Advances About Immunoinflammatory Pathogenesis and Treatment in Diabetic Peripheral Neuropathy

Exploring causal correlations between immune cells and diabetic neuropathy: a Mendelian randomization

BACKGROUND

Circulating immune cells reportedly affect diabetic neuropathy (DN). Although associations have been previously established between numerous biomarkers and diseases, elucidating their causal relationships remains challenging. Mendelian Randomization (MR) could overcome this difficulty by applying genetic instruments to discern causal links. In this study, we conducted bidirectional two-sample MR to address this problem.

METHODS

We used freely available genome-wide association study summary statistics. We obtained immune cell phenotype-related summary data from a study cohort comprising 3,757 Sardinian individuals that reported data concerning 731 immune cell phenotypes. We obtained DN-related summary data from the FinnGen database and conducted sensitivity analyses. Furthermore, we assessed horizontal pleiotropy using combined MR-Egger and MR-Presso methods. We evaluated heterogeneity using Cochran's Q test and applied False Discovery Rate correction to the findings.

RESULTS

Our MR analysis significantly associated 24 immune cell phenotypes with DN. Specifically, the presence of CD45 on CD66b + + myeloid cells, HLA DR on CD14 + CD16- monocytes, IgD- CD24- %B cells, and CD27 on IgD- CD38br lymphocytes significantly positively correlated with the risk of DN. In contrast, the presence of CD28- DN (CD4-CD8-) %T cells, FSC-A on HLA DR + T cells, and other four T cell types negatively correlated with DN. Finally, we further confirmed the relationship between different immune cell types and DN.

CONCLUSIONS

We demonstrated the immunological susceptibility of DN and clarified how immune responses influence the course of DN. These findings might help inform immunological therapy techniques as well as novel targets for DN diagnosis and treatment.

Raster Scan Optoacoustic Mesoscopy for detecting microvascular complications in diabetes mellitus: A narrative brief review

Diabetes mellitus (DM) may lead to microvascular and macrovascular complications. Screening for these complications is crucial, and so non-invasive methods with high-dissemination potential are needed. Diabetic peripheral neuropathy (DPN) is particularly challenging to screen due to the lack of reliable clinical markers and endpoints. In this context, Raster Scan Optoacoustic Mesoscopy (RSOM) emerges as a highly promising technique that offers hybrid, non-invasive imaging of optical absorption using light-induced ultrasound waves within tissue without the use of contrast agents. RSOM provides high-resolution visualisation of micro-vasculature and other tissue structures along with functional information. The technique has already assessed microvasculature loss as a function of diabetes progression and used it to characterise DPN severity. RSOM has also shown that cutaneous vessels in the mesoscopic range (mean diameters of 30-40 µm) are most prominently affected by DM and that the mean number of cutaneous vessels was lower in subjects with DM than in healthy participants (p < 0.001 and p < 0.05, respectively). Although experience is still limited, we present an overview of the novel technique in relation to its potential for detecting early DM onset and development of microvascular complications.

Prognostic nutritional index and diabetic peripheral neuropathy in type 2 diabetes: a machine learning approach

BACKGROUND

The prognostic nutritional index (PNI), an indicator of nutritional status, has been linked to various diabetic complications. However, its relationship with diabetic peripheral neuropathy (DPN) remains unclear. This study aimed to explore the association between PNI and DPN using machine learning (ML) approaches.

METHODS

A total of 625 patients with type 2 diabetes (T2D) were enrolled, with 282 diagnosed with DPN. PNI was calculated based on serum albumin and lymphocyte count. Random forest (RF) and eXtreme Gradient Boosting (XGBoost) models were developed to predict DPN using clinical and biochemical data. SHapley Additive exPlanations (SHAP) were applied to determine feature importance. Multivariate logistic regression was used to evaluate the relationship between PNI quartile and DPN risks.

RESULTS

Both RF and XGBoost models exhibited strong performance. The RF model achieved a recall of 78.4%, specificity of 87.8%, and accuracy of 84.0%, while the XGBoost model showed a recall of 77.4%, specificity of 92.1%, and accuracy of 84.8%. SHAP analysis identified lower PNI as a key factor for DPN. Multivariate logistic regression revealed that patients in the lowest PNI quartile had a significantly higher DPN risk compared to those in the highest quartile (OR: 3.271, 95% CI: 1.782-6.006, P < 0.001). Additionally, lower PNI levels were associated with impaired peripheral nerve function, including reduced motor and sensory nerve conduction velocity and action potential amplitudes.

CONCLUSIONS

Lower PNI levels were associated with increased DPN risk and poorer nerve function, highlighting the importance of nutritional status in DPN management. Further longitudinal studies are needed to confirm these findings.

Beneficial effects of resveratrol on diabetes mellitus and its complications: focus on mechanisms of action

Diabetes mellitus (DM) is a significant global health issue, associated with various microvascular and macrovascular complications that significantly impair patients' quality of life as well as healthspan and lifespan. Despite the availability of several anti-diabetic medications with different mechanisms of action, there remains no definite curative treatment. Hence, discovering new efficient complementary therapies is essential. Natural products have received significant attention due to their advantages in various pathological conditions. Resveratrol is a natural polyphenol that possesses antioxidant and anti-inflammatory properties, and its efficacy has been previously investigated in several diseases, including DM. Herein, we aimed to provide a holistic view of the signaling pathways and mechanisms of action through which resveratrol exerts its effects against DM and its complications.

Cytokine Signaling in Diabetic Neuropathy: A Key Player in Peripheral Nerve Damage

Diabetic peripheral neuropathy (DPN) is a debilitating complication of diabetes mellitus, characterized by progressive nerve damage driven by chronic hyperglycemia and systemic inflammation. The pathophysiology of DPN is significantly influenced by pro-inflammatory cytokines, such as IL-1β, IL-6, and TNF-α. These cytokines promote oxidative stress, vascular dysfunction, and neuronal degeneration by activating important signaling pathways including NF-κB and MAPK. While IL-6 promotes a pro-inflammatory microenvironment, increasing neuronal damage and neuropathic pain, TNF-α and IL-1β worsen Schwann cell failure by compromising axonal support and causing demyelination. Immune cell infiltration and TLR activation increase the inflammatory cascade in DPN, resulting in a persistent neuroinflammatory state that sustains peripheral nerve injury. The main characteristics of DPN are axonal degeneration, decreased neurotrophic support, and Schwann cell dysfunction, which weaken nerve transmission and increase susceptibility to damage. Advanced glycation end-products, TNF-α, and CXCL10 are examples of biomarkers that may be used for early diagnosis and disease progression monitoring. Additionally, crucial molecular targets have been found using proteomic and transcriptome techniques, enabling precision medicine for the treatment of DPN. This review emphasizes the importance of cytokine signaling in the pathogenesis of DPN and how cytokine-targeted treatments might reduce inflammation, restore nerve function, and improve clinical outcomes for diabetic patients.

