Circadian rhythmicity (e.g. secretory pattern of hormones) plays an important role in the control of reproductive function. We hypothesized that the alteration of feeding pattern via meal time shift/restriction might disrupt circadian rhythms in energy balance, and induce changes in reproductive activities. To test this hypothesis, we employed simple animal model that not allowing feeding but daytime only feeding. The animals of feeding group (Control) have free access to food for 4 weeks. The day feeding (=reverse feeding, RF) animals (RF group) have restricted access to food during daytime (0900-1800) for 4 weeks. After completing the feeding schedules, body weights, testis and epididymis weights of animals from both group were not significantly different. However, the weights of seminal vesicle (control : RF group = : , <0.01) and prostate (control : RF group = : , <0.001) were significantly lower in RF group animals. The mRNA levels of pituitary common alpha subunit (; control : RF group = AU : AU, <0.001) and (control : RF group = AU : AU, <0.05) were significantly decreased in RF group. The mRNA levels of ACTH were not significantly different. We were unable to find any prominent difference in the microstructures of epididymis, and there were slight alterations in those of seminal vesicles after 4 weeks of reversed feeding when compared to control samples. The present study demonstrates that the shift and/or restriction of feeding time could alter the pituitary gonadotropin expression and the weights of seminal vesicle and prostate in rats. These data suggest the lowered gonadotropin inputs may decrease androgen secretion form testis, and consequently results in poor response of androgen-dependent tissues such as seminal vesicle and prostate.

It is well known that adipose tissue or body fat has been proved as a crucial component of brain-peripheral axis which can modulate the activities of reproductive hormonal axis in female mammals including rodents and human. Concerning the male reproduction, however, the role of adipose tissue has not been thoroughly studied. The present study was carried out to elucidate the effect of a high-fat (HF) diet on the reproductive system of postpubertal male rats. The HF diet (45% energy from fat, HF group) was applied to male rats from week 8 after birth for 4 weeks. The blood glucose levels, body and tissue weights were measured. Histological studies were performed to assess the structural alterations in the reproductive tissues. To determine the transcriptional changes of reproductive hormone-related genes in hypothalamus and pituitary, total RNAs were extracted and applied to the semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). Body weights (p<0.01) and blood glucose levels (p<0.01) of HF group were significantly higher than those of control animals. Similarly, the weights of epididymis (p<0.05), prostate (p<0.01), seminal vesicle (p<0.01) in HF group were higher than control levels. The weights of testis were not changed. The weights of kidney (p<0.001) and spleen (p<0.01) were significantly higher than control levels while the adrenal and pancreas weights were not changed. There were only slight alterations in the microstructures of accessory sex organs; the shape of luminal epithelial cells in epididymis from HF group were relatively thicker and bigger than those from control animals. In the semi-quantitative RT-PCR studies, the mRNA levels of hypothalamic GnRH (p<0.05) in HF group were significantly higher than those from the control animals. The mRNA levels of kisspeptin in HF group tend to be higher than control levels, the difference was not significant. Unlike the hypothalamic GnRH expression, the mRNA levels of pituitary and were significantly decreased in HF group (p<0.05). The present study indicated that the 4-weeks feeding HF diet during the postpubertal period can alter the hypothalamus-pituitary (H-P) neuroendocrine reproductive system These results suggest that the increased body fat and the altered leptin input might disturb the H-P reproductive hormonal activities in male rats, and the changed activities seem to be responsible for the changes of tissue weights in accessory sex organs.