Effect of taurine on growth hormone and prolactin secretion in rats: possible interaction with opioid peptidergic system

Effects of exogenous taurine supplementation on the growth, antioxidant capacity, intestine immunity, and resistance against Streptococcus agalactiae in juvenile golden pompano (Trachinotus ovatus) fed with a low-fishmeal diet

Taurine has various biological functions in fish, playing an essential role in growth, resistance to oxidative stress, and intestine immunity. Here, we evaluated the effects of exogenous taurine added to low-fishmeal diets on the growth, anti-oxidative stress, intestine immunity, and Streptococcus agalactiae resistance in juvenile golden pompano (Trachinotus ovatus). Our study showed that exogenous taurine supplementation of 1.2% (T3 group) greatly enhanced the weight gain rate and specific growth rate (SGR) of juvenile golden pompano, significantly upregulating growth-related factor expression in the brain and liver, as well as the levels of growth-related parameters in the serum. Polynomial regression analysis using SGR estimated the optimal dietary taurine level for golden pompano at 1.18%. Moderate exogenous taurine also increased the muscular thickness and villus length within the intestine, maintained intestinal physical barrier stability, activated the Nrf2/Keap-1/HO-1 signaling pathway, increased intestinal antioxidant enzyme gene expression and antioxidant enzyme activity in the serum, and upregulated immunoglobulin and complement levels in parallel with declining reactive oxygen species (ROS) levels in the serum. Antioxidant factor expression was also upregulated in the intestine. Furthermore, supplementation suppressed NF-κB signaling and intestinal pro-inflammatory cytokine gene expression, increased anti-inflammatory cytokine gene expression, and improved intestine immunity. Finally, taurine supplementation improved the survival rate of golden pompano challenged with S. agalactiae. Overall, our findings provide additional information and support for the rational use of taurine in healthy aquatic animal farming.

Differences in free amino acid concentrations in milk between Wistar and Wistar Kyoto rats

Wistar Kyoto (WKY) rats, an animal depression model, display abnormal behaviors such as hypoactivity and depression-like behavior compared with Wistar (WIS) rats as a control. A previous study confirmed a dysfunction of amino acid metabolism in the brain of WKY rats compared with that of WIS rats. At the neonatal stage, free amino acids in milk are important nutrients because they act as immediate nutrients for offspring and may affect later health and behavior of the offspring. Therefore, the present study aimed to investigate free amino acid concentrations in milk and the relationships between free amino acid concentrations in milk and plasma in WIS and WKY rats. The concentrations of ten of the determined free amino acids in milk were significantly higher, but only L-methionine was significantly lower, in WKY rats. Six free amino acids had significantly higher concentrations in colostrum and two free amino acids had higher concentrations in matured milk. Free amino acid concentrations in plasma changed by both genetic background and lactation stage; however, the patterns of change in most free amino acid concentrations except for taurine in plasma were similar between WIS and WKY rats. The transport ratio of free amino acids from plasma to milk was not similar among the free amino acids tested, and each free amino acid was influenced by the genetic background and/or the type of milk.

Metabolomics approach in lung tissue of septic rats and the interventional effects of Xuebijing injection using UHPLC-Q-Orbitrap-HRMS

Sepsis is the dysregulated host response to an infection which leads to life-threatening organ dysfunction. Metabolomic profiling in bio-fluid or tissue is vital for elucidating the pathogenesis of sepsis and evaluating therapeutic effects of medication. In this study, an untargeted metabolomics approach was applied to study the metabolic changes in lung tissue of septic rats induced by cecal ligation and puncture (CLP) and investigate the treatment effects of Xubijing injection (XBJ). Metabolomics analyses were performed on ultra-high performance liquid chromatography-Q Exactive hybrid quadrupole-orbitrap high-resolution accurate mass spectrometry (UHPLC-Q-Orbitrap-HRMS) together with multivariate statistical analysis. A total of 26 differential metabolites between CLP and sham-operated group were identified. The altered metabolic pathways included energy metabolism, amino metabolism, lipid metabolism, fatty acid metabolism and hormone metabolism. Among the 26-varied metabolites, 15 were significantly regulated after XBJ treatment. The metabolic pathway network of sepsis was drawn to interpret the pathological feature of lung damage caused by sepsis and the underlying regulating mechanism of XBJ on the molecular levels. Our findings display that LC-MS-based metabolomics is a useful tool for uncovering the underlying molecular mechanism of sepsis, and XBJ may exert therapeutic effect by regulating multiple metabolic pathways.

