Diabetic polyneuropathy and pain, prevalence, and patient characteristics: a cross-sectional questionnaire study of 5,514 patients with recently diagnosed type 2 diabetes

Neuropathic Pain With and Without Diabetic Peripheral Neuropathy in Type 1 Diabetes

OBJECTIVE

Diabetic peripheral neuropathy (DPN) is common; however, the features and burden of neuropathic pain (NP) in type 1 diabetes (T1D) are poorly understood. We evaluated the incidence of first occurrence, annual prevalence, remission, and risk factors for NP during long-term follow-up of participants with T1D.

RESEARCH DESIGN AND METHODS

The Michigan Neuropathy Screening Instrument (MNSI) was administered annually (1994-2020) for 1,324 participants in the Epidemiology of Diabetes Interventions and Complications (EDIC) study. NP with clinical signs of DPN (NP DPN+) was defined according to self-reported NP plus an examination score >2, while NP without clinical signs of DPN (NP DPN-) was defined according to self-reported NP and an examination score ≤2.

RESULTS

At EDIC year 1, median age for participants was 36 years (interquartile range 30, 41), diabetes duration 13 years (10, 18), and HbA1c 7.9% (7.2, 8.9). At year 26 (median diabetes duration 39 years), cumulative incidence of NP was 57%, regardless of concomitant clinical signs of DPN (36% NP DPN+ vs. 46% NP DPN-). NP prevalence was 20% at 26 years (11% NP DPN+ and 9% NP DPN-), suggesting frequent remission. Annualized remission rates were similar regardless of pain medication use. In addition to HbA1c, female sex was associated with NP DPN-.

CONCLUSIONS

NP incidence in T1D was high and frequently occurred in the absence of clinical signs of neuropathy, as assessed with the MNSI. Pain remission was not explained by pain medication use. Effective clinical strategies for identification and management are needed.

Development and Progression of Polyneuropathy Over 5 Years in Patients With Type 2 Diabetes

BACKGROUND AND OBJECTIVES

There is a need for knowledge regarding the natural course of diabetic polyneuropathy (DPN), a complication in type 2 diabetes (T2D). The aim of this study was to examine the development of DPN over time.

METHODS

Patients with newly diagnosed T2D, recruited from a national cohort, and controls without diabetes of similar age and sex, underwent sensory phenotyping in 2016-2018. The Toronto consensus criteria were used to classify patients into possible, probable, and confirmed DPN. For this 5-year, observational, follow-up, cohort study, all participants were invited to a reexamination combining bedside sensory examination, quantitative sensory testing (QST), nerve conduction studies (NCSs), and skin biopsies measuring intraepidermal nerve fiber density (IENFD) in order to compare phenotypic and diagnostic changes over time.

RESULTS

Of the baseline 389 patients and 97 controls, 184 patients (median [interquartile range] diabetes duration 5.9 [4.1-7.4] years, mean hemoglobin A1c [HbA1c] 51 ± 11 mmol/mol at baseline) and 43 controls completed follow-up (46.9%). Confirmed DPN was present in 35.8% and 50.3%, probable DPN in 27.2% and 14.6%, possible DPN in 17.2% and 16.6%, and no DPN in 15.2% and 17.9% at baseline and follow-up, respectively. The estimated prevalence (95% CI) of confirmed DPN was 33.5% (24.9-42.1) compared with 22.7% (17.5-28.0) at baseline. During the follow-up period, 43.9% of patients with probable DPN developed confirmed DPN. Progression of neuropathy occurred in 16.5% and 24.7% and regression in 5.9% and 18.6% of patients based on NCS and IENFD, respectively. Progression based on NCS and/or IENFD was associated with higher baseline waist circumference and triglycerides, and regression with lower baseline HbA1c. Patients with at least probable DPN at baseline but neither patients without DPN nor controls developed increased spread of hyposensitivity, more hyposensitivity on QST and lower NCS z-scores at follow-up, and worsening of nerve parameters at follow-up correlated with higher baseline triglycerides.

DISCUSSION

In patients with well-regulated T2D, the proportion of patients with confirmed DPN increased over 5 years driven by progression from probable DPN. A large proportion of patients progressed, and a smaller proportion regressed on nerve parameters. Higher triglycerides correlated with this progression and may constitute a risk factor.

Lipid Levels and Risk of Diabetic Polyneuropathy in 2 Danish Type 2 Diabetes Cohorts

BACKGROUND AND OBJECTIVES

Reduction of blood lipids may aid in preventing diabetic polyneuropathy (DPN), but evidence remains conflicting. We investigated the association between lipid parameters and DPN risk in individuals with type 2 diabetes mellitus (T2DM).

METHODS

We conducted a population-based cohort study of individuals with newly diagnosed T2DM and a cross-sectional study using a clinically recruited T2DM cohort. Triglycerides, high-density lipoprotein (HDL), low-density lipoprotein (LDL), and non-HDL cholesterol were measured in routine diabetes care. Each lipid parameter was categorized according to the latest cutoffs in clinical guidelines on dyslipidemia. DPN was assessed with validated hospital diagnosis codes in the population-based cohort and with the Michigan Neuropathy Screening Instrument questionnaire in the clinical cohort. We calculated hazard ratios (HRs) using Cox regression and prevalence ratios (PRs) using Poisson regression.

RESULTS

We included 61,853 individuals in the population-based cohort (median age 63 [quartiles 54-72] years) and 4,823 in the clinical cohort (median age 65 [quartiles 57-72] years). The incidence rate of hospital-diagnosed DPN in the population-based cohort was 3.6 per 1000 person-years during a median follow-up of 7.3 years. Achieving guideline targets for HDL, LDL, and non-HDL cholesterol showed no association with DPN risk. By contrast, adjusted HRs (95% CI) for DPN were 1.02 (0.89-1.18) for triglyceride levels between 150 and 204 mg/dL (1.7-2.3 mmol/L) and 1.28 (1.13-1.45) for levels >204 mg/dL (2.3 mmol/L). In the clinical cohort with a DPN prevalence of 18%, DPN associated strongly with triglycerides >204 mg/dL (2.3 mmol/L) with an adjusted PR (95% CI) of 1.40 (1.21-1.62). The prevalence of DPN was modestly elevated for individuals with HDL cholesterol <39 mg/dL (1.0/1.3 mmol/L) in men and <50 mg/dL (1.3 mmol/L) in women (PR 1.13 [0.99-1.28]) and for individuals with non-HDL cholesterol >131 mg/dL (3.4 mmol/L) (PR 1.27 [1.05-1.52]). In both cohorts, spline models showed an increasing risk of DPN starting from triglyceride levels >124 mg/dL (1.4 mmol/L). All results were similar among statin users.

DISCUSSION

High triglyceride levels are a strong DPN risk factor. Future intervention studies shall determine whether triglyceride reduction is more important for DPN prevention than reduction of other lipids.

Contemporary prevalence of diabetic neuropathies in individuals with type 1 and type 2 diabetes in a Danish tertiary outpatient clinic

BACKGROUND

Population-based prevalence estimates of distal symmetric polyneuropathy (DPN) and diabetic autonomic neuropathy (DAN) are scares. Here we present neuropathy estimates and describe their overlap in a large cohort of people with type 1 and type 2 diabetes.

METHODS

In a large population of outpatient participants, DPN was assessed using vibration perception threshold, sural nerve function, touch, pain and thermal sensation. Definite DPN was defined by the Toronto Consensus Criteria. Painful DPN was defined by Douleur Neuropathique 4 Questions. DAN measures were: cardiovascular reflex tests, electrochemical skin conductance, and gastroparesis cardinal symptom index.

RESULTS

We included 822 individuals with type 1 (mean age (±SD) 54 ± 16 years, median [IQR] diabetes duration 26 [15-40] years) and 899 with type 2 diabetes (mean age 67 ± 11 years, median diabetes duration 16 [11-22] years). Definite DPN was prevalent in 54 % and 68 %, and painful DPN was in 5 % and 15 % of type 1 and type 2 participants, respectively. The prevalence of DAN varied between 6 and 39 % for type 1 and 9-49 % for type 2 diabetes. DPN without other neuropathy was present in 45 % with T1D and 50 % with T2D.

CONCLUSION

The prevalence of DPN and DAN was high. DPN and DAN co-existed in only 50 % of cases.

Serum Spexin Level Is Negatively Associated With Peripheral Neuropathy and Sensory Pain in Type 2 Diabetes

Background: Spexin is a novel peptide hormone and has shown antinociceptive effects in experimental mice. This study is aimed at evaluating the association of serum spexin level with diabetic peripheral neuropathy (DPN) and related pain in a Chinese population. Methods: We enrolled 167 type 2 diabetes mellitus (T2DM) including 56 patients without DPN (non-DPN), 67 painless DPN, and 44 painful DPN. Serum spexin was measured using ELISA. Logistic regression models were performed to analyze the independent effects of spexin on prevalence of DPN and painful DPN. In streptozotocin (STZ)-induced diabetic mice, mechanical pain threshold was measured using electronic von Frey aesthesiometer. Human peripheral blood mononuclear cells (PBMCs) were isolated and further stimulated with lipopolysaccharide without or with spexin. The gene expression was assayed by qPCR. Results: Compared with non-DPN, serum spexin level decreased in painless DPN and further decreased in painful DPN. The odds of DPN was associated with low spexin level in T2DM, which was similar by age, sex, BMI, and diabetes duration, but attenuated in smokers. The odds of having pain was associated with decreased spexin level in DPN, which was similar by age, sex, smoking status, and diabetes duration, but attenuated in normal weight. Furthermore, we observed that mechanical pain threshold increased in spexin-treated diabetic mice. We also found that lipopolysaccharide treatment increased the mRNA level of TNF-α, IL-6, and MCP-1 in human PBMCs, while spexin treatment prevented this increase. Conclusions: These results suggested that spexin might serve as a protective factor for diabetes against neuropathology and pain-related pathogenesis.

