The comparison of intra-abdominal fat distance (I-A Fat Distance) and visceral adipose tissue area (VAT) or visceral fat to skeletal muscle area ratio (VMR) measured by computed tomography (CT)

Kim, Soo Kyung; Kim, Se Hwa; Rhee, Yu Mie; Choi, Seung Hee; Cho, You Lee; Ahn, Chul Woo; Cha, Bong Soo; Lim, Sung Kil; Kim, Kyung Rae; Lee, Hyun Chul; Huh, Kap Bum

Abstract

BACKGROUND: Visceral fat accumulation plays a major role in metabolic syndrome and increased cardiovascular risks. Clinical evaluation of visceral fat by CT is not widely used because of high cost, low availability, and ionizing radiation risk, and alternative means are required. To assess the usefulness of ultrasound measurement of I-A fat distance for the evaluation of visceral obesity, we compared several length-associated parameters (I-A fat distance, I-A fat distance to thigh muscle length ratio, and I-A fat distance to abdominal subcutaneous fat length ratio) with area-associated parameters (VAT, visceral fat to subcutaneous fat area ratio [VSR] and VMR) measured by CT.
METHODS
We evaluated 65 patients with type 2 diabetes (34 men and 31 postmenopausal women). CT scans were obtained at the L4-5 level and the mid-portion between greater trochanter and upper margin patella. I-A fat distance was defined as the distance between the internal face of rectus muscle and the anterior wall of the aorta. Also ultrasonography for measurement of I-A fat distance was performed in 20 men of subjects.
RESULTS
Of the various parameters examined, I-A fat distance was most closely correlated with the VAT (r=0.76, p<0.001) and VMR (r=0.71, p<0.001) but not VSR (r=0.18, p=0.22). This distance positively correlated with serum triglyceride and free fatty acids in men (r=0.56 and r=0.59, p<0.05, respectively), and with uric acid (r=0.70, p<0.05), fasting insulin levels (r=0.70, p<0.001), insulin resistance index by HOMA (r=0.69, p<0.001), systolic blood pressure (SBP) (r=0.73, p<0.05), and diastolic blood pressure (DBP) (r=0.85, p<0.001) in women. When the clinical and laboratory data was considered by tertiles of I-A distance, serum uric acid, fasting insulin levels, insulin resistance index (HOMA), BMI, waist or hip circumference, SBP, and DBP were significantly higher in the top tertile, but not WHR. I-A fat distance measured by ultrasonography significantly correlated with VAT, VSR, and VMR (r=0.79, r=0.71, and r=0.79, p<0.05, respectively).
CONCLUSION
These results suggest that 1) I-A fat distance may substitute for the VAT in assessment of visceral fat content and may be relatively good parameter indicative of visceral obesity and/or insulin resistance, and 2) several parameters (e.g., VAT, VSR, and VMR) related with visceral fat by CT may be replaced with ultrasonographic I-A fat distance.