Qunhui Yang

Effects of Taurine on Myocardial cGMP/cAMP Ratio, Antioxidant Ability, and Ultrastructure in Cardiac Hypertrophy Rats Induced by Isoproterenol

Taurine is the most abundant free amino acid in the human body and accounts for more than 50% of the total amino acid pool in the mammalian heart. To investigate the preventive effects of taurine on cardiac hypertrophy in rats, myocardial injury was established by hypodermic injection of isoprenaline (ISO) (10 mg/kg d) for 7 days. The preventive effects of taurine (100 mg/kg d, 200 mg/kg d, and 300 mg/kg d, i.p) on heart coefficient; ultrastructure of cardiac muscle; the levels of creatine kinase heart isoenzyme (CK-MB), cAMP, and cGMP; and antioxidant ability were investigated. The results showed that taurine could significantly prevent the increase of heart coefficient induced by ISO. Compared with the model group, 100 mg/kg and 200 mg/kg taurine significantly decrease the levels of cAMP and cGMP, while 300 mg/kg taurine could significantly decrease the levels of cAMP in myocardium, and all the three concentrations of taurine could significantly increase the ratio of cGMP/cAMP. The level of serum CK-MB was significantly increased by ISO; 200 mg/kg taurine could significantly decrease it, but 100 mg/kg and 300 mg/kg taurine had no significant effect. As for the antioxidant ability, ISO administration could significantly increase the myocardial level of MDA but had no significant effects on the myocardial levels of SOD, GSH, GSH-Px, and T-AOC. However, taurine administration could significantly decrease the myocardial level of MDA and increase the levels of GSH and T-AOC compared with the model group. The serum levels of SOD, GSH-Px, GSH, and T-AOC were significantly reduced by ISO administration, but the level of MDA showed no significant changes compared with the control group. Taurine administration could significantly increase the serum levels of SOD, GSH-Px, GSH, and T-AOC and decrease the level of MDA compared with the model group. All the results indicated that 200 mg/kg taurine had better effects. The ultrastructure of cardiomyocytes showed that taurine administration could significantly reverse the injury caused by ISO. In conclusion, the present study demonstrated that taurine could inhibit the injury induced by ISO by increasing myocardial negative inotropic effect and antioxidant ability, decreasing the hypertrophic response to isoproterenol and protecting the integrity of -myocardial ultrastructure, decreasing myocardial leak of CK-MB.

Inhibitory effects of taurine on STZ-induced apoptosis of pancreatic islet cells.

The present research aims to investigate the inhibition effect of taurine on the apoptosis of pancreatic islet cells induced by Streptozotocin (STZ). One hundred male Wistar rats weighing 180-200 g were randomly divided into two groups, rats in the experimental were intraperitoneally injected with 2% STZ (50 mg/kg bw, dissolved in 0.1 mmol/L pH 4.2 citrate buffer), rats in the control group were injected with the same volume of citrate buffer. Rats with the fasting blood glucose level higher than 16.7 mmol/L were selected and randomly divided into four groups: Rats in M group were STZ-induced diabetes rats, rats in T1, T2, and T3 groups were intragastrically administered with taurine (dissolved in 0.5% sodium carboxymethyl cellulose as thickening agent) once a day for 4 weeks with the contents of 0.6 g/kg, 1.2 g/kg, and 2.4 g/kg bw, respectively, while rats in group C and M were given the same amount of thickening agent as T2 group. Four weeks later, pancreatic tissues were fixed and processed for paraffin section. The results showed that STZ induced a significant increase in apoptotic rate of pancreatic islet cells, up-regulated the expression of bax and Fas and down-regulated the expression of Bcl-2, which were significantly blocked by taurine (P < 0.05). The results indicated that taurine could significantly restrain apoptosis of pancreatic islet cells induced by STZ.

