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 r ats may have led to the survival of mutants with metabolic aberrations but without evident disease phenotype. Therefore, in the present study, we comp ared metabolic traits between so-called disease-resistant inbred rat strain s Dark Agouti (DA), Brown Norway (BN), Lewis (LEW), Wistar-Kyoto (WKY), Fis cher 344 (F344) and wild rats (Rattus norvegicus). 2. Twelve males of each strain at 12, 13 and 14 weeks of age were studied f or bodyweight, body mass index (BMI), blood glucose, serum triglycerides, t otal 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 als o significantly heavier than wild rats. 4. There were also significant differences between the different disease-re sistant strains and WKY rats were the biggest animals with the highest body weight, 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 su ggest a substantial strain dependence in feeding behaviour and energy balan ce caused by the different genotypes.