Insights into the pathogenesis and treatment of painful diabetic neuropathy

Decrypting the multifaceted peripheral neuropathy based on molecular pathology and therapeutics: a comprehensive review

CONTEXT

Peripheral neuropathy (PN) is a multifaceted complication characterized by nerve damage due to oxidative stress, inflammatory mediators, and dysregulated metabolic processes. Early PN manifests as sensory changes that develop progressively in a "stocking and glove" pattern.

METHODS AND MECHANISMS

A thorough review of literature has been done to find the molecular pathology, clinical trials that have been conducted to screen the effects of different drugs, current treatments and novel approaches used in PN therapy. Diabetic neuropathy occurs due to altered protein kinase C activity, elevated polyol pathway activity in neurons, and Schwann cells-induced hyperglycemia. Other causes involve chemotherapy exposure, autoimmune ailments, and chronic ethanol intake.

CONCLUSION

Symptomatic treatments for neuropathic pain include use of tricyclic antidepressants, anticonvulsants, and acetyl-L-carnitine. Patients will have new hope if clinicians focus on novel therapies including gene therapy, neuromodulation techniques, and cannabidiol as an alternative to traditional medications, as management is still not ideal.

New concepts drive the development of delivery tools for sustainable treatment of diabetic complications

Diabetic complications, especially diabetic retinopathy, diabetic nephropathy and painful diabetic neuropathy, account for a large portion of patients with diabetes and display rising global prevalence. They are the leading causes of blindness, kidney failure and hypersensitivity to pain caused by diabetes. Current approved therapeutics against the diabetic complications are few and exhibit limited efficacy. The enhanced cell-specificity, stability, biocompatibility, and loading capacity of drugs are essential for the mitigation of diabetic complications. In the article, we have critically discussed the recent studies over the past two years in material sciences and biochemistry. The insightful concepts in these studies drive the development of novel nanoparticles and mesenchymal stem cells-derived extracellular vesicles to meet the need for treatment of diabetic complications. Their underlying biochemical principles, advantages and limitations have been in-depth analyzed. The nanoparticles discussed in the article include double-headed nanodelivery system, nanozyme, ESC-HCM-B system, soft polymer nanostars, tetrahedral DNA nanostructures and hydrogels. They ameliorate the diabetic complication through attenuation of inflammation, apoptosis and restoration of metabolic homeostasis. Moreover, mesenchymal stem cell-derived extracellular vesicles efficiently deliver therapeutic proteins to the retinal cells to suppress the angiogenesis, inflammation, apoptosis and oxidative stress to reverse diabetic retinopathy. Collectively, we provide a critical discussion on the concept, mechanism and therapeutic applicability of new delivery tools to treat these three devastating diabetic complications.

Cognitive function in diabetic persons with peripheral neuropathy: a systematic review and meta-analysis

OBJECTIVES

The aim of this study is to improve our knowledge of cognitive function in individuals with type 1 (T1DM) or type 2 (T2DM) diabetes mellitus and with peripheral diabetic neuropathy (DPN).

METHODS

A systematic review and meta-analysis was performed of publications included in PubMed, Scopus, PsycInfo and Web of Science databases until November 2021. The study protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO) with reference number: CRD42021229163.

RESULTS

A total of 832 articles were identified, 19 of which were selected. The presence of DPN was associated with global cognitive impairment in the T1DM persons in two studies (p=0.046; p=0.03) and T2DM persons in four (p<0.001; p<0.02; p=0.011; p=<0.05). Differences in specific dimensions - memory, attention, and psychomotor speed - were found in both kinds of diabetes. The meta-analysis showed that the individuals with T2DM and DPN presented a lower mean cognitive performance than those without DPN (-1.0448; 95% CI: -1.93%; -0.16%). Depression was associated with impaired cognitive function in these diabetic persons (p<0.01).

CONCLUSION

The review reveals the great variability in instruments and methodologies, while providing results that support the presence of both global and domain-specific cognitive impairment in diabetic persons with DPN.

Assessment of peripheral neuropathy in type 2 diabetes by diffusion tensor imaging

BACKGROUND

To evaluate the diagnostic accuracy of diffusion tensor imaging (DTI) in diabetic peripheral neuropathy (DPN) for patients with type 2 diabetes and detect the correlations with electrophysiology.

