Intact vagal gut-brain signalling prevents hyperphagia and excessive weight gain in response to high-fat high-sugar diet.

AIM: The tools that have been used to assess the function of the vagus nerve lack specificity. This could explain discrepancies about the role of vagal gut-brain signalling in long-term control of energy balance. Here we use a validated approach to selectively ablate sensory vagal neurones that innervate the gut to determine the role of vagal gut-brain signalling in the control of food intake, energy expenditure and glucose homoeostasis in response to different diets. METHODS: Rat nodose ganglia were injected bilaterally with either the neurotoxin saporin conjugated to the gastrointestinal hormone cholecystokinin (CCK), or unconjugated saporin as a control. Food intake, body weight, glucose tolerance and energy expenditure were measured in both groups in response to chow or high-fat high-sugar (HFHS) diet. Willingness to work for fat or sugar was assessed by progressive ratio for orally administered solutions, while post-ingestive feedback was tested by measuring food intake after an isocaloric lipid or sucrose pre-load. RESULTS: Vagal deafferentation of the gut increases meal number in lean chow-fed rats. Switching to a HFHS diet exacerbates overeating and body weight gain. The breakpoint for sugar or fat solution did not differ between groups, suggesting that increased palatability may not drive HFHS-induced hyperphagia. Instead, decreased satiation in response to intra-gastric infusion of fat, but not sugar, promotes hyperphagia in CCK-Saporin-treated rats fed with HFHS diet. CONCLUSIONS: We conclude that intact sensory vagal neurones prevent hyperphagia and exacerbation of weight gain in response to a HFHS diet by promoting lipid-mediated satiation.

Blunted Vagal Cocaine- and Amphetamine-Regulated Transcript Promotes Hyperphagia and Weight Gain.

The vagus nerve conveys gastrointestinal cues to the brain to control eating behavior. In obesity, vagally mediated gut-brain signaling is disrupted. Here, we show that the cocaine- and amphetamine-regulated transcript (CART) is a neuropeptide synthesized proportional to the food consumed in vagal afferent neurons (VANs) of chow-fed rats. CART injection into the nucleus tractus solitarii (NTS), the site of vagal afferent central termination, reduces food intake. Conversely, blocking endogenous CART action in the NTS increases food intake in chow-fed rats, and this requires intact VANs. Viral-mediated Cartpt knockdown in VANs increases weight gain and daily food intake via larger meals and faster ingestion rate. In obese rats fed a high-fat, high-sugar diet, meal-induced CART synthesis in VANs is blunted and CART antibody fails to increase food intake. However, CART injection into the NTS retains its anorexigenic effect in obese rats. Restoring disrupted VAN CART signaling in obesity could be a promising therapeutic approach.

Validation and characterization of a novel method for selective vagal deafferentation of the gut.

There is a lack of tools that selectively target vagal afferent neurons (VAN) innervating the gut. We use saporin (SAP), a potent neurotoxin, conjugated to the gastronintestinal (GI) hormone cholecystokinin (CCK-SAP) injected into the nodose ganglia (NG) of male Wistar rats to specifically ablate GI-VAN. We report that CCK-SAP ablates a subpopulation of VAN in culture. In vivo, CCK-SAP injection into the NG reduces VAN innervating the mucosal and muscular layers of the stomach and small intestine but not the colon, while leaving vagal efferent neurons intact. CCK-SAP abolishes feeding-induced c-Fos in the NTS, as well as satiation by CCK or glucagon like peptide-1 (GLP-1). CCK-SAP in the NG of mice also abolishes CCK-induced satiation. Therefore, we provide multiple lines of evidence that injection of CCK-SAP in NG is a novel selective vagal deafferentation technique of the upper GI tract that works in multiple vertebrate models. This method provides improved tissue specificity and superior separation of afferent and efferent signaling compared with vagotomy, capsaicin, and subdiaphragmatic deafferentation.NEW & NOTEWORTHY We develop a new method that allows targeted lesioning of vagal afferent neurons that innervate the upper GI tract while sparing vagal efferent neurons. This reliable approach provides superior tissue specificity and selectivity for vagal afferent over efferent targeting than traditional approaches. It can be used to address questions about the role of gut to brain signaling in physiological and pathophysiological conditions.

PHOTOVOICE: Reducing pedestrian injuries in children.

Pedestrian injury is the second leading cause of injury related death for children. The purpose of this research project was to determine the effectiveness of pedestrian and road traffic safety education with children, as part of the Walk This Way program through Safe Kids USA. Through the implementation of PHOTOVOICE, a project that captured children's narratives coinciding with a photograph, children engaged in community exploration to identify pedestrian hazards in their communities and explore possible solutions utilizing their photography and narrations. Children participated in an engaging educational session, a community fieldtrip, and reflection. Results concluded that, despite a small increase in post test scores, an increase in awareness of hazards in the community and successful identification of community hazards was achieved. The goal of this research project was determine the effectiveness of a hands-on pedestrian and road traffic safety educational program with children. The results of this research project will be integrated with similar projects completed across the country through the program Walk This Way with Safe Kids USA. Both this research project and the Walk This Way program aim to promote behavior change in children and create safer communities to reduce pedestrian related injury. The overall goal of this research project andthe Walk This Way program is to increase education on a national level in regards to pedestrian safety for children and provide a basis for lobbying for public policy changes pertaining to road and pedestrian safety.