Low-Dose Pulsatile Interleukin-6 As a Treatment Option for Diabetic Peripheral Neuropathy

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.

Association of serum NF-κB levels with peripheral neuropathy in type 2 diabetes mellitus patients: a pilot study

OBJECTIVES

Hyperglycaemia-induced inflammation plays a vital role in the development of diabetic peripheral neuropathy (DPN). Recent evidences had reported the involvement of the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) in diabetic experimental models. So, this pilot study aimed to evaluate serum NF-κB levels in DPN patients.

METHODS

We recruited 50 T2DM patients, of which 25 were T2DM with neuropathy and 25 were T2DM without neuropathy. In all the participants peripheral neuropathy was diagnosed based on Total neuropathy score (TNS). Serum NF-κB levels were measured by ELISA.

RESULTS

We observed that the serum NF-κB levels were higher in DPN patients in comparison to T2DM patients without neuropathy. On spearman correlation, a positive correlation was found between serum NF-κB levels and TNS in the DPN group (r=0.741, p<0.001). The regression model shows the TNS to be an independent determinant of serum NF-κB levels after adjustment for potential confounders like age, duration of diabetes, and HbA1C (B=81.34; p<0.001).

CONCLUSIONS

NF-κB activation plays a key role in promoting inflammation which is associated with the progression of DPN. In this respect, the study of NF-κB levels in serum may be an additional diagnostic marker for DPN.

Exploring the molecular mechanism of Xuebifang in the treatment of diabetic peripheral neuropathy based on bioinformatics and network pharmacology

Background

Xuebifang (XBF), a potent Chinese herbal formula, has been employed in managing diabetic peripheral neuropathy (DPN). Nevertheless, the precise mechanism of its action remains enigmatic.

Purpose

The primary objective of this investigation is to employ a bioinformatics-driven approach combined with network pharmacology to comprehensively explore the therapeutic mechanism of XBF in the context of DPN.

Study design and Methods

The active chemicals and their respective targets of XBF were sourced from the TCMSP and BATMAN databases. Differentially expressed genes (DEGs) related to DPN were obtained from the GEO database. The targets associated with DPN were compiled from the OMIM, GeneCards, and DrugBank databases. The analysis of GO, KEGG pathway enrichment, as well as immuno-infiltration analysis, was conducted using the R language. The investigation focused on the distribution of therapeutic targets of XBF within human organs or cells. Subsequently, molecular docking was employed to evaluate the interactions between potential targets and active compounds of XBF concerning the treatment of DPN.

Results

The study successfully identified a total of 122 active compounds and 272 targets associated with XBF. 5 core targets of XBF for DPN were discovered by building PPI network. According to GO and KEGG pathway enrichment analysis, the mechanisms of XBF for DPN could be related to inflammation, immune regulation, and pivotal signalling pathways such as the TNF, TLR, CLR, and NOD-like receptor signalling pathways. These findings were further supported by immune infiltration analysis and localization of immune organs and cells. Moreover, the molecular docking simulations demonstrated a strong binding affinity between the active chemicals and the carefully selected targets.

Conclusion

In summary, this study proposes a novel treatment model for XBF in DPN, and it also offers a new perspective for exploring the principles of traditional Chinese medicine (TCM) in the clinical management of DPN.

Multiorgan locked-state model of chronic diseases and systems pharmacology opportunities

With increasing human life expectancy, the global medical burden of chronic diseases is growing. Hence, chronic diseases are a pressing health concern and will continue to be in decades to come. Chronic diseases often involve multiple malfunctioning organs in the body. An imminent question is how interorgan crosstalk contributes to the etiology of chronic diseases. We conceived the locked-state model (LoSM), which illustrates how interorgan communication can give rise to body-wide memory-like properties that 'lock' healthy or pathological conditions. Next, we propose cutting-edge systems biology and artificial intelligence strategies to decipher chronic multiorgan locked states. Finally, we discuss the clinical implications of the LoSM and assess the power of systems-based therapies to dismantle pathological multiorgan locked states while improving treatments for chronic diseases.

Novel therapeutical approaches based on neurobiological and genetic strategies for diabetic polyneuropathy - A review

BACKGROUND

Neuropathy is among the most often reported consequences of diabetes and the biggest cause of morbidity and mortality in people suffering from this life-long disease. Although different therapeutic methods are available for diabetic neuropathy, it is still the leading cause of limb amputations, and it significantly decreases patients' quality of life.

AIM

This study investigates potential novel therapeutic options that could ameliorate symptoms of DN.

METHODOLOGY

Research and review papers from the last 10 years were taken into consideration.

RESULTS

There are various traditional drugs and non-pharmacological methods used to treat this health condition. However, the research in the area of pathogenic-oriented drugs in the treatment of DN showed no recent breakthroughs, mostly due to the limited evidence about their effectiveness and safety obtained through clinical trials. Consequently, there is an urgent demand for the development of novel therapeutic options for diabetic neuropathy.

CONCLUSION

Some of the latest novel diagnostic methods for diagnosing diabetic neuropathy are discussed as well as the new therapeutic approaches, such as the fusion of neuronal cells with stem cells, targeting gene delivery and novel drugs.

