Young Diabetic Rats Research Articles

Hyperglycemia exerts disruptive effects on the secretion of TGF-β1 and its matrix ligands, decorin and biglycan, by mesenchymal sub-populations and macrophages during bone repair

IntroductionBone has a high capacity for repair, but for patients with uncontrolled type 2 diabetes mellitus (T2DM), the associated hyperglycemia can significantly delay osteogenic processes. These patients respond poorly to fracture repair and bone grafts, leading to lengthy care plans due to arising complications. Mesenchymal stromal cells (MSCs) and M2 macrophages are both major sources of transforming growth factor-β1 (TGF-β1), a recognized mediator for osteogenesis and whose bioavailability and activities are further regulated by matrix small leucine-rich proteoglycans (SLRPs), decorin and biglycan. The aim of this study was to investigate how in vivo and in vitro hyperglycemic (HGly) environments can influence levels of TGF-β1, decorin, and biglycan during bone repair, with additional consideration for how long-term glucose exposure and cell aging can also influence this process.ResultsFollowing bone healing within a T2DM in vivo model, histological and immuno-labeling analyses of bone tissue sections confirmed delayed healing, which was associated with significantly elevated TGF-β1 levels within the bone matrices of young diabetic rats, compared with normoglycemic (Norm) and aged counterparts. Studies continued to assess in vitro effects of normal (5.5 mM) and high (25 mM) glucose exposure on the osteogenic differentiation of compact bone derived mesenchymal stromal cells (CB-MSCs) at population doubling (PD)15, characterized to contain populations of lineage committed osteoblasts, and at PD150, where transit-amplifying cells predominate. Short-term glucose exposure increased TGF-β1 and decorin secretion by committed osteoblasts but had a lesser effect on transit-amplifying cells. In contrast, the long-term exposure of CB-MSCs to high glucose was associated with decreased TGF-β1 and increased decorin secretion. Similar assessments on macrophage populations indicated high glucose inhibited TGF-β1 secretion, preventing M2 formation.DiscussionCollectively, these findings highlight how hyperglycemia associated with T2DM can perturb TGF-β1 and decorin secretion by MSCs and macrophages, thereby potentially influencing TGF-β1 bioavailability and signaling during bone repair.

Gymnemic acid protects murine pancreatic β-cells by moderating hyperglycemic stress-induced inflammation and apoptosis in type 1 diabetic rats.

Type 1 diabetes is a chronic immune-mediated disease caused by pancreatic β-cell dysfunction with consequent severe insulin deficiency. Exacerbated blood glucose levels can cause oxidative stress in the pancreatic β-cells, which leads to inflammation, and apoptosis resulting in islet dysfunction. Although massive studies have been carried out to elucidate the causative factors for β-cell damage in diabetes, the therapeutic approach to pancreatic β-cell damage has not been extensively studied. Hence, the present study has been designed to delineate the role of gymnemic acid (GA) in protecting pancreatic β-cells in diabetic animals, with special reference to inflammation and apoptosis. Our data revealed that the treatment with GA significantly reverted the alteration in both biochemical and histochemical observations in young diabetic rats. Moreover, treatment with the GA downregulates the expression of proinflammatory markers (nuclear factor-κB, tumor necrosis factor-α, interleukin-[IL]-6, and IL-1β), proapoptotic proteins (Bax, cytochrome c, and cleaved caspase-3), as well as upregulates the expression of antiapoptotic protein Bcl-2 in diabetic rats. These findings suggest that the anti-inflammatory and antiapoptotic nature of GA mitigates β-cell damage in hyperglycemic rats.

LONG-TERM FOOD RESTRICTION AND DIABECON ADMINISTRATION AMELIORATES ALLOXAN-INDUCED HYPERGLYCEMIA, THYROID DYSFUNCTION, AND OXIDATIVE STRESS IN RAT.

