Effect of niacin and simvastatin on the mRNA abundance of SR-B1, LDL-R, CYP7A1, and HMGCR in liver of guinea pigs fed high fat diet. The mRNA levels, which were analyzed by quantitative real-time PCR, were calculated after being adjusted for β-actin using the method. Data are presented as mean ± SD of at least three independent experiments. ; versus CD group; versus HFD group.