METHODS

A total of 27 patients with type 2 diabetes with DPN, 24 patients with type 2 diabetes without peripheral neuropathy (NDPN), as well as 32 healthy controls (HC) were enrolled in this study. Clinical examinations and neurophysiologic tests were used to determine the presence of DPN. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of peripheral nerves, including the tibial nerve (TN) and common peroneal nerve (CPN), were calculated. Receiver operating characteristic (ROC) analysis was performed for FA and ADC values. Pearson's correlation coefficient was used to assess the correlation between DTI and electrophysiology parameters in the patient group.

RESULTS

The tibial and common peroneal nerve FAs were lowest (P=0.003, 0.001, respectively) and ADC was highest (P=0.004, 0.005, respectively) in the DPN group. The FA value of the axonal injury group was lower than that in the demyelination group (P=0.035, 0.01, respectively), while the ADC value was higher (P=0.02, 0.01, respectively). In the DPN group, FA value was positively correlated with motor conduction velocity (MCV) (tibial nerve: r=0.420, P=0.007; common peroneal nerve: r=0.581, P<0.001) and motor amplitude (MA) (tibial nerve: r=0.623, P<0.001; common peroneal nerve: r=0.513; P=0.001), while ADC values was negatively correlated with MCV (tibial nerve: r=-0.320, P=0.044; common peroneal nerve: r=-0.569; P<0.001), and MA (tibial nerve: r=-0.491, P=0.001; common peroneal nerve: r=-0.524; P=0.001).

CONCLUSIONS

With a lower FA value and higher ADC value, DTI accurately discriminated DPN. The DTI multi-parameter quantitative analysis of peripheral nerves differentiated DPN axonal injury from the demyelinating lesion, and hence, could be applied in the diagnosis of DPN.

Diabetic polyneuropathy with/out neuropathic pain in Mali: A cross-sectional study in two reference diabetes treatment centers in Bamako (Mali), Western Africa

INTRODUCTION

Diabetic polyneuropathy (DPN) with or without neuropathic pain is a frequent complication of diabetes. This work aimed to determine the prevalence of diabetic polyneuropathy, to describe its epidemiological aspects, and to analyze the therapeutic itinerary of patients with DPN.

METHODS

This was a cross-sectional, descriptive study performed synchronously over six months at two major follow-up sites for patients with diabetes in Mali. DPN was diagnosed based on the Michigan Neuropathy Screening Instrument (MNSI). The neuropathic nature of the pain and the quality of life of patients were evaluated by the DN4 and the ED-5D scale, respectively. We used three (3) different questionnaires to collect data from patients (one at inclusion and another during the follow-up consultation) and from the caregivers of patients with DPN.

RESULTS

We included 252 patients with diabetes, and DPN was found to have a healthcare facility-based prevalence of 69.8% (176/252). The sex ratio was approximately three females for every male patient. The patients were mostly 31 to 60 years of age, 83% had type 2 diabetes, and 86.9% had neuropathic pain Approximately half of the patients (48.3%) had autonomic neuropathy and they reported moderate to intense pain, which was mainly described as a burning sensation. The patients exhibited impaired exteroceptive and proprioceptive sensations in 51.7% of cases. The patients smoked tobacco in 3.4% of cases, while 36.6% of the patients were obese and had dyslipidemia. The caregivers clearly indicated that appropriate medications were not readily accessible or available for their patients with DPN.

CONCLUSION

The healthcare facility-based prevalence of DPN with or without neuropathic pain was high in our cohort. These inexpensive and easy-to-use tools (MNSI, DN4) can be used to adequately diagnose DPN in the African context. In Mali, screening and early treatment of patients at risk of DPN should allow for a reduction of the burden of the disease, while caregivers need to be adequately trained to manage DPN.

Traditional Chinese medicine foot bath combined with acupoint massage for the treatment of diabetic peripheral neuropathy: A systematic review and meta-analysis of 31 RCTs

