Category: Etiology

Chronic fatigue syndrome: intracellular immune deregulations as a possible etiology for abnormal exercise response

Abstract:

The exacerbation of symptoms after exercise differentiates Chronic fatigue syndrome (CFS) from several other fatigue-associated disorders. Research data point to an abnormal response to exercise in patients with CFS compared to healthy sedentary controls, and to an increasing amount of evidence pointing to severe intracellular immune deregulations in CFS patients. This manuscript explores the hypothetical interactions between these two separately reported observations.

First, it is explained that the deregulation of the 2-5A synthetase/RNase L pathway may be related to a channelopathy, capable of initiating both intracellular hypomagnesaemia in skeletal muscles and transient hypoglycemia. This might explain muscle weakness and the reduction of maximal oxygen uptake, as typically seen in CFS patients.

Second, the activation of the protein kinase R enzyme, a characteristic feature in at least subsets of CFS patients, might account for the observed excessive nitric oxide (NO) production in patients with CFS. Elevated NO is known to induce vasodilation, which may limit CFS patients to increase blood flow during exercise, and may even cause and enhanced postexercise hypotension.

Finally, it is explored how several types of infections, frequently identified in CFS patients, fit into these hypothetical pathophysiological interactions.

 

Source: Nijs J, De Meirleir K, Meeus M, McGregor NR, Englebienne P. Chronic fatigue syndrome: intracellular immune deregulations as a possible etiology for abnormal exercise response. Med Hypotheses. 2004;62(5):759-65. http://www.ncbi.nlm.nih.gov/pubmed/15082102

 

Acetylcholine mediated vasodilatation in the microcirculation of patients with chronic fatigue syndrome

Abstract:

The aetiology of chronic fatigue syndrome (CFS) remains controversial and a number of hypotheses have been put forward to explain it. Research into the condition is hindered by the considerable heterogeneity seen across patients but several reports have highlighted disturbances to cholinergic mechanisms in terms of central nervous system activity, neuromuscular function and autoantibodies to muscarinic cholinergic receptors. This paper examines an altogether separate function for acetylcholine and that is its role as an important and generalized vasodilator.

Most diseases are accompanied by a blunted response to acetylcholine but the opposite is true for CFS. Such sensitivity is normally associated with physical training so the finding in CFS is anomalous and may well be relevant to vascular symptoms that characterise many patients. There are several mechanisms that might lead to ACh endothelial sensitivity in CFS patients and various experiments have been designed to unravel the enigma. These are reported here.

 

Source: Spence VA, Khan F, Kennedy G, Abbot NC, Belch JJ. Acetylcholine mediated vasodilatation in the microcirculation of patients with chronic fatigue syndrome. Prostaglandins Leukot Essent Fatty Acids. 2004 Apr;70(4):403-7. http://www.ncbi.nlm.nih.gov/pubmed/15041034

 

Peripheral cholinergic function in humans with chronic fatigue syndrome, Gulf War syndrome and with illness following organophosphate exposure

Abstract:

In the present study, we have investigated whether the peripheral cholinergic abnormalities that we have reported previously [Spence, Khan and Belch (2000) Am. J. Med. 108, 736-739] in patients with chronic fatigue syndrome (CFS) are also present in those with Gulf War syndrome (GWS) and agricultural workers exposed to organophosphate pesticides, where cholinesterase inhibition is specifically implicated. We also looked at whether these abnormalities might be due to a reduction in the activity of cholinesterase expressed on the vascular endothelium.

We used laser Doppler imaging to measure the forearm skin blood flow responses to iontophoresis of acetylcholine and of methacholine (which is resistant to breakdown by cholinesterase) in patients with CFS, GWS and those with a history of ill health after definite organophosphate exposure, as well as in matched healthy controls.

The response to acetylcholine was significantly higher in patients with CFS than in controls ( P =0.029, repeated-measures ANOVA), but was normal in those with GWS and those exposed to organophosphates. The methacholine response was higher than the acetylcholine response in all patient groups except for those with CFS, where there was no difference between the responses. Although there are many clinical similarities between these three illnesses, our results indicate peripheral cholinergic abnormalities in the vascular endothelium of only patients with CFS, suggesting that this syndrome has a different aetiology, which might involve inhibition of vascular cholinesterase.

 

Source: Khan F, Kennedy G, Spence VA, Newton DJ, Belch JJ. Peripheral cholinergic function in humans with chronic fatigue syndrome, Gulf War syndrome and with illness following organophosphate exposure. Clin Sci (Lond). 2004 Feb;106(2):183-9. http://www.ncbi.nlm.nih.gov/pubmed/14503920

 

The investigation of chronic fatigue syndrome: a case-study of the limitations of inductive inferences and non-falsifiable hypotheses in medical research

Abstract:

Karl Popper’s argument that deductive logic and falsifiable hypotheses are necessary for the growth of scientific knowledge has been controversial. One approach to assess the relevance of his ideas to medical science has been to evaluate examples of successful research. Another approach is to analyze an unsuccessful investigation. The inconclusive search for a unique ‘chronic fatigue syndrome’ offers a well-documented case-study for this analysis. Over the past 130 years, numerous studies have provided clinical and epidemiological data, which have supported competing hypotheses about the etiology of chronic fatigue. However, few hypotheses have been refuted because it has not been possible to establish objective standards of inquiry for a subjective symptom like fatigue. As a result, intensive research efforts have not converged on correct explanations by eliminating erroneous ideas. This unsuccessful investigation illustrates how non-falsifiable hypotheses are insufficient to advance medical knowledge, even when there is an abundance of empirical data.

