Fig 1.
Irisin promoted the proliferation of pancreatic β cells.
(A) INS-1 cells were cultured and treated with different concentrations of irisin (0, 40, 60, 80, 100 and 150 ng/ml) for 24 h. * P<0.05 compared with the control (0 ng/ml) group; # P<0.05 compared with the 40, 60, 80 ng/ml irisin-treated group; Φ P>0.05 compared with the 100 ng/ml irisin-treated group. (B) INS-1 cells were treated with 100 ng/ml irisin for various time intervals (0, 6, 12, 18, 24, and 48 h). * P<0.05 compared with 0 h; # P<0.05 compared with 6, 12, 18 h; Φ P>0.05 compared with 24 h.
Fig 2.
Irisin increased the protein level of Ki67.
* P<0.05 compared with the control (0 ng/ml) group.
Fig 3.
Irisin reduced the body weight and blood glucose levels and improved the insulin secretion of T2DM rats.
After intervention with irisin, the body weight, FBG and serum insulin levels of the rats were determined. (A-C) The effects of irisin on body weight, FBG, and serum insulin levels, respectively. *P<0.05 compared with the NC group; # P<0.05 compared with the T2DM group.
Fig 4.
Irisin improved glucose tolerance.
At the end of the intervention with irisin, an OGTT was performed in overnight-fasted rats. (A) OGTT. (B) Area under curve of OGTT. *P<0.05 compared with the NC group; # P<0.05 compared with the T2DM group.
Fig 5.
Irisin promoted pancreatic β cell proliferation via the ERK and p38 MAPK signaling pathways.
INS-1 cells were pretreated with PBS (as a vehicle control), U0 (U0126, 10 μM for 30 min) or SB (SB203580, 10 μM for 30 min), and then, the cells were cultured and treated with irisin (100 ng/ml) or vehicle. (A) The protein levels of total ERK, p-ERK, total p38 and p-p38 were determined by Western blot analysis. (B) The data are expressed as OD values at 450 nm and are reported as the mean ± SD. * P<0.05 compared with the control. # P<0.05 compared with the irisin-treated group.
Fig 6.
Irisin attenuated apoptosis and improved the insulin secretion induced by high glucose in INS-1 cells.
(A) INS-1 cells were pretreated with PBS (control) or high glucose (25 mmol/l) for 24 h and then incubated with or without 100 ng/ml irisin for another 24 h. Apoptosis of INS-1 cells was detected by annexin V-FITC/PI staining. (B) The insulin levels were detected from cell-free supernatant after incubation with glucose at 16.7 mmol/l for 1 h. The data are expressed as the mean ± SD. * P<0.05 compared with the control. # P<0.05 compared with the high-glucose group.
Fig 7.
Irisin modulated apoptosis-related gene expression and protein levels in INS-1 cells.
INS-1 cells were pretreated with PBS (control) or 25 mmol/l glucose for 24 h and incubated with or without 100 ng/ml irisin for 24 h. The apoptosis-related proteins cleaved caspase-3, cleaved caspase-9, Bad, Bax, Bcl-2 and Bcl-xl were detected by Western blotting. The data are reported as the mean ± SD. * P<0.05 compared with the control. # P<0.05 compared with the high-glucose group.