Category: Pathophysiology

Metabolic adaptation and fragility in healthy 3-D in vitro skeletal muscle tissues exposed to Chronic Fatigue Syndrome and Long COVID-19 sera

Abstract:

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Long COVID-19 (LC-19) are complex conditions with no diagnostic markers or consensus on disease progression. Despite extensive research, no in vitro model exists to study skeletal muscle wasting, peripheral fatigue, or potential therapies. We developed 3D in vitro skeletal muscle tissues to map muscle adaptations to patient sera over time.

Short exposures (48 hours) to patient sera led to a significant reduction in muscle contractile strength. Transcriptomic analysis revealed the upregulation of glycolytic enzymes, disturbances in calcium homeostasis, hypertrophy, and mitochondrial hyperfusion. Structural analyses confirmed myotube hypertrophy and elevated mitochondrial oxygen consumption in ME/CFS. While muscles initially adapted by increasing glycolysis, prolonged exposure (96-144 hours) caused muscle fragility and fatigue, with mitochondria fragmenting into a toroidal conformation.

We propose that skeletal muscle tissue in ME/CFS and Long COVID-19 progresses through a hypermetabolic state, leading to severe muscular and mitochondrial deterioration. This is the first study to suggest such transient metabolic adaptation

Source: Mughal S, Andújar-Sánchez F, Sabater-Arcis M, Garrabou G, Fernández-Solà J, Alegre-Martin J, Sanmartin Sentañes R, Castro-Marrero J, Esteve-Codina A, Casals E, Fernández-Costa JM, Ramón-Azcón J. Metabolic adaptation and fragility in healthy 3-D in vitro skeletal muscle tissues exposed to Chronic Fatigue Syndrome and Long COVID-19 sera. Biofabrication. 2025 Jul 31. doi: 10.1088/1758-5090/adf66c. Epub ahead of print. PMID: 40744071. https://iopscience.iop.org/article/10.1088/1758-5090/adf66c (Full text available as PDF file)

Comparing DNA Methylation Landscapes in Peripheral Blood from Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Long COVID Patients

Abstract:

Post-viral conditions, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Long COVID (LC), share > 95% of their symptoms, but the connection between disturbances in their underlying molecular biology is unclear. This study investigates DNA methylation patterns in peripheral blood mononuclear cells (PBMC) from patients with ME/CFS, LC, and healthy controls (HC).

Reduced Representation Bisulphite Sequencing (RRBS) was applied to the DNA of age- and sex-matched cohorts: ME/CFS (n = 5), LC (n = 5), and HC (n = 5). The global DNA methylomes of the three cohorts were similar and spread equally across all chromosomes, except the sex chromosomes, but there were distinct minor changes in the exons of the disease cohorts towards more hypermethylation.

A principal component analysis (PCA) analysing significant methylation changes (p < 0.05) separated the ME/CFS, LC, and HC cohorts into three distinct clusters. Analysis with a limit of >10% methylation difference and at p < 0.05 identified 214 Differentially Methylated Fragments (DMF) in ME/CFS, and 429 in LC compared to HC. Of these, 118 DMFs were common to both cohorts. Those in promoters and exons were mainly hypermethylated, with a minority hypomethylated. There were rarer examples with either no change in methylation in ME/CFS but a change in LC, or a methylation change in ME/CFS but in the opposite direction in LC. The differential methylation in a number of fragments was significantly greater in the LC cohort than in the ME/CFS cohort.

Our data reveal a generally shared epigenetic makeup between ME/CFS and LC but with specific, distinct changes. Differences between the two cohorts likely reflect the stage of the disease from onset (LC 1 year vs. ME/CFS 12 years), but specific changes imposed by the SARS-CoV-2 virus in the case of the LC patients cannot be discounted. These findings provide a foundation for further studies with larger cohorts at the same disease stage and for functional analyses to establish clinical relevance.

