Defective autophagy contributes to bupivacaine-induced aggravation of painful diabetic neuropathy in db/db mice

Current evidence suggests that hyperactivated or impaired autophagy can lead to neuronal death. The effect of local anesthetics on painful diabetic neuropathy (PDN) and the role of autophagy in the above pathological process remain unclear, warranting further studies. So, PDN models were established by assessing the paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) in leptin gene-mutation (db/db) mice. Wild type (WT) and PDN mice received intrathecal 0.75% bupivacaine or/with intraperitoneal drug treatment (rapamycin or bafilomycin A1). Subsequently, the PWT and PWL were measured to assess hyperalgesia at 6 h, 24 h, 30 h, and 48 h after intrathecal bupivacaine. Also, sensory nerve conduction velocity (SNCV) and motor nerve conduction velocity (MNCV) were measured before and 48 h after intrathecal bupivacaine treatment. The spinal cord tissue of L4-L6 segments and serum were harvested to evaluate the change of autophagy, oxidative stress, oxidative injury, and apoptosis. We found that bupivacaine induced the activation of autophagy but did not affect the pain threshold, SNCV and MNCV in WT mice at predefined time points. Conversely, bupivacaine lowered autophagosome generation and degradation, slowed SNCV and aggravated spinal dorsal horn neuron oxidative injury and hyperalgesia in PDN mice. The autophagy activator (rapamycin) could decrease spinal dorsal horn neuron oxidative injury, alleviate the alterations in SNCV and hyperalgesia in bupivacaine-treated PDN mice. Meanwhile, the autophagy inhibitor (bafilomycin A1) could exacerbate spinal dorsal horn neuron oxidative injury, the alterations in SNCV and hyperalgesia in bupivacaine-treated PDN mice. Our results showed that bupivacaine could induce defective autophagy, slowed SNCV and aggravate spinal dorsal horn neuron oxidative injury and hyperalgesia in PDN mice. Restoring autophagy may represent a potential therapeutic approach against nerve injury in PDN patients with local anesthesia and analgesia.

Neuropathic Pain in Aged People: An Unresolved Issue Open to Novel Drug Approaches, Focusing on Painful Diabetic Neuropathy

A majority of older patients suffer from neuropathic pain (NP) that significantly alters their daily activities and imposes a significant burden on health care. Multiple comorbidities and the risk of polypharmacy in the elderly make it challenging to determine the appropriate drug, dosage, and maintenance of therapy. Age-dependent processes play a contributing role in neuropathy given that diabetic neuropathy (DN) is the most common form of neuropathy. This narrative review is mainly focused on the drug treatment approach for neuropathy-associated pain in aged people including both drugs and dietary supplements, considering the latter as add-on mechanism-based treatments to increase the effectiveness of usual treatments by implementing their activity or activating other analgesic pathways. On one hand, the limited clinical studies assessing the effectiveness and the adverse effects of existing pain management options in this age segment of the population (> 65), on the other hand, the expanding global demographics of the elderly contribute to building up an unresolved pain management problem that needs the attention of healthcare providers, researchers, and health authorities as well as the expansion of the current therapeutic options.

Observation of the neuroprotective efficacy of vitamin K in a streptozocin-induced diabetes model in chick embryos

Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia due to insulin deficiency and/or resistance. Vitamin K (VK) is a group of fat-soluble molecules, including naturally occurring vitamin K1 (phylloquinone). vitamin K2 (menaquinone), and synthetic vitamin K3 (menadione). Beyond coagulation, the health benefits of VK have been described to play different roles in both physiological and pathological processes such as inflammation, energy metabolism, neuroprotection, cellular growth, and survival. It was aimed to observe the antioxidant and/or neuroprotective activity of vitamin K1 in our model of chick embryo diabetic neuropathy (DN) induced by streptozotocin (STZ). Ninety White Leghorn, fertile and 0-day-old SPF (specific pathogen-free) eggs (57 ± 4 gr) were used in the study. Chick embryo blood brain tissues were taken for biochemical evaluation. Plasma insulin and glucose levels were measured. In addition, brain tissue total antioxidant level (TAS), total oxidant level (TOS), malondialdehyde (MDA), and vascular endothelial growth factor (VEGF) levels were measured. Plasma glucose levels were higher in the STZ-treated groups and lower in the treatment groups. Plasma insulin levels were observed to be higher in STZ groups in groups treated with high VK. Low TAS, high MDA, TOS, and VEGF levels were recorded in brain tissue STZ groups. Low VEGF, TOS, and MDA levels were recorded in the group treated with the highest VK, while high TAS levels were observed. In our STZ-induced chick embryo diabetic neuropathy model, we observed that VK1 reduced oxidant damage by showing antioxidant properties or by modulating antioxidant enzymes.

Effect of miR-146a polymorphism on lipoic acid therapy in patients with T2DM peripheral polyneuropthy

For investigating the impact of miR-146a rs2910164 polymorphism on the therapeutic efficacy of lipoic acid therapy in patients with type 2 diabetes mellitus (T2DM) peripheral neuropathy (DPN). 106 T2DM-DPN patients in our hospital from Jan. 2020- 2022 were selected. The probe detection method was utilized to determine the polymorphism of the miR-146a rs2910164 gene in peripheral blood. All patients were treated with zinc sulfate for 3 weeks period. According to the treatment effect, 37 patients who were ineffective in treatment will be divided into an ineffective group, and 79 patients who were effective in treatment will be divided into an effective group. The condition of miR-146a gene peptides was analyzed after treatment in both groups. The motor nerve conduction velocity (MNCV), sensory nerve conduction velocity (SNCV), and Toronto Clinical Scoring System (TCSS) scores of the median nerve and common peroneal nerve with different genotypes were compared between the 2 sets. The genotype frequencies of alleles G, GG, and GC in the valid group were lower than those in the invalid group; After treatment, MNCV and SNCV of CC genotype median nerve and common peroneal nerve in DPN patients were higher than those before treatment; The TCSS scores of the three genotypes less than post-treatment. The above results showed statistically significant differences (P<0.05). Lipoic acid is influenced by the miR-146a polymorphism gene in the treatment of T2DM-DPN patients, with the CC genotype having a lower susceptibility and the best clinical treatment effect.

Painful diabetic peripheral neuropathy of the feet: integrating prescription-strength capsaicin into office procedures

Prescription-strength (8%) capsaicin topical system is a US FDA-approved treatment for painful diabetic peripheral neuropathy of the feet. A 30 min application of the capsaicin 8% topical system can provide sustained (up to 3 months) local pain relief by desensitizing and reducing TRPV1-expressing cutaneous fibers. Capsaicin is not absorbed systemically; despite associated application-site discomfort, capsaicin 8% topical system is well tolerated, with no known drug interactions or contraindications, and could offer clinical advantages over oral options. Capsaicin 8% topical system are not for patient self-administration and require incorporation into office procedures, with the added benefit of treatment compliance. This article reviews existing literature and provides comprehensive, practical information regarding the integration of capsaicin 8% topical systems into office procedures.

Cucurbita pepo seeds improve peripheral neuropathy in diabetic rats by modulating the inflammation and oxidative stress in rats

BACKGROUND

Cucurbita pepo (C. pepo) is cultivated and used traditionally as vegetable as well as medicine in different parts of the world. The aim of current study was to investigate the potential of C. pepo in attenuation of diabetic neuropathy via using streptozotocin (STZ)-induced diabetes model in male wistar rats.

MATERIALS AND METHODS

Diabetic neuropathy was induced by administration of STZ; 65 mg/kg, i.p. and Nicotinamide (NAD; 230 mg/kg i.p.) and assessed by measuring thermal hyperalgesia, mechanical hyperalgesia and motor nerve conduction velocity (MNCV) in experimental animals. Treatment with different doses of (100, 200 and 400 mg/kg, p.o.) petroleum ether extract of C. pepo (CPE) and hydroethanolic extract of C. pepo (CHE) was started from the 60th day of STZ/NAD administration and continued upto 90th day.

RESULTS

CPE and CHE significantly attenuated the behavioural changes including hyperalgesia, allodynia and MNCV linked to diabetic neuropathy. Moreover, the oxidative stress and level of TNF-α, TGF-β and IL-1β was found to be significantly attenuated in experimental animals.

CONCLUSION

Thus C. pepo might ameliorate the progression of diabetic neuropathy via modulation of chronic hyperglycemia and therefore and have therapeutic potential for treatment of diabetic neuropathic pain.

Pharmacological evaluation of Thuja occidentalis for the attenuation of neuropathy via AGEs and TNF-α inhibition in diabetic neuropathic rats

When diabetes neuropathy occurs, the oxidative stress caused by chronic hyperglycemia may result in chronic neuronal damage. To mitigate the effects of hyperglycemia-induced neuronal damage, it may be beneficial to address oxidative stress and inflammation in the body. The current study evaluated the neuroprotective efficacy of Thuja occidentalis in streptozotocin (STZ)-nicotinamide (NAD)-induced diabetic neuropathy in male Wistar rats. A single dose of STZ (65 mg/kg, i.p.) was used to induce diabetic neuropathy in Wistar rats. Serum insulin, glucose, hyperalgesia, oxidative stress, inflammatory markers, and histopathology of the sciatic nerve were evaluated for neuropathy. Wistar rats were treated with varying doses of hydroalcoholic extracts of Thuja occidentalis (HAETO) and gabapentin for 30 days. Thuja occidentalis considerably corrected the levels of inflammatory markers and oxidative stress caused by hyperglycemia; also, it led to the restoration of neuronal functions, indicating that it is effective in treating diabetic neuropathy. Furthermore, the molecular docking of thujone at the active pockets of various inflammatory mediators (IL-1β, IL-6, TGF-β1, and TNF-α) has shown good interactions with critical amino acid residues. These findings indicate that the hydroalcoholic extract of Thuja occidentalis effectively inhibits the development of diabetic neuropathy. The hypoglycemic, antioxidant, anti-hyperalgesia, and anti-inflammatory properties of Thuja occidentalis are thought to be responsible for the neuroprotective benefit.

Selective blood-nerve barrier leakiness with claudin-1 and vessel-associated macrophage loss in diabetic polyneuropathy

Diabetic polyneuropathy (DPN) is the most common complication in diabetes and can be painful in up to 26% of all diabetic patients. Peripheral nerves are shielded by the blood-nerve barrier (BNB) consisting of the perineurium and endoneurial vessels. So far, there are conflicting results regarding the role and function of the BNB in the pathophysiology of DPN. In this study, we analyzed the spatiotemporal tight junction protein profile, barrier permeability, and vessel-associated macrophages in Wistar rats with streptozotocin-induced DPN. In these rats, mechanical hypersensitivity developed after 2 weeks and loss of motor function after 8 weeks, while the BNB and the blood-DRG barrier were leakier for small, but not for large molecules after 8 weeks only. The blood-spinal cord barrier remained sealed throughout the observation period. No gross changes in tight junction protein or cytokine expression were observed in all barriers to blood. However, expression of Cldn1 mRNA in perineurium was specifically downregulated in conjunction with weaker vessel-associated macrophage shielding of the BNB. Our results underline the role of specific tight junction proteins and BNB breakdown in DPN maintenance and differentiate DPN from traumatic nerve injury. Targeting claudins and sealing the BNB could stabilize pain and prevent further nerve damage. KEY MESSAGES: • In diabetic painful neuropathy in rats: • Blood nerve barrier and blood DRG barrier are leaky for micromolecules. • Perineurial Cldn1 sealing the blood nerve barrier is specifically downregulated. • Endoneurial vessel-associated macrophages are also decreased. • These changes occur after onset of hyperalgesia thereby maintaining rather than inducing pain.

A new synthetic protectin D1 analog 3-oxa-PD1n-3 DPA reduces neuropathic pain and chronic itch in mice

The resolution of inflammation is a biosynthetically active process controlled by the interplay between oxygenated polyunsaturated mediators and G-protein coupled receptor-signaling pathways. These enzymatically oxygenated polyunsaturated fatty acids belong to distinct families of specialized pro-resolving autacoids. The protectin family of mediators has attracted an interest because of their potent pro-resolving and anti-inflammatory actions verified in several in vivo disease models. Herein, we present the stereoselective synthesis and biological evaluations of 3-oxa-PD1n-3 DPA, a protectin D1 analog. Results from mouse models indicate that the mediators protectin D1, PD1n-3 DPA and the new analog 3-oxa-PD1n-3 DPA all relieved streptozotocin-induced diabetic neuropathic pain at doses of 90 and 300 pmol, equivalent to 30 and 100 ng, respectively, following intrathecal (I.T.) injection. Of interest, at a low dose of only 30 pmol (10 ng; I.T.) only 3-oxa PD1n-3 DPA was able to alleviate neuropathic pain, directly compared to vehicle controls. Moreover, using a chronic itch model of cutaneous T-cell lymphoma (CTCL), all three compounds at 300 pmol (100 ng) showed a significant reduction in itching for several hours. The biomolecular information on the structure-functions of the protectins and the new synthetic analog 3-oxa-PD1n-3 DPA is of interest towards developing new immunoresolvents.

Compound XiongShao Capsule ameliorates streptozotocin-induced diabetic peripheral neuropathy in rats via inhibiting apoptosis, oxidative - nitrosative stress and advanced glycation end products

ETHNOPHARMACOLOGICAL RELEVANCE

Compound XiongShao Capsule (CXSC), a traditional herb formula, has been approved for using to treat diabetic peripheral neuropathy (DPN) by the Shanghai Food and Drug Administration, with significant efficacy in clinic.

AIM OF THE STUDY

This study aimed to investigate the multidimensional pharmacological mechanisms and synergism of CXSC against DPN in rats.

METHODS

The quality analysis of CXSC was performed by high-performance liquid chromatography (HPLC) and thin-layer chromatography. Rats with DPNinduced by streptozotocin/high-fat diet for 4 weeks were treated with CXSC at three doses (1.2 g/kg, 0.36 g/kg, and 0.12 g/kg), or epalrestat (15 mg/kg) daily for 8 weeks continuously. During the treatment period, body weight, serum glucose levels, and nerve function, including nerve conduction velocity (NCV), and mechanical and thermal hyperalgesia were tested and assessed every 4 weeks. In the 13th week, the histopathological examination in the sciatic nerve was performed using a transmission electron microscope. The expression of apoptosis-related proteins of BAX, BCL2, and caspase-3 in the sciatic nerve was examined using hematoxylin and eosin staining. The serum levels of advanced glycation end products (AGEs), oxidative-nitrosative stress biomarkers of superoxide dismutase (SOD), and nitric oxide synthase (NOS) were measured using a rat-specific ELISA kit.

RESULTS

CXSC had no significant effect on body weight or serum glucose levels (P > 0.05), but it significantly improved mechanical hyperalgesia (F_5,36 = 18.24, P < 0.0001), thermal hyperalgesia (F_5,36 = 8.45, P < 0.0001), and NCV (motor NCV: F_5,36 = 7.644, P < 0.0001, sensory NCV: F_5,36 = 12.83, P < 0.0001). Besides, it maintained myelin and axonal structure integrity, downregulated the expression of apoptosis-related proteins in the sciatic nerve tissue, reduced AGEs and NOS levels, and enhanced antioxidant enzyme SOD activities in the serum.

CONCLUSION

CXSC exerted neuroprotective effects against rats with DPN through multidimensional pharmacological mechanisms including antiapoptotic activity in the sciatic nerve and downregulation of the level of serum NOS, SOD and AGEs.

Treatment-Induced Neuropathy in Diabetes (TIND)-Developing a Disease Model in Type 1 Diabetic Rats

Treatment-induced neuropathy in diabetes (TIND) is defined by the occurrence of an acute neuropathy within 8 weeks of an abrupt decrease in glycated hemoglobin-A1c (HbA1c). The underlying pathogenic mechanisms are still incompletely understood with only one mouse model being explored to date. The aim of this study was to further explore the hypothesis that an abrupt insulin-induced fall in HbA1c may be the prime causal factor of developing TIND. BB/OKL (bio breeding/OKL, Ottawa Karlsburg Leipzig) diabetic rats were randomized in three groups, receiving insulin treatment by implanted subcutaneous osmotic insulin pumps for 3 months, as follows: Group one received 2 units per day; group two 1 unit per day: and group three 1 unit per day in the first month, followed by 2 units per day in the last two months. We serially examined blood glucose and HbA1c levels, motor- and sensory/mixed afferent conduction velocities (mNCV and csNCV) and peripheral nerve morphology, including intraepidermal nerve fiber density and numbers of Iba-1 (ionized calcium binding adaptor molecule 1) positive macrophages in the sciatic nerve. Only in BB/OKL rats of group three, with a rapid decrease in HbA1c of more than 2%, did we find a significant decrease in mNCV in sciatic nerves (81% of initial values) after three months of treatment as compared to those group three rats with a less marked decrease in HbA1c <2% (mNCV 106% of initial values, p ≤ 0.01). A similar trend was observed for sensory/mixed afferent nerve conduction velocities: csNCV were reduced in BB/OKL rats with a rapid decrease in HbA1c >2% (csNCV 90% of initial values), compared to those rats with a mild decrease <2% (csNCV 112% of initial values, p ≤ 0.01). Moreover, BB/OKL rats of group three with a decrease in HbA1c >2% showed significantly greater infiltration of macrophages by about 50% (p ≤ 0.01) and a decreased amount of calcitonin gene related peptide (CGRP) positive nerve fibers as compared to the animals with a milder decrease in HbA1c. We conclude that a mild acute neuropathy with inflammatory components was induced in BB/OKL rats as a consequence of an abrupt decrease in HbA1c caused by high-dose insulin treatment. This experimentally induced neuropathy shares some features with TIND in humans and may be further explored in studies into the pathogenesis and treatment of TIND.

Metformin Preserves Peripheral Nerve Damage with Comparable Effects to Alpha Lipoic Acid in Streptozotocin/High-Fat Diet Induced Diabetic Rats

BACKGROUND

Metformin is widely marketed medication for the treatment of diabetes, but its pharmacological effect on diabetic peripheral neuropathy remains unclear. In this study, the effect of metformin on peripheral nerves in diabetic rats was investigated using diverse neuronal parameters of nerve fibers.

METHODS

Rats were assigned to one of four groups (n=7 to 10 per group): normal, diabetes mellitus (DM), DM+metformin (100 mg/kg), and DM+alpha lipoic acid (ALA, 100 mg/kg). DM was induced by streptozotocin/high-fat diet (STZ/HFD). After 12 weeks, the sensory thresholds to mechanical and heat stimuli were assessed. Repeated sensory tests, immunofluorescence microscopic comparison of peripheral nerves, and biochemical blood analysis were performed after 24 weeks.

RESULTS

Both DM+metformin and DM+ALA groups showed similar trends to diverse sensory tests at 24 weeks compared to DM group although the degree of change were different according to the stimulated senses. There was no significant difference in the comparison of the intraepidermal nerve fiber density (IENFD) of peripheral nerves between the DM+metformin and DM+ALA groups (11.83±0.07 fibers/mm vs. 12.37±1.82 fibers/mm, respectively). Both groups showed preserved IENFD significantly compared with DM group (8.46±1.98 fibers/mm, P<0.05). Sciatic nerve morphology of the experimental animals showed a similar trend to the IENFD, with respect to axonal diameter, myelin sheath thickness, and myelinated fiber diameter.

CONCLUSION

Metformin has beneficial pharmacological effects on the preservation of peripheral nerves in diabetic rats and its effects are comparable to those of ALA.

Analgesic and Antiallodynic Effects of 4-Fluoro-N-(4-Sulfamoylbenzyl) Benzene Sulfonamide in a Murine Model of Pain

INTRODUCTION

Physical, chemical, thermal injuries along with infectious diseases lead to acute pain with associated inflammation, being the primary cause of hospital visits. Moreover, neuropathic pain associated with diabetes is a serious chronic disease leading to high morbidity and poor quality of life.

OBJECTIVE

Earlier multiple sulphonamides have been reported to have an antinociceptive and antiallodynic profile. 4-Fluoro-N-(4-sulfamoylbenzyl) Benzene Sulfonamide (4-FBS), a synthetic sulfonamide with reported carbonic anhydrase inhibitory activity, was investigated for its potential effects in mice model of acute and diabetic neuropathic pain.

METHODS AND RESULTS

4-FBS was given orally (p.o.) one hour before the test and then mice were screened for antinociceptive activity by using the tail immersion test, which showed significant antinociceptive effect at both 20 and 40 mg/kg doses. To explore the possible mechanisms, thermal analgesia of 4-FBS was reversed by the 5HT3 antagonist ondansetron 1mg/kg intraperitoneally (i.p.) and by the µ receptor antagonist naloxone (1 mg/kg i.p.), implying possible involvement of serotonergic and opioidergic pathways in the analgesic effect of 4-FBS. Diabetes was induced in mice by a single dose of streptozotocin (STZ) 200 mg/kg i.p. After two weeks, animals first became hyperalgesic and progressively allodynic in the fourth week, which was evaluated through behavioral parameters like thermal and mechanical tests. 4-FBS at 20 and 40 mg/kg p.o. significantly reversed diabetes-induced hyperalgesia and allodynia at 30, 60, 90, and 120 minutes.

CONCLUSION

These findings are significant and promising while further studies are warranted to explore the exact molecular mechanism and the potential of 4-FBS in diabetic neuropathic pain.

Bergenin Reduces Experimental Painful Diabetic Neuropathy by Restoring Redox and Immune Homeostasis in the Nervous System

Diabetic neuropathy is a frequent complication of diabetes. Symptoms include neuropathic pain and sensory alterations—no effective treatments are currently available. This work characterized the therapeutic effect of bergenin in a mouse (C57/BL6) model of streptozotocin-induced painful diabetic neuropathy. Nociceptive thresholds were assessed by the von Frey test. Cytokines, antioxidant genes, and oxidative stress markers were measured in nervous tissues by ELISA, RT-qPCR, and biochemical analyses. Single (3.125–25 mg/kg) or multiple (25 mg/kg; twice a day for 14 days) treatments with bergenin reduced the behavioral signs of diabetic neuropathy in mice. Bergenin reduced both nitric oxide (NO) production in vitro and malondialdehyde (MDA)/nitrite amounts in vivo. These antioxidant properties can be attributed to the modulation of gene expression by the downregulation of inducible nitric oxide synthase (iNOS) and upregulation of glutathione peroxidase and Nrf2 in the nervous system. Bergenin also modulated the pro- and anti-inflammatory cytokines production in neuropathic mice. The long-lasting antinociceptive effect induced by bergenin in neuropathic mice, was associated with a shift of the cytokine balance toward anti-inflammatory predominance and upregulation of antioxidant pathways, favoring the reestablishment of redox and immune homeostasis in the nervous system. These results point to the therapeutic potential of bergenin in the treatment of painful diabetic neuropathy.

Statins-related peripheral neuropathy among diabetic patients

BACKGROUND

Peripheral neuropathy (PN) is a complaint with often unidentified reasons. Some medicines, including statins therapy, are anticipated to be amongst the reasons for PN.

AIMS

This study intended to assess the association of peripheral neuropathy with statins therapy amongst Type 2 diabetic patients.

METHODS

At Penang General Hospital, 757 cases were categorized into two groups (564 with statins therapy and 193 without statins therapy). The diagnosis of PN was investigated retrospectively for a period of 10 years (2006-2016). Confounding risk factors as age, diabetes period, hypertension, glycemic control, other co-morbidity, and prescriptions were matched.

RESULTS

About 129 (22.9%) cases from 564 statins users had PN. Only 30 (15.5%) subjects had PN from 193 statins non-users. Chi-square test showed a significant variance among statins treatment cohort and statin-free cohort in the occurrence of PN (P-value: 0.001). Spearman's investigation presented a positive correlation (r: 0.078, p-value: 0.031) among statins use and PN prevalence. Binary logistic regression was statistically significant for statins therapy as a predictor of peripheral neuropathy incidence (r²: 0.006, p-value: 0.027) amid diabetic patients. The relative risk of peripheral neuropathy connected with statins therapy is (RR: 1.47, 95% CI: 1.02-2.11). The excess relative risk is 47.1%. While the absolute risk (AR) is 7.3% and the number needed to harm (NNH) is 14.

CONCLUSIONS

The study indicated a positive association between peripheral neuropathy and statins utilization. Peripheral neuropathy was higher amongst statins users than the statins-free group.

Catecholaminergic and opioidergic system mediated effects of reboxetine on diabetic neuropathic pain

RATIONALE

Current data indicate that the noradrenergic system plays a critical role in neuropathic pain treatment. Notably, drugs that directly affect this system may have curative potential in neuropathy-associated pain.

OBJECTIVES

The aim of this study was to evaluate the potential therapeutic efficacy of reboxetine, a potent and selective noradrenaline reuptake inhibitor, on hyperalgesia and allodynia responses in rats with experimental diabetes. Furthermore, mechanistic studies were performed to elucidate the possible mode of actions.

METHODS

Experimental diabetes was induced by a single dose of streptozotocin. Mechanical hyperalgesia, mechanical allodynia, thermal hyperalgesia, and thermal allodynia responses in diabetic rats were evaluated by Randall-Selitto, dynamic plantar, Hargreaves, and warm plate tests, respectively.

RESULTS

Reboxetine treatment (8 and 16 mg/kg for 2 weeks) demonstrated an effect comparable to that of the reference drug, pregabalin, improving the hyperalgesic and allodynic responses secondary to diabetes mellitus. Pretreatment with phentolamine, metoprolol, SR 59230A, and atropine did not alter the abovementioned effects of reboxetine; however, the administration of α-methyl-para-tyrosine methyl ester, propranolol, ICI-118,551, SCH-23390, sulpiride, and naltrindole significantly inhibited these effects. Moreover, reboxetine did not induce a significant difference in the rat plasma glucose levels.

CONCLUSIONS

Our findings indicate that the antihyperalgesic and antiallodynic effects of reboxetine are mediated by the catecholaminergic system; β₂-adrenoceptors; D₁-, D₂/D₃-dopaminergic receptors; and δ-opioid receptors. The results suggest that this analgesic effect of reboxetine, besides its neutral profile on glycemic control, may be advantageous in the pharmacotherapy of diabetic neuropathy-induced pain.

Treatment-Induced Neuropathy of Diabetes (TIND) in Pediatrics: A Case Report and Review of the Literature

CONTEXT

Treatment-induced neuropathy of diabetes (TIND) is a rarely reported but important consideration in patients presenting with an acute onset of neuropathic symptoms following rapid correction of hyperglycemia in diabetes. Although it has been reported in children, the preponderance of literature focuses on adults with TIND.

CASE DESCRIPTION

We report an 18-year-old male with this condition and his clinical course. We then discuss the proposed pathophysiology of TIND and review the literature. We also provide a standard workup for the diagnosis of TIND.

CONCLUSION

In both pediatric and adult populations, TIND should be considered in diabetic patients who develop neuropathy acutely following rapid correction of hyperglycemia. Because the pathophysiology of TIND remains poorly understood, there is insufficient information regarding how to target susceptible individuals and prevent the development of TIND.

"Adjusting internal organs and dredging channel" electroacupuncture treatment prevents the development of diabetic peripheral neuropathy by downregulating glucose-related protein 78 (GRP78) and caspase-12 in streptozotocin-diabetic rats

BACKGROUND

The clinical efficacy of electroacupuncture in treating diabetic peripheral neuropathy (DPN) is significant, but the underlying mechanism of action is not clear. Considering that glucose-regulated protein 78 (GRP78) and caspase-12 are major proteins participating in cell apoptosis, we investigated the effects of "adjusting internal organs and dredging channel" electroacupuncture therapy on GRP78 and caspase-12 levels in streptozotocin (STZ)-diabetic rats to elucidate the mechanism of action.

