Serum Levels of Inflammatory Proteins Are Associated With Peripheral Neuropathy in a Cross-Sectional Type-1 Diabetes Cohort

Elevated Inflammatory Cytokines Persist in the Aqueous Humor Years After Cataract Surgery

Purpose

There is currently limited information regarding inflammation and cytokine levels in the aqueous humor (AH) of adult patients with cataract who have undergone phacoemulsification cataract extraction without other ocular comorbidities.

Methods

AH samples were collected from healthy, non-surgical donors and donors with a history of cataract surgery performed 3 to 12 years prior. Sixty-three cytokines and growth factors were measured using bead-based ProcartaPlex immunoassays. Data analysis included normal distribution assessment, pairwise correlation, logistic regression, and ridge regression.

Results

Of the 63 molecules analyzed, 34 were selected for further study. Cytokines, such as CD40L, IL-7, MIP-1α, and LIF, were found at significantly higher concentrations in AH samples from donors with a history of cataract surgery compared with non-cataract controls. In contrast, lower concentrations of IL-23, TRAIL, IL-12p70, IFNγ, MIP-3α, and SCF were observed in post-surgical samples. Pairwise correlation analysis identified clusters of significantly correlated molecules, suggesting their potential involvement in the inflammatory environment of AH post-cataract surgery. AH concentration of 34 proteins was combined into a post-cataract surgery inflammation index (PCSII) using ridge regression, which differs significantly between post-cataract surgery donors and non-cataract controls. This PCSII shows that any increase in AH levels of these molecules can stratify cataract surgery donors into low and high-risk of inflammatory groups.

Conclusions

This study indicates that cataract surgery may lead to a chronic inflammatory state in the AH, which can persist for extended periods post-surgery.

The role of activated partial thrombin time in mediating the impact of poorly glycemic control on diabetic peripheral neuropathy in patients with type 2 diabetes mellitus

Aim

This study aims to investigate the role of activated partial thrombin time (APTT) as a potential mediator in the relationship between suboptimal glycemic control and diabetic peripheral neuropathy (DPN) in individuals with type 2 diabetes mellitus (T2DM).

Methods

A total of 183 T2DM patients were enrolled in this study. Comprehensive clinical data, including coagulation parameters and nerve conduction velocity, were collected and compared between patients with and without DPN. Subsequent correlation and regression analyses were conducted to explore the associations among APTT, HbA1c levels, and nerve conduction velocities. Moreover, mediation analyses were performed to evaluate the total, direct, and indirect effects of HbA1c on specific nerve conduction velocities, with APTT serving as a mediator.

Results

In comparison to 101 patients without DPN, 82 patients with DPN exhibited significantly elevated levels of HbA1c and decreased levels of APTT. Notably, levels of APTT and HbA1c were correlated with conduction velocities of Tibial nerve motor fibers, as well as sensory fibers of the Ulnar nerve, Median nerve, and Sural nerve. Furthermore, both elevated HbA1c and decreased APTT were identified as risk factors for DPN in T2DM individuals. Mediation analysis showed that APTT mediated the indirect effect of HbA1c on the conduction velocities of sensory fibers in both the ulnar nerve and sural nerve (95% CI: -0.3448, -0.0135; -0.3523, -0.0180). APTT mediated the relationship between HbA1c and the conduction velocities of sensory fibers in the ulnar nerve or sural nerve by 34.66% or 22.03%, respectively.

Conclusions

In patients with T2DM, uncontrolled HbA1c and shorter APTT emerges as risk factors for DPN. Additionally, the effect of increased HbA1c upon DPN, especially for influenced conduction velocities of sensory fibers in both the ulnar nerve and sural nerve may partly medicated by decreased APTT.

Causal association between matrix metalloproteinases and diabetic neuropathy: a two-sample Mendelian randomization study

Objective

Diabetic neuropathy (DN), a common and debilitating complication of diabetes, significantly impairs the quality of life of affected individuals. While multiple studies have indicated changes in the expression of specific matrix metalloproteinases (MMPs) in patients with DN, and basic research has reported the impact of MMPs on DN, there is a lack of systematic research and the causal relationship remains unclear. The objective of this research is to investigate the casual relationship between MMPs and DN through two-sample Mendelian randomization (MR).

