The aim of this preclinical study is to test the hypothesis that skin capillary amylin deposition correlates with cerebral small vessel amylin deposition and is higher in rats with pancreatic overexpression of amyloidogenic human amylin polypeptide (HIP rats) compared to wild type (WT) rats that express non-amyloidogenic rat amylin.

Human amylin is a 37 amino-acid pancreatic peptide that forms neuro-toxic aggregates that deposits in the endothelium of brain and skin capillaries of diabetic patients causing cerebral small vessel vasculopathy and peripheral neuropathy, respectively. Endothelial amylin deposition causes cell membrane injury by lipid peroxidation and production of reactive aldehydes such as 4-hydroxynonenal (4-HNE). Amylin also deposits on erythrocyte membranes and impairs tissue oxygen delivery thereby activating hypoxia pathways mediated by hypoxia inducing factor (HIF).

Immunohistochemistry (IHC) was performed for human amylin and collagen IV in brain and skin sections of HIP and WT rats using antibodies binding amylin as well as those binding HIF -1α and HIF-2α. Amylin-4HNE adduct was measured in the skin from HIP and WT rats.

Brain capillaries isolated from HIP rats had 1.7 times higher amylin content compared to WT rats using Western blot with anti-amylin antibody. The immunoreactivity signal of HIF-1α and HIF-2α in skin tissue from HIP rats was 4 times higher than WT rats. Amylin-4HNE adduct formation was 2.2 times higher in HIP rats compared to WT rats. In both HIP and WT rats, there was a phenotypic similarity between brain and skin capillary amylin when co-stained for human amylin and collagen IV.

Skin capillary amylin deposition resembles brain capillary amylin deposition indicating greater cell membrane injury and chronic hypoxia in HIP rats compared to WT rats. This study also provides preliminary evidence that a skin biopsy might reflect the extent of brain amylin vasculopathy.