The Mas-related G protein-coupled receptor d (Mrgprd) mediates pain hypersensitivity in painful diabetic neuropathy

ABSTRACT

Painful diabetic neuropathy (PDN) is one of the most common and intractable complications of diabetes. Painful diabetic neuropathy is characterized by neuropathic pain accompanied by dorsal root ganglion (DRG) nociceptor hyperexcitability, axonal degeneration, and changes in cutaneous innervation. However, the complete molecular profile underlying the hyperexcitable cellular phenotype of DRG nociceptors in PDN has not been elucidated. This gap in our knowledge is a critical barrier to developing effective, mechanism-based, and disease-modifying therapeutic approaches that are urgently needed to relieve the symptoms of PDN. Using single-cell RNA sequencing of DRGs, we demonstrated an increased expression of the Mas-related G protein-coupled receptor d (Mrgprd) in a subpopulation of DRG neurons in the well-established high-fat diet (HFD) mouse model of PDN. Importantly, limiting Mrgprd signaling reversed mechanical allodynia in the HFD mouse model of PDN. Furthermore, in vivo calcium imaging allowed us to demonstrate that activation of Mrgprd-positive cutaneous afferents that persist in diabetic mice skin resulted in an increased intracellular calcium influx into DRG nociceptors that we assess in vivo as a readout of nociceptors hyperexcitability. Taken together, our data highlight a key role of Mrgprd-mediated DRG neuron excitability in the generation and maintenance of neuropathic pain in a mouse model of PDN. Hence, we propose Mrgprd as a promising and accessible target for developing effective therapeutics currently unavailable for treating neuropathic pain in PDN.

Vitamin D deficiency increases the risk of diabetic peripheral neuropathy in elderly type 2 diabetes mellitus patients by predominantly increasing large-fiber lesions

AIMS

This study explores the link between Vitamin D deficiency (VDD) and diabetic peripheral neuropathy (DPN) in elderly type 2 diabetes mellitus (T2DM) patients.

METHODS

Involving 257 elderly T2DM patients, the study utilized propensity score matching to balance age, sex, and diabetes duration. VDD was defined as serum 25-hydroxyvitamin D [25(OH)D] levels below 20 ng/ml. Large nerve fiber lesions were evaluated by electromyogram, while small nerve fiber lesions were assessed by measuring skin conductance.

RESULTS

DPN patients had notably lower serum 25(OH)D levels than non-DPN patients [15.05 vs. 18.4 ng/ml, P = 0.018]. VDD was identified as an independent risk factor for DPN (odds ratio = 2.488, P = 0.008) in multivariate logistic regression analysis. Spearman's correlation showed negative correlations between serum 25(OH)D levels and specific nerve latencies, and positive correlations with specific nerve velocities and amplitudes. The VDD group exhibited longer median sensory nerve latencies and motor evoked potential latencies compared to the vitamin D-sufficient group. Further, VDD is associated with the prolongation of the median motor nerve latency (odds ratio = 1.362, P = 0.038).

CONCLUSIONS

VDD is independently associated with a higher risk of DPN. VDD may promote the development of DPN by affecting large nerve fibers.

Pramipexole protects against diabetic neuropathy: Effect on oxidative stress, TLR4/IRAK-1/TRAF-6/NF-κB and downstream inflammatory mediators

BACKGROUND

Diabetic neuropathy (DN) is a serious microvascular complication and a major cause of morbidity and mortality in diabetes mellitus. It is characterized by neurodegeneration of terminal sensory nerve fibers with subsequent pain, loss of sensation, and paresthesia, thus compromising the quality of life of diabetic patients. It is considered the leading cause of non-traumatic amputations worldwide, reflecting the insufficiency of current therapies. Pramipexole (PPX) is a dopamine receptor agonist used for the treatment of Parkinson's disease. The current study aims to investigate the potential neuroprotective effect of PPX in an experimental model of DN.

METHODS

Sprague Dawley rats were randomly assigned into five groups: normal control, Normal + PPX (1 mg/kg) group, STZ control, STZ + PPX (0.25 and 1 mg/kg/day for eight weeks). The neuroprotective effect of PPX in rats was evaluated in terms of sciatic nerve histological alterations, oxidative stress, and protein expression of TLR4/MyD88/IRAK-1/TRAF-6/NF-κB axis and downstream inflammatory mediators.

RESULTS

PPX administration ameliorated histopathological signs of neuronal inflammation and apoptosis. Additionally, PPX attenuated STZ-induced sciatic nerve oxidative stress and downregulated neural tissue expression of TLR4, MyD88, IRAK-1, TRAF-6, NF-κB and downstream mediators (TNF-α, IL-1β and ICAM-1).

CONCLUSION

Collectively, the current study sheds light on PPX as a potential protective medication to alleviate neuropathy progression in diabetic patients. PPX neuroprotective effect can be attributed to modulating TLR4/ MyD88/IRAK-1/TRAF-6/ NF-κB axis signaling in nerve tissues with subsequent attenuation of oxidative stress and inflammation.

Clinical observation of perioperative negative emotional changes in patients with percutaneous balloon compression for primary trigeminal neuralgia: A prospective cohort study

OBJECTIVE

To investigate the prevalence of negative emotions in trigeminal neuralgia (TN) patients, to identify risk factors associated with anxiety and depression, and further to explore the impact of percutaneous balloon compression (PBC) on anxiety and depression in TN patients during the perioperative period.

METHODS

400 patients with primary TN treated with PBC at our institution from November 2021 to April 2023 were included. We analyzed visual analogue scale (VAS) and the Hospital Anxiety and Depression Scale (HADS) scores. The patients' clinical data and short-term clinical outcomes were gathered and subjected to statistical analysis.

RESULTS

This study included a total of 400 patients diagnosed with primary TN. Patients who had high pain intensity (OR 1.20, 95 % CI 1.02-1.41; p = 0.025) or a history of multiple previous TN procedures (OR 1.49, 95 % CI 1.03-2.16; p = 0.036), were more prone to anxiety. Patients who were female (OR 1.59, 95 % CI 1.03-2.44; p = 0.036), had high pain intensity (OR 1.28, 95 % CI 1.08-1.52; p = 0.004) or had a history of multiple previous TN procedures (OR 1.48, 95 % CI 1.11-1.98; p = 0.008), were more likely to have depression. Significant improvements in anxiety and depressive symptoms were observed in patients who experienced pain relief after PBC (p < 0.001).

CONCLUSIONS

Female gender, high pain intensity, and a history of multiple prior TN procedures are associated risk factors for anxiety and depression in TN patients. PBC can provide patients with a high pain relief rate and significantly improve their anxiety and depression symptoms during the perioperative period.

Perineural injections of incobotulinumtoxin-A for diabetic neuropathic pain of the lower extremities: protocol for a phase II, single-centre, double-blind, randomised, placebo-controlled trial (the PINBOT study)

INTRODUCTION

Diabetic neuropathic pain (DNP) is a debilitating complication affecting 15-20% of people with diabetes and is a predictor of depression, poor sleep and decreased quality of life. Current pharmacological treatments are often insufficient and have significant side-effects. Subcutaneous or intradermal botulinumtoxin-A (BonT-A) is an effective and safe treatment for neuropathic pain but is limited by the need to cover the entire affected area with injections. For large cutaneous areas, infiltration of the sensory nerve supply with BonT-A could provide similar effects, with a single injection. We aim to investigate the safety, efficacy, and effects on quality of life, physical activity, depressive symptoms and activities of daily living of perineural injections of BonT-A in patients with DNP of both lower extremities.

METHODS

This study is a double-blind, randomised, placebo-controlled clinical trial. 80 participants with moderate to severe DNP of both legs will be randomised 1:1 to receive injections of either 100 units incobotulinumtoxin-A or a saline placebo around each distal sciatic nerve for two cycles of 12 weeks. Average daily pain scores will be recorded once a day from 1 week prior to the first treatment and through the entire study period. Primary outcomes are differences between groups in daily and weekly mean pain scores. Secondary outcomes are levels of physical activity, depression scores, health-related quality of life, activities of daily living, sensory profiles and motor function, recorded at baseline, 4, 12, 16 and 24 weeks. The use of rescue medication and adverse events will be recorded throughout the study period.

ETHICS AND DISSEMINATION

The study is approved by the Danish Committee on Health Research Ethics and the Danish Medicines Agency. EU-Clinical Trial Information System (EU: 2022-500727-68-01), clinicaltrials.gov (ID: NCT05623111). Results will be published in peer-reviewed journals in open-access formats and data made available in anonymised form.

TRIAL REGISTRATION NUMBER

NCT05623111.

Evaluating the effect of acupuncture on symptoms of diabetic peripheral neuropathy (DPN) among individuals with diabetic neuropathy: A single-blind, randomized trial study

Purpose

This study aimed to investigate the impact of acupuncture on Diabetic peripheral neuropathy (DPN) symptoms among individuals with diabetic neuropathy.

Methods

In a single-blind, randomized trial conducted between 2019 and 2020, 60 patients diagnosed with diabetic neuropathy were enrolled. These participants were randomly assigned to either the intervention or control group. The intervention group received real acupuncture alongside routine treatment once a week for seven sessions, each lasting 20 min. Meanwhile, the control group received sham acupuncture as an adjunct to their routine treatment, following the same schedule. To evaluate treatment efficacy, the study assessed primary outcomes, such as pain intensity measured using the Visual Analogue Scale (VAS). Secondary outcomes included evaluating fatigue severity and diabetic peripheral neuropathy (DPN) side effects, measured using the multidimensional fatigue inventory (MFI-20) and a standard questionnaire after each session.

Results

No statistically significant differences in pain and fatigue scores were observed between the two groups throughout all visits, even after adjusting for baseline characteristics, age, sex, type of diabetes, discopathy, and carpal tunnel syndrome parameters (P > 0.05). The findings did not provide strong evidence supporting a significant effect of real acupuncture compared to sham acupuncture on pain and fatigue values (P = 0.267 and 0.634, respectively). However, the 95% confidence interval for pain scores (-0.35, 1.28) was inconclusive, encompassing effect sizes favoring sham acupuncture.

Conclusion

Findings suggest that using acupuncture as an adjunctive therapy alongside routine treatment may not lead to a significant reduction in the symptoms of peripheral neuropathy and fatigue severity among individuals with diabetic neuropathy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01314-1.

Structural changes in Schwann cells and nerve fibres in type 1 diabetes: relationship with diabetic polyneuropathy

AIMS/HYPOTHESIS

Our aim was to investigate structural changes of cutaneous Schwann cells (SCs), including nociceptive Schwann cells (nSCs) and axons, in individuals with diabetic polyneuropathy. We also aimed to investigate the relationship between these changes and peripheral neuropathic symptoms in type 1 diabetes.

