Cortex Of Diabetic Rats Research Articles

The Possible Effect of Grape Seed Extract on the Adrenal Cortex in Streptozotocin-Induced Diabetes in Male Albino Rats: A Histological Study

Abstract Introduction Induction of diabetes in rat models injected with streptozotocin (STZ) had led to increase activity of the hypothalamic-pituitary-adrenal (HPA) axis accompanied with hypercortisolism and adrenocortical growth. Proanthocyanidin, a grape seed extract (GSE) that was observed to have beneficial effect on different metabolic and inflammatory diseases. Aim To study the structural changes of the adrenal cortex in diabetic rats and the beneficial effect of GSE on the suprarenal cortical injury. Materials and methods 35 adult male albino rats were divided randomly into 4 groups. Group I (control). Group II (GSE), rats received GSE orally (200 mg/kg), daily for 21 days. Group III (STZ), rats were injected with STZ (40 mg/kg) given intraperitoneal once. Group IV (STZ + GSE), rats received STZ as in group III. After rats confirmed to be diabetic, they were treated with GSE as in group II. After 21 days, the adrenal glands from all groups were dissected and processed for light microscopic examination. Morphometric and statistical analysis were also done. Results H&E stained section of Group III (STZ) showed increase in the capsular thickness and congested blood capillaries. Both zona glomerulosa & zona fasciculata showed increased thickness with some cells appeared with vacuolated acidophilic cytoplasm while others were shrunken with closely packed pyknotic nuclei. Inflammatory cells infiltration was also observed. Moreover, silver stain showed focal significant increase in thickness of the capsule, dense trabeculae and dense irregular reticular fibers of the cortex. Meanwhile, immunohistochemical results showed significant increase in the reaction for caspase 3 antibodies. Group IV (STZ + GSE) showed restoration of the cortical structure & organization nearly similar to that of control group. Conclusion It can be considered that GSE might have a protective effect on the structure of diabetic rats’ adrenal gland.

N-Acetylcysteine Attenuates Hyperalgesia in Rats with Diabetic Neuropathic Pain: Role of Oxidative Stress and Inflammatory Mediators and CXCR4

Objectives. CXCR4 plays critical roles in the development of diabetic neuropathic pain (DNP) in rats, and its mechanism is unknown. This study was aimed at evaluating the potential therapeutic value of the antioxidant N-acetylcysteine (NAC) against DNP in rats and how CXCR4 participates in the formation of DNP. Methods. Control or streptozotocin- (STZ-) induced diabetic Sprague-Dawley rats received vehicle or NAC for four weeks starting one week after STZ injection. Von Frey and Hargreaves Apparatus were used to analyze the behavioral changes of mechanical allodynia and heat hyperalgesia. CXCR4, p-CXCR4, interleukin- (IL-) 6, and tumor necrosis factor- (TNF-) α in the spinal cord and the prefrontal cortex were detected by western blotting. Plasma IL-6, TNF-α, superoxide dismutase- (SOD-) 1, SOD-2, and lipid peroxidation products malondialdehyde (MDA) and 15-F2t-Isoprostane were detected by ELISA. Results. The values of paw withdrawal threshold (PWT) and paw withdrawal latencies (PWL) were reduced in diabetic rats compared to control rats that were concomitant with significant increases of CXCR4, p-CXCR4, IL-6, and TNF-α protein expressions in the spinal cord and prefrontal cortex. The treatment with NAC decreased the IL-6 and TNF-α protein expression and further increased CXCR4 and p-CXCR4 in the spinal cord and the cortex of diabetic rats that were accompanied with enhancement of PWT and PWL. NAC also significantly attenuated or reverted the increases of plasma IL-6, TNF-α, SOD-1, SOD-2, MDA, and 15-F2t-Isoprostane in diabetic rats. Conclusion. It is concluded that NAC treatment could effectively alleviate DNP and that induction of CXCR4 and p-CXCR4 may represent a mechanism whereby NAC attenuates DNP.

