Diabetic neuropathy

Nanotechnology-mediated photodynamic therapy: Focus on overcoming tumor hypoxia

The oxygen level in the tumor is a critical marker that determines response to different treatments. Cancerous cells can adapt to hypoxia and low pH conditions within the tumor microenvironment (TME) to regulate tumor metabolism, proliferation, and promote tumor metastasis as well as angiogenesis, consequently leading to treatment failure and recurrence. In recent years, widespread attempts have been made to overcome tumor hypoxia through different methods, such as hyperbaric oxygen therapy (HBOT), hyperthermia, O2 carriers, artificial hemoglobin, oxygen generator hydrogels, and peroxide materials. While oxygen is found to be an essential agent to improve the treatment response of photodynamic therapy (PDT) and other cancer treatment modalities, the development of hypoxia within the tumor is highly associated with PDT failure. Recently, the use of nanoparticles has been a hot topic for researchers and exploited to overcome hypoxia through Oxygen-generating hydrogels, O2 nanocarriers, and O2 -generating nanoparticles. This review aimed to discuss the role of nanotechnology in tumor oxygenation and highlight the challenges, prospective, and recent advances in this area to improve PDT outcomes. This article is categorized under: Nanotechnology Approaches to Biology > Cells at the Nanoscale Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Screening for diabetic peripheral neuropathy in resource-limited settings

BACKGROUND

Diabetic neuropathy is the most common microvascular complication of diabetes mellitus and a major risk factor for diabetes-related lower-extremity complications. Diffuse neuropathy is the most frequently encountered pattern of neurological dysfunction and presents clinically as distal symmetrical sensorimotor polyneuropathy. Due to the increasing public health significance of diabetes mellitus and its complications, screening for diabetic peripheral neuropathy is essential. Consequently, a review of the principles that guide screening practices, especially in resource-limited clinical settings, is urgently needed.

MAIN BODY

Numerous evidence-based assessments are used to detect diabetic peripheral neuropathy. In accordance with current guideline recommendations from the American Diabetes Association, International Diabetes Federation, International Working Group on the Diabetic Foot, and National Institute for Health and Care Excellence, a screening algorithm for diabetic peripheral neuropathy based on multiphasic clinical assessment, stratification according to risk of developing diabetic foot syndrome, individualized treatment, and scheduled follow-up is suggested for use in resource-limited settings.

CONCLUSIONS

Screening for diabetic peripheral neuropathy in resource-limited settings requires a practical and comprehensive approach in order to promptly identify affected individuals. The principles of screening for diabetic peripheral neuropathy are: multiphasic approach, risk stratification, individualized treatment, and scheduled follow-up. Regular screening for diabetes-related foot disease using simple clinical assessments may improve patient outcomes.

Vitamin D in Neurological Diseases

Vitamin D may have multiple effects on the nervous system and its deficiency can represent a possible risk factor for the development of many neurological diseases. Recent studies are also trying to clarify the different effects of vitamin D supplementation over the course of progressive neurological diseases. In this narrative review, we summarise vitamin D chemistry, metabolism, mechanisms of action, and the recommended daily intake. The role of vitamin D on gene transcription and the immune response is also reviewed. Finally, we discuss the scientific evidence that links low 25-hydroxyvitamin D concentrations to the onset and progression of severe neurological diseases, such as multiple sclerosis, Parkinson's disease, Alzheimer's disease, migraine, diabetic neuropathy and amyotrophic lateral sclerosis. Completed and ongoing clinical trials on vitamin D supplementation in neurological diseases are listed.

The effect of tropisetron on peripheral diabetic neuropathy: possible protective actions against inflammation and apoptosis

Diabetic peripheral neuropathy (DPN) is a common nerve disorder of diabetes. The aim of this study was to explore the protective effects of tropisetron in DPN. Type 1 diabetes was created by a single injection of streptozotocin (50 mg/kg, ip). Tropisetron (3 mg/kg, ip) was administered daily for 2 weeks. Our analysis showed that nerve fibers and their myelin sheaths were thinned with decreased myelinated fiber number in diabetic animals. The intensity of Bcl-2 staining decreased and the intensity of Bax staining increased in the sciatic nerves of diabetic rats by using immunohistochemical staining. Furthermore, diabetes significantly increased tumor necrosis factor-alpha, interleukin 1-β (TNFα and IL-1β) and Bax/Bcl-2 ratio in sciatic nerves of rats. However, intraperitoneal injection of tropisetron significantly reversed these alterations induced by diabetes. These findings suggest that tropisetron attenuates diabetes-induced peripheral nerve injury through its anti-inflammatory and anti-apoptotic effects, and may provide a novel therapeutic strategy to ameliorate the process of peripheral neuropathy in diabetes.

Association between sarcopenia and the severity of diabetic polyneuropathy assessed by nerve conduction studies in Japanese patients with type 2 diabetes mellitus

AIMS/INTRODUCTION

This study examined the association between the severity of diabetic polyneuropathy (DPN) based on the Baba classification, and sarcopenia and its related factors.

MATERIALS AND METHODS

The participants were 261 patients with type 2 diabetes mellitus. DPN was classified as stages 0-4 according to the Baba classification. Sarcopenia was diagnosed based on measurements of the skeletal mass index, grip strength and walking speed, using the Asia Working Group for Sarcopenia 2019 diagnostic criteria.

RESULTS

The median age of the participants was 67 years, the proportion of men was 58.6%, the median estimated duration of diabetes was 10 years and the median values for glycated hemoglobin were 10.3%. With regard to DPN, the prevalence of Baba classification stages 0-2 was 90.8% (n = 237), and that of stage 3 or 4 was 9.2% (n = 24). The prevalence of sarcopenia was 19.9%. A trend toward an increase in the frequency of slow walking speed was seen as the stage of DPN progressed. The frequencies of sarcopenia and slow walking speed were higher in the group with the Baba classification stages 3 and 4 than in the group with stages 0-2. On multiple logistic regression analyses, however, DPN was not significantly related to sarcopenia and walking speed.

CONCLUSIONS

Although severe DPN might be related to sarcopenia, the frequency of severe DPN is low in the clinical setting, indicating that its contribution to sarcopenia is modest.

Lower Extremity Nerve Decompression for Diabetic Peripheral Neuropathy: A Systematic Review and Meta-analysis

Background:

Diabetic peripheral neuropathy (DPN) is a leading cause of morbidity. This systematic review and meta-analysis evaluate the efficacy of lower extremity nerve decompression in reducing DPN symptoms and complications.

Methods:

A database search was performed using Medline, Embase, Google Scholar, and Cochrane Central Register of Controlled Trials. Articles addressing surgical decompression of lower limb peripheral nerves in patients with diabetes were screened for inclusion. Two independent reviewers undertook the assessment. Methodological quality measures were the Cochrane risk of bias and Newcastle-Ottawa scale.

