Vanadate induces normolipidemia and a reduction in the levels of hepatic lipogenic enzymes in obese Zucker rat

The effects of vanadate administration on the plasma lipids and hepatic lipogenic enzymes were investigated in Zucker (fa/fa) rat, a model for obesity and non insulin-dependent diabetes. These animals were administered sodium orthovanadate through drinking water for a period of four months. The plasma levels of insulin, triacylglycerols and total cholesterol were significantly (p<0.001) elevated in untreated obese control rats as compared to the lean animals. In the livers of obese rats, the number of insulin receptors decreased by 60% and the activities of lipogenic enzymes acetyl-CoA carboxylase and ATP-citrate lyase increased by 4.7- and 5.6-folds, respectively. The messenger RNA for ATP-citrate lyase as measured by Northern blot analysis showed a parallel increase in obese control rats. Treatment of these rats with vanadate caused 56–77% decreases in the plasma levels of insulin, triacylglycerols and total cholesterol. The insulin receptor numbers in vanadate-treated obese rats increased (119%) compared to levels in untreated obese animals. The elevated activities of acetyl-CoA carboxylase and ATP-citrate lyase observed in livers of obese rats were significantly reduced by vanadate. The messenger RNA for ATP-citrate lyase also decreased in vanadate-treated obese rats back to the lean control levels. This study demonstrates that vanadate exerts potent actions on lipid metabolism in diabetic animals in addition to the recognized effects on glucose homeostasis.     

In vivo effects of vanadate on hepatic glycogen metabolizing and lipogenic enzymes in insulin-dependent and insulin-resistant diabetic animals

The insulin-mimetic action of vanadate is well established but the exact mechanism by which it exerts this effect is still not clearly understood. The role of insulin in the regulation of hepatic glycogen metabolizing and lipogenic enzymes is well known. In our study, we have, therefore, examined the effects of vanadate on these hepatic enzymes using four different models of diabetic and insulin-resistant animals. Vanadate normalized the blood glucose levels in all animal models. In streptozotocin-induced diabetic rats, the amount of liver glycogen and the activities of the active-form of glycogen synthase, both active and inactive-forms of phosphorylase, and lipogenic enzymes like glucose 6-phosphate dehydrogenase and malic enzyme were decreased and vanadate treatment normalized all of these to near normal levels. The other three animal models (db/db mouse, sucrose-fed rats and fa/fa obese Zucker rats) were characterized by hyperinsulinemia, hypertriglyceridemia, increases in activities of lipogenic enzymes, and marginal changes in glycogen metabolizing enzymes. Vanadate treatment brought all of these values towards normal levels. It should be noted that vanadate shows differential effects in the modulation of lipogenic enzymes activities in type I and type II diabetic animals. It increases the activities of lipogenic enzymes in streptozotocin-induced diabetic animals and prevents the elevation of activities of these enzymes in hyperinsulinemic animals. The insulin-stimulated phosphorylation of insulin receptor subunit and its tyrosine kinase activity was increased in streptozotocin-induced diabetic rats after treatment with vanadate. Our results support the view that insulin receptor is one of the sites involved in the insulin-mimetic actions of vanadate.     

Decrease in protein tyrosine phosphatase activities in vanadate-treated obese Zucker (fa/fa) rat liver

The inhibitory action of vanadate towards protein tyrosine phosphatase (PTPase) has been considered as a probable mechanism by which it exerts insulin-like effects. In this study, we have examined thein vivo effects of vanadate on PTPases in the liver of obese Zucker rats, a genetic animal model for obesity and type II diabetes. These animals were characterized by hyperinsulinemia and mild hyperglycemia. The number of insulin receptors were significantly (p<0.01) decreased in liver. After chronic administration of vanadate in obese rats, 80% decrease in the plasma levels of insulin was observed. The insulin receptor numbers were significantly (p<0.01) higher in vanadate-treated obese rats as compared to the untreated ones. The hepatic PTPase activities in cytosolic and particulate fractions, with phosphorylated poly glu:tyr (41) and the insulin receptor peptide (residues 1142–1153) as substrates, increased in obese rats. In vanadate-treated obese rat livers, the PTPase activities in both subcellular fractions with these substrates decreased significantly (p<0.001). The decreases in PTPase activities from these groups of rats were further supported by chromatography on a Mono Q column. These data support the view that inhibition of PTPases plays a role in the insulin-mimetic action of vanadate.     

