Effects of topiramate on diabetes mellitus induced by streptozotocin in rats

Neuropathic pain in cats: Mechanisms and multimodal management

PRACTICAL RELEVANCE

Chronic pain is a significant welfare concern in cats, and neuropathic pain, which arises from aberrant processing of sensory signals within the nervous system, is a subcategory of this type of pain. To comprehend this condition and how multimodal pharmacotherapy plays a central role in alleviating discomfort, it is crucial to delve into the anatomy of nociception and pain perception. In addition, there is an intricate interplay between emotional health and chronic pain in cats, and understanding and addressing the emotional factors that contribute to pain perception, and vice versa, is essential for comprehensive care.Clinical approach:Neuropathic pain is suspected if there is abnormal sensation in the area of the distribution of pain, together with a positive response to trial treatment with drugs effective for neuropathic pain. Ideally, this clinical suspicion would be supported by confirmation of a lesion at this neurolocalisation using diagnostic modalities such as MRI and neuroelectrophysiology. Alternatively, there may be a history of known trauma at that site. A variety of therapies, including analgesic, anti-inflammatory and adjuvant drugs, and neuromodulation (eg, TENS or acupuncture), can be employed to address different facets of pain pathways.Aim:This review article, aimed at primary care/ general practitioners, focuses on the identification and management of neuropathic pain in cats. Three case vignettes are included and a structured treatment algorithm is presented to guide veterinarians in tailoring interventions.Evidence base:The review draws on current literature, where available, along with the author's extensive experience and research.

Protective Effect of Topiramate against Diabetic Retinopathy and Computational Approach Recognizing the Role of NLRP3/IL-1β/TNF-α Signaling

The possible impact of topiramate against diabetic retinopathy (DREN) and its molecular mechanisms in relation to the nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome has not been studied before. Thus, in the present study, we aimed to utilize a computational approach to investigate the possible protective effect of topiramate on experimental DREN and explore its impact on NLRP3/interlukin-1β signaling and brain-derived neurotrophic factor (BDNF) expression. Male albino mice were distributed to four experimental groups and assigned the following categorizations: (i) saline, (ii) diabetic, (iii) diabetic + topiramate 10 mg/kg and (iv) diabetic + topiramate 30 mg/kg. We observed shrinkage of total retinal thickness and elevation in retinal glutamate, malondialdehyde, NLRP3 and interlukin-1β but decreased glutathione (GSH) levels in the diabetic mice. Additionally, retinal ultra-structures in the diabetic group showed abnormalities and vacuolations in the pigmented epithelium, the photoreceptor segment, the outer nuclear layer, the inner nuclear layer and the ganglion cell layer (GCL). Mice treated with topiramate 10 or 30 mg/kg showed downregulation in retinal malondialdehyde, NLRP3 and interlukin-1β levels; improvements in the retinal pathologies; enhanced immunostaining for BDNF and improved ultra-structures in different retinal layers. Overall, the current results suggest topiramate as a neuroprotective agent for DREN, and future studies are warranted to further elucidate the mechanism of its protective action.

Disruption of the hippocampal and hypothalamic blood-brain barrier in a diet-induced obese model of type II diabetes: prevention and treatment by the mitochondrial carbonic anhydrase inhibitor, topiramate

BACKGROUND

Type II diabetes is a vascular risk factor for cognitive impairment and increased risk of dementia. Disruption of the blood-retinal barrier (BRB) and blood-brain barrier (BBB) are hallmarks of subsequent retinal edema and central nervous system dysfunction. However, the mechanisms by which diet or metabolic syndrome induces dysfunction are not understood. A proposed mechanism is an increase in reactive oxygen species (ROS) and oxidative stress. Inhibition of mitochondrial carbonic anhydrase (mCA) decreases ROS and oxidative stress. In this study, topiramate, a mCA inhibitor, was examined for its ability to protect the BRB and BBB in diet-induced obese type II diabetic mice.

