Biological Effects of Long-Term Caloric Restriction: Adaptation with Simultaneous Administration of Caloric Stress Plus Repeated Immobilization Stress in Rats

Abstract

In the present study, we have established the biological effects during 8 weeks of (i) caloric restriction (Cal) and (ii) simultaneous administration of Cal plus 2 hr daily immobilization stress using male Sprague-Dawley rats. Animals were divided into three equal groups: (i) ad libitum fed, (ii) 30% restriction of food intake of the ad libitum diet, and (iii) 30% restriction of food intake plus 2 hr daily immobilization stress. Caloric-restricted animals gained only 30% of the total body weight of the unrestricted animals but received 70% of the food of those rats. Cal animals showed a significant loss in their relative liver and thymus weight and a significant gain in their relative adrenal and testis weight as compared to the control animals. Cal animals had almost 2-fold higher levels of plasma corticosterone levels with a dramatic decrease in the total glucocorticoid receptor (GR) levels in the liver, thymus, heart, and testis as compared to ad libitum fed control animals. Interestingly, Cal animals showed higher levels of lipid peroxidation in both the liver and heart, indicating increased oxidative activities in these tissues when compared with the control animals. In addition, Cal animals had increased heat shock protein 70 (HSP 70) content in the testis. Surprisingly, hardly any significant differences were observed in either total body weight gain, organ weights, Plasma corticosterone levels, or lipid peroxidation between Cal animals and Cal plus immobilization-stressed animals. The results obtained suggest that (i) several stress-related responses such as inhibition of total body weight gain, increased adrenal weight, decreased thymus weight, increased plasma corticosterone, and lipid peroxidation levels in the liver and heart are associated with Cal, but (ii) no additional effects were observed on the parameters that were measured when two stress regimens were given simultaneously, suggesting that animals subjected to two stress regimens can protect themselves by controlling their stress-related thresholds of response through adaptation.

Effects of random food deprivation on body mass, behavior and serum leptin levels inEothenomys miletus(Mammalia: Rodentia: Cricetidae)

“…In the present study, activity was significantly higher in FD voles than in the control group on FD days; a similar result was found in mice (Sherwin 1998), which indicates that small mammals increase activity to search for food when the food is limited or unpredictable (Alvarenga et al 2005). But FD voles had a higher percentage of feeding behavior on ad libitum days, which suggests that while animals increase feeding behavior, they seem to reduce activity and energy expenditure to compensate for the shortage of food resources (Gursoy et al 2001). …”

Testicular angiogenic activity in response to food restriction in rabbits

“…Mice subjected to food restriction exhibited a decline in testicular and epididymal weights, and reduced serum testosterone levels (Santos et al 2004). However, in contrast with these findings, rats subjected to a 30% caloric restriction for 8 weeks showed an increase in testicular weight when compared with unrestricted control animals (Gursoy et al 2001).…”

“…Testicular regression has also been reported in white-footed mice (Peromyscus leucopus) in response to receiving 70% of control intake for 8 weeks (Young et al 2000). On the contrary, Sprague-Dawley rats receiving 70% of a control diet showed significant testicular weight gain as compared with control animals (Gursoy et al 2001). Also in Sprague-Dawley rats, a similar food restriction produced no Leydig cell atrophy, hematological, blood biochemical, and pathological changes, in contrast to males receiving only 55% of food ad libitum (Seki et al 1997).…”

Growth patterns in male rats exposed to concurrent long-term environmental challenges

“…It is known that body size growth is constrained by the amount of energy available and the maintenance expenditure of individuals (Gursoy et al, 2001;Griffiths and Brook, 2005). The abrupt decline of weekly body mass gain (wBMG) experienced by the rats with restricted resources reflected an attempt to allocate the resources acquired to fulfil maintenance costs, reducing the resources directed to somatic growth.…”