Serum levels of TGF-β1 in patients of diabetic peripheral neuropathy and its correlation with nerve conduction velocity in type 2 diabetes mellitus

Correlation between Neutrophil-to-Lymphocyte Ratio and Diabetic Neuropathy in Chinese Adults with Type 2 Diabetes Mellitus Using Machine Learning Methods

Objective

One of the most frequent consequences of diabetes mellitus has been identified as diabetic peripheral neuropathy (DPN), and numerous inflammatory disorders, including diabetes, have been documented to be reflected by the neutrophil-to-lymphocyte ratio (NLR). This study aimed to explore the correlation between peripheral blood NLR and DPN, and to evaluate whether NLR could be utilized as a novel marker for early diagnosis of DPN among those with type 2 Diabetes Mellitus (T2DM).

Methods

We reviewed the medical records of 1154 diabetic patients treated at Tongji Hospital Affiliated to Tongji University from January 2022 to March 2023. These patients did not have evidence of acute infections, chronic inflammatory status within the past three months. The information included the clinical, laboratory, and demographic characteristics of the patient. Finally, a total of 442 T2DM individuals with reliable, complete, and accessible medical records were recruited, including 216 T2DM patients without complications (DM group) and 226 T2DM patients with complications of DPN (DPN group). One-way ANOVA and multivariate logistic regression were applied to analyze data from the two groups, including peripheral blood NLR values and other biomedical indices. The cohort was divided in a 7 : 3 ratio into training and internal validation datasets following feature selection and data balancing. Based on machine learning, training was conducted using extreme gradient boosting (XGBoost) and support vector machine (SVM) methods. K-fold cross-validation was applied for model assessment, and accuracy, precision, recall, F1-score, and the area under the receiver operating characteristic curve (AUC) were used to validate the models' discrimination and clinical applicability. Using Shapley Additive Explanations (SHAP), the top-performing model was interpreted.

Results

The values of 24-hour urine volume (24H UV), lower limb arterial plaque thickness (LLAB thickness), carotid plaque thickness (CP thickness), D-dimer and onset time were significantly higher in the DPN group compared to the DM group, whereas the values of urine creatinine (UCr), total cholesterol (TC), low-density lipoprotein (LDL), alpha-fetoprotein (AFP), fasting c-peptide (FCP), and nerve conduction velocity and wave magnitude of motor and sensory nerve shown in electromyogram (EMG) were considerably lower than those in the DM group (P < 0.05, respectively). NLR values were significantly higher in the DPN group compared to the DM group (2.60 ± 4.82 versus 1.85 ± 0.98, P < 0.05). Multivariate logistic regression analysis revealed that NLR (P = 0.008, C = 0.003) was a risk factor for DPN. The multivariate logistic regression model scores were 0.6241 for accuracy, 0.6111 for precision, 0.6667 for recall, 0.6377 for F1, and 0.6379 for AUC. Machine learning methods, XGBoost and SVM, built prediction models, showing that NLR can predict the onset of DPN. XGBoost achieved an accuracy of 0.6541, a precision of 0.6316, a recall of 0.7273, a F1 value of 0.6761, and an AUC value of 0.690. SVM scored an accuracy of 0.5789, a precision of 0.5610, a recall of 0.6970, an F1 value of 0.6216, and an AUC value of 0.6170.

Conclusions

Our findings demonstrated that NLR is highly correlated with DPN and is an independent risk factor for DPN. NLR might be a novel indicator for the early diagnosis of DPN. XGBoost and SVM models have great predictive performance and could be reliable tools for the early prediction of DPN in T2DM patients. This trial is registered with ChiCTR2400087019.

Association of serum biomarkers level transforming growth factor-β and tumor necrosis factor-α with diabetic neuropathy

BACKGROUND

Many studies have examined the role of inflammation in the development of diabetic neuropathy (DPN).

OBJECTIVE

Evaluate the relation of the serum level of Transforming Growth Factor-β and Tumor Necrosis Factor-α and development of diabetic peripheral neuropathy DPN.

METHODS

In a case-control study, randomly selected 140 diabetic patients were included, the randomly selected patients were divided equally and matched into a case group who have diabetic peripheral neuropathy and diabetic neuropathy-free patients as a control group. For both groups whole blood sample was examined to compare for (TGF-β), and (TNF-α) levels determination by ELISA technique.