Stimulation of insulin-like growth factor II receptor binding and insulin receptor kinase activity in rat adipocytes. Effects of vanadate and H2O2

Autophosphorylation of the insulin receptor on tyrosine residues and activation of the endogenous insulin receptor kinase is postulated to be a critical step in the mechanism of action of insulin. To investigate this hypothesis, the insulin-mimicking effects of vanadate (sodium orthovanadate) and H2O2 (hydrogen peroxide) alone and in combination were examined in freshly isolated rat adipocytes. Vanadate and H2O2 stimulated the translocation of insulin-like growth factor II (IGF-II) receptors to the plasma membrane of rat adipocytes in a manner analogous to insulin. IGF-II binding was increased by maximally effective doses of vanadate (1 mM), H2O2 (1 mM), and insulin (10 ng/ml) to 172 +/- 10, 138 +/- 12, and 289 +/- 16% of control, respectively. Previously (Kadota, S., Fantus, I. G., Hersh, B., and Posner, B. I. (1986) Biochem. Biophys. Res. Commun. 138, 174-178), we showed that the combination of these concentrations of vanadate plus insulin was not more potent than insulin alone. In this study, similar results were found with H2O2 plus insulin. In contrast, the combination of vanadate plus H2O2 was synergistic, effecting an increase of IGF-II binding to 488 +/- 23% of control. Amiloride inhibited the effects of vanadate, H2O2, and insulin. Adipocyte insulin receptors purified by wheat germ agglutinin chromatography were assayed for tyrosine kinase activity using the synthetic substrate poly(Glu,Tyr) (4:1). Basal activity (no in vitro insulin) was stimulated by exposure of intact cells to vanadate, H2O2, insulin, and vanadate + H2O2 to 147.7 +/- 4.3, 178.2 +/- 43.4, 495.0 +/- 67.1, and 913.2 +/- 92.0% of control, respectively. The stimulation of tyrosine kinase activity by these agents was accounted for by the insulin receptor as the augmented activity was completely immunoprecipitated with insulin receptor antibody. In these studies, the increase in IGF-II binding correlated significantly with the activation of the insulin receptor-tyrosine kinase (r = 0.927, p less than 0.001). These data support the hypothesis that activation of the insulin receptor kinase is linked to insulin action.     

Effects of vanadate and insulin on glucose 1,6-P2 and fructose 2,6-P2 levels in rat skeletal muscle

Levels of glucose 1,6-P2 but not fructose 2,6-P2 were found decreased in skeletal muscle of alloxan-diabetic ketotic rats. Administration of both insulin and vanadate restored the altered values without affecting fructose 2,6-P2 concentrations. In normal rats, insulin increased muscle levels of both sugars, and vanadate decreased glucose 1,6-P2 without changing fructose 2,6-P2 levels. Enzymatic activities involved in glucose 1,6-P2 and fructose 2,6-P2 metabolism were not affected under any experimental condition.     

Does the insulin-mimetic action of vanadate involve insulin receptor kinase?

Effects of vanadate administration on the insulin receptor status in liver were examined in streptozotocin-induced diabetic rats. Diabetic rats were characterized by hyperglycemia (4-fold increase), hypoinsulinemia (81% decrease) and a significant (P<0.01) increase in hepatic insulin receptor numbers. Autophosphorylation of the subunit of insulin receptor and its tyrosine kinase activity towards the synthetic peptide (poly glut₄tyr₁) decreased by approximately 60% as a result of diabetes. After chronic treatment of these rats with sodium orthovanadate, the plasma glucose levels were normalized to near control values with the hypoinsulinemia remaining unaltered. The insulin-stimulated phosphorylation of the subunit increased significantly (P<0.001) in diabetic rats after treatment with vanadate. However, the improvement in the tyrosine kinase activity was marginal.In vitro, vanadate prevented the dephosphorylation of the phosphorylated insulin receptor and increased its tyrosine kinase activity in the absence as well as presence of insulin. The findings of this study further support the view that insulin receptor is one of the sites involved in the insulin-mimetic actions of vanadate.     

