Fig. 3

Effects of CR on insulin resistance and islets function. The diabetic Sprague–Dawley rats model was induced by feeding HFD for 8 weeks, followed by a single STZ injection (30 mg/kg). The rats were either provided HFD ab libitum (HFD + AL + STZ group) or fed HFD with a 30% restriction regimen (HFD + CR + STZ group). Rats given free access to normal chow diet served as a blank control (ND + AL group). All interventions lasted for 20 weeks. a ITT (n = 6); b GSIS (n = 6); c AUC of GSIS; d HOMA-IR (n = 6–10); e glucose uptake in muscle (n = 4); data were presented as the mean ± standard deviation (SD). *p < 0.05 between the two groups; CR, calorie restriction; HFD, high-fat diet; STZ, streptozotocin; ITT, insulin tolerance test; GSIS, glucose simulate insulin secretion; AUC, area under curve; HOMA-IR, homeostasis model assessment of insulin resistance; IOD, integrated optical density; ND + AL, normal diet provided ad libitum (BCT group); HFD + AL + STZ, HFD provided ad libitum and STZ injection (MCT group); HFD + CR + STZ, HFD with 30% CR and STZ injection (CR group)