Expression of matrix metalloproteinase-11 is increased under conditions of insulin resistance

Figure 1 Expression of matrix metalloproteinase-11 during adipocyte differentiation in 3T3-L1 cells. Total RNA was extracted from 3T3-L1 cells at preadipocyte and confluent (day 0) stages, and after induction of differentiation (days 3, 5, 7 and 9). MMP-11 mRNA expression was measured by RT-PCR. Results are the means ± SE of three independent experiments, each performed in triplicate. ^aP < 0.05 vs undifferentiated preadipocytes. MMP-11: Matrix metalloproteinase-11.

Figure 2 Matrix metalloproteinase-11 expression in insulin-resistant 3T3-L1 adipocytes. A: Fully differentiated 3T3-L1 adipocytes were co-treated with TNF-α (2.5 nmol/L) and hpoxia (O₂ 1%) for 24 h, and MMP-11 mRNA was measure by RT-PCR. Results are the means ± SE of three independent experiments, each in triplicate. ^bP < 0.01 vs untreated (control) cells. A representative western blot (WB) of MMP-11 is shown for each experimental condition. Lanes: 1 and 2, MMP-11 protein expression in untreated 3T3-L1 cells (control); 3 and 4, MMP-11 protein expression in insulin-resistant 3T3-L1 cells. Tubulin (Tub), control of protein loading; B: 3T3-L1 adipocytes were treated with TNF-α alone, at a final concentration of 2.5 nmol/L, and MMP-11 mRNA levels were measured 24 h later by RT-PCR. Results are the means ± SE from three independent experiments. ^bP < 0.01 vs untreated control cells; C: 3T3-L1 adipocytes were incubated in normoxic (control) or hypoxic condition (O₂ 1%) for 24 h, total RNA was extracted and the expression of MMP-11 was determined by RT-PCR. Results are the means ± SE from three independent experiments in triplicate. ^bP < 0.01 vs control; D: Time-course of MMP-11 mRNA expression in differentiated 3T3-L1 adipocytes, in the presence of TNF-α (2.5 nmol/L) alone. MMP-11 mRNA was measured by RT-PCR at the indicated time points, after TNF-α treatment. Results are the means ± SE from three independent experiments, each in triplicate. ^bP < 0.01 vs time 0. MMP-11: Matrix metalloproteinase-11.

Figure 3 Intraperitoneal insulin tolerance test and the expression of matrix metalloproteinase-11, collagen type VI alpha 3 and fibroblast-specific protein 1 in mice under different dietary conditions. A: IITT. Insulin tolerance was assessed in 12 h fasted mice, intraperitoneally injected with insulin (0.25 U/kg body weight). LFD (n = 6); HFD (n = 10). ^bP < 0.01 vs LFD; B: MMP-11, Col6α3 and FSP-1 mRNA expression in WAT of mice fed a low-fat (LFD) or high-fat (HFD) diet (n = 6 per each group). Results are the means ± SE of three independent measurements from each animal. ^dP < 0.001 vs LFD, for each group. MMP-11: Matrix metalloproteinase-11; IITT: Intraperitoneal insulin tolerance test; Col6α3: Collagen type VI alpha 3; FSP-1: Fibroblast-specific protein 1.