hypothesis – Page 4 – American ME and CFS Society

The inflammatory hypothesis of mood spectrum broadened to fibromyalgia and chronic fatigue syndrome

Abstract:

OBJECTIVES: The present paper aimed at reviewing literature data on the inflammatory hypothesis of mood spectrum, as well as the overlapping features with some chronic rheumatologic disorders, in particular fibromyalgia and chronic fatigue syndrome.

METHODS: A literature search was carried out for English papers published in the years 2000-2014, while using the following words: mood spectrum, depression, bipolar disorders, fibromyalgia, chronic fatigue syndrome, neurotransmitters, inflammation, neuroinflammation, cytokines.

RESULTS: Overlapping features were highlighted between mood spectrum, fibromyalgia and chronic fatigue syndrome suggesting common underlying mechanisms at pathophysiological level involving both central nervous and the immune systems.

CONCLUSIONS: Taken together, the literature would suggest that the borders between different medical domains should be reconsidered in the light of common processes linking them.

Source: Dell’Osso L, Bazzichi L, Baroni S, Falaschi V, Conversano C, Carmassi C, Marazziti D. The inflammatory hypothesis of mood spectrum broadened to fibromyalgia and chronic fatigue syndrome. Clin Exp Rheumatol. 2015 Jan-Feb;33(1 Suppl 88):S109-16. Epub 2015 Mar 18. https://www.ncbi.nlm.nih.gov/pubmed/25786052

Allostatic overload in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)

Abstract:

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating condition characterised by diverse symptoms such as fatigue, pain, sleep disturbance and autonomic dysfunction. There remains to be a singular biomarker identified for this illness, hence numerous theories about its development and perpetuation have been posited in the literature.

This brief report presents the model of ‘allostasis’ as a framework for understanding ME/CFS, specifically the notion that the physiological mechanisms employed in the body to deal with stress termed here as ‘allostatic states’ (e.g. elevation of inflammatory cytokines), may in and of themselves contribute to the perpetuation of the disorder. This theoretical assertion has important consequences for the understanding of ME/CFS and treatment; rather than searching for a singular pathogen responsible for this condition, ME/CFS can be conceptualised as a maladaptive stress disorder and interventions aimed at addressing the allostatic states may be incorporated into current symptom management programmes.

Source: Arroll MA. Allostatic overload in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Med Hypotheses. 2013 Sep;81(3):506-8. doi: 10.1016/j.mehy.2013.06.023. Epub 2013 Jul 11. https://www.ncbi.nlm.nih.gov/pubmed/23850395

Chronic fatigue syndrome from vagus nerve infection: a psychoneuroimmunological hypothesis

Abstract:

Chronic fatigue syndrome (CFS) is an often-debilitating condition of unknown origin. There is a general consensus among CFS researchers that the symptoms seem to reflect an ongoing immune response, perhaps due to viral infection. Thus, most CFS research has focused upon trying to uncover that putative immune system dysfunction or specific pathogenic agent. However, no single causative agent has been found.

In this speculative article, I describe a new hypothesis for the etiology of CFS: infection of the vagus nerve. When immune cells of otherwise healthy individuals detect any peripheral infection, they release proinflammatory cytokines. Chemoreceptors of the sensory vagus nerve detect these localized proinflammatory cytokines, and send a signal to the brain to initiate sickness behavior. Sickness behavior is an involuntary response that includes fatigue, fever, myalgia, depression, and other symptoms that overlap with CFS.

The vagus nerve infection hypothesis of CFS contends that CFS symptoms are a pathologically exaggerated version of normal sickness behavior that can occur when sensory vagal ganglia or paraganglia are themselves infected with any virus or bacteria. Drawing upon relevant findings from the neuropathic pain literature, I explain how pathogen-activated glial cells can bombard the sensory vagus nerve with proinflammatory cytokines and other neuroexcitatory substances, initiating an exaggerated and intractable sickness behavior signal. According to this hypothesis, any pathogenic infection of the vagus nerve can cause CFS, which resolves the ongoing controversy about finding a single pathogen. The vagus nerve infection hypothesis offers testable hypotheses for researchers, animal models, and specific treatment strategies.

