Approaches to discern if microbiome associations reflect causation in metabolic and immune disorders.

Our understanding of microorganisms residing within our gut and their roles in the host metabolism and immunity advanced greatly over the past 20 years. Currently, microbiome studies are shifting from association and correlation studies to studies demonstrating causality of identified microbiome signatures and identification of molecular mechanisms underlying these interactions. This transformation is crucial for the efficient translation into clinical application and development of targeted strategies to beneficially modulate the intestinal microbiota.

The Intestinal Fate of Citrus Flavanones and Their Effects on Gastrointestinal Health.

Citrus flavanones, with hesperidin and naringin as the most abundant representatives, have various beneficial effects, including anti-oxidative and anti-inflammatory activities. Evidence also indicates that they may impact the intestinal microbiome and are metabolized by the microbiota as well, thereby affecting their bioavailability. In this review, we provide an overview on the current evidence on the intestinal fate of hesperidin and naringin, their interaction with the gut microbiota, and their effects on intestinal barrier function and intestinal inflammation.

A Critical Evaluation of In Vitro Hesperidin 2S Bioavailability in a Model Combining Luminal (Microbial) Digestion and Caco-2 Cell Absorption in Comparison to a Randomized Controlled Human Trial.

Scope: Bioavailability strongly determines polyphenol bioactivity, and is strongly influenced by food matrix, enzymatic and microbial degradation, and gastrointestinal absorption. To avoid human trials for pre-screening of polyphenol bioavailability, studies have focused on in vitro model development. Nevertheless, their predictive value for bioavailability can be questioned.

Vasorelaxant activity of twenty-one physiologically relevant (poly)phenolic metabolites on isolated mouse arteries.

Polyphenols are beneficial for health, but are metabolised after consumption. We compared the vasorelaxant capacity of twenty-one physiologically relevant polyphenol metabolites in isolated mouse arteries. Hesperetin, urolithins and ferulic acid-4-O-sulfate - not their glucuronidated forms or ferulic acid - caused vasorelaxation.

Ferulic acid-4-O-sulfate rather than ferulic acid relaxes arteries and lowers blood pressure in mice.

Consumption of foods rich in ferulic acid (FA) such as wholegrain cereals, or FA precursors such as chlorogenic acids in coffee, is inversely correlated with risk of cardiovascular disease and type 2 diabetes. As a result of digestion and phase II metabolism in the gut and liver, FA is converted predominantly into ferulic acid-4-O-sulfate (FA-sul), an abundant plasma metabolite. Although FA-sul is the main metabolite, very little has been reported regarding its bioactivities.