Histomorphometric and immunohistochemical evaluation of the frontal cerebral cortex in diabetic rats after treatment with melatonin

ABSTRACT: The central nervous system is vulnerable to complications caused by diabetes. These complications lead to increased oxidative stress in the brain, resulting in damage to the cerebral cortex, among other regions. Insulin and hypoglycemic agents are still the most widely used treatments. However, current research with an experimental model of diabetes suggests the use of antioxidants, such as melatonin. Thus, we tested the hypothesis that exogenous melatonin may decrease or prevent the effects of diabetes in the frontal cortex of the rat brain. Fifty albino rats were allocated into five groups: GC = rats without diabetes induction, GD = diabetic rats induced by streptozotocin, GDM = streptozotocin-induced and melatonin-treated diabetic rats, GDI = diabetic rats induced by streptozotocin and treated with insulin, GDMI = diabetic rats induced by streptozotocin and treated with melatonin and insulin simultaneously. Diabetes was induced by intraperitoneal administration of streptozotocin (60mg/kg). Insulin (5U/day) was administered subcutaneously and melatonin (10mg/kg) by drinking water; both treatments last days after. We analyzed animals’ weight, the cytokines IL-6 and TNF-α, apoptosis, glycogen, and did morphometry and histopathology of the frontal cortex were analyzed. The results showed that the cerebral cortex of the diabetic animals presented axonal degeneration, reduced number of neurons in the cortex, reduced glycogen, increased IL-6 and TNF-α expression, high apoptotic index, and reduced animal weight and the brain. Treatment with melatonin associated or not with insulin prevented such effects. Thus, we conclude that melatonin associated with insulin may be an alternative for avoiding the impact of diabetes in the brain’s frontal cortex.

Fish oil supplementation attenuates cognitive impairment by inhibiting neuroinflammation in STZ-induced diabetic rats.

Type 2 diabetes mellitus (T2DM) markedly impairs human health. During T2DM development, some patients experience cognitive dysfunction and behavioral deficits, which are characterized by neuronal injury and memory loss. It has been reported that the incidence of dementia in middle-aged and elderly patients with diabetes is significantly higher than that in normal elderly patients. Currently, the pathogenesis of cognitive dysfunction in diabetes remains unknown, and there is no standard or specific method to diagnose the disease in clinical practice. Evidence has shown that fish oil (FO) can alleviate depressive-like behaviors by attenuating neuroinflammation in a rat model, and improve cognitive dysfunction by inhibiting apoptosis. Therefore, it is reasonable to speculate that FO may reduce cognitive impairment by attenuating neuroinflammation in diabetic rats. In the present study, we investigated the effects of FO supplementation on cognitive dysfunction in a streptozotocin-induced diabetic rat model. FO administration for 10 weeks improved spatial learning and memory as evaluated by performance in the Morris water maze (MWM). Besides, FO significantly improved the morphology of neurons in the hippocampus and cortex of diabetic rats and reduced the neuronal nuclear condensation. Moreover, FO decreased the mRNA expression of IL-1β, IL -6, and TNF-α and increased the mRNA expression of IL-4 and IL-10 in the cortex and hippocampus. FO also attenuated the brain inflammatory cascade and simultaneously reduced diabetes-induced oxidative stress. In addition, FO increased the protein expression of Nrf2 and HO-1 in cortex and hippocampus of diabetic rats. These results provide a novel horizon for the study of neuroprotective effect of FO and further clarify the connections among inflammation, oxidative stress and diabetes-induced cognitive impairment.

