Pancreatic nitric oxide and oxygen free radicals in the early stages of streptozotocin-induced diabetes mellitus in the rat

Kolaviron modulates dysregulated metabolism in oxidative pancreatic injury and inhibits intestinal glucose absorption with concomitant stimulation of muscle glucose uptake

This present study investigated the antioxidative and antidiabetic properties of kolaviron by analysing its inhibitory effect on key metabolic activities linked to T2D, in vitro and ex vivo. Kolaviron significantly inhibited α-glucosidase and α-amylase activities, and intestinal glucose absorption dose-dependently, while promoting muscle glucose uptake. Induction of oxidative pancreatic injury significantly depleted glutathione level, superoxide dismutase, catalase, and ATPase activities, while elevating malondialdehyde and nitric oxide levels, acetylcholinesterase and chymotrypsin activities. These levels and activities were significantly reversed in tissues treated with kolaviron. Kolaviron depleted oxidative-induced metabolites, with concomitant restoration of oxidative-depleted metabolites. It also inactivated oxidative-induced ascorbate and aldarate metabolism, pentose and glucuronate interconversions, fructose and mannose metabolism, amino sugar and nucleotide sugar metabolism, and arginine and proline metabolism, while reactivating selenocompound metabolism. These results depict the antidiabetic properties of kolaviron as indicated by its ability to attenuate oxidative-induced enzyme activities and dysregulated metabolisms, and modulated the enzyme activities linked to hyperglycaemia.

Ferulic acid promotes muscle glucose uptake and modulate dysregulated redox balance and metabolic pathways in ferric-induced pancreatic oxidative injury

The antidiabetic properties of ferulic acid and its protective role against Fe²⁺ -induced oxidative pancreatic injury were investigated in this study using in vitro and ex vivo models. Induction of oxidative injury in the pancreas was achieved by incubating normal pancreatic tissue with 0.1 mM FeSO₄ and treated by co-incubating with different concentrations of ferulic acid for 30 min at 37°C. Ferulic acid inhibited the activities of α-glucosidase, α-amylase, and pancreatic lipase significantly (p < .05) and promoted glucose uptake in isolated rat psoas muscles. Induction of oxidative pancreatic injury caused significant (p < .05) depletion of glutathione (GSH) level, superoxide dismutase (SOD), and catalase activities, as well as elevation of malondialdehyde (MDA) and nitric oxide (NO) levels, acetylcholinesterase and chymotrypsin activities. Treatment of tissues with ferulic acid significantly (p < .05) reversed these levels and activities. LC-MS analysis of the extracted metabolites revealed 25% depletion of the normal metabolites with concomitant generation of m-Chlorohippuric acid, triglyceride, fructose 1,6-bisphosphate, and ganglioside GM1 in oxidative-injured pancreatic tissues. Treatment with ferulic acid restored uridine diphosphate glucuronic acid and adenosine tetraphosphate and generated P1,P4-Bis(5'-uridyl) tetraphosphate and L-Homocysteic acid, while totally inactivating oxidative-generated metabolites. Ferulic acid also inactivated oxidative-activated pathways, with concomitant reactivation of nucleotide sugars metabolism, starch and sucrose metabolism, and rostenedione metabolism, estrone metabolism, androgen and estrogen metabolism, porphyrin metabolism, and purine metabolism pathways. Taken together, our results indicate the antidiabetic and protective potential of ferulic acid as depicted by its ability to facilitate muscle glucose uptake, inhibit carbohydrate and lipid hydrolyzing enzymes, and modulate oxidative-mediated dysregulated metabolisms. PRACTICAL APPLICATIONS: There have been increasing concerns on the side effects associated with the use of synthetic antidiabetic drug, coupled with their expenses particularly in developing countries. This has necessitated continuous search for alternative treatments especially from natural products having less or no side effects and are readily available. Ferulic acid is among the common phenolics commonly found in fruits and vegetables. In this present study, ferulic acid was able to attenuate oxidative stress, cholinergic dysfunction, and proteolysis in oxidative pancreatic injury, as well as inhibit carbohydrate digesting enzymes. Thus, indicating the ability of the phenolic to protect against complications linked to diabetes. Crops rich in ferulic acid maybe beneficial in managing this disease.

