Showing posts with label Lactose intolerance. Show all posts
Showing posts with label Lactose intolerance. Show all posts

Saturday, December 26, 2020

Genes and microbes

The body’s assortment of microorganisms depends on what we eat, drugs we take, the stress we are subjected to and the environment we interact with (eg, the infamous SARS-CoV-2 virus). Yet genes also have their say.

In a study of 977 twins in UK, the most heritable taxonomic group of bacteria was found to be Christensenellaceae (Goodrich et al, 2014). These bacteria is present in higher amounts in genetically-lean individuals. It encourages growth of other microbes connected to body weight and energy conservation such as methanogenic Archaea.

A study of over 1500 healthy individuals in Canada (Turpin et al, 2016), associated another abundant bacteria Faecalibacterium with immune system gene CNTN6 (rs1394174), and linked several other genes and bacteria of minor clinical importance (rs59846192 of DMRTB1 - Lachnospira, rs28473221 of SALL3 - Eubacterium, ), rs62171178 nearest UBR3 - Rikenellaceae).

A new paper posted this month on BioRxiv, reports results of a larger genome-wide association study performed for 7,738 individuals from the northern Netherlands.

The authors investigated 5.5 million common genetic variants using linear mixed models on hundreds of bacterial groups and pathways. Potential confounders such as medication usage, anthropometric data and stool characteristics were carefully considered along with dietary information. 

The strongest associations were identified in intronic regions of genes. In particular, between rs182549 in intronic region of the MCM6 gene and Bifidobacteria. This SNP was found to be responsible for lactose intolerance in European population. And so was Bifidobacteria - the most researched and most effective probiotic against lactose intolerance.

Another interesting microbe Collinsella and its family Coriobacteriaceae, associated with rheumatoid arthritis, cholesterol metabolism and leaky gut, was linked to several SNPs regulating genes responsible for the blood group antigens. Blood types does matter. 

Genetic factors might influence our preferences of vegetables, fruit, starchy foods, meat, fish, dairy and snacks. The Dutch study confirmed an earlier finding that rs642387, a genetic variation near genes influencing brain function, is linked to microbial family Rikenellaceae. The paper found that these bacteria, when present in large numbers in the gut, led to decreased consumption of salt. They also showed that an increase in the bacterial pathway of histidine degradation led to increased intake of processed meat.

The paper provides a wealth of information and comes with a lot of supplementary material.



REEFERENES

Goodrich JK, Waters JL, Poole AC, Sutter JL, Koren O, Blekhman R, Beaumont M, Van Treuren W, Knight R, Bell JT, Spector TD. Human genetics shape the gut microbiome. Cell. 2014 Nov 6;159(4):789-99. 

Turpin W, Espin-Garcia O, Xu W, Silverberg MS, Kevans D, Smith MI, Guttman DS, Griffiths A, Panaccione R, Otley A, Xu L. Association of host genome with intestinal microbial composition in a large healthy cohort. Nature genetics. 2016 Nov;48(11):1413.

Lopera-Maya EA, Kurilshikov A, van der Graaf A, Hu S, Andreu-Sánchez S, Chen L, Vila AV, Gacesa R, Sinha T, Collij V, Klaassen MA. Effect of host genetics on the gut microbiome in 7,738 participants of the Dutch Microbiome Project. bioRxiv. 2020 Jan 1.

Thursday, May 7, 2009

IBS Resources

Mirrored from Aurametrix

IBS is a disorder of heterogeneous pathophysiology for which there are no good diagnostic tests nor effective treatments (online study on unmet needs conducted by IFFGD and UNC). Existing tests are performed to exclude diseases such as IBD, colorectal cancer, diseases associated with malabsorption, systemic hormonal disturbances, and enteric infections.
Routine serologic screening for celiac sprue in patients with IBS-D or IBS-M may be useful.
Lactose intolerance can cause IBS-D, intolerances to other food groups such as

Percentage of population with IBS reported in ...Image via Wikipedia

fructose could be also implicated. Problems with serotonin signaling, or the transmission of messages between the nerves, can lead to IBS-C

The guidelines, issued by the American College of Gastroenterology were published in the January2009 issue of The American Journal of Gastroenterology.

Most IBS treatments relieve symptoms rather than resolve the condition itself.

The new guidelines encompass existing evidence on conventional treatments for IBS as well as new therapies (probiotics, for example) and alternative therapies (acupuncture and more).

Fiber products -- including psyllium, anti-spasmodic medications and peppermint oil -- may be effective in some people. "The evidence is poor, but some patients say they feel better,"

More data is needed on probiotics, live microorganisms (usually bacteria) similar to the "good" organisms found normally in the gut. The dichotomous data suggest that all probiotic
therapies have a trend for being efficacious in IBS, whereas the
continuous data indicate that Lactobacilli have no impact on
symptoms; probiotic combinations improve symptoms; and
there is a trend for Bi fidobacteria to improve IBS symptoms.Researchers and practitioners still need to figure out the species of bacteria used, how many species, and dosages.

Non-absorbable antibiotics -- those targeted to the gut only, such as rifaximin (Xifaxan) -- also seem to help some people, especially those who have "diarrhea-predominant IBS."

Selective C-2 chloride channel activators, notably lubiprostone (Amitiza), are effective for "constipation-predominant IBS."
5HT 3 antagonists such as alosetron (Lotronex) relieve symptoms of diarrhea but can cause constipation and colon ischemia, a restriction of blood flow.
5HT 4 agonists, though effective against constipation, are not available in North America because of a heightened risk of cardiovascular problems.

There is yet to be conclusive evidence on Chinese herbal mixtures, and the mixtures run the risk of causing liver failure and other problems. Differences in the content of compounds and the purity of ingredients complicate evaluation of benefits.

Similarly, the evidence on acupuncture remains inconclusive.

There is no evidence at this point that testing for food allergies or following diets that exclude certain foods alleviates IBS symptoms.

Routine diagnostic testing for IBS is not recommended, although some testing should be performed in certain subgroups of patients.

More about IBS at the U.S. National Institute of Diabetes and Digestive and Kidney Diseases site.


To ease IBS with diarrhea, avoid fried foods, too much fiber, especially insoluble such as apple skins, chocolate, alcohol, caffeine, carbonated drinks, the artificial sweetener sorbitol (found in sugarless gum and mints), and fructose (the simple sugar found in honey and many fruits). These can worsen diarrhea symptoms. Drink six to eight glasses of plain water a day - not with meals, but an hour before or an hour after meals. Avoid drinking hot teas.

To ease IBS with constipation, drink water and exclude beverages as suggested above. Eat small frequent meals and be careful with fiber. Soluble is better at reducing severety of symptoms, as was shown in this 2005-2007 clinical trial, but all types of fiber could potentially worsen the syndrome. You may also want to exclude broccoli and other dark green vegetables from your diet. Keep an IBS symptom journal, it would help you and your doctor to find what foods and situations trigger your IBS symptoms.

Not Censored IBS Diet Links:

More Links:


International Foundation for Functional Gastrointestinal Disorders (IFFGD) sites:
Chronic Constipation aboutConstipation.org
Acid Reflux Disease (GERD) aboutGERD.org
Motility Disorders aboutGImotility.org
Irritable Bowel Syndrome (IBS) aboutIBS.org
IAMIBS.org
Incontinence or Urgency aboutIncontinence.org
Digestive Disorders in Kids
and Teens
aboutKidsGI.org
Digestive Health Research giResearch.org
Participate in IBS survey


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