RESULTS

The age of the study samples ranged from 25 to 80 years with a male ratio of 1.45:1 although the sex differences between both groups were not significant. The mean levels of (TNF-α) and (TGF-β) was significantly higher among cases group than that of controls group (254.86 ± 75.9 vs158.01 ± 50.600) for TNF-α and for TGF- β (312.85 ± 62.27 vs. 217.82 ± 52.95) respectively. Both TNF-α and TGF-β have high sensitivity and specificity in detection of DPN. The sensitivity of TNF-α was 95.7% and specificity of 61.4% area under the ROC curve (AUC) of 0.870 ± 0.029, while the sensitivity of TGF-β was 91.4%, and specificity of 67.1 with good area under the ROC curve (AUC) of 0.891 ± 0.026 (P=0.000).

CONCLUSIONS

TNF-α and TGF -β are significantly elevated levels in patients with DPN, these cytokines could be used as indicators for the development of DPN.

Inflammation in diabetes complications: molecular mechanisms and therapeutic interventions

At present, diabetes mellitus (DM) has been one of the most endangering healthy diseases. Current therapies contain controlling high blood sugar, reducing risk factors like obesity, hypertension, and so on; however, DM patients inevitably and eventually progress into different types of diabetes complications, resulting in poor quality of life. Unfortunately, the clear etiology and pathogenesis of diabetes complications have not been elucidated owing to intricate whole-body systems. The immune system was responsible to regulate homeostasis by triggering or resolving inflammatory response, indicating it may be necessary to diabetes complications. In fact, previous studies have been shown inflammation plays multifunctional roles in the pathogenesis of diabetes complications and is attracting attention to be the meaningful therapeutic strategy. To this end, this review systematically concluded the current studies over the relationships of susceptible diabetes complications (e.g., diabetic cardiomyopathy, diabetic retinopathy, diabetic peripheral neuropathy, and diabetic nephropathy) and inflammation, ranging from immune cell response, cytokines interaction to pathomechanism of organ injury. Besides, we also summarized various therapeutic strategies to improve diabetes complications by target inflammation from special remedies to conventional lifestyle changes. This review will offer a panoramic insight into the mechanisms of diabetes complications from an inflammatory perspective and also discuss contemporary clinical interventions.

Effects of diabetes mellitus and glycemic traits on cardiovascular morpho-functional phenotypes

BACKGROUND

The effects of diabetes on the cardiac and aortic structure and function remain unclear. Detecting and intervening these variations early is crucial for the prevention and management of complications. Cardiovascular magnetic resonance imaging-derived traits are established endophenotypes and serve as precise, early-detection, noninvasive clinical risk biomarkers. We conducted a Mendelian randomization (MR) study to examine the association between two types of diabetes, four glycemic traits, and preclinical endophenotypes of cardiac and aortic structure and function.

METHODS

Independent genetic variants significantly associated with type 1 diabetes, type 2 diabetes, fasting insulin (FIns), fasting glucose (FGlu), 2 h-glucose post-challenge (2hGlu), and glycated hemoglobin (HbA1c) were selected as instrumental variables. The 96 cardiovascular magnetic resonance imaging traits came from six independent genome-wide association studies. These traits serve as preclinical endophenotypes and offer an early indication of the structure and function of the four cardiac chambers and two aortic sections. The primary analysis was performed using MR with the inverse-variance weighted method. Confirmation was achieved through Steiger filtering and testing to determine the causal direction. Sensitivity analyses were conducted using the weighted median, MR-Egger, and MR-PRESSO methods. Additionally, multivariable MR was used to adjust for potential effects associated with body mass index.

RESULTS

Genetic susceptibility to type 1 diabetes was associated with increased ascending aortic distensibility. Conversely, type 2 diabetes showed a correlation with a reduced diameter and areas of the ascending aorta, as well as decreased distensibility of the descending aorta. Genetically predicted higher levels of FGlu and HbA1c were correlated with a decrease in diameter and areas of the ascending aorta. Furthermore, higher 2hGlu levels predominantly showed association with a reduced diameter of both the ascending and descending aorta. Higher FIns levels corresponded to increased regional myocardial-wall thicknesses at end-diastole, global myocardial-wall thickness at end-diastole, and regional peak circumferential strain of the left ventricle.

CONCLUSIONS

This study provides evidence that diabetes and glycemic traits have a causal relationship with cardiac and aortic structural and functional remodeling, highlighting the importance of intensive glucose-lowering for primary prevention of cardiovascular diseases.

MACHINE LEARNING ANALYSIS OF THE UK BIOBANK REVEALS PROGNOSTIC AND DIAGNOSTIC IMMUNE BIOMARKERS FOR POLYNEUROPATHY AND NEUROPATHIC PAIN IN DIABETES

AIMS

We assessed the health data of 11,047 people with diabetes in the UK Biobank to rank 329 risk factors for diabetic polyneuropathy (DPN) and DPN with chronic neuropathic pain without a priori assumption.