The chronic effect of pulsed 1800 MHz electromagnetic radiation on amino acid neurotransmitters in three different areas of juvenile and young adult rat brain

The extensive use of mobile phones worldwide has raised increasing concerns about the effects of electromagnetic radiation (EMR) on the brain due to the proximity of the mobile phone to the head and the appearance of several adverse neurological effects after mobile phone use. It has been hypothesized that the EMR-induced neurological effects may be mediated by amino acid neurotransmitters. Thus, the present study investigated the effect of EMR (frequency 1800 MHz, specific absorption rate 0.843 W/kg, power density 0.02 mW/cm2, modulated at 217 Hz) on the concentrations of amino acid neurotransmitters (glutamic acid, aspartic acid, gamma aminobutyric acid, glycine, taurine, and the amide glutamine) in the hippocampus, striatum, and hypothalamus of juvenile and young adult rats. The juvenile and young adult animals were each divided into two groups: control rats and rats exposed to EMR 1 h daily for 1, 2, and 4 months. A subgroup of rats were exposed daily to EMR for 4 months and then left without exposure for 1 month to study the recovery from EMR exposure. Amino acid neurotransmitters were measured in the hippocampus, striatum, and hypothalamus using high-performance liquid chromatography. Exposure to EMR induced significant changes in amino acid neurotransmitters in the studied brain areas of juvenile and young adult rats, being more prominent in juvenile animals. It could be concluded that the alterations in amino acid neurotransmitters induced by EMR exposure of juvenile and young adult rats may underlie many of the neurological effects reported after EMR exposure including cognitive and memory impairment and sleep disorders. Some of these effects may persist for some time after stopping exposure.

Restraint stress in lactating mice alters the levels of sulfur-containing amino acids in milk

It is well known that maternal stress during the gestation and lactation periods induces abnormal behavior in the offspring and causes a lowering of the offspring’s body weight. Various causes of maternal stress during the lactation period, relating to, for example, maternal nutritional status and reduced maternal care, have been considered. However, little is known about the effects on milk of maternal stress during the lactation period. The current study aimed to determine whether free amino acids, with special reference to sulfur-containing amino acids in milk, are altered by restraint stress in lactating mice. The dams in the stress group were restrained for 30 min at postnatal days 2, 4, 6, 8, 10 and 12. Restraint stress caused a reduction in the body weight of lactating mice. The concentration of taurine and cystathionine in milk was significantly higher in the stress group, though stress did not alter their concentration in maternal plasma. The ratio of taurine concentration in milk to its concentration in maternal plasma was significantly higher in the stress group, suggesting that stress promoted taurine transportation into milk. Furthermore, taurine concentration in milk was positively correlated with corticosterone levels in plasma. In conclusion, restraint stress in lactating mice caused the changes in the metabolism and in the transportation of sulfur-containing amino acids and resulted in higher taurine concentration in milk. Taurine concentration in milk could also be a good parameter for determining stress status in dams.

