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Figure 2. Exosome structure. Exosomes are microvesicles delineated by a membrane enriched in phosphatidylserine and contain DNA,
mRNA, miRNA, proteins and lipids

thus, leads to release of fatty acids and glycerol in the cytoplasm with reduced plasma triglyceride levels
and obesity [61,62] .

Adipose tissue is a key organ that controls lipid metabolism and energy distribution, as well as regulation
of endocrine function related to cardiovascular disease. Endocrine functions of adipose tissue are mostly
attributed to their ability to secrete adipokines, hormones and cytokines that regulate energy homeostasis
[7]
and satiety . There are over 600 known adipokines but the most well-studied are the anti-inflammatory
adiponectin, which is decreased in obesity, and leptin, which is secreted mostly by WAT and is present
unbound in the circulation at higher levels in obesity [63-65] . Adipokines are carried by human adipocyte
exosomes and leptin has been detected in mouse serum exosomes while adiponectin has been found in rat
adipose tissue exosomes [66-68] .

EXOSOMES AND ADIPOCYTE-DERIVED EXOSOMES
Exosomes are a type of extracellular vesicle with a size of 30-150 nm and a specific density of 1.13-1.21 g/mL.
They are found in blood and other biological fluids. Exosomes are released into the extracellular space
when multivesicular bodies fuse with the cellular plasma membrane [69,70] . Exosomes carry nucleic acids
such as microRNA (miRNA), messenger RNA (mRNA) and mitochondrial DNA as well as proteins and
lipids [Figure 2]. These exosome components are encased in a phospholipid membrane rich in ceramides,
cholesterol and sphingomyelin, often with high phosphatidylserine content [71-73] . Exosomes help mediate
signal transduction and provide a means for cell-to-cell communication over a distance and between organ
[74]
systems . Signaling pathways can be impacted by exosomes through the miRNAs they carry. miRNAs
are small non-coding RNAs that negatively regulate gene expression by impeding translation or inciting
[75]
instability of complementary mRNA targets, thus inhibiting protein formation . Exosomes carrying
[76]
miRNAs can be taken up via endocytosis or pinocytosis into recipient cells .
It should be noted that there are different circulating particles in the blood and bodily fluids, collectively
known as extracellular vesicles. These are heterogeneous in size and include not only exosomes, but also