One of the most intriguing aspects of relationships -- human and microbial -- has been the change associated with aging. As we grow older, our bodies change both on the outside as well as beneath the skin. A hallmark of the process known as immunosenescence in which the immune system begins to wane and tends to move towards the rather unwanted state of chronic inflammation.
Inflammation has significant effect on the elderly. On the skin, the lack of proper immunity decreases the ability to deal with the UV rays from the sun. This can lead to sagging, wrinkling, loss of elasticity and a higher risk for skin cancer. In the brain, this can lead to greater susceptibility to infection and also chronic conditions such as Alzheimer's Disease. In our blood, inflammation is known to play a significant role in the development of cardiac problems.
When the focus changes to the gastrointestinal tract, particularly the intestines, the picture becomes more complicated. While the impact of immunosenescence leaves us more prone to infection and chronic diseases, the changes also have an effect on the trillions of microbial residents, known as the gut microbiome.
The first examinations of chronic inflammation in aging revealed an overhaul in the types of bacteria present. They found septuagenarians were pretty much the same as their younger counterparts. But when the number of candles on the cake rose, the shift became greater. Subsequent analyses uncovered a complexity of complications.
The most problematic observation was the reduction in bacteria with anti-inflammatory properties and a rise in the number of potentially pathogenic species. In those over a century in age, researchers revealed the major bacterial species were less than beneficial. Their presence reduced the levels of good metabolites needed for reduced inflammation. The overall outcome was worsening health.
The results suggested the microbial makeup of the gut was dependent on the inflammatory status of the individual. Yet, by the early part of last year the view was reversed. A review of the collection of studies involving the microbiome and aging revealed inflammation and its associated consequences of aging were modulated by the microbes present. In essence, having a good gut microbiome meant the scourges of aging could be lessened if not eliminated.
Granted, having a good microbiome does not provide a guarantee of immortality or wrinkle-free skin, but the results did suggest microbes might have the ability to control when it's time for us to descend into the final stages of life. This past week, a European team of researchers took on the question and came up with a rather ominous hypothesis they called "Microbiome Mutiny."
Unlike previous postulates, "Microbiome Mutiny" was not based on a cause and effect relationship. The team chose not to believe our bodies were controlled by microbes or vice versa. Instead, they looked at the relationship as a give and take in which we do our part and microbes do theirs. The trouble happens when one of the pair -- usually us -- does not contribute equally.
As we age, if we continue to harbour good bacteria through proper diet and lifestyle, the microbes will give back in the form of healthy metabolites, neurochemicals, anti-inflammatory chemicals and protection against infection. However, should our activities change -- as a consequence of infection, chronic disease, or disability -- then the microbes will sense something is wrong. This is where the problems begin.
Microbes are less than philanthropic when it comes to relationships. They need nutrients and a safe environment to live. When that happens, they share back. But if the conditions become unfavourable, they tend to either hitch a ride on the next bowel movement or fight back with the production of inflammation-causing byproducts and toxins. Moreover, those bacteria more interested in causing us harm -- the pathogens -- can easily come in and find a home.
As a consequence of the changes, the gut suffers what the authors call a 'regime shift' in which the environment becomes virulent in nature and messages are sent out to all microbes to begin combat. A chain reaction ensues leaving the body with little to no option but to fight. For those with strength, they may live but they may be forever impacted. For the weakest, they may suffer the greatest, succumbing due to terminal frailty.
The authors added one final point to the hypothesis making it even more painful to absorb. Based on their analyses, mutiny is not only related to physical and/or immunological duress but also to emotional. As they discuss, the regime shift can happen when we are at our lowest moments, such as the loss of a loved one. The accompanying levels of stress, neurological changes and lack of proper lifestyle associated with grief can signal the microbes the time is right for a coup d'état. This could lead to the spread of pathogens within the body and increase the chances of turning a broken heart into a heart attack.
Despite the rather depressing nature of the hypothesis, there was a silver lining. If a person continued to supplement bacteria with our health in its best interests, such as probiotics, mutiny may be prevented or at least belayed. While there have been no studies to prove this part, the mere mention of at least a possible positive option is helpful. With more research, we may be able to prove this point and find a means to offer the elderly, the sick and even the brokenhearted a way to prevent the onslaught of virulence and live a happier, longer life.
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