Tag: review

Role of mitochondria, oxidative stress and the response to antioxidants in myalgic encephalomyelitis/chronic fatigue syndrome: a possible approach to SARS-CoV-2 ‘long-haulers’?

Abstract:

A significant number of SARS-CoV-2 (COVID-19) pandemic patients have developed chronic symptoms lasting weeks or months which are very similar to those described for myalgic encephalomyelitis/chronic fatigue syndrome. This paper reviews the current literature and understanding of the role that mitochondria, oxidative stress and antioxidants may play in the understanding of the pathophysiology and treatment of chronic fatigue. It describes what is known about the dysfunctional pathways which can develop in mitochondria and their relationship to chronic fatigue. It also reviews what is known about oxidative stress and how this can be related to the pathophysiology of fatigue, as well as examining the potential for specific therapy directed at mitochondria for the treatment of chronic fatigue in the form of antioxidants. This review identifies areas which require urgent, further research in order to fully elucidate the clinical and therapeutic potential of these approaches.

Source: Wood E, Hall KH, Tate W. Role of mitochondria, oxidative stress and the response to antioxidants in myalgic encephalomyelitis/chronic fatigue syndrome: a possible approach to SARS-CoV-2 ‘long-haulers’? Chronic Dis Transl Med. 2020 Nov 21. doi: 10.1016/j.cdtm.2020.11.002. Epub ahead of print. PMID: 33251031; PMCID: PMC7680046.  https://pubmed.ncbi.nlm.nih.gov/33251031/

ME (Ramsay) and ME-International Case Criteria (ME-ICC): two distinct clinical entities

Excerpt:

The review of the differences and similarities in the different case definitions for myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS) by Lim and Son [1] deserves appreciation. Based on their analysis the authors acknowledge the “distinct view of ME and CFS” [2] and recognize four categories of case definitions: ME, ME/CFS, CFS [3] and Systemic Exertion Intolerance Disorder (SEID) [4].

Indeed these labels reflect very different case definitions [5]. According to Lim and Son [1] the first category comprises two ‘ME’ case definitions: ME (Ramsay) [6] and ME according to the International Case Criteria (ME-ICC) [7]. However as can be deduced from Table 2 [1], ME [6] and ME-ICC [7] are two distinct clinical entities [8].

Source: Twisk FNM. ME (Ramsay) and ME-International Case Criteria (ME-ICC): two distinct clinical entities. J Transl Med. 2020 Nov 25;18(1):447. doi: 10.1186/s12967-020-02617-0. PMID: 33239008. https://translational-medicine.biomedcentral.com/articles/10.1186/s12967-020-02617-0 (Full text)

The Interplay between Oxidative Stress, Exercise, and Pain in Health and Disease: Potential Role of Autonomic Regulation and Epigenetic Mechanisms

Abstract:

Oxidative stress can be induced by various stimuli and altered in certain conditions, including exercise and pain. Although many studies have investigated oxidative stress in relation to either exercise or pain, the literature presents conflicting results. Therefore, this review critically discusses existing literature about this topic, aiming to provide a clear overview of known interactions between oxidative stress, exercise, and pain in healthy people as well as in people with chronic pain, and to highlight possible confounding factors to keep in mind when reflecting on these interactions. In addition, autonomic regulation and epigenetic mechanisms are proposed as potential mechanisms of action underlying the interplay between oxidative stress, exercise, and pain.

This review highlights that the relation between oxidative stress, exercise, and pain is poorly understood and not straightforward, as it is dependent on the characteristics of exercise, but also on which population is investigated. To be able to compare studies on this topic, strict guidelines should be developed to limit the effect of several confounding factors. This way, the true interplay between oxidative stress, exercise, and pain, and the underlying mechanisms of action can be revealed and validated via independent studies.

Source: Hendrix J, Nijs J, Ickmans K, Godderis L, Ghosh M, Polli A. The Interplay between Oxidative Stress, Exercise, and Pain in Health and Disease: Potential Role of Autonomic Regulation and Epigenetic Mechanisms. Antioxidants (Basel). 2020 Nov 23;9(11):1166. doi: 10.3390/antiox9111166. PMID: 33238564; PMCID: PMC7700330. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7700330/  (Full text)

Using structural and functional MRI as a neuroimaging technique to investigate chronic fatigue syndrome/myalgic encephalopathy: a systematic review

Abstract:

Objective: This systematic review aims to synthesise and evaluate structural MRI (sMRI) and functional MRI (fMRI) studies in chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME).

