Markers of non-coeliac wheat sensitivity in patients with myalgic encephalomyelitis/chronic fatigue syndrome

Recent research in myalgic encephalomyelitis/chronic fatigue syndrome: an evidence map

Background

Myalgic encephalomyelitis/chronic fatigue syndrome is a chronic condition, classified by the World Health Organization as a nervous system disease, impacting around 17 million people worldwide. Presentation involves persistent fatigue and postexertional malaise (a worsening of symptoms after minimal exertion) and a wide range of other symptoms. Case definitions have historically varied; postexertional malaise is a core diagnostic criterion in current definitions. In 2022, a James Lind Alliance Priority Setting Partnership established research priorities relating to myalgic encephalomyelitis/chronic fatigue syndrome.

Objective(s)

We created a map of myalgic encephalomyelitis/chronic fatigue syndrome evidence (2018-23), showing the volume and key characteristics of recent research in this field. We considered diagnostic criteria and how current research maps against the James Lind Alliance Priority Setting Partnership research priorities.

Methods

Using a predefined protocol, we conducted a comprehensive search of Cochrane, MEDLINE, EMBASE and Cumulative Index to Nursing and Allied Health Literature. We included all English-language research studies published between January 2018 and May 2023. Two reviewers independently applied inclusion criteria with consensus involving additional reviewers. Studies including people diagnosed with myalgic encephalomyelitis/chronic fatigue syndrome using any criteria (including self-report), of any age and in any setting were eligible. Studies with < 10 myalgic encephalomyelitis/chronic fatigue syndrome participants were excluded. Data extraction, coding of topics (involving stakeholder consultation) and methodological quality assessment of systematic reviews (using A MeaSurement Tool to Assess systematic Reviews 2) was conducted independently by two reviewers, with disagreements resolved by a third reviewer. Studies were presented in an evidence map.

Results

Of the 11,278 identified studies, 742 met the selection criteria, but only 639 provided sufficient data for inclusion in the evidence map. These reported data from approximately 610,000 people with myalgic encephalomyelitis/chronic fatigue syndrome. There were 81 systematic reviews, 72 experimental studies, 423 observational studies and 63 studies with other designs. Most studies (94%) were from high-income countries. Reporting of participant details was poor; 16% did not report gender, 74% did not report ethnicity and 81% did not report the severity of myalgic encephalomyelitis/chronic fatigue syndrome. Forty-four per cent of studies used multiple diagnostic criteria, 16% did not specify criteria, 24% used a single criterion not requiring postexertional malaise and 10% used a single criterion requiring postexertional malaise. Most (89%) systematic reviews had a low methodological quality. Five main topics (37 subtopics) were included in the evidence map. Of the 639 studies; 53% addressed the topic 'what is the cause?'; 38% 'what is the problem?'; 26% 'what can we do about it?'; 15% 'diagnosis and assessment'; and 13% other topics, including 'living with myalgic encephalomyelitis/chronic fatigue syndrome'.

Discussion

Studies have been presented in an interactive evidence map according to topic, study design, diagnostic criteria and age. This evidence map should inform decisions about future myalgic encephalomyelitis/chronic fatigue syndrome research.

Limitations

An evidence map does not summarise what the evidence says. Our evidence map only includes studies published in 2018 or later and in English language. Inconsistent reporting and use of diagnostic criteria limit the interpretation of evidence. We assessed the methodological quality of systematic reviews, but not of primary studies.

Conclusions

We have produced an interactive evidence map, summarising myalgic encephalomyelitis/chronic fatigue syndrome research from 2018 to 2023. This evidence map can inform strategic plans for future research. We found some, often limited, evidence addressing every James Lind Alliance Priority Setting Partnership priority; high-quality systematic reviews should inform future studies.

Funding

This article presents independent research funded by the National Institute for Health and Care Research (NIHR) Evidence Synthesis programme as award number NIHR159926.

An overview of progress in establishing a diagnostic tool for non-celiac gluten sensitivity

INTRODUCTION

Non-Celiac Gluten Sensitivity (NCGS) is a common disorder characterized by symptoms resembling those of irritable bowel syndrome. In recent years there has been progress in the understanding of the pathogenic pathways and data suggest that NCGS has a distinct immunological profile that differs from celiac disease (CeD). This has fostered the search for a specific biomarker of NCGS.

AREAS COVERED

In this review we will firstly update on pioneer NCGS diagnostic tools, particularly the gluten challenge, serum IgG class antigliadin antibodies, and certain histological characteristics seen at the small intestinal biopsy. Then we will examine the most recent research on potential biomarkers of NCGS, specifically focusing on markers of damage to enterocytes, of translocation of bacteria from the gut into the bloodstream, intestinal permeability, and inflammation.

