Depot-Specific Hormonal Characteristics of Subcutaneous and Visceral Adipose Tissue and their Relation to the Metabolic Syndrome

Abstract

Visceral adipose tissue (VAT) imaged by computed tomography (CT) or magnetic resonance imaging (MRI) is associated with the metabolic syndrome features, being morphologically and functionally different from subcutaneous adipose tissue (SAT). Insulin effect is lower and catecholamine effect higher in visceral adipose tissue, with its metabolites and its secretions draining through portal system, partially at least, to the liver. Thus, visceral cells transfer and release fatty acids more extensively, have increased glucocorticoid and reduced thiazolidinedione responses, produce more angiotensinogen, interleukin-6 and plasminogen activator inhibitor-1, and secrete less leptin and adiponectin than SAT. Furthermore, there are regional differences in the intrinsic characteristics of the preadipocytes, with those of SAT presenting greater differentiation and fat cell gene expression but less apoptosis than that of VAT. All features contribute to the morbidity associated with increased VAT. To evaluate the relationship between VAT and components of the metabolic syndrome, 55 non-diabetic women, 11 lean (VAT < 68 cm 2) and 44 obese were studied. The obese with VAT within the normal range (VAT < or = 68 cm 2) had higher BMI, WHR, BP and resistance to FFA suppression during oGTT in comparison to the lean controls. The obese with VAT > 68 cm 2 compared to those with VAT < or = 68 cm 2 had similar body mass index (BMI) but significantly higher in vivo homeostasis model assessment for insulin resistance (HOMA IR ) results and triglycerides. By pooling all data, correlation analysis indicated that VAT contributes more to insulin resistance (HOMA IR ) than SAT does, but not when insulin-suppressed plasma free fatty acids during oral glucose tolerance test as an index of insulin resistance are taken into consideration.