Long-term taurine supplementation reduces mortality rate in streptozotocin-induced diabetic rats

Summary. Oxidative stress is implicated in the pathogenesis of diabetes mellitus. Taurine and vitamin E+selenium supplementation has some benefits in experimental models of diabetes mellitus. This study evaluates whether taurine and vitamin E+selenium supplementations reduce a hard end-point such as mortality due to diabetes. Streptozotocin-induced diabetic rats were fed with standard diet or taurine (5%, w/w) or vitamin E (500UI/Kg)+selenium (8mg/Kg) enriched diets. Taurine significantly decreased mortality rate (p<0.04), while vitamin E failed to increase survival. In the late phase of the disease, taurine significantly decreased glycaemia, being vitamin E ineffective. No correlation between glycaemia and survival was found. None of supplementations modified body weight. Thus, only taurine decreases the mortality rate and glycaemia. These results encourage new research in the field, since classical hypoglycaemic agents are unable to decrease mortality in diabetic patients.     

Role of taurine supplementation to prevent exercise-induced oxidative stress in healthy young men

Summary. To evaluate the protective effects of taurine supplementation on exercise-induced oxidative stress and exercise performance, eleven men aged 18–20 years were selected to participate in two identical bicycle ergometer exercises until exhaustion. Single cell gel assay (SCG assay) was used to study DNA damage in white blood cells (WBC). Pre-supplementation of taurine, a significant negative correlation was found between plasma taurine concentration before exercise and plasma thiobaribituric-acid reactive substance (TBARS) 6hr after exercise (r=–0.642, p<0.05). WBC showed a significant increase in DNA strand breakage 6hr and 24hr after exercise. Seven-day taurine supplementation reduced serum TBARS before exercise (p<0.05) and resulted in a significantly reduced DNA migration 24hr after exercise (p<0.01). Significant increases were also found in VO₂max, exercise time to exhaustion and maximal workload in test with taurine supplementation (p<0.05). After supplementation, the change in taurine concentration showed positive correlations with the changes in exercise time to exhaustion and maximal workload. The results suggest that taurine may attenuate exercise-induced DNA damage and enhance the capacity of exercise due to its cellular protective properties.     

Betaine or taurine administration prevents fibrosis and lipid peroxidation induced by rat liver by ethanol plus carbon tetrachloride intoxication

Summary. The aim of this study was to investigate the effect of betaine or taurine on liver fibrogenesis and lipid peroxidation in rats. Fibrosis was induced by treatment of rats with drinking water containing 5% ethanol and CCl₄ (2×weekly, 0.2ml/kg, i.p.) for 4 weeks. Ethanol plus CCl₄ treatment caused increased lipid peroxidation and disturbed antioxidant system in the liver. Histopathological findings suggested that the development of liver fibrosis was prevented in rats treated with betaine or taurine (1% v/v in drinking water) together with ethanol plus CCl₄ for 4 weeks. When hepatic taurine content was depleted with -alanine (3% v/v in drinking water), portal-central fibrosis induced by ethanol+CCl₄ treatment was observed to proceed cirrhotic structure. Betaine or taurine was also found to decrease serum transaminase activities and hepatic lipid peroxidation without any change in hepatic antioxidant system in rats with hepatic fibrosis. In conclusion, the administration of betaine or taurine prevented the development of liver fibrosis probably associated with decreased oxidative stress.     

Characteristics of basal taurine release in the rat striatum measured by microdialysis

Summary. Taurine is a sulfur-containing amino acid thought to be an osmoregulator, neurotransmitter or neuromodulator in the brain. Our objective was to establish how much taurine is released in the striatum and examine the mechanisms controlling extracellular taurine concentrations under resting conditions. The experiments were made on rats by microdialysis in vivo. Changes in taurine were compared with those in glutamate, glycine and the non-neuroactive amino acid threonine. Using the zero net flux approach we showed the extracellular concentration of taurine to be 25.2±5.1M. Glutamate was increased by tetrodotoxin and decreased by Ca²⁺ omission, glycine and threonine were not affected and both treatments increased extracellular taurine. The basal taurine release was increased by the taurine transport inhibitor guanidinoethanesulfonate and reduced by the anion channel blocker 4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid.     

Beneficial effects of taurine on serum lipids in overweight or obese non-diabetic subjects

Summary. Taurine has beneficial effects on lipid metabolism in experimental animals fed with high-cholesterol or high fat diets. Whether taurine benefits lipid metabolism in humans has rarely been investigated. The aim of this study was to evaluate the effects of taurine on serum lipids in overweight or obese young adults. Thirty college students (age: 20.3±1.7 years) with a body mass index (BMI) 25.0kg/m², and with no evidence of diabetes mellitus were selected and assigned to either the taurine group (n=15) or the placebo group (n=15) by double-blind randomization. Taurine 3g/day or placebo was taken orally for 7 weeks. Triacylglycerol (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and plasma glucose were measured before and after supplementation. The atherogenic index (AI) was calculated as (TC–HDL-C)/HDL-C. There were no differences in any baseline parameter between the two groups. Taurine supplementation decreased TG and AI significantly. Body weight also reduced significantly in the taurine group. These results suggest that taurine produces a beneficial effect on lipid metabolism and may have an important role in cardiovascular disease prevention in overweight or obese subjects.     

Augmented taurine release is not the mechanism of ischemic preconditioning’s cardioprotection

Summary. In ischemic preconditioning (IPC) a brief ischemic period protects the heart from a subsequent ischemic insult by an unknown mechanism. Osmotic swelling has been proposed to be a major cause of cell death when ischemic tissue is reperfused. The present study tests whether the preconditioned heart during reperfusion might release more taurine, an important osmolyte in the cardiac myocytes, to decrease cellular osmolarity, oppose swelling, and preserve viability. We collected the coronary effluent from isolated rabbit hearts for 10min before and 10min after preconditioning with 5min of global ischemia. The heart then experienced 15min of global ischemia and effluent was collected during reperfusion for 40min. A control group was studied similarly but without the preconditioning ischemia. Fifteen min of ischemia was chosen to avoid any taurine release caused by ischemic cell death. Taurine was measured with HPLC. In the IPC group there was a postischemic release over baseline of 5.09±1.51mol (approx 3.3% of the total taurine pool), whereas in the control group the release was not significantly different, 5.72±1.67mol. The percent of the taurine pool lost from each heart during reperfusion was calculated based on an assumption of a total content of 20M taurine/gm wet weight. Since the amount of taurine released by the isolated rabbit heart following ischemia was not different in preconditioned and non-preconditioned hearts, we conclude that reduced swelling through taurine release is not the mechanism of the cardioprotective effects of IPC.     

Defective remethylation of homocysteine is related to decreased synthesis of coenzymes B2 in thyroidectomized rats

Summary. We investigated the influence of hypothyroidism on homocysteine metabolism in rats, focusing on a hypothetical deficient synthesis of FAD by riboflavin kinases. Animals were allocated in control group (n=7), thyroidectomized rats (n=6), rats with diet deficient in vitamin B2, B9, B12, choline and methionine (n=7), thyroidectomized rats with deficient diet (n=9). Homocysteine was decreased in operated rats (2.6±1.01 vs. 4.05±1.0mol/L, P=0.02) and increased in deficient diet rats (29.56±4.52 vs. 4.05±1.0mol/L, P=0.001), when compared to control group. Erythrocyte-Glutathione-Reductase-Activation-Coefficient (index of FAD deficiency) was increased in thyroidectomized or deficient diet rats (P=0.004 for both). Methylenetetrahydrofolate-reductase and methionine-synthase activities were decreased in thyroidectomized rats but not in those subjected to deficient diet. Cystathionine--synthase was increased only in operated rats. Taken together, these results showed a defective re-methylation in surgical hypothyroidism, which was due in part to a defective synthesis of vitamin B2 coenzymes. This defective pathway was overcompensated by the increased Cystathionine--synthase activity.     