In this study, we aim to evaluate the efficiency and safety of traditional Chinese medicine foot bath combined with acupoint massage for the treatment of diabetic peripheral neuropathy. A total of eight online databases were searched to collect studies published up to February 2019. Study quality of each included article was evaluated by the Cochrane Collaboration risk of bias tool. Systematic reviews and meta-analyses were conducted based on the Cochrane systematic review method by using the RevMan 5.3 software. Traditional Chinese medicine foot bath combined with acupoint massage was the main therapy in experimental group. Interventions in control groups include western medicine, oral traditional Chinese medicine, other symptomatic treatment of western medicine, and blank control. Primary outcomes in this study include sensory nerve conduction velocity (SNCV), motor nerve conduction velocity (MNCV), total effective rate, and neuropathic syndrome score. Finally, 31 trials involving 3284 participants were included. The results of systematic reviews and meta-analyses showed that traditional Chinese medicine foot bath combined with acupoint massage was significantly better compared with the control groups in terms of the total effective rate, SNCV, MNCV, and neuropathic syndrome score. No case of adverse effect was reported. These findings show that traditional Chinese medicine foot bath combined with acupoint massage may be safer and more effective for the treatment of DPN. However, due to the low methodological quality, further research with randomized controlled trials (RCTs) of higher quality is required to prove its efficacy and better evidence for clinical treatment.

Chronic pain and central sensitization in immuno-inflammatory rheumatic diseases: pathogenesis, clinical manifestations, the possibility of using targeted disease modifying antirheumatic drugs

Chronic pain is one of the main manifestations of immuno-inflammatory rheumatic diseases (IIRD), such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA), which determines the severity of suffering, reduced quality of life and disability of patients. Unfortunately, the use of synthetic and biological disease modifying antirheumatic drugs, as well as non-steroidal anti-inflammatory drugs does not always provide sufficient control of pain in IIRD, even when it is possible to achieve a significant reduction in inflammatory activity. The reason for this is the complex mechanism of chronic pain. It includes not onlystimulation of pain receptors caused by damage of the elements of the musculoskeletal system, but also a change in the perception of pain associated with the phenomenon of central sensitization (CS). CS is characterized by a significant and persistent increase in the sensitivity of nociceptive neurons to pain and nonpain stimuli. One of the main theories of the CS development consider this phenomenon as an inflammatory reaction of the neuronenvironmentthe activation of astrocytes and microglial cells, local hyperproduction of cytokines, inflammatory mediators and neurotrophic factors. Factors contributing to the development of CS in IIRD are obesity, depression and anxiety, damage of the somatosensory system, insufficient relief of pain in the onset of the disease. Clinical manifestations of CS in IIRD is hyperalgesia, allodinia, «expanded pain» and secondary fibromyalgia. An important role in the development of chronic pain and CS plays the intracellular inflammatory pathway JAK-STAT. Therefore, JAK inhibitors, such as tofacitinib, used in RA and PsA, can also be considered as an effective means of controlling chronic pain in these diseases.

Type 1 diabetes-associated cognitive impairment and diabetic peripheral neuropathy in Chinese adults: results from a prospective cross-sectional study

BACKGROUND

To compare neurocognitive functioning of Type 1 diabetic mellitus (T1DM) and healthy adults, and explore risk factors of cognitive dysfunction of T1DM patients, especially the association between cognitive impairment and diabetic peripheral neuropathy (DPN).

METHODS

Seventy T1DM (age: 32.17 ± 9.57 yr., duration: 8.99 ± 7.02 yr) patients and 48 healthy volunteers were included. All subjects received evaluation of MMSE and MoCA scales. Cognitive function of T1DM patients was evaluated in different cognitive domains. Risk factors affecting cognitive function were further explored.

RESULTS

Three patients with educational level ≤ 6-year were excluded from final analysis. Scores of both MMSE (28.4 ± 1.7 vs. 29.1 ± 1.0, P = 0.005) and MoCA scales (25.9 ± 2.7 vs.27.1 ± 2.4, P = 0.017) in T1DM group were lower than that in control group. For MMSE scale, scores of orientation (9.60 ± 0.79 vs.9.87 ± 0.39, P < 0.001) and language function (8.56 ± 0.65 vs.8.83 ± 0.38, P < 0.001) in T1DM groups were lower than that in control group. For MoCA scale, scores of attention and concentration (2.30 ± 0.74 vs.2.57 ± 0.58, P < 0.001), visuospatial/executive function (4.32 ± 0.91 vs.4.64 ± 0.63, P < 0.001), memory (2.96 ± 1.50 vs.3.66 ± 1.28, P < 0.001), language function (5.71 ± 0.69 vs.5.87 ± 0.39, P = 0.007), and abstraction (1.55 ± 0.68 vs.1.82 ± 0.42, P < 0.001) were lower in T1DM group than that in control group. Logistic regression showed age, fasting C peptide, educational level and nerve conduction velocity (NCV) were associated with cognitive dysfunction diagnosed by MoCA scores for the patients with type 1 diabetes.