METHODS

The Integrated Disease Explanation and Risk Scoring (IDEARS) platform applies machine learning algorithms to multimodal data to determine individual disease risk, and rank risk factor importance using mean SHapley Additive exPlanations (SHAP) score.

RESULTS

IDEARS models showed discriminative performances with AUC > 0.64. Lower socioeconomic status, being overweight, poor overall health, cystatin C, HbA1C, and immune activation marker, C-reactive protein (CRP), predict DPN risk. Neutrophils and monocytes were higher in males and lymphocytes lower in females with diabetes that develop DPN. Neutrophil-to-Lymphocyte Ratio (NLR) was increased and IGF-1 levels decreased in people with type 2 diabetes that later develop DPN. CRP was significantly elevated in those with DPN and chronic neuropathic pain compared to DPN without pain.

CONCLUSIONS

Lifestyle factors and blood biomarkers predict the later development of DPN and may relate to DPN pathomechanisms. Our results are consistent with DPN as a disease involving systemic inflammation. We advocate for the use of these biomarkers clinically to predict future DPN risk and improve early diagnosis.

The predictive value of fibrinogen in the occurrence of mild cognitive impairment events in patients with diabetic peripheral neuropathy

BACKGROUND

Research suggests that fibrinogen (Fib) is related to mild cognitive impairment (MCI) and diabetic peripheral neuropathy (DPN) and the risk of MCI in patients with DPN is greatly increased, although no studies have evaluated the predictive value of Fib for the risk of MCI in patients with DPN.

METHODS

This prospective observational clinical study enrolled 207 type 2 diabetes mellitus (T2DM) patients, who were divided into diabetes with no neuropathy (102 cases) and diabetes with neuropathy (105 cases) groups. Meanwhile, 90 healthy unrelated subjects were recruited as controls. The incidence of MCI in the DPN patients was followed up for 2 years. Divide patients in the DPN group into subgroups according to whether MCI occur, use multivariate logistic regression to analyze independent factors of MCIs in DPN patients within 2 years, and use ROC curve to analyze the predictive value of Fib for MCI in DPN patients.

RESULTS

Fib levels were significantly higher in diabetic subjects with neuropathy compared with those without (P < 0.001). In further subgroup analysis of DPN patients who were divided according to the occurrence of MCI, baseline data of the MCI subgroup showed Fib levels were higher than that in the non-MCI group while education levels declined (P < 0.001). The education level and increased Fib levels were independent factors for the occurrence of MCI within 2 years after the onset of DPN (OR = 0.769, 95% CI: 0.605 ~ 0.968, P = 0.037; OR = 2.674, 95% CI: 1.094 ~ 3.168, P = 0.002). The ROC curve indicated that the predictive value of Fib was (AUC = 0.764, 95% CI: 0.671 ~ 0.842, P < 0.001).

CONCLUSIONS

Fib may function as a predictor for assessing the risk of MCI in DPN patients.

Polyphenols target miRNAs as a therapeutic strategy for diabetic complications

MiRNAs are a large group of non-coding RNAs which participate in different cellular pathways like inflammation and oxidation through transcriptional, post-transcriptional, and epigenetic regulation. In the post-transcriptional regulation, miRNA interacts with the 3'-UTR of mRNAs and prevents their translation. This prevention or dysregulation can be a cause of pathological conditions like diabetic complications. A huge number of studies have revealed the association between miRNAs and diabetic complications, including diabetic nephropathy, cardiomyopathy, neuropathy, retinopathy, and delayed wound healing. To address this issue, recent studies have focused on the use of polyphenols as selective and safe drugs in the treatment of diabetes complications. In this article, we will review the involvement of miRNAs in diabetic complications' occurrence or development. Finally, we will review the latest findings on targeting miRNAs by polyphenols like curcumin, resveratrol, and quercetin for diabetic complications therapy.

Serum uric acid and diabetic peripheral neuropathy: a double-edged sword

BACKGROUND AND OBJECTIVES

Research suggests that diabetic peripheral neuropathy (DPN) is related to high serum uric acid (SUA) level, although its correlation with low SUA level has not been reported. Here, diabetic patients with hyperuricemia were excluded, and the correlation between low SUA level and DPN was explored.

SUBJECTS AND METHODS

This prospective observational clinical study enrolled 525 type 2 diabetes mellitus (T2DM) patients without hyperuricemia, who were divided into the diabetes with symptomatic neuropathy (150 cases), diabetes with asymptomatic neuropathy (125 cases) and diabetes with no neuropathy (250 cases) groups.

RESULTS

The SUA slightly decreased in subjects with asymptomatic DPN compared with those with no neuropathy and greatly decreased in subjects with symptomatic DPN compared with those without (P < 0.001). The association of the SUA with diabetic neuropathy was independent of the hyperglycemic state and other potential confounders (odds ratio 0.985 [0.981-0.988], P < 0.001). The SUA was closely correlated with the means of motor/sensory nerve amplitude and CV (all P < 0.001). The optimal cut-off point for SUA to distinguish patients with diabetic neuropathy from those without was 324 umol/L, with a sensitivity of 76.0% and a specificity of 79.2% (AUC = 0.806).

CONCLUSIONS

The low SUA level is closely associated with DPN. Future studies are warranted to clarify the relationship.

Fully Convolutional Neural Network Deep Learning Model Fully in Patients with Type 2 Diabetes Complicated with Peripheral Neuropathy by High-Frequency Ultrasound Image

This study was aimed at exploring the diagnostic value of high-frequency ultrasound imaging based on a fully convolutional neural network (FCN) for peripheral neuropathy in patients with type 2 diabetes (T2D). A total of 70 patients with T2D mellitus were selected and divided into a lesion group (n = 31) and a nonlesion group (n = 39) according to the type of peripheral neuropathy. In addition, 30 healthy people were used as controls. Hypervoxel-based and FCN-based high-frequency ultrasound images were used to examine the three groups of patients to evaluate their diagnostic performance and to compare the changes of peripheral nerves and ultrasound characteristics. The results showed that the Dice coefficient (92.7) and mean intersection over union (mIOU) (82.6) of the proposed algorithm after image segmentation were the largest, and the Hausdorff distance (7.6) and absolute volume difference (AVD) (8.9) were the smallest. The high-frequency ultrasound based on the segmentation algorithm showed higher diagnostic accuracy (94.0% vs. 86.0%), sensitivity (87.1% vs. 67.7%), specificity (97.1% vs. 94.2%), positive predictive value (93.1% vs. 86.7%), and negative predictive value (94.4% vs. 84.0%) (P < 0.05). There were significant differences in the detection values of the three major nerve segments of the upper limbs in the control group, the lesion group, and the nonlesion group (P < 0.05). Compared with the nonlesion group, the patients in the lesion group were more likely to have reduced nerve bundle echo, blurred reticular structure, thickened epineurium, and unclear borders of adjacent tissues (P < 0.05). In summary, the high-frequency ultrasound processed by the algorithm proposed in this study showed a high diagnostic value for peripheral neuropathy in T2D patients, and high-frequency ultrasound can be used to evaluate the morphological changes of peripheral nerves in T2D patients.

Fibrinogen function indexes are potential biomarkers of diabetic peripheral neuropathy

BACKGROUND AND OBJECTIVES

Research suggests that diabetic peripheral neuropathy (DPN) is related to plasma fibrinogen (Fib) concentrations, although its correlation with Fib function has not been reported. Here, the k value and angle α, reflecting the plasma Fib function, were used to analyse its correlation with DPN, and their potential as biological indicators for diagnosing DPN was explored.

SUBJECTS AND METHODS

This prospective observational clinical study enrolled 561 type 2 diabetes mellitus (T2DM) patients, who were divided into the diabetes with symptomatic neuropathy (161 cases), diabetes with asymptomatic neuropathy (132 cases) and diabetes with no neuropathy (268 cases) groups. Meanwhile, 160 healthy unrelated subjects were recruited as controls.

RESULTS

Fib levels increased slightly in diabetic subjects with neuropathy compared with those without. The angle α levels increased slightly in subjects with asymptomatic DPN compared with those with no neuropathy and increased greatly in subjects with symptomatic DPN compared with those without. The k value levels slightly decreased in subjects with asymptomatic DPN compared with those with no neuropathy and greatly decreased in subjects with symptomatic DPN compared with those without. The association of the k value and angle α with diabetic neuropathy was independent of the hyperglycaemic state and other potential confounders (odds ratio 0.080 [0.051-0.124], P < 0.001; odds ratio 1.131 [1.063-1.204], P < 0.001). The k value and angle α levels were closely correlated with neuropathy stage (r  = - 0.686, P < 0.000; r  = 0.314, P < 0.001). The optimal cut-off point for k value levels to distinguish patients with diabetic neuropathy from those without was 1.8 min, with a sensitivity of 73.7% and a specificity of 83.2% (AUC = 0.873). The optimal cut-off point for angle α levels was 60°, with a sensitivity of 41.0% and a specificity of 95.6% (AUC = 0.669).