Methods: We systematically searched Medline and Ovid and included articles from 1991 (date of Oxford diagnostic criteria for CFS/ME) to first April 2019. Studies were selected by predefined inclusion and exclusion criteria. Two reviewers independently reviewed the titles and abstracts to determine articles for inclusion, full text and quality assessment for risk of bias.

Results: sMRI studies report differences in CFS/ME brain anatomy in grey and white matter volume, ventricular enlargement and hyperintensities. Three studies report no neuroanatomical differences between CFS/ME and healthy controls. Task-based fMRI investigated working memory, attention, reward and motivation, sensory information processing and emotional conflict. The most consistent finding was CFS/ME exhibited increased activations and recruited additional brain regions. Tasks with increasing load or complexity produced decreased activation in task-specific brain regions.

Conclusions: There were insufficient data to define a unique neural profile or biomarker of CFS/ME. This may be due to inconsistencies in finding neuroanatomical differences in CFS/ME and the variety of different tasks employed by fMRI studies. But there are also limitations with neuroimaging. All brain region specific volumetric differences in CFS/ME were derived from voxel-based statistics that are biased towards group differences that are highly localised in space. fMRI studies demonstrated both increases and decreases in activation patterns in CFS/ME, this may be related to task demand. However, fMRI signal cannot differentiate between neural excitation and inhibition or function-specific neural processing. Many studies have small sample sizes and did not control for the heterogeneity of this clinical population. We suggest that with robust study design, subgrouping and larger sample sizes, future neuroimaging studies could potentially lead to a breakthrough in our understanding of the disease.

Source: Almutairi B, Langley C, Crawley E, Thai NJ. Using structural and functional MRI as a neuroimaging technique to investigate chronic fatigue syndrome/myalgic encephalopathy: a systematic review. BMJ Open. 2020;10(8):e031672. Published 2020 Aug 30. doi:10.1136/bmjopen-2019-031672 https://bmjopen.bmj.com/content/10/8/e031672.long (Full text)

Neuroimaging characteristics of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): a systematic review

Abstract:

Background: Since the 1990s, neuroimaging has been utilised to study Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), a debilitating illness with unknown aetiology. While brain abnormalities in ME/CFS have been identified, relatively little is known regarding which specific abnormalities are consistently observed across research groups and to what extent the observed abnormalities are reproducible.

Method: To identify consistent and inconsistent neuroimaging observations in ME/CFS, this retrospective and systematic review searched for studies in which neuroimaging was used to investigate brain abnormalities in ME/CFS in Ovid MEDLINE, PubMed (NCBI), and Scopus from January 1988 to July 2018. A qualitative synthesis of observations was performed to identify brain abnormalities that were consistently and inconsistently reported.

Results: 63 full-text articles were included in the synthesis of results from 291 identified papers. Additional brain area recruitment for cognitive tasks and abnormalities in the brain stem are frequent observations in 11 and 9 studies using different modalities from different research teams respectively. Also, sluggish blood oxygenation level-dependent (BOLD) signal responses to tasks, reduced serotonin transporters, and regional hypometabolism are consistent observations by more than two research teams. Single observations include abnormal brain tissue properties, regional metabolic abnormalities, and association of brain measures with ME/CFS symptoms. Reduced resting cerebral blood flow and volumetric brain changes are inconsistent observations across different studies.

Conclusion: Neuroimaging studies of ME/CFS have frequently observed additional brain area recruitment during cognitive tasks and abnormalities in the brain stem. The frequent observation of additional brain area recruitment and consistent observation of sluggish fMRI signal response suggest abnormal neurovascular coupling in ME/CFS.

Source: Shan ZY, Barnden LR, Kwiatek RA, Bhuta S, Hermens DF, Lagopoulos J. Neuroimaging characteristics of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): a systematic review. J Transl Med. 2020;18(1):335. Published 2020 Sep 1. doi:10.1186/s12967-020-02506-6  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7466519/ (Full text)

Environmental, Neuro-immune, and Neuro-oxidative Stress Interactions in Chronic Fatigue Syndrome

Abstract:

Chronic fatigue syndrome/myalgic encephalomyelitis (CFS) is a complex, multisystem disease that is characterized by long-term fatigue, exhaustion, disabilities, pain, neurocognitive impairments, gastrointestinal symptoms, and post-exertional malaise, as well as lowered occupational, educational, and social functions. The clinical and biomarker diagnosis of this disorder is hampered by the lack of validated diagnostic criteria and laboratory tests with adequate figures of merit, although there are now many disease biomarkers indicating the pathophysiology of CFS.