Source: Peppercorn K, Sharma S, Edgar CD, Stockwell PA, Rodger EJ, Chatterjee A, Tate WP. Comparing DNA Methylation Landscapes in Peripheral Blood from Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Long COVID Patients. Int J Mol Sci. 2025 Jul 10;26(14):6631. doi: 10.3390/ijms26146631. PMID: 40724879. https://www.mdpi.com/1422-0067/26/14/6631 (Full text)

Steroid dynamics in myalgic encephalomyelitis / chronic fatigue syndrome: a case-control study using ultra performance supercritical fluid chromatography tandem mass spectrometry

Abstract:

Background: Myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) is a multisystem disorder characterised by unrelenting fatigue, post-exertional malaise, and dysfunction across immune, nervous, metabolism, and endocrine systems. Given the broad role of steroid hormones in regulating these systems, this study investigated differences in the steroid metabolome and network dynamics between ME/CFS patients and matched controls.

Methods: Blood plasma steroid levels were quantified using Ultra-Performance Supercritical Fluid Chromatography- Tandem Mass Spectrometry (UPSFC-MS/MS) in ME/CFS patients (n = 24) and age and gender matched controls (n = 24). Group comparisons of absolute steroid concentrations were performed using Mann-Whitney U tests. Partial Spearman correlation networks were evaluated to examine direct associations between steroids within each group, and centrality metrics were used to evaluate structural differences. Steroid-steroid ratios were analysed to reflect biochemical relationships. Multivariate analysis with Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) was also conducted.

Results: No significant group differences in absolute steroid concentrations were observed following FDR correction. However, network analysis revealed a marked reduction in direct steroid-steroid relationships in ME/CFS, with controls exhibiting 52 significant partial correlations, while the ME/CFS group retained only one (cortisol – corticosterone). Centrality analysis further revealed a shift in network structure, with cortisone emerging as highly central in ME/CFS (degree = 7, betweenness = 16.7), despite being peripheral in controls, and progesterone showing reduced integration in ME/CFS (degree = 3 vs. 12, eigenvector = 0.40 vs. 0.93). Steroid-steroid ratio analysis revealed a higher cortisol-to-pregnanolone ratio and a lower pregnanolone-to-progesterone ratio in ME/CFS, although these findings did not remain significant after FDR correction. OPLS-DA indicated a modest relationship between steroid levels and group classification (R²Y = 22.8%), but negative Q² values suggested poor predictive power.

Conclusions: Despite no significant differences in absolute steroid levels, network analysis revealed profound disruptions in steroid-steroid relationships in ME/CFS compared to controls, suggesting disrupted steroid homeostasis. Collectively the results suggest dysregulation of HPA axis function and progestogen pathways, as demonstrated by altered partial correlations, centrality profiles, and steroid ratios. These findings illustrate the importance of hormone network dynamics in ME/CFS pathophysiology and underscores the need for more research into steroid metabolism.

Source: Thomas, N., Ubhayasekera, S.J.K.A., Armstrong, C.W. et al. Steroid dynamics in myalgic encephalomyelitis / chronic fatigue syndrome: a case-control study using ultra performance supercritical fluid chromatography tandem mass spectrometry. J Transl Med 23, 829 (2025). https://doi.org/10.1186/s12967-025-06841-4 https://link.springer.com/article/10.1186/s12967-025-06841-4 (Full text)

Intelligent Eye Tracker Integrated with Cylindrical Capacitive Sensors for Chronic Fatigue Assessment

Abstract:

Fatigue negatively impacts health, safety, and productivity, yet current monitoring methods are often subjective, labor-intensive, and inaccurate. To address these challenges, this study presents a capacitive sensor-based eye tracker leveraging cylindrical carbon nanotube-paper composite (CCPC) sensors for chronic fatigue (CF) assessment.

Fabricated by novel wet-fracture and paper-rolling methods, CCPC sensors demonstrate superior proximity sensitivity with a small form factor. These one-dimensional sensors are seamlessly integrated into an eyeglass frame for noncontact monitoring of blink rates and eye closures. A 15-minute testing protocol, combining cognitive tasks and noise exposure, is designed to induce acute fatigue and identify CF. By analyzing changes in the digital markers against established fatigue indicators, CF is assessed with the aid of machine learning models for the evaluation of accuracy, sensitivity, and specificity.

This real-time, wearable monitoring platform provides an objective, effortless, and noncontact approach to fatigue assessment. With further testing and optimization, it holds the potential for user-friendly evaluation of acute fatigue or fatigue-associated diseases, such as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).

