Hypothesis: Matrix metalloproteinase inhibition with low-dose doxycycline in Long COVID and ME/CFS

Abstract:

Nonselective matrix metalloproteinase (MMP) inhibition with FDA approved subantimicrobial dose doxycycline formulations could improve systemic symptoms in at least a subset of patients with Long COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) as compared to those who receive placebo.

Source: Sanders, E.C. (2023). Hypothesis: Matrix metalloproteinase inhibition with low-dose doxycycline in Long COVID and ME/CFS. Patient-Generated Hypotheses Journal for Long COVID & Associated Conditions, Vol. 1, 21-29 https://patientresearchcovid19.com/hypothesis-matrix-metalloproteinase-inhibition-with-low-dose-doxycycline-in-long-covid-and-me-cfs-pghj-issue1-may2023/ (Full text)

Hypothesis: Symptomatic myodesopsia/vitreous floaters may constitute a risk factor for Long COVID and ME/CFS

Abstract:

The ophthalmological condition known as myodesopsia or vitreous floaters results from aggregates of proteins or cellular debris in the vitreous body casting shadows onto the retina that are perceived as objects moving through the visual field. While this is commonly viewed as a benign condition associated with aging, a growing body of research suggests that for some patients it can severely impact visual function and quality of life. Myodesopsia is often caused by posterior vitreous detachment, but can also result from other conditions such as asteroid hyalosis, uveitis, or myopic vitreopathy.

There are strong reasons to suspect that its presence may be indicative of a susceptibility to collagen degradation in response to inflammatory triggers, which may represent a risk factor for the development of Long COVID, ME/CFS, or related chronic illnesses. Evidence for such susceptibility includes the presence of collagen-degrading enzymes in the vitreous, associations with other connective tissue disorders, and links between myodesopsia and infections with various pathogens.

Source: Mazewski, M. (2023). Hypothesis: Symptomatic myodesopsia/vitreous floaters may constitute a risk factor for Long COVID and ME/CFS. Patient-Generated Hypotheses Journal for Long COVID & Associated Conditions, Vol. 1, 13-20 https://patientresearchcovid19.com/hypothesis-symptomatic-myodesopsia-vitreous-floaters-may-constitute-a-risk-factor-for-long-covid-and-me-cfs-pghj-issue1-may2023/ (Full text)

Hypothesis: Astrocyte dysregulation of sympathetic nervous system causes metabolic dysfunction in subset of Long COVID and ME/CFS patients

Abstract:

An overactive sympathetic nervous system (SNS) may cause one subtype of Long COVID. People who are genetically at risk for noradrenergic nerve problems may develop an overactive SNS after an infection. Alternatively, genetic or virus-induced dysregulation of astrocytes could lead to overactivation of the SNS. An overactive SNS could disrupt regulation of immune cells, energy metabolism, sleep homeostasis, respiratory rate, gastrointestinal function, and systemic and cerebral blood pressure, causing fatigue and cognitive dysfunction.

Hypothesis: Long COVID refers to symptoms that continue for more than four weeks after onset of acute COVID-19 illness. This umbrella term includes a wide variety of symptoms and presentations. Long COVID patients may have different types of biological dysfunction, meaning that there may be distinct subtypes of Long COVID. One possible subtype is sympathetic nervous system (SNS) over-activation. This subtype may exist in both Long COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)1.

Underlying mechanisms of the SNS overactivation subtype: Theoretically, patients with this subtype already have a genetic dysregulation of neuronal norepinephrine (NE) release/clearance or noradrenergic receptor sensitivity2. This latent genetic dysfunction of NE signaling may not cause significant problems unless there is a trigger that causes excess NE release.

As NE affects immune cell signaling, this could result in an over-activation or prolonged activation of the immune system in response to infection with SARS-CoV-2, the virus that causes COVID-193 . This subtype could explain why ME/CFS is often triggered by a virus or brain injury, as these occurrences can trigger noradrenergic signaling3.

