Effect of individual SCFA on the epithelial barrier of sheep rumen under physiological and acidotic luminal pH conditions

TLR5 ligand induces the gene expression of antimicrobial peptides and CXCL8 through IL-1β gene expression in cultured rumen epithelial cells

High grain feeding or weaning, which could compromise the rumen epithelium by increasing ruminal short-chain fatty acid (SCFA) concentrations with pH reduction, is associated with high levels of ruminal toll-like receptor 5 (TLR5). This study aimed to determine the role of TLR5 in the rumen epithelium. Immunohistochemistry revealed that TLR5 was localized in cells on the basal side (i.e., basal and spinous layers) rather than in the granular layer in the rumen epithelium, where tight junctions are most potent, in pre- and post-weaning calves (n = 9). Primary bovine rumen epithelial cells (BRECs) obtained from Holstein cows (n = 3) were cultured to investigate the factors that upregulate TLR5; however, SCFA, low pH (pH 5.6), BHBA, L-lactate, D-lactate, and LPS did not upregulate TLR5 gene expression in BREC. Primary BREC treated with flagellin (TLR5 ligand) had higher expression of interleukin-1β (IL-1β) (P < 0.05) than BREC treated with vehicle. In addition, BREC treated with IL-1β had higher expression of antimicrobial peptides and C-X-C motif chemokine ligand 8 than BREC treated with vehicle (P < 0.05). These results suggest that ruminal TLR5 may recognize epithelial disruption via flagellin and mediate the immune response via IL-1β during high-grain feeding or weaning.

Effect of increased intake of concentrates and sodium butyrate supplementation on reticulorumen macroanatomy and reticulorumen fermentation in growing rams

Increased ruminal butyrate production is considered to have mostly positive impacts on rumen macro- and microanatomy and its functions. However, excessive ruminal butyrate production may also affect the rumen negatively. Forty-two growing rams were allocated into six treatments and fed a diet with low (22.5% of diet DM; LOW) or high (60% of diet DM; HIGH) inclusion of concentrates in combination with no, low (1.6% of diet DM) or high (3.2% of diet DM) sodium butyrate (SB) supplementation to obtain low or high reticuloruminal (RR) pH with different concentrations of butyrate. Both absolute (L/day) and relative (% of BW) water intake increased linearly with increasing dose of SB (P ≤ 0.02). The RR fluid pH was lower for HIGH compared to LOW treatments (P < 0.01) but was not affected by SB supplementation (P = 0.35). Total short-chain fatty acid concentration, propionate and valerate concentrations in the RR fluid were higher for HIGH compared to LOW treatments (P ≤ 0.01), but were not affected by SB supplementation (P ≥ 0.22). Reticuloruminal butyrate was higher for HIGH compared to LOW treatments and increased linearly with increasing dose of SB (P < 0.01). High concentrate inclusion in the diet (P < 0.01) decreased and SB supplementation tended to (P = 0.10) decrease fibrolytic activity in the RR. Increasing doses of SB linearly decreased acetate, isovalerate and NH3-N concentrations in RR fluid, and RR digesta DM weight (g DM/kg BW; P ≤ 0.02). Relative RR and rumen tissue weights (g/kg BW) were higher for LOW compared to HIGH (P ≤ 0.03) treatments but were not affected by SB inclusion in the diet (P ≥ 0.35). Also, there was no impact of concentrates or SB inclusion in the diet on ruminal epithelium DM weight (mg/cm2), either in the ventral or dorsal sac of the rumen (P ≥ 0.14). Under conditions of the current study, SB supplementation in the diet decreased RR digesta DM concentration and weight, acetate, isovalerate and NH3-N concentration in the RR fluid, and tended to reduce fibrolytic activity in the RR. At least part of this response could be due to increased intake of water, and consequently passage of digesta from the RR to lower regions of the gastrointestinal tract.

Effect of increased intake of concentrates and sodium butyrate supplementation on ruminal epithelium structure and function in growing rams

Increased ruminal butyrate production is considered to have a positive impact on rumen epithelium growth and function. However, excessive ruminal butyrate production may affect the rumen negatively, particularly when the rumen is already challenged with low pH. The aim of this study was to determine the effect of the inclusion of concentrates in the diet and sodium butyrate (SB) supplementation on ruminal epithelium growth and function in growing rams. Forty-two rams (27.8 ± 7.3 kg; 9-14 months of age) were allocated into six treatments and fed a diet with low (22.5% of diet DM; LOW) or high (60% of diet DM; HIGH) inclusion of concentrates in combination with no (SB0), 1.6% (SB1.6) or 3.2% (SB3.2) of diet DM inclusion of SB. There was no impact of the investigated factors on papilla dimensions and mucosa surface area, either in the atrium ruminis or ventral rumen (P ≥ 0.11). Stratum corneum thickness was higher for HIGH compared to LOW treatments (P ≤ 0.04), independently of the location in the rumen. In the atrium ruminis, the epithelium and living strata thickness quadratically increased due to SB supplementation for LOW treatments but quadratically decreased for HIGH treatments (concentrate inclusion × butyrate supplementation interaction; P ≤ 0.03); conversely, in the ventral sac of the rumen, a thicker epithelium was observed due to both increased concentrate inclusion in the diet and SB supplementation (P < 0.01) but living strata thickness was increased only by SB supplementation (linear effect; P < 0.01). The epithelium damage index in the ventral sac of the rumen was higher for LOW compared to HIGH treatments (P = 0.02). Increased inclusion of concentrates in the diet increased mRNA expression of monocarboxylate transporter 1 in both the epithelium of the atrium ruminis and ventral rumen, occludin in the epithelium of the atrium ruminis and downregulated in adenoma in the epithelium of the ventral rumen (P ≤ 0.02). Protein expression of claudin-4 in the epithelium of the ventral rumen was the highest for the HIGH/SB1.6 and HIGH/SB3.2 treatments (significant effect of interaction between main effects; P < 0.01). Under the conditions of the current study, increased intake of concentrates had mostly positive effects on ruminal epithelium in growing rams, and the same was observed for the effect of SB supplementation. However, the effect of SB supplementation was at least partially affected by the inclusion of concentrates in the diet.

Effect of sodium concentration and mucosal pH on apical uptake of acetate and butyrate, and barrier function of the isolated bovine ruminal epithelium

This study was conducted to investigate the role of Na+ on ruminal short-chain fatty acid (SCFA) absorption and barrier function when isolated ruminal epithelium was exposed to high and low pH ex vivo. Nine Holstein steer calves (322 ± 50.9 kg of body weight) consuming 7.05 ± 1.5 kg dry matter of a total mixed ration were euthanized and ruminal tissue was collected from the caudal-dorsal blind sac. Tissues were mounted between 2 halves of Ussing chambers (3.14 cm2) and exposed to buffers that contained low (10 mM) or high (140 mM) Na+ with low (6.2) or high (7.4) mucosal pH. The same buffer solutions were used on the serosal side except that pH was maintained at 7.4. Buffers used to evaluate SCFA uptake contained bicarbonate to determine total uptake or excluded bicarbonate and included nitrate to determine noninhibitable uptake. Bicarbonate-dependent uptake was calculated as the difference between the total and noninhibitable uptake. Acetate (25 mM) and butyrate (25 mM) were spiked with 2-3H-acetate and 1-14C-butyrate, respectively, and were then added to the mucosal side, incubated for 1 min, and tissues were analyzed to evaluate rates of SCFA uptake. Tissue conductance (Gt) and the mucosal-to-serosal flux of 1-3H-mannitol were used to assess barrier function. There were no Na+ × pH interactions for butyrate or acetate uptake. Decreasing mucosal pH from 7.4 to 6.2 increased total acetate and butyrate uptake, and bicarbonate-dependent acetate uptake. Flux of 1-3H-mannitol was not affected by treatment. However, high Na+ concentration reduced Gt and prevented an increase in Gt from flux period 1 to flux period 2. The results of this study indicate that although providing more Na+ to the ruminal epithelium does not affect SCFA uptake or mannitol flux, it may help stabilize tissue integrity.

Genome-Wide Acetylation Modification of H3K27ac in Bovine Rumen Cell Following Butyrate Exposure

