Hyperglycaemia Aggravates Oxidised Low-Density Lipoprotein-Induced Schwann Cell Death via Hyperactivation of Toll-like Receptor 4.

Increased low-density lipoprotein levels are risk factors for diabetic neuropathy. Diabetes mellitus is associated with elevated metabolic stress, leading to oxidised low-density lipoprotein formation. Therefore, it is important to investigate the mechanisms underlying the pathogenesis of diabetic neuropathy in diabetes complicated by dyslipidaemia with increased levels of oxidised low-density lipoprotein. Here, we examined the effects of hyperglycaemia and oxidised low-density lipoprotein treatment on Schwann cell death and its underlying mechanisms. Immortalised mouse Schwann cells were treated with oxidised low-density lipoprotein under normo- or hyperglycaemic conditions. We observed that oxidised low-density lipoprotein-induced cell death increased under hyperglycaemic conditions compared with normoglycaemic conditions. Moreover, hyperglycaemia and oxidised low-density lipoprotein treatment synergistically upregulated the gene and protein expression of toll-like receptor 4. Pre-treatment with TAK-242, a selective toll-like receptor 4 signalling inhibitor, attenuated hyperglycaemia- and oxidised low-density lipoprotein-induced cell death and apoptotic caspase-3 pathway. Our findings suggest that the hyperactivation of toll-like receptor 4 signalling by hyperglycaemia and elevated oxidised low-density lipoprotein levels synergistically exacerbated diabetic neuropathy; thus, it can be a potential therapeutic target for diabetic neuropathy.

Simplified electrophysiological approach combining a point-of-care nerve conduction device and an electrocardiogram produces an accurate diagnosis of diabetic polyneuropathy.

AIMS/INTRODUCTION: This study aimed to investigate the diagnostic potential of two simplified tests, a point-of-care nerve conduction device (DPNCheck™) and a coefficient of variation of R-R intervals (CVR-R ), as an alternative to traditional nerve conduction studies for the diagnosis of diabetic polyneuropathy (DPN) in patients with diabetes. MATERIALS AND METHODS: Inpatients with type 1 or type 2 diabetes (n = 167) were enrolled. The study population consisted of 101 men, with a mean age of 60.8 ± 14.8 years. DPN severity was assessed using traditional nerve conduction studies, and differentiated based on Baba's classification (BC). To examine the explanatory potential of variables in DPNCheck™ and CVR-R regarding the severity of DPN according to BC, a multiple regression analysis was carried out, followed by a receiver operating characteristic analysis. RESULTS: Based on BC, 61 participants (36.5% of the total) were categorized as having DPN severity of stage 2 or more. The multiple regression analysis yielded a predictive formula with high predictive power for DPN diagnosis (estimated severity of DPN in BC = 2.258 - 0.026 × nerve conduction velocity [m/s] - 0.594 × ln[sensory nerve action potential amplitude (µV)] + 0.528In[age(years)] - 0.178 × ln[CVR-R ], r = 0.657). The area under the curve in receiver operating characteristic analysis was 0.880. Using the optimal cutoff value for DPN with severer than stage 2, the predictive formula showed good diagnostic efficacy: sensitivity of 83.6%, specificity of 79.2%, positive predictive value of 51.7% and negative predictive value of 76.1%. CONCLUSIONS: These findings suggest that DPN diagnosis using DPNCheck™ and CVR-R could improve diagnostic efficiency and accessibility for DPN assessment in patients with diabetes.

The efficacy of switching basal-bolus insulin therapy to basal insulin-supported oral therapy with a glinide and an α-glucosidase inhibitor in patients with type 2 diabetes depends on insulin secretory capacity, but not on blood glucose profiles and insulin dosages prior to the switching.

