Specific timing of taurine supplementation affects learning ability in mice

Pre/postnatal taurine supplementation improves neurodevelopment and brain function in mice offspring: A persistent developmental study from puberty to maturity

Taurine (TAU) is a sulfur-containing amino acid abundantly found in the human body. Endogenously, TAU is synthesized from cysteine in the liver. However, newborns rely entirely on TAU's dietary supply (milk). There is no investigation on the effect of long-term TAU administration on next-generation neurological development. The current study evaluated the effect of long-term TAU supplementation during the maternal gestational and litter weaning time on several neurological parameters in mice offspring. Moreover, the effects of TAU on mitochondrial function and oxidative stress biomarkers as plausible mechanisms of its action in the whole brain and hippocampus have been evaluated. TAU (0.5 % and 1 % w/v) was dissolved in the drinking water of pregnant mice (Day one of pregnancy), and amino acid supplementation was continued during the weaning time (post-natal day; PND = 21) until litters maturity (PND = 65). It was found that TAU significantly improved cognitive function, memory performance, reflexive motor activity, and emotional behaviors in F1-mice generation. TAU measurement in the brain and hippocampus revealed higher levels of this amino acid. TAU and ATP levels were also significantly higher in the mitochondria isolated from the whole brain and hippocampus. Based on these data, TAU could be suggested as a supplement during pregnancy or in pediatric formula. The effects of TAU on cellular mitochondrial function and energy metabolism might play a fundamental role in the positive effects of this amino acid observed in this investigation.

Taurine ameliorates volatile organic compounds-induced cognitive impairment in young rats via suppressing oxidative stress, regulating neurotransmitter and activating NMDA receptor

Long-term exposure to volatile organic compounds (VOCs) in children leads to intellectual and cognitive impairment. Taurine is an essential nutritional amino acid for children, which can improve neurological development in children. However, the neuroprotective effect of taurine on VOCs-induced cognitive impairment in children remains unclear. The aim of this study was to investigate the neuroprotective effects of taurine on VOCs-induced cognitive impairment in young rats. The rats were nose-only exposed to VOCs for a period of 4 weeks to create a model of cognitive impairment, and 0.5% and 1% taurine in tap water were administered throughout the trial period, respectively. Our results showed that young rats adjusted the recovery of their physiological functions by voluntarily increasing the intake of taurine in tap water when exposed to excessive VOCs by inhalation. In addition, taurine enhanced grasp, shortened the latency period of escape, and improved the learning and memory function of young rats. Moreover, taurine decreased malondialdehyde (MDA), γ-aminobutyric acid (GABA), Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), Urea, Creatinine (CREA) and injury biomarker level, enhanced superoxide dismutase (SOD), reduced glutathione (GSH) and glutamic acid (Glu) activities, up-regulated the protein expression of brain derived neurotrophic factor (BDNF) and N-Methyl-d-aspartate receptor 1 (NMDAR1) in model rats, and in most of cases 1% but not 0.5%, ameliorated the defects induced by VOCs. Collectively, these findings suggested that taurine protected against VOCs-induced cognitive-behavioral impairment in young rats through inhibiting oxidative stress and regulating neurotransmitter homeostasis. In addition, taurine were capable of restoring abilities of learning and memory in young rats exposed to VOCs by activating the N-Methyl-d-aspartate (NMDA) receptor. The findings suggest taurine as a potential novel drug for the treatment of cognitive behavioral disorders in children.

The effect of intracerebroventricular amyloid beta 1-42 application on cognitive functions in aged rats supplemented with taurine and the change of peroxisomal proteins in this process

OBJECTIVE

The aim of our study is to investigate the change of peroxisomal proteins in the neurodegenerative and oxidative process caused by the neurotoxicity of Aβ 1-42 in aged rats supplemented with taurine and to show the possible positive effects of taurine in this process.

METHODS

30 Wistar albino rats were randomly divided into 5 groups as control, sham, Aβ 1-42, taurine, and Aβ 1-42+taurine. Taurine administration continued for 6 weeks (1000 mg/kg/day with drinking water). Stereotaxic surgery was applied to all groups (intracerebroventricular per lateral ventricle needle only or 5 μl, PBS, or Aβ 1-42). Spatial learning and memory performances of the animals were evaluated with Morris water maze and elevated plus maze. The levels of MDA and GSH were measured as oxidative stress parameters in the cerebral cortex and hippocampus. Expressions of CAT, PEX14, PMP70 of peroxisomal membrane proteins were indicated by Western blot analysis.