Optimization of Hyperglycemic Induction in Zebrafish and Evaluation of Its Blood Glucose Level and Metabolite Fingerprint Treated with Psychotria malayana Jack Leaf Extract

A standard protocol to develop type 1 diabetes in zebrafish is still uncertain due to unpredictable factors. In this study, an optimized protocol was developed and used to evaluate the anti-diabetic activity of Psychotria malayana leaf. The aims of this study were to develop a type 1 diabetic adult zebrafish model and to evaluate the anti-diabetic activity of the plant extract on the developed model. The ability of streptozotocin and alloxan at a different dose to elevate the blood glucose levels in zebrafish was evaluated. While the anti-diabetic activity of P. malayana aqueous extract was evaluated through analysis of blood glucose and LC-MS analysis fingerprinting. The results indicated that a single intraperitoneal injection of 300 mg/kg alloxan was the optimal dose to elevate the fasting blood glucose in zebrafish. Furthermore, the plant extract at 1, 2, and 3 g/kg significantly reduced blood glucose levels in the diabetic zebrafish. In addition, LC-MS-based fingerprinting indicated that 3 g/kg plant extract more effective than other doses. Phytosterols, sugar alcohols, sugar acid, free fatty acids, cyclitols, phenolics, and alkaloid were detected in the extract using GC-MS. In conclusion, P. malayana leaf aqueous extract showed anti-diabetic activity on the developed type 1 diabetic zebrafish model.

Histone deacetylase inhibitor MGCD0103 protects the pancreas from streptozotocin-induced oxidative stress and β-cell death

Inhibition of histone deacetylase (HDAC) suppresses inflammation of pancreatic islets and apoptosis of β-cells. However, the underlying molecular mechanism is unclear. In the present study, we demonstrate that MGCD0103 (MGCD), an HDAC inhibitor, protects the pancreas from streptozotocin (STZ)-induced oxidative stress and cell death. Sprague-Dawley rats were intraperitoneally injected with STZ (40 mg/kg) to induce type I diabetes. MGCD (10 μg/day) was infused with osmotic mini-pump for 4 weeks. Pancreatic insulin and macrophage infiltration were analyzed by immunohistochemistry. Cellular level of reactive oxygen species (ROS) was evaluated with fluorescence-activated cell sorting. Tetramethylrhodamine ethyl ester was used to analyze mitochondrial membrane potential. Activation of caspase-3 was analyzed by western blotting. Chromatin immunoprecipitation was performed to investigate the binding affinity of specificity protein 1 (SP1) on the promoters of target genes. mRNA expression was analyzed by quantitative real-time polymerase chain reaction. As a result, we found that MGCD infusion ameliorated STZ-induced hyperglycemia, islet deformation, decreased insulin level, and macrophage infiltration. STZ injection promoted the production of ROS, which induced caspase activity and β-cell death. 4-Hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL), a mimetic of superoxide dismutase (SOD), reduced STZ-induced caspase activity and β-cell death. MGCD treatment increased SOD expression and histone acetylation level on promoters. Infusion of MGCD promoted acetylation of SP1 and its enrichment on SOD promoters. Thus, MGCD protects pancreatic β-cells from STZ-induced oxidative stress and cell death through the induction of antioxidant enzymes such as SODs.

HX-1171 attenuates pancreatic β-cell apoptosis and hyperglycemia-mediated oxidative stress via Nrf2 activation in streptozotocin-induced diabetic model

Streptozotocin (STZ) acts specifically on pancreatic beta cells, inducing cell destruction and cell dysfunction, resulting in diabetes. Many studies have reported that nuclear factor-erythroid 2-related factor 2 (Nrf2), a main regulator of antioxidant expression, prevents and improves diabetes-related diseases. In this study, we investigated the antidiabetic effect of the newly discovered Nrf2 activator, HX-1171, in the STZ-induced diabetic mouse model. HX-1171 enhanced insulin secretion by reducing STZ-induced cell apoptosis, and decreased intracellular reactive oxygen species (ROS) generation by upregulating the expression of antioxidant enzymes through Nrf2 activation in INS-1 pancreatic beta cells. In STZ-induced diabetic mice, HX-1171 administration significantly lowered blood glucose levels and restored blood insulin levels. In the STZ-only injected mice, the pancreatic islets showed morphological changes and loss of function, whereas the HX-1171-treated group was similar to that of the control group. These results suggest that HX-1171 may be developed as a promising therapeutic agent for diabetes-related diseases.

