Total Taurine Research Articles

Taurine reduces the risk for metabolic syndrome: a systematic review and meta-analysis of randomized controlled trials

BackgroundMetabolic syndrome (MetS) is a cluster of interconnected risk factors that significantly increase the likelihood of cardiovascular disease and type 2 diabetes. Taurine has emerged as a potential therapeutic agent for MetS. This meta-analysis of randomized controlled trials (RCTs) aimed to evaluate the effects of taurine supplementation on MetS-related parameters.MethodsWe conducted electronic searches through databases like Embase, PubMed, Web of Science, Cochrane CENTRAL, and ClinicalTrials.gov, encompassing publications up to December 1, 2023. Our analysis focused on established MetS diagnostic criteria, including systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting blood glucose (FBG), triglyceride (TG), and high-density lipoprotein cholesterol (HDL-C). Meta-regression explored potential dose-dependent relationships based on the total taurine dose administered during the treatment period. We also assessed secondary outcomes like body composition, lipid profile, and glycemic control.ResultsOur analysis included 1024 participants from 25 RCTs. The daily dosage of taurine in the studies ranged from 0.5 g/day to 6 g/day, with follow-up periods varying between 5 and 365 days. Compared to control groups, taurine supplementation demonstrated statistically significant reductions in SBP (weighted mean difference [WMD] = −3.999 mmHg, 95% confidence interval [CI] = −7.293 to −0.706, p = 0.017), DBP (WMD = −1.509 mmHg, 95% CI = −2.479 to −0.539, p = 0.002), FBG (WMD: −5.882 mg/dL, 95% CI: −10.747 to −1.018, p = 0.018), TG (WMD: −18.315 mg/dL, 95% CI: −25.628 to −11.002, p < 0.001), but not in HDL-C (WMD: 0.644 mg/dl, 95% CI: −0.244 to 1.532, p = 0.155). Meta-regression analysis revealed a dose-dependent reduction in DBP (coefficient = −0.0108 mmHg per g, p = 0.0297) and FBG (coefficient = −0.0445 mg/dL per g, p = 0.0273). No significant adverse effects were observed compared to the control group.ConclusionTaurine supplementation exhibits positive effects on multiple MetS-related factors, making it a potential dietary addition for individuals at risk of or already experiencing MetS. Future research may explore dose-optimization strategies and potential long-term benefits of taurine for MetS management.

Gender-Specific Bile Acid Profiles in Non-Alcoholic Fatty Liver Disease.

Non-alcoholic fatty liver disease (NAFLD) is increasing worldwide. A main cause is the obesogenic, so-called Western lifestyle. NAFLD follows a long, unperceived course, and ends potentially fatally. Early diagnosis of aggressive subtypes saves lives. So far, non-invasive means of detection are limited. A better understanding of the pathogenic interplay among insulin resistance, immune inflammation, microbiome, and genetic background is important. Metabolomics may give insight into these interlaced processes. In this study, we measured bile acids (BA) in the plasma of adult NAFLD and alcohol-associated liver disease (ALD) patients and healthy controls with targeted mass spectrometry. We focused on gender-related bile acid production pathology in NAFLD and ALD. Compared to healthy controls, women with NAFLD had significantly higher concentrations of total BA, total primary BA, total cholic (CA), total chenodeoxycholic (CDCA), total glycine-conjugated, and total non-12-a-OH BA. Concerning subtypes, glycocholic (GCA) and glycochenodeoxycholic (GCDCA), BA were elevated in women with NAFLD. In contrast, men with NAFLD had no significantly altered total BA fractions. However, the subtypes GCA, glycodeoxycholic (GDCA), glycolithocholic (GLCA), lithocholic (LCA), taurolithocholic (TLCA), and tauroursodeoxycholic acid (TUDCA) were elevated, while CA was significantly decreased. In NAFLD, except ursodeoxycholic acid (UDC), all total BA correlated significantly positively in both sexes with the ELF score, while in ALD, only males showed significant correlations exceptive for total UDC BA. In NAFLD, total BA, total primary BA, total secondary BA, total free secondary BA, total CA, total CDCA, total taurine conjugated, total glycine conjugated, total 12-a-OH, and total non-12-a-OH were significantly higher in cases of a high enhanced liver fibrosis (ELF) score above 9.8. In ALD, total UDC was additionally elevated. Between NAFLD with and without NASH, we found no significant differences. Our data show gender-specific bile acid profiles in NAFLD and markedly different BA patterns in ALD. Women with NAFLD had more severe cholestasis. Men may better compensate fat storage-driven bile acid dynamics, indicated by higher levels of taurine-conjugated BA, which associate with beneficial metabolic functions.

