Evaluation of Serum Neurofilament Light Chain and Nerve Ultrasound in Diabetic Neuropathy

OBJECTIVE

To assess the role of serum neurofilament light chain (NfL) levels in individuals with diabetic polyneuropathy (DPN) compared with controls, as well as to highlight the different sonographic changes in DPN and determine if NfL correlates with sonographic, clinical, and functional parameters.

METHODS

Diabetic individuals with signs or symptoms consistent with peripheral nerve involvement were recruited. They were evaluated by examination, functional neuropathy severity scores, laboratory assessments (including NfL), nerve conduction studies (NCS), and ultrasound. Ultrasound was performed of the bilateral median, ulnar, tibial, fibular, sural, and vagus nerves, and cervical roots 5 and 6. Results were compared with age, sex, and body mass index matched healthy controls.

RESULTS

A total of 320 nerves from 20 patients and 480 nerves from 30 controls were evaluated. NfL was significantly elevated in those with diabetes with a mean and standard deviation of 6.95 ± 2.95 pg/mL in the diabetic group and 2.83 ± 0.77 pg/mL in controls (P < .001). Nerve cross-sectional area and serum NfL levels correlated significantly with clinical and functional parameters and with each other (P < .05).

CONCLUSION

Individuals with DPN have significantly higher NfL levels than healthy controls, and NfL levels correlate with ultrasonographic parameters. These findings may be useful for the diagnosis, prognosis, and disease monitoring of those with DPN, though further exploration is needed.

Tryptophan metabolism and small fibre neuropathy: a correlation study

Small nerve fibres located in the epidermis sense pain. Dysfunction of these fibres decreases the pain threshold known as small fibre neuropathy. Diabetes mellitus is accompanied by metabolic changes other than glucose, synergistically eliciting small fibre neuropathy. These findings suggest that various metabolic changes may be involved in small fibre neuropathy. Herein, we explored the correlation between pain sensation and changes in plasma metabolites in healthy Japanese subjects. The pain threshold evaluated from the intraepidermal electrical stimulation was used to quantify pain sensation in a total of 1021 individuals in the 2017 Iwaki Health Promotion Project. Participants with a pain threshold evaluated from the intraepidermal electrical stimulation index <0.20 mA were categorized into the pain threshold evaluated from the intraepidermal electrical stimulation index-low group (n = 751); otherwise, they were categorized into the pain threshold evaluated from the intraepidermal electrical stimulation index-high group (n = 270). Metabolome analysis of plasma was conducted using capillary electrophoresis time-of-flight mass spectrometry. The metabolite set enrichment analysis revealed that the metabolism of tryptophan was significantly correlated with the pain threshold evaluated from the intraepidermal electrical stimulation index in all participants (P < 0.05). The normalized level of tryptophan was significantly decreased in participants with a high pain threshold evaluated from the intraepidermal electrical stimulation index. In addition to univariate linear regression analyses, the correlation between tryptophan concentration and the pain threshold evaluated from the intraepidermal electrical stimulation index remained significant after adjustment for multiple factors (β = -0.07615, P < 0.05). These findings indicate that specific metabolic changes are involved in the deterioration of pain thresholds. Here, we show that abnormal tryptophan metabolism is significantly correlated with an elevated pain threshold evaluated from the intraepidermal electrical stimulation index in the Japanese population. This correlation provides insight into the pathology and clinical application of small fibre neuropathy.

Assessment of the severity of diabetic polyneuropathy aids in predicting the risk of developing diabetic complications in patients with untreated diabetes

This study aimed to determine the efficacy of assessing the severity of diabetic polyneuropathy (DPN) in patients with untreated diabetes. Seventy-two patients with untreated type 2 diabetes who were hospitalized for glycemic control were enrolled and divided into the following two groups: patients who had no prior diagnosis and patients who were unattended or had discontinued treatment. Electrophysiological criteria consistent with Baba's classification were used to diagnose and assess the severity of DPN. The patients were divided into three subgroups: no DPN (stage 0), mild DPN (stage 1), and moderate or more-severe DPN (stages 2-4). Intergroup comparisons were performed for the clinical characteristics and the results of the nerve conduction studies. Twenty-two (30%), 25 (35%), and 25 (35%) patients were categorized into the no DPN, mild DPN, and moderate or more-severe DPN subgroups, respectively. The number of patients who were unattended or had discontinued treatment in the moderate or more-severe DPN subgroup was significantly higher than that in the no DPN subgroup. The patients in the moderate or more-severe DPN subgroup had an increased risk of developing diabetic retinopathy and nephropathy, with odds ratios of 19.5 and 11.0 for advanced stages of retinopathy and nephropathy, respectively. Thus, the assessment of the severity of DPN could aid in the prediction of the risk of developing diabetic complications in patients with untreated diabetes.

Vitamin D-A New Therapeutic Target in the Management of Type 2 Diabetes Patients

Background: Vitamin D is a fat-soluble vitamin that prevents cardiovascular diseases and diabetes mellitus (DM). The present research aimed to study the impact of 25-hydroxyvitamin D (25(OH)D) level on the health status of patients with type 2 DM (T2DM) hospitalized in the "Pius Brînzeu" Emergency Clinical County University Hospital in Timisoara, Romania. Methods: The study retrospectively included 160 patients with T2DM who were clinically and biologically evaluated during hospitalization. Results: 13.1% of patients had optimal, 23.1% insufficient, and 63.8% deficient 25(OH)D values. Patients with 25(OH)D deficiency presented poorer glycemic control and were older, with higher weight, but had altered renal function, anemia, and lower iron values. Also, patients with associated neoplasia, diabetic neuropathy, cardiovascular disease (CVD), dementia, and grade 3 arterial hypertension (HTN) had lower values of 25(OH)D. An age > 55 years (sensitivity 69.9, specificity 82.5, AUROC 0.786, p < 0.001) and an HbA1c > 7.7% (sensitivity 89.3, specificity 92.9, AUROC 0.938, p < 0.001) predict 25(OH)D deficiency in T2DM patients. Conclusions: Vitamin D influences almost every system and organ in the body, so it should be a routine test for all patients with DM to correct the deficiency and prevent other diseases and complications.

Effectiveness of alpha-lipoic acid in patients with neuropathic pain associated with type I and type II diabetes mellitus: A systematic review and meta-analysis

BACKGROUND

This systematic review explores the most current evidence regarding the mechanisms of neuropathic pain in patients with different types of diabetes and how this pain affects different functional and structural components of the neuroanatomical pain pathways. The review also seeks to provide guidelines for the best approach and treatment for patients experiencing this type of pain. The objective is to determine the effectiveness of alpha-lipoic acid (ALA) in improving functional and symptomatic outcomes in patients with diabetes mellitus type I and type II.

OBJECTIVE

To determine the effectiveness of alpha-lipoic acid (ALA) in improving functional and symptomatic outcomes in patients with diabetes mellitus type I and type II.

METHODS

We systematically search MEDLINE (via PubMed), EMBASE, SCOPUS, the Cochrane Central Register of Controlled Trials, the Cumulative Index to Nursing and Allied Health Literature, and Web of Science databases.

RESULTS

The findings of this review show that different forms of ALA do not present statistically significant changes for any of the scales included, including total symptom score (standardized mean difference [SMD] = -3.59, confidence interval [CI] = -4.16 to -3.02, and P < .00001), neuropathy impairment score (SMD = -1.42, CI = -3.68 to 0.84, and P = .22), and neuropathy symptom checklist (SMD = -0.09, CI = -0.15 to -0.02, and P = .01).

CONCLUSION

In comparison to the use of a placebo, the findings suggest that ALA does not exhibit significant differences in terms of pain reduction and different functional scales. Moreover, no specific dosages are identified to support the use of ALA for the reduction of neuropathic pain.

Diabetic Polyneuropathy and Physical Activity in Type 1 Diabetes Mellitus: A Cross-Sectional Study

BACKGROUND

The purpose of this study is to access whether a personal attitude to physical activity (PA) may influence the appearance of diabetic polyneuropathy (DPN) patients with well-controlled type 1 diabetes mellitus.

METHODS

Ninety patients attending the diabetes technology outpatient clinic were enrolled. DPN was investigated according to the Toronto consensus diagnostic criteria. PA was assessed using the International Physical Activity Questionnaire.

RESULTS

PA was low in 21.1%, moderate in 42.2% and high in 36.7% of patients. According to Toronto criteria, we defined two categories: the first one with DPN absent or possible (57 (63.3%)) and a second one with DPN certain or probable (33 (36.7%)). The χ2-test of the PA groups and the DPN categories showed a statistically significant difference (p < 0.001), with less neuropathy in patients belonging to the group of moderate/high PA. Exposure to a minimum of 600 MET minutes/week was protective factor against the onset of DPN (odd ratio 0.221, c.i. 0.068-0.720, p = 0.012).

CONCLUSIONS

This study suggests that DPN is less present in type 1 diabetic patients with good metabolic control and a good personal habit of PA. Moderate-to-vigorous PA of at least 600 MET minutes/week might be a protective factor against DPN.

Nociceptive flexion reflex in small fibers neuropathy and pain assessments†

BACKGROUND

The nociceptive flexion reflex (NFR) is a polysynaptic and multisegmental spinal reflex that develops in response to a noxious stimulus and is characterized by the withdrawal of the affected body part. The NFR possesses two excitatory components: early RII and late RIII. Late RIII is derived from high-threshold cutaneous afferent A-delta fibers, which are prone to injury early in the course of diabetes mellitus (DM) and may lead to neuropathic pain. We investigated NFR in patients with DM with different types of polyneuropathies to analyze the role of NFR in small fiber neuropathy (SFN).

