Effects of a caloric restrictive diet and a polyphenol in a rat model of induced obesity: impact on sweet preference, taste reactivity and adipose tissues.

2019 edition

Adam Alvarez

Obesity is widely considered one of the major epidemic of modern times, however, much remains to be understood about both its development and consequences. It is believed that obese individuals could develop sugar resistance, and that it could be associated with a high preference for sweet food and drink. In addition, the reversibility of diet-induced obesity and its consequences on sweet preference when adopting a restricted caloric diet is not known. The present study was aimed to evaluate whether a restricted caloric diet, administered alone or supplemented with a polyphenol, modified sweet taste preference and sweet taste reactivity in rats previously fed with the obesogenic cafeteria diet (CAF). We fed male Sprague-Dawley rats (n=30) with the cafeteria diet (bacon, carrots, muffins, cookies, pâté, cheese and sugared milk) to induce obesity. A control group (STD; n=10) was fed with standard chow for the duration of the study. After 2 months, the cafeteria group was subdivided in three subgroups fed as following: CAF (n=10), remaining with cafeteria diet ad libitum; CAFr (n=10), fed with the same cafeteria diet ingredients but placed under a caloric restriction of 30% vs the cafeteria diet; and CAFrO (n=10), fed with the same restriction as the CAFr group plus an oral treatment of oleuropein (dose of 25mg/kg·day), a polyphenolic compound found in green olives and olive leaves which we hypothesize should have an effect upon the parameters measured. After 3 months with the corresponding new diets, the animals conducted the two bottle preference and taste reactivity tests to evaluate respectively sweet preference and the hedonic and aversive behaviors evoked by the consumption of increasingly concentrated solutions of sucrose (0, 0.01, 0.03, 0.06, 0.1, 0.3, 0.6, 1M). Both behavioral tests were first evaluated in a preliminary experiment to test for gender differences, showing that females reached their consumption peak at 0.1M (117.3±11.9 gr intake/day), whereas males reached their peak at 0,3M (112.1±5.2 gr intake/day). Differences were found in a higher concentration (0,6M) in which males had a higher sucrose intake than females (F(1,14)=5,177; p=0,039). In the cafeteria diet experiment performed with males, all groups reached their peak intake at 0.3M, which is consistent with data from the preliminary experiment, with the STD group showing the highest intakes overall. More specifically, the STD intake was greater than CAF at 0.01M and 1M; than CAFr at 0.01M; and than CAFrO at 0,6M and 1M, suggesting a differential effect of the oleuropein treatment with respect to the caloric restriction alone. Data of the taste reactivity test for the second experiment is being analyzed and expected to provide us with a deeper insight on the mechanisms underlying obesity and sugar consumption and resistance.