Vanadium compounds are potent in controlling elevated
blood glucose levels in experimentally induced diabetes. However the toxicity associated with
vanadium limits its role as therapeutic agent for diabetic treatment. A
vanadium compound
sodium orthovanadate (SOV) was given to
alloxan-induced diabetic Wistar rats in lower doses in combination with Trigonella foenum graecum, a well-known
hypoglycemic agent used in traditional Indian medicines. The effect of this combination was studied on lens morphology and
glucose metabolism in diabetic rats. Lens, an
insulin-independent tissue, was found severely affected in diabetes showing visual signs of
cataract. Alterations in the activities of
glucose metabolizing
enzymes (
hexokinase,
aldose reductase,
sorbitol dehydrogenase,
glucose-6-phosphate dehydrogenase) and
antioxidant enzymes (
glutathione peroxidase,
glutathione reductase) besides the levels of related metabolites, [
sorbitol,
fructose,
glucose,
thiobarbituric acid reactive species (
TBARS) and
reduced glutathione (GSH)] were observed in the
lenses from diabetic rats and diabetic rats treated with
insulin (2 IU/day), SOV (0.6 mg/ml), T. f. graecum seed
powder (TSP, 5%) and TSP (5%) in combination with lowered dose of
vanadium SOV (0.2 mg/ml), for a period of 3 weeks. The activity of the
enzymes,
hexokinase,
aldose reductase and
sorbitol dehydrogenase was significantly increased whereas the activity of
glucose-6-phosphate dehydrogenase,
glutathione peroxidase and
glutathione reductase decreased significantly in
lenses from 3 week diabetic rats. Significant increase in accumulation of metabolites,
sorbitol,
fructose,
glucose was found in diabetic
lenses.
TBARS measure of peroxidation increased whereas the levels of
antioxidant GSH decreased significantly in diabetic condition.
Insulin restored the levels of altered
enzyme activities and metabolites almost to control levels.
Sodium orthovanadate (0.6 mg/ml) and Trigonella administered separately to diabetic animals could partially reverse the diabetic changes, metabolic and morphological, while
vanadate in lowered dose in combination with Trigonella was found to be the most effective in restoring the altered lens metabolism and morphological appearance in diabetes. It may be concluded that
vanadate at lowered doses administered in combination with Trigonella was the most effective in controlling the altered
glucose metabolism and
antioxidant status in diabetic
lenses, these being significant factors involved in the development of
diabetic complications, that reflects in the reduced
lens opacity.