Ebselen exhibits glycation-inhibiting properties and protects against osmotic fragility of human erythrocytes in vitro.

Diabetic status is associated with an increase on oxidative stress markers in humans and animal models. We have investigated the in vitro effects of high concentrations of glucose on the profile of oxidative stress and osmotic fragility of blood from control and diabetic patients; we considered whether its antioxidant properties could afford some protection against glucose-induced osmotic fragility, and whether ebselen could act as an inhibitor of hemoglobin glycation. Raising blood glucose to 5-100 mmol/L resulted in a concentration-dependent increase of glycated hemoglobin (HbA1c; P < 0.001) and thiobarbituric acid reactive species (TBA-RS) content (P < 0.004). Non-protein SH groups (NPSH) also increased significantly as the concentration of glucose increased up to 30 mmol/L (P < 0.001). The osmotic fragility was more pronounced in blood of uncontrolled diabetic patients than in these non-diabetic subjects. Ebselen significantly reduced the glucose-induced increase in osmotic fragility and inhibited HbA1c formation (P < 0.0001). These results indicate that blood from patients with uncontrolled diabetes are more sensitive to osmotic shock than from patients with controlled diabetes and control subjects in relation to increased production of free radicals in vivo.

Long-term sucrose and glucose consumption decreases the delta-aminolevulinate dehydratase activity in mice.

OBJECTIVE: This study evaluated the long-term effects of high-glucose (GLU) and high-sucrose (SUC) diets on the development of obesity, abdominal fat deposition, glucose intolerance, oxidative stress and effects on delta-aminolevulinate dehydratase (delta-ALA-D) activity in various organs. In particular, the effect of aging on these parameters was evaluated. METHODS: Mice were assigned to a baseline, control, or experimental group. The control group was provided with tap water and experimental groups with solutions of glucose or sucrose for 30 wk. To verify the effect of aging, young mice (baseline group, 8 wk old) were compared with aged animals (control and experimental groups, 38 wk old). RESULTS: Consumption of GLU or SUC diets caused increases in body weight, abdominal fat index, and fasting plasma glucose levels. A positive correlation was observed between the abdominal fat index and fasting glucose levels. There was a significant increase in levels of thiobarbituric acid-reactive species (TBARS) and a significant decrease in delta-ALA-D activity in various tissues of GLU and SUC feeding mice. Importantly, the dithiothreitol-induced enzymatic reactivation in the GLU and SUC groups was significantly higher than in the control group, and in the aged group it was significantly higher than in the baseline group. After 30 wk, the experimental groups had a decrease in delta-ALA-D activity and an increase in TBARS levels in relation to the baseline group. CONCLUSION: Alterations in the activity of the delta-ALA-D found in this work demonstrate the possible contributions of hyperglycemia and aging for protein oxidation, leading to impairment of its biologic function.

Diphenyl diselenide and 2,3-dimercaptopropanol increase the PTZ-induced chemical seizure and mortality in mice.

The aim of the present study was to evaluate the interaction between a classic GABAergic antagonist -- pentylenetetrazol (PTZ) with an organoselenium compound -- diphenyl diselenide (PhSe)(2) and with the metal chelating agent -- 2,3 dimercaptopropanol (BAL). Mice were pre-treated with 150 micromol/kg (PhSe)(2) or BAL (250, 500 or 1000 micromol/kg) before treatment with PTZ. Pre-treatment with (PhSe)(2) reduced the latency for PTZ-induced seizure at doses of 40 and 60 mg/kg and cause a decrease in the latency for PTZ-induced death at the dose of 60 mg/kg. However, treatment with PTZ at dose of 80 mg/kg was not affected by (PhSe)(2) pre-treatment. Pre-treatment with BAL reduced the latency for PTZ-induced seizure at doses of 40 and 50 mg/kg. In addition, the latency for PTZ-induced death at the dose of 40 mg/kg was decreased significantly by pre-treatment with all doses of BAL. At the dose of 50mg/kg, a significant decrease in the latency for death occurred only in mice pre-treated with 500 and 1000 micromol/kg of BAL. Our results indicate that the PTZ-induced chemical seizures and mortality was enhanced by (PhSe)(2) and BAL. These results indicated that (PhSe)(2) and BAL interact with PTZ possibly by modulating the GABAergic system.

A high fat diet inhibits delta-aminolevulinate dehydratase and increases lipid peroxidation in mice (Mus musculus).

