Abstract

Underweight in pregnant women adversely affects the next generation. Although young female underweight has become an important issue even in developed countries, the precise mechanisms that induce an underweight status in young women remains unknown. To examine the influence of feeding timing in young women on the following underweight conditions, we examined the effects of chronic light–dark cycle-reversed feeding restriction on post-restriction dietary behaviors using adult and young adult female rats. Eight- and 24-week-aged female Wistar rats were classified into three groups: (1) the control group (without time or calorie restriction), (2) the night-time-fed group that was fed only during the active phase, and (3) the daytime-fed group that was fed only during the non-active phase. After a 4-week feeding restriction, all groups were additionally fed ad libitum for 7 weeks with daily food intake and weight gain measurements. After sacrifice, mRNA expressions of neuropeptide Y (NPY), agouti-related protein (AgRP), orexin-A, pro-opiomelanocortin (POMC), and thyrotropin-releasing hormone (TRH) in the hypothalamus and leptin in the fatty tissues were examined by real-time PCR. Daytime-fed groups decreased food intake during restriction. After stress relief, adult rats showed a rebound increase in food intake beyond the level of the control group, whereas young adult rats showed no significant rebound response. At the end of the non-restricted period, both adult and young adult rats in the daytime-fed group reduced NPY expression in the hypothalamus. These findings indicate that recovery responses in food intake against chronic light–dark cycle-reversed stress are different between adult and young adult rats. The lower response in young adult rats may provide clues to elucidating a new mechanism for underweight status in young females.

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