Patterns of Nerve Conduction Abnormalities in Patients with Type 2 Diabetes Mellitus According to the Clinical Phenotype Determined by the Current Perception Threshold

Cross-Sectional Study of the Relationship Between Medial Plantar Nerve Conduction Studies and Severity of Diabetic Neuropathy

Objective

Diabetic peripheral neuropathy (DPN), a complication of diabetes, is detected only in later stages. Medial plantar nerve (MPL) can identify earlier stages of neuropathy. We evaluated the correlation of MPL sensory nerve action potentials (SNAPs) and severity of DPN measured using the Toronto Clinical Neuropathy Score (TCNS).

Methods

In this hospital-based, cross-sectional study, we recruited diabetic subjects referred for suspected DPN. Neuropathy was graded with TCNS. Sural nerve conduction studies were performed using standard techniques. MPL studies were conducted using the modified Ponsford technique. All evaluations were performed on Nihon Kohden (model MEB 9200K). Averaged MPL SNAP was correlated with TCNS using Pearson's correlation coefficient. To estimate a correlation of 0.4 with 80% power (P = 0.05), we needed 46 subjects. Linear regression was conducted to adjust for age, duration, and diabetic control. Receiver operating characteristic (ROC) curve analysis was performed to obtain the cutoff for MPL SNAP values using the Youden index.

Results

Fifty-one subjects with a mean age of 53.5 years (8.7) and mean duration of diabetes of 10.2 years (7.2) were included. MPL SNAPs were recordable in 12 patients, and the mean amplitude was 5.15 (2.9) µV. There was correlation between MPL SNAP and TCNS (r = -0.43, P = 0.02). No confounding was seen. Use of MPL SNAP resulted in diagnosis of DPN in an additional six (11.8%) patients. The ROC curve suggested that MPL SNAP cutoff of 1.05 µV had an accuracy of 67% in identifying neuropathy as defined by TCNS.

Conclusions

MPL SNAP has a moderate correlation with clinical score and identifies more diabetic neuropathy than sural nerve.

Loss of ATP-sensitive channel expression and function decreases opioid sensitivity in a mouse model of type 2 diabetes

During diabetes, β-cell dysfunction due to loss of potassium channels sensitive to ATP, known as KATP channels occurs progressively over time contributing to hyperglycemia. KATP channels are additionally present in the central and peripheral nervous systems and are downstream targets of opioid receptor signaling. The aim of this study is to investigate if KATP channel expression or activity in the nervous system changes in diabetic mice and if morphine antinociception changes in mice fed a high fat diet (HFD) for 16 weeks compared to controls. Mechanical thresholds were also monitored before and after administration of glyburide or nateglinide, KATP channel antagonists, for four weeks. HFD mice have decreased antinociception to systemic morphine, which is exacerbated after systemic treatment with glyburide or nateglinide. HFD mice also have lower rotarod scores, decreased mobility in an open field test, and lower burrowing behavior compared to their control diet counterparts, which is unaffected by KATP channel antagonist delivery. Expression of KATP channel subunits, Kcnj11 (Kir6.2) and Abcc8 (SUR1), were decreased in the peripheral and central nervous system in HFD mice, which is significantly correlated with baseline paw withdrawal thresholds. Upregulation of SUR1 through an adenovirus delivered intrathecally increased morphine antinociception in HFD mice, whereas Kir6.2 upregulation improved morphine antinociception only marginally. Perspective: This article presents the potential link between KATP channel function and neuropathy during diabetes. There is a need for increased knowledge in how diabetes affects structural and molecular changes in the nervous system to lead to the progression of chronic pain and sensory issues.

Adherence and the Diabetic Foot: High Tech Meets High Touch?

Diabetic foot ulcers, which are a common complication of diabetes, can have a negative impact on a person's physical and mental health, including an increased risk of depression. Patients suffering from depression are less likely to keep up with diabetic foot care, thus increasing the risk of developing ulcers. However, with the use of artificial intelligence (AI), at-home patient care has become easier, which increases adherence. To better understand how new technologies, including machine learning algorithms and wearable sensors, might improve patient adherence and outcomes, we conducted a literature review of several sensor technologies, including SmartMat© and Siren Care© socks for temperature, SurroSense Rx/Orpyx© for pressure, and Orthotimer© for adherence. An initial search identified 143 peer-reviewed manuscripts, from which we selected a total of 10 manuscripts for further analysis. We examined the potential benefits of personalized content and clinician support for those receiving mobile health interventions. These findings may help to demonstrate the current and future utility of advanced technologies in improving patient adherence and outcomes, particularly in the context of diabetes management and the link between behavior and complications in diabetes, such as diabetic foot ulcers.