 

Source: Hyams KC. The investigation of chronic fatigue syndrome: a case-study of the limitations of inductive inferences and non-falsifiable hypotheses in medical research. Med Hypotheses. 2003 May;60(5):760-6. http://www.ncbi.nlm.nih.gov/pubmed/12710915

 

Diverse etiologies for chronic fatigue syndrome

Comment on: Markers of viral infection in monozygotic twins discordant for chronic fatigue syndrome. [Clin Infect Dis. 2002]

 

SIR—Koelle et al.  recently studied 22 pairs of identical twins discordant for chronic fatigue syndrome and concluded that there was no major contribution for viral infections in the perpetuation of chronic fatigue syndrome (CFS). The authors should be commended for their methodology and the use of well-matched control subjects. However, the study raised several issues.

First, similar to previous studies, the approach of Koelle et al.  was to look for statistical differences among the well-matched pairs with respect to the presence of viral antibodies and, more specifically, the presence of DNA of the viruses studied. Although these viruses were no more prevalent among the patients with CFS than among their healthy twins, one cannot conclude that these viruses are not the cause of CFS in a small subset of patients. CFS has been described in a small number of patients who had had well-documented acute Epstein-Barr virus (EBV), cytomegalovirus (CMV), and parvovirus B19 infections, and many of the patients responded to specific antiviral therapy. Of the first 200 patients with CFS who we evaluated for viral etiologies , only ∼10% had etiologies that were attributed to the viruses studied by Koelle et al. Chlamydia pneumoniae infection, an uncommon, although treatable, cause of CFS, was also dismissed in a previous, smaller study .

You can read the rest of this comment here: http://cid.oxfordjournals.org/content/36/5/671.long

 

Source: Chia JK, Chia A. Diverse etiologies for chronic fatigue syndrome. Clin Infect Dis. 2003 Mar 1;36(5):671-2; author reply 672-3. http://cid.oxfordjournals.org/content/36/5/671.long (Full article)

 

Chronic fatigue syndrome in patients with macrophagic myofasciitis

Macrophagic myofasciitis (MMF), a condition first reported in France in 1998, is defined by the presence of a stereotyped and immunologically active lesion at deltoid muscle biopsy . It was recently demonstrated that this lesion is an indicator of long-term persistence of the immunologic adjuvant aluminum hydroxide within the cytoplasm of macrophages at the site of previous intramuscular (IM) injection. MMF is typically detected in patients with diffuse arthromyalgias that have appeared subsequent to aluminum hydroxide administration in the absence of a clearly defined anatomic substratum. Patients also report unexplained chronic fatigue. These manifestations are reminiscent of the so-called chronic fatigue syndrome (CFS), a poorly understood condition manifesting as disabling fatigue, musculoskeletal pain, sleep disturbance, impaired concentration, and headaches. The present study was conducted to determine the proportion of MMF patients fulfilling international criteria for CFS.

You can read the rest of this article here: http://onlinelibrary.wiley.com/doi/10.1002/art.10740/full

 

Source: Authier FJ, Sauvat S, Champey J, Drogou I, Coquet M, Gherardi RK. Chronic fatigue syndrome in patients with macrophagic myofasciitis. Arthritis Rheum. 2003 Feb;48(2):569-70. http://onlinelibrary.wiley.com/doi/10.1002/art.10740/full (Full article)

 

Unconscious amygdalar fear conditioning in a subset of chronic fatigue syndrome patients

Abstract:

Here, a novel hypothesis for chronic fatigue syndrome (CFS) is proposed. CFS may be a neurophysiological disorder focussing on the amygdala. During a ‘traumatic’ neurological event often involving acute psychological stress combined with a viral infection or other chemical or physiological stressor, a conditioned network or ‘cell assembly’ may be created in the amygdala. The unconscious amygdala may become conditioned to be chronically sensitised to negative symptoms arising from the body. Negative signals from the viscera or physiological, chemical and dietary stressors, become conditioned stimuli and the conditioned response is a chronic sympathetic outpouring from the amygdala via various brain pathways including the hypothalamus.

