Axonal transport and tissue contents of substance P in rats with long-term streptozotocin-diabetes. Effects of the aldose reductase inhibitor ‘statil’

This study examined the axonal transport of substance P-like immunoreactivity (SPLI) and its content in dorsal root ganglion, trigeminal ganglion, stomach and ileum of non-diabetic rats and two groups of rats with streptozotocin-induced diabetes of 9 months duration. One diabetic group received the aldose reductase inhibitor ‘Statil’ throughout the period of study. To reduce morbidity all diabetic animals were given twice-weekly injections of a long-acting insulin which restricted weight loss but did not prevent regular and severe hyperglycaemia. Axonal transport of SPLI was studied by measurement of accumulation at 12 h ligatures on the left sciatic nerve. There were no differences between the 3 groups either in the calculated anterograde and retrograde mean rates of accumulation (ranges 6.0 to 7.6 and 0.38 to 0.72 mm/h respectively) or mobile fractions of SPLI (means from 0.54 to 0.58). There were, however, marked reductions in anterograde and retrograde accumulations of SPLI in the constricted nerves of the ‘untreated’ diabetics (respectively 57 and 33% of controls;P < 0.01 for both). In the ‘Statil’-treated rats these deficits were attenuated (80 and 75% of controls). Diabetes also reduced the SPLI content of unligated sciatic nerve and trigeminal ganglion (65 and 75% of controls). ‘Statil’ prevented the deficit in the ganglion, but not in the nerve. ‘Statil’ treatment prevented themyo-inositol depletion and attenuated the sorbitol and fructose accumulation seen in the sciatic nerves of the untreated diabetic animals suggesting effective inhibition of aldose reductase in this tissue. The total SPLI content of the stomach and 1-cm segments of ileum were unaltered in the diabetic animals but due to the increased weights of these tissues the SPLI content per unit weight was reduced. These changes were unaffected by ‘Statil’.     

Cystometric changes in the early phase of streptozotocin-induced diabetes in rats: evidence for sensory changes not correlated to diabetic neuropathy

Summary 1. The effect of streptozotocin (STZ) induced diabetes on rat urinary bladder function was investigated by means of in vivo cystometry and in vitro recording of bladder strips contractility. A group of sucrose-fed animals was included to determine to what extent the STZ-induced changes were ascribable to the increased diuresis. 2. After 7–9 weeks from STZ injection there was a marked increase in weight of bladder and ureters. Cystometry revealed a marked increase in bladder capacity (volume threshold) although pressure threshold and amplitude of micturition contraction were unaffected. Sucrose-fed animals, having normal blood glucose levels but a similar increase in urine production exhibited cystometric changes identical to those of STZ animals. 3. In vitro experiments indicated that the response to field stimulation (0.1–20 Hz) is reduced in STZ-pretreated but increased in sucrose-fed animals, as compared to controls. 4. The content of urinary bladder and ureters in sensory neuropeptides (substance-P, neurokinin-A and calcitonin-gene related peptide-like immunoreactivity) was increased by STZ diabetes when values were corrected for the increased weight of these organs. 5. The capsaicin-induced contraction of the rat isolated bladder strips, presumably caused by neuropeptides released from intramural sensory nerves, is unaffected by STZ diabetes. 6. These findings indicate that STZ diabetes produces, at an early stage, changes similar to those reported to occur in the human disease, e. g. a greater bladder capacity with unimpaired voiding function. The increased bladder capacity of STZ-rats seems largely, if not solely, ascribable to changes in physical properties of the detrusor muscle, thereby allowing accomodation of greater than normal volumes with similar increase of intraluminal pressure. No sign of diabetic neuropathy of the capsaicin-sensitive sensory nerves can be observed at this stage (7–9 weeks) of STZ diabetes. Send offprint requests to P. Santicioli at the above address     

Comparison of in situ hybridization and immunocytochemistry for the detection of residual beta cells in the pancreas of streptozotocin-treated diabetic rats