Source: VanElzakker MB. Chronic fatigue syndrome from vagus nerve infection: a psychoneuroimmunological hypothesis. Med Hypotheses. 2013 Sep;81(3):414-23. doi: 10.1016/j.mehy.2013.05.034. Epub 2013 Jun 19. https://www.ncbi.nlm.nih.gov/pubmed/23790471

Brain dysfunction as one cause of CFS symptoms including difficulty with attention and concentration

Abstract:

We have been able to reduce substantially patient pool heterogeneity by identifying phenotypic markers that allow the researcher to stratify chronic fatigue syndrome (CFS) patients into subgroups. To date, we have shown that stratifying based on the presence or absence of comorbid psychiatric diagnosis leads to a group with evidence of neurological dysfunction across a number of spheres.

We have also found that stratifying based on the presence or absence of comorbid fibromyalgia leads to information that would not have been found on analyzing the entire, unstratified patient group. Objective evidence of orthostatic intolerance (OI) may be another important variable for stratification and may define a group with episodic cerebral hypoxia leading to symptoms.

We hope that this review will encourage other researchers to collect data on discrete phenotypes in CFS to allow this work to continue more broadly. Finding subgroups of CFS suggests different underlying pathophysiological processes responsible for the symptoms seen. Understanding those processes is the first step toward developing discrete treatments for each.

Source: Natelson BH. Brain dysfunction as one cause of CFS symptoms including difficulty with attention and concentration. Front Physiol. 2013 May 20;4:109. doi: 10.3389/fphys.2013.00109. ECollection 2013. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3657628/ (Full article)

Neuromuscular strain as a contributor to cognitive and other symptoms in chronic fatigue syndrome: hypothesis and conceptual model

Abstract:

Individuals with chronic fatigue syndrome (CFS) have heightened sensitivity and increased symptoms following various physiologic challenges, such as orthostatic stress, physical exercise, and cognitive challenges. Similar heightened sensitivity to the same stressors in fibromyalgia (FM) has led investigators to propose that these findings reflect a state of central sensitivity.

A large body of evidence supports the concept of central sensitivity in FM. A more modest literature provides partial support for this model in CFS, particularly with regard to pain. Nonetheless, fatigue and cognitive dysfunction have not been explained by the central sensitivity data thus far.

Peripheral factors have attracted attention recently as contributors to central sensitivity. Work by Brieg, Sunderland, and others has emphasized the ability of the nervous system to undergo accommodative changes in length in response to the range of limb and trunk movements carried out during daily activity. If that ability to elongate is impaired-due to movement restrictions in tissues adjacent to nerves, or due to swelling or adhesions within the nerve itself-the result is an increase in mechanical tension within the nerve. This adverse neural tension, also termed neurodynamic dysfunction, is thought to contribute to pain and other symptoms through a variety of mechanisms. These include mechanical sensitization and altered nociceptive signaling, altered proprioception, adverse patterns of muscle recruitment and force of muscle contraction, reduced intra-neural blood flow, and release of inflammatory neuropeptides. Because it is not possible to differentiate completely between adverse neural tension and strain in muscles, fascia, and other soft tissues, we use the more general term “neuromuscular strain.”

In our clinical work, we have found that neuromuscular restrictions are common in CFS, and that many symptoms of CFS can be reproduced by selectively adding neuromuscular strain during the examination. In this paper we submit that neuromuscular strain is a previously unappreciated peripheral source of sensitizing input to the nervous system, and that it contributes to the pathogenesis of CFS symptoms, including cognitive dysfunction.

Source: Rowe PC, Fontaine KR, Violand RL. Neuromuscular strain as a contributor to cognitive and other symptoms in chronic fatigue syndrome: hypothesis and conceptual model. Front Physiol. 2013 May 16;4:115. doi: 10.3389/fphys.2013.00115. eCollection 2013. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3655286/ (Full article)

Chronic Fatigue Syndrome (CFS) and Cancer Related Fatigue (CRF): two “fatigue” syndromes with overlapping symptoms and possibly related aetiologies

Abstract:

In July 2010, at the Muscle Fatigue Meeting, I presented an overview of Chronic Fatigue Syndrome and Cancer Related Fatigue, emphasizing a critical interpretation of the potential association between Chronic Fatigue Syndrome and Cancer Related Fatigue and a newly discovered retrovirus: Xenotropic Murine Related Virus. Since this association was hotly debated at that time, I suggested at the Meeting that it was wrong and most likely due to the identification of the wrong virus culprit.

