 activity and increased transcription factor NF-κB activity. All of these findings were ameliorated in klotho-treated diabetic rats. Notably, klotho treatment did not alter blood glucose in diabetic rats. These results indicate that klotho reduction may increase susceptibility of the lens to oxidative and inflammatory insults, promoting cataract formation under diabetic conditions. Klotho treatment can ameliorate the onset and progression of diabetic cataract via enhancing Nrf2-mediated antioxidant defense and suppressing NF-κB-mediated inflammatory responses. Klotho in the lens may be a novel therapeutic target for prevention of cataract formation in diabetes.

Neuroprotective effects of isoquercitrin in diabetic neuropathy via Wnt/β-catenin signaling pathway inhibition.

Diabetic neuropathy is a peripheral nervous system disorder affecting both somatic and autonomic components of nervous system. A growing body of evidence have depicted that high glucose levels can induce activation of the Wnt/β-catenin pathway, however there are no studies targeting this pathway in DN. The intent of the present study was to investigate the effects of isoquercitrin (ISQ), a Wnt/β-catenin signaling pathway inhibitor, in diabetic neuropathy. Streptozotocin (50 mg/kg, i.p.) was used to induce diabetes in rats. 6-week diabetic rats were treated intrathecally with ISQ at 10 and 30 μM doses for 3 days. Furthermore, to confirm the results of the intrathecal study, a 2-week intraperitoneal treatment of ISQ was given to diabetic rats. After 6 weeks, diabetic rats developed neuropathy which was evident from reduced thermal and mechanical hyperalgesia thresholds and significant deterioration in motor nerve conduction velocity (MNCV), nerve blood flow (NBF). Sciatic nerves of diabetic neuropathy rats showed increased expression of Wnt pathway proteins namely β-catenin, c-myc and MMP2. Treatment with ISQ, both intrathecally (10 and 30 μM) and intraperitoneally (10 mg/kg), significantly ameliorated the alterations in behavioral pain thresholds and improved functional parameters in diabetic rats. Moreover, ISQ also downregulated the expression of Wnt/β-catenin pathway proteins significantly in diabetic rats as compared to vehicle-treated diabetic rats. Results of the present study suggest the neuroprotective potential of ISQ in the treatment of DN via inhibition of Wnt/β-catenin signaling pathway.

GLP-1 mediates the modulating effect of thymoquinone on feeding behaviors in diabetic rats.

Background: Thymoquinone (TQ) is a safe nutrient isolated from the seeds or volatile oil extract of Nigella sativa. In addition to its benefits in glucose regulation, TQ improves feeding disorders in diabetic animals. Glucagon-like peptide-1 (GLP-1) analogs improve glycemic control and ameliorate obesity or hyperphagia. Therefore, the present study aimed to investigate the role of GLP-1 in TQ-induced anorexia.Method: Type 2 diabetes was induced in rats by nicotinamide and streptozotocin injection. TQ was orally administered to diabetic rats at different doses for 45 days. Following TQ treatment, changes in serum glucose levels, GLP-1 concentration, body weight, food intake, and water intake were determined. To further explore the interaction between GLP-1 and TQ, the inhibitor of dipeptidyl peptidase 4, sitagliptin and the GLP-1 receptor antagonist exendin 9–39 (Ex 9–39) were separately administered to TQ- or vehicle-treated diabetic rats.Results: TQ treatment attenuated hyperglycemia and reduced hyperphagy and water intake in streptozotocin-induced diabetic rats in a dose-dependent manner. Moreover, TQ treatment elevated plasma GLP-1 levels compared to those in control rats. The effects of TQ were enhanced by treatment with sitagliptin and reduced by the injection of Ex 9–39 into the brain. In contrast, similar treatment with another antioxidant (either ascorbic acid or N-acetylcysteine) produced the same anorexic effect as TQ without changing the plasma GLP-1 levels in diabetic rats. Therefore, TQ attenuated hyperphagy while increasing plasma GLP-1 levels and had antioxidant-like effects.Conclusion: TQ increased endogenous GLP-1 levels to reduce hyperphagy in diabetic rats.

