The two-day exercise study results suggest that the ability to produce energy after exercise in chronic fatigue syndrome (ME/CFS) is blunted, and the search is on to identify blockages in cellular energy that could explain that. Lead by Cara Tomas, Julia Newton and company have stepped into the fray with the first published “Seahorse” ME/CFS study that I’m aware of.
Agilent’s Seahorse machine is, for the first time, making it easy for researchers to study cellular energetics. During a recent trip to Nancy Klimas’s lab at Nova Southeastern (she has one) Dr. Deth exclaimed at how the Seahorse has greatly expanded researchers ability to put cells under stress and measure their energy production. With at least five ME/CFS studies using the machine, the Seahorse is a case of technology evolving at just the right time to benefit ME/CFS research.
Cellular bioenergetics is impaired in patients with chronic fatigue syndrome. Cara Tomas, Audrey Brown,Victoria Strassheim, Joanna Elson, Julia Newton, Philip Manning. Plos, October 24, 2017. https://doi.org/10.1371/journal.pone.0186802
Because there’s no evidence that genetic mutations are affecting mitochondria output in chronic fatigue syndrome (ME/CFS), any mitochondrial problems that are present they are most likely “acquired” during an infection or other event which either damaged them or prevented them from functioning properly. Since the mitochondria can be inhibited by a number of factors ranging from immune activation to oxidative stress to psychological stress it’s probable that a number of different pathways lead to any mitochondrial dysfunction that might be present in ME/CFS.
The metabolomics studies suggest problems with glycolysis are present but studies actually examining mitochondrial functioning in chronic fatigue syndrome (ME/CFS) have been pretty rare.
An earlier study using a different means of measuring cellular energy production (ATP Profile test) in neutrophils in whole blood found that “all patients tested have measureable mitochondrial dysfunction which correlates with the severity of the illness.” Cell-free DNA measurement showed high levels of damage.
Other studies, however, do not suggest the mitochondrial play an important role in ME/CFS. Mitochondrial content was lower in ME/CFS but ATP production and other measures of mitochondrial health were normal. Likewise, Vermeulen found reduced exercise capacity in ME/CFS but normal ATP production. If an inhibiting factor in the blood plays a role Vermeulen’s extraction of PBMC’s from whole blood might have played a factor. Vermeulen, however, proposed that reduced oxygen delivery to the issues was the problem.
Most recently, a Stanford study found evidence of greatly increased mitochondrial activity in ME/CFS cells. The Stanford study suggested that left to themselves the mitochondria in ME/CFS might doing just fine and that glycolysis – the anaerobic portion of the energy cycle – might be the issue.
“Our results present an unorthodox view on CFS pathology: the fatigue is not caused by lack of ATP, and instead might be caused by a pathological process linked to non-mitochondrial ATP production such as glycolysis.”
That study, which did not use the Seahorse machine, provided yet another twist when the glycolysis results suggested that ME/CFS was a hyper not a hypometabolic conditions. Because the cells were tested outside of the plasma the effect of a possible inhibiting factor in the blood was not taken into account.
Now we have Tomas et. al. using the Seahorse machine to get very accurate direct measurements of cellular energy production in ME/CFS. Like Vermulen, this group used PBMC’s isolated from whole blood.
The first sign something was wrong came when Tomas assessed the energy production of cells in low and high glucose concentrations. (The Seahorse machine allows researchers to add materials to the cells to see the effect they have on energy production.) Tomas expected the addition of glucose would boost up glycolysis – the anaerobic portion of the energy cycle which runs on glucose – and it did – but only in the healthy controls. The inability of the ME/CFS patient’s cells to utilize the extra glucose seemed to suggest that something had gone wrong with glycolysis in ME/CFS but a glycolysis stress test indicated that glycolysis was operating normally.
Almost every indicator of energy production was lower in ME/CFS patients cells whether they were put into low or high glucose levels (basal respiration, ATP production, maximal respiration, reserve capacity, non-mitochondrial respiration, coupling efficiency).
Newton suggested that the ME/CFS cells were kind of stuck in a low energy mode. When given extra glucose they weren’t able to use it. When deprived of glucose they weren’t able to increase their mitochondrial energy production. A stimulation test in the Seahorse machine didn’t stimulate the ME/CFS patient’s cells much either. When asked to respond the ME/CFS cells were able to generate about 50% more energy while healthy control cells doubled their energy output. The study was on immune cells not muscle cells but each finding seemed to make sense given ME/CFS patient’s inability to mount the energy to engage in exercise.