Vitamin D status and its association with inflammatory markers among Kurdish type 2 diabetic patients with painful diabetic peripheral neuropathy

Several clinical studies have shown an association between vitamin D deficiency and painful diabetic peripheral neuropathy (DPN). However, it is still unclear whether vitamin D status and inflammatory markers correlate in patients with painful DPN. In this context, we aimed to investigate the associations between serum vitamin D levels and inflammatory status in Kurdish type 2 diabetes patients (T2DM) with painful DPN and without painful DPN. A clinical case-control study was conducted on 86 Kurdish patients with T2DM. The patients were divided into two groups: the case group consisted of 45 patients with painful DPN and the control group consisted of 41 age- and sex-matched diabetics without DPN. In T2DM patients with and without painful DPN, the prevalence of severe vitamin D deficiency was observed in 46.67% and 21.95% of the patients, respectively (p = 0.0283). The mean serum 25(OH)-vitamin D level in patients with painful DPN (mean = 12.00, SD = 5.78) was significantly lower than in patients without DPN (mean = 16.36, SD = 7.86; p = 0.0041). Regression analysis revealed that vitamin D deficiency (p = 0.0120) and higher glycated hemoglobin (HbA1c) (p = 0.00003) were identified as predictive risk factors for painful DPN. However, there was no significant association between inflammatory status and vitamin D levels. The duration of sun exposure was the only controlling factor for vitamin D in painful DPN patients. In the Kurdish population, lower vitamin D and high HbA1c levels were predictive factors for painful DPN.

Physiological role of cytokines in the regulation of mammalian metabolism

The innate cytokine system is involved in the response to excessive food intake. In this review, we highlight recent advances in our understanding of the physiological role of three prominent cytokines, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF), in mammalian metabolic regulation. This recent research highlights the pleiotropic and context-dependent functions in the immune-metabolic interplay. IL-1β is activated in response to overloaded mitochondrial metabolism, stimulates insulin secretion, and allocates energy to immune cells. IL-6 is released by contracting skeletal muscle and adipose tissue and directs energy from storing tissues to consuming tissues. TNF induces insulin resistance and prevents ketogenesis. Additionally, the therapeutic potential of modulating the activity of each cytokine is discussed.

The Ameliorative Effect of Thymoquinone on Vincristine-Induced Peripheral Neuropathy in Mice by Modulating Cellular Oxidative Stress and Cytokine

Thymoquinone (TQ), an active constituent of Nigella sativa, has been reported to exert a broad spectrum of pharmacological effects, including neuroprotective, anticancer, anti-inflammatory, antidiabetic, antiepileptic, antioxidant, and other modulatory roles in inflammation in experimental studies. The present study aims to evaluate the potential effects of TQ on vincristine-induced neuropathy in mice, as well as the possible role of oxidative stress, and pro- and anti-inflammatory cytokine in neuropathy development. A Swiss strain of male albino mice were randomly divided into seven groups, comprising of five animals each. Vincristine sulfate (0.1 mg/kg, i.p.) was administered for 10 consecutive days for the induction of peripheral neuropathy. The animals received their respective treatment of TQ (2.5, 5, and 10 mg/kg, p.o.) and pregabalin (10 mg/kg, p.o.) concurrently with vincristine for 10 days followed by 4 days post treatment. The animals were assessed for pain and related behavior on day 7 and 14 using hot and cold plates, and a rotarod test. TQ preventive treatment attenuated vincristine induced neuropathy in a dose dependent manner evidenced as a significant (p < 0.001) increase in reaction time on the hot plate and the cold plate, and a fall off time on the rotarod test. Further, TQ preventive treatment resulted in a significant (p < 0.001) reduction in the number of flinches and duration of paw elevation in a formalin test. Preventative treatment with TQ abolished the vincristine-induced rise in malondialdehyde and glutathione depletion in sciatic nerve tissue, as well as the blood IL-6 levels. In conclusion, TQ at 2.5, 5, and 10 mg/kg dose produced significant attenuation of neuropathic pain induced by vincristine which may be due to its antinociceptive, antioxidant, and anti-proinflammatory activity.

Molecular mechanisms of exercise contributing to tissue regeneration

Physical activity has been known as an essential element to promote human health for centuries. Thus, exercise intervention is encouraged to battle against sedentary lifestyle. Recent rapid advances in molecular biotechnology have demonstrated that both endurance and resistance exercise training, two traditional types of exercise, trigger a series of physiological responses, unraveling the mechanisms of exercise regulating on the human body. Therefore, exercise has been expected as a candidate approach of alleviating a wide range of diseases, such as metabolic diseases, neurodegenerative disorders, tumors, and cardiovascular diseases. In particular, the capacity of exercise to promote tissue regeneration has attracted the attention of many researchers in recent decades. Since most adult human organs have a weak regenerative capacity, it is currently a key challenge in regenerative medicine to improve the efficiency of tissue regeneration. As research progresses, exercise-induced tissue regeneration seems to provide a novel approach for fighting against injury or senescence, establishing strong theoretical basis for more and more "exercise mimetics." These drugs are acting as the pharmaceutical alternatives of those individuals who cannot experience the benefits of exercise. Here, we comprehensively provide a description of the benefits of exercise on tissue regeneration in diverse organs, mainly focusing on musculoskeletal system, cardiovascular system, and nervous system. We also discuss the underlying molecular mechanisms associated with the regenerative effects of exercise and emerging therapeutic exercise mimetics for regeneration, as well as the associated opportunities and challenges. We aim to describe an integrated perspective on the current advances of distinct physiological mechanisms associated with exercise-induced tissue regeneration on various organs and facilitate the development of drugs that mimics the benefits of exercise.

