Gurkan Yigitturk

Exenatide reduces TNF-α expression and improves hippocampal neuron numbers and memory in streptozotocin treated rats.

Recent studies suggest a possible link between type 2 diabetes and Alzheimers disease (AD). Glucogan-like peptide 1 (GLP-1) facilitates insulin release from pancreas under hyperglycemic conditions. In addition to its metabolic effects, GLP-1 and its long-lasting analogs, including exenatide can stimulate neurogenesis and improve cognition in rodent AD model. The aim of the present study was to investigate the effects of exenatide on hippocampal cellularity, cognitive performance and inflammation response in a rat model of AD. Fourteen rats were used to create AD model using intracerebroventricular (ICV) streptozotocin (STZ) infusion while 7 rats were administered 0.9% NaCl only (sham-operated group). Following stereotaxic surgery, STZ received rats were randomly distributed into two groups, and treated with either saline or exenatide 20 µgr/kg/day through intraperitoneally for two weeks. Then, cognitive performance (passive avoidance learning), brain tumor necrosis factor alpha (TNF-α) levels, choline acetyltransferase (ChAT) activity and hippocampal neuronal count were determined. While the brain TNF-α levels were significantly high in the saline-treated STZ group, exenatide treatment suppressed the increase in TNF-α levels. Saline-treated STZ group showed reduced ChAT activity compared to sham group. However, exenatide significantly preserved brain ChAT activity. The cognitive performance was also impaired in saline group while exenatide improved memory in rats. Moreover, exenatide treatment significantly prevented the decrease in hippocampal neurons. Overall, the results of the present study clearly indicated exenatide might have beneficial effects on impaired cognitive performance and hippocampal neuronal viability in AD by suppressing the inflammation response and increasing cholinergic activity.

Effects of Silk Sericin on Incision Wound Healing in a Dorsal Skin Flap Wound Healing Rat Model

Background The wound healing process is complex and still poorly understood. Sericin is a silk protein synthesized by silk worms (Bombyx mori). The objective of this study was to evaluate in vivo wound healing effects of a sericin-containing gel formulation in an incision wound model in rats. Material/Methods Twenty-eight Wistar-Albino rats were divided into 4 groups (n=7). No intervention or treatment was applied to the Intact control group. For other groups, a dorsal skin flap (9×3 cm) was drawn and pulled up with sharp dissection. The Sham operated group received no treatment. The Placebo group received placebo gel without sericin applied to the incision area once a day from day 0 to day 9. The Sericin Group 3 received 1% sericin gel applied to the incision area once a day from day 0 to day 9. Hematoxylin and eosin stain was applied for histological analysis and Mallory-Azan staining was applied for histoimmunochemical analysis of antibodies and iNOS (inducible nitric oxide synthase), and desmin was applied to paraffin sections of skin wound specimens. Parameters of oxidative stress were measured in the wound area. Results Epidermal thickness and vascularization were increased, and hair root degeneration, edema, cellular infiltration, collagen discoloration, and necrosis were decreased in Sericin group in comparison to the Placebo group and the Sham operated group. Malonyldialdehyde (MDA) levels were decreased, but superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities were increased in the sericin group. Conclusions We found that sericin had significant positive effects on wound healing and antioxidant activity. Sericin-based formulations can improve healing of incision wounds.

The antioxidant role of agomelatine and gallic acid on oxidative stress in STZ induced type I diabetic rat testes

Diabetes is a multisystem disorder and its effects are observed on the reproductive system. One of the main causes of testicular tissue damage is diabetes-induced overproduction of reactive oxygen species and glycated end products. The main objectives of this study were to investigate the possible effects of agomelatine (AG) and gallic acid (GA) in suppressing oxidative stress in Type I diabetes induced testicular damage. A total of 28 adult male rats were included in the study. Diabetes was induced by intraperitoneal injection of streptozocin (STZ, 55mg/kg) to 21 rats, which were then randomly assigned to 3 groups; 1mL saline solution was given to the diabetes+saline group by oral gavage, 20mg/kg/day oral AG was given to the diabetes+AG group, and 20mg/kg/day oral GA was given to the diabetes+GA group for 4 weeks. Tumor necrosis factor α (TNFα), nitric oxide synthase 2 (NOS2), fibronectin and vascular endothelial growth factor (VEGF) were used for the investigation of inflammation, fibrosis and vascular structures. The terminal-deoxynucleoitidyl-transferase mediated nick end-labeling assay (TUNEL) was used to detect apoptosis. Testicular tissue total antioxidant capacity values were tested by biochemical analysis. AG treatment showed an improvement on biochemical parameters and histopathological appearance on the rat testes. GA showed dose-related regenerative effects on biochemical parameters. Histologically, a minimal healing effect was determined on the testes damage. In conclusion, it was observed that AG is a potentially beneficial agent for reducing testicular damage by decreasing oxidative stress level. However, GA was seen to have a poor therapeutic effect.

