Low Taurine Concentrations Research Articles

Gastrointestinal signs and a need for nutritional management may persist long term in dogs and cats undergoing resection of the ileocolic junction: 35 cases (2008-2020).

To evaluate the effects of ileocecocolic junction (ICJ) resection on gastrointestinal signs, biochemical parameters, and nutritional variables in dogs and cats. 20 dogs and 15 cats that underwent ICJ resection between January 2008 and June 2020. Medical records of dogs and cats that underwent ICJ resection were reviewed, and clinical signs, laboratory abnormalities, and nutritional information were obtained. Additional follow-up information was obtained by contacting primary care veterinarians or owners. A subset of dogs (n = 6) and cats (2) were evaluated in the hospital via clinical examination, clinicopathologic testing, nutritional testing, and abdominal ultrasound. Twenty dogs and 15 cats underwent resection of the ICJ for treatment of a variety of conditions. Ten of 20 dogs (50%) and 11/15 cats (73%) were reported by their owners to have a good long-term outcome based on the lack of long-term gastrointestinal signs or the ability to control gastrointestinal signs with diet and supplements alone. Despite owner-reported good outcomes, long-term diarrhea, weight loss, and muscle loss were common. Of the 6 dogs evaluated in the hospital, 3/6 (50%) had muscle loss, 2/6 (33%) had low taurine concentrations, and 1 dog each had low cobalamin, folate, 25-hydroxyvitamin D, and ionized calcium. Neither of the 2 cats evaluated in the hospital had nutritional abnormalities identified. Owners should be informed of the possibility of long-term gastrointestinal clinical signs and the potential need for long-term nutritional management after ICJ resection.

The Role of Taurine in Skeletal Muscle Functioning and Its Potential as a Supportive Treatment for Duchenne Muscular Dystrophy.

Taurine (2-aminoethanesulfonic acid) is required for ensuring proper muscle functioning. Knockout of the taurine transporter in mice results in low taurine concentrations in the muscle and associates with myofiber necrosis and diminished exercise capacity. Interestingly, regulation of taurine and its transporter is altered in the mdx mouse, a model for Duchenne Muscular Dystrophy (DMD). DMD is a genetic disorder characterized by progressive muscle degeneration and weakness due to the absence of dystrophin from the muscle membrane, causing destabilization and contraction-induced muscle cell damage. This review explores the physiological role of taurine in skeletal muscle and the consequences of a disturbed balance in DMD. Its potential as a supportive treatment for DMD is also discussed. In addition to genetic correction, that is currently under development as a curative treatment, taurine supplementation has the potential to reduce muscle inflammation and improve muscle strength in patients.

Multimodal MRI Features of Medulloblastoma with Extensive Nodularity and Activated Sonic Hedgehog: A Case Report

: Medulloblastoma with extensive nodularity (MBEN) is a rare histological subtype of medulloblastomas in very young children. It is characterized by an aggressive grape-like appearance and favorable outcomes. Herein, we report the case of a nine-month-old patient with MBEN, associated with an activated sonic hedgehog (SHH), with rare multimodal magnetic resonance imaging (MRI) features. Conventional MRI findings indicated the dense homogeneous enhancement of a large unusual gyriform mass in the cerebellar vermis and both cerebellar hemispheres. The mass showed restricted diffusion on diffusion-weighted images, low concentrations of taurine on MR spectroscopy, and a relatively low cerebral blood volume on dynamic susceptibility contrast (DSC) MR perfusion image. The patient underwent partial tumor resection, chemotherapy, and autologous blood stem cell transplantation. After treatment, the lesion rapidly regressed in the serial follow-up imaging without recurrence.

Low plasma taurine levels in English cocker spaniels diagnosed with dilated cardiomyopathy.

The aims of this study were to evaluate taurine levels in English cocker spaniels with dilated cardiomyopathy and assess their survival time and natural progression of their disease. Retrospective comparison of English cocker spaniels with dilated cardiomyopathy phenotype with and without taurine deficiency at the cardiology department of a UK academic referral centre between 2008 and 2018. Taurine plasma concentration was available in 16 English cocker spaniels with dilated cardiomyopathy phenotype; 13 of 16 had congestive heart failure and three of 16 did not. Taurine concentration was low (<50 μmol/L) in 13 of 16 and normal in three of 16. Deficient dogs received taurine supplementation in addition to conventional cardiac medications. Eight dogs were still alive at the end of this study and eight were dead. MST for all dogs included in the study was 2800 days. Left ventricular systolic function improved and left ventricular dimensions reduced in English cocker spaniels with taurine deficiency following taurine supplementation and conventional cardiac therapy, although similar results were observed in English cocker spaniels with normal taurine concentration on cardiac therapy alone. Based on laboratory reference intervals, low taurine concentrations were common in English cocker spaniels with dilated cardiomyopathy, showing a possible association between dilated cardiomyopathy in English cocker spaniels and taurine deficiency; supplementation with taurine was not curative.

High taurine concentrations negatively effect stallion spermatozoa parameters in vitro

Article Details: Received: 2020-09-29 | Accepted: 2020-11-27 | Available online: 2021-01-31 https://doi.org/10.15414/afz.2021.24.mi-prap.15-19 Over the past decades natural substances are widely used in the maintaining of spermatozoa viability. The target of present study was to evaluate the effect of various taurine concentrations on stallion spermatozoa during 37°C cultivation. Fresh semen was collected from 10 breeding stallions. The experimental groups were supplemented with six different concentration of taurine (in mg/ml): A – 2.5, B – 5, C – 7.5, D – 10, E – 15, F – 20 and compared to control (CON – 0). Spermatozoa motility was assessed using the Computer Assisted Semen Analyzer (CASA) system in 6 time periods (0, 1, 2, 3, 4 and 5 hours). The MTT test was used for detection of viability. For measuring antioxidant activity FRAP and TOS methods were used. Significantly negative effect was observed in the samples with the highest concentration of taurine (20 mg/ml). Spermatozoa viability was not significantly affected in analysed concentrations of taurine. Significant higher antioxidant activity was detected in the sample with the highest taurine concentration. Data clearly showed negative effects of high taurine concentrations on stallion spermatozoa. Keywords: taurine, CASA, antioxidant activity, spermatozoa, stallion References Benzie, I. F. and Strain, J. J. (1996). The ferric reducing ability of plasma (FRAP) as a measure of “antioxidant power”: The FRAP assay. Analytical Biochemistry , 239 (1), 70-76. https://doi.org/10.1006/abio.1996.0292 Bucak, M. N. et al. (2007). The influence of trehalose, taurine, cysteamine and hyaluronan on ram semen: Microscopic and oxidative stress parameters after freeze–thawing process. Theriogenology , 67 (5), 1060-1067. https://doi.org/10.1016/j.theriogenology.2006.12.004 Erel, O. (2005). A new automated colorimetric method for measuring total oxidant status. Clinical Biochemistry , 38 (12), 1103-1111. https://doi.org/10.1016/j.clinbiochem.2005.08.008 Halo, M. and Tirpak, F. (2018) Stallion fertility - the basis of successful reproduction. Svet koni . 18. Halo Jr., M. et al. (2019) Time and dose-dependent effects of Viscum album quercus on rabbit spermatozoa motility and viability in vitro. Physiological Research, 68 (6), 955-972. https://doi.org/10.33549/physiolres.934223 Ijaz, A. and Ducharme, R. (1995). Effect of various extenders and taurine on survival of stallion sperm cooled to 5 C. Theriogenology , 44 (7), 1039-1050. https://doi.org/10.1016/0093-691x(95)00290-o Jambor, T. et al. (2017) In vitro effect of 4-nonylphenol on human chorionic gonadotropin (hCG) stimulated hormone secretion, cell viability and reactive oxygen species generation in mice Leydig cells. Environmental Pollution , 222, 219–225. https://doi.org/10.1016/j.envpol.2016.12.053 O'flaherty, L. et al. (1997) Intestinal taurine transport: a review. European Journal of Clinical Investigation , 27 (11), 873-880. https://doi.org/10.1046/j.1365-2362.1997.2000747.x Reddy, N. S. S. et al. (2010). Effects of adding taurine and trehalose to a tris-based egg yolk extender on buffalo (Bubalus bubalis) sperm quality following cryopreservation. Animal Reproduction Science , 119 (3-4), 183-190. https://doi.org/10.1016/j.anireprosci.2010.01.012 Slanina, T. et al. (2018) Effect of taurine on turkey (Meleagris gallopavo) spermatozoa viability and motility. Czech Journal of Animal Science , 63 (4),127-135. https://doi.org/10.17221/79/2017-CJAS Stephens, T. D. et al. (2013) Effects of pentoxifylline, caffeine, and taurine on post-thaw motility and longevity of equine frozen semen. Journal of Equine Veterinary Science , 33 (8), 615-621. https://doi.org/10.1016/j.jevs.2012.10.004 Tirpak, F. et al. (2017) Low taurine concentrations possitively affect rabbit spermatozoa properties in later time intervals. Journal of Microbiology, Biotechnology and Food Sciences , 7, 128-131. https://doi.org/10.15414/jmbfs.2017.7.2.128-131

