Intraperitoneal glucose tolerance tests (IPGTTs), plasma insulin levels, glucose-stimulated insulin secretion assays, and ATP levels in male BESTO and control mice and islets at 18–24 months of age. (A) Intraperitoneal glucose tolerance tests were conducted in male BESTO transgenic mice (closed circles) compared to controls (open circles) at 18–24 months of age in two independent transgenic lines. Following a 15 h fast, 2 g of 50% glucose (w/v) per kg body weight was injected intraperitoneally, and blood glucose values were assessed at 0, 15, 30, 60, and 120 min post-injection (line 431-2, n = 13–15; line 431-4, n = 6–7). (B) Plasma insulin levels in male BESTO mice (black bars) and controls (white bars) were measured at the 0 and 30 min time points during the IPGTTs (line 431-2, n = 13–15; line 431-4, n = 6–7). (C) Insulin secreted (ng mL−1 h−1) and (D) ATP levels (pmol islet−1) from transgenic (black bars) and control (white bars) islets were measured at the indicated glucose concentrations (line 431-2, n = 11; line 431-4, n = 9–12). Insulin secretion and ATP assays were performed on triplicate groups of 10 islets for each mouse. All results are expressed as mean ± standard error.