Network pharmacology and molecular docking to study the potential molecular mechanism of Qi Fu Yin for diabetic encephalopathy

Diabetic encephalopathy is a chronic complication of diabetes that lacks an optimized treatment strategy. The present study sought to elucidate the potential molecular mechanism of Qi Fu Yin in improving diabetic encephalopathy through network pharmacology. The active components and target information of Qi Fu Yin were obtained from the TCMSP and Swiss target databases, while the target information of diabetic encephalopathy was sourced from Gene cards, OMIM, and Pharm Gkb databases. Enrichment analyses of KEGG and GO were conducted utilizing drug-disease common targets, while protein-protein interactions were predicted through the utilization of the STRING database platform. Subsequently, molecular docking was executed via Auto Dock Vina to authenticate the interaction between core components and core targets. The findings revealed that Qi Fu Yin exhibited 178 common targets with diabetic encephalopathy, and the enrichment analyses demonstrated that these targets were associated with lipid and atherosclerosis, AGE-RAGE signaling pathways, and other related pathways. The findings of the molecular docking indicated a favorable binding affinity between the active components of drug and the core targets, with EGF and quercetin exhibiting the most notable docking score. Additionally, the molecular dynamics simulation corroborated this high affinity. These results suggested that the active ingredients of Qi Fu Yin, including quercetin and kaempferol, may modulated the expression of genes such as IL10, TNF, EGF, and MMP2, thereby activating the AGE-RAGE signaling pathways and potentially serving as a therapeutic intervention for diabetic encephalopathy.Communicated by Ramaswamy H. Sarma.

Tangzu granule alleviate neuroinflammation in diabetic peripheral neuropathy by suppressing pyroptosis through P2X7R /NLRP3 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes mellitus, mainly manifested as paresthesia. Tangzu granule (TZG) is derived from famous traditional Chinese medicine decoctions and optimized by long-term temporary practice. TZG has good efficacy in improving numbness, pain and pruritus of the lower extremities of DPN patients. However, the overall regulatory mechanisms underlying its effects on DPN remain unclear.

AIM OF THE STUDY

This study aims to explore the potential mechanism of TZG for treating DPN.

MATERIALS AND METHODS

Sprague-Dawley (SD) rats were used to establish an in vivo model of DPN with streptozotocin (STZ) injection and high-fat diet (HFD) feeding. Additionally, sciatic glial RSC96 cells were induced with high glucose in vitro. SD rats in intervention group received TZG treatment for 12 weeks. After 12 weeks of treatment, sciatic nerve function was evaluated by intelligent hot plate meter and neuro electrophysiology detector. The morphological changes of sciatic nerve cells were observed by hematoxylin-eosin staining and transmission electron microscope. IL-1β, IL-18 inflammatory cytokines, pyroptosis and P2X7R/NLRP3 signaling pathway were observed by Western blotting, immunofluorescence staining and ELISA.

RESULTS

TZG improved nerve conduction velocity and sciatic neuropathy rational structural changes in DPN rats. It also inhibited RSC96 inflammatory response and cell death that induced by high glucose. This may be related to TZG inhibiting P2X7R, decreasing the activation of NLRP3 inflammasomes, down-regulating the levels of pyroptosis proteins such as caspase-1, cleaved caspase-1, gasdermin D (GSDMD), and GSDMD-N, and inhibiting the release of interleuki (IL)-18 and IL-1β inflammatory cytokines.

CONCLUSIONS

TZG inhibited pyroptosis through P2X7R/NLRP3 signaling pathway, alleviated neuroinflammation, and showed protective effect in the treatment of DPN.

Okanin alleviates symptoms of nociceptive-like responses in diabetic peripheral neuropathy in type 1 diabetic Wistar rats by regulating the AGEs/NF-κB/Nrf-2 pathway

Elevated reactive species and AGEs contribute to deregulation of transcription factors e.g., NF-κB and Nrf2 in diabetic peripheral neuropathy (DPN). Okanin, a bioactive chalcone, is active against redox imbalance, immune response, and pro-inflammatory events. The current investigation assessed effects of okanin in streptozotocin-induced DPN in rats. Wistar rats were divided into 6 groups (n = 6): Control, DPN, Okanin 2.5, Okanin 5, Okanin 10, and Gpn (Gabapentin). After 6 weeks of streptozotocin (55 mg/kg) injection, okanin (2.5, 5, 10 mg/kg), and gabapentin (50 mg/kg), were administered for 4 weeks. The streptozotocin-induced reduction in body weight, and increased feed/water intake, insulin, glucose, and HbA1c levels were mitigated by okanin or gabapentin. In DPN rats, Okanin or gabapentin ameliorated insulin resistance and β-cell function, inflammatory indices, and oxidative stress in the sciatic nerve of rodents thereby culminating in a decrease in hyperalgesia and allodynia. Okanin and streptozotocin-treated rats had significantly declined levels of AGEs, the receptor for AGEs, and NF-κB, and an upsurge in Nrf2 expression. In streptozotocin-induced DPN model, okanin ameliorates nociceptive-like responses by regulating the AGEs/NF-κB/Nrf2 pathway, suggesting that okanin has therapeutic value against DPN which needs further studies involving human subjects.

Cilostazol for the treatment of distal symmetrical polyneuropathy in diabetes mellitus: Where do we stand?

INTRODUCTION

Diabetic Neuropathy (DN) is one of the most frequent chronic complications of diabetes mellitus. Its commonest form, distal symmetrical polyneuropathy (DSPN), is characterised by slowly progressing length-dependent nerve damage in the lower limbs, increasing the risk of foot ulcerations and leading to symptoms like tingling, pain, or numbness.

