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Adiponectin is partially associated with exosomes in mouse serum
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| Title: | Adiponectin is partially associated with exosomes in mouse serum |
| Other Titles: | マウスの血清においてアディポネクチンのー部はエキソソームに存在する |
| Authors: | PHOONSAWAT, WORRAWALAN Browse this author |
| Issue Date: | 25-Sep-2014 |
| Publisher: | Hokkaido University |
| Abstract: | Exosomes are membrane vesicles with a size of 30–120 nm that arereleased by many different cell types. They have been found in many biological fluidsincluding blood, bronchoalveolar lavage fluid, urine, bile, and breast milk. Exosomesharbor a wide variety of proteins, lipids, mRNA, and microRNA, which can betransferred to another cell, and are implicated in cell-to-cell communication bytransferring molecules. Thus, exosomes play an important role in physiological andpathophysiological processes and also are applicable as a source of disease biomarkers.Previous studies suggest that adipocyte-derived exosomes play a role incell-to-cell communication during the development of metabolic diseases. However,the characteristics and function of exosomes released from adipocytes in vivo remainto be elucidated. Clearly, exosomes released from adipocytes could exist in thecirculation. In addition, because the composition of exosomes is heterogenic,depending on the cellular origin of the exosome, adipocyte-derived exosomes could beaccompanied by molecules produced specifically in adipocytes. In this context, thisstudy postulated that such molecules associated with exosomes in the serum could bemarkers for adipocyte-derived exosomes in vivo. This study particularly focused onsecretory proteins produced specifically in adipocytes, namely adipocytokinesincluding adiponectin, leptin, and resistin.1. Serum adiponectin is partially associated with exosomesBased on western blotting, CD63, a well-known protein marker ofexosomes, was concentrated in the pellet of mouse serum after ultracentrifugation,suggesting successful isolation of exosomes. Western blotting detected adiponectin butno leptin and only trace amounts of resistin in the exosome fraction. Afterultracentrifugation on a discontinuous gradient, both adiponectin and CD63 weredetected in a fraction at a density of 1.17 g/mL, consistent with the density ofexosomes. The adiponectin signal in the exosome fraction was decreased by proteinaseK treatment and completely quenched by a combination of proteinase K and Triton X-100. These results suggest that a portion of adiponectin exists as a transmembraneprotein in the exosomes in mouse serum.2. Exosome-associated adiponectin may be a physiologically relevant formAdiponectin exists as low-molecular-weight (LMW), middle-molecularweight(MMW) and high-molecular-weight (HMW) forms in the circulation, and thelatter has more relevant roles in its physiological functions (e.g., protecting metabolicdiseases). Western blotting following SDS-PAGE under nonreducing and unheatedconditions indicated that, although MMW forms are the predominant form in theserum, HMW forms are present principally in the exosome fraction. These findingssuggest that exosome-associated adiponectin and exosome-free adiponectin may havedifferent physiological and pathological functions in vivo. Indeed, quantitative ELISAshowed that the concentration of adiponectin in the serum and the ratio of adiponectinto total protein in the exosome fraction were lower in obese mice than in lean mice.In conclusion, this study showed that serum adiponectin is partiallyassociated with exosomes in mice. Considering that adiponectin is producedexclusively by adipocytes, adiponectin-associated exosomes in serum could be derivedfrom adipocytes. This study proposes that adiponectin could be a marker for exosomesreleased from adipocytes in vivo. |
| Conffering University: | 北海道大学 |
| Degree Report Number: | 甲第11541号 |
| Degree Level: | 博士 |
| Degree Discipline: | 農学 |
| Examination Committee Members: | (主査) 教授 川端 潤, 教授 原 博, 准教授 園山 慶 （生命科学院） |
| Degree Affiliation: | 農学院（応用生物科学専攻） |
| Type: | theses (doctoral) |
| URI: | http://hdl.handle.net/2115/57186 |
| Appears in Collections: | 学位論文 (Theses) > 博士 （農学）
課程博士 (Doctorate by way of Advanced Course) > 農学院(Graduate School of Agriculture)
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