The aim of this study was examine the effects of high starch (HS) vs. high fat (HF) feeding on blood glycated hemoglobin (GHbA(1c)) level, thiobarbituric acid-reactive species (TBA-RS) concentration and delta-aminolevulinate dehydratase (delta-ALA-D) activity in mice. The GHbA(1c) level was significantly higher in mice fed the HF diet compared with those fed the HS diet. Hepatic, renal, and cerebral TBA-RS concentrations in mice fed the HF diet were significantly greater than in mice fed the HS diet. In addition, positive correlations were found between the GHbA(1c) and TBA-RS levels for hepatic (P < 0.05; r = 0.46), renal (P < 0.003; r = 0.65), and cerebral (P < 0.001; r = 0.69) tissues. The delta-ALA-D hepatic, renal and cerebral activities of mice fed the HF diet were significantly lower than those of mice fed the HS diet. Furthermore, a negative correlation was found between the GHbA(1c) level and delta-ALA-D activity in hepatic (P < 0.001; r = -0.77), renal (P < 0.007; r = -0.60), and cerebral (P < 0.007; r = -0.60) tissues. The results of this study indicate that consumption of a high fat diet promotes oxidative stress related to hyperglycemia, which in turn can stimulate glycation of proteins leading to delta-ALA-D inhibition in mice.

Influence of dietary selenium supplementation and exercise on thiol-containing enzymes in mice.

OBJECTIVE: Exercise markedly increases oxygen uptake by active muscles and consequently increases generation of reactive oxygen species. A dietary deficiency in selenium (Se) can increase the sensitivity of the living system to oxidative stress. delta-Aminolevulinate dehydratase (delta-ALA-D), succinate dehydrogenase (SDH), and lactate dehydrogenase (LDH) are sulfhydryl-containing enzymes, and their activities are sensitive to the presence of oxidizing agents. We investigated the effect of Se deficiency and supplementation on delta-ALA-D, SDH, and LDH activities in mice subjected to swim training for 8 wk. METHODS: Three-month-old female mice were randomly assigned and fed a basal diet, a basal diet plus 1 ppm of Se, and a basal diet plus 40 ppm of Se. These groups were further divided into sedentary and swim-trained groups. A mass equivalent of 5% of the animal's body weight was fixed to the tail. Animals were then exercised for 60 min/d, 4 d/wk. RESULTS: Swim-training associated with Se-deficient diet diminished delta-ALA-D activity in the livers and kidneys. SDH activity was diminished in the skeletal and cardiac muscles of this group. CONCLUSIONS: These results indicated that exercise associated with dietary Se deficiency can inhibit the production of thiol-containing enzymes, delta-ALA-D and SDH, from different tissues; however, LDH activity was not changed. The decrease in enzyme activities can be tentatively attributed to oxidation of thiol groups by the reactive oxygen species produced by exercise.

Oxidative stress in mice is dependent on the free glucose content of the diet.

In animals, chronic intake of diets with high proportions of rapidly absorbable glucose promotes the development of insulin resistance. High levels of glucose can produce permanent chemical alterations in proteins and lipid peroxidation. delta-Aminolevulinate dehydratase (delta-ALA-D) is a sulfhydryl-containing enzyme essential for all aerobic organisms and is highly sensitive to the presence of pro-oxidants elements. The heme synthetic pathway is impaired in porphyria and a frequent coexistence of diabetes mellitus and porphyria disease has been reported in humans and experimental animal models, which can be casually linked to the delta-ALA-D inhibition found in diabetics. The present study was designed to evaluate the effect of two different diets, a high glucose (HG) diet and a high starch (HS) diet, on lipid peroxidation levels in different tissues (brain, liver, and kidney) and on delta-ALA-D activity (from liver and kidney) in mice. Plasma glucose and triglyceride levels were significantly higher in mice fed HG than in mice fed HS (P < 0.02 and P < 0.03, respectively). Thiobarbituric acid reactive species (TBA-RS) content was significantly increased in kidney and liver from HG diet-fed mice when compared with animals fed HS diets (P < 0.001). Hepatic delta-ALA-D activity of HG diet-fed animals was significantly lower than that of HS diet-fed animals (P < 0.01). The results of this study support the hypothesis that consumption of a diet with high free glucose can promote the development of oxidative stress that we tentatively attribute to hyperglycemia.