Effect of Lower Doses of Vanadate in Combination with Azadirachta indica Leaf Extract on Hepatic and Renal Antioxidant Enzymes in Streptozotocin-Induced Diabetic Rats

The present study was undertaken to investigate short-term (21 days) effects of oral administration of Azadirachta indica leaf extract and vanadate, separately and in combination, on the activities of antioxidant enzymes in streptozotocin-induced diabetic rats. Vanadate is a remarkable antidiabetic agent and shows insulin mimetic effect. However, severe toxicity is associated with vanadate when used in high concentration while at lower concentration the hypoglycemic property of vanadate is reduced. So, we used a low dose of vanadate in combination with A. indica leaf extract and evaluated their effect on the antioxidant defense system. Streptozotocin-diabetic rats were treated separately with insulin, vanadate (0.6 mg/ml), A. indica, and with combined dose of vanadate (0.2 mg/ml) and A. indica. At the end of the experiment, rats were sacrificed and serum glucose levels and activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase were determined in cytosolic fraction of liver and kidney. Diabetic rats showed hyperglycemic condition and alteration in antioxidant enzyme activities. Treatment with antidiabetic compounds resulted in the reduction of glucose levels and restoration of enzyme activities to normal. Results showed that combined treatment of vanadate and A. indica leaf extract was the most effective in normalizing altered antioxidant enzyme system.     

Effects of high sucrose diet on insulin-like effects of vanadate in diabetic rats

The insulin-like effects of vanadate were compared in streptozotocin-induced diabetic rats fed on high starch control and high sucrose diets for a period of six weeks. Diabetic rats in both diet groups were characterized by hypoinsulinemia, hyperglycemia (6.8–7.0 fold increase) and significant decreases (p<0.001) in the activities of glycogen synthase, phosphorylase and lipogenic enzymes, ATP-citrate lyase, glucose 6-phosphate dehydrogenase and malic enzyme in liver. There were no diet-dependent differences in these abnormalities. However, the insulin-mimetic agent vanadate was more effective in diabetic rats fed sucrose diet as compared to animals fed control starch diet. Vanadate administration resulted in 30% and 64% decreases in plasma glucose levels in diabetic rats fed control and sucrose diets, respectively. The activities of glycogen synthase (active) and phosphorylase (active and total) were restored significantly by vanadate in control (p<0.05–0.01) and sucrose (p<0.001) diets fed diabetic rats. This insulin-mimetic agent increased the activities of hepatic lipogenic enzymes in control diet fed rats to 38–47% of normal levels whereas in sucrose fed group it completely restored the activities. Sucrose diet caused a distinct effect on the plasma levels of triacylglycerol (4-fold increase) and apolipoprotein B (2.8-fold increase) in diabetic rats and vanadate supplementation decreased their levels by 65–75%. These data indicate that vanadate exerts insulin-like effects in diabetic rats more effectively in sucrose fed group than the animals fed control diet. In addition, vanadate also prevents sucrose-induced hypertriglyceridemia.     

Modulation of some gluconeogenic enzyme activities in diabetic rat liver and kidney: effect of antidiabetic compounds

The effects of insulin, sodium orthovanadate and a hypoglycemic plant material, Trigonella foenum graecum (fenugreek) seed powder were studied on the activities of glucose-6-phosphatase and fructose-1,6-bisphosphatase in diabetic liver and kidney. The significantly increased activities of the two enzymes during diabetes in liver and kidney were found to be lowered to almost control values by the use of the antidiabetic compounds. Diabetic liver exhibited a much greater increase in the activities of the two enzymes than diabetic kidney. The highest percentage of reversal to normal values was seen using the combination of vanadate and Trigonella seed powder. The lowered rate of growth of the animals as well as the increased blood sugar were reversed almost to the control levels by the Trigonella seed powder and vanadate treatment. The inclusion of the Trigonella seed powder overcame the toxicity of vanadium encountered when it was given alone as insulin mimetic agent. Much lower levels of vanadate were needed when it was given in combination with Trigonella seed powder. Their combined effects were better at restoring the above parameters than those induced by insulin administration.     

Effect of inhibitors and activators of tyrosine kinase on insulin imprinting in Tetrahymena.

Primary exposure of Tetrahymena cells to insulin gave rise to hormonal (insulin) imprinting in the offspring generations, as judged from the increase in binding upon reexposure to insulin. Vanadate mimicked the action of insulin, inasmuch as it also induced imprinting for insulin, whereas the other tyrosine kinase activator tested, namely H2O2, had no such effect. However, combined treatment with vanadate+H2O2 + insulin induced a more pronounced imprinting for insulin than either insulin or vanadate on their own. The tyrosine kinase inhibitor genistein, a plant flavonoid, did not change the value for insulin binding significantly relative to the control immediately after exposure, but increased it slightly in the offspring generations after 24 h at high dilution. Upon combination with insulin, 10(-4)M genistein inhibited imprinting by insulin. These experimental observations suggest that there may be a key role for tyrosine kinase activity in the mechanism (development) of imprinting.     

Protective effect of ascorbic acid against lipid peroxidation and oxidative damage in cardiac microsomes

Effects of feeding sucrose rich diet supplemented with and without the insulinmimetic agent vanadate for a period of six weeks were studied in rats. Sucrose diet caused hypertriglyceridemia (140% increase), hyperinsulinemia (120% increase) and significant elevations in the levels of glucose (p<0.001) and cholesterol (p<0.05) in plasma as compared to control starch fed rats. Activities of hepatic lipogenic enzymes, ATP-citrate lyase, glucose 6-phosphate dehydrogenase and malic enzyme increased by 100–150% as a result of sucrose feeding. However, glycogen content and the activities of glycogen synthase and phosphorylase in liver remained unaltered in these animals. The plasma levels of triacylglycerols and insulin in the rats fed on vanadate supplemented sucrose diet were 65% and 85% less, respectively as compared to rats on sucrose diet without vanadate. The concentrations of glucose and cholesterol in plasma and the activities of lipogenic enzymes in liver did not show any elevation in sucrose fed rats when supplemented with vanadate. These data indicate that the sucrose diet-induced metabolic aberrations can be prevented by the insulin-mimetic agent, vanadate.     

Vanadate down-regulates cell surface insulin and growth hormone receptors and inhibits insulin receptor degradation in cultured human lymphocytes

Insulin is able to down-regulate its specific cell surface receptor in cultured human lymphocytes. The effect of vanadate, a known insulinomimetic agent, was examined to determine whether it could mimic insulin to down-regulate the insulin receptor. Exposure of cultured human lymphocytes (IM-9) to vanadate (0-200 microM) resulted in a time- and dose-dependent decrease in cell surface insulin receptors to 60% of control, while insulin (100 nM) down-regulated to 40%. The vanadate effect, in contrast to the rapid effect of insulin, was slow to develop (4-6 h). Surface receptor recovery after 18 h exposure was rapid after vanadate removal (20 min), but it required hours after insulin suggesting the presence of an intracellular (cryptic) pool of receptors after vanadate treatment. Insulin binding to Triton X-100-solubilized whole cells after 18 h treatment revealed that total cell receptors had decreased to 50% of control after insulin but increased to 120 and 189% of control after 100 and 200 microM vanadate, respectively. Furthermore, vanadate inhibited the insulin-mediated loss of total cell receptors from 50 to 28%. Removal of cell surface receptors by trypsin before cell solubilization revealed that 100 microM vanadate increased insulin binding to 321% of control indicating an accumulation of intracellular receptors. Labeling of cell surface proteins with Na125I and lactoperoxidase followed by immunoprecipitation of solubilized receptors with anti-receptor antibody after incubation for various times up to 20 h and quantitation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that, while insulin shortened t1/2 from 7.3 to 5.3 h, vanadate prolonged receptor t1/2 to 14 h. No effect of vanadate was detected on insulin receptor tyrosine kinase activity with up to 4 h incubation at the vanadate concentrations used in this study. Furthermore, human growth hormone surface receptors were similarly down-regulated by vanadate. We conclude that 1) vanadate has an apparent insulin-like effect to down-regulate cell surface insulin receptors in cultured human lymphocytes; 2) in contrast to insulin-induced down-regulation which is associated with receptor degradation vanadate causes an accumulation of intracellular (cryptic) receptors and inhibits insulin receptor degradation; and 3) these effects of vanadate may be exerted on other cell surface receptors.     

Modulation of glucose transporter (GLUT4) by vanadate and Trigonella in alloxan-diabetic rats

Oral administration of vanadate is an effective treatment for diabetes in animal models. However, vanadate exerts these effects at high doses and several toxic effects are produced. Low doses of vanadate are relatively safe but are unable to elicit any antidiabetic effect. The present study explored the prospect of using low doses of vanadate in combination with Trigonella seed powder (TSP) to evaluate their antidiabetic effect in alloxan-diabetic rats. Alloxan-diabetic rats were treated with insulin, vanadate, TSP and vanadate and TSP in combination for 3 weeks. The effect of these antidiabetic compounds was examined on general physiological parameters and distribution of glucose transporter (GLUT4) in skeletal muscle by immunoblotting and immunohistochemistry. Treatment of alloxan-diabetic rats with insulin, vanadate, TSP and vanadate in combination with TSP revived normoglycemia and restored the disturbances in the distribution of GLUT4 in skeletal muscle. TSP treatment was only partially effective in the restoration of diabetic alterations. The treatment of diabetic rats with combined doses of vanadate and TSP was most effective in the normalization of plasma glucose levels and correction of altered GLUT4 distribution.     

Effect of Olea europaea leaves extract on streptozotocin induced diabetes in male albino rats

The present study was aimed to evaluate the effect of olive (Olea europaea) leaves extract on streptozotocin (STZ)-induced diabetic male rats. The experimental rats were divided into six groups. Rats of the first group were served as normal controls. Rats of the second group were diabetic control. The third and fourth groups were diabetic rats, treated with olive leaves extract at low and high doses respectively. The fifth and sixth groups were non diabetic rats, subjected to olive leaves extract at the same doses given to the third and fourth groups respectively. The minimum of body weigh gain was noted in diabetic rats of the second group. the levels of serum glucose, insulin, total protein, albumin, triglycerides, cholesterol, low density lipoprotein cholesterol (LDL-C), very low density lipoprotein cholesterol (VLDL-C), creatine kinase (CK), lactate dehydrogenase (LDH) and malondialdehyde (MDA) were significantly increased, while the levels of high density lipoprotein cholesterol (HDL-C), superoxide dismutase, (SOD) glutathione (GSH) and catalase (CAT) were statistically decreased in diabetic rats of the second group. The levels of liver insulin receptor substrate 1 (IRS1) and insulin receptor A (IRA) were significantly declined in diabetic rats of the second group. The diabetic pancreatic sections from diabetic rats of the second group showed several histopathological changes. Administration of low and high doses of olive leaves extract improved the observed physiological, molecular and histopathological alterations. Collectively, the obtained results confirmed that the protective effects of olive leaves extract are attributed to the antioxidant activities of olive leaves extract and its active constituents.     

Insulin-like effect of vanadate on malic enzyme and glucose-6-phosphate dehydrogenase activities in streptozotocin-induced diabetic rat liver

The effect of oral administration of sodium orthovanadate on hepatic malic enzyme (EC 1.1.1.40) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) activities was investigated in nondiabetic and diabetic rats. Streptozotocin-induced diabetic rats were characterized by 4.7-fold increase in plasma glucose and 82% decrease in plasma insulin levels. The activities of hepatic malic enzyme and glucose-6-phosphate dehydrogenase were also diminished (P less than 0.001). Vanadate treatment in diabetic rats led to a significant decrease (P less than 0.001) in plasma glucose levels and to the normalization of enzyme activities, but it did not alter plasma insulin levels. In nondiabetic rats vanadate decreased the plasma insulin level by 64% without altering the enzyme activities. Significant correlation was observed between plasma insulin and hepatic lipogenic enzyme activities in untreated and vanadate-treated rats. Vanadate administration caused a shift to left in this correlation suggesting improvement in insulin sensitivity.     

Insulin-like effects of vanadate on glucose uptake and on maturation in Xenopus laevis oocytes.

Vanadate, an inhibitor of phosphotyrosyl phosphatases that exerts insulin-like effects in intact cells, stimulated both maturation and glucose uptake in isolated Xenopus laevis oocytes. Vanadate enhanced the effects of insulin/IGF-I and progesterone on maturation in a dose-dependent manner, with an effective concentration of 750 microM and a maximum at 2 mM, whereas, in the absence of hormone, activation of maturation was seen at 10 mM vanadate. Further, vanadate at 2 mM increased glucose uptake, but this effect was not additive to that of the hormone. In cell-free systems, vanadate caused a 12-fold stimulation of autophosphorylation of the oocyte IGF-I receptor in the absence, but not in the presence, of IGF-I and inhibited largely, but not totally, receptor dephosphorylation induced by an extract of oocytes rich in phosphotyrosyl phosphatase activities. These effects were dose dependent, with effective concentrations of 50-100 microM and maxima at 2 mM. Moreover, using an acellular assay to study the effect of vanadate on the activation of maturation promoting factor (MPF), we found that vanadate at 2 mM stimulated the activation of the MPF H1 kinase. This suggests that vanadate did not prevent dephosphorylation of p34cdc2 on tyrosine residues. Vanadate thus exerted insulin-like effects in oocytes, including stimulation of maturation. These effects might result from a direct or indirect action of vanadate on the IGF-I receptor kinase and on MPF activity.     

