Among postmenopausal women and women with low estrogen levels, high volumes of paracardial adipose tissue (PAT) were associated with an increased risk for cardiovascular disease, researchers reported.
The presence of coronary artery calcification (CAC) among postmenopausal women was significantly associated with greater amounts of PAT, the fat surrounding the parietal pericardium of the heart (per 1 SD unit greater in Log PAT) (OR 2.02, 95% CI, 1.02-3.99; P=0.04), according to Samar R. El Khoudary, PhD, MPH, of the Epidemiology Data Center at the University of Pittsburgh and colleagues.
The results of SWAN (the Study of Women's Health Across the Nation), published online in the Journal of the American Heart Association, found that higher volumes of PAT were also linked to an increased extent of CAC among postmenopausal versus premenopausal women and early peri-menopausal women (OR 79.83, 16.88-176.67; P=0.01). This relationship was also strongest among women with lower levels of estradiol (P for interaction=0.004).
While the researchers did find a link between epicardial adipose tissue (EAT) with increased risk for the presence or extent of CAC, the relationship was not modified by menopausal status.
"For the first time, we've pinpointed the type of heart fat, linked it to a risk factor for heart disease, and shown that menopausal status and estrogen levels are critical modifying factors of its associated risk in women," El Khoudary said in a press statement.
Because lower estrogen levels and menopausal status were only linked to the associations between PAT and CAC, and not with EAT, the authors wrote that these findings "add to the lines of evidence that EAT and PAT are distinct heart fat depots with different endocrine properties, and thus should be evaluated separately."
The team also noted that additional research is required to fuller understand why estradiol levels were related only to the relationship between PAT and CAC, and not with EAT, but suggested that "it is possible that estrogen receptors Er-a are more expressed in PAT than in EAT, which in turn could make any changes in E2 levels impact PAT more than EAT."
Levels of estrogen and menopausal status significantly modified the relationship between PAT and CAC (P for interaction ? 0.01). Additionally, after the researchers adjusted for endogenous estradiol levels and hormone therapy use, the associations between PAT and CAC extent were less significant. However, the cardioprotective impacts of hormone therapy use are largely ambiguous, due to "the lack of any publication on the impact of hormone therapy use on heart fat volumes," the team said.
Participant data were collected through the ongoing SWAN study. The final analysis included 478 women in menopause (58% pre-/early peri-, 10% late peri-, 32% post-menopausal). Data on CAC, EAT, and PAT volumes were measured with electron beam computerized tomography scans. The presence of CAC was classified as a CAC Agatstron score ? 10.
Due to the potentially harmful effects of high volumes of PAT among postmenopausal women, the authors emphasized the importance of finding ways to mitigate the risk for cardiovascular disease through methods to reduce fat surrounding the heart.
A previous meta-analysis identified the benefits of diet and bariatric surgery with significant reductions in heart fat, such as PAT. The study found that exercise alone did not have a significant benefit for heart fat reduction. The authors cited another study, which reported that "heart fat can be decreased by 17% in abdominally obese postmenopausal women on weight-loss interventions of equal energy deficit with or without aerobic exercise."
Regarding the new study, El Khoudary and co-authors noted that, overall, the cross-sectional design may limit the findings, in addition to the small sample size. The team recommended additional studies in the future to evaluate the role of hormone therapy on heart fat volume accumulation and the impact of hormone therapy on the associations between heart fat volumes and subclinical measures of atherosclerosis.
El Khoudary added: "Epicardial and paracardial fat are distinct types of heart fat that are found to be greater in postmenopausal women for different reasons with different effects on heart disease risk -- and thus should be evaluated separately when searching for ways to help women avoid heart disease."
The study was funded by grants from the National Institutes of Health and the American Heart Association (AHA).
Some authors disclosed receiving grants from the AHA or the National Institutes of Health during the conduct of the study.
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