Glucose treatment reduces memory deficits in young adult rats fed high-fatdiets

Feeding rats high-fat diets for 7 months produces a widespread cognitive de ficit that affects performance on a wide range of learning and memory tasks . The present study tested the hypothesis that this effect is related to a fat-induced impairment in glucose metabolism. Following 3 months of dietary intervention (20% by weight fat diets, composed primarily of either beef t allow or soybean oil versus standard laboratory chow), male Long-Evans rats were tested on a variable interval delayed alternation (VIDA) task that me asures learning and memory functions that differentially involve specific b rain regions. Relative to rats fed chow, rats consuming the high-fat diets were impaired on all aspects of VIDA performance. Following baseline testin g, rats were maintained on their respective diets and the effect of glucose administration (100 mg/kg BW; i.p.) was examined. For the next 6 days, ani mals alternately received injections of saline or glucose 30 min prior to V IDA testing. Glucose treatment improved performance, with the effect being most pronounced at the longer intertrial intervals where task performance i s sensitive to hippocampal impairment. Importantly, the beneficial effect o f glucose were confined to those animals consuming the high-fat diets and w ere not observed in rats fed chow. These results demonstrate that glucose a dministration can overcome those deficits associated with hippocampal funct ion in rats fed high-fat diets and are consistent with the hypothesis that high-fat diets, in part, mediate their effect through the development of in sulin resistance and glucose intolerance. (C) 2001 Academic Press.