Dietary Soybean Protein Decreases Plasma Taurine in Cats

Commercial dry and canned diets fed to cats cause ∼two- and fourfold increase in the taurine requirement, respectively, as compared with that observed for purified diets. In two experiments, the effect of source and level of protein and fiber in the diet on the concentration of taurine in plasma and whole blood of cats was studied. All diets contained 1 g taurine/kg dry matter. When a casein-based diet containing either 25% or 50% protein was given to cats for 6 wk, no difference in plasma taurine concentration was observed; however, substituting soybean protein for casein resulted in a significant (P < 0.01) decrease in plasma taurine concentration of cats in the 50% soybean protein group, but not in the 25% soybean protein group. In Experiment 2, the food intake of cats was limited [26 g dry matter/(kg body weight·d)], and the protein was 30 or 60% of the diet. Cats fed 60% soybean protein or casein diets had significantly lower plasma taurine concentrations than cats fed a 30% casein diet, with the 60% soybean protein diet causing the greater decrease. There was no effect of either 2 or 4% soybean fiber on plasma taurine concentration as compared with the same diet without the added fiber. The taurine concentration in plasma was higher (P < 0.05) in male cats than in female cats. Protein source, amount in the diet and gender did not affect the whole blood taurine concentration. Cats given diets containing 60% casein or soybean protein diets excreted a greater amount of fecal total bile acid and total taurine than cats given a 30% casein diet. Cats with higher plasma concentrations of taurine excreted a greater amount of free taurine in urine, and a lesser amount of taurine and bile acids in feces. These results show that although protein source (soybean protein) and the quantity in the diet have a significant effect on the excretion pattern of taurine by cats, these effects are not sufficient to account for the marked increase in the taurine requirement found when canned heat-processed diets are fed.

Effects of taurine supplementation on growth performance and feed utilization in aquatic animals: A meta-analysis

Evidence from many studies indicates that taurine addition may yield an influence on growth in aquaculture animals. Nevertheless, the application efficacy of taurine remains inconsistent across studies. This meta-analysis was conducted to quantify the effects of dietary taurine supplementation on response variables in aquaculture animals, including final body weight (FBW), feed conversion ratio (FCR) and protein efficiency ratio (PER). Hedges' g effect size was computed to quantify the primary outcomes. The sensitivity and subgroup analyses were conducted to assess the robustness of the pooled estimates. Additionally, the effect of different moderators and variability across species was determined by several analyses. Meta-regression was conducted to appraise the effect of different taurine inclusion in diet and taurine content in basal diet on the response variables. The results indicated that taurine supplementation in the diets significantly increased FBW and PER and decreased FCR in fish. Moreover, taurine inclusion yielded larger effects on growth and feed utilization in marine fishes than freshwater fishes. For all species, ‘species’ and ‘basal taurine content in control group’ were two significant moderators on all response variables, and ‘fishmeal content in diet’ as moderator variable was significant in FBW and PER. Interestingly, the beneficial effect of taurine addition on growth performance and feed utilization was significantly reduced as the taurine level in the basal diet increased. In addition, dietary taurine requirement of aquaculture animals was estimated to 0.79% based on broken line regression between total taurine content in diet and FBW effect size.

