RUMINANT NUTRITION SYMPOSIUM: Molecular adaptation of ruminal epithelia to highly fermentable diets1

Abstract

Feeding highly fermentable diets to ruminants is one strategy to increase energy intake. The increase in short-chain fatty acid (SCFA) production and reduced ruminal pH associated with highly fermentable diets imposes a challenge to the metabolism and the regulation of intracellular pH homeostasis of ruminal epithelia. The ruminal epithelia respond to these challenges in a coordinated manner. Whereas the enlargement of absorptive surface area is well documented, emerging evidence at the mRNA and transporter and enzyme activity levels indicate that changes in epithelial cell function may be the initial response. It is not surprising that gene expression analysis has identified pathways involved in fatty acid metabolism, ion transport, and intracellular homeostasis to be the pathways dominantly affected during adaptation and after adaptation to a highly fermentable diet. These findings are important because the intraepithelial metabolism of SCFA, particularly butyrate, helps to maintain the concentration gradient between the cytosol and lumen, thereby facilitating absorption. Butyrate metabolism also controls the intracellular availability of butyrate, which is widely regarded as a signaling molecule. Current data indicate that for butyrate metabolism, 3-hydroxy-3-methylglutaryl-CoA synthase and acetyl-CoA acetyltransferase are potential regulatory points with transient up- and downregulation during diet adaptation. In addition to nutrient transport and utilization, genes involved in the maintenance of cellular tight junction integrity and induction of inflammation have been identified as differentially expressed genes during adaptation to highly fermentable diets. This may have important implications on ruminal epithelial barrier function and the inflammatory response often associated with subacute ruminal acidosis. The objective of this review is to summarize ruminal epithelial adaptation to highly fermentable diets focusing on the changes at the enzyme and transporter activity levels, as well as the underlying molecular changes at the mRNA and protein expression levels.

Total mixed ration pellets for light fattening lambs: effects on animal health

“…In this sense, if animal health is threatened by a disease (as in the case of rumen acidosis), the risk of associated disorders increases (e.g. parakeratosis-rumenitis, liver abscesses, laminitis) (Penner et al, 2011) and blood cell counts, especially leucocyte counts, and their response to stimuli (lipopolysaccharide (LPS), endotoxins) can be modified, thereby compromising the animal's immune response (Penner et al, 2011;Ceroni et al, 2012).…”

Transcriptomic Changes in Ruminal Tissue Induced by the Periparturient Transition in Dairy Cows

“…It is known that ruminal SCFA concentration is largely affected by dietary formulation and nutrient ecology Gabel and Sehested, 1997;Kristensen et al, 1998;Penner et al, 2011) and not as an adaptive mechanism during the transition period. The SCFA concentrations agree with previously published reports from our group using diets of similar composition (Dionissopoulos et al, 2013;Steele et al, 2012b).…”

A high-grain diet causes massive disruption of ruminal epithelial tight junctions in goats

“…In addition, the prominent histological alterations during HG feeding strongly suggest an impaired barrier function (35-37) that may provide the opportunity for the translocation of toxins and bacteria from the rumen into the blood, ultimately affecting animal health and productivity (28). Although there is fundamental knowledge about the consequences of HG feeding on ruminal epithelial barrier function, remarkably little information is currently available about the underlying molecular changes in ruminal epithelial barrier function during HG diet feeding.The rumen epithelium (RE) of sheep and cattle has extensive barrier-forming properties, depending on the multicellular structure (stratum corneum, granulosum, spinosum, and basale) and the junctional complex that establish a barrier between sometimes hostile external environments and the internal milieu (12,27,38). Tight junctions (TJs) located in the middle layers (stratum granulosum and spinosum) play a key role in maintaining the polarity of epithelial cells, regulating the permeability of the epithelial barrier and preventing the translocation of LPS and other toxins (12,27).…”

“…The rumen epithelium (RE) of sheep and cattle has extensive barrier-forming properties, depending on the multicellular structure (stratum corneum, granulosum, spinosum, and basale) and the junctional complex that establish a barrier between sometimes hostile external environments and the internal milieu (12,27,38). Tight junctions (TJs) located in the middle layers (stratum granulosum and spinosum) play a key role in maintaining the polarity of epithelial cells, regulating the permeability of the epithelial barrier and preventing the translocation of LPS and other toxins (12,27).…”