METHODS

We included 37 patients with DM and 20 healthy participants of similar age and sex. We performed the Composite Autonomic Neuropathy Scale-31, modified Toronto Neuropathy Scale, and routine nerve conduction studies. We grouped the patients into large fiber neuropathy (LFN), SFN, and no overt neurological symptom/sign groups. In all participants, NFR was recorded on anterior tibial (AT) and biceps femoris (BF) muscles after train stimuli on the sole of the foot, and NFR-RIII findings were compared.

RESULTS

We identified 11 patients with LFN, 15 with SFN, and 11 with no overt neurological symptoms or signs. The RIII response on the AT was absent in 22 (60%) patients with DM and 8 (40%) healthy participants. The RIII response on the BF was absent in 31 (73.8%) patients and 7 (35%) healthy participants (P = .001). In DM, the latency of RIII was prolonged, and the magnitude was reduced. Abnormal findings were seen in all subgroups; however, they were more prominent in patients with LFN compared to other groups.

CONCLUSIONS

The NFR-RIII was abnormal in patients with DM even before the emergence of the neuropathic symptoms. The pattern of involvement before neuropathic symptoms was possibly related to an earlier loss of A-delta fibers.

Dysmetabolism-related Early Sensory Deficits and Their Relationship With Peripheral Neuropathy Development

AIM

To investigate the association of early peripheral sensory dysfunction (EPSD) identified through quantitative sensory testing (QST) with factors related to a dysmetabolic status in individuals with and without type 2 diabetes (T2DM) without peripheral neuropathy (PN), and the impact of those factors on PN development.

METHODS

A total of 225 individuals (117 and 108 without and with T2DM, respectively) without PN based on clinical and electrophysiological criteria were analyzed. Comparative analysis was conducted between those identified as "healthy" and those with EPSD based on a standardized QST protocol. A total of 196 were followed-up over a mean of 2.64 years for PN occurrence.

RESULTS

Among those without T2DM, apart from male sex, height, and higher fat and lower lean mass, only higher insulin resistance (IR; homeostatic model assessment for IR: odds ratio [OR], 1.70; P = .009; McAuley index OR, 0.62, P = .008), was independently associated with EPSD. In T2DM, metabolic syndrome (OR, 18.32; P < .001) and skin advanced glycation end-products (AGEs; OR, 5.66; P = .003) were independent predictors of EPSD. In longitudinal analysis, T2DM (hazard ratio [HR], 3.32 vs no diabetes mellitus; P < .001), EPSD (adjusted HR, 1.88 vs healthy; P = .049 adjusted for diabetes mellitus and sex), higher IR and AGEs predicted PN development. Among the 3 EPSD-associated sensory phenotypes, "sensory loss" was most strongly associated with PN development (adjusted HR, 4.35; P = .011).

CONCLUSION

We demonstrate for the first time the utility of a standardized QST-based approach in identifying early sensory deficits in individuals with and without T2DM. These are associated with a dysmetabolic status signified by IR markers, metabolic syndrome, and higher AGEs, which in turn are shown to influence PN development.

Inflammatory Markers Used as Predictors of Subclinical Atherosclerosis in Patients with Diabetic Polyneuropathy

BACKGROUND

peripheral arterial disease (PAD) is identified late in diabetic patients because, in the majority of cases, it is associated with diabetic peripheral neuropathy, resulting in little or no symptoms, or symptoms that are completely neglected.

METHODS

In this study were enrolled all patients over 18 years of age, with diabetes mellitus type II for more than a year with poor glycemic control, diagnosed with diabetic polyneuropathy admitted to the Diabetology Department, Emergency County Hospital of Targu Mures, Romania between January 2020 and March 2023. We divided the patients into two groups, based on the presence or absence of subclinical atherosclerosis in the lower limb, named "SA" and "non-SA".

RESULTS

Patients in the SA group were older (p = 0.01) and had a higher incidence of IHD (p = 0.03), history of MI (p = 0.02), and diabetic nephropathy (p = 0.01). Moreover, patients with subclinical atherosclerosis had a higher BMI (p < 0.0001) and a longer duration of diabetes (p < 0.0001). Among all patients, the systemic inflammatory markers, MLR (r = 0.331, p < 0.001), NLR (r = 0.517, p < 0.001), PLR (r = 0.296, p < 0.001), SII (r = 0.413, p < 0.001), as well as BMI (r = 0.241, p < 0.001) and HbA1C (r = 0.489, p < 0.001), demonstrated a strong positive correlation with the diabetes duration. The multivariate logistic regression analysis showed that older patients (OR: 2.58, p < 0.001), the male gender (OR: 2.30, p = 0.006), a higher baseline levels of BMI (OR: 7.71, p < 0.001), and the duration of diabetes (OR: 8.65, p < 0.001) are predictors of subclinical atherosclerosis in DN patients. Additionally, the high baseline levels of all systemic inflammatory markers (for all: p < 0.001) and poor diabetes management (OR: 10.4, p < 0.001 for HbA1C; OR: 10.78, p < 0.001 for admission glucose) are independent predictors of SA.

CONCLUSIONS

the inflammatory markers, NLR, MLR, PLR, and SII, being cheap and easy to collect in routine medical practice from the standard blood tests, could be an important step in predicting vascular outcomes in diabetic patients and the disease's progression, playing a key role in follow-up visits in type-2 diabetic patients and PAD patients.

miR-499a rs3746444 A>G Polymorphism Is Correlated with Type 2 Diabetes Mellitus and Diabetic Polyneuropathy in a Romanian Cohort: A Preliminary Study

Type 2 diabetes mellitus (T2DM) is a common metabolic disorder that results from complex interactions of both environmental and genetic factors. Many single nucleotide polymorphisms (SNPs), including noncoding RNA genes, have been investigated for their association with susceptibility to T2DM and its complications, with little evidence available regarding Caucasians. The aim of the present study was to establish whether four miRNA SNPs (miR-27a rs895819 T>C, miR-146a rs2910164 G>C, miR-196a2 rs11614913 C>T, and miR-499a rs3746444 A>G) are correlated with susceptibility to T2DM and/or diabetic polyneuropathy (DPN) in a Romanian population. A total of 167 adult T2DM patients and 324 age- and sex-matched healthy controls were included in our study. miRNA SNPs were detected by real-time PCR using a TaqMan genotyping assay. A significant association with T2DM was observed only for the miR-499a rs3746444 A>G SNP in all the tested models, and the frequencies of both the miR-499a rs3746444 AG and the GG genotypes were higher in the T2DM patients compared to the controls. No correlation was observed for the miR-27a rs895819 T>C, miR-146a rs2910164 G>C, or miR-196a2 rs11614913 C>T SNPs in any genetic model. When we assessed the association of these SNPs with DPN separately, we found a positive association for the miR-499a rs3746444 SNP in both codominant and dominant models (OR 6.47, 95% CI: 1.71-24.47; OR 2.30, 95% CI: 1.23-4.29, respectively). In conclusion, this study shows that miR-499a rs3746444 A>G may influence both T2DM and DPN susceptibility, with carriers of the GG genotype and the G allele being at an increased risk in the Romanian population.

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.

Stem Cell Therapy in Diabetic Polyneuropathy: Recent Advancements and Future Directions

Diabetic polyneuropathy (DPN) is the most frequent, although neglected, complication of long-term diabetes. Nearly 30% of hospitalized and 20% of community-dwelling patients with diabetes suffer from DPN; the incidence rate is approximately 2% annually. To date, there has been no curable therapy for DPN. Under these circumstances, cell therapy may be a vital candidate for the treatment of DPN. The epidemiology, classification, and treatment options for DPN are disclosed in the current review. Cell-based therapies using bone marrow-derived cells, embryonic stem cells, pluripotent stem cells, endothelial progenitor cells, mesenchymal stem cells, or dental pulp stem cells are our primary concern, which may be a useful treatment option to ease or to stop the progression of DPN. The importance of cryotherapies for treating DPN has been observed in several studies. These findings may help for the future researchers to establish more focused, accurate, effective, alternative, and safe therapy to reduce DPN. Cell-based therapy might be a permanent solution in the treatment and management of diabetes-induced neuropathy.

[Efficacy and safety of Cytoflavin in the treatment of diabetic polyneuropathy: results of a multicenter, double-blind, placebo-controlled, randomized CYLINDER study]

OBJECTIVE

The purpose of the present double-blind, placebo-controlled, randomized clinical trial was to evaluate the efficacy and safety of Cytoflavin in patients with diabetic polyneuropathy (DPN).

MATERIAL AND METHODS

Investigational therapy was administered in two steps: intravenous infusions of experimental drug/placebo for 10 days followed by oral administration for 75 days. In 10 clinical centers, 216 patients aged 45-74 years with a diagnosis of type 2 diabetes mellitus, symptomatic distal sensorimotor DPN, confirmed no earlier than 1 year before screening, on stable therapy (no change of drugs and doses) by oral hypoglycemic drugs, intermediate-acting, long-acting or extra-long-acting insulin, and/or GLP-1 receptor agonists.