Changes in the levels of 12/15-lipoxygenase, apoptosis-related proteins and inflammatory factors in the cortex of diabetic rats and the neuroprotection of baicalein

This study was designed to investigate the neuroprotective effects of baicalein and the effect of the cortical 12/15-lipoxygenase (12/15-LOX) pathway on diabetic cognitive dysfunction. Our results showed that spatial learning and memory ability, as well as cortex neurons, were significantly impaired after the onset of diabetes. The fasting blood glucose and random blood glucose levels in the model group were significantly higher than those in the normal group. The levels of TG and TC in the plasma of the model group were significantly increased, but there was no significant difference in the LDL level. The insulin content in the plasma of diabetic rats was significantly lower than that of the normal group. The levels of inflammatory factors and 12(S)-HETE were significantly increased in diabetic rats, as were the protein expression levels of cPLA2, 12/15-LOX, p38MAPK, phospho-p38MAPK, caspase-3, caspase-9 and Aβ1–42; by contrast, protein expression of Bcl-2 was significantly decreased. Administration of baicalein was shown to improve the spatial learning and memory ability and significantly decrease the levels of inflammatory cytokines. However, baicalein did not significantly influence the levels of blood glucose, lipids or insulin in rats. Baicalein treatment significantly protected diabetes rats from neuron death; significantly attenuated the overexpression of cPLA2, 12/15-LOX, p38MAPK, phospho-p38MAPK, caspase-3, caspase-9 and Aβ1–42; and upregulated the expression of Bcl-2. These findings suggest that baicalein improves the cognitive function of diabetic rats by directly acting in the brain rather than by regulating the levels of blood glucose, lipids or insulin. In addition, baicalein can protect rat cortical neurons from damage caused by diabetes via inhibiting the 12/15-LOX pathway and relieving inflammation and apoptosis of the central nervous system.

The role of TGF-β1/SGK1 signaling pathway in diabetic nephropathy

Objective To explore the role of transforming growth factor-β1/serum and glucocorticoid induced kinase 1 (TGF-β1/SGK1) signaling pathway in diabetic nephropathy (DN). Methods Totally 60 clean grade healthy male Sprague-Dawley (SD) rats were divided into normal control (Con group, n=20) and diabetic model group (diabetic group, n=40). Type 2 diabetic animal model was induced by intraperitoneal injection of streptozotocin (STZ, 45 mg/kg) to SD rats. Half of rats in each group were sacrificed after implemented for 4 weeks and 8 weeks, respectively. Fasting glucose, serum urea and creatinine, as well as urine protein in 24 h were detected. Pathological changes of rats' kidney cortex tissue were examined by hematoxylin-eosin staining. The expression of SGK1 was detected by immunohistochemistry in renal tissue. The mRNA level of SGK1 was analyzed by real-time polymerase chain reaction (PCR). The protein expression of TGF-β1 and SGK1 were determined by Western blotting. Results Compared to the control group, the blood glucose of the diabetic group rats was significantly increased, kidney hypertrophy index, serum urea and creatinine, 24 h urine volume and urinary microalbumin as well as kidney index were significantly higher (P<0.05). The mRNA expressed of SGK1, protein expression of TGF-β1 and SGK1 were also increased obviously in the renal cortex of diabetic rats (all P<0.05 vs Control). Conclusions TGF-β1/SGK1 signaling pathway is closely related to the TIF damage of kidney cortex in diabetic rats. Key words: Transforming growth factor beta/ME; Protein kinases/ME; Diabetic nephropathies/ME

Metabolic profile of visual cortex in diabetic rats measured with in vivo proton MRS.

The purpose of the present study was to characterize the metabolic profile of the visual cortex in streptozotocin-induced Type 1 diabetic rats by means of in vivo proton MRS. Several metabolite concentration ratios in the visual cortex were calculated. In addition, postmortem histologic analyses for retinal ganglion cell (RGC) loss, optic nerve injury and visual cortex alterations were monitored. The results showed that diabetes induced several changes in visual cortex metabolites, such as reduced N-acetylaspartate, glutamate, γ-aminobutyric acid, taurine and choline-containing compound levels. Nevertheless, myo-inositol levels increased significantly as compared with controls. Remarkable RGC loss and optic nerve degeneration were observed by morphological analysis. Moreover, the results showed significant neuronal loss and glial activation in the visual cortex. These findings indicated that, besides vascular abnormalities, neuronal loss and degeneration in the visual pathway were induced due to disrupted glucose homeostasis in diabetes. Metabolic or functional abnormalities were induced in cerebral neurons of the visual cortex by diabetes.