CONCLUSIONS

The k value and angle α are closely associated with DPN. The levels of the k value and angle α may be helpful in the early diagnosis of DPN.

Serum free triiodothyronine is inversely associated with diabetic peripheral neuropathy but not with carotid atherosclerotic lesions in euthyroid patients with type 2 diabetes

BACKGROUND

The associations between serum free triiodothyronine (FT3) and diabetic peripheral neuropatprohy (DPN)/carotid atherosclerotic lesions in euthyroid patients with type 2 diabetes are still unclear. The purpose of our study was to explore the relations of FT3 to DPN and carotid atherosclerotic lesions in Chinese type 2 diabetes inpatients with euthyroid function.

METHODS

2477 euthyroid inpatients with type 2 diabetes were recruited and they were stratified into quartiles by FT3 levels in this cross-sectional study. Peripheral neuropathy was assessed by neurological symptoms and signs as well as nerve conduction velocity tests. Carotid atherosclerotic lesions, including carotid intima-media thickness, plaque and stenosis, were evaluated by Doppler ultrasound.

RESULTS

The prevalence of DPN in type 2 diabetic patients exhibited the significant decrease across the FT3 quartiles (23.5%, 20.9%, 18.8%, and 11.2%, respectively, p < 0.001). Multiple logistical regression analysis also revealed that FT3 quartiles were significantly and inversely associated with DPN. Compared with the subjects in the highest FT3 quartile, the adjusted odds ratios (95% confidence interval) of DPN from the first to third FT3 quartile were successively 2.338 (1.407-3.884), 1.903 (1.134-3.194) and 1.598 (0.960-1.125). The patients with DPN had significantly higher prevalence of carotid atherosclerotic lesions compared with non-DPN patients. However, no statistical association was observed between FT3 quartiles and carotid atherosclerotic lesions after adjusting for confounder factors.

CONCLUSIONS

Lower FT3 within the normal range was independently associated with DPN, but not with carotid atherosclerotic lesions in Chinese euthyroid inpatients with type 2 diabetes.

Tocotrienol-Rich Vitamin E (Tocovid) Improved Nerve Conduction Velocity in Type 2 Diabetes Mellitus Patients in a Phase II Double-Blind, Randomized Controlled Clinical Trial

Diabetic peripheral neuropathy (DPN) is the most common microvascular complication of diabetes that affects approximately half of the diabetic population. Up to 53% of DPN patients experience neuropathic pain, which leads to a reduction in the quality of life and work productivity. Tocotrienols have been shown to possess antioxidant, anti-inflammatory, and neuroprotective properties in preclinical and clinical studies. This study aimed to investigate the effects of tocotrienol-rich vitamin E (Tocovid Suprabio^TM) on nerve conduction parameters and serum biomarkers among patients with type 2 diabetes mellitus (T2DM). A total of 88 patients were randomized to receive 200 mg of Tocovid twice daily, or a matching placebo for 12 months. Fasting blood samples were collected for measurements of HbA1c, renal profile, lipid profile, and biomarkers. A nerve conduction study (NCS) was performed on all patients at baseline and subsequently at 2, 6, 12 months. Patients were reassessed after 6 months of washout. After 12 months of supplementation, patients in the Tocovid group exhibited highly significant improvements in conduction velocity (CV) of both median and sural sensory nerves as compared to those in the placebo group. The between-intervention-group differences (treatment effects) in CV were 1.60 m/s (95% CI: 0.70, 2.40) for the median nerve and 2.10 m/s (95% CI: 1.50, 2.90) for the sural nerve. A significant difference in peak velocity (PV) was also observed in the sural nerve (2.10 m/s; 95% CI: 1.00, 3.20) after 12 months. Significant improvements in CV were only observed up to 6 months in the tibial motor nerve, 1.30 m/s (95% CI: 0.60, 2.20). There were no significant changes in serum biomarkers, transforming growth factor beta-1 (TGFβ-1), or vascular endothelial growth factor A (VEGF-A). After 6 months of washout, there were no significant differences from baseline between groups in nerve conduction parameters of all three nerves. Tocovid at 400 mg/day significantly improve tibial motor nerve CV up to 6 months, but median and sural sensory nerve CV in up to 12 months of supplementation. All improvements diminished after 6 months of washout.

