The synthesis and role of taurine in the Japanese eel testis

Effects of Dietary Taurine on Maturation Indices, Antioxidant Capacity, Ovaries Amino and Fatty Acids Profile, and Vitellogenin Gene Transcription Level in Penaeus vannamei Female Brooders

A 30-day research was carried out to examine the impacts of dietary taurine (Tau) on ovaries maturation and physiological responses of Penaeus vannamei female brooders (29.4 ± 0.2 g). A basal diet (497 g kg-1 protein and 140 g kg-1 lipid) was administered with graded levels of Tau ranging from 0 (control) to 2, 4, 6, 8, and 10 g kg-1. A total of 180 shrimp brooders were stocked into 18 250 L black circular polyethylene tanks. Female (n = 5) and male (n = 5) shrimps were stocked in each tank and supplied with seawater (35.2 ± 3.1 g L-1 salinity, 28.9 ± 1.4°C) and the experimental feeds were offered to shrimp twice a day at 5% of their biomass. Supplementing diet with 4-8 g Tau kg-1 reduced latency period after eye stalk ablation to spawning (5-6 days) that was associated with higher hepatopancreatic and gonadosomatic (except for 8 g Tau kg-1 diet) indices (p < 0.05). With 10 g Tau kg-1 diet hepatopancreas glutathione peroxidase activity and total antioxidant capacity increased and catalase activity increased by 6 g Tau kg-1 diet. Supplementing diet with Tau-enhanced bile-salt dependent lipase activity in the gut. Docosahexaenoic acid and Tau levels were elevated in the ovaries with the increment of dietary Tau level (p < 0.05). Plasma total protein, calcium, cholesterol, and high-density lipoprotein increased with inclusion of 6-10 g Tau kg-1 diet. The transcription levels of vitellogenin, insulin-like growth factor II, superoxide dismutase, prophenoloxidase, and lysozyme genes transcription levels were upregulated in the hepatopancreas of shrimp brooders fed 6-10 g Tau kg-1 diet (p < 0.05). It seems that Tau at 4-8 g kg-1 diet by modulating lipid metabolism, antioxidant capacity, and immunocompetence can improve maturation and health status of P. vannamei brooders.

Polymorphisms in the cysteine dioxygenase gene and their association with taurine content in the Pacific oyster Crassostrea gigas

The Pacific oyster Crassostrea gigas is rich in taurine, which is crucial for its adaptation to the fluctuating intertidal environment and presents significant potential in improving taurine nutrition and boosting immunity in humans. Cysteine dioxygenase (CDO) is a key enzyme involved in the initial step of taurine biosynthesis and plays a crucial role in regulating taurine content in the body. In the present study, polymorphisms of CDO gene in C. gigas (CgCDO) and their association with taurine content were evaluated in 198 individuals. A total of 24 single nucleotide polymorphism (SNP) loci were identified in the exonic region of CgCDO gene by direct sequencing. Among these SNPs, c.279G>A and c.287C>A were found to be significantly associated with taurine content, with the GG and AA genotype at the two loci exhibiting enhanced taurine accumulation (p < 0.05). Haplotype analysis revealed that the 279GG/287AA haplotype had the highest taurine content of 29.24 mg/g, while the 279AA/287CC haplotype showed the lowest taurine content of 21.19 mg/g. These results indicated that the SNPs of CgCDO gene could influence the taurine content in C. gigas and have potential applications in the selective breeding of high-taurine varieties.

Effect of Four Functional Feed Additives on Growth, Serum Biochemistry, Antioxidant Capacity, Gene Expressions, Histomorphology, Digestive Enzyme Activities and Disease Resistance in Juvenile Olive Flounder, Paralichthys olivaceus

