stilbenes and Diabetic-Neuropathies

Resveratrol is a naturally occurring phytoalexin found in many plants, nuts and fruits and is abundant in grapes and red wine. Resveratrol possesses a wide range of biological activities which include antioxidant, anti-inflammatory, chemoprotective, chemopreventive etc. Resveratrol has been investigated extensively in diabetes and its complications which suggest its anti-diabetic activity and protective effect against various diabetic complications. Neurons are extremely susceptible to oxidant-induced damage which may be due to their high rate of oxygen consumption and low levels of antioxidant defence enzymes. Traditionally, it was thought that the protective actions of resveratrol in diabetic neuropathy are due to its intrinsic radical scavenger properties. However, recently many other associated or separate mechanisms like upregulation of Nrf2, SIRT1 and inhibition of NF-κB, AP-1 have been proposed for its beneficial effect against nerve dysfunction. This present review discusses the neuroprotective effects of resveratrol that have been observed in experimental diabetic neuropathy and possible mechanistic explanations, as these effects may provide directions for the development of newer therapies. Futuristic therapies can be based on either resveratrol or its analogs with better bioavailability, or combining the resveratrol with existing therapies.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Diabetic Neuropathies; Humans; Neuroprotective Agents; Resveratrol; Stilbenes

Mitochondrial dysfunction has been implicated as a one of the major factors linked to the development of painful diabetic neuropathy (DN). Several studies have demonstrated that sirtuin (SIRT1) activation recuperates nerve function by activating mitochondrial biogenesis. Polydatin, a resveratrol glycoside, has been explored to improve mitochondrial function via SIRT1 activation. However, the neuroprotective effects of polydatin in DN remain elusive. In this study, polydatin (25 and 50 mg/kg, oral) was administered for last 2 weeks of 8-week study to diabetic Sprague-Dawley rats weighing 250-300 g (post 6-weeks of streptozotocin 55 mg/kg, intraperitoneal). Treatment with polydatin significantly attenuated mechanical and thermal hyperalgesia in diabetic rats. Treated diabetic rats also showed improvement in motor/sensory nerve conduction velocities and nerve blood flow. For in vitro studies, Neuro2a cells were exposed to high-glucose (30 mM) condition to simulate short-term hyperglycemia. Polydatin was evaluated for its role in SIRT1 and Nrf2 activation at a dose of 5, 10, and 20 µM concentrations. Polydatin exposure normalized the mitochondrial superoxides, membrane potentials and improved neurite outgrowth in high-glucose-exposed Neuro2a cells. Increased SIRT1 activation by polydatin resulted in peroxisome proliferator activated receptor-gamma coactivator-1α (PGC-1α) directed mitochondrial biogenesis. SIRT1 activation also facilitated Nrf2-directed antioxidant signaling. Study results inferred that decline in mitochondrial biogenesis and oxidative function in diabetic rats and high-glucose-exposed Neuro2a cells, could be counteracted by polydatin administration, postulated via enhancing SIRT1 and Nrf2 axis.

Topics: Animals; Antioxidants; Diabetes Mellitus, Experimental; Diabetic Neuropathies; Glucosides; Mice; Mitochondria; Organelle Biogenesis; Oxidative Stress; Sirtuin 1; Stilbenes; Streptozocin

Damages to the enteric nervous system caused by diabetes mellitus (DM) are frequently attributed to oxidative and nitrosative stress. We aimed to investigate the effect of Resveratrol (RSV) (10 mg/kg) on oxidative and nitrosative stress in the intestinal wall and morphoquantitative aspects of the myenteric plexus of the duodenum, jejunum and ileum in diabetic rats. Twenty-four rats were distributed into four groups (n = 6/group): control (C group), control treated with RSV (CR group), diabetic (D group), and diabetic treated with RSV (DR group) for 120 days. Immunohistochemical staining techniques for the general neuronal population, nitrergic and calretinin neuronal subpopulations, enteric glial cells and glial fibrillary acid protein were performed in the myenteric plexus. Furthermore, parameters of oxidative and nitrosative stress were analyzed in the intestinal wall. RSV attenuated oxidative and nitrosative stress and prevented neuronal loss and hypertrophy of the HuC/D-IR, nNOS-IR and CALR-IR neuronal subpopulations in the DR group compared with the D group (P < 0.05). In addition, RSV prevented the increase in glial fibrillary acid protein fluorescence in the DR group compared with the D (P < 0.05). These results suggest that RSV has antioxidant and neuroprotective effects in myenteric plexus in rats with experimental DM.

