Gastrointestinal hormone research – with a Scandinavian annotation

Abstract

Gastrointestinal hormones are peptides released from neuroendocrine cells in the digestive tract. More than 30 hormone genes are currently known to be expressed in the gut, which makes it the largest hormone-producing organ in the body. Modern biology makes it feasible to conceive the hormones under five headings: The structural homology groups a majority of the hormones into nine families, each of which is assumed to originate from one ancestral gene. The individual hormone gene often has multiple phenotypes due to alternative splicing, tandem organization or differentiated posttranslational maturation of the prohormone. By a combination of these mechanisms, more than 100 different hormonally active peptides are released from the gut. Gut hormone genes are also widely expressed outside the gut, some only in extraintestinal endocrine cells and cerebral or peripheral neurons but others also in other cell types. The extraintestinal cells may release different bioactive fragments of the same prohormone due to cell-specific processing pathways. Moreover, endocrine cells, neurons, cancer cells and, for instance, spermatozoa secrete gut peptides in different ways, so the same peptide may act as a blood-borne hormone, a neurotransmitter, a local growth factor or a fertility factor. The targets of gastrointestinal hormones are specific G-protein-coupled receptors that are expressed in the cell membranes also outside the digestive tract. Thus, gut hormones not only regulate digestive functions, but also constitute regulatory systems operating in the whole organism. This overview of gut hormone biology is supplemented with an annotation on some Scandinavian contributions to gastrointestinal hormone research.

Key Words:

• biosynthesis
• cell biology
• digestion
• endocrine cells
• gastrointestinal tract
• growth factors
• hormone genes
• hormone receptors
• hormones
• neuropeptides
• peptides

Acknowledgement

The skillful and patient assistance of secretary Connie Bundgaard is gratefully acknowledged.

Declaration of interest: The author states no conflict of interest and has received no payment in preparation of this manuscript.