Role of exosome-associated microRNA in diagnostic and therapeutic applications to metabolic disorders

Abstract

Metabolic disorders are classified clinically as a complex and varied group of diseases including metabolic syndrome, obesity, and diabetes mellitus. Fat toxicity, chronic inflammation, and oxidative stress, which may change cellular functions, are considered to play an essential role in the pathogenetic progress of metabolic disorders. Recent studies have found that cells secrete nanoscale vesicles containing proteins, lipids, nucleic acids, and membrane receptors, which mediate signal transduction and material transport to neighboring and distant cells. Exosomes, one type of such vesicles, are reported to participate in multiple pathological processes including tumor metastasis, atherosclerosis, chronic inflammation, and insulin resistance. Research on exosomes has focused mainly on the proteins they contain, but recently the function of exosome-associated microRNA has drawn a lot of attention. Exosome-associated microRNAs regulate the physiological function and pathological processes of metabolic disorders. They may also be useful as novel diagnostics and therapeutics given their special features of non-immunogenicity and quick extraction. In this paper, we summarize the structure, content, and functions of exosomes and the potential diagnostic and therapeutic applications of exosome-associated microRNAs in the treatment of metabolic disorders.

Keywords: Metabolic disorders; Exosome; Exosome-associated microRNA; Non-alcoholic fatty liver disease; Obesity; Diabetes mellitus.

Fig. 1

Release of exosomes Red triangles symbolize stimulations including cellular transformation, stress, or infection. Cellular endocytosis begins with some stimulation and is followed by the formation of early multivesicular endosomes (MVEs) containing intraluminal vesicles (ILVs). After a series of processes, early MVEs can be transformed into later MVEs which contain various RNAs and proteins. Exosomes are released via one of two pathways followed by later MVEs (Note: for interpretation of the references to color in this figure legend, the reader is referred to the web version of this article)

Fig. 2

Molecular structure of exosomes Exosome membranes consist of a lipid bilayer, similar to that of the cell plasma membrane, and some functional proteins, symbolized as shown in the key. The cargo carried by exosomes contains proteins (shown as blobs) and RNAs (shown as green ribbons) (Note: for interpretation of the references to color in this figure legend, the reader is referred to the web version of this article)