Possible mechanisms for the SNS overactivation subtype include viral reservoirs, antibody reaction, and dysregulation of noradrenergic receptor expression. In Long COVID patients, viral antigens and reservoirs that remain in the body long after the initial infection may keep the overactive immune system in an inflammatory state4,5. A healthy person may not react to these SARS-CoV-2 reservoirs, as their functional immune cells should develop immune tolerance. Another possibility is that the immune system is reacting to SARS-CoV-2 antibodies.

Finally, it is possible that excess extracellular NE could keep the SNS and noradrenergic systems in the brain stuck in an overactive state. A prolonged period of increased levels of extracellular NE could lead to dysregulation of noradrenergic receptor expression. The excess extracellular NE may be due to a prolonged release of excess NE during the initial infection, or a failure of the negative feedback mechanisms that should reduce NE release.

Symptoms of an overactive SNS: An overactive SNS explains many of the symptoms found in Long COVID patients, such as IBS/gastrointestinal symptoms6, heart palpitations7, and sleep disturbance8. Additionally, in orthostatic intolerance, which is common in Long COVID and ME/CFS, the release of NE causes pronounced tachycardia. This rapid heart rate may cause palpitations, breathlessness, and chest pain.

Dysfunctional energy metabolism causes fatigue and cognitive dysfunction: An important piece of the puzzle is to explain how a dysregulated SNS could lead to chronic fatigue and brain fog (cognitive dysfunction). The most likely explanation is a dysregulation of metabolic function. There are many ways excess NE could affect metabolism, including enhancing aerobic glycolysis and depleting glycogen stores.

Source: Carnac, T. (2023). Hypothesis: Astrocyte dysregulation of sympathetic nervous system causes metabolic dysfunction in subset of Long COVID and ME/CFS patients. Patient-Generated Hypotheses Journal for Long COVID & Associated Conditions, Vol. 1, 36-43 https://patientresearchcovid19.com/hypothesis-astrocyte-dysregulation-of-sympathetic-nervous-system-causes-metabolic-dysfunction-in-subset-of-long-covid-and-me-cfs-patients-pghj-issue1-may2023/ (Full text)

Comparison of T-cell Receptor Diversity of people with Myalgic Encephalomyelitis versus controls

Abstract:

Objective: Myalgic Encephalomyelitis (ME; sometimes referred to as Chronic Fatigue Syndrome or CFS) is a chronic disease without laboratory test, detailed aetiological understanding or effective therapy. Its symptoms are diverse, but it is distinguished from other fatiguing illnesses by the experience of post-exertional malaise, the worsening of symptoms even after minor physical or mental exertion. Its frequent onset after infection might indicate that it is an autoimmune disease or that it arises from abnormal T-cell activation.

Results: To test this hypothesis, we sequenced the genomic loci of a/d, b and g T-cell receptors (TCR) from 40 human blood samples from each of four groups: severely affected people with ME/CFS; mildly or moderately affected people with ME/CFS; people diagnosed with Multiple Sclerosis, as disease controls; and, healthy controls. Seeking to automatically classify these individuals’ samples by their TCR repertoires, we applied P-SVM, a machine learning method. However, despite working well on a simulated data set, this approach did not partition samples into the four subgroups, beyond what was expected by chance alone.  Our findings do not support the hypothesis that blood samples from people with ME/CFS frequently contain altered T-cell receptor diversity.

Source: Joshua J Dibble, Ben Ferneyhough, Matthew Roddis et al. Comparison of T-cell Receptor Diversity of people with Myalgic Encephalomyelitis versus controls, 19 July 2023, PREPRINT (Version 1) available at Research Square [https://doi.org/10.21203/rs.3.rs-3164397/v1]  https://www.researchsquare.com/article/rs-3164397/v1 (Full text)

A phenomenological study on the lived experience of men with Chronic Fatigue Syndrome

Abstract:

Whilst chronic fatigue syndrome (CFS) has been widely researched amongst women, studies investigating how men experience a CFS diagnosis is limited.

This study utilised an interpretative phenomenological approach to interview five men who have a medical diagnosis of CFS.

Six themes emerged to demonstrate the participants’ experiences prior to, during and after obtaining their CFS diagnosis.

Findings revealed that participants were initially reluctant to accept their condition, confounded by their perception that symptoms compromised their sense of masculinity. They also felt that healthcare professionals had limited recognition of CFS leading them to seek social support and legitimisation from other sources.

The struggle to come to terms with a different lifestyle and sense of masculinity prevailed. Such knowledge could be effectively utilised by researchers, practitioners and employers to facilitate an increased understanding of male accounts of the condition and more bespoke interventions where required.

Source: Snell GE, Seage CH, Mercer J. A phenomenological study on the lived experience of men with Chronic Fatigue Syndrome. J Health Psychol. 2023 Jul 17:13591053231186385. doi: 10.1177/13591053231186385. Epub ahead of print. PMID: 37455618. https://pubmed.ncbi.nlm.nih.gov/37455618/

 

Invisibility and diagnosis stigma: disabling factors for female adults with myalgia encephalomyelitis (ME)/chronic fatigue syndrome (CFS) in a small-scale qualitative study in England

Abstract:

Purpose: Female adults diagnosed with myalgia encephalomyelitis (ME) and chronic fatigue syndrome (CFS) often are marginalised because their condition is not fully recognised by medical and health-care systems. The purpose of this small-scale study was to explore the lived experiences of adult females with ME/CFS in England in relation to contributing factors that impact their occupational participation.

Design/methodology/approach: A qualitative study design using semi-structured interviews was used with nine female adult participants who were selected using a purposive sampling method. A Thematic Networks tool was used to analyse data.

Findings: Four organising themes were identified: impairment-, person-, environment- and society-related factors. Two global themes, invisibility and diagnosis stigma, were identified as the overarching issues that female adults with ME/CFS face in occupational participation.

Originality/value: Many of the issues that contribute to lack of participation by this population are associated with environmental factors which are secondary to their illness.

Source: Khalafbeigi, M., Yazdani, F., Genis, F., Hess, K.Y. and Kirve, S. (2023), “Invisibility and diagnosis stigma: disabling factors for female adults with myalgia encephalomyelitis (ME)/chronic fatigue syndrome (CFS) in a small-scale qualitative study in England”, Irish Journal of Occupational Therapy, Vol. ahead-of-print No. ahead-of-print. https://doi.org/10.1108/IJOT-08-2022-0032 https://www.emerald.com/insight/content/doi/10.1108/IJOT-08-2022-0032/full/html (Full text)

Early Biological Markers of Post-Acute Sequelae of SARS-CoV-2 Infection

Abstract:

To understand the roles of acute phase viral dynamics and host immune responses in PASC, we enrolled 136 participants within 5 days of their first positive SARS-CoV-2 real-time PCR. Participants self-collected nasal specimens up to 21 times within the first 28 days after symptom onset; Interviewer-administered clinical questionnaires and blood samples were collected at enrollment and days 9, 14, 21, 28, and month 4 and 8 post-symptom.

Defining PASC as the presence of any symptom new or worse since infection reported at their 4-month visit, we compared viral markers (quantity and duration of viral RNA load, infectious viral load, and plasma N-antigen level) and host immune markers (IL-6, IL-10, TNF-a, IFN-a, IFN-g, MCP, IP-10, and Spike IgG) over the acute period.

In comparison to those who fully recovered, those who developed PASC demonstrated significantly higher maximum levels of SARS-CoV-2 RNA, infectious virus, and N-antigen, longer duration of viral shedding, and lower Spike-specific IgG levels within the first 10 days of the acute phase of illness. No significant differences were identified among a panel of host immune markers, though there was a trend toward higher initial levels of certain markers (e.g., MCP-1, IFN-a, and IFN-g) in those who went on to develop PASC.

Early viral dynamics and the associated host immune responses play a role in the pathogenesis of PASC. These findings highlight the importance of understanding the early biological markers from acute SARS-CoV-2 infection in the natural history of PASC.

Source: Scott Lu, Michael J. Peluso, David V. Glidden, Michelle C. Davidson, Kara Lugtu, Jesus Pineda-Ramirez, Michel Tassetto, Miguel Garcia-Knight, Amethyst Zhang, Sarah A. Goldberg, Jessica Y. Chen, Maya Fortes-Cobby, Sara Park, Ana Martinez, Matthew So, Aidan Donovan, Badri Viswanathan, Rebecca Hoh, Kevin Donohue, David R. McIlwain, Brice Gaudiliere, Khamal Anglin, Brandon C. Yee, Ahmed Chenna, John W. Winslow, Christos Petropoulos, Steven G. Deeks, Melissa Briggs-Hagen, Raul Andino, Claire M. Midgley, Jeffrey N. Martin, Sharon Saydah, J. Daniel Kelly. Early Biological Markers of Post-Acute Sequelae of SARS-CoV-2 Infection. medRxiv 2023.07.14.23292649; doi: https://doi.org/10.1101/2023.07.14.23292649 https://www.medrxiv.org/content/10.1101/2023.07.14.23292649v1.full-text (Full text)

Utility of Serum Ferritin for Predicting Myalgic Encephalomyelitis/Chronic Fatigue Syndrome in Patients with Long COVID

Abstract:

Objective: The most common symptom of post-acute coronavirus disease 2019 (COVID-19) is fatigue, and it potentially leads to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS); however, a specific prognosticator is lacking. We aimed to elucidate the clinical characteristics of patients who developed ME/CFS after COVID-19.
Methods: In this retrospective observational study, patients who visited Okayama University Hospital for long COVID between February 2021 and March 2022 were investigated.
Results: Of the 234 patients, 139 (59.4%) had fatigue symptoms. Fifty patients with fatigue symptoms (21.4%) met the criteria for ME/CFS (ME/CFS group), while the other 89 patients did not (non-ME/CFS group); 95 patients had no fatigue complaints (no-fatigue group). Although the patients’ backgrounds were not significantly different between the three groups, the ME/CFS group presented the highest scores on the self-rating symptom scales, including the Fatigue Assessment Scale (FAS), EuroQol, and the Self-Rating Depression Scale (SDS). Furthermore, serum ferritin levels, which were correlated with FAS and SDS scores, were significantly higher in the ME/CFS group (193.0 μg/mL, interquartile range (IQR): 58.8–353.8) than in the non-ME/CFS group (98.2 μg/mL, 40.4–251.5) and no-fatigue group (86.7 μg/mL, 37.5–209.0), and a high serum ferritin level was prominent in female patients. Endocrine workup further showed that the ME/CFS group had higher thyrotropin levels but lower growth hormone levels in serum and that insulin-like growth factor-I levels were inversely correlated with ferritin levels (R = −0.328, p < 0.05).
Conclusions: Serum ferritin level is a possible predictor of the development of ME/CFS related to long COVID, especially in female patients.
Source: Yamamoto Y, Otsuka Y, Tokumasu K, Sunada N, Nakano Y, Honda H, Sakurada Y, Hasegawa T, Hagiya H, Otsuka F. Utility of Serum Ferritin for Predicting Myalgic Encephalomyelitis/Chronic Fatigue Syndrome in Patients with Long COVID. Journal of Clinical Medicine. 2023; 12(14):4737. https://doi.org/10.3390/jcm12144737 https://www.mdpi.com/2077-0383/12/14/4737 (Full text)

Fatigue presentation, severity, and related outcomes in a prospective cohort following post-COVID-19 hospitalization in British Columbia, Canada

Abstract:

Introduction: Increasing evidence on long-term health outcomes following SARS CoV-2 infection shows post-viral symptoms can persist for months. These symptoms are often consistent with those of Myalgic Encephalomyelitis or Chronic Fatigue Syndrome (ME/CFS). The aim of the present study was to examine the prevalence and outcome predictors of post-viral fatigue and related symptoms 3- and 6-months following symptom onset.