Butyrate contributes epigenetically to the changes in cellular function and tissue development of the rumen in ruminant animals, which might be achieved by its genetic or epigenetic regulation of gene expression. To explore the role of butyrate on bovine rumen epithelial function and development, this study characterized genome-wide H3K27ac modification changes and super-enhancer profiles in rumen epithelial primary cells (REPC) induced with butyrate by ChIP-seq, and analyzed its effects on gene expression and functional pathways by integrating RNA-seq data. The results showed that genome-wide acetylation modification was observed in the REPC with 94,675 and 48,688 peaks in the butyrate treatment and control group, respectively. A total of 9750 and 5020 genes with increased modification (H3K27ac-gain) and decreased modification (H3K27ac-loss) were detected in the treatment group. The super-enhancer associated genes in the butyrate-induction group were involved in the AMPK signaling pathway, MAPK signaling pathway, and ECM-receptor interaction. Finally, the up-regulated genes (PLCG1, CLEC3B, IGSF23, OTOP3, ADTRP) with H3K27ac gain modification by butyrate were involved in cholesterol metabolism, lysosome, cell adhesion molecules, and the PI3K-Akt signaling pathway. Butyrate treatment has the role of genome-wide H3K27ac acetylation on bovine REPC, and affects the changes in gene expression. The effect of butyrate on gene expression correlates with the acetylation of the H3K27ac level. Identifying genome-wide acetylation modifications and expressed genes of butyrate in bovine REPC cells will expand the understanding of the biological role of butyrate and its acetylation.

Blend of Cinnamaldehyde, Eugenol, and Capsicum Oleoresin Improved Rumen Health of Lambs Fed High-Concentrate Diet as Revealed by Fermentation Characteristics, Epithelial Gene Expression, and Bacterial Community

We investigated the effects of CEC on the fermentation characteristics, epithelial gene expression, and bacterial community in the rumen of lambs fed a high-concentrate diet. Twenty-four 3-month-old female crossbred lambs with an initial body weight of 30.37 ± 0.57 kg were randomly allocated to consume a diet supplemented with 80 mg/kg CEC (CEC) or not (CON). The experiment consisted of a 14 d adaptation period and a 60 d data collection period. Compared with the CON group, the CEC group had higher ADG, epithelial cell thickness, ruminal butyrate proportion, and lower ammonia nitrogen concentration. Increases in the mRNA expression of Occludin and Claudin-4, as well as decreases in the mRNA expression of apoptotic protease activating factor-1 (Apaf-1), cytochrome c (Cyt-C), Caspase-8, Caspase-9, Caspase-3, Caspase-7, and toll-like receptor 4 (TLR4), were observed in the CEC group. Moreover, CEC treatment also decreased the concentration of IL-1β, IL-12, and TNF-α. Supplementation with CEC altered the structure and composition of the rumen bacterial community, which was indicated by the increased relative abundances of Firmicutes, Synergistota, Rikenellaceae_RC9_gut_group, Olsenella, Schwartzia, Erysipelotrichaceae_UCG-002, Lachnospiraceae_NK3A20_group, Acetitomaculum, [Eubacterium]_ruminantium_group, Prevotellaceae_UCG-004, Christensenellaceae_R-7_group, Sphaerochaeta, Pyramidobacter, and [Eubacterium]_eligens_group, and the decreased relative abundances of Acidobacteriota, Chloroflexi, Gemmatimonadota, and MND1. Furthermore, Spearman correlation analysis revealed that the altered rumen bacteria were closely correlated with rumen health-related indices. Dietary CEC supplementation improved growth performance, reduced inflammation and apoptosis, protected barrier function, and modulated the bacterial community of lambs fed a high-concentrate diet.

Rumen Epithelial Development- and Metabolism-Related Genes Regulate Their Micromorphology and VFAs Mediating Plateau Adaptability at Different Ages in Tibetan Sheep

The rumen is an important hallmark organ of ruminants and plays an important role in the metabolism and immune barrier of Tibetan sheep on the Plateau. However, there are few studies on rumen development and metabolism regulation in Tibetan sheep at different ages. Here, we comprehensively analyzed the immune function, fermentation function, rumen epithelial micromorphology and transcriptome profile of Tibetan sheep at different ages. The results showed that the concentration of IgG decreased and the concentration of IgM increased with age (p < 0.05), and the highest concentration of IgA was observed at 1.5 and 3.5 years of age. In terms of rumen fermentation characteristics, VFAs of 4-month-old lambs were the highest, followed by VFAs and NH3-N of Tibetan sheep at 3.5 years of age. Hematoxylin-eosin staining and transmission electron microscopy section examination of rumen epithelial tissue showed that the rumen papilla width increased with age (p < 0.001), the thickness of the stratum corneum decreased, the cells in the stratum corneum showed accelerated migration and the thickness of the rumen muscle layer increased (p < 0.001). Desmosomal junctions between the layers of rumen epithelium increased at 1.5 and 3.5 years old, forming a compact barrier structure, and the basal layer had more mitochondria involved in the regulation of energy metabolism. RNA-seq analysis revealed that a total of 1006 differentially expressed genes (DEGs) were identified at four ages. The DEGs of Tibetan sheep aged 4 months and 6 years were mainly enriched in the oxidation−reduction process and ISG15-protein conjugation pathway. The 1.5 and 3.5-year-olds were mainly enriched in skeletal muscle thin filament assembly, mesenchyme migration and the tight junction pathway. WGCNA showed that DEGs related to rumen microbiota metabolite VFAs and epithelial morphology were enriched in “Metabolism of xenobiotics by cytochrome P450, PPAR signaling pathway, Butanoate metabolism pathways” and participated in the regulation of rumen epithelial immune and fermentation metabolism functions of Tibetan sheep at different ages. This study systematically revealed the regulatory mechanism of rumen epithelial development and metabolism in the plateau adaptation of Tibetan sheep, providing a new approach for the study of plateau adaptation.

