Food intake and energy balance are controlled by a dynamic interplay of gut-brain signaling pathways; however, the molecular underpinnings in these processes and their dysregulation in obesity remain poorly understood. Recent work from the DiPatrizio lab suggests that our bodies? cannabis-like signaling molecules, the endocannabinoids (eCBs), are critical mediators of gut-brain signaling important for food intake, and are upregulated in the gut in diet-induced obesity (DIO). These seminal studies suggest that eCB signaling in the gut is an orexigenic signal that is activated under several behavioral and metabolic conditions, and may become dysregulated in obesity. The mechanism(s) of gut-brain eCB control of food intake and reorganization of these pathways in obesity is unknown. Preliminary data, however, suggests that in DIO, increased eCB signaling in the intestinal epithelium inhibits fat-induced release of satiation peptides, which increases meal size and delays satiation. We propose the central hypothesis that the eCB system in the gut plays a critical role in maintaining a setpoint of nutrient sensing and gut-brain satiation signaling, which is remodeled after chronic exposure to high-energy nutrients and contributes to overeating in DIO. We propose the following specific aims to test this hypothesis: SA1. To determine if CB1Rs in the gut control gut-brain satiation signaling. Based on preliminary data, we hypothesize that CB1Rs in the intestinal epithelium are key modulators of a setpoint of nutrient sensing and gut-brain satiation signaling that become dysregulated in DIO. To test this hypothesis, we will examine the role for CB1Rs in controlling feeding behavior by evaluating dietary fat-induced release of satiation peptides in vivo and in vitro using our first-of-kind mouse model that conditionally lacks CB1Rs in intestinal epithelium in combination with peripherally-restricted CB1R antagonists, and enteroendocrine cell lines.
This aim will provide evidence of a previously unidentified control mechanism of gut- brain satiation signaling. SA2. To determine the mechanism of eCB system remodeling in DIO, and the impact of dietary intervention on these pathways. Mechanisms of dysregulated eCB signaling in DIO, including specific dietary components involved, are unknown, as is the impact of dietary intervention on these pathways and behavioral outcomes. We hypothesize that chronic exposure to diets high in specific dietary fats that serve as precursors to the eCBs (e.g., linoleic acid) leads to remodeling of the eCB system in the gut, which promotes overeating and development and maintenance of DIO. To test this hypothesis, we will use our intestinal CB1R-null mice in combination with targeted lipidomics and advanced UPLC/MS/MS-based assays of eCB system function to identify specific dietary components in DIO that drive heightened eCB system activity and overeating, and the mechanism of remodeling that occurs in DIO. Furthermore, weight loss following dieting is all-too-often met with high levels of recidivism to overeating and obesity; thus we will assess the ability for low- calorie dietary intervention to normalize the setpoint of gut-brain eCB signaling in DIO.
The American Medical Association recently announced that obesity is a disease, which affects nearly one-third of American adults, significantly reduces life expectancy, and is promoted by excessive consumption of a Western diet containing very high levels of fats and sugars. The proposed project aims to identify the role for gut-brain endocannabinoid signaling pathways that are proposed to control feeding behavior and become dysregulated in obesity. This work will support the discovery and development of novel therapeutic strategies to safely treat of obesity, cardiovascular disease, and diabetes in humans.
