SPLTRAK Abstract Submission
Behavioral and Physiological Predictors of Diet-Induced Weight Gain
HS WALD, ZY ONG, X SUN, AL ALHADEFF, HJ GRILL
Department of Psychology, University of Pennsylvania, Philadelphia, PA, United States
   In the current obesogenic environment, some become obese and others do not. The factors underlying individual differences in susceptibility to weight gain are unclear. Outbred Sprague-Dawley (SD) rats also differ in propensity to gain weight when maintained on 32% high fat diet (HFD), making them a suitable model to investigate the factors that contribute to differences in body weight (BW) gain. We hypothesized that differential responsivity to [1] palatable food and [2] gastrointestinal (GI) satiation signals would predict individual differences in BW gain. To test this, prior to HFD maintenance, we examined responsivity to palatable food by measuring intakes of 15% sucrose solution and HFD; and determined sensitivity to GI satiation signals via dose response analysis of cholecystokinin (CCK;0.1, 0.5, 2g/kg)-induced suppression of sucrose intake. To examine a mechanism by which CCK sensitivity predicts BW gain, we performed immunohistochemistry for CCK-induced c-Fos in the nucleus tractus solitarius (NTS). Rats that drank more sucrose or consumed more and took larger meals in initial HFD exposure, gained more BW during HFD maintenance. Rats with lesser CCK-induced intake inhibition gained more BW on HFD. CCK-induced intake suppression also positively correlated with NTS c-fos activation. Results suggest that individual differences in responsivity to palatable food and GI satiation signals predict susceptibility to obesity in SD rats and that the differences in GI signal sensitivity may be due to differential NTS neuron activation.

Supported By: DK-21397