hepatic lipase gene expression is upregulated by a cystinerich diet in male but not in female rats male and female rats fed a cystinerich diet 5 lcystine became hypercholesterolemic after 2 months with 2fold higher cholesterol levels carried mainly by the hdl1 and hdl2 lipoprotein fractions postheparin lipoprotein lipase activity was increased in male rats only 60 p 001 while hepatic lipase hl activity was increased in both males and females 48 p 0001 and 27 p 001 respectively in the liver hl activity and mrna levels were increased in males 30 p 001 and 70 p 0001 respectively but not in females a higher correlation between hdl1cholesterol and liver hl activity was found in male rats than in female rats in the latter although the cystine diet induced a virtually identical increase in hdl1cholesterol hl gene expression was not promoted it is suggested that hl gene expression may be triggered by the uptake of hdl1cholesterol in male rats while oestrogens in female rats would counteract this effect