The timing point of exercise intervention regulates neuropathic pain-related molecules in the ipsilateral dorsal root ganglion neurons after sciatic nerve injury

The purpose of this study was to determine whether the timing of tread-mill exercise application can control expression levels of neuropathic pain- and regeneration-related proteins in the ipsilateral lumbar 4 (L4) to 6 (L6) dorsal root ganglion cells (DRG) after sciatic nerve injury (SNI). The experimental rats were randomly divided into five groups: the normal control, SNI+sedentary (IS), exercise+SNI (EI), SNI+exercise (IE), exercise+SNI+exercise (EIE) groups. The rats in exercise groups per-formed treadmill exercise at a speed of 8 m/min for 30 min once a day during 14 days before and/or after SNI. For investigating the expression of specific neuropathic pain and regeneration-related proteins in DRG, we prepared L4 to L6 DRG in the ipsilateral side. In the quantitative analysis, growth associated protein 43 (GAP-43) and brain-derived neurotrophic factor levels were further increased in the ipsilateral DRG at all treadmill exercise groups than those in IS group. In the histological findings, GAP-43 was qualitatively increased IE and EIE groups than IS group at DRG. Wnt3a and β-catenin were dramatically downregulated in EIE and IE groups than IS groups. In addition, nuclear factor kappa-light-chain-enhancer of activated B cells and tumor necrosis factor-α were significantly decreased in IE and EIE groups than IS group in the ipsilateral DRG. Our findings suggested novel information that regular low-intensity exercise before and/or after SNI might be a therapeutic and preventive approaches for relieving neuropathic pain and improving axonal elongation after peripheral nerve injury.

Programming of Regulatory T Cells In Situ for Nerve Regeneration and Long-Term Patency of Vascular Grafts

Rapid integration into the host tissue is critical for long-term patency after small diameter tissue engineering vascular grafts (sdTEVGs) transplantation. Neural recognition may be required for host integration and functionalization of the graft. However, immune rejection and inflammation hinder nerve regeneration of sdTEVGs. Here, a CRISPR/dCas9-nanocarrier was used for targeted programming of regulatory T cells (Treg cells) in situ to promote nerve regeneration of sdTEVGs by preventing excessive inflammation. Treg cells and (C-C chemokine receptor) CCR2+ macrophage recruitment occurred after transplantation. The nanodelivery system upregulated ten eleven translocation (TET2) in Treg cells in vitro. Reprogrammed Treg cells upregulated anti-inflammatory cytokines and decreased the proportion of CCR2+ macrophages. IL-6 concentrations decreased to the levels required for nerve regeneration. Implantation of CRISPR/dCas9 nanodelivery system-modified sdTEVGs in rats resulted in Treg cell editing, control of excessive inflammation, and promoted nerve regeneration. After 3 months, nerve regeneration was similar to that observed in normal blood vessels; good immune homeostasis, consistency of hemodynamics, and matrix regeneration were observed. Neural recognition promotes further integration of the graft into the host, with unobstructed blood vessels without intimal hyperplasia. Our findings provide new insights into vascular implant functionalization by the host.

CEBPβ regulation of endogenous IGF-1 in adult sensory neurons can be mobilized to overcome diabetes-induced deficits in bioenergetics and axonal outgrowth

Aberrant insulin-like growth factor 1 (IGF-1) signaling has been proposed as a contributing factor to the development of neurodegenerative disorders including diabetic neuropathy, and delivery of exogenous IGF-1 has been explored as a treatment for Alzheimer's disease and amyotrophic lateral sclerosis. However, the role of autocrine/paracrine IGF-1 in neuroprotection has not been well established. We therefore used in vitro cell culture systems and animal models of diabetic neuropathy to characterize endogenous IGF-1 in sensory neurons and determine the factors regulating IGF-1 expression and/or affecting neuronal health. Single-cell RNA sequencing (scRNA-Seq) and in situ hybridization analyses revealed high expression of endogenous IGF-1 in non-peptidergic neurons and satellite glial cells (SGCs) of dorsal root ganglia (DRG). Brain cortex and DRG had higher IGF-1 gene expression than sciatic nerve. Bidirectional transport of IGF-1 along sensory nerves was observed. Despite no difference in IGF-1 receptor levels, IGF-1 gene expression was significantly (P < 0.05) reduced in liver and DRG from streptozotocin (STZ)-induced type 1 diabetic rats, Zucker diabetic fatty (ZDF) rats, mice on a high-fat/ high-sugar diet and db/db type 2 diabetic mice. Hyperglycemia suppressed IGF-1 gene expression in cultured DRG neurons and this was reversed by exogenous IGF-1 or the aldose reductase inhibitor sorbinil. Transcription factors, such as NFAT1 and CEBPβ, were also less enriched at the IGF-1 promoter in DRG from diabetic rats vs control rats. CEBPβ overexpression promoted neurite outgrowth and mitochondrial respiration, both of which were blunted by knocking down or blocking IGF-1. Suppression of endogenous IGF-1 in diabetes may contribute to neuropathy and its upregulation at the transcriptional level by CEBPβ can be a promising therapeutic approach.