Creatine kinase and creatine kinase isoenzyme responses to heat stress

During this investigation the effects of heat acclimation and exercise on creatine kinase and creatine kinase BB isoenzyme responses in various tissues and serum of male Sprague-Dawley rats were ascertained. Forty rats were randomly divided into two groups of 20 rats each. One group was housed at 22+/-1 degrees C and the other at 33+/-1 degrees C. Each of the two groups were subdivided into two subgroups of ten rats each. One subgroup of each group was subjected to a programme of treadmill running of progressive intensity over a period of 6 weeks at the temperature at which it was housed while the other served as a resting control. At the end of the acclimation programme the rats were running at 23 m/min for 80 min. On the day of sacrifice all four subgroups were subjected to a discontinuous exercise protocol (10 min running alternated by a 2-min rest period; repeated three times) at 30+/-1 degrees C on a rodent treadmill at 23 m/min. The tissues investigated were kidney, heart and muscle. The rats were anaesthetized with pentobarbital sodium (6 mg/100 g body mass) injected intraperitoneally. The tissues were freeze-clamped and stored in liquid air until analysed. The body temperature of the four subgroups at the end of the experimental protocol were not significantly different. Acclimation at 33+/-1 degrees C resulted in significantly lower creatine kinase activity levels. Exercise at 30+/-1 degrees C also resulted in decreased creatine kinase activity levels in both acclimated groups. A similar trend was observed regarding creatine kinase BB isoenzyme activity levels, especially in kidney.     

Effect of vanadate administration on polyol pathway in diabetic rat kidney.

Effect of oral administration of sodium orthovanadate for three weeks on polyol pathway in renal cortex and medulla was studied in control and alloxan diabetic rats. An enhancement in aldose reductase in cortex and medulla and sorbitol dehydrogenase in cortex was observed in alloxan diabetic rats. Despite depressed insulin secretion, vanadate treatment to diabetic rats counteracted hyperglycemia, normalized elevated enzyme activities and glucose level, prevented medullary sorbitol accumulation and markedly checked increase in kidney weight. These results show that vanadate causes marked improvement in renal hypertrophy and has an antidiabetogenic effect on polyol pathway in diabetic kidney.     

Oral administration of orthovanadate and Trigonella foenum graecum seed powder restore the activities of mitochondrial enzymes in tissues of alloxan-induced diabetic rats

The effect of oral administration of sodium orthovanadate (SOV) and Trigonella foenum graecum seed powder (TSP), a medicinal plant used extensively in Asia, on the mitochondrial metabolism in the alloxan diabetic rats has been investigated. Rats were injected with alloxan monohydrate (20 mg/100 g body wt) or vehicle (Na-acetate buffer), the former were treated with either 2 IU insulin i.p., 0.6 mg/ml SOV ad libitum, 5% TSP ad libitum, and a combination of 0.2% SOV and 5% TSP ad libitum for 21 days. Selected rate-limiting enzymes of the tricarboxylic acid cycle, hydrogen shuttle system, ketone body metabolism, amino acid metabolism and urea cycle were measured in the mitochondrial and cytosolic fractions of liver, kidney and brain tissues of the experimental rats. Majority of the mitochondrial enzymes in the tissues of the diabetic rats had significantly higher activities compared to the control rats. Similarly, the activities of mitochondrial and cytosolic aminotransferases and arginase were significantly higher in liver and kidney tissues of the diabetic rats. The separate administrations of SOV and TSP to diabetic rats were able to restore the activities of these enzymes to control values. The lower dose of SOV (0.2%) administered in combination with TSP to diabetic rats lowered the enzyme activities more significantly than when given in a higher dose (0.6%) separately. This is the first report of the effective combined action of oral SOV and TSP in ameliorating the altered mitochondrial enzyme activities during experimental type-1 diabetes. Our novel combined oral administration of SOV and TSP to diabetic rats thus conclusively proves as a possible method to minimize potential vanadate toxicity without compromising its positive effects in the therapy of experimental type-1 diabetes.