Aims: We aimed to identify patients who would benefit from basal insulin-supported oral therapy (BOT) with a glinide and an α-glucosidase inhibitor (a fixed-dose combination tablet of mitiglinide 10 mg and voglibose 0.2 mg) in Japanese type 2 diabetic patients. Methods: Patients who were hospitalized to improve hyperglycemia received basal-bolus insulin therapy. After the reduction of glucose toxicity, a 75 g oral glucose tolerance test and a glucagon test were performed. Thereafter, the basal-bolus insulin therapy was switched to BOT with mitiglinide, followed by further addition of voglibose. Interstitial glucose levels were continuously monitored throughout the study period. Diurnal glucose profile was recorded and analyzed. Patients were divided into two groups according to whether their percentage of time in range (TIR, 70-180 mg/dL) under BOT with mitiglinide/voglibose was higher than 70% or not, and the differences in clinical characteristics between the groups were analyzed. Results: Twenty patients were enrolled, and 19 of them completed the study. BOT with mitiglinide/voglibose achieved ≥ 70% of TIR in thirteen patients. The area under the curve of serum C-peptide levels during the oral glucose tolerance test was significantly higher in the patients with ≥ 70% of TIR. The daily insulin dosages and blood glucose profiles were comparable between the two groups. Conclusions: The efficacy of BOT with mitiglinide/voglibose depended on residual insulin secretory abilities. This therapy would be a useful therapeutic option for patients with type 2 diabetes.

Prevalence and characteristics of diabetic symmetric sensorimotor polyneuropathy in Japanese patients with type 2 diabetes: the Japan Diabetes Complication and its Prevention Prospective study (JDCP study 10).

Aim/introduction: This study aims to investigate the prevalence and characteristics of diabetic symmetric sensorimotor polyneuropathy (DSPN) in patients with type 2 diabetes registered in the Japan Diabetes Complication and its Prevention Prospective (JDCP) study. Materials and methods: In the study, 6338 patients with diabetes who had been treated by diabetes specialists were registered in 2007-2009. Of these, patients with type 2 diabetes who could be evaluated for DSPN were analyzed using t test, chi-square test, and logistic regression analyses. DSPN was diagnosed using the Simple Diagnostic Criteria for Diabetic Polyneuropathy proposed by the Diabetic Neuropathy Study Group in Japan. Results: Of the total participants, 5451 patients (mean age 61.4 years old and duration of diabetes 10.8 years) were analyzed. Based on the criteria, 35.8% of patients were diagnosed with DSPN. The prevalence of sensory symptoms was 25.8%. The following factors increased risk for DSPN: age [odds ratio (OR) 1.57, 95% confidence intervals (CI) 1.42-1.73], duration of diabetes (OR 1.32, 95% CI 1.21-1.43), body mass index (OR 1.19, 95% CI 1.09-1.30), systolic blood pressure (OR 1.06, 95% CI 1.01-1.10), hemoglobin A1c (OR 1.15, 95% CI 1.09-1.22), biguanides (OR 1.22, 95% CI 1.06-1.39), and insulin therapy (OR 1.59, 95% CI 1.36-1.84). The following factors decreased risk for DSPN: total cholesterol (OR 0.98, 95% CI 0.96-1.00) and exercise therapy (OR 0.85, 95% CI 0.73-0.98). Conclusions: The baseline survey clarified the prevalence and characteristics of DSPN in Japanese patients with type 2 diabetes. The survey also revealed the risk factors of DSPN.

Prevalence and characteristics of diabetic symmetric sensorimotor polyneuropathy in Japanese patients with type 2 diabetes: The Japan Diabetes Complication and its Prevention Prospective study (JDCP study 10).

This study aimed to investigate the prevalence and characteristics of diabetic symmetric sensorimotor polyneuropathy (DSPN) in patients with type 2 diabetes registered in the Japan Diabetes Complication and its Prevention Prospective study. In the study, 6,338 patients with diabetes who had been treated by diabetes specialists were registered in 2007-2009. Of these, patients with type 2 diabetes who could be evaluated for DSPN were analyzed using the t-test, χ2 -test and logistic regression analyses. DSPN was diagnosed using the Simple Diagnostic Criteria for Diabetic Polyneuropathy proposed by the Diabetic Neuropathy Study Group in Japan. Of the total participants, 5,451 patients (mean age 61.4 years, duration of diabetes 10.8 years) were analyzed. Based on the criteria, 35.8% of patients were diagnosed with DSPN. The prevalence of sensory symptoms was 25.8%. The following factors increased the risk for DSPN: age (odds ratio [OR] 1.57, 95% confidence interval [CI] 1.42-1.73), duration of diabetes (OR 1.32, 95% CI 1.21-1.43), body mass index (OR 1.19, 95% CI 1.09-1.30), systolic blood pressure (OR 1.06, 95% CI 1.01-1.10), hemoglobin A1c (OR 1.15, 95% CI 1.09-1.22), biguanides (OR 1.22, 95% CI 1.06-1.39) and insulin therapy (OR 1.59, 95% CI 1.36-1.84). The following factors decreased the risk for DSPN: total cholesterol (OR 0.98, 95% CI 0.96-1.00) and exercise therapy (OR 0.85, 95% CI 0.73-0.98). The baseline survey clarified the prevalence and characteristics of DSPN in Japanese patients with type 2 diabetes. The survey also showed the risk factors of DSPN.

