Abstract
The objectives of this study were to characterize plasma lipid phenotypes and dissect the genetic basis of plasma lipid levels in an obese DDD.Cg-Ay mouse strain. Plasma triglyceride (TG) levels were significantly higher in the DDD.Cg-Ay strain than in the B6.Cg-Ay strain. In contrast, plasma total-cholesterol (CHO) levels did not substantially differ between the two strains. As a rule, the Ay allele significantly increased TG levels, but did not increase CHO levels. Quantitative trait locus (QTL) analyses for plasma TG and CHO levels were performed in two types of F2 female mice [F2Ay (F2 mice carrying the Ay allele) and F2 non- Ay mice (F2 mice without the Ay allele)] produced by crossing C57BL/6J females and DDD.Cg-Ay males. Single QTL scan identified one significant QTL for TG levels on chromosome 1, and two significant QTLs for CHO levels on chromosomes 1 and 8. When the marker nearest to the QTL on chromosome 1 was used as covariates, four additional significant QTLs for CHO levels were identified on chromosomes 5, 6, and 17 (two loci). In contrast, consideration of the agouti locus genotype as covariates did not detect additional QTLs. DDD.Cg-Ay showed a low CHO level, although it had Apoa2b, which was a CHO-increasing allele at the Apoa2 locus. This may have been partly due to the presence of multiple QTLs, which were associated with decreased CHO levels, on chromosome 8.