RESULTS

By the end of treatment, the change of the Total Symptom Score (TSS) in the experimental group was -2.65 points, in the placebo group -1.73 points (p<0.001). Improvement of symptoms in the experimental group was achieved regardless of the degree of compensation for type 2 diabetes (both in those with Hb1Ac <8.0% and in those with Hb1Ac ≥8.0%), but demonstrated better results in patients with less severe baseline symptoms (TSS <7.5). Improvement in the components of the TSS scale «paresthesia» and «numbness» occurred as early as on day 11 of therapy; by the end of treatment, a significant decrease in the «burning» component was also demonstrated. The experimental drug had a positive safety profile.

CONCLUSION

Cytoflavin, intravenous solution and enteric-coated tablets (SPTF Polysan Ltd.) is indicated for the symptomatic treatment of DPN.

[The role of inflammation in the development of diabetic polyneuropathy and the possibility of its correction]

OBJECTIVE

To study the effect of the combined drug Cytoflavin on the mechanisms of nonspecific inflammation in the treatment of diabetic polyneuropathy (DPN) with an assessment of the dynamics of the TNF-α index.

MATERIAL AND METHODS

An open comparative prospective observation of patients with a history of DPN for more than 5 years and a high level of TNF-α was carried out. All patients underwent basic oral combined hypoglycemic therapy, the main group used the combined drug Cytoflavin 10 ml (per 200 ml 0.9% NaCl) for 10 days, followed by the transition to the enteral form of the drug, 2 tablets 2 times a day for 1 months The main indication for the appointment of Cytoflavin was the presence of comorbid pathology in the form of cerebrovascular disease in all studied patients. The severity of clinical symptoms of DPN, the quality of life (QOL) of patients, as well as the dynamics of the level of TNF-α as an indicator reflecting the process of inflammation were assessed.

RESULTS

As a result of the treatment in the study group, there was an improvement in QoL, a decrease in the severity of sensory complaints and a decrease in the level of TNF-α, which may indicate a possible anti-inflammatory mechanism of the combined drug Cytoflavin.

CONCLUSION

Cytoflavin can inhibit inflammation and reduce the severity of sensitive disorders in patients with DPN.

Clinical Utility of Boston-CTS and Six-Item CTS Questionnaires in Carpal Tunnel Syndrome Associated with Diabetic Polyneuropathy

Diabetic polyneuropathy (DPN) is the most frequent complication of diabetes. Carpal tunnel syndrome (CTS), one of the most common neuropathies, is a chronic compression of the median nerve at the wrist. In our prospective cross-sectional study, we enrolled patients with type 2 diabetes presenting with signs and symptoms suggestive of DPN (n = 53). We aimed to compare two clinical scales: the Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) and the six-item CTS symptoms scale (CTS-6), with nerve conduction studies (NCS) for detecting CTS in patients with DPN. Carpal tunnel syndrome and DPN were clinically evaluated, and the diagnosis was confirmed by NCS. Depending on the NCS parameters, the study group was divided into patients with and without DPN. For each group, we selected patients with CTS confirmed through NCS, and the results were compared with the BCTQ and CTS-6 scales. The clinical evaluation of CTS performed through BCTQ and CTS-6 was statistically significantly different between patients with and without CTS. When comparing the BCTQ questionnaire with the NCS tests, we found area under the curve (AUC) = 0.76 (95% CI 0.65-0.86) in patients with neuropathy and AUC = 0.72 (95% CI 0.55-0.88) in patients without neuropathy. At the same time, the AUC values of the CTS-6 scale were 0.76 (95% CI 0.61-0.88) in patients with neuropathy and 0.70 (95% CI 0.51-0.86) in patients without neuropathy. Using multiple logistic regression, we demonstrated that DPN increased the chances of detecting CTS using the two questionnaires. The Boston Carpal Tunnel Syndrome and CTS-6 questionnaires can be used in the diagnosis of CTS in diabetic patients with and without DPN but with moderate AUC. The presence of DPN increased the chances of detecting CTS using the BCTQ questionnaire and the CTS-6 scale.

Recent updates in the treatment of diabetic polyneuropathy

Distal symmetric diabetic peripheral polyneuropathy (DPN) is the most common form of neuropathy in the world, affecting 30 to 50% of diabetic individuals and resulting in significant morbidity and socioeconomic costs. This review summarizes updates in the diagnosis and management of DPN. Recently updated clinical criteria facilitate bedside diagnosis, and a number of new technologies are being explored for diagnostic confirmation in specific settings and for use as surrogate measures in clinical trials. Evolving literature indicates that distinct but overlapping mechanisms underlie neuropathy in type 1 versus type 2 diabetes, and there is a growing focus on the role of metabolic factors in the development and progression of DPN. Exercise-based lifestyle interventions have shown therapeutic promise. A variety of potential disease-modifying and symptomatic therapies are in development. Innovations in clinical trial design include the incorporation of detailed pain phenotyping and biomarkers for central sensitization.

SEPT9 Upregulation in Satellite Glial Cells Associated with Diabetic Polyneuropathy in a Type 2 Diabetes-like Rat Model

Despite the worldwide prevalence and severe complications of type 2 diabetes mellitus (T2DM), the pathophysiological mechanisms underlying the development of diabetic polyneuropathy (DPN) are poorly understood. Beyond strict control of glucose levels, clinical trials for reversing DPN have largely failed. Therefore, understanding the pathophysiological and molecular mechanisms underlying DPN is crucial. Accordingly, this study explored biochemical and neuropathological deficits in a rat model of T2DM induced through high-fat diet (HFD) feeding along with two low-dose streptozotocin (STZ) injections; the deficits were explored through serum lipid, neurobehavioral, neurophysiology, neuropathology, and immunohistochemistry examinations. Our HFD/STZ protocol induced (1) mechanical hyperalgesia and depression-like behaviors, (2) loss of intraepidermal nerve fibers (IENFs) and reduced axonal diameters in sural nerves, and (3) decreased compound muscle action potential. In addition to hyperglycemia, which was correlated with the degree of mechanical hyperalgesia and loss of IENFs, we observed that hypertriglyceridemia was the most dominant deficit in the lipid profiles of the diabetic rats. In particular, SEPT9, the fourth component of the cytoskeleton, increased in the satellite glial cells (SGCs) of the dorsal root ganglia (DRG) in the T2DM-like rats. The number of SEPT9(+) SGCs/DRG was correlated with serum glucose levels and mechanical thresholds. Our findings indicate the putative molecular mechanism underlying DPN, which presumably involves the interaction of SGCs and DRG neurons; nevertheless, further functional research is warranted to clarify the role of SEPT9 in DPN.

Diabetic neuropathy is a generalized phenomenon with impact on hand functional performance and quality of life

BACKGROUND

Diabetic sensorimotor peripheral neuropathy (DSPN) is usually considered to affect predominantly the lower limbs (LL-N), while the impact of upper limb neuropathy (UL-N) on hand functional performance and quality of life (QoL) has not been evaluated systematically. This study aims to investigate the prevalence and characteristics of UL-N and its functional and psychosocial consequences in type 2 diabetes.

METHODS

Individuals with type 2 diabetes (n=141) and an age- and sex-matched control group (n=73) underwent comprehensive assessment of neuropathy, hand functional performance and psychosocial status.

RESULTS

The prevalence of UL-N was 30.5% in patients with diabetes and that of LL-N 49.6%, with 25.5% exhibiting both. Patients with diabetes showed similar sensory phenotype regarding both large and small fiber functions in hands and feet. Patients with UL-N showed reduced manual dexterity, but normal hand grip force. Additionally, there was a correlation between reduced dexterity and sensory deficits. Patients with UL-N had reduced estimates of psychosocial health including health-related QoL compared to control subjects and patients without UL-N. UL-N correlated with the severity of LL-N, but not with duration of diabetes, glycaemia, age, or sex.

CONCLUSIONS

This study points to a substantial prevalence of UL-N in type 2 diabetes. The sensory phenotype of patients with UL-N was similar to LL-N and was characterized by loss of sensory function. Our study demonstrated an association of UL-N with impaired manual dexterity and reduced health-related QoL. Thus, upper limb sensorimotor functions should be assessed early in patients with diabetes.

Matrix Metalloproteinase-2 (MMP-2) and-9 (MMP-9) Gene Variants and Microvascular Complications in Type 2 Diabetes Patients

Vascular complications are the leading cause of increased morbidity and mortality of diabetic patients. It has been postulated that matrix metalloproteinases MMP-2 and MMP-9, zinc-dependent endopeptidases through remodeling of the extracellular matrix, can contribute to the onset and progression of diabetic vascular complications. The aim of our study was to assess whether there is a major difference in single nucleotide polymorphisms in the MMP-2 (at position -1306C˃T) and MMP-9 (at position -1562C˃T) gene in type 2 diabetic patients and healthy controls and to determine whether there is an association of these gene variants with the presence of microvascular complications in diabetic patients. Our study included 102 type 2 diabetes patients and a control group which was comprised of 56 healthy controls. All diabetic patients were screened for microvascular diabetes complications. Genotypes were detected by polymerase chain reactions followed by restriction analyses with specific endonucleases and their frequencies were determined. The MMP-2 variant -1306C>T showed a negative correlation with type 2 diabetes (p=0.028). It was also shown that the presence of the -1306C allele increases the probability of developing type 2 diabetes. This was a 2.2 fold increase and that the -1306 T allele has a protective role in regards to type 2 diabetes. The MMP-2 variant -1306T showed a negative correlation with diabetic polyneuropathy (p=0.017), meaning that allele-1306T has a protective role in regards to diabetic polyneuropathy while the presence of allele -1306C increases the probability of developing diabetic polyneuropathy by 3.4 fold. Our study showed that the MMP-2 gene variant (-1306C) doubles the risk of developing type 2 diabetes, and for the first time an association of this gene variant and the presence of diabetic polyneuropathy was shown.