Objective: The comparative effects of food restriction (FR), Diabecon treatment (DT) and their combined therapy (FR+DT) were studied in the regulation of alloxan-induced diabetes mellitus, alterations in thyroid hormones (TH) and oxidative stress.
 Methods: Young diabetic rats were either kept on 50% FR and/or DT (2 gm/Kg body weight) for two months and then alterations in serum glucose, insulin, TH concentrations, hepatic glycogen and pancreatic antioxidants along with oxidative stress markers were evaluated.
 Results: Significantly increased serum glucose, tissue stress markers with decreased TH, hepatic glycogen (P<0.0001 for all) and pancreatic antioxidants (P<0.05-0.001) were observed in diabetic rats. Rats kept on different therapies exhibited significant (P<0.05) improvements than diabetic rats in all studied parameters. FR+DT group showed a significantly more decrease in serum glucose (P<0.05) that FR or DT group, while in other parameters improvement was found to be more or less equally improved in all treated groups.
 Conclusion: FR appeared to mimic the effects of Diabecon in most of the indices. However, FR+DT appears to be more effective. Possibly both therapies ameliorate diabetes and oxidative stress following some common metabolic pathways.

Delayed Administration of Angiotensin Receptor (AT2R) Agonist C21 Improves Survival and Preserves Sensorimotor Outcomes in Female Diabetic Rats Post-Stroke through Modulation of Microglial Activation.

About 70% of stroke victims present with comorbid diseases such as diabetes and hypertension. The integration of comorbidities in pre-clinical experimental design is important in understanding the mechanisms involved in the development of stroke injury and recovery. We recently showed that administration of compound C21, an angiotensin II type 2 receptor agonist, at day 3 post-stroke improved sensorimotor outcomes by lowering neuroinflammation in diabetic male animals. In the current study, we hypothesized that a delayed administration of C21 would also lower chronic inflammation post-stroke in diabetic female animals. Young female diabetic rats were subjected to 1 h of middle cerebral artery occlusion (MCAO). Three days post-stroke, rats were administered C21 or vehicle in drinking water at a dose of 0.12 mg/kg/day for 4 weeks. The impact of C21 on microglial polarization was analyzed by flow cytometry in vivo and in vitro. Compound 21 treatment improved fine motor skills after MCAO through modulation of the microglia/macrophage inflammatory properties. In addition, C21 increased M2 polarization and reduced the M1:M2 ratio in vitro. In conclusion, delayed administration of C21 downregulates post-stroke inflammation in female diabetic animals. C21 may be a useful therapeutic option to lower neuro-inflammation and improve the post-stroke recovery in diabetes.

Comparative Study of the Steroidogenic Effects of Human Chorionic Gonadotropin and Thieno[2,3-D]pyrimidine-Based Allosteric Agonist of Luteinizing Hormone Receptor in Young Adult, Aging and Diabetic Male Rats.

Low-molecular-weight agonists of luteinizing hormone (LH)/human chorionic gonadotropin (hCG) receptor (LHCGR), which interact with LHCGR transmembrane allosteric site and, in comparison with gonadotropins, more selectively activate intracellular effectors, are currently being developed. Meanwhile, their effects on testicular steroidogenesis have not been studied. The purpose of this work is to perform a comparative study of the effects of 5-amino-N-tert-butyl-4-(3-(1-methylpyrazole-4-carboxamido)phenyl)-2-(methylthio)thieno[2,3-d] pyrimidine-6-carboxamide (TP4/2), a LHCGR allosteric agonist developed by us, and hCG on adenylyl cyclase activity in rat testicular membranes, testosterone levels, testicular steroidogenesis and spermatogenesis in young (four-month-old), aging (18-month-old) and diabetic male Wistar rats. Type 1 diabetes was caused by a single streptozotocin (50 mg/kg) injection. TP4/2 (20 mg/kg/day) and hCG (20 IU/rat/day) were administered for 5 days. TP4/2 was less effective in adenylyl cyclase stimulation and ability to activate steroidogenesis when administered once into rats. On the 3rd–5th day, TP4/2 and hCG steroidogenic effects in young adult, aging and diabetic rats were comparable. Unlike hCG, TP4/2 did not inhibit LHCGR gene expression and did not hyperstimulate the testicular steroidogenesis system, moderately increasing steroidogenic proteins gene expression and testosterone production. In aging and diabetic testes, TP4/2 improved spermatogenesis. Thus, during five-day administration, TP4/2 steadily stimulates testicular steroidogenesis, and can be used to prevent androgen deficiency in aging and diabetes.

