Tissue taurine content, activity of taurine synthesis enzymes and conjugated bile acid composition of taurine-deprived and taurine-supplemented rhesus monkey infants at 6 and 12 mo of age

Associations between serum taurine concentrations in mothers and neonates and the children's anthropometrics and early neurodevelopment: Results from the Seychelles Child Development Study, Nutrition Cohort 2

BACKGROUND

High concentrations of taurine are present in the developing human brain and maternal breast milk. Taurine is thought to influence fetal growth and brain development based on experimental rodent studies. As fish is an important dietary source of taurine, we investigated associations between taurine concentrations and child outcomes in a high fish consuming population.

OBJECTIVE

To examine associations between maternal and cord serum taurine concentrations and birth anthropometric measures and cognitive development in children at 20 months of age.

METHODS

Pregnant women were recruited between 2008 and 2011 as part of Nutrition Cohort 2 (NC2) of the Seychelles Child Development Study (SCDS). Maternal taurine serum concentrations were measured at 28 week's gestation and in cord serum. Child weight, length and head circumference were measured at birth and neurodevelopment was assessed using Bayley Scales of Infant Development II (BSID-II) at 20 months of age. Associations between taurine status, birth measures and neurodevelopmental outcomes were examined (n = 300) using regression models and adjusted for relevant covariates.

RESULTS

Mean (SD) maternal and cord taurine concentrations were 124.9 (39.2) µmol/L (range 28.2-253.9 µmol/L) and 187.6 (60.0) µmol/L (range 55.0-417.4 µmol/L) respectively. We found no associations between maternal taurine concentrations and child anthropometric and neurodevelopmental measures (weight β = -0.001, SE=0.001; length β = -0.006, SE=0.006; head circumference β = -0.002, SE=0.002; MDI β = -0.005, SE=0.015; PDI β = -0.004, SE=0.016; all P > 0.05), or between cord taurine concentrations and outcomes (weight β = -0.001, SE<0.000; length β = -0.001, SE=0.004; head circumference β < 0.000, SE=0.002; MDI β = 0.004, SE=0.010; PDI β = -0.015, SE=0.012; all P > 0.05).

CONCLUSION

The Seychellois population have high maternal and cord taurine concentrations owing to their high fish intake and may be considered taurine replete compared to individuals who consume a Westernised diet. This high taurine status may explain why there were no significant associations between maternal and cord taurine concentrations and outcomes after adjusting for covariates.

Quantification of common and planar bile acids in tissues and cultured cells

Bile acids (BAs) have been established as ubiquitous regulatory molecules implicated in a large variety of healthy and pathological processes. However, the scope of BA heterogeneity is often underrepresented in current literature. This is due in part to inadequate detection methods, which fail to distinguish the individual constituents of the BA pool. Thus, the primary aim of this study was to develop a method that would allow the simultaneous analysis of specific C24 BA species, and to apply that method to biological systems of interest. Herein, we describe the generation and validation of an LC-MS/MS assay for quantification of numerous BAs in a variety of cell systems and relevant biofluids and tissue. These studies included the first baseline level assessment for planar BAs, including allocholic acid, in cell lines, biofluids, and tissue in a nonhuman primate (NHP) laboratory animal, Macaca mulatta, in healthy conditions. These results indicate that immortalized cell lines make poor models for the study of BA synthesis and metabolism, whereas human primary hepatocytes represent a promising alternative model system. We also characterized the BA pool of M. mulatta in detail. Our results support the use of NHP models for the study of BA metabolism and pathology in lieu of murine models. Moreover, the method developed here can be applied to the study of common and planar C24 BA species in other systems.

Bile acids in drug induced liver injury: Key players and surrogate markers

Bile acid research has gained great momentum since the role of bile acids as key signaling molecules in the enterohepatic circulation was discovered. Their physiological function in regulating their own homeostasis, as well as energy and lipid metabolism make them interesting targets for the pharmaceutical industry in the context of diseases such as bile acid induced diarrhea, bile acid induced cholestasis or nonalcoholic steatohepatitis. Changes in bile acid homeostasis are also linked to various types of drug-induced liver injury (DILI). However, the key question whether bile acids are surrogate markers for monitoring DILI or key pathogenic players in the onset and progression of DILI is under intense investigation. The purpose of this review is to summarize the different facets of bile acids in the context of normal physiology, hereditary defects of bile acid transport and DILI.

