Previously, we demonstrated that the shift and/or restriction of feeding time during relatively short-term period (4 weeks) could alter the pituitary gonadotropin expression and the weights of seminal vesicle and prostate in rats. We also found that the reverse feeding (RF) schedule (up to 8 weeks) might induce an adaptable metabolic stress and cause impairment of androgen-dependent reproductive tissues. In the present study, we extended the RF time regimen up to 12 weeks, and measured the reproductive tissue weights. After 4 and 8 weeks of RF, the weights of epididymis were not significantly different. After 12 weeks, however, epididymis weights of RF animals were significantly different (CON 12W : RF 12W = 48.26±0.62mg : 44.05±1.57mg, p＜0.05). After 4 and 12 weeks of feeding, seminal vesicle weights of RF animals were significantly decreased (CON 4W : RF 4W = 79.36±8.34mg : 46.28±2.43mg, p＜0.001; CON 12W : RF 12W = 72.04±3.76mg : 46.71±2.27mg, p＜0.001, respectively). Prostate weights were not changed by RF. Kidney and spleen weights of RF animals were significantly different on weeks 4 and 12 (Kidney, CON 4W : RF 4W = 249.72±4.20mg : 228.41±3.03mg, p＜0.001; CON 12W : RF 12W = 309.15±7.49mg : 250.72±6.13mg, p＜0.001, respectively, Spleen, CON 4W : RF 4W = 111.26±3.76mg : 96.88±4.69mg, p＜0.05; CON 12W : RF 12W = 123.93±10.72mg : 94.68±5.65mg, p＜0.05, respectively). Histology analysis of seminal vesicle revealed that the thinner epithelial cell layers, reduced complexities of swollen papilla folding in the exocrine glands on weeks 4 and 12 of RF. There was no histological difference between control and RF group on week 8. The present study indicates that up to 12 weeks RF induced differential changes in tissue weights of male mice. In particular, seminal vesicle, kidney and spleen seemed to temporarily adapted to the RF-induced metabolic stress on week 8 of feeding schedule. These results confirmed the our previous study that the RF might induce an adaptable metabolic stress and cause impairment of androgen-dependent reproductive tissues such as epididymis and seminal vesicle as well as non-reproductive tissues such as kidney and spleen. Further studies will be needed to achieve a better understanding of the how does mealtime shift affect the reproductive function and exact nature of adaptation.

Circadian timing system plays a major role in a wide range of reproductive function. However it is plausible idea that other environmental and/or internal cue might be simultaneously participated in the optimal regulation of reproductive system. In the present study we extended the reverse feeding (RF) time regimen up to 8 weeks, then measured the general and reproductive indices of the animals. The animals of ad libitum feeding group (Control, CON) have free access to food for 4, 6 and 8 weeks, respectively. The day feeding animals (reverse feeding, RF group) have restricted access to food during daytime (09:00-18:00) for 4, 6 and 8 weeks, respectively. When the feeding schedules were over, key indices were measured. After 4 weeks and 8 weeks of feeding, body weights of animals were not significantly different. However, body weights of 6 weeks RF animals were significantly smaller than those of control animals (CON : RF = g : g, p<0.01). The blood glucose levels of 4 weeks RF animals were significantly decreased compared to the levels of control animals (CON : RF = mg/dL : mg/dL, p<0.01) while the levels of 6 weeks RF and 8 weeks RF animals were not different form those of control animals. Reproductive and non-reproductive tissue weights from 6 weeks RF group were significantly lowered than those from CON group (testis, CON : RF = g : g, p<0.001; epididymis, CON : RF = g : g, p<0.001; seminal vesicle, CON : RF = g : g, p<0.001; prostate, CON : RF = g : g, p<0.01). After 4 weeks and 8 weeks of reverse feeding, sperm counts in RF animals were markedly reduced than those in control animals[CON 4W : RF 4W = : , p<0.001; CON 8W : RF 8W= : , p<0.001]. Present study indicates that RF may induce an adaptable metabolic stress and cause impairment of androgen-dependent reproductive tissues. On-going longitudinal studies will allow a better understanding of the how does mealtime shift affect the reproductive function and exact nature of adaptation.