Effects of sucrose and high fructose corn syrup consumption on spatial memory function and hippocampal neuroinflammation in adolescent rats

Excessive consumption of added sugars negatively impacts metabolic systems; however, effects on cognitive function are poorly understood. Also unknown is whether negative outcomes associated with consumption of different sugars are exacerbated during critical periods of development (e.g., adolescence). Here we examined the effects of sucrose and high fructose corn syrup-55 (HFCS-55) intake during adolescence or adulthood on cognitive and metabolic outcomes. Adolescent or adult male rats were given 30-day access to chow, water, and either (1) 11% sucrose solution, (2) 11% HFCS-55 solution, or (3) an extra bottle of water (control). In adolescent rats, HFCS-55 intake impaired hippocampal-dependent spatial learning and memory in a Barne's maze, with moderate learning impairment also observed for the sucrose group. The learning and memory impairment is unlikely based on nonspecific behavioral effects as adolescent HFCS-55 consumption did not impact anxiety in the zero maze or performance in a non-spatial response learning task using the same mildly aversive stimuli as the Barne's maze. Protein expression of pro-inflammatory cytokines (interleukin 6, interleukin 1β) was increased in the dorsal hippocampus for the adolescent HFCS-55 group relative to controls with no significant effect in the sucrose group, whereas liver interleukin 1β and plasma insulin levels were elevated for both adolescent-exposed sugar groups. In contrast, intake of HFCS-55 or sucrose in adults did not impact spatial learning, glucose tolerance, anxiety, or neuroinflammatory markers. These data show that consumption of added sugars, particularly HFCS-55, negatively impacts hippocampal function, metabolic outcomes, and neuroinflammation when consumed in excess during the adolescent period of development.