Today, 20 months after the Meeting, the first part of our prediction has turned out to be correct, as Xenotropic Murine Related Virus was shown to be a laboratory-created artefact. Still, the potential association of fatigue-syndromes with an infection (most likely viral) is sustained by a plethora of evidence and this overview will initially summarize data suggesting prior viral infection(s). The principal hypothesized mechanisms for both peripheral and central Chronic Fatigue Syndrome/Cancer Related Fatigue will be then summarized, also indicating plausible associations and triggering factors.

All evidence accrued so far suggests that further research work should be performed in this interesting area and in order to identify an infectious agent for Chronic Fatigue Syndrome/Cancer Related Fatigue. One candidate RNA virus, Micro-Foci inducing Virus, will be described in this overview.

Source: Rovigatti U. Chronic Fatigue Syndrome (CFS) and Cancer Related Fatigue (CRF): two “fatigue” syndromes with overlapping symptoms and possibly related aetiologies. Neuromuscul Disord. 2012 Dec;22 Suppl 3:S235-41. doi: 10.1016/j.nmd.2012.10.018. https://www.ncbi.nlm.nih.gov/pubmed/23182646

Increased nuclear factor-κB and loss of p53 are key mechanisms in Myalgic Encephalomyelitis/chronic fatigue syndrome (ME/CFS)

Abstract:

Fukuda’s criteria are adequate to make a distinction between Myalgic Encephalomyelitis/chronic fatigue syndrome (ME/CFS) and chronic fatigue (CF), but ME/CFS patients should be subdivided into those with (termed ME) and without (termed CFS) post exertional malaise [Maes et al. 2012].

ME/CFS is considered to be a neuro-immune disease. ME/CFS is characterized by activated immuno-inflammatory pathways, including increased levels of pro-inflammatory cytokines, nuclear factor κB (NF-κB) and aberrations in mitochondrial functions, including lowered ATP. These processes may explain typical symptoms of ME/CFS, e.g. fatigue, malaise, hyperalgesia, and neurologic and autonomic symptoms.

Here we hypothesize that increased NF-κB together with a loss of p53 are key phenomena in ME/CFS that further explain ME/CFS symptoms, such as fatigue and neurocognitive dysfunction, and explain ME symptoms, such as post-exertional malaise following mental and physical activities. Inactivation of p53 impairs aerobic mitochondrial functions and causes greater dependence on anaerobic glycolysis, elevates lactate levels, reduces mitochondrial density in skeletal muscle and reduces endurance during physical exercise. Lowered p53 and increased NF-κB are associated with elevated reactive oxygen species. Increased NF-κB induces the production of pro-inflammatory cytokines, which increase glycolysis and further compromise mitochondrial functions.

All these factors together may contribute to mitochondrial exhaustion and indicate that the demand for extra ATP upon the commencement of increased activity cannot be met. In conditions of chronic inflammation and oxidative stress, high NF-κB and low p53 may conspire to promote neuron and glial cell survival at a price of severely compromised metabolic brain function. Future research should examine p53 signaling in ME/CFS.

Source: Morris G, Maes M. Increased nuclear factor-κB and loss of p53 are key mechanisms in Myalgic Encephalomyelitis/chronic fatigue syndrome (ME/CFS). Med Hypotheses. 2012 Nov;79(5):607-13. doi: 10.1016/j.mehy.2012.07.034. Epub 2012 Aug 27. https://www.ncbi.nlm.nih.gov/pubmed/22951418

Loss of stress response as a consequence of viral infection: implications for disease and therapy

Abstract:

Herein, we propose that viral infection can induce a deficient cell stress response and thereby impairs stress tolerance and makes tissues vulnerable to damage. Having a valid paradigm to address the pathological impacts of viral infections could lead to effective new therapies for diseases that have previously been unresponsive to intervention. Host response to viral infections can also lead to autoimmune diseases like type 1 diabetes. In the case of Newcastle disease virus, the effects of viral infection on heat shock proteins may be leveraged as a therapy for cancer. Finally, the search for a specific virus being responsible for a condition like chronic fatigue syndrome may not be worthwhile if the disease is simply a nonspecific response to viral infection.

Source: Hooper PL, Hightower LE, Hooper PL. Loss of stress response as a consequence of viral infection: implications for disease and therapy. Cell Stress Chaperones. 2012 Nov;17(6):647-55. doi: 10.1007/s12192-012-0352-4. Epub 2012 Jul 14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3468676/ (Full article)

Could cadmium be responsible for some of the neurological signs and symptoms of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Abstract:

According to the World Health Organization, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a neurological disease characterized by widespread inflammation and multi-systemic neuropathology. Aetiology and pathogenesis are unknown, and several agents have been proposed as causative agents or as factors perpetuating the syndrome. Exposure to heavy metals, with particular reference to mercury and gold in dental amalgams, has been considered among the triggers of ME/CFS.