Apoptosis in pancreatic β-cells is induced by arsenic and atorvastatin in Wistar rats with diabetes mellitus type 2

INTRODUCTION

Diabetes Mellitus type 2 (T2D) is a multifactorial disease. However, it is known that there is an important effect in pancreatic β-cells caused by apoptosis of pro-apoptotic proteins, possibly related to arsenic exposure and atorvastatin treatment.

OBJECTIVE

The goal of this study was to evaluate the effects of atorvastatin treatment on apoptosis of pancreatic β-cells in Wistar rats with induced diabetes type 2 exposed to arsenic.

MATERIAL & METHODS

T2D in Wistar rats was induced by administration of Streptozotocin. The plasmatic glucose concentrations were measured using the glucose oxidase method, and the concentration of glycated hemoglobin (HbA1c) in whole blood was determined. Exposure to arsenic was measured from urine using atomic absorption with hydride generation, and pro-apoptotic proteins in pancreatic β-cells were observed using the Western blotting technique.

RESULTS

Caspase-3 was present in rats that were treated with 10 mg/kg of oral atorvastatin and exposed to 0.01 and 0.025 mg/L of arsenic, but no others proteins were present, such as pro Caspase-8, bcl-2, and Fas. The glycemic levels were 129.2 ± 7.0 mg/dL in the control group and 161.8 ± 14.6 mg/dL and 198.3 ± 18.2 mg/dL (p < .05) in the study groups. HbA1c increased from 2.53% to 3.64% (p < .05) in the control and study groups.

CONCLUSIONS

Atorvastatin treatment and arsenic exposure alone are capable of generating apoptosis in pancreatic β-cells of Wistar rats with T2D. Together, all of these factors induce apoptosis in pancreatic cells.

Quercetin improves endothelial function in diabetic rats through inhibition of endoplasmic reticulum stress-mediated oxidative stress

Endoplasmic reticulum (ER) stress attributes a crucial role in diabetes-induced endothelial dysfunction. The present study investigated the effects of quercetin, a potent antioxidant on the attenuation of ER stress-modulated endothelial dysfunction in streptozotocin (STZ)-induced diabetic rats. Oral administration of quercetin for six weeks to diabetic rats dose-dependently reduced the blood glucose levels and improved insulin secretion. Histopathological examination of pancreatic tissues in diabetic rats showed pathological changes such as shrunken islets, reduction in islet area and distorted β-cells, which were found to be restored by quercetin treatment. In addition, quercetin reduced the pancreatic ER stress-induced endothelial dysfunction as assessed by immunohistochemical analysis of C/ERB homologous protein (CHOP) and endothelin-1 (ET-1). Moreover, quercetin administration progressively increased the expression of vascular endothelial growth factor (VEGF) and its receptor, VEGFR2 in diabetes rats. Quercetin-mediated decrease in the nitric oxide (NO∙) and cyclic 3',5'- guanosine monophosphate (cGMP) levels were also observed in the diabetic rats. Quercetin treatment reduced the lipid peroxidation in the diabetic rats, meanwhile increased the total antioxidant capacity in the pancreas from diabetic rats. Altogether, these results demonstrated the vasoprotective effect of quercetin against STZ-induced ER stress in the pancreas of diabetic rats.

Streptozotocin (STZ) and schistosomiasis mansoni change the biodistribution of radiopharmaceutical sodium (99m)Tc-pertechnetate in mice

INTRODUCTION

Technetium-99m ((99m)Tc) is a radionuclide commonly used in nuclear medicine to obtain (99m)Tc-radiopharmaceuticals, which can be used to evaluate either physiological processes or changes related to diseases. It is also used in some experimental studies. Streptozotocin (STZ) administration to rodents causes lesions in very early stages and induces severe and permanent diabetes. Most morbidity of schistosomiasis mansoni is attributed to a granulomatous inflammatory response and associated liver fibrosis. This study was designed to investigate whether STZ administration and schistosomiasis modify the biodistribution of the radiopharmaceutical sodium (99m)Tc-pertechnetate.

METHODS

Adult female mice were infected by exposure to 100Schistosoma mansoni cercariae (BH strain, Belo Horizonte, Brazil) and euthanized after nine weeks. STZ was administered by a single intraperitoneal injection of 100mg/kg body weight, 3 or 15days before euthanasia. Each animal received 100μl of sodium (Na) (99m)Tc-pertechnetate ((99m)TcO4(-)) (740kBq). The animals were divided into four groups: A, uninfected; B, infected; C, uninfected + STZ; and D, infected + STZ. Blood, brain, thyroid, heart, lungs, liver, spleen, pancreas and kidneys were removed. The radioactivity was counted and the percentage of the injected dose of Na(99m)TcO4 per gram of the organ (% ID/g) was determined.