T lymphocyte and monocyte subsets are dysregulated in type 1 diabetes patients with peripheral neuropathic pain

Diabetic neuropathic pain is a common and devastating complication of type 1 diabetes, but the mechanism by which it develops and persists is yet to be fully elucidated. This study utilised high-dimensional suspension mass cytometry in a pilot cohort to investigate differences in peripheral blood immunophenotypes between type 1 diabetes patients with (n ​= ​9) and without (n ​= ​9) peripheral neuropathic pain. The abundance and activation of several leukocyte subsets were investigated with unsupervised clustering approaches FlowSOM and SPADE, as well as by manual gating. Major findings included a proportional increase in CD4+ central memory T cells and an absolute increase in classical monocytes, non-classical monocytes, and mature natural killer cells in type 1 diabetes patients with pain compared to those without pain. The expression of CD27, CD127, and CD39 was upregulated on select T cell populations, and the phosphorylated form of pro-inflammatory transcription factor MK2 was upregulated across most populations. These results provide evidence that distinct immunological signatures are associated with painful neuropathy in type 1 diabetes patients. Further research may link these changes to mechanisms by which pain in type 1 diabetes is initiated and maintained, paving the way for much needed targeted treatments.

Determination of the transcriptional level of long non-coding RNA NEAT-1, downstream target microRNAs, and genes targeted by microRNAs in diabetic neuropathy patients

BACKGROUND

Diabetic neuropathy (DN) is one of the microvascular complications of diabetes that leads to peripheral sensorimotor and autonomic nervous system damages. In this study, we first examined the expression of lncRNA NEAT-1 and its downstream microRNAs, miR-183-5p, miR-433-3p, and then examined mRNA expression of ITGA4, ITGB1, SESN1, and SESN3 as the downstream targets of miR-183-5p, miR-433-3p.

METHODS

The blood sample was obtained from a total of 40 patients with type 2 diabetes (20 DN patients and 20 non-DN diabetic cases) and ten healthy individuals. After RNA extraction from peripheral blood samples and cDNA synthesis, expression measurements were performed by the RT-qPCR technique.

RESULTS

Our results showed that the expression level of lncRNA NEAT-1 was significantly higher, and the expression level of miR-183-5p was significantly lower in DN patients compared to the healthy control group. Besides, the expression level of miR-433-3p was significantly lower, and the mRNA expression of ITGA4, SESN1, and SESN3 was significantly higher in DN patients compared to the diabetes group. The ROC curve analysis showed that the miR-183-5p with high levels of accuracy could discriminate DN patients from healthy control (AUC = 0.836) and NEAT-1, SESN1, SESN3, ITGA4 have a high ability to distinguish DN from non-DN patients (AUC = 0.701, 0.772, 0.815 and 0.780, respectively).

CONCLUSION

It seems that the NEAT-1 probably targets miR-183-5p and miR-433-3p, as a result of which the expression of ITGA4, SESN1, and SESN3 is affected. Dysregulated expression of NEAT-1 and related miRNAs and genes might be involved in the pathogenesis of DN.

Emerging Roles of microRNAs as Biomarkers and Therapeutic Targets for Diabetic Neuropathy

Diabetic neuropathy (DN) is the most prevalent chronic complication of diabetes mellitus. The exact pathophysiological mechanisms of DN are unclear; however, communication network dysfunction among axons, Schwann cells, and the microvascular endothelium likely play an important role in the development of DN. Mounting evidence suggests that microRNAs (miRNAs) act as messengers that facilitate intercellular communication and may contribute to the pathogenesis of DN. Deregulation of miRNAs is among the initial molecular alterations observed in diabetics. As such, miRNAs hold promise as biomarkers and therapeutic targets. In preclinical studies, miRNA-based treatment of DN has shown evidence of therapeutic potential. But this therapy has been hampered by miRNA instability, targeting specificity, and potential toxicities. Recent findings reveal that when packaged within extracellular vesicles, miRNAs are resistant to degradation, and their delivery efficiency and therapeutic potential is markedly enhanced. Here, we review the latest research progress on the roles of miRNAs as biomarkers and as potential clinical therapeutic targets in DN. We also discuss the promise of exosomal miRNAs as therapeutics and provide recommendations for future research on miRNA-based medicine.

