Dr David Patrick and colleagues
School of Population and Public Health, University of British Columbia, British Columbia, Canada
National Institutes of Health & ME Research UK
Background and aim
A hallmark of ME/CFS is that symptoms are made worse by exercise, sometimes 24-48 hours afterwards, even if the exercise is quite mild by normal standards. Even the 2007 NICE Clinical Guideline requires “post-exertional” symptoms (delayed, with slow recovery over several days) for a diagnosis to be made. This is why various research groups over the years have tried to measure physiological changes before and after exercise, and have reported differences in immune parameters and oxidative stress following exercise in ME/CFS patients compared with healthy people (see a review).
Exercise involves an increase in gene activity to produce many of the substances needed for movement. This process is called ‘gene expression’, and measuring gene expression can be a sensitive way of assessing the body’s (global) response to the demands of exercise. To date, there have been a number of these investigations in ME/CFS patients, with some evidence of post-exercise increases in immune cell gene expression (specifically in interleukin-10 and Toll-like receptor genes). However, these gene expression studies have tended to focus on pathways relevant to the immunity, none have employed the more comprehensive high-throughput RNA sequencing approach, and very few have followed measurements through to the recovery phase from symptom flare.
For this reason, Dr David Patrick and colleagues in British Columbia have devised a study to examine the post-exercise fatigue and malaise of ME/CFS patients using newly available gene sequencing technologies with standardized exercise testing, which provides a measured stimulus and also allows objective categorization of patients according to their exercise response. The next generation sequencing will allow a much deeper probe of host gene expression (especially as it relates to immune signaling after exercise) than has previously been possible. They hope to identify specific patterns or response that might explain prolonged fatigue symptoms.
For the experiment, 15 female patients with ME/CFS (Canadian Consensus criteria and Fukuda-defined) and 15 healthy controls, matched for sedentary lifestyle, will be enrolled. Each person will receive two maximal cardiopulmonary exercise tests (CPET) approximately 24 hours apart, involving an incremental exercise test, with ECG monitoring and pulse oximetry. Questionnaires on fatigue, experienced symptoms and time to recovery will be administered before each exercise test, within 15 minutes of completion of each test and at follow-up on day 3 and day 7. Study blood for mRNA will be collected pre-exercise for both the first and second exercise tests, and at a home visit on days 3 and 7. Total RNA will be extracted from each specimen, for identification of differentially expressed genes pre-and post-exercise samples. Then, qRT-PCR analyses will be performed to validate a subset of the most significant differentially expressed genes.
Dr Patrick obtained funding from the National Institutes of Health in the US for most of the work in this investigation (see project information), involving RNA sequencing of samples collected pre-exercise on the first day and pre-exercise on the second day. The aim of ME Research UK’s funding is to allow him to undertake additional measurements of mRNA expression before and after exercise on days 3 and 7, to better determine if patterns associated with post-exertional symptom flare are seen to resolve with clinical recovery.