Mechanistic insight into the role of dietary fibers and short chain fatty acids in the regulation of metabolism and inflammation in the pig
Abstract
Dietary fiber is a diverse mixture of polysaccharides exerting multiple functions as it passes through the gastrointestinal tract (GIT). Besides the influence on nutrient digestibility, dietary fiber affects growth performance and host metabolism via modulation of gut microbial community structure and production of short chain fatty acids (SCFA). A series of in vivo experiments were conducted to determine the effects of dietary fiber on pig growth performance and gut microbial community as well as host metabolism. In the first study, a comparison between soluble and insoluble fibers was conducted in terms of pig growth, gut microbial structure and SCFA production in response to high fat diet (HFD). Compared to insoluble fiber, soluble fiber alleviated HFD induced back fat accumulation without a significant influence on body weight gain and casued changes in gut microbial structure and SCFA production. In the second study, effect of dietary resistant starch (RS) content on serum metabolite and hormone concentrations, milk composition, and fecal microbial profiling in lactating sows, as well as offspring performance was investigated. The high-RS diet increased serum triglyceride and non-esterified fatty acids (NEFAs) levels and milk nutrients in sow, which provided extra nutrients for postnatal growth of piglets. These changes in host metabolites were highly associated with the changes in fecal microbial community structure and SCFA production. Because dietary fiber and RS exert significant effects on performance and host metabolism through increases in gut microbial diversity and SCFA production, in vitro studies were conducted to reveal the underlying mechanisms using both adipocyte and intestinal epithelial cell models. For the adipocyte experiment, the role of SCFA in adipogenesis, adipokine secretion and lipid metabolism in adipocytes derived from porcine stromovascular cells were determined. Butyrate, not acetate or propionate, exhibited profound influence on adipocyte differentiation and lipid metabolism. Butyrate induced adipogenesis and thereby increased adiponectin secretion, leading to improved insulin sensitivity and enhanced glucose uptake. Butyrate inhibited lipolysis in a free fatty acid receptor 3 (FFAR3)-dependent manner and increased triglyceride synthesis through induction of related lipogenic enzymes gene expression. For the experiment in intestinal epithelial cells, the protective effect of butyrate on cell integrity and tight junction expression with LPS stimulation in porcine intestinal epithelial cells (IPEC-J2) was determined. Butyrate prevented LPS-induced impairment on the intestinal barrier integrity and tight junction permeability in a dose-dependent manner, resulting from increased expression of tight junction claudins. Butyrate restored LPS-induced reduction in Akt and 4E-BP1 expression levels, accounting for its effect in enhancing tight junction intergrity. In addition, butyrate also acted as energy source fueling epithelial cell recovery, evidenced by the changes in AMPK abundance and intracellular ATP level. In conclusion, dietary fiber affects pig growth performance and metabolism through changing gut microbial community structure and increasing SCFA production. SCFA, especially butyrate, have been involved multiple roles in the regulation of metabolism and signaling transduction pathways. Our studies present a novel paradigm for the effects of dietary fiber and related fermentation products and show that these are capable of improving growth performance and gut health as well as improving insulin sensitivity and preventing metabolic syndrome in both animals and human.
Degree
Ph.D.
Advisors
Ajuwon, Purdue University.
Subject Area
Animal sciences|Physiology
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