CONCLUSIONS

T1DM adults had mild to moderate cognitive impairment, mainly presenting as dysfunctions of attention and concentration, visuospatial/executive, language, and abstraction. In addition to age, fasting C peptide level, and educational level, DPN, as a diabetic complication, was identified to be associated with cognitive impairments.

Methylglyoxal and a spinal TRPA1-AC1-Epac cascade facilitate pain in the db/db mouse model of type 2 diabetes

Painful diabetic neuropathy (PDN) is a devastating neurological complication of diabetes. Methylglyoxal (MG) is a reactive metabolite whose elevation in the plasma corresponds to PDN in patients and pain-like behavior in rodent models of type 1 and type 2 diabetes. Here, we addressed the MG-related spinal mechanisms of PDN in type 2 diabetes using db/db mice, an established model of type 2 diabetes, and intrathecal injection of MG in conventional C57BL/6J mice. Administration of either a MG scavenger (GERP10) or a vector overexpressing glyoxalase 1, the catabolic enzyme for MG, attenuated heat hypersensitivity in db/db mice. In C57BL/6J mice, intrathecal administration of MG produced signs of both evoked (heat and mechanical hypersensitivity) and affective (conditioned place avoidance) pain. MG-induced Ca²⁺ mobilization in lamina II dorsal horn neurons of C57BL/6J mice was exacerbated in db/db, suggestive of MG-evoked central sensitization. Pharmacological and/or genetic inhibition of transient receptor potential ankyrin subtype 1 (TRPA1), adenylyl cyclase type 1 (AC1), protein kinase A (PKA), or exchange protein directly activated by cyclic adenosine monophosphate (Epac) blocked MG-evoked hypersensitivity in C57BL/6J mice. Similarly, intrathecal administration of GERP10, or inhibitors of TRPA1 (HC030031), AC1 (NB001), or Epac (HJC-0197) attenuated hypersensitivity in db/db mice. We conclude that MG and sensitization of a spinal TRPA1-AC1-Epac signaling cascade facilitate PDN in db/db mice. Our results warrant clinical investigation of MG scavengers, glyoxalase inducers, and spinally-directed pharmacological inhibitors of a MG-TRPA1-AC1-Epac pathway for the treatment of PDN in type 2 diabetes.

Review of Diabetic Polyneuropathy: Pathogenesis, Diagnosis and Management According to the Consensus of Egyptian Experts

Diabetic polyneuropathy (DPN) is a complex and multifactorial entity in which various factors besides hyperglycemia play an important role. Symptoms of DPN are sensory, motor or autonomic. Intensive research proved that oxidative stress is the common denominator for the four major destructive pathways of hyperglycemia including increased hexosamine pathway flux, activation of Protein kinase-C (PKC) pathway, increased Advanced Glycated End-products (AGEs) formation, and increased Polyol Pathway flux. National data in Egypt confirms that more than 60% of Egyptian diabetic patients suffer from neuropathy. The most common complications of DPN are Cardiac Autonomic Neuropathy (CAN), diabetic foot and ulcers, neuromuscular disability, and anxiety. In addition, DPN affects the Quality of Life (QoL). According to common clinical practice, the common diagnostic tools are bed-side diagnosis and electrophysiological tests. Early diagnosis is critical to improve the prognosis of DPN and therapeutic intervention in the early phase. In this review, we provide a clear understanding of the pathogenesis, early diagnosis and the good management of DPN. Since the pathogenesis of DPN is multifactorial, its management is based on combination therapy of symptomatic; either pharmacological or non-pharmacological treatments, and pathogenic treatment. Alpha Lipoic Acid (ALA) is a potent anti-oxidant that has several advantages as a pathogenic treatment of DPN. So, in clinical practice, ALA may be prescribed for patients with early neuropathic deficits and symptoms. Patient education has an important role in the managemement of DPN.

Cerebral Biochemical Effect of Pregabalin in Patients with Painful Diabetic Neuropathy: A Randomized Controlled Trial

INTRODUCTION

With the development of new neuroimaging tools it has become possible to assess neurochemical alterations in patients experiencing chronic pain and to determine how these factors change during pharmacological treatment. The goal of this study was to examine the exact neurochemical mechanism underlying pregabalin treatment, utilizing magnetic resonance spectroscopy (¹H-MRS), in a population of patients with painful diabetic polyneuropathy (PDN), with the overall aim to ultimately objectify the clinical effect of pregabalin.

