Synergistic interaction of magnesium and vanadate on glucose metabolism indiabetic rats

The effect of vanadate (V) alone, magnesium (Mg) alone, and the combination of Mg plus V (MgV) on insulin-mediated glucose disposal and glucose tolera nce was investigated in normal and streptozotocin-induced diabetic rats. Mg V, magnesium sulfate (MgSO4) and sodium metavanadate (NaV) were added to th e drinking water of normal or diabetic rats (similar to 300 g) for 3 weeks. After 3 weeks of V treatment (both MgV and NaV), diabetic rats demonstrate d a normal meal tolerance test without any increase in the plasma insulin r esponse. Rats also received a euglycemic insulin clamp (12 mU/kg . min for 120 minutes) with 3-H-3-glucose infusion to quantify total body glucose dis posal, glycolysis ((H2O)-H-3 production), and glycogen synthesis (total bod y glucose disposal minus glycolysis). Total glucose disposal was decreased in diabetic versus control rats (29 +/- 2 v 35 +/- 2 mg/kg . min, P < .01) and returned to levels greater than the nondiabetic control values after Mg V (41 +/- 2, P < .01). Supersensitivity to insulin was not observed in diab etic rats treated with NaV (34 +/- 1). Glycogen synthesis was increased by both MgV and NaV treatment (23 +/- 21, P < .01 and 18 +/- 1, P < .05 v 14 /- 2 mg/kg . min) in diabetic rats. A small increase in glycolysis was obse rved in MgSO4 and MgV rats (18 +/- 1 and 18 +/- 1 v 16 +/- 1, P < .05). NaV alone had no effect on glycolysis. Thus, Mg has a synergistic effect with V to increase muscle glycogen synthesis in diabetic rats. In normal rats, n either MgSO4 nor NaV had any effect on glucose utilization. However, MgV in creased glucose disposal to rates that were significantly higher than the r ate in untreated control rats (P < .05). Based on these results, MgV is sup erior to either V alone or Mg alone in improving insulin sensitivity and gl ycogen synthesis in diabetic rats. Copyright (C) 1999 by W.B. Saunders Comp any.