Interleukin-6 Levels in Patients With Diabetic Polyneuropathy

Introduction

Diabetic polyneuropathy (DPN) is a common chronic complication of type 2 diabetes. The pathogenesis of DPN is still debated, but proinflammatory cytokine mediators like interleukin-6 (IL-6) are possibly involved. We conducted this cross-sectional observational study to assess whether IL-6 levels increase in patients with DPN.

Materials and methods

This study was conducted at the Institute of Post Graduate Medical Education and Research Hospital in Kolkata, India, from 2016 to 2017. The study included 57 patients aged 30 to 60 years diagnosed with type 2 diabetes with neuropathy on clinical examination and nerve conduction study. Patients with neuropathy due to other causes were excluded. The study participants were assigned into one of four groups. Group 1 (n=15) served as healthy control patients, Group 2 (n=12) contained patients with type 2 diabetes without neuropathy, Group 3 (n=20) contained patients with type 2 diabetes with painful neuropathy, and Group 4 (n=10) contained patients with type 2 diabetes with painless neuropathy. We compared IL-6 levels between each group. 

Results

There was no significant difference in serum IL-6 levels between healthy controls (Group 1) and patients with type 2 diabetes without neuropathy (Group 2). However, we noted a significant increase in serum IL-6 levels among patients with painful DPN (Group 3) compared to control groups. Interestingly, serum IL-6 levels were higher in patients with painful DPN (Group 3) than patients with painless DPN (Group 4).

Conclusions

IL-6 increases significantly in painful diabetic neuropathy patients compared to patients with diabetes with painless neuropathy and thus may have a role in the pathogenesis of pain in DPN. Serum IL6 level can be a potential noninvasive marker of painful DPN, and it can help distinguish painful DPN from other causes of pain in patients with diabetes.

Perspectives of glycemic variability in diabetic neuropathy: a comprehensive review

Diabetic neuropathy is one of the most prevalent chronic complications of diabetes, and up to half of diabetic patients will develop diabetic neuropathy during their disease course. Notably, emerging evidence suggests that glycemic variability is associated with the pathogenesis of diabetic complications and has emerged as a possible independent risk factor for diabetic neuropathy. In this review, we describe the commonly used metrics for evaluating glycemic variability in clinical practice and summarize the role and related mechanisms of glycemic variability in diabetic neuropathy, including cardiovascular autonomic neuropathy, diabetic peripheral neuropathy and cognitive impairment. In addition, we also address the potential pharmacological and non-pharmacological treatment methods for diabetic neuropathy, aiming to provide ideas for the treatment of diabetic neuropathy.

Zhang et al. describe metrics for evaluating glycaemic variability (GV) in clinical practice and summarize the role and related mechanisms of GV in diabetic neuropathy, including cardiovascular autonomic neuropathy, diabetic peripheral neuropathy and cognitive impairment. They aim to stimulate ideas for the treatment of diabetic neuropathy.

Chondroitin sulfate produces antinociception and neuroprotection in chronic constriction injury-induced neuropathic pain in rats by increasing anti-inflammatory molecules and reducing oxidative stress

OBJECTIVES

Damage to the peripheral and central nervous system lead to Neuropathic pain (NP) which is a widespread and devitalizing condition. chondroitin sulfate (CS), has been used in managing joint pain and osteoarthritis. In this study, the effectiveness of CS on NP induced by chronic constriction injury (CCI) is examined.

METHODS

Thirty Wistar rats were distributed at random into six groups (n = 5). Sciatic nerve ligation was carried out by encircling the nerve with four loose ligatures to induce NP. Allodynia (cold and mechanical) and heat hyperalgesia were assessed using Acetone, von Frey filament and Hot plate tests. CCI induction resulted to NP, prominent from the 3rd day after surgery. Structural architecture of sciatic nerves was evaluated via histological examination of the transverse section of the nerves.

RESULTS

Oral administration of CS (600 mg/kg and 900 mg/kg for 21 days) resulted in significant (P < 0.05) inhibition of allodynia (cold and mechanical) and thermal hyperalgesia. Lipid peroxidation, tumor necrosis factor-α (TNF-α), calcitonin gene related peptide (CGRP), C reactive protein (CRP), and oxidative stress were attenuated by CS. CS also improved interleukin (IL)-6, nitric oxide (NO), total antioxidant capacity (TAC).

CONCLUSION

These findings suggest that CS attenuates allodynia, and thermal hyperalgesia induced by CCI by downregulating TNF-α, CRP, CGRP, oxidative enzymes, and upregulating IL-6, NO, and TAC. Nociceptive behavioral studies and histological findings showed significant improvement in the CS treated groups compared to CCI rats. These findings are responsible for the beneficial effect of CS in NP.

