Original articleAmyloid oligomers in diabetic and nondiabetic human pancreas
Section snippets
Experimental reagents
Full-length hIAPP1-37 peptides were custom synthesized at the Keck Biotechnology Center at Yale University and were purified in-house by reverse-phase high-performance liquid chromatography. The polyclonal rabbit antiamyloid oligomer antibody (Catalog# AB9234, A11) was purchased from Chemicon International (Temecula, Calif). This antibody binds specifically to cytotoxic oligomers formed by hIAPP, Alzheimer's Aβ, or other amyloidogenic peptides, but not to their monomeric or fibrillar form.3 The
Amyloid oligomers in human pancreatic islets
The specificity of the antioligomer antibody (A11) was shown by dot blot (Fig 1, A), whereas no crossreactivity between the antioligomer and anti-IAPP antibodies was detected by Western blot (Fig 1, B). The conformation-dependent structure of hIAPP-derived oligomers might be denatured by the SDS gel, and thus no oligomer-specific band was demonstrated by the Western blot assays. The Western blot assays with the anti-IAPP antibody showed hIAPP protein bands at the positions of 4 kD (monomers),
Discussion
This study provides direct evidence that (1) IAPP oligomers exist in adult human pancreatic islets; (2) hIAPP oligomers are either intracellular small puncta predominantly found in islet cells that express insulin/IAPP or are extracellular large curvilinear structures adjacent to fibril deposits; (3) oligomers of small spherical puncta are mainly found in nondiabetic islets, whereas larger curvilinear structures are predominantly detected in diabetic islets that include those islets with
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Supported by grants CUHK4462/06M and CUHK4302/04M from the Research Grants Council of the Hong Kong Special Administrative Region, China.