Evoked sensations with transcutaneous electrical stimulation with different frequencies, waveforms, and electrode configurations

BACKGROUND

Current Perception Threshold (CPT) is a technique used for diagnostic purposes that applies sinusoidal currents transcutaneously at 5 Hz, 250 Hz, and 2KHz to preferentially excite C, Aδ, and Aβ afferent nerve fibers correspondingly. This fact may be interesting for evoking different electrotactile sensations for a wide variety of applications.

METHODS

Sensations evoked by 5 Hz, 250 Hz, and 2KHz frequencies; sinusoidal, square, and 250 μs-pulsed waveforms; and conventional and concentric electrode configurations were analyzed in 19 healthy volunteers. Stimuli were applied in the dorsum of the hand in a double-blind manner and CPTs were defined based on participants' verbal feedback. After each stimulus participants filled in a form with sensation modality, irradiation, intensity, and emotion descriptors.

RESULTS

The frequency showed a significant effect on the four domains of evoked sensations and the waveform showed a significant effect on the modality domain. For most waveform and electrode configuration combinations, 5 Hz evoked mostly a low-intensity prickling sensation; 250 Hz mostly evoked an uncomfortable medium-intensity tingling sensation; and 2KHz mostly evoked a low-intensity tingling sensation. No thermal or noxious sensations were evoked. A significant interaction effect was only found between the frequency and the waveform factors. The electrode configuration did not show either a significant effect on the evoked sensations or an interaction effect with the frequency or waveform type.

CONCLUSIONS

Transcutaneous electrical stimulation may evoke different sensations at different frequencies due to the preferential activation of different fiber types. The results of these analysis could be used to enhance human-machine/computer-interaction systems based on electrotactile feedback.

Glomerular filtration Rate, urine Albumin/ creatinine ratio and current perception threshold in patients with diabetic kidney disease

BACKGROUND

Diabetic microvascular complications, including diabetic kidney disease (DKD), retinopathy (DR), and neuropathy (DN), were major causes of morbidity and mortality in diabetic patients worldwide. It has been suggested that urinary albumin-to-creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) were not the only indicators of renal function impairment in DKD and that they were also associated with diabetic peripheral neuropathy (DPN) which might affect nerve conduction velocity (NCV). As 30-40% of DPN patients had no subjective symptoms, while current perception threshold (CPT) could detect sensory nerve damage at an early stage. As a result, we aimed to investigate correlation between UACR, eGFR and CPT in DKD patients.

METHODS

A total of 273 DKD patients from the First Affiliated Hospital of Kunming Medical University from January 2018 to June 2020 were enrolled to complete the CPT test. CPT values of the bilateral median nerve and superficial and deep peroneal nerves at 2000 Hz, 250 Hz, and 5 Hz were collected.

RESULTS

In normoesthesia and hypaesthesia patients with DKD, MDRD-eGFR correlated negatively with TC (r = -0.135, P = 0.037), left superficial peroneal and deep peroneal nerve 2000 Hz CPT (r = -0.205, P = 0.001) and right superficial peroneal and deep peroneal nerve 2000 Hz CPT (r = -0.154, P = 0.017). Besides, left and right superficial peroneal and deep peroneal nerve 2000 Hz CPT correlated with CKD-EPI-eGFR and UACR. Multivariate logistic regression analysis found left superficial peroneal and deep peroneal nerve 2000 Hz CPT was independently associated with both MDRD-eGFR and CKD-EPI-eGFR.

CONCLUSION

Decreased MDRD-eGFR and CKD-EPI-eGFR were expected to be a predictor of peripheral nerve injury in normoesthesia and hypaesthesia patients with DKD.