Potential Physiological and Cellular Mechanisms of Exercise That Decrease the Risk of Severe Complications and Mortality Following SARS-CoV-2 Infection

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has unmasked mankind's vulnerability to biological threats. Although higher age is a major risk factor for disease severity in COVID-19, several predisposing risk factors for mortality are related to low cardiorespiratory and metabolic fitness, including obesity, cardiovascular disease, diabetes, and hypertension. Reaching physical activity (PA) guideline goals contribute to protect against numerous immune and inflammatory disorders, in addition to multi-morbidities and mortality. Elevated levels of cardiorespiratory fitness, being non-obese, and regular PA improves immunological function, mitigating sustained low-grade systemic inflammation and age-related deterioration of the immune system, or immunosenescence. Regular PA and being non-obese also improve the antibody response to vaccination. In this review, we highlight potential physiological, cellular, and molecular mechanisms that are affected by regular PA, increase the host antiviral defense, and may determine the course and outcome of COVID-19. Not only are the immune system and regular PA in relation to COVID-19 discussed, but also the cardiovascular, respiratory, renal, and hormonal systems, as well as skeletal muscle, epigenetics, and mitochondrial function.

Therapeutic Potential of Complementary and Alternative Medicines in Peripheral Nerve Regeneration: A Systematic Review

Despite the progressive advances, current standards of treatments for peripheral nerve injury do not guarantee complete recovery. Thus, alternative therapeutic interventions should be considered. Complementary and alternative medicines (CAMs) are widely explored for their therapeutic value, but their potential use in peripheral nerve regeneration is underappreciated. The present systematic review, designed according to guidelines of Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols, aims to present and discuss the current literature on the neuroregenerative potential of CAMs, focusing on plants or herbs, mushrooms, decoctions, and their respective natural products. The available literature on CAMs associated with peripheral nerve regeneration published up to 2020 were retrieved from PubMed, Scopus, and Web of Science. According to current literature, the neuroregenerative potential of Achyranthes&nbsp;bidentata, Astragalus&nbsp;membranaceus, Curcuma&nbsp;longa, Panax&nbsp;ginseng, and Hericium&nbsp;erinaceus are the most widely studied. Various CAMs enhanced proliferation and migration of Schwann cells in vitro, primarily through activation of MAPK pathway and FGF-2 signaling, respectively. Animal studies demonstrated the ability of CAMs to promote peripheral nerve regeneration and functional recovery, which are partially associated with modulations of neurotrophic factors, pro-inflammatory cytokines, and anti-apoptotic signaling. This systematic review provides evidence for the potential use of CAMs in the management of peripheral nerve injury.

Role of IL-6 in the regulation of neuronal development, survival and function

The pleiotropic cytokine interleukin-6 (IL-6) is emerging as a molecule with both beneficial and destructive potentials. It can exert opposing actions triggering either neuron survival after injury or causing neurodegeneration and cell death in neurodegenerative or neuropathic disorders. Importantly, neurons respond differently to IL-6 and this critically depends on their environment and whether they are located in the peripheral or the central nervous system. In addition to its hub regulator role in inflammation, IL-6 is recently emerging as an important regulator of neuron function in health and disease, offering exciting possibilities for more mechanistic insight into the pathogenesis of mental, neurodegenerative and pain disorders and for developing novel therapies for diseases with neuroimmune and neurogenic pathogenic components.

Adipose-derived mesenchymal stem cells attenuate dialysis-induced peritoneal fibrosis by modulating macrophage polarization via interleukin-6

Background

Life-long peritoneal dialysis (PD) as a renal replacement therapy is limited by peritoneal fibrosis. Previous studies showed immunomodulatory and antifibrotic effects of adipose-derived mesenchymal stem cells (ADSCs) on peritoneal fibrosis. However, the role of the peritoneal macrophage in this process remains uninvestigated.

Methods

We examined the therapeutic effects of ADSC and bone marrow-derived mesenchymal stem cells (BM-MSC) in the rat model of dialysis-induced peritoneal fibrosis using methylglyoxal. In addition, treatment of macrophages with the conditioned medium of ADSC and BM-MSC was performed individually to identify the beneficial component of the stem cell secretome.

Results

In the in vivo experiments, we found dialysis-induced rat peritoneal fibrosis was attenuated by both ADSC and BM-MSC. Interestingly, ADSC possessed a more prominent therapeutic effect than BM-MSC in ameliorating peritoneal membrane thickening while also upregulating epithelial cell markers in rat peritoneal tissues. The therapeutic effects of ADSC were positively associated with M2 macrophage polarization. In the in vitro experiments, we confirmed that interleukin-6 (IL-6) secreted by MSCs upon transforming growth factor-β1 stimulation promotes M2 macrophage polarization.

Conclusions

In dialysis-induced peritoneal fibrosis, MSCs are situated in an inflammatory environment of TGF-β1 and secrete IL-6 to polarize macrophages into the M2 phenotype. Our findings reveal a previously unidentified role of tissue macrophage in this antifibrotic process. ADSC has the advantage of abundance and accessibility, making the application values extremely promising.