Acute effects of taurine on sarcoplasmic reticulum Ca2+ accumulation and contractility in human type I and type II skeletal muscle fibers

Taurine occurs in high concentrations in muscle and is implicated in numerous physiological processes, yet its effects on many aspects of contractility remain unclear. Using mechanically skinned segments of human vastus lateralis muscle fibers, we characterized the effects of taurine on sarcoplasmic reticulum (SR) Ca2+ accumulation and contractile apparatus properties in type I and type II fibers. Prolonged myoplasmic exposure (>10 min) to taurine substantially increased the rate of accumulation of Ca2+ by the SR in both fiber types, with no change in the maximum amount accumulated; no such effect was found with carnosine. SR Ca2+ accumulation was similar with 10 or 20 mM taurine, but was significantly slower at 5 mM taurine. Cytoplasmic taurine (20 mM) had no detectable effects on the responsiveness of the Ca2+ release channels in either fiber type. Taurine caused a small increase in Ca2+ sensitivity of the contractile apparatus in type I fibers, but type II fibers were unaffected; maximum Ca2+-activated force was unchanged in both cases. The effects of taurine on SR Ca2+ accumulation 1) only became apparent after prolonged cytoplasmic exposure, and 2) persisted for some minutes after complete removal of taurine from the cytoplasm, consistent with the hypothesis that the effects were due to an action of taurine from inside the SR. In summary, taurine potentiates the rate of SR Ca2+ uptake in both type I and type II human fibers, possibly via an action from within the SR lumen, with the degree of potentiation being significantly reduced at low physiological taurine levels.

Plasma taurine as a predictor of poor outcome in patients with mild neurological deficits after aneurysmal subarachnoid hemorrhage

Object

The object of this study was to determine the relationship between plasma taurine and subarachnoid hemorrhage (SAH) outcome.

Methods

Forty patients with SAH and mild neurological deficits were included in this prospective, blinded cohort study. Plasma taurine levels were measured using high-performance liquid chromatography on admission and were correlated with patient outcomes at discharge.

Results

Twenty-five percent of the patients ultimately had a poor outcome. Plasma taurine concentrations at admission were increased (2-fold) in SAH patients with a favorable outcome and were further increased (6-fold) in those who had a poor outcome. Increased taurine levels identified patients who would be discharged with a poor outcome, with sensitivity and specificity values of approximately 80% and 100%, respectively, and positive and negative predictive values of approximately 90%. Delayed cerebral vasospasm showed an OR of 27.9 (95% CI 1.090–714.9) for a poor outcome, whereas an increased taurine concentration had an OR of 105 for a poor outcome (95% CI 8.3–1328.0, p < 0.001).

Conclusions

Increased plasma taurine concentrations on admission predict a poor outcome in SAH.

Differential regulation of TauT by calcitriol and retinoic acid via VDR/RXR in LLC-PK1 and MCF-7 cells

The interaction between taurine and the absorption of fat-soluble -vitamins, such as vitamin A and D, has been an interesting topic in the field of -nutrition science, because taurine-conjugated bile acid optimizes fat and fat-soluble vitamin absorption. However, whether the hormone calcitriol (1,25-dihydroxyvitamin D(3)) and retinoic acid regulate the expression of the TauT gene is unknown. In this study, we test the hypothesis that the TauT gene is regulated by vitamin D(3) (VD(3)) and retinoic acid (RA) via activation of the vitamin D receptor (VDR) and retinoic acid receptor (RXR). Taurine uptake, Western blotting, gene reporter assay, and immunohistochemical analysis of TauT, VDR, and RXR were used in VD(3)- and/or RA-treated LLC-PK1 and MCF-7 cells. We demonstrated that VD(3) alone had little effect on TauT expression in both LLC-PK1 and MCF-7 cells. Expression of TauT was significantly increased by RA, which was synergized by the addition of VD(3) after RXR activation in LLC-PK1 cells. In contrast, expression of TauT was significantly decreased by the combination of VD(3) and RA in MCF-7 cells. Regulation of TauT by VD(3)/RA appears to occur at the transcriptional level, as determined by a reporter gene assay of the TauT promoter. Immunohistochemical study showed that VDR and RXR were activated by VD(3) and RA, respectively, in both LLC-PK1 and MCF-7 cells. The activated VDR and RXR also colocated in nuclei of both cells, suggesting that a VDR/RXR complex is involved in the transcriptional regulation of TauT. Our results show that expression of TauT is differentially regulated by VD(3) and RA via formation of VDR and RXR complexes in the nuclei in a cell type-dependent manner.

Dietary taurine manipulations in aged male Fischer 344 rat tissue: taurine concentration, taurine biosynthesis, and oxidative markers11Abbreviations: CA, cysteic acid; CSA, cysteine sulfinic acid; CSD, cysteine sulfinic acid decarboxylase; CDO, cysteine dioxygenase; DNPH, 2,4-dinitrophenylhydrazin; DPPH, α,α-diphenyl-β-picrylhydrazyl; F344, Fischer 344; HPLC-ECD, high performance liquid chromatography with electrochemical detection; MDCK, Madin Darby canine kidney; PCA, perchloric acid; TAU, taurine; TBARS, thiobarbituric acid; and TCA, trichloroacetic acid

Taurine (TAU) is a ubiquitous sulfur-containing amino acid that has been proposed to be an antioxidant. The concentration of TAU decreases during aging, which may increase susceptibility to oxidative stress. Our study attempted to elucidate the mechanism for the age-dependent decrease in TAU content by examining TAU biosynthesis in aged rats. We also examined the effects of dietary TAU manipulations on TAU content and oxidative markers in aged male Fischer 344 (F344) rats. Adult (9 months) and aged (26 months) rats fed control diets, aged rats fed control diet and TAU-supplemented (1.5%) water, and aged rats fed a TAU-deficient diet were used. We observed a significant age-related decrease in TAU content in liver, kidney, and cerebellum. Dietary TAU supplementation increased tissue TAU content, whereas dietary TAU restriction had no effect. Enzyme-dependent TAU synthesis showed an age-dependent reduction in liver that was decreased further by TAU supplementation. Protein carbonyl content was elevated in the cerebral cortex and kidney of aged rats and was attenuated by TAU supplementation. A trend for a decrease in protein and acid-soluble thiol contents in hepatic tissue of aged rats was observed, and this was attenuated with dietary TAU supplementation. Our data show that a decrease in hepatic TAU biosynthesis may cause, in part, the observed decline in tissue TAU content in aged F344 rats, and TAU supplementation can restore TAU levels. Our study indicates that a decline in TAU content may exacerbate oxidative stress in aged rats, which can be reversed by dietary TAU supplementation.

Spinal taurine levels are increased 7 and 30 days following methylprednisolone treatment of spinal cord injury in rats

The amino acid taurine serves many functions in the nervous system serving as inhibitory neurotransmitter/neuromodulator, neurotrophin, antioxidant, and osmolyte. Taurine levels are increased following brain injury and glucocorticoid administration. Thus, the purpose of this study was to examine spinal taurine concentrations following spinal cord injury (SCI) and methylprednisolone (MP) treatment of SCI. A total of 44 adult male Sprague-Dawley rats were divided into control and lesion groups. Control rats received a T6 vertebral laminectomy while lesioned rats received a laminectomy followed by complete spinal transection. Half of the animals in each group received MP intravenously following sham-operation or SCI. Rats survived for 7 or 30 days and concentrations of taurine in spinal gray and white matter, in spinal segments both near and distant from the injury epicenter, were resolved by HPLC analysis. Taurine levels were increased 7 and 30 days following transection in spinal segments immediately adjacent to the lesion and were further elevated by MP treatment. No increases were seen in far rostral/caudal segments, and MP treatment alone had no effect on spinal taurine levels. These findings demonstrate that spinal injury results in increased taurine concentrations in spinal segments undergoing the greatest degree of cellular reactivity and tissue reorganization and that MP therapy potentiates these increases. These findings are significant in that they further characterize the effects of acute MP therapy in spinal tissue. Since taurine is thought to be involved in neuroprotection and/or regeneration following injury, the potentiation of taurine levels by MP treatment may relate to its therapeutic properties.

Taurine in pediatric nutrition

The past 20 years have seen the status of taurine change from an end product of methionine and cysteine metabolism and substance conjugated to bile acids to that of an important, and sometimes essential, nutrient. It is now added to most synthetic human infant formulas and pediatric parenteral solutions throughout the world. This article describes the research that led to this end.

Retinal morphology and visual pigment levels in 6- and 12-month-old rhesus monkeys fed a taurine-free human infant formula

Rhesus monkey infants were raised from birth until 6 or 12 months of age on a taurine-free soy protein-based human infant formula or on the same formula supplemented with taurine. An additional group received taurine-free formula until 6 months and then the supplemented diet from 6 until 12 months. The densities of rod and cone visual pigments were measured by fundus reflectometry at 6 and 12 months, and retinal morphology was then examined by light and electron microscopy. The densities of rhodopsin, measured in the near periphery after a white bleach, and of cone pigment, measured in the macula after a red bleach, were significantly reduced in the taurine-deprived monkeys at 6 months but not at 12 months. The retinas of 6-month-old taurine-deprived infants showed degenerative morphological changes in photoreceptors, particularly in cones in the foveal region, which were somewhat less severe than those seen in a previous study at 3 months of age. The prevalence and degree of these abnormalities continued to decrease with age in taurine-deprived animals, but changes persisted in some animals at 12 months. Recovery was more complete in monkeys reversed to the supplemented diet from 6 to 12 months. Thus, monkey infants are dependent on dietary taurine to maintain normal retinal structure until at least 6 months of age; the effects of taurine deprivation regress spontaneously but incompletely by 12 months.