Associations of visceral and liver fat with the metabolic syndrome across the spectrum of obesity: the AGES-Reykjavik study

Abstract

Visceral adipose tissue (VAT) is a key pathogenic fat depot in the metabolic syndrome (MetS), but liver fat (LF) may also play an important role. We evaluated associations of VAT and LF with MetS in normal weight, overweight, and obese men and women (BMI <25, 25-29.9, and ≥30 kg/m2, respectively). This analysis included 2,495 participants from the Age, Gene/Environment Susceptibility (AGES)-Reykjavik study with computed tomography measurements for VAT and LF. MetS was defined by ≥3 of the following: larger abdominal circumference, hypertension, elevated triglyceride (TG), low high-density lipoprotein (HDL), impaired fasting glucose (IFG), and microalbuminuria. We estimated the odds of MetS per 1-s.d. increase in VAT and LF, adjusting for key covariates. VAT was associated with an increased odds of MetS in normal weight, overweight, and obese women (odds ratios (OR) = 2.78, 1.63, and 1.43, respectively; all P < 0.01) that diminished in magnitude with increasing BMI (VAT × BMI class interaction P < 0.001). In men, VAT was related to MetS only among the overweight (OR = 1.69, P < 0.01). LF was associated with MetS in the overweight and obese groups in women (OR = 1.38 and 1.45; both P < 0.001) and in men (OR = 1.38, P = 0.01; and OR = 1.27, P = 0.10), but not in the normal weight groups. These BMI-specific relationships persisted when both fat depots were included in the model. VAT and LF were associated with MetS independently of each other, and these relationships were modified by BMI class such that, VAT was the more important depot at lower levels of obesity and LF at higher levels. Importantly, fatty liver may be a novel metabolic risk factor in overweight and obese individuals.

FIGURE 1

Age-Adjusted Mean Levels of Visceral Adipose Tissue (A) and Liver Fat (B) by MetS Status

FIGURE 2

Comparison of Standardized β Coefficients for Visceral Adipose Tissue and Liver Fat in Normal Weight, Overweight, and Obese Women and Men Standardized β coefficients were estimated from logistic regression model for MetS adjusting for age, height, estrogen use (women only), smoking history, alcohol intake, total body fat, and thigh subcutaneous fat.

FIGURE 3

Prevalence of MetS Components across Tertiles of Liver Fat in Normal Weight, Overweight, and Obese Women and Men WC indicates waist circumference; HTN hypertension; TG triglyceride; HDL high density lipoprotein; and IFG impaired fasting glucose. Data are not presented for microalbuminuria due to low overall prevalence of 4% in women and 10% in men.