Cerebral Ketone Body Oxidation Is Facilitated by a High Fat Diet Enriched with Advanced Glycation End Products in Normal and Diabetic Rats

Diabetes mellitus (DM) causes important modifications in the availability and use of different energy substrates in various organs and tissues. Similarly, dietary manipulations such as high fat diets also affect systemic energy metabolism. However, how the brain adapts to these situations remains unclear. To investigate these issues, control and alloxan-induced type I diabetic rats were fed either a standard or a high fat diet enriched with advanced glycation end products (AGEs) (HAGE diet). The HAGE diet increased their levels of blood ketone bodies, and this effect was exacerbated by DM induction. To determine the effects of diet and/or DM induction on key cerebral bioenergetic parameters, both ketone bodies (β-hydroxybutyric acid) and lactate oxidation were measured. In parallel, the expression of Monocarboxylate Transporter 1 (MCT1) and 2 (MCT2) isoforms in hippocampal and cortical slices from rats submitted to these diets was assessed. Ketone body oxidation increased while lactate oxidation decreased in hippocampal and cortical slices in both control and diabetic rats fed a HAGE diet. In parallel, the expression of both MCT1 and MCT2 increased only in the cerebral cortex in diabetic rats fed a HAGE diet. These results suggest a shift in the preferential cerebral energy substrate utilization in favor of ketone bodies in animals fed a HAGE diet, an effect that, in DM animals, is accompanied by the enhanced expression of the related transporters.

Effect of green tea on the ultrastructure of the zona glomerulosa of the adrenal cortex in diabetic rats

Introduction Green tea is reported to have hypoglycemic effect on diabetic rats. However, studies about its effect on the structure of the zona glomerulosa of the adrenal cortex are limited. Aim This work aimed at studying the ultrastructural changes induced by green tea on the zona glomerulosa of the adrenal cortex in diabetic rats. Materials and methods Forty adult male Wistar albino rats were divided into four groups of 10 each: group I was the control group; group II received green tea extract at a dose of 300 mg/kg/day intragastrically; group III included rats with streptozotocin (STZ)-induced diabetes; and group IV received green tea extract after inducing diabetes. Rats were sacrificed after 12 weeks, and the adrenal glands were processed for semithin and ultrathin sections. Plasma level of aldosterone, total thickness of both the adrenal cortex and the zona glomerulosa, volume of both mitochondrial and lipid droplet, and surface area of mitochondrial cristae and smooth endoplasmic reticulum were measured. Results STZ-induced diabetes resulted in a significant decrease in body weight and serum aldosterone level and a significant increase in adrenal weight and thickness and thickness of the zona glomerulosa compared with the other groups. Zona glomerulosa cells in STZ-induced diabetic rats showed a significant increase in the number and size of lipid droplets and degenerated mitochondria. In addition, STZ-induced diabetes resulted in a significant decrease in volume of mitochondrial droplet, surface area of mitochondrial cristae, and surface area of smooth endoplasmic reticulum, as well as a significant increase in the volume of lipid droplet compared with the other groups. The green tea-treated diabetic rat group showed a significant increase in body weight, a significant decrease in adrenal weight, a significant increase in aldosterone level in serum, and decrease in the thickness of the adrenal cortex and the zona glomerulosa compared with the diabetic group. The ultrastructure of the zona glomerulosa was nearly similar to that of the control group. Conclusion Green tea extract administration improved the biochemical and ultrastructural changes induced by diabetes in the zona glomerulosa.