Swimming training potentiates the recovery of femoral neck strength in young diabetic rats under insulin therapy

OBJECTIVE:To test whether swimming training benefits femoral neck strength in young diabetic rats under insulin therapy.METHODS:A total of 60 male Wistar rats (age: 40 days) were divided equally into the following six groups: control sedentary, control exercise, diabetic sedentary, diabetic exercise, diabetic sedentary plus insulin and diabetic exercise plus insulin. Diabetes was induced with a unique intraperitoneal injection (60 mg/kg body weight) of streptozotocin. Seven days after the injection and after 12 hours of fasting, the animals with blood glucose levels ≥300 mg/dL were considered diabetic. Seven days after the induction of diabetes, the animals in the exercise groups were subjected to progressive swimming training (final week: 90 min/day; 5 days/week; 5% load) for eight weeks. The animals in the insulin groups received a daily dose of insulin (2-4 U/day) for the same period.RESULTS:Severe streptozotocin-induced diabetes reduced the structural properties of the femoral neck (trabecular bone volume, trabecular thickness and collagen fiber content). The femoral neck mechanical properties (maximum load and tenacity) were also impaired in the diabetic rats. Insulin therapy partially reversed the damage induced by diabetes on the structural properties of the bone and mitigated the reductions in the mechanical properties of the bone. The combination of therapies further increased the femoral neck trabecular bone volume (∼30%), trabecular thickness (∼24%), collagen type I (∼19%) and type III (∼13%) fiber contents, maximum load (∼25%) and tenacity (∼14%).CONCLUSIONS:Eight weeks of swimming training potentiates the recovery of femoral neck strength in young rats with severe streptozotocin-induced diabetes under insulin therapy.

Effect of Enriched Environment on the Cognitive and Behavioural Changes in the Streptozotocin-Induced Young Diabetic Rats

Introduction: Effects of juvenile diabetes on the central nervous system are less well documented. Effective management of T1DM is another major challenge as insulin is the only available effective treatment. Hence, easily available, affordable, non-invasive therapies like enriched environment are the need of time. Objectives: The present study aimed to determine the effect of an enriched environment on cognitive and behavioral changes in juvenile diabetic rats. Methods: Diabetes was induced in 25 days old, albino Wistar rats, by streptozotocin (STZ). Animals were reared in an enriched environment and treated with herbal formulae with Salacia R and Clitoria T. Then, rats were tested in the elevated passive maze, passive avoidance box and Morris water maze (n=6). Values are expressed as means ± SE and differences assessed by using one way ANOVA test followed by Bonferroni multiple comparison test. Results: Statistically significant (p<0.05) difference was observed between the enriched environment and diabetic group of rats. Additionally, effects are comparable to conventional insulin therapy, in the animals which received combined therapy (SR+CT+EE) (p<0.01). Conclusion: Authors have shown that diabetic rats reared in enriched housing conditions, showed improved cognitive measures compared to diabetics. The combined treatment is found to be more beneficial in restoring normoglycemic levels and preventing behavioral and cognitive deficits.

