The adipose conversion process: regulation by extracellular and intracellular factors

Abstract

-White adipose tissue regulates lipid metabolism and acts as a secretory organ. Because of its importance for human health and animal production, many studies have attempted to better understand its development at the cellular and molecular levels by culturing preadipose cells in vitro. This synthesis article describes our current knowledge, acquired by this approach, concerning the regulation of the different steps of the adipocyte differentiation program by extracellular (hormones, cytokines, growth factors, retinoids and fatty acids) and intracellular agents (second messengers and transcription factors). The discrepant effects that have been observed for some of these factors are also discussed. This information is very important in the perspective of a better control of fat deposits in human and breeding species.preadipocyte / differentiation / hormonal agent / second messenger / transcription factor Résumé -Le processus d'adipoconversion : sa régulation par des facteurs extracellulaires et intracellulaires. Le tissu adipeux blanc régule le métabolisme lipidique et agit comme un organe de sécrétion. Étant donné son importance pour la santé humaine et la production animale, de nombreuses études ont tenté de mieux comprendre son développement aux niveaux cellulaire et moléculaire en utilisant des cultures de préadipocytes. Cet article de synthèse décrit notre connaissance actuelle, issue de cette approche, concernant la régulation des différentes étapes du programme de la diffé-renciation adipocytaire par des facteurs extracellulaires (hormones, cytokines, facteurs de croissance, rétinoïdes et acides gras) et intracellulaires (seconds messagers et facteurs de transcription). Les effets divergents observés pour certains de ces facteurs sont également discutés. Ces informations sont très importantes dans la perspective d'un meilleur contrôle des dépôts adipeux chez l'humain et les espèces d'élevage.préadipocyte / différenciation / hormone / second messager / facteur de transcription Reprod. Nutr. Dev. 40 (2000) 325-358 325

Intramuscular fat content in meat-producing animals: development, genetic and nutritional control, and identification of putative markers

“…Picard et al, 1995 and2002) and adipose tissues (e.g. reviews from Boone et al, 2000;Hausman et al, 2009) in different species, the precise pattern of IMF ontogenesis and its regulation remains still poorly characterized. At the cellular level, triglycerides are generally initially stored within muscle fibres in mammals.…”

Regulation of lipid accumulation in 3T3-L1 cells: insulin-independent and combined effects of fatty acids and insulin

“…In the first step of hyperplastic expansion, progenitor cells are thought to become committed to the adipocyte lineage, after which they cannot revert back to a less differentiated 'stem-like' cell (Thompson et al, 1998;Boone et al, 2000). Once committed, adipoblasts undergo an exponential replication phase that terminates and the cell cycle arrests at gap 1 (G1).…”

“…Once committed, adipoblasts undergo an exponential replication phase that terminates and the cell cycle arrests at gap 1 (G1). Early markers of differentiation, such as lipoprotein lipase (LPL) are then expressed, and these cells, known as preadipocytes, may then undergo proliferation (Boone et al, 2000). After preadipocytes stop proliferating, late markers of differentiation, such as glycerol-3-phosphate dehydrogenase (GPDH) and fatty acid synthetase (FAS) are detected.…”

“…After preadipocytes stop proliferating, late markers of differentiation, such as glycerol-3-phosphate dehydrogenase (GPDH) and fatty acid synthetase (FAS) are detected. Cells then begin lipid accumulation in the cytosol at which time cells are termed adipocytes (Boone et al, 2000).Much of our understanding of these processes has developed through the use of in vitro models. A common approach when using in vitro models is to culture cells thought (or previously shown) to express adipogenesis lineage genes until they become confluent and then to apply a hormonal or xenobiotic agent 'cocktail' to 'induce' adipogenesis.…”

Differentiation-dependent expression of Adhfe1 in adipogenesis

“…The remaining cell population of adipose tissue, collectively referred to as the stromal-vascular fraction comprised of endothelial cells, nerve cells, macrophages, fibroblast-like interstitial cells, preadipocytes, and likely other as yet to be identified cell types. In adipose tissue development mature adipocytes are thought to be formed by differentiation of preadipocyte precursors present in adipose tissue [3,10,17,18,40]. This process is accompanied by upregulation of genes that encode molecules central to adipogenesis and adipocyte function including those critical in lipogenesis, lipolysis, lipid transport, and hormone signaling [53].…”