The relative efficacy of immunocytochemistry versus in situ hybridization in identifying residual beta cells was studied in rats with streptozotocin-induced diabetes. Consecutive sections of pancreas of streptozotocin-treated diabetic rats and control animals were alternately subjected to in situ hybridization (synthetic oligonucleotides complementary to rat preproinsulin mRNA) and immunocytochemistry (monoclonal antibodies to insulin). The results obtained with both methods were quantitated with the use of computer-assisted image analysis, and the ratio of cells positive by immunocytochemistry to those positive by in situ hybridization was determined. Under normoglycaemic conditions the values obtained by immunocytochemistry correlated well with those obtained by in situ hybridization (immuno/in situ > 95%). In the streptozotocin diabetic animals, however, immunocytochemistry resulted in a distinct underestimation of the number of residual beta cells (immuno/in situ < 80%). This difference was even more striking in small islet cell clusters (<100 m) immuno/in situ 20%). These results suggest that in situ hybridization for prohormone mRNA is the method of choice for the identification of residual or regenerating beta cells with very low insulin content. Caution should be used when interpreting quantitative data in diabetic conditions that are based exclusively on immunocytochemical detection methods.     

Oxidative stress and HNE conjugation of GLUT3 are increased in the hippocampus of diabetic rats subjected to stress

Recent studies demonstrate that cellular, molecular and morphological changes induced by stress in rats are accelerated when there is a pre-existing strain upon their already compromised adaptive responses to internal or external stimuli, such as may occur with uncontrolled diabetes mellitus. The deleterious actions of diabetes and stress may increase oxidative stress in the brain, leading to increases in neuronal vulnerability. In an attempt to determine if stress, diabetes or stress+diabetes increases oxidative stress in the hippocampus, radioimmunocytochemistry was performed using polyclonal antisera that recognize proteins conjugated by the lipid peroxidation product 4-hydroxy-2-nonenal (HNE). Radioimmunocytochemistry revealed that HNE protein conjugation is increased in all subregions of the hippocampus of streptozotocin (STZ) diabetic rats, rats subjected to restraint stress and STZ diabetic rats subjected to stress. Such increases were not significant in the cortex. Because increases in oxidative stress may contribute to stress- and diabetes-mediated decreases in hippocampal neuronal glucose utilization, we examined the stress/diabetes mediated HNE protein conjugation of the neuron specific glucose transporter, GLUT3. GLUT3 immunoprecipitated from hippocampal membranes of diabetic rats subjected to stress exhibited significant increases in HNE immunolabeling compared to control rats, suggesting that HNE protein conjugation of GLUT3 contributes to decreases in neuronal glucose utilization observed during diabetes and exposure to stress. Collectively, these results demonstrate that the hippocampus is vulnerable to increases in oxidative stress produced by diabetes and stress. In addition, increases in HNE protein conjugation of GLUT3 provide a potential mechanism for stress- and diabetes-mediated decreases in hippocampal neuronal glucose utilization.     

Acute hyperglycemia attenuates nerve conduction velocity and nerve blood flow in male Sprague–Dawley rats: reversal by adenosine

Hyperglycemia is implicated to play a major role in development of diabetic neuropathy. Since most of the diabetics are hyperglycemic much before they develop full-blown diabetes, we felt, it would be very important to know the effects of acute hyperglycemia on nerve function so that early pathophysiological events could be understood and appropriate therapeutic intervention can be made. Moreover, effect of acute hyperglycemia on motor nerve conduction velocity (MNCV) and nerve blood flow (NBF) is not known. Hence, we studied the effects of acute hyperglycemia on sciatic MNCV and sciatic NBF in healthy male Sprague-Dawley (SD) rats. Three different animal models of acute hyperglycemia (50% glucose (3 g kg(-1), i.v. (intra-venous) or i.p. (intra-peritoneally)) or 24 h post-streptozotocin (STZ) injected rats were used. Acute hyperglycemia but not mannitol or sucrose significantly attenuated MNCV and NBF. Adenosine (10 mg kg(-1), i.p.) prevented the acute hyperglycemia-induced attenuation of MNCV and NBF in all the three rat models of acute hyperglycemia. Adenosine effects were blocked by theophylline (50 mg kg(-1), i.p.) suggesting the role of adenosinergic receptor mediated mechanisms in acute hyperglycemia-induced neuropathy. Acute glucose administration in 8 weeks, STZ diabetic rats did not further affect MNCV or NBF. Adenosine (10 mg kg(-1), i.p.) did not produce any adverse effects on the blood pressure and heart rate. From the results, we conclude that acute hyperglycemia attenuates MNCV and NBF via an adenosinergic receptor-dependent mechanism.     