METHODS

Rats were first divided into two groups: one group was rendered diabetic with a single injection of 50 mg/kg STZ, whereas the other normal control group was injected with an equivalent volume of citrate buffer. The STZ-diabetic rats were randomly divided into three groups: model control and electroacupuncture- and mecobalamin-treated groups. After 12 weeks treatment, the therapeutic efficacy of electroacupuncture was assessed using sciatic nerves isolated from rats. In the electroacupuncture group, rats were treated by electroacupuncture for 20 minutes once daily for 6 days each week, with 1 day off, for 12 consecutive weeks. The selected acupressure points include bilateral acupressure points of BL13 (Fehu), BL20 (Pishu), BL23 (Shenshu), LI4 (Hegu), LR3 (faichong), ST36 (Zusanli), and SP6 (Sanyiniiao). Acupressure points were stimulated using a HuaTuo SDZ-V Electric Acupuncture Therapy Apparatus. The acupressure points of BL13 and BL23, as well as SP6 and LR3, were connected on the same side with a dilatational wave of 3 Hz (frequency ratio of 1 : 5) to stimulate the parts of the body to the extent that could be tolerated by the rat. As for the mecobalamin-treated groups, mecobalamin was administrated to rats intragastrically at a dose of 20 mg/kg once daily for 12 consecutive weeks. Immunofluorescence and western blot analysis were used to determine GRP78 and caspase-12 levels in sciatic nerves. In addition, cell apoptosis in sciatic nerves was determined using the terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labeling (TUNEL) assay.

RESULTS

Electroacupuncture markedly reduced the pathological injury to sciatic nerves in STZ-diabetic rats. Moreover, electroacupuncture significantly downregulated GRP78 and caspase-12 and reduced cell apoptosis of sciatic nerves in DPN rats.

CONCLUSIONS

Electroacupuncture improved DPN by downregulating GRP78 and caspase-12 and reducing cell apoptosis of sciatic nerves in STZ-diabetic rats, and further inhibited the occurrence of endoplasmic reticulum stress, thus preventing sciatic nerve injuries.

Raman spectroscopy of dorsal root ganglia from streptozotocin-induced diabetic neuropathic rats submitted to photobiomodulation therapy

In this study, we used Raman spectroscopy as a new tool to investigate pathological conditions at the level of chemical bond alterations in biological tissues. Currently, there have been no reports on the spectroscopic alterations caused by diabetic neuropathy in the dorsal root ganglia (DRG). DRG are a target for the treatment of neuropathic pain, and the need for more effective therapies is increasing. Photobiomodulation therapy (PBMT) through infrared low-level laser irradiation (904 nm) has shown analgesic effects on the treatment of neuropathy. Thus, the aim of this study was to use Raman spectroscopy to characterize the spectral DRG identities of streptozotocin (STZ)-induced diabetic neuropathic (hyperalgesic) rats and to study the influence of PBMT over such spectra. Characteristic DRG peaks were identified at 2704, 2850, 2885, 2940, 3061 and 3160 cm^-1 , whose assignments are CH₂ /CH₃ symmetric/asymmetric stretches, and C─H vibrations of lipids and proteins. DRG from hyperalgesic rats showed an increased normalized intensity of 2704, 2850, 2885 and 3160 cm^-1 . These same peaks had their normalized intensity reduced after PBMT treatment, accompanied by an anti-hyperalgesic effect. Raman spectroscopy was able to diagnose spectral alterations in DRG of hyperalgesic rats and the PBMT reduced the intensity of hyperalgesia and the altered Raman spectra.

Sigma 1 receptor mediated HMGB1 expression in spinal cord is involved in the development of diabetic neuropathic pain

No study has been conducted to examine the interactions of sigma-1 receptor (Sigma-1R) and high mobility group box 1 protein (HMGB1) in the development of diabetic peripheral neuropathy. Thus, we examined the effects of streptozotocin (STZ) treatment on expression of HMGB1 in subcellular levels in the dorsal root ganglion (DRG) in both wild-type and Sigma-1R-/- mice and evaluated the effects of repeated intrathecal administrations of selective Sigma-1R antagonists BD1047, agonist PRE-084, or HMGB1 inhibitor glycyrrhizin on peripheral neuropathy in wild-type mice. We found that STZ-induced tactile allodynia and thermal hyperalgesia was associated with increased total HMGB1 expression in DRG. STZ treatment promoted the distribution of HMGB1 into cytoplasm. Furthermore, STZ induced modest peripheral neuropathy and did not alter HMGB1 levels in DRG or the distribution of either cytoplasmic or nuclear HMGB1 in Sigma-1R-/- mice compared to sham control mice. Additionally, repeated stimulation of Sigma-1R in the spinal cord induced tactile allodynia and thermal hyperalgesia at 1 week. This phenomenon was associated with increased cytoplasmic HMGB1 translocation and HMGB1 expression in DRG. Finally, we found that repeated blockade of either Sigma-1R or HMGB1 in the spinal cord after STZ treatment prevent the development of tactile allodynia and thermal hyperalgesia at 1 week. These effects were associated with decreased cytoplasmic HMGB1 translocation and HMGB1 expression in DRG. Taken together, our results suggest that Sigma-1R-mediated enhancement of HMGB1 expression in the DRG is critical for the development of peripheral neuropathy in type 1 diabetes.

A novel curcumin derivative for the treatment of diabetic neuropathy

Neuropathy is a common complication of long-term diabetes. Proposed mechanisms of neuronal damage caused by diabetes that are downstream of hyperglycemia and/or loss of insulin signaling include ischemic hypoxia, inflammation and loss of neurotrophic support. The curcumin derivative J147 is a potent neurogenic and neuroprotective drug candidate initially developed for the treatment of neurodegenerative conditions associated with aging that impacts many pathways implicated in the pathogenesis of diabetic neuropathy. Here, we demonstrate efficacy of J147 in ameliorating multiple indices of neuropathy in the streptozotocin-induced mouse model of type 1 diabetes. Diabetes was determined by blood glucose, HbA1c, and insulin levels and efficacy of J147 by behavioral, physiologic, biochemical, proteomic, and transcriptomic assays. Biological efficacy of systemic J147 treatment was confirmed by its capacity to decrease TNFα pathway activation and several other markers of neuroinflammation in the CNS. Chronic oral treatment with J147 protected the sciatic nerve from progressive diabetes-induced slowing of large myelinated fiber conduction velocity while single doses of J147 rapidly and transiently reversed established touch-evoked allodynia. Conduction slowing and allodynia are clinically relevant markers of early diabetic neuropathy and neuropathic pain, respectively. RNA expression profiling suggests that one of the pathways by which J147 imparts its protection against diabetic induced neuropathy may be through activation of the AMP kinase pathway. The diverse biological and therapeutic effects of J147 suggest it as an alternative to the polypharmaceutical approaches required to treat the multiple pathogenic mechanisms that contribute to diabetic neuropathy.

Treatment-Induced Neuropathy of Diabetes

PURPOSE OF REVIEW

Treatment-induced neuropathy of diabetes (TIND) is an under-recognized iatrogenic painful sensory and autonomic neuropathy. This review highlights the clinical symptoms and signs, raises awareness of the cause, and provides education about prevention of TIND.

RECENT FINDINGS

TIND may be triggered by a rapid decline in the blood glucose levels following the use of insulin, oral hypoglycemic medications, or even diet only to control diabetes. This may be seen in up to 10% of patients with diabetic neuropathy and has the potential for significant long-term complications that could be avoided through careful disease management. Based on the available evidence, a decrease in the glycosylated hemoglobin A1C of more than 3 points in 3 months in individuals with chronic hyperglycemia increases the risk of developing TIND. TIND is more common than previously suspected, and is tied to rates of glycemic control. Slower changes to glucose control are suggested, although there is no prospective data on disease prevention. Future research is necessary to guide treatment recommendations.

Clinically relevant concentration of pregabalin has no acute inhibitory effect on excitation of dorsal horn neurons under normal or neuropathic pain conditions: An intracellular calcium-imaging study in spinal cord slices from adult rats

Pregabalin is thought to exert its therapeutic effect in neuropathic pain via binding to α2δ-1 subunits of voltage-gated calcium (Ca(2+)) channels. However, the exact analgesic mechanism after its binding to α2δ-1 subunits remains largely unknown. Whether a clinical concentration of pregabalin (≈10μM) can cause acute inhibition of dorsal horn neurons in the spinal cord is controversial. To address this issue, we undertook intracellular Ca(2+)-imaging studies using spinal cord slices with an intact attached L5 dorsal root, and examined if pregabalin acutely inhibits the primary afferent stimulation-evoked excitation of dorsal horn neurons in normal rats and in rats with streptozotocin-induced painful diabetic neuropathy. Under normal conditions, stimulation of a dorsal root evoked Ca(2+) signals predominantly in the superficial dorsal horn. Clinically relevant (10μM) and a very high concentration of pregabalin (100μM) did not affect the intensity or spread of dorsal root stimulation-evoked Ca(2+) signals, whereas an extremely high dose of pregabalin (300μM) slightly but significantly attenuated Ca(2+) signals in normal rats and in diabetic neuropathic (DN) rats. There was no difference between normal rats and DN rats with regard to the extent of signal attenuation at all concentrations tested. These results suggest that the activity of dorsal horn neurons in the spinal cord is not inhibited acutely by clinical doses of pregabalin under normal or DN conditions. It is very unlikely that an acute inhibitory action in the dorsal horn is the main analgesic mechanism of pregabalin in neuropathic pain states.

