Short-term effects of a Western diet on the number of brainderived neurotrophic factor immunoreactive neurons in the hypothalamic arcuate, ventromedial and paraventricular nuclei

Brain-derived neurotrophic factor (BDNF) is an important anorexogenic factor and has been shown to be involved in obesity. It is important to know when changes in BDNF expression occur to possibly prevent development of dietary obesity. BDNF mRNA decreases in response to long-term western diet (WD) exposure in the ventromedial hypothalamus (VMH), yet no study has investigated the short-term effects of WD on BDNF expression in the hypothalamus. It was hypothesized BDNF protein would mirror a decrease in BDNF mRNA in the VMH when mice were fasted for 48-hours or fed WD for 6-hours, 48-hours, 1-week and 3-week and decrease the number of BDNF immunoreactive (IR) cells. Immunohistochemistry was used to stain for BDNF-IR cells in the arcuate (ARC), VMH, paraventricular hypothalamus (PVN) and cortex. Sections were imaged using confocal microscopy and cells were counted using Image J software. Fasting resulted in decreases of BDNF-IR cell number in the ARC (32%) but not in the VMH. No changes were seen at 6-hour, 48-hour and 3-weeks in any of the brain areas between any of the diet manipulations. Near-significant increasing trends were observed at 48 hours which become significant at 1-week in the VMH (29%) and CORTEX (17%). Longer fasts may be necessary to see significant decreases in the VMH in fasted animals. An increase in BDNF-IR cell number at 1-week in the WD group is likely to have occurred in attempt to inhibit overeating and food intake