Conditioned pain modulation is more efficient in patients with painful diabetic polyneuropathy than those with nonpainful diabetic polyneuropathy

ABSTRACT

Endogenous pain modulation, as tested by the conditioned pain modulation (CPM) protocol, is typically less efficient in patients with chronic pain compared with healthy controls. We aimed to assess whether CPM is less efficient in patients with painful diabetic polyneuropathy (DPN) compared with those with nonpainful DPN. Characterization of the differences in central pain processing between these 2 groups might provide a central nervous system explanation to the presence or absence of pain in diabetic neuropathy in addition to the peripheral one. Two hundred seventy-one patients with DPN underwent CPM testing and clinical assessment, including quantitative sensory testing. Two modalities of the test stimuli (heat and pressure) conditioned to cold noxious water were assessed and compared between patients with painful and nonpainful DPN. No significant difference was found between the groups for pressure pain CPM; however, patients with painful DPN demonstrated unexpectedly more efficient CPMHEAT (-7.4 ± 1.0 vs -2.3 ± 1.6; P = 0.008). Efficient CPMHEAT was associated with higher clinical pain experienced in the 24 hours before testing (r = -0.15; P = 0.029) and greater loss of mechanical sensation (r = -0.135; P = 0.042). Moreover, patients who had mechanical hypoesthesia demonstrated more efficient CPMHEAT (P = 0.005). More efficient CPM among patients with painful DPN might result from not only central changes in pain modulation but also from altered sensory messages coming from tested affected body sites. This calls for the use of intact sites for proper assessment of pain modulation in patients with neuropathy.

Magnetic Resonance Neurography Reveals Smoking-Associated Decrease in Sciatic Nerve Structural Integrity in Type 2 Diabetes

Objective

It is controversially discussed in how far smoking contributes to diabetic polyneuropathy (DPN) in type 2 diabetes (T2D). Diffusion-weighted magnetic resonance neurography (MRN) at 3 Tesla has been shown to provide objective values for structural nerve integrity in patients with T2D. The aim of this study was to investigate the contribution of cigarette smoking on structural nerve integrity in T2D.

Methods

This cross-sectional prospective cohort study investigated the structural integrity of the sciatic nerve in 10 smokers, 40 never-smokers, and 20 ex-smokers with T2D and 10 healthy control subjects, using diffusion tensor imaging MRN at 3 Tesla and semi-automated nerve fiber tracking. Results were correlated with clinical, electrophysiological, and serological data.

Results

The sciatic nerve’s fractional anisotropy (FA), a parameter for structural nerve integrity, was significantly lower in smokers with T2D when compared to controls (p = 0.002) and never-smokers (p = 0.015), and lower in ex-smokers when compared to controls (p = 0.015). In addition, sciatic nerve radial diffusivity, a marker of myelin damage, was increased in smokers versus controls and never-smokers (p = 0.048, p = 0.049, respectively). Furthermore, FA in T2D patients was negatively correlated with clinical and electrophysiological markers of DPN. FA also showed negative correlations with the pulse wave velocity, a marker of arterial stiffness and associated microangiopathy, in controls (r = −0.70; p = 0.037), never-smokers (r = −0.45; p = 0.004), ex-smokers (r = −0.55; p = 0.009), and a similar trend in smokers (r = −0.63; p = 0.076). Negative correlations were found between FA and skin auto-fluorescence, a marker of tissue advanced glycation end product accumulation and therefore long-term glycemic stress in T2D, in never-smokers (r = −0.39; p = 0.020) and smokers (r = −0.84; p = 0.004), but not in ex-smokers (r = −0.07; p = 0.765).

Conclusion

The findings indicate that smoking contributes to sciatic nerve damage in T2D, potentially worsening DPN due to glycemic stress and less microangiopathy-associated myelin damage in active smokers, while angiopathic effects predominate in ex-smokers. To stop smoking may therefore pose a promising preventive measure to slow the progression of DPN in T2D.

Recent updates in the treatment of diabetic polyneuropathy

Distal symmetric diabetic peripheral polyneuropathy (DPN) is the most common form of neuropathy in the world, affecting 30 to 50% of diabetic individuals and resulting in significant morbidity and socioeconomic costs. This review summarizes updates in the diagnosis and management of DPN. Recently updated clinical criteria facilitate bedside diagnosis, and a number of new technologies are being explored for diagnostic confirmation in specific settings and for use as surrogate measures in clinical trials. Evolving literature indicates that distinct but overlapping mechanisms underlie neuropathy in type 1 versus type 2 diabetes, and there is a growing focus on the role of metabolic factors in the development and progression of DPN. Exercise-based lifestyle interventions have shown therapeutic promise. A variety of potential disease-modifying and symptomatic therapies are in development. Innovations in clinical trial design include the incorporation of detailed pain phenotyping and biomarkers for central sensitization.

The Effect of Structured Exercise Compared with Education on Neuropathic Signs and Symptoms in People at Risk of Neuropathic Diabetic Foot Ulcers: A Randomized Clinical Trial

Background and Objectives: Lifestyle interventions such as exercise prescription and education may play a role in the management of peripheral neuropathy in people with diabetes. The aim of this study was to determine the effect of undertaking an exercise program in comparison with an education program on the signs and symptoms of peripheral neuropathy in people with diabetes at risk of neuropathic foot ulceration. Materials and Methods: Twenty-four adult participants with diabetes and peripheral neuropathy were enrolled in this parallel-group, assessor blinded, randomised clinical trial. Participants were randomly allocated to one of two 8-week lifestyle interventions, exercise or education. The primary outcome measures were the two-part Michigan Neuropathy Screening Instrument (MNSI) and vibratory perception threshold (VPT). Secondary outcome measures included aerobic fitness, balance and lower limb muscular endurance. Results: Participants in both lifestyle interventions significantly improved over time for MNSI clinical signs (MD: −1.04, 95% CI: −1.68 to −0.40), MNSI symptoms (MD: −1.11, 95% CI: −1.89 to −0.33) and VPT (MD: −4.22, 95% CI: −8.04 to −0.40). Although the interaction effects did not reach significance, changes in values from pre to post intervention favoured exercise in comparison to control for MNSI clinical signs (MD −0.42, 95% CI −1.72 to 0.90), MNSI clinical symptoms (MD −0.38, 95% CI −1.96 to 1.2) and VPT (MD −4.22, 95% CI −12.09 to 3.65). Conclusions: Eight weeks of exercise training or lifestyle education can improve neuropathic signs and symptoms in people with diabetes and peripheral neuropathy. These findings support a role for lifestyle interventions in the management of peripheral neuropathy.

The Effects of Diabetic Polyneuropathy and Autonomic Neuropathy on Bone Turnover

Background: The effect of diabetic polyneuropathy (DPN) and autonomic neuropathy (AN) on bone turnover in type 2 diabetes mellitus (DM) is uncertain due to the lack of data. In this study, we tried to determine the effect of DPN and AN on bone metabolism. Materials and Methods: The study included patients with type 2 DM (aged 18-80 years) and age-matched healthy individuals who presented to the Departments of Metabolism and Diabetes, Geriatrics, and General Internal Medicine, Cerrahpaşa Medical School, Istanbul University. The patients were examined to find out whether they had AN, and neuropathy scores were recorded by exploring peripheral neuropathy. Bone mineral density was measured by dual-energy X-ray (DXA). Demographic characteristics, the presence of microvascular complications, and biochemical data were obtained from patients' files. Serum cross-linked C-telopeptide (Ctx), osteocalcin, and bone-specific alkaline phosphatase (B-ALP) were analyzed. Results: The study comprised a total of 64 patients: 23 had type 2 DM and osteoporosis (OP) (duration of diabetes 10.1 ± 7 years; mean age 63 ± 9.1 years; female/male 18/5; Group 1), 41 had type 2 DM and non-OP (duration of diabetes 10.3 ± 7.6 years; mean age 58 ± 7.4 years; female/male 30/11; Group 2), and 26 healthy volunteers made up the control group (mean age 62 ± 11.9 years; female/male 14/12; Group 3). The bone turnover parameters were lower in type 2 DM individuals. The levels of osteocalcin (13.3 ± 5.2 ng/mL) and B-ALP (44.7 ± 10.9 IU/L) in patients with type 2 DM were lower than those of healthy subjects: osteocalcin (20.6 ± 10 ng/mL) and B-ALP (111 ± 31.4 IU/L; P = 0.001 and P = 0.000, respectively). Ctx levels (193.5 ± 49.3; 207.6 ± 40 ng/mL) were recorded to be similar (P = 0.2). AN was also noted as a risk factor for OP. For patients without AN, the likelihood of developing OP (odds ratio) was 0.7. The corresponding ratio for patients with AN was 9.3. Conclusions: Among the independent variables, the neuropathy score was determined to have an impact on bone turnover. AN was identified to be a significant risk factor for OP.

Zinc deficiency correlates with severity of diabetic polyneuropathy

OBJECTIVES

There are controversies about the role of zinc in the development of both types 1 and 2 diabetes. The aim of this study was to assess serum zinc level in diabetic patients with and without peripheral neuropathy in comparison to healthy controls and to explore the possible relationship between serum zinc level and severity of peripheral neuropathy.

