Food restriction(FR) and refeeding(Re) have been suggested to impair body mass regulation and thereby making it easier to regain the lost weight and develop over-weight when FR ends. However, it is unclear if this is the case in small mammals showing seasonal forging behaviors. In the present study, energy budget, body fat and serum leptin level were measured in striped hamsters that were exposed to FR-Re. The effects of leptin on food intake, body fat and genes expressions of several hypothalamus neuropeptides were determined. Body mass, fat content and serum leptin level decreased during FR and then increased during Re. Leptin supplement significantly attenuated the increase in food intake during Re, decreased genes expressions of neuropepetide Y(NPY) and agouti-related protein(AgRP) of hypothalamus and leptin of white adipose tissue(WAT). Hormone-sensitive lipase(HSL) gene expression of WAT increased in leptin-treated hamsters that were fed ad libitum, but decreased in FR-Re hamsters. This indicates that the adaptive regulation of WAT HSL gene expression may be involved in the mobilization of fat storage during Re, which partly contributes to the resistance to FR-Re-induced overweight. Leptin may be involved in the down regulations of hypothalamus orexigenic peptides gene expression and consequently plays a crucial role in controlling food intake when FR ends.
Zhi-Jun ZHAOYong-An LIUJing-Ya XINGMao-Lun ZHANGXiao-Ying NIJing CAO
Reproduction is the highest energy demand period for small mammals, during which both energy intake and expenditure are increased to cope with elevated energy requirements of offspring growth and somatic protection. Oxidative stress life history theory proposed that reactive oxygen species(ROS) were produced in direct proportion to metabolic rate, resulting in oxidative stress and damage to macromolecules. In the present study, several markers of oxidative stress and antioxidants activities were examined in brain, liver, kidneys, skeletal muscle and small intestine in non-lactating(Non-Lac) and lactating(Lac) KM mice. Uncoupling protein(ucps) gene expression was examined in brain, liver and muscle. During peak lactation, gross energy intake was 254% higher in Lac mice than in Non-Lac mice. Levels of H2O2 of Lac mice were 17.7% higher in brain(P<0.05), but 21.1%(P<0.01) and 14.5%(P<0.05) lower in liver and small intestine than that of Non-Lac mice. Malonadialdehyde(MDA) levels of Lac mice were significantly higher in brain, but lower in liver, kidneys, muscle and small intestine than that of Non-Lac mice. Activity of glutathione peroxidase(GSH-PX) was significantly decreased in brain and liver in the Lac group compared with that in the Non-Lac group. Total antioxidant capacity(TAOC) activity of Lac mice was significantly higher in muscle, but lower in kidneys than Non-Lac mice. Ucp4 and ucp5 gene expression of brain was 394% and 577% higher in Lac mice than in Non-Lac mice. These findings suggest that KM mice show tissuedependent changes in both oxidative stress and antioxidants. Activities of antioxidants may be regulated physiologically in response to the elevated ROS production in several tissues during peak lactation. Regulations of brain ucp4 and ucp5 gene expression may be involved in the prevention of oxidative damage to the tissue.
In the present study,we examined metabolic,morphological and neurochemical changes in male striped hamsters(Cricetulus barabensis)in response to variations in food availability.Males with low and high levels of metabolic rate(MR:L-MR and H-MR,respectively),defined by their activity MR,were compared.In Experiment 1,36-h food deprivation was found to significantly decrease MR levels,body fat content,mass of small and large intestines,and leptin gene expression in the white adipose tissues in male hamsters.Interestingly,L-MR males displayed decreased MR during both the day and night phases of circadian cycles,whereas H-MR males only showed a decrease in MR during the day(resting phase).These data indicate that individual differences in physical activity were associated with animals’different metabolic responses to food deprivation.In Experiment 2,both groups of males went through a 4-week fasting and re-feeding(re)paradigm.H-re males showed a persistent high level of MR,with decreased body fat content and a trending decrease in leptin mRNA expression,compared to L-re males.Together,our data indicate that male striped hamsters with different levels of physical activity display altered,adaptive changes in response to variations in food availability.The neurochemical involvement of such adaptive changes needs to be further studied.
