The Role of SNARE Complex in Adipokine Secretion

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 649-677-Adipocyte Biology
Basic
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-656
Yu-Chun Lin1, Yu-Tzu Chang1, Chih-Tien Wang2, Yu-Ting Chiang1 and Juu-Chin Lu*1
1Chang Gung University, Tao-yuan, Taiwan, 2National Taiwan University, Taipei, Taiwan
The adipose tissue is recognized as an endocrine organ due to its active secretion of many peptide hormones, collectively named adipokines, which regulate many important physiological functions. Despite the discovery of many adipokines in the past decades, the secretory mechanism of adipocytes remains poorly understood. SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) proteins, including vesicle-associated membrane protein (VAMP), syntaxin and synaptosomal-associated protein (SNAP), are known to mediate exocytosis in neuronal and endocrine cells. Moreover, the SNARE complex of syntaxin 4, SNAP23, and VAMPs (2, 3, 8) has been shown to mediate insulin-stimulated translocation of glucose transporter 4 (GLUT4) in adipocytes. However whether these SNARE proteins are involved in the secretion of adipokines in adipocytes has not been studied. We depleted SNARE proteins in 3T3-L1 adipocytes to investigate their roles in adipokine secretion. Depletion of these SNARE proteins suppressed insulin-stimulated glucose uptake, consistent with their role in insulin-stimulated GLUT4 translocation. Depletion of VAMP2 or VAMP8, but not syntaxin 4, SNAP23 or VAMP3, suppressed both basal and insulin-stimulated leptin secretion. In contrast, depletion of these SNARE proteins minimally affected secretion of monocyte chemoattractant protein-1 (MCP-1), a chemokine playing an important role in obesity-associated chronic diseases. These results suggested different secretory mechanisms of these two adipokines in adipocytes. To see if hypertrophy of adipocytes may affect their secretory mechanism, we examined adipokine secretion and SNARE expression during adipocyte differentiation. While secretion of leptin and triglyceride accumulation were increased at late differentiated adipocytes, the expression of SNARE proteins remained unchanged. Further studies will be required to elucidate the mechanism by which obesity modulates the secretory function of adipocytes.

Nothing to Disclose: YCL, YTC, CTW, YTC, JCL

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: This work was supported by research grants NSC 101-2320-B-182-007 and CMRPD180511, CMRPD180512, CMRPD180513 from Chang Gung Memorial Hospital.