The healthy controls cells, on the other hand, responded to all three tests – they basically demonstrated the flexibility and capacity that healthy cells need to have to respond adequately to a number of different situations.
Newton’s explanation about the healthy control cells being more “adaptable” or responsive to their environment than the ME/CFS patient’s cells sounded somewhat like Bob Naviaux’s idea of the cells being thrown into a cell danger response and hunkering down and trying to ride out some threat. Unless Naviaux’s CDR hypothesis includes cells getting stuck without an outside factor to keep them reined in (which it may), however, it didn’t seem to apply: Newton’s cells were tested outside of the plasma where the threat is believed present.
Beside their unresponsiveness the ME/CFS patient’s cells also had lower reserve capacity; i.e. they may have already been operating near their maximum level. The low coupling efficiency suggested that when pushed, they simply didn’t have the resources to respond.
All in all it was a remarkable set of findings. At least two thirds of the tests done were abnormally low in whatever situation they were put in.
A earlier model of mitochondrial dysfunction in ME/CFS seems, at least to this laymen’s eyes, reflect the situation Newton found. When stressed the cells lacked the capacity to respond. Their reduced mitochondrial capacity had caused the cells to dig into their adenine reserves resulting in long recovery periods after exercise. The model predicted it would take 3-5 times longer for the ATP levels in the muscles of ME/CFS patients to return to normal after exercise than for healthy controls. The model also predicted that short (30 seconds), intense exercise periods would be easier for ME/CFS patients to recover from.
Newton’s findings certainly seemed to make sense given the fatigue and energy problems highlighted in ME/CFS but, as she acknowledged, they conflicted with some of the past results.
The combination of the detection of significant differences in OXPHOS alongside the lack of detectable differences in glycolysis has potentially uncovered a previously unknown phenotype of CFS PBMCs Newton et. al.
Newton isolated ME/CFS patients PBMC’s from whole blood but still found reduced cellular energy production. The Stanford group did the same thing but found increased energy production with a highlight on increased glycolysis. Newton’s finding of reduced energy production in cells found outside the plasma suggests that problems may exist in the cells themselves.
Newton’s findings of normal glycolysis conflicted with the Stanford group’s finding on increased glycolysis and with metabolomic studies pointing to glycolysis issues.
In broad way, though, Newton’s findings do fit. Almost all the studies point to problems with cellular energy production that may be manifesting themselves in different ways. A somewhat similar situation may be showing up in exercise studies where different issues (ventilation, VO2 max, anaerobic threshold) are appearing in different patients. Those studies suggest that the exercise incapacity present in ME/CFS is being produced different ways. That may not be surprising given what we know about disease. If the molecular roots of say, lung cancer, differ between patients, it would make sense for a variety of different pathways to cause the energy production problems in ME/CFS.
Newton’s rather stunning findings – that the vast majority of tests of cellular energy production were significantly lower in ME/CFS patients’ immune cells – made sense. The good news is that most studies are finding evidence of whole body (exercise, metabolomics) or cellular energy production problems. The bad news is that they’re coming to different conclusions as to how that’s happening.
The cure to the energy production puzzle is, of course, bigger and better studies and they seem to be coming. The Seahorse machine, which looks like it’s going to be floating around ME/CFS research circles for a while, will mean more methodological consistency and allow for better comparisons between studies.
Avindra Nath is using one in his NIH intramural study, and Maureen Hanson appears to be using one in two studies, one of which will hopefully be a large, robust study at her NIH funded ME/CFS research center. Ron Davis has used one, Isabel Barao is using one in her SMCI funded study, and Newton reported she will be seeking larger, longitudinal studies. Anyone, it seems, who wants to know about energy production in ME/CFS is using one.
Avindra Nath’s intramural study is small – approximately 40 patients – but with its metabolic chamber, exercise study and other features it’s digging into so many different parameters that one wonders if it might be able to uncover different subsets and their pathways all on its own. Brian Vastag reported that the early Seahorse results were so unusual that the researcher involved felt compelled to stop by and chat…
By the time all is said and done the Seahorse will hopefully tell us much about ME/CFS.