Metabolic variability among disease-resistant inbred rat strains and in comparison with wild rats (Rattus norvegicus)

1. Inbreeding and optimization of environmental conditions for laboratory rats may have led to the survival of mutants with metabolic aberrations but without evident disease phenotype. Therefore, in the present study, we compared metabolic traits between so-called disease-resistant inbred rat strains Dark Agouti (DA), Brown Norway (BN), Lewis (LEW), Wistar-Kyoto (WKY), Fischer 344 (F344) and wild rats (Rattus norvegicus). 2. Twelve males of each strain at 12, 13 and 14 weeks of age were studied for bodyweight, body mass index (BMI), blood glucose, serum triglycerides, total cholesterol, insulin and leptin. 3. In comparison with wild rats, the cholesterol values were significantly increased in all inbred rats studied. Except for DA rats, all rats were also significantly heavier than wild rats. 4. There were also significant differences between the different disease-resistant strains and WKY rats were the biggest animals with the highest bodyweight, BMI and cholesterol values. 5. The strains could be separated into groups with either very high (F344, LEW, WKY) or low values (DA, BN) of serum insulin and leptin levels. 6. Because all rats were studied under the same conditions, the findings suggest a substantial strain dependence in feeding behaviour and energy balance caused by the different genotypes.