Isorhamnetin Reduces Glucose Level, Inflammation, and Oxidative Stress in High-Fat Diet/Streptozotocin Diabetic Mice Model

Abstract

Background: Isorhamnetin is a flavonoid that is found in medical plants. Several studies showed that isorhamnetin has anti-inflammatory and anti-obesity effects. This study aims to investigate the anti-diabetic effects of isorhamnetin in a high-fat diet and Streptozotocin-(HFD/STZ)-induced mice model of type 2 diabetes. Materials and Methods: Mice were fed with HFD followed by two consecutive low doses of STZ (40 mg/kg). HFD/STZ diabetic mice were treated orally with isorhamnetin (10 mg/kg) or (200 mg/kg) metformin for 10 days before sacrificing the mice and collecting plasma and soleus muscle for further analysis. Results: Isorhamnetin reduced the elevated levels of serum glucose compared to the vehicle control group (p < 0.001). Isorhamnetin abrogated the increase in serum insulin in the treated diabetic group compared to the vehicle control mice (p < 0.001). The homeostasis model assessment of insulin resistance (HOMA-IR) was decreased in diabetic mice treated with isorhamnetin compared to the vehicle controls. Fasting glucose level was significantly lower in diabetic mice treated with isorhamnetin during the intraperitoneal glucose tolerance test (IPGTT) (p < 0.001). The skeletal muscle protein contents of GLUT4 and p-AMPK-α were upregulated following treatment with isorhamnetin (p > 0.01). LDL, triglyceride, and cholesterol were reduced in diabetic mice treated with isorhamnetin compared to vehicle control (p < 0.001). Isorhamnetin reduced MDA, and IL-6 levels (p < 0.001), increased GSH levels (p < 0.001), and reduced GSSG levels (p < 0.05) in diabetic mice compared to vehicle control. Conclusions: Isorhamnetin ameliorates insulin resistance, oxidative stress, and inflammation. Isorhamnetin could represent a promising therapeutic agent to treat T2D.

Keywords: diabetes; inflammation; insulin resistance; isorhamnetin; oxidative stress.

Figure 1

The anti-diabetic effect of isorhamnetin. Isorhamnetin significantly reduced glucose (A) and insulin (B) levels in diabetic mice. HOMA-IR (C) was significantly reduced with isorhamnetin treatment. Mice were fed with HFD for 8 weeks followed by two low doses of STZ injection (40 mg/kg) after diabetes confirmed, mice were treated with 10 mg/kg isorhamnetin or 200 mg/kg metformin for 10 days, mice were then sacrificed, and serum collected for ELISA analysis. One-way ANOVA followed by Tukey post hoc, *** p < 0.001. VC; vehicle control, Iso; isorhamnetin, Met; metformin.

Figure 2

Isorhamnetin reduced glucose level during intraperitoneal glucose tolerance test (IPGTT). Isorhamnetin significantly reduced glucose in diabetic mice during intraperitoneal glucose tolerance test. Mice were fed with HFD for 8 weeks followed by two low doses of STZ injection (40 mg/kg), after diabetes confirmed, mice were treated with 10 mg/kg isorhamnetin or 200 mg/kg metformin for 10 days, mice were then fasted overnight before injection with 0.5 g/kg glucose intraperitoneally, and glucose level determined at 0, 30, 60, and 120 min. Two-way ANOVA followed by Tukey post hoc, *** p < 0.001. VC; vehicle control, Iso; isorhamnetin, Met; metformin.

Figure 3

Water and food consumption was higher in diabetic groups. Water consumption (A) was significantly higher in diabetic groups compared to non-diabetic group. Food consumption (B) was higher in diabetic groups compared to non-diabetic group. Two-way ANOVA followed by Tukey post hoc. VC; vehicle control, Iso; isorhamnetin, Met; metformin.

Figure 4

Isorhamnetin upregulated GLUT4 and p-AMPK-α expression in soleus muscle. Isorhamnetin significantly upregulated GLUT4 (A), and AMPK (B) expression in diabetic mice. Mice were fed with HFD for 8 weeks followed by two low doses of STZ injection (40 mg/kg), after diabetes confirmed, mice were treated with 10 mg/kg isorhamnetin or 200 mg/kg metformin for 10 days, mice were then sacrificed, and soleus muscle was isolated and homogenized before western blotting performed. One-way ANOVA followed by Tukey post hoc, * p < 0.05, ** p < 0.01, *** p < 0.001. VC; vehicle control, Iso; isorhamnetin, Met; metformin.

Figure 5

Isorhamnetin improves lipid profile in diabetes. Isorhamnetin significantly reduced triglyceride (A), cholesterol (B), and LDL (C) levels in diabetic mice. Mice were fed with HFD for 8 weeks followed by two low doses of STZ injection (40 mg/kg) after diabetes confirmed, mice were treated with 10 mg/kg isorhamnetin or 200 mg/kg metformin for 10 days, mice were then sacrificed, and serum collected for ELISA analysis. One-way ANOVA followed by Tukey post hoc, *** p < 0.001. VC; vehicle control, Iso; isorhamnetin, Met; metformin.

Figure 6

The anti-inflammatory effect of isorhamnetin. Isorhamnetin significantly increased GSH (A), and reduced GSSG (B), MDA (C), and IL-6 (D) levels in diabetic mice. Mice were fed with HFD for 8 weeks followed by two low doses of STZ injection (40 mg/kg) after diabetes confirmed, mice were treated with 10 mg/kg isorhamnetin or 200 mg/kg metformin for 10 days, mice were then sacrificed, and serum collected for ELISA analysis. One-way ANOVA followed by Tukey post hoc, * p < 0.05, *** p < 0.001. VC; vehicle control, Iso; isorhamnetin, Met; metformin.