Taurine and Chinese Traditional Medicine Accelerate Alcohol Metabolism in Mice

Excessive alcohol consumption is dangerous and causes serious damage to health. The main organ capable of alcohol oxidizing is liver which is also the main organ synthesizing taurine, a sulfur-containing β-amino acid, which is the major free intracellular amino acid presenting in many tissues of human and animals and exerting many physiologic and pharmacologic functions. To investigate the effect of taurine and Chinese traditional medicine on alcohol metabolism after acute alcoholic intake, male Kunming mice were administered with 60% alcohol (0.4 ml) intragastrically. Water, taurine, or taurine coadministration with Chinese traditional medicine was intragastrically administered to mice 30 min before or after alcohol intake. The disappearance of body-righting reflex was used to determine the intoxication of mice. Durations between alcohol intake and intoxication (tolerance time), intoxication and recovery (maintenance time) were recorded. The concentration of blood alcohol, levels of hepatic alcohol dehydrogenase (ADH), and acetaldehyde dehydrogenase (ALDH) were detected at 20, 50, 90, 120, and 150 min after alcohol intake. The results showed that taurine administered alone or together with Chinese traditional medicine could both significantly reduce the number of intoxicated mice, postpone the tolerance time, shorten the maintenance time, and could obvisouly decrease blood level of alcohol, increase hepatic levels of ADH and ALDH. The results indicated that taurine administered alone or together with traditional Chinese medicine could significantly accelerate the metabolism of alcohol, reduce the toxicity of alcohol, and coadministration of taurine and traditional Chinese medicine had better effects.

Antidepressant effect of taurine in chronic unpredictable mild stress-induced depressive rats

Depression, a psychiatric and dysthymic disorder, severely affects the learning, work and life quality. The main pathogenesis of depression is associated with central nervous system (CNS) dysfunction. Taurine has been demonstrated to exert protective effects on the brain development and can improve learning ability and memory. Our study investigated the antidepressant-like effects of taurine pre-treatment by examining the changes in depression-like behavior, hormones, neurotransmitters, inflammatory factors and neurotrophic factors in the hippocampus of a chronic unpredictable mild stress (CUMS)-induced depressive rat model. Taurine was found to inhibit the decrease of sucrose consumption and prevent the deficiency of spatial memory and anxiety in rats exposed to CUMS, suggesting a preventive effect of taurine on depression-like behavior. Furthermore, the decreased levels of 5-hydroxytryptamine, dopamine, noradrenaline; the increased levels of glutamate, corticosterone; and the decreased expressions of fibroblast growth factor-2, vascular endothelial growth factor and brain derived neurotrophic factor in depressive rats were hindered by taurine pre-administration. However, tumor necrosis factor-α and interleukin-1β levels were not significantly changed by taurine. The results demonstrated that the anti-depressive effect of taurine may be involved in the regulation of hypothalamic-pituitary-adrenal (HPA) axis and the promotion of neurogenesis, neuronal survival and growth in the hippocampus.

Synergistic effects of taurine and L-arginine on attenuating insulin resistance hypertension.

To elucidate the synergistic effects of taurine and L-arginine on hypertension, 25% fructose were administered to male Wistar rats for 3 months to establish insulin resistance hypertensive models. Rats with the systolic blood pressure (SBP) higher than 150 mmHg were considered as model rats. Forty-two model rats were randomly divided into six groups and administered with 3% taurine, 2.7% taurine + 0.3% L-arginine, 2.1% taurine + 0.9% L-arginine, 1.5% taurine + 1.5% L-arginine and 3% L-arginine in drinking water respectively. The results showed that coadministration of taurine (1.5%) and L-arginine (1.5%) could bring the levels of SBP, blood glucose, and insulin down to normal levels after 4 weeks. The thickness of blood vessels increased significantly in model group, which could be reversed by taurine and L-arginine. Serum NO, cGMP, and ET levels could return to normal levels. These data indicated that both taurine and L-arginine could ameliorate vascular remodeling and showed obvious antihypertensive effects, and taurine (1.5%) and L-arginine (1.5%) in the drinking water showed a better result in the cure of hypertension.