Results:

The pooled sample size from 21 studies was 2169 patients. Meta-analysis of 16 observational studies showed significant improvement in the visual analog scale (VAS) (P < 0.00001) and two-point discrimination (P = 0.003), with strong reliability. Decompression of the tarsal tunnel region had the highest improvement in VAS [MD, 6.50 (95% CI, 3.56–9.44)]. A significant low-risk ratio (RR) of ulcer development and lower limb amputation was detected (P < 0.00001). Lowest RR of ulcer development was detected with tarsal tunnel release [RR, 0.04 (95% CI, 0.00–0.48)]. Improvements in VAS, two-point discrimination, and nerve conduction velocity were nonsignificant in the meta-analysis of five randomized controlled trials (RCTs). The RCT analysis was limited to only two studies for each outcome.

Conclusions:

Meta-analysis of observational studies highlights the efficacy of lower extremity nerve decompression in reducing DPN symptoms, ulcerations, and amputations. Releasing the tibial nerve in the tarsal tunnel region was the most effective observed procedure. Nevertheless, high-quality RCTs are required to support the utility of this intervention in DPN.

Effect of Acupuncture on Diabetic Neuropathy: A Narrative Review

Diabetic neuropathy, a major complication of diabetes mellitus, refers to a collection of clinically diverse disorders affecting the nervous system that may present with pain. Although the number of patients suffering from severe neuropathy is increasing, no optimal treatment method has been developed yet. Acupuncture is well known for its ability to reduce various kinds of pain, and a number of studies have also reported its effect on diabetes mellitus; however, its effect and underlying mechanism against diabetic neuropathy are not yet clearly understood. In this review, ten and five studies performed in humans and animals, respectively, were analyzed. All studies reported that acupuncture significantly relieved diabetic neuropathy. ST36, BL13, BL20, SP6, and SP9 were the most widely used acupoints. Five studies used electro-acupuncture, whereas other studies used manual acupuncture. Furthermore, the effect of acupuncture was shown to be mediated through the various molecules present in the peripheral nerves and spinal cord, such as P65, GPR78, and TRPV1. Five studies reported side effects, such as swelling, numbness, and nausea, but none were reported to be serious. Based on these results, we suggest that acupuncture should be considered as a treatment option for diabetic neuropathy.

Inflammatory biomarkers as a part of diagnosis in diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN), a chronic neurological complication of diabetes mellitus, remains scantily addressed area of research. Many lacunae in the temporal sequence between cause and effect of DPN still remain unfilled and therefore treatment of DPN remains unsatisfactory. This is largely due to the conventional glucocentric focus to resolve the problem. This focus over hyperglycemia should be shifted to consider, chronic low grade inflammation as the major determinant in DPN. Rapidly emerging evidences from recent studies suggest that chronic low grade inflammation leads to the activation of innate immune system response, loss of insulin signaling and insulin resistance, endoplasmic reticulum stress, mitochondrial stress, leading to production of kinases like protein kinase C, mitogen activated protein kinase and jun-N-terminal kinase, pro-inflammatory cytokines and inter leukins-1b, 2, 6 and 8, tumour necrosis factor-alpha and other chemokines, leading to DPN. These biomarkers can be early predictors of DPN and therefore should be the focus of work testing their clinical utility to identify high-risk individuals as well as perhaps to target interventions. In this paper, we would like to review all the aspects of DPN, laying greater emphasis on inflammatory biomarkers as a tool for early diagnosis of DPN and the possible research approaches to address it satisfactorily.

Novel idebenone analogs block Shc's access to insulin receptor to improve insulin sensitivity

There has been little innovation in identifying novel insulin sensitizers. Metformin, developed in the 1920s, is still used first for most Type 2 diabetes patients. Mice with genetic reduction of p52Shc protein have improved insulin sensitivity and glucose tolerance. By high-throughput screening, idebenone was isolated as the first small molecule 'Shc Blocker'. Idebenone blocks p52Shc's access to Insulin Receptor to increase insulin sensitivity. In this work the avidity of 34 novel idebenone analogs and 3 metabolites to bind p52Shc, and to block the interaction of p52Shc with the Insulin receptor was tested. Our hypothesis was that if an idebenone analog bound and blocked p52Shc's access to insulin receptor better than idebenone, it should be a more effective insulin sensitizing agent than idebenone itself. Of 34 analogs tested, only 2 both bound p52Shc more tightly and/or blocked the p52Shc-Insulin Receptor interaction more effectively than idebenone. Of those 2 only idebenone analog #11 was a superior insulin sensitizer to idebenone. Also, the long-lasting insulin-sensitizing potency of idebenone in rodents over many hours had been puzzling, as the parent molecule degrades to metabolites within 1 h. We observed that two of the idebenone's three metabolites are insulin sensitizing almost as potently as idebenone itself, explaining the persistent insulin sensitization of this rapidly metabolized molecule. These results help to identify key SAR = structure-activity relationship requirements for more potent small molecule Shc inhibitors as Shc-targeted insulin sensitizers for type 2 diabetes.

Diagnostic capability of retinal thickness measures in diabetic peripheral neuropathy

PURPOSE

To examine the diagnostic capability of the full retinal and inner retinal thickness measures in differentiating individuals with diabetic peripheral neuropathy (DPN) from those without neuropathy and non-diabetic controls.

METHODS

Individuals with (n=44) and without (n=107) diabetic neuropathy and non-diabetic control (n=42) participants underwent spectral domain optical coherence tomography (SDOCT). Retinal thickness in the central 1mm zone (including the fovea), parafovea and perifovea was assessed in addition to ganglion cell complex (GCC) global loss volume (GCC GLV) and focal loss volume (GCC FLV), and retinal nerve fiber layer (RNFL) thickness. Diabetic neuropathy was defined using a modified neuropathy disability score (NDS) recorded on a 0-10 scale, wherein, NDS ≥3 indicated neuropathy and NDS indicated <3 no neuropathy. Diagnostic performance was assessed by areas under the receiver operating characteristic curves (AUCs), 95 per cent confidence intervals (CI), sensitivities at fixed specificities, positive likelihood ratio (+LR), negative likelihood ratio (-LR) and the cut-off points for the best AUCs obtained.

RESULTS

The AUC for GCC FLV was 0.732 (95% CI: 0.624-0.840, p<0.001) with a sensitivity of 53% and specificity of 80% for differentiating DPN from controls. Evaluation of the LRs showed that GCC FLV was associated with only small effects on the post-test probability of the disease. The cut-off point calculated using the Youden index was 0.48% (67% sensitivity and 73% specificity) for GCC FLV. For distinguishing those with neuropathy from those without neuropathy, the AUCs of retinal parameters ranged from 0.508 for the central zone to 0.690 for the inferior RNFL thickness. For distinguishing those with moderate or advanced neuropathy from those with mild or no neuropathy, the inferior RNFL thickness demonstrated the highest AUC of 0.820, (95% CI: 0.731-0.909, p<0.001) with a sensitivity of 69% and 80% specificity. The cut-off-point for the inferior RNFL thickness was 97μm, with 81% sensitivity and 72% specificity.

CONCLUSIONS

The GCC FLV can differentiate individuals with diabetic neuropathy from healthy controls, while the inferior RNFL thickness is able to differentiate those with greater degrees of neuropathy from those with mild or no neuropathy, both with an acceptable level of accuracy. Optical coherence tomography represents a non-invasive technology that aids in detection of retinal structural changes in patients with established diabetic neuropathy. Further refinement of the technique and the analytical approaches may be required to identify patients with minimal neuropathy.