RESULTS

Three days after the STZ injection, there was a decrease of Na(99m)TcO4 uptake by the liver, lungs, pancreas and kidneys (p<0.05) in group D when compared with group A. After 15days, the decrease of Na(99m)TcO4 uptake occurred also in the brain, thyroid, heart, spleen and blood (p<0.05) in group D.

CONCLUSION

We demonstrated modifications on the biodistribution of Na(99m)TcO4 due to STZ administration and schistosomiasis, possibly due to physiological alterations in some organs.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

The biodistribution of radiopharmaceutical Na(99m)TcO4 should be carefully evaluated in subjects with diabetes and/or schistosomiasis infection.

Hepatoprotection by active fractions from Desmostachya bipinnata stapf (L.) against tamoxifen-induced hepatotoxicity

Objective:

The aim was to evaluate the effect of the polyphenolic fraction of Desmostachya bipinnata Stapf (PFDB) (Poaceae) on tamoxifen (TAM)-induced liver damage in female Sprague-Dawley rats.

Materials and Methods:

The roots of Desmostachya bipinnata were extracted in 70% methanol, and the polyphenolic fraction was isolated. Protection of BRL3A cells against ethanol-induced damage was determined by 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Hepatotoxicity was induced in rats by oral administration of TAM (45 mg/kg/day) for 21 days. The PFDB was administered to experimental animals at two selected doses (100 and 200 mg/kg/day) during the treatment. The serum levels of various biochemical parameters and the antioxidant enzymes were examined by standard procedures.

Results:

A dose-dependent increase in percentage viability was observed when ethanol-exposed BRL3A cells were treated with PFDB. Both the treatment groups upon pretreatment with PFDB exhibited a significant (P ≤ 0.05) protective effect by lowering serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, alkaline phosphatase, triglycerides, cholesterol, urea, uric acid, bilirubin and creatinin levels and improving protein level in serum in dose-dependent manner, which was comparable to that of silymarin group. In addition, PFDB prevented elevation of reduced glutathione, glutathione peroxidase, superoxide dismutase and catalase in the TAM-intoxicated rats in concentration-dependent manner and significantly (P < 0.05) reduced the lipid peroxidation in the liver tissue. The biochemical observations were supplemented with histopathological reports, which showed the attenuation of hepatocellular necrosis.

Conclusions:

The results of this study strongly indicate that the polyphenolic fraction of the plant roots has a potent hepatoprotective action against TAM-induced hepatic damage in rats.

Side-to-Side Jejunoileal Bypass Induces Better Glucose-Lowering Effect than End-to-Side Jejunoileal Bypass on Nonobese Diabetic Rats

BACKGROUND

Jejunoileal bypass (JIB) can markedly ameliorate diabetes in obese patients and rodents. The aim of this study is to systematically evaluate the role of the operational manner and the retained distal small bowel length in mediating changes in glucose homeostasis after intestinal bypass surgeries in nonobese diabetic rats.

METHODS

Streptozotocin-induced diabetic rats underwent side-to-side jejunoileal bypass plus proximal loop ligation (SSJIBL), end-to-side jejunoileal bypass (ESJIB), proximal small bowel resection (PBR), and sham operation. Each operational manner included two subgroups, in which 30 cm (L-30) or 40 cm (L-40) distal small bowel was retained. Main outcome measures were fasting blood glucose levels (FBG), insulin sensitivity, serum insulin, glucagon-like peptide-1 (GLP-1), bilirubin (BIL), and total bile acids (TBA) levels.

RESULTS

Global food intake in the sham group was higher than in the operation groups, and global body weight and food intake in the SSJIBL group were higher than in the ESJIB and PBR groups. Global body weight and food intake in L-40 group were higher than in L-30 group. The SSJIBL procedure induced better improvement in glucose homeostasis and insulin sensitivity than the ESJIB and PBR procedures, and L-30 group showed better antidiabetic effects than L-40 group. Serum GLP-1, BIL, and TBA levels in SSJIBL group were higher than in ESJIB and PBR groups.

CONCLUSIONS

This study shows that side-to-side jejunoileal bypass induced better glucose-lowering effects than end-to-side jejunoileal bypass and proximal small bowel resection, and intestinal bypass surgery that retained shorter distal small bowel yielded better antidiabetic effects.

