Rutin suppresses human-amylin/hIAPP misfolding and oligomer formation in-vitro, and ameliorates diabetes and its impacts in human-amylin/hIAPP transgenic mice

Abstract

Pancreatic islet β-cells secrete the hormones insulin and amylin, and defective β-cell function plays a central role in the pathogenesis of type-2 diabetes (T2D). Human amylin (hA, also termed hIAPP) misfolds and forms amyloid aggregates whereas orthologous mouse amylin does neither. Furthermore, hA elicits apoptosis in cultured β-cells and β-cell death in ex-vivo islets. In addition, hA-transgenic mice that selectively express hA in their β-cells, manifest β-cell apoptosis and progressive islet damage that leads to diabetes closely resembling that in patients with T2D. Aggregation of hA is thus linked to the causation of diabetes.We employed time-dependent thioflavin-T spectroscopy and ion-mobility mass spectrometry to screen potential suppressors of hA misfolding for anti-diabetic activity. We identified the dietary flavonol rutin as an inhibitor of hA-misfolding and measured its anti-diabetic efficacy in hA-transgenic mice. In vitro, rutin bound hA, suppressed misfolding, disaggregated oligomers and reverted hA-conformation towards the physiological. In hA-transgenic mice, measurements of glucose, fluid-intake, and body-weight showed that rutin-treatment slowed diabetes-progression by lowering of rates of elevation in blood glucose (P = 0.030), retarding deterioration from symptomatic diabetes to death (P = 0.014) and stabilizing body-weight (P < 0.0001).In conclusion, rutin treatment suppressed hA-aggregation in vitro and doubled the lifespan of diabetic mice (P = 0.011) by a median of 69 days compared with vehicle-treated control-diabetic hA-transgenic mice.