METHODS

Skin biopsies (3 mm) taken from carefully phenotyped participants with type 1 diabetes without polyneuropathy (T1D, n=25), type 1 diabetes with painless diabetic polyneuropathy (T1DPN, n=30) and type 1 diabetes with painful diabetic polyneuropathy (P-T1DPN, n=27), and from healthy control individuals (n=25) were immunostained with relevant antibodies to visualise SCs and nerve fibres. Stereological methods were used to quantify the expression of cutaneous SCs and nerve fibres.

RESULTS

There was a difference in the number density of nSCs not abutting to nerve fibres between the groups (p=0.004) but not in the number density of nSCs abutting to nerve fibres, nor in solitary or total subepidermal SC soma number density. The overall dermal SC expression (measured by dermal SC area fraction and subepidermal SC process density) and peripheral nerve fibre expression (measured by intraepidermal nerve fibre density, dermal nerve fibre area fraction and subepidermal nerve fibre density) differed between the groups (all p<0.05): significant differences were seen in participants with T1DPN and P-T1DPN compared with those without diabetic polyneuropathy (healthy control and T1D groups) (all p<0.05). No difference was found between participants in the T1DPN and P-T1DPN group, nor between participants in the T1D and healthy control group (all p>0.05). Correlational analysis showed that cutaneous SC processes and nerve fibres were highly associated, and they were weakly negatively correlated with different neuropathy measures.

CONCLUSIONS/INTERPRETATION

Cutaneous SC processes and nerves, but not SC soma, are degenerated and interdependent in individuals with diabetic polyneuropathy. However, an increase in structurally damaged nSCs was seen in individuals with diabetic polyneuropathy. Furthermore, dermal SC processes and nerve fibres correlate weakly with clinical measures of neuropathy and may play a partial role in the pathophysiology of diabetic polyneuropathy in type 1 diabetes.

Post hoc analysis of the SONAR trial indicates that the endothelin receptor antagonist atrasentan is associated with less pain in patients with type 2 diabetes and chronic kidney disease

Pain is prevalent among patients with diabetes and chronic kidney disease (CKD). The management of chronic pain in these patients is limited by nephrotoxicity of commonly used drugs including non-steroidal anti-inflammatory drugs (NSAIDs) and opioids. Since previous studies implicated endothelin-1 in pain nociception, our post hoc analysis of the SONAR trial assessed the association between the endothelin receptor antagonist atrasentan and pain and prescription of analgesics. SONAR was a randomized, double-blind, placebo-controlled clinical trial that recruited participants with type 2 diabetes and CKD (estimated glomerular filtration rate 25-75 ml/min/1.73 m2; urinary albumin-to-creatinine ratio 300-5000 mg/g). Participants were randomized to receive atrasentan or placebo (1834 each arm). The main outcome was pain-related adverse events (AEs) reported by investigators. We applied Cox regression to assess the effect of atrasentan compared to placebo on the risk of the first reported pain-related AE and, secondly, first prescription of analgesics. We used the Anderson-Gill method to assess effects on all (first and subsequent) pain-related AEs. During 2.2-year median follow-up, 1183 pain-related AEs occurred. Rates for the first pain-related event were 138.2 and 170.2 per 1000 person-years in the atrasentan and placebo group respectively (hazard ratio 0.82 [95% confidence interval 0.72-0.93]). Atrasentan also reduced the rate of all (first and subsequent) pain-related AEs (rate ratio 0.80 [0.70-0.91]). These findings were similar after accounting for competing risk of death (sub-hazard ratio 0.81 [0.71-0.92]). Patients treated with atrasentan initiated fewer analgesics including NSAIDs and opioids compared to placebo during follow-up (hazard ratio = 0.72 [0.60-0.88]). Thus, atrasentan was associated with reduced pain-related events and pain-related use of analgesics in carefully selected patients with type 2 diabetes and CKD.

Quality of life of persons with painful diabetic neuropathy: How can we improve it?

Painful diabetic neuropathy (PDN) is difficult to treat, with pharmacological treatments providing only partial pain relief that is limited by medication side effects. This necessitates a holistic approach to pain control,with pharmacological treatments supplemented by the management of psychosocial aspects of pain experience. Pain catastrophising and psychological flexibility are among the psychological constructs impacting persons' adaptation to PDN. While the former increases disability and reduces quality of life (QoL), the latter leads to less functional impairment and depression. Specific fears, and in particular, fear of falling, are significantly associated with pain-related disability and reduced QoL. The role of secondary parameters ofpain experience, including sleep and mood disturbancesas the potential guides to the selection of pharmacological treatmentsis yet to be established. Over the past decade there has been a steady increase in studies testing psychological interventions, including cognitive behavioural therapy and its several modifications, to manage pain in DN sufferers.Thesepilot and feasibility studies demonstrated the potential beneficial effects on pain severity and pain interference, depression and QoL in adults with PDN.Adequately powered trials are needed to confirm the effectiveness of these interventions in terms of pain experience and their impact on QoL.

The prevalence of anxiety in adult endocrinology outpatients: A systematic review and meta-analysis

INTRODUCTION

Anxiety disorders and anxiety symptoms are common mental disorders in the medically unwell and have significant impacts on patients' quality of life and engagement with psychiatric and medical services. Several systematic reviews have examined the prevalence of anxiety in specific endocrinology settings with estimates varying significantly from study to study. No meta-analysis has examined anxiety rates across the endocrinology outpatient setting. The aim of this meta-analysis is to provide endocrinologists with a precise estimate of the prevalence of anxiety - and impacting factors - in their outpatient clinics.

METHOD

PubMed, Embase, Cochrane and PsycINFO databases and Google Scholar were searched to identify studies that assessed anxiety prevalence in endocrinology outpatients published up to 23 January 2023. This was part of a larger systematic review search of anxiety prevalence in common medical outpatient clinics. Data characteristics were extracted independently by two investigators. Studies of patients 16 years and older and representative of the clinic were included. The point prevalence of anxiety or anxiety symptoms was measured using validated self-report questionnaires or structured interviews. Risk of bias was assessed using the Joanna Briggs Institute Critical Appraisal Checklist. Pooled estimates were analysed under the random-effects model and subgroup analyses on relevant variables were conducted under a mixed-effects model. Heterogeneity was assessed using the I2 statistic.

RESULTS

Fifty-nine studies with a total of 25,176 participants across 37 countries were included in this study. The overall pooled prevalence of anxiety or anxiety symptoms was 25·1% (95%CI 21·4-29·2; 6372/25,176; n = 59). Subgroup analyses revealed no difference in prevalence between outpatients with diabetes mellitus compared to other grouped endocrine disorders. Generalized Anxiety Disorder (GAD) was the most frequent clinical diagnosis 11·7% (95%CI 8·1-16·7; I2=87·93%; 443/4604; n = 17), while panic disorder was significantly higher in the non-diabetes group 9·5% (95%CI 5·9-14·9; I2=57·28%; 56/588; n = 8), compared to the diabetes group 5·2% (95%CI 3·7-7·3; I2=32·18%; 184/3669; n = 6). Estimates of prevalence were higher when assessed with a self-report scale 32·4% (95%CI 25·6-40·0; I2=96·06%; 1565/4675; n = 21) compared to diagnostic interview 17·6% (95%CI 12·2-24·7; I2=94·39%; 636/5168; n = 21). Outpatients in developing countries had higher rates of anxiety than those in developed countries. Female diabetes patients reported higher rates of anxiety compared to males.

CONCLUSION

Our study provides evidence that anxiety occurs frequently amongst endocrinology outpatients and at a higher rate than is estimated in the general population. Given the impact anxiety has on patient outcomes, it is important that effective management strategies be developed to support endocrinologists in identifying and treating these conditions in their outpatient clinics.

The pathogenesis of painful diabetic neuropathy and clinical presentation

Diabetic neuropathy is a common complication of diabetes that affects up to 50% of patients during the course of the disease; 20-30% of the patients also develop neuropathic pain. The mechanisms underlying neuropathy are not known in detail, but both metabolic and vascular factors may contribute to the development of neuropathy. The development of the most common type of neuropathy is insidious, often starting distally in the toes and feet and gradually ascending up the leg and later also involving fingers and hands. The symptoms are mainly sensory with either sensory loss or positive symptoms with different types of paresthesia or painful sensations. In more advanced cases motor dysfunction may occur, causing gait disturbances and falls. The diagnosis of neuropathy is based on history and a careful examination, which includes a sensory examination of both large and small sensory nerve fiber function, as well as an examination of motor function and deep tendon reflexes of the lower limbs. Attention needs to be paid to the feet including examination of the skin, joints, and vascular supply. Nerve conduction studies are rarely needed to make a diagnosis of neuropathy. In patients with clear motor deficit or with an asymmetrical presentation, additional electrophysiological examination may be necessary. Early detection of diabetic neuropathy is important to avoid further irreversible injury to the peripheral nerves.

BTD: A TRPC5 activator ameliorates mechanical allodynia in diabetic peripheral neuropathic rats by modulating TRPC5-CAMKII-ERK pathway

Mechanical allodynia is a serious complication of painful diabetic neuropathy (PDN) with limited treatment options. The transient receptor potential canonical 5 (TRPC5) channel is a promising target in pain; however, its role in painful diabetic neuropathy has not yet been elucidated. In this study, we have investigated the role of TRPC5 channels using BTD [N-{3-(adamantan-2-yloxy)-propyl}-3-(6-methyl-1,1-dioxo-2H-1λ6,2,4-benzothiadiazin-3-yl)-propanamide)],a potent TRPC5 activator and HC070, as TRPC5 channel inhibitor in rat model of PDN. In this study, streptozotocin was used to induce diabetes in male Sprague-Dawley rats. The alterations in mechanical and thermal pain thresholds, nerve functional deficits in diabetic animals were assessed by various behavioral and functional parameters.TRPC5 involvement was investigated by treating neuropathic rats with BTD, TRPC5 channel activator (1 and 3 mg/kg, i.p. for 14 days) and HC070, a TRPC5 channel inhibitor (1 and 3 mg/kg). BTD and HC070 effects in pain reduction were assessed by western blotting, estimating oxidative stress and inflammatory markers in the lumbar spinal cord. BTD treatment (3 mg/kg, i.p.) once daily for 14 days ameliorated mechanical allodynia but not thermal hyposensation or nerve functional deficit in diabetic neuropathic rats. BTD treatment down-regulated TRPC5 expression by increasing the activity of protein kinase C. It also subsequently down-regulated the downstream pain markers (CAMKII, ERK) in the spinal cord. Additionally, a decrease in inflammatory cytokines (TNF-α, IL-6) also demonstrated BTD's potent anti-inflammatory properties in reducing mechanical allodynia. On the other hand, HC070 did not exert any beneficial effects on behavioural and nerve functional parameters. The study concludes that BTD ameliorated mechanical allodynia in a rat model of painful diabetic neuropathy not only through modulation of the TRPC5-CAMKII-ERK pathway but also through its anti-inflammatory and anti-apoptotic properties. Overall, BTD is a promising therapeutic molecule in the treatment of mechanical allodynia in painful diabetic neuropathy.

