Treatment of painful diabetic neuropathy

Efficacy and Safety of the Combination of Superoxide Dismutase, Alpha Lipoic Acid, Vitamin B12, and Carnitine for 12 Months in Patients with Diabetic Neuropathy

Aim: To investigate the efficacy of Superoxide Dismutase, Alpha Lipoic Acid, Acetyl L-Carnitine, and Vitamin B12 (B12) in one tablet in Diabetic Neuropathy (DN). Patients–methods: In this prospective, double-blind, placebo-controlled study, 85 patients with Diabetes Mellitus Type 2 (DMT2) were randomly assigned, either to receive the combination of four elements (active group, n = 43), or placebo (n = 42) for 12 months. We used the Michigan Neuropathy Screening Instrument Questionnaire and Examination (MNSIQ and MNSIE), measured the vibration perception threshold (BIO), and Cardiovascular Autonomic Reflex Tests (CARTs). Nerve function was assessed by DPN Check [sural nerve conduction velocity (SNCV) and amplitude (SNAP)]. Pain (PS) and quality of life (QL) questionnaires were administered. Results: At follow-up, BIO, MNSIQ, QL, PAIN, and SNCV, SNAP, and B12 levels had significantly improved inactive group (p < 0.001, p < 0.001, p < 0.001, p < 0.001, p = 0.027, p = 0.031, and p < 0.001 respectively), whereas the inplacebo group MCR (mean circular resultant) and PAIN deteriorated (p < 0.001, p < 0.001). The changes in MNSIQ, QL, SNCV, BIO, and PAIN differed significantly between groups (p < 0.001, p < 0.001, p = 0.031, p < 0.001, and p < 0.001 respectively). Conclusions: The combination of the four elements in one tablet for 12 months in patients with DMT2 improved all indices of peripheral neuropathy, including SNAP and SNCV, pain, and Quality of Life perception, except CARTs and MNSIE.

Relation of exercise and pain in patients with idiopathic distal axonal polyneuropathies

Although exercise is associated with better outcomes in patients with some peripheral neuropathies, data in idiopathic peripheral neuropathies is lacking. This study was completed to do a comprehensive data analysis about the benefits of regular exercise in a well-characterized cohort of patients with idiopathic distal, symmetrical, axonal polyneuropathy enrolled in the Peripheral Neuropathy Research Registry (PNRR) at Johns Hopkins University School of Medicine. From the patient-reported exercise habits, metabolic equivalents (METs) were calculated and the patient information was grouped into four categories. The PNRR data set, including patient reported pain, numbness, and weakness, was analyzed using the METs categories to evaluate for the benefits of exercise. We controlled for the components of metabolic syndrome including Hemoglobin A1c (HbA1c), systolic and diastolic blood pressure (BP), high density lipids (HDL) and triglyceride level, and body mass index (BMI) as defined by the Adult Treatment Panel III Guidelines. Lower METs were associated with neuropathic pain, but not with other peripheral neuropathy symptoms. Patients with IPN who exercised were less likely to have painful neuropathy independent of the average METs per week (P < .01). No significant differences were seen for patient reported numbness, weakness, or balance issues. The data suggests that patients with idiopathic neuropathy benefit from exercises even if performed on a low intensity level or less frequently, and patients are less likely to have severe pain symptoms when exercising on a regular basis.

Prevalence and risk factors for diabetic neuropathy and painful diabetic neuropathy in primary and secondary healthcare in Qatar

Aims/Introduction

This study determined the prevalence and risk factors for diabetic peripheral neuropathy (DPN) and painful DPN (pDPN) in patients with type 2 diabetes in primary healthcare (PHC) and secondary healthcare (SHC) in Qatar.

Materials and Methods

This was a cross‐sectional multicenter study. Adults with type 2 diabetes were randomly enrolled from four PHC centers and two diabetes centers in SHC in Qatar. Participants underwent assessment of clinical and metabolic parameters, DPN and pDPN.

Results

A total of 1,386 individuals with type 2 diabetes (297 from PHC and 1,089 from SHC) were recruited. The prevalence of DPN (14.8% vs 23.9%, P = 0.001) and pDPN (18.1% vs 37.5%, P < 0.0001) was significantly lower in PHC compared with SHC, whereas those with DPN at high risk for diabetic foot ulceration (31.8% vs 40.0%, P = 0.3) was comparable. The prevalence of undiagnosed DPN (79.5% vs 82.3%, P = 0.66) was comparably high, but undiagnosed pDPN (24.1% vs 71.5%, P < 0.0001) was lower in PHC compared with SHC. The odds of DPN and pDPN increased with age and diabetes duration, and DPN increased with poor glycemic control, hyperlipidemia and hypertension, whereas pDPN increased with obesity and reduced physical activity.

Conclusions

The prevalence of DPN and pDPN in type 2 diabetes is lower in PHC compared with SHC, and is attributed to overall better control of risk factors and referral bias due to patients with poorly managed complications being referred to SHC. However, approximately 80% of patients had not been previously diagnosed with DPN in PHC and SHC. Furthermore, we identified a number of modifiable risk factors for PDN and pDPN.

Influence of the complex drug Cocarnit on the sciatic nerve in the development of diabetic polyneuropathy in rats

Ulcers and slow wound healing are common in diabetic polyneuropathy (DP), as well as shooting or burning pain, sensitivity to touch or lack of sensitivity, low oxygenation of nerve tissue, conductivity disorders and various vascular disorders. The mechanisms of DP development are complex and have not been completely studied. To take into account the role of B group vitamins, we investigated histological structure of nerve tissue, the level of different growth factors and the qualitative composition of active proteolytic enzymes in rats with DP and after the use of the metabolic drug Cocarnit for 9 days. This drug composition include nicotinamide, cocarboxylase, cyanocobalamin, adenosine triphosphate disodium trihydrate. We used an histological study of sciatic nerve; enzyme-linked immunosorbent assay and enzyme electrophoresis methods. In rats with DP, fragmentation of nerve tissue and their necrosis was established. Moreover, degraded forms of plasmin that has a fully functional serine proteinase domain are evident, and, therefore, it exhibits proteolytic properties. DP led to a decrease of neuron growth factor (NGF), vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). After treatment, the histological structure of nerve tissue was significantly improved, and the expression of growth factors NGF and bFGF was increased. Our study demonstrated that administration of Corcarnit brought about the complete restoration of the activation potential of plasmin and the almost disappearance of all degraded forms which were evident in the group with DP.

Increased Risk of Falls, Fall-related Injuries and Fractures in People with Type 1 and Type 2 Diabetes - A Nationwide Cohort Study

INTRODUCTION

People with diabetes could have an increased risk of falls as they show more complications, morbidity and use of medication compared to the general population. This study aimed to estimate the risk of falls and to identify risk factors associated with falls in people with diabetes. The second aim was to estimate fall-related injuries, such as lesions and fractures, including their anatomic localization in people with diabetes compared with the general population.

METHODS

From the Danish National Patient Register, we identified people with Type 1 Diabetes (T1D) (n=12,975) Type 2 Diabetes (T2D) (n=407,009). The cohort was divided into two groups, with respective control groups matched on age and sex (1:1). All episodes of people hospitalized with a first fall from 1996 to 2017 were analyzed using a Cox proportional-hazards model. Risk factors such as age, sex, diabetic complications, a history of alcohol abuse and the use of medication were included in an adjusted analysis. The incidence rate, incidence rate difference and incidence rate ratio (IRR) of falls and the anatomic localization of fall-related injuries as lesions and fractures were identified.

