Plasticity in energy budget and behavior in Swiss mice and striped hamsters under stochastic food deprivation and refeeding
ABSTRACT Plasticity is employed to match environmental variability in many animal species, and consequently increases their performance under different environmental conditions. Plasticity in body mass, energy budget, behavioral patterns and gastrointestinal (GI) tract was examined in Swiss mice and striped hamsters (Cricetulus barabensis) acclimated to a stochastic food deprivation (FD) and then an ad libitum refeeding (Re). FD leaded to a significant decrease in body mass on FD days and an increase in food intake on feeding days in both animals. Larger GI tract in size was employed to meet the higher food intake in FD mice and hamsters. Unexpectedly, activity increased significantly on FD days for both animals. Carcass and fat mass decreased significantly in FD hamsters but not in FD mice. This suggested that mice compensated completely for stochastic FD by increasing food intake on feeding days, whereas hamsters by both increasing food intake and mobilizing energy deposition. After 4 weeks of Re, all of above parameters recovered to levels of controls indicating a significant plasticity in both species over a short timescale. Finally, the current study provided a support for the hypothesis that there were species specific responses of plasticity in energy budget and behavioral patterns to unpredictable changes in food availability for non-foraging mice and foraging hamsters.
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ABSTRACT: Abstract Proper adjustments of physiology and behavior are required for small mammals to cope with seasonal climate change. The aim of this study was to examine the role of leptin in the regulation of body mass and energy budget in striped hamsters. We first investigated seasonal changes in body mass, energy budget, and serum leptin levels in hamsters acclimated to outdoor natural daylight and ambient temperature. Then we assessed the effect of leptin administration on energy budget, serum lipoprotein lipase (LPL) and hepatic lipase (HL) activities, and gene expression of uncoupling protein 1 (UCP1) in brown adipose tissue and of hypothalamic neuropeptides associated with the regulation of energy balance in hamsters maintained at 21° and 5°C. Hamsters showed constant body mass throughout the four seasons but significantly increased food intake and thermogenesis in winter, compared to summer. Minimum body fat was observed in winter, and minimum serum leptin was found in autumn. Hamsters housed at 5°C showed higher energy intake, upregulated gene expression of UCP1 and hormone-sensitive lipase, and lower fat content and LPL and HL activity than the animals maintained at 21°C. Leptin administration had no effect on energy intake but increased maximal thermogenic capacity, as indicated by upregulated UCP1 gene expression at both 21° and 5°C. Body fat and activity of LPL and HL were decreased in hamsters treated with leptin. The results suggest that leptin plays an important role in the seasonal regulation of thermogenic capacity and body composition in striped hamsters. Leptin may be involved in increasing maximal thermogenesis in the cold rather than acting as a starvation signal to increase energy intake.Physiological and Biochemical Zoology 03/2014; 87(2):245-256. · 2.46 Impact Factor
- Italian Journal of Zoology 08/2014; 81(2):227-234. · 0.87 Impact Factor
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ABSTRACT: Physiological and behavioral adjustments of small mammals are important strategies in response to variations in food availability. Although numerous of studies have been carried out in rodents, behavioral patterns in response to food deprivation and re-feeding (FD-RF) are still inconsistent. Here we examined effects of a 24 h FD followed by RF on general activity, serum leptin concentrations and gene expression of orexigenic and anorexigenic hypothalamic neuropeptides in striped hamsters (Cricetulus barabensis) with/without leptin supplements. The time spent on activity was increased by 2.5 fold in FD hamsters compared with controls fed ad libitum (P < 0.01). Body mass, fat mass as well as serum leptin concentrations were significantly decreased in FD hamsters in comparison with ad libitum controls, which were in parallel with hyperactivity. During re-feeding, leptin concentrations increased rapidly to pre-deprivation levels by 12 hours, but locomotor activity decreased gradually and did not return to pre-deprivation levels until 5 days after re-feeding. Leptin administration to FD hamsters significantly attenuated the increased activity. Gene expression of hypothalamic neuropeptide Y (NPY) was upregulated in FD hamsters and fell down to control levels when hamsters were re-fed ad libutm, similar to that observed in activity behavior. Leptin supplement induced increases in serum leptin concentrations (184.1%, P < 0.05) in FD hamsters and simultaneously attenuated the increase in activity (45.8%, P < 0.05) and NPY gene expression (35%, P < 0.05). This may allow us to draw a more generalized conclusion that decreased leptin concentrations function as a starvation signal in animals under food shortage; to induce an increase in activity levels, leading animals to forage and/or migrate, and consequently increasing the chance of survival. Decreased concentrations of serum leptin in animals subjected to food shortage may induce an upregulation of gene expression of hypothalamus NPY, consequently driving a significant increase in foraging behavior.Hormones and Behavior 04/2014; · 4.51 Impact Factor