**4.2 Targets for prebiotics: gut microbiota and intestinal health**

Fermentation of resistant starches and dietary fiber caused by bacteria in colon release short chain fatty acid metabolites (SCFA). SCFA are well known for gut health as well as their part in provision of supplementary energy to the host in fatness is in debate. On contrary, 10% of entire energy in humans is provided by SCFA. According to energy yield hypothesis, dysbioticmicrobiomes have an amplified capacity to remove energy from the food, so that the bacterial conversion of non-digestible carbohydrates and dietary fiber to SCFAs could give additional energy to the host and result fatness of individual over time. Likewise, G-protein coupled receptors (GPR) can sense SCFAs that tie them with lipid and glucose breakdown. SCFAs activate the two major proteins, GPR41 and GPR43 which are expressed on adipocytes and enter endocrine L cells. Peptide YY is released by stimulation of intestinal GPR41 which enhances gut passage time and increase satiety. Inflammation lessens by activation of intestinal GPR43 as well as it simulates glucagon-like peptide (GLP), a hormone which contributes in regulation of insulin secretion. Enteroendocrine L cells express GLP-1 as well as secrete the gut-trophic

hormone GLP-2. Chief stimulus for GLP-2 secretion is nutrient consumption. SCFAs maintain the release of GLP-2 which is important in regulation of the gut fence system and decreases lipopolysaccharide translocation [99].