Effects of Taurine on Blood Index of Hypothalamic Pituitary Adrenal (HPA) Axis of Stress-Induced Hypertensive Rat

To elucidate the protective mechanism of taurine against stress induced hypertension, 32 male Wistar rats were randomly divided into four groups: normal control group; stress control group; β–alanine stress group and taurine stress group. Rats of the two control groups were administered physiological saline while the β–alanine treated group was administered β–alanine (200 mg/kg/day) and the taurine treated group was administered taurine (200 mg/kg/day). The hypertensive model was produced by stressing the rats for 3 weeks. Serum levels of angiotensin converting enzyme (ACE), angiotensin II (AngII), glucocorticoid hormone (CRH), adrenocorticotropic hormone (ACTH), Glucocorticoid (GC), epinephrine (EPI), norepinephrine (NA) in the β–alanine stress group was significantly higher than those of the other groups (P < 0.05). However, serum of the taurine stress group contained more angiotensin converting enzyme 2 (ACE2) than those of the other groups (P < 0.05). These data indicate that taurine regulates the hypothalamus pituitary adrenal (HPA) axis of the renin-angiotensin-aldosterone system (RAAS), thereby contributing to the prevention of stress-induced hypertension.

Taurine Recovers Testicular Steroidogenesis and Spermatogenesis in Streptozotocin-Induced Diabetic Rats

A great deal of investigations have verified that diabetic male reproductive impairment is associated with the dysfunction of testicular steroidogenesis and spermatogenesis resulted from insulin deficiency and hyperglycaemia-induced oxidative stress. It has been identified taurine is profitable for diabetes mellitus and diabetic implications through its insulin-like and islet cells protective activity. Furthermore, our previous studies found that taurine could increase testicular antioxidative ability, stimulate the endocrine activity of hypothalamic-pituitary-testicular axis, elevate testosterone level, raise sperm quality, suppress the deterioration of testicular function. Accordingly, we hypothesized that taurine may have beneficial effects on testicular dysfunction under diabetic mellitus status. Here, we investigated the effects of taurine on testicular steroidogenesis and spermatogenesis in streptozotocin (STZ)-induced type I diabetic rats. We observed that taurine treatment can markedly increase the body and testis weights, testicular SDH and G6PDH activities, decrease the serum fasting glucose concentration of diabetic rats. Serum contents of GnRH, LH, FSH, T, and testicular StAR, 3β-HSD, 17β-HSD mRNA expression levels were also obviously raised by taurine administration, indicating that taurine can improve testicular steroidogenesis in diabetic animals. Finally, we found taurine supplementation effectively elevated the sperm count and motility, reduced sperm abnormality, suggesting that taurine can increase the testicular spermatogenesis function of diabetic rat. In summary, the present data indicated that taurine can rescue the function of testicular steroidogenesis and spermatogenesis in STZ-induced type I diabetic rats possibly by increasing the endocrine activity of hypothalamic-pituitary-testicular axis.

Taurine accelerates alcohol and fat metabolism of rats with alcoholic Fatty liver disease.