Correction: A consensus statement from the Japan Diabetes Society (JDS): a proposed algorithm for pharmacotherapy in people with type 2 diabetes.

[This corrects the article DOI: 10.1007/s13340-022-00605-x.].

Clinical parameters correlated with the psoas muscle index in Japanese individuals with type 2 diabetes mellitus.

Aims: Muscle atrophy is a diabetic complication, which results in a deterioration in glycemic control in type 2 diabetes mellitus (T2DM) individuals. The psoas muscle mass index (PMI) is a reliable indicator for estimating whole-body muscle mass. We aimed to examine the relationship between clinical parameters and the PMI to clarify the mechanism underlying muscle atrophy in diabetes. Methods: This retrospective, cross-sectional study examined 51 patients (31 men and 20 women) with T2DM and a mean HbA1c value of 9.9 ± 1.7%. These patients were admitted to Aichi Medical University Hospital and underwent abdominal computed tomography imaging from July 2020 to April 2021. Multiple clinical parameters were assessed with the PMI. Results: In a multiple regression analysis adjusted for age and sex, the PMI was correlated with body weight, body mass index, serum concentrations of corrected calcium, aspartate aminotransferase, alanine aminotransferase, creatine kinase, thyroid-stimulating hormone (TSH), urinary C-peptide concentrations, the free triiodothyronine/free thyroxine (FT3/FT4) ratio, and the young adult mean score at the femur neck. Receiver operating characteristic curves were created using TSH concentrations and the FT3/FT4 ratio for diagnosing a low PMI. The area under the curve was 0.593 and 0.699, respectively. The cut-off value with maximum accuracy for TSH concentrations was 1.491 µIU/mL, sensitivity was 56.1%, and specificity was 80.0%. Corresponding values for the FT3/FT4 ratio were 1.723, 78.0, and 66.7%, respectively. Conclusion: TSH concentrations and the FT3/FT4 ratio are correlated with the PMI, and their thresholds may help prevent muscle mass loss in Japanese individuals with T2DM.

Multifocal Neuroarthropathy of the Knee and Foot Induced by Physical Training of the Lower Extremities in a Patient With Latent Autoimmune Diabetes in Adults.

Charcot neuroarthropathy is a progressive arthropathy associated with neuropathy. In patients with diabetes, Charcot neuroarthropathy mostly affects the foot. In the present case, we encountered a rare presentation of Charcot neuroarthropathy of the knee and foot in a patient with latent autoimmune diabetes in adults. The patient, who may have developed the disease as a result of inappropriate physical exercise, was treated with total knee arthroplasty.

Protocol to image and analyze the morphology of mouse peripheral nerves using transmission electron microscopy.

Morphological analysis of peripheral nerves in mouse models can be used to characterize the pathophysiology of peripheral nerve disease, but obtaining high-quality electron micrographs can be challenging. Here, we present a protocol to obtain electron micrographs of mouse peripheral nerves. We detail the procedures of sampling, fixation, and embedding of peripheral nerves. We then outline the steps for ultrathin sectioning and transmission electron microscopy imaging. Finally, we describe morphological evaluation of nerve fibers in these images using ImageJ and AxonSeg. For complete details on the use and execution of this protocol, please refer to Nakai-Shimoda et al. (2021).

Thermal gradient ring reveals thermosensory changes in diabetic peripheral neuropathy in mice.

