12 January - 20 June 2016

Review - gut microbiota linked to common diseases of the elderly

A review by Japanese researcher Yukihiro Shimizu, published in the World Journal of Gastroenterology, highlights the role that gut microbes may play in medical conditions affecting the elderly. With ageing populations in many countries (including Japan, where over a quarter of citizens are over 65), and a global increase in life expectancy, ways to improve the quality of later life could be extremely valuable.

A review by Japanese researcher Yukihiro Shimizu, published in the World Journal of Gastroenterology, highlights the role that gut microbes may play in medical conditions affecting the elderly. With ageing populations in many countries (including Japan, where over a quarter of citizens are over 65), and a global increase in life expectancy, ways to improve the quality of later life could be extremely valuable.

The microbiota of the human gut - comprising many species of bacteria, weighing several kilograms, are known to influence the rest of the body through various pathways. Shimizu notes that there are three possible mechanisms by which gut microbiota can have an effect on other organs in the body: by affect the absorption of nutrients from food; by interaction with and regulation of the systemic immune system; and by translocating bacteria/bacterial products through mucosal barriers into the blood

Shimizu identified a number of diseases, including Alzheimer’s Disease (AD), osteoporosis, sarcopenia, and cerebro- and cardiovascular diseases which can decrease a person’s ‘activities of daily living’ (ADL) for instance, walking or performing household tasks, and which are “major causes of being bedridden” and looked at whether manipulation of gut microbiota could play a role in prevention or treatment of these. Shimizu notes that the review is intended to summarise “current knowledge of the role of gut microbiota in the regulation of the development” of the noted diseases.

In the case of Alzheimer’s Disease, there is evidence that some gut microbes could contribute to a chronic inflammatory response in the brain, leading to the formation of lesions (amyloid plaques) seen in the disease. Additionally, while no specific gut microbe has been associated with AD, lack of microbial diversity is correlated with increased incidence of Alzheimer’s in some populations. Conversely, Shimizu notes that studies have shown that probiotics may have a positive effect in improving cognitive function and suggests that maintenance of a balance between “good” and “bad” bacteria by use of probiotics may therefore “have possible therapeutic potential in patients with AD.”

For cardiovascular disease, the observations are similar, with certain microbial profiles and products conferring both protective and aggravating effects. Short-chain fatty acids (SCFAs), by-products of bacterial metabolism, are also implicated in the workings of skeletal muscle, improving biogenesis and function of mitochondria.

In osteoporosis, mouse models demonstrate that, again, microbial balance and certain prebiotics can increase calcium uptake and promote new bone formation. Shimizu states that while there is only limited evidence on the effectiveness of prebiotics in postmenopausal or senile osteoporosis, probiotic or prebiotic supplementation may “be a potential therapeutic intervention for the prevention or treatment of osteoporosis in humans”

In conclusion, Shimizu reiterates that “Gut microbiota may be important regulators in the development of diseases that affect ADL”. While Shimizu notes that exercise and diet are important factors to preserve ADL, it is concluded that intervention which targets gut microbes “may be a promising strategy” for ensuring that the daily life of elderly patients is not limited by these conditions.

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