Role of gut nutrient sensing in stimulating appetite and conditioning food preferences

Abstract

The discovery of taste and nutrient receptors (chemosensors) in the gut has led to intensive research on their functions. Whereas oral sugar, fat, and umami taste receptors stimulate nutrient appetite, these and other chemosensors in the gut have been linked to digestive, metabolic, and satiating effects that influence nutrient utilization and inhibit appetite. Gut chemosensors may have an additional function as well: to provide positive feedback signals that condition food preferences and stimulate appetite. The postoral stimulatory actions of nutrients are documented by flavor preference conditioning and appetite stimulation produced by gastric and intestinal infusions of carbohydrate, fat, and protein. Recent findings suggest an upper intestinal site of action, although postabsorptive nutrient actions may contribute to flavor preference learning. The gut chemosensors that generate nutrient conditioning signals remain to be identified; some have been excluded, including sweet (T1R3) and fatty acid (CD36) sensors. The gut-brain signaling pathways (neural, hormonal) are incompletely understood, although vagal afferents are implicated in glutamate conditioning but not carbohydrate or fat conditioning. Brain dopamine reward systems are involved in postoral carbohydrate and fat conditioning but less is known about the reward systems mediating protein/glutamate conditioning. Continued research on the postoral stimulatory actions of nutrients may enhance our understanding of human food preference learning.

The role of dopamine in the pursuit of nutritional value

“…Such infusions may be made in the absence of any behaviour or be triggered by an operant response. These techniques have formed the basis for a pioneering collection of flavour-nutrient conditioning studies by Sclafani and colleagues, which have provided a great deal of fundamental knowledge regarding how post-ingestive effects interact with behaviour [20]. Moreover, infusions into different sites may be used to probe the exact mechanisms by which nutrients are signalled to the brain.…”

The oral lipid sensor GPR120 is not indispensable for the orosensory detection of dietary lipids in mice

“…The behavior observed during long-term two-bottle preference tests is greatly infl uenced by post-ingestive regulatory feedback ( 26 ). The brief-access lick paradigm, by limiting post-ingestive cues, is believed to primarily by guest, on May 11, 2018 www.jlr.org…”

Neuroendocrine control of satiation

“…Finally, we also emphasize that most, probably all, of the physiological controls of meal size that we review are powerfully modulated, first, by sex and, second, by experience. We do not review these topics; the interested reader is referred to [31] and [32][33][34][35][36], respectively.…”