Effect of taurine supplementation on cytochrome P450 2E1 and oxidative stress in the liver and kidneys of rats with streptozotocin-induced diabetes

The Impact of Taurine on Obesity-Induced Diabetes Mellitus: Mechanisms Underlying Its Effect

This review explores the potential benefits of taurine in ameliorating the metabolic disorders of obesity and type 2 diabetes (T2D), highlighting the factors that bridge these associations. Relevant articles and studies were reviewed to conduct a comprehensive analysis of the relationship between obesity and the development of T2D and the effect of taurine on those conditions. The loss of normal β-cell function and development of T2D are associated with obesity-derived insulin resistance. The occurrence of diabetes has been linked to the low bioavailability of taurine, which plays critical roles in normal β-cell function, anti-oxidation, and anti-inflammation. The relationships among obesity, insulin resistance, β-cell dysfunction, and T2D are complex and intertwined. Taurine may play a role in ameliorating these metabolic disorders through different pathways, but further research is needed to fully understand its effects and potential as a therapeutic intervention.

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.

Dose-dependent effects of taurine against testicular damage in a streptozotocin-induced type 1 diabetes mellitus rat model

OBJECTIVES

Testicular dysfunction has been associated with chronic hyperglycemia in diabetes mellitus patients. We investigated taurine's possible mechanisms and protective effects against testicular damage using a rat model of streptozotocin-induced diabetes.

METHODS

Wistar rats (N = 56) were divided into seven equal groups. Untreated control rats received saline, and treated control rats received taurine 50 mg/kg orally. To induce diabetes, rats received a single dose of streptozotocin. Metformin-treated diabetic rats received metformin at a dose of 300 mg/kg. Taurine-treated groups received 10, 25, or 50 mg/kg. All treatments were provided orally once a day for 9 weeks following the streptozotocin injection. Levels of blood glucose, serum insulin, cholesterol, testicular tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-1beta (IL-1β), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione (GSH), and catalase (CAT) were examined. Sperm count, progressive sperm motility, and sperm abnormalities were examined. Body and relative reproductive gland weights were assessed. Histopathological examinations of the testes and epididymis were performed.

RESULTS

Metformin as well as taurine (in a dose-dependent manner) resulted in significant improvements in body and relative reproductive gland weights, blood glucose, serum cholesterol, and insulin levels, as well as cytokine and oxidative parameters. These findings were associated with significant improvement in sperm count, progressive sperm motility, sperm abnormalities, and histopathological lesions in the testes and epididymis.

CONCLUSION

Taurine can potentially improve hyperglycemia, hypercholesterolemia, and testicular damage associated with diabetes mellitus, possibly by controlling inflammation and oxidative stress.

Mental Performance and Sport: Caffeine and Co-consumed Bioactive Ingredients

The plant defence compound caffeine is widely consumed as a performance enhancer in a sporting context, with potential benefits expected in both physiological and psychological terms. However, although caffeine modestly but consistently improves alertness and fatigue, its effects on mental performance are largely restricted to improved attention or concentration. It has no consistent effect within other cognitive domains that are important to sporting performance, including working memory, executive function and long-term memory. Although caffeine's central nervous system effects are often attributed to blockade of the receptors for the inhibitory neuromodulator adenosine, it also inhibits a number of enzymes involved both in neurotransmission and in cellular homeostasis and signal propagation. Furthermore, it modulates the pharmacokinetics of other endogenous and exogenous bioactive molecules, in part via interactions with shared cytochrome P450 enzymes. Caffeine therefore enjoys interactive relationships with a wide range of bioactive medicinal and dietary compounds, potentially broadening, increasing, decreasing, or modulating the time course of their functional effects, or vice versa. This narrative review explores the mechanisms of action and efficacy of caffeine and the potential for combinations of caffeine and other dietary compounds to exert psychological effects in excess of those expected following caffeine alone. The review focusses on, and indeed restricted its untargeted search to, the most commonly consumed sources of caffeine: products derived from caffeine-synthesising plants that give us tea (Camellia sinensis), coffee (Coffea genus), cocoa (Theabroma cacao) and guaraná (Paullinia cupana), plus multi-component energy drinks and shots. This literature suggests relevant benefits to mental performance that exceed those associated with caffeine for multi-ingredient energy drinks/shots and several low-caffeine extracts, including high-flavanol cocoa and guarana. However, there is a general lack of research conducted in such a way as to disentangle the relative contributions of the component parts of these products.