β-Hydroxybutyrate improves β-cell mitochondrial function and survival

Pharmacological interventions aimed at improving outcomes in type 2 diabetes and achieving normoglycaemia, including insulin therapy, are increasingly common, despite the potential for substantial side effects. Carbohydrate-restricted diets that result in increased ketogenesis have effectively been used to improve insulin resistance, a fundamental feature of type 2 diabetes. In addition, limited evidence suggests that states of ketogenesis may also improve β-cell function in type 2 diabetics. Considering how little is known regarding the effects of ketones on β-cell function, we sought to determine the specific effects of β-Hydroxybutyrate (βHB) on pancreatic β-cell physiology and mitochondrial function. βHB treatment increased β-cell survival and proliferation, while also increasing mitochondrial mass, respiration and adenosine triphosphate (ATP) production. Despite these improvements, were unable to detect an increase in β-cell or islet insulin production and secretion. Collectively, these findings have two implications. Firstly, they indicate that β-cells have improved survival and proliferation in the midst of βHB, the circulating form of ketones. Secondly, insulin secretion does not appear to be directly related to apparent improvements in mitochondrial function and cellular proliferation.

Neuroprotective effects of octreotide on diabetic neuropathy in rats

The purpose of the present study is to investigate the possible healing effects of octreotide (OCT) on motor performance, electrophysiological and histopathological findings of diabetic neuropathy in a rat model of diabetes mellitus (DM). To induce diabetes, rats were administered a single dose (60mg/kg) of streptozotocin (STZ). Diabetic rats were treated either with saline (1ml/kg/day, n=7) or OCT (0.1mg/kg/day, n=7) for four weeks. Seven rats served as control group and received no treatment. At the end of the study, electromyography (EMG), gross motor function (inclined plate test), general histology and the perineural thickness of sciatic nerve were evaluated. At the end of study, weight loss was significantly lower in OCT treated rats than that of saline treated ones (p<0.001). Electrophysiologically, compound muscle action potential (CMAP) amplitudes of the saline treated DM group were significantly reduced than those of controls (p<0.0001). Also, distal latency and CMAP durations were significantly prolonged in saline treated DM group (p<0.05) compared to control. However, treatment of diabetic rats with OCT significantly counteracted these alterations in EMG. Furthermore, OCT significantly improved the motor performance scores in diabetic rats (p<0.05). Histomorphometric assessment of the sciatic nerve demonstrated a significant reduction in perineural thickness in OCT treated group compared to saline group. In conclusion, OCT possesses beneficial effects against STZ-induced diabetic neuropathy, which promisingly support the use of OCT as a neuroprotective agent in patients with diabetic neuropathy.

Recognition and management of psychosocial issues in diabetic neuropathy

Although psychosocial aspects of diabetic neuropathy (DN) have received far less attention than biological aspects, research conducted over the last decade has begun to illuminate several important pathways between DN and psychosocial outcomes, including depression, anxiety, and self-management of diabetic foot ulcer (DFU)-risk. Growing body of evidence indicates that DN is a risk factor for depression predicting both the severity and increments in depression over time. Whereas painful DN contributes to depression, postural instability is the DN symptom with the strongest, cumulative effect on depression. Furthermore, depression and foot self-care, while having no impact on the development of recurrent diabetic foot ulcers (DFU), play a substantial role in incident first DFU. Patient common sense misconceptions about DFU risks and associated emotional responses play an important role in shaping foot self-care. Depression, and especially DFU-specific emotions, may be linked to DFU chronicity through biological and behavioral pathways that are at present under investigation in several ongoing trials. Integrative approaches that target psychological factors such as anxiety and depression while concurrently optimizing treatment and self-management may therefore be most powerful. Cognitive behavioral therapy-based techniques that are informed by these findings deserve investigation.

The Impact of Diabetic Neuropathy on Balance and on the Risk of Falls in Patients with Type 2 Diabetes Mellitus: A Cross-Sectional Study

INTRODUCTION

Diabetic neuropathy (DN) is a prevalent complication of Type 2 Diabetes Mellitus (T2DM) with a major impact on the health of the affected patient. We hypothesized that mediated by the dysfunctionalities associated with DN's three major components: sensitive (lack of motion associated sensory), motor (impairments in movement coordination) and autonomic (the presence of postural hypotension), the presence of DN may impair the balance in the affected patients. Our study's main aim is to evaluate the possible association between the presence and severity of DN and both the balance impairment and the risk of falls in patients with T2DM.

MATERIAL AND METHOD

In this cross-sectional study we enrolled, according to a consecutive-case population-based setting 198 patients with T2DM. The presence and severity of DN was evaluated using the Michigan Neuropathy Screening Instrument, a tool which allows both diagnosing and severity staging of DN. The balance impairment and the risk of falls were evaluated using four validated and standardized tools: Berg Balance Scale (BBS), Timed-up and Go test (TUG), Single Leg Stand test (SLS) and Fall Efficacy Scale (FES-I).

RESULTS

The presence of DN was associated with significant decreases in the BBS score (40.5 vs. 43.7 points; p<0.001) and SLS time (9.3 vs. 10.3 seconds; p = 0.003) respectively increases in TUG time (8.9 vs. 7.6 seconds; p = 0.002) and FES-I score (38 vs. 33 points; p = 0.034). The MNSI score was reverse and significantly correlated with both BBS score (Spearman's r = -0.479; p<0.001) and SLS time (Spearman's r = -0.169; p = 0.017). In the multivariate regression model, we observed that patient's age, DN severity and depression's symptoms acted as independent, significant predictors for the risk of falls in patients with T2DM.

CONCLUSIONS

The presence of DN in patients with DM is associated with impaired balance and with a consecutively increase in the risk of falls.

Retinal Tissue Thickness is Reduced in Diabetic Peripheral Neuropathy

AIM

To investigate the relationship between diabetic peripheral neuropathy (DPN) and retinal tissue thickness.

METHODS

Full retinal thickness in the central retinal, parafoveal, and perifoveal zones and thickness of the ganglion cell complex and retinal nerve fiber layer (RNFL) were assessed in 193 individuals (84 with type 1 diabetes, 67 with type 2 diabetes, and 42 healthy controls) using spectral domain optical coherence tomography. Among those with diabetes, 44 had neuropathy defined using a modified neuropathy disability score recorded on a 0-10 scale. Multiple regression analysis was performed to investigate the relationship between diabetic neuropathy and retinal tissue thickness, adjusted for the presence of diabetic retinopathy (DR), age, sex, duration of diabetes, and HbA_1c levels.

RESULTS

In individuals with diabetes, perifoveal thickness was inversely related to the severity of neuropathy (p < 0.05), when adjusted for age, sex, duration of diabetes, and HbA_1c levels. DR was associated with reduced thickness in parafovea (p < 0.01). The RNFL was thinner in individuals with greater degrees of neuropathy (p < 0.04).

CONCLUSIONS

DPN is associated with structural compromise involving several retinal layers. This compromise may represent a threat to visual integrity and therefore warrants examination of functional correlates.

