Anti-hyperglycemic and hypolipidemic effects of black ginseng extract containing increased Rh4, Rg5, and Rk1 content in muscle and liver of type 2 diabetic db/db mice

Abstract

Black ginseng (BG), which is produced by repeated steaming and drying of fresh ginseng, has various pharmacological and therapeutic properties. This study investigated the anti-hyperglycemic and hypolipidemic effects of BG ethanolic extract in type 2 diabetic db/db mice. The levels of fasting blood glucose, HbA1c, insulin levels and thiobarbituric acid reactive substances values were decreased in the groups fed BG extract (BG) (100 and 900 mg/kg BW/day), compared to the control group (CON). In the BG compared with the CON, hepatic steatosis in the liver and the size of adipocytes in muscle tissue were improved. The administration of BG regulated the glucose transporter type (GLUT) 4 and 2, and peroxisome proliferator-activated receptor (PPAR) α and γ in muscle and liver. Moreover, ginsenosides (Rh4, Rg5, and Rk1), which profiled by HPLC, regulated the markers for lipid metabolism and glucose metabolism; PPARs and GLUTs in muscle and C2C12 rather than liver cells and tissue. These findings suggested that ginsenosides (Rh4, Rg5, and Rk1) from BG extract can ameliorate type 2 diabetes through their anti-hyperglycemic and hypolipidemic effects.

Keywords: Anti-hyperglycemic; Black ginseng; Hypolipidemic; Type 2 diabetic db/db mice.

Fig. 1

Effect of black ginseng (BG) extract on (A) body weight, (B) food intake, (C) fasting blood glucose levels, (D) hemoglobin A1c content in blood, (E) Insulin concentration in serum of mice, and (F) malondialdehyde (MDA) levels in liver tissue. WT (non-diabetic control group, wild type), ROG (diabetic + rosiglitazone group), CON (diabetic control group), BG100 (diabetic + black ginseng extract 100 mg/kg BW/day group), BG900 (diabetic + black ginseng extract 900 mg/kg BW/day group). Values are expressed as the mean ± SD (n = 6). *p values < 0.05, **p values < 0.01 and ***p values < 0.001 are considered statistically significant when compared with controls (CON), and ^#p values < 0.05, ^##p values < 0.01 and ^###p values < 0.001 are considered statistically significant when compared with wild type (WT) only by Student’s t-test

Fig. 2

Histological changes in muscle and liver following treatment with black ginseng extract. Hematoxylin and eosin-stained photomicrographs showing the muscle (×200, Bar = 50 μm) and the liver (×400, Bar = 25 μm). Effects of black ginseng extract treatment for 5 weeks on morphological changes of the gastrocnemius muscles and liver in db/db mice. Morphological changes were visualized with a light microscope after hematoxylin and eosin (H&E) staining (→: steatosis in liver; →: adipocytes in muscle). WT (non-diabetic control group, wild type), ROG (diabetic + rosiglitazone group), CON (diabetic control group), BG100 (diabetic + black ginseng extract 100 mg/kg BW/day group), BG900 (diabetic + black ginseng extract 900 mg/kg BW/day group)

Fig. 3

The effect of BG on relative mRNA expression level. The glucose transporter 4 (GLUT4) mRNA level in the muscle (A) and the GLUT2 mRNA level in the liver (B) of db/db mice. The peroxisome proliferator-activated receptor α (PPARα) mRNA level in the muscle (C) and in liver (D) of db/db mice. The PPARγ mRNA level in the muscle (E) and in liver (F) of db/db mice. WT (non-diabetic control group, wild type), ROG (diabetic + rosiglitazone group), CON (diabetic control group), BG100 (diabetic + black ginseng extract 100 mg/kg BW/day group), BG900 (diabetic + black ginseng extract 900 mg/kg BW/day group). Bar diagram represents the mean ± standard deviation (n = 5). *p values < 0.05, **p values < 0.01 and ***p values < 0.001 are considered statistically significant when compared with controls (CON), and ^#p values < 0.05, ^##p values < 0.01 and ^###p values < 0.001 are considered statistically significant when compared with wild type (WT) only by Student’s t-test

Fig. 4

HPLC chromatogram of ginsenosides in (A) white ginseng (WG) and (B) red ginseng (RG) and (C) black ginseng (BG)

Fig. 5

(A) Viability in C2C12 Cells and HepG2 cells treated with different concentration of BG. After a 24 h exposure to BG and ginsenosides, cell viability was measured using the MTT assay. (B) Effects of BG and ginsenosides (Rh 4, Rg 5, Rk 1) on cell viability. C2C12 and HepG2 cells were treated with three types of ginsenosides (Rh4, 0.89 μM; Rg5, 0.69 μM; Rk1, 2.8 μM) found in 125 μg/mL of BG extract in equivalent amounts and the three combined ginsenosides (MIX: Rh4, 0.89 μM; Rg5, 0.69 μM; Rk1, 2.8 μM). (C) The effect of BG 125 μg/mL, ginsenoside and mixed material (Rh 4 + Rg 5 + Rk 1) on relative PPARs and GLUTs protein levels in C2C12 and HepG2 after 24 h samples treated. *p values < 0.05, **p values < 0.01 and ***p values < 0.001 are considered statistically significant when compared with the control group by Student’s t-test