Understanding the interplay between food structure, intestinal bacterial fermentation and appetite control

Epidemiological and clinical evidence highlight the benefit of dietary fibre consumption on body weight. This benefit is partly attributed to the interaction of dietary fibre with the gut microbiota. Dietary fibre possesses a complex food structure which resists digestion in the upper gut and therefore reaches the distal gut where it becomes available for bacterial fermentation. This process yields SCFA which stimulate the release of appetite-suppressing hormones glucagon-like peptide-1 and peptide YY. Food structures can further enhance the delivery of fermentable substrates to the distal gut by protecting the intracellular nutrients during upper gastrointestinal digestion. Domestic and industrial processing can disturb these food structures that act like barriers towards digestive enzymes. This leads to more digestible products that are better absorbed in the upper gut. As a result, less resistant material (fibre) and intracellular nutrients may reach the distal gut, thus reducing substrates for bacterial fermentation and its subsequent benefits on the host metabolism including appetite suppression. Understanding this link is essential for the design of diets and food products that can promote appetite suppression and act as a successful strategy towards obesity management. This article reviews the current evidence in the interplay between food structure, bacterial fermentation and appetite control.

Expression and NMR Structural Studies of Isotopically Labeled Cannabinoid Receptor Type II

Cannabinoid receptor type II (CB₂) is an integral membrane protein with seven transmembrane helices that belongs to the large superfamily of rhodopsin-like G protein-coupled receptors. The CB₂ is a part of the endocannabinoid system that plays a vital role in regulation of immune response, inflammation, pain, and other metabolic processes. Information about the structure and function of CB₂ in cell membranes is essential for development of specific pharmaceuticals that target CB₂ signaling. Methodology for recombinant expression, stable isotope labeling, purification, reconstitution into liposomes, and NMR characterization of functionally active CB₂ is presented. Uniformly ¹³C-, ¹⁵N-labeled CB₂ protein is expressed by fermentation of Escherichia coli in a medium of defined composition under controlled aeration, pH, and temperature and purified by tandem affinity chromatography. The receptor reconstituted into lipid bilayers is suitable for structural studies by solid-state NMR spectroscopy.