OBJECTIVE:
Subantimicrobial-dose doxycycline (SDD) treatment has been reported to reduce the severity of chronic inflammation and to increase serum high-density lipoprotein cholesterol. In a double-blind, placebo-controlled clinical trial, we determined whether SDD affects the ability of serum to facilitate cholesterol removal from macrophages.

METHODS:
Forty-five postmenopausal osteopenic women with periodontitis were randomly assigned to take placebo (n = 26) or doxycycline hyclate (20 mg, n = 19) tablets twice daily for 2 years. Serum samples were collected at baseline, 1-, and 2-year appointments. The cholesterol efflux capacity of serum from cultured human macrophages (THP-1) was measured.

RESULTS:
SDD subjects demonstrated a significant increase in serum-mediated cholesterol efflux from macrophages at both time points compared to baseline (p < 0.04 for each). Mean cholesterol efflux levels over the first year of follow-up were 3.0 percentage points (unit change) higher among SDD subjects compared to placebo subjects (p = 0.010), while there was no significant difference in 2-year changes. There were no significant differences in the changes of apolipoprotein A-I, apolipoprotein A-II, or serum amyloid A levels between the groups.

CONCLUSIONS:
Our results suggest that SDD treatment may reduce the risk of cardiovascular disease in this patient group by increasing the cholesterol efflux capacity of serum.