METHODS

A double blind, randomized, placebo-controlled study was conducted. A total of 27 patients with PDN were enrolled in the study, of whom 13 received placebo treatment (control group) and 14 received pregabalin (intervention group). Pregabalin treatment consisted of stepwise dose escalation over the study period from 75 mg daily ultimately to 600 mg daily. ¹H-MRS was performed at 3T on four regions of interest in the brain: the rostral anterior cingulate cortex (rACC), left and right thalamus and prefrontal cortex. The absolute concentrations of N-acetyl aspartate, glutamate, glutamine, gamma-amino-butyric-acid (GABA), glucose (Glc) and myo-inositol (mINS) were determined using LCModel.

RESULTS

The concentration of most neurometabolites in the placebo and pregabalin group did not significantly differ over time, with only a small significant difference in Glc level in the left thalamus (p = 0.049). Comparison of the effects of the different doses revealed significant differences for mINS in the rACC (baseline 2.42 ± 1.21 vs. 450 mg 1.58 ± 0.94; p = 0.022) and dorsolateral prefrontal cortex (75 mg 2.38 ± 0.89 vs. 450 mg 1.59 ± 0.85; p = 0.042) and also for GABA in the rACC (75 mg 0.53 ± 0.51 vs. 225 mg 0.28 ± 0.19; p = 0.014).

CONCLUSION

No differences were found in metabolite concentrations between the placebo (control) and intervention groups, but some differences, although small, were found between the different doses.

TRIAL REGISTRATION

This study is registered at ClinicalTrials.gov (NCT01180608).

FUNDING

Lyrica Independent Investigator Research Award (LIIRA) 2010 (Pfizer) funded the study.

Efficacy and Safety of the Injection of the Traditional Chinese Medicine Puerarin for the Treatment of Diabetic Peripheral Neuropathy: A Systematic Review and Meta-Analysis of 53 Randomized Controlled Trials

OBJECTIVE

The injection of the traditional Chinese patent medicine puerarin has been widely used in the treatment of various diseases such as angina pectoris or ischemic stroke. We aim to evaluate the efficacy and safety of puerarin injection for the treatment of diabetic peripheral neuropathy (DPN).

METHODS

A systematic literature search was performed in seven medical databases from their inception until June 2017. 53 studies with RCTs, totaling 3284 patients, were included in this meta-analysis. The included studies were assessed by the Cochrane risk of bias and analyzed by Review Manager 5.3 software.

RESULTS

The meta-analysis showed that puerarin injection for the treatment of DPN was significantly better compared with the control group in terms of the total effective rate. The result showed that puerarin injection for the treatment of DPN can significantly increase the probability of sensory nerve conduction velocity (SNCV) and motor nerve conduction velocity (MNCV) of the median and peroneal nerves.

CONCLUSIONS

This meta-analysis demonstrated that puerarin injection may be more effective and safe for the treatment of DPN. However, further and higher quality RCTs are required to prove its efficacy and provide meaningful evidence for clinical treatment due to the poor methodological quality.

Stem Cells for Diabetes Complications: A Future Potential Cure

Long-standing diabetes leads to structural and functional alterations in both the micro- and the macrovasculature. Designing therapies to repair these abnormalities present unique and sophisticated challenges. Vascular endothelial cells are the primary cells damaged by hyperglycemia-induced adverse effects. Vascular stem cells that give rise to endothelial progenitor cells and mesenchymal progenitor cells represent an attractive target for cell therapy for diabetic patients. In this review, we shed light on challenges and recent advances surrounding stem cell therapies for diabetes vascular complications and discuss limitations for their clinical adoption.

Lipids: A Suitable Therapeutic Target in Diabetic Neuropathy?