Exenatide improves ovarian and endometrial injury and preserves ovarian reserve in streptozocin induced diabetic rats.

Abstract We aimed to evaluate: (1) endometrial and ovarian tissue injury caused by the glucose toxicity in diabetic rat model and (2) the effect of GLP-1 analog (exenatide) on endometrial and ovarian diabetes induced injury with emphasizing the underlying mechanism. The study group composed of 24 female rats assigned randomly into 3 groups. Group 1 was the control group (n = 8) and received no treatment. Diabetes was induced by intraperitoneal injection of streptozocin for 16 rats which are further assigned randomly into 2 groups: 1 ml/kg intraperitoneal saline was given to Group-2 (diabetic non-treated control group, 8 rats) and 10 µg/kg/day of intraperitoneal exenatide was given to Group 3 (exenatide treated group, 8 rats) for four weeks. After four weeks, blood samples were collected and hysterectomy with bilateral oophorectomy was performed for histopathological examination. Diabetes caused endometrial and ovarian tissue injury in rats (p < 0.0001). Serum transforming growth factor beta (TGF-ß), malonylaldehyde (MDA), pentraxin-3 (PTX-3) levels were higher in diabetic rats (p < 0.0001), whereas antimullerian hormone (AMH) was lower (p < 0.001). Serum levels of these markers reflected that Diabetes induced injury in the reproductive tract occured via oxidative stress, fibrosis and severe inflammation. Diabetes diminished ovarian reserve. Exenatide treatment improved the histological degeneration and fibrosis in the endometrium and ovary with concomitant decrease in inflammatory and oxidative stress markers (p < 0.05). Exenatide also improved ovarian reserve (p < 0.05). Glucose toxicity occured severely in ovary and endometrium in DM. After exenatide treatment; ovarian and endometrial injury and fibrosis seems to decrease significantly. The effects of exenatide in rat models give hope to prevent the women with DM from premature ovarian failure and endometrial dysfunction.

Neuroprotective effects of erythropoietin on Alzheimer’s dementia model in rats

BACKGROUND Although Alzheimers disease (AD) is the most common age-related neurodegenerative disease and characterized by memory impairment, only symptomatic treatments are available. OBJECTIVES Because recombinant human erythropoietin (rhEPO) has various neuroprotective effects and improves cognitive function in animal models of neurodegenerative disorders, we investigated the therapeutic effects of rhEPO in an intracerebroventricular (ICV)-streptozotocin (STZ) animal model of sporadic-AD. MATERIAL AND METHODS A total of 24 Sprague-Dawley adult rats were divided into 4 groups of naive control (n = 6), sham-operated (n = 6), ICV-STZ + saline (n = 6) and ICV-STZ + rhEPO (n = 6). Twelve rats with Alzheimers disease, induced by STZ injection (3 mg/kg) into both lateral ventricles using a stereotaxic frame (bilaterally ICV-STZ), were divided into 2 groups 5 days after the STZ injection: one treated with rhEPO 5000 (IU/kg/day, i.p.) and the other with 0.9% NaCl (1 mL/kg/day, i.p.) for 2 weeks. The sham-operated rats received bilaterally ICV-0.9% NaCl. No surgical operation or treatment was given to the naive-control animals. On day 20, a passive avoidance learning (PAL) test was used followed by sacrification and removal of the brain tissue in all animals. Brain TNF-α and ChAT levels were determined, and neurons in the hippocampal CA1 and CA3 regions were counted by Cresyl violet staining. RESULTS ICV-STZ was found to significantly shorten the latency time on the PAL, increase brain TNF-α level, and decrease brain ChAT activity and the number of neurons in the hippocampal CA1 and CA3 regions. On the other hand, rhEPO significantly attenuated all these detrimental effects induced by STZ. CONCLUSIONS RhEPO treatment significantly prevented the ICV-STZ-induced memory deficit by attenuating the hippocampal neuronal loss, neuroinflammation and cholinergic deficit in rats. This result suggests that rhEPO may be beneficial for treating AD.