Prevalence and risk factors of diabetic peripheral neuropathy: A population-based cross-sectional study in China

AIMS

To assess the prevalence of diabetic peripheral neuropathy (DPN) and its risk factors in the type 2 diabetes mellitus (T2DM) population.

METHODS

This cross-sectional study enroled patients with T2DM between July and December 2017 from 24 provinces in China. Diabetic peripheral neuropathy and its severity were assessed by the Toronto clinical scoring system, neuropathy symptoms score (NSS) and neuropathy disability score. The prevalence of DPN and its risk factors were analysed.

RESULTS

A total of 14,908 patients with T2DM were enroled. The prevalence of DPN was 67.6%. Among 10,084 patients with DPN, 4808 (47.7%), 3325 (33.0%), and 1951 (19.3%) had mild, moderate, and severe DPN, respectively. The prevalence of DPN in females was higher than in males (69.0% vs. 66.6%, P = 0.002). The prevalence of DPN increased with age and course of diabetes and decreased with body mass index (BMI) and education level (all P for trend <0.05). The comorbidities and complications in patients with DPN were higher than in those without DPN, including hypertension, myocardial infarction, diabetic retinopathy, and diabetic nephropathy (all P < 0.001). Age, hypertension, duration of diabetes, diabetic retinopathy, diabetic nephropathy, glycated haemoglobin, high-density lipoprotein cholesterol, and lower estimated glomerular filtration rate were positively associated with DPN, while BMI, education level, fasting C-peptide, and uric acid were negatively associated with DPN.

CONCLUSIONS

Among patients with T2DM in China, the prevalence of DPN is high, especially in the elderly, low-income, and undereducated patients.

Analysis of Japanese nationwide health datasets: association between lifestyle habits and prevalence of neuropathic pain and fibromyalgia with reference to dementia-related diseases and Parkinson's disease

OBJECTIVES

Chronic pain is defined as pain that persists or recurs for more than 3 months. This study focuses on neuropathic pain (NP) and fibromyalgia (FM) which are chronic pain states, and aims to identify lifestyle habits associated with their prevalence. Other neurological disorders are also analyzed as references.

METHODS

Association between the variable referring to disease prevalence (number of claims for reimbursement of marker drugs) and the variable for lifestyle habits/health examination results (collected from insured individuals aged 40-74 years) was determined by analyzing Japanese nationwide datasets, which were collected in 2018 and aggregated by prefecture. Pregabalin, donepezil, and levodopa were used as marker drugs for the chronic pain states, dementia-related diseases (Alzheimer's disease and Lewy body dementia) and Parkinson's disease (PD), respectively. Pearson's correlation analysis and multiple linear regression analysis were conducted.

RESULTS

Variables showing correlation coefficient (|r|)>0.5 were put into the multiple linear regression. Exercise habits (ꞵ=-0.3182), smoking habits (0.3218), daily drinking (0.2683), and alanine aminotransferase>51 U/L (0.2309) were finally incorporated in the equation for pregabalin (R 2=0.7268). Walking speed (-0.4543) and daily drinking (0.5077) were incorporated in the equation for donepezil (R 2=0.5718).

CONCLUSIONS

The prevalence of chronic pain states is associated with lifestyle habits, just like the dementia-related diseases. Exercise in daily life is negatively associated with the prevalence of the chronic pain states, although excessive alcohol drinking, smoking, and high serum ALT are positively associated with it. The prevalence of PD seems less associated with lifestyle habits.

Diabetic Neuropathies

OBJECTIVE

This article provides an up-to-date review of the diagnosis and management of the most common neuropathies that occur in patients with diabetes.

LATEST DEVELOPMENTS

The prevalence of diabetes continues to grow worldwide and, as a result, the burden of diabetic neuropathies is also increasing. Most diabetic neuropathies are caused by hyperglycemic effects on small and large fiber nerves, and glycemic control in individuals with type 1 diabetes reduces neuropathy prevalence. However, among people with type 2 diabetes, additional factors, particularly metabolic syndrome components, play a role and should be addressed. Although length-dependent distal symmetric polyneuropathy is the most common form of neuropathy, autonomic syndromes, particularly cardiovascular autonomic neuropathy, are associated with increased mortality, whereas lumbosacral radiculoplexus neuropathy and treatment-induced neuropathy cause substantial morbidity. Recent evidence-based guidelines have updated the recommended treatment options to manage pain associated with distal symmetric polyneuropathy of diabetes.

ESSENTIAL POINTS

Identifying and appropriately diagnosing the neuropathies of diabetes is key to preventing progression. Until better disease-modifying therapies are identified, management remains focused on diabetes and metabolic risk factor control and pain management.

Gut microbiota modulate distal symmetric polyneuropathy in patients with diabetes

The pathogenic mechanisms underlying distal symmetric polyneuropathy (DSPN), a common neuropathy in patients with diabetes mellitus (DM), are not fully understood. Here, we discover that the gut microbiota from patients with DSPN can induce a phenotype exhibiting more severe peripheral neuropathy in db/db mice. In a randomized, double-blind, and placebo-controlled trial (ChiCTR1800017257), compared to 10 patients who received placebo, DSPN was significantly alleviated in the 22 patients who received fecal microbiota transplants from healthy donors, independent of glycemic control. The gut bacterial genomes that correlated with the Toronto Clinical Scoring System (TCSS) score were organized in two competing guilds. Increased guild 1, which had higher capacity in butyrate production, and decreased guild 2, which harbored more genes in synthetic pathway of endotoxin, were associated with improved gut barrier integrity and decreased proinflammatory cytokine levels. Moreover, matched enterotype between transplants and recipients showed better therapeutic efficacy with more enriched guild 1 and suppressed guild 2. Thus, changes in these two competing guilds may play a causative role in DSPN and have the potential for therapeutic targeting.

Structural Changes of Cutaneous Immune Cells in Patients With Type 1 Diabetes and Their Relationship With Diabetic Polyneuropathy

BACKGROUND AND OBJECTIVES

Diabetic polyneuropathy (DPN) is a complication of diabetes characterized by pain or lack of peripheral sensation, but the underlying mechanisms are not yet fully understood. Recent evidence showed increased cutaneous macrophage infiltration in patients with type 2 diabetes and painful DPN, and this study aimed to understand whether the same applies to type 1 diabetes.

METHODS

The study included 104 participants: 26 healthy controls and 78 participants with type 1 diabetes (participants without DPN [n = 24], participants with painless DPN [n = 29], and participants with painful DPN [n = 25]). Two immune cells, dermal IBA1⁺ macrophages and epidermal Langerhans cells (LCs, CD207⁺), were visualized and quantified using immunohistological labeling and stereological counting methods on skin biopsies from the participants. The IBA1⁺ macrophage infiltration, LC number density, LC soma cross-sectional area, and LC processes were measured in this study.

RESULTS

Significant difference in IBA1⁺ macrophage expression was seen between the groups (p = 0.003), with lower expression of IBA1 in participants with DPN. No differences in LC morphologies (LC number density, soma cross-sectional area, and process level) were found between the groups (all p > 0.05). In addition, IBA1⁺ macrophages, but not LCs, correlated with intraepidermal nerve fiber density, Michigan neuropathy symptom inventory, (questionnaire and total score), severity of neuropathy as assessed by the Toronto clinical neuropathy score, and vibration detection threshold in the whole study cohort.

DISCUSSION

This study showed expressional differences of cutaneous IBA1⁺ macrophages but not LC in participants with type 1 diabetes-induced DPN compared with those in controls. The study suggests that a reduction in macrophages may play a role in the development and progression of autoimmune-induced diabetic neuropathy.

Cardiovascular autonomic neuropathy in patients with type 2 diabetes with and without sensorimotor polyneuropathy

BACKGROUND AND AIMS

Cardiovascular autonomic neuropathy (CAN) in patients with diabetes is associated with poor prognosis. We aimed to assess signs of CAN and autonomic symptoms and to investigate the impact of sensorimotor neuropathy on CAN by examining type 2 diabetes patients with (DPN [distal sensorimotor polyneuropathy]) and without distal sensorimotor polyneuropathy (noDPN) and healthy controls (HC). Secondarily, we aimed to describe the characteristics of patients with CAN.

METHODS

A population of 374 subjects from a previously described cohort of the Danish Centre for Strategic Research in Type 2 Diabetes (DD2) were included. Subjects were examined with the Vagus™ device for the diagnosis of CAN, where two or more abnormal cardiovascular autonomic reflex tests indicate definite CAN. Autonomic symptoms were assessed with Composite Autonomic Symptom Score 31 (COMPASS 31) questionnaire. DPN was defined according to the Toronto consensus panel definition.

RESULTS

Definite CAN was present in 22% with DPN, 7% without DPN and 3% of HC, and 91% of patients with definite CAN had DPN. Patients with DPN and definite CAN reported higher COMPASS 31 scores compared to patients with noDPN (20.0 vs. 8.3, p < 0.001) and no CAN (22.1 vs. 12.3, p = 0.01). CAN was associated with HbA1c and age in a multivariate logistic regression analysis but was not associated with IEFND or triglycerides.

INTERPRETATION

One in five patients with DPN have CAN and specific CAN characteristics may help identify patients at risk for developing this severe diabetic complication. Autonomic symptoms were strongly associated with having both DPN and CAN, but too unspecific for diagnosing CAN.

Efficacy of Pregabalin and Duloxetine in Patients with Painful Diabetic Peripheral Neuropathy (PDPN): A Multi-Centre Phase IV Clinical Trial-BLOSSOM

INTRODUCTION

Our trial (ClinicalTrials.gov Identifier: NCT04246619) evaluates the efficacy of two generic medications, pregabalin and duloxetine, for treating pain in PDPN patients.

METHODS

The patients were randomised either into the pregabalin (99) or the duloxetine (102) arm. Pain was evaluated using the DN-4 questionnaire, and visual analogue scales (VASs, 0-100 mm) were used to measure the average pain intensity (API), worst pain intensity (WPI) in the last 24 h and current pain intensity (CPI).

RESULTS

The proportion of patients with a clinically significant improvement in the API at Week 12 was 88.3% [CI 81.7%, 94.8%] in the pregabalin arm and 86.9% [CI 76.7%, 97.1%] in the duloxetine arm. After 12 weeks, the CPI, API, and WPI decreased by -35.3 [-40.5, -30.0], -37.0 [-41.4, -32.6], and -41.6 [-46.6, -36.5] in the pregabalin arm, and by -35.0 [-39.2, -30.7], -36.9 [-41.5, -32.3], and -40.0 [-44.8, -35.2] in the duloxetine arm (all in mm, all p < 0.001).

CONCLUSION

Our results demonstrate that pregabalin and duloxetine are effective medications for treating pain in PDPN in more than 86% of all randomised patients.

Painful Diabetic Peripheral Neuropathy - A Survey of Patient Experiences

Purpose

An online survey was conducted in the USA to obtain information about the knowledge and experiences of patients with painful diabetic peripheral neuropathy (pDPN).

Patients and Methods

506 adults with diabetes and pDPN affecting the feet for ≥6 months, for which pain medication had been prescribed for ≥6 months, completed an online survey questionnaire in March 2021.

Results

79% of respondents had type 2 diabetes, 60% were male, 82% were Caucasian and 87% had comorbidities. Pain was significant to severe in 49% of respondents, and 66% had disability due to nerve pain. Anticonvulsants, over-the-counter pills and supplements were the most commonly used medications. Topical creams/patches were prescribed in 23% of respondents. 70% had tried multiple medications for their pain. 61% of respondents had to see ≥2 doctors before receiving a correct diagnosis of pDPN. 85% of respondents felt that the doctor understood their pain and its impact on their life. 70% had no difficulty finding the information they wanted. 34% felt insufficiently informed about their condition. A medical professional was the primary, and most trusted, source of information. Frustration, worry, anxiety and uncertainty were the most commonly reported emotions. Respondents were generally eager to find new medications for pain relief and desperate for a cure. Lifestyle changes because of nerve pain were most commonly associated with physical disabilities and sleep disturbance. Better treatments and freedom from pain were the overriding perspectives when considering the future.

Conclusion

Patients with pDPN are generally well informed about their pain and trust their doctor but remain unsatisfied with their current treatment and struggle to find a lasting solution for their pain. Early identification and diagnosis of pain in diabetics, and education about treatments, is important to minimize the impact of pain on quality of life and emotional well-being.

l-Methylfolate in Diabetic Peripheral Neuropathy: A Narrative Review

OBJECTIVE

One of the most frequently occurring complications of diabetes mellitus is peripheral neuropathy. Despite the painful symptoms associated with diabetic peripheral neuropathy (DPN), the current treatment landscape focuses on managing symptoms without addressing the underlying causes of DPN. This narrative review describes the mechanistic effects and clinical trial data supporting the use of l-methylfolate calcium (LMF), the bioactive form of folate, which is available in the United States as a prescription medical food that also contains other B vitamins for the dietary management of DPN.

METHODS

Preclinical and clinical trial data evaluating the impact of LMF on DPN was identified using PubMed searches for articles published between 2010 and 2023. Search terms included: folate, l-methylfolate, diabetes, neuropathy, and neuropathic pain. Additionally, a literature search was conducted to identify studies related to LMF, genetic polymorphisms, and DPN pathophysiology.

RESULTS

Several studies show that the C677T variant of the methylenetetrahydrofolate reductase (MTHFR) gene is linked to greater risk of DPN than other MTHFR variants due to its inhibitory effects on several folic acid metabolic pathways. One double-blind, randomized controlled trial, five open-label studies, and one retrospective study found that LMF has a significant beneficial effect on DPN that extends beyond symptomatic relief to include modulating the underlying pathophysiology that leads to the progression and symptoms of DPN. LMF also significantly improves patient quality of life, with minimal adverse effects.

CONCLUSION

Preclinical and clinical studies have found that LMF can be used to treat the underlying causes of DPN and provide long-lasting symptomatic relief.

Assessing Corneal Confocal Microscopy and Other Small Fiber Measures in Diabetic Polyneuropathy

BACKGROUND AND OBJECTIVES

Damage to small nerve fibers is common in diabetic polyneuropathy (DPN), and the diagnosis of DPN relies on subjective symptoms and signs in a combination with objective confirmatory tests, typically electrophysiology or intraepidermal nerve fiber density (IENFD) from skin biopsy. Corneal confocal microscopy (CCM) has been introduced as a tool to detect DPN. However, it is unclear if CCM can reliably be used to diagnose DPN and how the technique compares with other commonly used measures of small fiber damage, such as IENFD, cold detection threshold (CDT), and warm detection threshold (WDT). Therefore, we assessed and compared the use of CCM, IENFD, CDT, and WDT in the diagnosis of DPN in patients with type 2 diabetes.

METHODS

In this cohort study, the participants underwent detailed neurologic examination, electrophysiology, quantification of IENFD, CCM, and quantitative sensory testing. Definition of DPN was made in accordance with the Toronto criteria for diabetic neuropathy (without relying on IENFD and thermal thresholds).

RESULTS

A total of 214 patients with at least probable DPN, 63 patients without DPN, and 97 controls without diabetes were included. Patients with DPN had lower CCM measures (corneal nerve fiber length [CNFL], nerve fiber density, and branch density), IENFD, CDT, and WDT compared with patients without DPN (p ≤ 0.001, <0.001, 0.002, p < 0.001, p = 0.003, and <0.005, respectively), whereas there was no difference between controls and patients with diabetes without DPN. All 3 CCM measures showed a very low diagnostic sensitivity with CNFL showing the highest (14.4% [95% CI 9.8-18.4]) and a specificity of 95.7% (88.0-99.1). In comparison, the sensitivity of abnormal CDT and/or WDT was 30.5% (24.4-37.0) with a specificity of 84.9% (74.6-92.2). The sensitivity of abnormal IENFD was highest among all measures with a value of 51.1% (43.7-58.5) and a specificity of 90% (79.5-96.2). CCM measures did not correlate with IENFD, CDT/WDT, or neuropathy severity in the group of patients with DPN.

DISCUSSION

CCM measures showed the lowest sensitivity compared with other small fiber measures in the diagnosis of DPN. This indicates that CCM is not a sensitive method to detect DPN in recently diagnosed type 2 diabetes.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that CCM measures aid in the detection of DPN in recently diagnosed type 2 diabetics but with a low sensitivity when compared with other small fiber measures.

Excitatory and inhibitory neuronal signaling in inflammatory and diabetic neuropathic pain

Pain, although unpleasant, is an essential warning mechanism against injury and damage of the organism. An intricate network of specialised sensors and transmission systems contributes to reception, transmission and central sensitization of pain. Here, we briefly introduce some of the main aspects of pain signal transmission, including nociceptors and nociceptive signals, mechanisms of inflammatory and neuropathic pain, and the situation of diabetes-associated neuropathic pain. The role of glia-astrocytes, microglia, satellite glia cells-and their specific channels, transporters and signaling pathways is described. A focus is on the contribution of inhibitory synaptic signaling to nociception and a possible role of glycine receptors in glucose-mediated analgesia and treatment-induced diabetic neuropathy. Inhibitory receptors such as GABA_A- and glycine receptors are important contributors to nociceptive signaling; their contribution to altered pain sensation in diabetes may be of clinical relevance, and they could be promising therapeutic targets towards the development of novel analgesics.

Diagnosis, management and impact of painful diabetic peripheral neuropathy: A patient survey in four European countries

AIMS

The aim of this study was to assess patient perspectives and experiences of the impact of neuropathic pain, painful diabetic neuropathy (pDPN) diagnosis and treatment, and the patient-healthcare professional (HCP) relationship.

METHODS

We conducted a quantitative online survey in Germany, the Netherlands, Spain, and the UK among adults with diabetes who responded "yes" to at least four of ten questions of in the Douleur Neuropathique en 4 Questions (DN4) questionnaire.

RESULTS

Of 3626 respondents, 576 met the eligibility criteria. Daily pain was rated as moderate or severe by 79 % of respondents. Most participants reported a negative impact of their pain on sleep (74 %), mood (71 %), exercise (69 %), concentration (64 %) and daily activities (62 %), and 75 % of those in employment had missed work because of their pain in the past year. Overall, 22 % of respondents avoided discussing pain with their HCP, 50 % had not received formal pDPN diagnosis, and 56 % had not used prescribed pain medications. Although two-thirds (67 %) of respondents reported feeling satisfied or very satisfied with treatment, 82 % of these patients still experienced daily moderate or severe pain.

CONCLUSIONS

Neuropathic pain in people with diabetes affects daily life and remains underdiagnosed and undertreated in clinical practice.

Training and External Validation of a Predict Nomogram for Type 2 Diabetic Peripheral Neuropathy

Background: Diabetic peripheral neuropathy (DPN) is a critical clinical disease with high disability and mortality rates. Early identification and treatment of DPN is critical. Our aim was to train and externally validate a prediction nomogram for early prediction of DPN. Methods: 3012 patients with T2DM were retrospectively studied. These patients were hospitalized between 1 January 2017 and 31 December 2020 in the First Affiliated Hospital of Xinjiang Medical University in Xinjiang, China. A total of 901 patients with T2DM from the Suzhou BenQ Hospital in Jiangsu, China who were hospitalized between 1 January 2019 and 31 December 2020 were considered for external validation. The least absolute shrinkage and selection operator (LASSO) and multivariate logistic regression were performed to identify independent predictors and establish a nomogram to predict the occurrence of DPN. The performance of the nomogram was evaluated using a receiver operating characteristic curve (ROC), a calibration curve, and a decision curve analysis (DCA). Findings: Age, 25-hydroxyvitamin D3 [25(OH)D3], Duration of T2DM, high-density lipoprotein (HDL), hemoglobin A1c (HbA1c), and fasting blood glucose (FBG) were used to establish a nomogram model for predicting the risk of DPN. In the training and validation cohorts, the areas under the curve of the nomogram constructed from the above six factors were 0.8256 (95% CI: 0.8104–0.8408) and 0.8608 (95% CI: 0.8376–0.8840), respectively. The nomogram demonstrated excellent performance in the calibration curve and DCA. Interpretation: This study has developed and externally validated a nomogram model which exhibits good predictive ability in assessing DPN risk among the type 2 diabetes population. It provided clinicians with an accurate and effective tool for the early prediction and timely management of DPN.