METHODS

This case control study was conducted on 120 subjects: 40 patients fulfilled the criteria for diagnosis of probable diabetic polyneuropathy (DPN), 40 diabetic patients without polyneuropathy (N-DPN) and 40 healthy controls. DPN patients were submitted to clinical assessment of diabetic neuropathy using neuropathy symptom and change (NSC) scale, Michigan Neuropathy Screening Instrument Physical Assessment (MNSI) scale and electrophysiological assessment using nerve conduction study. Zinc serum level was measured in all subjects included in this study using direct colorimetric test method.

RESULTS

Diabetic patients with and without neuropathy were found to have significantly lower mean values of serum zinc than healthy controls (p = .025,  .03 respectively). There is a statistically significant negative correlation between zinc serum level and hemoglobin A1C (HA1C) (p ˂ .001), NSC score (p = .001) and MNSI score (p = .003) in DPN group. There were also statistically significant correlations between zinc serum level and nerve conduction study values.

CONCLUSION

Zinc deficiency significantly correlates with the severity of DPN and glycemic control.

Sustainable Effects of Human Dental Pulp Stem Cell Transplantation on Diabetic Polyneuropathy in Streptozotocine-Induced Type 1 Diabetes Model Mice

Dental pulp stem cells (DPSCs) are suitable for use in regenerative medicine. Cryopreserved human DPSCs (hDPSCs) ameliorate diabetic polyneuropathy, and the effects of hDPSC transplantation are related to VEGF and NGF secretion. This study evaluated the long-term effects of a single transplantation of hDPSCs on diabetic polyneuropathy. hDPSCs were obtained from human third molars extracted for orthodontic treatment, which were then transplanted into the unilateral hindlimb skeletal muscles 8 weeks after streptozotocin injection in nude mice. The effects of hDPSC transplantation were analyzed at 16 weeks post-transplantation. DPSC transplantation significantly improved delayed nerve conduction velocity, decreased blood flow, and increased sensory perception thresholds. Furthermore, the hDPSC-conditioned medium promoted the neurite outgrowth of dorsal root ganglion neurons. In conclusion, the therapeutic effects of hDPSC transplantation with a single injection last for prolonged periods and may be beneficial in treating long-term diabetic polyneuropathy.

Falls in individuals with type 2 diabetes; a cross-sectional study on the impact of motor dysfunction, postural instability and diabetic polyneuropathy

AIM

To estimate the incidence of falls in individuals with type 2 diabetes compared to healthy controls and to describe the characteristics of fallers with type 2 diabetes in relation to motor dysfunction, postural instability and diabetic polyneuropathy (DPN).

METHODS

This is a cross-sectional study of individuals with type 2 diabetes with DPN (n = 54), without DPN (n = 38) and healthy controls (n = 39). Falls were recorded within the preceding year. DPN was defined by clinical scores and nerve conduction studies. Motor function was assessed by a 6-min walk test (6 MWT), five-time sit-to-stand test (FTSST) and isokinetic dynamometry at the non-dominant ankle and knee. An instability index (ST) was measured using static posturography. Univariate and bivariate descriptive statistics were used for group comparisons.

RESULTS

Compared with healthy controls, individuals with diabetes had a higher incidence of falls 36%, (n = 33) versus 15%, (n = 6), p = 0.02. There were no differences in falls when comparing individuals with and without DPN. Fallers had an impaired 6 MWT versus non-fallers (450 ± 153 m vs. 523 ± 97 m respectively), a slower FTSST (11.9 ± 4.2 s vs. 10.3 ± 2.9 s respectively) and a higher ST (53 ± 29 vs. 41 ± 17 respectively), p < 0.02 for all.

CONCLUSION

Individuals with type 2 diabetes reported a higher number of falls within the preceding year compared to healthy controls, irrespective of the presence of DPN. The main factors associated with falls were increased postural instability, lower walking capacity and slower sit-to-stand movements. The 6 MWT, FTSST and posturography should be considered in future screening programs in identification of individuals at risk for falls.

Diabetic polyneuropathy: Bridging the translational gap

Clinical trials for diabetic polyneuropathy (DPN) have failed to identify therapeutic impacts that have arrested or reversed the disorder, despite a long history. This review considers DPN in the context of a unique neurodegenerative disorder that targets peripheral neurons and their companion glial cells. The approach is to examine what cells, cell substructures, and pathways are implicated in causing DPN and how they might be addressed therapeutically. These include axonopathy, neuronopathy, hyperglycemia, polyol flux, advanced glycation endproduct (AGE)-receptor AGE signaling, growth factor disruption, abnormal insulin signaling, and abnormalities of other intrinsic neuron pathways. Mitochondrial dysfunction and lipid toxicity are largely delegated to the companion review in this issue by Stino and Feldman. Finally, the linkage between axon plasticity of cutaneous nerves, peripheral neuroregenerative pathways, and diabetes are discussed.

A Review of Alternative Treatment Options in Diabetic Polyneuropathy

Currently there is no recognized curative treatment for diabetic polyneuropathy (DPN). Strict glucose control and symptomatic pain relief are the first line management routes. DPN is a common complication of diabetes and has a major detrimental influence on the quality of life (QOL) for many patients. Due to the scope of the problem, it is imperative that treatment options which impede DPN's progression and restore sensorineural function should be researched comprehensively and made available to the masses at an economical cost. We reviewed a multitude of atypical treatment options for DPN including capsaicin, lidocaine, acupuncture, electrical nerve stimulation, alpha lipoic acid, benfotiamine, and acetyl-l-carnitine and explored the evidence to date regarding their safety and efficacy. Most of these options have been around for a long time and have promising pilot studies or small-scale trials focused on DPN treatment.

Assessing the epidemiological disease burden and health insurance treatment cost of diabetic polyneuropathy based on health insurance claims data

Összefoglaló. Bevezetés: Az idegrendszeri károsodás az egyik leggyakrabban kialakuló komplikáció a cukorbetegek körében, mely az egyénnek és a finanszírozónak is jelentős terhet jelent. Célkitűzés: Elemzésünk célja volt a diabeteses polyneuropathia okozta epidemiológiai és egészségbiztosítási betegségteher elemzése. Adatok és módszerek: Az adatok a Nemzeti Egészségbiztosítási Alapkezelő (NEAK) finanszírozási adatbázisából származnak, és a 2018. évet fedik le. Meghatároztuk az éves betegszámokat és a 100 000 lakosra jutó igénybevételi prevalenciát, továbbá az éves egészségbiztosítási kiadásokat korcsoportos és nemenkénti bontásban és ellátási típusonként. A vizsgált kórképet a Betegségek Nemzetközi Osztályozása (10. revízió) szerinti G6320-as kóddal azonosítottuk. Eredmények: A diabeteses polyneuropathia kezelésére a NEAK 6,63 milliárd Ft (24,52 millió USD; 20,78 millió EUR) egészségbiztosítási kiadást fordított 2018-ban. E költségek legnagyobb hányadát a gyógyszerek ártámogatása adta (78,29%). A teljes népességre számolt, 100 000 főre vetített prevalencia 862/100 000 fő volt a férfiak, 981/100 000 fő a nők esetében, együtt 924/100 000 fő a járóbeteg-szakellátásban. A 65-74 évesek jelentek meg a legnagyobb számban az egyes ellátási szinteken. A nemek eloszlása között a legtöbb vizsgált korcsoport tekintetében számottevő különbség nem tapasztalható, 65 év felett azonban már jóval magasabb a nők aránya. Következtetés: A betegség előfordulási gyakorisága a nők esetében 15,6%-kal magasabb. Idősebb korban jelentősen magasabb betegszámot figyeltünk meg. A neuropathiás szövődmények elkerülése érdekében a terápiás kezelésen túl a megelőzésre is sokkal nagyobb figyelmet javasolunk fordítani. Orv Hetil. 2021; 162(Suppl 1): 38-45.

SUMMARY

INTRODUCTION

Neurological complications are the most common type of complications among type 2 diabetes mellitus patients, which put a heavy burden on both individuals and health insurance organizations.

OBJECTIVE

The aim of our study was to determine the epidemiological and health insurance disease burden of non-insulin-dependent diabetes with neurological complications.

DATA AND METHODS

Data were derived from the financial database of the National Health Insurance Fund Administration (NHIFA) of Hungary for the year 2018. Data analysed included annual patient numbers and prevalence of care utilisation per 100 000 population according to age groups and sex. Patients were identified with the following code of the International Classification of Diseases, 10th revision: G6320.

RESULTS

In 2018, NHIFA spent 6.63 billion HUF (24.52 million USD; 20.78 million EUR) on treating diabetic polyneuropathy. Reimbursement of pharmaceuticals was the main cost driver (78.29% of total expenditure). Based on patient numbers in outpatient care, prevalence in 100 000 population was 862 men, 981 women, together 924 people based on outpatient-care utilization. Most patients were aged between 65-74 years in all forms of care. Regarding sex, no significant differences were found among most age groups, however, the ratio of women tends to be higher above 65 years of age.

CONCLUSION

Prevalence was found to be by 15.6% higher among women. Significantly higher patient numbers were found in old age. Besides therapeutic interventions, prevention should gain considerably more attention to avoid polyneuropathic complications. Orv Hetil. 2021; 162(Suppl 1): 38-45.

