by Lisa Nainggolan
Winston-Salem, NC- A new study has shown that fat around the heart—so-called pericardial fat—predicts coronary heart disease (CHD) independent of conventional risk factors [1].
In fact, pericardial fat may be a better predictor of an individual's future risk of CHD than either body-mass index (BMI) or waist circumference, say Dr Jingzhong Ding (Wake Forest University School of Medicine, Winston-Salem, NC) and colleagues in their paper in the September 2009 issue of the American Journal of Clinical Nutrition.
Ding told heartwire: "We and other groups have previously found in cross-sectional studies that pericardial fat is related to coronary artery disease. Our new study extends the findings to demonstrate that pericardial fat predicts the future development of clinical events of CHD and that this kind of prediction is beyond that conferred by conventional obesity measures—the first time this has been shown."
Inflammatory cytokines secreted by pericardial fat could be the culprits
Ding et al conducted a case-cohort study in 998 individuals randomly selected from the more than 6000 participants of the Multi-Ethnic Study of Atherosclerosis (MESA), who had no history of CVD. The volume of pericardial fat was measured using cardiac CT scans performed at baseline in MESA.
Of the 998 individuals, 26 developed incident CHD during follow-up, from 2000 to 2005. Pericardial fat was positively correlated with both BMI (correlation coefficient=0.45; p<0.0001) and waist circumference (correlation coefficient=0.57; p<0.0001).
In unadjusted analyses, pericardial fat (relative hazard per one standard deviation increment 1.33), but not BMI (1.00), was associated with the risk of CHD. Waist circumference was marginally associated with CHD risk (1.14; p=0.1). The relation between pericardial fat and CHD remained significant after further adjustment for BMI and other cardiovascular disease risk factors (1.26).
"Our data support the idea that pericardial fat is a better predictor of incident CHD than are more general measures of adiposity (eg, BMI or waist circumference)," say Ding et al. "The present study extends the findings of other research in this field by relating pericardial fat to incident CHD in community-based adults without a history of CVD," they add.
Ding says he and his colleagues have a theory as to the possible mechanism underlying the link between pericardial fat and CHD. "The pericardial fat secretes many chemicals, such as inflammatory cytokines like IL-6," he noted. "We can postulate that direct secretion of such substances might lead to the development of atherosclerosis in the coronary arteries." Pericardial fat is also known to secrete such inflammatory cytokines at a higher rate than subcutaneous fat, he adds.
More research needed on pericardial fat
He told heartwire that much more research is needed on pericardial fat. In general, older people have been found to have more pericardial fat than younger ones, and the volume of pericardial fat does seem to correlate with BMI and other obesity measures, as shown in the current study. But slim people also have pericardial fat, he noted, and it is not known what amount is "normal," if any. Whether babies have pericardial fat present at birth, for example, is unclear. Nor is it known whether there is any kind of cutoff amount of this fat above which it becomes hazardous.
Future studies should also examine whether pericardial fat is the primary fat depot regarding the risk of developing CHD, after other regional fat depots are controlled for, say he and his colleagues. "If the hypothesis is confirmed, pericardial fat may serve as a more specific and sensitive marker of CHD than other fat measures."
However, they note that routine CT scans are not feasible for mass screenings at the present time, but the echocardiographic measurement of pericardial fat "has potential for CHD risk stratification."
"Ultimately, with a better understanding of the determinants of pericardial fat accumulation and the underlying mechanism of the link between pericardial fat and CHD, new therapeutic targets may be identified in the prevention of CHD," they conclude.
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