Butyrate Induces Modifications of the CTCF-Binding Landscape in Cattle Cells

Butyrate is produced in the rumen from microbial fermentation and is related to several functions, including cell differentiation and proliferation. Butyrate supplementation in calves can accelerate rumen development. DNA-protein interactions, such as the CCCTC-binding factor (CTCF), play essential roles in chromatin organization and gene expression regulation. Although CTCF-binding sites have been identified recently in cattle, a deeper characterization, including differentially CTCF-binding sites (DCBS), is vital for a better understanding of butyrate’s role in the chromatin landscape. This study aimed to identify CTCF-binding regions and DCBS under a butyrate-induced condition using ChIP-seq in bovine cells; 61,915 CTCF peaks were identified in the butyrate and 51,347 in the control. From these regions, 2265 DCBS were obtained for the butyrate vs. control comparison, comprising ~90% of induced sites. Most of the butyrate DCBS were in distal intergenic regions, showing a potential role as insulators. Gene ontology enrichment showed crucial terms for the induced DCBS, mainly related to cellular proliferation, cell adhesion, and growth regulation. Interestingly, the ECM-receptor interaction pathway was observed for the induced DCBS. Motif enrichment analysis further identified transcription factors, including CTCF, BORIS, TGIF2, and ZIC3. When DCBS was integrated with RNA-seq data, putative genes were identified for the repressed DCBS, including GATA4. Our study revealed promising candidate genes in bovine cells by a butyrate-induced condition that might be related to the regulation of rumen development, such as integrins, keratins, and collagens. These results provide a better understanding of the function of butyrate in cattle rumen development and chromatin landscape regulation.

Direct effect of lipopolysaccharide and histamine on permeability of the rumen epithelium of steers ex vivo

Disruption of the ruminal epithelium barrier occurs during subacute ruminal acidosis due to low pH, hyper-osmolality, and increased concentrations of lipopolysaccharide and histamine in ruminal fluid. However, the individual roles of lipopolysaccharide and histamine in the process of ruminal epithelium barriers disruption are not clear. The objective of the present investigation was to evaluate the direct effect of lipopolysaccharide and histamine on the barrier function of the ruminal epithelium. Compared with control (CON), histamine (HIS, 20 μM) increased the short-circuit current (Isc; 88.2%, P < 0.01), transepithelial conductance (Gt; 29.7%, P = 0.056), and the permeability of fluorescein 5(6)-isothiocyanate (FITC) (1.04-fold, P < 0.01) of ruminal epithelium. The apparent permeability of LPS was 1.81-fold higher than HIS (P < 0.01). The mRNA abundance of OCLN in ruminal epithelium was decreased by HIS (1.1-fold, P = 0.047). The results of the present study suggested that mucosal histamine plays a direct role in the disruption of ruminal epithelium barrier function, whereas lipopolysaccharide (at a pH of 7.4) has no effect on the permeability of rumen tissues ex vivo.

