A functional leptin system is essential for sodium tungstate antiobesity action

Effect of Tungstate Administration on the Lipid Peroxidation and Antioxidant Parameters in Salivary Glands of STZ-Induced Diabetic Rats

Sodium tungstate is an alternative to reduce hyperglycemia for the treatment of diabetes. In previous work, we showed that the administration of sodium tungstate increased the specific activity of salivary amylase in the parotid gland. Here, we investigated the effect of the administration of sodium tungstate on the lipid peroxidation and some antioxidant parameters in the submandibular (SM) and parotid (PA) salivary glands of streptozotocin (STZ)-induced diabetic rats. Thirty-two male Wistar rats were divided into four groups (n = 8, each): control (C), control treated with sodium tungstate (CT), diabetic (D), and diabetic treated with sodium tungstate (CT). Sodium tungstate (2 mg/ml) was administered to the STZ-induced diabetic rats for 15 days. Malondialdehyde (MDA), reduced (GSH) and oxidized (GSSG) glutathione, and blood glucose concentrations were quantified. In addition, superoxide dismutase (SOD) and catalase (CAT) activities were assessed. Results revealed that diabetes caused an increase in MDA concentration in both glands, a reduction in the SOD activity in SM, and an increase in catalase activity in PA glands. Administration of sodium tungstate reduced the blood glucose levels and normalized the SOD activity in the SM and MDA levels in both glands of the STZ-induced diabetic rats. Catalase activity was increased in PA glands of diabetic and tungstate-treated animals (p < 0.05). The GSH/GSSG ratio was increased in SM glands of tungstate-treated animals (p < 0.05). Overall, the reduction of hyperglycemia by sodium tungstate reduced lipid peroxidation and caused alterations in the antioxidant system in the salivary glands of STZ-induced diabetic rats.

Preclinical and Clinical Studies for Sodium Tungstate: Application in Humans

Diabetes is a complex metabolic disorder triggered by the deficient secretion of insulin by the pancreatic β-cell or the resistance of peripheral tissues to the action of the hormone. Chronic hyperglycemia is the major consequence of this failure, and also the main cause of diabetic problems. Indeed, several clinical trials have agreed in that tight glycemic control is the best way to stop progression of the disease. Many anti-diabetic drugs for treatment of type 2 diabetes are commercially available, but no ideal normoglycemic agent has been developed yet. Moreover, weight gain is the most common side effect of many oral anti-diabetic agents and insulin, and increased weight has been shown to worsen glycemic control and increase the risk of diabetes progression. In this sense, the inorganic salt sodium tungstate (NaW) has been studied in different animal models of metabolic syndrome and diabetes, proving to have a potent effect on normalizing blood glucose levels and reducing body weight, without any hypoglycemic action. Although the liver has been studied as the main site of NaW action, positive effects have been also addressed in muscle, pancreas, brain, adipose tissue and intestine, explaining the effective anti-diabetic action of this salt. Here, we review NaW research to date in these different target organs. We believe that NaW deserves more attention, since all available anti-diabetic treatments remain suboptimal and new therapeutics are urgently needed.

Addition of a low dose of rimonabant to orlistat therapy decreases weight gain and reduces adiposity in dietary obese rats

1. The aim of the present study was to determine whether the addition of a subeffective dose of rimonabant (1 mg/kg) to orlistat would be beneficial in the treatment of diet-induced obesity in rats compared with orlistat monotherapy. 2. Male rats were divided into five groups: (i) rats fed a low-fat diet for 4 months; (ii) rats fed a high-fat diet (HFD) for 4 months and treated daily with vehicle (0.2% Tween-80 solution); (iii) orlistat (10 mg/kg per day)-treated HFD-fed rats; (iv) rimonabant (1 mg/kg per day)-treated HFD-fed rats; and (v) HFD-fed rats treated with a combination of orlistat plus rimonabant. Fasting blood glucose, serum insulin, leptin and adiponectin levels were measured. Liver and adiposity indices were calculated and liver and adipose tissues were processed for histological examination. 3. Over the 4 months of the study, vehicle-treated HFD-fed rats exhibited increased cumulative food intake, bodyweight and liver and adiposity indices. Moreover, vehicle-treated HFD-fed rats exhibited a deterioration in liver function and an abnormal lipid profile. Insulin resistance and serum leptin were increased in this group, whereas serum adiponectin levels were decreased. Orlistat monotherapy or combination therapy with orlistat plus rimonabant improved all these parameters. 4. The addition of the low subeffective dose of rimonabant to orlistat therapy ameliorated HFD-induced obesity to a much greater extent than orlistat monotherapy. This combination showed better weight control and metabolic profile compared with orlistat alone. Therefore, the results of the present study encourage reassessment of the use of a low dose of rimonabant to potentiate the effect of orlistat in the clinical management of obesity if proper clinical safety data are available.