Endogenous Taurine Downregulation Is Required for Renal Injury in Salt-Sensitive Hypertensive Rats via CBS/H2S Inhibition

Although taurine is known to exert an antihypertensive effect, it is unclear whether it is involved in the mechanism for hypertension-related target organ injury. To reveal the role of endogenous taurine in renal injury formation during salt-sensitive hypertension and clarify its mechanisms, both salt-sensitive Dahl rats and salt-resistant SS-13BN rats were fed a high-salt diet (8% NaCl) and given 2% taurine for 6 weeks. Rat systolic blood pressure (SBP) was measured by the tail-cuff method and artery catheterization. Kidney ultrastructure was observed under an electron microscope. Taurine content and mRNA and protein levels of taurine synthases, cysteine dioxygenase type 1 (CDO1) and cysteine sulfinic acid decarboxylase (CSAD), were decreased in Dahl rats fed a high-salt diet. However, taurine supplementation and the resulting increase in renal taurine content reduced the increased SBP and improved renal function and structural damage in high-salt diet-fed Dahl rats. In contrast, taurine did not affect SS-13BN SBP and renal function and structure. Taurine intervention increased the renal H₂S content and enhanced cystathionine-β-synthase (CBS) expression and activity in Dahl rats fed a high-salt diet. Taurine reduced the renin, angiotensin II, and aldosterone contents and the levels of oxidative stress indices in Dahl rat renal tissues but increased antioxidant capacity, antioxidant enzyme activity, and protein expression. However, taurine failed to achieve this effect in the renal tissue of SS-13BN rats fed a high-salt diet. Pretreatment with the CBS inhibitor HA or renal CBS knockdown inhibited H₂S generation and subsequently blocked the effect of taurine on renin, superoxide dismutase 1 (SOD1), and superoxide dismutase 2 (SOD2) levels in high-salt-stimulated Dahl renal slices. In conclusion, the downregulation of endogenous taurine production resulted in a decrease in the renal CBS/H₂S pathway. This decrease subsequently promoted renin-angiotensin-aldosterone system (RAAS) activation and oxidative stress in the kidney, ultimately contributing to renal injury in salt-sensitive Dahl rats.

Ameliorative effect of taurine against diabetes and renal-associated disorders (Review)

To develop novel therapeutic methods for both diabetic and renal disorders, scientists had initially focused on elucidating the molecular mechanisms of taurine in established cell lines and mouse models. Although a large amount of data have been revealed, taurine has been confirmed to be the next step of novel promising therapeutic interventions against diabetic disorders. Taurine appears to ameliorate diabetes 1-related complications in various organs through its antioxidant, anti-inflammatory and anti-hormonal actions. In type 2 diabetes, taurine has been positively implicated in glucose homeostasis, exerting potent hypoglycemic, anti-obesity, hypotensive and hypolipidemic effects. Of particular interest is that taurine provides protection against renal dysfunction, including hypertension and proteinuria, specific glomerular and tubular disorders, acute and chronic renal conditions, and diabetic nephropathy. The ameliorative effects of taurine against renal disorders are based on its osmoregulatory properties, its association with signaling pathways and its association with the renin-angiotensin-aldosterone system (RAAS). Further clinical studies are required to ensure the importance of research findings.