Source: Li T, Park SH, Lee C, Kim S, Kwon Y, Kim H, Chung JH. Intelligent Eye Tracker Integrated with Cylindrical Capacitive Sensors for Chronic Fatigue Assessment. Adv Sens Res. 2025 Jul;4(7):e00027. doi: 10.1002/adsr.202500027. Epub 2025 May 22. PMID: 40662140; PMCID: PMC12259227. https://pmc.ncbi.nlm.nih.gov/articles/PMC12259227/ (Full text)

Brain and muscle chemistry in myalgic encephalitis/chronic fatigue syndrome (ME/CFS) and long COVID: a 7T magnetic resonance spectroscopy study

Abstract:

Myalgic encephalitis/chronic fatigue syndrome (ME/CFS) is a common debilitating medical condition, whose main symptoms – fatigue, post-exertional malaise and cognitive dysfunction – are also present in many cases of long COVID. Magnetic resonance spectroscopy (MRS) allows the insight into their pathophysiology through exploration of a range of biochemicals putatively relevant to aetiological processes, in particular mitochondrial dysfunction and energy metabolism.

24 patients with ME/CFS, 25 patients with long COVID and 24 healthy controls (HC) underwent brain (pregenual and dorsal anterior cingulate cortex, respectively, pgACC and dACC) and calf muscle MRS scanning at 7 Tesla, followed by a computerised cognitive assessment. Compared to HC, ME/CFS patients had elevated levels of lactate in both pgACC and dACC, while long COVID patients had lowered levels of total choline in dACC. By contrast, skeletal muscle metabolites at rest did not significantly differ between the groups.

The changes in lactate in ME/CFS are consistent with the presence of energetic stress and mitochondrial dysfunction. A reduction in total choline in long COVID is of interest in the context of the recently reported association between blood clots and ‘brain fog’, and earlier animal studies showing that choline might prevent intravascular coagulation.

Importantly, differences in findings between ME/CFS and long COVID suggest that the underlying neurobiological mechanisms, while leading to similar clinical presentations, may differ. An important implication is that patients with ME/CFS and those with fatigue in the course of long COVID should not be studied as a single group, at least until the mechanisms are better understood.

Source: Godlewska BR, Sylvester AL, Emir UE, Sharpley AL, Clarke WT, Williams SR, Gonçalves AJ, Raman B, Valkovič L, Cowen PJ. Brain and muscle chemistry in myalgic encephalitis/chronic fatigue syndrome (ME/CFS) and long COVID: a 7T magnetic resonance spectroscopy study. Mol Psychiatry. 2025 Jul 12. doi: 10.1038/s41380-025-03108-8. Epub ahead of print. PMID: 40652046. https://www.nature.com/articles/s41380-025-03108-8 (Full text)

Unwilling or unable? Interpreting effort task performance in myalgic encephalomyelitis/chronic fatigue syndrome

Introduction:

In a recent, high-profile study of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome (PI-ME/CFS), Walitt et al. (2024) assessed the performance of patients and healthy volunteers on the Effort-Expenditure for Rewards Task (EEfRT), among a host of other measures. The EEfRT is a widely used behavioral index of reward motivation and effort-based decision-making that requires repeatedly choosing between an easy task and a hard task, each involving rapid, repetitive button-pressing (Treadway et al., 2009). Walitt et al.’s study—the first to investigate effort-based decision-making in PI-ME/CFS—found that patients were less likely to choose the hard task than healthy volunteers. The authors interpreted this difference as evidence of altered “effort preference,” which they defined as “how much effort a person subjectively wants to exert” (p. 9). Walitt et al. concluded that “effort preference, not fatigue, is the defining motor behavior of this illness” (p. 10). Here we interrogate this conclusion. Were PI-ME/CFS patients less likely to choose the hard task because they wanted to exert less effort, consciously or otherwise? Or were they less able to complete the hard task, and thus chose it less often? We argue that the data support the latter interpretation.

