Aloe barbadensis Mill. as a therapeutic option for irritable bowel syndrome – properties, bioactivity and mode of action

Abstract

Irritable bowel syndrome (IBS) is a chronic and prevalent functional gastrointestinal disorder, with an incompletely understood pathophysiology. Because of the disease complexity and heterogeneity, the currently available treatment options for IBS are limited. These limitations have led to the popularity of alternative therapeutic strategies, such as the use of Aloe barbadensis Mill. (Aloe), despite the paucity of controlled clinical studies supporting efficacy of these treatment options. This thesis therefore aimed to determine the importance of intestinal microenvironment, as well as the therapeutic effects and potential mode of action of an Aloe gel derived extract in patients with IBS. An integrated faecal microbiota and metabolite profile, as a joint representative of the intestinal microenvironment, distinguished IBS patients from healthy subjects, and further established the role of an altered intestinal microenvironment in the pathogenesis of IBS. The overall safety of Aloe treatment in patients with IBS was confirmed and supported the beneficial treatment effect of Aloe gel extract in subsets of IBS patients, which may depend on gut microbiota composition and function. Further, a potential mode of action for the therapeutic effect of Aloe gel extract, including dampening of immune cell activity and modulating intestinal microenvironment, was proposed. Finally, with the help of metabolomics, we expanded the knowledge of the complex and synergistic bioactive composition of Aloe gel. In conclusion, this thesis strengthens the role of an altered intestinal microenvironment in the pathogenesis of IBS. Further, it supports the role of an Aloe gel derived extract as a therapeutic option for the symptom management of IBS.