Abundance of ruminal bacteria, epithelial gene expression, and systemic biomarkers of metabolism and inflammation are altered during the peripartal period in dairy cows

Abstract

Seven multiparous Holstein cows with a ruminal fistula were used to investigate the changes in rumen microbiota, gene expression of the ruminal epithelium, and blood biomarkers of metabolism and inflammation during the transition period. Samples of ruminal digesta, biopsies of ruminal epithelium, and blood were obtained during -14 through 28d in milk (DIM). A total of 35 genes associated with metabolism, transport, inflammation, and signaling were evaluated by quantitative reverse transcription-PCR. Among metabolic-related genes, expression of HMGCS2 increased gradually from -14 to a peak at 28 DIM, underscoring its central role in epithelial ketogenesis. The decrease of glucose and the increase of nonesterified fatty acids and β-hydroxybutyrate in the blood after calving confirmed the state of negative energy balance. Similarly, increases in bilirubin and decreases in albumin concentrations after calving were indicative of alterations in liver function and inflammation. Despite those systemic signs, lower postpartal expression of TLR2, TLR4, CD45, and NFKB1 indicated the absence of inflammation within the epithelium. Alternatively, these could reflect an adaptation to react against inducers of the immune system arising in the rumen (e.g., bacterial endotoxins). The downregulation of RXRA, INSR, and RPS6KB1 between -14 and 10 DIM indicated a possible increase in insulin resistance. However, the upregulation of IRS1 during the same time frame could serve to restore sensitivity to insulin of the epithelium as a way to preserve its proliferative capacity. The upregulation of TGFB1 from -14 and 10 DIM coupled with upregulation of both EGFR and EREG from 10 to 28 DIM indicated the existence of 2 waves of epithelial proliferation. However, the downregulation of TGFBR1 from -14 through 28 DIM indicated some degree of cell proliferation arrest. The downregulation of OCLN and TJP1 from -14 to 10 DIM indicated a loss of tight-junction integrity. The gradual upregulation of membrane transporters MCT1 and UTB to peak levels at 28 DIM reflected the higher intake and fermentability of the lactation diet. In addition, those changes in the diet after calving resulted in an increase of butyrate and a decrease of ruminal pH and acetate, which partly explain the increase of Anaerovibrio lipolytica, Prevotella bryantii, and Megasphaera elsdenii and the decrease of fibrolytic bacteria (Fibrobacter succinogenes, Butyrivibrio proteoclasticus). Overall, these multitier changes revealed important features associated with the transition into lactation. Alterations in ruminal epithelium gene expression could be driven by nutrient intake-induced changes in microbes; microbial metabolism; and the systemic metabolic, hormonal, and immune changes. Understanding causes and mechanisms driving the interaction among ruminal bacteria and host immunometabolic responses merits further study.

Innate immune responses to metabolic stress can be detected in rumen fluids

“…Moreover, some of the signs attributed to SARA are dysfunctions common also to other digestive and metabolic disorders. These may affect the complex perception of satiety (Sartin et al, 2011), cause the release and absorption of immune-stimulating molecules such as lipopolysaccharides or histamine (Eckel and Ametaj, 2016;Minuti et al, 2014;Minuti et al, 2015;Nocek, 1997) and determine the modification of the microbiota (Minuti et al, 2015;Weimer, 2015;Yáñez-Ruiz et al, 2015). Because of this complexity, we have investigated the possible role of other factors involved in the forestomach functions.…”

“…Thus, our data make a case for new research efforts concerning the origin and clearance of rumen leukocytes. Regardless of the actual origin of leukocytes in rumen fluids, a powerful amplification of inflammatory signals could take place for local and systemic responses, which may also involve the rumen microbiota (Minuti et al, 2015;Yáñez-Ruiz et al, 2015).…”

“…This phase is characterized by a condition of negative energy balance, since high-yielding dairy cows are unable to achieve nutrient intake matching their high production requirements (Drackley, 1999). During this period also the rumen milieu is markedly challenged by the drastic changes of the diet necessary to cover the increased requirements for milk production, which alters the microbiota, the profile of fermentations and the epithelial permeability (Minuti e al., 2015). This is particularly relevant to genetically selected cattle breeds, which have to manage high production levels underlying an increased prevalence of diseases, as observed e.g.…”

Aspects of rumen adaptation in dairy cattle : morphological, functional, and gene expression changes of the rumen papillae and changes of the rumen microbiota during the transition period

“…For example, feeding high amounts of grain caused high rumen VFA concentrations and concurrent low pH values, but upregulation of VFA transporter genes was generally not observed. During the transition period, some changes in expression of genes associated with VFA transport, metabolism, and proliferation have been observed by Minuti et al (2015) and but these studies did not examine VFA absorption in situ, leaving any relationships between gene expression and functional changes largely unknown. Moreover, few studies report changes in expression at the protein level in lieu of expression at mRNA level Metzler-Zebeli et al, 2013;Minuti et al, 2015), further limiting functional interpretation of results.…”

“…During the transition period, some changes in expression of genes associated with VFA transport, metabolism, and proliferation have been observed by Minuti et al (2015) and but these studies did not examine VFA absorption in situ, leaving any relationships between gene expression and functional changes largely unknown. Moreover, few studies report changes in expression at the protein level in lieu of expression at mRNA level Metzler-Zebeli et al, 2013;Minuti et al, 2015), further limiting functional interpretation of results. Thus, an integrated set of observations on changes in rumen morphology and function, and associated changes in gene expression in response to nutrition is currently still lacking.…”