METHODS

BBB and BRB permeability were assessed using 14C-sucrose and 99mTc-albumin in CD-1 mice fed a low-fat (control) or a high-fat diet. Topiramate administration was compared to saline controls in both preventative and efficacy arms examining BRB and BBB disruption. Body weight and blood glucose were measured weekly and body composition was assessed using EchoMRI. Metabolic activity was measured using a comprehensive laboratory animal monitoring system. Brain tissues collected from the mice were assessed for changes in oxidative stress and tight junction proteins.

RESULTS

High-fat feeding caused increased entry of 14C-sucrose and 99mTc-albumin into the brains of diet-induced obese type II diabetic mice. Increased permeability to 14C-sucrose was observed in the hypothalamus and hippocampus, and attenuated by topiramate treatment, while increased permeability to 99mTc-albumin occurred in the whole brain and was also attenuated by topiramate. Treatment with topiramate decreased measures of oxidative stress and increased expression of the tight junction proteins ZO-1 and claudin-12. In the retina, we observed increased entry of 99mTc-albumin simultaneously with increased entry into the whole brain during the preventative arm. This occurred prior to increased entry to the retina for 14C-sucrose which occurred during the efficacy arm. Treatment with topiramate had no effect on the retina.

CONCLUSIONS

Blood-brain barrier and blood-retinal barrier dysfunction were examined in a mouse model of diet-induced obese type II diabetes. These studies demonstrate that there are spatial and temporal differences in 14C-sucrose and 99mTc-albumin permeability in the brain and retina of diet-induced obese type II diabetic mice. Topiramate, a mitochondrial carbonic anhydrase inhibitor, is efficacious at both preventing and treating BBB disruption in this diet-induced obese type II diabetic mouse model.

The safety profile of new antidiabetic xanthine derivatives and their chitosan based formulations

The safety profile of new antidiabetic xanthine derivatives with thiazolidine‑4‑one scaffold (6, 7) and their new chitosan based formulations (CS-6, CS-7), administrated to diabetic rats, have been evaluated in terms of biochemical markers of liver and kidney function as well as of hematological markers. The effect on lipid profile and clinic parameters (body weight, food and water intake) has been also evaluated. The treatment of diabetic rats with xanthine derivatives (6, 7) and chitosan based formulations (CS-6, CS-7) was associated with lower liver enzymes (AST, ALT, LDH) and bilirubin (direct, total) values compared to the non-treated diabetic rats, that means the tested derivatives/formulations have improved the liver function injured in diabetes mellitus conditions. Also the kidney biochemical markers (creatinine, uric acid, urea) were significantly decreased in diabetic rats treated with 6, 7 and chitosan microparticles (CS-6, CS-7). The values of biochemical markers of liver and kidney functions were even better than the values recorded for pioglitazone, used as standard antidiabetic drug. The improving effect on kidney function was proved by the histopathological study. Moreover, the xanthine derivatives and their chitosan based formulation were associated with improved hematological markers compared to the non-treated diabetic rats which mean the improving of the hemorheological state. These results support the safety profile of new xanthine derivatives with thiazolidine‑4‑one scaffold (6, 7) and their new chitosan based formulations (CS-6, CS-7) and their potential applications for the treatment of diabetes mellitus syndrome.

A Review on Central Nervous System Effects of Gastrodin

Rhizoma Gastrodiae (also known as Tian ma), the dried rhizome of Gastrodia elata Blume, is a famous Chinese herb that has been traditionally used for the treatment of headache, dizziness, spasm, epilepsy, stoke, amnesia and other disorders for centuries. Gastrodin, a phenolic glycoside, is the main bioactive constituent of Rhizoma Gastrodiae. Since identified in 1978, gastrodin has been extensively investigated on its pharmacological properties. In this article, we reviewed the central nervous system (CNS) effects of gastrodin in preclinical models of CNS disorders including epilepsy, Alzheimer's disease, Parkinson's disease, affective disorders, cerebral ischemia/reperfusion, cognitive impairment as well as the underlying mechanisms involved and, where possible, clinical data that support the pharmacological activities. The sources and pharmacokinetics of gastrodin were also reviewed here. As a result, gastrodin possesses a broad range of beneficial effects on the above-mentioned CNS diseases, and the mechanisms of actions include modulating neurotransmitters, antioxidative, anti-inflammatory, suppressing microglial activation, regulating mitochondrial cascades, up-regulating neurotrophins, etc. However, more detailed clinical trials are still in need for positioning it in the treatment of neurological disorders.

