Food Intake is Influenced by Gastric Emptying, Motility, and Compliance
Authors: Clyburn Courtney , Travagli R. Alberto , Browning Kirsteen N. 
Published: April 2020

Obesity, which results from an increase in caloric intake relative to energy expenditure, is often associated with an alterations in gastric emptying. The exact relationship between gastric emptying and food intake, however, is unclear. Some reports have suggested that obesity is associated with an accelerated liquid but a delayed solid gastric emptying rate, while more recent studies have suggested that there may be no significant correlation between BMI and gastric emptying. The purpose of the present study is to test the hypothesis that food intake in rodents is influenced by a combination of gastric emptying, gastric tone and motility, and compliance.Male and female Sprague‐Dawley rats (4–8 weeks of age) were fed a control or HFD (14% or 60% kcal from fat, respectively) for 3–5 days prior to experimentation (acute HFD). Food intake and body weight were measured twice daily prior to, and throughout, HFD exposure. The 13C octanoic acid breath test was used to measure gastric emptying rates in rats repeatedly throughout exposure to the high fat diet. Miniature strain gauges were sewn onto the ventral surface of the corpus and the antrum of the stomach in anesthetized rats to allow measurement of basal gastric motility and tone. Gastric compliance was measured via a latex balloon inserted into the stomach via the pylorus in anesthetized rats. Following placement, the balloon was maximally inflated (2mL; 1min) before deflation. After 10min recovery, the balloon was then inflated in 0.2mL increments for 1 minute each, and the balloon pressure measured continuously.Acute high fat diet exposure induced a brief (24hr) period of hyperphagia before rats regulate their food intake and restore caloric balance within a 3–5 day period (74.7±4.0 kcal/day at day 1 vs. 59±3.7 kcal/day at days 3–5, P<0.05, N=16), as described previously (PMID: 29368945). While gastric emptying rate was not significantly different during the hyperphagic period following high fat diet exposure (120±14.1% of baseline, P>0.05, N=6), emptying was significantly delayed after 4 days HFD exposure (144±15.8% of baseline, P>0.05, N=6), when caloric intake is restored to baseline levels. Neither gastric compliance (total AUC throughout distention volume range: 37±1.7 vs. 38±1.1, P>0.05, N=6–8) nor basal gastric motility (104±12.2 vs. 110±16.3mg/min P>0.05, N=10–13) was altered during this time period.These data suggest that i) gastric emptying rates are more closely associated with the regulation of caloric intake and energy balance than either basal gastric motility or compliance, and ii) gastric emptying may be disrupted without any observed alterations in local gastric functions. We have shown previously, that restoration of caloric balance is associated with neuroplasticity within central vagal neurocircuits (PMID: 29368945). These data suggest that dysregulation of gastric emptying may be important in the central control of food intake, even under conditions where alterations in peripheral gastric functions, including motility and compliance, are not observed.Support or Funding InformationNIH DK111667 to KNB NIH F31 118833 to CC