Insulin mimetic effect of a tungstate cluster. Effect of oral administration of homo-polyoxotungstates and vanadium-substituted polyoxotungstates on blood glucose level of STZ mice
K. Nomiya et al., Insulin mimetic effect of a tungstate cluster. Effect of oral administration of homo-polyoxotungstates and vanadium-substituted polyoxotungstates on blood glucose level of STZ mice, J INORG BIO, 86(4), 2001, pp. 657-667
Aqueous vanadate and aqueous tungstate have been known to mimic all or most
of the actions of insulin in intact cell systems with respect to normaliza
tion of the blood glucose level. By carrying out oral administration in viv
o experiments on the blood glucose level of streptozotocin (STZ)-induced di
abetes (STZ mice), the insulin-mimetic (IM) effects of metal-oxide clusters
of all-inorganic composition were examined using many types of polyoxometa
lates (POM) with and without vanadium substitution. Several homo-POM and va
nadium-substituted POM showed hypoglycemic effects. The observed hypoglycem
ic effects indicated that POM with the Dawson structure ([alpha -P2W18O62](
6-) (W-2), [alpha -(P2W17VO62)-O-v](7-) (V-19) and [alpha -1,2,3-(P2W15VO62
)-O-v](9-) (V-04)) are more effective than those with the Keggin structure
([alpha -P2W12O40](6-) (W-1), [alpha -(PW11VO40)-O-v](4-) (V-01), [alpha -1
,2-(PW10V2O40)-O-v](5-) (V-02), [alpha -1,2,3-(PW9V3O40)-O-v](6-) (V-03) an
d [alpha -1,4,9-(PW9V3O40)-O-v](6-) (V-13)). The vanadate cluster [VtoO28](
6-) (V-15) also showed a hypoglycemic effect. P-31 and V-51 NMR 3 measureme
nts showed that the Dawson POM (W-2, V-04 and V-19) are stable in aqueous s
olution under the conditions used. The effect of all POM on the body weight
of STZ mice was also examined. The decrease in body weight after administr
ation of W-2 was much less than for V-19, V-04 and V-15, This suggests that
not only monomeric tungstate and vanadate, but also the structure factors
of tungstate and vanadate clusters, can play a significant role in their bi
ological action. (C) 2001 Elsevier Science BY. All rights reserved.