Screening for diabetic peripheral neuropathy in resource-limited settings

BACKGROUND

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

MAIN BODY

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

CONCLUSIONS

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

Development and external validation of multivariable risk models to predict incident and resolved neuropathic pain: a DOLORisk Dundee study

Neuropathic pain is difficult to treat, and an understanding of the risk factors for its onset and resolution is warranted. This study aimed to develop and externally validate two clinical risk models to predict onset and resolution of chronic neuropathic pain. Participants of Generation Scotland: Scottish Family Health Study (GS; general Scottish population; n = 20,221) and Genetic of Diabetes Audit and Research in Tayside Scotland (GoDARTS; n = 5236) were sent a questionnaire on neuropathic pain and followed- -up 18 months later. Chronic neuropathic pain was defined using DN4 scores (≥ 3/7) and pain for 3 months or more. The models were developed in GS using logistic regression with backward elimination based on the Akaike information criterion. External validation was conducted in GoDARTS and assessed model discrimination (ROC and Precision-Recall curves), calibration and clinical utility (decision curve analysis [DCA]). Analysis revealed incidences of neuropathic pain onset (6.0% in GS [236/3903] and 10.7% in GoDARTS [61/571]) and resolution (42.6% in GS [230/540] and 23.7% in GoDARTS [56/236]). Psychosocial and lifestyle factors were included in both onset and resolved prediction models. In GoDARTS, these models showed adequate discrimination (ROC = 0.636 and 0.699), but there was evidence of miscalibration (Intercept = - 0.511 and - 0.424; slope = 0.623 and 0.999). The DCA indicated that the models would provide clinical benefit over a range of possible risk thresholds. To our knowledge, these are the first externally validated risk models for neuropathic pain. The findings are of interest to patients and clinicians in the community, who may take preventative or remedial measures.

Possible Neuropathic Pain in Clinical Practice-Review on Selected Diagnostic Tools and Its Further Challenges

BACKGROUND

Neuropathic pain (NeP) is a wide group of conditions provoked by many different causes and with different patterns. The creation of a grading system was intended to determine the level of certainty that the pain is of neuropathic nature.

METHODS

The aim of this review is to update previously published data on some NeP questionnaires and their measurement properties. The selection of articles is based on the basic neurological units. To assess the usefulness and credibility of the questionnaires, the authors searched for a commonly used measure of reliability, as well as sensitivity and specificity.

RESULTS

Studies regarding the usefulness and credibility of questionnaires used in NeP were realized. Different patient cohorts, etiologies and sample sizes, do not allow for an unambiguous comparison of the presented scales; however, all of these studies found good measures of reliability, specificity and sensitivity.

CONCLUSIONS

NeP tools seem to be beneficial screening instruments that should be utilized by specialists and general practitioners to improve the recognition of "possible" NeP and to determine the epidemiology of this disorder. They have been developed to distinguish perceived pain into neuropathic and non-neuropathic, and, therefore, patients with a mixed pain can still present a diagnostic challenge. Clinical examination and interview play an essential role in the diagnostic process and monitoring, and cannot be neglected.

The conundrum of diabetic neuropathies-Past, present, and future

Diabetic neuropathy (DN) remains arguably the most prevalent chronic complication in people with both type 1 and type 2 diabetes, including in youth, despite changes in the current standards of clinical care. Additionally, emerging evidence demonstrates that neuropathy affects a large proportion of people with undiagnosed diabetes and/or prediabetes, as well as those with obesity. Here we summarize the latest epidemiology of DN, recent findings regarding the pathophysiology of the disease, as well as current outcome measures for screening and diagnosis, in research and clinical settings. The authors discuss novel perspectives on the impact of social determinants of health in DN development and management, and the latest evidence on effective therapies, including pharmacological and nonpharmacological therapies for neuropathic pain. Throughout the publication, we identify knowledge gaps and the need for future funding to address these gaps, as well as needs to advocate for a personalized care approach to reduce the burden of DN and optimize quality of life for all affected individuals.

Reversing painful and non-painful diabetic neuropathy with the capsaicin 8% patch: Clinical evidence for pain relief and restoration of function via nerve fiber regeneration

Introduction

Current oral treatments for pain in diabetic peripheral neuropathy (DPN) do not affect the progression of DPN i.e., "disease modification." We assessed whether Capsaicin 8% patch treatment can provide pain relief and also restore nerve density and function via nerve regeneration, in both painful (PDPN) and non-painful (NPDPN) diabetic peripheral neuropathy.

Methods

50 participants with PDPN were randomized to receive Capsaicin 8% patch Qutenza with Standard of Care (SOC) (PDPN Q+SOC group), or SOC alone (PDPN SOC group). Pain symptoms were assessed with a diary (Numerical Pain Rating Scale, NRPS) and questionnaires. Investigations included quantitative sensory testing (QST) and distal calf skin biopsies, at baseline and 3 months after baseline visit; subsequent options were 3-monthly visits over 1 year. 25 participants with NPDPN had tests at baseline, and 3 months after all received Capsaicin 8% patch treatment.

Results

At 3 months after baseline, PDPN Q+SOC group had reduction in NPRS score (p = 0.0001), but not PDPN SOC group. Short-Form McGill Pain Questionnaire (SF-MPQ) showed significant reductions in scores for overall and other pain descriptors only in the PDPN Q+SOC group. Warm perception thresholds were significantly improved only in the PDPN Q+SOC group (p = 0.02), and correlated with reduction in SF-MPQ overall pain score (p = 0.04). NPDPN Q+SOC group did not report pain during the entire study. Density of intra-epidermal nerve fibers (IENF) with PGP9.5 was increased at 3 months in PDPN Q+SOC (p = 0.0002) and NPDPN Q+SOC (p = 0.002) groups, but not in the PDPN SOC group. Increased sub-epidermal nerve fibers (SENF) were observed with GAP43 (marker of regenerating nerve fibers) only in PDPN Q+SOC (p = 0.003) and NPDPN Q+SOC (p = 0.0005) groups. Pain relief in the PDPN Q+SOC group was correlated with the increased PGP9.5 IENF (p = 0.0008) and GAP43 (p = 0.004), whereas those with lack of pain relief showed no such increase; in some subjects pain relief and increased nerve fibers persisted over months. PGP9.5 IENF increase correlated with axon-reflex vasodilatation in a NPDPN Q+SOC subset (p = 0.006).

Conclusions

Capsaicin 8% patch can provide pain relief via nerve regeneration and restoration of function in DPN (disease modification). It may thereby potentially prevent diabetic foot complications, including ulcers.

American Association of Clinical Endocrinology Clinical Practice Guideline: Developing a Diabetes Mellitus Comprehensive Care Plan-2022 Update

OBJECTIVE

The objective of this clinical practice guideline is to provide updated and new evidence-based recommendations for the comprehensive care of persons with diabetes mellitus to clinicians, diabetes-care teams, other health care professionals and stakeholders, and individuals with diabetes and their caregivers.

METHODS

The American Association of Clinical Endocrinology selected a task force of medical experts and staff who updated and assessed clinical questions and recommendations from the prior 2015 version of this guideline and conducted literature searches for relevant scientific papers published from January 1, 2015, through May 15, 2022. Selected studies from results of literature searches composed the evidence base to update 2015 recommendations as well as to develop new recommendations based on review of clinical evidence, current practice, expertise, and consensus, according to established American Association of Clinical Endocrinology protocol for guideline development.

RESULTS

This guideline includes 170 updated and new evidence-based clinical practice recommendations for the comprehensive care of persons with diabetes. Recommendations are divided into four sections: (1) screening, diagnosis, glycemic targets, and glycemic monitoring; (2) comorbidities and complications, including obesity and management with lifestyle, nutrition, and bariatric surgery, hypertension, dyslipidemia, retinopathy, neuropathy, diabetic kidney disease, and cardiovascular disease; (3) management of prediabetes, type 2 diabetes with antihyperglycemic pharmacotherapy and glycemic targets, type 1 diabetes with insulin therapy, hypoglycemia, hospitalized persons, and women with diabetes in pregnancy; (4) education and new topics regarding diabetes and infertility, nutritional supplements, secondary diabetes, social determinants of health, and virtual care, as well as updated recommendations on cancer risk, nonpharmacologic components of pediatric care plans, depression, education and team approach, occupational risk, role of sleep medicine, and vaccinations in persons with diabetes.

CONCLUSIONS

This updated clinical practice guideline provides evidence-based recommendations to assist with person-centered, team-based clinical decision-making to improve the care of persons with diabetes mellitus.

Preferential impairment of parasympathetic autonomic function in type 2 diabetes

OBJECTIVE

Cardiovascular autonomic neuropathy is a known complication in type 2 diabetes (T2D). However, the extent of sympathetic dysfunction and its relation to blood pressure (BP) dysregulation is insufficiently studied. We therefore assessed the cardiovascular sympathetic function using a standardized autonomic test-battery.

RESEARCH DESIGN AND METHODS

Forty T2D patients (mean age and duration of diabetes ±SD, 65.5 ± 7.3 and 9.5 ± 4.2 years) and 40 age- and gender-matched controls were examined through autonomic testing, assessing cardiovascular responses to deep breathing, Valsalva maneuver and tilt-table testing. Additionally, 24-hour oscillometric BP and self-reported autonomic symptoms on COMPASS-31 questionnaire was recorded.

RESULTS

Patients with T2D had reduced parasympathetic activity with reduced deep breathing inspiratory:expiratory-ratio (median [IQR] T2D 1.11 [1.08-1.18] vs. controls 1.18 [1.11-1.25] (p = 0.01)), and reduced heart rate variability (p < 0.05). We found no differences in cardiovascular sympathetic function measured through BP responses during the Valsalva maneuver (p > 0.05). 24-hour-BP detected reduced night-time systolic BP drop in T2D (9.8 % ± 8.8 vs. controls 15.8 % ± 7.7 (p < 0.01)) with more patients having reverse dipping. Patients with T2D reported more symptoms of orthostatic intolerance on the COMPASS-31 (p = 0.04).

