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Basic science
The importance of the small bowel microbiota in nutrition
Martinez-Guryn K, Hubert N, Frazier K, et al. Small Intestine Microbiota Regulate Host Digestive and Absorptive Adaptive Responses to Dietary Lipids. Cell Host Microbe 2018 23:458–469.
The small intestine, a major site of nutrient digestion and absorption, harbours a complex array of microbes albeit less numerous and diverse than the large intestine. Studies interrogating the small intestinal microbiota in relation to caloric intake and the effect of dietary manipulation are limited. Microbial populations in the small intestine are subjected to a number of adverse environmental factors, including rapid transit time, low pH, bile acids and the presence of antimicrobial peptides. Bacterial populations which reside in the small intestine have been shown to be more tolerant of these factors. The impact of high-fat diet on small intestinal bacterial composition has not been assessed. Martinez-Guryn and colleagues demonstrated that germ-free (GF) mice, while resistant to diet-induced obesity, had impaired lipid digestion and absorption compared with conventionally raised counterparts. This highlights the role of gut microbes and their mediators in this process. The presence of small intestinal microbes directed host adaption to dietary lipid changes, which occurred through regulation of gut epithelial processes intrinsic to dietary lipid processing. Increased lipid absorption was also demonstrated in GF animals fed a low-fat diet when conventionalised with a high-fat-induced small intestinal microbiota. Increased lipid absorption was shown to be driven by the presence of bacterial-derived metabolites and not necessarily live organisms. This study highlights the role that the small intestinal microbiota plays in shaping the host’s relationship with dietary processing. Understanding the composition and impact of the small intestine microbiota will afford a greater understanding of conditions of overnutrition and undernutrition.
Hepatocyte origin in health and acute liver injury
Lin S, Nascimento EM, Gajera CR et al. Distributed hepatocytes expressing telomerase repopulate the liver in homeostasis and injury. Nature 2018;566: 244–248.
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Footnotes
Competing interests None declared.
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Provenance and peer review Not commissioned; internally peer reviewed.