Differential gene expression identified by RNA-Seq and qPCR in two sizes of pearl oyster (Pinctada fucata)

Differential growth of the pearl oyster Pinctada fucata still exists in the aquaculture production. There is no systematic study of the entire transcriptome of differential gene expression in P. fucata in the literature. In this study, high-throughput Illumina/HiSeq™ 2000 RNA-Seq was used to examine the differences of gene expression in large (L) and small oysters (S). In total, 74,293 and 76,635 unigenes were generated from L and S oysters, respectively. RT quantitative PCR (qPCR) analysis showed that the differential expression pattern of 19 out of 34 selected genes was consistent with the results of RNA-Seq analysis: 14 genes (11 for growth, 1 for reproduction and 2 for shell formation) were expressed more highly in S, 5 genes (1 for growth, 1 for reproduction and 3 for the immune system) were expressed more highly in L; 3 genes associated with the immune system were opposite to it; and no difference was found for the remaining 12 genes. Another 9 shell formation-related genes in L and S were examined by qPCR: 1 gene was expressed more highly in L, 5 genes were expressed more highly in S and no difference was found for the remaining 3 genes. Some genes related to growth and development, shell formation and reproduction were expressed more highly in S compared to L. This phenomenon could be explained by "catch-up growth". The results of this study will help toward a comprehensive understanding of the complexity of differential growth between P. fucata individuals and provide valuable information for future research.

Maternal taurine supplementation in the late pregnant rat stimulates postnatal growth and induces obesity and insulin resistance in adult offspring

An adequate supply of taurine during fetal life is important for normal beta-cell development and insulin action. An altered availability of taurine may programme glucose metabolism in utero and result in type 2 diabetes in adult age. We examined whether maternal taurine supplementation in late pregnant rats affects postnatal growth, adult body composition, insulin sensitivity and endogenous insulin secretion in intrauterine growth restricted (IUGR) and normal offspring. Uterine artery ligation or sham operations were performed on gestational day (GD) 19. Taurine supplementation was given to half of the dams from GD 18 until term, resulting in four groups of offspring: sham (n = 22), sham/taurine (n = 22), IUGR (n = 22) and IUGR/taurine (n = 24). The offspring were studied at 12 weeks of age. In offspring with normal birth weight, fetal taurine supplementation markedly stimulated postnatal growth. In sham/taurine females, fat depots, plasma free fatty acid and leptin concentrations were increased, and insulin sensitivity was reduced. Insulin sensitivity was unaltered in IUGR and IUGR/taurine offspring. However, whereas IUGR offspring showed little catch-up growth, 50% of IUGR/taurine animals displayed complete catch-up at 12 weeks of age, and these animals had increased fat depots and reduced insulin sensitivity. In conclusion, taurine supplementation in late gestation resulted in accelerated postnatal growth, which was associated with adult obesity and insulin resistance in both IUGR and normal offspring. This effect was particularly evident in females. These data suggest that fetal taurine availability is an important determinant for postnatal growth, insulin sensitivity and fat accumulation.

Effects of oral cadmium exposure through puberty on plasma prolactin and gonadotropin levels and amino acid contents in various brain areas in pubertal male rats

This work was undertaken to analyze if the effects of oral cadmium exposure through puberty, on plasma prolactin and gonadotropin levels are mediated by changes in amino acid contents in various brain areas in male rats. The contents of glutamate, glutamine, aspartate, GABA and taurine in the median eminence, anterior, mediobasal and posterior hypothalamus and prefrontal cortex in pubertal male rats exposed to 50 ppm of cadmium chloride (CdCl2) in the drinking waterfor 1 month (through puberty) were measured by high performance liquid chromatography (HPLC). Plasma prolactin, LH and FSH levels were measured by specific RIA methodology. Plasma prolactin levels decreased after cadmium exposure, whereas plasma levels of LH and FSH were not changed by the metal administration. After cadmium exposure, both glutamine and glutamate contents decreased in the median eminence and in anterior and posterior hypothalamus. Metal exposure also decreased aspartate content in anterior and posterior hypothalamus, but increased it in prefrontal cortex. GABA content decreased in any studied brain region after cadmium administration. Besides, the metal decreased taurine content in the median eminence, anterior and posterior hypothalamus and in prefrontal cortex. The results suggest that cadmium effects on plasma prolactin levels may be partially explained by the changes in aspartate, glutamate or taurine contents, but not by the decrease in GABA content in the brain regions studied.