Challenges and issues with streptozotocin-induced diabetes - A clinically relevant animal model to understand the diabetes pathogenesis and evaluate therapeutics

Streptozotocin (STZ) has been extensively used over the last three decades to induce diabetes in various animal species and to help screen for hypoglycemic drugs. STZ induces clinical features in animals that resemble those associated with diabetes in humans. For this reason STZ treated animals have been used to study diabetogenic mechanisms and for preclinical evaluation of novel antidiabetic therapies. However, the physiochemical characteristics and associated toxicities of STZ are still major obstacles for researchers using STZ treated animals to investigate diabetes. Another major challenges in STZ-induced diabetes are sustaining uniformity, suitability, reproducibility and induction of diabetes with minimal animal lethality. Lack of appropriate use of STZ was found to be associated with increased mortality and animal suffering. During STZ use in animals, attention should be paid to several factors such as method of preparation of STZ, stability, suitable dose, route of administration, diet regimen, animal species with respect to age, body weight, gender and the target blood glucose level used to represent hyperglycemia. Therefore, protocol for STZ-induced diabetes in experimental animals must be meticulously planned. This review highlights specific skills and strategies involved in the execution of STZ-induced diabetes model. The present review aims to provide insight into diabetogenic mechanisms of STZ, specific toxicity of STZ with its significance and factors responsible for variations in diabetogenic effects of STZ. Further this review also addresses ways to minimize STZ-induced mortality, suggests methods to improve STZ-based experimental models and best utilize them for experimental studies purported to understand diabetes pathogenesis and preclinical evaluation of drugs.

Effects of warfarin and L-carnitine on hemostatic function and oxidative stress in streptozotocin-induced diabetic rats

Diabetes mellitus (DM) is a complex progressive disease characterized by hyperglycemia and a high risk of atherothrombotic disorders affecting the coronary, cerebral, and peripheral arterial trees. Oxidative stress is reported in diabetic patients. We investigated the hemostatic functions and oxidative stress in streptozotocin (STZ)-induced diabetic rats and the effects of warfarin and L-carnitine on those parameters. Forty male Sprague-Dawley rats were divided into four groups: control, DM, and DM received warfarin or L-carnitine. In all rats, blood glucose, insulin, hemoglobin A1c (HbA1c), fibrinogen, factor VII (FVII), plasminogen activator inhibitor-1 (PAI-1), fibrin degradation products (FDP), protein C, antithrombin III (ATIII), malondialdehydes (MDA), and antioxidants (superoxide dismutase, catalase, glutathione peroxidase, glutathione) were measured. Also, prothrombin time (PT), activated partial thromboplastin time (aPTT), coagulation time, and platelet aggregation were evaluated. In diabetic rats, plasma glucose, HbA1c, MDA, fibrinogen, FVII, FDP, PAI-1, and platelet aggregation increased while insulin, PT, aPTT, coagulation time, protein C, ATIII, and antioxidants decreased. Warfarin administration to diabetic rats decreased FVII and FDP and increased PT, aPTT, and coagulation time with no effect on MDA, antioxidants, PAI-1, protein C, ATIII, and platelet aggregation. On the other hand, L-carnitine decreased fibrinogen, FVII, FDP, PAI-1, MDA, and platelet aggregation and increased PT, aPTT, coagulation time, protein C, ATIII, and antioxidants in diabetic rats. Therefore, we concluded that hyperglycemia plays an important role in hypercoagulation state and oxidative stress in STZ-induced DM. While L-carnitine improves oxidative stress and decreases the hypercoagulation state in DM, warfarin normalizes the hypercoagulation state with no effect on oxidative stress.

Prenatal hyperandrogenization induces metabolic and endocrine alterations which depend on the levels of testosterone exposure