Erythropoietin Attenuates Cardiac Dysfunction in Rats by Inhibiting Endoplasmic Reticulum Stress-Induced Diabetic Cardiomyopathy.

Enhanced endoplasmic reticulum (ER) stress and down-regulated SERCA2a expression play crucial roles in diabetes. We aimed to verify whether erythropoietin (EPO) attenuates cardiac dysfunction by suppressing ER stress in diabetic rats. Forty male SD rats were randomly divided into four groups: control, EPO-treated control, vehicle-treated diabetic, and EPO-treated diabetic groups. The animals in the EPO-treated control and diabetic groups were administered recombinant human EPO (1000U/kg body weight) once per week for 12weeks. RT-PCR and Western blotting assays were performed to detect the expression of 78-kDa glucose-regulated protein precursor (GRP78) and sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA2a). We cultured neonatal rat cardiomyocytes and investigated the protective effects of EPO against high glucose (HG)-induced apoptosis. Intracellular calcium levels were measured through confocal microscopy. We observed increased myocardial GRP78 expression and decreased myocardial SERCA2a expression in diabetic rats. EPO prevented the changes in GRP78, SERCA2a expression and cardiac dysfunction in diabetic rats. The levels of GRP78 protein were significantly reduced in EPO-treated diabetic rats compared with vehicle-treated diabetic rats (GRP78 protein 0.09±0.03 vs. 0.54±0.04, P<0.01). The levels of the SERCA2a proteins were significantly increased in EPO-treated diabetic rats compared with vehicle-treated diabetic rats (SERCA2a protein 0.60±0.05 vs. 0.13±0.04, P<0.01). A reduction in apoptosis was observed in the cardiomyocytes treated with 20U/mL EPO compared with the cardiomyocytes cultured under HG conditions (apoptosis rate 18.9±1.94 vs. 37.9±1.59%, P<0.01). This study demonstrates that EPO treatment improved the parameters of cardiac function following HG-induced injury by suppressing ER stress and inducing SERCA2a expression.

ALOE-EMODIN GLYCOSIDES AMELIORATE GLUCOSE UTILIZATION VIA INSULIN DOWNSTREAM REGULATORS: AN IN VIVO INVESTIGATION

&lt;p&gt;ABSTRACT&lt;br /&gt;Objective: Aloe-emodin glycosides (AEG) isolated from Cassia fistula stimulates glucose transport and glycogen storage through a phosphatidylinositol&lt;br /&gt;3 kinase (PI3K)-dependent mechanism in L6 myotubes and inhibits adipocytes differentiation in 3T3L1 adipocytes was previously reported. This&lt;br /&gt;study intended to investigate the insulin mimetic effect of AEG by in vivo method.&lt;br /&gt;Methods: Male Wistar albino rats were randomly allocated into two groups and fed for a period of 3-week. The high-fat diet group animals were&lt;br /&gt;injected with a low dose (35 mg/kg) of streptozotocin to induce Type-2 diabetes. The diabetic rats were then treated with low dose: 10 mg/kg and&lt;br /&gt;high dose: 30 mg/kg for a period of 21-day. A dose-dependent decrease in fasting blood glucose, cholesterol, and triglycerides levels on treatment&lt;br /&gt;with AEG. The carbohydrate metabolism in diabetic rats appeared to improve due to regulation in hepatic enzymes such as hexokinase, glucose-6phosphatase,&lt;br /&gt;and fructose&lt;br /&gt;1,6-bisphosphatase with a concomitant increase&lt;br /&gt;in glycogen&lt;br /&gt;content.&lt;br /&gt;Results: AEG decreased lipid peroxidation and improved the antioxidant (enzymatic and nonenzymatic) levels in the liver of diabetic rats. Treatment&lt;br /&gt;with AEG (30 mg/kg) augmented the phosphorylation of insulin downstream regulators such as insulin receptor beta, insulin receptor substrate 1,&lt;br /&gt;PI3K, glucose transporter 4, glycogen synthase kinase 3 beta, and peroxisome proliferator activator receptor gamma in the skeletal muscle tissue of&lt;br /&gt;the Type-2 diabetic rats compared to vehicle-treated diabetic rats.&lt;br /&gt;Conclusion: The present results suggested that AEG could serve as an interesting candidate in the drug development for the management of diabetes.&lt;br /&gt;Keywords: Aloe-emodin glycoside, Type-2 diabetes, High-fat diet/streptozotocin, Carbohydrate Metabolism, Glycogen, Antioxidant enzyme.&lt;/p&gt;