AIM

The aim of this review was to discuss the utility of cilostazol, a phosphodiesterase inhibitor with known antiplatelet, vasodilatory, anti-inflammation properties, in the treatment of DSPN.

RESULTS

Preclinical studies in animals have demonstrated the ability of cilostazol to improve nerve function and to protect from peripheral nerve disruption and central sensitisation. However, clinical trials in humans are very sparse and have so far not been encouraging.

CONCLUSIONS

Further research is needed to fully understand the mechanisms and potential efficacy of cilostazol in treating DSPN.

Bibliometric and visualized analysis of 2014-2024 publications on therapy for diabetic peripheral neuropathy

Background

This research aimed to examine the global developing patterns in the treatment of diabetic peripheral neuropathy (DPN) using a bibliometric analysis of published literature.

Methods

We extracted publication data from papers published between 2014 and 2024 using a specific topic search in the "Web of Science Core Collection" (WoSCC) database. Various metrics, such as the number of papers, citations, authors, countries, institutions, and references, were collected for analysis. To further explore the data, CiteSpace was employed to examine co-citation patterns among authors, identify collaborative efforts between countries and institutions, and uncover emerging trends using burst keywords and reference analysis.

Results

The study encompassed 2,488 publications that exhibited an increasing trend in annual output. Notably, the journal PAIN, the United States, the Pfizer institution, and the author Feldman, EvaL emerged as the most prolific contributors to this research domain. The term "placebo-controlled trial" was the most prominent burst keyword from 2014 to 2017, whereas "spinal cord stimulation" held this distinction in the recent 5-year span. Furthermore, the publication titled "Pharmacotherapy for neuropathic pain in adults: a systematic review and meta-analysis-2015" demonstrated the highest burst in terms of references.

Conclusion

This study is the first to objectively reveal the current hotspots and trends in DPN treatment. The results indicate that drug therapy remains the primary first-line treatment for DPN and that future research on DPN treatment will likely focus on "spinal cord stimulation" and "pain management." These findings provide valuable insights into DPN treatment.

Acupuncture treatment of diabetic peripheral neuropathy: an overview of systematic reviews based on evidence mapping

Objective

The study attempted to evaluate the meta-analyses (MAs) of the acupuncture treatment of diabetic peripheral neuropathy (DPN) to provide a basis for clinical decision-making.

Methods

Eight databases, such as PubMed, Cochrane Library, Embase, Web of Science, CNKI, Wanfang Data, CQVIP, and CBM, were searched from database creation to December 22, 2023. The MAs of DPN treatment using acupuncture or acupuncture combined with conventional Western medicine were included. AMSTAR-2 and PRISMA 2020 helped evaluate the methodological and reporting quality of the included studies. The GRADE methodology helped assess the evidence quality of outcome indicators. Evidence mapping was performed to display evaluation results.

Results

A total of 18 MAs involving 23,240 DPN patients were included. Based on the methodological quality evaluation, four MAs were of "moderate" quality, seven had a quality grade of "low," and another seven were of "critically low" quality. The evidence quality evaluation showed that among studies of acupuncture vs. conventional Western medicine, four had an evidence quality of "moderate," 18 had an evidence quality of "low," and 17 had an evidence quality of "critically low" and that among studies of acupuncture + conventional Western medicine vs. conventional Western medicine, 12 had an evidence quality of "moderate," 29 had an evidence quality of "low," and 33 had an evidence quality of "critically low." Compared with conventional Western medicine, simple acupuncture and acupuncture + conventional Western medicine significantly improved total effective rate (TER) and nerve conduction velocity (NCV).

Conclusion

Acupuncture treatment of DPN significantly improves TER and NCV with proven safety. However, the MAs of the acupuncture treatment of DPN must strictly refer to relevant standards and specifications regarding methodological and reporting quality, along with the design, execution, and reporting of primary randomized controlled trials (RCTs).

Update on Biomarkers of Chronic Inflammatory Processes Underlying Diabetic Neuropathy

There is an increasing prevalence of diabetes mellitus (DM), particularly type 2 DM (T2DM), and its associated complications. T2DM is linked to insulin resistance, chronic inflammation, and oxidative stress, which can lead to both macrovascular and microvascular complications, including peripheral diabetic neuropathy (PDN). Inflammatory processes play a key role in the development and progression of T2DM and its complications, with specific markers like C-reactive protein (CRP), interleukins (ILs), and tumor necrosis factor (TNF)-α being associated with increased risk. Other key inflammatory markers such as nuclear factor kappa B (NF-κB) are activated under hyperglycemic and oxidative stress conditions and contribute to the aggravation of PDN by regulating inflammatory gene expression and enhancing endothelial dysfunction. Other important roles in the inflammatory processes are played by Toll-like receptors (TLRs), caveolin 1 (CAV1), and monocyte chemoattractant protein 1 (MCP1). There is a relationship between vitamin D deficiency and PDN, highlighting the critical role of vitamin D in regulating inflammation and immune responses. The involvement of macrophages in PDN is also suspected, emphasizing their role in chronic inflammation and nerve damage in diabetic patients. Vitamin D supplementation has been found to reduce neuropathy severity, decrease inflammatory markers, and improve glycemic control. These findings suggest that addressing vitamin D deficiency could offer therapeutic benefits for PDN. These molecular pathways are critical in understanding the pathogenesis of DM complications and may offer potential biomarkers or therapeutic targets including anti-inflammatory treatments, vitamin D supplementation, macrophage phenotype modulation, and lifestyle modifications, aimed at reducing inflammation and preventing PDN. Ongoing and more extensive clinical trials with the aim of investigating anti-inflammatory agents, TNF-α inhibitors, and antioxidants are needed to advance deeper into the understanding and treatment of painful diabetic neuropathy.

Efficacy and safety of hyperbaric oxygen therapy for diabetes peripheral neuropathy: A systematic review and meta-analysis

BACKGROUND

Diabetes peripheral neuropathy (DPN) is mainly treated with diabetes as a whole, and there is no targeted treatment. Some studies have reported that adjuvant hyperbaric oxygen therapy (HBOT) for DPN has achieved a good effect, our study aimed to evaluate the clinical efficacy and safety of HBOT for DPN and provide reference for the clinic by using a systematic review and meta-analysis.

