A systematic review published in “Physiology & Behaviour” found positive outcomes for the neuromodulatory possibility of gut peptides on reward responses.  Opposite secretion patterns are witnessed in Glucagon-like peptide-1 (GLP-1) and Ghrelin (gastrointestinal hormones). They also have opposite influences on metabolism and intake of food intake. Apart from energy homeostasis, gastrointestinal hormones have also been implicated to transform the reward system. This review by Corinna Schulz et al. aimed to explore the possibility of ghrelin and GLP-1 to modify reward responses in people.

A multilevel kernel density research of studies reporting a positive link of ghrelin and negative link of GLP-1 were considered to investigate the convergence of issued outcomes. The task functional magnetic resonance imaging (fMRI) (measure minor differences in blood flow that occur with brain activity) helped to determine the reward responses. Later, a systematic publications review based on distinct reward phases and uses in clinical populations was performed that may be reason for variability across studies.

Ghrelin augmented the reward responses across investigations in vital nodes of the motivation and action circuit, for example- the nucleus accumbens, pallidum, ventral tegmental area, putamen, substantia nigra and dorsal mid-insula. The study authors did not find adequate convergence supporting decreased reward responses for GLP-1 peptide. Instead, the possible variations of GLP-1 on anticipatory against the consummatory reward responses were recognized.

Future investigations can move beyond expected rewards to cover other reward aspects to reveal the likelihood of Ghrelin and GLP-1 for clinical spheres.