• maitake mushroom;
  • effects on insulin;
  • maitake Fraction X;
  • effects on insulin;
  • KK mice;
  • effects of maitake mushroom fraction

Aim: We examined benefits of a water-soluble extract of maitake mushroom designated as Fraction X (FXM) on the glucose/insulin metabolism of insulin-resistant KK mice, and compared the results of FXM with those of a sulphonylurea, Glipizide.

Design: In several acute studies, insulin-resistant KK mice were gavaged with a single dose of varying concentrations of FXM, or a single dose of one concentration of the oral hypoglycaemic drug, Glipizide. In the one chronic study, KK mice were gavaged with FXM, Glipizide, or an equal volume of isotonic saline (baseline control) twice daily. Retro-orbital blood was drawn on the morning of the 4th and 7th days before the early gavage. Blood glucose was measured by routine laboratory procedures, and serum insulin was estimated by a radioimmunoassay (RIA) assay developed specifically for rodents.

Results: At a dose of FXM (140 mg/mouse), a statistically significant lowering of circulating glucose concentrations was again seen at 8–12 h and 16–18 h after oral gavage. The lowering approximated 25% of the original concentration. Oral gavage of Glipizide resulted in statistically significantly lower values of circulating glucose (25–37% lower compared with baseline) at 8–24 h post dosing. In the chronic study, the circulating concentrations of glucose and insulin of mice taking 140 mg FXM per day were decreased significantly at days 4 and 7.

Conclusions: FXM, a natural extract obtained from maitake mushroom, favourably influences glucose/insulin metabolism in insulin-resistant KK mice. The lowering of both circulating glucose and insulin concentrations suggests that FXM works primarily by enhancing peripheral insulin sensitivity.