Dendritic Cells Aid Intestinal Homeostasis and Disease
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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]
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Vegas, Pregnancy, Immunity and Allergy Prevention!
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.
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Vitamin D Halves Asthma Hospitalisation Risk
There seems no end to the illnesses this secasteroid is capable of influencing, although it should be of no real surprise that Vit D deficiency is linked to the respiratory condition asthma. The reason….mucosal tissues such as those found in the lung are rich with immune receptors that are intimately tied into the Vit D receptor family. Vitamin D up regulates a specific gene that produces over 200 anti-microbial peptides, some of which work like a broad-spectrum antibiotic.
Because of its beneficial role in respiratory tract infections and immune system modulation, it has been hypothesised that vitamin D status might affect the risks for exacerbations.[1] This paper shows show that children with initial circulating vitamin D levels of 30 ng/mL or less (vitamin D insufficiency) have a 50% greater risk for severe exacerbation over the course of a 4-year clinical trial of asthma treatment than children with circulating vitamin D levels of 30 ng/mL or greater (vitamin D sufficiency) at the start of the trial.
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More Evidence to Support Vit D as an Anti Viral Compound
Last year I wrote a number of posts relating to mechanisms related to mucosal immune defences, in particular the innate immune defences and how we as Nutritional Therapists may advise our patients of evidence based strategies. This paper out in the open access journal Plos One adds further validity to the vitamin D recommendations I proposed.
Declining serum concentrations of 25-hydroxyvitamin D seen in the fall and winter as distance increases from the equator may be a factor in the seasonal increased prevalence of influenza and other viral infections.[1]
This paper in PLOS Biology describes how almost 200 adults had their serum 25-hydroxyvitamin D levels measured, without knowing what was been investigated.
One hundred ninety-eight participants, 85 men and 113 women, with an age range of 20–88, were enrolled in the study.
The researcher found that people with fair skin, lean body mass and who supplemented with vitamin D had the highest levels of 25-hydroxyvitamin D. People who achieved 38ng/ml or higher 25-hydroxyvitamin D level had a remarkable 50% reduction in the risk of developing acute respiratory tract infections and a significant reduction in the number of days ill (p<0.0001).
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Is There A Rural/Urban Gradient In The Prevalence Of Eczema? A Systematic Review And What Can Be Done About It?
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.
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Fat – I’m Not To Blame Its My Bugs!
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.
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Neurological/Dietary Control Over the Immune System – The Role of Fats
The immune system in humans and animal is complex, all the more so because it crosses over all tissues. The traditional view has been that the immune system keeps itself in check, and that is mostly the case. However, for some years there has been a development of a neural feedback loop comprehension that helps to answer some of the complex mechanisms and remarkably ties in the role of a nutritional strategy for immune management. This is known as the inflammatory reflex.
The inflammatory reflex, a prototypical neural circuit that modulates innate immunity, is activated by the presence of cytokines or other inflammatory products in tissues that triggers afferent (a nerve that passes impulses from receptors toward or to the central nervous system) action potentials travelling in the vagus nerve. The ascending information is relayed to brainstem nuclei that control efferent (nerves that convey nervous stimulus from the brain to other parts) neural signals in the form of action potentials transmitted back to the periphery via the vagus nerve.
Whilst this may sound complex – few subjects that combine neurology and immunology aren’t… the outcome suggested meets simple strategies, based on complex mechanisms.
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A Bacteria Triggers Arthritis.
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.
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What Do Bacteria Do To Our Immune System?
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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.
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Do Diets Leave You Micronutrient Deficient?
The shortage of essential micronutrients in the human diet has been linked to multiple health and disease related problems. Dr Bruce Ames has described how the micronutrient triage theory can account for disease induction and more rapid levels of poor quality aging. I have written about the expensive urine myth and how the failure to recognise the differing demands placed by cells at different times can lead to altered and compromised health function.
This paper looks at the nutritional intake of people following a weight loss diet.[1] Based on the USA figures, the authors say that about 1/3 of the population are following some sort of weight loss orientated nutritional programme. The study looked to see if 27 micronutrients could be ingested in sufficient quantities whilst following 4 well known diets to meet minimum RDA levels as determined by the USA regulatory body the FDA.
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