Graphical abstract

In dialysis-induced peritoneal fibrosis, peritoneal mesothelial cells secrete transforming growth factor-β1 (TGF-β1) when exposed to methylglyoxal (MGO)-containing peritoneal dialysate. When situated in TGF-β1, the inflammatory environment induces mesenchymal stem cells to secrete interleukin-6 (IL-6), IL-6 polarizes macrophages into the M2 phenotype. The dominant peritoneal tissue M2 macrophages, marked by upregulated Arg-1 expression, account for the attenuation of MGO-induced dedifferentiation of peritoneal mesothelial cells to maintain epithelial integrity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02270-4.

Prospects for the application of transcranial magnetic stimulation in diabetic neuropathy

Encouraging results have been reported for the use of transcranial magnetic stimulation-based nerve stimulation in studies of the mechanisms of neurological regulation, nerve injury repair, and nerve localization. However, to date, there are only a few reviews on the use of transcranial magnetic stimulation for diabetic neuropathy. Patients with diabetic neuropathy vary in disease progression and show neuropathy in the early stage of the disease with mild symptoms, making it difficult to screen and identify. In the later stage of the disease, irreversible neurological damage occurs, resulting in treatment difficulties. In this review, we summarize the current state of diabetic neuropathy research and the prospects for the application of transcranial magnetic stimulation in diabetic neuropathy. We review significant studies on the beneficial effects of transcranial magnetic stimulation in diabetic neuropathy treatment, based on the outcomes of its use to treat neurodegeneration, pain, blood flow change, autonomic nervous disorders, vascular endothelial injury, and depression. Collectively, the studies suggest that transcranial magnetic stimulation can produce excitatory/inhibitory stimulation of the cerebral cortex or local areas, promote the remodeling of the nervous system, and that it has good application prospects for the localization of the injury, neuroprotection, and the promotion of nerve regeneration. Therefore, transcranial magnetic stimulation is useful for the screening and early treatment of diabetic neuropathy. Transcranial magnetic stimulation can also alleviate pain symptoms by changing the cortical threshold and inhibiting the conduction of sensory information in the thalamo-spinal pathway, and therefore it has therapeutic potential for the treatment of pain and pain-related depressive symptoms in patients with diabetic neuropathy. Additionally, based on the effect of transcranial magnetic stimulation on local blood flow and its ability to change heart rate and urine protein content, transcranial magnetic stimulation has potential in the treatment of autonomic nerve dysfunction and vascular injury in diabetic neuropathy. Furthermore, oxidative stress and the inflammatory response are involved in the process of diabetic neuropathy, and transcranial magnetic stimulation can reduce oxidative damage. The pathological mechanisms of diabetic neuropathy should be further studied in combination with transcranial magnetic stimulation technology.

Managing diabetic foot in times of COVID-19: time to put the best 'foot' forward

Introduction

The COVID-19 pandemic has had an unparalleled impact on the socio-economic and healthcare structure of India. Due to our large populations of diabetic patients, who have an increased risk of worse outcomes with COVID-19 infection, it is of utmost public health importance to analyse the relationship between the two. The aim of our review was to analyse the possible relationship between COVID-19 infection and DFUs, which are a fairly common, yet serious complication in diabetic patients, as well as their management, under the given changing circumstances.

Methodology

An extensive review of related educational articles was analysed from various databases.

Results

The two main pathogenic mechanisms described in COVID-19 infection are a cytokine storm (causing ARDS) as well as an acquired coagulopathy, with widespread thrombosis. DFUs are associated with an underlying peripheral neuropathy, a chronic low-grade inflammatory state and peripheral arterial disease, which lead to chronic non-healing ulcers. Similarities seen in the pathogenic mechanisms of these two conditions make a bidirectional relationship highly plausible.

Conclusion

Due to the disruptions in the healthcare system brought on by the COVID-19 pandemic, changes in practice to a telehealth-driven approach, with emphasis on homecare and community clinics, need to be adopted, to ensure best possible care to patients with DFUs, in order to reduce their risk of DFU-related complications and need for hospitalization.

Macrophages and Associated Ligands in the Aged Injured Nerve: A Defective Dynamic That Contributes to Reduced Axonal Regrowth

The regenerative capacity of injured peripheral nerves is diminished with aging. To identify factors that contribute to this impairment, we compared the immune cell response in young vs. aged animals following nerve injury. First, we confirmed that macrophage accumulation is delayed in aged injured nerves which is due to defects in monocyte migration as a result of defects in site-specific recruitment signals in the aged nerve. Interestingly, impairment in both macrophage accumulation and functional recovery could be overcome by transplanting bone marrow from aged animals into young mice. That is, upon exposure to a youthful environment, monocytes/macrophages originating from the aged bone marrow behaved similarly to young cells. Transcriptional profiling of aged macrophages following nerve injury revealed that both pro- and anti-inflammatory genes were largely downregulated in aged compared to young macrophages. One ligand of particular interest was macrophage-associated secreted protein (MCP1), which exhibited a potent role in regulating aged axonal regrowth in vitro. Given that macrophage-derived MCP1 is significantly diminished in the aged injured nerve, our data suggest that age-associated defects in MCP1 signaling could contribute to the regenerative deficits that occur in the aged nervous system.