Prenatal hyperandrogenism is able to induce polycystic ovary syndrome (PCOS) in rats. The aim of the present study was to establish if the levels of prenatal testosterone may determine the extent of metabolic and endocrine alterations during the adult life. Pregnant Sprague Dawley rats were prenatally injected with either 2 or 5 mg free testosterone (groups T2 and T5 respectively) from day 16 to day 19 day of gestation. Female offspring from T2 and T5 displayed different phenotype of PCOS during adult life. Offspring from T2 showed hyperandrogenism, ovarian cysts and ovulatory cycles whereas those from T5 displayed hyperandrogenism, ovarian cysts and anovulatory cycles. Both group showed increased circulating glucose levels after the intraperitoneal glucose tolerance test (IPGTT; an evaluation of insulin resistance). IPGTT was higher in T5 rats and directly correlated with body weight at prepubertal age. However, the decrease in the body weight at prepubertal age was compensated during adult life. Although both groups showed enhanced ovarian steroidogenesis, it appears that the molecular mechanisms involved were different. The higher dose of testosterone enhanced the expression of both the protein that regulates cholesterol availability (the steroidogenic acute regulatory protein (StAR)) and the protein expression of the transcriptional factor: peroxisome proliferator-activated receptor gamma (PPAR gamma). Prenatal hyperandrogenization induced an anti-oxidant response that prevented a possible pro-oxidant status. The higher dose of testosterone induced a pro-inflammatory state in ovarian tissue mediated by increased levels of prostaglandin E (PG) and the protein expression of cyclooxygenase 2 (COX2, the limiting enzyme of PGs synthesis). In summary, our data show that the levels of testosterone prenatally injected modulate the uterine environment and that this, in turn, would be responsible for the endocrine and metabolic abnormalities and the phenotype of PCOS during the adult life.

Rutin Ameliorates Cyclophosphamide-induced Reproductive Toxicity in Male Rats

Cyclophosphamide (CYC) as an anticancer alkylating agent has been known as a male reproductive toxicant. This study was aimed to evaluate the protective effect of rutin (RUT) on CYC-induced reproductive toxicity. Sexually mature Wistar rats (weighing 199 ± 10 g with five animals in each group) were given CYC (15 mg/kg) and/or RUT (30 mg/kg) twice a week via gavage for 4 weeks. The sperm counts, sperm motility, sperm morphology, daily sperm production (DSP), testicular, and epididymal antioxidant systems: superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), glutathione reductase (GR), glutathione-S-transferase (GST), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), and testicular steroidogenic enzymes (3β-hydroxysteroid dehydrogenase and 17β-HSD and spermatogenesis marker enzymes (lactate dehydrogenase (LDH), sorbitol dehydrogenase (SDH), alkaline phosphatase (ALP), acid phosphatase (ACP) in the testes, epididymis and seminal vesicles were investigated at the end of the fourth week. By the end of the fourth week, RUT prevented lower sperm counts, sperm motility, DSP, and higher abnormal sperm numbers induced by CYC. In testes, RUT decreased SOD, LDH, and SDH and increased CAT, 3β-HSD, 17β-HSD, ALP, and ACP induced by CYC. In epididymis, RUT increased SOD, CAT, GSH, GSH-Px, GR, GST SDH, ALP and ACP and decreased MDA and LDH induced by CYC. In seminal vesicles, marker enzymes were unchanged in rats given CYC alone or in combination with RUT. It appears that RUT ameliorates CYC reproductive toxicity at the investigated dose.

Anal pressure in experimental diabetes

PURPOSE

Diabetes mellitus is a metabolic endocrine disorder that affects many systems, the gastrointestinal system often being among the affected systems. This experimental study work was designed to demonstrate altered anal sphincter pressures in an experimental model of diabetes mellitus (DM).

MATERIALS AND METHODS

Male Wistar rats (mean weight = 250 g) were used and randomized in two groups (n = 10): CO = control and DM. DM was induced by administering a single dose of streptozotocin. Glycemic levels were measured at the start (time = 0) and end (time = 60) of the experiment and anorectal manometry at the end.

RESULTS

DM rats presented a significant increase in glycemia at day 60 (DM = 407.14 +/- 73.76) as compared to the control group (time 0 = 175.7 +/- 18.62 and time 60 = 198.04 +/- 28.66). Anorectal manometry showed a significant decrease in anal pressure in the DM group at day 60 (DM = 34.2 +/- 4.97) as compared to the CO group at the same time (CO = 67.4 +/- 2.06), with P < 0.01 and P < 0.001 (Student's t test).

CONCLUSIONS

The results suggest that DM, due to the high glycemic levels, lead to alterations such as anal sphincter hypotony, which may cause complications such as fecal incontinence.

Leptin in embryos from control and diabetic rats during organogenesis: a modulator of nitric oxide production and lipid homeostasis

BACKGROUND

Leptin is involved in many metabolic and reproductive events and its levels are altered by the diabetic pathology. In this study, leptin concentrations and leptin effects on both nitric oxide (NO) and lipid concentrations were investigated in embryos from control and diabetic rats.

