Transcriptional integration of distinct microbial and nutritional signals by the small intestinal epithelium

To preserve its physiologic functions, the intestine must interpret and adapt to complex combinations of stimuli from dietary and microbial sources. However, the transcriptional strategies by which the intestinal epithelium integrates and adapts to dietary and microbial information remains unresolved. We compared adult mice reared germ free (GF) or conventionalized with a microbiota (CV) either fed normally or after a single high-fat meal (HFM). Jejunal epithelium preparations were queried using genomewide assays for RNA-seq, the activating histone mark H3K27ac ChIP-seq, and ChIP-seq of the microbially-responsive transcription factor HNF4A. We identified distinct nutritional and microbial responses at certain genes, but also apparent simultaneous influence of both stimuli at many other loci and regulatory regions. Increased expression levels and H3K27ac enrichment following HFM at a subset of these sites was dependent on microbial status. H3K27ac sites that were preferentially increased by HFM in the presence of microbes neighbor lipid anabolism and proliferation genes as well as intestinal stem cell (ISC) markers, were usually active only in ISCs, and were not HNF4A targets. In contrast, H3K27ac sites that were preferentially increased by HFM in the absence of microbes neighbored targets of the nuclear receptor and energy homeostasis regulator PPARA, were frequently accessible only in enterocytes, and were HNF4A bound. These results reveal that HNF4A supports a differentiated enterocyte and FAO program in GF, and that suppression of HNF4A by the combination of microbes and HFM may result in preferential activation of IEC proliferation programs. Microbial and nutritional responses are therefore integrated with some of the same transcriptional programs that regulate intestinal proliferation and differentiation.

Acceleration of Small Intestine Development and Remodeling of the Microbiome following Hyaluronan 35 kDa Treatment in Neonatal Mice

The beneficial effects of human milk suppressing the development of intestinal pathologies such as necrotizing enterocolitis in preterm infants are widely known. Human milk (HM) is rich in a multitude of bioactive factors that play major roles in promoting postnatal maturation, differentiation, and the development of the microbiome. Previous studies showed that HM is rich in hyaluronan (HA) especially in colostrum and early milk. This study aims to determine the role of HA 35 KDa, a HM HA mimic, on intestinal proliferation, differentiation, and the development of the intestinal microbiome. We show that oral HA 35 KDa supplementation for 7 days in mouse pups leads to increased villus length and crypt depth, and increased goblet and Paneth cells, compared to controls. We also show that HA 35 KDa leads to an increased predominance of Clostridiales Ruminococcaceae, Lactobacillales Lactobacillaceae, and Clostridiales Lachnospiraceae. In seeking the mechanisms involved in the changes, bulk RNA seq was performed on samples from the terminal ileum and identified upregulation in several genes essential for cellular growth, proliferation, and survival. Taken together, this study shows that HA 35 KDa supplemented to mouse pups promotes intestinal epithelial cell proliferation, as well as the development of Paneth cells and goblet cell subsets. HA 35 KDa also impacted the intestinal microbiota; the implications of these responses need to be determined.

The Role of pHi in Intestinal Epithelial Proliferation–Transport Mechanisms, Regulatory Pathways, and Consequences

During the maturation of intestinal epithelial cells along the crypt/surface axis, a multitude of acid/base transporters are differentially expressed in their apical and basolateral membranes, enabling processes of electrolyte, macromolecule, nutrient, acid/base and fluid secretion, and absorption. An intracellular pH (pHi)-gradient is generated along the epithelial crypt/surface axis, either as a consequence of the sum of the ion transport activities or as a distinctly regulated entity. While the role of pHi on proliferation, migration, and tumorigenesis has been explored in cancer cells for some time, emerging evidence suggests an important role of the pHi in the intestinal stem cells (ISCs) proliferative rate under physiological conditions. The present review highlights the current state of knowledge about the potential regulatory role of pHi on intestinal proliferation and differentiation.

Biological activities of commercial bovine lactoferrin sources

Lactoferrin (Lf) samples from several manufacturers were evaluated in vitro. The purity and protein form of each Lf were examined by SDS-PAGE, Western blot, and proteomics analysis. Assays were conducted to evaluate uptake of Lfs and iron from Lfs by enterocytes as well as Lf bioactivities, including effects on intestinal cell proliferation and differentiation, IL-18 secretion, TGF-β1 transcription, and growth of enteropathogenic Escherichia coli (EPEC). Composition of the Lfs varied; some only contain a major Lf band (~80 kDa), and some also contain minor forms. All Lfs and iron from the Lfs were absorbed by Caco-2 cells with varying efficiencies. The bioactivities of the Lfs varied considerably, but there was no consistent trend. All Lfs promoted intestinal cell proliferation, secretion of IL-18, and transcription of TGF-β1. Some Lfs exhibited pro-differentiation effects on Caco-2 cells. Effects of pasteurization (62.5°C for 30 min, 72°C for 15 sec, or 121°C for 5 min) on integrity, uptake and bioactivities were examined using Dicofarm, Tatua, and native bovine Lfs. Results show that pasteurization did not affect protein integrity, but variously affected uptake of Lf, and its effects on intestinal proliferation, differentiation, and EPEC growth. To choose a Lf source for a clinical trial, assessment of bioactivities is recommended.

Ceftriaxone Administration Disrupts Intestinal Homeostasis, Mediating Noninflammatory Proliferation and Dissemination of Commensal Enterococci

ABSTRACTEnterococci are Gram-positive commensals of the mammalian intestinal tract and harbor intrinsic resistance to broad-spectrum cephalosporins. Disruption of colonization resistance in humans by antibiotics allows enterococci to proliferate in the gut and cause disseminated infections. In this study, we usedEnterococcus faecalis(EF)-colonized mice to study the dynamics of enterococci, commensal microbiota, and the host in response to systemic ceftriaxone administration. We found that the mouse model recapitulates intestinal proliferation and dissemination of enterococci seen in humans. Employing a ceftriaxone-sensitive strain of enterococci (E. faecalisJL308), we showed that increased intestinal abundance is critical for the systemic dissemination of enterococci. Investigation of the impact of ceftriaxone on the mucosal barrier defenses and integrity suggested that translocation of enterococci across the intestinal mucosa was not associated with intestinal pathology or increased permeability. Ceftriaxone-induced alteration of intestinal microbial composition was associated with transient increase in the abundance of multiple bacterial operational taxonomic units (OTUs) in addition to enterococci, for example, lactobacilli, which also disseminated to the extraintestinal organs. Collectively, these results emphasize that ceftriaxone-induced disruption of colonization resistance and alteration of mucosal homeostasis facilitate increased intestinal abundance of a limited number of commensals along with enterococci, allowing their translocation and systemic dissemination in a healthy host.