An 8-week feeding trial was executed to evaluate the efficacy of four functional feed additives in replacing antibiotics in juvenile olive flounder, Paralichthys olivaceus, fed with a low-fish-meal diet. A basal diet without feed additives was used as a control (CON); other diets were formulated by supplementing 0.50% taurine (TW), 0.30% peptide (PT), 0.23% mineral water (MW), 0.35% yeast-extracted nucleotides (GRO), 0.35% GRO + 0.50% taurine (GROTW), 0.35% GRO + 0.30% peptide (GROPT) and 0.35% GRO + 0.23% mineral water (GROMW) into the basal diet; in addition, one diet was supplemented with oxytetracycline (OTC) at 0.5% as a positive control. Triplicate groups of 25 fish with an average weight of 5.15 ± 0.06 g (mean ± SD) were fed one of the nine experimental diets. At the end of the feeding trial, the weight gain, specific growth rate and protein efficiency ratio of fish fed the GRO, GROMW, GROPT and GROTW diets were significantly higher than those of fish fed the CON diet (p < 0.05). The feed efficiency of fish fed the GRO, GROMW, GROPT and GROTW diets was significantly higher than that of fish fed the TW and OTC diets. However, the survival, hepatosomatic index, viscerosomatic index and condition factor of fish, as well as their whole-body proximate composition, were not significantly affected by the experimental diets (p > 0.05). The serum glutamic pyruvic transaminase of fish fed the GROPT diet was significantly lower than that of fish fed the CON diet. However, glutamic oxaloacetic transaminase, glucose and total protein were not significantly affected by the experimental diets (p > 0.05). The serum superoxide dismutase activity of fish fed the PT, TW, GRO, GROMW, GROPT and GROTW diets was significantly higher than that of fish fed the CON diet. The lysozyme activity of fish fed the PT, GRO, GROMW, GROPT and GROTW diets was significantly higher than that of fish fed the CON and OTC diets. The myeloperoxidase activity of fish fed the TW, GRO, GROMW, GROPT and GROTW diets was significantly higher than that of fish fed the CON, PT and MW diets (p < 0.05). The flounder growth hormone gene expression of fish fed the TW, GRO, GROMW, GROPT, GROTW and OTC diets was significantly higher than that of fish fed the CON, PT and MW diets (p < 0.05). The interleukin 1β and interleukin 10 gene expressions of fish fed the GRO, GROMW, GROPT and GROTW diets were significantly higher than those of fish fed the CON, PT, TW and MW diets (p < 0.05). Intestinal histology showed a significantly higher villi length for fish fed the GRO, GROMW, GROPT and GROTW diets compared to that of fish fed the CON diet (p < 0.05). Digestive enzyme activities such as trypsin activity were significantly higher in fish fed the GROMW, GROPT and GROTW diets than those in the rest of the diet groups (p < 0.05). Amylase activity in fish fed the MW, GRO, GROMW, GROPT, GROTW and OTC diets was significantly higher than that of fish fed the PT, TW and CON diets (p < 0.05). On the other hand, the lipase activity of fish fed the TW, GRO, GROMW, GROPT and GROTW diets was significantly higher than that of fish fed the CON, PT, MW and OTC diets (p < 0.05). The cumulative survival rate of fish fed the PT, GROTW, GROPT and GROMW diets was significantly higher than that of fish fed the CON, TW and MW diets after thirteen days of the challenge testing. Overall, the results demonstrate that the GRO, GROMW, GROPT and GROTW diets could be beneficial feed additives to replace antibiotics in juvenile olive flounder fed low-fish-meal diets.

The role of taurine in male reproduction: Physiology, pathology and toxicology

Taurine, a sulfur-containing amino acid, has a wide range of biological effects, such as bile salt formation, osmotic regulation, oxidative stress inhibition, immunomodulation and neuromodulation. Taurine has been proved to be synthesized and abundant in male reproductive organs. Recently, accumulating data showed that taurine has a potential protective effect on reproductive function of male animals. In physiology, taurine can promote the endocrine function of the hypothalamus-pituitary-testis (HPT) axis, testicular tissue development, spermatogenesis and maturation, delay the aging of testicular structure and function, maintain the homeostasis of the testicular environment, and enhance sexual ability. In pathology, taurine supplement may be beneficial to alleviate pathological damage of male reproductive system, including oxidative damage of sperm preservation in vitro, testicular reperfusion injury and diabetes -induced reproductive complications. In addition, taurine acts as a protective agent against toxic damage to the male reproductive system by exogenous substances (e.g., therapeutic drugs, environmental pollutants, radiation). Related mechanisms include reduced oxidative stress, increased antioxidant capacity, inhibited inflammation and apoptosis, restored the secretory activity of the HPT axis, reduced chromosomal variation, enhanced sperm mitochondrial energy metabolism, cell membrane stabilization effect, etc. Therefore, this article reviewed the protective effect of taurine on male reproductive function and its detailed mechanism, in order to provide reference for further research and clinical application.

Taurine induces autophagy and inhibits oxidative stress in mice Leydig cells

OBJECTIVES

This study evaluated taurine (TAU) effects on autophagy, apoptosis and oxidative stress in mice Leydig TM3 cells.

METHODS

We treated TM3 cells with TAU (100 µg/mL) or 3-Methyladenine (3-MA, an autophagy inhibitor) for 24 h, and assessed cell viability, testosterone level, oxidative stress, apoptosis, and autophagy.

RESULTS

The results showed that TAU markedly increased cell viability, testosterone levels, expression of autophagy-related genes and percentage of LC3-II-positive cells. TAU significantly reduced malondialdehyde (MDA) contents and reactive oxygen species (ROS) levels and increased the activities of SOD (superoxide dismutase) and CAT (Catalase) enzymes in the TM3 cells. TAU in the presence of autophagy inhibitor (3-MA) increased oxidative stress and decreased testosterone levels.

