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Genes, Viruses, Microbes and IBD

Monday, 09 August 2010 by
Reading Time: 3 minutes

Crohn’s disease is common and miserable to suffer from, yet its actual cause is still under some debate as no clear understanding has yet been fully elucidated. It is known that there are some gene variations and that the environment has an impact. A paper out in Cell suggests, based on a mouse model that it may be a virus that makes the difference between health and inflammation. demonstrate that a viral infection, a toxic insult to the gut, commensal bacteria, and a Crohn’s disease susceptibility gene collude to cause inflammatory disease in the mouse gut.[1]

To be clear, Cadwell and co-workers are not arguing that Crohn’s disease is caused by infection with norovirus (as used in this study) or by any other single microbe. The environmental factors that predispose to and protect from Crohn’s disease remain uncertain, but the balance among commensal and pathogenic gut bacteria and viral infections is likely to be part of the story. These studies make an urgent and compelling case for characterising the human virome as well as the microbiome and defining its effects on physiology and gene expression. In addition, further explanations to help us to understand how the virome interacts with polymorphisms in the host genome and how numerous toxins in the environment alter this complex interplay will need to be unravelled.

Reading Time: 2 minutes

Inside our gastrointestinal tract live a family of specialised cells, co-dependent on bacteria and nutrients to send a calming message to the mucosal tissues. They have a number of variations in their make up but they are vital in their role as diplomats, passing sensitive information across the borders to provide a long term peaceful mission and maintain oral tolerance. Essentially they induce either protective immunity to infectious agents or tolerance to innocuous antigens, including food and commensal bacteria. This recent article out in the Journal of Clinical Investigation explores the current understanding of how these cells contribute to health and illness.[1]

Reading Time: 19 minutes

The saying is ‘what happens in Vegas stays in Vegas’, or if you are English ‘what happens in Blackpool….’ but the same cannot be said about what happens in utero, as increasing evidence supports the understanding that the maternal nutritional environment and early feeding affects the health of the foetus beyond infancy and into adulthood.[1],[2] An article in Nature’s Mucosal Immunology this month explores some of the key events in foetal and neonatal immune management.[3] It stimulated a revisit to the area of what to consider for parents to be and mums of young children when they ask ‘is there anything I can do to prevent or reduce the risk of allergy or atopy in my child’.

The first moments, weeks and months of life can determine the health outcomes of an individual over the duration of their lifetime and this knowledge represents a significant choice for prospective parents. Fortunately the remarkable adaptability of the immune and central nervous system means that there are numerous opportunities in the early years of life to positively influence health outcomes even if the early stages were less than optimal.

Reading Time: 2 minutes

One in 10 schoolchildren in the western world suffers from eczema and even developing nations have also seen an increasing trend in the last few decades. There are many proposals to explain the increased incidence, one area of relevance is the environmental impact. Falling under the often misused ‘hygeine hypothesis’ title it has been proposed that there is a reflective difference in the gradient between rural and urban children. Implying the environmental impact on the developing immune system of children is different and therefore less protective in the urban setting.

This concept has now been studied in a recent article in the British Journal of Dermatology.[1] By conducting a Medline and Embase data base review studies that compared the incidence between the two environments were reviewed. Some 26 papers were assessed with 19 demonstrating a higher risk for eczema in an urbanised area, of these 11 were regarded as being statistically significant. A further 6 studies showed a lower risk of eczema in an urbanised area, of which just 1 was statistically significant.

Reading Time: 6 minutes

A trial to see if the ingestion of a probiotic bacterium enriched drink might have a beneficial impact on central obesity was funded by Snow Brand Milk Products company in Japan and the results were published in the European Journal of Clinical Nutrition this June 2010. [i]

Whilst it may seem a stretch that bacteria can influence our body mass, (I have written a previous review) it is an area of growing interest and investigation as bacteria have previously been implicated in the metabolic storage of fat. Studies in mice have shown up to 30% greater fat storage in mice with gastrointestinal colonies of commensals rather than their skinnier counterparts operating with sterile guts.

