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Metabolic effects of ginseng

Numerous animal studies indicate that Korean ginseng [1] and American ginseng [2] have significant hypoglycemic action. Sotaniemi et al conducted human clinical study and demonstrated a reduction in the levels of fasting blood glucose and glycosylated hemoglobin A1c (HbA1c) in persons with type 2 diabetes mellitus treated with ginseng relative to placebo[3]. A preliminary clinical study by Canadian scientists revealed that American ginseng has significant blood glucose-lowering action both in nondiabetic subjects and subjects with type 2 diabetes mellitus when ginseng was given 40 minutes prior to the test meal. Therefore, ginseng may be used as a means to lower the glycemic index of diabetic diet, in order to improve glucose control [4].

Mechanism of Action

How ginseng lowers blood glucose level is unknown. Several hypotheses have been proposed.

I.Ginseng slows food digestion, thus decreasing the rate of carbohydrate absorption. Digestion may be slowed by the following two mechanisms. American ginseng slows rat gastric motility by inhibition of neuronal discharge from brain stem [5]. Korean ginseng is shown to inhibit gastric secretion in rats [6].

II.Ginseng increases nitric oxide (NO) synthesis in endothelium of lung, heart, kidney and corpus cavernosum [7]. Enhanced NO synthesis may increase glucose transport in the following tissues. Glucose transport in liver and red blood cells may be increased. Korean ginseng increases hepatic glucose transporter protein in a dose-dependent manner. It also increases glucose uptake into sheep red blood cells in the same manner [8]. NO may also increase insulin-stimulated glucose uptake in rat skeletal muscle and adipose tissue.

III. Some ginseng fractions have been shown to increase glucose-dependent insulin secretion in alloxan diabetic mice [9]. This effect may also be mediated by NO [10].

References: [1]Liu CX et al. Recent advances on ginseng research in China. J Ethnopharmacol. 1992;36:27-38.[2]Oshima Y, Sato K, Hikino H. Isolation and hypoglycemic activity of quinquefolans A, B, and C, glycans of Panax quinquefolium roots. J Nat Prod. 1987;50:188-190. [3]Sotaniemi, EA et al.Diabetes care.18(10)1995:1373-1375.[4]Vuksan, V et al.Arch Intern Med,160(7).2000:1009-1013.[5]Yuan CS et al. Gut and brain effects of American ginseng root on brainstem neuronal activities in rats. Am J Chin Med. 1998;26:47-55. [6]Suzuki Y et al. Effects of tissue cultured ginseng on gastric secretion and pepsin activity [in Japanese]. Yakugaku Zasshi. 1991;111:770-774. [7]Gillis CN. Panax ginseng pharmacology: a nitric oxide link? Biochem Pharmacol. 1997;54:1-8.[8]Hasegawa H et al. Interactions of ginseng extract, ginseng separated fractions, and some triterpenoid saponins with glucose transporters in sheep erythrocytes. Planta Med. 1994;60:153-157. [9]Kimura M et al. Effects of hypoglycemic components in ginseng radix on blood insulin level in alloxan diabetic mice and on insulin release from perfused rat pancreas. J Pharmacobiodyn. 1981;4:410-417. [10]Spinas GA et al. The early phase of glucose-stimulated insulin secretion requires nitric oxide. Diabetologia. 1998;41:292-299.