METHODS

A comprehensive search was conducted across several databases, including PubMed, Embase, Cochrane Library, Web of Science, China National Knowledge Internet Database, Chinese BioMedical Database, China Scientific Journal Database, and Wanfang Database, for relevant randomized controlled trials published before July 2022. The population, intervention, comparison, outcomes, study design criteria were used to guide the selection of studies. Meta-analysis was performed using RevMan 5.4 and STATA 14.0, with odds ratios and mean differences along with 95% confidence intervals serving as measures of effect size.

RESULTS

Fourteen randomized controlled trials were included in the final analysis, comprising 675 patients in the HBOT group and 648 in the standard therapy (ST) group. The HBOT group demonstrated a significantly higher effective treatment rate compared to the ST group (P < .001). Additionally, the HBOT group showed significant improvements in motor nerve conduction velocity (MNCV) and sensory nerve conduction velocity (SNVC) across multiple nerves: median nerve (PMNCV < 0.001, PSNCV = 0.001), ulnar nerve (PMNCV = 0.02, PSNCV < 0.001), peroneal nerve (PMNCV < 0.001, PSNCV < 0.001), and tibial nerve (PMNCV = 0.001, PSNCV = 0.008). Six adverse events were reported in the HBOT group, while no adverse events occurred in the ST group, with no significant difference between the 2 groups. Publication bias was identified in some outcome variables through funnel plots, Begger test, and Egger test.

CONCLUSIONS

HBOT significantly enhances treatment efficacy and nerve conduction velocity in patients with DPN, with few adverse events, making it a safe and effective adjunctive therapy for DPN.

Metformin improves diabetic neuropathy by reducing inflammation through up-regulating the expression of miR-146a and suppressing oxidative stress

PURPOSE

Diabetic neuropathy (DN) is a notable complication of diabetes mellitus. The potential involvement of miR-146a in DN regulation is presently under investigation. Metformin, a commonly prescribed medication for diabetes, is the primary therapeutic intervention. This study aimed to unveil the potential protective effects of metformin on diabetic neuropathy and explore the mechanisms underlying its action.

METHOD

Six-weeks male Sprague Dawley rats (n = 40) were randomly divided into 5 groups. The rat model of diabetic neuropathy (DN) was established by administering streptozotocin (STZ). To investigate the effects on the sciatic nerve and resident Schwann cells (RSCs), metformin and miR-146a mimics were administered, and our research explored the potential underlying mechanism.

RESULT

The sciatic nerve samples obtained from diabetic rats exhibited noticeable morphological damage, accompanied by decreased miR-146a expression (2.61 ± 0.11 vs 5.0 ± 0.3, p < 0.01) and increased inflammation levels (p65: 1.89 ± 0.04 vs 0.82 ± 0.05, p < 0.01; TNF-α: 0.93 ± 0.03 vs 0.33 ± 0.03, p < 0.01). Notably, the administration of metformin effectively ameliorated the structural alterations in the sciatic nerve by suppressing the inflammatory pathway (p65: 1.15 ± 0.05 vs 1.89 ± 0.04, p < 0.01; TNF-α: 0.67 ± 0.04 vs 0.93 ± 0.03, p < 0.01) and reducing oxidative stress (NO: 0.062 ± 0.004 vs 0.154 ± 0.004umol/mg, p < 0.01; SOD: 3.08 ± 0.09 vs 2.46 ± 0.09 U/mg, p < 0.01). The miR-146a mimics intervention group exhibited comparable findings.

CONCLUSION

This study's findings implied that metformin can potentially mitigate diabetic neuropathy in rats through the modulation of miR-146a expression.

How inflammation dictates diabetic peripheral neuropathy: An enlightening review

BACKGROUND

Diabetic peripheral neuropathy (DPN) constitutes a debilitating complication associated with diabetes. Although, the past decade has seen rapid developments in understanding the complex etiology of DPN, there are no approved therapies that can halt the development of DPN, or target the damaged nerve. Therefore, clarifying the pathogenesis of DPN and finding effective treatment are the crucial issues for the clinical management of DPN.

AIMS

This review is aiming to summary the current knowledge on the pathogenesis of DPN, especially the mechanism and application of inflammatory response.

METHODS

We systematically summarized the latest studies on the pathogenesis and therapeutic strategies of diabetic neuropathy in PubMed.

RESULTS

In this seminal review, the underappreciated role of immune activation in the progression of DPN is scrutinized. Novel insights into the inflammatory regulatory mechanisms of DPN have been unearthed, illuminating potential therapeutic strategies of notable clinical significance. Additionally, a nuanced examination of DPN's complex etiology, including aberrations in glycemic control and insulin signaling pathways, is presented. Crucially, an emphasis has been placed on translating these novel understandings into tangible clinical interventions to ameliorate patient outcomes.

CONCLUSIONS

This review is distinguished by synthesizing cutting-edge mechanisms linking inflammation to DPN and identifying innovative, inflammation-targeted therapeutic approaches.

The association between variability of risk factors and complications in type 2 diabetes mellitus: a retrospective study

The variability in diabetes risk factors, such as uric acid and lipids, may influence the development of complications. This study aimed to investigate the influence of such variability on the occurrence of diabetic complications. A retrospective analysis of electronic medical records was conducted with type 2 diabetic patients who received treatment at a tertiary care hospital in Chengdu, Sichuan Province, between 2013 and 2022. The risk factor variability is presented as the standard deviation (SD). The associations between the variability and complications were examined using a binary logistic regression model. The study included 369 patients with type 2 diabetes. The findings revealed that outpatient special disease management served as a protective factor against the development of complications [OR = 0.53, 95% confidence interval (CI) (0.29-0.10)], particularly for the prevention of diabetic peripheral neuropathy [OR = 0.51, 95% CI (0.30-0.86)]. Variability in total cholesterol (TC-SD) was found to be a risk factor for the development of complications [OR = 2.42, 95% CI (1.18-4.97)] and acted as a risk factor for diabetic peripheral vasculopathy [OR = 2.50, 95% CI (1.25-5.02)]. TC-SD is a risk factor for the occurrence of diabetic peripheral neuropathy and diabetic peripheral vasculopathy, whereas outpatient special disease management functions as a protective factor against complications and diabetic peripheral neuropathy. Thus, in addition to glycaemic control, the regulation of lipid levels should be emphasized, particularly among patients without outpatient special disease management, to delay the onset of complications.