One proposal for this is that certain bacteria (Bacteroides Thetaiotaomicron is one likely contender) are able to manipulate energy to be stored in adipocytes through a pathway that involves microbial regulation of the intestinal epithelial expression of fasting-induced adipocyte protein (Fiaf), a circulating inhibitor of lipoprotein lipase (LPL).[ii]

The microbiota can then, based on this and other studies be viewed as a metabolic “organ” exquisitely tuned to our physiology and performing functions that we have not had to evolve on our own.

A Bacteria Triggers Arthritis.

Thursday, 01 July 2010 by | Comments: 2
Reading Time: 4 minutes

The gut microbiomes of humans and mice are broadly similar which is helpful as this paper has used the mouse model to explain how a resident bacteria in the gut can induce arthritis. In both hosts human and mouse upwards of ∼1000 different microbial species from ∼10 different divisions colonise the gastrointestinal tract, but just two bacterial divisions—the Bacteroidetes and Firmicutes—and one member of the Archaea appear to dominate, together accounting for ∼98% of the 16S rRNA sequences obtained from this site.[1] 16SrRNA is a laboratory method for analysing bacterial and provides species-specific signature sequences useful for bacterial identification but is not routinely used in diagnostic settings yet.

Their analysis revealed that despite the enormous species variation in the gut a single species of bacteria that lives here is able to trigger a cascade of immune responses that can ultimately result in the development of arthritis.[2] Gut-residing bacteria can also play a role in disorders of the immune system, especially autoimmune disorders in which the body attacks its own cells. The gut microbiota is now known to shape intestinal immune responses during health and disease with systemic effects.

What Do Bacteria Do To Our Immune System?

Thursday, 01 July 2010 by | Comments: 3
Reading Time: 2 minutes

The germ theory that has so modernised medicine and driven us, the western world living human to regard all bugs as bad has been undergoing a dramatic rethink over the last few years. Firstly the recognition that your body is teeming with bacteria, providing a warm residence to approximately 10 times as many bacterial cells as human cells. Our mutual inhabitants live on skin, in the respiratory tract and throughout the digestive tract. Your digestive tract alone is home to between 1,000 and 40,000 bacterial species depending on your choice of journal.

Butyrate Improves Bowel Transit

Wednesday, 02 June 2010 by | Comments: 3
Reading Time: 4 minutes

Problems such as poor transit or constipation are common, and can produce significant misery for the individual compromised in this manner. Butyrate is a short chain fatty acid, manufactured in the gut by the anaerobic fermentation of dietary fibres by resident microbiota. It is proposed that apart from its already well understood properties that it has another remarkable effect – the ability to increase the neuronal concentration of the Enteric Nervous System.[1]

Butyrate-generating foods and supplements might become an effective and simple option to prevent or treat functional gut disorders via modulation of enteric neuroplasticity.

Can Bacteria Make You Smarter?

Wednesday, 02 June 2010 by
Reading Time: 2 minutes

The potential cognitive gains linked to the role of gastrointestinal bacteria continues to attract international interest. The scientific community are becoming entranced with the notion that our bacterial exposure affects not only the local tissues, but also others including the brain.

Exposure to specific bacteria in the environment, already believed to have antidepressant qualities, could increase learning behaviour.  Mice fed live cultures of Mycobacterium vaccae were able to learn and complete a maze twice as fast as control mice were the key comments delivered at the 110th General Meeting of the American Society for Microbiology last week.

Mycobacterium vaccae is a natural soil bacterium which people likely ingest or breath in when they spend time in nature,” says Dorothy Matthews of The Sage Colleges in Troy, New York, who conducted the research with her colleague Susan Jenks.

Reading Time: 7 minutes

Michael Ash looks at leaky gut with a contemporary approach to investigation, relevance and restoration. It is quite clear that in order to extract nutrients and other sentinel information carrying agents the barrier that divides the contents of the gastric lumen from the host must be permeable. The question that has interested clinicians for many years is – when is it too permeable and what does that mean in terms of health and illness.

A paper in the March edition of Mucosal Immunology explores this concept in some detail and delivers some much needed information and potential direction in terms of dietary management and risk.[1]

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