Abstract 027: Hyperglycemia and Oxidative Stress Contribute to Impaired CerebralAutoregulation in Association With Dementia in Diabetes

Diabetes mellitus is characterized by hyperglycemia and is well established to associate with oxidative stress. The present study examines whether impaired myogenic response of middle cerebral artery MCA and autoregulation of cerebral blood flow (CBF) in our T2DN diabetic rats is due to hyperglycemia and oxidative stress induced actin cytoskeleton reorganization, and if this contributes to dementia. We identified that both young (4-month) and older (18-month) T2DN diabetic rats exhibit impaired pressure-induced myogenic response in isolated MCAs. Forced dilatation occurred at pressures above 140 mmHg in MCAs isolated from elderly T2DN rats with mild hypertension but not controls. Cortical blood flow measured by laser Doppler flowmetry rose by 137 ± 15% and 36 ± 5%, respectively, in T2DN and SD rats when MAP was increased from 100 to 180 mmHg. Autoregulation of CBF was shifted to lower pressures in elderly T2DN rats and they exhibited breakthrough at pressures above 140 mmHg. The F-Actin distribution area was significantly reduced in the vascular smooth muscle cells (VSMCs) freshly isolated from MCAs of T2DN rats compared with normal Sprague Dawley (SD) rats. The F-actin was disrupted similarly in VSMCs treated with high glucose or H 2 O 2 . Superoxide production is elevated in fresh isolated middle cerebral arteries (MCA) in T2DN diabetic rats compared to normal SD rats. We also found increased production of superoxide in primary VSMCs isolated from normal SD rats cultured in high glucose condition or freshly isolated from diabetic rats. T2DN rats exhibited neurons death in the hippocampus and cortex. Elderly T2DN rats showed memory disabilities. These results indicate that hyperglycemia induced elevated superoxide production causes actin cytoskeleton reorganization in cerebral VSMCs of diabetic T2DN rats, which may contribute to impaired cerebral vascular function, neurodegeneration and cognitive impairment.

Evaluation of antidiabetic activity of Ipomoea batatas L. extract in alloxan-induced diabetic rats.

Different allopathic drugs are being used for the treatment of diabetes mellitus but more emphasis are being placed on the use of medicinal plants, herbs, and natural extracts of fruits and vegetables due to their easy availability, easy consummation with low cost, and with no well-reported side effects. White skinned sweet potato (WSSP; Ipomoea batatas L.) peel-off was selected to find out its antidiabetic potential as well as to explore the effects on selected biochemical parameters in diabetes-induced Wistar rats. In young (3–4 months) and old (up to 1 year) diabetic Wistar rats, it was found that WSSP (I. batatas L.) peel-off significantly (P < 0.05) decreased blood glucose level, protein glycation level, total cholesterol, triglycerides, and low-density lipoprotein (LDL)-cholesterol. A significant (P < 0.05) increase in high-density lipoprotein (HDL)-cholesterol level after treatment was also reported. Furthermore, it was also found that WSSP peel-off also had beneficial effects on total protein concentration, albumin, globulin, and liver enzymes (serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT)). It might be concluded that antidiabetic potential of WSSP extract is due to the presence of bioactive compounds like glycoprotein, anthocyanins, alkaloids, and flavonoids, which act as insulin-like molecules or insulin secretagogues constituents in sweet potatoes peel-off and these antidiabetic proteins were extracted out in more concentration in methanol due to its organic nature. Further research is needed to purify and quantify the antidiabetic components responsible for antidiabetic effects of WSSP and it should be available in compact dose form for the treatment of diabetic patients.

Recovery of hippocampal functions and modulation of muscarinic response by electroacupuncture in young diabetic rats

