Adipose tissue angiogenesis1,2

Abstract

A review of adipose tissue angiogenesis includes the morphological and cytochemical development of adipose tissue vasculature and the concept of primitive fat organs. Spatial and temporal relationships between fetal vascular and fat cell development are discussed, including depot- and genetic-dependent arteriolar differentiation. The relationship between connective tissue deposition and elaboration of adipose tissue vasculature is discussed with respect to regulating adipocyte development in a depot-dependent manner. In vitro studies indicated that depot-dependent vascular traits may be attributable to intrinsic growth characteristics of adipose tissue endothelial cells. These studies indicate that adipogenesis may be regulated by factors that drive angiogenesis. Fundamental aspects of angiogenesis, including basement membrane breakdown, vasculogenesis, angiogenic remodeling, vessel stabilization, and vascular permeability were reviewed. Critical angiogenic factors include vascular endothelial growth factor (VEGF), VEGF receptors, angiopoietins (Ang), ephrins, matrix metalloproteinases, and the plasminogen enzymatic system. Vascular endothelial growth factor is the most critical factor because it initiates the formation of immature vessels and disruption of a single VEGF allele leads to embryonic lethality in mice. Expression of VEGF is influenced by hypoxia, insulin, growth factors, and several cytokines. Angiogenic factors secreted and/or produced by adipocytes or preadipocytes are discussed. Vascular endothelial growth factor expression and secretion by adipocytes is regulated by insulin and hypoxia, and is associated with adipose tissue accretion. Vascular endothelial growth factor accounts for most of the angiogenic activity of adipose tissue. The proposed role of leptin as an adipogenic factor is reviewed with respect to efficacy on various aspects of angiogenesis relative to other angiogenic factors. The VEGF and leptin genes are both hypoxia inducible, but potential links between VEGF and leptin gene expression have not been examined. Finally, several studies including a study of mice treated with antiangiogenic factors indicate that adipose tissue accretion can be controlled through the vasculature per se.

Increased nitric oxide availability attenuates high fat diet metabolic alterations and gene expression associated with insulin resistance

“…It is also documented that adipose tissue endothelial cells promote preadipocyte differentiation [46]. Vascularity of adipose tissue is, therefore, critical for development, maturation, plasticity and functions of adipose tissue as a metabolic and an endocrine organ [47,48]. Thus, it may seem counterintuitive that, if angiogenesis promotes lipogenesis, then the DDAH animals (which have an enhanced angiogenic response) have a normalized metabolic state.…”

BOARD-INVITED REVIEW: The biology and regulation of preadipocytes and adipocytes in meat animals1,2

“…Adipose tissue characteristically possesses substantial blood vessels and associated nerves (Hausman et al, 1980;Crandall and DiGirolamo, 1990;Crandall et al, 1997;Hausman and Richardson, 2004), and the overall mass of adipose tissue increases with age in meat animals but not in all birds (Cartwright, 1991;Owens et al, 1993;Hill et al, 2003;Scanes, 2003).…”

“…The embryonic development of mesodermal cells to form committed preadipocytes/adipofibroblasts has been described (Otto and Lane, 2005). Cells within budding embryonic and fetal adipose tissue depots undergo adipogenesis in an asynchronous manner (Hausman and Richardson, 2004), and postnatal adipocytes form more rapidly (as a function of available energy and regulation; Azain, 2004). Strategies to alter initial formation of adipose depots through the manipulation of embryonic mesodermal cells or initially formed preadipocytes/adipofibroblasts have been suggested (McMillen et al, 2004;Mir et al, 2008).…”

Cold Exposure Differentially Stimulates Angiogenesis in BAT and WAT of Mice: Implication in Adrenergic Activation

“…The vasculature provides correct oxygen tension, nutrients, hormones and growth factors to adipose tissue, meanwhile, removing metabolic wastes [7, 8]. The vessels also supply progenitor cells that can differentiate into preadipocytes and vascular endothelial cells [7].…”