Kynurenine, Tetrahydrobiopterin, and Cytokine Inflammatory Biomarkers in Individuals Affected by Diabetic Neuropathic Pain

Neuropathic pain is a common complication of diabetes with high morbidity and poor treatment outcomes. Accumulating evidence suggests the immune system is involved in the development of diabetic neuropathy, whilst neuro-immune interactions involving the kynurenine (KYN) and tetrahydrobiopterin (BH4) pathways have been linked to neuropathic pain pre-clinically and in several chronic pain conditions. Here, using a multiplex assay, we quantified serum levels of 14 cytokines in 21 participants with type 1 diabetes mellitus, 13 of which were classified as having neuropathic pain. In addition, using high performance liquid chromatography and gas chromatography-mass spectrometry, all major KYN and BH4 pathway metabolites were quantified in serum from the same cohort. Our results show increases in GM-CSF and IL-8, suggesting immune cell involvement. We demonstrated increases in two inflammatory biomarkers: neopterin and the KYN/TRP ratio, a marker of indoleamine 2,3-dioxygenase activity. Moreover, the KYN/TRP ratio positively correlated with pain intensity. Total kynurenine aminotransferase activity was also higher in the diabetic neuropathic pain group, indicating there may be increased production of the KYN metabolite, xanthurenic acid. Overall, this study supports the idea that inflammatory activation of the KYN and BH4 pathways occurs due to elevated inflammatory cytokines, which might be involved in the pathogenesis of neuropathic pain in type 1 diabetes mellitus. Further studies should be carried out to investigate the role of KYN and BH4 pathways, which could strengthen the case for therapeutically targeting them in neuropathic pain conditions.

Deficits in systemic biomarkers of neuroinflammation and growth factors promoting nerve regeneration in patients with type 2 diabetes and polyneuropathy

INTRODUCTION

The determinants and mechanisms contributing to diabetic sensorimotor polyneuropathy (DSPN) remain unclear. Since neuroinflammation and altered nerve regeneration have been implicated in the pathogenesis of both DSPN and neuropathic pain, we hypothesized that the corresponding biomarkers could be associated with DSPN in general and could have the potential to discriminate between the painful and painless DSPN entities.

METHODS

In a cross-sectional study using multimarker proximity extension assay technology we assessed 71 serum biomarkers including cytokines, chemokines, growth factors, receptors, and others in patients with type 2 diabetes with DSPN (DSPN+) (n=304) or without DSPN (DSPN-) (n=158) and persons with normal glucose tolerance (NGT) without polyneuropathy (n=354).

RESULTS

After adjustment for multiple testing and sex, age, body mass index, HbA1c, and smoking, the serum levels of 17 biomarkers (four cytokines, five chemokines, four growth factors, two receptors, two miscellaneous) were lower in DSPN+ than in DSPN- and NGT. In DSPN+, six of these biomarkers were associated with peripheral nerve function. The concentrations of 15 other biomarkers differed between NGT and both DSPN+ and DSPN-, but not between DSPN+ and DSPN-. No differences in biomarker levels were found between patients with painful (n=164) and painless DSPN (n=140).

CONCLUSIONS

Deficits in systemic cytokines, chemokines, and growth factors promoting nerve regeneration in patients with type 2 diabetes are linked to polyneuropathy in general but not specifically to the painful or painless entity.

TRIAL REGISTRATION NUMBER

NCT02243475.

Downregulation of IL-22 can be considered as a risk factor for onset of type 2 diabetes

There is some controversy as for the roles played by tumor growth factor-β (TGF-β), interleukin-1β (IL-1β), and IL-22 in the onset process of type 2 diabetes (T2D). The main aim of this project was to examine serum levels of TGF-β, IL-1β, and IL-22 in the new cases and long period T2D patients as well as healthy controls. In this study, 115 new T2D patient cases (group 1), 434 T2D patients who have suffered from the disease more than 2 years (group 2), and 104 healthy controls have been selected from 6240 (3619 females) patients who were under study population from Kerman Coronary Artery Disease Risk Factor Study. Serum levels of TGF-β, IL-1β, and IL-22 have been evaluated using commercial kits. Serum levels of TGF-β and IL-1β significantly increased, while IL-22 decreased in 2 groups in comparison to healthy controls. Serum levels of IL-22, but not TGF-β and IL-1β, were significantly decreased in group 1 in comparison to healthy controls. There were no significant differences between groups 1 and 2 as for the cytokine levels. Serum levels of IL-22 increased in the females in group 2 when compared to females in group 1. It appears that TGF-β and IL-1β participate in the induction of inflammation after establishment of T2D, while decrease in IL-22 may be considered as a key factor for onset of the disease. Gender can also be considered as the main risk factor for variation in cytokine levels.