Source: Kirvin-Quamme A, Kirke KD, Junge O, Edwards JCW, Holmes KJ. Unwilling or unable? Interpreting effort task performance in myalgic encephalomyelitis/chronic fatigue syndrome. Front Psychol. 2025 Jun 13;16:1593269. doi: 10.3389/fpsyg.2025.1593269. PMCID: PMC12202612. https://pmc.ncbi.nlm.nih.gov/articles/PMC12202612/ (Full text)

Core features and inherent diversity of post-acute infection syndromes

Abstract:

Post-acute infection syndromes (PAIS), i.e., long-lasting pathologies subsequent to infections that do not properly resolve, have both a common core and a broad diversity of manifestations. PAIS include a group of core symptoms (pathological fatigue, cognitive problems, sleep disorders and pain) accompanied by a large set of diverse symptoms. Core and diverse additional symptoms, which can persist for years, exhibiting periods of relapses and remissions, usually start suddenly after an apparently common infection.

PAIS display highly variable clinical features depending on the nature of the initial pathogen, and to an even larger extent, on the diversity of preexisting individual terrains in which PAIS are rooted. In a first part, I discuss biological issues related to the persistence of microbial antigens, dysregulated immune responses, reactivation of latent viruses, different potential self-sustained inflammatory loops, mitochondrial dysfunction, metabolic disorders in the tryptophan- kynurenin pathway (TKP) with impact on serotonin, and consequences of a dysfunctional bidirectional microbiota-gut-brain axis.

The second part deals with the nervous system dependence of PAIS. I rely on the concept of interoception, the process by which the brain senses, integrates and interprets signals originating from within the body, and sends feebacks aimed at maintaining homeostasis. Interoception is central for understanding the origin of fatigue, dysautonomia, dysfunctioning of the hypothalamus-pituitary-adrenal (HPA) axis, and its relation with stress, inflammation or depression.

I propose that all individual predispositions leading to self-sustained vicious circles constitute building blocks that can self-assemble in many possible ways, to give rise to both core and diverse features of PAIS. A useful discrimination between different PAIS subtypes should be obtained with a composite profiling including biomarkers, questionnaires and functional tests so as to take into account PAIS multidimensionality.

Source: Trautmann A. Core features and inherent diversity of post-acute infection syndromes. Front Immunol. 2025 Jun 3;16:1509131. doi: 10.3389/fimmu.2025.1509131. PMID: 40529374; PMCID: PMC12170329. https://pmc.ncbi.nlm.nih.gov/articles/PMC12170329/ (Full text)

Concentrations of uremic bacterial metabolites in patients with post-COVID-19 syndrome

Abstract:

Post-COVID-19 syndrome (PCS) is characterized by persistent symptoms and reduced mental and physical performance following the acute phase of COVID-19. The underlying mechanisms remain unclear but may involve gut microbiota dysbiosis and immune-related changes in amino acid metabolism. This pilot study aimed to investigate whether specific bacterial uremic metabolites (BUM) are altered in patients with post-infectious syndromes and whether these alterations are associated with PCS symptoms.

We examined BUM in 25 PCS patients, 8 Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) patients, and 8 healthy controls (Ctrls). Concentrations of BUM were determined in second morning urine samples using mass spectrometry (Biovis Diagnostik, Limburg, Germany). Standardized questionnaires assesed physical, cognitive, psychological, and somatic symptoms and mental health status.

PCS and ME/CFS patients exhibited significantly higher scores for post-exertional malaise (PEM) and somatic symptom severity compared to healthy controls (p<0.001). Elevated BUM concentrations were found in 64% of PCS patients, compared to 37.5% of both healthy controls and ME/CFS patients. While overall BUM levels did not significantly differ between groups, heatmap clustering revealed distinct metabolic patterns.

Elevated tryptamine and 4-hydroxyphenylpropionic acid (HPHPA) and higher hippuric acid and trimethylamine concentrations, were exclusively analysed in patients with post-infectious syndromes. Our pilot study suggests that urine metabolomic analysis may be a useful approach for investigating the role of gut dysbiosis and BUM in patients with PCS.

