Researchers identify biomarkers associated with chronic fatigue syndrome severity

Stanford Medicine| Mon Jul 31 16:01:46 EDT 2017
Researchers identify biomarkers associated with chronic fatigue syndrome severity

Montoya, who oversees the Stanford ME/CFS Initiative, came across his first ME/CFS patient in 2004, an experience he said he’s never forgotten.

 “I have seen the horrors of this disease, multiplied by hundreds of patients,” he said. “It’s been observed and talked about for 35 years now, sometimes with the onus of being described as a psychological condition. But chronic fatigue syndrome is by no means a figment of the imagination. This is real.”

Antivirals, anti-inflammatories and immune-modulating drugs have led to symptomatic improvement in some cases, Montoya said. But no single pathogenic agent that can be fingered as the ultimate ME/CFS trigger has yet been isolated, while previous efforts to identify immunological abnormalities behind the disease have met with conflicting and confusing results.

Still, the sporadic effectiveness of antiviral and anti-inflammatory drugs has spurred Montoya to undertake a systematic study to see if the inflammation that’s been a will-o’-the-wisp in those previous searches could be definitively pinned down.

To attack this problem, he called on Davis, who helped create the Human Immune Monitoring Center. Since its inception a decade ago, the center has served as an engine for large-scale, data-intensive immunological analysis of human blood and tissue samples. Directed by study co-author Holden Maecker, PhD, a professor of microbiology and immunology, the center is equipped to rapidly assess gene variations and activity levels, frequencies of numerous immune cell types, blood concentrations of scores of immune proteins, activation states of intercellular signaling models, and more on a massive scale.

This approach is akin to being able to look for and find larger patterns — analogous to whole words or sentences — in order to locate a desired paragraph in a lengthy manuscript, rather than just try to locate it by counting the number of times in which the letter A appears in every paragraph.

The scientists analyzed blood samples from 192 of Montoya’s patients, as well as from 392 healthy control subjects. The average age of patients and controls was about 50. Patients’ average duration of symptoms was somewhat more than 10 years.

Importantly, the study design took into account patients’ disease severity and duration. The scientists found that some cytokine levels were lower in patients with mild forms of ME/CFS than in the control subjects, but elevated in ME/CFS patients with relatively severe manifestations. Averaging the results for patients versus controls with respect to these measures would have obscured this phenomenon, which Montoya said he thinks may reflect different genetic predispositions, among patients, to progress to mild versus severe disease.

I have seen the horrors of this disease, multiplied by hundreds of patients.

When comparing patients versus control subjects, the researchers found that only two of the 51 cytokines they measured were different. Tumor growth factor beta was higher and resistin was lower in ME/CFS patients. However, the investigators found that the concentrations of 17 of the cytokines tracked disease severity. Thirteen of those 17 cytokines are pro-inflammatory.

TGF-beta is often thought of as an anti-inflammatory rather than a pro-inflammatory cytokine. But it’s known to take on a pro-inflammatory character in some cases, including certain cancers. ME/CFS patients have a higher than normal incidence of lymphoma, and Montoya speculated that TGF-beta’s elevation in ME/CFS patients could turn out to be a link.

One of the cytokines whose levels corresponded to disease severity, leptin, is secreted by fat tissue. Best known as a satiety reporter that tells the brain when somebody’s stomach is full, leptin is also an active pro-inflammatory substance. Generally, leptin is more abundant in women’s blood than in men’s, which could throw light on why more women than men have ME/CFS.

More generally speaking, the study’s results hold implications for the design of future studies of disease, including clinical trials testing immunomodulatory drugs’ potential as ME/CFS therapies.

“For decades, the ‘case vs. healthy controls’ study design has served well to advance our understanding of many diseases,” Montoya said. “However, it’s possible that for certain pathologies in humans, analysis by disease severity or duration would be likely to provide further insights.”

Other Stanford co-authors of the study are clinical research coordinator Jill Anderson; Tyson Holmes, PhD, senior research engineer at the Institute for Immunity, Transplantation and Infection; Yael Rosenberg-Hasson, PhD, immunoassay and technical director at the institute; Cristina Tato, PhD, MPH, research and science analyst at the institute; former study coordinator Ian Valencia; and Lily Chu, MSHS, a board member of the Stanford University ME/CFS Initiative.

The study was funded by the National Institutes of Health (grant U19AI057229), the Stanford ME/CFS Initiative Fund and an anonymous donor.

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