Adipose Tissue Paracrine-, Autocrine-, and Matrix-Dependent Signaling during the Development and Progression of Obesity

Figures

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  Figure 1. Cellular and functional differences in lean and obese adipose tissue. (A) Lean adipose tissue displays functional adipocytes that maintain a homeostatic balance of lipolysis and lipogenesis and is sufficiently vascularized to maintain the nutrient supply required for adipose tissue. (B) Obese adipose tissue is characterized by hypertrophic adipocytes that have a lower capillary density to supply the necessary nutrients, resulting in a hypoxic and proinflammatory environment.

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  Figure 2. Paracrine, autocrine, and matrix signaling present in adipose tissue. Adipose tissue contains many subpopulations of cells, including inflammatory cells, stem cells and progenitors, and endothelial cells, which are in constant communication with each other and their surroundings. These signals occur in the following contexts: (1) Inflammatory cytokines, including IL-6 and TNF, tend to be abundantly present in obese adipose tissue. These cytokines stimulate a proinflammatory cascade in both adipocytes and the vasculature while also stimulating dedifferentiation within both adipocytes and endothelial cells. (2) Adipokines, leptin, and adiponectin are readily released from adipocytes but act in both an autocrine and paracrine manner, and leptin, a cytokine upregulated in obese adipose tissue, induces the production of reactive oxygen species in endothelial cells while affecting the proliferative capacity and adipogenicity of adipose precursor cells. (3) Vasocrine factors, including vasoconstrictors and vasodilators, are released by both adipocytes and endothelial cells to regulate vascular tone while also altering adipocyte functionality. (4) Matrix-regulating molecules are released…