Antidiabetic and Anti-oxidative Effects of Honokiol on Diabetic Rats Induced by High-fat Diet and Streptozotocin

Objective To study the antidiabetic and anti-oxidative effects of honokiol(Hon)in Magnolia officinalis and its underlying molecular mechanism in diabetic rats induced by high-fat diet(HFD)and streptozotocin(STZ).Methods After ig administration with Hon[25,50,and 100 mg/(kg·d)]to diabetic rats for consecutive 10 weeks,the levels of blood glucose(BG),oral glucose tolerance(OGT),blood lipids including total cholesterol(TC),triglyceride(TG),high density lipoprotein-cholesterol(HDL-C),and low density lipoprotein-cholesterol(LDL-C),hepatic oxidative stress including the activities of superoxide dismutase(SOD),catalase(CAT),glutathione peroxidase(GSH-Px),methane dicarboxylic aldehyde(MDA),and cytochrome P4502E1(CYP2E1)in diabetic rats were measured.Results Compared to the diabetic control rats,ig administration of Hon resulted in significant decrease in BG,TC,TG,and LDL-C levels in serum,as well as hepatic CYP2E1 activity and MDA content in diabetic rats,whereas the level of OGT and activities of hepatic CAT,SOD,and GSH-Px in diabetic rats were significantly increased.Conclusion Hon could alleviate hyperglycemia,hyperlipemia,hepatic oxidative damage,and insulin resistance in diabetic rats by inhibiting hepatic CYP2E1 activity.     

Decreased muscarinic M1 receptor gene expression in the cerebral cortex of streptozotocin-induced diabetic rats and Aegle marmelose leaf extract's therapeutic function

AIM: In the present study we have investigated the changes in the total muscarinic and muscarinic M1 receptor ([(3)H]QNB) binding and gene expression in the cerebral cortex of streptozotocin (STZ) induced diabetic, insulin and aqueous extract of Aegle marmelose leaf treated diabetic rats. MATERIALS AND METHODS: Diabetes was induced in rats by intrafemoral injection of streptozotocin. Aegle marmelose leaves was given orally to one group of rats at a dosage of 1g/kg body weight per day for fourteen days. Blood glucose and plasma insulin level were measured. Muscarinic and Muscarinic M1 receptor binding studies were done in the cerebral cortex of experimental rats. Muscarinic M1 receptor gene expression was studied using real-time PCR. RESULTS: Scatchard analysis for total muscarinic receptors in cerebral cortex showed that the B(max) was decreased significantly (p<0.001) in diabetic rats with a significant decrease (p<0.01) in the K(d) when compared to control group. Binding analysis of Muscarinic M1 receptors showed that B(max) was decreased significantly (p<0.001) in diabetic group when compared to control group. The K(d) also decreased significantly (p<0.01) when compared to control group. The binding parameters were reversed to near control by the treatment of diabetic rats with Aegle marmelose. Real-Time PCR analysis also showed a similar change in the mRNA levels of muscarinic M1 receptors. CONCLUSION: The results showed that there is decrease in total muscarinic and muscarinic M1 receptors during diabetes which is up regulated by insulin and Aegle marmelose leaf extract treatment. This has clinical significance in therapeutic management of diabetes.     

Antidiabetic effect of alcoholic extract of Caralluma sinaica L. on streptozotocin-induced diabetic rabbits