Resveratrol regulates oxidative biomarkers and antioxidant enzymes in the brain of streptozotocin-induced diabetic rats

CONTEXT

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.

OBJECTIVE

The present study determines if resveratrol ameliorates oxidative stress and molecular changes in the brain frontal cortex of streptozotocin-induced diabetic rats.

MATERIALS AND METHODS

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.

RESULTS

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.

DISCUSSION AND CONCLUSION

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.

The role of nerve inflammation and exogenous iron load in experimental peripheral diabetic neuropathy (PDN)

BACKGROUND

Iron is an essential but potentially toxic metal in mammals. Here we investigated a pathogenic role of exogenous iron in peripheral diabetic neuropathy (PDN) in an animal model for type 1 diabetes.

METHODS

Diabetes was induced by a single injection of streptozotocin (STZ) in 4-month-old Sprague-Dawley rats. STZ-diabetic rats and non-diabetic rats were fed with high, standard, or low iron diet. After three months of feeding, animals were tested.

RESULTS

STZ-rats on standard iron diet showed overt diabetes, slowed motor nerve conduction, marked degeneration of distal intraepidermal nerve fibers, mild intraneural infiltration with macrophages and T-cells in the sciatic nerve, and increased iron levels in serum and dorsal root ganglion (DRG) neurons. While motor fibers were afflicted in all STZ-groups, only a low iron-diet led also to reduced sensory conduction velocities in the sciatic nerve. In addition, only STZ-rats on a low iron diet showed damaged mitochondria in numerous DRG neurons, a more profound intraepidermal nerve fiber degeneration indicating small fiber neuropathy, and even more inflammatory cells in sciatic nerves than seen in any other experimental group.

CONCLUSIONS

These results indicate that dietary iron-deficiency rather than iron overload, and mild inflammation may both promote neuropathy in STZ-induced experimental PDN.

Secoisolariciresinol diglycoside, a flaxseed lignan, exerts analgesic effects in a mouse model of type 1 diabetes: Engagement of antioxidant mechanism

Peripheral painful neuropathy is one of the most common complications in diabetes and necessitates improved treatment. Secoisolariciresinol diglycoside (SDG), a predominant lignan in flaxseed, has been shown in our previous studies to exert antidepressant-like effect. As antidepressant drugs are clinically used to treat chronic neuropathic pain, this work aimed to investigate the potential analgesic efficacy of SDG against diabetic neuropathic pain in a mouse model of type 1 diabetes. We subjected mice to diabetes by a single intraperitoneal (i.p.) injection of streptozotocin (STZ, 200 mg/kg), and Hargreaves test or von Frey test was used to assess thermal hyperalgesia or mechanical allodynia, respectively. Chronic instead of acute SDG treatment (3, 10 or 30 mg/kg, p.o., twice per day for three weeks) ameliorated thermal hyperalgesia and mechanical allodynia in diabetic mice, and these analgesic actions persisted about three days when SDG treatment was terminated. Although chronic treatment of SDG to diabetic mice did not impact on the symptom of hyperglycemia, it greatly attenuated excessive oxidative stress in sciatic nerve and spinal cord tissues, and partially counteracted the condition of weight decrease. Furthermore, the analgesic actions of SDG were abolished by co-treatment with the reactive oxygen species donor tert-butyl hydroperoxide (t-BOOH), but potentiated by the reactive oxygen species scavenger phenyl-N-tert-butylnitrone (PBN). These findings indicate that chronic SDG treatment can correct neuropathic hyperalgesia and allodynia in mice with type 1 diabetes. Mechanistically, the analgesic actions of SDG in diabetic mice may be associated with its antioxidant activity.

Naringenin neutralises oxidative stress and nerve growth factor discrepancy in experimental diabetic neuropathy

OBJECTIVES

Present study aims to investigate the ameliorative effects of naringenin (NG) on experimentally induced diabetic neuropathy (DN) in rats.

METHODS

Diabetes was induced by single intraperitoneal injection of streptozotocin (STZ, 60  g/kg). Naringenin (25 and 50 mg/kg/day) treatment was started 2 weeks after the diabetes induction and continued for five consecutive weeks. Pain threshold behaviour tests were performed at the end of the treatment. Serum levels of glucose, insulin and pro-inflammatory cytokines were assessed. In sciatic tissues, markers oxidative stress, cytokines and neurotrophic factors were measured.

RESULTS

NG treatments showed significant decrease in paw-withdrawal (P < 0.01) and tail-flick latency (P < 0.01). The drug attenuated the diabetic-induced changes in serum glucose, insulin and pro-inflammatory cytokines including tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-6 (IL-6). In sciatic nerve, the diabetic-induced alterations in interleukins and oxidative stress biomarkers were significantly attenuated by NG. Decreased sciatic expressions of insulin growth factor (IGF) and nerve growth factor (NGF) in diabetic rats were also ameliorated by NG. Diabetes-induced dysregulated levels of nitric oxide (NO), thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) were ameliorated by NG. Histological analysis showed that NG corrected the altered sciatic changes in diabetic animals.

DISCUSSION

We suggest that neuro-protective effect of NG molecules in sciatic nerve of diabetic rats, through its anti-diabetic as well as antioxidant and anti-inflammatory properties.

Statin use before diabetes diagnosis and risk of microvascular disease: a nationwide nested matched study

BACKGROUND

The role of statins in the development of microvascular disease in patients with diabetes is unknown. We tested the hypothesis that statin use increases the risk of diabetic retinopathy, diabetic neuropathy, diabetic nephropathy, and gangrene of the foot in individuals with diabetes.

METHODS

We identified all patients living in Denmark who were aged 40 years or older and were diagnosed with incident diabetes between Jan 1, 1996, and Dec 31, 2009. We obtained patients' data from the Danish Patient Registry and information on drug use from the Danish Registry of Medicinal Product Statistics. We randomly selected 15,679 individuals from the database who had used statins regularly until their diagnosis of diabetes (statin users) and matched them in a 1:3 ratio with 47,037 individuals who had never used statins before diagnosis (non-statin users). Our primary outcome was to compare the cumulative incidence of diabetic retinopathy, diabetic neuropathy, diabetic nephropathy, or gangrene of the foot in statin users versus non-statin users. We analysed data with Cox regression models, adjusted for covariates including sex, age at diabetes diagnosis, and method of diabetes diagnosis. To address potential biases between statin users and non-statin users, we made adjustments to our analysis with a propensity score and with other factors. Median follow-up was 2·7 years (range 0-13).

FINDINGS

During 215,725 person-years of follow-up, 2866 patients developed diabetic retinopathy, 1406 developed diabetic neuropathy, 1248 developed diabetic nephropathy, and 2392 developed gangrene of the foot. Compared with non-statin users, statin users had a lower cumulative incidence of diabetic retinopathy (hazard ratio 0·60, 95% CI 0·54-0·66; p<0·0001), diabetic neuropathy (0·66, 0·57-0·75; p<0·0001), and gangrene of the foot (0·88, 0·80-0·97; p=0·010), but not diabetic nephropathy (0·97, 0·85-1·10; p=0·62). These results were similar after adjusting for the competing risk of death, after matching for a propensity score, after adjusting for visits to a family doctor, and by stratification on covariates. The corresponding multivariable adjusted hazard ratio for risk of diabetes in the total population was 1·17 (95% CI 1·14-1·21; p<0·0001).

INTERPRETATION

Use of statins before diagnosis of incident diabetes was not associated with an increased risk of microvascular disease. Whether statins are protective against some forms of microvascular disease-a possibility raised by these data-will need to be addressed in other studies similar to ours, in mendelian randomisation studies, and preferably in randomised controlled trials.

FUNDING

Herlev Hospital, Copenhagen University Hospital.

Neutralization of schwann cell-secreted VEGF is protective to in vitro and in vivo experimental diabetic neuropathy

The pathogenetic role of vascular endothelial growth factor (VEGF) in long-term retinal and kidney complications of diabetes has been demonstrated. Conversely, little is known in diabetic neuropathy. We examined the modulation of VEGF pathway at mRNA and protein level on dorsal root ganglion (DRG) neurons and Schwann cells (SC) induced by hyperglycaemia. Moreover, we studied the effects of VEGF neutralization on hyperglycemic DRG neurons and streptozotocin-induced diabetic neuropathy. Our findings demonstrated that DRG neurons were not affected by the direct exposition to hyperglycaemia, whereas showed an impairment of neurite outgrowth ability when exposed to the medium of SC cultured in hyperglycaemia. This was mediated by an altered regulation of VEGF and FLT-1 receptors. Hyperglycaemia increased VEGF and FLT-1 mRNA without changing their intracellular protein levels in DRG neurons, decreased intracellular and secreted protein levels without changing mRNA level in SC, while reduced the expression of the soluble receptor sFLT-1 both in DRG neurons and SC. Bevacizumab, a molecule that inhibits VEGF activity preventing the interaction with its receptors, restored neurite outgrowth and normalized FLT-1 mRNA and protein levels in co-cultures. In diabetic rats, it both prevented and restored nerve conduction velocity and nociceptive thresholds. We demonstrated that hyperglycaemia early affected neurite outgrowth through the impairment of SC-derived VEGF/FLT-1 signaling and that the neutralization of SC-secreted VEGF was protective both in vitro and in vivo models of diabetic neuropathy.