The day-night pattern of colonic contractility is not impaired in type 1 diabetes and distal symmetric polyneuropathy

Colonic contractility normally shows circadian variability regulated by sleep and especially food intake. However, individuals with type 1 diabetes have a reduced or even absent gastrocolic response to a meal, indicating that colonic contractility may be affected by the disease. We hypothesized that individuals with type 1 diabetes and distal symmetric polyneuropathy (DSPN) have decreased motility (expressed as the motility index) and contractility of the colon and a reduced increase in motility index from night to morning compared to healthy controls and individuals with type 1 diabetes without DSPN. Cohorts of 35 individuals with type 1 diabetes and DSPN, 40 individuals with type 1 diabetes without DSPN, and 28 healthy controls were included in this post-hoc, cross-sectional analysis. We investigated, using a wireless motility capsule that measures pH, temperature, and pressure throughout the gastrointestinal tract, whether individuals with type 1 diabetes with and without DSPN, compared to healthy controls, exhibit altered colonic contractility in the evening, night, and morning. Max amplitude, mean peak amplitude, mean contraction, and motility index of the colon were calculated at the afore-designated times. Motility index of the colon tended to be higher in individuals with type 1 diabetes and DSPN compared to controls in the evening (P = .064), but the effect size was small (1.74%). There was no difference in motility index between the groups in the morning or evening. Furthermore, there was no difference in max amplitude, mean peak amplitude, or mean contraction between groups in the morning, evening, and night. As expected, overall contractility increased from night to morning in all groups, but there was no difference between groups in the increase in contractility from night to morning. Colonic contractility generally peaked in the morning, decreased in the evening, and was almost absent at night. Type 1 diabetes and/or DSPN did not impair contractility of the colon at any time point. Contractility and motility increased from morning to night unaffected by type 1 diabetes and/or DSPN.

Diffusion Tensor Imaging of the Sciatic Nerve as a Surrogate Marker for Nerve Functionality of the Upper and Lower Limb in Patients With Diabetes and Prediabetes

Background

Nerve damage in diabetic neuropathy (DN) is assumed to begin in the distal legs with a subsequent progression to hands and arms at later stages. In contrast, recent studies have found that lower limb nerve lesions in DN predominate at the proximal sciatic nerve and that, in the upper limb, nerve functions can be impaired at early stages of DN.

Materials and Methods

In this prospective, single-center cross-sectional study, participants underwent diffusion-weighted 3 Tesla magnetic resonance neurography in order to calculate the sciatic nerve’s fractional anisotropy (FA), a surrogate parameter for structural nerve integrity. Results were correlated with clinical and electrophysiological assessments of the lower limb and an examination of hand function derived from the Purdue Pegboard Test.

Results

Overall, 71 patients with diabetes, 11 patients with prediabetes and 25 age-matched control subjects took part in this study. In patients with diabetes, the sciatic nerve’s FA showed positive correlations with tibial and peroneal nerve conduction velocities (r = 0.62; p < 0.001 and r = 0.56; p < 0.001, respectively), and tibial and peroneal nerve compound motor action potentials (r = 0.62; p < 0.001 and r = 0.63; p < 0.001, respectively). Moreover, the sciatic nerve’s FA was correlated with the Pegboard Test results in patients with diabetes (r = 0.52; p < 0.001), prediabetes (r = 0.76; p < 0.001) and in controls (r = 0.79; p = 0.007).

Conclusion

This study is the first to show that the sciatic nerve’s FA is a surrogate marker for functional and electrophysiological parameters of both upper and lower limbs in patients with diabetes and prediabetes, suggesting that nerve damage in these patients is not restricted to the level of the symptomatic limbs but rather affects the entire peripheral nervous system.

Glucagon Prevents Cytotoxicity Induced by Methylglyoxal in a Rat Neuronal Cell Line Model

Although diabetic polyneuropathy (DPN) is a frequent diabetic complication, no effective therapeutic approach has been established. Glucagon is a crucial hormone for glucose homeostasis but has pleiotropic effects, including neuroprotective effects in the central nervous system. However, the importance of glucagon in the peripheral nervous system (PNS) has not been clarified. Here, we hypothesized that glucagon might have a neuroprotective function in the PNS. The immortalized rat dorsal root ganglion (DRG) neuronal cell line 50B11 was treated with methylglyoxal (MG) to mimic an in vitro DPN model. The cells were cultured with or without glucagon or MG. Neurotoxicity, survival, apoptosis, neurite projection, cyclic adenosine monophosphate (cAMP), and protein kinase A (PKA) were examined. Glucagon had no cytotoxicity and rescued the cells from neurotoxicity. Cell survival was increased by glucagon. The ratio of apoptotic cells, which was increased by MG, was reduced by glucagon. Neurite outgrowth was accelerated in glucagon-treated cells. Cyclic AMP and PKA accumulated in the cells after glucagon stimulation. In conclusion, glucagon protected the DRG neuronal cells from MG-induced cellular stress. The cAMP/PKA pathway may have significant roles in those protective effects of glucagon. Glucagon may be a potential target for the treatment of DPN.

Pathogenesis and Molecular Treatment Strategies of Diabetic Neuropathy Collateral Glucose-Utilizing Pathways in Diabetic Polyneuropathy

Diabetic polyneuropathy (DPN) is the most common neuropathy manifested in diabetes. Symptoms include allodynia, pain, paralysis, and ulcer formation. There is currently no established radical treatment, although new mechanisms of DPN are being vigorously explored. A pathophysiological feature of DPN is abnormal glucose metabolism induced by chronic hyperglycemia in the peripheral nerves. Particularly, activation of collateral glucose-utilizing pathways such as the polyol pathway, protein kinase C, advanced glycation end-product formation, hexosamine biosynthetic pathway, pentose phosphate pathway, and anaerobic glycolytic pathway are reported to contribute to the onset and progression of DPN. Inhibitors of aldose reductase, a rate-limiting enzyme involved in the polyol pathway, are the only compounds clinically permitted for DPN treatment in Japan, although their efficacies are limited. This may indicate that multiple pathways can contribute to the pathophysiology of DPN. Comprehensive metabolic analysis may help to elucidate global changes in the collateral glucose-utilizing pathways during the development of DPN, and highlight therapeutic targets in these pathways.

Small and large fiber sensory polyneuropathy in type 2 diabetes: Influence of diagnostic criteria on neuropathy subtypes

Diabetic polyneuropathy (DPN) can be classified based on fiber diameter into three subtypes: small fiber neuropathy (SFN), large fiber neuropathy (LFN), and mixed fiber neuropathy (MFN). We examined the effect of different diagnostic models on the frequency of polyneuropathy subtypes in type 2 diabetes patients with DPN. This study was based on patients from the Danish Center for Strategic Research in Type 2 Diabetes cohort. We defined DPN as probable or definite DPN according to the Toronto Consensus Criteria. DPN was then subtyped according to four distinct diagnostic models. A total of 277 diabetes patients (214 with DPN and 63 with no DPN) were included in the study. We found a considerable variation in polyneuropathy subtypes by applying different diagnostic models independent of the degree of certainty of DPN diagnosis. For probable and definite DPN, the frequency of subtypes across diagnostic models varied from: 1.4% to 13.1% for SFN, 9.3% to 21.5% for LFN, 51.4% to 83.2% for MFN, and 0.5% to 14.5% for non-classifiable neuropathy (NCN). For the definite DPN group, the frequency of subtypes varied from: 1.6% to 13.5% for SFN, 5.6% to 20.6% for LFN, 61.9% to 89.7% for MFN, and 0.0% to 6.3% for NCN. The frequency of polyneuropathy subtypes depends on the type and number of criteria applied in a diagnostic model. Future consensus criteria should clearly define sensory functions to be tested, methods of testing, and how findings should be interpreted for both clinical practice and research purpose.

Effectiveness of Intravenous Immunoglobulin for Management of Neuropathic Pain: A Narrative Review

Administrations of intravenous immunoglobulin (IVIG), an immune-modulating blood-derived product, may be beneficial for managing neuropathic pain. Here, we review previous studies to investigate the effectiveness of IVIG in managing neuropathic pain due to various neurological disorders. The electronic databases PubMed, Scopus, Embase, and the Cochrane Library were searched for studies published up to February 2020. Two reviewers independently assessed the studies using strict inclusion criteria. Ten studies were included and qualitatively analyzed. The review included patients with pain due to complex regional pain syndrome (CRPS), diabetic polyneuropathy, and others, such as postherpetic neuralgia and trigeminal neuralgia. We found that IVIG may be one of the beneficial options for managing neuropathic pain from various neurological disorders. In the four articles reviewed, no major adverse effects were reported, and the trend was toward a positive pain-reducing effect in eight articles. However, to confirm the benefits of IVIG on reducing neuropathic pain, more high-quality studies are required.

Increased Oxidative Stress Underlies Abnormal Pain Threshold in a Normoglycemic Japanese Population

Normal-high HbA1c levels are a risk factor for attenuated pain sensation in normoglycemic subjects. It is unclear, however, what mechanisms underlie the pathogenesis of attenuated pain sensation in such a population. We, therefore, explored the relationship between oxidative stress (OS) and pain sensation in a rural Japanese population. A population-based study of 894 individuals (average age 53.8 ± 0.5 years) and 55 subjects with impaired fasting glucose (IFG) were enrolled in this study. Individuals with diabetes were excluded. Relationships between pain threshold induced by intraepidermal electrical stimulation (PINT) and clinico-hematological parameters associated with OS were evaluated. Univariate linear regression analyses revealed age, BMI, HbA1c, the OS biomarker urine 8-hydroxy-2'-deoxyguanosine (8-OHdG), systolic blood pressure, and decreased Achilles tendon reflex on the PINT scores. Adjustments for age, gender, and multiple clinical measures confirmed a positive correlation between PINT scores and urine 8-OHdG (β = 0.09, p < 0.01). Urine 8-OHdG correlated positively with higher HbA1c levels and age in the normoglycemic population. Unlike in the normoglycemic population, both inflammation and OS were correlated with elevated PINT scores in IFG subjects. OS may be a major contributing factor to elevated PINT scores in a healthy Japanese population.