People of Asir region of Saudi Arabia chew Caralluma sinaica (CS) to lower glucose level. To establish its utility in diabetes mellitus we have under taken this study. The effect of CS on streptozotocin (STZ)-induced diabetic model as well as effect on oral glucose tolerance test were studied. The extract was shown to have positive test for possessing following chemical constituents like phenolic alkaloids, glycosides, flavonoids, coumarins, steroids and tannins. Administration of CS in different doses (50, 100, 150 and 200mg/kg, p.o.) to normal animals caused significant (P<0.01) decrease in glucose level. Prior administration of either CS (100mg/kg, p.o.) or glibenclamide (GB) (5mg/kg, p.o.) blocked the rise of glucose caused by the streptozotocin. Antidiabetic activity of CS was compared with clinically available drug GB. Administration of CS (100mg/kg, p.o.) to diabetic rabbits for 30 days has been shown to decrease plasma glucose level to almost normal level (P<0.001). Liver and kidney weight expressed as percentage of body weight significantly (P<0.05; P<0.01) increased in diabetic rabbits versus normal control (CNT). CS significantly (P<0.05) reversed the increasing weight of liver caused by STZ but not GB. STZ induced lowering of glycogen content of liver and muscle was reversed by both CS and GB. STZ induced a significant (P<0.001) increase in renal glycogen content this was almost normalized by CS (P<0.001) whereas GB significantly decreased (P<0.002) glycogen content. In oral glucose tolerance test administration of glucose increased plasma glucose level significantly in the diabetic control over the 2-h period. Compared to diabetic control plasma glucose levels in rabbits given CS or GB were significantly lower at all the time points that blood was sampled after oral glucose load. Comparing with the GB treatment blood glucose lowering effect was more pronounced for diabetic rabbits given CS. All these effects could explain the basis for use of this plant extract to manage diabetes mellitus.     

巴马小型猪1型糖尿病模型胰腺病理及生化指标的变化

目的 探讨腹腔多次注射链脲佐菌素(STZ)对巴马小型猪糖尿病胰腺病理学及生化指标的影响,为糖尿病相关研究提供安全稳定的动物模型。方法 选用健康雄性巴马小型猪12只,分为正常对照组(n=6)和糖尿病模型组(n=6)。糖尿病模型组腹腔注射STZ,第一次腹腔注射STZ 75 mg/kg,1周后第二次腹腔注射STZ 150 mg/kg,正常对照组注射等量柠檬酸钠溶液,动态监测2组小型猪空腹血糖;实验结束后行葡萄糖耐量试验(OGTT)、胰岛素释放试验(IRT)及胰腺组织病理学检查、胰岛β细胞免疫组化染色分析。结果 ①糖尿病模型组所有小型猪均造模成功,成模后均表现多尿、多饮、多食及体质量减轻“三多一少”的症状;②自链脲佐菌素给药后13 d开始,糖尿病模型组空腹血糖明显升高并稳定在(7.6~17.1)mmol/L水平;③造模成功1周后,糖尿病模型组OGTT各时点血糖水平均高于正常对照组(P<0.01),IRT各时点胰岛素水平均低于正常对照组(P<0.01);④糖尿病模型组胰腺组织病理学检查结果显示,胰岛细胞团及胰岛β细胞数目明显减少;⑤胰岛β细胞免疫组化结果提示,糖尿病模型组胰岛中胰岛素染色阳性面积显著低于正常对照组[(10.68±2.78)% vs (43.63±2.83)%, P<0.01]。结论 采用腹腔多次注射STZ可成功构建巴马小型猪1型糖尿病(T1DM)模型,该方法操作简单、成模率高、安全性强,是比较理想的制备小型猪T1DM模型的造模方法。     

Wound healing effect of flavonoid rich fraction and luteolin isolated from Martynia annua Linn. on streptozotocin induced diabetic rats

ObjectiveTo evaluate wound healing potential of flavonoid fractions of Martynia annua (M. annua) Linn. leaves in diabetic rats on the basis of folkloric information and preliminary study.MethodsThe flavonoid compound luteolin and apigenin were isolated from dried leaves of plant by column chromatography. The two concentrations (0.2% and 0.5% w/w) of luteolin and flavonoid fraction were selected for topically applied as ointment on diabetic wound. The Povidone Iodine Ointment USP was used as a reference. On 18th days, protein content, hydroxyproline and antioxidants (SOD, CAT and GSH) level in granuloma tissues were determined.ResultsThe results showed that, percent wound contraction were observed significantly (P<0.01) greater in MAF fraction and 0.5% w/w of luteolin treatment groups. Presence of matured collagen fibres and fibroblasts with better angiogenesis were observed in histopathological studies.ConclusionsIn conclusion, our findings suggest that flavonoid fraction (MAF) and luteolin (0.5% w/w) may have potential benefit in enhancing wound healing in diabetic condition, possibly due to free-radical scavenging activity of plant.