CONCLUSIONS

Patients with T2D showed reduced parasympathetic activity but preserved short-term cardiovascular sympathetic function, compared to controls, indicating autonomic dysfunction with predominantly parasympathetic impairment. Despite this, T2D patients reported more symptoms of orthostatic intolerance in COMPASS-31 and had reduced nocturnal BP dipping, indicating that these are not a consequence of cardiovascular sympathetic dysfunction.

Factors related to cognitive function in type-2 diabetes and neuropathic pain patients, the role of mood and sleep disorders in this relationship

To compare cognitive function in patients with diabetes mellitus type-2 (T2DM) both with and without diabetic neuropathic pain (DNP). To analyse the relationship between mood and sleep disorders, quality of life and cognitive function in patients with DNP. Cross-sectional study conducted in patients with T2DM and neuropathy. The presence of DNP, cognitive function, mood status, sleep quality, health-related quality of life, pain intensity and phenotype of pain were measured. Descriptive, bivariate and multivariate analyses were performed. A total of 149 patients (71 with DNP) were included. Patients with and without DNP presented similar scores on the TYM (41.46; SD = 6.70 vs. 41.97; SD = 5.50) and those with DNP had a slightly higher frequency of cognitive impairment (TYM score ≤ 41: 40.8% vs. 43.6%). The patients without DNP performed better in the verbal fluency dimension (mean = 3.53; SD = 0.98 vs. mean = 3.82; SD = 0.66). Being older (B = − 0.258) and under treatment with insulin (B = − 2.919) were related with greater cognitive impairment. Obesity (OR = 17.277) and a longer duration of diabetes (OR = 1.317) were also related to greater risk of cognitive impairment. Impaired cognitive function in patients with DNP is more related to T2DM factors than pain factors. The presence of depression and a worse quality of life were related to a greater risk of cognitive impairment. Identifying and controlling these factors should be an essential intervention for maintaining the cognitive function in patients with T2DM and DNP.

Peripheral Ion Channel Gene Screening in Painful- and Painless-Diabetic Neuropathy

Neuropathic pain is common in diabetic peripheral neuropathy (DN), probably caused by pathogenic ion channel gene variants. Therefore, we performed molecular inversion probes-next generation sequencing of 5 transient receptor potential cation channels, 8 potassium channels and 2 calcium-activated chloride channel genes in 222 painful- and 304 painless-DN patients. Twelve painful-DN (5.4%) patients showed potentially pathogenic variants (five nonsense/frameshift, seven missense, one out-of-frame deletion) in ANO3 (n = 3), HCN1 (n = 1), KCNK18 (n = 2), TRPA1 (n = 3), TRPM8 (n = 3) and TRPV4 (n = 1) and fourteen painless-DN patients (4.6%-three nonsense/frameshift, nine missense, one out-of-frame deletion) in ANO1 (n = 1), KCNK18 (n = 3), KCNQ3 (n = 1), TRPA1 (n = 2), TRPM8 (n = 1), TRPV1 (n = 3) and TRPV4 (n = 3). Missense variants were present in both conditions, presumably with loss- or gain-of-functions. KCNK18 nonsense/frameshift variants were found in painless/painful-DN, making a causal role in pain less likely. Surprisingly, premature stop-codons with likely nonsense-mediated RNA-decay were more frequent in painful-DN. Although limited in number, painful-DN patients with ion channel gene variants reported higher maximal pain during the night and day. Moreover, painful-DN patients with TRP variants had abnormal thermal thresholds and more severe pain during the night and day. Our results suggest a role of ion channel gene variants in neuropathic pain, but functional validation is required.

Neuroinflammation Involved in Diabetes-Related Pain and Itch

Diabetes mellitus (DM) is a global epidemic with increasing incidence, which results in diverse complications, seriously affects the patient quality of life, and brings huge economic burdens to society. Diabetic neuropathy is the most common chronic complication of DM, resulting in neuropathic pain and chronic itch. The precise mechanisms of diabetic neuropathy have not been fully clarified, hindering the exploration of novel therapies for diabetic neuropathy and its terrible symptoms such as diabetic pain and itch. Accumulating evidence suggests that neuroinflammation plays a critical role in the pathophysiologic process of neuropathic pain and chronic itch. Indeed, researchers have currently made significant progress in knowing the role of glial cells and the pro-inflammatory mediators produced from glial cells in the modulation of chronic pain and itch signal processing. Here, we provide an overview of the current understanding of neuroinflammation in contributing to the sensitization of the peripheral nervous system (PNS) and central nervous system (CNS). In addition, we also summarize the inflammation mechanisms that contribute to the pathogenesis of diabetic itch, including activation of glial cells, oxidative stress, and pro-inflammatory factors. Targeting excessive neuroinflammation may provide potential and effective therapies for the treatment of chronic neuropathic pain and itch in DM.

Systematic Review of Voltage-Gated Calcium Channel α2δ Subunit Ligands for the Treatment of Chronic Neuropathic Pain and Insight into Structure-Activity Relationship (SAR) by Pharmacophore Modeling

BACKGROUND

Neuropathic pain (NP) is a complex symptom related to the nerve damage. The discovery of new drugs for treating chronic NP has been continuing for several decades, while more progress is still needed to be made because of the unsatisfactory efficacy and the side effects of the currently available drugs. Among all the approved drugs for chronic NP, voltage-gated calcium channel (VGCC) α2δ subunit ligands, also known as gabapentinoids, are among the first-line treatment and represent a class of efficacious and relatively safe therapeutic agents. However, new strategies are still needed to be explored due to the unsatisfied response rate.

OBJECTIVES

To review the latest status of the discovery and development of gabapentinoids for the treatment of chronic NP by covering both the marketed and the preclinical/clinical ones. To analyze the structure-activity relationship (SAR) of gabapentinoids to facilitate the future design of structurally novel therapeutic agents targeting VGCC α2δ subunit.

METHODS

We searched PubMed Central, Embase, Cochrane Library, Web of Science, Scopus and Espacenet for the literature and patents of diabetic peripheral neuropathic pain, postherpetic neuralgia, fibromyalgia, voltage-gated calcium channel α2δ subunit and related therapeutic agents from incipient to June 10, 2021. The SAR of gabapentinoids were analyzed by pharmacophore modeling using Phase module in Schrödinger suite.

RESULTS

A variety of gabapentinoids were identified as VGCC α2δ ligands that have ever been under development for the treatment of chronic NP. Among them, four gabapentinoids are marketed, one is at the active late clinical trials, and eight have been discontinued. Pharmacophore models were generated by using Phase module in Schrödinger suite, and common pharmacophores were predicted based on pharmacophoric features and analyzed.

CONCLUSION

The latest progress of the discovery and development of gabapentinoids for the treatment of chronic NP was reviewed. Moreover, the structure-activity relationship (SAR) of gabapentinoids is analyzed by pharmacophore modeling, which will be valuable for the future design of structurally novel therapeutic agents targeting VGCC α2δ subunit.

Is diabetic neuropathy associated with increased risk of developing mental disorders?

OBJECTIVE

It is largely unknown whether individuals with diabetic neuropathy face an increased risk of developing mental illness. Therefore, in a population-based cohort study, we aimed to examine whether individuals with diabetic neuropathy are at elevated risk of being diagnosed with a mental disorder compared to diabetes-duration-matched individuals without diabetic neuropathy.

METHODS

We used the nationwide Danish registers to identify all individuals diagnosed with diabetic neuropathy between January 1, 1996, and January 1, 2019. For each of these individuals, we identified up to five individuals with diabetes, matched on the duration of illness, who were not diagnosed with diabetic neuropathy. We then compared incidence rates of mental disorders between individuals with diabetic neuropathy and the diabetes-duration-matched individuals using a Cox proportional-hazards model.

RESTULTS

Individuals with diabetic neuropathy had a substantial and statistically significant increased risk of being diagnosed with any mental disorder (age- and sex-adjusted hazard rate ratio: 1.40, 95% CI: 1.31-1.48) as well as all specific mental disorders (psychotic disorder, bipolar disorder, unipolar depression, and/or anxiety disorder) compared with diabetes-duration-matched individuals without diabetic neuropathy.

CONCLUSIONS

Diabetic neuropathy appears to be associated with a substantially increased risk of developing a mental disorder. Knowledge of the potential mechanisms underlying this association could inform prevention and treatment and should therefore be pursued further.

Simple Quantitative Sensory Testing Reveals Paradoxical Co-existence of Hypoesthesia and Hyperalgesia in Diabetes

Background: Diabetic neuropathy is characterized by the paradoxical co-existence of hypo- and hyperalgesia to sensory stimuli. The literature shows consistently sensory differences between healthy and participants with diabetes. We hypothesized that due to differences in pathophysiology, advanced quantitative sensory testing (QST) might reveal sensory discrepancies between type 1 (T1D) and type 2 diabetes (T2D). Furthermore, we investigated whether vibration detection thresholds (VDT) were associated with sensory response.

Method: Fifty-six adults with T1D [43 years (28–58)], 99 adults with T2D [65 years (57–71)], and 122 healthy individuals [51 years (34–64)] were included. VDT, pressure pain detection thresholds (pPDT) and tolerance (pPTT), tonic cold pain (hand-immersion in iced water), and central pain mechanisms (temporal summation and conditioned pain modulation) were tested and compared between T1D and T2D. VDT was categorized into normal (< 18 V), intermediary (18–25 V), or high (> 25 V).

Results: In comparison to healthy, analysis adjusted for age, BMI, and gender revealed hypoalgesia to tibial (pPDT): p = 0.01, hyperalgesia to tonic cold pain: p < 0.01, and diminished temporal summation (arm: p < 0.01; abdomen: p < 0.01). In comparison to participants with T2D, participants with T1D were hypoalgesic to tibial pPDT: p < 0.01 and pPTT: p < 0.01, and lower VDT: p = 0.02. VDT was not associated with QST responses.

Conclusion: Participants with T1D were more hypoalgesic to bone pPDT and pPTT independent of lower VDT, indicating neuronal health toward normalization. Improved understanding of differentiated sensory profiles in T1D and T2D may identify improved clinical endpoints in future trials.

