Age-related changes in plasma lipid levels and tissue lipoprotein lipase activities of Fischer-344 rats.

Fischer-344 rats of 6, 12, 18, 21 and 24 mth of age were investigated. The data were collected from groups of rats ranging from 5-10 rats per age group. Modest age-related increases were noted in body weight, plasma triglycerides, total cholesterol and free (unesterified) cholesterol. Much more significant changes were noted in tissue lipoprotein lipase activities where the adipose tissue lipases declined sharply (r = -0.90, P less than 0.0001; r = -0.86, P less than 0.0001) and the muscle tissue lipases decreased moderately (r = -0.86, P less than 0.0001; r = -0.58, P less than 0.0001) with age. These observed trends suggest that enzymatic parameters, specifically tissue lipoprotein lipase activities, may be considerably more accurate indicators of age-related physiological changes than levels of plasma lipids such as cholesterol and triglyceride.