Diabetic polyneuropathy (DPN) encompasses multiple syndromes with a common pathogenesis. Glycemic control shows a limited correlation with DPN, arguing in favor of major involvement of other factors, one of which is alterations of lipid and lipoprotein metabolism. Consistent associations have been found between plasma triglycerides/remnant lipoproteins and the risk of DPN. Studies in cultured nerve tissue or in murine models of diabetes have unveiled mechanisms linking lipid metabolism to DPN. Deficient insulin action increases fatty acids flux to nerve cells, inducing mitochondrial dysfunction, anomalous protein kinase C signaling, and perturbations in the physicochemical properties of the plasma membrane. Oxidized low-density lipoproteins bind to cellular receptors and promote generation of reactive oxygen species, worsening mitochondrial function and altering the electrical properties of neurons. Supplementation with specific fatty acids has led to prevention or reversal of different modalities of DPN in animal models. Post hoc and secondary analyses of clinical trials have found benefits of cholesterol reducing (statins and ezetimibe), triglyceride-reducing (fibrates), or lipid antioxidant (thioctic acid) therapies over the progression and severity of DPN. However, these findings are mostly hypothesis-generating. Randomized trials are warranted in which the impact of intensive plasma lipids normalization on DPN outcomes is specifically evaluated.

Prunella vulgaris L. active components and their hypoglycemic and antinociceptive effects in alloxan-induced diabetic mice

Prunella vulgaris L. (Lamiaceae) (PV) is a herbaceous plant traditionally utilized in management of diabetes and it has immunomodulatory activity. In this study, acute and subchronic antidiabetic, in-vivo antioxidant and antinociceptive effects of PV were evaluated in alloxan-induced type 1 diabetes (T1D) in a mouse model. Bio-guided fractionation, isolation, RP-HPLC, and ¹H and ¹³C NMR identification of the active components responsible for PV effects were determined. RP-HPLC analysis showed that PV contained rosmarinic acid (RA) 4.5%, caffeic acid (CA) 9.8% and p-coumaric acid (pCA) 11.6%. Bio-guided fractionation showed that PV most active fraction was rich in caffeic acid, hence named, caffeic acid-rich fraction (CARF). RP-HPLC, and ¹H and ¹³C NMR experiments showed that CARF contained CA (93.4%) and RA (6.6%). CARF reduced blood glucose levels and improved in-vivo oxidative-stress. It also inhibited the carbohydrate-hydrolyzing enzymes (alpha-amylase and alpha-glucosidase) and reduced HbA1c levels more significantly (p≤0.05) than that of PV and equivalent amounts of CA or RA. For longer times, CARF had significantly (p≤0.05) increased serum-insulin, ameliorated thermal hyperalgesia and tactile allodynia more significantly (p≤0.05) than the effects of PV and equivalent amounts of CA or RA. Moreover, the tested compounds showed potential restoration of the lipid peroxide levels. Consequently, CARF and PV observed increase in serum-insulin, attenuation of alpha-amylase and alpha-glucosidase, and their antioxidant potentials might be responsible for their antidiabetogenic and antinociceptive properties. In conclusion, CARF isolated from PV could be a potential therapeutic agent to ameliorate T1D and related complications.

The Diabetes Telephone Study: Design and challenges of a pragmatic cluster randomized trial to improve diabetic peripheral neuropathy treatment

BACKGROUND

Challenges to effective pharmacologic management of symptomatic diabetic peripheral neuropathy include the limited effectiveness of available medicines, frequent side effects, and the need for ongoing symptom assessment and treatment titration for maximal effectiveness. We present here the rationale and implementation challenges of the Diabetes Telephone Study, a randomized trial designed to improve medication treatment, titration, and quality of life among patients with symptomatic diabetic peripheral neuropathy.

METHODS

We implemented a pragmatic cluster randomized controlled trial to test the effectiveness of an automated interactive voice response tool designed to provide physicians with real-time patient-reported data about responses to newly prescribed diabetic peripheral neuropathy medicines. A total of 1834 primary care physicians treating patients in the diabetes registry at Kaiser Permanente Northern California were randomized into the intervention or control arm. In September 2014, we began identification and recruitment of patients assigned to physicians in the intervention group who receive three brief interactive calls every 2 months after a medication is prescribed to alleviate diabetic peripheral neuropathy symptoms. These calls provide patients with the opportunity to report on symptoms, side effects, self-titration of medication dose and overall satisfaction with treatment. We plan to compare changes in self-reported quality of life between the intervention group and patients in the control group who receive three non-interactive automated educational phone calls.

