Dietary modulation of the expression of genes involved in short-chain fatty acid absorption in the rumen epithelium is related to short-chain fatty acid concentration and pH in the rumen of goats

Abstract

We have tested the hypothesis that increased concentrate intake induces mRNA abundance alterations of genes involved in short-chain fatty acid (SCFA) absorption in the rumen epithelium of goats and these changes of mRNA abundance are probably related to ruminal SCFA concentration and ruminal pH. Goats (n=12) were randomly allocated to 2 groups and fed either a low-concentrate (LC) diet (10% concentrate; n=6) or a medium-concentrate (MC) diet (35% concentrate; n=6) in 2 equal portions daily. Goats were fed separately with their respective diet for 3 wk. The goats were slaughtered 6h after the morning feeding on d 22. In vivo, goats in the MC treatment exhibited a greater ruminal SCFA concentration (81.9mM) compared with those in the LC treatment (58.0mM), and the pH decreased from 7.03 to 6.63. Correspondingly, mRNA expression of candidates for SCFA(-)/HCO3(-) exchangers, namely downregulated in adenoma (DRA), putative anion transporter 1 (PAT1), and anion exchanger 2 (AE2) were increased in the MC group. Further, upregulation in monocarboxylate transporter 1 (MCT1) and monocarboxylate transporter 4 (MCT4) mRNA abundances was observed in the MC group. The expression of genes that help the rumen epithelial cells to maintain intracellular pH, including Na(+)/H(+) exchanger 1 (NHE1), NHE2, NHE3, vacuolar H(+) ATPase subunit B (vH(+)ATPase), and Na(+)/K(+) ATPase pump subunit α1 (Na(+)/K(+)ATPase) were also enhanced in the MC group relative to the LC group. During in vitro studies with isolated rumen epithelial cells from goats, exposure to a pH of 6.8 increased MCT1 mRNA expression after 24h of culture, whereas the mRNA expression of AE2 was downregulated. The presence of SCFA (20mM) in the medium increased DRA, PAT1, AE2, MCT1, and Na(+)/K(+)ATPase mRNA expression. The expression of vH(+)ATPase was decreased by increased SCFA concentration. The mRNA expression of MCT4 did not vary in vitro with pH (6.8) or SCFA (20mM). The expression of DRA was increased by synergistic effects of higher SCFA concentration and lower pH, similar to that of MCT1. Thus, diet-dependent rumen epithelial mRNA expression changes in genes involved in SCFA absorption are probably related to ruminal SCFA concentration and pH.

Subacute ruminal acidosis suppressed the expression of MCT1 in rumen of cows

“…In this study, the physiological pH and the physiological concentration of SCFAs promoted the expression of MCT1 in the ruminal epithelium cells, which were consistent with the available in vivo data. Yan, Zhang, and Shen () reported that the decline of rumen pH and the rise of SCFAs concentration in the physiological range of rumen promoted the expression of the gene of MCT1 and MCT4. Thus, the balance between the rates of production and resorption SCFAs in rumen fluid played an important role in maintaining health through maintaining the metabolic balance.…”

Rapid Fermentable Substance Modulates Interactions between Ruminal Commensals and Toll-Like Receptors in Promotion of Immune Tolerance of Goat Rumen

“…Glyceraldehyde-3-phosphate dehydrogenase (GADPH) was chosen as the housekeeping gene. The primers of 11 genes were designed in this study according to the available sequences in NCBI, and the primers of the remaining 11 genes were synthesized according to the description of Yan et al (2014) (Supplementary Table S2). The amplification efficiency of the primers was determined by means of a dilution series of epithelial cDNA.…”

“…A study on mice revealed that diet enhanced immune tolerance also by affecting the interactions of pattern-recognition receptors (PRPs) and commensals in GI tract (Zelante et al, 2013). Our previous studies have shown that the increased intake of non-fiber carbohydrate (NFC), which can be rapidly fermented by GI microbes, causes the significant increases in the concentrations of butyrate, acetate and propionate in goat rumen (Yan et al, 2014; Lu et al, 2015). However, yet little is known about the diet-induced specification of ruminal microbiota and their effects on the immune tolerance of rumen epithelium.…”

Increases in the expression of Na+/H+ exchanger 1 and 3 are associated with insulin signalling in the ruminal epithelium

“…Furthermore, previous study has demonstrated that the classical “job sharing” in epithelia between NHE3 (transepithelial Na transport) and NHE1 (regulation of pH i ) probably also occurred in the rumen epithelium (Rabbani, Siegling‐Vlitakis, Noci, & Martens, ). Our previous work has shown that feeding high concentrate diets could upregulate the expression of NHE in rumen epithelium, which help to the maintenance of intracellular pH homeostasis (Yan, Zhang, & Shen, ; Yang et al., ).…”