Effects of Chronic Intake of a Low Concentration of Taurine on Physical Strength and Body Composition in Mice.

Most studies of taurine on athletic performance have been conducted at acute and high doses in rodents. These doses and duration of administration are not reasonable for normal human life. Thus, it is not valid to extrapolate these animal results to people. Dose and duration that mimic human use of taurine in normal life can help to clarify the taurine effect in humans. This study investigated whether long-term, low-dose taurine (2% taurine drinking water for 25weeks), similar to normal taurine intake in humans, can affect endurance exercise and body composition. Twenty ICR mice were divided into two groups. The control group received normal drinking water, and the taurine treated group received 2% taurine drinking water for 25weeks. The mice were evaluated for body composition by mass and for physical strength by treadmill exhaustion and suspension tests. The supply of chronic 2% taurine drinking water has a slight effect on weight gain. In body composition analysis, a slight increase in body weight was due to an increase in muscle mass, not an increase in body fat. However, taurine ingestion did not increase endurance exercise. In conclusion, these results indirectly suggest that acute, high-dose taurine treatment is better than long-term, low-dose treatment to increase athletic performance.

Is Taurine a Biomarker in Autistic Spectrum Disorder?

Taurine is a sulfur-containing amino acid which is not incorporated into protein. However, taurine has various critical physiological functions including development of the eye and brain, reproduction, osmoregulation, and immune functions including anti-inflammatory as well as anti-oxidant activity. The causes of autistic spectrum disorder (ASD) are not clear but a high heritability implicates an important role for genetic factors. Reports also implicate oxidative stress and inflammation in the etiology of ASD. Thus, taurine, a well-known antioxidant and regulator of inflammation, was investigated here using the sera from both girls and boys with ASD as well as their siblings and parents. Previous reports regarding taurine serum concentrations in ASD from various laboratories have been controversial. To address the potential role of taurine in ASD, we collected sera from 66 children with ASD (males: 45; females: 21, age 1.5-11.5 years, average age 5.2±1.6) as well as their unaffected siblings (brothers: 24; sisters: 32, age 1.5-17 years, average age 7.0±2.0) as controls of the children with ASD along with parents (fathers: 49; mothers: 54, age 28-45 years). The sera from normal adult controls (males: 47; females: 51, age 28-48 years) were used as controls for the parents. Taurine concentrations in all sera samples were measured using high performance liquid chromatography (HPLC) using a phenylisothiocyanate labeling technique. Taurine concentrations from female and male children with ASD were 123.8±15.2 and 145.8±8.1μM, respectively, and those from their unaffected brothers and sisters were 142.6±10.4 and 150.8±8.4μM, respectively. There was no significant difference in taurine concentration between autistic children and their unaffected siblings. Taurine concentrations in children with ASD were also not significantly different from their parents (mothers: 139.6±7.7μM, fathers: 147.4±7.5μM). No significant difference was observed between adult controls and parents of ASD children (control females: 164.8±4.8μM, control males: 163.0±7.0μM). However, 21 out of 66 children with ASD had low taurine concentrations (<106μM). Since taurine has anti-oxidant activity, children with ASD with low taurine concentrations will be examined for abnormal mitochondrial function. Our data imply that taurine may be a valid biomarker in a subgroup of ASD.