Menthol stimulates calcium absorption in the rumen but not in the jejunum of sheep

Stimulation of Ca²⁺ absorption can counteract hypocalcemia at the onset of lactation. The plant bioactive lipid compound (PBLC) menthol is an agonist for nonselective cation channels of the transient receptor potential (TRP) family. It acutely stimulated Ca²⁺ absorption in ruminal epithelia of nonadapted animals ex vivo and caused higher plasma Ca²⁺ concentrations in cows and sheep in vivo. To elucidate the pathway by which menthol feeding increases plasma Ca²⁺ level, the present study aimed to investigate the long-term dose-dependent effects of dietary menthol-rich PBLC on Ca²⁺ absorption and mRNA abundances of TRP channels in both rumen and jejunum. Twenty-four growing Suffolk sheep were equally distributed to a Con, PBLC-L, and PBLC-H group, which received 0, 80, and 160 mg/d of a menthol-rich PBLC. After 4 wk, ruminal and jejunal epithelia were analyzed for mRNA abundances of TRPA1, TRPV3, TRPV5-6, and TRPM6-8 genes. The Ca²⁺ flux rates and electrophysiological properties of epithelia from rumen and mid-jejunum were measured in Ussing chambers in the presence and absence of mucosal Na⁺. Acute changes in Ca²⁺ flux rates were measured after mucosal application of 50 µM menthol. Ruminal epithelia had quantifiable transcripts of TRPV3 = TRPM6 >TRPM7 >TRPA1 with no difference among feeding groups. Jejunum had quantifiable transcripts of TRPM7 >TRPA1 ≥ TRPM6 ≥ TRPV6 >TRPV5, where TRPA1, TRPV5, and TRPV6 tended to decrease linearly with increasing PBLC dose. Absorptive net flux of Ca²⁺ was detected only in the rumen, whereas jejunum showed a high passive permeability to Ca²⁺. Net flux rates of Ca²⁺ in the rumen increased in a quadratic manner (highest in PBLC-L animals) and were systematically decreased with the omission of mucosal Na⁺. Short-circuit current increased in both PBLC feeding groups compared with Con only in the rumen. Acute application of menthol-stimulated mucosal-to-serosal and net Ca²⁺ flux rates only in ruminal epithelia with higher stimulation in PBLC-fed animals. We conclude that Ca²⁺ transport is mainly active and transcellular in the rumen. It most likely involves TRPV3 that can be stimulated by menthol. Pre-feeding of menthol-rich PBLC enhances ruminal Ca²⁺ absorption and sensitizes it to acute stimulation by menthol. By contrast, intestinal Ca²⁺ absorption is not sensitive to menthol stimulation. Menthol could be used as a tool to enhance ruminal Ca²⁺ absorption and to prevent hypocalcemia in dairy cows.

Effects of lipopolysaccharide exposure on the inflammatory response, butyrate flux, and metabolic function of the ruminal epithelium using an ex vivo model

Acidotic conditions in the rumen have been associated with compromised barrier function of the ruminal epithelium and translocation of microbe-associated molecular patterns (MAMP) such as lipopolysaccharide (LPS). Interaction of MAMP with the ruminal epithelium may also induce a local proinflammatory response. The aim of this study was to evaluate the potential proinflammatory response of the ruminal epithelium following LPS exposure in Ussing chambers, to investigate whether LPS exposure affects the flux and metabolism of butyrate. Ruminal epithelial tissue from 9 Holstein bull calves were mounted into Ussing chambers and exposed to 0, 10,000, 50,000, or 200,000 endotoxin units (EU)/mL LPS for a duration of 5 h. Radiolabeled ¹⁴C-butyrate (15 mM) was added to the mucosal buffer to assess the mucosal-to-serosal flux of ¹⁴C-butyrate. Additional Ussing chambers, without radioisotope, were exposed to either 0 or 200,000 EU/mL LPS and were used to measure the release of β-hydroxybutyrate (BHB) and IL1B into the buffer, and to collect epithelial tissue for analysis of gene expression. Genes associated with inflammation (TNF, IL1B, CXCL8, PTGS2, TGFB1, TLR2, TLR4), nutrient transport (MCT1, MCT4, SLC5A8, GLUT1), and metabolic function (ACAT1, BDH1, MCU, IGFBP3, IGFBP5) were selected and analyzed using quantitative real-time PCR. Butyrate flux was not significantly affected by LPS exposure; however, we detected a tendency for the mucosal-to-serosal butyrate flux to increase linearly with LPS dose. Bidirectional releases of BHB and IL1B were not affected by LPS exposure. Expression of PTGS2, TGFB1, TLR4, and MCU were downregulated following exposure to LPS ex vivo. We detected no effects on the expression of genes associated with nutrient transport. The results of the present study are interpreted to indicate that, although the inflammatory response of the ruminal epithelium was slightly suppressed, exposure to LPS may have altered metabolic function.

