Detection of rat model useful for genetic analysis of intramuscular fat accumulation

Abstract

It has been known that genetic predisposition is involved in intramuscular fat accumulation in beef cattle. However, causative gene (s) for intramuscular fat accumulation still remain (s) unidentified. In order to detect the gene (s) responsible for intramuscular fat accumulation which is thought as a quantitative trait, the application of inbred rat models is an essential component due to usefulness of them in quantitative trait loci (QTL) analysis, congenic analysis, and positional candidate cloning approach. It is, therefore, important to detect rat model for intramuscular fat accumulation. Our investigation was designed to detect inbred rat strains, in which intramuscular fat content is preferentially markedly increased as compared to intra-abdominal and subcutaneous fat contents, by measuring intramuscular, intra-abdominal, and subcutaneous fat contents in males and females of 10 obese inbred strains at 25 weeks of age. These strains exhibited higher levels of intramuscular fat content than normal control rat, and fatty (fa) mutation affected an increase of intramuscular fat content. OLETF strain possessed sex difference in degree of intramuscular fat accumulation. Three strains, Zucker fatty, LEA, and SHC, but not other strains, irrespective of sex, exhibited preference of accumulation of intramuscular fat to of intra-abdominal and subcutaneous fats. Thus, these three strains seem to be useful as rat model for genetic analysis of intramuscular fat accumulation. In addition, we observed the correlation between plasma triglyceride levels and body fat contents, suggesting an important role of the plasma triglyceride level as a concise diagnostic indicator for prediction of body fat contents.