The muscarinic receptor response to acetylcholine regulates the hippocampal-related learning, memory, neural plasticity and the production and processing of the pro-nerve growth factor (proNGF) by hippocampal cells. The development and progression of diabetes generate a mild cognitive impairment reducing the functions of the septo-hippocampal cholinergic circuitry, depressing neural plasticity and inducing proNGF accumulation in the brain. Here we demonstrate, in a rat model of early type-1 diabetes, that a physical therapy, the electroacupuncture, counteracts the diabetes-induced deleterious effects on hippocampal physiology by ameliorating hippocampal-related memory functions; recovering the impaired long-term potentiation at the dentate gyrus (DG-LTP) and the lowered expression of the vesicular glutamate transporter 1; normalizing the activity-dependent release of proNGF in diabetic rat hippocampus. Electroacupuncture exerted its therapeutic effects by regulating the expression and activity of M1- and M2-acetylcholine muscarinic receptors subtypes in the dentate gyrus of hippocampus. Our results suggest that a physical therapy based on repetitive sensory stimulation could promote hippocampal neural activity, neuronal metabolism and functions, and conceivably improve the diabetes-induced cognitive impairment. Our data can support the setup of therapeutic protocols based on a better integration between physical therapies and pharmacology for the cure of diabetes-associated neurodegeneration and possibly for Alzheimer’s disease.

Effect of Salacia reticulata W. and Clitoria ternatea L. on the cognitive and behavioral changes in the streptozotocin-induced young diabetic rats.

Diabetes mellitus (DM) of juvenile onset affects both the peripheral and central nervous systems (CNS). However, central effects are less documented and studied than peripheral deficits. Currently, the only feasible treatment available for type 1 DM (T1DM) is insulin which has its own limitations. Hence, an alternative therapy, especially a newer herbal formulation is very much the need of the time. The present study aimed to determine the effects of the alcoholic extracts of roots of the Salacia reticulata W. (SR) and Clitoria ternatea L. (CT) on cognitive and behavioral changes in juvenile diabetic rats. Diabetes was induced in 25-day-old Wistar rats by streptozotocin (50 mg/kg bw, IP). Animals were divided into seven groups (n=6). Rats were treated with root extracts of SR and CT (100 mg/kg BW each) for 30 days, from day 1 and day 20 of diabetes confirmation. Then, rats were tested in elevated plus maze (EPM) and Morris water maze (MWM). A statistically significant (p<0.05) difference was observed between the SRCT group and diabetic groups of rats. Apart from decreasing FBS, the combined therapy also proved beneficial as nootropic agent in rats with early-onset diabetes. However, significant improvement is observed only in the learning and memory among preventive group, but not in the curative group. SRCT, a herbal formula, when used in combination, has a more potent effect in preventing the deleterious effects of juvenile diabetes on cognitive and behavioral changes.

Pulsed electromagnetic field (PEMF) promotes collagen fibre deposition associated with increased myofibroblast population in the early healing phase of diabetic wound.

The present study evaluated the effects of PEMF on collagen fibre deposition, collagen fibril alignment and collagen fibre orientation. The potential relationships between collagen fibre deposition and myofibroblast population in diabetic wound healing were also examined. Forty young male streptozotocin-induced diabetic Sprague-Dawley rats were randomly assigned to PEMF group or control group. 2cm×2cm square wounds were made at their back. The PEMF group received daily exposure of PEMF to the wounds, while control group was handled in the same manner except that the PEMF device was not activated. Wound tissues harvested on post-wounding day 7, 10 and 14 were fixed, processed and sectioned. The abundance, fibril alignment and fibre orientation of type I collagen were quantified with picro-sirius polarization method and image analysis software (Nikon NIS Element AR). Myofibroblast population data were adopted from our previous study. Correlation between myofibroblast population and collagen fibre deposition was examined. There was significantly greater abundance of type I collagen fibre in the PEMF group than in the control on day 7 (P=.013), but not on day 10 or 14. No significant between-group differences were found in collagen fibril alignment and collagen fibre orientation at any measured time points. Positive correlation was found between collagen fibre deposition and myofibroblast population only on day 7 (r=.729, P=.007). In conclusion, PEMF can significantly increase collagen fibre in the early phase of diabetic wound healing, which is associated with the enhancement of myofibroblast population.