RESULTS AND DISCUSSION

The cumulative incidence, of falls requiring hospital treatment, was 13.3% in T1D, 11.9% in T2D. In the adjusted analysis, T1D and T2D were associated with a higher risk of falls [T1D, Hazard Ratio (HR): 1.33 (95% CI: 1.25 - 1.43), T2D, HR: 1.19 (95% CI:1.16 - 1.22), respectively]. Women [group 1, HR 1.21 (CI:95%:1.13 - 1.29), group 2, HR 1.61 (CI:95%:1.58-1.64)], aged >65 years [groups 1, HR 1.52 (CI:95%:1.39 - 1.61), group 2, HR 1.32 (CI:95%:1.58-1.64)], use of selective serotonin receptor inhibitors (SSRI) [group 1, HR 1.35 (CI:95%:1.1.30 - 1.40), group 2, HR 1.32 (CI:95%:1.27-1.38)], opioids [group 1, HR 1.15 (CI:95%:1.12 - 1.19), group 2, HR 1.09 (CI:95%:1.05-1.12)] and a history of alcohol abuse [group 1, HR 1.77 (CI:95%:1.17 - 2.15), group 2, HR 1.88 (CI:95%:1.65-2.15)] were significantly associated with an increased risk of falls in both groups. The IRR of fall-related injuries as hip, radius, humerus and skull/facial fractures were higher in people with T2D than controls [IRR 1.02 (CI:95%:1.01-1.04), IRR 1.39 (CI:95%: 1.18-1.61), IRR 1.24 (CI:95%: 1.12-1.37) and IRR 1.15 (CI:95%:1.07-1.24)]. People with T1D had a higher IRR of hip fractures than controls [IRR: 1.11 (CI:95%:1.02 - 1.23)].

CONCLUSION

People with diabetes have an increased risk of first fall and a higher incidence of fall- related injuries, including fractures. Advanced aging and sex are non-modifiable risk factors, whereas diabetes, the use of SSRIs and opioids and alcohol abuse could be potentially modifiable risk factors for falls. Gaining information on risk factors for falls could guide the management of diabetes treatment, i.e., choice of drugs, which enables us to improve treatment, particularly in people with a high risk of falls and fractures associated with high mortality.

State-of-the-art pharmacotherapy for diabetic neuropathy

INTRODUCTION

The global epidemic of diabetes has led to an epidemic of diabetes complications. Diabetic neuropathy is the most common microvascular complication, of which diabetic peripheral neuropathy (DPN) and autonomic neuropathy (AN) are the most prevalent, affecting ~50% of patients. DPN results in pain with a poor quality of life and a loss of sensation with an increased risk of foot ulceration. Autonomic neuropathy can cause significant morbidity in a minority and is associated with increased mortality. The cornerstone of treatment to prevent or limit the progression of DPN/AN is multifactorial risk factor modification including treatment of glycemia, lipids and blood pressure. Whilst, there are no FDA-approved disease-modifying therapies, there are a number of therapies to relieve symptoms in DPN and AN.

AREAS COVERED

The authors discuss current approved therapies for painful diabetic neuropathy and autonomic neuropathy. They also address the potential role of improving risk factors to limit the development and progression of diabetic neuropathy and new pathogenetic and pain-relieving treatments.

EXPERT OPINION

The FDA-approved Pregabalin and Duloxetine over 25 years ago and Tapentadol, 6 years ago for painful diabetic neuropathy. There are currently no FDA-approved disease-modifying treatments for diabetic neuropathy which has been attributed to inappropriate models of the disease with limited translational capacity and major limitations of trial designs and endpoints in clinical trials.

Psychosocial Factors in Painful Diabetic Neuropathy: A Systematic Review of Treatment Trials and Survey Studies

OBJECTIVE

Diabetes mellitus is associated with a number of complications that can adversely impact patients' quality of life. A common and often painful complication is painful diabetic neuropathy. The aims of this study were to systematically review and summarize evidence from studies of psychological treatments and psychosocial factors related to painful diabetic neuropathy and assess the methodological quality of these studies.

METHODS

Electronic databases, related reviews, and associated reference lists were searched. Summaries of participants' data relating to the efficacy of psychological treatments and/or to associations between psychosocial factors and outcomes in painful diabetic neuropathy were extracted from the included studies. The methodological quality of included studies was assessed using two standardized quality assessment tools.

RESULTS

From 2,921 potentially relevant titles identified, 27 studies were included in this systematic review. The evidence suggests that depression, anxiety, sleep, and quality of life are the most studied variables in relation to pain outcomes in painful diabetic neuropathy and are consistently associated with pain intensity. The magnitude of the associations ranged from small to large.

CONCLUSIONS

Research into psychosocial factors in painful diabetic neuropathy is unexpectedly limited. The available evidence is inconsistent and leaves a number of questions unanswered, particularly with respect to causal associations between variables. The evidence reviewed indicates that depression, anxiety, low quality of life, and poor sleep are associated with pain in painful diabetic neuropathy. The disproportionate lack of research into psychological treatments for painful diabetic neuropathy represents a significant opportunity for future research.

Diabetic Peripheral Neuropathy: Diagnosis and Treatment

BACKGROUND

Diabetic peripheral neuropathy (DPN) is traditionally divided into large and small fibre neuropathy (SFN). Damage to the large fibres can be detected using nerve conduction studies (NCS) and often results in a significant reduction in sensitivity and loss of protective sensation, while damage to the small fibres is hard to reliably detect and can be either asymptomatic, associated with insensitivity to noxious stimuli, or often manifests itself as intractable neuropathic pain.

OBJECTIVE

To describe the recent advances in both detection, grading, and treatment of DPN as well as the accompanying neuropathic pain.

METHODS

A review of relevant, peer-reviewed, English literature from MEDLINE, EMBASE and Cochrane Library between January 1st 1967 and January 1st 2020 was used.

RESULTS

We identified more than three hundred studies on methods for detecting and grading DPN, and more than eighty randomised-controlled trials for treating painful diabetic neuropathy.

CONCLUSION

NCS remains the method of choice for detecting LFN in people with diabetes, while a gold standard for the detection of SFN is yet to be internationally accepted. In the recent years, several methods with huge potential for detecting and grading this condition have become available including skin biopsies and corneal confocal microscopy, which in the future could represent reliable endpoints for clinical studies. While several newer methods for detecting SFN have been developed, no new drugs have been accepted for treating neuropathic pain in people with diabetes. Tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors and anticonvulsants remain first line treatment, while newer agents targeting the proposed pathophysiology of DPN are being developed.

Understanding Diabetic Neuropathy: Focus on Oxidative Stress

Diabetic neuropathy is one of the clinical syndromes characterized by pain and substantial morbidity primarily due to a lesion of the somatosensory nervous system. The burden of diabetic neuropathy is related not only to the complexity of diabetes but also to the poor outcomes and difficult treatment options. There is no specific treatment for diabetic neuropathy other than glycemic control and diligent foot care. Although various metabolic pathways are impaired in diabetic neuropathy, enhanced cellular oxidative stress is proposed as a common initiator. A mechanism-based treatment of diabetic neuropathy is challenging; a better understanding of the pathophysiology of diabetic neuropathy will help to develop strategies for the new and correct diagnostic procedures and personalized interventions. Thus, we review the current knowledge of the pathophysiology in diabetic neuropathy. We focus on discussing how the defects in metabolic and vascular pathways converge to enhance oxidative stress and how they produce the onset and progression of nerve injury present in diabetic neuropathy. We discuss if the mechanisms underlying neuropathy are similarly operated in type I and type II diabetes and the progression of antioxidants in treating diabetic neuropathy.

