Endothelial Cells From Visceral Adipose Tissue Disrupt Adipocyte Functions in a Three-Dimensional Setting: Partial Rescue by Angiopoietin-1

Abstract

During obesity, chronic inflammation of human white adipose tissue (WAT) is associated with metabolic and vascular alterations. Endothelial cells from visceral WAT (VAT-ECs) exhibit a proinflammatory and senescent phenotype and could alter adipocyte functions. We aimed to determine the contribution of VAT-ECs to adipocyte dysfunction related to inflammation and to rescue these alterations by antiinflammatory strategies. We developed an original three-dimensional setting allowing maintenance of unilocular adipocyte functions. Coculture experiments demonstrated that VAT-ECs provoked a decrease in the lipolytic activity, adipokine secretion, and insulin sensitivity of adipocytes from obese subjects, as well as an increased production of several inflammatory molecules. Interleukin (IL)-6 and IL-1b were identified as potential actors in these adipocyte alterations. The inflammatory burst was not observed in cocultured cells from lean subjects. Interestingly, pericytes, in functional interactions with ECs, exhibited a proinflammatory phenotype with diminished angiopoietin-1 (Ang-1) secretion in WAT from obese subjects. Using the anti-inflammatory Ang-1, we corrected some deleterious effects of WAT-ECs on adipocytes, improving lipolytic activity and insulin sensitivity and reducing the secretion of proinflammatory molecules. In conclusion, we identified a negative impact of VAT-ECs on adipocyte functions during human obesity. Therapeutic options targeting EC inflammation could prevent adipocyte alterations that contribute to obesity comorbidities.

MicroRNA-181b Improves Glucose Homeostasis and Insulin Sensitivity by Regulating Endothelial Function in White Adipose Tissue

“…15, 16 ECs of inflamed adipose tissue from obese subjects have adverse effects on insulin signaling in adipocytes such as reduced expression of phospho-Akt at Ser473, increased endoplasmic reticulum stress, and release of inflammatory mediators. 17 On the other hand, EC function is subjected to the regulation by insulin-mediated signaling. For example, transient activation of endothelial PI3K/Akt signaling inhibits the expression of adhesion molecules involved in leukocyte rolling and adhesion to the vascular luminal wall.…”

“…19, 20 Indeed, ECs from visceral adipose tissue of obese mice or human subjects exhibit a marked inflammatory state with increased expression of chemokines, cytokines, and adhesion molecules. 17, 21 Several studies have shown insulin signaling in ECs protect endothelial function and attenuates the progression of atherosclerosis. 22–25 However, it remains unknown whether enhancing endothelial insulin signaling in adipose tissue may improve systemic insulin resistance.…”

Human Adipocytes Induce Inflammation and Atrophy in Muscle Cells During Obesity

“…We tested the role of the two proinflammatory cytokines IL-6 and IL-1b as drivers of myotube inflammation observed in cocultures based on previous reports (26,33,34). After 3 days of culture, in the presence of the neutralizing IL-6/IL-1b antibodies, the inflammatory response of cocultured cells was reduced with decreased levels of G-CSF (271.4%); fractalkine (258%); IL-7 (256%); and the chemokines CXCL1/2/3 (253%), CCL7 (242%), IL-8 (243.5%), interferon-g-induced protein-10 (236%), and CCL5 (238%) (Fig.…”

“…Mature adipocytes and muscle cells were then embedded in separate hydrogels (Supplementary Fig. 2A and B), which were previously characterized by the ability to maintain altered functions of obese adipocytes (26). Direct cocultures of human cells in a 3D setting are of great value because they allow the study of a complex set from adipocyte-derived signals that regulate skeletal muscle functions without confounding the effects of other organ systems, while maintaining signals including labile diffusible factors.…”

“…Total cell extracts were prepared in a buffer containing a cocktail of protease and phosphatase inhibitors (Roche Diagnostics, Mannheim, Germany) and were analyzed as previously described (26). Apparent molecular sizes were estimated by using the SeeBlue Plus2 Pre-Stained Protein Standard (Life Technologies, Foster City, CA), as indicated on immunoblots.…”