Hypoglycemic effect of Ganoderma lucidum polysaccharides.
OBJECTIVE
To investigate the hypoglycemic effect of Ganoderma lucidum polysaccharides (Gl-PS) in the normal fasted mice and its possible mechanism.


METHODS
Normal fasted mice were given a single dose of Gl-PS 25, 50, and 100 mg/kg by i.p. and the serum glucose was measured at 0, 3, and 6 h after administration. Gl-PS 100 mg/kg were also given by i.p. and the serum glucose and insulin levels were measured at 0 min, 30 min, 1 h, 3 h, 6 h, and 12 h. Pancreatic islets were isolated and incubated with glucose 5.6 mmol/L and different concentration of Gl-PS, the insulin content of islets and insulin release were examined. The islets fluorescent intensity of [Ca2+]i was also studied with a confocal microscope. Verapamil and egtazic acid were used to testify whether the insulin-releasing effect of Gl-PS was mediated by its ability to raise the Ca2+ influx.


RESULTS
Gl-PS dose-dependently lowered the serum glucose levels at 3 h and 6 h after administration. Gl-PS 100 mg/kg raised the circulating insulin levels at 1 h after administration. In vitro, Gl-PS had no effect on islets insulin content, but it stimulated the insulin release after incubation with glucose 5.6 mmol/L. Confocal microscope showed that Gl-PS 100 mg/L had the capacity to raise the [Ca2+]i. The insulin-releasing effect of Gl-PS was inhibited by verapamil/egtazic acid.


CONCLUSIONS
Gl-PS possesses the hypoglycemic effect on normal mice; one mechanism is through its insulin-releasing activity due to a facilitation of Ca2+ inflow to the pancreatic beta cells.
Zhang
Hui-na
HN
Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing 100083, China.
Lin
Zhi-bin
ZB
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D007004:Hypoglycemic Agents / Q000302:isolation & purification / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism; D007515:Islets of Langerhans / Q000378:metabolism; D008297:Male; D051379:Mice; D010946:Plants, Medicinal / Q000737:chemistry; D011134:Polysaccharides / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D020940:Reishi / Q000737:chemistry
D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D011134:Polysaccharides; D002118:Calcium