Changes in the faecal bile acid profile in dogs fed dry food vs high content of beef: a pilot study

BackgroundDogs are fed various diets, which also include components of animal origin. In humans, a high-fat/low-fibre diet is associated with higher faecal levels of bile acids, which can influence intestinal health. It is unknown how an animal-based diet high in fat and low in fibre influences the faecal bile acid levels and intestinal health in dogs. This study investigated the effects of high intake of minced beef on the faecal bile acid profile in healthy, adult, client-owned dogs (n = 8) in a 7-week trial. Dogs were initially adapted to the same commercial dry food. Thereafter, incremental substitution of the dry food by boiled minced beef over 3 weeks resulted in a diet in which 75% of each dog’s total energy requirement was provided as minced beef during week 5. Dogs were subsequently reintroduced to the dry food for the last 2 weeks of the study. The total taurine and glycine-conjugated bile acids, the primary bile acids chenodeoxycholic acid and cholic acid, and the secondary bile acids lithocholic acid, deoxycholic acid (DCA) and ursodeoxycholic acid (UDCA) were analysed, using liquid chromatography–tandem mass spectrometry.ResultsThe faecal quantities of DCA were significantly higher in dogs fed the high minced beef diet. These levels reversed when dogs were reintroduced to the dry food diet. The faecal levels of UDCA and taurine-conjugated bile acids had also increased in response to the beef diet, but this was only significant when compared to the last dry food period.ConclusionsThese results suggest that an animal-based diet with high-fat/low-fibre content can influence the faecal bile acids levels. The consequences of this for canine colonic health will require further investigation.

Past Taurine Intake Has a Positive Effect on Present Cognitive Function in the Elderly.

This study investigated the associations between dietary history of past taurine intake and cognitive function in the elderly. Subjects of this study were 40 elderly persons with dementia (men 14, women 26) and 37 normal elderly persons (men 5, women 32). Data were collected using questionnaires by investigator-based interview to the elderly and family caregivers. We examined their general characteristics, anthropometric data, cognitive function, and taurine index. Cognitive function was measured using MMSE-DS and higher score means better cognitive function. As dietary history of past taurine intake, taurine index was evaluated by scoring the intake frequency of 41 kinds of taurine-containing foods. Part correlation analysis (sex, age, and school educational period correction) was used to analyze associations between taurine index and cognitive function. The analysis of all data was carried out by the SPSS 20.0 program for windows. The age, height, weight, and BMI of elderly with dementia showed no statistical significance compared to normal elderly. The elderly with dementia had significantly higher school education period (7.4 years) than the normal elderly (4.8 years) (p<0.01). Nevertheless, the average total score of cognitive function (MMSE-DS) of the elderly with dementia (18.1 points) was significantly lower than score of the normal elderly (21.7 points) (p<0.05). The average taurine index of the elderly with dementia (104.7 points) was significantly lower than average taurine index of the normal elderly (123.7 points) (p<0.01). There were positive correlations between total taurine index and total score of cognitive function in all the elderly subjects (p<0.05). In particular, as taurine index was higher, there were significantly higher scores of cognitive function such as 'time orientation' and 'judgement and abstract thinking' (p<0.01). In conclusion, these results suggest that past taurine intake may have a positive effect on present cognitive function in the elderly.

Su1252 Gastric Juice Composition and Acid Suppression in Pediatric Gastroesophageal Reflux Disease

INTRODUCTION: Gastric acid suppression is justified to prevent severe gastro esophageal reflux (GER) disease related complications. However, it does not reduce the total amount and proximal extent of GER in the esophagus and non-acid components are able to induce (extra-esophageal) GER symptoms as well. No data on the composition of gastric juice (GJ) in children using gastric acid suppression exists. We therefore aimed to assess whether the composition of gastric juice in children using proton pump inhibitors (PPIs) differs, compared to that of their controls. METHODS: Infants and children (0-18 years) on proton pump inhibitors (PPIs) for at least six weeks and a control group not using anti reflux medication, were included. GJ was obtained through an existing nasogastric or a percutaneous endoscopic gastrostomy tube/ Mic-key gastrostomy. In the collected GJ (5 ml), pH, pepsin activity, bile salts and endotoxin (LPS) levels were determined. Pepsin was measured using a fluorometric assay using 4-Methyl-Coumaryl-7-Amide (MCA) substrate with/without pepstatin. Concentrations of deconjugated and taurine/glycine-conjugated bile salts were assessed by reversephase HPLC. Levels of LPS were determined using the spectrophotometric Limulus Amebocyte Lysate assay. RESULTS: GJ was analyzed from 16 children with (median: 3.8 yrs, range: 17.6 years) and 16 children (4.0 yrs, range: 16.0) without PPI therapy. Median duration of PPI treatment was 24 weeks (range: 514 weeks). Gastric pH was 5.0 (range: 5.0) and 1.0 (range: 4.5) in the PPI and control group respectively (p <0.001). Pepsin, unconjugated bile salts, and endotoxin were not significantly different in the two groups. Total taurine conjugated bile salts, and specifically taurocholate, was significantly higher in the PPI group (p=0.01 and p=0.005). pH and concentration of deconjugated bile and conjugated bile salts were significantly associated (p=0.006 and p=0.02). Endotoxin and bile salts were not significantly associated. CONCLUSION: Taurine conjugated bile acids are significantly higher in children chronically using PPIs compared to controls. Moreover acidity of gastric pH correlated negatively with deconjugated and conjugated bile salts. These findings imply that GJ under chronic proton pump inhibition contains nonacid components potentially harmful to esophageal mucosa and bronchial tissue.

Su1253 Abnormal Dynamics of Endogenous Acylated Ghrelin Mediates Decreases in Gastric Phase III-Like Contraction, Leading to Delayed Gastric Emptying in Urocortin1-Induced Stress Rats

INTRODUCTION: Gastric acid suppression is justified to prevent severe gastro esophageal reflux (GER) disease related complications. However, it does not reduce the total amount and proximal extent of GER in the esophagus and non-acid components are able to induce (extra-esophageal) GER symptoms as well. No data on the composition of gastric juice (GJ) in children using gastric acid suppression exists. We therefore aimed to assess whether the composition of gastric juice in children using proton pump inhibitors (PPIs) differs, compared to that of their controls. METHODS: Infants and children (0-18 years) on proton pump inhibitors (PPIs) for at least six weeks and a control group not using anti reflux medication, were included. GJ was obtained through an existing nasogastric or a percutaneous endoscopic gastrostomy tube/ Mic-key gastrostomy. In the collected GJ (5 ml), pH, pepsin activity, bile salts and endotoxin (LPS) levels were determined. Pepsin was measured using a fluorometric assay using 4-Methyl-Coumaryl-7-Amide (MCA) substrate with/without pepstatin. Concentrations of deconjugated and taurine/glycine-conjugated bile salts were assessed by reversephase HPLC. Levels of LPS were determined using the spectrophotometric Limulus Amebocyte Lysate assay. RESULTS: GJ was analyzed from 16 children with (median: 3.8 yrs, range: 17.6 years) and 16 children (4.0 yrs, range: 16.0) without PPI therapy. Median duration of PPI treatment was 24 weeks (range: 514 weeks). Gastric pH was 5.0 (range: 5.0) and 1.0 (range: 4.5) in the PPI and control group respectively (p <0.001). Pepsin, unconjugated bile salts, and endotoxin were not significantly different in the two groups. Total taurine conjugated bile salts, and specifically taurocholate, was significantly higher in the PPI group (p=0.01 and p=0.005). pH and concentration of deconjugated bile and conjugated bile salts were significantly associated (p=0.006 and p=0.02). Endotoxin and bile salts were not significantly associated. CONCLUSION: Taurine conjugated bile acids are significantly higher in children chronically using PPIs compared to controls. Moreover acidity of gastric pH correlated negatively with deconjugated and conjugated bile salts. These findings imply that GJ under chronic proton pump inhibition contains nonacid components potentially harmful to esophageal mucosa and bronchial tissue.

