Bethesda, MD — New research into the mechanisms underlying myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID is aimed at identifying potential approaches to treatment of the two overlapping illnesses.
According to a new data brief from the National Center for Health Statistics, in 2021-2022, 1.3% of US adults had ME/CFS, a complex, multisystem illness characterized by activity-limiting fatigue, worsening of symptoms after exertion, unrefreshing sleep, and other symptoms.
A 2-day conference, Advancing ME/CFS Research: Identifying Targets for Potential Intervention and Learning from Long COVID, was held in December 12-13 on the main campus of the US National Institutes of Health (NIH) and was livestreamed. The last such meeting, also featuring results from NIH-funded research, was held in April 2019.
"Things have changed since 2019…The idea of this meeting is to try and identify pathways that will be treatable and druggable and really make an impact for patients based on the things that we've learned over the last number of years and including, fortunately or unfortunately, the huge number of people who are suffering from long COVID, where the symptoms overlap so much with those who have been suffering for a long time with ME/CFS," said Conference Chair Joe Breen, PhD, of the National Institute of Allergy and Infectious Diseases.
As in 2019, the meeting was preceded by a day of research presentations from young investigators, some of whom also presented their findings at the main meeting. New this year were four "lived experience" speakers who described their physical, emotional, and financial struggles with ME/CFS or long COVID. Two of them presented virtually because they were too ill to travel.
Social worker and patient advocate Terri Wilder of Minneapolis, Minnesota, reported some feedback she received on social media after she asked people with ME/CFS about their priorities for the research and clinical communities.
Among the top responses were the need to recognize and study the phenomenon of "post-exertional malaise" and to stop recommending exercise for people with these illnesses, to accelerate research to find effective treatments, and to put an end to stigma around the condition. "People don't believe us when we tell them we're sick, people make fun of us, misperceptions persist," Wilder said.
One person commented, "[Clinicians] shouldn't be afraid to try off-label meds with us if needed. There may be some secondary effects, but they are better options than us taking our own lives because we can't stand the suffering."
Research areas covered at the conference included immunology, virology, metabolism, gene regulation, and neurology of both ME/CFS and long COVID, as well as the latest findings regarding the overlap between the two conditions.
Oxidative Stress in Both ME/CFS and Long COVID: A Role for Metformin?
Mark M. Davis, PhD, professor and director of the Institute for Immunity, Transplantation, and Infection at Stanford University, Palo Alto, California, summarized published data suggesting that oxidative stress is a shared characteristic of both ME/CFS and long COVID. Most cellular reactive oxygen species (ROS) are produced in the cell's mitochondria, and T-cell activation is ROS-dependent.
Women in particular with ME/CFS show high ROS levels with consistent T-cell hyperproliferation, "which can be suppressed with specific drugs such as metformin. This raises the prospect of optimizing drug treatment and drug discovery with a simple in vitro assay of the effects on a patient's lymphocytes," Davis said. He also cited a study suggesting that metformin may help prevent long COVID.
Asked to comment on that, longtime ME/CFS researcher Anthony L. Komaroff, MD, of Harvard University, Cambridge, Massachusetts, cautioned that although metformin is used safely by millions of people with type 2 diabetes worldwide, it's possible that some people with ME/CFS may be more likely to experience its known adverse effects such as lactic acidosis.
To repurpose metformin or any other already-marketed drugs for ME/CFS and/or long COVID, Komaroff said, "We should entertain treatment trials." However, as he and many others lamented at the conference, funding for off-patent drugs often isn't forthcoming.
Addressing the Microbiome, Innate Immunity
W. Ian Lipkin, MD, of Columbia University, New York, NY, was one of two speakers who discussed the role of disruptions in the microbiome and innate immunity in ME/CFS. He presented data suggesting that "dysregulation of the gut microbiome in ME/CFS may interfere with butyrate production, resulting in inflammation and porosity to bacteria and bacterial products that trigger innate immunity."
Lipkin highlighted a "really intriguing" paper in which exogenous administration of interleukin 37 (IL-37), a naturally occurring inhibitor of inflammation, reversed the decrease in exercise performance observed during inflammation-induced fatigue and increased exercise performance, both in mice.
"Although we do not fully understand the pathophysiology of ME/CFS, it is not premature to consider randomized clinical trials of pro- and pre-biotics that address dysbiosis as well as drugs that modify innate immune responses such as poly (I:C) and IL-37," Lipkin said.
Alleviating Endoplasmic Reticulum (ER) Stress: A Strategy to Increase Energy?
Paul Hwang, MD, PhD, from the Cardiovascular Branch of the National Heart, Lung, and Blood Institute, Bethesda, Maryland, described work that he and his colleagues recently published around a case of a 38-year-old woman with Li-Fraumeni syndrome, a genetic early-onset cancer, who also had extensive fatigue, exercise intolerance, and post-exertional malaise that began after she contracted mononucleosis as a teenager.
Testing revealed that her cells had increased expression of Wiskott-Aldrich Syndrome Protein Family Member 3 (WASF3), a "top candidate" gene found to be associated with ME/CFS in a bioinformatics study published more than a decade ago. Moreover, immunoblotting of deidentified skeletal muscle biopsy samples obtained from patients with postinfectious ME/CFS also revealed significantly increased WASF3 levels.