Taurine protected myocardial mitochondria injury induced by hyperhomocysteinemia in rats

Summary. Taurine can protect against cardiovascular diseases, whereas elevated levels of plasma homocysteine are associated with atherosclerotic and thromboembolic cardiovascular diseases. To illustrate the effects of taurine on hyperhomocysteinemia, we observed the myocardial mitochondria dysfunction in the rats with hyperhomocysteinemia induced by diet methionine loading, and the therapeutic effect of taurine. A methionine diet increased plasma homocysteine concentration (133.51±27.91mol/L vs 12.31±2.58mol/L in control, P<0.01), stimulated the production of reactive oxygen species (ROS) in the myocardial mitochondria, and inhibited the activities of mitochondrial Mn-superoxide dismutase and catalase. The ⁴⁵Ca uptake and Ca²⁺-ATPase activity in the myocardial mitochondria were significantly lowered in rats with hyperhomocysteinemia. Taurine supplements effectively attenuated the hyperhomocysteinemia-induced ROS production and inhibition of Mn-superoxide dismutase and catalase activities in the myocardial mitochondria, and increased its ⁴⁵Ca uptake and Ca²⁺-ATPase activity. Thus, taurine antagonizes the oxidative stress injury in the myocardial mitochondria induced by the hyperhomocysteinemia.     

Protective effect of taurine on the detachment of cultured cardiac fibroblasts from the substratum induced by calcium depletion

Summary. Removal of Ca²⁺ from the incubation medium of cultured rat cardiac fibroblasts causes cellular morphological changes, such as the formation of blebs, the ballooning of the cell membrane and the detachment from the culture dish. A 24hr preincubation with 20mM taurine blocked the Ca²⁺ depletion-induced detachment of the cardiac fibroblasts. However, taurine treatment did not prevent other morphological changes induced by Ca²⁺ depletion. The data suggest that taurine plays an important role in cell adhesion in the heart.     

Optimal and effective oral dose of taurine to prolong exercise performance in rat

Summary. The aim of this study was to determine the effective and optimum dose of taurine for exercise performance and to maintain tissue taurine concentration. Rats received a respective daily dose of 0, 20, 100, and 500mg/kg body weight of taurine (EC and ET-1, -2, -3 groups, respectively) for two weeks, and then, were subjected to treadmill until exhaustion. The running time to exhaustion was significantly prolonged by 25% and 50% in the ET-2 and -3 groups, respectively, compared to that in the EC group accompanied with maintenance of taurine tissue concentrations. Furthermore, the oxidative glutathione per total glutathione ratio in tissues was inhibited in the ET-2 and -3 groups whereas it was higher in the EC group than in both the no exercise and taurine-administered groups. Therefore the effective and optimal doses of oral taurine administration for two weeks on a transient exercise performance were between 100 and 500mg/kg/day.     

Evidence for expression of a single distinct form of mammalian cysteine dioxygenase

Summary. Cysteine dioxygenase (CDO) plays a critical role in the regulation of cellular cysteine concentration. Because multiple forms of CDO (23kDa, 25kDa, and 68kDa) have been claimed based upon separation and detection using SDS-PAGE/western blotting (with antibodies demonstrated to immunoprecipitate CDO), we further investigated the possibility of more than one CDO isoform. Using either rabbit antibody raised against purified rat liver CDO or against purified recombinant his₆-tagged CDO (r-his₆-CDO) and using 15% (wt/vol) polyacrylamide for the SDS-PAGE, we consistently detected the 25kDa band, but never detected a 68kDa band, in rat liver, kidney, lung and brain. Nondenatured gel electrophoresis of r-his₆-CDO yielded a molecular mass estimate of 25.7kDa and no evidence of dimerization. Mass spectrometry of r-his₆-CDO yielded two peaks with molecular masses of 24.1kDa and 24.3kDa. Anion-exchange FPLC of r-his₆-CDO also gave two peaks, with the first containing CDO that was 7.5-times as active as the more anionic form that eluted second. When the two peaks recovered from FPLC were run on SDS/PAGE, the first (more active) CDO fraction yielded two bands (perhaps as an artifact of SDS/PAGE), whereas the second (less active) CDO fraction yielded only the 23kDa band. We conclude that the physiologically active form of CDO is the 25kDa (i.e., 23.5kDa based on mass spectrometry) monomer and that this active form is probably derived by post-translational modification of the 23kDa gene product.     