Higher circulating bile acid concentrations in obese patients with type 2 diabetes

Bile acids (BAs) play an important role in releasing incretin hormones via the enteroendocrine L-cell surface TGR5 receptors. The aim of this study was to investigate the difference in BA concentration at baseline and in response to a meal stimulus between type 2 diabetes mellitus (T2DM) and a matched normoglycaemic group. A cross-sectional study of 12 patients with known T2DM and 12 matched normoglycaemic controls compared BA fractions after an overnight fast and following a standard meal. The T2DM group had higher baseline glucose (P < 0.001), but baseline total BA, total glycine conjugated BAs (GCBA) and total taurine conjugated BA (TCBA) were similar between both groups. The T2DM group compared to the normoglycaemic group had a higher post-prandial peak change in total BAs 4.28 (3.51-5.38) µmol/L vs. 0.88 (0.60-1.57) µmol/L (P < 0.001) and peak total GCBA 2.77 (1.07-4.19) µmol/L vs. 0.94 (0.34-1.15) µmol/L (P < 0.0001), but similar peak total TCBA 0.36 (0.02-0.76) µmol/L vs. 0.08 (0.04-0.22) µmol/L (P=0.91). The post-prandial bile acid response is elevated in obese patients with T2DM compared to matched normoglycaemic individuals.

Metabolomic profiling of 17 bile acids in serum from patients with primary biliary cirrhosis and primary sclerosing cholangitis: A pilot study

BackgroundPrimary biliary cirrhosis and primary sclerosing cholangitis are two cholestatic diseases characterised by hepatic accumulation of bile acids. AimsThis study compares serum bile acid levels in patients with primary biliary cirrhosis and primary sclerosing cholangitis and from age and sex-matched non cholestatic donors. MethodsSeventeen bile acids were quantified using liquid chromatography coupled to tandem mass spectrometry. Serum samples from cholestatic patients were compared with those of non-cholestatic donors. ResultsThe concentration of total bile acids, taurine and glycine conjugates of primary bile acids was elevated in both patients with primary biliary cirrhosis and primary sclerosing cholangitis when compared to non-cholestatic donors. Samples from primary sclerosing cholangitis patients displayed reduced levels of secondary acids, when compared to non cholestatic and primary biliary cirrhosis sera. The ratio of total glycine versus total taurine conjugates was reduced in patients with primary biliary cirrhosis, but not in primary sclerosing cholangitis. ConclusionThe present study suggests that circulating bile acids are altered differentially in primary biliary cirrhosis and primary sclerosing cholangitis patients.

Absorption, tissue distribution, metabolism and elimination of taurine given orally to rats

Three biodisposition studies with taurine were performed in male and female adult rats at dosages of 30 and 300 mg/kg. A single oral dose of (14)C-taurine was rapidly absorbed, distributed to tissues and excreted unchanged in urine. Elimination of radioactivity from intracellular pools was slow. Pre-treatment of animals for 14 days with unlabelled taurine did not significantly affect the fate of (14)C-taurine. At the higher dose there was more extensive excretion combined with a lower percentage of the dose in the carcass, indicating the possibility of saturation of the tubular reabsorption mechanism for taurine. Daily administration of unlabelled taurine for 14 days did not result in an increase in total taurine in the brain. The data indicate that exogenous taurine rapidly equilibrates with endogenous body pools and that any excess is rapidly eliminated by the kidneys.