Comparison of cell cycle components, apoptosis and cytoskeleton-related molecules and therapeutic effects of flavopiridol and geldanamycin on the mouse fibroblast, lung cancer and embryonic stem cells.

Similarities and differences in the cell cycle components, apoptosis and cytoskeleton-related molecules among mouse skin fibroblast cells (MSFs), mouse squamous cell lung carcinomas (SqCLCs) and mouse embryonic stem cells (mESCs) are important determinants of the behaviour and differentiation capacity of these cells. To reveal apoptotic pathways and to examine the distribution and the role of cell cycle–cell skeleton comparatively would necessitate tumour biology and stem cell biology to be assessed together in terms of oncogenesis and embryogenesis. The primary objectives of this study are to investigate the effects of flavopiridol, a cell cycle inhibitor, and geldanamycin, a heat shock protein inhibitor on mouse somatic, tumour and embryonic stem cells, by specifically focusing on alterations in cytoskeletal proteins, cell polarity and motility as well as cell cycle regulators. To meet these objectives, expression of several genes, cell cycle analysis and immunofluorescence staining of intracellular cytoskeletal molecules were performed in untreated and flavopiridol- or geldanamycin-treated cell lines. Cytotoxicity assays showed that SqCLCs are more sensitive to flavopiridol than MSFs and mESCs. Keratin-9 and keratin-2 expressions increased dramatically whereas cell cycle regulatory genes decreased significantly in the flavopiridol-treated MSFs. Flavopiridol-treated SqCLCs displayed a slight increase in several cell cytoskeleton regulatory genes as well as cell cycle regulatory genes. However, gene expression profiles of mESCs were not affected after flavopiridol treatment except the Cdc2a. Cytotoxic concentrations of geldanamycin were close to each other for all cell lines. Cdkn1a was the most increased gene in the geldanamycin-treated MSFs. However, expression levels of cell cytoskeleton-associated genes were increased dramatically in the geldanamycin-treated SqCLCs. Our results revealing differences in molecular mechanisms between embryogenesis and carcinogenesis may prove crucial in developing novel therapeutics that specifically target cancer cells.

Exogenously administered adenosine attenuates renal damage in streptozotocin-induced diabetic rats.

Abstract Background: Diabetic nephropathy (DNP) is one of the most serious complications of diabetes mellitus (DM). In the present study, we investigated the potential of adenosine as a therapeutic candidate for preventing DNP. Methods: Twenty-one adult male rats were included in the study. Fourteen rats were administered a single dose of 60 mg/kg streptozotocin (STZ) to induce diabetes. Seven rats served as normal control group. Diabetic rats were randomly divided into two groups: one group was treated with 1 mL/kg saline/day (DM + saline) and the other group was treated with 5 mg/kg/day adenosine (DM + adenosine) for 6 weeks. After 6 weeks, biochemical parameters including urea, creatinine, blood urea nitrogen (BUN), kidney injury molecule-1 (KIM-1) and tumor necrosis factor-α (TNF-α) were measured in plasma samples. Also, kidneys were removed for histopathological assessment. Results: Both of plasma KIM-1 and TNF-α levels were significantly higher in DM + saline group compared to controls. However, treatment of diabetic rats with adenosine significantly decreased the plasma KIM-1 and TNF-α levels compared to DM + saline group. Significant histopathological changes were observed in diabetic rats whereas adenosine treatment effectively prevented these changes. Conclusions: The findings of the present study suggest that adenosine may be a useful therapeutic agent for preventing DNP.

