Insulin upregulates betatrophin expression via PI3K/Akt pathway

Figures

• 

  Figure 1. Betatrophin levels are only increased by insulin in different insulin resistant models. Western blot analysis of pAkt Ser473 before and after 10 min of 100 nM insulin stimulation in L02 for the control and the six IR models (A). Betatrophin protein (B) and relative mRNA (C) expression of control and six IR models. Betatrophin mRNA expression of control and cells treated with insulin combined another agent (D). The data represent mean ± SEM. **P < 0.01 vs. the CON. CON: control; PA: palmitic acid; DXM: dexamethasone; TNF-α: tumor necrosis factor-α; IL-1β: interleukin-1β; HG: high glucose; INS: insulin.

• 

  Figure 2. Dose-dependent and time course response of betatrophin production to insulin. Betatrophin in culture media of L02 cells exposed to insulin as indicated concentrations for 24 h (A), and in culture media of L02 cells exposed to 103 nM insulin for different time as indicated (B). The data represent mean ± SEM. *P < 0.05, **P < 0.01 vs. the 0 nM or 0 h.

• 

  Figure 3. Insulin stimulates betatrophin secretion through PI3K/Akt signaling pathway. Betatrophin in culture media of L02 cells pre-treated with LY294002 (50 μM), MK-2206 (10 μM) or U0126 (10 μM) for 1 h before incubation with insulin (103 nM) for 24 h (A). Betatrophin in culture media of L02 cells exposed to different concentrations of IGF-1 as indicated for 24 h (B) and in culture media of L02 cells exposed to IGF-1 (100 nM) with or without LY294002 (50 μM) for 24 h (C). Western blot analysis of pAkt Ser473 in cells exposed to insulin (103 nM) or IGF-1 (100 nM) with or without LY294002 (50 μM) for 24 h (D). The data represent mean ± SEM. *P < 0.05, **P < 0.01. CON: control; LY: LY294002; INS: insulin.

• 

  Figure 4. Insulin and metformin upregulate betatrophin expression in mice. Betatrophin levels in serum of C57BL/6 mice 12 hours after received insulin administration (A) and received saline or insulin 6 U/kg once daily for 15 days and 30 days (B). Fasting glucose (C), fasting insulin (D), HOMA-IR (E), betatrophin (F) levels of db/db mice received saline or metformin 400 mg/kg intragastric administration once daily for 30 days. The data represent mean ± SEM. *P < 0.05, **P < 0.01 vs. the 0 U/kg or CON. CON: control; INS: insulin; MET: metformin.

• 

  Figure 5. Correlation of betatrophin with insulin levels. Circulating betatrophin is associated with fasting insulin levels in all studied individuals (r = 0.497, P < 0.01) (A) and in T2D patients with insulin treatment (r = 0.541, P < 0.01) (B). Scatter plots illustrate correlation (r) between betatrophin and fasting insulin levels. ▴ illustrates patients with insulin treatment, and Δ illustrates patients without insulin treatment.