Anti-obesity sodium tungstate treatment triggers axonal and glial plasticity in hypothalamic feeding centers

Objective

This study aims at exploring the effects of sodium tungstate treatment on hypothalamic plasticity, which is known to have an important role in the control of energy metabolism.

Methods

Adult lean and high-fat diet-induced obese mice were orally treated with sodium tungstate. Arcuate and paraventricular nuclei and lateral hypothalamus were separated and subjected to proteomic analysis by DIGE and mass spectrometry. Immunohistochemistry and in vivo magnetic resonance imaging were also performed.

Results

Sodium tungstate treatment reduced body weight gain, food intake, and blood glucose and triglyceride levels. These effects were associated with transcriptional and functional changes in the hypothalamus. Proteomic analysis revealed that sodium tungstate modified the expression levels of proteins involved in cell morphology, axonal growth, and tissue remodeling, such as actin, CRMP2 and neurofilaments, and of proteins related to energy metabolism. Moreover, immunohistochemistry studies confirmed results for some targets and further revealed tungstate-dependent regulation of SNAP25 and HPC-1 proteins, suggesting an effect on synaptogenesis as well. Functional test for cell activity based on c-fos-positive cell counting also suggested that sodium tungstate modified hypothalamic basal activity. Finally, in vivo magnetic resonance imaging showed that tungstate treatment can affect neuronal organization in the hypothalamus.

Conclusions

Altogether, these results suggest that sodium tungstate regulates proteins involved in axonal and glial plasticity. The fact that sodium tungstate could modulate hypothalamic plasticity and networks in adulthood makes it a possible and interesting therapeutic strategy not only for obesity management, but also for other neurodegenerative illnesses like Alzheimer’s disease.

Comparison of urine toxic metals concentrations in athletes and in sedentary subjects living in the same area of Extremadura (Spain)

Cadmium (Cd), tungsten (W), tellurium (Te), beryllium (Be), and lead (Pb), are non-essential metals pervasive in the human environment. Studies on athletes during training periods compared to non-training control subjects, indicate increased loss of minerals through sweat and urine. The aim of this study was to compare the level of these trace elements, determined by inductively coupled plasma mass spectrometry (ICP-MS) in urine samples, between athletes and age-matched sedentary subjects living in the same geographical area, although anthropometric and cardiovascular measurements showed that athletes have significantly (P ≤ 0.001) lower BMI, body fat and heart rate, whereas the muscle and bone percentage was significantly (P ≤ 0.001) higher than in sedentary subjects. The validity of the methodology was checked by the biological certified reference material. Trace element analysis concentrations, expressed in μg/mg creatinine, of five toxic elements in urine from athletes (n = 21) versus sedentary subjects, (n = 26) were as follows: Cd (0.123 ± 0.075 vs. 0.069 ± 0.041, P ≤ 0.05); W (0.082 ± 0.053 vs. < limit of detection); Te (0.244 ± 0.193 vs. 0.066 ± 0.045, P ≤ 0.001), Be (0.536 ± 0.244 vs. 0.066 ± 0.035, P ≤ 0.001); Pb (0.938 ± 0.664 vs. 2.162 ± 1.444 P ≤ 0.001). With the exception of Pb, urine toxic metal concentrations from athletes were higher than from sedentary subjects. This fact suggests that physical activity counteracts, at least in part, the cumulative effect of toxic environment by increasing the urine excretion of toxic metals in trained people.

Tissue distribution of tungsten in mice following oral exposure to sodium tungstate

