Imatinib improves insulin resistance and inhibits injury-induced neointimal hyperplasia in high fat diet-fed mice

Abstract

Imatinib, a PDGF receptor tyrosine kinase inhibitor, has been shown to suppress intimal hyperplasia in different animal models under normal metabolic milieu, diabetic, and/or hypercholesterolemic conditions. However, the impact of imatinib treatment on injury-induced neointimal hyperplasia has not yet been investigated in the setting of insulin resistance without frank diabetes. Using a mouse model of high fat diet (HFD)-induced insulin resistance and guidewire-induced arterial injury, the present study demonstrates that intraperitoneal administration of imatinib (25 mg/kg/day) for ~3 weeks resulted in a marked attenuation of neointimal hyperplasia (intima/media ratio) by ~78% (n = 6-9 per group; P < 0.05). Imatinib treatment also led to significant improvements in key metabolic parameters. In particular, imatinib improved insulin resistance and glucose tolerance, as revealed by complete inhibition of HFD-induced increase in HOMA-IR index and AUC_IPGTT, respectively. In addition, imatinib treatment led to diminutions in HFD-induced increases in plasma total cholesterol and triglycerides by ~73% and ~59%, respectively. Furthermore, imatinib decreased HFD-induced increase in visceral fat accumulation by ~51% (as determined by epididymal white adipose tissue weight). Importantly, imatinib treatment in HFD-fed mice enhanced plasma levels of high-molecular-weight adiponectin by ~2-fold without affecting total adiponectin. However, there were no significant changes in mean arterial pressure in insulin-resistant state or after imatinib exposure, as measured by tail-cuff method. Together, the present findings suggest that targeting PDGF receptor tyrosine kinase using imatinib may provide a realistic treatment option to prevent injury-induced neointimal hyperplasia and diet-induced insulin resistance in obesity.

Keywords: Adiponectin; Arterial injury; Imatinib; Insulin resistance; Neointimal hyperplasia; PDGF.

Fig. 1.

Effects of imatinib on body weight in HFD-fed mice. Eight-week old mice were fed a ND or HFD for 6 weeks (42 days). Imatinib was injected intraperitoneally (25 mg/kg/day) on the day prior to femoral artery injury (day 21) and for 3 weeks post-femoral artery injury (day 22 to day 42). A) Linear graph shows body weights determined once a week for 6 weeks. B) Bar graph shows changes in body weights after imatinib treatment (body weight at the end of 6^th week of diet minus body weight before starting imatinib/vehicle treatment). The data shown are means ± S.E.M. (n = 5–6 mice/group). * P < 0.05 compared with ND; ^# P < 0.05 compared with HFD, using repeated measures two-way ANOVA followed by Bonferroni multiple comparisons test (A) or regular two-way ANOVA followed by Tukey multiple comparisons test (B). ND: normal diet; HFD: high fat diet.

Fig. 2.

Effects of imatinib on food and caloric intakes, and feeding and energy efficiencies in HFD-fed mice. A) Linear graph shows average daily food intakes in ND- and HFD-fed mice. B) Linear graph shows changes in caloric intakes for 6 weeks. C-D) Bar graphs show changes in feeding and caloric efficiencies after imatinib treatment (day 21–42). The data shown are the means ± S.E.M. (n = 6 mice/group). * P < 0.05 compared with ND; ^# P < 0.05 compared with HFD, using repeated measures two-way ANOVA followed by Bonferroni multiple comparisons test (A-B) or regular two-way ANOVA followed by Tukey multiple comparisons test (C-D). BW, body weight.

Fig. 3.

Effects of imatinib on glucose tolerance in HFD-fed mice. A) Linear graph shows changes in blood glucose levels during IPGTT. IPGTT was performed in mice on day 41 by injecting fresh glucose solution (2 g/kg) and determining blood glucose at the indicated time points. B) Bar graph shows changes in AUC_IPGTT. The data shown are the means ± S.E.M. (n = 6 mice/group). * P < 0.05 compared with ND; ^# P < 0.05 compared with HFD, using repeated measures two-way ANOVA followed by Bonferroni multiple comparisons test (A) or regular two-way ANOVA followed by Tukey multiple comparisons test (B). IPGTT: intraperitoneal glucose tolerance test; AUC: area under the curve.

Fig. 4.

Effects of imatinib on injury-induced neointimal hyperplasia in HFD-fed mice. Imatinib was administered intraperitoneally (25 mg/kg/day) on the day prior to femoral artery injury and for 3 weeks post-femoral artery injury. Subsequently, uninjured and injured femoral artery segments from ND-fed mice and HFD-fed mice (− or + imatinib treatment) were subjected to staining procedures for: A) H&E and B) EVG, as described in ‘Materials and methods’. The arrowheads indicate internal and external elastic laminae; scale bars represent 20 μm; magnification. C-D) Morphometric analyses of injured femoral arteries that include neointima/media ratio and neointimal area. The data shown are the means ± S.E.M. (n = 6–9 mice/group). * P < 0.05 compared with ND; ^# P < 0.05 compared with HFD; using regular two-way ANOVA followed by Tukey multiple comparisons test.

Fig. 4.

Effects of imatinib on injury-induced neointimal hyperplasia in HFD-fed mice. Imatinib was administered intraperitoneally (25 mg/kg/day) on the day prior to femoral artery injury and for 3 weeks post-femoral artery injury. Subsequently, uninjured and injured femoral artery segments from ND-fed mice and HFD-fed mice (− or + imatinib treatment) were subjected to staining procedures for: A) H&E and B) EVG, as described in ‘Materials and methods’. The arrowheads indicate internal and external elastic laminae; scale bars represent 20 μm; magnification. C-D) Morphometric analyses of injured femoral arteries that include neointima/media ratio and neointimal area. The data shown are the means ± S.E.M. (n = 6–9 mice/group). * P < 0.05 compared with ND; ^# P < 0.05 compared with HFD; using regular two-way ANOVA followed by Tukey multiple comparisons test.

Fig. 5.

Effects of imatinib on injury-induced neointimal hyperplasia as revealed by SM α-actin immunoreactivity. Confocal immunofluorescence analysis of SM α-actin in femoral artery sections: uninjured, left panel; injured, middle panel; and injured + imatinib, right panel. The representative images for SM α-actin immunoreactivity (red) are shown along with nuclei staining (DAPI, blue), elastin autofluorescence (laminae, green), and merged images. The arrowheads indicate internal and external elastic laminae; scale bars represent 20 μm. The images shown are representative of arterial injury from 3 mice/group.