Vascular Impairment of Epineurial Arterioles of the Sciatic Nerve: Implications for Diabetic Peripheral Neuropathy

This article reviews the impact of diabetes and its treatment on vascular function with a focus on the reactivity of epineurial arterioles, blood vessels that provide circulation to the sciatic nerve. Another focus is the relationship between the dysregulation of neurovascular function and diabetic peripheral neuropathy. Diabetic peripheral neuropathy is a debilitating disorder that occurs in more than 50 percent of patients with diabetes. The etiology involves metabolic, vascular, and immunologic pathways besides neurohormonal growth factor deficiency and extracellular matrix remodeling. In the light of this complex etiology, an effective treatment for diabetic peripheral neuropathy has not yet been identified. Current opinion postulates that any effective treatment for diabetic peripheral neuropathy will require a combination of life style and therapeutic interventions. However, a more comprehensive understanding of the factors contributing to neurovascular and neural dysfunction in diabetes is needed before such a treatment strategy can be developed. After reading this review, the reader should have gained insight into the complex regulation of vascular function and blood flow to the sciatic nerve, and the impact of diabetes on numerous elements of vascular reactivity of epineurial arterioles of the sciatic nerve.

The effect of exercise on the peripheral nerve in streptozotocin (STZ)-induced diabetic rats

The exact effectiveness of supportive care activities, such as exercise, in diabetes patients has yet to be elucidated in the diabetic peripheral neuropathy (DPN) field. Therefore, this study was designed to investigate the effect of regular exercise on the peripheral nerves of streptozotocin-induced diabetic rats. The animals were divided as follows into six groups according to exercise combination and glucose control: Normal group, normal group with exercise (EXE), diabetic group (DM), DM group with EXE, DM+glucose control with insulin (INS), and DM+INS+EXE. Animals in the exercise groups were made to walk on a treadmill machine everyday for 30 min at a setting of 8 m/min without inclination. After 8 weeks, sensory parameters were evaluated, and after 16 weeks, biochemicals and peripheral nerves were quantified by immunohistochemistry and compared among experimental groups. The resulting data showed that fasting blood glucose levels and HbA1c levels were not influenced significantly by exercise in normal and DM groups. However, the current perception threshold and the von Frey stimulation test revealed higher thresholds in the DM+INS+EXE group than in the DM+INS group (P<0.05). Significantly lower thresholds were observed in untreated DM groups (DM or DM+EXE) compared to the normal and insulin-treated DM groups (P<0.05). Intra-epidermal nerve fiber density was reduced in a lesser degree in the DM+INS+EXE group than in the DM+INS group (9.8±0.4 vs. 9.1±0.5, P<0.05). Exercise alone was not associated with a significant protective effect on the peripheral nerve in the normal or DM groups; however, a beneficial effect from exercise was observed when hyperglycemia was controlled with insulin in the DM group. These findings suggest that exercise has a potential protective effect against DPN based on the preferential effort for glucose control, although exercise alone cannot prevent peripheral nerve damage from hyperglycemia.

Aqueous fraction of Beta vulgaris ameliorates hyperglycemia in diabetic mice due to enhanced glucose stimulated insulin secretion, mediated by acetylcholine and GLP-1, and elevated glucose uptake via increased membrane bound GLUT4 transporters

Background

The study was designed to investigate the probable mechanisms of anti-hyperglycemic activity of B. Vulgaris.

Methodology/Principal Findings

Aqueous fraction of B. Vulgaris extract was the only active fraction (50mg/kg). Plasma insulin level was found to be the highest at 30 mins after B. Vulgaris administration at a dose of 200mg/kg. B. Vulgaris treated mice were also assayed for plasma Acetylcholine, Glucagon Like Peptide-1 (GLP-1), Gastric Inhibitory Peptide (GIP), Vasoactive Intestinal Peptide, Pituitary Adenylate Cyclase-Activating Peptide (PACAP), Insulin Like Growth Factor-1 (IGF-1), Pancreatic Polypeptides (PP), and Somatostatin, along with the corresponding insulin levels. Plasma Acetylcholine and GLP-1 significantly increased in B. Vulgaris treated animals and were further studied. Pharmacological enhancers, inhibitors, and antagonists of Acetylcholine and GLP-1 were also administered to the test animals, and corresponding insulin levels were measured. These studies confirmed the role of acetylcholine and GLP-1 in enhanced insulin secretion (p<0.05). Principal signaling molecules were quantified in isolated mice islets for the respective pathways to elucidate their activities. Elevated concentrations of Acetylcholine and GLP-1 in B. Vulgaris treated mice were found to be sufficient to activate the respective pathways for insulin secretion (p<0.05). The amount of membrane bound GLUT1 and GLUT4 transporters were quantified and the subsequent glucose uptake and glycogen synthesis were assayed. We showed that levels of membrane bound GLUT4 transporters, glucose-6-phosphate in skeletal myocytes, activity of glycogen synthase, and level of glycogen deposited in the skeletal muscles all increased (p<0.05).

Conclusion

Findings of the present study clearly prove the role of Acetylcholine and GLP-1 in the Insulin secreting activity of B. Vulgaris. Increased glucose uptake in the skeletal muscles and subsequent glycogen synthesis may also play a part in the anti-hyperglycemic activity of B. Vulgaris.

Targeting inflammation in diabetes: Newer therapeutic options

Inflammation has been recognised to both decrease beta cell insulin secretion and increase insulin resistance. Circulating cytokines can affect beta cell function directly leading to secretory dysfunction and increased apoptosis. These cytokines can also indirectly affect beta cell function by increasing adipocyte inflammation.The resulting glucotoxicity and lipotoxicity further enhance the inflammatory process resulting in a vicious cycle. Weight reduction and drugs such as metformin have been shown to decrease the levels of C-Reactive Protein by 31% and 13%, respectively. Pioglitazone, insulin and statins have anti-inflammatory effects. Interleukin 1 and tumor necrosis factor-α antagonists are in trials and NSAIDs such as salsalate have shown an improvement in insulin sensitivity. Inhibition of 12-lipo-oxygenase, histone de-acetylases, and activation of sirtuin-1 are upcoming molecular targets to reduce inflammation. These therapies have also been shown to decrease the conversion of pre-diabetes state to diabetes. Drugs like glicazide, troglitazone, N-acetylcysteine and selective COX-2 inhibitors have shown benefit in diabetic neuropathy by decreasing inflammatory markers. Retinopathy drugs are used to target vascular endothelial growth factor, angiopoietin-2, various proteinases and chemokines. Drugs targeting the proteinases and various chemokines are pentoxifylline, inhibitors of nuclear factor-kappa B and mammalian target of rapamycin and are in clinical trials for diabetic nephropathy. Commonly used drugs such as insulin, metformin, peroxisome proliferator-activated receptors, glucagon like peptide-1 agonists and dipeptidyl peptidase-4 inhibitors also decrease inflammation. Anti-inflammatory therapies represent a potential approach for the therapy of diabetes and its complications.

Laryngeal sensory neuropathy in patients with diabetes mellitus

OBJECTIVE

To determine the prevalence of laryngeal sensory neuropathy in patients with type 2 diabetes mellitus.

