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Biochim Biophys Acta Proteins Proteom. 2018 Nov 28. pii: S1570-9639(18)30207-3. doi: 10.1016/j.bbapap.2018.11.009. [Epub ahead of print]

Exosomal proteins constitute an essential part of the human adipose tissue secretome.

Author information

1
Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Duesseldorf, Germany; German Center for Diabetes Research (DZD e.V.), München, Germany.
2
German Center for Diabetes Research (DZD e.V.), München, Germany; Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Duesseldorf, Germany.
3
Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Duesseldorf, Germany; German Center for Diabetes Research (DZD e.V.), München, Germany; Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Leibniz Center for Diabetes Research, Medical Faculty, Heinrich Heine University, Duesseldorf, Germany.
4
German Center for Diabetes Research (DZD e.V.), München, Germany; Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Duesseldorf, Germany; Division of Endocrinology and Diabetology, Medical Faculty, Heinrich Heine University, Duesseldorf, Germany.
5
Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Duesseldorf, Germany; German Center for Diabetes Research (DZD e.V.), München, Germany. Electronic address: stefan.lehr@ddz.uni-duesseldorf.de.

Abstract

Adipose tissue is an endocrine organ, secreting various adipokines, either directly or via extracellular vesicles, including exosomes. Exosomes are vesicles of 40-150 nm size that represent a novel concept of biomolecule release. We purified exosomes from isolated primary human preadipocytes differentiated to mature adipocytes. The analyses of these exosomal preparations by LC-MS identified 884 proteins, so called exoadipokines. The comparison of exoadipokines with previously identified human exosome-associated proteins in ExoCarta database show an overlap of 817 proteins, but also revealed 67 proteins not assigned to human exosomes, yet. We further compared all exoadipokines to our previously reported reference secretome of human adipose tissue (http://diabesityprot.org/), finding 212 common proteins, whereas 672 proteins were specific for the exosomal fraction. Bioinformatic analyses revealed that the 212 common proteins can be assigned to all major functions of adipose tissue secreted proteins e.g. molecules involved in fibrotic processes or inflammation. In contrast, the exosome-specific proteins were rather assigned to signaling pathways and membrane-mediated processes. In conclusion, the isolation of exosomes allows to further specify the functionality of adipokines and exoadipokines as part of the adipocyte secretome in signaling and interorgan crosstalk.

KEYWORDS:

Adipokines; Exosomes; Mass spectrometry; Proteomic profiling

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