RESULTS

Our results showed that injection of Aβ 1-42 decreased the spatial learning and memory performance, cortex CAT and hippocampus PEX14, PMP70 and GSH levels, and increased cortex and hippocampus MDA levels (p < 0.05). Although the administration of taurine partially ameliorated the adverse effects of Aβ 1-42 injection, a significant difference was found only at the hippocampus GSH levels (p < 0.05). Also, taurine caused anxiety at this dose (p < 0.05).

DISCUSSION

In conclusion, decreased peroxisomal proteins and antioxidant capacity in neurodegenerative and oxidative processes induced by intracerebroventricular Aβ 1-42 injection showed that peroxisomes may play a role in this process and taurine supplementation may have positive effects especially in increasing antioxidant capacity.

Supplemental taurine during adolescence and early adulthood has sex-specific effects on cognition, behavior and neurotransmitter levels in C57BL/6J mice dependent on exposure window

The mammalian brain goes through final maturation during late adolescence and early adulthood with sex differences in timing. The key cellular processes, including changes in neurotransmitter receptor density and synaptic pruning, make this age uniquely vulnerable to neurotoxic insults. Teenagers and young adults are the major consumers of energy drinks, which contain high levels of taurine and caffeine. Taurine is one of the most abundant amino acids in the central nervous system, but the effects of supplemental taurine consumption during adolescence has not been well studied. We conducted an initial short-term exposure study with 0.12% taurine in drinking water and a long-term exposure dose-response study using 0.06 and 0.12% taurine in male and female C57BL/6J mice. We examined a broad range of cognitive functions and behaviors and measured neurotransmitter levels. We found no significant differences in anxiety, open field locomotor activity, or sensorimotor gating. However, we found impairments in novel object recognition and sex differences in Morris water maze. When taurine treatment stopped before behavioral experiments began, male mice had significant impairments in spatial learning and memory. In the dose-response study when taurine treatment continued throughout behavioral experiments, females had significant impairments. We also found sex differences in neurotransmitter levels with females having higher levels of glutamate, DOPAC and 5-HIAA. We conclude that both females and males are at risk from excess taurine consumption during final brain maturation.

Taurine, caffeine, and energy drinks: Reviewing the risks to the adolescent brain

Energy drinks are emerging as a major component of the beverage market with sales projected to top $60 billion globally in the next five years. Energy drinks contain a variety of ingredients, but many of the top-selling brands include high doses of caffeine and the amino acid taurine. Energy drink consumption by children has raised concerns, due to potential caffeine toxicity. An additional risk has been noted among college-aged consumers of energy drinks who appear at higher risk of over-consumption of alcohol when the two drinks are consumed together. The differential and combinatorial effects of caffeine and taurine on the developing brain are reviewed here with an emphasis on the adolescent brain, which is still maturing. Key data from animal studies are summarized to highlight both reported benefits and adverse effects reported following acute and chronic exposures. The data suggest that age is an important factor in both caffeine and taurine toxicity. Although the aged or diseased brain might benefit from taurine or caffeine supplementation, it appears that adolescents are not likely to benefit from supplementation and may, in fact, suffer ill effects from chronic ingestion of high doses. Additional work is needed though to address gaps in our understanding of how taurine affects females, since the majority of animal studies focused exclusively on male subjects.

Understanding taurine CNS activity using alternative zebrafish models

Taurine is a highly abundant "amino acid" in the brain. Despite the potential neuroactive role of taurine in vertebrates has long been recognized, the underlying molecular mechanisms related to its pleiotropic effects in the brain remain poorly understood. Due to the genetic tractability, rich behavioral repertoire, neurochemical conservation, and small size, the zebrafish (Danio rerio) has emerged as a powerful candidate for neuropsychopharmacology investigation and in vivo drug screening. Here, we summarize the main physiological roles of taurine in mammals, including neuromodulation, osmoregulation, membrane stabilization, and antioxidant action. In this context, we also highlight how zebrafish models of brain disorders may present interesting approaches to assess molecular mechanisms underlying positive effects of taurine in the brain. Finally, we outline recent advances in zebrafish drug screening that significantly improve neuropsychiatric translational researches and small molecule screens.