METHODS

A cross-sectional study was performed, comprising 50 patients diagnosed with type 2 diabetes mellitus and 36 healthy controls. In the diabetic group, glycaemic control level, disease duration and presence of neuropathy were assessed. Participants were diagnosed with laryngeal sensory neuropathy if they had a cough, globus pharyngeus or throat clearing lasting for more than six weeks, in the absence of laryngopharyngeal reflux disease, allergies, asthma, angiotensin-converting enzyme inhibitor intake or psychogenic disorders.

RESULTS

In the diabetic group, the mean age ± standard deviation was 44.66 ± 10.07 years. Sixty per cent of patients were male, 42 per cent had had diabetes for more than five years and 52 per cent had average to poor glycaemic control. The prevalence of laryngeal sensory neuropathy was 42 per cent in the diabetic group, compared with 13.9 per cent in controls; this difference was statistically significant (p = 0.005). There was no association between the prevalence of laryngeal sensory neuropathy and glycaemic control level, disease duration or presence of neuropathy.

CONCLUSION

Laryngeal sensory neuropathy is more common in patients with type 2 diabetes mellitus than in controls.

Efficacy and safety of methylcobalamin, alpha lipoic acid and pregabalin combination versus pregabalin monotherapy in improving pain and nerve conduction velocity in type 2 diabetes associated impaired peripheral neuropathic condition. [MAINTAIN]: Results of a pilot study

Background and Objective:

To assess whether methylcobalamin and alpha lipoic acid (ALA) added to pregabalin provide additional benefit compared to pregabalin alone in type 2 diabetes mellitus associated peripheral neuropathy.

Setting and Design:

An open label, randomized, controlled parallel-group pilot study.

Materials and Methods:

Thirty adult patients with type 2 diabetes mellitus with symptoms of peripheral neuropathy for ≥6 months were randomized to receive pregabalin 75 mg, methylcobalamin 750 μg, and ALA 100 mg (PMA, n = 15); or pregabalin 75 mg (PG, n = 15) for 12 weeks. Assessment variables were numeric rating scale (NRS), sleep interference scores (SIS), response rate to pain, and global assessment for the usefulness of therapy. The nerve conduction velocity was assessed for sensory and motor nerves. Safety assessment included adverse events reported by the patients, clinical laboratory, and general medical, neurological examinations.

Statistical Analysis:

Efficacy analyses were done on per-protocol (PP) population, whereas safety analyses were done on intent-to-treat (ITT) population.

Results:

Significant improvement was seen in pain and sleep interference in both groups. Mean nerve conduction velocity of left common peroneal nerve (CPN) showed significant improvement in PMA group at week 12 compared to baseline (P = 0.018). For right CPN both groups showed significant improvement. (PMA, P = 0.002, PG, P = 0.007). For sensory testing, at week 12, right superficial peroneal nerve showed reduction in nerve conduction velocity in PG group compared to baseline (P = 0.043).

Conclusion:

Methylcobalamine, ALA and pregabalin combination provides pain relief and improves sleep interference. Addition of methylcobalamin and ALA to pregabalin improves the nerve function. Due to small sample size, most of the efficacy parameters could not reach significant difference between groups; hence benefit of the 3-drug-combimation should be interpreted with reservation.

Autonomic neuropathy in experimental models of diabetes mellitus

Autonomic neuropathy complicates diabetes by increasing patient morbidity and mortality. Surprisingly, considering its importance, development and exploitation of animal models has lagged behind the wealth of information collected for somatic symmetrical sensory neuropathy. Nonetheless, animal studies have resulted in a variety of insights into the pathogenesis, neuropathology, and pathophysiology of diabetic autonomic neuropathy (DAN) with significant and, in some cases, remarkable correspondence between rodent models and human disease. Particularly in the study of alimentary dysfunction, findings in intrinsic intramural ganglia, interstitial cells of Cajal and the extrinsic parasympathetic and sympathetic ganglia serving the bowel vie for recognition as the chief mechanism. A body of work focused on neuropathologic findings in experimental animals and human subjects has demonstrated that axonal and dendritic pathology in sympathetic ganglia with relative neuron preservation represents one of the neuropathologic hallmarks of DAN but it is unlikely to represent the entire story. There is a surprising selectivity of the diabetic process for subpopulations of neurons and nerve terminals within intramural, parasympathetic, and sympathetic ganglia and innervation of end organs, afflicting some while sparing others, and differing between vascular and other targets within individual end organs. Rather than resulting from a simple deficit in one limb of an effector pathway, autonomic dysfunction may proceed from the inability to integrate portions of several complex pathways. The selectivity of the diabetic process appears to confound a simple global explanation (e.g., ischemia) of DAN. Although the search for a single unifying pathogenetic hypothesis continues, it is possible that autonomic neuropathy will have multiple pathogenetic mechanisms whose interplay may require therapies consisting of a cocktail of drugs. The role of multiple neurotrophic substances, antioxidants (general or pathway specific), inhibitors of formation of advanced glycosylation end products and drugs affecting the polyol pathway may be complex and therapeutic elements may have both salutary and untoward effects. This review has attempted to present the background and current findings and hypotheses, focusing on autonomic elements including and beyond the typical parasympathetic and sympathetic nervous systems to include visceral sensory and enteric nervous systems.

Diabetic neuropathy

Diabetic neuropathy (DN) is the most common and troublesome complication of diabetes mellitus, leading to the greatest morbidity and mortality and resulting in a huge economic burden for diabetes care. The clinical assessment of diabetic peripheral neuropathy and its treatment options are multifactorial. Patients with DN should be screened for autonomic neuropathy, as there is a high degree of coexistence of the two complications. A review of the clinical assessment and treatment algorithms for diabetic neuropathy, painful neuropathy, and autonomic dysfunction is provided.

Assessment of Diabetic Polyneuropathy in Inpatient Care: Fasting Blood Glucose, HbA1c, Electroneuromyography and Diabetes Risk Factors

CONFLICT OF INTEREST: NONE DECLARED

Persistent mechanical allodynia positively correlates with an increase in activated microglia and increased P-p38 mitogen-activated protein kinase activation in streptozotocin-induced diabetic rats

BACKGROUND

In experimental early painful diabetic neuropathy, persistent hyperglycaemia induces dys-regulated sodium channel (Navs) expression in the dorsal root ganglion (DRG) and activates microglia in the spinal dorsal horn (SDH). However, information on diabetes-induced chronic neuropathic pain is limited. Therefore, we investigated abnormal Navs in the DRG and activated glial cells in the SDH of diabetic rats with chronic neuropathic pain.

METHODS

Sixty-six rats were divided into diabetic and control groups: control rats (n = 18; 1 mL of normal saline via the right femoral vein) and diabetic rats [n = 48; 60 mg/kg streptozotocin (STZ) via the right femoral vein]. Hindpaw behavioural tests, Navs expression in the DRG, activation of glial cells in the SDH and the number of neurons in the SDH were measured at 1 and 2 weeks, and 1, 2, 3 and 6 months following saline and STZ administration.

