PHENYLTHIOCARBAMIDE TASTING STATUS AFFECTS QUININE-MEDIATED REDUCTION OF FOOD INTAKE

Background and aim: Intra-duodenal administration of quinine is able to reduce calorie intake, likely acting on gut bitter taste receptors (T2R) expressed by enteroendocrine cells in the gut. Genetic variability to taste phenylthiocarbamide (PTC) is closely related to oral bitter taste perception of quinine. Our aim is to assess whether PTC tasting status could affect quinine-mediated reduction of food intake. Material and methods: Twenty healthy subjects (12 women, 8 men; median age 27 years) were screened to determine PTC tasting status. In two different days, each subject received an acid-resistant capsule containing either placebo or 18 mg of hydrochloride (HCl) quinine in a double-blind crossover fashion. After 60 minutes, all subjects were allowed to eat an ad libitum meal until they achieve satiation. Calorie intake and meal duration were recorded at the end of the test. Data (mean±SD) were compared by using unpaired t test. Results: Eleven out of 20 subjects were identified as “tasters”, while 9 subjects were not able to identify any bitter sensation and were classified as “non-tasters”. PTC tasters ingested a significantly lower amount of calories when they received quinine compared to placebo (526±275 vs. 659±320 kcal; p=0.005), whereas no significant differences were found for PTC non-tasters (499±227 vs. 519±231 kcal; p=NS). PTC tasters presented a significantly higher difference in calorie intake between two experiments (1 kcal = kcal quinine − kcal placebo) compared to non-tasters (−134±124 vs. −20±89 kcal; p=0.034). Conclusions: Intra-duodenal administration of quinine is able to reduce calorie intake in PTC tasters but not in PTC non-tasters. This result suggests that the mechanism involved in PTC perception in the oral cavity is analogousin the gut, enhancing the role of T2R in quinine-mediated reduction of food intake. Further studies are needed to elucidate the role of T2R in the control of food intake.