Methods

Data for this investigation were derived from genome-wide association studies (GWAS) of MMPs and DN. For the analysis using two-sample MR, methods such as inverse variance weighted (IVW), weighted median, weighted mode, and MR-Egger were utilized, with IVW serving as the primary measure for determining causative impacts. To evaluate the analysis' heterogeneity and potential pleiotropy, sensitivity examinations including MR-PRESSO analysis, Cochran's Q test, and the leave-one-out test were conducted.

Results

IVW analysis revealed that genetically decreased serum MMP-2 level were causally associated with a high risk of DN (OR = 0.88, 95% CI: 0.79-0.99, P = 0.026). Genetically elevated serum MMP-16 level were causally associated with a high risk of DN (OR = 1.15, 95% CI: 1.01-1.32, P = 0.038). Genetic prediction results showed no causal association between other MMPs (MMP14/17/9/12/7/3) and DN. Sensitivity analyses showed no significant heterogeneity or pleiotropy.

Conclusion

In summary, this research uncovered a genetic causal relationship between heightened MMP-16 levels and reduced MMP-2 concentrations, and DN risk. These discoveries offer new perspectives on the role of MMPs in DN etiology and establish a foundational premise for further investigations into MMP-targeted therapeutic interventions.

Sex-specific cytokine, chemokine, and growth factor signatures in T1D patients and progressors

Numerous studies have reported altered cytokine levels in type 1 diabetes (T1D) patients, yet findings remain inconsistent. In this pilot study, we tested the hypothesis that circulating immune markers exhibit sex-based differences in T1D, both prior to and after disease onset. We analyzed 47-48 cytokine, chemokine, and growth factor levels in two cohorts. To assess post-disease differences, we analyzed serum samples from 25 controls and 25 T1D patients. To examine pre-disease progression, we utilized samples from 21 control children and 16 T1D progressors, collected at age 5 years before disease onset. Across all T1D patients and controls, only macrophage colony-stimulating factor and interleukin (IL)-6 showed significant differences. However, we identified notable alterations when comparing sex-age-matched controls and T1D samples. Female T1D patients exhibited lower levels of inflammatory cytokines (tumor necrosis factor-α, IL-6, IL-1a), Th2 cytokines (IL-4, IL-13), and chemokines (macrophage inflammatory protein (MIP)-1α, regulated upon activation, normal T cell expressed and secreted, MIP-3) compared to female controls, differences that were not observed in males. Notably, IL-22 was lower in female T1D patients compared to female controls, whereas it was higher in male T1D patients compared to male controls. Male T1D patients showed elevated levels of growth factors (epidermal growth factor, platelet-derived growth factor-AB/BB) compared to male controls. In T1D progressors, growth-regulated alpha was lower compared to controls in both sexes. Multiple regression analysis further revealed associations between cytokine levels and factors such as age, BMI, and breastfeeding duration. Overall, our findings serve as a proof of concept, highlighting the importance of sex-specific differences in T1D pathogenesis. However, follow-up studies with larger sample sizes are needed to validate and generalize these results.

The role of novel inflammation-associated biomarkers in diabetic peripheral neuropathy

Diabetic neuropathy is one of the commonest complications of diabetes mellitus. Its most frequent form is diabetic peripheral neuropathy (DPN). Currently, there is no established and widely used biomarker for diagnosis and clinical staging of DPN. There is accumulating evidence that low-grade systemic inflammation is a key element in its pathogenesis. In this context, several clinical studies have so far identified potential biomarkers of DPN. These studies have enrolled both subjects with type 1 diabetes mellitus (T1DM) and subjects with type 2 diabetes mellitus (T2DM), including children with T1DM and elderly T2DM subjects. They have also evaluated participants with prediabetes. Potential biomarkers include a wide spectrum of cytokines, chemokines and immune receptors, notably interleukins (IL), mostly IL-1, IL-6 or IL-10, as well as mediators of the tumour necrosis factor-α (TNF-α) related pathway. Cell-ratios, such as neurtrophil-to-lymphocyte ratio (NLR), have yielded promising results as well. Other works have focused on adipokines and identified several signalling molecules (adiponectin, neuregulin 4, isthmin-1 and omentin) as promising biomarkers of DPN. Finally, epigenetic biomarkers have been investigated. Further experience is being gathered with the use of biomarkers in specific age groups and in the discrimination between painless and painful DPN. Prospective studies appear promising in monitoring of DPN progression, but experience is rather limited. Finally, certain cut-off values have been proposed for DPN screening, but these need confirmation. Future large-scale studies are now required to validate biomarkers and to investigate their potential clinical utility.

Exploring neuroinflammation: A key driver in neuropathic pain disorders

Inflammation is a fundamental part of the body's natural defense mechanism, involving immune cells and inflammatory mediators to promote healing and protect against harm. In the event of a lesion or disease of the somatosensory nervous system, inflammation, however, triggers a cascade of changes in both the peripheral and central nervous systems, ultimately contributing to chronic neuropathic pain. Substantial evidence links neuroinflammation to various conditions associated with neuropathic pain. This chapter will explore the role of neuroinflammation in the initiation, maintenance, and resolution of peripheral and central neuropathic pain. Additionally, biomarkers of neuroinflammation in humans will be examined, emphasizing their relevance in different neuropathic pain disorders.

Sex-Specific Cytokine, Chemokine, and Growth Factor Signatures in T1D Patients and Progressors

While studies have reported altered levels of cytokines in type 1 diabetes (T1D) patients, the results are inconsistent, likely because of variable factors. This study tests the hypothesis that there are sex-based differences in cytokine levels in T1D, prior to and after disease onset. We analyzed 48 blood cytokine, chemokine, and growth factor levels using a multiplex assay. We found only two cytokines, M-CSF and IL-6, with significant differences between T1D patients (n=25) versus controls overall (n=25). However, we identified notable alterations when comparing sex-age-matched controls and T1D samples. Inflammatory cytokines (TNF-α, IL-6, IL-1a), Th2 cytokines (IL-4, IL-13), and chemokines (MIP-1α, RANTES, MIP-3) were lower in female T1D patients compared to female controls, but not in males. IL-22 was lower in female T1D patients compared to female controls, while it was higher in male T1D patients compared to male controls. In contrast, growth factors (EGF, PDGF-AB/BB) were higher in male T1D patients compared to male controls. In T1D progressors (children who developed the disease years after the sample collection, n=16-21), GROa was lower compared to controls in both sexes. Our findings underscore the importance of understanding sex-specific differences in T1D pathogenesis and their implications for developing personalized treatments.

S100A9 exerts insulin-independent antidiabetic and anti-inflammatory effects

Type 1 diabetes mellitus (T1DM) is characterized by insulin deficiency leading to hyperglycemia and several metabolic defects. Insulin therapy remains the cornerstone of T1DM management, yet it increases the risk of life-threatening hypoglycemia and the development of major comorbidities. Here, we report an insulin signaling-independent pathway able to improve glycemic control in T1DM rodents. Co-treatment with recombinant S100 calcium-binding protein A9 (S100A9) enabled increased adherence to glycemic targets with half as much insulin and without causing hypoglycemia. Mechanistically, we demonstrate that the hyperglycemia-suppressing action of S100A9 is due to a Toll-like receptor 4-dependent increase in glucose uptake in specific skeletal muscles (i.e., soleus and diaphragm). In addition, we found that T1DM mice have abnormal systemic inflammation, which is resolved by S100A9 therapy alone (or in combination with low insulin), hence uncovering a potent anti-inflammatory action of S100A9 in T1DM. In summary, our findings reveal the S100A9-TLR4 skeletal muscle axis as a promising therapeutic target for improving T1DM treatment.

