Jejunum: The understudied meeting place of dietary lipids and the microbiota

Abstract

Although the jejunum is the main intestinal compartment responsible for lipid digestion and absorption, most of the studies assessing the impact of dietary lipids on the intestinal microbiota have been performed in the ileum, colon and faeces. This lack of interest in the jejunum is due to the much lower number of microbes present in this intestinal region and to the difficulty in accessing its lumen, which requires invasive methods. Recently, several recent publications highlighted that the whole jejunal microbiota or specific bacterial members are able to modulate lipid absorption and metabolism in enterocytes. This information reveals new strategies in the development of bacterial-and metabolite-based therapeutic interventions or nutraceutical recommendations to treat or prevent metabolic-related disorders, including obesity, cardiovascular diseases and malnutrition. This review is strictly focused on the following triad: dietary lipids, the jejunal epithelium and the jejunal microbiota. First, we will describe each member of the triad: the structure and functions of the jejunum, the composition of the jejunal microbiota, and dietary lipid handling by enterocytes and by microorganisms. Then, we will present the mechanisms leading to lipid malabsorption in small intestinal bacterial overgrowth (SIBO), a disease in which the jejunal microbiota is altered and which highlights the strong interactions among this triad. We will finally review the recent literature about the interactions among members of the triad, which should encourage research teams to further explore the mechanisms by which specific microbial strains or metabolites, alone or in concert, can mediate, control or modulate lipid absorption in the jejunum.

Transcriptomics informs design of a planar human enterocyte culture system that reveals metformin enhances fatty acid export

“…Single-cell transcriptomics of jejunal and ileal human mucosa define early, intermediate, and mature nutrient-handling enterocytes First, we sought to characterize the baseline transcriptomic profiles of human AEs in vivo to guide the development of an in vitro model of human FA-handling. The distal SI (jejunum and ileum) represents the majority of absorptive epithelium in the human SI 39 ; however, lipid-handling transcriptional profiles of jejunal and ileal absorptive lineages have not been fully described at the single-cell level. Endoscopic biopsies have enabled single-cell transcriptomics to be performed on human duodenal 40 and ileal 41 mucosa; however, single-cell transcriptomics has only recently been reported for the jejunum 42,43 , with limited characterization of absorptive function 39,43. .…”

Distribution of α-synuclein in normal human jejunum and its relations with the chemosensory and neuroendocrine system

“…13,14 The jejunum is composed of repeating crypts and villi with an important niche of stem cells to sustain the rapid turnover of its epithelium. 15 The intestinal stem cells (ISCs) are located at the base of the crypts and produce five different cell types: enterocytes, which are the real absorptive cells, the goblet cells, which secrete mucus into the lumen, the tuft cells, which are considered luminal sensory cells, the enteroendocrine cells (EECs), which are able to produce several hormones, and Paneth cells with antimicrobial activity. 16 Some of these cell types are crucial in the interactions between the intestinal epithelium and the enteric nervous system (ENS), forming an effective interface between the lumen and nerve fibers: 17,18 these are the tuft cells and EECs.…”

Gut microbiome is affected by gut region but robust to host physiological changes in captive active-season ground squirrels

“…Ileum lumen and mucosa microbiomes were markedly different, which could be due to the larger influence of transient microbes. Functionally, the ileum is predominantly involved in absorption of vitamins, fatty acids, and bile acids [ 25 ]. We detected lower bacterial diversity in both the ileum lumen and mucosa than in the cecum, which matches results across different vertebrate taxa, such as birds [ 26 ], pigs [ 27 , 28 ], and rodents [ 29 , 30 ].…”