METHODS

Diabetes was induced by neonatal streptozotocin administration (90 mg/kg). Embryos from control and diabetic rats were obtained on days 10.5 and 13.5 of gestation, corresponding to early organogenesis and post-placentation periods respectively. Leptin was analysed by enzyme immunoanalysis and immunohistochemistry. Nitrates and nitrites were assessed as an index of NO production. Lipid concentrations were analysed by thin layer chromatography.

RESULTS

Leptin concentrations were decreased in embryos obtained from diabetic rats on days 10.5 and 13.5 of gestation when compared to controls. NO concentrations, elevated in diabetic embryopathy, were diminished in the presence of leptin in the embryos obtained from control and diabetic animals both during early organogenesis and after placentation. Leptin additions reduced phospholipid, cholesterol and cholesteryl ester concentrations in embryos obtained from diabetic rats during early organogenesis, although no leptin effects on lipid concentrations were observed in control embryos at this developmental stage. In embryos obtained on day 13.5 of gestation leptin additions reduced cholesteryl ester concentrations in controls, and diminished cholesteryl ester, triglycerides and phospholipids in embryos from diabetic rats.

CONCLUSIONS

We demonstrated that leptin plays a role in the regulation of NO concentrations and lipid homeostasis during embryo organogenesis and that the diabetic environment causes a reduction of leptin concentrations in rat embryos.

Pretreatment effect of resveratrol on streptozotocin-induced diabetes in rats

This study was planned to investigate the pretreatment effect of resveratrol on streptozotocin-induced diabetic rats. The control group consisted of 10 male albino Sprague-Dawley rats, 10-12 weeks of age, weighing approximately 295 g. The first experimental group consisted of 15 albino Sprague-Dawley rats, 10-12 weeks of age, weighing approximately 305 g. This group was administered streptozotocin (55 mg/kg, intraperitoneally). The second experimental group (n = 15) was administered resveratrol (0.5 ml/day) 10 days before streptozotocin induction. A training period was performed for all groups before the experimental procedure, and systolic arterial blood pressures and heart rates were recorded daily. At the end of the 10th day, blood samples of control and experimental groups were drawn. Total nitrite, nitrite, nitrate, malondialdehyde (MDA), copper, and zinc concentrations in plasma were measured both in control and experimental groups. Additionally, superoxide dismutase, catalase activities, and copper and zinc concentrations in red cell were determined in each group. At the end of the study, increases in catalase activity, nitric oxide level, and zinc concentrations and decreases in lipid peroxidation product MDA and copper concentrations were found in the resveratrol-pretreated diabetic group when compared to the diabetic group.

Diabetes mellitus and anal sphincter pressures: an experimental model in rats

PURPOSE

Symptoms of the gastrointestinal tract, frequent in patients with diabetes mellitus, which may be related to an increase in the production of free radicals, include alterations in the function of the sphincter anal musculature. Such alterations are characterized by a decrease of muscular tone associated with different degrees of fecal incontinence. This study was performed to show the alterations in the anal sphincter pressures of diabetic rats and to evaluate the role of nitric oxide and oxidative stress in this situation.

METHODS

Male Wistar rats weighing 250 to 400 g were used. The animals were divided in two groups: control and diabetic. Diabetes was induced through intraperitoneal injection of streptozotocin and the anal pressures were gauged by anorectal manometry. Nitric oxide was evaluated through measures of nitrites and nitrates, and oxidative stress through the technique of chemoluminescence.

RESULTS

There was a significant decrease in the sphincter anal pressure of diabetic animals 60 days after induction (P < 0.05). This pressure returned to basal values after administration of a nitric oxide synthase antagonist. The levels of nitrites and nitrates as well as of lipoperoxidation were significantly increased in the diabetic compared with the control group (P < 0.05).

CONCLUSIONS

In this study, hyperglycemia of diabetes mellitus caused an increase in the oxidative stress. Apparently the elevation of nitric oxide levels was one of the responsible factors for the decrease of anal sphincter pressures.

