The adipose tissue of the body is classified into two types:white adipose tissue and brown adipose tissue;the former is mainly responsible for storing energy and the latter is to produce heat and dissipate energy.Recent research has shown that there is a third type of adipose tissue,namely white adipose tissue browning,i.e.,brown adipose tissue existing inside the white adipose tissue.Brown adipose tissue,which is converted from white adipose tissue,is similar to brown adipocytes in function.Browning is one of the important features of lipid metabolism of cancer cachexia.On the one hand,white adipose tissue affects metabolism through increasing the amount of heat consumption after browning,resulting in a decrease in fat;on the other hand,the browning process participates in the process of the occurrence and development of cancer cachexia.Two driving factors,interleukin-6 and parathyroid hormone related protein,play an important role in this browning process.They are secreted by tumor tissue,mainly through the exciting sympathetic nervous system to release norepinephrine,and act on β3 adrenergic receptor of the adipocytes and further activate the the transcription factors which corresponded heat-production gene expression such as uncoupling protein 1 (UCP1),leading to white adipose tissue browning.The browning process is the early event of the occurrence of cancer cachexia and continues throughout the entire process of cancer cachexia.Therefore,early detection of the browning process will facilitate the development of intervention approach,improving the clinical outcome of diagnosis,prevention,and treatment for cancer cachexia.
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