Source: Brigo N, Mayr W, Taenzer M, Löffler-Ragg J, Schroll A, Engl S, Schütz B, Rappl P, Heine T, Weiss G, Kurz K. Concentrations of uremic bacterial metabolites in patients with post-COVID-19 syndrome. Front Cell Infect Microbiol. 2025 May 29;15:1582972. doi: 10.3389/fcimb.2025.1582972. PMID: 40510799; PMCID: PMC12159039. https://pmc.ncbi.nlm.nih.gov/articles/PMC12159039/ (Full text)

The Implications and Predictability of Sleep Reversal for People with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Machine Learning Approach

Abstract:

Background/objectives: Impaired sleep is one of the core symptoms of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), yet the mechanisms and impact of sleep-related issues are poorly understood. Sleep dysfunctions for patients with ME/CFS include frequent napping, difficulties falling asleep, waking up early, and sleep reversal patterns (e.g., sleeping throughout the day and staying awake throughout the night). The current study focuses on sleep reversal for patients with ME/CFS.

Methods: We explored the symptoms and functional impairment of those with and without sleep reversal by analyzing the responses of a large international sample (N = 2313) using the DePaul Symptom Questionnaire (DSQ) and Medical Outcomes Study 36-item Short-Form Health Survey (SF-36).

Results: We found that those in our Sleep Reversal group (N = 327) compared to those without sleep reversal (N = 1986) reported higher symptom burden for 53 out of 54 DSQ symptoms and greater impairments for all six SF-36 subscales. The most accurate predictors of sleep reversal included age (p < 0.05), body mass index (p < 0.05), eleven DSQ symptoms (p < 0.01), and two SF-36 subscales (p < 0.01).

Conclusions: These features provide clues regarding some of the possible pathophysiological underpinnings of sleep reversal among those with ME/CFS.

Source: Dietrich MP, Pravin R, Furst J, Jason LA. The Implications and Predictability of Sleep Reversal for People with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Machine Learning Approach. Healthcare (Basel). 2025 May 26;13(11):1255. doi: 10.3390/healthcare13111255. PMID: 40508869. https://www.mdpi.com/2227-9032/13/11/1255 (Full text)

The Relation Between Cardiac Output and Cerebral Blood Flow in ME/CFS Patients with a POTS Response During a Tilt Test

Abstract:

Background/Objectives: Orthostatic intolerance is prevalent in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and is caused by an abnormal reduction in cerebral blood flow (CBF). In healthy controls (HCs), CBF is regulated complexly, and cardiac output (CO) is an important determinant of CBF. A review in HC showed that a 30% reduction in CO results in a 10% reduction in CBF. In contrast, we showed in ME/CFS patients with a normal HR (HR) and blood pressure response during a tilt test that CO and CBF decreased to a similar extent. The relation between CO and CBF in ME/CFS patients with postural orthostatic tachycardia syndrome (POTS) is unknown.

Therefore, the aim of this study is to assess the relation between CBF and CO, in ME/CFS patients with POTS. The methods used in this retrospective study analyze this relation in a large group of patients. We also analyzed the influence of clinical data. A total of 260 ME/CFS patients with POTS underwent tilt testing with measurements of HR, BP, CBF, CO, and end-tidal PCO2. We measured CBF using extracranial Doppler flow velocity and vessel diameters obtained with a General Electric echo system, and suprasternal aortic flow velocities were measured using the same device. We recorded end-tidal PCO2 using a Nonin Lifesense device.

Results: End-tilt HR and the HR increase were significantly higher in the patients with a %CO reduction ≥ -15% than in the other group. End-tilt CO was higher and the %CO reduction was lower in patients with %CO reduction ≥ -15% than in the other group. CBF data (supine, end-tilt and the %CBF reduction) were not different between the two patient groups. The use of HR increases and %SV reductions were not as discriminative as the %CO reduction.

Conclusions: In ME/CFS patients with POTS during tilt testing with measurements of both the CO and the CBF, two different patterns were observed: (1) appr. two-thirds of patients had an almost 1:1 relation between the %CBF reduction and the %CO reduction. (2) Appr. one-third of patients showed a limited reduction in CO together with a substantial increase in HR. In these patients, there was no relation between the CO and CBF reduction. These data suggest the presence of a hyperadrenergic response.

Source: van Campen CLMC, Visser FC. The Relation Between Cardiac Output and Cerebral Blood Flow in ME/CFS Patients with a POTS Response During a Tilt Test. J Clin Med. 2025 May 22;14(11):3648. doi: 10.3390/jcm14113648. PMID: 40507411. https://www.mdpi.com/2077-0383/14/11/3648 (Full text)