Gut Inflammation in Chronic Fatigue Syndrome

Shaheen E Lakhan; Annette Kirchgessner

Disclosures

Nutr Metab. 2010;7(1) 

In This Article

Gut Microbiota

The human GI tract contains a complex and delicately balanced ecosystem of more than 17 bacterial families encompassing 400 to 500 different microbial species. The main genera of these commensal bacteria are: Lactobacillus, Bifidobacteria, Bacteroides, Clostridia, Fusobacteria, Eubacteria, Peptococcus, Streptococcus, Escherichia and Veillonella. They regulate a myriad of host processes and provide several nutrients to their host and their symbionts within the microbial community. In healthy individuals, these relationships are thought to occur in equilibrium; however, the normal balance of gut microbiota can be altered by a number of factors and this is turn can contribute to certain functional disorders.[39] For example, the number of different commensal bacteria is altered in inflammatory bowel disease (IBD). IBD patients have increased bacteroides, adherent or invasive Escherichia coli, and enterococci, and reduced Bifidobacteria and Lactobacillus species.[40]

The composition of the gut microbiota can be altered by various factors including stress. Psychological stress alters the gut microbiota towards decreased numbers of Bifidobacteria and Lactobacilli.[41]Bifidobacteria are a group of bacteria that have been shown to reduce intestinal LPS levels and LPS-induced activation of nuclear factor-kappa B (NF-κB) in mice.[42] Inhibition of LPS-induced NF-κB activation was accompanied by a dose-dependent decrease of pro-inflammatory cytokines and cyclooxygenase 2.[42] Stress in neonatal Rhesus monkeys was reported to suppress the numbers of Lactobacilli in the fecal flora in association with increased susceptibility for opportunistic infections.[43] Restraint conditions, acoustic stress and food deprivation have all been shown to negatively alter gut microbiota in various animal studies.[44,45] Interestingly, stress (e.g., psychological, physical exhaustion) is a well-established trigger factor for CFS.[12]

Investigations have documented that there are marked alterations in the gut microbiota of CFS patients, with lower levels of Bifidobacteria and higher levels of aerobic bacteria.[18] Dr. Henry Butt and colleagues from the University of Newcastle, Australia have been examining the intestinal microbiota of CFS patients for a number of years. In 1998, they presented the first evidence of altered fecal microbiota in CFS patients compared to normal, healthy controls.[46] The mean distribution of the Gram negative Escherichia coli as a percentage of the total aerobic flora of control subjects was 92.3% compared to 49% in CFS patients. Among aerobes, the D-lactic acid producing Enterococcus and Streptococcus species were strongly over-represented in CFS patients. These findings were recently confirmed.[22] Among anaerobic bacteria, Prevotella was the most commonly overgrown bacteria. Moreover, it was shown that the higher the aerobic enterococcal count, the more severe the neurological and cognitive deficits including nervousness, memory loss, forgetfulness and confusion.[46] Consequently, high plasma LPS levels in CFS could result from an increased production of endotoxin upon changes in the gut microbiota.[47]

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