Inflammation: why and how much? Dr. Nicola Keay
Inflammation: optimal or overreaction
Systemic autoimmune disease is a chronic overreaction of the inflammatory system. Exercise training is structured to provoke the optimal level of inflammation for adaptation to facilitate sport performance. This blog describes some of the recent significant advances in the understanding of the underlying mechanisms of inflammation and its interactions with the endocrine system, immunity and the microbiome, in relation to autoimmune disease. Applying this knowledge to the adaptive inflammatory effects of training in sport represents a potentially hugely beneficial area of future research.
The ubiquitous microbiome
There has been much discussion on the key role of the microbiome, eloquently described by Professor Tim Spector, Professor of Genetic Epidemiology, King’s College, London at recent conferences at the Royal Society of Medicine and The Royal College of Physicians. The microbiome is the DNA of all the microbes in our body. The diversity of the microbiota community in the gut wall of the colon appears to have the most profound effects in terms of disease prediction and indeed a better indicator of developing autoimmune conditions (such as inflammatory bowel disease and rheumatoid arthritis) and metabolic conditions (such as obesity and diabetes mellitus) than our own DNA. So how does the diversity of the gut microbiome have such a profound impact?
It appears that in order to promote diversity of the gut micobiota, prebiotics such as inulin found in fibrous foods should be ingested and then “fertilised” with probiotics found in fermented foods. Enhancing the diversity of the gut microbiome supports the production of short-chain fatty acids which have far reaching influences on epigenetic and immune regulation, the brain, gut hormones and the liver. Furthermore, the diurnal rhythmic movement of the gut microbiota have been shown to regulate host circadian epigenetic, transcriptional and metabolite oscillations which impacts host physiology and disease susceptibility.
In inflammatory conditions such as autoimmune disease, a decrease in the diversity of “good” microbiota has been described. Furthermore, if a decrease in beneficial microbiota is the primary event, then this can lead to an increase in the likelihood of developing autoimmune disease. What is the mechanism of this dynamic interaction between the microbiome and immunity?
Immunity and inflammation
In recent research, the protein receptor marker of microbiota in the gut has been shown to modulate intestinal serotonin transporter activity. Serotonin (5-hydroxytryptamine 5-HT) has shown to be an essential intestinal physiological neuromodulator that is also involved in inflammatory bowel disease. In addition, an increase in inflammatory cytokines such as interleukin 6 and tumour necrosis factor alpha, is know to be associated with low levels of cerebral serotonin and dopamine. The causal link between disrupted immune function and increased inflammation, as in autoimmune disease, is an unfavourable microbiome. Development of autoimmune disease is often multifactorial, for example, a change in the microbiome might trigger gene expression with adverse effects. Indeed gene expression (independent of sex steroids) has been shown to account for increased prevalence of autoimmune disease in women.
Depression of serotonin levels
Low levels of the neurotransmitter serotonin are know to be linked to depression. Hence prescription of selective serotonin uptake inhibitors to those suffering with depression. However recent research has now revealed a dynamic interaction between peripheral and cerebral effects of the microbiome on immunity and mood, mediated via the circadian release of key hormones such as serotonin. Serotonin is synthesised from precursor tryptophan in the gastrointestinal tract and central nervous system. Low mood in autoimmune disease could be due to psychological factors: knowing that this is a chronic condition with reduced life expectancy. Reduced serotonin, may be a further biochemical reason. Potentially lack of sleep due to pain in autoimmune disease would also suppress serotonin levels.
Applications for microbiome/immunity/inflammation interactions
How will these findings from recent research help in optimising inflammatory mediated adaptations to exercise training and support the understanding and treatment of autoimmune disease? It has been suggested that serotonin could be a treatment for rheumatoid arthritis, as 5HT appears to have a peripheral immuno-regulatoty role in the pathophysiology of this autoimmune disease. Optimising the microbiome, with prebiotics and probiotics, may improve disease activity and improve response to treatment with biologics.
Is the nature of an autoimmune disease such as rheumatoid arthritis (RA) changing? Deformed hands with swollen joints were a perennial favourite for medical examinations. However as described recently at a conference at Royal College of Physicians, although joint destruction is still a feature of RA, this seems to be accompanied by less joint swelling and involvement of greater range of joints. Are the triggers changing rather than a change in the nature of disease? How do nutrition and medication impact the microbiome?
For athletes, apart from periodising energy requirements and micronutrients to support training, encouraging a diverse microbiome will potentially support adaptive changes to training.
Balance of recovery and adaptation for sports performance. Dr Nicky Keay, 27 Jan 2017 British Association of Sports and Exercise Medicine
Sleep for health and sports performance. Dr N. Keay 7 Feb, 17 British Journal of Sport and Exercise Medicine
Conference Royal Society of Medicine. “Food: the good, the bad and the ugly” 1/2/17
“Food, microbes and health” Professor Tim Spector, Professor of Genetic Epidemiology, King’s College, London
“Nutrition and the gut: food as trigger for disease; food as medicine” Dr Charlie Lees, Chair Scottish Society of Gastroenterology IBD Interest Group. European Crohn’s and Colitis Organisation Committe
“Nutrition and its effect on the immune system” Dr Liam O’Mahony, Head of Molecular Immunology, swiss Institute of Allergy and Asthma Research
Advanced Medicine Conference. Royal College of Physicians 13-16 February 2017
” The gut microbiome clinical and physiological tolerance” Professor Tim Spector, Professor of Genetic Epidemiology, King’s College, London
“Rheumatoid arthritis-ensuring everyone gets the best treatment” Dr Neil Snowden
Microbiota Diurnal Rhythmicity Programs Host Transcriptome Oscillations Cell Volume 167, Issue 6, p1495–1510.e12, 1 December 2016
Intestinal Serotonin Transporter Inhibition by Toll-Like Receptor 2 Activation. A Feedback Modulation. Eva Latorre , Elena Layunta, Laura Grasa, Marta Castro, Julián Pardo, Fernando Gomollón, Ana I. Alcalde †, José E. Mesonero. Published: December 29, 2016
A gene network regulated by the transcription factor VGLL3 as a promoter of sex-biased autoimmune diseases. Yun Liang, Lam C Tsoi, Xianying Xing, Maria A Beamer, William R Swindell, Mrinal K Sarkar, Celine C Berthier, Philip E Stuart, Paul W Harms, Rajan P Nair, James T Elder, John J Voorhees, J Michelle Kahlenberg & Johann E Gudjonsson
Nature Immunology 18, 152–160 (2017)
Serotonin Is Involved in Autoimmune Arthritis through Th17 Immunity and Bone Resorption. Yasmine Chabbi-Achengli, Tereza Coman, Corinne Collet, Jacques Callebert, Michelangelo Corcelli, Hilène Lin, Rachel Rignault, Michel Dy, Marie-Christine de Vernejoul, Francine Côté. The American Journal of Pathology. April 2016 Volume 186, Issue 4, Pages 927–937