CONCLUSION

The results showed that autophagy might be involved in TAU-increased testosterone levels in mice Leydig TM3 cells.

Female Mimicry by Sneaker Males Has a Transcriptomic Signature in Both the Brain and the Gonad in a Sex-Changing Fish

Phenotypic plasticity represents an elegant adaptive response of individuals to a change in their environment. Bluehead wrasses (Thalassoma bifasciatum) exhibit astonishing sexual plasticity, including female-to-male sex change and discrete male morphs that differ strikingly in behavior, morphology, and gonadal investment. Using RNA-seq transcriptome profiling, we examined the genes and physiological pathways underlying flexible behavioral and gonadal differences among female, dominant (bourgeois) male, and female-mimic (sneaker) male blueheads. For the first time in any organism, we find that female mimicry by sneaker males has a transcriptional signature in both the brain and the gonad. Sneaker males shared striking similarity in neural gene expression with females, supporting the idea that males with alternative reproductive phenotypes have "female-like brains." Sneaker males also overexpressed neuroplasticity genes, suggesting that their opportunistic reproductive strategy requires a heightened capacity for neuroplasticity. Bourgeois males overexpressed genes associated with socio-sexual behaviors (e.g., isotocin), but also neuroprotective genes and biomarkers of oxidative stress and aging, indicating a hitherto unexplored cost to these males of attaining the reproductively privileged position at the top of the social hierarchy. Our novel comparison of testicular transcriptomes in a fish with male sexual polymorphism associates greater gonadal investment by sneaker males with overexpression of genes involved in cell proliferation and sperm quality control. We propose that morphological female-mimicry by sneaker male teleosts entails pervasive downregulation of androgenesis genes, consistent with low androgen production in males lacking well-developed secondary sexual characters.

Taurine Increases Spermatozoa Quality and Function in Asthenospermia Rats Impaired by Ornidazole

Asthenospermia has been considered as one of the crucial causes of male infertility, which was closely related to epididymal dysfunction. Lots of documents have revealed that taurine palys an important role in male reproduction, including antioxidation, membrane stabilization, stimulation of sexual hormone secretion and elevation of sperm quality. The objective of this study was to expose the effect of taurine on spermatozoa quality and function in ornidazole-induced asthenospermia rats. We found that taurine treatment could obviously recover the decline of cauda epididymal sperm count, viability and motility, and the elevation of sperm abnormality in asthenospermia animals. Spermatozoa acrosin, LDH-X, SDH and CCO activities of model rats also were notably increased by taurine administration. The present data indicated that taurine could raise spermatozoa quality and function by elevating mitochondrial energy metabolism. Notably, taurine supplementation markedly raised serum GnRH, LH and T levels in asthenospermia rays, suggesting taurine rescued asthenosperm by means of stimulating hypothalamic-pituitary-testicular axis secretion. We also found that concentrations of asthenospermia epididymal carnitine, SA, α-Glu and ACP, and mRNA expression levels of MMP7 and IDO2 were significantly rised by taurine administration, indicating taurine may protect epididymal epithelium structure, improve secretion activity, and maintain intraluminal microenvironment homeostasis. Finally, the present results showed taurine effectively increased cauda epididymal SOD, GSH and γ-GT levels in model rats, reduced ROS and MDA production, suggesting epididymal antioxidant ability of asthenospermia rats could be elevated by taurine treatment. To sum up, our results indicated that taurine can promote spermatozoa quality and function in ornidazole-induced asthenospermia rats by facilitating epididymal epithelium secretion and luminal microenvironment homeostasis.

Differential regulation of taurine biosynthesis in rainbow trout and Japanese flounder

Animals have varied taurine biosynthesis capability, which was determined by activities of key enzymes including cysteine dioxygenase (CDO) and cysteine sulfinate decarboxylase (CSD). However, whether CDO and CSD are differentially regulated across species remains unexplored. In the present study, we examined the regulations of CDO and CSD in rainbow trout and Japanese flounder, the two fish species with high and low taurine biosynthesis ability respectively. Our results showed that the expression of CDO was lower in rainbow trout but more responsive to cysteine stimulation compared to that in Japanese flounder. On the other hand, both the expression and catalytic efficiency (k(cat)) of CSD were higher in rainbow trout than those of Japanese flounder. A three-residue substrate recognition motif in rainbow trout CSD with sequence of F126/S146/Y148 was identified to be responsible for high k(cat), while that with sequence of F88/N108/F110 in Japanese flounder led to low k(cat), as suggested by site-directed mutagenesis studies. In summary, our results determined new aspects of taurine biosynthesis regulation across species.

