Cumulative autophagy insufficiency in mice leads to progression of ß-cell failure.

ABSTRACT

Autophagy is known to play a pivotal role in ß-cell function. While the lifelong inhibition of autophagy through Atg7 deletion in ß cells has been demonstrated to lead to impaired glucose tolerance together with ß-cell dysfunction, the temporal association between autophagy inhibition and ß-cell dysfunction remains unclear. To address such questions, inducible ß-cell-specific Atg7-knockout (ißAtg7KO) mice were generated, and autophagy inhibition was induced for two different time durations. Whereas 2 weeks of Atg7 ablation was sufficient to induce autophagy deficiency, confirmed by the accumulation of p62, ißAtg7KO mice exhibited normal glucose tolerance. In contrast, prolonged autophagy deficiency for 6 weeks resulted in glucose intolerance together with impaired insulin secretion. Direct mRNA sequencing and pathway analysis revealed that the gene set associated with insulin secretion was downregulated only after the 6-week prolonged autophagy inhibition. Furthermore, we identified a novel gene, Sprr1a, which was expressed at more than 50-fold higher levels during both the 2-week and 6-week autophagy inhibition. These findings suggest that autophagy insufficiency cumulatively leads to ß-cell failure after a certain interval, accompanied by stepwise alterations of gene expression patterns.