Amyloidogenic amylin deposits on red blood cells of stroke patients

Background: Amylin, a 37-residue amyloidogenic peptide, is co-secreted with insulin by pancreatic beta-cells (Verma et al. 2020). Vascular deposition of amylin has been noted in patients with diabetes and neurocognitive disorders (Ly et al., 2017) Emergent large vessel occlusions (ELVOs) result in severe ischemic strokes without appropriate treatment. Growth factors, including erythropoietin (EPO), are involved in post-stroke recovery as a potential neuroprotectant target, inhibiting apoptosis and decreasing inflammation (Jerndal et al., 2010). Here, amylin accumulation in plasma, red blood cells (RBCs), and ELVOs (where available) and plasma EPO levels were compared between stroke and control patients. Due to amylin’s amyloidogenic propensity, we hypothesized that there would be an association between amylin uptake and stroke incidence. Method: A prospective registry (Blood and Clot Thrombectomy Registry and Collaboration; BACTRAC) was developed to analyze blood and thrombus directly in patients presenting with an ELVO. Total protein concentration and amylin concentrations of clot lysates, plasma, and RBC lysates were obtained via bicinchoninic acid assay (BCA) and competitive enzyme-linked immunosorbent assay (ELISA), respectively. Plasma EPO concentrations were obtained via ELISA. An amylin uptake coefficient (the level of amylin in RBC lysates divided by the sum of amylin present in RBC lysates and plasma) was calculated to determine the degree to which circulating amylin is depositing on RBCs. Result: Due to a significant difference between control and stroke RBCs (p = 0.0012, Figure 1) in total protein concentration, all downstream analyses were normalized to respective protein concentrations. A significant difference in amylin uptake by RBCs between stroke and control patients is shown in Figure 2 (p = 0.0073). An uptake coefficient greater than 0.50 indicates uptake of amylin by RBCs. Finally, a significant difference in plasma EPO concentration was observed between stroke and control (p = 0.0017; Figure 3). Conclusion: Consistent with our hypotheses, the present data indicates that amylin uptake by RBCs is significantly increased in stroke patients than in control patients. However, both groups show evidence of accumulation, as indicated by uptake coefficients greater than 0.50. Further, levels of erythropoietin are significantly increased in stroke patients. Further investigation into whether amylin may be thrombogenic is warranted.