Session: SAT 834-867-Islet Biology
Bench to Bedside
Poster Board SAT-857
Heparan sulphate proteoglycans (HSPG) exist predominantly in cell membranes and the extracellular matrix. HSPG has a core protein component, to which HS glycosaminoglycan side chains are attached. The HS chains consist of disaccharides that can be sulfated in four different positions, creating a marked diversity in HS in different tissues. Specific motifs of HS modulate the binding of growth factors to their cognate receptors. HS co-localizes with extracellular amyloid deposits in humans with type 2 diabetes and evidence suggests a role for HS in insulin secretion. Although HS seems to modulate important interactions in the islet microenvironment, the intra-islet structures of HS in health or altered glucose homeostasis are currently unknown.
A panel of antibodies against specific HS motifs was used in dual immunolocalisation studies with the antibodies against islet hormones insulin and glucagon and the basement membrane protein laminin in pancreases from adult Sprague Dawley, homozygous Zucker fatty, heterozygous Zucker lean rats and human pancreatic tissue from a normoglycaemic adult female donor.
In wild type Sprague Dawley rats the antibodies HS4E4 (epitopeGlcNAc/GlcNS-IdoA) and EV3C3 (epitope GlcNS-IdoA2S)stained glucagon producing alpha cells in the peripheral edge of islet, the antibodies RbEa12 (epitope IdoA-GlcNS6S )and AOB08 (epitope GlcNS6S-IdoA2S ) localized mainly in insulin producing beta cells, whereas the antibody 10E4 (epitope GlcA-GlcNS-GlcA-GlcNAc) bound to basement membranes. The immortalized beta cell lines INS1 and MIN6 stained mostly with the HS4E4 and 10E4 antibodies. In human pancreas the antibodies HS4E4 and EV3C3 localized mainly with alpha cells, whereas all RbEa12, AOB08 and 10E4 antibodies stained beta cells. In Zucker fatty rats, alpha cells lost the peripheral localization and become more dispersed in the islets. This was accompanied by a reduction in the alpha-cell HS staining.
Our data demonstrate distinct topography in HS epitope distribution in islets, with conserved motifs between humans and rats. Beta cell HS has domains rich in N, 2O and 6O-sulfation. HS with non-sulfated domains, and 2O- but not-6O sulfated domains characterizes alpha cells. In leptin-resistant animals, alpha cell HS is reduced, suggesting the involvement of HS in alpha cell metabolism.
Nothing to Disclose: AT, SP, YH, SG, PS, AO, JT, BCEK, BD, TV, PMGB
*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm
See more of: Abstracts - Orals, Featured Poster Presentations, and Posters