Correlativity between blood measures related to blood stasis blocking collaterals and gene expression of angiotensin-converting enzyme of renal cortex in diabetic rats and effect of stasis removing and collaterals dredging

ObjectiveTo investigate the correlativity between the changes of blood measures related to blood stasis blocking collaterals and gene expression levels of angiotensin-converting enzyme (ACE) and ACE2 ofrenal cortex in diabetic rats with stasis blocking collaterals syndrome, as well as the effectof stasis removing and collaterals dredging. MethodsMale Sprague-Dawley rats were divided randomly into normal control group (C group), high-carbohydrate-fat control group (H group) and streptozotocin (STZ)-injecting group. The diabeti-crats were induced from rats in the STZ-injecting groupby high-carbohydrate-fat diet combined with STZ intraperitoneal injection, with sustained high-carbohydrate-fat diet fed afterwards, and were further divided into model group (M group) and Chinese medicine of stasis removing and collaterals dredging group (Z group). Rats in the Z group were fed with stasis-removing-and-collaterals-dredging herbal granule suspension intragastrically daily for 16 weeks, while drinking water of corresponding volume was administrated to the rats in other groups. At the end of the 16th week after successful establishment of models, the ultrastructures of glomeruli in different groups were detected by a transmission electron microscopy; and blood measures related to blood stasis blocking collaterals, including lipid profile and blood viscosity measures, were tested, as well as the relative gene expressions of ACE and ACE2. ResultsChanges in ultrastructures of glomeruli in the M group were characterized by lack of clarity in structure and occasional thickening of glomerular basement membrane and extensive fusion in foot processes. The correlation analysis showed that there were positive correlations between lipid profile, blood viscosity, and the ACE mRNA expression levels in the M group (P<0.05), except for cholesterol. And except for triglyceride, the blood measures were in negative correlation with the ACE2 mRNA expression levels in the M group (P<0.05). Compared with the C and H groups, the lipid profile, plasma viscosity and blood viscosity were significantly higher (P<0.01). All the above-mentioned measures were significantly improved in the Z group rats (P<0.05). ACE mRNA expression was significantly higher in the M group thanin the C group (P<0.05). ACE2 mRNA level was significantly lower in the M group than in the C and H groups (P<0.01); and its levelin the Z group was higher than that in the M group (P<0.01). ConclusionBlood measuresrelated to blood stasis blocking collaterals had positive linear correlations with ACE mRNAexpression and negative linear correlations with ACE2 mRNA expression in the M group. Chinese recipe of stasis removing and collaterals dredging could play a renal protecting role for diabetic rats by reducing lipid profile and blood viscosity, down-regulating ACE mRNA expression and up-regulating ACE2 mRNA expression.

Amelioration of Diabetes-induced Cognitive Deficits by GSK-3β Inhibition is Attributed to Modulation of Neurotransmitters and Neuroinflammation

Chronic type 2 diabetes (T2D) causes cognitive deficits which are debilitating to the young as well as the older population. Glycogen synthase kinase-3β (GSK-3β) signaling has been reported to be impaired in insulin-resistant and T2D animal models. In this study, we have investigated the involvement of GSK-3β in cognitive deficits associated with T2D using SB216763, a GSK-3 β inhibitor. In high-fat diet-streptozotocin (HFD-STZ) model of T2D in rats, cognitive deficits appeared on the 15th week after induction of diabetes. Treatment with GSK-3β inhibitor SB216763 (i.p. daily for 3weeks) reversed impaired cognitive performance in the Morris water maze, Y-maze, and passive avoidance tests. Administration of SB216763 also significantly improved acetylcholine esterase activity, GABA, and glutamate levels in the hippocampus and cortex of diabetic rats. Importantly, GSK-3β inhibition showed an increase in pGSK-3β and pCREB expression and reduction in pNF-κB-p65 expression in both hippocampus and cortex. Neuroinflammation was reduced by SB216763 in diabetic rats as evident from reduction in IL-6, TNF-α, COX-2, and inducible nitric oxide synthase levels. This study suggests that cognitive deficits associated with diabetes involved intricate compartmental interaction between transcription factors and neurotransmitter homeostasis/energy metabolism, and GSK-β might play a central role in diabetes-induced cognitive impairment.

Increased expression of receptor for advanced glycation end-products worsens focal brain ischemia in diabetic rats.