Activation of synaptic and extrasynaptic glycine receptors by taurine in preoptic hypothalamic neurons

Taurine is an essential amino-sulfonic acid having a fundamental function in the brain, participating in both cell volume regulation and neurotransmission. Using a whole cell voltage patch clamp technique, the taurine-activated neurotransmitter receptors in the preoptic hypothalamic area (PHA) neurons were investigated. In the first set of experiments, different concentrations of taurine were applied on PHA neurons. Taurine-induced responses were concentration-dependent. Taurine-induced currents were action potential-independent and sensitive to strychnine, suggesting the involvement of glycine receptors. In addition, taurine activated not only α-homomeric, but also αβ-heteromeric glycine receptors in PHA neurons. Interestingly, a low concentration of taurine (0.5mM) activated glycine receptors, whereas a higher concentration (3mM) activated both glycine and gamma-aminobutyric acid A (GABAA) receptors in PHA neurons. These results suggest that PHA neurons are influenced by taurine and respond via glycine and GABAA receptors.

Differential Effects of Intrauterine Growth Restriction on the Regional Neurochemical Profile of the Developing Rat Brain.

Intrauterine growth restricted (IUGR) infants are at increased risk for neurodevelopmental deficits that suggest the hippocampus and cerebral cortex may be particularly vulnerable. Evaluate regional neurochemical profiles in IUGR and normally grown (NG) 7-day old rat pups using in vivo 1H magnetic resonance (MR) spectroscopy at 9.4T. IUGR was induced via bilateral uterine artery ligation at gestational day 19 in pregnant Sprague-Dawley dams. MR spectra were obtained from the cerebral cortex, hippocampus and striatum at P7 in IUGR (N=12) and NG (N=13) rats. In the cortex, IUGR resulted in lower concentrations of phosphocreatine, glutathione, taurine, total choline, total creatine (P<0.01) and [glutamate]/[glutamine] ratio (P<0.05). Lower taurine concentrations were observed in the hippocampus (P<0.01) and striatum (P<0.05). IUGR differentially affects the neurochemical profile of the P7 rat brain regions. Persistent neurochemical changes may lead to cortex-based long-term neurodevelopmental deficits in human IUGR infants.

A novel cysteine sulfinic Acid decarboxylase knock-out mouse: immune function.

AbstractWe have studied the anti-inflammatory effects of taurine using both cat and rodent models with or without taurine supplementation in the food or drinking water, respectively. Our previous data demonstrate that taurine deficient cats have altered immune functions. Both cats and rodents have limitations for understanding the immune function of taurine. We developed a novel CSAD KO mouse to investigate immune function. The CSAD KO mouse has low plasma taurine concentrations (86 %) and low taurine concentration in the liver (95 %) compared to WT. However, taurine concentrations in the G3 CSAD−/− splenocytes (56 %) were decreased to a lesser extent than was plasma and liver taurine concentration. There was no difference in spleen size between wild type (WT) and homozygote mice (G3 CSAD−/−). Lipopolysaccharide (LPS), a mitogen for B cells, and Concanavalin A (Con A), a mitogen for T cells, was used for lymphocyte proliferation in spleen cells measured using 3H-thymidine incorporation. LPS-induced cellular proliferation was significantly decreased in spleen cells from both G3 CSAD−/− (p < 0.01) females (33 %) and males (51 %). In contrast, Con A induced cellular proliferation was significantly decreased in only females from G3 CSAD−/− (p < 0.01) (65 %). In order to examine whether exogenous taurine may affect lymphocyte transformation, 10 or 50 mM taurine was added in vitro to LPS and Con A stimulated spleen cells from G3 CSAD−/−. Both 10 and 50 mM taurine in WT and CSAD−/− were without effect.These data implicate that taurine may be actively transported into the spleen through taurine transporter because of higher taurine concentrations in the G3 CSAD−/− splenocytes (44 % of WT) compared to those in the G3 CSAD−/− liver (10 % of WT) and plasma (20 % of WT). CSAD KO may have immune defects in both B cells important for antibody production and T cells involved in acquired cellular immunity. These changes in immune function may be absence of CSAD gene but not due to lower taurine levels in CSAD KO.KeywordsTaurineCysteine sulfinic acid decarboxylase knockout miceLymphocyte proliferationLipopolysaccharideConcanavalin ASpleen indexCysteine sulfinic acid decarboxylase knockout mouseTaurineCellular proliferationLPSCon A