Vitamin D Status in a Bulgarian Population With Type 2 Diabetes and Diabetic Foot Ulcers

The aim of this study was to assess vitamin D status in patients with type 2 diabetes and diabetic foot ulcers (DFU). A total of 242 participants with type 2 diabetes, mean age 59.1 ± 10 years, mean body mass index 31.4 ± 6.3 kg/m², and estimated glomerular filtration rate ≥45 mL/min/1.73m², were divided into 2 groups: 73 with DFU (35 with and 38 without active infection) and 169 without DFU (106 with diabetic peripheral neuropathy, 63 without complications). Neuropathy was assessed by 10 g monofilament, Rydel-Seiffer 128 Hz tuning fork, and temperature discrimination. Serum 25(OH)D (25-hydroxy vitamin D) was assessed by ECLIA (electro-chemiluminescence immunoassay) method. Median 25(OH)D level was 12.6 ng/mL (IQR [interquartile range] 9.3-17.6 ng/mL) in the studied cohort. The DFU group presented with lower 25(OH)D level as compared with diabetic patients without foot ulcers (non-DFU group): 11.6 ng/mL (IQR 8.5-15.8 ng/mL) versus 13.5 ng/mL (IQR 9.6-18.6 ng/mL), P = .001; the diabetic peripheral neuropathy subgroup demonstrated lower 25(OH)D level in comparison with participants without complications: 12.5 ng/mL (IQR 9-17.2 ng/mL) versus 15.9 ng/mL (IQR 10.4-20.8 ng/mL), P = .031. This remained significantly different even after correction for age and duration of diabetes. There was no difference in 25(OH)D level between the subgroups according to the presence of active infection. In conclusion, vitamin D deficiency may play a role in the development of diabetes complications.

Diabetic Polyneuropathy Is Associated With Pathomorphological Changes in Human Dorsal Root Ganglia: A Study Using 3T MR Neurography

Diabetic neuropathy (DPN) is one of the most severe and yet most poorly understood complications of diabetes mellitus. In vivo imaging of dorsal root ganglia (DRG), a key structure for the understanding of DPN, has been restricted to animal studies. These have shown a correlation of decreased DRG volume with neuropathic symptom severity. Our objective was to investigate correlations of DRG morphology and signal characteristics at 3 Tesla (3T) magnetic resonance neurography (MRN) with clinical and serological data in diabetic patients with and without DPN. In this cross-sectional study, participants underwent 3T MRN of both L5 DRG using an isotropic 3D T2-weighted, fat-suppressed sequence with subsequent segmentation of DRG volume and analysis of normalized signal properties. Overall, 55 diabetes patients (66 ± 9 years; 32 men; 30 with DPN) took part in this study. DRG volume was smaller in patients with severe DPN when compared to patients with mild or moderate DPN (134.7 ± 21.86 vs 170.1 ± 49.22; p = 0.040). In DPN patients, DRG volume was negatively correlated with the neuropathy disability score (r = −0.43; 95%CI = −0.66 to −0.14; p = 0.02), a measure of neuropathy severity. DRG volume showed negative correlations with triglycerides (r = −0.40; 95%CI = −0.57 to −0.19; p = 0.006), and LDL cholesterol (r = −0.33; 95%CI = −0.51 to −0.11; p = 0.04). There was a strong positive correlation of normalized MR signal intensity (SI) with the neuropathy symptom score in the subgroup of patients with painful DPN (r = 0.80; 95%CI = 0.46 to 0.93; p = 0.005). DRG SI was positively correlated with HbA1c levels (r = 0.30; 95%CI = 0.09 to 0.50; p = 0.03) and the triglyceride/HDL ratio (r = 0.40; 95%CI = 0.19 to 0.57; p = 0.007). In this first in vivo study, we found DRG morphological degeneration and signal increase in correlation with neuropathy severity. This elucidates the potential importance of MR-based DRG assessments in studying structural and functional changes in DPN.

Corneal nerves in diabetes-The role of the in vivo corneal confocal microscopy of the subbasal nerve plexus in the assessment of peripheral small fiber neuropathy

The cornea's intense innervation is responsible for corneal trophism and ocular surface hemostasis maintenance. Corneal diabetic neuropathy affects subbasal nerve plexus, with progressive alteration of nerves' morphology and density. The quantitative analysis of nerve fibers can be performed with in vivo corneal confocal microscopy considering the main parameters such as corneal nerve fibers length, corneal nerve fibers density, corneal nerve branching density, tortuosity coefficient, and beadings frequency. As the nerve examination permits the detection of early changes occurring in diabetes, the invivo corneal confocal microscopy becomes, over time, an important tool for diabetic polyneuropathy assessment and follow-up. In this review, we summarize the actual evidence about corneal nerve changes in diabetes and the relationship between the grade of alterations and the duration and severity of the disease. We aim at understanding how diabetes impacts corneal nerves and how it correlates with sensorimotor peripheral polyneuropathy and retinal complications. We also attempt to analyze the safety of the most common surgical procedures such as cataract and refractive surgery in diabetic patients and to highlight the specific risk factors. We believe that information about the corneal nerve fibers' condition obtained from the in vivo subbasal nerve plexus investigation may be crucial in monitoring peripheral small fiber polyneuropathy and that it will help with decision-making in ophthalmic surgery in diabetic patients.

Direct Comparison of Therapeutic Effects on Diabetic Polyneuropathy between Transplantation of Dental Pulp Stem Cells and Administration of Dental Pulp Stem Cell-Secreted Factors

Stem cell transplantation is a potential novel therapy for diabetic polyneuropathy. Dental pulp stem cells (DPSCs) are attractive stem cell sources because DPSCs can be isolated from extracted teeth and cryopreserved while retaining viability. In this study, we directly compared the efficacy of the transplantation of DPSCs and the administration of the secreted factors from DPSCs (DPSC-SFs) on diabetic polyneuropathy. Eight weeks after streptozotocin injection, DPSCs (1.0 × 10⁶ cells/rat) or DPSC-SFs (1.0 mL/rat) were administered into the unilateral hindlimb skeletal muscles of diabetic Sprague-Dawley rats. DPSC transplantation and DPSC-SF administration did not affect blood glucose levels and body weights in the diabetic rats. Both DPSC transplantation and DPSC-SF administration significantly ameliorated sciatic nerve conduction velocity and sciatic nerve blood flow, accompanied by increases in muscle bundle size, vascular density in the skeletal muscles and intraepidermal nerve fiber density in the diabetic rats, while there was no difference between the results for DPSCs and DPSC-SFs. These results suggest that the efficacy of both DPSC transplantation and DPSC-SF administration for diabetic polyneuropathy four weeks after transplantation/administration was mainly due to the multiple secretomes secreted from transplanted DPSCs or directly injected DPSC-SFs in the early phase of transplantation/administration.

Diabetic Polyneuropathy - Advances in Diagnosis and Intervention Strategies

Over half of people with diabetes mellitus develop diabetic polyneuropathy (DPN), which is a major cause of reduced quality of life due to disabling neuropathic pain, sensory loss, gait instability, fall-related injury, and foot ulceration and amputation. The latter represents a major health and economic burden, with lower limb amputation rates related to diabetes increasing in the UK. There is a need for early diagnosis of DPN so that early management strategies may be instigated, such as achieving tight glucose control and management of cardiovascular risk factors, in an attempt to slow its progression. To this end, a one-stop microvascular assessment involving a combined eye, foot and renal screening clinic has proven feasible in the UK. Unfortunately, there are currently no approved disease-modifying therapies for DPN. Some disease-modifying agents have demonstrated efficacy, but further large trials using appropriate clinical endpoints are required before these treatments can be routinely recommended. There has been emerging evidence highlighting a reduction in vitamin D levels in cases of painful DPN and the potential for vitamin D supplementation in deficient individuals to improve neuropathic pain; however, this needs to be proved in randomised clinical trials. The use of established agents for neuropathic pain in DPN is limited by poor efficacy and adverse effects, but patient stratification using methods such as pain phenotyping are being tested to determine whether this improves the outcomes of such agents in clinical studies. In addition, innovative approaches such as the topical 8% capsaicin patch, new methods of electrical stimulation and novel therapeutic targets such as NaV1.7 offer promise for the future. This article aims to discuss the challenges of diagnosing and managing DPN and to review current and emerging lifestyle interventions and therapeutic options.