Multiplex analysis of inflammatory proteins associated with risk of coronary artery disease in type-1 diabetes patients

BACKGROUND

Chronic uncontrolled hyperglycemia, a precursor to chronic low-grade inflammation, is a leading cause of coronary artery disease (CAD) due to plaque buildup in type-1 diabetes (T1D) patients. We evaluated levels of 22 inflammatory markers in cross-sectional serum samples from 1222 subjects to evaluate their potential as risk factors for CAD in T1D patients.

HYPOTHESIS

Circulating levels of markers of inflammation may be the risk factors for incident CAD.

METHODS

The T1D subjects were divided into two groups: those without CAD (n = 1107) and with CAD (n = 115). Serum levels of proteins were assayed using multiplex immunoassays on a Luminex Platform. Differences between the two groups were made by univariate analysis. Multivariate logistic regression was used to ascertain the potential of proteins as risk factors for CAD. Influence of age, duration of diabetes, sex, hypertension, and dyslipidemia was determined in a stepwise manner. Serum levels of 22 proteins were combined into a composite score using Ridge regression for risk-based stratification.

RESULTS

Mean levels of CRP, IGFBP1, IGFBP2, insulin-like growth factors binding protein-6 (IGFBP6), MMP1, SAA, sTNFRI, and sTNFRII were elevated in CAD patients (n = 115) compared to T1D patients without CAD (nCAD, n = 1107). After adjusting for age, duration of diabetes, sex, hypertension, and dyslipidemia, higher levels of sTNFRI (odds ratio [OR] = 2.18, 1.1 × 10-3 ), sTNFRII (OR = 1.52, 1 × 10-2 ), and IGFBP6 (OR = 3.62, 1.8 × 10-3 ) were significantly associated with CAD. The composite score based on Ridge regression, was able to stratify CAD patients into low, medium, and high-risk groups.

CONCLUSIONS

The results show activation of the TNF pathway in CAD patients. Evaluating these markers in serum can be a potential tool for identifying high-risk T1D patients for intensive anti-inflammatory therapeutic interventions.

Therapeutic Potential of Quercetin in Diabetic Neuropathy and Retinopathy: Exploring Molecular Mechanisms

Diabetes mellitus poses a significant health challenge globally, often leading to debilitating complications, such as neuropathy and retinopathy. Quercetin, a flavonoid prevalent in fruits and vegetables, has demonstrated potential therapeutic effects in these conditions due to its antioxidant, anti-inflammatory, and neuroprotective properties. This review summarizes and provides a comprehensive understanding of the molecular mechanisms underlying the efficacy of quercetin in ameliorating diabetic neuropathy and retinopathy. A thorough search was carried out across scientific databases, such as SciFinder, PubMed, and Google Scholar, to gather pertinent literature regarding the effect of quercetin on diabetic neuropathy and retinopathy till February 2024. Preclinical studies indicate that quercetin mitigates neuropathic pain, sensory deficits, and nerve damage associated with diabetic neuropathy by improving neuronal function, reducing DNA damage, regulating pro-inflammatory cytokines, enhancing antioxidant enzyme levels and endothelial function, as well as restoring nerve injuries. In diabetic retinopathy, quercetin shows the potential to preserve retinal structure and function, inhibiting neovascularization, preventing retinal cell death, reducing pro-inflammatory cytokines, and increasing neurotrophic factor levels. Moreover, through modulating key signaling pathways, such as AMP-activated Protein Kinase (AMPK) activation, Glucose Transporter 4 (GLUT 4) upregulation, and insulin secretion regulation, quercetin demonstrates efficacy in reducing oxidative stress and inflammation, thereby protecting nerve and retinal tissues. Despite promising preclinical findings, challenges, such as limited bioavailability, necessitate further research to optimize quercetin's clinical application in order to establish its optimal dosage, formulation, and long-term efficacy in clinical settings.

