A 72-hour high fat diet increases transcript levels of the neuropeptide galanin in the dorsal hippocampus of the rat

Ling Gan, Emily England, Jeong-Yeh Yang, Natalie Toulme, Suresh Ambati, Diane L Hartzell, Richard B Meagher, Clifton A Baile

Recent evidence identifies the hippocampus, a brain structure commonly associated with learning and memory, as key to the regulation of food intake and the development and consequences of obesity. Intake of a high fat diet (HFD) results in altered consumptive behavior, hippocampal damage, and cognitive deficits. While many studies report the effects of HFD after chronic consumption and in the instance of obesity, few examine the events that occur following acute HFD consumption. In this study, male rats were fed either a control diet (10% fat by kcal) or HFD (45% fat by kcal) for 72 h. At the end of the 72-h period, serum and tissues were collected and weighed. Brains were rapidly frozen or formalin-fixed in preparation for qRT-PCR or immunohistochemistry, respectively. Acute intake of HFD resulted in higher serum levels of leptin and cholesterol, with no significant changes in final body weight or adipose tissue mass. In the dorsal hippocampus, transcription of the neuroprotective peptide galanin was significantly upregulated along with a trend for an increase in brain-derived neurotrophic factor and histone deacetylase 2 in the rats fed HFD. In the ventral hippocampus, there was a significant increase in histone deacetylase 4 and a decrease in galanin receptor 1 in this group. Results from immunohistochemistry validate strong presence of the galanin peptide in the CA1/CA2 region of the dorsal hippocampus. These results provide evidence for a distinct response in specific functional regions of the hippocampus following acute HFD intake.