Cell metabolism pathways involved in the pathophysiological changes of diabetic peripheral neuropathy

Diabetic peripheral neuropathy is a common complication of diabetes mellitus. Elucidating the pathophysiological metabolic mechanism impels the generation of ideal therapies. However, existing limited treatments for diabetic peripheral neuropathy expose the urgent need for cell metabolism research. Given the lack of comprehensive understanding of energy metabolism changes and related signaling pathways in diabetic peripheral neuropathy, it is essential to explore energy changes and metabolic changes in diabetic peripheral neuropathy to develop suitable treatment methods. This review summarizes the pathophysiological mechanism of diabetic peripheral neuropathy from the perspective of cellular metabolism and the specific interventions for different metabolic pathways to develop effective treatment methods. Various metabolic mechanisms (e.g., polyol, hexosamine, protein kinase C pathway) are associated with diabetic peripheral neuropathy, and researchers are looking for more effective treatments through these pathways.

A neuroprotective effect of pentoxifylline in rats with diabetic neuropathy: Mitigation of inflammatory and vascular alterations

BACKGROUND

Treatment of diabetic neuropathic pain does not change the natural history of neuropathy. Improved glycemic control is the recommended treatment in these cases, given that no specific treatment for the underlying nerve damage is available, so far. In the present study, the potential neuroprotective effect of pentoxifylline in streptozotocin (50 mg/kg) induced diabetic neuropathy in rats was investigated.

METHODS

Pentoxifylline was administered at doses equivalent to 50, 100 & 200 mg/kg, in drinking water, starting one week after streptozotocin injection and for 7 weeks. Mechanical allodynia, body weight and blood glucose level were assessed weekly. Epidermal thickness of the footpad skin, and neuroinflammation and vascular alterations markers were assessed.

RESULTS

Tactile allodynia was less in rats that received pentoxifylline at doses of 100 and 200 mg/kg (60 % mechanical threshold increased by 48 % and 60 %, respectively). The decrease in epidermal thickness of footpad skin was almost completely prevented by the same doses. This was associated with a decrease in spinal tumor necrosis factor alpha (TNFα) and nuclear factor kappa B levels and a decrease in microglial ionized calcium binding adaptor molecule 1 immunoreactivity, compared to the control diabetic group. In sciatic nerve, there was decrease in TNF-α and vascular endothelial growth factor levels and intercellular adhesion molecule immunoreactivity.

CONCLUSION

Pentoxifylline showed a neuroprotective effect in streptozotocin-induced diabetic neuropathy, which was associated with a suppression of both the inflammatory and vascular pathogenic pathways that was not associated with a hypoglycemic effect. Thus, it may represent a potential neuroprotective drug for diabetics.

Integrating plasma metabolomics and gut microbiome to reveal the mechanisms of Huangqi Guizhi Wuwu Decoction intervene diabetic peripheral neuropathy

ETHNOPHARMACOLOGICAL RELEVANCE

Huangqi Guizhi Wuwu Decoction (HGWD) is a classic traditional Chinese herbal formula from "Synopsis of Golden Chamber," which is used to treat blood stagnation and has been used for alleviating diabetic peripheral neuropathy (DPN) in the clinic. However, the mechanisms of HGWD intervention DPN are still to be discovered.

AIM OF THE STUDY

This study aims to explore the mechanism of HGWD intervention DPN by integrating plasma metabolomics and gut microbiome.

MATERIALS AND METHODS

BKS Cg-m+/+Leprdb/J (db/db) mice with DPN were at 16 weeks of age. The indices of DPN phenotypes in db/db mice, pathomorphology of the sciatic nerve, intraepithelial nerve fibers (IENF) of the foot pad, levels of blood lipids and oxidative stress, and inflammatory reaction were used to appraise the HGWD efficacy. Finally, the pharmacological mechanisms of HGWD intervening DPN were explored by metabolomics and 16S rRNA gene sequencing.

RESULTS

HGWD reversed DPN phenotypes in db/db mice, improved peripheral nerve structure, ameliorated the level of blood lipids and nerve growth factor in plasma, enhanced antioxidant capacity, and alleviated inflammatory responses. Plasma metabolomics disclosed that HGWD remarkably regulated the unusual levels of thirty-seven metabolites involved in sphingolipid metabolism, biosynthesis of unsaturated fatty acids, arachidonic acid metabolism, and amino acid biosynthesis pathways. The gut microbiome showed that nine bacteria were highly correlated with the efficacy of HGWD in DPN. Integrating analysis of microbiome and metabolomics demonstrated that the interaction of four bacteria with four metabolic pathways might be the significant mechanism of HGWD intervention in DPN.

CONCLUSIONS

The mediation of gut microbiota and plasma metabolism may be the potential mechanism of HGWD ameliorating DPN in db/db mice. The interaction of Lactobacillus, Alloprevotella, Bacteroides, and Desulfovibio with four metabolic pathways might be the critical mechanism for HGWD treating DPN.

Technological Trends Involving Probiotics in the Treatment of Diabetic Neuropathy: A Patent Review (2009-2022)

BACKGROUND

Diabetic neuropathy (DN) causes neuropathic pain, and current treatments are unsatisfactory. Recently studies have demonstrated an assertive correlation between gut microbiota and pain modulation.

OBJECTIVE

Considering the emerging search for new therapies for the control of DN and the growing commercial interest in the probiotics market, this study aimed to provide patents on the use of probiotics in the control of DN.

METHODS

This is a patent prospection performed in the Espacenet Patent database, using the association of keywords and IPC related to probiotics in medical preparations and foods, from 2009 to December 2022.

RESULTS

Results have shown that in 2020, there was a boom in patent filing in the area. Asian countries accounted for more than 50% of all 48 inventions (n = 48), with Japan as the only applicant in 2021. Products being developed in recent years point to effects that may represent an advancement in DN treatment, such as reduced concentration of pro-inflammatory mediators, metabolites and neurotransmitters release, and hypoglycemic potential. All effects were more related to the Lactobacillus and Bifidobacterium genera, associated with more than one property mentioned.

CONCLUSION

The mechanisms attributed to the microorganisms suggest the therapeutic potential of probiotics in the non-pharmacological treatment of pain. New applications for probiotics have resulted from great research interest by academia, but also reflect commercial interests despite the paucity of clinical trials. Thus, the present work supports the evolution of research to explore the benefits of probiotics and their clinical use in DN.

