Evaluation of circulating microRNA profiles in blood as potential candidate biomarkers in a subacute ruminal acidosis cow model - a pilot study.

BACKGROUND: Subacute ruminal acidosis (SARA) is a metabolic disorder often observed in high-yielding dairy cows, that are fed diets high in concentrates. We hypothesized that circulating miRNAs in blood of cows could serve as potential candidate biomarkers to detect animals with metabolic dysbalances such as SARA. MicroRNAs (miRNAs) are a class of small non-coding RNAs, serving as regulators of a plethora of molecular processes. To test our hypothesis, we performed a pilot study with non-lactating Holstein-Friesian cows fed a forage diet (FD; 0% concentrate, n = 4) or a high-grain diet (HG; 65% concentrate, n = 4) to induce SARA. Comprehensive profiling of miRNA expression in plasma and leucocytes were performed by next generation sequencing (NGS). The success of our model to induce SARA was evaluated based on ruminal pH and was evidenced by increased time spent with a pH threshold of 5.8 for an average period of 320 min/d. RESULTS: A total of 520 and 730 miRNAs were found in plasma and leucocytes, respectively. From these, 498 miRNAs were shared by both plasma and leucocytes, with 22 miRNAs expressed exclusively in plasma and 232 miRNAs expressed exclusively in leucocytes. Differential expression analysis revealed 10 miRNAs that were up-regulated and 2 that were down-regulated in plasma of cows when fed the HG diet. A total of 63 circulating miRNAs were detected exclusively in the plasma of cows with SARA, indicating that these animals exhibited a higher number and diversity of circulating miRNAs. Considering the total read counts of miRNAs expressed when fed the HG diet, differentially expressed miRNAs ( log2 fold change) and known function, we have identified bta-miR-11982, bta-miR-1388-5p, bta-miR-12034, bta-miR-2285u, and bta-miR-30b-3p as potential candidates for SARA-biomarker in cows by NGS. These were further subjected to validation using small RNA RT-qPCR, confirming the promising role of bta-miR-30b-3p and bta-miR-2285. CONCLUSION: Our data demonstrate that dietary change impacts the release and expression of miRNAs in systemic circulation, which may modulate post-transcriptional gene expression in cows undergoing SARA. Particularly, bta-miR-30b-3p and bta-miR-2285 might serve as promising candidate biomarker predictive for SARA and should be further validated in larger cohorts.

Short-chain fatty acids promote jejunal barrier function and caecal muscle contractibility in laying hens ex vivo.

1. Short-chain fatty acids (SCFA) exert beneficial actions in the gut; nevertheless, information about the effect of SCFA on physiological responses in the small intestine of chickens is rare.2. The aim of this study was to assess the effect of 1) different molar acetate:butyrate ratios (Ac:But; Experiment 1; 78.5% acetate and 7.3% butyrate versus 71.4% acetate and 14.0% butyrate) and 2) SCFA concentrations (Experiment 2; final concentration in chambers: 70.5 versus 141 µmol SCFA/ml buffer) on the jejunal and caecal contractibility and jejunal barrier function in laying hens. The change in muscle contractibility due to the SCFA was measured in mid-jejunal and caecal segments (n = 4 each per hen) from four laying hens using the organ bath system after precontraction with acetylcholine for 15 min. Changes in short-circuit current (ISC) and transepithelial tissue conductivity (GT) as indicators for net ion flux and barrier function, respectively, were measured in mid-jejunal tissue (n = 3/hen and treatment), mounted into Ussing chambers.3. In Experiment 1, the addition of SCFA, irrespective of the Ac:But ratio, decreased jejunal muscle tension (P < 0.05), jejunal GT as well as caused a less negative ISC (P < 0.05). In Experiment 2, the increasing SCFA concentrations increased the caecal muscle contraction and jejunal ISC by 75.6% while decreasing the GT by up to 19.6% (P < 0.05).4. In conclusion, results demonstrate that increasing butyrate proportions and SCFA concentrations stimulate caecal muscle contraction, thereby increasing caecal mixing and emptying in vivo. Jejunal ISC and GT support a strong SCFA sensing capacity in the jejunum, as both, more butyrate and higher SCFA, increased mucosal ion uptake and barrier function.

Cinnamon bark oil and coconut oil emulsions modified small intestinal motility and barrier function in laying hens in an ex vivo experiment.

1. Plant extracts and oils are supplemented in diets for chickens due to their antimicrobial capacities; however, little information exists whether they influence intestinal motility and barrier function.2. The present study aimed to determine the effect of increasing levels of cinnamon bark oil (CBO; 0%, 0.038%, 0.076% and 0.151%) and coconut oil emulsions prepared with soy and sunflower lecithin on the contractile function of enteric wall muscles in the jejunum and ileum and jejunal barrier function in laying hens.3. For testing muscle contraction, mid-jejunal and ileal segments (n = 4 each per hen) from four laying hens were placed in a longitudinal orientation into isolated organ baths filled with Krebs buffer and fastened to force transducers. Muscle segments were induced to contract with acetylcholine and the effects of the oil emulsions on contraction were measured.4. For barrier function, distal jejunal pieces were stripped of serosa before mounting into Ussing chambers and recording changes in short-circuit current (ISC) and transepithelial tissue conductivity (GT) before and after addition of the respective emulsion.5. The CBO decreased the muscle tone, representing a relaxation of on average 36.2% and 42.6% for the jejunum and ileum, respectively, compared to before the addition (P < 0.001). Moreover, CBO linearly decreased the ISC and GT of the jejunal mucosa, indicating a greater absorption of anions and increased barrier function (P < 0.001). Only the coconut oil-sunflower lecithin emulsion relaxed the muscles, whereas both coconut oil-lecithin emulsions increased the ISC but reduced the GT of the jejunal mucosa, which suggested an increased cation absorption and decreased paracellular permeability, respectively (P < 0.05).6. In conclusion, CBO and coconut oil-lecithin emulsions showed the potential to increase jejunal barrier function, whereas CBO may be more efficacious to slow down digesta passage in the small intestine.