Heavy metal tungsten alloys have replaced lead and depleted uranium in many munitions applications, due to public perception of these elements as environmentally unsafe. Tungsten materials left in the environment may become bioaccessible as tungstate, which might lead to population exposure through water and soil contamination. Although tungsten had been considered a relatively inert and toxicologically safe material, recent research findings have raised concerns about possible deleterious health effects after acute and chronic exposure to this metal. This investigation describes tissue distribution of tungsten in mice following oral exposure to sodium tungstate. Twenty-four 6-9 weeks-old C57BL/6 laboratory mice were exposed to different oral doses of sodium tungstate (0, 62.5, 125, and 200 mg/kg/d) for 28 days, and after one day, six organs were harvested for trace element analysis with inductively coupled plasma mass spectrometry (ICP-MS). Kidney, liver, colon, bone, brain, and spleen were analyzed by sector-field high-resolution ICP-MS. The results showed increasing tungsten levels in all organs with increased dose of exposure, with the highest concentration found in the bones and the lowest concentration found in brain tissue. Gender differences were noticed only in the spleen (higher concentration of tungsten in female animals), and increasing tungsten levels in this organ were correlated with increased iron levels, something that was not observed for any other organ or either of the two other metals analyzed (nickel and cobalt). These findings confirmed most of what has been published on tungsten tissue distribution; they also showed that the brain is relatively protected from oral exposure. Further studies are necessary to clarify the findings in splenic tissue, focusing on possible immunological effects of tungsten exposure.

Sodium tungstate regulates food intake and body weight through activation of the hypothalamic leptin pathway

AIMS

Sodium tungstate is an anti-obesity drug targeting peripheral tissues. In vivo, sodium tungstate reduces body weight gain and food intake through increasing energy expenditure and lipid oxidation, but it also modulates hypothalamic gene expression when orally administered, raising the possibility of a direct effect of sodium tungstate on the central nervous system.

METHODS

Sodium tungstate was administered intraperitoneally (ip) to Wistar rats, and its levels were measured in cerebrospinal fluid through mass spectrometry. Body weight gain and food intake were monitored for 24 h after its administration in the third ventricle. Hypothalamic protein was obtained and subjected to western blot. In vitro, hypothalamic N29/4 cells were treated with 100 µM sodium tungstate or 1 nM leptin, and protein and neural gene expression were analysed.

RESULTS

Sodium tungstate crossed the blood-brain barrier, reaching a concentration of 1.31 ± 0.07 mg/l in cerebrospinal fluid 30 min after ip injection. When centrally administered, sodium tungstate decreased body weight gain and food intake and increased the phosphorylation state of the main kinases and proteins involved in leptin signalling. In vitro, sodium tungstate increased the phosphorylation of janus kinase-2 (JAK2) and extracellular signal-regulated kinase-1/2 (ERK1/2), but the activation of each kinase did not depend on each other. It regulated c-myc gene expression through the JAK2/STAT system and c-fos and AgRP (agouti-related peptide) gene expression through the ERK1/2 pathway simultaneously and independently.

CONCLUSIONS

Sodium tungstate increased the activity of several kinases involved in the leptin signalling system in an independent way, making it a suitable and promising candidate as a leptin-mimetic compound in order to manage obesity.

Sodium tungstate and vanadyl sulfate effects on blood pressure and vascular prostanoids production in fructose-overloaded rats

This study analyzes the effects of sodium tungstate and vanadyl sulphate in the fructose-overloaded rat, a model of metabolic syndrome. Fructose (9 weeks) increased blood pressure, triglycerydemia, glycemia, and reduced release of vasodilator prostaglandins (prostacyclin and prostaglandin E2 ) in the mesenteric vascular bed. Sodium tungstate prevented those alterations; meanwhile vanadyl sulfate only prevented the increase in glycemia. In conclusion, the present experiments showed that sodium tungstate is more effective than vanadyl sulfate for the treatment of experimental metabolic syndrome in rats.

Proof-of-concept trial on the efficacy of sodium tungstate in human obesity

AIM

Considering the poor long-term success of current dietary and pharmacological interventions, we aimed to evaluate the potential effect of sodium tungstate in the treatment of grade I and II obesity (ClinicalTrials.gov identifier: NCT00555074).

METHODS

Prospective, randomized, placebo-controlled, double-blind, proof-of-concept study was carried out. Following a 2-week lead-in period, 30 obese (body mass index, BMI 30.0-39.9 kg/m(2)), non-diabetic subjects were randomized to receive either sodium tungstate (100 mg bid) or placebo for 6 weeks. The primary study endpoint was the absolute change in body weight relative to the time of randomization.

RESULTS

Treatment with sodium tungstate [-0.135 ± 0.268 kg (95% CI -0.686 to +0.416 kg)] was not associated with a significant weight loss compared to placebo [-0.063 ± 0.277 kg (95% CI -0.632 to +0.507 kg)] (p = 0.854). Likewise, treatment with sodium tungstate was not associated with significant changes in fat mass (DEXA), resting energy expenditure (indirect calorimetry) or caloric consumption (3-day food records).

CONCLUSION

Our data do not support sodium tungstate as a pharmacological agent in the treatment of human obesity.