Peri-aortic fat, cardiovascular disease risk factors, and aortic calcification: The Framingham Heart Study
Introduction
There is increasing evidence of an association between specific adipose tissue depots and cardiovascular disease, including cardio-metabolic risk factors and sub-clinical atherosclerosis [1], [2], [3], [4], [5]. Fat deposits immediately surrounding blood vessels (perivascular adipose tissue) are metabolically active and may play a pathogenic role in mediating local vascular disease [3], [6], [7], [8], [9], [10].
We and others have shown that pericardial fat is associated with coronary artery calcification (CAC), suggesting a local toxic effect on the vasculature [5], [11], [12]. Perivascular fat is known to be highly metabolically active, secreting substances with known vascular actions [3], [13], [14]. Further, mediastinal fat, which encases the thoracic aorta, has been associated with abdominal aortic but not coronary calcification [5]. Calcification of the aorta is an important cardiovascular disease risk marker, predicting future events and mortality [15], [16]. Therefore, uncovering an association between local peri-aortic fat deposits and sub-clinical atherosclerosis is of great interest to test the hypothesis of a local pathogenic effect of adipose tissue on the vessel wall.
Therefore, the aim of this study is to examine the correlation of adipose tissue immediately surrounding the thoracic aorta with other clinical and radiographic measures of adiposity; metabolic and cardiovascular disease risk profiles; and the extent of thoracic and abdominal aortic calcification in a large community based cohort.
Section snippets
Study sample
In 1971, the Framingham Offspring Study enrolled spouses and children of the original Framingham Heart Study cohort [17], [18]. Between June 2002 and April 2005, there were 1418 subjects from the Framingham Offspring Study who underwent chest and abdominal multi-detector computed tomography (MDCT). Our study includes these participants from the Framingham Heart Study Offspring cohort who were free of established cardiovascular disease. An interpretable scan for peri-aortic fat depots was
Study sample characteristics
The mean age of the cohort was 59 years, with 56.1% women (Table 1). The mean thoracic peri-aortic fat volume was higher in men (20.3 cm3) than in women (11.9 cm3, p < 0.05).
Pearson's correlation coefficients between peri-aortic fat and CVD risk factors
In both men and women, thoracic peri-aortic fat volume was associated with increasing age (p < 0.001) and clinical and radiographic measures of adiposity (Table 2). In both genders, thoracic peri-aortic fat was correlated with BMI (p < 0.001), WC (p < 0.001), and VAT (p < 0.0001). Modest correlations were observed between thoracic
Principal findings
We describe a novel body fat depot, thoracic peri-aortic fat, that can be quantified with high reproducibility using CT. In participants free of CVD, thoracic peri-aortic fat was correlated with several CVD risk factors despite adjustment for clinical measures of obesity. In addition, peri-aortic fat was correlated with VAT, a well-established body fat depot with important implications for cardiovascular disease. Lastly, thoracic peri-aortic fat was associated with abdominal aortic and coronary
Conclusions
Peri-aortic fat depots are associated with cardiovascular disease risk profiles and existing measures of adiposity. Thoracic peri-aortic fat is associated with coronary and abdominal aortic calcification.
Funding sources
This work was supported by the National Heart, Lung and Blood Institute's Framingham Heart Study (N01-HC-25195). Dr. Lehman is supported by grants from the National Heart Foundation of Australia and Royal Australian College of Physicians Research and Education Committee.
Disclosures
Dr. Fox, Hoffmann, Schlett and Lehman conceived the study, performed analysis, drafted and revised the manuscript. Dr. Massaro performed analysis, drafted and revised the manuscript. Dr. O’Donnell provided critical revisions to the manuscript and analysis. All authors have approved the manuscript as written. There are no conflicts of interest to disclose. Drs. Fox and Lehman had full access to the data, and take responsibility for its integrity.
Acknowledgement
We gratefully acknowledge the thoughtful comments and insights of Dr. John S. Yudkin.
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