Association of Diabetic Peripheral Neuropathy with Vitamin D Levels Depends on Vitamin D Status

Background

Vitamin D deficiency has been reported to be associated with diabetic peripheral neuropathy (DPN). Our objective here was to evaluate the association between vitamin D levels and neuropathic symptoms in a Chinese population.

Material/Methods

A total of 4435 patients with type 2 diabetes (T2D) were recruited in this cross-sectional study. 25-dihydroxyvitamin D (25-(OH) D) serum concentration was measured by electrochemiluminescence assay (Cobas e601, Roche). DPN was clinically diagnosed by assessing neurological symptoms and performing current perception threshold (CPT) testing. Of all the patients, 2910 were CPT-positive and had assessed neurological symptoms.

Results

In the vitamin D insufficiency group (<30 ng/mL 25-(OH) D), patients with neurological symptoms had higher serum 25-(OH) D levels than those without neurological symptoms (24.65±3.42 ng/mL vs 23.61±4.54 ng/mL, p≤0.001). The risk of numbness and pain increased by 0.5-fold for every 6 ng/mL increase in 25-(OH) D. In the vitamin D sufficiency group (≥30 ng/mL 25-(OH) D), patients with neurological symptoms had lower serum 25-(OH) D levels than those without neurological symptoms (32.96±3.18 ng/mL vs 33.45±4.27 ng/mL, p<0.01). For every 4 ng/mL decrease in 25-(OH) D, the risk of numbness and pain increased by 0.2-fold.

Conclusions

The association of neuropathy symptoms with 25-(OH) D levels differed depending on whether the patients had insufficient or sufficient vitamin D.

Association between Sleep Quality and Painless Diabetic Peripheral Neuropathy Assessed by Current Perception Threshold in Type 2 Diabetes Mellitus

BACKGROUND

It is known that the painful sensation of diabetic peripheral neuropathy (DPN) results in sleep problems in type 2 diabetes mellitus (T2DM). However, it is not known that the painless DPN also is associated with poor sleep quality in T2DM. The purpose of the current study was to investigate the association between painless DPN and poor sleep quality in T2DM.

METHODS

A total of 146 patients of T2DM who do not have any painful symptoms of DPN were recruited into the study. Among the patients, painless DPN was diagnosed by using the current perception threshold test. Sleep quality was assessed using the Pittsburgh Sleep Quality Index questionnaire.

RESULTS

The percentage of painless DPN was significantly higher in the poor sleep quality group than the good sleep quality group (70.0% vs. 35.5%, P<0.001). In the subscale results, stimulus values at 2,000 Hz, hypoesthesia and hyperesthesia were more common in the poor sleep quality group than in the good sleep quality group (45.7% vs. 25.0%, P=0.009; 34.3% vs. 18.4%, P=0.029; 40.0% vs. 19.7%, P=0.007, respectively). The association of painless DPN and poor sleep quality remained significant after adjustment for significant covariates (odds ratio, 3.825; 95% confidence interval, 1.674 to 8.742; P<0.001).

CONCLUSION

The current study showed that painless DPN was associated with poor sleep quality. Future studies are required to clarify the pathophysiologic causal relationship between painless DPN and sleep quality.

The relationship between exacerbated diabetic peripheral neuropathy and metformin treatment in type 2 diabetes mellitus

Metformin-treated diabetics (MTD) showed a decrease in cobalamin, a rise in homocysteine, and methylmalonic acid, leading to accentuated diabetic peripheral neuropathy (DPN). This study aimed to determine whether or not metformin is a risk factor for DPN. We compared MTD to non-metformin-treated diabetics (NMTD) clinically using the Toronto Clinical Scoring System (TCSS), laboratory (methylmalonic acid, cobalamin, and homocysteine), and electrophysiological studies. Median homocysteine and methylmalonic acid levels in MTD vs. NMTD were 15.3 vs. 9.6 µmol/l; P < 0.001 and 0.25 vs. 0.13 µmol/l; P = 0.02, respectively with high statistical significance in MTD. There was a significantly lower plasma level of cobalamin in MTD than NMTD. Spearman’s correlation showed a significant negative correlation between cobalamin and increased dose of metformin and a significant positive correlation between TCSS and increased dose of metformin. Logistic regression analysis showed that MTD had significantly longer metformin use duration, higher metformin dose > 2 g, higher TCSS, lower plasma cobalamin, and significant higher homocysteine. Diabetics treated with metformin for prolonged duration and higher doses were associated with lower cobalamin and more severe DPN.