리치 저분자 폴리페놀인 Oligonol의 Streptozotocin 투여 당뇨 쥐에서 산화적 스트레스와 관련된 간 손상에 미치는 영향

This study was conducted to examine whether or not oligonol, a low molecular weight polyphenol derived from lychee fruit, has an ameliorative effect on diabetes-induced oxidative stress-related hepatic damage in streptozotocin (STZ)-induced diabetic rats. Oligonol (10 or 20 mg/kg body weight; O10 or O20, respectively) was orally administered every day for 10 days to STZ-induced diabetic rats, and its effects were compared to vehicle-treated diabetic (Veh) and non-diabetic rats. Administration of 20 mg/kg of oligonol significantly decreased liver weight compared with the Veh group (P<0.05). Elevated levels of hepatic glucose, reactive oxygen species, peroxynitrite, and lipid peroxidation were detected in diabetic vehicle rats, whereas oligonol treatment significantly attenuated these levels (P<0.05). In diabetic vehicle rats, hepatic antioxidant enzyme protein levels decreased, whereas oligonol treatment showed significant elevated results. For inflammation-related protein expression, oligonol-treated groups showed insignificant reduction. Oligonol improved expression of proapoptotic protein caspase-3 in the liver of diabetic rats (P<0.05). In conclusion, these results provide important evidence that oligonol exhibits an inhibitory effect on oxidative stress and apoptosis-related protein expression as well as a hepato-protective effect against the development of diabetic complications in STZ-induced type 1 diabetic rats.

Nephro-Protective Effect of Cortex Lycii Radicis Extracts in Streptozotocin- Induced Diabetic Rats

Background: To evaluate the effects of aqueous Cortex Lycii Radicis (CLR) extracts on diabetic nephrology in a streptozotocin-induced diabetic nephropathy rat model, and to explore the underlying mechanisms of CLR action. Methods: We induced diabetes mellitus via a single intravenous streptozotocin injection (30 mg/kg) and subsequent high-fat diet for 3 weeks in male Sprague Dawley rats. Rats that developed diabetes mellitus were randomized to receive normal saline (vehicle, n=10), low-dose CLR (15 g/kg/day, n=10), or high-dose CLR (30 g/kg/day, n=10), and rosiglitazone (2 mg/kg/day, n=10) daily for 8 weeks. In addition, 10 normal rats served as controls. Kidneys were removed to evaluate histological renal glomeruli alterations using periodic acid–Schiff (PAS) staining. Results: Fructosamine, and blood urea nitrogen concentrations, as well as the urinary albumin excretion rate (AER), were increased in vehicle-treated diabetic rats compared to control rats (P<0.05). These parameters decreased upon CLR treatment, particularly at low-dosage CLR (P<0.05). Morphologic observations showed that high-dosage CLR markedly attenuated diabetes-associated renal injury. The renal protective effects of CLR may be mediated by downregulation of cytokine expression, including TGF-α and interleukin 6. Conclusion: CLR accelerates functional and histological kidney recovery, thereby delaying diabetic nephropathy progression. Therefore, it may be a novel therapeutic approach for the treatment of diabetic nephrology. Keywords: Chinese medicine, Cortex Lycii Radicis, diabetic nephropathy, traditional.