RESULTS

Successful implementation of this clinical trial required robust stakeholder engagement to help tailor the intervention and to address pragmatic concerns such as provider time constraints. As of 27 October 2015, we had screened 2078 patients, 1447 of whom were eligible for participation. We consented and enrolled 1206 or 83% of those eligible. Among those enrolled, 53% are women and the mean age is 67 (standard deviation = 12) years. The racial ethnic make-up is 56% White, 8% Asian, 13% Black or African American, and 19% Hispanic or Latino.

CONCLUSION

Innovative strategies are needed to guide improvements in healthcare delivery for patients with symptomatic diabetic peripheral neuropathy. This trial aims to assess whether real-time collection and clinical feedback of patient treatment experiences can reduce patient symptom burden. Implementation of a clinical trial closely involving clinical care required researchers to partner with clinicians. If successful, this intervention provides a critical information feedback loop that would optimize diabetic peripheral neuropathy medication titration through widely available interactive voice response technology.

Pyruvate Dehydrogenase Kinase-mediated Glycolytic Metabolic Shift in the Dorsal Root Ganglion Drives Painful Diabetic Neuropathy

The dorsal root ganglion (DRG) is a highly vulnerable site in diabetic neuropathy. Under diabetic conditions, the DRG is subjected to tissue ischemia or lower ambient oxygen tension that leads to aberrant metabolic functions. Metabolic dysfunctions have been documented to play a crucial role in the pathogenesis of diverse pain hypersensitivities. However, the contribution of diabetes-induced metabolic dysfunctions in the DRG to the pathogenesis of painful diabetic neuropathy remains ill-explored. In this study, we report that pyruvate dehydrogenase kinases (PDK2 and PDK4), key regulatory enzymes in glucose metabolism, mediate glycolytic metabolic shift in the DRG leading to painful diabetic neuropathy. Streptozotocin-induced diabetes substantially enhanced the expression and activity of the PDKs in the DRG, and the genetic ablation of Pdk2 and Pdk4 attenuated the hyperglycemia-induced pain hypersensitivity. Mechanistically, Pdk2/4 deficiency inhibited the diabetes-induced lactate surge, expression of pain-related ion channels, activation of satellite glial cells, and infiltration of macrophages in the DRG, in addition to reducing central sensitization and neuroinflammation hallmarks in the spinal cord, which probably accounts for the attenuated pain hypersensitivity. Pdk2/4-deficient mice were partly resistant to the diabetes-induced loss of peripheral nerve structure and function. Furthermore, in the experiments using DRG neuron cultures, lactic acid treatment enhanced the expression of the ion channels and compromised cell viability. Finally, the pharmacological inhibition of DRG PDKs or lactic acid production substantially attenuated diabetes-induced pain hypersensitivity. Taken together, PDK2/4 induction and the subsequent lactate surge induce the metabolic shift in the diabetic DRG, thereby contributing to the pathogenesis of painful diabetic neuropathy.

Metformin attenuates hyperalgesia and allodynia in rats with painful diabetic neuropathy induced by streptozotocin

Painful diabetic neuropathy is a common complication of diabetes mellitus, which often makes the patients suffer from severe hyperalgesia and allodynia. Thus far, the treatment of painful diabetic neuropathy remains unsatisfactory. Metformin, which is the first-line drug for type-2 diabetes, has been proved to attenuate hyperexcitability in sensory neurons linked to chemotherapy-induced neuropathic pain, highlighting its potential in alleviating pain related with painful diabetic neuropathy. The present study was designed to investigate the potential beneficial effect of metformin on hyperalgesia and allodynia in diabetic rats. The mechanical sensitivity, heat nociception, and cold allodynia were examined. The levels of malondialdehyde, superoxide dismutase, and advanced glycation end-products in the blood were measured. The expression of adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and AMPK target genes were examined in the sciatic nerves of the animals. It was found that metformin was capable of attenuating diabetes-induced mechanical hyperalgesia, heat hyperalgesia and cold allodynia. In addition, metformin was capable of decreasing malondialdehyde and glycation end-products levels in blood, as well as increasing superoxide dismutas activity, indicating the inhibitory effect of metformin against diabetes-induced oxidative stress. Further studies showed that metformin could activate AMPK and increase the AMPK target genes in sciatic nerves in diabetic rats. In conclusion, metformin is able to attenuate diabetes-induced hyperalgesia and allodynia, which might be associated its anti-oxidative effect through AMPK pathway. Metformin might be used as an effective drug, especially with fewer side effects, for abnormal sensation in painful diabetic neuropathy.