A dysfunction in the immune system can disturb the gut bacteria in certain ways that lead to age-related changes in the body, as per the scientists at the École Polytechnique Fédérale de Lausanne (EPFL), present in Switzerland.
A research paper present in the journal Immunity tells the details that scientists utilized genetically-altered fruit flies to reach these conclusions. They caused a dysfunction in the immune systems of these flies by switching off a particular gene. This caused an imbalance in the gut bacteria that started producing an excessive amount of lactic acid.
The lactic acid in excess led to the generation of chemicals known as reactive oxygen species that may damage cells and have associations related to age-related changes in tissues and organs. The scientists of this study have suggested that mammals may experience a similar mechanism. They further say that this study identifies a specific member of the gut microbiota and its metabolite that may influence the process of aging in the host organism.
Understanding Commensal Dysbiosis
The guts of all the animals consist of massive colonies of microorganisms including bacteria. These colonies are collectively known as the commensal microbes.
An increasing number of studies suggest that these commensal microbes can influence the immune system and several other functions of your body and live in balance with them.
Any disturbance occurring in this balanced co-existence is called as commensal dysbiosis. This condition can occur due to a number of reasons, for example, the use of certain medications and several illnesses.
Studies have also established links between commensal dysbiosis and various disease-related changes in addition to a shorter lifespan. The biological nature of these associations as well as the mechanisms that link them together are yet to be clarified.
The team decided to investigate this further by using the fruit fly, Drosophila melanogaster, as their model organism. Scientists often use this species to study gut bacteria and genetics.
Commensal Dysbiosis Shortens Life Spans
In previous attempts, a gene has been identified that activates the immune system in fruit flies in order to detect the potentially harmful bacteria and attack them. The gene is named as peptidoglycan recognition protein SD (PGRP-SD)
For a new investigation, the researchers bred a mutant strain of fruit flies which were immune-impaired due to switching off the gene PGRP-SD.
As a consequence, the immune-impaired flies were not able to live as long as the normal flies. They were also found to have a higher amount of Lactobacillus plantarum in their bodies.
L.planatarum is a type of gut bacteria responsible for producing lactic acid. The researchers found a high quantity of lactic acid in these immune-impaired flies as well as an associated heightening of reactive oxygen species.
The activation of PGRP-SD, on the other hand, stopped commensal dysbiosis in these flies and allowed them to live longer.
Lactic acid is a metabolite produced by L. plantarum which gets incorporated and processed in the intestine of the fly. The side effect of this process is the production of reactive oxygen species leading to epithelial damage.
The scientists warrant further studies to find more information about the reactions between commensal bacteria and the body during the process of aging.