Taurine as an additive for improving the fouling resistance of nanofiltration composite membranes

ABSTRACTA hydrophilic compound, taurine, was investigated as an additive in the interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC) to prepare thin‐film composite (TFC) membranes. The resulting membranes were characterized by X‐ray photoelectron spectroscopy and attenuated total reflectance–Fourier transform infrared spectroscopy. The morphology and hydrophilicity of the membranes were investigated through scanning electronic microscopy and water contact angle measurements. The separation performance of the TFC membranes was investigated through water flux and salt rejection tests. The protein‐fouling resistance of the films was evaluated by water recovery rate measurements after the treatment of bovine serum albumin. The membrane containing 0.2 wt % taurine showed the best performance of 92% MgSO4 rejection at a flux of 31 L m−2 h−1 and better antifouling properties than the PIP–TMC membranes. An appropriately low concentration of taurine showed the same MgSO4 rejection as the PIP–TMC membranes but a better fouling resistance performance. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41620.

Amino acid content of selected plant, algae and insect species: a search for alternative protein sources for use in pet foods

In response to global economic duress and heightened consumer awareness of nutrition and health, sustainable and natural ingredients are in demand. Identification of alternative sources of nitrogen and amino acids, including taurine, may help meet dietary requirements while fostering sustainability and natural feeding approaches. Twenty plants, eighteen marine algae and five insect species were analysed. All samples were freeze-dried, hydrolysed and filtered prior to amino acid analysis. Samples for amino acids were analysed in duplicate and averaged. Nitrogen was analysed and crude protein (CP) determined by calculation. With the exception of taurine concentration in soldier fly larvae, all insects exceeded both the National Research Council's canine and feline minimal requirements (MR) for growth of all essential amino acids (EAA) and CP. Although some plants and marine algal species exceeded the canine and feline MR for growth for EAA and CP, only very low concentrations of taurine were found in plants. Taurine concentration in insects was variable but high, with the greatest concentration found in ants (6·42mg/g DM) and adult flesh flies (3·33mg/g DM). Taurine was also high in some macroalgae, especially the red algal species: Mazaella spp. (4·11mg/g DM), Porphyra spp. (1·22mg/g DM) and Chondracanthus spp. (6·28 mg/g DM). Preliminary results suggest that insects and some marine algal species may be practical alternatives to traditional protein and supplemental taurine sources in pet foods. Safety, bioavailability, palatability and source variability of alternative items as food ingredients should be investigated prior to incorporation into canine and feline diets.

Amino acid concentrations in the hamster central auditory system and long‐term effects of intense tone exposure