Effects of culture conditions on taurine uptake by various variants of human endometrial carcinoma cells in culture

Summary. The general properties of the taurine uptake in human endometrial tumoral Ishikawa cells were similar to those usually found in other tissues. Uptake was notably affected by the oxygen pressure, being higher at the physiological pO₂ of the endometrium (40mm Hg, equivalent to 5% O₂) compared to that used under standard experimental culture conditions (160mm Hg or 20% O₂). Uptake of taurine was also density-dependent in Ishikawa cells and was significantly decreased at confluence. Uptake regulation by PKC driven phosphorylation occurs only in growing cells and not in resting cells. The taurine uptake of three Ishikawa cell lines was very different. The taurine uptake of one of the cell lines was affected by estradiol, probably through a non-genomic pathway, whereas tamoxifen had no effect in all cell lines.     

Taurine restores ethanol-induced depletion of antioxidants and attenuates oxidative stress in rat tissues

Summary. Ethanol by its property of generating free radicals during the course of its metabolism causes damage to cell structure and function. The study investigates the protective effects of the antioxidant aminoacid taurine on ethanol-induced lipid peroxidation and antioxidant status. Male Wistar rats of body weight 170–190g were divided into 4 groups and maintained for 28 days as follows: a control group and taurine-supplemented control group, taurine supplemented and unsupplemented ethanol-fed group. Ethanol was administered to rats at a dosage of 3g/kg body weight twice daily and taurine was provided in the diet (10g/kg diet). Lipid peroxidation products and antioxidant potential were quantitated in plasma and in following tissues liver, brain, kidney and heart.Increased levels of thiobarbituric acid substances (TBARS) and lipid hydroperoxides (LHP) in plasma and tissues, decreased activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were observed in hemolysate and tissues of ethanol-fed rats. The contents of reduced glutathione (GSH), -tocopherol and ascorbic acid in plasma and tissues were significantly reduced in these animals as compared to control animals. Simultaneous administration of taurine along with ethanol attenuated the lipid peroxidation process and restored the levels of enzymatic and non-enzymatic antioxidants. We propose that taurine may have a bioprotective effect on ethanol-induced oxidative stress.     

Effect of a swim training on homocysteine and cysteine levels in rats

Summary. The purpose of this study was to investigate the effects of a 8-week of swim training on total plasma homocysteine and cysteine levels in 16 male Sprague-Dawley rats aged 17 weeks. We also evaluated the activity of hepatic cystathionine -synthase (CBS), an enzyme involved in the metabolism of Hcy, the concentration of plasma glutathione, taurine, and a fraction of vitamin B6: the pyridoxal 5-phosphate (PLP). After one week of acclimatization, rats were randomly divided into two groups: 8 non-trained (NTR) and 8 trained rats (TR). Following the training period, body weight gain was lower in TR than in NTR. Plasma homocysteine did not differ among groups while significantly lower plasma cysteine and taurine levels were found in TR (157.83±8.6mol/L; 133.01±9.32mol/L; P<0.05) compared with data of NTR (176.19±4.9mol/L; 162.57±8.16mol/L; P<0.05). No significant changes in hepatic CBS activity were observed in TR compared with NTR. Moreover, values for plasma glutathione and PLP concentrations were not affected by training.These results indicate that training reduces plasma cysteine and taurine levels whereas it does not modify other studied parameters. Thus, physical training may regulate cysteine metabolism.     