Hesperidin, a flavanoglycone attenuates experimental diabetic neuropathy via modulation of cellular and biochemical marker to improve nerve functions

AIM

Diabetic neuropathy (DN) is one of the most common long-term complications of diabetes mellitus and clinically can be characterized by an elevated nociceptive response with electrophysiological conduction abnormalities. The present investigation was designed to evaluate the neuroprotective effect of hesperidin against STZ induced diabetic neuropathic pain in laboratory rats.

MATERIALS AND METHODS

DN was induced in Sprague-Dawley rats (150-200 g) by intraperitoneal administration of streptozotocin (STZ) (55 mg/kg, p.o.). Rats were divided into various groups, namely, STZ control (vehicle), hesperidin (25, 50, and 100 mg/kg, p.o.), insulin (10 IU/kg, s.c.), and combination of hesperidin (100 mg/kg, p.o.) with insulin (10 IU/kg, s.c.) for 4 weeks. Various behavioral (allodynia and hyperalgesia), biochemical parameters [oxido-nitosative stress, Na-K-ATPase, aldose reductase (AR)], and molecular changes (TNF-α and IL-1β) along with hemodynamic changes were determined.

RESULTS

Rats treated with hesperidin (50 and 100 mg/kg, p.o., 4 weeks) significantly reduced (p < 0.05) hyperglycemia and its metabolic abnormalities induced by intraperitoneal administration of STZ. The decreased nociceptive threshold, motor nerve conduction velocity (MNCV) and sensory nerve conduction velocity (SNCV), serum insulin as well as Na-K-ATPase activity were significantly increase (p < 0.05) by hesperidin (50 and 100 mg/kg, p.o.) treatment. It significantly attenuated (p < 0.05) elevated glycated hemoglobin, AR activity, oxido-nitrosative stress, neural calcium, and pro-inflammatory cytokines (TNF-α and IL-1β) levels. Histological aberration induced after STZ administration was restored by administration of hesperidin (50 and 100 mg/kg, p.o.)

CONCLUSION

In combination with insulin, hesperidin not only attenuated the diabetic condition but also reversed neuropathic pain via control over hyperglycemia as well as hyperlipidemia to down-regulate generation of free radical, release of pro-inflammatory cytokines as well as elevation in membrane bound enzyme.

Zinc supplementation alleviates diabetic peripheral neuropathy by inhibiting oxidative stress and upregulating metallothionein in peripheral nerves of diabetic rats

We investigated the effect of zinc supplementation on the expression of metallothionein, lipid peroxidation (malondialdehyde, MDA), and poly(ADP-ribose) polymerase-1 (PARP-1) in the sciatic nerve, motor nerve conduction velocity of the left sciatic posterior tibial nerve in streptozotocin (STZ)-induced diabetic rats. Twenty-four male rats were equally divided into four groups. The first group served as untreated controls although the second group received 5 mg/kg/day zinc chloride. The third group was treated with STZ to induce diabetes, and the fourth group was treated with STZ and supplemented with zinc. A gradual but insignificant decline in motor nerve conduction velocity was observed at 2 weeks of induction of diabetes. Zinc supplementation markedly attenuated the decrease in motor nerve conduction velocity at week 8 post-induction of diabetes. Furthermore, the tactile response threshold of diabetic rats receiving normal saline was lower than that of diabetic rats receiving zinc supplementation. Additionally, zinc supplementation accentuated the increase in the mRNA transcript levels of metallothionein but attenuated the increase in the mRNA transcript levels of PARP-1. At week 8 post-induction of diabetes, diabetic rats receiving normal saline had markedly higher MDA contents than diabetic rats receiving zinc supplementation. In conclusion, the present study shows that zinc has a protective effect against diabetes-induced peripheral nerve damage by stimulating metallothionein synthesis and downregulating oxidative stress.

Activation of spinal GABAB receptors normalizes N-methyl-D-aspartate receptor in diabetic neuropathy

N-methyl-D-aspartate receptor (NMDAR) activity is increased, while GABAB receptor is downregulated in the spinal cord dorsal horn in diabetic neuropathy. In this study, we determined the interaction of NMDARs and GABAB receptors in streptozotocin (STZ)-induced diabetic neuropathy. The paw withdrawal threshold (PWT) was significantly lower in STZ-treated rats than in vehicle-treated rats. Intrathecal injection of baclofen, a GABAB receptor agonist, significantly increased the PWT in STZ-treated rats, an effect that was abolished by pre-administration of the GABAB receptor specific antagonist CGP55845. Spinal NR2B, an NMDA receptor subunit, protein and mRNA expression levels were significantly higher in STZ-treated rats than in vehicle-treated rats. Intrathecal baclofen significantly reduced the NR2B protein and mRNA expression levels in STZ-treated rats. Intrathecal administration of CGP55845 eliminated baclofen-induced reduction of NR2B protein and mRNA levels in STZ-treated rats. In addition, the phosphorylated cAMP response element-binding (CREB) protein level was significantly higher in the spinal cord dorsal horn in STZ-treated rats compared with vehicle-treated rats. Intrathecal injection of baclofen significantly decreased phosphorylated CREB protein level in STZ-treated rats; an effect was blocked by CGP55845. These data suggest that activation of GABAB receptors in the spinal cord dorsal horn normalizes NMDAR expression level in diabetic neuropathic pain.

The application of support vector regression for prediction of the antiallodynic effect of drug combinations in the mouse model of streptozocin-induced diabetic neuropathy

Drug interactions are an important issue of efficacious and safe pharmacotherapy. Although the use of drug combinations carries the potential risk of enhanced toxicity, when carefully introduced it enables to optimize the therapy and achieve pharmacological effects at doses lower than those of single agents. In view of the development of novel analgesic compounds for the neuropathic pain treatment little is known about their influence on the efficacy of currently used analgesic drugs. Below we describe the preliminary evaluation of support vector machine in the regression mode (SVR) application for the prediction of maximal antiallodynic effect of a new derivative of dihydrofuran-2-one (LPP1) used in combination with pregabalin (PGB) in the streptozocin-induced neuropathic pain model in mice. Based on SVR the most effective doses of co-administered LPP1 (4mg/kg) and PGB (1mg/kg) were predicted to cause the paw withdrawal threshold at 6.7g in the von Frey test. In vivo for the same combination of doses the paw withdrawal was observed at 6.5g, which confirms good predictive properties of SVR.

Pregabalin attenuates excitotoxicity in diabetes

Diabetes can exacerbate seizures and worsen seizure-related brain damage. In the present study, we aimed to determine whether the standard antiepileptic drug pregabalin (PGB) protects against pilocarpine-induced seizures and excitotoxicity in diabetes. Adult male Sprague-Dawley rats were divided into either a streptozotocin (STZ)-induced diabetes group or a normal saline (NS) group. Both groups were further divided into subgroups that were treated intravenously with either PGB (15 mg/kg) or a vehicle; all groups were treated with subcutaneous pilocarpine (60 mg/kg) to induce seizures. To evaluate spontaneous recurrent seizures (SRS), PGB-pretreated rats were fed rat chow containing oral PGB (450 mg) for 28 consecutive days; vehicle-pretreated rats were fed regular chow. SRS frequency was monitored for 2 weeks from post-status epilepticus day 15. We evaluated both acute neuronal loss and chronic mossy fiber sprouting in the CA3 area. In addition, we performed patch clamp recordings to study evoked excitatory postsynaptic currents (eEPSCs) in hippocampal CA1 neurons for both vehicle-treated rats with SRS. Finally, we used an RNA interference knockdown method for Kir6.2 in a hippocampal cell line to evaluate PGB's effects in the presence of high-dose ATP. We found that compared to vehicle-treated rats, PGB-treated rats showed less severe acute seizure activity, reduced acute neuronal loss, and chronic mossy fiber sprouting. In the vehicle-treated STZ rats, eEPSC amplitude was significantly lower after PGB administration, but glibenclamide reversed this effect. The RNA interference study confirmed that PGB could counteract the ATP-sensitive potassium channel (K_ATP)-closing effect of high-dose ATP. By opening K_ATP, PGB protects against neuronal excitotoxicity, and is therefore a potential antiepileptogenic in diabetes. These findings might help develop a clinical algorithm for treating patients with epilepsy and comorbid metabolic disorders.

Association of statin use with peripheral neuropathy in the U.S. population 40 years of age or older

BACKGROUND

Peripheral neuropathy is a serious complication of diabetes and several conditions that may lead to the loss of lower extremity function and even amputations. Since the introduction of statins, their use has increased markedly. Recent reports suggest a role for statins in the development of peripheral neuropathy. The aims of the present study were to assess the association between statin use and peripheral neuropathy, and to determine whether this association varied by diabetes status.

METHODS

Data from the lower extremity examination supplement of the 1999-2004 National Health and Nutrition Examination Survey were used.

RESULTS

The overall prevalence of statin use was 15% and the prevalence of peripheral neuropathy was 14.9%. The prevalence of peripheral neuropathy was significantly higher among those who used statins compared with those who did not (23.5% vs 13.5%, respectively; P < 0.01). Multivariate logistic regression revealed that statin use (adjusted odds ratio 1.3; 95% confidence interval 1.1-1.6; Wald P = 0.04) was significantly associated with peripheral neuropathy, controlling for diabetes status, age, gender, race, height, weight, blood lead levels, poverty, glycohemoglobin, use of vitamin B12 , alcohol abuse, hypertension, and non-high-density lipoprotein-cholesterol. Diabetes status, age, gender, height, weight, blood lead levels, poverty, and glycohemoglobin were also significantly associated with peripheral neuropathy. We found no effect modification between statin use and diabetes status, race, gender, age, vitamin B12 , blood lead levels, or alcohol abuse.

