Myrcia bella Leaf Extract Presents Hypoglycemic Activity via PI3k/Akt Insulin Signaling Pathway

Abstract

Species of Myrcia are used by indigenous people and in traditional communities in Brazil for the treatment of Diabetes mellitus. We investigated the hypoglycemic effect of the extract of leaves of Myrcia bella in diabetic mice. The chemical fingerprinting of the 70% EtOH extract characterized as main constituents flavonoid aglycones, flavonoid-O-glycosides, and acylated flavonoid-O-glycosides derivatives of quercetin and myricetin. Mice were treated with saline or extract of M. bella (300 or 600 mg/Kg b.w.) for 14 days. Body weight and water and food intake were measured every day. Fasting blood glucose was measured weekly. At the end of the treatment, blood insulin, triglycerides, total cholesterol, and protein were measured. Glycogen content and expression of proteins of the insulin signaling pathway were measured in liver. The treatment with 600 mg/Kg reduced the fasting blood glucose in diabetic mice of the 7th day as water and food intake and increased hepatic glycogen. Total cholesterol and triglycerides were reduced in diabetic treated mice. The treatment increased the expression of IRS-1, PI3-K, and AKT in the livers of diabetic treated mice. The results indicate that the extract of the leaves of Myrcia bella has hypoglycemic properties and possibly acts to regulate glucose uptake by the liver.

Figure 1

Chemical profile of Myrcia bella's extract. Typical direct flow injection analysis FIA-ESI-IT-MS fingerprint spectra obtained in negative ion mode of the 70% EtOH from the leaves of M. bella. (●) Characteristics constituents fragmented.

Figure 2

Body weight during acute toxicity test on male normoglycemic mice. Effect of acute administration of saline (CTL SAL) or crude extract of M. bella (2,000 mg/Kg-CTL EXT) on the body weight of normoglycemic mice. Data are Means ± SEM, n = 10, P < 0.05. Student's t-test.

Figure 3

Effect of Myrcia bella administration (300 and 600 mg/Kg) on fast blood glucose. Fast blood glucose (mg/dL) of control and diabetic mice treated with saline (CTL SAL and STZ SAL), 300 mg/Kg (a) or 600 mg/Kg (b) of the crude extract of M. bella (CTL EXT and STZ EXT) during 14 days. Data are Means ± SEM. ∗ versus STZ SAL; @ versus CTL SAL, & versus CTL EXT, n = 10, P < 0.05. ANOVA followed by Tukey's posttest.

Figure 4

Intraperitoneal glucose tolerance test. Glycemia after intraperitoneal glucose administration (2 g/Kg) (a) and area under the curve (AUC) (b) in control and diabetic mice treated with saline (CTL SAL and STZ SAL) or with 600 mg/Kg of the crude extract of M. bella (CTL EXT and STZ EXT) during 14 days (CTL EXT and STZ EXT). Data are Means ± SEM. ∗ versus STZ SAL; @ versus CTL SAL, & versus CTL EXT, n = 8, P < 0.05. ANOVA followed by Tukey's posttest.

Figure 5

Effect of Myrcia bella administration (600 mg/Kg) on the body weight. Body weight (g) of control and diabetic animals treated with saline (CTL SAL and STZ SAL) or with 600 mg/Kg of the crude extract of M. bella during 14 days (CTL EXT and STZ EXT). Data are Means ± SEM. @ versus CTL SAL, n = 8, P < 0.05. ANOVA followed by Tukey's posttest.

Figure 6

Effect of Myrcia bella administration (600 mg/Kg) on water and food intake. Water intake (mL/animal) (A) and food intake (B) of control and diabetic mice treated with saline (CTL SAL and STZ SAL) or with 600 mg/Kg of the crude extract of M. bella (CTL EXT and STZ EXT) during 14 days. Data are Means ± SEM. ∗ versus STZ SAL; @ versus CTL SAL, & versus CTL EXT, n = 8, P < 0.05. ANOVA followed by Tukey's posttest.

Figure 7

Protein expression in liver. Western blot analysis of IRS-1 (a), PI3-K(b), and AKT (c) from liver of control and diabetic mice treated with saline (CTL SAL and STZ SAL) or with 600 mg/Kg of the crude extract of M. bella during 14 days (CTL EXT and STZ EXT). p-IRS-1, p-PI3-K, and P-AKT are the phosphorylated forms of the respective proteins. Data are Means ± SEM. ∗ versus STZ SAL, @ versus CTL SAL, & versus CTL EXT, n = 6, P < 0.05. ANOVA followed by Tukey's posttest.