Diabetes, affecting almost 3% of the world's population, is one of the major global health problems. In particular, there is a high incidence among the elderly population. It has been shown that the root of P. ginseng and other ginseng species has antihyperglycemic activity in vitro (23,24) and in vivo (2528). More than 90% of patients with diabetes have type 2 diabetes, which is related to aging and diet. Although type 2 diabetes is more common and has serious complications, even reducing life expectancy by 8-10 years (29), most in vivo animal studies using ginseng have been conducted using type 1 rather than type 2 diabetes models. In this study, we focus on the effects of ginseng on type 2 diabetes.
The root of P. ginseng has been used to improve glucose homeostasis and insulin sensitivity (30) and clinically to treat type 2 diabetes (2,31). It has been observed that blood glucose level falls significantly in genetically obese diabetic mice after treatment with a single 90 mg/kg ginseng root extract at an i.p. dose (28). It has also been demonstrated that 3 g of American ginseng root given 40 min before a test meal significantly lowered blood glucose level in nondiabetic subjects and type 2 diabetic patients (32). Oral administration of P. ginseng root to diabetic KKAy mice for 4 weeks reduced blood glucose levels similar to that of an insulin sensitizer (rosiglitazone)-treated group (33). Moreover, ginseng therapy for type 2 diabetes elevates mood, improves psychophysical performance, and reduces fasting blood glucose and body weight. A 200-mg dose of ginseng improves glycated hemoglobin, serum lipid, ammo-terminal propeptide concentration, and physical activity. These observations suggest that ginseng is beneficial for patients with type 2 diabetes and to prevent development of diabetes in nondiabetic subjects.
The main component of P. ginseng is ginsenosides (ginseng saponins). Ginsenoside Rb2 was found to be the most effective component of ginsenosides for streptozotocin-diabetic rats (27). Rats treated with ginsenoside Rb2 had a significant decrease in blood glucose levels with increased activity of glucokinase and decreased activity of glucose-6-phosphatase. Recently, anti-hyperglycemic and antiobese effects of P. ginseng berry extract have been demonstrated, and its major constituent, ginsenoside Re, has been observed (5). Treatment with the berry extract by daily i.p. injection for 12 days in obese diabetic C56BL/6J mice reduced glucose to levels similar to normal control value; after treatment the mice also had significantly improved glucose tolerance. The improvement of blood glucose level in the extract-treated ob/ ob mice is associated with a significant reduction in serum insulin level in fed and fasting mice. A hyperinsulinemic-euglycemic clamp study revealed more than a twofold increase in the rate of insulin-stimulated glucose disposal in treated ob/ob mice. In addition, the extract-treated ob/ob mice lost a significant amount of weight, which was associated with a significant reduction in food intake and very significant increase in energy expenditure and body temperature.
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