Natural compounds efficacy in complicated diabetes: A new twist impacting ferroptosis

Ferroptosis, as a way of cell death, participates in the body's normal physiological and pathological regulation. Recent studies have shown that ferroptosis may damage glucose-stimulated islets β Insulin secretion and programmed cell death of T2DM target organs are involved in the pathogenesis of T2DM and its complications. Targeting suppression of ferroptosis with specific inhibitors may provide new therapeutic opportunities for previously untreated T2DM and its target organs. Current studies suggest that natural bioactive compounds, which are abundantly available in drugs, foods, and medicinal plants for the treatment of T2DM and its target organs, have recently received significant attention for their various biological activities and minimal toxicity, and that many natural compounds appear to have a significant role in the regulation of ferroptosis in T2DM and its target organs. Therefore, this review summarized the potential treatment strategies of natural compounds as ferroptosis inhibitors to treat T2DM and its complications, providing potential lead compounds and natural phytochemical molecular nuclei for future drug research and development to intervene in ferroptosis in T2DM.

Unraveling the Role of Tumor Necrosis Factor-Alpha in Diabetic Peripheral Neuropathy: A Systematic Review and Meta-Analysis

Diabetic peripheral neuropathy (DPN) is a prevalent and debilitating complication of diabetes mellitus, leading to sensory abnormalities, decreased balance, and increased risk of foot problems. Although tumor necrosis factor-alpha (TNF-α) has emerged as a potential factor in the pathogenesis of DPN, its role remains contested. This study intends to thoroughly analyze the association between TNF-α and DPN by combining data from various global studies. This systematic review and meta-analysis adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and included 23 articles investigating TNF-α levels in DPN patients for systematic review and 11 articles for meta-analysis. Data were extracted, and heterogeneity was examined. A random-effect model was chosen due to high heterogeneity. The major outcome measure across studies was serum TNF-α levels. The meta-analysis found a significant mean difference of 15.2464 (95% confidence interval = 4.4963; 25.9965) under the random-effect model due to the substantial heterogeneity (I2 = 98.1%) among included studies. The meta-analysis indicates a consistent elevation in TNF-α levels in individuals with DPN compared to those without neuropathy. This underlines the potential of TNF-α as a biomarker and contributor to diabetic neuropathy. Despite heterogeneity, the study's extensive scope and systematic approach enhance the trustworthiness and generalizability of the findings.

Sweat gland nerve fiber density and association with sudomotor function, symptoms, and risk factors in adolescents with type 1 diabetes

PURPOSE

To quantify sweat gland nerve fiber density in adolescents with diabetes. Additionally, to investigate associations between sudomotor innervation, sweat responses, and possible risk factors for sudomotor neuropathy.

METHODS

Cross-sectional study where 60 adolescents with type 1 diabetes (duration > 5 years) and 23 control subjects were included. Clinical data, quantitative sudomotor axon reflex test, and skin biopsies were obtained. Skin tissue was immunostained and imaged by confocal microscopy. Quantification of the sweat gland volume and three-dimensional reconstruction of the nerve fibers was performed using a design-unbiased technique.

RESULTS

Adolescents with diabetes had a significant reduction of maximum and mean values of nerve fiber length and nerve fiber density in sweat glands compared to controls (p values < 0.05). No association between nerve fiber density and sweat responses was found (p = 0.21). In cases with reduced sweat gland nerve fiber length, nerve fiber density, and volume, the sweat response was reduced or absent. Height, systolic blood pressure, time in hypoglycemia, and total daily and basal/total insulin dose were positively correlated to sweat response, while low-density lipoprotein, and HbA1c were negatively correlated with sweat response (p values < 0.05). Other microvascular complications and high cholesterol levels increased the relative risk for reduced sweat gland nerve fiber density.

CONCLUSION

Our findings of reduced sweat gland innervation in a selected group of adolescents add new knowledge about the structural changes that occur in autonomic nerves due to diabetes. Evaluating both the sweat gland innervation and sweat gland volume was important for understanding the association with sweat responses. Further research is needed to understand its clinical relevance.

Is acupoint injection the optimal way to administer mecobalamin for diabetic peripheral neuropathy? A meta-analysis and trial sequential analysis

Objective

Mecobalamin is a commonly used drug in the treatment of diabetic peripheral neuropathy (DPN). This study aimed to systematically evaluate the efficacy and safety of acupoint injection of mecobalamin for DPN.

Methods

Relevant clinical trials on acupoint injection of mecobalamin for DPN published before 31 January 2023 were searched in eight commonly used databases. After screening and confirming the included studies, meta-analysis and trial sequential analysis were performed.

Results

A total of 10 relevant studies were confirmed, and the total sample size was 927 cases. On the efficacy endpoints, meta-analysis showed that compared with other administration methods, acupoint injection of mecobalamin significantly increased the clinical effective rate by 27% [RR = 1.27, 95% CI = (1.19, 1.36), P < 0.00001], motor nerve conduction velocity (median nerve) by 5.93 m/s [MD = 5.93, 95% CI = (4.79, 7.07), P < 0.00001], motor nerve conduction velocity (common peroneal nerve) by 5.66 m/s [MD = 5.66, 95% CI = (2.89, 8.43), P < 0.0001], sensory nerve conduction velocity (median nerve) by 4.83 m/s [MD = 4.83, 95% CI = (3.75, 5.90), P < 0.00001], and sensory nerve conduction velocity (common peroneal nerve) by 3.60 m/s [MD = 3.60, 95% CI = (2.49, 4.71), P < 0.00001], and trial sequential analysis showed these benefits were conclusive. In terms of safety endpoints, meta-analysis indicated that the total adverse events for acupoint injection were comparable to other methods of administration, and trial sequential analysis suggested that the results needed to be validated by more studies. Subgroup analysis demonstrated that the benefits of acupoint injections of mecobalamin were not limited by the dose, duration of treatment, or number of acupoints reported in the included studies. Harbord's test showed no significant publication bias (P = 0.106).

Conclusion

The efficacy of acupoint injection of mecobalamin for DPN was significantly better than other administrations, and its safety was comparable to other administrations. Therefore, acupoint injection may be the optimal method of mecobalamin for DPN.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=454120, identifier: CRD42023454120.

