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Fat quality, as measured by tissue attenuation on computed tomography (CT) imaging, is associated with metabolic risk factors above and beyond generalized adiposity and ectopic fat tissue volume, according to a new study published in JACC: Cardiovascular Imaging .

The study, which used pre-existing CT images of 3,198 participants in the Framingham Heart Study CT Substudy, found lower CT attenuation of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) to be correlated with higher body mass index (BMI) levels in both sexes. Mean VAT Hounsfield units (HU) for women was -103.2 and -99.6 for men. Mean SAT HU for women was -92.4 for women and -99.6 for men (p<00001).

 

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Risk factors, including BMI, increased waist circumference, increased blood pressure, elevated fasting plasma glucose, metabolic syndrome, insulin resistance, total cholesterol, HDL cholesterol and triglycerides, were generally more adverse with decreasing HU values. For example, study investigators noted that in women the odds ratio (OR) was increased for hypertension (OR 1.80), impaired fasting glucose (OR 2.10), metabolic syndrome (OR 3.65), and insulin resistance (OR 3.36; all p < 0.0001), per every 1 standard deviation decrease in VAT HU. In models that further adjusted for VAT volume, impaired fasting glucose, metabolic syndrome, and insulin resistance remained significant. According to investigators, these trends were similar but less pronounced for SAT and for men.

Overall, the authors note that lower CT attenuation as measured by HU is associated with increased cardiometabolic risk. The risk association persisted despite adjustment for BMI and absolute fat volume. There also was an association between the quantity and quality of fat. Further, individuals with both the highest visceral fat volumes and the lowest HU had the most adverse risk profiles.

"These findings provide a unique, novel framework by which to interpret CT imaging of fat depots and may potentially add to our understanding of the metabolic sequelae of obesity," the authors said.

Keywords: Odds Ratio, Blood Pressure, Risk Factors, Insulin Resistance, Glucose, Metabolic Syndrome, Cholesterol, Waist Circumference, Body Mass Index, Tomography, Adiposity, Cholesterol, HDL, Triglycerides, Hypertension, Subcutaneous Fat

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