One‐step analysis of major bile components in human bile using 1H NMR spectroscopy

Human gallbladder bile dissolved in dimethylsulfoxide provides sharp and resolved signals for major bile components in 1H NMR spectra. Characteristic well-resolved marker signals that invariably appear in 1H NMR spectra of bile were identified for cholesterol (H18 methyl signal at 0.643 ppm), lipids (glycerol CH signal at 5.064 ppm), total bile acids (H18 signals in the range 0.520-0.626 ppm), total glycine conjugated bile acids (NH signal at 6.958 ppm), total taurine conjugated bile acids (NH signal at 7.646 ppm), and urea (NH2 signal near 5.48 ppm), which enabled their rapid and accurate analysis. Excellent linearity and precision of quantitative analysis was observed for all the identified bile components (R2 > 0.99 for all). The method was demonstrated on gallbladder bile from 19 patients with gallbladder diseases. Urea in bile was identified by NMR for the first time and its quantitative analysis, along with several other bile components, is presented. The majority of the bile components could be analyzed in a single step. Accurate and rapid quantification of several bile components noninvasively by using the method presented herein may have far-reaching implications in the study of bile acid metabolism and pathophysiology of various hepatobiliary and gastrointestinal diseases.

Taurine-induced long-lasting potentiation in the rat hippocampus shows a partial dissociation from total hippocampal taurine content and independence from activation of known taurine transporters.

Perfusion with high millimolar levels of taurine evoked a long-lasting potentiation (LLP-TAU) of synaptic transmission in the Schaffer-collateral CA1 region of the rat hippocampus. Although LLP-TAU showed some correlations to increases in the total taurine content of hippocampal slices, it could not be blocked by the taurine transport inhibitor guanidinoethanesulfonic acid (GES), which was able to significantly reduce total slice taurine uptake. Inhibition of GABA transport by either nipecotic acid or beta-guanidinopropionate failed to abolish LLP-TAU and had no significant effect on taurine uptake. The combination of GES and nipecotic acid also had no significant effect on LLP-TAU. Experiments with transportable structural analogs of taurine (beta-aminoisobutyric acid, homotaurine, and isethionic acid) suggest that activation of classical taurine transport pathways does not always yield a robust LLP-TAU. Hippocampal LLP-TAU could be significantly attenuated, however, by pre-incubation with submillimolar levels of taurine. In summary, the development of LLP-TAU in the rat hippocampus appears to be associated with the intracellular accumulation rather than the activation of known transporters of taurine, but the precise means of its accumulation remains to be identified.

A study on the estimation of sulfur-containing amino acid metabolism by the determination of urinary sulfate and taurine.

Sulfate and taurine are major end products of sulfur-containing amino acid metabolism in mammals including humans, and they are excreted in urine. Average excretions micromol/mg of creatinine) in the morning urine of 58 female college students were: total (free plus ester) sulfate (a). 12.53 +/- 3.85; free sulfate, 11.57 +/- 3.69; taurine, 0.78 +/- 0.53. Ratio of total sulfate and taurine was 10 : 0.6. Regression lines obtained by plotting total sulfate, free sulfate, or total sulfate plus taurine against urea have shown that the former excretions are significantly correlated with urea excretion. Excretion of total sulfate at zero point of urea excretion (b). was 5.30, which corresponded to 42.3% of average excretion (12.53) and was assumed to be derived from dietary sulfate. The difference 7.23 (a - b) seemed to be derived from sulfur-containing amino acids. It was pointed out that the difference of average sulfate excretion and sulfate excretion at zero urea excretion, namely a - b, was appropriate for the metabolic index of sulfur-containing amino acids of the group examined. As free sulfate constituted 92.3% of total sulfate, excretion of ester sulfate was at a constant level, and that of taurine was not significantly correlated with urea excretion, the value of free sulfate corresponding to the value a - b of total sulfate mentioned above seemed to be a reliable and convenient index in the assessment of sulfur-containing amino acid metabolism.