Comparison of diabetic and idiopathic sensory polyneuropathies with respect to nerve fibre affection and risk factors

Background and purpose

Chronic distal sensory or sensorimotor polyneuropathy is the most common pattern of polyneuropathy. The cause of this pattern is most often diabetes or unknown. This cross-sectional study is one of the first studies to compare the demographics, cardiovascular risk factors and clinical characteristics of diabetic polyneuropathy (DPN) with idiopathic polyneuropathy (IPN).

Methods

Patients with DPN were included from a sample of 389 patients with type 2 diabetes mellitus (T2DM) enrolled from a national cohort of patients with recently diagnosed T2DM (Danish Centre for Strategic Research in Type 2 Diabetes cohort). Patients with IPN were included from a regional cohort of patients with symptoms of polyneuropathy referred for workup at a combined secondary and tertiary neurological centre (database cohort).

Results

A total of 214 patients with DPN were compared with a total of 88 patients with IPN. Patients with DPN were older (67.4 vs 59 years) and had a longer duration of neuropathy symptoms. Patients with DPN had greater body mass index (32 vs 27.4 kg/m²) and waist circumference (110 cm vs 97 cm); higher frequency of hypertension diagnosis (72.9% vs 30.7%); lower total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol levels; and a higher prevalence of use of statins (81.8% vs 19.3%). DPN was associated with a slightly higher autonomic score and total score on the Neuropathy Symptom Score; lower frequency of hyperalgesia, allodynia and decreased vibration on quantitative sensory testing; lower intraepidermal nerve fibre density count and higher frequency of small-fibre neuropathy.

Conclusion

DPN and IPN showed clear differences in neuropathy characteristics, indicating that these two entities are to be regarded as aetiologically and pathogenetically distinct.

The characteristics of pain and dysesthesia in patients with diabetic polyneuropathy

Introduction/aims

Patients with diabetic polyneuropathy (DPN) may experience paresthesia, dysesthesia, and pain. We aimed to characterize the predictors, symptoms, somatosensory profile, neuropathy severity, and impact of painful DPN and dysesthetic DPN.

Methods

This study was a cross-sectional study of type 2 diabetes patients with confirmed DPN, diagnosed using widely accepted methods including a clinical examination, skin biopsy, and nerve conduction studies.

Findings

Of 126 patients with confirmed DPN, 52 had DPN without pain or dysesthesia, 21 had dysesthetic DPN, and 53 painful DPN. Patients with painful DPN were less physically active and suffered from more pain elsewhere than in the feet compared to patients with DPN without pain. Patients with painful DPN had the largest loss of small and large sensory fiber function, and there was a gradient of larger spatial distribution of sensory loss from DPN without dysesthesia/pain to dysesthetic DPN and to painful DPN. This could indicate that patients with dysesthesia had more severe neuropathy than patients without dysesthesia but less than patients with painful DPN. Patients with dysesthetic and painful DPN had higher symptom scores for depression and fatigue than those without dysesthesia/pain with no difference between dysesthetic and painful DPN.

Conclusions

There was a gradient of increasing sensory loss from DPN without dysesthesia/pain to dysesthetic DPN and to painful DPN. Pain and dysesthesia are common in DPN and both interfere with daily life. It is therefore important to consider dysesthesia when diagnosing and treating patients with neuropathy.

New horizons of biomaterials in treatment of nerve damage in diabetes mellitus: A translational prospective review

BACKGROUND

Peripheral nerve injury is a serious concern that leads to loss of neuronal communication that impairs the quality of life and, in adverse conditions, causes permanent disability. The limited availability of autografts with associated demerits shifts the paradigm of researchers to use biomaterials as an alternative treatment approach to recover nerve damage.

PURPOSE

The purpose of this study is to explore the role of biomaterials in translational treatment approaches in diabetic neuropathy.

STUDY DESIGN

The present study is a prospective review study.

METHODS

Published literature on the role of biomaterials in therapeutics was searched for.

RESULTS

Biomaterials can be implemented with desired characteristics to overcome the problem of nerve regeneration. Biomaterials can be further exploited in the treatment of nerve damage especially associated with PDN. These can be modified, customized, and engineered as scaffolds with the potential of mimicking the extracellular matrix of nerve tissue along with axonal regeneration. Due to their beneficial biological deeds, they can expedite tissue repair and serve as carriers of cellular and pharmacological treatments. Therefore, the emerging research area of biomaterials-mediated treatment of nerve damage provides opportunities to explore them as translational biomedical treatment approaches.

CONCLUSIONS

Pre-clinical and clinical trials in this direction are needed to establish the effective role of several biomaterials in the treatment of other human diseases.

Scores of peripheral neuropathic pain predicting long-term mortality in patients with type 2 diabetes: A retrospective cohort study

OBJECTIVES

Diabetic peripheral neuropathic pain (DPNP) is a prevalent chronic complication in patients with diabetes. Using a questionnaire is helpful for DPNP screening in outpatients. In this retrospective cohort, we aimed to examine whether DPNP diagnosed based on scoring questionnaires could predict long-term mortality in outpatients with type 2 diabetes.

METHODS

We enrolled 2318 patients who had joined the diabetes pay-for-performance program and completed the annual assessments, including both the identification pain questionnaire (ID pain) and Douleur Neuropathique en 4 questionnaire (DN4), between January 2013 and October 2013. Information on registered deaths was collected up to August 2019.

RESULTS

There was high consistency in the scores between the ID pain and DN4 (r = 0.935, P < 0.001). During the median follow-up of 6.2 years (interquartile range: 5.9-6.4 years), 312 patients deceased. Patients with an ID pain score of ≥ 2 had a higher mortality risk than those with a score of < 2 (hazard ratio [HR] = 1.394, 95%CI: 1.090-1.782), and patients with a DN4 score of ≥ 4 had a higher mortality risk than those with a score of < 4 (HR = 1.668, 95% confidence interval [CI]: 1.211-2.297). Patients consistently diagnosed with DPNP by the ID pain and DN4 had a significantly higher mortality risk (HR = 1.713, 95% CI: 1.223-2.398, P = 0.002), but not those discrepantly diagnosed with DPNP (P = 0.107), as compared with those without DPNP.

CONCLUSIONS

Both the ID pain and DN4 for DPNP screening were predictive of long-term mortality in patients with type 2 diabetes. However, a discrepancy in the diagnosis of DPNP weakened the power of mortality prediction.

The Treatment of Painful Diabetic Neuropathy

Painful diabetic peripheral neuropathy (painful-DPN) is a highly prevalent and disabling condition, affecting up to one-third of patients with diabetes. This condition can have a profound impact resulting in a poor quality of life, disruption of employment, impaired sleep, and poor mental health with an excess of depression and anxiety. The management of painful-DPN poses a great challenge. Unfortunately, currently there are no Food and Drug Administration (USA) approved disease-modifying treatments for diabetic peripheral neuropathy (DPN) as trials of putative pathogenetic treatments have failed at phase 3 clinical trial stage. Therefore, the focus of managing painful- DPN other than improving glycaemic control and cardiovascular risk factor modification is treating symptoms. The recommended treatments based on expert international consensus for painful- DPN have remained essentially unchanged for the last decade. Both the serotonin re-uptake inhibitor (SNRI) duloxetine and α2δ ligand pregabalin have the most robust evidence for treating painful-DPN. The weak opioids (e.g. tapentadol and tramadol, both of which have an SNRI effect), tricyclic antidepressants such as amitriptyline and α2δ ligand gabapentin are also widely recommended and prescribed agents. Opioids (except tramadol and tapentadol), should be prescribed with caution in view of the lack of definitive data surrounding efficacy, concerns surrounding addiction and adverse events. Recently, emerging therapies have gained local licenses, including the α2δ ligand mirogabalin (Japan) and the high dose 8% capsaicin patch (FDA and Europe). The management of refractory painful-DPN is difficult; specialist pain services may offer off-label therapies (e.g. botulinum toxin, intravenous lidocaine and spinal cord stimulation), although there is limited clinical trial evidence supporting their use. Additionally, despite combination therapy being commonly used clinically, there is little evidence supporting this practise. There is a need for further clinical trials to assess novel therapeutic agents, optimal combination therapy and existing agents to determine which are the most effective for the treatment of painful-DPN. This article reviews the evidence for the treatment of painful-DPN, including emerging treatment strategies such as novel compounds and stratification of patients according to individual characteristics (e.g. pain phenotype, neuroimaging and genotype) to improve treatment responses.

Optical coherence tomography of the retina combined with color Doppler ultrasound of the tibial nerve in the diagnosis of diabetic peripheral neuropathy

OBJECTIVE

To investigate the value of the retinal nerve fiber layer (RNFL) thickness in the optic disc and the cross-sectional area (CSA) of lower limb nerves in the diagnosis of diabetic peripheral neuropathy (DPN) separately and in combination.

METHODS

A total of 140 patients with type 2 diabetes were enrolled, including 51 patients with DPN (DPN group) and 89 patients without DPN (NDPN group). Clinical data and biochemical parameters were collected. Electromyography/evoked potential instrument was performed for nerve conduction study. Optical coherence tomography was performed to measure the RNFL thickness of the optic disc. Color Doppler ultrasound was performed to measure CSA of lower limb nerves.

RESULTS

The RNFL thickness was lower and the CSA of the tibial nerve (TN) in the DPN group was larger than that in the NDPN group. The album/urine creatinine ratio, diabetic retinopathy, and CSA of TN at 3 cm were positively correlated with DPN. The RNFL thickness in the superior quadrant of the optic disc was negatively correlated with DPN. For RNFL thickness to diagnose DPN, the area under the curve (AUC) of the superior quadrant was the largest, which was 0.723 (95% confidence interval [CI]: 0.645-0.805), and the best cutoff value was 127.5 μm (70.5% sensitivity, 72.1% specificity). For CSA of TN to diagnose DPN, the AUC of the distance of 5 cm was the largest, which was 0.660 (95% CI: 0.575-0.739), and the best cutoff value was 13.50 mm² (82.0% sensitivity, 41.6% specificity). For the combined index, the AUC was greater than that of the above two indicators, which was 0.755 (95% CI: 0.664-0.846), and the best cutoff value was 0.376 (64.3% sensitivity, 83.0% specificity).

CONCLUSIONS

Patients with DPN have a reduction of the RNFL thickness and an increase in the CSA of TN, and these two changes are related to DPN. The RNFL thickness of the optic disc and the CSA of TN can be used as diagnostic indicators of DPN, and the combination of the two indicators has a higher diagnostic value.