Chronic hyperglycemia impairs mitochondrial unfolded protein response and precipitates proteotoxicity in experimental diabetic neuropathy: focus on LonP1 mediated mitochondrial regulation

BACKGROUND

Disturbed mitochondrial homeostasis has been identified to contribute to the pathogenesis of diabetic neuropathy (DN). However, the role of Mitochondrial Lon peptidase 1 (Lonp1) and Heat shock proteins (HSP's) in DN remains elusive. Here we studied the role of these proteins in experimental DN.

METHODS

Rats were injected with STZ (55 mg/kg, ip) to induce diabetes. After confirmation of diabetes, animals were maintained for 8 weeks to develop neuropathy. Resveratrol was administered at two dose levels 10 and 20 mg/kg for last 2 weeks. Neuronal PC12 cells was challenged with 30 mM of β-D glucose to evaluate the molecular changes.

RESULTS

Diabetic rats showed reduced expression of various mitochondrial proteases in dorsal root ganglions (DRG). This effect may increase proteotoxicity and diminish electron transport chain (ETC) activity as evident by increased protein oxidation and reduced ETC complexes activities under diabetic condition. In particular, we focused on our efforts to characterize the expression pattern of Lonp1 which was found to be significantly (p < 0.01 vs. control group) under expressed in DRG of diabetic rats. We used Resveratrol to characterize the importance of Lonp1 in regulation of mitochondrial function. High glucose (HG) (30 mM) exposed PC12 cells suggested that Resveratrol treatment attenuated the HG induced mitochondrial damage via induction of mitochondrial proteases. Moreover, siRNA directed against Lonp1 has impaired the activity of Resveratrol in attenuating the HG induced mitochondrial dysfunction.

CONCLUSION

These results would signify the importance of modulating mitochondrial proteases for the therapeutic management of DN.

Role of platelet-derived growth factor in type II diabetes mellitus and its complications

Type 2 diabetes mellitus is a type of metabolic disorder characterized by hyperglycaemia with multiple serious complications, such as diabetic neuropathies, diabetic nephropathy, diabetic retinopathy, and diabetic foot. Platelet-derived growth factors are growth factors that regulate cell growth and division, playing a critical role in diabetes and its harmful complications. This review focused on the cellular mechanism of platelet-derived growth factors and their receptors on diabetes development. Furthermore, we raise some proper therapeutic molecular targets for the treatment of diabetes and its complications.

Transcranial direct current stimulation improves quality of life and physical fitness in diabetic polyneuropathy: a pilot double blind randomized controlled trial

Purpose

Diabetes Mellitus (DM) is a chronic disease which presents a big prevalence in the world and several patients with this condition fail to respond to the available treatments. There is a huge unmet clinical need for the development of new therapeutic approaches for this condition. This study aims to evaluate the effects of anodal tDCS on Quality of Life and physical fitness in patients with diabetic polyneuropathy.

Methods

A pilot, parallel, sham, randomized, double-blind trial was conducted with twenty patients. Five consecutive sessions of C3/Fp2 tDCS montage were performed. To assess the primary outcome Short Form 36 Health Survey (SF-36) was used. Physical fitness level, according to lower and upper body strength, flexibility, Time Up and Go Test (TUG) and Six-Minute Walking Test (6MWT) were measured as secondary outcomes. The measures were performed at 3 different times (baseline, 1st and 2nd weeks).

Results

SF-36 increased throughout the protocol, but no difference between groups were found. However, there was a significant difference between groups at 1st and 2nd weeks, which shows a permanent growth in the active-tDCS group. Physical health and functioning, functional capacity and bodily pain showed significant improvements in active-tDCS group in 1st and 2nd weeks during inter-group analysis. Emotional scores showed significant interaction group-time with interaction effects only for active-group in 1st and 2nd weeks. TUG and 6MWT showed significant improvements only in active-tDCS group.

Conclusions

It is suggested that five sessions of anodal M1 tDCS improves QoL and functionality of patients with diabetic polyneuropathy.

Short-term outcomes of mirogabalin in patients with peripheral neuropathic pain: a retrospective study

Background

Mirogabalin, which is approved for the treatment of peripheral neuropathic pain in Japan, is a ligand for the α2δ subunit of voltage-gated calcium channels. Both pregabalin and mirogabalin act as nonselective ligands at the α2δ-1 and α2δ-2 subunits. Mirogabalin has a unique binding profile and long duration of action. Pregabalin has been reported to produce intolerable adverse effects in some patients. This study investigated outcomes associated with mirogabalin administration in patients with peripheral neuropathic pain who ceased treatment with pregabalin.

Methods

We retrospectively assessed peripheral neuropathic pain using the neuropathic pain screening questionnaire (NeP score) in 187 patients (58 men, 129 women) who were treated with mirogabalin. All patients had switched from pregabalin to mirogabalin due to lack of efficacy or adverse events. Differences in the treatment course (i.e., numeric rating scale (NRS) scores) were compared using one-way analysis of variance with Bonferroni post hoc tests.

Results

The mean age of the patients was 72.3 years (range, 30–94 years), and the mean duration of disease was 37 months (range, 3–252 months). After treatment with mirogabalin for 1 week, NRS scores significantly decreased compared with baseline and continued to decrease over time. After 8 weeks, NRS scores improved by ≥ 30% from baseline in 113 patients (69.3%). Twenty-four patients (12.8%) stopped mirogabalin treatment due to adverse events. Somnolence (26.7%), dizziness (12.3%), edema (5.9%), and weight gain (0.5%) were noted as adverse events of mirogabalin.

Conclusions

The results of this investigation indicate that mirogabalin is safe and effective for reducing peripheral neuropathic pain.

Non-coding RNA regulators of diabetic polyneuropathy

Diabetic polyneuropathy is a common and disturbing complication of diabetes mellitus, presenting patients and caregivers with a substantial disease burden. Emerging mechanisms which are underlying diabetes may provide novel pathways to understand diabetic polyneuropathy (DPN). Specifically, non-coding RNA molecules consisting of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are implicated in the biological processes underlying DPN, and may link it to clinical spheres such as other metabolic and neural pathologies. Here, we elaborate on several candidate non-coding RNAs which may be associated with DPN via regulatory roles governing phenomena related to inflammatory, pain-provoking, and metabolic syndrome pathways. Specific examples include miRNAs such as miR-106a, -146a, -9, -29b, -466a, and -98; likewise, lncRNAs MIAT, PVT1, H19, MEG3, and MALAT1 are implicated, often co-affecting the involved pathways. Incorporating newly discovered regulators into what we know about specific clinical applications may highlight novel avenues for diagnosis, prevention, and intervention with DPN.

The impact of demographic and clinical characteristics on diabetic painful neuropathy

INTRODUCTION

Diabetic neuropathy (DN) is one of the most devastating complications of diabetes mellitus; however, in contrast to other countries, there are no scientific studies in Portugal evaluating the impact of demographic and clinical characteristics of this pathological entity. The aim of this study was to evaluate the impact of gender, metabolic control, age of diabetic patients, as well as time of disease progression, the appearance of complaints related to neuropathic pain.