Cysteine-induced hypoglycemic brain damage: an alternative mechanism to excitotoxicity

Summary. Central neural damage caused by L-cysteine (L-Cys) was first reported more than 30 years ago. Nevertheless, the exact mechanisms of L-Cys-mediated neurotoxicity are still unclear. Preliminary study in mice demonstrated that, following L-Cys injection, animals developed tachypnea, tremor, convulsions, and death in conjunction with documented hypoglycemia. The aim of the present study was to further investigate the mechanism of L-Cys-mediated hypoglycemic effect and neural damage. Neonatal ICR mice (n=6) were injected with L-Cys (0.5–1.5mg/g body weight [BW]), and their blood glucose and insulin levels were determined up to 90min following the injection. Experiments were repeated in chemically (streptozotocin [STZ]) pancreatectomized animals. Brain histology was assessed. Mice injected with L-Cys exhibited dose-dependent neurotoxicity and higher mortality as compared with controls. L-Cys (1.2–1.5mg/g BW) caused severe hypoglycemia (glucose<42mg/dl) (P<0.001). In STZ-treated (diabetic) animals, L-Cys (1.5mg/g BW) increased plasma insulin levels 2.3-fold and decreased serum glucose levels by 50% (P<0.01). Brain histology revealed destruction of as much as 51% of hippocampal neurons in the L-Cys-treated mice but not in the glucose-resuscitated animals. These findings suggest that L-Cys injection can cause pronounced hypoglycemia and central neural damage which is glucose reversible. Since L-Cys is chemically different from the other excitatory amino acids (glutamate and aspartate), L-Cys-mediated neurotoxicity may be connected to its hypoglycemic effect.     

Kinetic study of racemization of aspartyl residues in synthetic elastin peptides

Summary. We previously reported that biologically uncommon D-aspartyl residues are present in sun-damaged skin from elderly people, possibly in elastin. Here, we report the kinetics of Asp racemization in model peptides corresponding to elastin sequences from exons 6 and 26. We estimated the activation energy (E) of racemization of Asp residues, the racemization rates (RR) at 37°C and the time (t) required for the D/L ratio of Asp to approximate to 1.0 (D/L ratio of Asp=0.99) at 37°C. For an exon 6 peptide, E=29.0kcal/mol, RR=2.59×10^–2/yr and t=101.0yr. For an exon 26A peptide E=26.2kcal/mol, RR=4.27×10^–2/yr and t=61.3yr; and for a second exon 26A peptide E=25.7kcal/mol, RR=5.55×10^–2/yr and t=47.0yr. These results suggest that racemization of Asp residues in elastin could occur within a human life span. We propose that D-Asp could be a useful molecular indicators of aging.     

Nefopam inhibits calcium influx, cGMP formation, and NMDA receptor-dependent neurotoxicity following activation of voltage sensitive calcium channels

Summary. Nefopam hydrochloride is a potent non sedative benzoxazocine analgesic that possesses a profile distinct from that of anti-inflammatory drugs. Previous evidence suggested a central action of nefopam but the detailed mechanism remains unclear. We have investigated the actions of nefopam on voltage sensitive calcium channels and calcium-mediated pathways. We found that nefopam prevented N-methyl-D-aspartate (NMDA)-mediated excitotoxicity following stimulation of L-type voltage sensitive calcium channels by the specific agonist BayK8644. Nefopam protection was concentration-dependent. 47M nefopam provided 50% protection while full neuroprotection was achieved at 100M nefopam. Neuroprotection was associated with a 73% reduction in the BayK8644-induced increase in intracellular calcium concentration. Nefopam also inhibited intracellular cGMP formation following BayK8644 in a concentration-dependent manner, 100M nefopam providing full inhibition of cGMP synthesis and 58M allowing 50% cGMP formation. Nefopam reduced NMDA receptor-mediated cGMP formation resulting from the release of glutamate following activation of channels by BayK8644. Finally, we also showed that nefopam effectively reduced cGMP formation following stimulation of cultures with domoic acid, while not providing neuroprotection against domoic acid. Thus, the novel action of nefopam we report here may be important both for its central analgesic effects and for its potential therapeutic use in neurological and neuropsychiatric disorders involving an excessive glutamate release.     

