Gut–brain nutrient signaling. Appetition vs. satiation

Abstract

Multiple hormonal and neural signals are generated by ingested nutrients that limit meal size and suppress postmeal eating. However, the availability of sugar-rich and fat-rich foods can override these satiation/satiety signals and lead to overeating and obesity. The palatable flavor of these foods is one factor that promotes overeating, but sugar and fat also have postoral actions that can stimulate eating and increase food preferences. This is revealed in conditioning studies in which rodents consume flavored solutions paired with intragastric sugar or fat infusions. The significant flavor preferences and increased intake produced by the nutrient infusions appear to involve stimulatory gut-brain signals, referred to here as appetition signals, that are distinct from the satiation signals that suppress feeding. Newly developed rapid conditioning protocols may facilitate the study of postoral appetition processes.

Post-oral appetite stimulation by sugars and nonmetabolizable sugar analogs

“…The present study focused on the appetite-stimulating actions of sugars in the gut, which are distinct from the appetiteinhibitory or satiation actions of sugars, as reviewed elsewhere (48). Of particular interest here are studies related to SGLT involvement in sugar satiation and satiety.…”

“…This is demonstrated in laboratory rodents by the intake stimulation and learned preferences for arbitrary flavors (conditioned stimuli, CS) that are paired with gastric or intestinal infusions of sugar, fat, and proteins (or glutamate) (50). However, relatively little is known about the sites and identities of the sensors that mediate the post-oral appetite-stimulating actions of nutrients, a process we refer to as appetition (48). In the case of sugars, several findings implicate the upper small intestine as a primary site of action for glucose appetition.…”

The Importance of the Gastrointestinal Tract in Controlling Food Intake and Regulating Energy Balance

“…Studies report that the presence of dietary sugar or fat in the gut can generate postoral signals that lead to conditioned food preferences and stimulation of appetite and energy intake, a process termed "appetition" by Sclafani and colleagues 112 .…”

Fructose- and glucose-conditioned preferences in FVB mice: strain differences in post-oral sugar appetition

“…Mouse strains with the Sac B variant of the Tas1r3 gene are more sensitive to sugars (e.g., sucrose) and noncaloric sweeteners (e.g., saccharin) than are strains with the Sac D variant. In addition, sugar intake and preference are stimulated by the post-oral actions of sugars, a process referred to as appetition to distinguish it from the satiation process that inhibits sugar intake (27). Appetition is demonstrated by the intake and preference-stimulating effects of intragastric (IG) sugar infusions in mice and rats (3,21,27,30).…”