Inflammatory state does not affect the antiplatelet efficacy of potent P2Y12 inhibitors in ACS

Inflammation leads to atherosclerosis and acute coronary syndromes (ACS). We performed a prospective, observational study to assess association between the concentrations of inflammatory markers (high sensitivity C-reactive protein, hsCRP; high sensitivity interleukin6, hsIL-6; soluble CD40 ligand, sCD40 L) and platelet reactivity in 338 patients with ACS treated with ticagrelor and prasugrel. We also assessed whether hsCRP, hsIL-6, and sCD40 L are associated with standard inflammatory markers (white blood cell [WBC] and fibrinogen), and whether they differ according to patient diabetic status and pre-treatment with statins. Concentrations of hsCRP and concentrations of hsIL-6 and sCD40 L were assessed using turbidimetric assay and enzyme-linked immunosorbent assay, respectively. Platelet reactivity was measured using multiple electrode aggregometry. There was only a weak inverse correlation between hsIL-6 and platelet reactivity (r≤-0.125). In contrast, concentration of hsIL6 and hsCRP positively correlated with WBC and fibrinogen (r ≥ 0.199). Insulin-dependent diabetes mellitus (IDDM) was associated with higher concentration of hsIL-6 (p = .014), whereas pre-treatment with statins - with lower concentration of hsIL-6 (p = .035). In conclusion, inflammatory state does not affect the antiplatelet efficacy of potent P2Y12 inhibitors in the acute phase of ACS, confirming the safety and efficacy of potent P2Y12 inhibitors in patients with a high inflammatory burden.

Schwann cells apoptosis is induced by high glucose in diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes mellitus that affects approximately half of patients with diabetes. Current treatment regimens cannot treat DPN effectively. Schwann cells (SCs) are very sensitive to glucose concentration and insulin, and closely associated with the occurrence and development of type 1 diabetic mellitus (T1DM) and DPN. Apoptosis of SCs is induced by hyperglycemia and is involved in the pathogenesis of DPN. This review considers the pathological processes of SCs apoptosis under high glucose, which include the following: oxidative stress, inflammatory reactions, endoplasmic reticulum stress, autophagy, nitrification and signaling pathways (PI3K/AKT, ERK, PERK/Nrf2, and Wnt/β-catenin). The clarification of mechanisms underlying SCs apoptosis induced by high glucose will help us to understand and identify more effective strategies for the treatment of T1DM DPN.

Current Therapeutic Strategies in Diabetic Foot Ulcers

Diabetic foot ulcers (DFUs) are the fastest growing chronic complication of diabetes mellitus, with more than 400 million people diagnosed globally, and the condition is responsible for lower extremity amputation in 85% of people affected, leading to high-cost hospital care and increased mortality risk. Neuropathy and peripheral arterial disease trigger deformities or trauma, and aggravating factors such as infection and edema are the etiological factors for the development of DFUs. DFUs require identifying the etiology and assessing the co-morbidities to provide the correct therapeutic approach, essential to reducing lower-extremity amputation risk. This review focuses on the current treatment strategies for DFUs with a special emphasis on tissue engineering techniques and regenerative medicine that collectively target all components of chronic wound pathology.

Emerging Biomarkers, Tools, and Treatments for Diabetic Polyneuropathy

Diabetic neuropathy, with its major clinical sequels, notably neuropathic pain, foot ulcers, and autonomic dysfunction, is associated with substantial morbidity, increased risk of mortality, and reduced quality of life. Despite its major clinical impact, diabetic neuropathy remains underdiagnosed and undertreated. Moreover, the evidence supporting a benefit for causal treatment is weak at least in patients with type 2 diabetes, and current pharmacotherapy is largely limited to symptomatic treatment options. Thus, a better understanding of the underlying pathophysiology is mandatory for translation into new diagnostic and treatment approaches. Improved knowledge about pathogenic pathways implicated in the development of diabetic neuropathy could lead to novel diagnostic techniques that have the potential of improving the early detection of neuropathy in diabetes and prediabetes to eventually embark on new treatment strategies. In this review, we first provide an overview on the current clinical aspects and illustrate the pathogenetic concepts of (pre)diabetic neuropathy. We then describe the biomarkers emerging from these concepts and novel diagnostic tools and appraise their utility in the early detection and prediction of predominantly distal sensorimotor polyneuropathy. Finally, we discuss the evidence for and limitations of the current and novel therapy options with particular emphasis on lifestyle modification and pathogenesis-derived treatment approaches. Altogether, recent years have brought forth a multitude of emerging biomarkers reflecting different pathogenic pathways such as oxidative stress and inflammation and diagnostic tools for an early detection and prediction of (pre)diabetic neuropathy. Ultimately, these insights should culminate in improving our therapeutic armamentarium against this common and debilitating or even life-threatening condition.