Hwang and colleagues showed in mice that ER stress–induced WASF3 protein localizes to mitochondria and disrupts respiratory supercomplex assembly, leading to decreased oxygen consumption and exercise endurance.
However, use of the investigational protein phosphatase 1 inhibitor salubrinal in the female patient's cells inhibited the ER stress, which in turn decreased WASF3 expression and improved mitochondrial supercomplex formation and respiration, "suggesting a treatment strategy in ME/CFS," Hwang said.
Neurovascular Dysregulation During Exercise: A Role for Pyridostigmine?
David M. Systrom, MD, a pulmonary and critical care medicine specialist at the Brigham and Women's Hospital, Boston, Massachusetts, gave an update of his work investigating neurovascular dysregulation during exercise in both ME/CFS and long COVID using invasive cardiopulmonary testing.
In a 2021 publication, Systrom and his colleagues identified the mechanism of "preload failure," or lower filling pressures of blood in the heart chambers because of insufficient vein constriction and reduced return of blood to the right side of the heart in people with ME/CFS, compared with healthy controls.
Subsequently, in a randomized trial of 45 patients with ME/CFS, Systrom and his colleagues published in November 2022, use of the cholinesterase inhibitor pyridostigmine, currently approved for treating myasthenia gravis and related conditions, improved peak Vo2 by increasing cardiac output and filling pressures.
Now, Systrom's team is conducting a randomized trial comparing 60 mg pyridostigmine with or without low-dose naltrexone (LDN) vs placebo in 160 patients with ME/CFS for 3 months. Metabolomic, transcriptomic, proteomic, and other assessments will be conducted on urine and blood samples. Participants will also wear devices that measure steps, sleep, heart rate, and other metrics.
Komaroff cautioned that pyridostigmine, too, has potential adverse effects. "I'm not sure pyridostigmine is ready for prime time…It's a drug developed for a very different purpose…Now will it hold up in a larger trial, and will there be any side effects that turn up in larger studies? It's not unreasonable to study."
Brain Inflammation: Measuring and Treating It
Hannah F. Bues, clinical research coordinator at Massachusetts General Hospital, Boston, presented data now in preprint (ie, not yet peer-reviewed) in which researchers used [11C]PBR28 PET neuroimaging, a marker of neuroinflammation, to compare 12 individuals with long COVID vs 43 healthy controls. They found significantly increased neuroinflammation in several different brain regions in the long COVID group compared with controls.
Samples of peripheral blood plasma also showed significant correlations between neuroinflammation and circulating analytes related to vascular dysfunction. This work is ongoing in both long COVID and pre-COVID ME/CFS populations, Bues said.
Jarred Younger, PhD, of the Neuroinflammation, Pain, and Fatigue Laboratory at the University of Alabama, Birmingham, also gave an update of his ongoing work demonstrating significant brain inflammation seen in neuroimaging of people with ME/CFS compared with healthy controls.
Younger has been investigating the use of LDN for pain in fibromyalgia. Anecdotally, there have been reports of fatigue reduction with LDN in ME/CFS.
Younger conducted a post hoc analysis of his previous trial of LDN for 12 weeks in 30 patients with fibromyalgia. Of those, 16 met older CFS criteria. There was a significant reduction in their fatigue severity, with P <.0001 from baseline and P < .009 compared with placebo. The P values were high because the data included daily symptom reports. The average fatigue reduction was 25%.
"It wasn't a study designed for ME/CFS, but I think it's compelling evidence and enough with the other types of data we have to say we need to do a proper clinical trial of low-dose naltrexone in ME/CFS now," Younger said.
'We Need to Do Something' About the Underfunding
Another NIH-funded ME/CFS researcher, Maureen Hanson, PhD, of Cornell University, Ithaca, NY, noted that the NIH currently funds ME/CFS research at about $13 million compared with $1.15 billion for the Researching COVID to Enhance Recovery Initiative granted to NIH by Congress for "post-acute sequelae of SARS-CoV-2 (PASC)" in 2021 "because of the urgency of studying this. Most of us here are well aware of the underfunding of ME/CFS relative to the burden of illness," she said.
Current 2024 funding for AIDS research is $3294 million. "There are 1.2 million individuals living with HIV in the United States, and there are over 3 million who are barely living with ME/CFS in the United States. We need to do something about this…It's certainly possible that future funding for PASC is now going to disappear," Hanson cautioned.
Wilder, the patient advocate, reminded the audience that "There is a cohort of people with ME who got sick in the 1980s and 1990s in the prime of their life…They have dreamed of a day when there would be a major announcement that a treatment has been discovered to take away the suffering of this disease…They keep waiting and waiting, year after year, missing more and more of their lives with each passing day…We're all depending on you."
Systrom has received funding from the Solve ME/CFS Initiative, Department of Defense, and Open Medicine Foundation. Younger's work is funded by the NIH, Department of Defense, SolveME, the American Fibromyalgia Association, and ME Research UK. Lipkin and Hanson receive NIH funding. Komaroff has no disclosures.
Miriam E. Tucker is a freelance journalist based in the Washington DC area. She is a regular contributor to Medscape Medical News, with other work appearing in the Washington Post, NPR's Shots blog, and Diabetes Forecast magazine. She is on X (formerly known as Twitter): @MiriamETucker.
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