Increased serum high-density lipoprotein cholesterol level is associated with a reduction in peripheral monocyte...

Monocytes and high-density lipoprotein cholesterol (HDL-C) both play important roles in the process of atherosclerosis. This retrospective study investigated whether an increase in serum HDL-C level would be followed by a reduction in monocyte count.

A total of 781 participants in a health check program in 1996 who had received a second health check in 1997, 1998, or 1999 were included. Based on the change in HDL-C at the second health check, the subjects were divided into the following 3 groups: 1) increase in HDL-C of >or= 5% (n = 426); 2) change of HDL-C of < 5% (n = 162); and 3) decrease of HDL-C of >or= 5% (n = 193). The relations between the change in HDL-C and the change in monocyte count were analyzed.

A significant inverse relation between the change in HDL-C level and the change in monocyte count was found among the 3 study groups by 1-way analysis of variance (p = 0.002). Subjects with increased HDL-C had significantly decreased monocyte count at the second check while subjects with decreased HDL-C had increased monocyte count. Multivariate regression analysis of data from all subjects revealed that the change of HDL-C was independently associated with a significant inverse change in monocyte count (p = 0.007).

In view of the documented inflammatory nature of atherosclerosis, the inverse relation between the change of HDL-C level and the change of monocyte count may partly explain why a higher serum HDL-C level can protect arteries against atherosclerosis.