Traditional chinese medicine in treatment of metabolic syndrome

Abstract

In management of metabolic syndrome, the traditional Chinese medicine (TCM) is an excellent representative in alternative and complementary medicines with a complete theory system and substantial herb remedies. In this article, basic principle of TCM is introduced and 25 traditional Chinese herbs are reviewed for their potential activities in the treatment of metabolic syndrome. Three herbs, ginseng, rhizoma coptidis (berberine, the major active compound) and bitter melon, were discussed in detail on their therapeutic potentials. Ginseng extracts made from root, rootlet, berry and leaf of Panax quinquefolium (American ginseng) and Panax ginseng (Asian ginseng), are proved for anti-hyperglycemia, insulin sensitization, islet protection, anti-obesity and anti-oxidation in many model systems. Energy expenditure is enhanced by ginseng through thermogenesis. Ginseng-specific saponins (ginsenosides) are considered as the major bioactive compounds for the metabolic activities of ginseng. Berberine from rhizoma coptidis is an oral hypoglycemic agent. It also has anti-obesity and anti-dyslipidemia activities. The action mechanism is related to inhibition of mitochondrial function, stimulation of glycolysis, activation of AMPK pathway, suppression of adipogenesis and induction of low-density lipoprotein (LDL) receptor expression. Bitter melon or bitter gourd (Momordica charantia) is able to reduce blood glucose and lipids in both normal and diabetic animals. It may also protect beta cells, enhance insulin sensitivity and reduce oxidative stress. Although evidence from animals and humans supports the therapeutic activities of ginseng, berberine and bitter melon, multi-center large-scale clinical trials have not been conducted to evaluate the efficacy and safety of these herbal medicines.

Fig. 1

Structure of ginsenosides (ginseng-specific saponins). A. The ginseng saponins of protopanaxadiol include Ra1, Ra₂, Ra₃, Rb₁, Rb₂, Rb₃, Rc, Rd, Rg₂, Rg₃, Rs₁, Rs₂, et al. B. The ginseng saponins of protopanaxatriol include Re, Rf, Rg₁, Rg₂, Rh₁, et al.

Fig. 2

Ginseng is able to improve glucose metabolism through multiple pathways: 1) Glucose disposal is increased partially due to activation of insulin signaling pathway and GLUT4 translocation by ginseng; 2) Ginseng is able to suppress food intake through inhibition of NPY expression in hypothalamus; 3) Physical activity is increased with ginseng through improvement of mood and psychophysical performance; 4) Fat composition and body weight are reduced partially related to up-regulation of thermogenesis and energy expenditure; 5) Antioxidant and anti-inflammation of ginseng may be involved in the mechanisms of insulin sensitization; 6) Ginseng protects islet function through antioxidant and inhibition of β cell apoptosis.

Fig. 3

Structure of berberine

Fig. 4

Mechanism of berberine in regulation of metabolism: 1) Berberine enhances glucose uptake through induction of glycolysis, which is due to inhibition of aerobic respiratory; 2) AMPK activation stimulated by berberine is a consequence of inhibition of mitochondrial function; 3) Berberine suppresses adipogenesis through inhibition of PPARγ and C/EBPα function; 4) Berberine is able to decrease intestinal glucose absorption by inhibition of α-glucosidase; 5) Berberine up-regulates LDL receptor (LDLR) expression through increasing LDLR mRNA, which is related to inactivation of ERK and activation of JNK pathway.

Fig. 5

Mechanism of bitter melon in reduction of blood glucose. Antioxidant and β-cells protection are considered the major mechanisms of bitter melon action in the treatment of diabetes. Additionally, bitter melon is able to inhibit glucose absorption in intestine, reduce hepatic gluconeogenesis, and increase glucose uptake, glucose oxidation and hepatic glycogen content.