SAT-290 Food Restriction Effects on the Hypothalamus-Pituitary-Gonadal Axis

Abstract

It is well known that nutritional status affects the reproduction, since an adequate amount of energy is necessary for puberty onset and fertility. However, the neural mechanisms by which energy homeostasis affects reproduction is not completely elucidated. To determine if acute or chronic food restriction (FR) are able to modulate the estrous cycle, adult female mice were used in the experiments. The estrous cycle was evaluated by daily observation of vaginal smear. To determine the effects of an acute FR protocol on estrous cycle, females were individualized and kept on ad libitum diet (control, n=17) or fasted for 24 hours (n= 21). A subgroup of animals was euthanized shortly after the 24-hours test to collect hypothalamus and determinate Kiss1 mRNA levels, while another group of mice were regrouped and fed ad libitum. To determine the effects of a chronic FR protocol on estrous cycle, control mice were individualized and maintained with 100% of daily food content (average of 5 g per day, n = 6), or submitted to 60% of FR (n= 12). Animals were fed ad libitum after test. As expected, mice fasted for 24-hours exhibited a significant weight loss (control: 21.7 g ± 0.5 vs 21.6 ± 0.5 g; fasted: 22.7g ± 0.5 vs 18.7g ± 0.4, P=0.0001). This effect was followed by a significant reduction of hypothalamic Kiss1 mRNA expression (control: 1.0 ± 0.2; fasted: 0.3 ± 0.05, P=0.04, n=4/4 per group). Surprisingly, even under lower Kiss1 mRNA levels, 24-hours fasting induced no changes on estrous cycle. On the other hand, chronic FR induced a gradual weight loss (body weight at the 5th day of FR, control: 21.5g ± 0.2; FR: 17.3g ± 0.7, P=0.0002). The chronic FR was follow by the disruption of estrous cyclicity. While control mice exhibited a regular pattern of cyclicity during the period of evaluation, only leukocytes were identified in the vaginal smear of mice submitted to 60% of FR, even though they had a normal cycling pattern before the test. Therefore, by comparing 30 days of estrous cycle evaluation, including the period before chronic FR, while control mice exhibited cornified cells in the vaginal smear 58.5 ± 4.9% of days, female mice submitted to FR exhibited cornified cells in 38.3 ± 3.8% of days (P= 0.0068). Approximately 3-4 days after the end of the chronic FR females returned to exhibit estrous cyclicity, however the length of the estrous cycle was prolonged compared to control group. Our data suggest that chronic nutritional status variations are required to disrupt the hypothalamus-pituitary-gonadal axis and therefore the estrous cyclicity.