Postural orthostatic tachycardia syndrome (POTS) is one of the most devastating symptom complexes that are included in the definition of ME/CFS. There is much about POTS that is poorly understood. The syndrome clearly involves both the cardiopulmonary as well as the peripheral vascular systems because they are both modulated by the autonomic nervous system. Why these systems become dysregulated causing dizziness, fatigue, inability to exercise, lightheadedness, fainting, and sometimes fast heart rate, nausea, anxiety, and blurred vision, is not known. It is likely that intense study of the interaction of these systems will lead to a much better understanding of the origin of this devastating symptom complex.
Cardiopulmonary exercise testing together with direct measurement of peripheral and pulmonary arterial catheterization (iCPET) has been useful to define the reason for unexplained dyspnea in general populations thought to be heart or lung in origin. Using this diagnostic tool many ME/CFS patients have been evaluated and found to demonstrate a preload failure (PLF) pattern when maximal exercise tolerance has been tested. There are two forms of this PLF that has been observed: low flow and high flow. The low flow phenotype appears to be consistent with a failure of the autonomic nervous system to shift blood from the venous to the arterial side of the circulation or another possibility is a reduced total blood volume. On the other hand, the high flow phenotype appears as an arterial to venous shunt in the peripheral circulation or another possibility is a reduced oxygen delivery to peripheral circulatory beds or a reduced utilization by the mitochondria. Aspects of this PLF are highly consistent with mechanisms that result in POTS and post-exertional malaise (PEM), which are seen in many ME/CFS patients. These proposed studies offer significant opportunities for the identification of new drug targets and drug therapies for ME/CFS.
There are two previous studies that strongly suggest that highly useful information might be obtained by targeted and non-targeted proteomic and metabolic analyses on the plasma of patients undergoing exercise in the iCPET studies. Blood sampling comes from two blood compartments (radial and pulmonary artery catheter samples) and at three timepoints (resting, peak, and one-hour post exercise) before, during, and after their iCPET procedure. In a previous study in patients with pulmonary artery hypertension (PAH), proteomic analysis of plasma from these two compartments at the three time points showed that between pre-exercise and post-exercise, 41 proteins were differentially regulated proteins in normal volunteers who had dyspnea but no PAH or lung disease and a different set of 101 proteins were differentially regulated in patients with PAH. It is likely that comparable findings will be seen in ME/CFS patients. Understanding the mechanisms for these differences in regulation will likely lead to tremendous insights into the dyspnea and fatigue seen in ME/CFS.
In other studies that evaluate exercise-induced metabolic effects, small molecule plasma responses to intense exercise were evaluated. These results identified multiple plasma indicators of glycogenolysis, tricarboxylic acid cycle (TCA) activity, and lipolysis, as well as modulators of insulin sensitivity and fatty acid oxidation. These studies, which are done during exercise, sample from two plasma compartments at the three time-points that have never been evaluated in ME/CFS patients. For the reasons above, these studies have an increased likelihood to provide a much better understanding of the origin of fatigue in ME/CFS patients.
A blood tissue repository has been underway at the BWH for ME/CFS patients undergoing iCPET for many years and blood is available to study 84 ME/CFS patients and 30 normal volunteers for comparison. We will study ME/CFS patient blood samples obtained before, during, and one hour after an iCPET procedure for comparison to those from control volunteers also undergoing iCPET testing. Blood samples were obtained from 84 ME/CFS patients who had a confirmed diagnosis of ME/CFS including POTS symptoms and 30 control volunteers who have undergone iCPET will be evaluated using proteomic, phospho-proteomic, and metabolomic methods. 684 plasma blood samples are available that have been rendered from the two compartments (radial and pulmonary artery catheter samples) at all three timepoints (resting, peak, and one-hour post exercise) before, during, and after their iCPET procedure for these proteomic and metabolite analyses. We will use outside longstanding vendors and collaborating institutions for many of these proteomic and metabolomic analyses.
There is a critical likelihood that using proteomics and metabolic analysis, critical clues to the origin of fatigue and inability to exercise may be identified in the blood of ME/CFS patients undergoing strenuous exercise while being monitored using iCPET. Currently IRB applications and Material Transfer Agreements (MTAs) are being prepared for approval to study these precious plasma samples. Once these approvals have been received, samples will be analyzed.
There are two types of proteomic analyses that are immediately proposed: plasma proteomics and phospho-proteomics. Certainly, these analyses have never been done in ME/CFS patients. Plasma proteomics have been conducted in ME/CFS patients but always at rest and not under stress exercise conditions when fatigue and exercise-induced differences are most likely to become evident. Plasma proteomics and phospho-proteomics, for the entire 684 samples will be conducted. The results of these analyses will be evaluated and explored by computational methods in the Immuno-metabolic Computational Center (IMCC). We are very enthusiastic to pursue this thrust area and would wish to use preliminary results from evaluation of these studies for an NIH RO1 grant.
Participation in the Studies
These studies have been ongoing at the BWH to create a biorepository of those patients with ME/CFS undergoing iCPET for unexplained dyspnea and fatigue. Research has advanced over the recent years and have created important questions to address in these very precious biorepository samples. This study will be evaluating samples already collected. Therefore, the opportunity to participate in this study resides in the possibility that one would be referred to Dr. Systrom’s program with an indication for evaluation by iCPET.