A rat model of diabetes mellitus was induced by a high fat diet, followed by focal brain ischemia induced using the thread method after 0.5 month. Immunohistochemistry showed that expression of receptor for advanced glycation end-products was higher in the ischemic cortex of diabetic rats compared with non-diabetic rats with brain ischemia. Western blot assay revealed increased phosphorylated c-Jun N-terminal kinase expression, and unchanged phosphorylated extracellular signal-regulated protein kinase protein expression in the ischemic cortex of diabetic rats compared with non-diabetic rats with brain ischemia. Additionally, phosphorylated p38 mitogen-activated protein kinase protein was not detected in any rats in the two groups. Severity of limb hemiplegia was worse in diabetic rats with brain ischemia compared with ischemia alone rats. The results suggest that increased expression of receptor for advanced glycation end-products can further activate the c-Jun N-terminal kinase pathway in mitogen-activated protein kinase, thereby worsening brain injury associated with focal brain ischemia in diabetic rats.

Impaired expression and function of breast cancer resistance protein (Bcrp) in brain cortex of streptozocin-induced diabetic rats

The aim of this study was to investigate whether diabetes mellitus (DM) affected breast cancer resistance protein (Bcrp) function and expression in rat brain. 5-week and 8-week diabetic rats were induced by streptozocin (STZ). Bcrp expression and function in brain cortex were assessed by western blot and measuring the brain-to-plasma concentration ratios of two typical substrates prazosin and cimetidine, respectively. The diabetic rats were treated with three different agents insulin, aminoguanidine (AG) and metformin (MET). It was found that the brain-to-plasma ratios of prazosin and cimetidine in diabetic rats were significantly higher than those of control rats, which were dependent on duration of diabetes. Lower levels of Bcrp were found in brain cortex of diabetic rats, which were in parallel with increase of brain-to-plasma ratios. Insulin treatment may attenuate the impairment of Bcrp expression and function induced by diabetes. Aminoguanidine and metformin treatment did not prevent the impairment of Bcrp function and expression in brain cortex of diabetic rats. All results gave a conclusion that STZ-induced DM may induce the impairment of function and expression of Bcrp in brain cortex, and lower levels of insulin may mainly contribute to Bcrp dysfunction in brain.

Expression of serum and glucocorticoid-inducible kinase1 in diabetic rats and its modulation by fluvastatin

The expression of serum and glucocorticoid-induced protein kinase in the renal cortex of diabetic rats was examined, and the function of signal transduction mediated by SGK1 in diabetic nephropathy and its modulatiqn by fluvastatin were also investigated. 24 male Wistar rats were randomly divided into normal control group (n = 8), diabetic nephropathy group (n = 8) and fluvastatin-treated diabetic nephropathy group (15 mg/kg/d, n = 8). The metabolic parameters were measured at the 8th week. The expression of transforming growth factor beta1 (TGF-beta1) and fibronectin (FN) was immunohistochemically examined. The expression of SGK1 was detected by RT-PCR and Western blot, and CTGF mRNA was assessed by RT-PCR. As compared to DN, blood glucose, 24-h urinary protein, Cer and kidney weight index were all decreased and the weight was increased obviously in group F. At the same time, mesangial cells and extracellular matrix proliferation were relieved significantly. The levels of cortex SGK1 mRNA and protein were up-regulated, and both TGF-beta1 and FN were down-regulated by fluvastatin. The mRNA of SGK1 was positively correlated with the CTGF, TGF-beta1 and FN. SGK1 expression is markedly up-regulated in the renal cortex of DN group and plays an important role in the development and progress of diabetic nephropathy by means of signal transduction. Fluvastatin suppressed the increased SGK1mRNA expression in renal cortex and postponed the development of diabetic nephropathy.