DIFFERENT PHYSIOLOGICAL MECHANISMS CONTROL ISOVOLUMETRIC REGULATION AND REGULATORY VOLUME DECREASE IN CHICK EMBRYO CARDIOMYOCYTES

Cultured chick embryo cardiac myocytes submitted to a 180mOsm/kg hyposmotic solution swell present a regulatory volume decrease (RVD). This RVD is mediated by a Ca2+influx followed by a 40% loss of total taurine content accompanied by the loss of lesser amounts of other osmolytes. Kidney cells respond to a gradual change in osmolality by maintaining their volume at the initial level. This is termed isovolumetric regulation (IVR), which may activate regulatory processes other than those observed with sudden changes in osmolality. When cardiac myocytes were exposed to a gradual change in osmolality, they show a partial IVR which is not dependent upon extracellular Ca2+. Potassium channel blockers, quinidine and Ba2+, and the chloride channel blocker, diphenylamine-2-carboxylate (DPC), compromise IVR in our model. Tritiated taurine loss and total intracellular K+contents were analyzed in cultured cardiomyocytes submitted to a gradual change in osmolality. The cultured cells lost approximately 10% of their taurine and 35% of their total K+. These findings suggest that different compensatory mechanisms are activated when cells are exposed to stepwise and gradual changes in osmolality. Inorganic osmolytes (through conductive pathways) are preferentially mobilized during the physiological and/or patho-physiological IVR situation, perhaps reflecting energetic conservation in response to a less traumatic event for the cardiac myocytes.

Determination of Total Taurine in Pet Foods by Liquid Chromatography of the Dansyl Derivative: Collaborative Study

A liquid chromatographic (LC) method for the determination of total taurine in pet foods was evaluated in a collaborative study. Ten laboratories assayed 6 blind duplicate pairs of wet and dry pet foods. The taurine in the 6 sample pairs ranged from low (170 mg/kg) to high (2250 mg/kg) concentrations as is. Collaborators also assayed a sample of known taurine concentration for familiarization purposes. Samples were hydrolyzed to release bound taurine, which was subsequently converted to the dansyl derivative and quantitated by gradient-elution LC with fluorescence detection. Repeatability relative standard deviations, RSDr, ranged from 3.2 to 10.0%; reproducibility relative standard deviations, RSDR, ranged from 6.1 to 16.1%. The method has been adopted Official First Action status by AOAC INTERNATIONAL.

Effect of hydrazine upon vitamin B 12-dependent methionine synthase activity and the sulphur amino acid pathway in isolated rat hepatocytes

The effect of the industrial chemical, hydrazine (4–12 mM), on methionine synthase (EC 2.1.1.13) activity and levels of the sulphur amino acids homocysteine, cysteine, and taurine as well as GSH were investigated in vitro in isolated rat hepatocyte suspensions and monolayers in order to explain some of the adverse in vivo effects of hydrazine. None of the concentrations of hydrazine were overtly cytotoxic in hepatocyte suspensions (measured as lactate dehydrogenase [LDH] leakage) after 3 hr. However, after 24 hr in culture cells treated with 12 mM, hydrazine showed a significant increase in LDH leakage. Methionine synthase activity was reduced by hydrazine (8 and 12 mM) in suspensions (by 45 and 55%, after 3 hr) and monolayers (12 mM; 65–80% after 24 hr). This was not due to nitric oxide production and the inhibitor of nitric oxide synthase, N ω-nitro- l-arginine, failed to protect against the hydrazine-induced loss of ATP and GSH and the reduction in urea synthesis at 24 hr. Homocysteine export was increased by 6 mM hydrazine, and total taurine content of treated cells was increased by 12 mM hydrazine. Thus, hydrazine was found to have several important and possibly deleterious effects on some parts of the sulphur amino acid pathway.

Reliability of taurine concentrations measured in single urine samples obtained from dogs eight hours after eating

