Abstract - Kevin Lemaire

The sweet taste of sugars is thought to be the primary determinate of intake and preference. However, sugars also have post-oral effects in the gut that may affect sugar preference. This study used the conditioned flavor-preference paradigm with “sweet-tasteless” and normal mice to study the oral and post-oral actions of three different sugars, glucose, fructose, and galactose. Trpm5 knockout mice (KO), with non-functioning sweet taste cells, and normal mice (B6) were trained 24 hr/day with flavored (CS+) 8% sugar solutions and flavored (CS-) water. The mice were then given two-bottle tests with the CS+ vs. CS- flavors in water only, followed by sugar vs. water tests with no added flavors. The B6 mice preferred all CS+ flavors to CS- flavors and all three sugars to plain water. The B6 mice consumed more glucose than fructose and galactose. The KO mice preferred both glucose- and galactose-paired CS+ flavors to CS- flavors, as well as both sugars to plain water. They did not, however, prefer the fructose-paired CS+ flavor and only weakly preferred plain fructose. The KO mice consumed more glucose than galactose, and more galactose than fructose. The KO data indicate that the relative potency of the sugars’ post-oral effects is glucose > galactose > fructose. Yet, B6 data from this and other studies indicate that the relative sweetness of the sugars is fructose > glucose > galactose. Ultimately, both taste and post-oral effects determine sugar preference.

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