The Sertoli cell: one hundred fifty years of beauty and plasticity

It has been one and a half centuries since Enrico Sertoli published the seminal discovery of the testicular 'nurse cell', not only a key cell in the testis, but indeed one of the most amazing cells in the vertebrate body. In this review, we begin by examining the three phases of morphological research that have occurred in the study of Sertoli cells, because microscopic anatomy was essentially the only scientific discipline available for about the first 75 years after the discovery. Biochemistry and molecular biology then changed all of biological sciences, including our understanding of the functions of Sertoli cells. Immunology and stem cell biology were not even topics of science in 1865, but they have now become major issues in our appreciation of Sertoli cell's role in spermatogenesis. We end with the universal importance and plasticity of function by comparing Sertoli cells in fish, amphibians, and mammals. In these various classes of vertebrates, Sertoli cells have quite different modes of proliferation and epithelial maintenance, cystic vs. tubular formation, yet accomplish essentially the same function but in strikingly different ways.

Estradiol decreases taurine level by reducing cysteine sulfinic acid decarboxylase via the estrogen receptor-α in female mice liver

Cysteine sulfinic acid decarboxylase (CSAD) and cysteine dioxygenase (CDO) are two rate-limiting enzymes in taurine de novo synthesis, and their expressions are associated with estrogen concentration. The present study was designed to determine the relationship between 17β-estradiol (E₂) and taurine in female mice liver. We initially observed the mice had lower levels of CSAD, CDO, and taurine during estrus than diestrus. We then, respectively, treated the ovariectomized mice, the cultured hepatocytes, and Hep G2 cells with different doses of E₂, and the CSAD and CDO expressions and taurine levels were analyzed. The results showed that E₂ decreased taurine level in the serum and the cultured cells by inhibiting CSAD and CDO expressions. Furthermore, we identified the molecular receptor types through which E₂ plays its role in regulating taurine synthesis, and our results showed that estrogen receptor-α (ERα) expression was much higher than estrogen receptor-β (ERβ) in the liver and hepatocytes, and the inhibiting effects of E₂ on CSAD, CDO, and taurine level were partially abrogated in the ICI-182,780-pretreated liver and hepatocytes, and in ERα knockout mice. These results indicate that estradiol decreases taurine content by reducing taurine biosynthetic enzyme expression in mice liver.

Trypsin regulates meiotic initiation in the Japanese eel (Anguilla japonica) by promoting the uptake of taurine into germ cells during spermatogenesis

Meiosis is a unique and critical process in reproduction. Although the key molecular components of meiosis have been identified, the molecular mechanisms regulating the entry into this pathway remain unclear. We previously demonstrated that a progestin in teleost fish, 17alpha, 20beta-dihydroxy-4-pregnen-3-one, is essential for meiotic initiation, and up-regulates taurine synthesis and the production of trypsin in Sertoli cells. In the present study, we found that trypsin promotes the uptake of taurine into germ cells through the up-regulation of solute carrier family 6 (neurotransmitter transporter, taurine), member 6 (Slc6a6) expression. We further found that this up-regulation of the taurine signal is required for Spo11a expression and meiotic initiation.

Fishy aroma of social status: urinary chemo-signalling of territoriality in male fathead minnows (Pimephales promelas)

Chemical structures of several urinary reproductive pheromones in fish have been identified, and their role in the chemical communication of reproductive condition is well characterized. On the contrary, the role of chemical communication in signalling of social/territorial status in fish is poorly understood. Fathead minnows are an example of a fish species whose life history traits appear conducive to evolution of chemical communication systems that confer information about social/territorial status. Male reproduction in this species is dependent upon their ability to acquire and defend a high quality nesting territory, and to attract a female to the nest. We hypothesized that fathead minnow males use visual and urine-derived chemical cues to signal territorial status. To test this hypothesis, effects of territorial acquisition on male-specific secondary sex characteristics (SSCs) and urine volumes were first assessed. Second, frequencies of male urination in varying social contexts were examined. Finally, nuclear magnetic resonance-based metabolomics was used to identify urinary metabolites that were differentially excreted in the urine of territorial versus non-territorial males. The expression of SSCs, sperm, and urine volumes increased with territory acquisition, and either remained unchanged or decreased in non-territorial males. Frequency of male urination increased significantly in the presence of females (but not males), suggesting that females are the main target of the urinary signals. Territorial and non-territorial males had distinct urinary metabolomic profiles. An unforeseen finding was that one could discern future territorial status of males, based on their initial metabolomic profiles. Bile acids and volatile amines were identified as potential chemical signals of social status in the fathead minnow. The finding that trimethylamine (a fishy smelling volatile amine) may be a social cue is particularly interesting, because it is known to bind trace amine-associated receptors, indicating that these receptors may play role in chemical signalling of social status in fish.