Individuals with central (visceral) adiposity are in a chronic pro-inflammatory state as shown by higher circulating levels of cytokines such as interleukins (IL), tumor necrosis factor-alpha (TNF-a), C-reactive protein (CRP), etc. Based on animal and limited human data, visceral AT (VAT) tissue shows higher levels of inflammation and is considered to be the source of these cytokines. We hypothesized that pro-inflammatory adipokines are differentially secreted between VAT andsubcutaneous AT (SAT) and that these secretions are associated with BMI.
VAT and SAT samples were obtained from 30 subjects (67% women, mean age: 54±12 years, BMI: 41.2±10.4 kg/m2) undergoing elective abdominal surgery after extensive pre-operative phenotyping. VAT and SAT were cultured for 24 hours and supernatant was collected. Multiple adipokines were measured in the supernatant using multiplex immunoassay (e.g. IL-6, TNF-alpha, granulocyte – colony stimulating factor (G-CSF), vascular endothelial growth factor (VEGF), macrophage inflammatory protein (MIP) -1a) and concentrations from VAT and SAT were compared. These adipokine concentrations were further correlated with BMI and waist circumference (WC).
The concentrations of IL-6, TNF-α, G-CSF, MIP-1a, MIP-1b, and VEGF in VAT were significantly higher than in SAT supernatant (p<0.05). None of the adipokines measured in SAT supernatant were correlated significantly with the BMI or WC. However, VAT secretion of IL-6, TNF-a, MIP-1a, and G-CSF were positively associated with BMI and WC (p<0.05). Further, the difference between VAT and SAT concentrations of IL-6 and G-CSF were correlated with BMI (p<0.05).
In this study, we showed that human VAT secretion of pro-inflammatory cytokines in higher than from SAT and that these secretions are associated with BMI and WC. This is one of the moderately large studies that evaluated secretions of multiple adipokines from paired samples of human adipose tissue and their association with adiposity.