Physiological role of taurine--from organism to organelle

Taurine is often referred to as a semi-essential amino acid as newborn mammals have a limited ability to synthesize taurine and have to rely on dietary supply. Taurine is not thought to be incorporated into proteins as no aminoacyl tRNA synthetase has yet been identified and is not oxidized in mammalian cells. However, taurine contributes significantly to the cellular pool of organic osmolytes and has accordingly been acknowledged for its role in cell volume restoration following osmotic perturbation. This review describes taurine homeostasis in cells and organelles with emphasis on taurine biophysics/membrane dynamics, regulation of transport proteins involved in active taurine uptake and passive taurine release as well as physiological processes, for example, development, lung function, mitochondrial function, antioxidative defence and apoptosis which seem to be affected by a shift in the expression of the taurine transporters and/or the cellular taurine content.

Taurine in drinking water recovers learning and memory in the adult APP/PS1 mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a lethal progressive neurological disorder affecting the memory. Recently, US Food and Drug Administration mitigated the standard for drug approval, allowing symptomatic drugs that only improve cognitive deficits to be allowed to accelerate on to clinical trials. Our study focuses on taurine, an endogenous amino acid found in high concentrations in humans. It has demonstrated neuroprotective properties against many forms of dementia. In this study, we assessed cognitively enhancing property of taurine in transgenic mouse model of AD. We orally administered taurine via drinking water to adult APP/PS1 transgenic mouse model for 6 weeks. Taurine treatment rescued cognitive deficits in APP/PS1 mice up to the age-matching wild-type mice in Y-maze and passive avoidance tests without modifying the behaviours of cognitively normal mice. In the cortex of APP/PS1 mice, taurine slightly decreased insoluble fraction of Aβ. While the exact mechanism of taurine in AD has not yet been ascertained, our results suggest that taurine can aid cognitive impairment and may inhibit Aβ-related damages.

Perinatal taurine exposure programs patterns of autonomic nerve activity responses to tooth pulp stimulation in adult male rats

Perinatal taurine excess or deficiency influences adult health and disease, especially relative to the autonomic nervous system. This study tests the hypothesis that perinatal taurine exposure influences adult autonomic nervous system control of arterial pressure in response to acute electrical tooth pulp stimulation. Female Sprague-Dawley rats were fed with normal rat chow with 3% β-alanine (taurine depletion, TD), 3% taurine (taurine supplementation, TS), or water alone (control, C) from conception to weaning. Their male offspring were fed with normal rat chow and tap water throughout the experiment. At 8-10 weeks of age, blood chemistry, arterial pressure, heart rate, and renal sympathetic nerve activity were measured in anesthetized rats. Age, body weight, mean arterial pressure, heart rate, plasma electrolytes, blood urea nitrogen, plasma creatinine, and plasma cortisol were not significantly different among the three groups. Before tooth pulp stimulation, low- (0.3-0.5 Hz) and high-frequency (0.5-4.0 Hz) power spectral densities of arterial pressure were not significantly different among groups while the power spectral densities of renal sympathetic nerve activity were significantly decreased in TD compared to control rats. Tooth pulp stimulation did not change arterial pressure, heart rate, renal sympathetic nerve, and arterial pressure power spectral densities in the 0.3-4.0 Hz spectrum or renal sympathetic nerve firing rate in any group. In contrast, perinatal taurine imbalance disturbed very-low-frequency power spectral densities of both arterial pressure and renal sympathetic nerve activity (below 0.1 Hz), both before and after the tooth pulp stimulation. The power densities of TS were most sensitive to ganglionic blockade and central adrenergic inhibition, while those of TD were sensitive to both central and peripheral adrenergic inhibition. The present data indicate that perinatal taurine imbalance can lead to aberrant autonomic nervous system responses in adult male rats.