Comparison of MicroRNA Transcriptomes Reveals the Association between MiR-148a-3p Expression and Rumen Development in Goats

Simple Summary

In ruminants, the rumen epithelium plays an important role in nutrient absorption, metabolism and transport. MicroRNAs (miRNAs) have been reported to regulate the proliferation of diverse epithelial cells. In this study, we profiled the miRNA transcriptomes of goat rumens at four development stages and screened for candidate miRNAs related to rumen development. MiR-148a-3p was found to be highly expressed in the rumen tissues and induced the proliferation of GES-1 cells by targeting QKI. Our findings provide some insights into the functional roles of miRNAs in rumen growth and functional development in ruminants.

Abstract

The rumen is an important digestive organ of ruminants. From the fetal to adult stage, the morphology, structure and function of the rumen change significantly. However, the knowledge of the intrinsic genetic regulation of these changes is still limited. We previously reported a genome-wide expression profile of miRNAs in pre-natal goat rumens. In this study, we combined and analyzed the transcriptomes of rumen miRNAs during pre-natal (E60 and E135) and post-natal (D30 and D150) stages. A total of 66 differentially expressed miRNAs (DEMs) were identified in the rumen tissues from D30 and D150 goats. Of these, 17 DEMs were consistently highly expressed in the rumens at the pre-weaning stages (E60, E135 and D30), while down-regulated at D150. Noteworthy, annotation analysis revealed that the target genes regulated by the DEMs were mainly enriched in MAPK signaling pathway, Jak-STAT signaling pathway and Ras signaling pathway. Interestingly, the expression of miR-148a-3p was significantly high in the embryonic stage and down-regulated at D150. The potential binding sites of miR-148a-3p in the 3′-UTR of QKI were predicted by the TargetScan and verified by the dual luciferase report assay. The co-localization of miR-148a-3p and QKI through in situ hybridization was observed in the rumen tissues but not in the intestinal tracts. Moreover, the expression of miR-148a-3p in the epithelium was significantly higher than that in the other layers of the rumen, suggesting that miR-148a-3p is involved in the development of the rumen epithelial cells by targeting QKI. Subsequently, miR-148a-3p inhibitor was found to induce the proliferation of GES-1 cells. Taken together, our study identified DEMs involved in the development of the rumen and provides insights into the regulation mechanism of rumen development in goats.

Colchicine increases intestinal permeability, suppresses inflammatory responses, and alters gut microbiota in mice

Although colchicine (COL) has been used to treat gout for more than a thousand years, it has been shrouded in a dark history for a long time due to its high toxicity, especially for the gastrointestinal tract. With the widespread clinical application of COL, COL's toxicity to the gastrointestinal tract has raised concerns. This study's objective was to address the exact intestinal toxicity of COL, with particular attention to the effects of COL on gut microbiota homeostasis. The mice were exposed to various dosages of COL (0.1, 0.5, and 2.5 mg kg^-1 body weight per day) for a week, and the results showed that COL exposure caused serious intestinal injuries, reducing the relative expression levels of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) and tight junction proteins (zo-1, claudin-1, and occludin) in the ileum and colon tissue. The 16S rRNA gene sequencing analysis of mice feces samples revealed that the composition and diversity of intestinal microbiome underwent a profound remodeling at the dosage of 2.5 mg kg^-1 body weight per day, which may increase the toxic load in the gut. In addition, elevated levels of diamine oxidase (DAO) and lipopolysaccharide (LPS) in serum indicated that COL increased intestinal permeability, impairing intestinal barrier. In conclusion, our results demonstrate that COL's toxicity to the gut microbiome is compatible with intestinal injuries, inflammatory pathway inhibition, and increased intestinal permeability; our results also represent a novel insight to uncover the adverse reactions of COL in the gastrointestinal tract.

Comparing the gastrointestinal barrier function between growth-retarded and normal yaks on the Qinghai-Tibetan Plateau

Background

Yak (Bos grunniens) is an ancient bovine species on the Qinghai-Tibetan Plateau. Due to extremely harsh condition in the plateau, the growth retardation of yaks commonly exist, which can reduce the incomes of herdsman. The gastrointestinal barrier function plays a vital role in the absorption of nutrients and healthy growth. Functional deficiencies of the gastrointestinal barrier may be one of the contributors for yaks with growth retardation.

Methods

To this end, we compared the growth performance and gastrointestinal barrier function of growth-retarded (GRY) and normal yaks (GNY) based on average daily gain (ADG), serum parameters, tissue slice, real-time PCR, and western blotting, with eight yaks in each group.

