OBJECTIVETo investigate the effects of peroxisome proliferator-activated receptor (PPAR) α/γ agonist on atherosclerotic plaque stabilization in diabetic LDL receptor knockout (LDLr-/-) mice.

METHODSFemale 4-week-old LDLr-/- mice fed with high-glucose and high-fat diet for 4 weeks were randomly divided into three groups (n = 15 each): control group (only fed with high-glucose and high-fat diet), diabetic group [induced by high-glucose and high-fat diet combined with a low-dose of streptozotocin (STZ)] without tesaglitazar and with tesaglitazar (20 µg/kg oral treatment). After 6 weeks, the mice were sacrificed, body weight, fasting blood glucose (Glu), total cholesterol (TC), triglyceride (TG) levels were measured. The expression of ICAM-1, VCAM-1, MCP-1 in the brachiocephalic atherosclerotic lesions were determined by Western blot and immunohistochemistry, respectively. Brachiocephalic artery was prepared for morphologic study (HE, oil red O, Sirius red staining) and immunohistochemical analysis (macrophage surface molecule-3, α-smooth muscle actin), respectively.

RESULTSSerum TC [(32.34 ± 3.26) mmol/L vs. (16.17 ± 1.91) mmol/L], TG [(3.57 ± 0.99) mmol/L vs. (2.21 ± 0.11) mmol/L] and Glu [(15.21 ± 4.67) mmol/L vs. (6.89 ± 0.83) mmol/L] levels were significantly higher in diabetic group than in the control group (all P < 0.01). The expression of ICAM-1 (2.31 ± 0.35 vs.1.34 ± 0.21), VCAM-1 (1.65 ± 0.14 vs.0.82 ± 0.26), MCP-1 (2.27 ± 0.16 vs.1.56 ± 0.23) were significantly upregulated in diabetic group compared with control group (all P < 0.01). Brachiocephalic atherosclerotic plaque area [(4.597 ± 1.260)×10(3) µm(2) vs. (0.075 ± 0.030)×10(3) µm(2)], lipid deposition [(47.23 ± 2.64)% vs. (9.67 ± 1.75)%], Mac-3 positive area [(19.15 ± 3.51)% vs. (1.72 ± 0.16)%], α-smooth muscle actin [(5.54 ± 1.17)% vs. (2.13 ± 0.41)%] and collagen content [(4.27 ± 0.74)% vs. (0.43 ± 0.09)%] were all significantly larger/higher in diabetic LDLr-/- mice than in the control group (all P < 0.01). While tesaglitazar treatment significantly reduced serum TC [(30.47 ± 3.18) mmol/L], TG [(3.14 ± 0.71) mmol/L] and Glu [(7.92 ± 1.28) mmol/L] levels (all P < 0.01). Similarly, the expression of ICAM-1 [(1.84 ± 0.22)], VCAM-1 [(1.27 ± 0.11)], MCP-1 [(1.83 ± 0.24)], brachiocephalic atherosclerotic lesion area[(1.283 ± 0.410)×10(3) µm(2)], lipid deposition[(23.52 ± 1.39)%] were also significantly reduced by tesaglitazar (all P < 0.05). Moreover, tesaglitazar increased α-smooth muscle actin [(9.46 ± 1.47)%] and collagen content [(6.32 ± 1.15)%] in diabetic LDLr-/- mice (all P < 0.05). In addition, lipid deposition and Mac-3 positive areas [(10.67 ± 0.88)% vs. (15.83 ± 1.01)%] in the aortic root were also reduced in tesaglitazar treated diabetic LDLr-/- mice (P < 0.01).

CONCLUSIONSTesaglitazar has anti-inflammatory effects in the diabetic LDLr-/- mice. Tesaglitazar could reduce lipid deposition, increase collagen and α-SMA content in the brachiocephalic atherosclerotic lesions, thus, stabilize atherosclerotic plaque in this model.