MATERIAL AND METHODS

A multicentre study with a non-probabilistic, convenience sample of 359 patients was performed employing the quantitative method, using the Statistical Package for Social Science 24 software. The p-value of p < 0.05 was defined to consider a result statistically significant. The Spearman correlation coefficient (r) was determined to determine the relationship between categorical variables.

RESULTS

There was no statistically significant difference in the prevalence of DN between genders (p = 0.633 and r = 0.025). There was a statistically significant relationship between the value of HbA1c and DN, with p = 0.010 and r = 0.136. There is a relationship between age and complaints of neuropathic pain, with p = 0.034 and r = 0.112. The variable, time of disease progression, is also correlated with the appearance of complaints of neuropathic pain with p = 0.020 and r = 0.112.

CONCLUSION

The prevalence of neuropathic pain in subjects with diabetes is not negligible and is associated with modifiable risk factors that can be identified, possibly modified and prevented. The correct approach for these patients, which involves screening and early treatment, is decisive improving functionality and quality of life.

Corneal confocal microscopy detects small nerve fibre damage in patients with painful diabetic neuropathy

Neuropathic pain is believed to arise from damage to nociceptive C fibres in diabetic neuropathy (DN). We have utilised corneal confocal microscopy (CCM) to quantify the severity of small nerve fibre damage in relation to the severity of neuropathic pain and quality of life (QoL) in patients with and without painful DN. 30 controls and patients with painful (n = 78) and painless (n = 62) DN underwent assessment of large and small nerve fibre function, CCM, neuropathic symptoms (small fibre neuropathy symptom inventory questionnaire, neuropathic pain scale) and QoL (SF-36, pre-R-ODS and hospital anxiety and depression scale). Patients with painful compared to painless DN, had comparable neurophysiology and vibration perception, but lower corneal nerve fibre density (20.1 ± 0.87 vs. 24.13 ± 0.91, P = 0.005), branch density (44.4 ± 3.31 vs. 57.74 ± 3.98, P = 0.03), length (19.61 ± 0.81 vs. 22.77 ± 0.83, P = 0.01), inferior whorl length (18.03 ± 1.46 vs. 25.1 ± 1.95, P = 0.005) and cold sensation threshold (21.35 ± 0.99 vs. 26.08 ± 0.5, P < 0.0001) and higher warm sensation threshold (43.7 ± 0.49 vs. 41.37 ± 0.51, P = 0.004) indicative of small fibre damage. There was a significant association between all CCM parameters and the severity of painful neuropathic symptoms, depression score and QoL. CCM identifies small nerve fibre loss, which correlates with the severity of neuropathic symptoms and reduced QoL in patients with painful diabetic neuropathy.

Treatment of diabetic peripheral neuropathy: a review

OBJECTIVES

This review surveys current pharmacotherapies available for the treatment of diabetic peripheral neuropathy (DPN), emphasising their mechanisms of action.

METHODS

A comprehensive literature review focusing on the 'pharmacotherapy and treatment of diabetic peripheral neuropathy' was conducted. The Database of International Pharmaceutical Abstracts, EMBASE, PubMed, OVID, Scopus, Google and Google Scholar were searched, and reference lists of relevant articles were also included.

KEY FINDINGS

Diabetic peripheral neuropathy is often inadequately treated, and the role of improving glycaemic control specifically in type-2 diabetes remains unclear. It is crucial to explore the mechanisms of action and effectiveness of available therapies. Major international clinical guidelines for the management of DPN recommend several symptomatic treatments. First-line therapies include tricyclic antidepressants, serotonin-noradrenaline reuptake inhibitors, and anticonvulsants that act on calcium channels. Other therapies include opioids and topical agents such as capsaicin and lidocaine. The objectives of this paper are to review current guidelines for the pharmacological management of DPN and to discuss research relevant to the further development of pharmacological recommendations for the treatment of diabetic neuropathy.

SUMMARY

Diabetic neuropathy is a highly prevalent, disabling condition, the management of which is associated with significant costs. Evidence supports the use of specific anticonvulsants and antidepressants for pain management in patients with diabetic peripheral neuropathy. All current guidelines advise a personalised approach with a low-dose start that is tailored to the maximum response having the least side effects or adverse events.

Pragmatic Opioid Use in Painful Diabetic Neuropathy

The management of painful diabetic neuropathy poses a tough clinical challenge. Although opioid analgesics are considered as second- or third-line agents in the management of moderate-to-severe neuropathic pain, prescription of opioids for this indication is higher than expected. This narrative review is a recommendation on how to ensure pragmatic use of opioids for those with painful diabetic neuropathy while avoiding complications such as opioid overdose, opioid diversion and the development of opioid-use disorder. Risk mitigation strategies at the level of the clinician include periodic assessment and documentation of clinical details, treatment history and psychosocial status. Using a multimodal approach to pain management, medication counselling, adherence monitoring programmes, evidence-based opioid dosing strategies and empowering patients to make treatment decisions are effective strategies in reducing risk associated with prolonged opioid use. At the organisational and policy level, using prescription drug monitoring programmes, carrying out periodic opioid utilisation reviews and providing training to patients and physicians on safe opioid use are useful, implementable strategies.

Downregulation of spinal angiotensin converting enzyme 2 is involved in neuropathic pain associated with type 2 diabetes mellitus in mice

We have previously reported that the spinal angiotensin (Ang) system is involved in the modulation of streptozotocin (STZ)-induced diabetic neuropathic pain in mice. An important drawback of this model however is the fact that the neuropathic pain is independent of hyperglycemia and produced by the direct stimulation of peripheral nerves. Here, using the leptin deficient ob/ob mouse as a type 2 diabetic model, we examined whether the spinal Ang system was involved in naturally occuring diabetic neuropathic pain. Blood glucose levels were increased in ob/ob mice at 5-15 weeks of age. Following the hyperglycemia, persistent tactile and thermal hyperalgesia were observed at 11-14 and 9-15 weeks of age, respectively, which was ameliorated by insulin treatment. At 12 weeks of age, the expression of Ang-converting enzyme (ACE) 2 in the spinal plasma membrane fraction was decreased in ob/ob mice. Spinal ACE2 was expressed in neurons and microglia but the number of NeuN-positive neurons was decreased in ob/ob mice. In addition, the intrathecal administration of Ang (1-7) and SB203580, a p38 MAPK inhibitor, attenuated hyperalgesia in ob/ob mice. The phosphorylation of spinal p38 MAPK was also attenuated by Ang (1-7) in ob/ob mice. These inhibitory effects of Ang (1-7) were prevented by A779, a Mas receptor antagonist. In conclusion, we revealed that the Ang (1-7)-generating system is downregulated in ob/ob mice and is accompanied by a loss of ACE2-positive neurons. Furthermore, Ang (1-7) decreased the diabetic neuropathic pain through inhibition of p38 MAPK phosphorylation via spinal Mas receptors.