Melatonin administration in diabetes: regulation of plasma Cr, V, and Mg in young male Zucker diabetic fatty rats

The use of melatonin, a neurohormone present in plants, represents an exciting approach for the maintenance of optimum health conditions. Melatonin administration ameliorates glucose homeostasis in Zucker diabetic fatty (ZDF) rats. The objective of this study was to investigate the effects of melatonin in diabetes in relation to the levels and regulation of plasma chromium (Cr), vanadium (V), and magnesium (Mg) in Zucker diabetic fatty (ZDF) and Zucker lean (ZL) rats. At the age of 6 weeks, ZDF (n = 30) and ZL (n = 30) groups were each subdivided into three groups: control (C) (n = 10), vehicle-treated (V') (n = 10) and melatonin-treated (M) (10 mg kg(-1) per day; n = 10) groups for a 6 week period. After treatment, plasma mineral concentrations were measured by flame (Mg) and electrothermal (Cr and V) atomic absorption spectrometry. No significant differences were found between the C and V' groups (p > 0.05). Plasma Mg levels were significantly lower in C-ZDF vs. C-ZL rats, demonstrating the presence of hypomagnesemia in this diabetes mellitus model. Plasma V and Cr levels were significantly higher in M-ZDF vs. C-ZDF rats. Plasma Mg levels in ZDF rats were not affected by melatonin treatment (p > 0.05). Melatonin administration ameliorates the diabetic status of ZDF rats by enhancing plasma Cr and V concentrations. This appears to be the first report of a beneficial effect of melatonin treatment on plasma Cr and V regulation in ZDF rats.

Low‐glycemic index diets prevent type 2 diabetes in the Nile rat

The Nile rat (NR) is a novel model for type 2 diabetes (T2DM) and metabolic syndrome sensitive to metabolic stress from simple carbohydrates (CHO). Three experiments assessed the effects of a low‐glycemic index CHO (green lentils, GL) on T2DM. Expt 1 compared a GL diet directly with a semipurified hiCHO diet having identical %En from CHO:fat:protein (70:10:20). Expt 2 assessed reversibility of hyperglycemia by comparing a modCHO‐GL diet (45:25:30) to diabetogenic semipurified hiCHO (70:10:20) or lab chow (#5020) diets in 3 separate studies. Expt 3 examined young Nile rats “primed” from weaning for 7wks with the modCHO‐GL diet (45:25:30) before being challenged with stressful semipurified hiCHO (70:10:20) or modCHO (40:40:20) diets based on glucose and starch. 1. Compared to the hiCHO semipurified diet with the same macronutrient composition, the GL diet induced significantly less diabetes. 2. GL substantially reversed hyperglycemia, especially in young (&lt;4mo) diabetic rats. 3.”Priming” rats with GL prior to hiCHO resulted in less severe diabetes compared to previous studies without priming. Positive influences on other metabolic parameters such as liver and kidney weight and plasma lipids also were observed. Since the NR mimics T2DM in humans, GL or components therein may represent a potentially useful adjunct for T2DM control in humans.Funding source: Foster Biomed Res Lab and the Malaysian Palm Oil Board

A 6-week training program increased muscle antioxidant system in elderly diabetic fatty rats

SummaryBackgroundIt is widely accepted that oxidative stress is associated with the physiopathology of type 2 diabetes mellitus. In fact, it has been pointed out as a therapeutic target in T2DM. Fortunately, several papers have reported that long-term training programs improved the antioxidant system in young and adult diabetic rats. Accordingly, this study was designed to assess the influence of a shorter training program in elderly diabetic fatty rats.Material/MethodsStudy subjects were 24 male homozygous Zucker diabetic fatty rats (Gmi, fa/fa) aged 18 weeks with an average weight of 370–450 g. After a 2-week period of environmental adaptation, animals were randomly distributed into the Exercised Group (n=12) that performed a 6-week swimming training protocol and the Sedentary Group (n=12). Animals were sacrificed under anesthesia 24 h after the last exercise session. Serum metabolic profile was determined. Total antioxidant status (TAS), MnSOD expression, glutathione status and ROS generation were assayed in gastrocnemius muscle.ResultsWhen compared with controls, exercised rats significantly improved their metabolic profile. Total antioxidant status (0.19±0.002 vs. 0.13±0.002 μg/mg protein; p<0.001) and MnSOD expression (8471±90 vs. 6258±102 U/μg protein; p=0.003) were also increased in exercised rats.ConclusionsA 6-week swimming training program improved the antioxidant system in elderly fatty diabetic rats. Fortunately, this improvement was enough to reduce oxidative damage, expressed as protein oxidation. A major finding of this study was that our training protocol lasted just 6 weeks, in contrast to longer protocols previously published.