RESULTS

All diabetic rats exhibited hyperglycaemia from day 7 to 6 months. The diabetic rats decreased withdrawal threshold to mechanical stimuli but had blunted responses to thermal stimuli. Consistent up-regulation of Nav1.3 and down-regulation of Nav1.8 was observed. Microglial cells were activated early in the SDH and lasted for 6 months. A positive correlation between mechanical allodynia, Nav1.3 and microglial activation was observed. In addition, microglia activation in the SDH of STZ-induced diabetes was mediated, in part, by phosphorylation of p-38 mitogen-activated protein kinase.

CONCLUSIONS

Diabetic rats showed hindpaw mechanical allodynia for 6 months. Persistent mechanical allodynia was positively associated with sustained increased activation of Nav1.3 and increased p38 phosphorylation in activated microglia.

Diabetes, lower extremity amputation, loss of protective sensation, and neuronal nitric oxide synthase associated protein in the chronic renal insufficiency cohort study

Lower extremity amputation (LEA) is a life-altering complication of diabetes. The goal of our study was to investigate the possibility that genetic variation in neuronal nitric oxide synthase associated protein (NOS1AP) is associated with LEA and diabetic peripheral neuropathy (DPN). Our work used data from the Chronic Renal Insufficiency Cohort (CRIC) study. CRIC is a multicenter investigation undertaken to pursue the relationship between chronic renal insufficiency and cardiovascular disease. We evaluated 3,040 CRIC study subjects; 1,490 individuals were African Americans and 1,550 were whites. LEA occurred in 162 (5.3%) subjects, 93 (6.2%) of African Americans and 69 (4.4%) of whites. In whites, NOS1AP single nucleotide polymorphism rs1963645 was most strongly associated with LEA (1.73 [1.23, 2.44]). In African Americans three NOS1AP single nucleotide polymorphisms were associated with LEA: rs6659759 (1.65 [1.21, 2.24]); rs16849113 (1.58 [1.16, 2.14]); rs880296 (1.54 [1.14, 2.10]). We tested a subset of 100 CRIC participants for DPN using Semmes-Weinstein filaments. DPN in those with diabetes was associated with rs1963645 (16.97 [2.38, 120.97]) in whites and rs16849113 and rs6659759 (3.62 [1.11, 11.83] and 3.02 [0.82, 11.12], respectively) in African Americans. In conclusion, this is one of the first studies to show that NOS1AP gene variants are associated with DPN and LEA.

Back to basics: ankle reflex in the evaluation of peripheral neuropathy in type 2 diabetes mellitus

BACKGROUND

Ankle reflex is a simple screening tool frequently used in the detection of peripheral neuropathy.

AIM

The purpose of this study is to assess the performance characteristics of ankle reflex in detecting diabetic peripheral neuropathy (DPN) by evaluating the sensitivity, specificity and the predictive ability of the ankle reflex, a component of Neuropathy Disability Score (NDS) with reference to Nerve Conduction Studies (NCS).

METHODS

A total of 151 patients with type 2 diabetes were assessed (47 males, 104 females). Grading of neuropathy was done using Neuropathy Symptom Score (NSS), NDS and NCS. Patients were divided into two groups, those with abnormal NCS (Group 1) and those with normal NCS (Group 2). Demographic characteristics, biochemistry, NSS and NDS were assessed between the two groups. Taking NCS as the gold standard, sensitivity, specificity and predictive ability of the ankle reflex were calculated and compared with other tests included in NDS, namely vibration sense, superficial pain and temperature sensation.

RESULTS

There were 59 (39.1%) patients in Group 1 and 92 (60.9%) in Group 2. NSS and NDS demonstrated strong positive association with NCS. Taking NCS as the gold standard, ankle reflex yielded the highest sensitivity and specificity (91.5 and 67.4%, respectively), closely followed by that of vibration sense.

CONCLUSION

Ankle reflex is a powerful screening tool with high sensitivity and negative predictive value, but a combination of ankle reflex and vibration sense has superior sensitivity and specificity compared with either of them done alone for the detection of DPN in clinical settings.

Does Vitamin D deficiency play a role in peripheral neuropathy in Type 2 diabetes?

AIM

Despite recent reports linking vitamin D deficiency with increased risk of diabetes mellitus and complications, there is limited data on patients with diabetic peripheral neuropathy. We aimed to evaluate the incidence and associations of vitamin D deficiency in 210 patients with Type 2 diabetes with and without diabetic peripheral neuropathy.

METHODS

Renal, liver, lipid profile and HbA(1c) were measured. Vitamin D status was determined by measuring 25-dihydroxyvitamin D. Presence or absence of coronary heart disease was determined and early-morning urine microalbumin:creatinine ratio was measured. All patients were assessed clinically using neuropathy symptom score, neuropathy disability score and nerve conduction study.

RESULTS

Eighty-seven patients had diabetic peripheral neuropathy and these patients had significantly longer duration of diabetes and higher HbA(1c). Age, gender, incidence of retinopathy and coronary heart disease were not significantly different from those without neuropathy. Mean (SD) vitamin D was significantly lower in those with neuropathy [36.9 (39.9) nmol/l] compared with those without [58.32 (58.9) nmol/l] and 81.5% of patients with neuropathy had vitamin D deficiency compared with 60.4% of those without. Vitamin D showed significant (P < 0.05) correlations with total cholesterol, LDL-cholesterol and urine microalbumin:creatinine ratio. Binary logistic regression analysis showed that diabetic peripheral neuropathy was significantly associated with vitamin D deficiency (odds ratio = 3.47; 95% CI = 1.04-11.56, P = 0.043) after inclusion of potential confounders such as duration of diabetes, HbA(1c) and LDL-cholesterol.

CONCLUSION

Vitamin D deficiency is an independent risk factor for diabetic peripheral neuropathy, and further studies are required to confirm if Vitamin D supplementation could prevent or delay the onset.

Painful diabetic neuropathy: an update

Diabetes, a silent killer, is a leading cause of neuropathy. Around 50% of diabetic patients develop peripheral neuropathy in 25 years. Painful diabetic neuropathy manifests as burning, excruciating, stabbing or intractable type of pain or presents with tingling or numbness. The pathophysiology of this condition is due to primarily metabolic and vascular factors. There is increase in sorbitol and fructose, glycated endproducts, reactive oxygen species and activation of protein kinase C in the diabetic state. All these factors lead to direct damage to the nerves. The first step in the management of painful diabetic neuropathy is a tight glycaemic control. Currently there is no drug which can halt or reverse the progression of the disease. Most of the therapies prevalent aim at providing symptomatic relief. Antidepressants like tricyclic antidepressants (TCAs) and selective norepinephrine reuptake inhibitors (SNRIs) have good efficacy in controlling the symptoms. Selective serotonin reuptake inhibitors have not shown the same consistent results. Anticonvulsants including pregabalin, gabapentin and lamotrigine have shown good results in the control of symptoms whereas same was not found with carbamazepine, oxcarbazepine and topiramate. Topical agents (capsaicin, topical nitrates and topical TCAs) and local anaesthetics have also been used with good results. Use of opioids and non steroidal anti-inflammatory drugs although common but is not preferable. The newer therapies under studies are NMDA antagonists, aldose reductase inhibitors, neurotropic factors, vascular endothelial growth factor, Gamma linolenic acid, protein kinase C beta inhibitors, immune therapy, hyperbaric oxygen and alpha lipoic acid.