EXPERT OPINION

So far, no specific biomarker of NCGS has been detected. The diagnosis of NCGS still relies on clinical criteria. A gluten challenge may be useful for diagnostic purposes, however a strong nocebo effect limits the efficacy of this procedure. Additional investigation is necessary to identify biomarkers for NCGS, that may be useful to investigate the epidemiology, clinical spectrum, and natural history of this common disorder.

Homeostatic disturbance of thermoregulatory functions in rats with chronic fatigue

Chronic fatigue syndrome (CFS) is characterized by long-lasting fatigue, and a range of symptoms, and is involved in homeostasis disruption. CFS patients frequently complain of low grade fever or chill even under normal body temperature indicating that thermosensory or thermoregulatory functions might be disturbed in CFS. However, little is known about the detailed mechanisms. To elucidate whether and how thermoregulatory function was altered during the development of chronic fatigue, we investigated temporal changes in body temperature with advance of fatigue accumulation in a chronic fatigue rat model using a wireless transponder. Our findings demonstrated that the body temperature was adaptively increased in response to fatigue loading in the early phase, but unable to retain in the late phase. The tail heat dissipation was often observed and the frequency of tail heat dissipation gradually increased initially, then decreased. In the late phase of fatigue loading, the body temperature for the tail heat dissipation phase decreased to a value lower than that for the non-dissipation phase. These results suggest that adaptive changes in thermoregulatory function occurred with fatigue progression, but this system might be disrupted by long-lasting fatigue, which may underlie the mechanism of fatigue chronification.

Phenotypic shift of small intestinal intra-epithelial type 1 innate lymphoid cells in celiac disease is associated with enhanced cytotoxic potential

The small intestinal (SI) epithelium harbors a heterogeneous population of lymphocytes that mediate mucosal damage and repair in celiac disease (CD). The composition and roles of human proximal SI intra-epithelial innate lymphoid cells (ILCs), and their alterations in CD, are not well understood. We report that duodenal intra-epithelial ILCs predominantly consist of natural killer (NK)p44⁺ CD127^- cytotoxic ILC1s and NKp44^- CD127⁺ helper ILC1s, while ILC3s only represent a minor population. In patients with newly diagnosed or active CD (ACD) and refractory CD type 1 (RCD I), the frequency of SI NKp44⁺ ILCs is decreased, with restoration of NKp44⁺ ILC frequency observed in patients adhering to a gluten-free diet who show evidence of mucosal healing. Moreover, the frequency of SI NKp44^- ILCs is increased in ACD and RCD I patients and correlates with the severity of villous atrophy and epithelial damage, as assessed by serum levels of fatty acid binding protein 2 (FABP2). We show that the ILC alterations in CD represent a phenotypic shift of cytotoxic ILC1s rather than an increase in helper ILC1s or transdifferentiation of ILC1s to ILC3s, and activation-induced loss of NKp44 by cytotoxic ILC1s is associated with increased interferon (IFN)-γ expression and release of lytic granules. These findings suggest that intra-epithelial NKp44^- CD127^- cytotoxic ILC1s may contribute to mucosal damage in CD.

Nonceliac Wheat Sensitivity: An Immune-Mediated Condition with Systemic Manifestations

Non-celiac wheat sensitivity (NCWS) is characterized by gastrointestinal and extra-intestinal symptoms following the ingestion of gluten-containing cereals in subjects without celiac disease or wheat allergy. The identity of the molecular triggers in these cereals responsible for the symptoms of NCWS remains to be delineated. Recent research has identified a biological basis for the condition, with the observation of systemic immune activation in response to microbial translocation that appears to be linked to intestinal barrier defects. Ongoing research efforts are aimed at further characterizing the etiology, mechanism, and biomarkers of the condition.

Prospective Biomarkers from Plasma Metabolomics of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Implicate Redox Imbalance in Disease Symptomatology

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a disease of enigmatic origin with no established cure. Its constellation of symptoms has silently ruined the lives of millions of people around the world. A plethora of hypotheses have been vainly investigated over the past few decades, so that the biological basis of this debilitating condition remains a mystery. In this study, we investigate whether there is a disturbance in homeostasis of metabolic networks in the plasma of a female 32-patient cohort compared to 19 healthy female controls. Extensive analysis of the 832-metabolite dataset generated by Metabolon^®, covering eight biological classes, generated important insight into metabolic disruptions that occur in ME/CFS. We report on 14 metabolites with differences in abundance, allowing us to develop a theory of broad redox imbalance in ME/CFS patients, which is consistent with findings of prior work in the ME/CFS field. Moreover, exploration of enrichment analysis using www.MetaboAnalyst.ca provides information concerning similarities between metabolite disruptions in ME/CFS and those that occur in other diseases, while its biomarker analysis unit yielded prospective plasma biomarkers for ME/CFS. This work contributes key elements to the development of ME/CFS diagnostics, a crucial step required for discovering a therapy for any disease of unknown origin.