Regulation of elongation factor-1 expression by vitamin E in diabetic rat kidneys

Translation elongation factor-1 (EF-1) forms a primary site of regulation of protein synthesis and has been implicated amongst others in tumorigenesis, diabetes and cell death. To investigate whether diabetes-induced oxidative stress affects EF-1 gene expression, we used a free radical scavenger, vitamin E. The following groups of rats (5/group) were studied: control, vitamin E control, diabetic and diabetic treated with vitamin E. Markers of hyperglycemia, kidney function, oxidative stress, and kidney hypertrophy were elevated in diabetic rats. Increased urinary protein excretion indicated early signs of glomerular and tubular dysfunction. The mRNA and protein levels of the three EF-1 subunits (A, Balpha, and Bgamma) were determined in renal cortex extracts using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR), northern blot analysis and western blotting. EF-1A mRNA expression in renal cortex extracts was significantly increased by at least 2-fold (p < 0.002) in diabetic rats; however, there was no change in the mRNA levels of EF-1Balpha and EF-1Bgamma subunits. Similar results were observed at the protein level. Treatment of diabetic rats with vitamin E for 10 days suppressed both glycemic and oxidative stresses in renal cortex and kidney hypertrophy. EF-1A mRNA and protein levels were also reduced to control levels. In conclusion, EF-1A but not EF-1Balpha and EF-1Bgamma gene expression is significantly enhanced in the renal cortex of diabetic rats. Normalization of enhanced EF-1A expression by vitamin E treatment suggests a role for EF-1A during diabetes-induced oxidative stress.

TGF-beta1mRNA levels in renal cortex and peripheral blood mononuclear cells of diabetic rats

To investigate the effect of hyperglycemia and pioglitazone on TGF-beta(1) gene expression in peripheral blood mononuclear cells (PBMC) and renal cortex, and the correlation of TGF-beta(1)mRNA levels between PBMC and renal cortex in STZ induced diabetic rats. Fifty-four Sprague-Dawley rats were randomly divided into three groups: 18 normal control rats (group C), 18 diabetic rats (group D) and 18 diabetic rats treated with pioglitazone (20 mg x kg(-1)x d(-1), group DP). Six rats from each group were sacrificed at 2, 4, 8 weeks. TGF-beta(1)mRNA levels of PBMC and renal cortex were examined by RT-PCR+Slit hybridization analysis. TGF-beta(1)mRNA level of renal cortex in group D was significantly higher than that in group C at each time point (P<0. 05); TGF-beta(1)mRNA level of PMBC in group D was slightly higher than that of group C at 4 weeks, and significantly higher at 8 weeks (P=0.01). There was positive correlation of TGF -beta(1)mRNA level between PBMC and renal cortex before (r=0.83, P=0.02) and after pioglitazone treatment at 8 weeks (r=0.82, P=0.03). TGF-beta(1)mRNA level of PBMC may reflect the change of TGF-beta(1) gene expression of renal cortex in diabetic rats.

Increase of glial fibrillary acidic protein and S-100B in hippocampus and cortex of diabetic rats: effects of vitamin E

Glial interactions with neurones play vital roles during the ontogeny of the nervous system and in the adult brain. Physical and metabolic insults cause rapid changes in the glial cells and this phenomenon is called reactive gliosis. One of the important events during astrocyte differentiation is the increased expression of glial markers, glial fibrillary acidic protein (GFAP) and S-100B protein. Diabetes mellitus is the most common serious metabolic disorder, which is characterised by functional and structural changes in the peripheral as well as in the central nervous system. In the present study, we aimed to investigate glial reactivity in hippocampus, cortex and cerebellum of streptozotocin-induced diabetic rats by determining the expression of GFAP and S-100B and also to examine the protective effects of vitamin E against gliosis. Western blotting showed increases in total and degraded GFAP content and S-100B protein expression in brain tissues of diabetic rats compared with those of controls. In addition, there was a significant increase in lipid peroxidation in these brain regions of diabetic rats. Both glial markers and lipid peroxidation levels were reversed by vitamin E administration. These findings indicate that streptozotocin-induced diabetes alters degradation and production of GFAP and S-100B, which are markers of reactive astrocytosis. Thus, determination of GFAP and S-100B may provide a relevant marker in the central nervous system for studying neurodegenerative changes in experimental diabetes mellitus. This study also suggests that the gliosis that occurs in diabetes mellitus is mediated, at least indirectly, by free radical formation and antioxidants may prevent reactive gliosis possibly by reducing damaging effects of reactive oxygen species in the central nervous system.