Involvement of AMPA/kainate and GABAA receptors in topiramate neuroprotective effects against methylphenidate abuse sequels involving oxidative stress and inflammation in rat isolated hippocampus

Abuses of methylphenidate (MPH) as psychostimulant cause neural damage of brain cells. Neuroprotective properties of topiramate (TPM) have been indicated in several studies but its exact mechanism of action remains unclear. The current study evaluates protective role of various doses of TPM and its mechanism of action in MPH induced oxidative stress and inflammation. The neuroprotective effects of various doses of TPM against MPH induced oxidative stress and inflammation were evaluated and then the action of TPM was studied in presence of domoic acid (DOM), as AMPA/kainate receptor agonist and bicuculline (BIC) as GABAA receptor antagonist, in isolated rat hippocampus. Open Field Test (OFT) was used to investigate motor activity changes. Oxidative, antioxidant and inflammatory factors were measured in isolated hippocampus. TPM (70 and 100mg/kg) decreased MPH induced motor activity disturbances and inhibit MPH induced oxidative stress and inflammation. On the other hand pretreatment of animals with DOM or BIC, inhibit this effect of TPM and potentiate MPH induced motor activity disturbances and increased lipid peroxidation, mitochondrial oxidized form of glutathione (GSSG) level, interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in isolated hippocampal cells and decreased reduced form of glutathione (GSH) level, superoxide dismutase, glutathione peroxidase and glutathione reductase activity. It seems that TPM can protect cells of hippocampus from oxidative stress and neuroinflammation and it could be partly by activation of GABAA receptor and inhibition of AMPA/kainite receptor.

Effects of Thymoquinone on the Pharmacokinetics and Pharmacodynamics of Glibenclamide in a Rat Model

Glibenclamide and thymoquinone plasma concentrations were analysed using a sensitive RP-HPLC method, and non-compartmental model pharmacokinetic parameters were calculated. The maximum reduction in blood glucose level was observed 3 hours following glibenclamide administration, which reached 47.4% of baseline, whereas it was reduced by 53.0% to 56.2% when co-administrated with thymoquinone. Plasma concentration of glibenclamide was increased by 13.4% and 21.8% by the co-administration of thymoquinone as single and multiple doses, respectively ( P<0.05). The AUC and T1/2 of glibenclamide were also increased respectively by 32.0% and 17.4% with a thymoquinone single dose, and by 52.5% and 92.8% after chronic treatment. Furthermore, diabetic rats treated with thymoquinone demonstrated a marked decrease in hepatic protein expressions of CYP3A2 and CYP2C11 enzymes that are responsible for the metabolism of glibenclamide. The current data suggest that thymoquinone exhibits a synergistic effect with glibenclamide on glucose level, which could be explained by reducing CYP450 activity at the protein level.