Diabetic peripheral neuropathy (DPN) includes symptoms of thermosensory impairment, which are reported to involve changes in the expression or function, or both, of nociceptive TRPV1 and TRPA1 channels in rodents. In the present study, we did not find changes in the expression or function of TRPV1 or TRPA1 in DPN mice caused by STZ, although thermal hypoalgesia was observed in a murine model of DPN or TRPV1-/- mice with a Plantar test, which specifically detects temperature avoidance. With a Thermal Gradient Ring in which mice can move freely in a temperature gradient, temperature preference can be analyzed, and we clearly discriminated the temperature-dependent phenotype between DPN and TRPV1-/- mice. Accordingly, we propose approaches with multiple behavioral methods to analyze the progression of DPN by response to thermal stimuli. Attention to both thermal avoidance and preference may provide insight into the symptoms of DPN.

Docosahexaenoic Acid Suppresses Oxidative Stress-Induced Autophagy and Cell Death via the AMPK-Dependent Signaling Pathway in Immortalized Fischer Rat Schwann Cells 1.

Autophagy is the process by which intracellular components are degraded by lysosomes. It is also activated by oxidative stress; hence, autophagy is thought to be closely related to oxidative stress, one of the major causes of diabetic neuropathy. We previously reported that docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) induced antioxidant enzymes and protected Schwann cells from oxidative stress. However, the relationship between autophagy and oxidative stress-induced cell death in diabetic neuropathy has not been elucidated. Treatment with tert-butyl hydroperoxide (tBHP) decreased the cell survival rate, as measured by an MTT assay in immortalized Fischer rat Schwann cells 1 (IFRS1). A DHA pretreatment significantly prevented tBHP-induced cytotoxicity. tBHP increased autophagy, which was revealed by the ratio of the initiation markers, AMP-activated protein kinase, and UNC51-like kinase phosphorylation. Conversely, the DHA pretreatment suppressed excessive tBHP-induced autophagy signaling. Autophagosomes induced by tBHP in IFRS1 cells were decreased to control levels by the DHA pretreatment whereas autolysosomes were only partially decreased. These results suggest that DHA attenuated excessive autophagy induced by oxidative stress in Schwann cells and may be useful to prevent or reduce cell death in vitro. However, its potentiality to treat diabetic neuropathy must be validated in in vivo studies.

High Protein Diet Feeding Aggravates Hyperaminoacidemia in Mice Deficient in Proglucagon-Derived Peptides.

(1) Background: Protein stimulates the secretion of glucagon (GCG), which can affect glucose metabolism. This study aimed to analyze the metabolic effect of a high-protein diet (HPD) in the presence or absence of proglucagon-derived peptides, including GCG and GLP-1. (2) Methods: The response to HPD feeding for 7 days was analyzed in mice deficient in proglucagon-derived peptides (GCGKO). (3) Results: In both control and GCGKO mice, food intake and body weight decreased with HPD and intestinal expression of Pepck increased. HPD also decreased plasma FGF21 levels, regardless of the presence of proglucagon-derived peptides. In control mice, HPD increased the hepatic expression of enzymes involved in amino acid metabolism without the elevation of plasma amino acid levels, except branched-chain amino acids. On the other hand, HPD-induced changes in the hepatic gene expression were attenuated in GCGKO mice, resulting in marked hyperaminoacidemia with lower blood glucose levels; the plasma concentration of glutamine exceeded that of glucose in HPD-fed GCGKO mice. (4) Conclusions: Increased plasma amino acid levels are a common feature in animal models with blocked GCG activity, and our results underscore that GCG plays essential roles in the homeostasis of amino acid metabolism in response to altered protein intake.

Not out of the woods yet: "Diabetic neuropathy" or "neuropathy associated with diabetes"?

The most frequent diabetic complication, diabetic neuropathy, lacks accessible objective assessments. The concept and definition of diabetic neuropathy should be rethought to achieve the successful development of diagnostic and therapeutic methods.

Kir6.2-deficient mice develop somatosensory dysfunction and axonal loss in the peripheral nerves.

