Relationship between gut microbiota, probiotics, and obesity in the cellular and molecular mechanisms for the activation of regulatory t cells and control of inflammatory processes: a systematic review

Abstract

Introduction: Obesity represents a pandemic represented as a long-term chronic imbalance between calorie intake and energy expenditure, resulting in more than 30% of the world's population (over two billion people) being overweight or obese. Studies show that Tregs regulate inflammatory cells such as macrophages and T lymphocytes by reducing the production of cytokines IL-6, IL-10, etc., and microRNAs can regulate the gene expression of inflammatory cells. Probiotics have been increasingly studied for modulating the gut microbiota. Objective: It was to develop a systematic review to describe the main considerations of the relationship between gut microbiota, probiotics, and obesity, to list the cellular and molecular mechanisms for the activation of regulatory T cells and control of inflammatory processes. Methods: The PRISMA Platform systematic review rules were followed. The search was carried out from March to May 2024 in the Web of Science, Scopus, PubMed, Science Direct, Scielo, and Google Scholar databases. The quality of the studies was based on the GRADE instrument and the risk of bias was analyzed according to the Cochrane instrument. Results and Conclusion: A total of 122 articles were found, and 40 articles were evaluated in full and 24 were included and developed in the present systematic review study. Considering the Cochrane tool for risk of bias, the overall assessment resulted in 25 studies with a high risk of bias and 22 studies that did not meet GRADE and AMSTAR-2. Most studies showed homogeneity in their results, with X2=78.7%>50%. It was concluded that probiotic therapy proved to be an important strategy associated with a nutritional change to improve the composition of the gut microbiota. In this context, the probiotics L. paracasei shirota, Akkermansia muciniphila, and Lactobacillus reuteri V3401 stand out, which are responsible for reducing inflammatory markers. Modulation of the gut microbiota through physical exercise, type of nutrients, and use of prebiotics, and/or probiotics have a positive effect on reducing inflammatory markers. Some miRNAs have been implicated in the control of body weight gain, glucose homeostasis, insulin resistance, and lipid metabolism, with crosstalk with the gut microbiota. Furthermore, an association was found between B. eggerthi abundance, miR-183-5p expression, and adiponectin levels. Expression of miR-15a-5p was found to be associated with H. parainfluenzae abundance and insulin levels.