Açaí berry ameliorates cognitive impairment by inhibiting NLRP3/ASC/CASP axis in STZ-induced diabetic neuropathy in mice

Diabetes complications such as diabetic peripheral neuropathy (DPN) are linked to morbidity and mortality. Peripheral nerve damages in DPN are accompanied by discomfort, weakness, and sensory loss. Some drugs may demonstrate their therapeutic promise by reducing neuroinflammation, but they have side effects. Based on these considerations, the objective of this study was to examine the beneficial properties of açaí berry in a mouse model of DPN generated by injection of streptozotocin (STZ). Açaí berry was given orally to diabetic and control mice every day beginning 2 wk after STZ injection. The animals were euthanized after 16 wk, and tissues from the spinal cord and sciatic nerve and urine were taken. Our findings showed that daily treatment of açaí berry at a dose of 500 mg/kg was able to prevent behavioral changes as well as mast cell activation and nerve deterioration via NOD-like receptor family pyrin-domain-containing-3 (NLRP3)/apoptosis-associated speck-like protein containing a card (ASC)/caspase (CASP) regulation after diabetes induction.NEW & NOTEWORTHY Our research shows that açaí berry reduces mast cells degranulation and histological damage in diabetic neuropathy, improves physiological defense against reactive oxygen species, modulates the NLRP3/ASC/CASP axis, and ameliorates inflammation and oxidative stress. Diet could help treatment for diabetic peripheral neuropathy.

Ropivacaine microsphere-loaded electroconductive nerve dressings for long-acting analgesia and functional recovery following diabetic peripheral nerve injury

In recent years, electroconductive hydrogels (ECHs) have shown great potential in promoting nerve regeneration and motor function recovery following diabetic peripheral nerve injury (PNI), attributed to their similar electrical and mechanical characteristics to innate nervous tissue. It is well-established that PNI causes motor deficits and pain, especially in diabetics. Current evidence suggests that ropivacaine (ROP) encapsulated in poly lactic-co-glycolic acid (PLGA) microspheres (MSs) yield a sustained analgesic effect. In this study, an ECH electroconductive network loaded with MS/ROP (ECH-MS/ROP) was designed as a promising therapeutic approach for diabetic PNI to exert lasting analgesia and functional recovery. This dual delivery system allowed ROP's slow and sequential release, achieving sustained analgesia as demonstrated by our in vivo experiments. Meanwhile, this system was designed like a lamellar dressing, with desirable adhesive and self-curling properties, convenient for treating injured nerve tissues via automatically wrapping tube-like structures, facilitating the process of implantation. Our in vitro assays verified that ECH-MS/ROP was able to enhance the adhesion and motility of Schwann cells. Besides, both in vitro and in vivo studies substantiated that ECH-MS/ROP stimulated myelinated axon regeneration through the MEK/ERK signaling pathway, thereby improving muscular denervation atrophy and facilitating functional recovery. Therefore, this study suggests that the ECH-MS/ROP dressing provides a promising strategy for treating diabetic PNI to facilitate nerve regeneration, functional recovery and pain relief.

Effect of 10.6 μm laser moxibustion on inflammation in diabetic peripheral neuropathy rats

Diabetic peripheral neuropathy (DPN) is the main cause of disability in diabetes patients but the efficacy of available drugs is poor. Moxibustion is an adjunctive treatment for DPN that can reduce symptoms. The peak value of the far infrared wavelength of 10.6 μm laser moxibustion is close to the infrared radiation spectrum of traditional moxibustion. Its effect is similar to that of moxibustion and does not cause pain, infection or produce irritating smoke. Twenty-four male SD rats were divided into control (Con), DPN, laser moxibustion (LM), and pyrrolidine dithiocarbamate (PDTC) groups (n=6/group). The DPN, LM and PDTC group rats were intraperitoneally injected with 1% streptozotocin (STZ) to induce a model of DPN. LM group rats were irradiated with a laser at bilateral ST36 acupoints for 15 min, once every other day, for 14 days. PDTC group rats were intraperitoneally injected with PDTC once a day. Body weight, blood glucose, and paw withdrawal mechanical threshold (PWMT) were measured and laser speckle imaging (LSI) performed before and after modeling and at 1 and 2 weeks after intervention. Two weeks after intervention, changes in serum interleukin 1β (IL1β), interleukin 6 (IL6), tumor necrosis factor α (TNFα) and nerve growth factor (NGF) were analyzed, and the abundance of NF-κB and IκB-α proteins and levels of NF-κB and IκB-α mRNAs in the sciatic nerve were observed. The results showed that 10.6 μm laser moxibustion can relieve pain, improve microcirculation, and alleviate inflammation in DPN rats, possibly via the NF-κB inflammatory pathway.

Exosomes-loaded electroconductive nerve dressing for nerve regeneration and pain relief against diabetic peripheral nerve injury

Over the years, electroconductive hydrogels (ECHs) have been extensively applied for stimulating nerve regeneration and restoring locomotor function after peripheral nerve injury (PNI) with diabetes, given their favorable mechanical and electrical properties identical to endogenous nerve tissue. Nevertheless, PNI causes the loss of locomotor function and inflammatory pain, especially in diabetic patients. It has been established that bone marrow stem cells-derived exosomes (BMSCs-Exos) have analgesic, anti-inflammatory and tissue regeneration properties. Herein, we designed an ECH loaded with BMSCs-Exos (ECH-Exos) electroconductive nerve dressing to treat diabetic PNI to achieve functional recovery and pain relief. Given its potent adhesive and self-healing properties, this laminar dressing is convenient for the treatment of damaged nerve fibers by automatically wrapping around them to form a size-matched tube-like structure, avoiding the cumbersome implantation process. Our in vitro studies showed that ECH-Exos could facilitate the attachment and migration of Schwann cells. Meanwhile, Exos in this system could modulate M2 macrophage polarization via the NF-κB pathway, thereby attenuating inflammatory pain in diabetic PNI. Additionally, ECH-Exos enhanced myelinated axonal regeneration via the MEK/ERK pathway in vitro and in vivo, consequently ameliorating muscle denervation atrophy and further promoting functional restoration. Our findings suggest that the ECH-Exos system has huge prospects for nerve regeneration, functional restoration and pain relief in patients with diabetic PNI.

