The Adipose Organ

Abstract

White and brown adipocytes form tissues (WAT and BAT, respectively) contained in a dissectible organ formed by subcutaneous and visceral depots. WAT and BAT have almost opposite roles in partitioning energy between two fundamental needs for survivals: metabolism and thermogenesis. All organs in mammals are composed by different tissues acting with different physiology to reach a common finalistic purpose. The plastic properties of adipocytes, i.e., their reversible physiologic transdifferentiation ability, offer an explanation to their common membership to adipose organ, but imply a new physiologic ability for mature cells: the physiologic reversible transdifferentiation property. This conversion ability of mature adipocytes is supported also by the plastic properties of mammary glands during pregnancy, lactation, and postlactation periods when white adipocytes convert reversibly to milk-secreting glandular cells (pink adipocytes). During chronic positive energy balance, the adipose organ undergoes a whitening phenomenon with hypertrophic adipocytes. Hypertrophic adipocytes show several alterations of their organelles including those able to activate the inflammasome system. Stressed adipocytes die leaving conspicuous debris that must be removed by macrophages. This last cell surrounds debris and form crown-like structures (CLS) responsible for a chronic low-grade inflammation that link obesity to T2 diabetes. The plastic properties of adipocytes could be used to reverse the phenomenon.

MicroRNA regulation of stem cell differentiation and diseases of the bone and adipose tissue: Perspectives on miRNA biogenesis and cellular transcriptome

“…While altered miRNA processing associated proteins have yet to be observed in osteogenesis, examples of these differences in disease states afflicting other tissues and organs provide the precedent to systematically evaluate alterations in the expression of genes associated with miRNA processing in the context of bone diseases [84]. Knock-out and siRNA studies involving Dicer and Drosha demonstrate that miRNA processing is required for normal development of both bone and adipose tissue [85]. Drosha is required for the development of normal adipose tissue and Dicer is required for bone development in neonatal mice.…”

“…Drosha is required for the development of normal adipose tissue and Dicer is required for bone development in neonatal mice. Interestingly, knock-out of Dicer in mature osteoblasts of adult mice led to increased bone formation [85]. Since altered miRNA expression patterns correlate with diseases associated with the adipogenic, myogenic and osteogenic lineage pathways (Table 2), insights into the miRNA maturation pathways may provide future avenues for preventive and therapeutic interventions for bone disorders.…”

The architecture of cellulite

“…BAT appears brown and its function is to use lipids to convert to chemical energy to heat [27,28]. The brown appearance of BAT is due to a dense vascular network that is associated with mitochondria [29]. BAT and WAT work in opposition to regulate energy metabolism and both are innervated by the noradrenergic sympathetic nervous system.…”

“…For example, brown adipocytes may appear "unilocular" when not being stimulated [32]. Similarly, as white adipocytes lose lipids in fasting states, their morphology can change into a more elongated and "multilocular appearance" [29]. More advanced techniques to detect the presence of uncoupling protein-1 (UCP-1), unique to brown adipocytes, are a more accurate method for identifying activated brown adipocytes [30].…”

The Interplay Between Sex, Ethnicity, and Adipose Tissue Characteristics

“…It consists of multiple adipose tissue depots, previously described as mini-organs [2] and their relative size and function determines the metabolic risk of each individual. The largest adipose tissue depot is the subcutaneous depot.…”