β2-adrenoceptor agonists as potential therapeutic drugs in diabetic peripheral neuropathy

Objectives: the aim of the current study was to assess the effect of a β2-adrenoceptor agonist; namely salbutamol, on hyperalgesic as well as nerve dysfunction components of diabetic peripheral neuropathy. Material and methods: the present study was conducted on 60 male Wistar albino rats divided into six groups. Groups I and II were normal control rats injected by a single i.p. injection of normal saline and received 2% gum acacia (Group I) or salbutamol (Group II) for six weeks, starting one week following saline injection. Groups III–VI: rats that were rendered diabetic by a single i.p. injection of STZ and received either 2% gum acacia, salbutamol, salbutamol and propranolol or salbutamol and atenolol, respectively daily orally for six weeks, starting one week following STZ injection. Results: vehicle-treated diabetic rats exhibited: significant sciatic nerve dysfunction in the form of significantly prolonged distal latency and significantly decreased maximum peak and peak to peak amplitude of compound muscular action potential, significant thermal and mechanical hyperalgesia evidenced by significant decrease in hot plate latency, tail-flick latency and vocalization threshold, respectively. Salbutamol administration improved nerve dysfunction as well as thermal and mechanical hyperalgesia. These effects of salbutamol are most likely mediated by β2-adrenoceptors evidenced by significant abolishment of salbutamol effects after administration of the non-selective rather than the selective beta blockers; propranolol and atenolol, respectively. Conclusions: chronic administration of salbutamol could ameliorate DPN, an effect which is most likely mediated by β2-adrenoceptors.

Reduction of Aldosterone Production Improves Renal Oxidative Stress and Fibrosis in Diabetic Rats

Aldosterone is increased in diabetes and contributes to the development of diabetic nephropathy. The authors hypothesized that reduction in aldosterone production in diabetes by amlodipine or aliskiren improves diabetic kidney disease by attenuating renal oxidative stress and fibrosis. Normoglycemic and streptozotocin-induced diabetic Sprague-Dawley rats were given vehicle, amlodipine, or aliskiren alone and combined for 6 weeks. At the end of study, we evaluated blood pressure (BP), 24-hour urinary sodium (UNaV) and aldosterone excretion rates, renal interstitial fluid (RIF) levels of nitric oxide (NO), cyclic guanosine 3',5'-monophosphate (cGMP), and 8-isoprostane, and renal morphology. BP was not significantly different between any of experimental groups. UNaV increased in diabetic animals and was not affected by different treatments. Urinary aldosterone excretion increased in diabetic rats receiving vehicle and decreased with amlodipine and aliskiren alone or combined. RIF NO and cGMP levels were reduced in vehicle-treated diabetic rats and increased with amlodipine or aliskiren given alone and combined. RIF 8-isoprostane levels and renal immunostaining for periodic acid-Schiff and fibronectin were increased in vehicle-treated diabetic rats and decreased with aliskiren alone or combined with amlodipine. The authors conclude that inhibition of aldosterone by amlodipine or aliskiren ameliorates diabetes induced renal injury via improvement of NO-cGMP pathway and reduction in oxidative stress and fibrosis, independent of BP changes.

The Antioxidant Capacity and Anti-diabetic Effect of Boswellia serrata Triana and Planch Aqueous Extract in Fertile Female Diabetic Rats and the Possible Effects on Reproduction and Histological Changes in the Liver and Kidneys

Boswellia serrata has been used in a wide variety of diseases, including diabetes mellitus and inflammatory diseases. This study focused on the effects of Boswellia serrata aqueous extract on blood glucose and the complications of diabetes in the liver and kidneys and examined the impact of plant on reproduction in diabetic rats. The antioxidant capacity of plant extract was performed using FRAP assay. Diabetic and control rats were administered 200, 400, and 600 mg/kg Boswellia serrata extract. Vaginal plaque was mentioned as a positive sign of pregnancy ;and treatment started with extract or vehicle from 1th to 17th day of gestation by gastric gavage. Blood glucose was measured during 17 days. The Administration of Boswellia serrata in diabetic rats significantly decreased the level of blood glucose and HbA1c after 17th days (P ≤ 0.01). In diabetic group that received no treatment, the abortion of fetus spontaneous was 19.14%. The percentage of absorptions significantly was elevated in vehicle-treated diabetic rats, in comparison with vehicle- treated healthy rats. In the diabetic group, separated necrosis of hepatocytes, anarchism of liver plates, and lymphocytic inflammation were improved. Diabetic complications were not seen and the severity of damage was reduced. These damages include: lymphocytic inflammation in the port areas, irregularities, apoptosis of liver cells, and dilatation of the sinusoids. The results suggest that Boswellia serrata extract has the antidiabetic effects and can prevent the complications of diabetes in the kidneys and liver.