This cell assembly then produces the CFS vicious circle, where an unconscious negative reaction to symptoms causes immune reactivation/dysfunction, chronic sympathetic stimulation, leading to sympathetic dysfunction, mental and physical exhaustion, and a host of other distressing symptoms and secondary complications. And these are exactly the symptoms that the amygdala and associated limbic structures are trained to monitor and respond to, perpetuating a vicious circle. Recovery from CFS may involve projections from the medial prefrontal cortex to the amygdala, to control the amygdala’s expressions. I shall firstly discuss predisposing, precipitating, and perpetuating factors involved in the possible etiology of chronic fatigue syndrome (CFS), followed by the patient’s experience of the illness. Finally, I shall look at a suggested explanation for the symptoms of CFS.

Copyright 2002 Elsevier Science Ltd.

 

Source: Gupta A. Unconscious amygdalar fear conditioning in a subset of chronic fatigue syndrome patients. Med Hypotheses. 2002 Dec;59(6):727-35. http://www.ncbi.nlm.nih.gov/pubmed/12445517

A status report on chronic fatigue syndrome

Abstract:

Medical history has shown that clinical disease entities or syndromes are composed of many subgroups–each with its own cause and pathogenesis. Although we cannot be sure, we expect the same outcome for chronic fatigue syndrome (CFS), a medically unexplained condition characterized by disabling fatigue accompanied by infectious, rheumatological, and neuropsychiatric symptoms. Although the ailment clearly can occur after severe infection, no convincing data exist to support an infectious (or immunologic) process in disease maintenance. Instead, data point to several possible pathophysiological processes: a covert encephalopathy, impaired physiological capability to respond to physical and mental stressors, and psychological factors related to concerns about effort exacerbating symptoms. Each of these is under intense investigation. In addition, some data do exist to indicate that environmental agents also can elicit a state of chronic fatigue. We expect data to accumulate to support the belief that CFS has multiple causes.

 

Source: Natelson BH, Lange G. A status report on chronic fatigue syndrome. Environ Health Perspect. 2002 Aug;110 Suppl 4:673-7. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1241224/ (Full article)

 

IgM serum antibodies to human cytomegalovirus nonstructural gene products p52 and CM2(UL44 and UL57) are uniquely present in a subset of patients with chronic fatigue syndrome

Abstract:

Human cytomegalovirus (HCMV) IgM serum antibodies to two nonstructural gene products UL44 and UL57 (p52 and CM2) were assayed in patients with the diagnosis of the chronic fatigue syndrome (CFS) according to criteria established by the US Centers for Disease Control and Prevention. A subset of 16 CFS patients demonstrated HCMV IgG, but no HCMV IgM serum antibodies to conformational structural HCMV antigens (designated, V). By convention, these findings are interpreted to indicate only a remote HCMV infection.

However, HCMV IgM p52 and CM2 antibodies were uniquely present in these 16 CFS patients. Other CFS patients with similar HCMV (V) IgG antibodies (18 patients), non-fatigued HCMV (V) IgG-positive control patients (18 patients), random HCMV (V) IgG-positive control patients from a clinical laboratory (26 patients), and non-fatigued HCMV (V) IgG-negative control patients (15 patients) did not have HCMV, IgM p52 or CM2 serum antibodies (p < 0.05). Control HCMV (V) IgG-positive patients had no serum IgM HCMV (V) antibodies to conventional structural HCMV (V) antigen. Thus, 77 various control patients did not contain IgM p52 or CM2 serum antibodies. The presence of IgM p52 and/or CM2 HCMV serum antibodies in this subset of CSF-specific patients may detect incomplete HCMV multiplication in which a part of the HCMV protein-coding content of the HCMV genome is processed, but remains unassembled.

These findings suggest that the presence of HCMV IgM p52 and CM2 serum antibodies may be a specific diagnostic test for the diagnosis of a subset of CFS patients. Further, these data suggest an etiologic relationship for HCMV infection in this group of CFS patients

 

Source: Lerner AM, Beqaj SH, Deeter RG, Fitzgerald JT. IgM serum antibodies to human cytomegalovirus nonstructural gene products p52 and CM2(UL44 and UL57) are uniquely present in a subset of patients with chronic fatigue syndrome. In Vivo. 2002 May-Jun;16(3):153-9. http://www.ncbi.nlm.nih.gov/pubmed/12182109

 

Elevated nitric oxide/peroxynitrite mechanism for the common etiology of multiple chemical sensitivity,chronic fatigue syndrome, and posttraumatic stress disorder

Abstract:

Various types of evidence implicate nitric oxide and an oxidant, possibly peroxynitrite, in MCS and chemical intolerance (CI). The positive feedback loops proposed earlier for CFS may explain the chronic nature of MCS (CI) as well as several of its other reported properties. These observations raise the possibility that this proposed elevated nitric oxide/peroxynitrite mechanism may be the mechanism of a new disease paradigm, answering the question raised by Miller earlier: “Are we on the threshold of a new theory of disease?”

 

Source: Pall ML, Satterlee JD. Elevated nitric oxide/peroxynitrite mechanism for the common etiology of multiple chemical sensitivity,chronic fatigue syndrome, and posttraumatic stress disorder.  Ann N Y Acad Sci. 2001 Mar;933:323-9. http://www.ncbi.nlm.nih.gov/pubmed/12000033