McMorrow, H. E. | Search bioRxiv

bioRxiv2024

Incretin hormones and pharmacomimetics rapidly inhibit AgRP neuron activity to suppress appetite

Analogs of the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) have become mainstays of obesity and diabetes management. However, both the physiologic role of incretin hormones in the control of appetite and the pharmacologic mechanisms by which incretin-mimetic drugs suppress caloric intake remain incompletely understood. Hunger-promoting AgRP-expressing neurons are an important hypothalamic population that regulates food intake. Therefore, we set out to determine how incretins analogs affect their activity in vivo. Using fiber photometry, we observed that both GIP receptor (GIPR) and GLP-1 receptor (GLP-1R) agonism acutely inhibit AgRP neuron activity in fasted mice and reduce the response of AgRP neurons to food. Moreover, optogenetic stimulation of AgRP neurons partially attenuated incretin-induced feeding suppression, suggesting that AgRP neuron inhibition is necessary for the full appetite-suppressing effects of incretin-based therapeutics. Finally, we found that GIP but not GLP-1 is necessary for nutrient-mediated AgRP neuron inhibition, representing a novel physiologic role for GIP in maintaining energy balance. Taken together, these findings reveal neural mechanisms underlying the efficacy of incretin-mimetic obesity therapies. Understanding these drugs mechanisms of action is crucial for the development of next-generation obesity pharmacotherapies with an improved therapeutic profile.

neuroscience↗

bioRxiv2023

Sucrose overconsumption impairs feeding circuit dynamics and promotes palatable food intake

Rapid gut-brain communication is critical to maintain energy balance and is disrupted in diet-induced obesity through mechanisms that remain obscure. Specifically, the role of carbohydrate overconsumption in the regulation of interoceptive circuits has been minimally examined in vivo. Here we report that an obesogenic high-sucrose diet (HSD) selectively blunts silencing of hunger-promoting AgRP neurons following intragastric delivery of glucose, whereas we previously showed that overconsumption of a high-fat diet (HFD) selectively attenuates lipid-induced neural silencing. By contrast, both HSD and HFD reversibly dampen rapid AgRP neuron sensory inhibition following chow presentation and promote intake of more palatable foods. Our findings reveal that excess sugar and fat pathologically modulate feeding circuit activity in both macronutrient-dependent and -independent ways, and thus may additively exacerbate obesity.

neuroscience↗