CONCLUSIONS

In the present cross-sectional study, we found a modest association between peripheral neuropathy and statin use. Prospective studies are required to determine the causal direction.

Full neurological recovery after extreme hypoglycemia during intensive insulin therapy: a case report

Since 2000, there has been an ongoing debate regarding tightness of glycemic control in critically ill patients. An increased risk of hypoglycemia is observed in patients treated with an intensive insulin protocol targeting "normoglycemia," probably accounting for a reduction of the overall benefit. Hypoglycemia is associated with neurological side effects and is found to be an independent predictor of mortality in most trials; however, long-term sequelae are rare if glucose is administered early. We describe a case of prolonged, extreme hypoglycemia in a critically ill patient treated according to an intensive insulin protocol who recovered without any neurological deficit at discharge.

Elevated prepronociceptin, nociceptin/orphanin FQ and nocistatin concentrations in rat chronic constriction nerve injury and diabetic neuropathic pain models

Nociceptin/orphanin FQ (N/OFQ) and nocistatin are derived from the same precursor peptide, prepronociceptin. N/OFQ and nocistatin have been postulated to participate in pain modulation. In this study, we investigated whether the prepronociceptin, N/OFQ and nocistatin concentrations in the brain and spinal cord would be altered in chronic constriction injury and diabetic rat neuropathic pain models. Total brain and spinal cord lysates as well as serum from rats that had undergone chronic constriction injury and streptozocin-induced diabetic neuropathy were used to determine the concentrations of three peptides using competitive radioimmunoassay. We found that N/OFQ and prepronociceptin concentrations were significantly raised in both rat neuropathic pain models. Nocistatin was raised in the brains of post traumatic neuropathy pain rats. Overall, our data have demonstrated for the first time that prepronociceptin, N/OFQ and nocistatin concentrations are significantly altered at different tissues of two rat neuropathy pain models.

Chronic treatment with D-chiro-inositol prevents autonomic and somatic neuropathy in STZ-induced diabetic mice

AIM

D-chiro-inositol (DCI) has been shown to prevent and reverse endothelial dysfunction in diabetic rats and rabbits. The present study evaluates the preventive effect of DCI on experimental diabetic neuropathy (DN).

METHODS

Streptozotocin-induced (STZ) diabetic mice were treated by oral gavage for 60 days with DCI (20 mg/kg/12 h) or saline (NaCl 0.9%; 0.1 ml/10 g/12 h; Diab) and compared with euglycaemic groups treated with saline (0.1 ml/10 g/12 h; Eugly). We compared the response of the isolated sciatic nerve, corpora cavernosa or vas deferens to electrical stimulation.

RESULTS

The electrically evoked compound action potential of the sciatic nerve was greatly blunted by diabetes. The peak-to-peak amplitude (PPA) was decreased from 3.24 ± 0.7 to 0.9 ± 0.2 mV (p < 0.05), the conduction velocity (CV) of the first component was reduced from 46.78 ± 4.5 to 26.69 ± 3.8 ms (p < 0.05) and chronaxy was increased from 60.43 ± 1.9 to 69.67 ± 1.4 ms (p < 0.05). These parameters were improved in nerves from DCI-treated mice (p < 0.05). PPA in the DCI group was 5.79 ± 0.8 mV (vs. 0.9 ± 0.2 mV-Diab; p < 0.05) and CV was 45.91 ± 3.6 ms (vs. 26.69 ± 3.8 ms-Diab; p < 0.05). Maximal relaxation of the corpus cavernosum evoked by electrical stimulation (2-64 Hz) in the Diab group was 36.4 ± 3.8% compared to 65.4 ± 2.8% in Eugly and 59.3 ± 5.5% in the DCI group (p < 0.05). Maximal contraction obtained in the vas deferens was 38.0 ± 9.2% in Eugly and 11.5 ± 2.6% in Diab (decrease of 69.7%; p < 0.05), compared to 25.2 ± 2.3% in the DCI group (p < 0.05 vs. diabetic). Electron microscopy of the sciatic nerves showed prevention of neuronal damage.

CONCLUSIONS

DCI has a neuroprotective action in both autonomic and somatic nerves in STZ-induced DN.

Neuropathy in a rat model of mild diabetes induced by multiple low doses of streptozotocin: effects of the antioxidant stobadine in comparison with a high-dose alpha-lipoic acid treatment

Hyperglycaemia-induced oxidative stress makes an important contribution to the aetiology of diabetic neuropathy. The aim of our study was to evaluate the effect of the antioxidant stobadine (STB) in comparison with a treatment by a high-dose of alpha-lipoic acid (ALA), on the neurological consequences of chronic hyperglycaemia in an animal model of diabetes in Wistar rats (16 weeks old), made diabetic by streptozotocin (STZ 3 x 20 mg i.v.). Neuropathy was evaluated electrophysiologically by measuring motor nerve conduction velocity (NCV) in the 4th and 8th week in vivo and motor NCV and resistance to ischaemic conduction failure (RICF) of the sciatic nerve in the 10th week of the experiment in vitro. The therapy with ALA (100 mg/kg i.p., 5 times a week) and STB (25 mg/kg i.p., 5 times a week) had a significant effect on NCV in vivo in the 8th week of the experiment and no effect in the 10th week in vitro. The RICF elevated in diabetic animals was significantly modified by ALA. The effect of the antioxidant STB on NCV was comparable with that of ALA, while RICF was affected only by ALA. We conclude that treatment with appropriate antioxidants might partially prevent nerve dysfunction in diabetic rats.

Functional and biochemical evidence indicating beneficial effect of Melatonin and Nicotinamide alone and in combination in experimental diabetic neuropathy

Oxidative stress resulting in excessive generation of ROS is a compelling initiator of DNA damage along with damage to various cellular proteins and other macromolecules. Poly(ADP-ribose) polymerase (PARP) activation in response to DNA damage, stirs an energy-consuming cellular metabolic cycle; culminating into cell death. The present study was designed to determine the effect of combining an antioxidant, Melatonin and a PARP inhibitor, Nicotinamide on the hallmark deficits developing in diabetic neuropathy (DN). Streptozotocin (STZ, 55 mg/kg, i.p.) was administered to induce diabetes. Six weeks post diabetes induction, two week treatment with Melatonin (3 and 10 mg/kg) and Nicotinamide (100 and 300 mg/kg) either alone or in combination was given. Effect of these interventions on the functional, behavioral and biochemical changes caused by hyperglycemia were studied in treated animals. Melatonin and Nicotinamide alone as well as in combination ameliorated the functional deficits along with improvement in pain parameters. The combination also demonstrated an essential reversal of biochemical alterations. Nitrotyrosine and Poly ADP Ribose (PAR) immunopositivity was significantly decreased in sciatic nerve micro-sections of treatment group. The results of this study advocate that simultaneous inhibition of oxidative stress-PARP activation cascade may prove useful for the pharmacotherapy of DN.

Antinociceptive property of Emblica officinalis Gaertn (Amla) in high fat diet-fed/low dose streptozotocin induced diabetic neuropathy in rats

Diabetic neuropathic pain is an important microvascular complication in diabetes mellitus and oxidative stress plays a vital role in associated neural and vascular complications. The present study investigated flavonoid rich fruit extract (ethyl acetate:methanol fraction) of E. officinalis (10 mg/kg), in type II diabetes (high fat diet fed/low dose streptozotocin) induced diabetic neuropathy in male Sprague-Dawley rats. Diabetic rats exhibited a significant hyperalgesia (nociception) as compared to control rats. Treatment with E. officinalis extract (EOE) and quercetin in diabetic rats showed significant increase in tail flick latency in hot immersion test and pain threshold level in hot plate test compared to control rats. The changes in lipid peroxidation status and anti-oxidant enzymes (superoxide dismutase and catalase) levels observed in diabetic rats were significantly restored by E. officinalis extract and quercetin treatment. Both, E. officinalis extract and quercetin attenuated diabetic induced axonal degeneration. The study provides experimental evidence of the preventive and curative effect of E. officinalis on nerve function and oxidative stress in animal model of diabetic neuropathy. Since, E. officinalis fruit is already in clinical use for diabetic patients it may be evaluated for preventive therapy in diabetic patients at risk of developing neuropathy.

Bradykinin receptors antagonists and nitric oxide synthase inhibitors in vincristine and streptozotocin induced hyperalgesia in chemotherapy and diabetic neuropathy rat model

PURPOSE

The influence of an irreversible inhibitor of constitutive NO synthase (L-NOArg; 1.0 mg/kg ip), a relatively selective inhibitor of inducible NO synthase (L-NIL; 1.0 mg/kg ip) and a relatively specific inhibitor of neuronal NO synthase (7-NI; 0.1 mg/kg ip), on antihyperalgesic action of selective antagonists of B2 and B1 receptors: D-Arg-[Hyp3,Thi5,D-Tic7,Oic8] bradykinin (HOE 140; 70 nmol/kg ip) or des Arg10 HOE 140 (70 nmol/kg ip) respectively, in model of diabetic (streptozotocin-induced) and toxic (vincristine-induced) neuropathy was investigated.

METHODS

The changes in pain thresholds were determined using mechanical stimuli--the modification of the classic paw withdrawal test described by Randall-Selitto.