Results

GRY exhibited lower (P < 0.05) average daily gain as compared to GNY. The diamine oxidase, D-lactic acid, and lipopolysaccharide concentrations in the serum of GRY were significantly higher (P < 0.05) than those of GNY. Compared to GNY, the papillae height in the rumen of GRY exhibited lower (P = 0.004). In jejunum, with the exception of higher villus height, width, and surface area in GNY, numerical difference (P = 0.61) was detected between two groups for crypt depth. Both in rumen and jejunum, the mRNA expression of interleukin-1beta in GRY was markedly higher (P < 0.05) than that in GNY, but an opposite trend was found in interleukin-10 expression. Moreover, GRY showed a higher (P < 0.05) tumor necrosis factor-alpha mRNA expression in the rumen. The claudin-1 (CLDN1), occludin (OCLN), and zonula occludens-1 (ZO1) expressions of GRY in rumen and jejunum were significantly down-regulated (P < 0.05) as compared to GNY. The correlation analysis identified that in rumen and jejunum, there was a positive correlation between interleukin-10 and CLDN1, OCLN, and ZO1 mRNA expressions, but the tumor necrosis factor-alpha was negatively correlated with CLDN1, OCLN, and ZO1. In the rumen, the ADG was positively correlated with papillae surface area, and a same relationship between ADG and CLDN1, OCLN, and ZO1 expressions was found.

Conclusion

The results indicated that the ruminal and jejunal barrier functions of GRY are disrupted as compared to GNY. In addition, our study provides a potential solution for promoting the growth of GRY by enhancing the gastrointestinal barrier function.

The Regulation of Ruminal Short-Chain Fatty Acids on the Functions of Rumen Barriers

The rumen barriers, constituted by the microbial, physical and immune barrier, prevent the transmission of pathogens and toxins to the host tissue in the maintenance of host-microbe homeostasis. Ruminal short-chain fatty acids (SCFAs), which are the important signaling molecules derived from the rumen microbiota, regulate a variety of physiological functions of the rumen. So far, how the ruminal SCFAs regulate the function of rumen barriers is unclear. By the combined methods of transcriptome sequencing, 16S rRNA gene sequencing, and metagenome shotgun sequencing, we have investigated the regulatory effects of ruminal SCFAs on the functions of rumen barriers, by determining the composition and functions of epimural microbiota and on the structure and immunity of the rumen epithelium in goats receiving a 10% (LC group), 35% (MC group), or 65% concentrate diet (HC group). We found that, when the dietary concentrate shifted from 10 to 35%, the increase of total SCFA is associated with the diversification of epimural microbiota and the diversity of its gene pool. Within the microbial community, the relative abundance of genera Sphingobium, Acinetobacter, and Streptococcus increase mostly. Meantime, the signals on pathways concerning the mechanical connections and growth homeostasis in the rumen epithelium were upregulated. Under these conditions, the responses of immune components in the rumen epithelium decrease. However, when the dietary concentrate shifted from 35 to 65%, the increase of acetate and reduction of pH decrease the diversity of epimural microbiota and the diversity of its gene pool. Within the microbial community, the relative abundance of genera Sphingobium, Acinetobacter, and Streptococcus significantly decrease. Concomitantly, the signals on pathways concerning the cell growth and tight junction disruption were upregulated, while the signals on pathways concerning paracellular permeability were downregulated. Under these conditions, the signals on the pathways relating to the immune components increase. Our data thus indicates that diet-SCFA axis maintains the host-microbe homeostasis via promoting the diversification of epimural microbiota and maintaining the integrity of rumen epithelium in healthy animals, while via enhancing the activities of immune barrier in animal with lower rumen pH.

Effects of glucagon-like peptides 1 and 2 and epidermal growth factor on the epithelial barrier of the rumen of adult sheep