New Perspective in Diabetic Neuropathy: From the Periphery to the Brain, a Call for Early Detection, and Precision Medicine

Diabetic peripheral neuropathy (DPN) is a common chronic complication of diabetes mellitus. It leads to distressing and expensive clinical sequelae such as foot ulceration, leg amputation, and neuropathic pain (painful-DPN). Unfortunately, DPN is often diagnosed late when irreversible nerve injury has occurred and its first presentation may be with a diabetic foot ulcer. Several novel diagnostic techniques are available which may supplement clinical assessment and aid the early detection of DPN. Moreover, treatments for DPN and painful-DPN are limited. Only tight glucose control in type 1 diabetes has robust evidence in reducing the risk of developing DPN. However, neither glucose control nor pathogenetic treatments are effective in painful-DPN and symptomatic treatments are often inadequate. It has recently been hypothesized that using various patient characteristics it may be possible to stratify individuals and assign them targeted therapies to produce better pain relief. We review the diagnostic techniques which may aid the early detection of DPN in the clinical and research environment, and recent advances in precision medicine techniques for the treatment of painful-DPN.

Pain-related changes in cutaneous innervation of patients suffering from bortezomib-induced, diabetic or chronic idiopathic axonal polyneuropathy

Consistent associations between the severity of neuropathic pain and cutaneous innervation have not been described. We collected demographic and clinical data, McGill Pain Questionnaires (MPQ) and skin biopsies processed for PGP9.5 and CGRP immunohistochemistry from patients with bortezomib-induced peripheral neuropathy (BiPN; n = 22), painful diabetic neuropathy (PDN; n = 16), chronic idiopathic axonal polyneuropathy (CIAP; n = 16) and 17 age-matched healthy volunteers. Duration of neuropathic symptoms was significantly shorter in patients with BiPN in comparison with PDN and CIAP patients. BiPN was characterized by a significant increase in epidermal axonal swellings and upper dermis nerve fiber densities (UDNFD) and a decrease in subepidermal nerve fiber densities (SENFD) of PGP9.5-positive fibers and of PGP9.5 containing structures that did not show CGRP labeling, presumably non-peptidergic fibers. In PDN and CIAP patients, intraepidermal nerve fiber densities (IENFD) and SENFD of PGP9.5-positive and of non-peptidergic fibers were decreased in comparison with healthy volunteers. Significant unadjusted associations between IENFD and SENFD of CGRP-positive, i.e. peptidergic, fibers and the MPQ sensory-discriminative, as well as between UDNFD of PGP9.5-positive fibers and the MPQ evaluative/affective component of neuropathic pain, were found in BiPN and CIAP patients. No significant associations were found in PDN patients. Cutaneous innervation changes in BiPN confirm characteristic features of early, whereas those in CIAP and PDN are in line with late forms of neuropathic pathology. Our results allude to a distinct role for non-peptidergic nociceptors in BiPN and CIAP patients. The lack of significant associations in PDN may be caused by mixed ischemic and purely neuropathic pain pathology.

Efficacy and safety of duloxetine and Pregabalin in Iranian patients with diabetic peripheral neuropathic pain: a double-blind, randomized clinical trial

Purpose

Diabetic peripheral neuropathic pain (DPNP) is one of the most sufferings, disabling, and dominant complications of diabetes. Duloxetine (DLX) and Pregabalin (PGB) are among first-line therapy and the most prescribed drugs for DPNP relief. The effectiveness-risk profile of drugs may differ from region to region due to variations in genetic and health situation of populations. This study aims to evaluate the efficacy and safety of DLX and PGB in a sample of Iranian population with DPNP.

Methods

A double-blind, randomized clinical trial was conducted on 180 type-2 diabetic patients with DPNP≥40 mm according to Visual Analogue Scale (VAS), with other eligibility criteria throughout twelve weeks. We divided the patients randomly into two equal groups: DLX and PGB. Each patient received ten days placebo as a washout period, then blind capsules of DLX (group 1) or PGB (group 2). We assessed the efficacy and safety of drugs by VAS and recorded the Adverse Drug Reactions (ADRs) during the study.

Results

In the DLX group, sixty-six and the PGB group, seventy-eight patients completed the study. The intensity of patients’ pain was improved by both drugs significantly (p˂0.001), but there was no significant difference between the two groups. Average daily doses of DLX and PGB were 42.5 and 235.5 mg, respectively. In the DLX group, 74% of patients and the PGB group, 37% reported ADRs. The discontinuation rates due to ADRs were 19% and 7% correspondingly.

Conclusion

We found that in Iranian patients, the mean effective doses of these drugs are different in comparison with several other studies. Surprisingly intolerance and discontinuation of DLX in our patients were attributed to mild and severe Serotonin Syndrome, which had not much occurred in other studies. Accordingly, despite the same efficacy, PGB was better tolerated than DLX in our patients. Thus we would recommend PGB for DPNP treatment in Iranian patients.

Ameliorative Effects Of N-Acetylcysteine As Adjunct Therapy On Symptoms Of Painful Diabetic Neuropathy

Purpose

Painful diabetic neuropathy (PDN) is a variant of diabetic peripheral neuropathy which is highly prevalent and distressing in diabetic patients. Despite its high burden, the optimal treatment of PDN has remained a clinical challenge. To explain the emergence and maintenance of PDN, increasing attention has been focused on dimensions of inflammation and oxidative toxic stress (OTS). Accordingly, the aim of this study was to investigate the effects of oral N-acetylcysteine (NAC), an agent with known anti-oxidant and anti-inflammatory effects, as an adjunct therapy in patients suffering from PDN.

Patients and methods

113 eligible patients with type 2 diabetes suffering from PDN were randomly assigned to either the pregabalin + placebo or pregabalin + NAC group for 8 weeks (pregabalin at a dose of 150 mg per day, NAC and matched placebo at doses of 600 mg twice a day). Mean pain score was evaluated at baseline, week 1, 2, 4, 6, and 8 of the study based on the mean 24 hr average pain score, using an 11-point numeric rating scale (NRS). As secondary efficacy measures, mean sleep interference score (SIS) resulting from PDN, responder rates, Patient Global Impression of Change (PGIC), Clinical Global Impression of Change (CGIC), and safety were also assessed. Additionally, serum levels of total antioxidant capacity (TAC), total thiol groups (TTG), catalase activity (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), nitric oxide (NO), and malondialdehyde (MDA) were assessed at baseline and at the end of the study.

Results

Ninety patients completed the eight-week course of the study. The decrease in mean pain scores and mean sleep interference score in pregabalin + NAC group was greater in comparison with pregabalin + placebo group (p value<0.001 in both conditions). Moreover, more responders (defined as ≥50% reduction in mean pain score from baseline to end-point) were observed in the pregabalin + NAC group, in comparison with pregabalin + placebo group (72.1% vs 46.8%). More improvement in PGIC and CGIC from baseline to the end of the study was reported in pregabalin + NAC group. Oral NAC had minimal adverse effects and was well tolerated in almost all patients. Furthermore, in respect to OTS biomarkers, adjuvant NAC significantly decreased serum level of MDA and significantly increased serum levels of SOD, GPx, TAC, and TTG.

Conclusion

The pattern of results suggests that compared to placebo and over a time period of 8 weeks, adjuvant NAC is more efficacious in improving neuropathic pain associated with diabetic neuropathy than placebo. Ameliorative effects of NAC on OTS biomarkers demonstrated that NAC may alleviate painful symptoms of diabetic neuropathy, at least in part by its antioxidant effects.