Liver is considered to be the main organ capable of oxidizing alcohol and fat. Chronic consumption of alcohol is the major cause of liver injury and the development of alcoholic fatty liver disease (AFLD). Liver is also the main organ capable of synthesizing taurine, and the effects of taurine on liver disease have aroused great attention. In the present study, alcohol and pyrazole were administered to male Wistar rats by way of intragastric administration and combined with a high fat diet in order to establish the AFLD model. Taurine was administered in the drinking water during and after the establishment of the AFLD model. The preventive experiment lasted for 12 weeks. The curative experiment was divided into 4 and 8 weeks. Hepatic activities of ADH, ALDH, serum ALT, AST, TC, TG, HDL-C, LDL-C, NEFA and hepatic NEFA were measured. The results showed that hepatic ADH and ALDH in AFLD rats were significantly lower while serum ALT, AST, TC, TG, LDL-C, NEFA and hepatic NEFA in model group were significantly higher than normal rats (P < 0.05), and serum HDL-C was obviously lower. Serum ALT, AST, TC, TG, LDL-C, NEFA, and hepatic NEFA were decreased in taurine preventive and curative groups (P < 0.05), while hepatic activities of ADH and ALDH, serum HDL-C were significantly increased in taurine groups (P < 0.05). Observation of the pathological sections showed that taurine can significantly attenuate fatty degeneration and the deposition of the liver caused by alcohol. The results indicated that taurine presumably accelerates the metabolism of alcohol and fat in the liver, thereby inhibiting and reversing hepatic fatty degeneration in AFLD rats.

Effects of Taurine on ACE, ACE2 and HSP70 Expression of Hypothalamic-Pituitary-Adrenal Axis in Stress-Induced Hypertensive Rats

The experiment was to elucidate protective mechanism of taurine against stress-induced hypertension. Thirty two male Wistar rats were randomly divided into four groups. Normal control group and stress control group were intragastrically administered saline; β-alanine stress group were fed with β-alanine (200 mg/kg/day) and taurine stress group with taurine (200 mg/kg/day). The hypertensive model was established by giving rats stress for 3 weeks.Results showed that significant expression levels of angiotensin converting enzyme (ACE) in the hypothalamus, pituitary and adrenal were observed in β-alanine stress group and stress control group (P < 0.05), but significant mRNA expression levels of angiotensin-converting enzyme 2 (ACE2) in taurine stress group and normal control group (P < 0.05). All the groups showed no significant differences in HSP70 mRNA expression levels in hypothalamus (P > 0.05), while taurine stress group exhibited the highest HSP70 mRNA expression levels both in pituitary and in adrenal (P < 0.05). It was also found that β-alanine stress group and stress control group had significantly higher protein expression levels of ACE in hypothalamus, pituitary and adrenal (P < 0.05), but significantly lower protein expression of ACE2 compared to taurine stress group and control groups (P < 0.05). The results indicated that taurine regulated the hypothalamus pituitary adrenal (HPA) axis of the renin-angiotensin-aldosterone system (RAAS) by inhibiting ACE gene and protein expressions and promoting ACE2 and HSP70 protein expressions, thereby contributing to the prevention of stress-induced hypertension.

Taurine Improves Sexual Function in Streptozotocin-Induced Diabetic Rats

Previous studies have identified that diabetic erectile dysfunction is associated with androgen and nitric oxide deficiency resulting from hyperglycemia. It has been demonstrated that taurine can stimulate testosterone secretion, increase nitric oxide synthase (NOS) activity and nitric oxide (NO) production, and reduce blood glucose levels in the diabetic animals. Furthermore, recent studies have found that taurine relaxes both the corpus cavernosum and the vasculature. Accordingly, we hypothesized that taurine might exert beneficial effects on erectile function of the diabetic rats. Here, we assessed the effects of taurine on sexual function in streptozotocin (STZ) -induced diabetic male rats. We observed that taurine treatment could markedly increase sexual response and mating ability of STZ-diabetic rats. The serum concentration of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone (T) were also significantly increased by taurine administration. Importantly, taurine supplementation notably increased mRNA levels and activity of endothelial NOS (eNOS) and neuronal NOS (nNOS), as well as NO and cGMP content, in the corpus cavernosum of the diabetic rats. In conclusion, the present data indicate that taurine can increase sexual function of STZ-induced diabetic male rats mainly by correcting the diabetes, increasing sexual desire, which is implicated in ameliorating the hypothalamic-pituitary-testicular axis function, and by improving penile erection, which requires increased signaling from the penile endothelial- and neuronal-dependent NO-cGMP pathway.