Impact of adolescent sucrose access on cognitive control, recognition memory, and parvalbumin immunoreactivity

Abstract

In this study we sought to determine the effect of daily sucrose consumption in young rats on their subsequent performance in tasks that involve the prefrontal cortex and hippocampus. High levels of sugar consumption have been associated with the development of obesity, however less is known about how sugar consumption influences behavioral control and high-order cognitive processes. Of particular concern is the fact that sugar intake is greatest in adolescence, an important neurodevelopmental period. We provided sucrose to rats when they were progressing through puberty and adolescence. Cognitive performance was assessed in adulthood on a task related to executive function, a rodent analog of the Stroop task. We found that sucrose-exposed rats failed to show context-appropriate responding during incongruent stimulus compounds presented at test, indicative of impairments in prefrontal cortex function. Sucrose exposed rats also showed deficits in an on object-in-place recognition memory task, indicating that both prefrontal and hippocampal function was impaired. Analysis of brains showed a reduction in expression of parvalbumin-immunoreactive GABAergic interneurons in the hippocampus and prefrontal cortex, indicating that sucrose consumption during adolescence induced long-term pathology, potentially underpinning the cognitive deficits observed. These results suggest that consumption of high levels of sugarsweetened beverages by adolescents may also impair neurocognitive functions affecting decision-making and memory, potentially rendering them at risk for developing mental health disorders.

Daily access to sucrose impairs aspects of spatial memory tasks reliant on pattern separation and neural proliferation in rats

“…Fast-spiking parvalbuminpositive GABAergic interneurons regulate early phases of adult hippocampal neurogenesis (Song et al 2013). Previously, we observed a reduction in parvalbumin neuron immunoreactivity within the dorsal hippocampus of rats that consumed sucrose on a daily basis (Reichelt et al 2015a), which may have contributed to the reduced neuroproliferation markers observed here.…”

“…Furthermore, these detrimental effects can be long lasting. For example, we (Reichelt et al 2015a) recently demonstrated that rats who consumed 10% sucrose for 2 h a day across their adolescence exhibited object-in-place memory deficits assessed 6 wk after cessation of sucrose access. Memory involves not only remembering information over time, but also keeping memories distinct and minimizing interference among them.…”

Early life exposure to obesogenic diets and learning and memory dysfunction

“…Results revealed sucrose-associated deficits in object-in-place task, which tests hippocampal-dependent episodic contextual memory. In this study access to the diet ended at the end of the adolescent period and the testing was performed during adulthood 5-weeks after the last sucrose treatment [45]. …”

Switching Adolescent High-Fat Diet to Adult Control Diet Restores Neurocognitive Alterations

“…We and others have also demonstrated significant deleterious effects on hippocampal function specifically following adolescent consumption of a high-fat diet (HF) and/or high-sugar diet. Rodents that consume a diet supplemented with fat and/or sugar throughout adolescence, but not during adulthood, show impaired performance on a range of hippocampal-dependent behavioral tasks including object location memory (Valladolid-Acebes et al, 2013; Reichelt et al, 2015), spatial memory (Boitard et al, 2014; Hsu et al, 2015; Klein et al, 2016) and relational memory (Boitard et al, 2012). These cognitive deficits are associated with overexpression of hippocampal pro-inflammatory cytokines (Boitard et al, 2014; Hsu et al, 2015) and decreased levels of hippocampal neurogenesis (Boitard et al, 2012).…”