Effects of the Soluble Fiber Complex PolyGlycopleX on Glucose Homeostasis and Body Weight in Young Zucker Diabetic Rats.

Dietary fiber can reduce insulin resistance, body weight, and hyperlipidemia depending on fiber type, water solubility, and viscosity. PolyGlycopleX® (PGX®) is a natural, novel water soluble, non-starch polysaccharide complex that with water forms a highly viscous gel compared to other naturally occurring dietary fiber. We determined the effect of dietary PGX® vs. cellulose and inulin on the early development of insulin resistance, body weight, hyperlipidemia, and glycemia-induced tissue damage in young Zucker diabetic rats (ZDFs) in fasted and non-fasted states. ZDFs (5 weeks old) were fed a diet containing 5% (wgt/wgt) cellulose, inulin, or PGX® for 8 weeks. Body weight, lipids, insulin, and glucose levels were determined throughout the study and homeostasis model assessment (HOMA) was used to measure insulin sensitivity throughout the study in fasted animals. At study termination, insulin sensitivity (oral glucose tolerance test, OGTT) and kidney, liver, and pancreatic histopathology were determined. Body weight and food intake were significantly reduced by PGX® vs. inulin and cellulose. Serum insulin in fasted and non-fasted states was significantly reduced by PGX® as was non-fasted blood glucose. Insulin resistance, measured as a HOMA score, was significantly reduced by PGX® in weeks 5 through 8 as well as terminal OGTT scores in fed and fasted states. Serum total cholesterol was also significantly reduced by PGX®. PGX® significantly reduced histological kidney and hepatic damage in addition to reduced hepatic steatosis and cholestasis. A greater mass of pancreatic β-cells was found in the PGX® group. PGX® therefore may be a useful dietary additive in the control of the development of the early development of the metabolic syndrome.

Preventive Effects of Vitamin E Against Oxidative Damage in Aged Diabetic Rat Bladders

To examine the effects of aging and/or diabetes mellitus on oxidative stress and the protective effect of vitamin E in the bladder. It was proposed that the balance between oxidant and antioxidant species is important regarding the aging process and prevention of diabetic complications. Young and aged rats were randomly allotted into six experimental groups: aged control, aged diabetic, aged diabetic and vitamin E-treated, young control, young diabetic, young diabetic and vitamin E-treated. Diabetes was induced by streptozotocin. Vitamin E was administered to the treated groups. Malondialdehyde and reduced glutathione levels were measured in all rat bladders, and histological changes were examined by electron microscopy. We found increased malondialdehyde and decreased glutathione levels in the young and aged diabetic groups compared with the nondiabetic control groups. Elevated malondialdehyde and reduced glutathione levels were observed in the aged compared with the young control groups. There were no significant differences in the malondialdehyde and glutathione levels between young and aged diabetic vitamin E-treated groups compared with the related control groups. Degeneration was greatest in the aged diabetic group. The protective effects of vitamin E were seen in young and aged diabetic groups, especially in the young diabetic group. Our results suggest that vitamin E supplementation prevents free radical damage in bladders of young and aged diabetic rats.

