Central obesity is a risk factor for dyslipidemia and cardiovascular disease in postmenopausal women. Low estrogen levels and increased intraabdominal fat (IAF) have been associated with increased activity of hepatic lipase and an atherogenic lipid profile, characterized by reduced concentrations of HDL2 cholesterol and increased small, dense LDL particles. Previous studies have shown that increasing amounts of intraabdominal fat correlate with higher levels of free cortisol in postmenopausal women. However, little is known about the relationship between endogenous cortisol secretion, hepatic lipase activity (HLA), and lipoprotein levels.
Methods To further investigate these relationships, we studied 25 women (13 premenopausal (Pre), mean ± SD age 35 ± 9 yrs, 6 postmenopausal not on HRT (PM), age 56 ± 6 yrs, and 6 postmenopausal on hormonal replacement therapy (PM + HRT), age 52 ± 6 yrs), matched for body weight. IAF was measured by CT scan, and 24-hour free cortisol was measured by 18-hour equilibrium dialysis on pooled samples of plasma drawn every 30 minutes for 24 hours.
Results There was a nonsignificant trend toward increased hepatic lipase activity in postmenopausal women (Pre 133 ± 67 nmol/ml/min, PM + HRT 123 ± 32 nmol/ml/min, PM 187 ± 50 nmol/ml/min; mean ± SD, p = 0.12). IAF was positively correlated with HLA (r=0.453, p=0.020) and negatively correlated with LDL relative flotation (Rf) (r=-0.524, p=0.006) and HDL2 (r=-0.515, p=0.007). 24-hour free cortisol was positively correlated with HLA (r=0.510, p=0.009) and negatively with HDL2 (r=-0.404, p=0.045). On multiple linear regression analysis, HLA was independently related to free cortisol (p=0.046) but not IAF (p=0.117).
Conclusion Increased IAF is associated with a more atherogenic lipid profile and contributes to formation of small, dense LDL and reduced HDL2 levels through its association with increased hepatic lipase activity. However, our data suggest that free cortisol levels not only have a role in the expression of visceral adiposity but also independently affect hepatic lipase activity, and may be important in determining HDL2 levels in women.