Here, we review multiple factors, such as immunological and environmental factors, which are associated with CFS and evaluate current concepts on the involvement of immune and environmental factors in the pathophysiology of CFS. The most frequently reported immune dysregulations in CFS are modifications in immunoglobulin contents, changes in B and T cell phenotypes and cytokine profiles, and decreased cytotoxicity of natural killer cells. Some of these immune aberrations display a moderate diagnostic performance to externally validate the clinical diagnosis of CFS, including the expression of activation markers and protein kinase R (PKR) activity. Associated with the immune aberrations are activated nitro-oxidative pathways, which may explain the key symptoms of CFS.

This review shows that viral and bacterial infections, as well as nutritional deficiencies, may further aggravate the immune-oxidative pathophysiology of CFS. Targeted treatments with antioxidants and lipid replacement treatments may have some clinical efficacy in CFS. We conclude that complex interactions between immune and nitro-oxidative pathways, infectious agents, environmental factors, and nutritional deficiencies play a role in the pathophysiology of CFS.

Source: Bjørklund G, Dadar M, Pivina L, Doşa MD, Semenova Y, Maes M. Environmental, Neuro-immune, and Neuro-oxidative Stress Interactions in Chronic Fatigue Syndrome [published online ahead of print, 2020 Aug 6]. Mol Neurobiol. 2020;10.1007/s12035-020-01939-w. doi:10.1007/s12035-020-01939-w  https://pubmed.ncbi.nlm.nih.gov/32761353/

Genetic Risk Factors of ME/CFS: A Critical Review

Abstract:

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex multisystem illness that lacks effective therapy and a biomedical understanding of its causes. Despite a prevalence of approximately 0.2-0.4% and its high public health burden, and evidence that it has a heritable component, ME/CFS has not yet benefited from the advances in technology and analytical tools that have improved our understanding of many other complex diseases.

Here we critically review existing evidence that genetic factors alter ME/CFS risk before concluding that most ME/CFS candidate gene associations are not replicated by the larger CFS cohort within UK Biobank. Multiple genome-wide association studies of this cohort also have not yielded consistently significant associations. Ahead of upcoming larger genome-wide association studies we discuss how these could generate new lines of enquiry into the DNA variants, genes and cell-types that are causally involved in ME/CFS disease.

Source: Dibble JJ, McGrath SJ, Ponting CP. Genetic Risk Factors of ME/CFS: A Critical Review [published online ahead of print, 2020 Aug 3]. Hum Mol Genet. 2020;ddaa169. doi:10.1093/hmg/ddaa169 https://pubmed.ncbi.nlm.nih.gov/32744306/

Review of case definitions for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)

Abstract:

Background: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating disease with unknown causes. From the perspectives on the etiology and pathophysiology, ME/CFS has been labeled differently, which influenced changes in case definitions and terminologies. This review sought to feature aspects of the history, developments, and differential symptoms in the case definitions.

Methods: A search was conducted through PubMed published to February 2020 using the following search keywords: case definition AND chronic fatigue syndrome [MeSH Terms]. All reference lists of the included studies were checked. Of the included studies, the number of citations and the visibility in the literatures of the definitions were considered for comparisons of the criteria.

Results: Since the first ‘ME’ case definition was developed in 1986, 25 case definitions/diagnostic criteria were created based on three conceptual factors (etiology, pathophysiology, and exclusionary disorders). These factors can be categorized into four categories (ME, ME/CFS, CFS, and SEID) and broadly characterized according to primary disorder (ME-viral, CFS-unknown, ME/CFS-inflammatory, SEID-multisystemic), compulsory symptoms (ME and ME/CFS-neuroinflammatory, CFS and SEID-fatigue and/or malaise), and required conditions (ME-infective agent, ME/CFS, CFS, SEID-symptoms associated with fatigue, e.g., duration of illness). ME and ME/CFS widely cover all symptom categories, while CFS mainly covers neurologic and neurocognitive symptoms. Fatigue, cognitive impairment, PEM, sleep disorder, and orthostatic intolerance were the overlapping symptoms of the 4 categories, which were included as SEID criteria.