RESULTS

The results of this paper confirm that inhibition of bradykinin receptors and inducible NO synthase but not neuronal NO synthase activity reduces diabetic hyperalgesia. Pretreatment with L-NOArg and L-NIL but not 7-NI, significantly increases antihyperalgesic activity both HOE 140 and des Arg10 HOE 140. It was also shown that both products of inducible NO synthase and neuronal NO synthase activation as well as bradykinin are involved in hyperalgesia produced by vincristine. Moreover, L-NOArg and 7-NI but not L-NIL intensify antihyperalgesic activity of HOE 140 or des-Arg10HOE 140 in toxic neuropathy.

CONCLUSIONS

Results of these studies suggest that B1 and B2 receptors are engaged in transmission of nociceptive stimuli in both diabetic and toxic neuropathy. In streptozotocin-induced hyperalgesia, inducible NO synthase participates in pronociceptive activity of bradykinin, whereas in vincristine-induced hyperalgesia bradykinin seemed to activate neuronal NO synthase pathway. Therefore, concomitant administration of small doses of bradykinin receptor antagonists and NO synthase inhibitors can be effective in alleviation of neuropathic pain, even in hospital care.

Alpha(1) and alpha(2)-adrenoreceptor antagonists in streptozotocin- and vincristine-induced hyperalgesia

The effect of alpha(1)- and alpha(2)-adrenoreceptor antagonists (prazosin and yohimbine, respectively) on streptozotocin (STZ)- and vincristine (VIN)-induced hyperalgesia in rats was studied. In two experimental models, yohimbine (1.0 mg/kg ip) completely abolished STZ and VIN-induced hyperalgesia. This effect was markedly prolonged in diabetic rats. Prazosin (0.3 mg/kg ip) attenuated and delayed development of STZ-induced hyperalgesia. In VIN-elicited neuropathy, the administration of prazosin not only delayed hyperalgesia but also produced antinociception. After cessation of drug administration, a significant decrease in nociceptive threshold was observed. The obtained results seem to indicate that both alpha(1)- and alpha(2)-adrenoreceptors are engaged in diabetic (STZ) and toxic (VIN) neuropathy.

High-fat diet induced neuropathy of pre-diabetes and obesity: effects of "healthy" diet and aldose reductase inhibition

OBJECTIVE

Subjects with dietary obesity and pre-diabetes have an increased risk for developing both nerve conduction slowing and small sensory fiber neuropathy. Animal models of this type of neuropathy have not been described. This study evaluated neuropathic changes and their amenability to dietary and pharmacological interventions in mice fed a high-fat diet (HFD), a model of pre-diabetes and alimentary obesity.

RESEARCH DESIGN AND METHODS

Female C57BL6/J mice were fed normal diets or HFDs for 16 weeks.

RESULTS

HFD-fed mice developed obesity, increased plasma FFA and insulin concentrations, and impaired glucose tolerance. They also had motor and sensory nerve conduction deficits, tactile allodynia, and thermal hypoalgesia in the absence of intraepidermal nerve fiber loss or axonal atrophy. Despite the absence of overt hyperglycemia, the mice displayed augmented sorbitol pathway activity in the peripheral nerve, as well as 4-hydroxynonenal adduct nitrotyrosine and poly(ADP-ribose) accumulation and 12/15-lipoxygenase overexpression in peripheral nerve and dorsal root ganglion neurons. A 6-week feeding with normal chow after 16 weeks on HFD alleviated tactile allodynia and essentially corrected thermal hypoalgesia and sensory nerve conduction deficit without affecting motor nerve conduction slowing. Normal chow containing the aldose reductase inhibitor fidarestat (16 mg x kg(-1) x day (-1)) corrected all functional changes of HFD-induced neuropathy.

CONCLUSIONS

Similar to human subjects with pre-diabetes and obesity, HFD-fed mice develop peripheral nerve functional, but not structural, abnormalities and, therefore, are a suitable model for evaluating dietary and pharmacological approaches to halt progression and reverse diabetic neuropathy at the earliest stage of the disease.

Mouse models of diabetic neuropathy

Diabetic neuropathy (DN) is a debilitating complication of type 1 and type 2 diabetes. Rodent models of DN do not fully replicate the pathology observed in human patients. We examined DN in streptozotocin (STZ)-induced [B6] and spontaneous type 1 diabetes [B6Ins2(Akita)] and spontaneous type 2 diabetes [B6-db/db, BKS-db/db]. Despite persistent hyperglycemia, the STZ-treated B6 and B6Ins2(Akita) mice were resistant to the development of DN. In contrast, DN developed in both type 2 diabetes models: the B6-db/db and BKS-db/db mice. The persistence of hyperglycemia and development of DN in the B6-db/db mice required an increased fat diet while the BKS-db/db mice developed severe DN and remained hyperglycemic on standard mouse chow. Our data support the hypothesis that genetic background and diet influence the development of DN and should be considered when developing new models of DN.

Effects of eugenol on nerve and vascular dysfunction in streptozotocin-diabetic rats

Hyperglycaemia in diabetes mellitus results in oxidative stress and pro-inflammatory changes which contribute to vascular complications including endothelial dysfunction and peripheral neuropathy. The aim of this study was to examine whether treatment with the dominant ingredient of clove oil, eugenol, which has antioxidant and anti-inflammatory properties, could improve diabetic vascular and nerve function in streptozotocin-induced diabetic rats. Intervention treatment was given for 2 weeks following 6 weeks of untreated diabetes. Dose-ranging studies on diabetic deficits in sciatic nerve motor and saphenous nerve sensory nerve conduction velocities gave ED50 values of 28 mg/kg and 9 mg/kg, respectively, conduction velocity being within the non-diabetic range at a dose of 200 mg/kg. Sciatic nerve endoneurial blood flow was 49% reduced by diabetes and this was completely corrected by 200 mg/kg eugenol treatment. Gastric fundus maximum nitrergic nerve-mediated relaxation was 44% reduced by diabetes; eugenol corrected this deficit by 69%. For renal artery rings, maximum endothelium-dependent relaxation to acetylcholine was 51% reduced by diabetes; eugenol corrected this deficit by 60%, with improvements in both nitric oxide and endothelium-derived hyperpolarising factor (EDHF)-mediated vasorelaxation components. Diabetes increased renal artery sensitivity to phenylephrine-mediated contraction, however, this was unaffected by eugenol treatment. Thus, aspects of both vascular and neural complications in experimental diabetes are improved by eugenol, which could have potential therapeutic implications for diabetic neuropathy and vasculopathy.

Enhanced inflammatory response via activation of NF-kappaB in acute experimental diabetic neuropathy subjected to ischemia-reperfusion injury

Reperfusion following ischemia increases ischemic fiber degeneration (IFD) in diabetic nerves compared to control normoglycemic nerves. The mechanism of this excessive susceptibility is unclear. Since reperfusion injury results in an inflammatory response, we tested the hypothesis that the diabetic state increases the inflammatory cascade. We used an animal model of unilateral ischemia-reperfusion (IR) injury to streptozotocin (STZ)-induced diabetic nerve to evaluate the density and localization of mediators of the inflammatory response using selective immunolabeling methods (for nuclear factor kappa B (NF-kappaB), intercellular adhesion molecule-1 (ICAM-1), cytokines and inflammatory cells). We studied a 1-month diabetic group and an age-matched control group (n=6 each). The right limb underwent 3 h ischemia at 35 degrees C and 7 days reperfusion. This was achieved by ligating the supplying arteries and collaterals to the right sciatic-tibial nerve for 3 h, followed by releasing the ties. Immunohistochemistry was performed on proximal sciatic and mid tibial nerves. NF-kappaB expression in diabetic sciatic endothelial cell and Schwann cell (SC) was significantly increased over that of controls subjected to identical IR injury. We observed a nearly 2-fold increase in density of NF-kappaB and ICAM-1 expression in microvessels of diabetic nerve compared with control nerve. Extensive infiltration of monocyte macrophages (1C7) was observed in the endoneurium of diabetic nerves, while only mild infiltration of granulocytes (HIS 48) occurred in the endoneurium of diabetic tibial nerves. This study provides evidence for an enhanced inflammatory response in diabetic nerves subjected to IR injury apparently via NF-kappaB activation.

Antinociceptive efficacy of lacosamide in a rat model for painful diabetic neuropathy

Lacosamide was tested in the streptozotocin rat model of diabetic neuropathic pain in comparison to drugs which are commonly used in the treatment of diabetic neuropathic pain, i.e. antidepressants and anticonvulsants. In diabetic rats, lacosamide attenuated cold (10, 30 mg/kg, i.p.), warm (3, 10, 30 mg/kg, i.p.) and mechanical allodynia (30 mg/kg, i.p.). Streptozotocin-induced thermal and mechanical hyperalgesia were reduced by lacosamide at doses of 10 and 30 mg/kg, i.p. Morphine (3 mg/kg) showed similar efficacy on allodynia and hyperalgesia. Amitriptyline (10 mg/kg), venlafaxine (15 mg/kg), levetiracetam (180 mg/kg) and pregabalin (100 mg/kg) exhibited significant effects on thermal allodynia and mechanical hyperalgesia. Only treatment with amitriptyline (30 mg/kg, i.p.) produced full reversal of thermal allodynia comparable to lacosamide. Lamotrigine (45 mg/kg, i.p.) had no effect on both behavioral readouts. Lacosamide's potency and efficacy in reversing pain behavior might be due to its new, yet unknown mechanism of action.