Lack of Sex Differences in High Density Lipoproteins in Pima Indians: Studies of Obesity, Lipase Activities, and Steroid Hormones

To Investigate the reasons for the lack of sex differences In high density llpoprotelns (HDL) observed In population studies of the Plma Indians, we selected 18 lean (9 men, 9 women, body mass Index (BMI) < 27) and 22 obese (12 men, 10 women, BMI > 27) Plma Indians for an Inpatlent study of HDL composition. We measured lipase activities and steroid hormone concentrations, both of which have previously been Implicated In the control of HDL. The lean women had higher concentrations of HDL and HDL2 than did either the obese women or the lean or obese men. Lean women had significantly lower hepatic lipase activities and significantly higher concentrations of estradlol compared to obese women. Lean women also had different HDL2 composition, as Indicated by the molar ratio of HDL2 cholesterol/A-l. Significant negative correlations between HDL and obesity measured by either BMI or percent body fat were observed In both sexes, but the slope of the relationship was steeper In women. Significant negative associations were observed between HDL or HDL2 concentrations and hepatic lipase In both sexes, and there were significant positive associations between HDL2 and plasma estradlol In women. The data suggest that obesity In this population has a stronger negative Influence on HDL concentrations In women, possibly through changes In estradlol and hepatic lipase activities. Since there are so few lean women In the Plma population, the net result Is that HDL levels In women In the population as a whole do not differ from those of men.