Trends in Endocrinology & Metabolism
ReviewSpecial Issue: Neuroendocrine control of appetiteNutrient sensing in the gut: new roads to therapeutics?
Section snippets
Taste: a measure of nutritional qualities of foods
Taste is the sensory modality designed to inform us about the nutritional qualities of the food we eat. For humans this means distinguishing the five basic tastes: sweet, salt, umami, bitter, and sour. Sweet foods signal the presence of carbohydrates that serve as an energy source. Salty taste governs the intake of Na+ and other salts, essential for maintaining the water balance of the body. Umami taste is associated with protein-rich foods. Bitter taste is innately aversive and protects
Map of chemosensory cells in the tongue
Gustatory processing is first achieved at the level of taste receptor cells (TRCs) which are clustered in taste buds on the tongue. Once activated by tastants, TRCs transmit the information via sensory afferent fibers to specific brain areas involved in taste perception. Taste cells are classified into four types depending on their morphological features [2]. Salty taste is transduced by some type I glial-like cells. Type II cells express G protein-coupled receptors (GPCRs) to sense sweet,
The gastrointestinal (GI) system as a sensory organ
The idea that the GI system is a sensory organ became evident when Bayliss and Starling [8] discovered the first gut hormone, secretin, and observed that it was released by luminal acid. Later, it became clear that the GI tract responds to a large array of signals in the lumen, including nutrient and non-nutrient chemicals, mechanical factors, and microorganisms. Recent progress in unraveling the nutrient-sensing mechanisms in the taste buds of the tongue has triggered studies on the existence
Concluding remarks
Our understanding of the molecular pharmacology, physiological function, and therapeutic potential of extra-oral nutrient-sensing receptors is evolving quickly. It is tempting to speculate that obesity and diabetes could be treated by selective targeting of nutrient sensors on endocrine cells to release satiety hormones that are often co-stored in conjunction with insulin from the pancreas, thereby mimicking the physiological effects of a meal and fooling the body that it has eaten. It could
Acknowledgments
This work was supported by grants from the Flemish Foundation for Scientific Research (contract FWO G.0670.10) and by a Methusalem grant from the University of Leuven for research on ‘The Brain–Gut Axis in Health and Disease: from Mucosal Integrity to Cortical Processing’.
Glossary
- Cholecystokinin (CCK)
- a hormone that circulates in different molecular forms (CCK8, CCK33/39, CCK58) and is secreted from the enteroendocrine K cells in the small intestine in response to fat and proteins. CCK causes the release of digestive enzymes and bile from the pancreas and gallbladder. In addition to its role in digestion, CCK is also a satiety signal that decreases meal size and delays gastric emptying.
- Ghrelin
- ghrelin is a 28 amino acid peptide with an octanoyl modification at Ser3 which
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