γ-Linolenic Acid versus α-Lipoic Acid for Treating Painful Diabetic Neuropathy in Adults: A 12-Week, Double-Placebo, Randomized, Noninferiority Trial

BACKGROUND

This study was a multicenter, parallel-group, double-blind, double-dummy, randomized, noninferiority trial to evaluate the efficacy and safety of γ-linolenic acid (GLA) relative to α-lipoic acid (ALA) over a 12-week treatment period in type 2 diabetes mellitus (T2DM) patients with painful diabetic peripheral neuropathy (DPN).

METHODS

This study included 100 T2DM patients between 20 and 75 years of age who had painful DPN and received either GLA (320 mg/day) and placebo or ALA (600 mg/day) and placebo for 12 weeks. The primary outcome measures were mean changes in pain intensities as measured by the visual analogue scale (VAS) and the total symptom scores (TSS).

RESULTS

Of the 100 subjects who initially participated in the study, 73 completed the 12-week treatment period. Per-protocol analyses revealed significant decreases in the mean VAS and TSS scores compared to baseline in both groups, but there were no significant differences between the groups. The treatment difference for the VAS (95% confidence interval [CI]) between the two groups was -0.65 (-1.526 to 0.213) and the upper bound of the 95% CI did not exceed the predefined noninferiority margin (δ₁=0.51). For the TSS, the treatment difference was -0.05 (-1.211 to 1.101) but the upper bound of the 95% CI crossed the noninferiority margin (δ₂=0.054). There were no serious adverse events associated with the treatments.

CONCLUSION

GLA treatment in patients with painful DPN was noninferior to ALA in terms of reducing pain intensity measured by the VAS over 12 weeks.

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

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

Supplementation with Korean Red Ginseng Improves Current Perception Threshold in Korean Type 2 Diabetes Patients: A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND

Many Type 2 diabetes (T2DM) patients in Korea take Korean Red Ginseng (KRG) for various reasons. In this study, we investigated the effects of KRG administration on diabetic peripheral neuropathy in T2DM patients.

METHODS

This study was a randomized, double-blind, placebo-controlled trial. Participants were randomly allocated to either the placebo or KRG group and took corresponding tablets for 24 weeks. The primary outcomes were changes in current perception threshold (CPT) at week 24. Secondary outcomes were altered fasting plasma glucose, HbA1c, and various metabolic and inflammatory markers at week 24.

RESULTS

Sixty-one patients completed the study. The CPT of the lower extremities at various frequencies exhibited significant improvements at week 24 in the KRG group. Other metabolic parameters were not altered after 24 weeks in both groups. In the subgroup analysis, CPT levels were improved in those with a longer diabetes duration or who already had neuropathy at the beginning of the study, and insulin resistance was improved in patients with a shorter diabetes duration.

CONCLUSION

Twenty-four week administration of KRG in T2DM patients resulted in a significant improvement in neuropathy, especially in those with a longer diabetes duration. A further, larger population study with a longer follow-up period is warranted to verify the effects of KRG on diabetic neuropathy.

Diabetic peripheral neuropathy: advances in diagnosis and strategies for screening and early intervention

Diabetic peripheral neuropathy (DPN) is a common complication of both type 1 and 2 diabetes. It is a leading cause of lower-limb amputation and disabling neuropathic pain. Amputations in patients with diabetes have a devastating effect on quality of life and are associated with an alarmingly low life expectancy (on average only 2 years from the amputation). Amputation also places a substantial financial burden on health-care systems and society in general. With the introduction of national diabetes eye screening programmes, the prevalence of blindness in working-age adults is falling. This is not the case, however, with diabetes related amputations. In this Review, we appraise innovative point-of-care devices that enable the early diagnosis of DPN and assess the evidence for early risk factor-based management strategies to reduce the incidence and slow the progression of DPN. We also propose a framework for screening and early multifactorial interventions as the best prospect for preventing or halting DPN and its devastating sequelae.