Chronic sphingosine 1-phosphate 1 receptor activation attenuates early-stage diabetic nephropathy independent of lymphocytes

Sphingosine 1-phosphate (S1P), a pleiotropic lipid mediator, binds to five related G-protein-coupled receptors to exert its effects. As S1P1 receptor (S1P1R) activation blocks kidney inflammation in acute renal injury, we tested whether activation of S1P1Rs ameliorates renal injury in early-stage diabetic nephropathy (DN) in rats. Urinary albumin excretion increased in vehicle-treated diabetic rats (single injection of streptozotocin), compared with controls, and was associated with tubule injury and increased urinary tumor necrosis factor-α (TNF-α) at 9 weeks. These effects were significantly reduced by FTY720, a non-selective, or SEW2871, a selective S1P1R agonist. Interestingly, only FTY720 was associated with reduced total lymphocyte levels. Albuminuria was reduced by SEW2871 in both Rag-1 (T- and B-cell deficient) and wild-type diabetic mice after 6 weeks, suggesting that the effect was independent of lymphocytes. Another receptor, S1P3R, did not contribute to the FTY720-mediated protection, as albuminuria was also reduced in diabetic S1P3R knockout mice. Further, both agonists restored WT-1 staining along with podocin and nephrin mRNA expression, suggesting podocyte protection. This was corroborated in vitro, as SEW2871 reduced TNF-α and vascular endothelial growth factor mRNA expression in immortalized podocytes grown in media containing high glucose. Whether targeting kidney S1P1Rs will be a useful therapeutic measure in DN will need direct testing.

Poly(ADP‐Ribose) Polymerase Inhibition Improves Erectile Function in Diabetic Rats

Erectile dysfunction (ED) is a common and hard-to-treat complication of diabetes mellitus (DM). Multiple lines of evidence have shown that poly(ADP-ribose) polymerase (PARP) activation plays an important role in neurovascular dysfunction in diabetes, which is the crucial mechanism for diabetic ED. To investigate the preventive benefit of a PARP inhibitor in a rat model of ED induced by diabetes. Established streptozotocin-diabetic male Sprague-Dawley rats were given PJ-34, a selective PARP inhibitor, by oral gavage at a dose of 10 mg/kg twice daily for 8 weeks. Erectile responses under electrical stimulation of the cavernous nerve, PARP activity and reactive oxygen species (ROS) production were measured. Nitric oxide synthase (NOS) isoforms were evaluated by Western blot and real-time quantitative PCR. Nuclear factor-kappa B activition and apoptosis in corpus cavernosa (CC) were also investigated. The effects of PARP inhibition on the development of diabetic ED were determined. Diabetes markedly attenuated the erectile responses (intracavernosal pressure/mean systemic arterial blood pressure) and these were partially prevented by PJ-34 treatment. Promoted oxidative stress associated PARP activation was found in CC from vehicle-treated diabetic rats. PJ-34 blocked PARP activity and the diabetes-associated ROS generation. Decreased expression and activity of constitutive NOS (cNOS), including endothelial NOS (eNOS) and neuronal NOS (nNOS), associated with enhanced inducible NOS (iNOS) expression and activity were observed in vehicle-treated diabetic rats. Although PJ-34 had no effect on eNOS expression, it significantly prevented the decrease in nNOS expression and cNOS activity, and inhibited iNOS expression and activity in diabetic rats. PARP blockade by PJ-34 to some extent prevented diabetes-associated apoptosis and NF-κB activation. Our results indicate that PARP activation plays an important role in the pathogenesis of diabetic ED and PARP inhibition may be a promising strategy to prevent development of diabetic ED.

