Role of Gut Microbiota in Allergies and Asthma - A Review

Introduction

The human gut microbiota is home to trillions of microorganisms, all coexisting in a dynamic environment, and majorly influences various organs and systems. They significantly affect immunity, inflammatory response, digestion, absorption of nutrients, and many others. Allergies and asthma are conditions primarily associated with a certain trigger for which the body produces a response. They have complex etiologies in which gut microbiota has recently been implicated. This article intends to explore the relationship between gut microbiota and allergic conditions, including asthma.

How Does Gut Microbiota Influence Allergies and Asthma?

The effect of gut microbiota on allergens and asthma is a complex and dynamic process comprising various mechanisms. A few of the ways by which this influence might occur include:

1. Immune System Effect: The microbial system is important for overall well-being by affecting the body in many ways. They have a vital role in educating the immune system in early life. Therefore, when the body system gets exposed to many organisms early on, it learns to recognize and get trained on when to mount a proper response against the foreign agent. Underreaction, and overreaction are mechanisms for developing allergic reactions and asthma.

2. Inflammation Regulation: When there is microbial balance in the gut, it greatly influences maintaining good immune reactions. This means the body is in a balanced state and can respond to any potentially harmful challenges without the need to trigger inflammatory responses. Chronic inflammation is a common feature seen in all allergic reactions and asthma. Hence, with the regulation of a healthy microbiota, it can be regulated and kept in control.

3. Short Chain Fatty Acids Production: Gut microbial organisms are prominent in the digestion of fibers and nutrient absorption. They break down the fibers into short-chain fatty acids. And these have their role in maintaining gut health. They are also linked to regulating the immune system. They are integral to supporting the barrier system and influence immune cell activity. These short-chain fatty acids have also been shown to affect the lungs' immune system positively. Therefore, a shortage of these products may result in allergies and asthmatic reactions.

4. T-Cell Activation: The gut microbiome is largely associated with activating many T regulatory cells. These immune cells are mainly responsible for preventing excess immune response to harmless agents. Exaggerated responses are discouraged, and the immune system is maintained in a balanced manner. This benefits allergies and asthma as it lightens the inflammatory allergic response.

5. Metabolites: The gut microbiota is beneficial and produces metabolites with many roles, such as modulating immune response and body sensitivity to allergic reactions and irritants. They also contain certain signaling and transforming molecules, directly affecting the immune system. But influencing the immune response, they play a role in allergic response and asthma.

6. Barrier Function: A healthy microbiome has a role in maintaining an intact barrier. The gut epithelial barrier is a physical difference that separates the gut microbiome from the underlying tissues. A healthy barrier is necessary to prevent the translocation of microorganisms, which can potentially trigger an allergic response, causing an allergic reaction or asthma.

What Are the Therapeutic Implications of Gut Microbiota on Allergens and Asthma?

As there is a significant link between gut microbiota and allergic reactions, several therapeutic strategies have been devised to modulate the gut microbiota, indirectly influencing the immune response to prevent allergic reactions and asthma. Some of them include:

1. Immunotherapy: This mode involves exposing the body to allergens in a controllable manner, intending to potentiate tolerance response. This helps reduce allergic reactions. When combined with treatments to increase the beneficial bacteria in the gut, the treatment outcomes have shown greater results. Hence, modulating the gut bacteria along with immunotherapy helps prevent many allergies.

2. Probiotics: They are live organisms that, when given adequate quantities, elicit beneficial responses in human beings by balancing the gut microbiota. They help decrease the ill effects of dysbiosis and promote a diverse microbial community. They also help regulate immune cells and help in preventing allergies and asthma.

Probiotic strains like Lactobacillus and Bifidobacterium are currently being studied for their antiallergic effects.

1. Fecal Microbiota Transplantation: This mode of treatment involves transferring fecal matter from a healthy individual to a diseased individual to replace the lost gut bacteria. This helps restore the microbial balance. It has been studied to check its immunomodulatory effects in allergic reactions and asthma.

2. Precision Medicine Approaches: Tailormade medicinal approaches for a particular individual, based on their clinical, environmental, genetic, and microbial profiles, are known as precision medicine. Advances in microbiology have helped identify the microbial patterns present in the gut, and by identifying specific microbes associated with allergies, treatment can be specifically targeted.

3. Using Antibiotics Judiciously: Currently, antibiotics are being misused regularly, leading to the growth of resistant strains and disruption of gut microbiota. This disrupted microbiome hampers the beneficial bacteria, too. Caution is advised while prescribing and consuming antibiotic medications, especially in early life, intending to preserve gut microbial diversity.

4. Lifestyle Modification: Moving towards a healthier lifestyle in terms of a balanced diet, adequate hydration and sleep, stoppage of junk, processed foods, and unhealthy habits like smoking and drinking alcohol not only helps restore the gut microbiota balance but also has a direct impact on allergic reactions and asthma triggers. They have an indirect effect on the gut microbiota.

Conclusion

Gut microbiota greatly impacts the whole body, organs, and systems. They have a major impact on immune response and modulating an allergic reaction. They cause allergies by impacting the immune response, regulating inflammation directly or through metabolites, and sending signals to generate an immune response when there is an imbalance. They also have a role in T cell regulation. With all these mechanisms, they affect allergies considerably. Therapeutic modalities focussed on gut microbiota like probiotics, prebiotics, healthy lifestyle, and judicious use of antibiotics also have a role in reducing allergies and asthma risks.