Electrophysiological measurements of diabetic peripheral neuropathy: A systematic review

INTRODUCTION

Peripheral neuropathy is one of the main complications of diabetes mellitus. One of the features of diabetic nerve damage is abnormality of sensory and motor nerve conduction study. An electrophysiological examination can be reproduced and is also a non-invasive approach in the assessment of peripheral nerve function. Population-based and clinical studies have been conducted to validate the sensitivity of these methods. When the diagnosis was based on clinical electrophysiological examination, abnormalities were observed in all patients.

METHOD

In this research, using a review design, we reviewed the issue of clinical electrophysiological examination of diabetic peripheral neuropathy in articles from 2008 to 2017. For this purpose, PubMed, Scopus and Embase databases of journals were used for searching articles.

RESULTS/FINDINGS

The researchers indicated that diabetes (both types) is a very disturbing health issue in the modern world and should be given serious attention. Based on conducted studies, it was demonstrated that there are different procedures for prevention and treatment of diabetes-related health problems such as diabetic polyneuropathy (DPN). The first objective quantitative indication of the peripheral neuropathy is abnormality of sensory and motor nerve conduction tests. Electrophysiology is accurate, reliable and sensitive. It can be reproduced and also is a noninvasive approach in the assessment of peripheral nerve function.

CONCLUSION

The methodological review has found that the best method for quantitative indication of the peripheral neuropathy compared with all other methods is clinical electrophysiological examination. For best results, standard protocols such as temperature control and equipment calibration are recommended.

Abnormal expressions of AGEs, TGF-β1, BDNF and their receptors in diabetic rat colon-Associations with colonic morphometric and biomechanical remodeling

Present study aims to investigate the role of AGEs, TGF-β1, BDNF and their receptors on diabetes-induced colon remodeling. Diabetes was induced by a single tail vein injection 40 mg/kg of STZ. The parameters of morphometric and biomechanical properties of colonic segments were obtained from diabetic and normal rats. The expressions of AGE, RAGE, TGF- β1, TGF- β1 receptor, BDNF and TrkB were immunohistochemically detected in different layers of the colon. The expressions of AGE, RAGE, TGF-β1 and TGF- β1 receptor were increased whereas BDNF and TrkB were decreased in the diabetic colon (P < 0.05, P < 0.01). AGE, RAGE and TGF-β1 receptor expressions were positively correlated whereas the BDNF expression was negatively correlated with most of the morphometry and biomechanical parameters (P < 0.05, P < 0.01, P < 0.001). AGE, TGF- β1 and BDNF in different layers correlated with their receptors RAGE, TGF- β1 receptor and TrkB respectively. STZ-induced diabetes up-regulated the expression of AGE, RAGE, TGF- β1 and TGF- β1 receptors and down-regulated BDNF and TrkB in different layers of diabetic colon mainly due to hyperglycemia. Such changes maybe important for diabetes-induced colon remodeling, however it is needed to further perform mechanistic experiments in order to study causality or approaches that explain the relevance of the molecular pathways.

Declining Skeletal Muscle Function in Diabetic Peripheral Neuropathy

PURPOSE

The present review highlights current concepts regarding the effects of diabetic peripheral neuropathy (DPN) in skeletal muscle. It discusses the lack of effective pharmacologic treatments and the role of physical exercise intervention in limb protection and symptom reversal. It also highlights the importance of magnetic resonance imaging (MRI) techniques in providing a mechanistic understanding of the disease and helping develop targeted treatments.

METHODS

This review provides a comprehensive reporting on the effects of DPN in the skeletal muscle of patients with diabetes. It also provides an update on the most recent trials of exercise intervention targeting DPN pathology. Lastly, we report on emerging MRI techniques that have shown promise in providing a mechanistic understanding of DPN and can help improve the design and implementation of clinical trials in the future.

FINDINGS

Impairments in lower limb muscles reduce functional capacity and contribute to altered gait, increased fall risk, and impaired balance in patients with DPN. This finding is an important concern for patients with DPN because their falls are likely to be injurious and lead to bone fractures, poorly healing wounds, and chronic infections that may require amputation. Preliminary studies have shown that moderate-intensity exercise programs are well tolerated by patients with DPN. They can improve their cardiorespiratory function and partially reverse some of the symptoms of DPN. MRI has the potential to bring new mechanistic insights into the effects of DPN as well as to objectively measure small changes in DPN pathology as a result of intervention.

IMPLICATIONS

Noninvasive exercise intervention is particularly valuable in DPN because of its safety, low cost, and potential to augment pharmacologic interventions. As we gain a better mechanistic understanding of the disease, more targeted and effective interventions can be designed.