Age-related variations in plasma and liver lipids of Yoshida rats: a comparison with Wistar rats

Lipoprotein and liver lipids of spontaneously hyperlipidemic Yoshida rats were compared with those of normolipidemic Wistar animals for studying their age- and strain-related differences. Both strains showed an age-related increase in the total plasma cholesterol concentration. However, the Yoshida strain had a higher content of cholesteryl esters and triglycerides than the Wistar strain in both young and adult animals (2- and 8-month-old animals, respectively). The free cholesterol content was also higher, but only in the 8-month-old animals. Both strains showed an age-related increase in the proportion of HDL1 and a symmetrical decrease in both the HDL2 and HDL3 subfractions, but the variations were more evident in the Yoshida strain. The study of strain-related differences suggested that the spontaneous hypertriglyceridemia of the Yoshida strain was not only related to the higher amount and proportion of the VLDL fraction, but also to the higher content of triglycerides in the LDL fraction. The livers of Yoshida rats accumulated more triglycerides (with an age-related progression) than those of Wistar rats. The major lipid classes in the liver of Yoshida rats contained a significantly higher proportion of monounsaturated fatty acyls. Furthermore, this proportion showed an age-related increase in all the lipid classes, but in cholesteryl esters. This suggested that liver desaturases had a relevant role in the development of hyperlipidemia, and of its age-related variations, in the Yoshida strain. In conclusion, Yoshida rats appeared a better model for the study of age-related alterations in the liver lipid metabolism since the alterations are stronger and earlier than in Wistar animals and are not complicated by the development of degenerative pathologies typical of old rats.