Local Inflammatory Mediators Involved in Neuropathic Pain

Polyneuropathy (PNP) is a term to describe diseases of the peripheral nervous system, 50% of which present with neuropathic pain. In some types of PNP, pain is restricted to the skin distally in the leg, suggesting a local regulatory process leading to pain. In this study, we proposed a pro-inflammatory pathway mediated by NF-κB that might be involved in the development of pain in patients with painful PNP. To test this hypothesis, we have collected nerve and skin samples from patients with different etiologies and levels of pain. We performed RT-qPCR to analyze the gene expression of the proposed inflammatory pathway components in sural nerve and in distal and proximal skin samples. In sural nerve, we showed a correlation of TLR4 and TNFα to neuropathic pain, and an upregulation of TNFα in patients with severe pain. Patients with an inflammatory PNP also presented a lower expression of TRPV1 and SIRT1. In distal skin, we found a reduced expression of TLR4 and miR-146-5p, in comparison to proximal skin. Our findings thus support our hypothesis of local inflammatory processes involved in pain in PNP, and further show disturbed anti-inflammatory pathways involving TRPV1 and SIRT1 in inflammatory PNP.

Systemic inflammatory markers in patients with polyneuropathies

Introduction

In patients with peripheral neuropathies (PNP), neuropathic pain is present in 50% of the cases, independent of the etiology. The pathophysiology of pain is poorly understood, and inflammatory processes have been found to be involved in neuro-degeneration, -regeneration and pain. While previous studies have found a local upregulation of inflammatory mediators in patients with PNP, there is a high variability described in the cytokines present systemically in sera and cerebrospinal fluid (CSF). We hypothesized that the development of PNP and neuropathic pain is associated with enhanced systemic inflammation.

Methods

To test our hypothesis, we performed a comprehensive analysis of the protein, lipid and gene expression of different pro- and anti-inflammatory markers in blood and CSF from patients with PNP and controls.

Results

While we found differences between PNP and controls in specific cytokines or lipids, such as CCL2 or oleoylcarnitine, PNP patients and controls did not present major differences in systemic inflammatory markers in general. IL-10 and CCL2 levels were related to measures of axonal damage and neuropathic pain. Lastly, we describe a strong interaction between inflammation and neurodegeneration at the nerve roots in a specific subgroup of PNP patients with blood-CSF barrier dysfunction.

Conclusion

In patients with PNP systemic inflammatory, markers in blood or CSF do not differ from controls in general, but specific cytokines or lipids do. Our findings further highlight the importance of CSF analysis in patients with peripheral neuropathies.

Mechanisms, Mediators, and Moderators of the Effects of Exercise on Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is an adverse effect of neurotoxic antineoplastic agents commonly used to treat cancer. Patients with CIPN experience debilitating signs and symptoms, such as combinations of tingling, numbness, pain, and cramping in the hands and feet that inhibit their daily function. Among the limited prevention and treatment options for CIPN, exercise has emerged as a promising new intervention that has been investigated in approximately two dozen clinical trials to date. As additional studies test and suggest the efficacy of exercise in treating CIPN, it is becoming more critical to develop mechanistic understanding of the effects of exercise in order to tailor it to best treat CIPN symptoms and identify who will benefit most. To address the current lack of clarity around the effect of exercise on CIPN, we reviewed the key potential mechanisms (e.g., neurophysiological and psychosocial factors), mediators (e.g., anti-inflammatory cytokines, self-efficacy, and social support), and moderators (e.g., age, sex, body mass index, physical fitness, exercise dose, exercise adherence, and timing of exercise) that may illuminate the relationship between exercise and CIPN improvement. Our review is based on the studies that tested the use of exercise for patients with CIPN, patients with other types of neuropathies, and healthy adults. The discussion presented herein may be used to (1) guide oncologists in predicting which symptoms are best targeted by specific exercise programs, (2) enable clinicians to tailor exercise prescriptions to patients based on specific characteristics, and (3) inform future research and biomarkers on the relationship between exercise and CIPN.