Conclusions: This study comprehensively described the journey of the development of case definitions and compared the symptom criteria. This review provides broader insights and explanations to understand the complexity of ME/CFS for clinicians and researchers.

Source: Lim EJ, Son CG. Review of case definitions for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). J Transl Med. 2020;18(1):289. Published 2020 Jul 29. doi:10.1186/s12967-020-02455-0 https://translational-medicine.biomedcentral.com/articles/10.1186/s12967-020-02455-0 (Full text)

A systematic review of mitochondrial abnormalities in myalgic encephalomyelitis/chronic fatigue syndrome/systemic exertion intolerance disease

Abstract:

Background: Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) or Systemic Exertion Intolerance Disease (SEID) present with a constellation of symptoms including debilitating fatigue that is unrelieved by rest. The pathomechanisms underlying this illness are not fully understood and the search for a biomarker continues, mitochondrial aberrations have been suggested as a possible candidate. The aim of this systematic review is to collate and appraise current literature on mitochondrial changes in ME/CFS/SEID patients compared to healthy controls.

Methods: Embase, PubMed, Scopus and Medline (EBSCO host) were systematically searched for articles assessing mitochondrial changes in ME/CFS/SEID patients compared to healthy controls published between January 1995 and February 2020. The list of articles was further refined using specific inclusion and exclusion criteria. Quality and bias were measured using the Joanna Briggs Institute Critical Appraisal Checklist for Case Control Studies.

Results: Nineteen studies were included in this review. The included studies investigated mitochondrial structural and functional differences in ME/CFS/SEID patients compared with healthy controls. Outcomes addressed by the papers include changes in mitochondrial structure, deoxyribonucleic acid/ribonucleic acid, respiratory function, metabolites, and coenzymes.

Conclusion: Based on the included articles in the review it is difficult to establish the role of mitochondria in the pathomechanisms of ME/CFS/SEID due to inconsistencies across the studies. Future well-designed studies using the same ME/CFS/SEID diagnostic criteria and analysis methods are required to determine possible mitochondrial involvement in the pathomechanisms of ME/CFS/SEID.

Source: Holden S, Maksoud R, Eaton-Fitch N, Cabanas H, Staines D, Marshall-Gradisnik S. A systematic review of mitochondrial abnormalities in myalgic encephalomyelitis/chronic fatigue syndrome/systemic exertion intolerance disease. J Transl Med. 2020;18(1):290. Published 2020 Jul 29. doi:10.1186/s12967-020-02452-3 https://translational-medicine.biomedcentral.com/articles/10.1186/s12967-020-02452-3 (Full text)

Review of the Quality Control Checks Performed by Current Genome-Wide and Targeted-Genome Association Studies on Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Introduction:

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a debilitating disease characterized by persistent fatigue and post-exertion malaise, accompanied by other symptoms (1, 2). The direct cause of the disease remains elusive, but it may include genetic factors alongside environmental triggers, such as strong microbial infections and other stressors (3, 4).

With the aim to identify putative genetic factors that could explain the pathophysiological mechanisms of ME/CFS, four genome-wide association studies (GWAS) and two targeted-genome association studies (TGAS) were conducted in the past decade (5–10). In the four GWAS, thousands of genetic markers located across the whole genome were evaluated for their statistical association with ME/CFS (5–8). The two TGAS had the same statistical objective of the four GWAS, but alternatively investigated the association of the disease with numerous genetic markers located in candidate genes related to inflammation and immunity (9) and in genes encoding diverse adrenergic receptors (10).

The findings from all these different studies suggested conflicting evidence of genetic association with ME/CFS: from absence of association (7), through mild association (10) up to moderate associations of a relatively small number of genetic markers (5, 6, 9). The most optimistic GWAS suggested more than 5,500 candidate gene-disease associations (8). This inconsistency in the reported findings prompted us to review the respective data. With this purpose, the present opinion paper first revisits the recommended quality control (QC) checks for GWAS and TGAS, and then summarizes which ones were performed by those studies on ME/CFS.

Source: Grabowska AD, Lacerda EM, Nacul L, Sepúlveda N. Review of the Quality Control Checks Performed by Current Genome-Wide and Targeted-Genome Association Studies on Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Front Pediatr. 2020;8:293. Published 2020 Jun 12. doi:10.3389/fped.2020.00293 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7304330/ (Full text)