Evidence of oxidative stress in the renal cortex of diabetic rats: favourable effect of vitamin E

The aim of this study was to determine whether there are any disturbances of red/ox balance in the renal cortex of rats during the course of experimental diabetes. In the renal cortex of rats with streptozotocin-induced diabetes, the activity of superoxide dismutase (SOD) isoenzymes, glutathione peroxidase (GSH-Pox), glutathione S-transferase (GST) and glutathione reductase (GSH-RED) was measured in the 5th, 10th and 15th weeks of diabetes. Free radical cell damage was assessed on the basis of malonyldialdehyde (MDA) concentration. The influence of lipophilic antioxidant vitamin E on these analytes was also studied. An increase in MDA concentration in the 10th and 15th weeks of diabetes correlated significantly with plasma glucose concentration (r = 0.47; p < 0.001). Moreover, MDA concentration was influenced by time (+); p < 0.001, diabetes (+); p < 0.001, vitamin E (-) p < 0.001 (ANOVA). Plasma creatinine concentration in rats was elevated by diabetes (p < 0.001), whereas vitamin E decreased the concentration (p < 0.05). Vitamin E lowered the activity of GSHPox (p < 0.001) and GST (p < 0.01) (ANOVA). Our results indicate that during experimental diabetes, disturbances of red/ox balance lead to disturbance in renal function manifested as increased creatinine blood concentration. We suggest that oral supplementation of vitamin E protects the renal cortex of rats during experimental diabetes.

Growth Hormone-Binding Protein (Gh-Bp) Induction in Renal Cortex of Streptozotocin (Stz) -Diabetic Rats

Growth hormone (GH) has been implicated in the pathogenesis of renal sclerosis. To determine the effects of long term diabetes on renal GH-R expression, we examined GH-R and GH-BP mRNA levels by solution hybridization-RNase protection assay in kidney of STZ-diabetic rats. Adult female Wistar rats received either i.v. STZ (55 mg/kg) or saline. Rats were sacrificed at 7, 30, 90, and 180 days following STZ treatment. Right kidney cortex was separated from medulla. Total RNA was extracted from both areas and analyzed for GH-R/GH-BP mRNA content. Blood glucose levels were 5-fold higher in diabetic animals (>25 nmol/L) and remained elevated throughout the study. Urinary albumin concentration were markedly elevated from days 30 to 180 in the diabetic animals. We observed no changes in either GH-R or GH-BP mRNA levels in the medulla of diabetic rats. A significant increase in GH-BP(p<0.05) but not in GH-R mRNA levels was observed in the cortex of diabetic rats at 30 (140.8±15.9%; mean±sem); 90 (147.0±14.9%); and 180 days (165.6±16.3%).

Inhibition of renal gluconeogenesis by guinolinate and hydrazine in diabetic rats.

Renal as well as hepatic gluconeogenesis is inappropriately accelerated in the diabetic state when plasma glucose levels are elevated. Known regulatory mechanisms influence gluconeogenesis in both organs. However, under certain circumstances gluconeogenesis may be affected in one organ and not the other. Recent studies with the tryptophan metabolite, quinolinate, suggest that hepatic gluconeogenesis in the diabetic is unaffected by this agent, whereas gluconeogenesis is blocked in the normal liver. These experiments have been interpreted as providing evidence for the lack of a specific physiologic repressor for gluconeogenesis in diabetic liver. In the present study quinolinate and hydrazine are shown to be effective inhibitors of the accelerated gluconeogenesis in the renal cortex of diabetic rats. Thus, the renal gluconeogenic mechanism in diabetics retains the capacity to recognize quinolinate as an inhibitor, but may be influenced by the depressed conversion of tryptophan to quinolinate in the intact diabetic organism.