Exposure to intense sounds often leads to loss of hearing of environmental sounds and hearing of a monotonous tonal sound not actually present, a condition known as tinnitus. Chronic physiological effects of exposure to intense tones have been reported for animals and should be accompanied by chemical changes present at long times after the intense sound exposure. By using a microdissection mapping procedure combined with high-performance liquid chromatography (HPLC), we have measured concentrations of nine amino acids, including those used as neurotransmitters, in the cochlear nucleus, inferior colliculus, medial geniculate, and auditory cortex of hamsters 5 months after exposure to an intense tone, compared with control hamsters of the same age. No very large differences in amino acid concentrations were found between exposed and control hamsters. However, increases of glutamate and γ-aminobutyrate (GABA) in some parts of the inferior colliculus of exposed hamsters were statistically significant. The most consistent differences between exposed and control hamsters were higher aspartate and lower taurine concentrations in virtually all regions of exposed hamsters, which reached statistical significance in many cases. Although these amino acids are not considered likely neurotransmitters, they indirectly have roles in excitatory and inhibitory neurotransmission, respectively. Thus, there is evidence for small, widespread, long-term increases in excitatory transmission and decreases in inhibitory transmission after a level of acoustic trauma previously shown to produce hearing loss and tinnitus.

Taurine Biosynthesis by Neurons and Astrocytes

The physiological roles of taurine, a product of cysteine degradation and one of the most abundant amino acids in the body, remain elusive. Taurine deficiency leads to heart dysfunction, brain development abnormalities, retinal degradation, and other pathologies. The taurine synthetic pathway is proposed to be incomplete in astrocytes and neurons, and metabolic cooperation between these cell types is reportedly needed to complete the pathway. In this study, we analyzed taurine synthesis capability as reported by incorporation of radioactivity from [(35)S]cysteine into taurine, in primary murine astrocytes and neurons, and in several transformed cell lines (human (SH-SY5Y) and murine (N1E-115) neuroblastoma, human astrocytoma (U-87 MG and 1321 N1), and rat glioma (C6)). Extensive incorporation of radioactivity from [(35)S]cysteine into taurine was observed in rat glioma cells as well as in primary mouse astrocytes and neurons, establishing the presence of an intact taurine synthesis pathway in these cells. Interestingly, exposure of cells to cysteine or cysteamine resulted in elevated intracellular hypotaurine without a corresponding increase in taurine levels, suggesting that oxidation of hypotaurine limits taurine synthesis in cells. Consistent with its role as an organic osmolyte, taurine synthesis was stimulated under hypertonic conditions in neurons.

Effect of taurine supplementation on the metabolism and body lipid-to-protein ratio in juvenile Atlantic salmon (Salmo salar)

Previously, we reported that methionine intake determined the taurine concentration in the liver of on-growing Atlantic salmon fed plant protein diets. Further, the methionine intake and/or the increased taurine concentration following increased methionine intake affected the liver lipid metabolism. The following study therefore aimed to test whether taurine affected the growth or the type of growth when added in high plant protein diets naturally low in taurine but equal and adequate in dietary methionine. Juvenile Atlantic salmon [initial body weight (BW) of 2 g] were fed plant protein diets (16.5% fishmeal), which were supplemented with taurine or not for a period of 56 days. As a control for growth and normal metabolism, a fishmeal-based commercial diet (68% fishmeal) was used. Supplementation with taurine to high plant protein diets had a slightly negative effect on weight gain, but the final body weight was not different. Interestingly, the pool of free amino acids in the liver and muscle was significantly higher in fish fed the supplemented diet as compared with fish fed the plant protein diet without taurine supplementation. Liver polyamine concentration was higher in fish fed the supplemented diet than in fish fed the similar diet without supplementation. Additionally, juvenile salmon fed the plant-based diet supplemented with taurine had a lower body lipid-to-protein ratio due to a reduced whole-body lipid content, while the whole-body protein content was similar between treatments. Our study thus indicates that the addition of a low concentration of taurine to high plant protein diets interacts with lipid metabolism and storage, concomitantly affecting the general metabolism as the concentrations of the free amino acids and polyamines in the liver were significantly higher. The possible reasons for these changes are discussed.

