The Emerging Importance of Cirsimaritin in Type 2 Diabetes Treatment

Abstract

Cirsimaritin is a dimethoxy flavon that has different biological activities such as antiproliferative, antimicrobial, and antioxidant activities. This study aims to investigate the anti-diabetic effects of cirsimaritin in a high-fat diet and streptozotocin-(HFD/STZ)-induced rat model of type 2 diabetes mellitus (T2D). Rats were fed HFD, followed by a single low dose of STZ (40 mg/kg). HFD/STZ diabetic rats were treated orally with cirsimaritin (50 mg/kg) or metformin (200 mg/kg) for 10 days before terminating the experiment and collecting plasma, soleus muscle, adipose tissue, and liver for further downstream analysis. Cirsimaritin reduced the elevated levels of serum glucose in diabetic rats compared to the vehicle control group (p < 0.001). Cirsimaritin abrogated the increase in serum insulin in the treated diabetic group compared to the vehicle control rats (p < 0.01). The homeostasis model assessment of insulin resistance (HOMA-IR) was decreased in the diabetic rats treated with cirsimaritin compared to the vehicle controls. The skeletal muscle and adipose tissue protein contents of GLUT4 (p < 0.01 and p < 0.05, respectively) and pAMPK-α1 (p < 0.05) were upregulated following treatment with cirsimaritin. Cirsimaritin was able to upregulate GLUT2 and AMPK protein expression in the liver (p < 0.01, <0.05, respectively). LDL, triglyceride, and cholesterol were reduced in diabetic rats treated with cirsimaritin compared to the vehicle controls (p < 0.001). Cirsimaritin reduced MDA, and IL-6 levels (p < 0.001), increased GSH levels (p < 0.001), and reduced GSSG levels (p < 0.001) in diabetic rats compared to the vehicle control. Cirsimaritin could represent a promising therapeutic agent to treat T2D.

Keywords: cirsimaritin; inflammation; insulin resistance; oxidative stress; type 2 diabetes.

Figure 1

Chemical structure of cirsimaritin.

Figure 2

The anti-diabetic effect of cirsimaritin. Cirsimaritin significantly reduced glucose (A) and insulin (B) levels in diabetic rats. HOMA-IR (C) was significantly reduced with cirsimaritin treatment. Rats were fed HFD for 3 weeks, followed by a single dose of STZ injection (40 mg/kg); and once diabetes was confirmed, rats were treated with 50 mg/kg cirsimaritin or 200 mg/kg metformin for 10 days. After the end of the experiment, serum was collected for ELISA analyses. One-way ANOVA was followed by Tukey post hoc multiple comparison test, * p < 0.05, ** p < 0.01, *** p < 0.001. ND; non-diabetic, VC; vehicle control.

Figure 3

Cirsimaritin reduced glucose levels during the intraperitoneal glucose tolerance test (IPGTT). Rats were fed with HFD for 3 weeks, followed by a single dose of STZ injection (40 mg/kg); once diabetes was confirmed, rats were treated with 50 mg/kg cirsimaritin or 200 mg/kg metformin for 10 days. Rats then fasted overnight before injection with 0.5 g/kg glucose intraperitoneally, and glucose levels were determined at 0, 30, 60, and 120 min. Two-way ANOVA followed by Tukey post hoc multiple comparison test, *** p < 0.001. ND; non-diabetic, VC; vehicle control.

Figure 4

Cirsimaritin upregulated GLUT4 and pAMPK-α1 expression in the soleus muscle. Cirsimaritin significantly upregulated GLUT4 (A) and pAMPK-α1 (B) expression within soleus muscle in diabetic rats. Rats were fed HFD for 3 weeks, followed by a single dose of STZ injection (40 mg/kg); once diabetes was confirmed, rats were treated with 50 mg/kg cirsimaritin or 200 mg/kg metformin for 10 days. Rats were then sacrificed and after the end of the experiment following euthanasia, soleus muscle was isolated and homogenized for downstream Western blotting. One-way ANOVA was followed by Tukey post hoc multiple comparison test, * p < 0.05, ** p < 0.01, *** p < 0.001. ND; non-diabetic, VC; vehicle control.

Figure 5

Cirsimaritin upregulated GLUT4 and pAMPK-α1 expression in adipose tissue. Cirsimaritin significantly upregulated adipose tissue GLUT4 (A) and pAMPK-α1 (B) expression in diabetic rats. Rats were fed HFD for 3 weeks, followed by a single dose of STZ injection (40 mg/kg); after diabetes was confirmed, rats were treated with 50 mg/kg cirsimaritin or 200 mg/kg metformin for 10 days. At the end of the experiment following euthanasia, adipose tissue was isolated and homogenized before Western blotting was performed. One-way ANOVA was followed by Tukey post hoc multiple comparison test, * p < 0.05, ** p < 0.01, *** p < 0.001. ND; non-diabetic, VC; vehicle control.

Figure 6

Cirsimaritin upregulated GLUT2 and pAMPK-α1 expression in the liver. Cirsimaritin significantly upregulated hepatic GLUT2 (A) and pAMPK-α1 (B) expression in diabetic rats. Rats were fed HFD for 3 weeks, followed by a single dose of STZ injection (40 mg/kg); and once diabetes was confirmed, rats were treated with 50 mg/kg cirsimaritin or 200 mg/kg metformin for 10 days. At the end of the experiment following euthanasia, the liver was isolated and homogenized before Western blotting performed. One-way ANOVA was followed by Tukey post hoc multiple comparison test, * p < 0.05, ** p < 0.01, *** p < 0.001. ND; non-diabetic, VC; vehicle control.

Figure 7

Cirsimaritin improves lipid profile in diabetes. Cirsimaritin significantly reduced LDL (A), total cholesterol (B), and triglyceride (C) systemic concentrations in diabetic rats. Rats were fed HFD for 3 weeks, followed by a single dose of STZ injection (40 mg/kg), and once diabetes was confirmed, rats were treated with 50 mg/kg cirsimaritin or 200 mg/kg metformin for 10 days. At the end of the experiment following euthanasia, serum was collected for ELISA analyses. One-way ANOVA was followed by Tukey post hoc multiple comparison test, * p < 0.05, ** p < 0.01, *** p < 0.001. ND; non-diabetic, VC; vehicle control.

Figure 8

The antioxidant and anti-inflammatory effect of cirsimaritin. Cirsimaritin significantly increased GSH (A) and reduced GSSG (B), and reduced MDA (C) and IL-6 (D) systemic concentrations in diabetic rats. Rats were fed HFD for 3 weeks, followed by a single dose of STZ injection (40 mg/kg), and once diabetes was confirmed, rats were treated with 50 mg/kg cirsimaritin or 200 mg/kg metformin for 10 days. After the end of the experiment following euthanasia, serum was collected for ELISA analysis. One-way ANOVA was followed by Tukey post hoc multiple comparison test, * p < 0.05, ** p < 0.01, *** p < 0.001. ND; non-diabetic, VC; vehicle control.