Systemic Factors During Metabolic Disease Progression Contribute to the Functional Decline of Adipose Tissue-Derived Mesenchymal Stem Cells in Reproductive Aged Females

It is known that advanced metabolic disorders such as type 2 diabetes compromise the functional and regenerative capacity of endogenous adipose-tissue resident stem cells (ADSCs). It is, however, still unclear at which stage of disease progression ADSCs become compromised and whether systemic factors contribute to their functional decline. It was therefore hypothesized that inflammatory changes in the systemic microenvironment during distinct stages of disease progression negatively affect the functional capacity of ADSCs. A total of forty-seven (n = 47) black African reproductive aged females (32 ± 8 years; mean ± SD) were included in this study and subdivided into: (a) healthy lean (C; body mass index, BMI ≤ 25 kg/m²), (b) healthy overweight/obese (OB; BMI ≥ 25 kg/m²), (c) obese metabolic syndrome (MetS; BMI ≥ 30 kg/m²), and (d) type 2 diabetes mellitus (T2DM; previously diagnosed and on treatment) groups. Participants underwent anthropometric assessments and a DXA scan to determine their body composition and adipose indices. Each persons’ systemic metabolic- (cholesterol, HDL, LDL, triglycerides, and blood glucose) and inflammatory profiles (CRP, SDF1α, TNFα, IL6, IL8, IL10, and IFNy) were also evaluated. Participant-derived serum was then used to treat an ADSC cell line in vitro and its effect on viability (MTT-based assay), proliferation (BrdU), migration (wound healing assay), and osteogenic differentiation assessed. When exposed to serum derived from overweight/obese individuals (with or without metabolic syndrome), both the proliferative and migratory responses of ADSCs were less pronounced than when exposed to healthy control serum. Serum IL6 concentrations were identified as a factor influencing the proliferation of ADSCs, suggesting that long-term disruption to the systemic cytokine balance can potentially disrupt the proliferative responses of ADSCs. Obese participant-derived serum (with and without metabolic syndrome) furthermore resulted in lipid accumulation during osteogenic differentiation. This study, therefore demonstrated that systemic factors in obese individuals, regardless of the presence of metabolic syndrome, can be detrimental to the multifunctional properties of ADSCs.

Involvement of microRNA-146a in diabetic peripheral neuropathy through the regulation of inflammation

Purpose

Recent evidence has shown the involvement of inflammation in the development of diabetic peripheral neuropathy (DPN). MicroRNA-146a (miR-146a) is closely involved in the inflammatory response. However, the role of miR-146a in the inflammatory reaction in DPN has not been clarified. This study was designed to explore the role of miR-146a in the regulation of inflammatory responses in DPN.

Methods

Rats were randomly divided into three groups (n=6 per group): control group, type 2 diabetes mellitus (T2DM) group and DPN group. T2DM and DPN rats were intraperitoneally injected with streptozotocin. Sciatic nerve conduction velocity (NCV) was determined at the 6th week and the 12th week in each group. The expression of microRNAs was detected by quantitative real-time polymerase chain reaction in three sciatic nerves for each group of rats. Expression of inflammatory cytokines in nerve tissues and plasma was measured by Western blot and Bio-Plex Pro™ assays.

Results

The NCV and expression levels of miR-146a in the DPN group were significantly decreased (P<0.01) compared to the other two groups. Expression of tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in the DPN group was significantly increased compared with the control and T2DM groups (P<0.01). Pearson’s correlation analysis showed that the expression level of miR-146a was negatively correlated with the levels of IL-1β, TNF-α and NF-κB.

Conclusion

miR-146a is involved in the pathogenesis of DPN, and its expression level is closely related to the inflammatory responses that aggravate sciatic nerve injuries.

Injury-induced gp130 cytokine signaling in peripheral ganglia is reduced in diabetes mellitus

Neuropathy is a major diabetic complication. While the mechanism of this neuropathy is not well understood, it is believed to result in part from deficient nerve regeneration. Work from our laboratory established that gp130 family of cytokines are induced in animals after axonal injury and are involved in the induction of regeneration-associated genes (RAGs) and in the conditioning lesion response. Here, we examine whether a reduction of cytokine signaling occurs in diabetes. Streptozotocin (STZ) was used to destroy pancreatic β cells, leading to chronic hyperglycemia. Mice were injected with either low doses of STZ (5×60mg/kg) or a single high dose (1×200mg/kg) and examined after three or one month, respectively. Both low and high dose STZ treatment resulted in sustained hyperglycemia and functional deficits associated with the presence of both sensory and autonomic neuropathy. Diabetic mice displayed significantly reduced intraepidermal nerve fiber density and sudomotor function. Furthermore, low and high dose diabetic mice showed significantly reduced tactile touch sensation measured with Von Frey monofilaments. To look at the regenerative and injury-induced responses in diabetic mice, neurons in both superior cervical ganglia (SCG) and the 4th and 5th lumbar dorsal root ganglia (DRG) were unilaterally axotomized. Both high and low dose diabetic mice displayed significantly less axonal regeneration in the sciatic nerve, when measured in vivo, 48h after crush injury. Significantly reduced induction of two gp130 cytokines, leukemia inhibitory factor and interleukin-6, occurred in diabetic animals in SCG 6h after injury compared to controls. Injury-induced expression of interleukin-6 was also found to be significantly reduced in the DRG at 6h after injury in low and high dose diabetic mice. These effects were accompanied by reduced phosphorylation of signal transducer and activator of transcription 3 (STAT3), a downstream effector of the gp130 signaling pathway. We also found decreased induction of several gp130-dependent RAGs, including galanin and vasoactive intestinal peptide. Together, these data suggest a novel mechanism for the decreased response of diabetic sympathetic and sensory neurons to injury.