Role of taurine on acid secretion in the rat stomach

BackgroundTaurine has chemical structure similar to an inhibitory neurotransmitter, γ-aminobutyric acid (GABA). Previous studies on GABA in the stomach suggest GABAergic neuron is involved in acid secretion, but the effects of taurine are poor understood.MethodsThe effects of taurine on acid secretion, signal transduction, and localization of taurinergic neurons were determined in the rat stomach using everted whole stomach, RIA kit and immunohistochemical methods.ResultsWe used antibodies against taurine-synthesizing enzyme, cysteine sulfuric acid decarboxylase (CSAD), and taurine. CSAD- and taurine-positive cells were found in the muscle and mucosal layers. Distributions of CSAD- and taurine-positive cells in both mucosal and muscle layers were heterogeneous in the stomach. Taurine at 10-9~10-4 M induced acid secretion, and the maximum secretion was at 10-5 M, 1.6-fold higher than the spontaneous secretion. Taurine-induced acid secretion was completely inhibited by bicuculline and atropine but not by cimetidine, proglumide, or strychnine. Atropine and tetrodotoxin (TTX) completely inhibited the acid secretion induced by low concentrations of taurine and partially inhibited induced by high concentrations. Verapamil, a calcium blocker agent, inhibited acid output elicited by taurine. We assumed all Ca2+ channels involved in the response to these secretagogues were equally affected by verapamil. Intracellular cAMP (adenosine 3', 5'-monophosphat) in the stomach significantly increased with taurine treatment in a dose-dependent manner. High correlation (r=0.859, p < 0.001) of taurine concentrations with cAMP was observed.ConclusionsOur results demonstrated for the first time in taurine-induced acid secretion due to increase intracellular calcium may act through the A type of GABA receptors, which are mainly located on cholinergic neurons though cAMP pathway and partially on nonneuronal cells in the rat stomach.

Neurochemical profile of the mouse hypothalamus using in vivo1H MRS at 14.1T

The hypothalamus plays an essential role in the central nervous system of mammals by among others regulating glucose homeostasis, food intake, temperature, and to some extent blood pressure. Assessments of hypothalamic metabolism using, e.g. (1)H MRS in mouse models can provide important insights into its function. To date, direct in vivo (1)H MRS measurements of hypothalamus have not been reported. Here, we report that in vivo single voxel measurements of mouse hypothalamus are feasible using (1)H MRS at 14.1T. Localized (1)H MR spectra from hypothalamus were obtained unilaterally (2-2.2 microL, VOI) and bilaterally (4-4.4 microL) with a quality comparable to that of hippocampus (3-3.5 microL). Using LCModel, a neurochemical profile consisting of 21 metabolites was quantified for both hypothalamus and hippocampus with most of the Cramér-Rao lower bounds within 20%. Relative to the hippocampus, the hypothalamus was characterized by high gamma-aminobutryric acid and myo-inositol, and low taurine concentrations. When studying transgenic mice with no glucose transporter isoform 8 expressed, small metabolic changes were observed, yet glucose homeostasis was well maintained. We conclude that a specific neurochemical profile of mouse hypothalamus can be measured by (1)H MRS which will allow identifying and following metabolic alterations longitudinally in the hypothalamus of genetic modified models.

CSD mRNA expression in rat testis and the effect of taurine on testosterone secretion

In the present study, the cysteine sulfinate decarboxylase (CSD) mRNA expression was detected in rat testis by RT-PCR. The results showed that CSD mRNA was expressed in rat testis, and the putative encoded-amino acid sequence was exactly the same as that in rat liver which was already known. At the same time, the effects of taurine on testosterone secretion were investigated both in vivo and in vitro. In vivo, taurine were administered to male rats by tap water. The results showed that taurine obviously stimulated the secretion of FSH, LH and testosterone in serum, but showed no significant effect on the secretion of estradiol. Taurine administered in water could significantly increase the concentration of taurine in the blood and testis of rats. In vitro, cultured Leydig cells were treated with taurine independently or incubated with human chorionic gonadotropin (HCG) and progesterone. The results showed that taurine had biphasic effects on basal testosterone secretion in cultured Leydig cells. Low concentrations of taurine (0.1-100 microg/ml) could stimulate testosterone secretion, whereas high concentration of taurine (400 microg/ml) could inhibit testosterone secretion. Testosterone secretion stimulated by HCG was significantly increased by 10 and 100 microg/ml of taurine administration, and obviously decreased by treating with 400 microg/ml of taurine. Testosterone secretion induced by progesterone was significantly stimulated by treating with 1.0 and 10 microg/ml of taurine, however, it was significantly inhibited when treated with 400 microg/ml of taurine. Meanwhile, the effect of silencing CSD mRNA by siRNA on testosterone secretion was analyzed. The results showed that testosterone secretion was obviously decreased after the inhibition of CSD mRNA expression in cultured Leydig cells. These results indicated that taurine can be synthesized in rat testis by CSD pathway, and it plays important roles in testosterone secretion both in vivo and in vitro which need to be further investigated.