Glucose-responsive ATP-sensitive potassium channels (KATP) are expressed in a variety of tissues including nervous systems. The depolarization of the membrane potential induced by glucose may lead to hyperexcitability of neurons and induce excitotoxicity. However, the roles of KATP in the peripheral nervous system (PNS) are poorly understood. Here, we determine the roles of KATP in the PNS using KATP-deficient (Kir6.2-deficient) mice. We demonstrate that neurite outgrowth of dorsal root ganglion (DRG) neurons was reduced by channel closers sulfonylureas. However, a channel opener diazoxide elongated the neurite. KATP subunits were expressed in mouse DRG, and expression of certain subunits including Kir6.2 was increased in diabetic mice. In Kir6.2-deficient mice, the current perception threshold, thermal perception threshold, and sensory nerve conduction velocity were impaired. Electron microscopy revealed a reduction of unmyelinated and small myelinated fibers in the sural nerves. In conclusion, KATP may contribute to the development of peripheral neuropathy.

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.

Impact of actual waiting time and perceived waiting time on treatment satisfaction in patients receiving outpatient diabetes care.

AIMS: We investigated the impact of actual waiting time and perceived waiting time on treatment satisfaction in patients with diabetes receiving outpatient care. METHODS: Three hundred and thirty-six outpatients diagnosed with diabetes mellitus or impaired glucose tolerance were selected and the time they spent in reception, blood collection, consultation, and accounting were recorded to measure the time they spent waiting in the hospital (actual waiting time). Simultaneously, we conducted a questionnaire survey that included questions on their perceptions of the waiting time (perceived waiting time) and satisfaction with treatment (DTSQ). RESULTS: No significant relationship was found between actual waiting time and DTSQ score, although associations were observed with perceived waiting time. The patients who felt the overall waiting time was long scored 23.0, those who felt it was short scored 26.0, and those who felt it was very short scored 34.0, with those who felt the waiting time was long having a significantly lower score (p = 0.004, p < 0.001, respectively) and those who felt it was short having a significantly lower score than those who felt it was very short (p = 0.008). In addition, more patients who felt the waiting time was long expressed dissatisfaction with the responses of doctors and staff than those who felt the waiting time was short. CONCLUSIONS: These results suggest that in addition to reducing actual waiting times, shortening perceived waiting times by improving the responses of medical staff could help to increase patient satisfaction.

Correction to: Impact of actual waiting time and perceived waiting time on treatment satisfaction in patients receiving outpatient diabetes care.

[This corrects the article DOI: 10.1007/s13340-020-00486-y.].

Small Fibre Neuropathy Is Associated With Impaired Vascular Endothelial Function in Patients With Type 2 Diabetes.

Diabetic polyneuropathy (DPN) and endothelial dysfunction are prevalent complications of diabetes mellitus. Currently, there are two non-invasive markers for endothelial dysfunction: flow-mediated dilation and reactive hyperaemia peripheral arterial tonometry (RH-PAT). However, the relationship between diabetic small fibre neuropathy and macroangiopathy remains obscure thus far. Corneal confocal microscopy (CCM) has emerged as a new diagnostic modality to assess DPN, especially of small fibre. To clarify the relationship between diabetic small fibre neuropathy and vascular dysfunction, we aimed to determine the functions of peripheral nerves and blood vessels through clinical tests such as nerve conduction study, coefficient of variation in the R-R interval, CCM, and RH-PAT in 82 patients with type 2 diabetes. Forty healthy control subjects were also included to study corneal nerve parameters. Correlational and multiple linear regression analyses were performed to determine the associations between neuropathy indices and markers for vascular functions. The results revealed that patients with type 2 diabetes had significantly lower values for most variables of CCM than healthy control subjects. RH-PAT solely remained as an explanatory variable significant in multiple regression analysis for several CCM parameters and vice versa. Other vascular markers had no significant multiple regression with any CCM parameters. In conclusion, endothelial dysfunction as revealed by impaired RH-PAT was significantly associated with CCM parameters in patients with type 2 diabetes. This association may indicate that small fibre neuropathy results from impaired endothelial dysfunction in type 2 diabetes. CCM parameters may be considered surrogate markers of autonomic nerve damage, which is related to diabetic endothelial dysfunction. This study is the first to report the relationship between corneal nerve parameter as small fibre neuropathy in patients with type 2 diabetes and RH-PAT as a marker of endothelial dysfunction.