Abstract
Accumulation of fat at ectopic sites has been gaining attention as pivotal contributor of insulin resistance, metabolic syndrome and related cardiovascular complications. Intermuscular adipose tissue (IMAT), located between skeletal muscle bundles and beneath muscle fascia, has been linked to physical inactivity, ageing and body mass index, but little is known about its relationship with the other AT compartments, in particular with increasing age. To address this issue, erector spinae IMAT, epicardial (EAT), intraabdominal (IAAT) and abdominal subcutaneous adipose tissue (SAT) were simultaneously measured by Magnetic Resonance Imaging (MRI) and related to waist circumference measurements and age in 32 sedentary subjects without cardiovascular disease (18 men; 14 women; mean age 48.5±14 years). Fasting glucose, triglycerides and HDL-cholesterol were also assessed. We observed that, after dividing individuals according to age (≤ or >50 years), IMAT and EAT depots were significantly more expanded in older subjects (63.2±8.3 years) than in the younger ones (38.4±5.2 years) (p<0.001). Overall, both IMAT and EAT showed stronger positive associations with increasing age (β = 0.63 and 0.67, respectively, p<0.001 for both) than with waist circumference (β = 0.55 and 0.49, respectively, p<0.01 for both) after adjusting for gender. In addition, the gender-adjusted associations of IMAT and EAT with waist circumference and IAAT were significant in individuals ≤50 years only (p<0.05 for all) and not in the older ones. In contrast, no age-related differences were seen in the relationships of IAAT and SAT with waist circumference. Finally, serum triglycerides levels turned out not to be independently related with ectopic IMAT and EAT. In conclusion, the expansion of IMAT and EAT in sedentary subjects is more strongly related to age than waist circumference, and a positive association of these ectopic depots with waist circumference and IAAT amount can be postulated in younger individuals only.
Highlights
The regional distribution of adipose tissue (AT) plays an important role in the development of metabolic and cardiovascular diseases [1]
Whereas no genderrelated differences were seen in epicardial adipose tissue (EAT) and intraabdominal adipose tissue (IAAT) depots, Intermuscular adipose tissue (IMAT) was significantly more represented in women than in men (W: 925.46491.3 mm2; M: 501.16337 mm2; p,0.05)
In the present study we observed that IMAT, as well as EAT, quantitative amounts are more strongly related with age than waist circumference in sedentary individuals, and that in younger subjects only (#50 yrs in our study population) a positive association of IMAT depots with waist circumference measures and IAAT amount can be postulated
Summary
The regional distribution of adipose tissue (AT) plays an important role in the development of metabolic and cardiovascular diseases [1]. Whereas AT stored in subcutaneous depots is able to buffer the energy excess and to protect against the development of the metabolic syndrome (MS), intraabdominal adipose tissue (IAAT) is part of a more complex phenotype including a dysfunctional subcutaneous adipose tissue (SAT) and triacylglycerol deposition at ectopic, undesirable sites such as liver [5], heart and skeletal muscle [6]. Ectopic adipose depots resulting from this defect in energy partitioning, have been gaining attention as potential and ‘‘regional’’ contributors to insulin resistance and obesity comorbidities. Epicardial adipose tissue (EAT), namely the ectopic fat located subepicardically around both ventricles and along the coronary arteries, is reported to correlate with BMI, waist circumference and IAAT [8,9], and to contribute independently to the development of coronary artery disease [10]
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