Nitric oxide synthase inhibition by L-NAME in streptozotocin induced diabetic rats: impacts on oxidative stress

The effects of nitric oxide synthase (NOS) inhibition by Nw-nitro-L-arginine methyl ester (L-NAME) administration on oxidative stress parameters were investigated in streptozotocin (STZ) induced diabetic rats. Lipid peroxidation as reflected by thiobarbituric acid reactive substances (TBARS) was insignificantly higher in diabetic rats. Plasma NO2+NO3 values (p < 0.05) and erythrocyte CuZn superoxide dismutase (CuZn SOD) and glutathione peroxidase (GSH Px) activities were significantly higher (p < 0.01, p < 0.001, respectively) in diabetic rats. L-NAME administration to diabetic rats caused significantly lower CuZn SOD and GSH Px activities (p < 0.01) and NO2+NO3 values (p < 0.001), whereas a significantly higher GSH level (p < 0.01). TBARS/GSH ratio was significantly higher in diabetic rats than controls (p < 0.05) and significantly lower in L-NAME administered diabetic rats than diabetic rats (p < 0.05). This experimental study highlightens the importance of NOS inhibition by L-NAME in the attenuation of oxidative stress in STZ diabetic rats.

Effect of Gosha-jinki-gan (Chinese herbal medicine: Niu-Che-Sen-Qi-Wan) on insulin resistance in streptozotocin-induced diabetic rats

Gosha-jinki-gan (GJG) is a Chinese herbal medicine that is known to be useful for the treatment of diabetic neuropathy. In the present study, the effect of GJG on insulin resistance in streptozotocin (STZ, 50 mgkg(-1) BW, i.v.) -induced diabetic rats was examined by means of the euglycemic clamp procedure. To accomplish this objective, diabetic and non-diabetic control rats were divided as follows: a single dose administration of GJG (800 mgkg(-1) BW, p.o.), saline (5 mlkg(-1) BW, p.o.), and GJG (p.o)+N(G)-monomethyl-L-arginine (L-NMMA, 1 mgkg(-1)min(-1) BW, i.v.). In diabetic rats, the incremental area (DeltaAUC [area under curve]) of the glucose metabolic clearance rate (MCR) during a 3.0 mUkg(-1)min(-1) insulin infusion rate was significantly higher in the GJG-administrated group compared to the saline-administrated one. On the other hand, the effect of GJG on the DeltaAUC of MCR in diabetic rats was abolished by L-NMMA. In addition, no significant differences in the DeltaAUC of MCR were observed in non-diabetic control rats. These results suggest that a single dose administration of GJG can improve the glucose utilization and insulin resistance in STZ-induced diabetic rats, probably via the nitric oxide (NO) pathway.

Streptozotocin-pancreatic damage in the rat: modulatory effect of 15-deoxy delta12,14-prostaglandin j(2) on nitridergic and prostanoid pathway

15-deoxy-delta (12,14)prostaglandin J(2) (15d-PGJ(2)) has been identified as a natural ligand of the PPARgamma subtype. PPAR activation in nonadipose tissues seems to inhibit iNOS and COX2 expression. Vasoactive compounds like nitric oxide and prostaglandins are increased in pancreatic tissue from streptozotocin-diabetic rats. We hypothesize that 15d-PGJ(2) may regulate the production of these proinflammatory compounds that lead to beta cell destruction in the diabetic pathology. In this work we evaluated Ca(2+)-dependent (cNOS) and Ca(2+)-independent (iNOS) activity, nitrate/nitrite levels, 15-dPGJ(2) and prostaglandin E(2) (PGE(2)) levels in isolated pancreatic islets, and 15d-PGJ(2) levels in plasma from control and streptozotocin-diabetic rats. Our results show that cNOS is predominant in control, while iNOS isoform is increased in the diabetic islets (P < 0.01). 15d-PGJ(2) 10(-5)M inhibits cNOS and iNOS activity both in control and diabetic islets (P < 0.05). Nitrate/nitrite and PGE(2) levels are higher in diabetic than in control islets (P < 0.05 and P < 0.01, respectively). 15d-PGJ(2) 10(-5)M decreases nitrate/nitrite and PGE(2) levels both in control and in diabetic islets. Bisphenol A diglycidyl ether (BADGE), a recently described PPARgamma antagonist, seems to act as a PPARgamma agonist, diminishing nitrate/nitrite and PGE2 levels in control and diabetic islets. 15d-PGJ(2) production is lower in islets from diabetic animals compared to control (P < 0.05). Our observations suggest that 15d-PGJ(2) is able to diminish the production of vasoactive proinflammatory agents in pancreatic islets. The diminished 15d-PGJ(2) levels in the diabetic islets are probably related to the diminished capacity to limit the inflammatory response due to experimental diabetes in the rat.