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REGULATION OF TASTE SIGNALING MOLECULES BY HIGH PROTEIN DIET IN THE PIG PYLORUS Vallorani C.*[1], Latorre R.[1], Mazzoni M.[1], Bacci M.L.[1], Monica F.[1], Giancola F.[1], Falconi M.[2], De Giorgio R.[3], Sternini C.[4], Clavenzani P.[1] [1]Department of Veterinary Medical Science, University of Bologna. ~ Bologna, [2]Department of Biomedical and Neuromotorial Sciences, University of Bologna ~ Bologna, [3]Department of Medical and Surgical Sciences, University of Bologna ~ Bologna, [4]CURE/DDRC, Division of Digestive Diseases, Department of Medicine, UCLA, Los Angeles, CA, USA ~ Los Angeles Taste receptors (TRs) and their signaling molecules are widely expressed in extra‐oral sites, including the gastrointestinal (GI) tract mucosa(1). Fasting and refeeding have been shown to modify the expression of α‐ transducin / α‐gustducin in enteroendocrine cells of the pig GI tract(2), however, the effects of individual nutrients on TR‐related molecules remain unknown. The gustatory system is fundamental for detecting dietary nutrients and evoking appropriate functional responses leading to digestion and absorption. Thus, the aim of this study was to test whether a short‐ and long‐term high protein diet (3 and 30 days, respectively) affected the enteroendocrine profile of the TRs signalling molecules α‐transducin / α‐ gustducin expressing cells in the pig gastric mucosa. Twelve hybrid (LW x D) female pigs (weighing 30‐40 Kg) were subdivided in three experimental groups (n= 4 each group): A) fed standard diet (controls, CTR, 14,5% protein); B) fed high protein diet for 3 days (HP‐3, 33% protein); and C) fed high protein diet for 30 days (HP‐30, 33% protein). The protein used to supplement the diet was fish and potatoes protein. Mucosal samples from pylorus were harvested, fixed and processed for single and double labelling immunofluorescence with a mixture of the following primary antisera to Gα‐transducin (Gαtran), Gα‐gustducin (Gαgust) and 5‐hydroxytryptamine (5‐HT). In the pyloric mucosa, the average number of Gαtran immunoreactive (‐IR) cells were 111.5 ± 26.2 (CTR), 148.8 ± 13.2 (HP3), and 218.3 ± 28.8 (HP30) (CTR vs HP‐3 P< 0.04; CTR vs HP‐30 P< 0.002; HP‐3 vs HP‐30 P< 0.005), while Gαgust‐IR cells were 138.8 ± 45.1 8 (CTR), 177.3 ± 14 (HP3), 211.5 ± 29.1 (HP30) (CTR vs HP‐30 P

SUMMARY - Transcripts for sweet and bitter taste receptors and the gustatory G proteins, alpha-gustducin and alpha-transducin, are expressed by the oral cavity and the gastrointestinal (GI) mucosa. This study evaluated: 1) distribution of alpha-transducin in the pig GI tract; 2) type of cells expressing alpha-transducin (chromogranin-A, gastrin/cholecystokinin, somatostatin, villin) 3) relationship between alpha-transducin cells and enteric fibres. The presence of alpha-transducin-IR in enteroendocrine cells supports an active chemosensory machinery in the GI mucosa and that taste signalling molecules contribute to luminal chemosensing. These mechanisms may occur via neuro-endocrine cross-talk activating digestive or protective reflex pathways (e.g. vomiting or food aversion).