Importance of Footwear Outsole Rigidity in Improving Spatiotemporal Parameters in Patients with Diabetes and Previous Forefoot Ulcerations

We aimed to identify if any differences existed in spatiotemporal parameters during gait among different densities of rocker soles in patients with a history of neuropathic ulcerations and the differences in comfort between shoe conditions. This study was a cross-sectional study of 24 patients with diabetes and a history of neuropathic diabetic foot ulcers (DFUs). Spatiotemporal parameters (duration of stance phase (ms), stride length (cm), and step velocity (m/s)) were analyzed in barefoot, semirigid outsole, and rigid outsole footwear conditions. A dynamic pressure measurement system (Footscan^® system, RSscan International, Olen, Belgium) was used to assess shoe conditions. We also analyzed differences in comfort between the shoe conditions using a visual analog scale. A Wilcoxon test for paired samples was used to assess gait differences. Result showed that a rigid outsole causes changes in the subphases of the stance phase (p < 0.001; Cohen d = 0.6) compared to a semirigid outsole. Stride length (p < 0.001; Cohen d = 0.66) and step velocity were significantly longer (p < 0.001; Cohen d = 2.03) with the use of rigid outsole footwear. A rigid rocker sole reduces the time of the stance phase, in addition to increasing the stride length and velocity of step in patients with a previous history of DFUs.

Pain thresholds are unaffected by age in a Japanese population

INTRODUCTION

Assessment of sensory impairment in diabetic patients by pain threshold test using intraepidermal electrical stimulation (IES) is a recently developed technique. However, there are no normative pain thresholds in healthy people.

METHODS

We examined pain, vibration, and pressure thresholds in 178 healthy subjects using IES, vibration perception testing (VPT), and Semmes-Weinstein monofilament testing (SWMT).

RESULTS

The mean values for each age group for pain threshold ranged from 0.07 to 0.12 mA. Pain thresholds were unaffected by age. As the age increased, VPT values decreased from 18.0 to 10.6 seconds and SWMT values increased from 21.4 to 45.3 g/mm² . There were no significant differences in pain threshold, VPT, and SWMT between men and women.

DISCUSSION

The pain threshold test appears to be useful for diabetic neuropathy screening because normative values are not affected by age.

Corrigendum: Normal High HbA1c a Risk Factor for Abnormal Pain Threshold in the Japanese Population

[This corrects the article DOI: 10.3389/fendo.2019.00651.].

[Early diagnosis of diabetic polyneuropathy based on the results of corneal nerve fibers examination]

Laser corneal confocal microscopy (CCM) is a method of objective visualization of thin corneal nerve fibers (CNF), the structure of which changes in patients with diabetes mellitus (DM).

PURPOSE

To conduct comparative analysis of the results of CNF assessment using CCM and other known neurological instrumental techniques as well as evaluate their applicability to the early diagnosis of diabetic polyneuropathy (DPN).

MATERIAL AND METHODS

We examined a total of 46 patients (85 eyes) with type 1 DM and either subclinical (24 patients), or clinical-stage DPN (22 patients) and 50 patients (87 eyes) with type 2 DM (subclinical DPN in 27 patients and clinical-stage DPN in 23 patients). The control group consisted of 34 healthy volunteers (68 eyes). All patients underwent standard ophthalmological examination, CCM with nerve tortuosity assessment (including calculation of coefficients of CNF orientation anisotropy, K_ΔL, and symmetry, K_sym) and interocular asymmetry, electroneuromyography (ENMG), and quantitative sensory testing (QST).

RESULTS

Analysis of the CCM results revealed a reliable decrease in the average K_ΔL values in patients with type 1 and type 2 DM compared with the control group. In the group of patients with type 1 DM and subclinical DPN, correlations were revealed between the CNF tortuosity coefficients and a number of ENMG parameters, such as the M-response amplitude of the peroneal nerve (r=0.73, p≤0.02), M-response amplitude of the tibial nerve (r=0.58, p≤0.01), residual latency (r= -0.62, p≤0.05), and peroneal nerve conduction velocity (r=0.57, p≤0.01). K_sym values correlated with the warm sensitivity threshold (r=0.6, p≤0.008). Among patients with type 2 DM and subclinical DPN, the K_ΔL coefficient correlated with the peroneal nerve conduction velocity (r=0.46, p≤0.02), M-response amplitude of the tibial nerve (r=0.6, p≤0.04), and residual latency of the peroneal nerve (r=-0.56, p≤0.05).

CONCLUSION

The state of thin corneal nerves correlates with functional changes in the peripheral nerves. Pathological changes in CNF in patients with DM can be detected at an early (subclinical) stage of DPN using laser CCM and a program for corneal nerve tortuosity analysis.

['Point of no return' in diabetic neuropathies: a dangerous delusion]

Polyneuropathy in patients with diabetes mellitus is manifested by a lesion of peripheral sensory, motor and autonomic nervous system. Different severity of damage of sensory, motor and autonomic fibers in typical and atypical forms of diabetic polyneuropathy, requires a differentiated approach to therapy, but not the rejection of its implementation. In an interdisciplinary consensus, consultations are held with physicians from different regions of the Russian Federation, and modern methods of diagnosing and assessing the severity of diabetic polyneuropathies, which determine the algorithm for treating patients, are discussed.

[Specifics of diagnosis and treatment of diabetic polyneuropathy in elderly patients]

AIM

To study the specifics of diagnosis and treatment of diabetic polyneuropathy in elderly patients.

MATERIAL AND METHODS

Forty-two patients (22 men and 20 women, aged from 65 to 75 years) with diabetes mellitus type 2 and diabetic polyneuropathy were studied using the following psychometric scales: the Michigan Neuropathy Screening Instrument (MNSI), Neurological symptoms scale (NSS), Neuropathy Disability Score (NDS), the Numerical Rating Scale (NRS), Kaplan-Feinstein index (KFI), the Covi Anxiety Scale (COVI), the Recovery Locus of Control Scale (RLOC). Patients were divided into group 1 (n=24) treated with neuromultivit injections, along with standard treatment, and group 2 (n=18), which received standard treatment only. Patients were examined at baseline and one month after treatment.

RESULTS

In elderly patients, diabetic distal symmetric sensorimotor polyneuropathy of moderate severity was comorbid mostly with cardio-vascular disease. Pain syndrome was associated with anxiety and significant direct correlation between anxiety and pain intensity was found. The level of motivation towards recovery was significantly lower and correlated with COVI scores.

CONCLUSION

Injections of neuromultivit decrease the intensity of pain, improve the emotional state and increase the level of motivation towards recovery.

[Lipoic acid: physiological role and prospects for clinical application]

α-Lipoic acid (also known as thioctic acid) is a natural vitamin-like compound. Lipoic acid contains asymmetrical carbon, which causes the presence of two possible optical isomers (enantiomers): R-lipoic acid (levogyrate isomer) and S-lipoic acid (rightspinning isomer). Lipoic acid functions as a cofactor for several important mitochondrial multienzyme complexes, enhances the uptake of glucose by the cells, and modulates the activity of various signaling molecules and transcription factors. It was shown that α-lipoic acid and its derivative, dihydrolipoic acid, have a direct antioxidant effect due to the neutralization of reactive oxygen species that are destructive to DNA, proteins and lipids of cells. Dihydrolipoic acid enhances the antioxidant properties of ascorbic acid, glutathione and ubiquinone. Available evidence suggests that supplementation with lipoic acid reduces the symptoms of peripheral diabetic neuropathy. Results from randomized controlled trials show that high doses of lipoic acid can improve the glycemic profile of subjects with metabolic disorders. Lipoic acid can be used to control body weight in people with obesity. R-Lipoic acid is synthesized in the human body and is contained in foods in a form covalently associated with lysine (lipoyllysine). Its dose in dietary supplements significantly exceeds the amount in the diet. Most dietary supplements contain a racemic mixture of R- and S-lipoic acid.

Can diabetic polyneuropathy and foot ulcers in patients with type 2 diabetes be accurately identified based on ICD-10 hospital diagnoses and drug prescriptions?

Purpose: We examined whether diabetic polyneuropathy (DPN) and diabetic foot ulcers in type 2 diabetes can be accurately identified using International Classification of Diseases, 10th revision discharge diagnosis codes, surgery codes, and drug prescription codes.

Methods: We identified all type 2 diabetes patients in the Central Denmark region, 2009–2016, who had ≥1 primary/secondary diagnosis code of “diabetes with neurological complication” (E10.4-E14.4), “diabetic polyneuropathy” (G63.2), or “polyneuropathy, unspecified” (G62.9). Patients with potential painful DPN and non-painful DPN were identified based on prescription history for serotonin–norepinephrine reuptake inhibitors, tricyclic antidepressants, or gabapentinoids. Likewise, type 2 diabetes patients with potential foot ulcers were identified based on diagnosis or surgery codes. We used medical record review as the reference standard and calculated positive predictive values (PPVs).

Results: Of 53 randomly selected patients with potential painful DPN, 38 were classified as having DPN when validated against medical records; of these, 18 also had neuropathic pain, yielding a PPV of 72% (95% CI: 58–83%) for DPN and 34% (95% CI: 22–48%) for painful DPN. Likewise, among 54 randomly selected patients with potential non-painful DPN, 30 had DPN based on medical record data; of these, 27 had non-painful DPN, yielding PPVs of 56% (95% CI: 41–69%) and 50% (95% CI: 36–64%), respectively. Secondary E-chapter codes often denoted stroke or mononeuropathies, rather than DPN. Excluding secondary E-chapter codes from the algorithm increased the PPV for DPN to 78% (95% CI: 63–89%) for the painful DPN cohort and to 74% (95% CI: 56–87%) for the non-painful DPN cohort. Of 53 randomly selected patients with potential diabetic foot ulcer, only 18 diagnoses were confirmed; PPV=34% (95% CI: 22–48%).

Conclusion: G-chapter and primary E-chapter diagnosis codes can detect type 2 diabetes patients with hospital-diagnosed DPN, and may be useful in epidemiological research. In contrast, our diabetic foot ulcer algorithm did not perform well.