Physiological mechanisms underlying alterations in diet preference

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ABSTRACT Obesity is a key risk factor for chronic health complications including hypertension and Type II diabetes. Alternate day fasting (ADF) which involve cycles of feeding and fasting have been effective for weight loss and improving metabolic measures in humans and rats. We have recently reported that rats presented both standard chow and a high energy (HE) diet show almost exclusive intake of the HE diet. Yet, rats on an ADF paradigm show decreased HE diet preference driven by increased chow intake. Meal pattern analyses that provide parameters such as meal size and number, reveal differences in male and female rats on an ADF schedule. Meal pattern parameters are driven by physiological signals that drive intake (e.g. orosensory stimulation and meal initiation) and terminate intake (e.g. satiety). Here, male and female ADF and control rats will be compared to investigate the role of 1) taste signaling and 2) gut peptide influences, in ADF-induced shifts in diet preference. Using cFos immunohistochemistry, activation of brain areas in central gustatory pathways associated with taste identification and reward will be compared between the groups (Experiment 1). These experiments are designed to test the hypothesis that rats on ADF and control feeding schedules show similar activation of brain regions involved in taste identification but that ADF rats show decreased neural activation of taste pathways involved in reward. Another cohort of male and female ADF and control rats will be used (Experiment 2) to investigate the role of gut peptides shown to be involved in satiety (CCK) and both satiety and reward (GLP-1). Groups will be administered agonists and antagonists of CCK and GLP-1 receptors to test the hypothesis that shifts in diet preference induced by an ADF schedule, reduces gut signals related to reward but not satiety. The experiments are designed to assess how meal pattern parameters are altered with feeding schedule and gut peptide administration. The findings from the proposed experiments will provide information about how neural mechanisms related to taste and gut signaling drive changes in diet preference.