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Gender differences of Sprague-Dawley Rats fed a Cafeteria Diet
Institute of Pharmacology and Toxicology, School of Veterinary Medicine, Free University Berlin, Koserstr. 20, 14195 Berlin, Germany
Obesity influences a wide-ranging level of the population. Animal models are suitable to study mechanisms of obesity as they are particularly helpful to clarify the involvement of single neurotransmitters and hormones, as for example leptin (e.g. Zucker-, ZDF-rat, ob/ob-, db/db-mouse).
Aim: Our purpose was to generate an obesity model which is not based on a genetic defect but on the manipulation of the diet. Such a model mimics the evolution of human obesity in a more lifelike way because it takes into account the important role of the environment for the development of obesity. Metabolic as well as behavioral changes induced by a so called cafeteria diet were detected in juvenile male and female Sprague-Dawley rats.
Method: Accessorily to standard chow, a selection of human food items with high caloric content (e.g. noodles, chocolate, cookies, cake, cheese) was offered over a period of 4 weeks to 6-week-old male and female Sprague-Dawley rats. Control groups of the same age received only standard chow. Water and food consumption, energy intake and body weight gain were documented daily. After 4 weeks of observation animals were subjected to behavioral testing in the Elevated plus maze-test (EPM) and Open field-test (OF). Rats were decapitated and fat tissue was dissected at the end of the study.
Results: In comparison to the control groups body weights of male and female animals fed the cafeteria diet were not significantly higher after 4 weeks of observation although they showed an elevated caloric intake. However, this increased energy intake resulted in a significantly augmented visceral fat mass in the cafeteria groups of both genders plus a significantly enlarged subcutaneous fat mass in male rats. This accretion in fat tissue was mainly due to a higher average consumption of fat. Upon behavioral testing, female cafeteria fed rats were not different from controls in the EPM, but showed significantly more rearings and entries into the inner zone of the open field. Within males the cafeteria diet had no effect on behavioral testing.
Conclusion: The results show that the cafeteria diet administered for 4 weeks produced no increase of body weight but an enlargement of fat tissue. Behavior was affected by the cafeteria diet only in female Sprague-Dawley rats as indicated by the results from the OF.
Correspondence: Wiebke Warneke, Free University Berlin, School of Veterinary Medicine, Dept. of Pharmacology and Toxicology, Koserstr. 20, 14195 Berlin, Germany. Tel.: +49 (0)30 / 838 532 24.
Acknowledgement: This study is supported by the ?Stiftung der Deutschen Wirtschaft? (sdw).