PARPs and ADP-Ribosylation in Chronic Inflammation: A Focus on Macrophages

Aberrant adenosine diphosphate-ribose (ADP)-ribosylation of proteins and nucleic acids is associated with multiple disease processes such as infections and chronic inflammatory diseases. The poly(ADP-ribose) polymerase (PARP)/ADP-ribosyltransferase (ART) family members promote mono- or poly-ADP-ribosylation. Although evidence has linked PARPs/ARTs and macrophages in the context of chronic inflammation, the underlying mechanisms remain incompletely understood. This review provides an overview of literature focusing on the roles of PARP1/ARTD1, PARP7/ARTD14, PARP9/ARTD9, and PARP14/ARTD8 in macrophages. PARPs/ARTs regulate changes in macrophages during chronic inflammatory processes not only via catalytic modifications but also via non-catalytic mechanisms. Untangling complex mechanisms, by which PARPs/ARTs modulate macrophage phenotype, and providing molecular bases for the development of new therapeutics require the development and implementation of innovative technologies.

Diabetes mellitus differently affects electrical membrane properties of vagal afferent neurons of rats

To study whether diabetes mellitus (DM) would cause electrophysiological alterations in nodose ganglion (NG) neurons, we used patch clamp and intracellular recording for voltage and current clamp configuration, respectively, on cell bodies of NG from rats with DM. Intracellular microelectrodes recording, according to the waveform of the first derivative of the action potential, revealed three neuronal groups (A0 , Ainf , and Cinf ), which were differently affected. Diabetes only depolarized the resting potential of A0 (from -55 to -44 mV) and Cinf (from -49 to -45 mV) somas. In Ainf neurons, diabetes increased action potential and the after-hyperpolarization durations (from 1.9 and 18 to 2.3 and 32 ms, respectively) and reduced dV/dtdesc (from -63 to -52 V s-1 ). Diabetes reduced the action potential amplitude while increasing the after-hyperpolarization amplitude of Cinf neurons (from 83 and -14 mV to 75 and -16 mV, respectively). Using whole cell patch clamp recording, we observed that diabetes produced an increase in peak amplitude of sodium current density (from -68 to -176 pA pF-1 ) and displacement of steady-state inactivation to more negative values of transmembrane potential only in a group of neurons from diabetic animals (DB2). In the other group (DB1), diabetes did not change this parameter (-58 pA pF-1 ). This change in sodium current did not cause an increase in membrane excitability, probably explainable by the alterations in sodium current kinetics, which are also induced by diabetes. Our data demonstrate that diabetes differently affects membrane properties of different nodose neuron subpopulations, which likely have pathophysiological implications for diabetes mellitus.

Research Progress on Mesenchymal Stem Cells for the Treatment of Diabetes and Its Complications

Diabetes mellitus (DM) is a chronic disease that threatens human health. Although many drugs are available to treat DM, various complications caused by DM are unavoidable. As an emerging treatment for DM, mesenchymal stem cells (MSCs) have shown many advantages and are gradually gaining public attention. This review summarizes the clinical studies on the use of MSCs to treat DM and the potential mechanisms of complications such as pancreatic dysfunction, cardiovascular lesions, renal lesions, neurological lesions, and trauma repair. This review focuses on the research progress on MSC-mediated secretion of cytokines, improvements in the microenvironment, repair of tissue morphology, and related signaling pathways. At present, the sample sizes in clinical studies of MSCs in treating DM are small, and there is a lack of standardized quality control systems in the preparation, transportation, and infusion methods, so we need to conduct more in-depth studies. In conclusion, MSCs have shown superior potential for use in the treatment of DM and its complications and will hopefully become a novel therapeutic approach in the future.

Multidisciplinary Progress in Obesity Research

Obesity is a chronic disease that endangers human health. In recent years, the phenomenon of obesity has become more and more common, and it has become a global epidemic. Obesity is closely associated with many adverse metabolic changes and diseases, such as insulin resistance, type 2 diabetes mellitus, coronary heart disease, nervous system diseases and some malignant tumors, which have caused a huge burden on the country's medical finance. In most countries of the world, the incidence of cancer caused by obesity is increasing year on year. Diabetes associated with obesity can lead to secondary neuropathy. How to treat obesity and its secondary diseases has become an urgent problem for patients, doctors and society. This article will summarize the multidisciplinary research on obesity and its complications.

Independent Association of 25[OH]D Level on Reduced Glutathione and TNF-α in Patients ‎with Diabetes and/or Hypertension

Purpose

Oxidative and inflammatory pathways play a significant role in the pathophysiology of a wide variety of non-communicable diseases such as type 2 diabetes mellitus (T2DM) and hypertension. However, the effect of serum 25-hydroxyvitamin D ‎‎(25[OH]D) on these pathways is still controversial. To evaluate the association of 25[OH]D on ‎antioxidant and pro-inflammatory biomarkers, reduced glutathione (GSH) and tumor ‎necrosis factor (TNF)-α, in T2DM and hypertensive patients.

Patients and Methods

This is a cross-sectional study of a consecutive sample of patients attending the the Family Medicine clinic at King Abdullah bin Abdulaziz University Hospital (KAAUH). Participants were screened for eligibility according to the following ‎criteria: aged above 18 years and diagnosed with T2DM and/or hypertension for at least one ‎year. Patients receiving any kind of vitamin D or calcium supplements within the last three ‎months were excluded, as were those with a history of ‎renal failure, cancer, liver, thyroid, or any other chronic inflammatory diseases.

Results

In total 424 T2DM and/or ‎hypertensive patients (mean age 55±12 years) were recruited. In addition to routine ‎physical and laboratory examinations, levels of serum 25[OH]D, GSH and TNF-α were ‎measured. The prevalence of 25[OH]D deficiency (<50 nmol/L) was 35.1%, which was ‎independent from GSH and TNF-α levels. In T2DM, hypertensive and patients having ‎both diseases, GSH levels were 349.3±19, 355.4±19 and 428.8±20 μmol/L, ‎respectively. Uncontrolled T2DM and hypertension patients showed significantly higher ‎GSH compared with the controlled group. ‎Males showed slightly higher level ‎of TNF-α compared with females and uncontrolled hypertensive patients had relatively ‎higher TNF-α level when evaluated against controlled hypertensive patients. ‎

Conclusion

25[OH]D level is independent of oxidative stress and inflammation, ‎assessed by levels of GSH and TNF-α, respectively, in T2DM and hypertensive Saudi ‎patients. ‎