Figure 8: Rapamycin treatment impairs insulin processing and CPE levels in mice and human islets in vitro.

(a) Circulating proinsulin in serum from mice treated with intraperitoneal injections of rapamycin or control vehicle (2% ethanol) every other day for 9 days (treatment started at 3 months of age). (b) Proinsulin:insulin levels measured by ELISA in islets obtained from mice treated with rapamycin as described in a. (c) Immunoblotting and quantitative band densitometry of proinsulin and insulin in islets obtained from control and Eif4ebp2^−/− mice treated with rapamycin or control vehicle (treatment started at 3 months of age). (d) Immunoblotting and quantification of CPE and actin in islets from Eif4ebp2^−/− and control mice treated with control vehicle and rapamycin (n=4 in a–d). (e) Immunoblotting and quantification of CPE and actin in human islets from different donors treated with vehicle control or rapamycin (30 nm) for 48 h (n=4 for quantification). (f) Staining for CPE (red), insulin (green) and DAPI (blue) in human islets treated with rapamycin (30 nM) or control vehicle (DMSO) for 48 h. Scale bars, 50 μM. Data are representative of three per group. (g) Immunoblotting and quantification of CPE and actin in human islets treated with 41ERCat (25 μm) or vehicle (DMSO) for 24 h (n=4). Data are shown as means±s.e.m., *P<0.05; nonparametric U-test (Mann–Whitney).