Peripheral nerve disease secondary to systemic conditions in children

This review is an overview of systemic conditions that can be associated with peripheral nervous system dysfunction. Children may present with neuropathic symptoms for which, unless considered, a causative systemic condition may not be recognized. Similarly, some systemic conditions may be complicated by comorbid peripheral neuropathies, surveillance for which is indicated. The systemic conditions addressed in this review are critical illness polyneuropathy, chronic renal failure, endocrine disorders such as insulin-dependent diabetes mellitus and multiple endocrine neoplasia type 2b, vitamin deficiency states, malignancies and reticuloses, sickle cell disease, neurofibromatosis, connective tissue disorders, bowel dysmotility and enteropathy, and sarcoidosis. In some disorders presymptomatic screening should be undertaken, while in others there is no benefit from early detection of neuropathy. In children with idiopathic peripheral neuropathies, systemic disorders such as celiac disease should be actively excluded. While management is predominantly focused on symptomatic care through pain control and rehabilitation, some neuropathies improve with effective control of the underlying etiology and in a small proportion a more targeted approach is possible. In conclusion, peripheral neuropathies can be associated with a diverse range of medical conditions and unless actively considered may not be recognized and inadequately managed.

Comparison of the Efficacy of Duloxetine and Pregabalin in Pain Relief Associated with Diabetic Neuropathy

Introduction

Painful diabetic peripheral neuropathy (PDPN) complicates 25% of type II diabetes mellitus. It has a profound impact on diabetes-related morbidity and worsens the quality of life. Both pregabalin and duloxetine may be indicated for PDPN. In this study, the efficacy of duloxetine and pregabalin was compared in patients with PDPN.

Methods

It was a single-centre open-label study conducted with patients of diabetes mellitus type II diagnosed with PDPN. Patients were randomized to receive 60 mg/daily duloxetine or 300 mg/daily pregabalin. Pain scores were recorded using visual analogue scale (VAS) on day 0, week 4, and week 12. Data was entered and analysed using SPSS version 22.0 (IBM Corp., Armonk, NY).

Results

In the duloxetine group, the mean VAS score decreased from 6.81 ± 0.91 to 4.01 ± 1.12 with 12 weeks of therapy (p <0.0001). In the pregabalin group, the mean VAS score decreased from 6.99 ± 1.12 to 4.91 ± 0.82 with 12 weeks of therapy (p <0.0001). At 12 weeks, duloxetine showed lower VAS scores than pregabalin (p <0.0001). In the duloxetine group, the mean change in VAS score over time was - 2.80 and in the pregabalin group, the mean change was - 2.80. Adverse events were reported in 17.9% of the participants. Lethargy/somnolence (8.1%) and peripheral edema (3.4%) were commonly reported in the pregabalin group and constipation (6.9%) and orthostatic hypotension (4.6%) were commonly reported in the duloxetine group.

Conclusions

Duloxetine at a daily fixed dose of 60 mg is efficacious in the relief of neuropathic pain. Pregabalin also showed a comparable outcome. Both duloxetine and pregabalin have a promising safety profile and are well-tolerated.

Low level laser therapy for the patients with painful diabetic peripheral neuropathy - A systematic review

BACKGROUND

Low Level Laser Therapy (LLLT) is an emerging treatment modality for management of neuropathic pain. It works by triggering biochemical changes with in cells.

OBJECTIVE

This systematic review focused on finding evidence on the effectiveness of LLLT on treatment of painful diabetic neuropathy.

METHODS

We conducted a systematic review (PubMed, Web of Science, CINAHL and Cochrane) to find the evidence on effectiveness of LLLT on treatment of painful diabetic neuropathy. Randomized and non-randomized studies were included in the review.

RESULTS

A total of 627 studies were screened. After the exclusion criteria (duplicate, animal studies, LLLT for treating other neuralgias) 6 studies were included in the study. The outcome measure that were considered were the difference in pain score and nerve conduction velocity test and quality of life questionnaire.

CONCLUSION

The evidence obtained shows LLLT has a positive effect in controlling diabetic neuropathic pain.

Effect of Low Level Laser Therapy on serum vitamin D and magnesium levels in patients with diabetic peripheral neuropathy - A pilot study

BACKGROUND

Diabetic Peripheral neuropathy (DPN) is the most distressing complication of diabetic population leading to loss of sensation, pain, and amputation. Low-level laser therapy (LLLT) has been used to manage nerve injuries as it holds the potential to induce a biostimulatory effect with no side effects. Hence we planned to study the biochemical effect and therapeutic outcomes of LLLT on patients with painful diabetic peripheral neuropathy as a preliminary work.

MATERIALS AND METHODS

Pre-posttest analysis was done on 40 patients diagnosed with DPN confirmed using 10 g Monofilament test and Michigan Neuropathy Screening Instrument (MNSI). Vibration sensation and pain measured by Vibration perception threshold (VPT) and Numeric pain rating scale (NPRS). All patients were given LLLT (3.1 J/cm²) on plantar and dorsal of the foot for 10 days. Serum samples were collected at baseline and 4 weeks after LLLT to estimate Vitamin D and Magnesium and compared the results.

RESULTS

There was a significant increase in Vitamin D and Magnesium levels after LLLT. We observed a considerable improvement in the quality of life after LLLT demonstrated by a decrease in VPT and MNSI and a reduction in NPRS in DPN patients.

CONCLUSION

In this study, we found that LLLT improved the QL and hence may be a useful therapeutic option in treating peripheral neuropathic pain in type 2 diabetic patients. The progress in the serum Magnesium and Vit. D levels were proportional to the QL and may be a good indicator of the prognosis of DPN after LLLT.

Nano curcumin supplementation reduced the severity of diabetic sensorimotor polyneuropathy in patients with type 2 diabetes mellitus: A randomized double-blind placebo- controlled clinical trial

BACKGROUND

Diabetic Sensorimotor Polyneuropathy (DSPN) is a common complication of diabetes mellitus. Curcumin is the most important ingredient found in turmeric which has a very high potential for eliminating free radicals and inhibiting oxidative stress as an antioxidant agent. The aim of this study was to determine the effect of Nano-curcumin supplementation on the severity of sensorimotor polyneuropathy in patients with Type 2 diabetes mellitus (T2DM).

METHOD

This parallel, double-blind randomized, placebo-controlled clinical trial was conducted on 80 diabetic patients. Participants were allocated randomly to the intervention (n = 40) and the control group (n = 40). They received 80 mg of nano-curcumin or placebo capsules for 8 weeks. Anthropometric measurements, dietary intake, physical activity, glycemic indices and the severity of DSPN were measured before and after the intervention.

RESULT

Supplementation of nano curcumin was accounted for a significant reduction in Glycated hemoglobin(HbA1c) (p < 0.001) and Fast Blood Sugar(FBS) (p = 0.004), total score of neuropathy (p < 0.001), total reflex score (p = 0.04) and temperature (p = 0.01) compared to placebo group.

CONCLUSION

Our findings indicated that curcumin supplementation for 2 months improved and reduced the severity of DSPN in patients with T2DM.

Topical treatments for diabetic neuropathic pain

Diabetic neuropathic pain (DNP) has a huge impact on quality of life and can be difficult to treat. Oral treatment is the most frequently used method for DNP, but its use is often limited by systemic side effects. Topical use of drugs as an alternative option for DNP treatment is currently gaining interest. In the present review, a summary is provided of the available agents for topical use in patients with DNP, including lidocaine plasters or patches, capsaicin cream, gel or patches, amitriptyline cream, clonidine gel, ketamine cream, extracts from medicinal plants including nutmeg extracts and Citrullus colocynthis extract oil, and certain compounded topical analgesics. Furthermore, the potential efficacy of these treatments is addressed according to the available clinical research literature. It has been indicated that these topical drugs have the potential to be valuable additional options for the management of DNP, with adequate safety and continuous long-term treatment efficacy. Compounded topical agents are also effective and safe for patients with DNP and could be another area worthy of further investigation based on the strategy of using low-dose, complementary therapies for DNP. The findings indicate that developing topical drugs acting on different targets in the process of DNP is a valuable area of future research.

Micronized Palmitoylethanolamide: A Post Hoc Analysis of a Controlled Study in Patients with Low Back Pain - Sciatica

BACKGROUND

Despite being widely prescribed, relatively few controlled trials have been conducted on the class of neurotrophic/antinociceptive nutraceuticals. While performing a search in the literature, we came across an old registration study on micronized palmitoylethanolamide in patients with low back pain - sciatica by Guida and colleagues.

METHODS

We contacted the authors of the article and obtained all the original material, which allowed us to reanalyze the study. We assessed its clinical relevance by calculating the numbers needed to treat for pain (visual analog scale) and function (Roland-Morris Questionnaire). After excluding patients for whom the information available was insufficient, we assigned each patient to one of the five categories of increasing probability of neuropathic pain: pure lumbago, lumbago with projecting pain to surrounding regions (e.g. gluteus or groin), lumbago with projecting pain to the thigh or leg, pure sciatica and radiculopathy, and investigated any correlations (Spearman) between the improvement in pain and function with these five classes.

RESULTS

Compared with placebo, palmitoylethanolamide 600 mg/die yielded a number needed to treat of 1.7 (95% confidence interval: 1.4-2) for pain, and 1.5 (95% confidence interval: 1.4-1.7) for function. The correlation between the five categories was highly significant for pain relief (P <0.0001), though not significant for reduced dysfunction.

CONCLUSION

Palmitoylethanolamide was extremely effective on pain and function in a large cohort of patients with low back pain - sciatica. Although, the multiple mechanisms of action of palmitoylethanolamide are ideal for mixed pain conditions such as low back pain - sciatica, the correlation between pain relief and the likelihood of neuropathic pain suggests that this drug exerts a predominant action on the neuropathic pain component.

Human-like cutaneous neuropathologies associated with a porcine model of peripheral neuritis: A translational platform for neuropathic pain

Despite enormous investment in research and development of novel treatments, there remains a lack of predictable, effective, and safe therapeutics for human chronic neuropathic pain (NP) afflictions. NP continues to increase among the population and treatments remain a major unmet public health care need. In recent years, numerous costly (time and money) failures have occurred attempting to translate successful animal pain model results, typically using rodents, to human clinical trials. These continued failures point to the essential need for better animal models of human pain conditions. To address this challenge, we have previously developed a peripheral neuritis trauma (PNT) model of chronic pain induced by a proximal sciatic nerve irritation in pigs, which have a body size, metabolism, skin structure, and cutaneous innervation more similar to humans. Here, we set out to determine the extent that the PNT model presents with cutaneous neuropathologies consistent with those associated with human chronic NP afflictions. Exactly as is performed in human skin biopsies, extensive quantitative multi-molecular immunofluorescence analyses of porcine skin biopsies were performed to assess cutaneous innervation and skin structure. ChemoMorphometric Analysis (CMA) results demonstrated a significant reduction in small caliber intraepidermal nerve fiber (IENF) innervation, altered dermal vascular innervation, and aberrant analgesic/algesic neurochemical properties among epidermal keratinocytes, which are implicated in modulating sensory innervation. These comprehensive pathologic changes very closely resemble those observed from CMA of human skin biopsies collected from NP afflictions. The results indicate that the porcine PNT model is more appropriate for translational NP research compared with commonly utilized rodent models. Because the PNT model creates cutaneous innervation and keratinocyte immunolabeling alterations consistent with human NP conditions, use of this animal model for NP testing and treatment response characteristics will likely provide more realistic results to direct successful translation to humans.

Diabetic neuropathy and the sensory neuron: New aspects of pathogenesis and their treatment implications

Diabetic polyneuropathy (DPN) continues to be generally considered as a "microvascular" complication of diabetes mellitus alongside nephropathy and retinopathy. The microvascular hypothesis, however, might be tempered by the concept that diabetes directly targets dorsal root ganglion sensory neurons. This neuron-specific concept, supported by accumulating evidence, might account for important features of DPN, such as its early sensory neuron degeneration. Diabetic sensory neurons develop neuronal atrophy alongside a series of messenger ribonucleic acid (RNA) changes related to declines in structural proteins, increases in heat shock protein, increases in the receptor for advanced glycation end-products, declines in growth factor signaling and other changes. Insulin is recognized as a potent neurotrophic factor, and insulin ligation enhances neurite outgrowth through activation of the phosphoinositide 3-kinase-protein kinase B pathway within sensory neurons and attenuates phenotypic features of experimental DPN. Several interventions, including glucagon-like peptide-1 agonism, and phosphatase and tensin homolog inhibition to activate growth signals in sensory neurons, or heat shock protein overexpression, prevent or reverse neuropathic abnormalities in experimental DPN. Diabetic sensory neurons show a unique pattern of microRNA alterations, a key element of messenger RNA silencing. For example, let-7i is widely expressed in sensory neurons, supports their growth and is depleted in experimental DPN; its replenishment improves features of DPN models. Finally, impairment of pre-messenger RNA splicing in diabetic sensory neurons including abnormal nuclear RNA metabolism and structure with loss of survival motor neuron protein, a neuron survival molecule, and overexpression of CWC22, a splicing factor, offer further novel insights. The present review addresses these new aspects of DPN sensory neurodegeneration.

The prevalence of painful diabetic neuropathy in 300 Moroccan diabetics

Painful diabetic neuropathy is a frequent complication of diabetes. Its diagnosis is clinical. Our goal is to determine the prevalence of painful diabetic neuropathy in this population. We also analyzed the relationship between this neuropathy and certain parameters, concerning the patient and his diabetes. It is a cross sectional study conducted at the department of endocrinology and internal medicine of Avicenne hospital Marrakech-Morocco, among a cohort of 300 diabetic outpatients. We used the DN4 questionnaire (Douleur Neuropathique en 4 questions), for diagnosis. The results showed a prevalence of 15%. In this study: advanced age, female gender, duration of diabetes greater than 10 years, and the lack of medical follow up were found to be statistically significant risk factors for painful diabetic neuropathy, in addition to some diabetes-related comorbidities such as hypertension, dyslipidemia, sedentary life style and diabetic retinopathy. Painful diabetic neuropathy remains undertreated, in fact 74% of our patients did not receive any specific treatment, knowing that the progress in developing effective and well-tolerated therapies has been disappointing.

Inhibitory effect of Ligustrum vulgare leaf extract on the development of neuropathic pain in a streptozotocin-induced rat model of diabetes

BACKGROUND

Chronic hyperalgesia and allodynia associated with progressive damage of peripheral neurons are the most prevalent complications of diabetes mellitus. Plants belonging to the family of Oleaceae were traditionally used in folk medicine for the management of diabetes.

HYPOTHESIS/PURPOSE

The aim of this study was to investigate whether an aqueous extract from the leaves of Ligustrum vulgare (common privet) could be useful to target neuropathic pain in a rat streptozotocin (STZ) model of diabetes.

