Increased intra-abdominal fat may lower HDL levels by increasing the fractional catabolic rate of Lp A-I in postmenopausal women.

High-density lipoprotein (HDL) particles without apolipoprotein A-II (Lp A-I) may be more anti-atherogenic than HDL with apo A-II (Lp A-I/AII) and Lp A-I is reported selectively to be reduced in cases of intra-abdominal obesity. We explored the mechanisms of this reduction by studying the turnover of Lp A-I and Lp A-I/A-II in postmenopausal women well characterized for total body, regional and sub-regional adiposity by body mass index (BMI), truncal girth ratio, and abdominal magnetic resonance imaging (MRI), respectively. We tested for possible cause-effect relationships by measuring inter-correlations among these variables. Intra-abdominal fat area correlated strongly and positively with the fractional catabolic rate (FCR) of Lp A-I (r=0.98, P=0.003). Intra-abdominal fat only showed a non-significant trend toward correlation with the FCR of Lp A-I/A-II (r=0.84, P=0.07), and had no correlation with the production or transport rate (TR) of either Lp A-I or Lp A-I/A-II (r=0.48 and 0.02, respectively, P>0.1). Subjects were studied both with and without estrogen replacement, allowing exploration of a possible interaction of adiposity with estrogen effects on HDL turnover. Response of HDL turnover to estrogen did not correlate with adiposity, except for a parameter of waist to hip ratio (WHR), which predicted the increase in LP A-I TR with estrogen (r=0.84, P=0.04). We conclude that intra-abdominal fat may lower HDL levels by increasing the FCR of Lp A-I, suggesting a mechanism by which central adiposity may be proatherogenic.