Acute 'adaptation' by the small intestinal enterocyte: a posttranscriptional mechanism involving apical translocation of nutrient transporters

Autor: Ali Tavakkolizadeh, Michael G. Sarr, Ye Zheng, Jeffrey S. Scow
Rok vydání: 2010
Předmět:
Zdroj: Surgery. 149(5)
ISSN: 1532-7361
Popis: The small intestine is an incredibly adaptable, “plastic” organ, the tissues of which are involved intimately in endocrine regulation, immune surveillance, multiple aspects of metabolism, excretion of metabolites, symbiosis with the enteric microbiome, and, of course, absorption of ingested nutrients. As the primary site of nutrient absorption, the gut must be adaptable to the quality, quantity, and timing of nutrient availability, in order to optimize nutrient absorption and maintain health. Indeed, intestinal adaptation, as evident by changes in gene expression as the neonate grows older and transitions from breast milk to oral nutrients, (i.e., ontogeny) are well described. Similarly, chronic changes in diet/nutrient supply alter gene expression resulting in different levels of nutrient transporters by the enterocytes. A dramatic example of this remodeling of the gut mucosa was demonstrated by Secor and Diamond in studying the onset of hyperplasia/hypertrophy in Burmese pythons in response to ingestion of a meal.1 Indeed, these forms of classic, genomic-mediated adaptation result in a change not only in function but also in structure of the mucosa, and typically occur over days. Similarly, when major parts of the intestinal absorptive surface area are lost (via resection for trauma, neoplasm, or disease) or bypassed (jejunoileal bypass), a remarkable hypertrophy/hyperplasia occurs, again through a complex set of changes in gene expression and cellular proliferation leading to villus hypertrophy and cellular hyperplasia. A less well understood and less well appreciated “acute adaptation,” deemed by some to be more of a physiologic effect, also occurs in the enterocyte itself, whereby its cellular absorptive capacity is altered acutely in response to luminal presence of specific nutrients – a form of cell biology that does not, at least initially, involve a change in genomic expression and reflects a post-transcriptional process. This acute adaptation involves a rapid alteration (occurring within minutes) in nutrient transporters in the apical membrane secondary to acute translocation of pre-formed transporter from the cytoplasm to the apical membrane of the enterocyte; this acute translocation of pre-formed transporters matches intestinal absorptive capacity to nutrient availability. This review will address (focusing on hexose transporters) this remarkable capacity of the enterocyte to undergo a rapid, post-transcriptional, increase in absorptive capacity, a process that appears different and complementary to the classic genomic-based forms of intestinal adaptation.
Databáze: OpenAIRE
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