Methods: A prospective cohort of patients hospitalized with Coronavirus disease (COVID-19) (n = 88) were recruited from a Post-COVID-19 Respiratory Clinic (PCRC) in Vancouver, Canada to examine predictors of long-term fatigue and substantial fatigue. Multivariable mixed effects analyses examined the relationship between patient predictors, including pre-existing comorbidities, patient reported outcome measures, and fatigue and substantial fatigue at follow-up.

Results: The number of patients experiencing fatigue or substantial fatigue at 3 months post-infection were 58 (67%) and 14 (16%) respectively. At 6 months these numbers declined to 47 (60%) patients experiencing fatigue and 6 (6%) experiencing substantial fatigue. Adjusted analysis, for sex, age, and time, revealed the number of pre-existing comorbidities to be associated with fatigue (OR 2.21; 95% CI 1.09-4.49; 0.028) and substantial fatigue (OR 1.73; 95% CI 1.06-2.95; 0.033) at 3 months follow-up. Except for shortness of breath, self-care, and follow-up time, all follow-up variables were found to be associated with fatigue and substantial fatigue at 3 months.

Conclusion: Fatigue and substantial fatigue are common after COVID-19 infection but often diminish over time. A significant number of patients continue to exhibit long-term fatigue at 6 months follow-up. Further research is needed to clarify the causality of viral infections in the development and severity of fatigue as a symptom and in meeting post-viral fatigue syndrome or ME/CFS diagnostic criteria.

Source: Magel T, Meagher E, Boulter T, Albert A, Tsai M, Muñoz C, Carlsten C, Johnston J, Wong AW, Shah A, Ryerson C, Mckay RJ, Nacul L. Fatigue presentation, severity, and related outcomes in a prospective cohort following post-COVID-19 hospitalization in British Columbia, Canada. Front Med (Lausanne). 2023 Jun 29;10:1179783. doi: 10.3389/fmed.2023.1179783. PMID: 37457578; PMCID: PMC10344448. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10344448/ (Full text)

Carotid body dysregulation contributes to the enigma of long COVID

Abstract:

The symptoms of long COVID, which include fatigue, breathlessness, dysregulated breathing, and exercise intolerance, have unknown mechanisms. These symptoms are also observed in heart failure and are partially driven by increased sensitivity of the carotid chemoreflex. As the carotid body has an abundance of ACE2 (the cell entry mechanism for SARS-CoV-2), we investigated whether carotid chemoreflex sensitivity was elevated in participants with long COVID. During cardiopulmonary exercise testing, the VE/VCO2 slope (a measure of breathing efficiency) was higher in the long COVID group than in the controls, indicating excessive hyperventilation.

The hypoxic ventilatory response, which measures carotid chemoreflex sensitivity, was increased in long COVID participants and correlated with the VE/VCO2 slope, suggesting that excessive hyperventilation may be related to carotid body hypersensitivity. Therefore, the carotid chemoreflex is sensitized in long COVID and may explain dysregulated breathing and exercise intolerance in these participants. Tempering carotid body excitability may be a viable treatment option for long COVID patients.

Source: Ahmed El-Medany, Zoe H Adams, Hazel C Blythe, Katrina A Hope, Adrian H Kendrick, Ana Paula Abdala Sheikh, Julian FR Paton, Angus K Nightingale, Emma C Hart. Carotid body dysregulation contributes to the enigma of long COVID. medRxiv 2023.05.25.23290513; doi: https://doi.org/10.1101/2023.05.25.23290513 https://www.medrxiv.org/content/10.1101/2023.05.25.23290513v1.full-text (Full text)