Muscarinic M1, M3 receptor modulation in the corpus striatum of streptozotocin induced diabetic rats as a function of age

In this study we have investigated muscarinic M₁, M₃ receptor kinetics and the functional role of IP3 and cGMP in the corpus striatum of both young and old diabetic and insulin-treated diabetic rats. Radioreceptor binding assays was done in the corpus striatum using specific antagonists QNB and DAMP. IP3 and cGMP assay using [3H]IP3 and [3H]cGMP Biotrak assay system kits. M₁ receptor increased and M₃ receptor decreased in control old rats when compared with young control rats. In young diabetic groups M₁ receptor increased and M₃ receptor decreased. Old diabetic groups showed reversed M₁ and M₃ receptors compared with their controls. IP3 and cGMP content increased in old control rats compared with young control rats. IP3 content increased in young diabetic rats and decreased in old diabetic rats. cGMP content was increased significantly in both young and old diabetic groups. Insulin treatment reversed these altered parameters near to control. Our studies showed that M₁ and M₃ receptors, IP3 and cGMP were functionally regulated during diabetes as function of age, which will have immense clinical significance.

Effect of an Aldose Reductase Inhibitor on Alveolar Bone Loss Associated with Periodontitis in Diabetic Rats

Periodontitis is a lesser known but frequent complication of diabetes mellitus and is the major cause of tooth loss in patients with diabetes. Dental therapy for this complication is primarily focused on the control of oral infections. No current therapy directly addresses the potential effects of diabetes itself on this complication. In studies conducted in young normal control and streptozotocin diabetic rats (100 g) treated with and without the aldose reductase inhibitor (ARI) imirestat, experimental periodontitis was induced in one side of the mouth by 3 injections of lipopolysaccharide (LPS) from Escherichia coli 055:B5 9 into the palatal gingiva between the first and second maxillary molars at 48-hour intervals. The other control side was injected with phosphate buffered saline (PBS). Fourteen days after the final injection, all rats were euthanized and the heads were defleshed. The maxillary area was separated from the remaining skull. The cleaned maxillary alveoli were stained in 5% aqueous toluidine blue to identify the cemento-enamel junction (CEJ) on the molars. Alveolar bone loss was measured according to standard methods by determining both the distance between the CEJ and the alveolar bone on the 2 molars between which the injections were made, and by measuring the ratio of root area/enamel area in the same region. These measurements showed that LPS injections resulted in significant bone loss compared with PBS injections in both control and diabetic rats, and that this bone loss was not present in the ARI-treated diabetic rats (P < 0.05). These results suggest that the sorbitol pathway plays a critical role in the pathophysiological mechanism(s) of diabetic periodontitis and that AR may be a direct pharmacological target for the treatment for this disease.

Age‐dependent diabetes induces endothelial dysfunction: the role of VEGF and TGF‐beta

Transforming growth factor (TGF) ‐ beta and vascular endothelial growth factor (VEGF) have been implicated in the endothelial dysfunction and the vasculopathy of diabetes; however, the specific mechanisms involved in the vasculopathic effect of these growth factors have not been clearly elucidated. Therefore, we hypothesized that diabetes induced by streptozotocin (STZ) leads to a reduction in endothelium‐derived relaxing agents, which may be caused by upregulation of VEGF and/or TGF‐beta in an age‐dependent manner. To test the hypothesis, young (4‐5 weeks old) and mature (&gt;7 months old) male Sprague‐Dawley rats were given a single injection of STZ to induce diabetes. Survival rate was age‐dependent [young (100%) vs. old (50%)]. The increase in blood glucose levels had no effect on blood pressure. Plasma nitric oxide and prostacyclin levels were reduced by 20% and 45% respectively in the young diabetic rats. STZ increased plasma thromboxane A2 levels in both groups. Furthermore, STZ amplified VEGF expression in both groups; however, only the mature rats showed a significant change in TGF‐beta expression. Taken together, these findings indicate that diabetes induced endothelial dysfunction/mortality is greater in older rats and due to the over expression of both TGF‐beta and VEGF. This research was funded, in part, by NIDDK grant 1SC1DK082385‐01.