Effect of nutritional stress on the hypothalamo-pituitary-gonadal axis in the growing male rat.

Background/objective: Nutritional dwarfing (ND) consists of a decrease in weight and height gain and delayed onset of puberty. The aim of the present investigation was to study the modifications induced in male rats by the nutritional stress of a mere 20% reduction in food intake which, however, started immediately after weaning.

Materials And Methods: At weaning, male Wistar rats were divided into two groups: Control (C) and ND. C rats were fed ad libitum with a balanced rodent diet. ND received 80% of the diet consumed by C for 4 weeks (T4); then they were fed ad libitum for another 4 (T8) and 8 weeks (T12). The rats were studied at T0, T4, T8 and T12 for the effects of nutritional stress and refeeding on nutritional status, body composition, hypothalamic-pituitary-gonadal axis, and sperm morphology and concentration.

Results: ND body weight and length diminished vs. C (p < 0.001). ND body fat percentage decreased 40% (p < 0.001) without change in the percentage of body protein content. The hypothalamic content of LHRH did not change. However, FSH, LH and testosterone serum levels had significantly decreased (p < 0.001) at T4 in ND rats. A 48.4 % decrease in serum leptin in the ND group was observed at T4 (p < 0.05). The absolute testicular and seminal vesicle weight was significantly decreased by ND at T4 (p < 0.001). At T4 the percentage of anomalies of caudal spermatozoa increased in about 64% (p < 0.001) of ND vs. C rats, despite the unchanged sperm concentrations. All parameters normalized during refeeding.

Conclusion: In this model, a decrease in leptin due to nutritional stress could be responsible, at least in part, for the inhibition of reproductive function. Refeeding normalized all parameters studied.