Emerging drugs for diabetic neuropathy

IMPORTANCE OF THE FIELD

Diabetic neuropathy (DN) is a very common and disabling diabetes-related complication. DN is associated with significant morbidity and mortality. Diabetic peripheral neuropathy (DPN) can be painful in the earlier stages of the disease before becoming painless. Most of the currently available therapies are symptomatic (focusing on pain relief) rather than disease-modifying. With the exception of good glycemic control, there is currently no effective treatment to slow the progression of or reverse DPN.

AREAS COVERED IN THIS REVIEW

In this article, we review the epidemiology, pathogenesis, currently available and future treatments for DPN, and the potential development issues/challenges related to such new therapies. Literature search was performed using PubMed, Medline and Pharmaprojects from 1950 onwards. Search terms include a combination of terms such as diabetic neuropathy, pathogenesis, pathophysiology, mechanisms, treatment, therapy, oxidative/nitrosative stress, anti-oxidants, serotonin, nitrotyrosine, protein kinase C, aldose reductase, sodium channels, taurine, lipoic acid and poly (ADP-ribose) polymerase.

WHAT THE READER WILL GAIN

The reader will gain an overview of the epidemiology, clinical features and risk factors of DN. In addition, the reader will have a better understanding of the mechanisms that underpin the development of DPN and their relationships to the current and future therapies. The reader will also develop an insight into the limitations of the current approach to DPN treatment and the potential avenues for future research.

TAKE HOME MESSAGE

DN is a very common and disabling complication that currently has no effective treatments other than diabetes control. The pathogenesis of DPN is complex and multi-factorial. Several disease-modifying and symptomatic treatments are currently under development. Oxidative and nitrosative stress have been identified as key pathogenic factors in the development of DPN and new treatments target these pathways and/or their downstream consequences. Gene therapy and growth factors have also emerged as potential new therapies that target particular cellular compartments as opposed to being delivered systemically. The recognition of the difficulty in reversing established DN has focused efforts on slowing its progression.

Review Paper: Basic Concepts to Novel Therapies: A Review of the Diabetic Foot

Diabetes mellitus is a global epidemic. Peripheral neuropathy and peripheral vascular disease are complications of diabetes mellitus and the primary causative factors for foot ulceration. Foot ulceration is the leading cause of hospitalization in people with diabetes mellitus. The burden of foot ulceration on health care systems and individual patients is immense. Despite conventional treatment, there persists a high incidence of amputation. A multidisciplinary approach is required to prevent ulcers. This review describes the etiology and risk factors for diabetic foot ulceration and a system for evaluating the diabetic foot. The assessment of neuropathy and the grading of foot ulcers are critically examined. This is important to allow for standardization in clinical trials. The management of diabetic foot syndrome is reviewed. The treatments to ensure vascular supply to the lower limb and control of infection as well as novel therapies, which are becoming available to treat nonhealing, “no-option” diabetic ulcers, are discussed.

Evaluation of the efficacy of pulsed electromagnetic field in the management of patients with diabetic polyneuropathy

AIM

The study was carried out to evaluate and compare the effect of low power, low frequency pulsed electromagnetic field (PEMF) of 600 and 800 Hz, respectively, in management of patients with diabetic polyneuropathy.

SETTINGS AND DESIGNS

The study was a randomized controlled trial performed in Guru Nanak Dev University and Medical College, Amritsar, India with different subject experimental design.

MATERIALS AND METHODS

Thirty subjects within an age group of 40-68 years with diabetic polyneuropathy stages N1a, N1b, N2a were randomly allocated to groups 1, 2, 3 with 10 subjects in each. Group 1 and 2 were treated with low power 600 and 800-Hz PEMF for 30 min for 12 consecutive days. Group 3 served as control on usual medical treatment of diabetic polyneuropathy (DPN). The subjects with neuropathy due to any cause other than diabetes were excluded. The pain and motor nerve conduction parameters (distal latency, amplitude, nerve conduction velocity) were assessed before and after treatment.

STATISTICAL ANALYSIS

Related t-test and unrelated t-test were used for data analysis.

RESULTS

Significant reduction in pain and statistically significant (P<0.05) improvement in distal latency and nerve conduction velocity were seen in experimental group 1 and 2.

CONCLUSIONS

Low-frequency PEMF can be used as an adjunct in reducing neuropathic pain as well as for retarding the progression of neuropathy in a short span of time.

The TRPV1 receptor is associated with preferential stress in large dorsal root ganglion neurons in early diabetic sensory neuropathy

Chronic diabetic neuropathy is associated with peripheral demyelination and degeneration of nerve fibers. The mechanism(s) underlying neuronal injury in diabetic sensory neuropathy remain poorly understood. Recently, we reported increased expression and function of transient receptor potential vanilloid 1 (TRPV1) in large dorsal root ganglion (DRG) neurons in diabetic sensory neuropathy. In this study, we examined the effects of TRPV1 activation on cell injury pathways in this subpopulation of neurons in the streptozotocin-induced diabetic rat model. Large DRG neurons from diabetic (6-8 weeks) rats displayed increased oxidative stress and activation of cell injury markers compared with healthy controls. Capsaicin (CAP) treatment induced decreased labeling of MitoTracker Red and increased cytosolic cytochrome c and activation of caspase 3 in large neurons isolated from diabetic rats. CAP treatment also induced oxidative stress in large diabetic DRG neurons, which was blocked by pre-treatment with caspase or calpain inhibitor. In addition, both mu-calpain expression and calpain activity were significantly increased in DRG neurons from diabetic rats after CAP treatment. Treatment with capsazepine, a competitive TRPV1 antagonist, markedly reduced these abnormalities in vitro and prevented activation of cell injury in large DRG neurons in diabetic rats in vivo. These results suggest that activation of the TRPV1 receptor activates pathways associated with caspase-dependent and calpain-dependent stress in large DRG neurons in STZ-diabetic rats. Activation of the TRPV1 receptor may contribute to preferential neuronal stress in large DRG neurons relatively early in diabetic sensory neuropathy.

Two styles of acupuncture for treating painful diabetic neuropathy--a pilot randomised control trial

In a pilot study, we evaluated the clinical and mechanistic effects of two styles of acupuncture, Traditional Chinese Medicine (TCM) and Japanese acupuncture, for the treatment of painful diabetic neuropathy. Out of seven patients enrolled, three received Traditional Chinese acupuncture while four received Japanese style acupuncture. Treatments were delivered once a week for 10 weeks. Acupuncturists were permitted to select the needle interventions. Substantial differences in diagnostic techniques, choice of acupuncture points, and needle manipulation were observed between TCM and Japanese acupuncturists. Clinically, patients allocated to Japanese acupuncture reported decreased neuropathy-associated pain according to the daily pain severity score, while the group allocated to the TCM acupuncture reported minimal effects. Both acupuncture styles, however, lowered pain according to the McGill Short Form Pain Score. The TCM style improved nerve sensation according to quantitative sensory testing while the Japanese style had a more equivocal effect. No evident changes were observed in glucose control or heart rate variability in either group.