Effect of taurine in rat milk on the growth of offspring

The physiological significance of taurine in milk in the growth of rat pups was investigated. Our results confirmed that taurine was at an exceptionally high concentration in rat milk during the lactational period, especially for the first few days after birth. Pups taking no milk from natural dams but from foster mothers at an advanced lactational period showed a slower growth rate. Intraperitoneal administration of taurine to the foster mothers in the first five days restored this growth retardation. On the other hand, intraperitoneal administration of beta-alanine, a transport antagonist of taurine, to the natural dams through the lactational period induced a slower growth rate of pups. This beta-alanine treatment to dams increased beta-alanine concentration, but did not decrease taurine concentrations in milk, and serum taurine concentration in the pups receiving this milk was elevated. Direct administration of beta-alanine to pups also increased the serum taurine concentrations dose-dependently. Beta-alanine administration to pups significantly decreased [3H]taurine incorporation into all the organs examined, and in contrast. [3H]taurine concentrations in serum and urine were elevated. Thus, beta-alanine inhibited taurine incorporation into cells and accelerated taurine excretion into either urine or milk. Serum IGF-I levels in pups receiving beta-alanine either directly or via their mothers was significantly lower than those in control pups. Cumulatively, taurine ingestion from milk at an early lactational period seems critical for normal growth of rat neonates due to its role in maintaining normal serum IGF-I levels.

Effects of dietary taurine supplementation or deprivation in aged male Fischer 344 rats

Taurine is a sulfur amino acid that is present in high concentration in mammalian tissues and previously has been reported to decline in a number of tissues with advancing age. The aims of the present study were to examine: (1) the effects of dietary taurine supplementation; (2) the effects of taurine-free diets; (3) the ability of aged rats to conserve urinary taurine; and (4) the consequences of these dietary manipulations on some biochemical parameters. Male F344 rats (n = 30/group) 18 months of age were placed on control diets, diets supplemented with 1.5% taurine in the drinking water, or a taurine-free diet for 10 months. An adult control group (12 months old at the end of the study) on normal diets was included for comparison purposes. Significant (P < 0.05) age-related declines in taurine content were observed in the spleen, kidney, eye, cerebellum and serum. Taurine supplementation corrected these deficits in tissue content in aged rats and in many cases increased taurine content above that of adult controls. Urinary excretion of taurine was significantly (P < 0.05) reduced in aged rats indicating an increased need to conserve taurine. Taurine-deficient diets did not further exacerbate the age-related decline in tissue taurine content, suggesting biosynthetic adaptations to the lack of dietary taurine. Dietary taurine supplementation blunted age-related declines in serum IGF-1 and increases in serum creatinine and blood urinary nitrogen (BUN). These studies suggest that advanced aging results in a taurine-deficient state that can be corrected by dietary supplementation.

K(+)- and temperature-evoked taurine efflux from hypothalamic astrocytes

Hypothalamic astrocytes in culture released taurine, a suspected inhibitory amino acid neurotransmitter/neuromodulator/osmoregulator, in response to isoosmotically increasing extracellular K+ in a dose-dependent fashion. In the absence of added Ca2+, basal release levels rose to approach those obtained after exposure to 60 mM K+ in the presence of 2.5 mM Ca2+, and were only partially lowered by the addition of 10 mM Mg2+. Stimulation with K+ (60 mM) did not further increase taurine efflux above the high basal levels seen in the absence of Ca2+. Under standard conditions complete replacement of Na+ with choline Cl had little effect on basal taurine release, but reduced K(+)-evoked (60 mM) efflux by 60%. The temperature dependence of the basal levels of taurine released from hypothalamic astrocytes was similar to that seen for cultured cerebellar astrocytes and neurons over the range 5-50 degrees C. Taurine release increased from 5 to 15 degrees C, remained constant between 15 and 33 degrees C, decreased between 33 and 37 degrees C and increased thereafter. The infection point of increased basal taurine release seen around 37 degrees C (most prominent in astrocytes), may be of physiological significance. Results presented also show that the ion (Na+, Ca2+ and K+) sensitivities of taurine efflux for cultured hypothalamic astrocytes are similar to those previously reported for cultured astrocytes from the cerebellum.