The microbiome and inflammatory bowel disease (IBD)
Crohn’s disease and ulcerative colitis, the two main forms of inflammatory bowel disease (IBD), can be really tough conditions to live with at times. They cause an inflamed gut and symptoms include severe pain, diarrhoea and fatigue.
Fortunately, although we do not yet know the exact cause of IBD, hope for new treatments is offered by a recent explosion of research into the microbiome, the teaming mass of microbes that inhabit our gut.
The microbiome operates as a complex and delicate ecosystem. However, for people with IBD it tends to be out of balance in a state known as ‘dysbiosis’. For example, of the 20-plus ‘families’ of bacteria within our microbiome, IBD patients often have fewer of the group known as Firmicutes but more Protobacteria. They also have lower bacterial diversity
Research suggests that IBD is probably the result of an unusual reaction by the immune system to dysbiosis in genetically-predisposed individuals. Around 200 IBD susceptibility genes have been identified so far.
But genes alone cannot explain the onset of IBD. It was once a very rare condition but incidence rocketed in the latter half of the twentieth century in Europe and North America, with cases now rising in regions undergoing economic development.
Something (or things) about the modern western lifestyle and environment is contributing to dysbiosis and soaring IBD rates around the world. There are a number of possible culprits here, which may include improved hygiene, pollution, antibiotic use and smoking.
The western diet, rich in fat, sugar and animal protein, is another obvious suspect, given that what we eats affects the make-up of our microbiome. Several studies have shown an increased risk of IBD in people who consume high levels of refined sugars and animal fat, compared with those who have a diet rich in fruit and veg.
Research into IBD and the microbiome has been propelled, in part, by advances in gene sequencing and computational approaches to studying biological data, but we also have some small furry friends to thank. Mouse models (mice used to investigate human diseases) are indispensable to this field of research.
Some of these mouse models mimic IBD, and make it possible to explore specific treatments, such as antibody therapies, for colitis and Crohn’s. ‘Germ-free’ mouse models are completely devoid of a microbiome and allow scientist to observe the effects of introducing specific microbes on the immune system and the development of IBD.
Other treatments in development include those that aim to rebalance the microbiome. Promising therapies under investigation include fecal transplants from healthy donors, probiotics and prebiotics. There are also some rather extreme diets available, such as exclusive enteral nutrition (EEN) – a temporary, and solely liquid, diet designed to induce remission.
Currently available medications to manage IBD (mainly anti-inflammatories, such as steroids) are not always successful and many patients have to undergo surgery to remove or repair sections of damaged digestive system. It is estimated that up to eight out of 10 people with Crohn’s will need surgery at some point. So while many mysteries still surround IBD, our flourishing understanding of the microbiome is thankfully opening up new possibilities for treating this difficult condition.