Rho kinase inhibition protects kidneys from diabetic nephropathy without reducing blood pressure

Rho-associated kinases (ROCK) are activated in the kidney as well as in cultured cells of diabetic models and have been implicated in renal pathophysiology. To explore whether inhibition of ROCK is protective, we studied its role in a model of accelerated diabetic nephropathy where uninephrectomized rats were made diabetic by streptozotocin. After establishing diabetes, rats were treated with the ROCK inhibitor fasudil continuously or for the final 6 weeks of an 18-week experimental period. The results were compared to similar rats given losartan, an established treatment of clinical and experimental diabetic nephropathy, or a combination of both agents. Vehicle-treated diabetic and non-diabetic uninephrectomized rats served as controls. Diabetes resulted in a rapid development of albuminuria, higher glomerulosclerosis and interstitial fibrosis scores, lower glomerular filtration rates, and increased expression of several molecular markers of diabetic nephropathy. Eighteen weeks of fasudil treatment reduced renal ROCK activity, and ameliorated diabetes-induced structural changes in the kidney and expression of the molecular markers in association with a modest anti-proteinuric effect but no change in blood pressure. Late intervention with fasudil reduced glomerulosclerosis, but did not influence proteinuria. Most effects of fasudil were comparable to those of losartan, although losartan lowered blood pressure and further lowered proteinuria. The combination of both treatments was no different than losartan alone. Thus, ROCK inhibition protected the kidney from diabetic nephropathy even though it did not reduce the blood pressure.

Ethanol extraction of Picrorhiza scrophulariiflora prevents renal injury in experimental diabetes via anti-inflammation action

There is evidence that inflammatory processes are involved in the development and/or progression of diabetic nephropathy. However, effective treatment for inflammation in the kidneys of diabetic is practically unknown. The rhizomes of Picrorhiza scrophulariiflora (PS) are a traditional medication long used to treat inflammatory diseases. The aim of the present study was to test the hypothesis that the ethanol extract of PS (EPS) may reduce inflammation in patients with diabetic kidneys. Streptozotocin-induced diabetic rats were randomly assigned to two groups treated with a gavage of either EPS or vehicle. A group of non-diabetic control rats was treated concurrently. Compared with vehicle-treated diabetic rats, EPS-treated animals displayed a significant decrease in renal macrophage infiltration and overexpression of chemokine (C-C motif) ligand 2 (CCL2) and TGFB1. This was associated with attenuation of the structural and functional abnormalities of early diabetic nephropathy, such as glomerular hypertrophy, mesangial expansion, and albuminuria. Administration of EPS significantly reduced NADPH oxidase-dependent superoxide generation and decreased expression of malondialdehyde and advanced oxidation protein products in diabetic kidney. These data suggest that EPS might improve diabetic nephropathy, probably through inhibition of redox-sensitive inflammation.

Advanced Oxidation Protein Products Promote Inflammation in Diabetic Kidney through Activation of Renal Nicotinamide Adenine Dinucleotide Phosphate Oxidase

The involvement of inflammatory processes has been recognized in development and/or progression of diabetic nephropathy. However, the mechanisms involved in the pathogenesis of renal inflammation have not been completely understood. In this study, we tested the hypothesis that accumulation of advanced oxidation protein products (AOPPs), which occurs in diabetes, may promote inflammatory responses in diabetic kidney. Streptozotocin-induced diabetic rats were randomized to iv injection of vehicle, native rat serum albumin (RSA), and AOPPs-modified RSA (AOPPs-RSA) in the presence or absence of oral administration of apocynin. A control group was followed concurrently. Compared with RSA- or vehicle-treated diabetic rats, AOPPs-RSA-treated animals displayed significant increase in renal macrophage infiltration and overexpression of monocyte chemoattractant protein-1 and TGF-beta1. This was associated with deteriorated structural and functional abnormalities of diabetic kidney, such as glomerular hypertrophy, fibronectin accumulation, and albuminuria. AOPP challenge significantly increased nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent superoxide generation in renal homogenates and up-regulated membrane expression of renal NADPH oxidase subunits p47(phox) and gp91(phox). All these AOPPs-induced perturbations in diabetic kidney could be prevented by the NADPH oxidase inhibitor apocynin. These data suggest that chronic accumulation of AOPPs may promote renal inflammation in diabetes probably through activation of renal NADPH oxidase.

