The effect of vanadate (V) alone, magnesium (Mg) alone, and the combination of Mg plus V (MgV) on insulin-mediated glucose disposal and glucose tolerance was investigated in normal and streptozotocin-induced diabetic rats. MgV, magnesium sulfate (MgSO4) and sodium metavanadate (NaV) were added to the drinking water of normal or diabetic rats (~300 g) for 3 weeks. After 3 weeks of V treatment (both MgV and NAY), diabetic rats demonstrated a normal meal tolerance test without any increase in the plasma insulin response. Rats also received a euglycemic insulin clamp (12 mU/kg · min for 120 minutes) with 3-3H-glucose infusion to quantify total body glucose disposal, glycolysis (3H2O production), and glycogen synthesis (total body 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 MgV (41 ± 2, P < .01). Supersensitivity to insulin was not observed in diabetic 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 observed in MgSO4 and MgV rats (18 ± 1 and 18 ± 1 v 16 ± 1, P < .05). NaY 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, neither MgSO4 nor NaY had any effect on glucose utilization. However, MgV increased glucose disposal to rates that were significantly higher than the rate in untreated control rats (P < .05). Based on these results, MgV is superior to either V alone or Mg alone in improving insulin sensitivity and glycogen synthesis in diabetic rats.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism