Adipose tissue is a dynamic organ In the sense that its cells are gradually replaced, though at a slow
pace. It is generally believed that it is replace in about 10 years.  Positive calorie balance and consequent additional triglyceride deposition in adipose tissue
is intially accommodated by adipocyte hypertrophy. The further positive calorie
balace is associated with the process of adipogenesis. During the process of
adipogenesis mesenchymal stem cells are recruited and prolifeated. Subsequently
they are committed to preadipocytes and further mature into a adipocyte. This
adipose tissue development and expansion is highly regulated process and is controlled
by the concerted actions of a number of factors that include a number of environmental, genetic, epigenetic, and
pharmacological factors. This highly regulated and integrated homeostatic network primarily designed
to maintain energy homeostasis. This process of adipogenesis
has been extensivly studied in vitro cell lines as well as animal models. These
experiment have identified a sequential cascade of
transcriptional events that control the process of adipogenesis. Fig. 1 shows the cmplexcities of thsis process. The most important among them are peroxisome proliferator-activated receptor
? (PPAR?) and CCAAT/enhancer binding protein a (C/EBPa).  Both of these
transcription factors coordinate and control the expression of
adipogenic genes. Additionally these master regulators also controls the factor
that binds to inducer of short transcripts (FBI) as well as extracellular
regulators such as Dickkopf proteins (Dkks) and Insulin-like Growth Factor
Binding Protein 2 (IGFBP2) (aP2, pyruvate carboxylate) 5-7. The expression of these genes characterize the
phenotype of terminally differentiated adipocytes. Their expression can be
further regulated by additional transcription factors, such as
sterol-regulatory element binding protein 1c (SREBP1c). Wnt signaling pathway, has also recently
been implicated in lineage determination and maintenance of the preadipocyte
phenotype 8. 


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