Caloric restriction experience reprograms stress and orexigenic pathways and promotes binge eating

Abstract

Long-term weight management by dieting has a high failure rate. Pharmacological targets have focused on appetite reduction, although less is understood as to the potential contributions of the stress state during dieting in long-term behavioral modification. In a mouse model of moderate caloric restriction in which a 10-15% weight loss similar to human dieting is produced, we examined physiological and behavioral stress measures. After 3 weeks of restriction, mice showed significant increases in immobile time in a tail suspension test and stress-induced corticosterone levels. Increased stress was associated with brain region-specific alterations of corticotropin-releasing factor expression and promoter methylation, changes that were not normalized with refeeding. Similar outcomes were produced by high-fat diet withdrawal, an additional component of human dieting. In examination of long-term behavioral consequences, previously restricted mice showed a significant increase in binge eating of a palatable high-fat food during stress exposure. Orexigenic hormones, melanin-concentrating hormone (MCH) and orexin, were significantly elevated in response to the high-fat diet only in previously restricted mice. Furthermore, administration of the MCH receptor-1 antagonist GSK-856464 [4-(4-ethyl-5-methylsulfanyl-1,2,4-triazol-3-yl)pyridine] significantly reduced total caloric intake in these mice during high-fat access. These results reveal reprogramming of key central pathways involved in regulating stress responsivity and orexigenic drives by moderate caloric restriction experience. In humans, such changes would be expected to reduce treatment success by promoting behaviors resulting in weight regain, and suggest that management of stress during dieting may be beneficial in long-term maintenance.

Figure 1.

Moderate calorie restriction promotes an increased stress state. A, Restraint stress-induced HPA axis corticosterone response was significantly elevated in calorically restricted (Rstr) mice (ad libitum, n = 11; Rstr, n = 12) (*p < 0.05). B, Maladaptive behavioral responses were detected in a tail suspension test in which restricted mice showed a significant increase in time spent immobile compared with ad libitum (ad libitum) fed mice (n = 11–12). Data are mean ± SEM.

Figure 2.

Moderate caloric restriction induces changes in stress pathways. A, There were no significant changes in CRF gene expression levels in the CeA compared with controls. B, CRF levels in the BNST were significantly decreased after 3 weeks of caloric restriction and remained reduced after 1 week of refeeding with chow (Refed) (*p < 0.01). C, There were no changes in methylation of the CRF promoter at individual cytosines in the CeA. D, In the BNST, there were significant decreases in methylation at multiple cytosines in calorically restricted mice that remained down after 1 week chow refeeding (Refed) (*post hoc, p < 0.05) [ad libitum, n = 4; Rstr, n = 4; Rstr-Chow (Refed), n = 4]. In addition, there was an overall effect of caloric restriction on methylation (p < 0.05). Data are mean ± SEM.

Figure 3.

High-fat withdrawal induces changes in stress pathways. A, There were no significant changes in CRF gene expression levels in the CeA compared with controls after high-fat exposure and subsequent withdrawal (n = 12). B, CRF levels in the BNST were significantly decreased by high-fat diet exposure and remained reduced for at least 8 weeks after withdrawal (n = 12) (*p < 0.01). C, In the CeA, there were no changes in methylation of the CRF promoter at individual cytosines or overall (n = 5). D, There was an overall significant decrease in methylation of the CRF promoter in the BNST (n = 5) after high-fat withdrawal (*p < 0.05). Data are mean ± SEM.

Figure 4.

Increased stress induced binge-like eating of a high-fat diet after 3 weeks of caloric restriction. A, B, Under control conditions, there were no differences in calories from high-fat diet over the course of the 10 d of testing or as a percentage of calories. C, Left panel, During CVS, calorically restricted mice consumed significantly more calories of high-fat diet compared with controls (ad libitum) over the 10 d of testing (^#p < 0.05). C, Right panel, Calorically restricted mice consumed significantly greater total amounts of high-fat diet (*p < 0.05). D, In addition, the total percentage of calories from high fat was significantly greater in the restricted mice (^#,*p < 0.05) (ad libitum-Ctrl, n = 8; ad libitum-CVS, n = 9; Rstr-Ctrl, n = 9; Rstr-CVS, n = 9). Data are mean ± SEM.

Figure 5.

Previous calorie reduction significantly enhances orexigenic hormone responses to high-fat diet. A, MCH levels in the LH were significantly increased in calorically restricted mice refed on a high-fat diet compared with ad libitum mice refed on high fat (n = 4–5) (*p < 0.05). B, Orexin levels in the LH were significantly increased in restricted mice refed on a high-fat diet compared with restricted mice refed on chow or ad libitum mice refed on high fat (n = 4–5) (*p < 0.05). Data are mean ± SEM.

Figure 6.

MCHr1 antagonist reduced caloric intake in calorically restricted mice after high-fat diet withdrawal. A, C, E, During 3 d limited access to a high-fat pellet, mice previously calorically restricted (Rstr) show increased binge-like consumption of high-fat diet compared with controls (ad libitum) (^#p < 0.001). (A) but not differences in 24 h chow (C) or total calories (E). B, On the fourth day of testing, increased caloric intake of the high-fat pellet continued in the restricted mice (^##p < 0.01). However, there was no effect of drug on high-fat caloric intake. D, The MCHr1 antagonist, GSK-856464, reduced chow caloric intake only in previously CR mice (*p < 0.05). F, The MCHr1 antagonist, GSK-856464, significantly reduced overall caloric intake only in previously CR mice (*p < 0.05) (ad libitum-VEH, n = 7; ad libitum-GSK, n = 8; ad libitum-CIT, n = 8; Rstr-VEH, n = 8; Rstr-GSK, n = 8; Rstr-CIT, n = 8). Data are mean ± SEM.