Comparative residual toxicities of pesticides to the predator Agistemus industani (Acari: Stigmaeidae) on citrus in Florida

Residual toxicities of registered and selected experimental pesticides used on citrus against Agistemus industani Gonzalez (Acari: Stigmaeidae) were compared. Pesticides considered highly toxic to A. industani were: abamectin 0.15 EC at 731ml/ha+FC 435-66 petroleum oil at 46.8l/ha, pyridaben 75WP at 469g/ha, ethion 4EC at 7.01l/ha+FC 435-66 petroleum oil at 46.8l/ha, propargite 6.55 EC at 3.51l/ha, chlorfenapyr 2SC at 1.46l/ha applied alone or in combination with FC 435-66 petroleum oil at 46.8l/ha, sulphur 80DF at 16.81kg/ha, dicofol 4EC at 7.01l/ha, fenbutatin oxide 50WP at 2.24kg/ha, benomyl 50WP at 2.24kg/ha, benomyl 50WP at 1.68kg/ha+ferbam 76 GF at 5.60kg/ha, ferbam 76GF at 11.21kg/ha, neem oil 90EC at 46.8l/ha, and copper hydroxide DF (40% metallic copper) at 4.48kg metallic copper/ha+FC 435-66 petroleum oil at 46.8l/ha. Pesticides that were moderately to slightly toxic included: copper sulphate 98% at 4.48kg metallic copper/ha+FC 435-66 petroleum oil at 46.8l/ha, fenbuconazole 2F at 280ml/ha+FC 435-66 petroleum oil at 46.8l/ha, FC 435-66 petroleum oil applied alone at 46.8l/ha or 23.4l/ha, and diflubenzuron 25WP at 1.40kg/ha. Pesticides that were non-toxic included: fenbuconazole 2F at 585ml/ha, malathion 57EC at 5.85l/ha, FC 435-66 petroleum oil at 46.8l/ha, carbaryl 80S at 3.36kg/ha, chlorpyrifos 4EC at 4.68l/ha, and formetanate 92SP at 1.12kg/ha. Understanding the toxic effects of field weathered pesticides against key predacious mite species is important for effective IPM. The results of this study provide a comparison of direct and indirect toxic effects of various pesticides to A. industani under field conditions.     

Recombinant Components of the EcoRII Restriction–Modification System: Restriction Endonuclease Can Interact with DNA · RNA Duplexes

To obtain recombinant restriction endonuclease (R) and methylase (M) of the EcoRII restriction–modification system, bacterial strains overproducing their functional hexahistidine derivatives were constructed. Active full-length R·EcoRII was produced only in cells that also expressed M·EcoRII from a multicopy plasmid. Recombinant R·EcoRII bound with hybrid DNA·RNA duplexes.     

Interaction of aluminium ions with some amino acids present in human blood

Summary. The interaction of aluminium with some amino acids present in human blood was studied combining ion-chromatography (IC), atomic absorption spectrometry (AAS) and ultrafiltration (UF) techniques. An IC system for simultaneous determination of ornithine, lysine, glutamic acid, aspartic acid and tyrosine was developed. By adding aluminium to standard solutions of the amino acids and keeping the pH at 6 and 7 it was possible to verify that aluminium caused a reduction on the amino acid chromatographic signals. Similar experiment, carried out for copper showed the same behaviour (with different percentage of signal reductions) and validated the results for aluminium, considering that the interaction Cu-amino acid is well-established. The AAS analysis of sample fractions (500l) after the IC separation showed that aluminium (as copper as well) is not present in the fractions in which the amino acid peaks appear in the chromatogram. These approaches carried out with serum samples after UF showed that part of the free fraction of serum aluminium is distributed, besides other ligands, among these amino acids. It was found that in serum the affinity for aluminium followed the sequence Lys>Orn>Tyr>GluAsp.