Second generation anti-epileptic drugs adversely affect reproductive functions in young non-epileptic female rats

Reproductive endocrine disturbances are a major health concern in women with epilepsy due to their long term use of antiepileptic drugs (AEDs). Second generation AEDs such as topiramate (TPM) and gabapentin are frequently used for the treatment of epilepsy as well as migraine, bipolar disorder etc. Despite the widespread clinical complications, however the definitive mechanism(s) mediating the side effects of TPM and gabapentin remain obscure. The present study was aimed to evaluate the long term effects of TPM and gabapentin on reproductive functions in young female Wistar rats. Estrous cyclicity, ovarian histology as well as estradiol, LH, leptin and insulin hormones level were studied to elucidate the long-term effect of these AEDs monotherapy on reproductive functions in non-epileptic animals. Further to explore the effects on gonadotropin releasing hormone (GnRH) neuroendocrine plasticity, the expression of GnRH, gamma-amino butyric acid (GABA), glutamic acid decarboxylase (GAD), glial fibrilliary acidic protein (GFAP) and polysialylated form of neural cell adhesion molecule (PSA-NCAM) was studied in median eminence (ME) region of these animals by immunohistochemistry, Western blot hybridization and RT-PCR. Our results demonstrate that TPM and gabapentin treatment for 8 weeks cause reproductive dysfunction as ascertained by disturbed hormonal levels and estrous cyclicity as well as alterations in GABAergic system and GnRH neuronal-glial plasticity. Our findings suggest that treatment with TPM and gabapentin disrupts the complete hypothalamo-hypophyseal-gonadal axis (HPG) through GnRH pulse generator in hypothalamus.

Analgesic effects of mad honey (grayanotoxin) in mice models of acute pain and painful diabetic neuropathy

Objectives:

The aim of this experimental study was to investigate the effects of mad honey (grayanotoxin, GTX), used in complementary medicine for a variety of purposes besides being food, on pain thresholds in normal mice as model for acute pain and diabetic mouse as model for neuropathic pain.

Methods:

Hind paw withdrawal pain threshold to thermal stimulus was measured with a plantar analgesia meter in a mice model using healthy intact animals for acute pain and streptozotocin-induced diabetic animals for chronic neuropathic pain. Time and dose-dependent effects of intraperitoneally (i.p.) administered GTX were investigated in both acute and neuropathic pain.

Results:

In the acute pain model, administration of GTX caused a dose- and time-dependent marked increase in the pain latency values. In diabetic mice, which had markedly increased threshold to pain, GTX (0.1 mg/kg, i.p.) restored the mean pain latencies by decreasing from the pre-GTX treatment values of 3.2 ± 0.6 to 3.0 ± 0.9s at 10 min, 3.2 ± 0.6s at 20 min, 3.4 ± 0.6s at 30 min, 2.6 ± 0.5s at 60 min and 2.4 ± 0.6s ( p < 0.05) at 100 min.

Conclusion:

The results from this experimental study indicate that GTX exhibits significant analgesic activity and has potential benefits against painful diabetic neuropathy. This is compatible with the widespread use of GTX containing mad honey for alleviating pain. Further studies involving long-term applications are needed for a more decisive conclusion regarding the usefulness of GTX as an analgesic, especially in the treatment of painful neuropathy.

Antihyperglycemic effect of Ginkgo biloba extract in streptozotocin-induced diabetes in rats

The Ginkgo biloba extract (GBE) has been reported to have a wide range of health benefits in traditional Chinese medicine. The aim of this study was to evaluate the antihyperglycemic effects of GBE on streptozotocin- (STZ-) induced diabetes in rats. Diabetes was induced in male Wistar rats by the administration of STZ (60 mg/kg b.w.) intraperitoneally. GBE (100, 200, and 300 mg/kg b.w.) was administered orally once a day for a period of 30 days. Body weight and blood glucose levels were determined in different experimental days. Serum lipid profile and antioxidant enzymes in hepatic and pancreatic tissue were measured at the end of the experimental period. Significant decreases in body weight and antioxidant ability and increases in blood glucose, lipid profile, and lipid peroxidation were observed in STZ-induced diabetic rats. The administration of GBE and glibenclamide daily for 30 days in STZ-induced diabetic rats reversed the above parameters significantly. GBE possesses antihyperglycemic, antioxidant, and antihyperlipidemia activities in STZ-induced chronic diabetic rats, which promisingly support the use of GBE as a food supplement or an adjunct treatment for diabetics.