Abstract Objective To evaluate the reliability of taurine concentrations measured in a single urine sample obtained from dogs 8 hours after eating, compared with taurine concentrations measured in 24-hour urine samples. Animals 18 healthy Beagles. Procedure After emptying the urinary bladder by transurethral catheterization, dogs were fed a canned maintenance diet. Approximately 8 hours later, urine, plasma, and serum samples were obtained for determination of fractional urinary excretion of taurine and urine taurine-to-creatinine concentration ratios (Utaur:Ucr). Results were compared with 24-hour urinary taurine excretion rate. Results Unbound and total fractional urinary taurine excretion correlated well with unbound and total 24- hour urinary taurine excretion. However, bound fractional urinary taurine excretion correlated poorly with bound 24-hour urinary taurine excretion. Unbound and total Utaur:Ucr correlated well with unbound and total 24-hour urinary taurine excretion. However, bound Utaur:Ucr correlated poorly with bound 24-hour urinary taurine excretion. Conclusion and Clinical Relevance Fractional urinary excretion of unbound and total taurine, and unbound and total Utaur:Ucr are reliable indicators of 24-hour urinary unbound and total taurine excretion in healthy dogs. However, determination of 24-hour urinary taurine excretion is recommended for evaluating urinary bound taurine concentrations of dogs. (Am J Vet Res 1999;60:186–189)

Excretion of taurine and sulfate in rats fed with a low protein diet.

The effects of a low protein diet on the excretion of sulfate and taurine, major metabolites of L-cysteine in mammals, were studied in rats fed with synthetic 10% (group A) and 25% (group B) casein diets. The average excretions of total taurine (taurine plus hypotaurine) and total sulfate (free plus ester sulfate) (mumol/kg of body weight per day after the adaptation to the synthetic diet) in group A were 14.2 +/- 13.4 and 122.3 +/- 39.6, respectively, which were very low compared with 280.4 +/- 93.8 and 943.2 +/- 144.8, respectively, in group B. The taurine/sulfate ratio in group A was 0.12 +/- 0.11, which was significantly lower than that (0.30 +/- 0.08) in group B. A single intraperitoneal injection of 5 mmol of L-cysteine per kg of body weight in group A resulted in an increase in average taurine and sulfate excretion to 693.4 +/- 195.6 and 2440.6 +/- 270.0, respectively, and thus the average taurine/sulfate ratio increased to 0.29. These increases were transient and low taurine excretion resumed again 24 h after the L-cysteine administration. L-Cysteine injection in group B resulted in a similar increase in taurine and sulfate excretion, but the ratio changed only slightly (0.28). The present results suggest that in vivo production of taurine is reduced preferentially over sulfate production when sulfur amino acid supply is limited.

Hyperosmotic exposure alters total taurine quantity and cellular transport in rat astrocyte cultures

Taurine content and cellular taurine transport were characterized in astrocytes from rat cerebral cortex after growth in isoosmotic or hyperosmotic culture conditions to investigate mechanisms of taurine accumulation during conditions of increased osmolality. Total taurine content of the culture dishes was significantly ( P < 0.05) elevated after 8, 24, and 48 h of hyperosmotic exposure compared to cultures grown for the same period in isoosmotic (300 mOsm, control) conditions. Hyperosmotic medium elevated intracellular taurine (nmol/mg protein) levels by 29–108% over control cultures. Significant ( P < 0.02) increases in carrier-mediated taurine uptake rates were observed in astrocytes exposed to 350, 400, and 450 mOsm culture medium for 24 h compared to control cultures at the same time point. The increase in uptake rate decreased to control values by 48 h in 450 mOsm treated cultures. The carrier-mediated transport binding constant for taurine uptake, K m was not altered at any time after hyperosmotic treatment. Maximal velocity of uptake, V max, increased by 70% and 36% after 24 h growth in 400 and 450 mOsm culture medium, respectively, compared to control cells at the same time. After 48 h of hyperosmotic exposure, V max returned to control values. The diffusional transport rate for taurine efflux, K diff, was not affected by hyperosmotic exposure at any time point. Taurine release rates were increased by over two-fold during the first 8 h of exposure to 450 mOsm medium compared with cells grown in control conditions. After 24 and 48 h hyperosmotic exposure, release rates decreased to 44–72% of the release from control cultures. These data indicate indicate at least three mechanisms contribute to taurine accumulation in cultured cerebral astrocytes exposed to hyperosmotic conditions. These mechanisms are (i) an increased rate of taurine uptake from the extracellular space within 24 h, (ii) a decrease in net taurine efflux by 48 h, and (iii) an enhanced rate of taurine synthesis.