Taurine supplementation enhances nutrient‐induced insulin secretion in pancreatic mice islets

Taurine (TAU), a naturally occurring sulfur-containing amino acid, is found at high concentrations in plasma and mammalian tissues and regulates osmolarity, ion channel activity, and glucose homeostasis. Several reports have shown that physiological plasma TAU levels seem to be important for adequate beta (beta)-cell function and insulin action, since low concentrations of TAU in the plasma have been reported in the pre-diabetic and diabetic states. Glucose tolerance and insulin sensitivity were investigated in mice supplemented with 2% (w/v) TAU in their drinking water for 30 days, as well as the insulin secretion from isolated islets stimulated by glucose or L-leucine. TAU-supplemented mice demonstrated improved glucose tolerance and higher insulin sensitivity, compared to controls (CTL). In addition, their islets secreted more insulin in response to high concentrations of glucose and L-leucine. L-[U-(14)C]leucine oxidation was higher in TAU than in CTL islets, whereas D-[U-(14)C]glucose oxidation, ATP levels, glucose transporter (GLUT) 2 and glucokinase (GCK) protein expressions were similar in both types of islets. The L-type beta(2) subunit voltage-sensitive Ca(2+) channel protein, as well as (45)Ca uptake, were significantly higher in TAU-supplemented than CTL islets. In addition, islets from TAU-supplemented mice secreted more glucagon than CTL islets at low glucose. TAU supplementation improves glucose tolerance and insulin sensitivity in mice, as well as insulin secretion from isolated islets. The latter effect seems to be, at least in part, dependent on a better Ca(2+) handling by the islets.

Taurine Is a Potent Activator of Extrasynaptic GABAAReceptors in the Thalamus

Taurine is one of the most abundant free amino acids in the brain. In a number of studies, taurine has been reported to activate glycine receptors (Gly-Rs) at moderate concentrations (> or = 100 microM), and to be a weak agonist at GABA(A) receptors (GABA(A)-Rs), which are usually activated at high concentrations (> or = 1 mM). In this study, we show that taurine reduced the excitability of thalamocortical relay neurons and activated both extrasynaptic GABA(A)-Rs and Gly-Rs in neurons in the mouse ventrobasal (VB) thalamus. Low concentrations of taurine (10-100 microM) decreased neuronal input resistance and firing frequency, and elicited a steady outward current under voltage clamp, but had no effects on fast inhibitory synaptic currents. Currents elicited by 50 microM taurine were abolished by gabazine, insensitive to midazolam, and partially blocked by 20 microM Zn2+, consistent with the pharmacological properties of extrasynaptic GABA(A)-Rs (alpha4beta2delta subtype) involved in tonic inhibition in the thalamus. Tonic inhibition was enhanced by an inhibitor of taurine transport, suggesting that taurine can act as an endogenous activator of these receptors. Taurine-evoked currents were absent in relay neurons from GABA(A)-R alpha4 subunit knock-out mice. The amplitude of the taurine current was larger in neurons from adult mice than juvenile mice. Taurine was a more potent agonist at recombinant alpha4beta2delta GABA(A)-Rs than at alpha1beta2gamma2 GABA(A)-Rs. We conclude that physiological concentrations of taurine can inhibit VB neurons via activation of extrasynaptic GABA(A)-Rs and that taurine may function as an endogenous regulator of excitability and network activity in the thalamus.