Here we hypothesize that cadmium, a widespread occupational and environmental heavy metal pollutant, might be associated with some of the neurological findings described in ME/CFS. In fact, ME/CFS patients show a decrease of the volume of the gray matter in turn associated with objective reduction of physical activity. Cadmium induces neuronal death in cortical neurons through a combined mechanism of apoptosis and necrosis and it could then be hypothesized that cadmium-induced neuronal cell death is responsible for some of the effects of cadmium on the central nervous system, i.e. a decrease in attention level and memory in exposed humans as well as to a diminished ability for training and learning in rats, that are symptoms typical of ME/CFS. This hypothesis can be tested by measuring cadmium exposure in a cohort of ME/CFS patients compared with matched healthy controls, and by measuring gray matter volume in un-exposed healthy controls, exposed non-ME/CFS subjects, un-exposed ME/CFS patients and exposed ME/CFS patients.

In addition, we hypothesize that cadmium exposure could be associated with reduced cerebral blood flow in ME/CFS patients because of the disruptive effects of cadmium on angiogenesis. In fact, cadmium inhibits angiogenesis and low global cerebral flow is associated with abnormal brain neuroimaging results and brain dysfunction in the form of reduced cognitive testing scores in ME/CFS patients. This hypothesis can be tested by measuring cerebral cortex blood flow in un-exposed healthy controls, exposed non-ME/CFS subjects, un-exposed ME/CFS patients and exposed ME/CFS patients.

If our hypothesis is demonstrated correct, the consequences could affect prevention, early diagnosis, and treatment of ME/CFS. Implications in early diagnosis could entail the evaluation of symptoms typical of ME/CFS in cadmium-exposed subjects as well as the search for signs of exposure to cadmium in subjects diagnosed with ME/CFS. Nutritional supplementation of magnesium and zinc could then be considered, since these elements have been proposed in the prophylaxis and therapy of cadmium exposure, and magnesium was demonstrated effective on ME/CFS patients’ symptom profiles.

Source: Pacini S, Fiore MG, Magherini S, Morucci G, Branca JJ, Gulisano M, Ruggiero M. Could cadmium be responsible for some of the neurological signs and symptoms of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Med Hypotheses. 2012 Sep;79(3):403-7. doi: 10.1016/j.mehy.2012.06.007. Epub 2012 Jul 12. https://www.ncbi.nlm.nih.gov/pubmed/22795611

Biological underpinnings of the commonalities in depression, somatization, and Chronic Fatigue Syndrome

Abstract:

BACKGROUND: Somatization is a multisomatoform disorder characterized by medically unexplained, functional or psychosomatic symptoms. Similar somatic symptoms are key components of depression and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).

METHODS: This paper reviews the evidence that such symptoms are organically based. We use the term “physio-somatic” to describe these symptoms.

RESULTS: Inflammation, cell-mediated immune (CMI) activation and alterations in the tryptophan catabolite (TRYCAT) pathway are associated with the physio-somatic symptoms of depression, ME/CFS and/or somatization. Proinflammatory cytokines, decreased tryptophan and aberrations in TRYCATs may cause physio-somatic symptoms, such as fatigue, autonomic symptoms, hyperalgesia and somatic presentations.

CONCLUSIONS: The data suggest co-ordinated and interacting biological pathways driving the occurrence of physio-somatic symptoms across these three disorders, giving a biologically validated “pathway phenotype”. These data have far-reaching implications for DSM-IV diagnostic conceptualizations of somatization (and ME/CFS) suggesting the presence of an emerging organic explanation. Future research should focus on the role of immune regulation, and co-ordination, of neuronal activity and, through larger data sets, ultimately creating new, biologically validated classification rules. These data have implications for the development of novel therapies utilizing these insights, buttressing the role of psychotherapy in psychosomatic presentations.

Source: Anderson G, Maes M, Berk M. Biological underpinnings of the commonalities in depression, somatization, and Chronic Fatigue Syndrome. Med Hypotheses. 2012 Jun;78(6):752-6. doi: 10.1016/j.mehy.2012.02.023. Epub 2012 Mar 23. https://www.ncbi.nlm.nih.gov/pubmed/22445460