Microangiopathy-A Potential Contributing Factor to Idiopathic Polyneuropathy: A Mini Review

Polyneuropathy in systemic sclerosis: exploring the causes and biomarkers

Introduction

Systemic sclerosis (SSc) is a rare autoimmune disease with multiple organ involvement; however, the contribution of the nervous system (NS) remains relatively understudied. There are no specific data on the role of the autoimmune response and inflammation in the development of peripheral nerve system (PNS) damage in SSc and markers to assess this damage have yet to be identified.

Objectives

The primary objective of this study was to define the autoimmune mechanisms that lead to neuropathy by identifying antibodies (Abs) that target certain component of the NS or are associated with SSc. The secondary objective was to identify markers of NS damage that correlate with the detection and progression of polyneuropathy (PNP).

Methods

This study included patients diagnosed with SSc who met ACR/EULAR 2013 classification criteria at two leading Latvian hospitals between January 2016 and December 2021. Patients underwent a nerve conduction study (NCS). The SSc-associated Abs, Abs against myelin-associated glycoprotein (MAG) and anti-ganglioside Abs (GM1, GM2, GD1a, GD1b and GQ1b) were analysed. Potential serum PNS biomarkers-neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), fibroblast growth factor 21 (FGF21) and growth/differentiation factor 15 (GDF15)-were measured.

Results

We recruited 103 Caucasian patients diagnosed with SSc. SSc-associated Abs did not differ significantly between patients with and without PNP (p > 0.05). Anti-MAG and anti-ganglioside Abs in patients with PNP did not present a significant increase above the reference range. NfL, GFAP and GDF15 were significantly elevated in the presence of PNP (p < 0.05), with a moderate to high effect size (r = 0.36-0.65). Our regression analysis revealed a strong association between the HAQ-DI score, older age, male gender and the risk of developing PNP.

Conclusion

The development of PNP in patients with SSc is most likely due to ageing, natural progression and the sequelae of the disease. Several serum biomarkers-NfL, GFAP and GDF15-could be used as relevant diagnostic biomarkers for PNP in patients with SSc. Future studies are warranted to validate the diagnostic efficacy of these biomarkers and to unravel the complex interplay of factors leading to PNP in patients with SSc.

Effects of Tang Luo Ning on diabetic peripheral neuropathy in rats revealed by LC-MS metabolomics approach

Diabetic peripheral neuropathy (DPN) is one of the most common complications of diabetes with limited therapies. Tang Luo Ning (TLN), a traditional Chinese medicine compound, has been proved to be effective in the treatment of DPN in clinical and experimental studies. However, the potential metabolic mechanism of TLN for the treatment of DPN is still unclear. Here the therapeutic effect of TLN on DPN was studied, and HPLC-IT-TOF/MS was used to explore the metabolic changes related to DPN and to explore the mechanism of TLN on DPN induced by high glucose. Furthermore, metabolic pathway analysis was used to explore the metabolic changes induced by DPN and TLN. As a result, TLN could improve the peripheral nerve function of DPN rats, and TLN could reduce the demyelination of the sciatic nerve in DPN rats. Metabolomics analysis showed that 14 potential biomarkers (citrate, creatine, fumarate, glyceric acid, glycine, succinate, etc.) of both DPN and TLN treatment were identified. Pathway analysis showed that the changes in these metabolites were mainly related to the citrate cycle (TCA cycle), glycine, serine and threonine metabolism, and glyoxylate and dicarboxylate metabolism.

An association between fibrinogen gene polymorphisms and diabetic peripheral neuropathy in young patients with type 1 diabetes

In complex etiopathogenesis of diabetic peripheral neuropathy (DPN), hemostatic dysfunction and subclinical inflammation play a possible role. Fibrinogen is involved in both the hemostatic and inflammatory pathways, so we hypothesize that fibrinogen gene polymorphisms might be associated with DPN. A total of 127 young patients with type 1 diabetes (T1D) (average age, 18.5 ± 4.65 years; average diabetes duration, 14.5 ± 2.26 years) and 90 healthy controls were enrolled into the study. Basic biochemical and coagulation parameters were measured and gene polymorphisms of fibrinogen alpha (rs6050) and beta (rs1800790) were established. DPN was diagnosed in 38 diabetic patients by neurological examination. AA genotype and A allele of rs1800790 polymorphism of fibrinogen beta were associated with increased risk of DPN (odds ratio [OR] 4.537, 95% confidence interval [95CI] 1.14-19.94, p = 0.019 and OR 1.958, 95CI 1.038-3.675, p = 0.029, respectively). No association was found between DPN and rs6050 gene polymorphisms. Plasma fibrinogen concentration significantly correlated with HbA1c (Spearman's correlation coefficient [r] = 0.54) and HDL cholesterol (r = - 0.67). A allele and AA genotype of rs1800790 seem to be associated with DPN in young patients with T1D. Further studies are appropriate to elucidate the role of fibrinogen gene polymorphisms in the complex etiology of DPN.

Chronic axonal idiopathic polyneuropathy: is it really benign

PURPOSE OF REVIEW

Chronic idiopathic axonal polyneuropathy (CIAP), a common neurological condition, is considered to be a benign neurological condition with a small risk of disability. However, many studies have shown a reduced quality of life and a nonnegligible affection of daily activities in patients with CIAP. Here we summarize recent data about CIAP.

RECENT FINDINGS

We discuss some of the latest articles regarding risk factors, comorbidities, and possible pathogenic factors regarding CIAP. Patients with chronic polyneuropathy have impaired walking capacity, disturbed balance, and an increased risk of falls. Idiopathic polyneuropathy has a negative impact on activities of daily living. Patients with CIAP may develop plantar ulcers and neuropathic arthropathy. Small fiber involvement may occur, and two recent studies indicate that neuropathic pain is present in about two thirds of the CIAP group. Furthermore, patients with CIAP with neuropathic pain have increased fatigue and poorer emotional well being.

SUMMARY

Despite the relatively mild motor impairment seen in most patients with CIAP, the condition causes limitations in life with decreased mobility, pain, and affection of basal daily activities. Because the pathogenesis of CIAP in unclear, there is no disease modifying treatment. Further studies regarding pathogenesis, and randomized controlled clinical trials regarding possible treatment options are needed.

Cardiovascular health and chronic axonal polyneuropathy: A population-based study

Background and purpose

Chronic axonal polyneuropathy is a common, usually multifactorial, disease for which there is no treatment yet available. We investigated the association between cardiovascular health, defined by the health score of the American Heart Association, and chronic axonal polyneuropathy.

Methods

Between June 2013 and January 2017, we investigated participants of the Rotterdam Study, a population‐based cohort study. Participants were screened for polyneuropathy and categorized as having no, possible, probable or definite polyneuropathy. The cardiovascular health score (range 0–14; higher score reflecting better health) consisted of four health behaviours (diet, physical activity, smoking and body mass index) and three health factors (blood pressure, serum cholesterol and fasting glucose level).

Results

We included 1919 participants, of whom 120 (6.3%) had definite polyneuropathy. The median (interquartile range [IQR]) age was 69.0 (58.6–73.7) years and 53.4% were women. A higher cardiovascular health score was associated with a lower prevalence of definite polyneuropathy (per point increase: odds ratio [OR] 0.90, 95% confidence interval [CI] 0.84–0.96). Optimal cardiovascular health (score≥10) was strongly associated with a lower prevalence of definite polyneuropathy (OR 0.55, 95% CI 0.32–0.90). An increase in health factors and health behaviour scores separately was associated with a lower prevalence of polyneuropathy (per point increase: OR 0.82, 95% CI 0.71–0.95 and OR 0.86, 95% CI 0.78–0.96, respectively). The association between a lower cardiovascular health score and lower sural nerve amplitude was not significant after correction for covariates (difference 0.07µV, 95% CI −0.02–0.17).

Conclusions

Better cardiovascular health, consisting of both modifiable health behaviours and health factors, is associated with a lower prevalence of chronic axonal polyneuropathy.

Treatable, motor-sensory, axonal neuropathies with C5b-9 complement on endoneurial microvessels

INTRODUCTION

Identification and treatment of immune-mediated polyneuropathies may lead to improved strength and function. We studied the clinical and laboratory features, and treatment response, in patients with motor-sensory axonal polyneuropathies who were found to have C5b-9 complement staining on endoneurial microvessels.

METHODS

Retrospective review of 16 consecutive adults with motor-sensory axonal polyneuropathies who were then found to have C5b-9 staining of endoneurial microvessels on nerve biopsy, and subsequently treated with intravenous corticosteroids (1 g methylprednisolone for 5 consecutive days, and then weekly). Strength measurements were done using quantitative handheld dynamometry. Nerve biopsy analysis included frozen and fixed tissue.

RESULTS

Patients (mean onset age, 59 ± 4 years; range, 34-83 years; 12 of 16 were males; 9 of 16 had diabetes) had progressive (median duration, 2 years), asymmetric, distal weakness, in the lower extremities (16 of 16) and/or upper extremities (7 of 16), and panmodal sensory loss. Electrodiagnostic studies showed axon loss. Nerve pathology showed abnormal C5b-9 staining on endoneurial microvessels. Axon loss was present in all nerves, often varied among fascicles. Inflammation was uncommon. Distal strength usually improved (mean improvement of 34 ± 6% of normal strength; P = .0003) with corticosteroid treatment.

DISCUSSION

Motor-sensory axonal polyneuropathies having noninflammatory, humoral immune pathology with C5b-9 staining of endoneurial microvessels (HIEM) frequently manifest progressive asymmetric, distal, lower extremity with or without upper extremity weakness that improves rapidly during corticosteroid treatment. HIEM may represent a new class of noninflammatory-vasculopathic, treatable axonal motor-sensory neuropathies.

Diet quality and chronic axonal polyneuropathy: a population-based study

OBJECTIVE

To investigate the association between diet quality and chronic axonal polyneuropathy.

METHODS

Between June 2013 and January 2017, among 1650 participants of the Rotterdam Study (median age 69.1 years, 54.2% women), diet quality was quantified based on food frequency questionnaires as a sum score of adherence (yes/no) to 14 components of the Dutch dietary guidelines. Presence of polyneuropathy was determined based on a questionnaire, neurological examination of the legs, and nerve conduction studies. We used logistic regression to associate diet quality with the presence of chronic axonal polyneuropathy and linear regression to associate with sural sensory nerve action potential (SNAP) amplitude in participants without polyneuropathy. Results were adjusted for age, sex, time between measurements, body mass index, blood pressure, diabetes mellitus, smoking, kidney function, and education.

RESULTS

Overall diet quality was not associated with chronic axonal polyneuropathy (odds ratio [OR] = 0.99, 95% confidence interval [CI] 0.88; 1.12, P = 0.842), nor with sural SNAP amplitude in participants without polyneuropathy (difference = 0.01, 95% CI -0.14; 0.15, P = 0.993). Although not surviving multiple testing, a nominally significant association was found between salt intake ≤6 g/day and presence of chronic axonal polyneuropathy (OR = 0.55, 95% CI 0.35; 0.86, P = 0.008).

INTERPRETATION

We did not find an association between diet quality and chronic axonal polyneuropathy.