Does lipoprotein or hepatic lipase activity explain the protective lipoprotein profile of premenopausal women?

Numerous studies have reported that women have a lipoprotein profile suggestive of a reduced risk of coronary heart disease (CHD). We have therefore tested whether the “protective” lipoprotein profile of women could be explained by differences in hepatic lipase (HL) or lipoprotein lipase (LPL) activities. In the present study, 14 non-obese healthy premenopausal women had higher plasma concentrations of high-density lipoprotein cholesterol (HDL-C), HDL2-C, HDL3-C, and HDL—apolipoprotein (apo) Al, and a higher ratio of HDL-C to low-density lipoprotein cholesterol (LDL-C) than 17 non-obese healthy men. Women also had lower plasma triglyceride (TG), HDL-TG, and apo B levels than men. Plasma postheparin LPL (PH-LPL) and HL activities showed no significant sex dimorphism, whereas abdominal and femoral adipose tissue (AT)-LPL activities were significantly higher in women (P < .005). In men, PH-LPL activity correlated significantly with plasma HDL2-C (r = .52, P < .05), LDL-C (r = −.47, P < .05), and apo B (r = −.56, P < .01) levels, as well as with the HDL-C LDL-C ratio (r = .67, P < .005). No such relationships were found in women, with the exception of HL activity, which was negatively correlated with HDL—apo Al levels. In both genders, abdominal AT-LPL activity showed no significant association with plasma lipoprotein levels. In contrast, femoral AT-LPL activity in women was positively correlated with plasma HDL-C, HDL2-C (r = .53, P < .05 and r = .69, P < .01, respectively), and HDL—apo Al (r = .52, P < .01) levels, as well as with the HDL-C LDL-C ratio (r = .62, P < .01). These associations were not found in men. Analysis of covariance (ANCOVA) showed that adjustment for HL activity could not explain sex differences in lipoprotein levels. When correction for PH-LPL activity was performed, gender differences observed in plasma lipoprotein levels remained significant. In ANCOVA with inclusion of abdominal AT-LPL activity as a covariate, men still had plasma TG levels significantly higher than women, whereas HDL-C, HDL2-C, HDL—apo Al, and HDL3-C concentrations were lower. Finally, femoral AT-LPL activity was the most powerful covariate explaining gender differences in plasma lipoprotein levels. Indeed, adjustment for femoral AT-LPL activity eliminated gender differences in plasma TG, HDL-C, HDL2-C, HDL—apo Al, and apo B levels and the HDL-C LDL-C ratio , with the exception being the HDL3-C level. Although these results do not provide evidence for a cause-and-effect relationship, they suggest that the high femoral AT-LPL activity is a significant correlate of the favorable plasma lipoprotein-lipid profile in women.