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.

C16, a novel advanced glycation endproduct breaker, restores cardiovascular dysfunction in experimental diabetic rats1

Advanced glycation endproducts (AGE) have been implicated in the pathogenesis of diabetic complications, including diabetic cardiovascular dysfunction. 3-[2-(4-Bromo-phenyl)-1-methyl-2-oxo-ethyl]-4,5,6,7-tetrahydro-benzothiazol-3-ium bromide (C16), a novel AGE breaker, was investigated for its effects on the development of cardiovascular disease in diabetic rats. Rats that had streptozotocin-induced diabetes for 12 weeks were divided into groups receiving C16 or vehicle by gavage. In hemodynamic studies of the left ventricle, C16 treatment (25 or 50 mg/kg) for 4 weeks resulted in a significant increase in left ventricular systolic pressure, +dp/dt(max), and -dp/dt(max) as compared with vehicle-treated diabetic rats. Furthermore, in hemodynamic studies of the cardiovascular system, C16 (12.5, 25, or 50 mg/kg) treatment for 4 weeks resulted in a dose-dependent and significant increase in cardiac output, a reduction of total peripheral resistance, and an increase in systemic arterial compliance when compared with vehicle-treated diabetic rats. Biochemical studies showed that C16 treatment also resulted in a significant decrease in immunoglobulin G-red blood cell surface crosslink content and an increase in collagen solubility. Morphological and immunohistochemical examinations indicated that C16 was able to prevent increases of the collagen type III/I ratio in the aorta and decrease the accumulation of AGE in the aorta. C16 has the ability to reduce AGE accumulation in tissues in vivo, and can restore diabetes-associated cardiovascular disorders in rats. This provides a potential therapeutic approach for cardiovascular disease associated with diabetes and aging in humans.

Topical Pretreatment of Diabetic Rats With All-trans Retinoic Acid Improves Healing of Subsequently Induced Abrasion Wounds

In the current study, rats were made diabetic with streptozotocin (STZ) and maintained for 8 weeks, during which time they were treated topically on alternative days with a solution of 0.1% all-trans retinoic acid in a vehicle of 70:30% ethanol/propylene glycol. STZ-induced diabetic rats treated with vehicle served as controls. Additional nondiabetic rats were treated with all-trans retinoic acid or vehicle in parallel. At the end of the 8-week period, rats from all four treatment groups were subjected to abrasion wound formation. Wounds healed more rapidly in vehicle-treated nondiabetic skin than in vehicle-treated diabetic skin (96% of the wound surface area closed in nondiabetic rats within 6 days vs. 41% closed in diabetic rats). Wounds in all-trans retinoic acid-treated diabetic skin healed more rapidly than wounds in vehicle-treated diabetic skin (85% of the wound surface area closed in all-trans retinoic acid-treated diabetic rats vs. 41% closed in vehicle-treated diabetic rats). At the histological level, recently healed skin from vehicle-treated diabetic rats was shown to contain a thin, wispy provisional matrix in which many of the embedded cells were rounded and some were pycnotic. In contrast, a much denser provisional matrix with large numbers of embedded spindle-shaped cells was observed in healed wounds from diabetic skin that had been pretreated with all-trans retinoic acid. The all-trans retinoic acid-treated diabetic skin was histologically similar to vehicle-treated (or all-trans retinoic acid-treated) skin from nondiabetic animals. In light of these findings, we suggest that prophylactic use of retinoid-containing preparations might be useful in preventing the development of nonhealing skin ulcers resultant from minor traumas in at-risk skin.