The therapeutic potential of gene transfer for the treatment of peripheral neuropathies

Peripheral neuropathy is a common medical problem with numerous aetiologies. Unfortunately, for the majority of cases there is no available medical solution for the underlying cause, and the only option is to try to treat the resulting symptoms. Treatment options exist when neuropathy results in positive symptoms such as pain, but there is a significant lack of treatments for negative symptoms such as numbness and weakness. Systemic application of growth factor peptides has shown promise in protecting nerves from neuropathic insults in preclinical animal studies, but translation into human trials has been problematic and disappointing. Significant advancements have been made in the past few years in utilising gene therapy approaches to treat peripheral neuropathy by expressing neuroprotective gene products either systemically or in specific nervous tissues. For example, plasmids expressing vascular endothelial growth factor injected into muscle, or herpes-simplex-virus-based vectors expressing neurotrophin gene products delivered to dorsal root ganglion neurons, have been used to protect peripheral nerve function in animal models of diabetes-associated peripheral neuropathy. Many published studies support the feasibility of this approach, although several questions still need to be addressed as gene therapy to treat peripheral neuropathy moves out of the laboratory and into the clinic.

Use of Tricyclic Antidepressants in Older Patients With Diabetic Peripheral Neuropathy

PURPOSE

To describe patterns of use of tricyclic antidepressants (TCAs) (eg, amitriptyline, nortriptyline) among older patients with diabetic peripheral neuropathy (DPN).

MATERIALS AND METHODS

Using a large, integrated, US health-insurance claims database, we identified all patients who received TCAs between January 1, 1999 and June 30, 2001 ("study period"). Among these persons, we then selected those who: (1) were aged >or=65 years as of the date of first receipt of a TCA during the study period; and (2) had one or more healthcare encounters with a diagnosis of DPN in the 30-day period immediately preceding date of first receipt of a TCA. We then examined the prevalence of selected comorbidities and concurrent use of medications which might render inappropriate the prescribing of TCAs, based on a listing of contraindications, warnings, and precautions found in the package inserts for these medications. Patterns of TCA prescribing were examined, based on information on paid claims.

RESULTS

There were 349 DPN patients, aged >or=65 years, who received TCAs. Mean age was 73.8 years, 55.9% were women, and 17.9% had diagnoses of depression. Most patients (84.0%) began therapy with amitriptyline. Almost one-half of study patients had indicators of potentially inappropriate TCA use, primarily cardiovascular comorbidities. Mean TCA dose among patients with and without these indicators was 23.3 (+/-13.4) mg and 25.4 (+/-15.3) mg, respectively (P=0.42).

CONCLUSIONS

The high prevalence of contraindications, warnings, or precautions and the low level of TCA exposure suggest that many older patients with DPN who receive TCAs may be inappropriately treated.

Neuregulins: Versatile growth and differentiation factors in nervous system development and human disease

The neuregulins are a family of growth and differentiation factors with a wide range of functions in the nervous system. The power and diversity of the neuregulin signaling system comes in part from a large number of alternatively-spliced forms of the NRG1 gene that can produce both soluble and membrane-bound forms. The soluble forms of neuregulin are unique from other factors in that they have a structurally distinct heparin-binding domain that targets and potentiates its actions. In addition, a finely tuned, bidirectional mechanism regulates when and where neuregulin is released from neurons in response to neurotrophic factors produced by both neuronal targets and supporting glial cells. Together, this produces a balanced intercellular signaling system that can be localized to distinct regions for both normal development and maintenance of the mature nervous system. Recent evidence suggests that neuregulin signaling plays important roles in many neurological disorders including multiple sclerosis, traumatic brain and spinal cord injury, peripheral neuropathy, and schizophrenia. Here, we review the basic biology of neuregulins and relate this to research suggesting their involvement with and potential therapeutic uses for neurological disorders.

Prognostic ability of a good outcome to carpal tunnel release for decompression surgery in the lower extremity

For years, patients who were treated successfully with carpal tunnel release were told there was nothing that could be done about their lower extremity symptoms. Now that lower extremity nerve decompression has been accepted as an option to treat appropriate patients, the authors looked for correlations between a successful outcome with carpal tunnel syndrome and its predictive value of success for lower extremity nerve decompression. Data from a recent study demonstrate that a good result from upper extremity peripheral nerve surgery predicts the outcome for lower extremity peripheral nerve surgery in 88% of patients, and is, therefore, information valuable for prognosis and clinical decision-making.

Use of tricyclic antidepressants in older patients with painful neuropathies

OBJECTIVE

To describe patterns of use of tricyclic antidepressants (TCAs) (e.g., amitriptyline, nortriptyline) in older patients with painful neuropathies.

RESEARCH DESIGN AND METHODS

Using a large US health insurance claims database, we identified all persons who: (1) received a TCA between 1 January 1999 and 30 June 2001, (2) were aged > or =65 years as of the date of their first prescription for a TCA during this period, and (3) had one or more health care encounters for the treatment of a painful neuropathy in the 30-day period immediately preceding their initial receipt of a TCA. We then examined the prevalence of selected comorbidities and/or concurrent use of medications that might render the prescribing of a TCA inappropriate, based on a listing of contraindications, warnings, and precautions found in the package inserts for these agents. Patterns of TCA use also were examined, based on information on paid claims.

RESULTS

A total of 1,732 patients met all inclusion and exclusion criteria for the study. Their mean age was 74.6 years; 60.3% were women. Amitriptyline was the most frequently prescribed TCA (79.4% of patients). Forty-one percent of study subjects receiving TCAs had conditions--primarily cardiovascular--that render the use of such agents potentially inappropriate. The mean daily dose of TCAs was universally low (about 23 mg).

CONCLUSIONS

The high prevalence of conditions rendering the use of TCAs potentially inappropriate, along with relatively low daily dosages, suggest that many older patients with painful neuropathies who are prescribed these agents may be suboptimally treated.

Altered expression and function of sodium channels in large DRG neurons and myelinated A-fibers in early diabetic neuropathy in the rat

Differential alterations of sodium channels in small nociceptive C-fiber DRG neurons have been implicated in diabetic neuropathy. In this study, we investigated sodium currents and the expression of sodium channels in large A-fiber DRG neurons in diabetic rats. Compared with controls, large neurons from diabetic rats showed significant increases in both total and TTX-S sodium currents and approximately -15mV shifts in their voltage-dependent activation kinetics. TTX-R Na(v)1.9 sodium current was also significantly increased, whereas no alteration of TTX-R Na(v)1.8 current was observed in neurons from diabetic rats. Sodium current induced by fast- or slow-voltage ramps increased markedly in the diabetic neurons as well. Immunofluorescence studies showed significant increases in the levels and number of large DRG neurons from diabetic rats expressing Na(v)1.2, Na(v)1.3, Na(v)1.7, and Na(v)1.9 whereas Na(v)1.8 decreased. We also observed a decrease in the number of nodes of Ranvier expressing Na(v)1.8 and in staining intensity of Na(v)1.6 and Na(v)1.8 at nodes. Our results suggest that alterations of sodium channels occur in large DRG neurons and A-fibers, and may play an important role in diabetic sensory neuropathy.