Epidermal growth factor (EGF) and glucagon-like peptides (GLP) modulate the tight junctions (TJ) of the intestinal epithelial barrier (EB) of monogastric animals. This work tried to elucidate whether GLP-1, GLP-2 and EGF can affect the EB of the rumen. Ovine ruminal epithelia were incubated in Ussing chambers for 7 hr with 25 or 250 nM of either GLP-1 or GLP-2 on the serosal side, with 2.5 nM of EGF on the serosal side or with 0.25 or 2.5 nM EGF on the mucosal side. No treatment affected tissue conductance. Short-circuit current (I_sc ) was affected by time and treatment and their interactions. Only 250 nM of either GLP-1 or GLP-2 decreased I_sc in certain periods compared with 25 nM GLP-1 or 0.25 nM mucosally applied EGF; however, not when compared to control epithelia. Fluorescein flux rates (J_fluor ) of ruminal epithelia were affected by treatment, time and time × treatment interaction. The time × treatment interaction was based on an increase in J_fluor between the first and last hour in epithelia incubated with 25 nM GLP-1 or GLP-2 and in epithelia incubated with EGF. After 7 hr incubation, claudin-7 mRNA expression was downregulated in all treatments. Claudin-1 mRNA was upregulated after incubation with 2.5 nM EGF on the serosal side, claudin-4 mRNA was downregulated by 2.5 nM EGF on the mucosal side, and occludin mRNA was increased after incubation with 250 nM GLP-2. The protein abundance of all tested TJ proteins was not influenced by treatment. We conclude that GLP-1, GLP-2, and EGF have no obvious acute effects on the EB of ruminal epithelia under simulated physiological conditions ex vivo. However, by decreasing the mRNA expression of claudin-7 and partly affecting other TJ proteins, they may modulate EB in the longer term or under certain conditions.

Growth of rumen papillae in weaned calves is associated with lower expression of insulin-like growth factor-binding proteins 2, 3, and 6

This study aimed to characterize the relationship between the growth of rumen papillae in calves and the mRNA expression of insulin-like growth factor-binding proteins (IGFBPs) in the rumen papillae. The length of rumen papillae, the mRNA expression of IGFBPs in rumen papillae by quantitative real-time PCR, and the presence of insulin-like growth factors I and II (IGF-I and II) by immunohistochemistry (IHC) were analyzed in nine Holstein calves divided into three groups: suckling (2 weeks, n = 3), milk-continued (8 weeks, n = 3), and weaned (8 weeks, n = 3). The length of rumen papillae was greater (p < 0.01) in weaned calves than in suckling and milk-continued calves, whereas the expressions of IGFBP2, IGFBP3, and IGFBP6 genes were lower (p < 0.05) in the rumen papillae of weaned calves than in milk-continued calves. Thus, rumen papillae length and IGFBP2, 3, and 6 expressions were negatively correlated. The IHC analysis showed that IGF-I and IGF-II were present in the rumen epithelium of calves. These results suggested that the growth of rumen papillae after weaning is associated with the induction of IGFs by the low levels of IGFBP2, IGFBP3, and IGFBP6.

Effect of exogenous butyrate on the gastrointestinal tract of sheep. I. Structure and function of the rumen, omasum, and abomasum

The aim of this study was to determine the effect of exogenous butyrate on the structure and selected functions of the stomach in sheep. Eighteen rams (30.8 ± 2.1 kg; 12 to 15 mo of age) were allocated to the study and fed a diet for 14 d without (CTRL) or with sodium butyrate (BUT; 36 g/kg of offered DM). Neither DMI nor initial BW differed between treatments (P ≥ 0.61), but final BW was greater for BUT compared with CTRL (P = 0.03). Butyrate concentration in the reticuloruminal fluid and abomasal digesta was greater for BUT compared with CTRL (P ≤ 0.01), but total short-chain fatty acids (SCFA) concentration, as well as concentration of other SCFA, did not differ between treatments (P ≥ 0.07). Relative to BW, reticuloruminal tissue mass tended (P = 0.09) to be greater and omasal digesta was less (P = 0.02) for BUT compared with CTRL. Dietary butyrate did not affect ruminal papillae length, width, and density nor did it affect ruminal epithelium thickness (P ≥ 0.12) in the ventral sac of the rumen. However, the DM of ruminal epithelium (mg/cm2) tended (P = 0.06) to be greater for BUT compared with CTRL. Omasal and abomasal epithelium thicknesses were greater (P ≤ 0.05) for BUT compared with CTRL. Mitosis-to-apoptosis ratio in the abomasal epithelium was less for BUT compared with CTRL (P = 0.04). Finally, the mRNA expression of peptide transporter 1 in the omasal epithelium was less (P = 0.02) and mRNA expression of monocarboxylate transporter 1 in the abomasal epithelium tended (P = 0.07) to be greater for BUT compared with CTRL. It can be concluded that exogenous butyrate supplementation affected not only the rumen but also omasum and abomasum in sheep.