Topics: Animals; Diabetes Mellitus, Experimental; Diabetic Neuropathies; Intestine, Small; Male; Myenteric Plexus; Neuroprotective Agents; Nitrosative Stress; Oxidative Stress; Rats, Wistar; Resveratrol; Stilbenes; Streptozocin

Oxidative stress has been implicated in the progression of pathogenesis in diabetes mellitus and leads to a variety of deformations in the central nervous system. Recent studies have provided several insights on therapeutic uses of resveratrol in diabetic complications.. The present study determines if resveratrol ameliorates oxidative stress and molecular changes in the brain frontal cortex of streptozotocin-induced diabetic rats.. Rats were divided into four groups: control, diabetic, resveratrol-treated control, and resveratrol-treated diabetic. After diabetes induction, resveratrol (20 mg/kg) was given intraperitoneally once daily for 4 weeks. In addition to enzymatic activities, gene and protein expression of brain antioxidant enzymes were utilized by qRT-PCR and Western blot, respectively.. The results indicated a significant elevation in total oxidant species (1.22-fold) and malonedialdehyde (1.38-fold) contents in diabetic rat brain cortex tissues. In addition, significant augmentation in the activities of catalase (1.38-fold) and superoxide dismutase (3-fold) was witnessed with the gene and protein expression levels reflecting a transcriptional regulation. Resveratrol treatment significantly normalized diabetic malonedialdehyde and oxidized glutathione levels and strengthens the action of all antioxidant enzymes. Recovery of the diabetes-associated changes reflects the reduction of oxidative conditions by resveratrol and reveals the decrease in the requirement for the activation of antioxidant defense systems in the brain tissues of diabetic rats.. Potent antioxidant and neuroprotective properties of resveratrol against diabetes-induced oxidative damage were demonstrated and the results support the conduct of new studies searching for the molecular mechanism of diabetes-induced changes in brain tissues.

Topics: Animals; Antioxidants; Biomarkers; Diabetes Mellitus, Experimental; Diabetic Neuropathies; Frontal Lobe; Gene Expression Regulation, Enzymologic; Glutathione; Male; Malondialdehyde; Neuroprotective Agents; Oxidative Stress; Rats, Wistar; Resveratrol; Stilbenes; Streptozocin

Resveratrol has shown array of biological actions, and is under clinical development for various disease conditions. The etiology of diabetic neuropathy revolves around oxidative stress, AGE formation, lipid peroxidation etc. All these stimulate inflammatory processes and NF-kappaB cascade is considered as one of the major players of inflammatory response. Activation of NF-kappaB results in elevated levels of inflammatory mediators. COX-2 and TNF-alpha activity have also been correlated with inflammatory damage in the pathophysiology of diabetic neuropathy (DN). Therefore we investigated the effect of resveratrol on NF-kappaB inflammatory cascade, COX-2, TNF-alpha and IL-6 levels in experimental DN. We found that resveratrol protected against various functional and behavioral deficits in diabetic neuropathy in line with our earlier published reports. In this study we found that the resveratrol treatment decreased the expression of p65 and IkappaB-alpha in treated rats. Treatment also ameliorated the elevated levels of TNF-alpha, IL-6 and COX-2. Resveratrol treatment produced significant decrease in nerve MDA levels in treated animals which may also be contributing to reduction in neuro-inflammation. This study confirms the NF-kappaB inhibitory activity and anti-inflammatory activity of resveratrol which may contribute to neuroprotection in diabetic neuropathy apart from its antioxidant effect.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Blood Glucose; Cyclooxygenase 2; Diabetic Neuropathies; I-kappa B Proteins; Interleukin-6; Male; Malondialdehyde; Neuroprotective Agents; NF-kappa B; NF-KappaB Inhibitor alpha; Oxidative Stress; Rats; Rats, Sprague-Dawley; Resveratrol; Stilbenes; Tumor Necrosis Factor-alpha

The present study investigated whether combination of resveratrol and 4-amino 1,8 naphthalimide (4-ANI) is effective in the development of diabetic neuropathy (DN). After 6 weeks of diabetes induction, rats were treated for 2 weeks with resveratrol and 4-amino 1,8 naphthalimide (4-ANI) either alone or in combination. Experimental end points included functional, behavioural and biochemical parameters along with PAR immunohistochemistry and were performed at the end of treatment. Combination of resveratrol (10 mg/kg) and 4-ANI (3 mg/kg) attenuated conduction and nerve blood flow deficits and resulted in amelioration of diabetic neuropathic pain. Significant reversal of biochemical alterations (peroxynitrite, MDA and NAD levels) were also observed, as well as PAR accumulation in the sciatic nerve. This study suggests the beneficial effect of combining resveratrol and 4-ANI in experimental diabetic neuropathy.

