Impact of Physical Exercise on Gut Microbiome, Inflammation, and the Pathobiology of Metabolic Disorders

Abstract

Background: The gastrointestinal tract (GIT) harbors a complex and diverse microbial composition that outnumbers our own body cells and their gene contents. These microbes play a significant role in host metabolism and energy homeostasis. Emerging evidence suggests that the GIT microbiome significantly contributes to host health and that impairments in the microbiome may cause the development of metabolic diseases. The microbiome architecture is shaped by several genetic and environmental factors, including nutrition and physical activity. Physical exercise has preventive or therapeutic effects in respiratory, cardiovascular, neuroendocrine, and muscular diseases. Yet, we still have little information of the beneficial effects of physical exercise on GIT health and microbial composition. Furthermore, we are not aware whether exercise-derived benefits on microbiome diversity can beneficially influence other tissues and body organs.

Objectives: The aim of this article is to review the available literature on exercise-induced microbiome changes and to explain how these changes may induce inflammatory, immune, and oxidative responses that may contribute to the improvement of metabolic disorders.

Methods: A systemic and comprehensive search of the relevant literature using MEDLINE and Google Scholar databases was conducted during fall 2018 and spring 2019. The search identified sixty-two research and review articles that discussed exercise-induced microbiome changes.

Results: The review of the relevant literature suggests that exercise-induced microbial changes affect the host's immune pathways and improve energy homeostasis. Microbes release certain neuroendocrine and immune-modulatory factors that may lower inflammatory and oxidative stress and relieve patients suffering from metabolic disorders.

Conclusions: Exercise-induced changes in microbial diversity are able to improve tissue metabolism, cardiorespiratory fitness, and insulin resistance.

Figure 1

The figure illustrates the search method used to collect research articles from Medline and Google Scholar databases.

Figure 2. Factors that influence the human microbiome architecture and different functions performed by our microbiome

Genetics and mode of delivery at birth are the first predisposing factors impacting the gastrointestinal (GIT) microbiome. They work together with breast-feeding, hygiene, exposure to medication (antibiotics), dietary habits, and physical exercise to shape GIT microbiome. The diagram also sketches the different functions of the GIT microbiome. The microbiome helps to digest food and control host body energy homeostasis. Microbes secrete several useful peptides and are part of our body’s largest immune system.

Figure 3. How does physical exercise influence the microbiome and how does the microbiome then impact on metabolism?

Physical exercise changes GIT barrier permeability, GIT motility, and microbial diversity, which subsequently change the metabolic profile of liver, adipose tissue, and muscles. An improvement in gut barrier permeability prevents systemic release of lipopolysaccharides (LPS) and inflammation. Furthermore, exercise-induced changes in the microbiome activate the hypothalamus-pituitary-adrenal (HPA) axis and reduce different types of stress. Subsequent release of short-chain fatty acid (SCFAs) and activation of adipokines and chemokines prevent inflammation and autoimmune destruction of beta-cells, and improve energy balance and tissue metabolism.