Decreased Expression of TRPM3 and mAChRM3 in the Small Intestine in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis

Introduction: Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) is often associated with gastrointestinal disturbance and inflammatory markers; however, there have been no histological studies performed in the small intestine from CFS/ME patients. The aim of this investigation was to assess the expression of certain inflammatory markers and inflammatory receptors, namely transient receptor potential melastin 3 (TRPM3) ion channels and muscarinic acetylcholine M3 (mAChRM3) receptors, in small intestinal tissues in a case controlled study comprising a CFS/ME patient and a healthy non-fatigued control. Method: Immunohistochemistry was performed on a small intestinal biopsy from a CFS/ME patient (age = 50; female) with self-reported symptoms of gastrointestinal disturbance and a non-fatigued control (NFC), (age = 28; female). Semi-quantitative analysis of expression was undertaken for interferon-gamma (IFNy), interleukin-1 alpha (IL-1α), tumour necrosis factor-alpha (TNFα), TRPM3 ion channels and mAChRM3 acetylcholine receptors. Results: There was significantly decreased expression of TRPM3 in the CFS/ME patient (35% ± 9%) and a significant decrease in mAChRM3 in the CFS/ME patient (54% ± 9%). There was no difference in IL-1α between CFS/ME patient and NFC, however; there was an increase in IFNy (13% ± 6%) in the CFS/ME patient compared to NFC. There was a difference observed in TNFα in CFS/ME compared to NFC. Conclusion: Differences were noted in the expression of specific TRP ion channels and cholinergic receptors in CFS/ME compared with NFC, with CFS/ME demonstrating decreased TRPM3 and mAChRM3. Further, IFNy was increased, and TNFα decreased, in the small intestine of the CFS/ME patient with reported gastrointestinal disturbance.