The efficacy of Aesculus hippocastanum seeds on diabetic nephropathy in a streptozotocin-induced diabetic rat model

Cytokines, such as transforming growth factor (TGF)-ß1, and increased oxidative stress are considered to be responsible for the development of diabetic nephropathy. We hypothesized that Aesculus hippocastanum (AH) seeds may have preventive effects on oxidative stress and TGF-β-related diabetic nephropathy in streptozotocin (STZ)-induced diabetic nephropathy in rats. Twenty-one male Sprague-Dawley albino rats were divided into three groups (n=7). Except for the control group, they all had diabetic nephropathy induced by an intraperitoneal injection of STZ. While the diabetes group did not receive any medication, the diabetes+AH group was given the medication for 4 weeks. After the experiment, analyses were performed to evaluate the glomerular area, severity of sclerosis, and fibronectin immunoexpression, as well as levels of malondialdehyde (MDA), TGF-β, blood urea nitrogen (BUN), blood glucose, creatinine, and proteinuria. It was found that glomerular area, severity of sclerosis, fibronectin immunoexpression, and levels of MDA, TGF-β, BUN, creatinine, and proteinuria were decreased in the diabetes+AH group. It is known that diabetic nephropathy is induced, to a large extent, by hyperglycemia. In the present study, AH extract ameliorated diabetic nephropathy without decrease in blood glucose levels. In the study, AH seeds showed beneficial effects on the functional properties of the kidney and microscopic improvements in diabetic nephropathy.

The protective effect of losartan on diabetic neuropathy in a diabetic rat model.

AIM Involvement of the peripheral and autonomic nervous systems is possibly the most frequent complication of diabetes. Important risk factors included hyperglycemia, dyslipidemia, hypertension, and smoking. Angiotensin-converting-enzyme inhibitor (ACE) inhibitors should be beneficial in all vascular beds, including neuropathy and retinopathy. In this study we aimed to evaluate the effect of the angiotensin receptor blocker losartan on diabetic neuropathy in a diabetic rat model. MATERIAL AND METHODS 24 male, Sprague Dawley albino mature rats were divided into 3 groups; (1) control group: No drug was administered to the remainder of rats which blood glucose levels were under 120 mg/dl, (2) diabetic control: rats were given no medication, but 4 ml per day of tap water was given by oral gavage, (3) losartan groups: rats were given 10 mg/kg/day oral of losartan for 4 weeks. Electromyography (EMG) was applied to anesthetized rats at the end of 4(th) weekend. Then, the animals were euthanized and sciatic nerve was performed for histopathological examination. RESULTS Compound Muscle Action Potential (CMAP) amplitude of diabetic rats receiving the Saline in the EMG was significantly reduced when compared to the control group. Distal latency value and CMAP duration of diabetic rats receiving the saline were meaningfully increased when compared to the control group. CMAP amplitude and CMAP duration of diabetic rats receiving the Losartan treatment in the EMG were meaningfully reduced when compared to diabetic rats receiving the Saline.Perineural thickness in the rats receiving the Losartan treatment was found to be significantly reduced when compared to the group receiving the Saline. CONCLUSIONS As a result, it has been shown in this study that perineural thickness of the Losartan treatment was significantly reduced when compared to saline receiving group, significantly increased the immunoexpression of NGF, and also provided a significantly recovery in EMG when compared to Saline receiving group.

Effect of platelet-rich plasma on reconstruction with nerve autografts

Despite advances in understanding of peripheral nerve injuries and regeneration and advances in surgical techniques, successful outcomes cannot be guaranteed after reconstructive surgery. Platelet‐rich plasma (PRP) has been reported to have positive effects on nerve regeneration, as well as on tissue healing. The present study was designed to evaluate the effect of PRP on nerve‐grafted defects. Sprague–Dawley rats were divided into four surgery groups (n = 7 in each). A 1‐cm long nerve defect was created in the upper thigh and then reconstructed using a nerve autograft in all groups. The wet muscle weights, electromyographic findings, and histomorphologic changes were evaluated 10 weeks later. As shown by both the electromyographic (p < 0.001) and histomorphologic findings (p < 0.001), PRP had more positive effects on nerve gap reconstruction in Group 3 then Group 4 as compared to the control groups. The present study is novel in that it evaluated the regeneration effect of PRP on a large nerve defect reconstructed with a nerve graft rather than primary repair. The results are encouraging for further experimental studies on the role of PRP in nerve healing.