Topics: 1-Naphthylamine; Animals; Antioxidants; Diabetic Neuropathies; Male; Malondialdehyde; NAD; Naphthalimides; Neural Conduction; Neuralgia; Neuroprotective Agents; Oxidative Stress; Pain Measurement; Peroxynitrous Acid; Poly Adenosine Diphosphate Ribose; Quinolones; Rats; Rats, Sprague-Dawley; Resveratrol; Sciatic Nerve; Stilbenes

Diabetic neuropathic pain, an important microvascular complication in diabetes mellitus, is recognized as one of the most difficult types of pain to treat. The underlying mechanisms of painful symptoms may be closely associated with hyperglycaemia but a lack of the understanding of its proper aetiology, inadequate relief, development of tolerance and potential toxicity of classical antinociceptives warrant the investigation of newer agents to relieve this pain. The aim of the present study was to explore the antinociceptive effect of insulin and its combinations with resveratrol and curcumin in attenuating diabetic neuropathic pain. The study also aimed to examine the effect of these combinations on tumour necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) levels in streptozotocin (STZ) induced diabetic mice. Four weeks after a single intraperitoneal injection of streptozotocin (200 mg/kg), mice were tested in the tail immersion and hot-plate assays. Diabetic mice exhibited significant hyperalgesia along with increased plasma glucose and decreased body weights compared with control mice. Chronic treatment with insulin (10 IU/kg/day, s.c.) and its combinations with antioxidants (resveratrol 20 mg/kg or curcumin 60 mg/kg, p.o.) for 4 weeks starting from the 4th week of STZ injection significantly attenuated thermal hyperalgesia and the hot-plate latencies. There was a significant inhibition of TNF-alpha and NO levels when these drugs were given in combination compared with their effects per se. These results indicate an antinociceptive activity of resveratrol and curcumin and point towards the beneficial effect of these combinations with insulin in attenuating diabetic neuropathic pain, possibly through the participation of NO and TNF-alpha.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Curcumin; Diabetes Mellitus, Experimental; Diabetic Neuropathies; Drug Therapy, Combination; Hot Temperature; Insulin; Male; Mice; Nitric Oxide; Pain; Pain Measurement; Phytotherapy; Plant Extracts; Plants, Medicinal; Resveratrol; Stilbenes; Streptozocin; Tumor Necrosis Factor-alpha

The objective of the present study was to investigate the possible neuroprotective effect of resveratrol against streptozotocin-induced hyperglycaemia in the rat brain and medulla spinalis. Thirty adult male Wistar rats were divided into three groups as follows: control group, streptozotocin-induced diabetic-untreated group, and streptozotocin-induced diabetic resveratrol-treated group. Diabetes was induced by a single injection of streptozotocin (STZ) (60 mg/kg body weight). Three days after streptozotocin injection, resveratrol (10 mg/kg) was injected intraperiteonally daily over 6 weeks to the rats in the treatment group. Six weeks later, seven rats from each group were killed and the brain stem and cervical spinal cord were removed. The hippocampus, cortex, cerebellum, brain stem and spinal cord were dissected for biochemical studies (lipid peroxidation measuring malondialdehyde [MDA], xanthine oxidase [XO], nitric oxide [NO] and glutathione). MDA, XO and NO levels in hippocampus, cortex, cerebellum, brain stem and spinal cord in the streptozotocin-induced diabetic-untreated group increased significantly. Treatment with resveratrol significantly reduced MDA, XO and NO production and increased glutathione levels when compared to the streptozotocin-induced diabetic-untreated group. This study demonstrates that resveratrol is a potent neuroprotective agent against diabetic oxidative damage.

Topics: Animals; Central Nervous System Diseases; Diabetes Mellitus, Experimental; Diabetic Neuropathies; Free Radical Scavengers; Glutathione; Hyperglycemia; Lipid Peroxidation; Male; Malondialdehyde; Medulla Oblongata; Neuroprotective Agents; Nitric Oxide; Oxidative Stress; Rats; Rats, Wistar; Resveratrol; Spinal Cord; Stilbenes; Vasodilator Agents; Xanthine Oxidase

Oxidative stress has been implicated in pathophysiology of diabetic neuropathy. All the pathways responsible for development of diabetic neuropathy are linked to oxidative stress in one way or the other. In the present study, we have targeted oxidative stress in diabetic neuropathy using resveratrol, a potent antioxidant. Eight weeks streptozotocin-diabetic rats developed neuropathy which was evident from significant reduction in motor nerve conduction velocity (MNCV), nerve blood flow (NBF) and increased thermal hyperalgesia. The 2-week treatment with resveratrol (10 and 20 mg/kg, i.p.) started 6 weeks after diabetes induction significantly ameliorated the alterations in MNCV, NBF, and hyperalgesia. Resveratrol also attenuated enhanced levels of malondialdehyde (MDA), peroxynitrite and produced increase in catalase levels in diabetic rats. There was marked reduction in DNA fragmentation observed after resveratrol treatment in diabetic rats as evident from decrease in Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positive cells in sciatic nerve sections. Results of the present study suggest the potential of resveratrol in treatment of diabetic neuropathy and its protective effect may be mediated through reduction in oxidative stress and DNA fragmentation.

Topics: Animals; Antioxidants; Apoptosis; Blood Glucose; Diabetes Mellitus, Experimental; Diabetic Neuropathies; DNA Fragmentation; Dose-Response Relationship, Drug; Humans; In Situ Nick-End Labeling; Lipid Peroxidation; Male; Neural Conduction; Oxidative Stress; Pain Measurement; Pain Threshold; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Resveratrol; Sciatic Nerve; Stilbenes