Perinatal taurine exposure affects adult arterial pressure control

Taurine is an abundant, free amino acid found in mammalian cells that contributes to many physiologic functions from that of a simple cell osmolyte to a programmer of adult health and disease. Taurine's contribution extends from conception throughout life, but its most critical exposure period is during perinatal life. In adults, taurine supplementation prevents or alleviates cardiovascular disease and related complications. In contrast, low taurine consumption coincides with increased risk of cardiovascular disease, obesity and type II diabetes. This review focuses on the effects that altered perinatal taurine exposure has on long-term mechanisms that control adult arterial blood pressure and could thereby contribute to arterial hypertension through its ability to program these cardiovascular regulatory mechanisms very early in life. The modifications of these mechanisms can last a lifetime and transfer to the next generation, suggesting that epigenetic mechanisms underlie the changes. The ability of perinatal taurine exposure to influence arterial pressure control mechanisms and hypertension in adult life appears to involve the regulation of growth and development, the central and autonomic nervous system, the renin-angiotensin system, glucose-insulin interaction and changes to heart, blood vessels and kidney function.

Cerebral antioxidant enzyme increase associated with learning deficit in type 2 diabetes rats

In this study, we examined alterations in the enzymatic antioxidant defenses associated with learning deficits induced by type 2 diabetes, and studied the effects of the peroxisome proliferator-activated receptor γ agonist pioglitazone on these learning deficits. Learning ability was assessed by visual discrimination tasks in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, as a model of spontaneous type 2 diabetes. Levels of the antioxidant enzymes glutathione peroxidase (GPx), Cu(2+)-Zn(2+) superoxide dismutase (CuZn-SOD) and manganese SOD were measured in the cortex, hippocampus and striatum. Half the rats received oral pioglitazone (20mg/kg/day) from the early stage of diabetes (22 weeks old) to 27 weeks old. OLETF rats showed learning deficits compared with control, Long-Evans Tokushima Otsuka (LETO) rats. GPx levels in the cortex and hippocampus were increased in OLETF rats compared with LETO rats, with an inverse correlation between GPx in the hippocampus and learning score. CuZn-SOD levels were also increased in the hippocampus in OLETF rats. Pioglitazone reduced blood glucose and increased serum adiponectin levels, but had no effect on learning tasks or antioxidant enzymes, except for CuZn-SOD. These results suggest that an oxidative imbalance reflected by increased brain antioxidant enzymes plays an important role in the development of learning deficits in type 2 diabetes. Early pioglitazone administration partly ameliorated diabetic symptoms, but was unable to completely recover cerebral oxidative imbalance and functions. These results suggest that diabetes-induced brain impairment, which results in learning deficits, may have occurred before the appearance of the symptoms of overt diabetes.

Evidence that acute taurine treatment alters extracellular AMP hydrolysis and adenosine deaminase activity in zebrafish brain membranes

Taurine is one of the most abundant free amino acids in excitable tissues. In the brain, extracellular taurine may act as an inhibitory neurotransmitter, neuromodulator, and neuroprotector. Nucleotides are ubiquitous signaling molecules that play crucial roles for brain function. The inactivation of nucleotide-mediated signaling is controlled by ectonucleotidases, which include the nucleoside triphosphate diphosphohydrolase (NTPDase) family and ecto-5'-nucleotidase. These enzymes hydrolyze ATP/GTP to adenosine/guanosine, which exert a modulatory role controlling several neurotransmitter systems. The nucleoside adenosine can be inactivated in extracellular or intracellular milieu by adenosine deaminase (ADA). In this report, we tested whether acute taurine treatment at supra-physiological concentrations alters NTPDase, ecto-5'-nucleotidase, and ADA activities in zebrafish brain. Fish were treated with 42, 150, and 400 mg L(-1) taurine for 1h, the brains were dissected and the enzyme assays were performed. Although the NTPDase activities were not altered, 150 and 400 mg L(-1) taurine increased AMP hydrolysis (128 and 153%, respectively) in zebrafish brain membranes and significantly decreased ecto-ADA activity (29 and 38%, respectively). In vitro assays demonstrated that taurine did not change AMP hydrolysis, whereas it promoted a significant decrease in ecto-ADA activity at 150 and 400 mg L(-1) (24 and 26%, respectively). Altogether, our data provide the first evidence that taurine exposure modulates the ecto-enzymes responsible for controlling extracellular adenosine levels in zebrafish brain. These findings could be relevant to evaluate potential beneficial effects promoted by acute taurine treatment in the central nervous system (CNS) of this species.