Alpha1-antitrypsin ameliorates islet amyloid-induced glucose intolerance and ?-cell dysfunction.

ABSTRACT:

Objective

Pancreatic ?-cell failure is central to the development and progression of type 2 diabetes (T2D). The aggregation of human islet amyloid polypeptide (hIAPP) has been associated with pancreatic islet inflammation and dysfunction in T2D. Alpha1-antitrypsin (AAT) is a circulating protease inhibitor with anti-inflammatory properties. Here, we sought to investigate the potential therapeutic effect of AAT treatment in a mouse model characterized by hIAPP overexpression in pancreatic ?-cells.

Methods

Mice overexpressing hIAPP (hIAPP-Tg) in pancreatic ?-cells were used as a model of amyloid-induced ?-cell dysfunction. Glucose homeostasis was evaluated by glucose tolerance tests and insulin secretion assays. Apoptosis and amyloid formation was assessed in hIAPP-Tg mouse islets cultured at high glucose levels. Dissociated islet cells were cocultured with macrophages obtained from the peritoneal cavity.

Results

Nontreated hIAPP-Tg mice were glucose intolerant and exhibited impaired insulin secretion. Interestingly, AAT treatment improved glucose tolerance and restored the insulin secretory response to glucose in hIAPP-Tg mice. Moreover, AAT administration normalized the expression of the essential ?-cell genes MafA and Pdx1, which were downregulated in pancreatic islets from hIAPP-Tg mice. AAT prevented the formation of amyloid deposits and apoptosis in hIAPP-Tg islets cultured at high glucose concentrations. Since islet macrophages mediate hIAPP-induced ?-cell dysfunction, we investigated the effect of AAT in cocultures of macrophages and islet cells. AAT prevented hIAPP-induced ?-cell apoptosis in these cocultures without reducing the hIAPP-induced secretion of IL-1? by macrophages. Remarkably, AAT protected ?-cells against the cytotoxic effects of conditioned medium from hIAPP-treated macrophages. Similarly, AAT also abrogated the cytotoxic effects of exogenous proinflammatory cytokines on pancreatic ?-cells.

Conclusions

These results demonstrate that treatment with AAT improves glucose homeostasis in mice overexpressing hIAPP and protects pancreatic ?-cells from the cytotoxic actions of hIAPP mediated by macrophages. These results support the use of AAT-based therapies to recover pancreatic ?-cell function for the treatment of T2D.

SUBMITTER: Rodriguez-Comas J 

PROVIDER: S-EPMC7186564 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature