Influence of Aging and Gender Differences on Feeding Behavior and Ghrelin-Related Factors during Social Isolation in Mice

Abstract

Psychological stress due to social isolation is known to cause abnormal feeding behaviors, but the influences of gender and aging on subchronic stress-induced changes in feeding behaviors are unknown. Thus, we examined the changes in body weight, food intake, and orexigenic ghrelin-related factors during 2 weeks of isolation stress in young and aged mice. Food intake increased significantly in young mice in the isolation group compared with the group-housed control throughout the experimental period. This isolation-induced increase in food intake was not observed in aged mice. In young mice, there were no significant differences in body weight between the isolated group and group-housed control up to 2 weeks. However, aged male mice exhibited significant weight loss at 2 weeks and a similar tendency was observed in aged female mice. Young male mice, but not female mice, had significantly increased (2.2-fold) plasma acylated ghrelin levels after 1 week of isolation compared with the group-housed control. A significant but lower increase (1.3-fold) was also observed in aged male mice. Hypothalamic preproghrelin gene expression decreased significantly with isolation in young male mice, whereas it increased significantly in female mice. The expression levels of NPY and AGRP in the hypothalamus, which are transmitted by elevated peripheral ghrelin signals, increased significantly in isolated young male mice, whereas the AGRP expression levels decreased significantly in young female mice. Isolation caused no significant differences in the expression levels of these genes in aged mice. In isolation, young female mice exhibited markedly increased dark- and light-phase locomotor activities compared with male mice, whereas male and female aged mice exhibited no obvious increases in activity immediately after the dark phase started. We conclude that the gender-specific homeostatic regulatory mechanisms required to maintain body weight operated during subchronic psychological stress in young mice but not in aged mice.

Antistress effects of Kampo medicine "Yokukansan" via regulation of orexin secretion

“…This animal model is used to study psychological stress induced by a loss of social interaction. Rats live in the wild in groups, and when housed alone, they show stress responses, such as adrenomegaly; increased secretion of adrenocorticotropin (ACTH), corticosterone, and catecholamine;16 aggressive behavior;11 locomotor hyperactivity;17 increase in food intake;18 and oxidative DNA damage 19. In the current study, to evaluate the antistress effect of YKS, we investigated the aggressive behavior of rats and changes in their food intake, plasma corticosterone levels, and orexin secretion.…”

Stress is irrelevant to the onset and exacerbation of sensorineural hearing loss: Evaluation using various types of stress models in mice

“…Changes in the body weight of animals have been reported to be a convenient index for stress exposure [14,15]. A marked decrease in the body weight occurs in WIRS-and SDS-exposed animals [16]; in contrast, SIS promotes food intake and body weight gain [15,17].…”

Binge-Eating Behavior in Socially-Insolated Female Mice

“…In rats, 6 but not 3 weeks of isolation increased bodyweight though both increased weekly food intake (Nakhate, Kokare, Singru, & Subhedar, 2011;Perez et al, 1997). In mice, neither 2 nor 8 weeks of isolation changed body weight in adult mice despite altering feeding (Sun et al, 2014;Yamada et al, 2015). Only after 13 weeks of continuous social isolation has body weight and fat mass increased with increased feeding (Sakakibara et al, 2012).…”

“…It is not possible to measure the food intake of individual mice when living together. So, for pair-housed mice, the total food intake per cage was divided by two to calculate the food intake per mouse for each cage, as performed by (Yamada et al, 2015). In other words, for n = 12 pair-housed mice, there were n = 6 data points.…”