Gastrointestinal Hormones

The mammalian gastrointestinal mucosa is a rapidly self-renewing tissue in the body, and its homeostasis is preserved through the strict regulation of epithelial cell proliferation, growth arrest, and apoptosis. The control of the growth of gastrointestinal mucosa is unique and, compared with most other tissue in the body, complex. Mucosal growth is regulated by the same hormones that alter metabolism in other tissues, but the gastrointestinal mucosa also responds to host events triggered by the ingestion and presence of food within the digestive tract. These gut hormones and peptides regulate the growth of the exocrine pancreas, gallbladder epithelium, and the mucosa of the oxyntic gland region of the stomach and the small and large intestines. Luminal factors, including nutrients or other dietary factors, secretions, and microbes that occur within the lumen and distribute over a proximal-to-distal gradient, are also crucial for maintenance of normal gut mucosal regeneration and could explain the villous-height-crypt-depth gradient and variety of adaptation, since these factors are diluted, absorbed, and destroyed as they pass down the digestive tract. Recently, intestinal stem cells, cellular polyamines, and noncoding RNAs are shown to play an important role in the regulation of gastrointestinal mucosal growth under physiological and various pathological conditions. In this book, we highlight key issues and factors that control gastrointestinal mucosal growth and homeostasis, with special emphasis on the mechanisms through which epithelial renewal and apoptosis are regulated at the cellular and molecular levels.

The discovery that the same or similar peptides are present in endocrine cells and in neurons is one of the most exciting and provocative recent developments in biology. Suddenly neurophysiologists and endocrinologists have found that they have a great deal to discuss with each other. Substances originally isolated as hypothalamic hormones turn out to be abundantly present in neurons of other parts of the brain and in endocrine cells and neurons of the gut and pancreas. Similarly, substances originally isolated as gut hormones are found not only in gut endocrine cells but also in gut neurons and in brain neurons. It turns out that the group of peptides that we are accustomed to call gastrointestinal hormones are not all confined to the gastrointestinal tract and are not all solely hormones. We are learning that the chemical transmitters of the neurocrine, endocrine, and paracrine systems form a single group of related substances. This volume contains the latest installments in this fascinating story. It tells how these pep tides were isolated and their amino acid sequences determined, how the heterogeneity of most, perhaps all, of these peptides is being revealed as variant forms of them are discovered, how antibodies to these peptides are used as powerful tools to measure their concentrations in body fluids and to localize the cells in which they are synthesized and stored, and, finally, how the role of these substances in normal physiology and in pathological states is being unraveled.

Advances in Metabolic Disorders, Volume 11: Gastrointestinal Hormones covers the developments in the study of gastrointestinal (GI) hormones. The book discusses the cytochemical techniques in work with GI hormones; the general aspects and problems for the radioimmunoassays of GI hormones in the 80s; and the response of the GI hormone system to the pathological changes. The text also describes the evolutional aspects of GI hormones; the cell membrane receptors for secretagogues on pancreatic acinar cells; and the synthesis of GI hormones using organic chemical or recombinant DNA techniques. Gastrin is reviewed with regard to its forms and fragments in tissues, circulating components during post- and perisecretory processing, cellular origins and distribution, actions and structure-function relations, metabolic disposal, nervous and chemical control for its release, and its role in human pathology. The book further tackles the chemical, anatomical, and biological studies on gastrin-releasing peptides, as well as the physiological actions of gastric inhibitory polypeptide. Discussions about the vasoactive intestinal peptide, incretin, enteroglucagon, neuropeptide Y, peptide HI, galanin, cholecystokinin-58, neuropeptide K, peptide YY, motilin, somatostatin-28, neurotensin, substance P, and opioid peptides are also encompassed. The text concludes by looking into the investigations on the structure and function of the head activator in hydra and in mammals. Molecular biologists, endocrinologists, histochemists, physiologists, and those involved in the research about GI hormones will find the book invaluable.

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