Developmental regulation of fear memories by an obesogenic high-saturated fat/high-sugar diet

ABSTRACT Background Anxiety and stress-related disorders are strongly linked with obesity and the consumption of obesogenic diets. Paralleling clinical findings, we showed that the consumption of an obesogenic diet during adolescence disrupts the structural integrity of amygdalar and prefrontal cortex circuits underlying emotional responses to stress. These abnormalities were associated with a PTSD-like phenotype, including heightened stress reactivity to predator odor trauma, anxiety-like behaviors, and profound learning deficits. The present follow-up study investigates how an obesogenic diet alters aversion-related associative memories across adolescence. Methods Adolescent Lewis rats were fed for eight weeks with an experimental Western-like high-saturated fat/high-sugar diet ( WD , 41% kcal from fat) or a matched control diet ( CD , 13% kcal from fat). Acoustic fear-potentiated startle (FPS) responses were assessed longitudinally at weeks 1, 4, and 8 after commencing the diets to determine the effects of the WD on cued fear conditioning, fear extinction learning, and fear extinction retention. Results We found that the rats that consumed the WD exhibited substantial attenuation of fear extinction and fear extinction retention when remote memory was tested. One-week WD consumption was sufficient to induce impairments in fear extinction learning. This phenotype was associated with reduced dopamine receptor 1 mRNA levels in the prefrontal cortex. Interestingly, our reconditioning paradigm revealed that early-acquired fear memories were resistant to the disruptive effects of chronic WD consumption on cued fear learning. Conclusions Our findings demonstrate that consumption of an obesogenic WD during adolescence heightens behavioral vulnerabilities associated with risk for anxiety and stress-related disorders. Given that fear extinction promotes resilience and that fear extinction principles are the foundation of psychological treatments for PTSD, understanding how obesity and obesogenic diets affect the acquisition and expression of fear extinction memories is of tremendous clinical relevance. HIGHLIGHTS Acute WD consumption impairs cued fear extinction learning in a fear-potentiated startle paradigm. WD consumption attenuates fear extinction memory retention WD consumption during adolescence increases acoustic startle responsivity over time Chronic WD consumption decreases dopamine receptor D1 mRNA levels in the prefrontal cortex.