Visceral adipose tissue (VAT), the more metabolically harmful fat depot, has been associated with a higher prevalence of diabetes, insulin resistance, and impaired glucose homeostasis. Higher levels of VAT are associated cross-sectionally with cardiovascular (CV) risk factors, specifically hypertension and unfavorable lipid profiles. Research on the effects of change in VAT on CV risk factors is extremely limited and no studies have explored these questions in minority cohorts. The Insulin Resistance Atherosclerosis Family (IRAS Family) Study offered the opportunity to explore whether changes in
VAT were associated with changes in CV risk, independent of changes in BMI, in a minority cohort.
Abdominal computed tomography (CT) scans were obtained at two time points spanning a five year interval among African-American (N=295) and Hispanic-American participants (N=719), aged 18-65 years. The CV risk factors included 5-year change in insulin resistance (HOMA), high density lipoprotein (HDL) cholesterol and systolic blood pressure (SBP). To account for family structure, we used mixed models stratified by gender to estimate change in CV risk factors as a function of change in VAT, adjusted for change in BMI, age category, race, physical activity level, smoking status, statin use (for HDL) and antihypertensive use (for SBP).
The cohort was 62% female, with an overall mean age of 40 years at baseline. The mean (SD) changes in BMI and VAT over 5-years were 1.1 (2.6) kg/m
2
and 4.2 (31.0) cm
2
, respectively; the mean (SD) changes in HOMA, HDL, and SBP over 5 years were 1.3 units (2.8), 4.8 (9.3) mg/dL and 2.4 (12.7) mm Hg, respectively. On average, a one standard deviation increase in VAT (31 cm
2
) was significantly associated with a 0.58 unit increase in HOMA in men (p<0.0001) and 0.42 unit increase in women (p=0.0048) in the adjusted model. A 31 cm
2
increase in VAT was significantly associated with a 1.8 mg/dL decrease in HDL in women (p=0.0007), but not in men (0.07 mg/dL increase, p=0.87). VAT change was not significantly associated with change in SBP in men or women.
In this study of change in CT measured abdominal fat area in a large minority cohort, modest increases in VAT were significantly related to changes in HOMA and HDL, independent of changes in BMI. Further research is needed to determine whether preventing VAT accumulation may lead to improvements in glucose homeostasis and lipid profile.
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