METHODS

The chemical composition of the aqueous extract from privet leaf was characterized with the UHPLC-DAD-MS method and the analytical quantification of its constituents was performed with HPLC-DAD. Mechanical hyperalgesia and allodynia were evaluated with the Randall-Selitto and von Frey tests.

RESULTS

Our investigation revealed the presence of secoiridoids: oleacein (23.48 ± 0.87 mg/g), oleocanthal (8.44 ± 0.08 mg/g), oleuropein (1.50 ± 0.01 mg/g), as well as phenylpropanoids: echinacoside (6.46 ± 0.07 mg/g), verbascoside (4.03 ± 0.04 mg/g) and p-coumaroyl glucarates in the dried aqueous extract of privet leaves. Behavioral data indicated that chronic intraperitoneal administration of the extract (50-200 mg/kg) for 21 days resulted in a decrease in diabetes-induced hyperalgesia and allodynia. Blood glucose levels remained unaltered, while body weight and water intake decreased significantly.

CONCLUSION

The aqueous privet leaf extract could serve useful in facilitating treatment of painful diabetic neuropathy. Additionally, the study showed that the antihyperalgesic activity of Ligustrum vulgare leaf extract is not likely related to its antihyperglycemic properties.

Mirogabalin and emerging therapies for diabetic neuropathy

There are currently no approved disease-modifying therapies for diabetic neuropathy, and there are only 3 US Food and Drug Administration-approved therapies (pregabalin, duloxetine, and tapentadol) for painful diabetic neuropathy. They each have moderate efficacy with adverse effects limiting optimal dose titration. There is a considerable need for new therapies for the management of painful diabetic neuropathy. We reviewed the potential role of mirogabalin, which like gabapentin and pregabalin modulates the alpha-2/delta-1 subunit of the voltage-gated calcium channel, allowing the influx of calcium and release of neurotransmitters at the synaptic cleft in the central nervous system and spinal cord. It has shown efficacy and good tolerability in a Phase II study in diabetic painful neuropathy and based on the results of two Phase III clinical trials in diabetic painful neuropathy and post-herpetic neuralgia, Daiichi Sankyo submitted a marketing application for neuropathic pain in Japan in February 2018. We have also reviewed potential new therapies, currently in Phase II clinical trials that may modify disease and/or relieve neuropathic pain through novel modes of action.

Antihyperalgesic Activity of Atomoxetine on Diabetes-Induced Neuropathic Pain: Contribution of Noradrenergic and Dopaminergic Systems

Atomoxetine is a selective noradrenaline reuptake inhibitor drug. Based on the knowledge that agents increasing monoamine levels in the central nervous system have therapeutic potential for neuropathic pain, it is planned to investigate the possible efficacy of atomoxetine on diabetes-induced hyperalgesia, in this study. Randall-Selitto (mechanical noxious stimuli) and Hargreaves (thermal noxious stimuli) tests were used to evaluate nociceptive perception of rats. Obtained data indicated that streptozotocin-induced diabetes causes significant decreases in the paw withdrawal threshold and paw withdrawal latency values of the animals, respectively. However, atomoxetine administered at 3 mg/kg/day for 7 and 14 days improved these diabetes-induced hyperalgesia responses. Furthermore, antihyperalgesic activity was antagonized with α-methyl-para-tyrosine methyl ester, phentolamine, propranolol, and sulpiride pre-treatments. The same effect was not reversed, however, by SCH 23390. These findings demonstrated, for the first time, that atomoxetine possesses significant antihyperalgesic activity on diabetes-induced neuropathic pain and this effect seems to be mediated by α- and β-adrenergic and D₂/D₃ dopaminergic receptors. Results of this present study seem to offer a new indication for an old drug; atomoxetine, but these preclinical data should first be confirmed with further well-designed clinical trials.

Therapeutic potential for leukocyte elastase in chronic pain states harboring a neuropathic component

Supplemental Digital Content is Available in the Text.

Inhibitors of leukocyte elastase inhibit spontaneous and evoked pain behaviors in mouse models of chronic pain of neuropathic, cancer, and diabetic origins.

Neuropathic pain is an integral component of several chronic pain conditions and poses a major health problem worldwide. Despite emerging understanding of mechanisms behind neuropathic pain, the available treatment options are still limited in efficacy or associated with side effects, therefore making it necessary to find viable alternatives. In a genetic screen, we recently identified SerpinA3N, a serine protease inhibitor secreted in response to nerve damage by the dorsal root ganglion neurons and we showed that SerpinA3N acts against induction of neuropathic pain by inhibiting the T-cell- and neutrophil-derived protease, leucocyte elastase (LE). In the current study, via detailed in vivo pharmacology combined with analyses of evoked- and spontaneous pain-related behaviors in mice, we report that on systemic delivery, a single dose of 3 independent LE inhibitors can block established nociceptive hypersensitivity in early and late phases in the spared nerve injury model of traumatic neuropathic pain in mice. We further report the strong efficacy of systemic LE inhibitors in reversing ongoing pain in 2 other clinically relevant mouse models—painful diabetic neuropathy and cancer pain. Detailed immunohistochemical analyses on the peripheral tissue samples revealed that both T-Lymphocytes and neutrophils are the sources of LE on peripheral nerve injury, whereas neutrophils are the primary source of LE in diabetic neuropathic conditions. In summary, our results provide compelling evidence for a strong therapeutic potential of generic LE inhibitors for the treatment of neuropathic pain and other chronic pain conditions harboring a neuropathic pain component.

Diabetic Peripheral Neuropathy: Epidemiology, Diagnosis, and Pharmacotherapy

PURPOSE

Diabetic peripheral neuropathy (DPN) is the commonest cause of neuropathy worldwide, and its prevalence increases with the duration of diabetes. It affects approximately half of patients with diabetes. DPN is symmetric and predominantly sensory, starting distally and gradually spreading proximally in a glove-and-stocking distribution. It causes substantial morbidity and is associated with increased mortality. The unrelenting nature of pain in this condition can negatively affect a patient's sleep, mood, and functionality and result in a poor quality of life. The purpose of this review was to critically review the current literature on the diagnosis and treatment of DPN, with a focus on the treatment of neuropathic pain in DPN.

METHODS

A comprehensive literature review was undertaken, incorporating article searches in electronic databases (EMBASE, PubMed, OVID) and reference lists of relevant articles with the authors' expertise in DPN. This review considers seminal and novel research in epidemiology; diagnosis, especially in relation to novel surrogate end points; and the treatment of neuropathic pain in DPN. We also consider potential new pharmacotherapies for painful DPN.

FINDINGS

DPN is often misdiagnosed and inadequately treated. Other than improving glycemic control, there is no licensed pathogenetic treatment for diabetic neuropathy. Management of painful DPN remains challenging due to difficulties in personalizing therapy and ascertaining the best dosing strategy, choice of initial pharmacotherapy, consideration of combination therapy, and deciding on defining treatment for poor analgesic responders. Duloxetine and pregabalin remain first-line therapy for neuropathic pain in DPN in all 5 of the major published guidelines by the American Association of Clinical Endocrinologists, American Academy of Neurology, European Federation of Neurological Societies, National Institute of Clinical Excellence (United Kingdom), and the American Diabetes Association, and their use has been approved by the US Food and Drug Administration.

IMPLICATIONS

Clinical recognition of DPN is imperative for allowing timely symptom management to reduce the morbidity associated with this condition.