Single or combined protective and therapeutic impact of taurine and hesperidin on carbon tetrachloride-induced acute hepatic injury in rat

Currently, hepatic injury due to environmental pollutants extremely threatens human health and elicits great concern. Hence, there is a high global interest to find natural novel formulation products with potent hepatoprotective activity to combat liver disease. Hence, we evaluated the protective or therapeutic effect of hesperidin (HSP) and taurine (TAU), individually and in combination, on carbon tetrachloride (CCl₄)-induced acute hepatic injury in rats. The pre- or posttreatment by HSP and/or TAU significantly depressed CCl₄-induced elevation of alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, gamma-glutamyl transferase, total bilirubin, direct bilirubin, indirect bilirubin, malondialdehyde, globulins (α1, α2, β, and γ), albumin/globulin ratio, triglycerides, total cholesterol, high-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, low-density lipoprotein cholesterol, nitric oxide, and myeloperoxidase levels. Also, the pre- or posttreatment by HSP and/or TAU significantly minimized CCl₄-induced reduction of superoxide dismutase, catalase, reduced glutathione, and albumin concentrations. Furthermore, the protective or therapeutic administration of HSP and/or TAU markedly restored the CCl₄-induced altered hepatic architecture, depleted glycogen, and DNA contents. Notably, alleviating CCl₄-induced hepatotoxicity was more prominent in the protective groups than the therapeutic groups. More importantly, most of biochemical and histopathological parameters of HSP+TAU did not significantly differ from those of separate TAU or HSP neither before nor after CCl₄ exposure. Conclusively, HSP or TAU could be candidate protective agents against CCl₄ hepatotoxic impacts but the combination of both bioactive offers only a limited synergistic effect. Graphical abstract.

Protective Effect of Curcumin on Acrylamide-Induced Hepatic and Renal Impairment in Rats: Involvement of CYP2E1

As a chemical extensively used in industrial areas and formed during heating of carbohydrate-rich foods and tobacco, acrylamide (ACR) has been demonstrated to exert a variety of systemic toxic effects including hepatotoxicity and nephrotoxicity. In the present study, we investigated the effect of curcumin, a natural polyphenolic compound in a popular spice known as turmeric, on the hepatic and renal impairment caused by ACR exposure to 40 mg/kg for 4 weeks in rats. The administration of curcumin at doses of 50 and 100 mg/kg to ACR-intoxicated rats significantly decreased the serum levels of alanine transaminase, aspartate transaminase, creatinine, and urea; improved the histological changes of liver and kidney caused by ACR; reduced the number of apoptotic cells; as well as relieved ACR-induced hepatic and renal oxidative stress. Moreover, curcumin inhibited the CYP2E1 overexpression induced by ACR in the liver and kidney tissues. Therefore, curcumin could be applied as a potential strategy for the intervention of ACR-induced systemic toxicity. The inhibition of CYP2E1 might be involved in the protection of curcumin against ACR-induced hepatotoxicity and nephrotoxicity.

The potential role of mitochondrial impairment in the pathogenesis of imatinib-induced renal injury

Imatinib is a tyrosine kinase inhibitor widely administered against chronic myeloid leukemia. On the other hand, drug-induced kidney proximal tubular injury, electrolytes disturbances, and renal failure is a clinical complication associated with imatinib therapy. There is no precise cellular mechanism(s) for imatinib-induced renal injury. The current investigation aimed to evaluate the role of mitochondrial dysfunction and oxidative stress in the pathogenesis of imatinib nephrotoxicity. Rats received imatinib (50 and 100 mg/kg, oral, 14 consecutive days). Serum and urine biomarkers of renal injury and markers of oxidative stress in the kidney tissue were assessed. Moreover, kidney mitochondria were isolated, and mitochondrial indices, including mitochondrial depolarization, dehydrogenases activity, mitochondrial permeabilization, lipid peroxidation (LPO), mitochondrial glutathione levels, and ATP content were determined. A significant increase in serum (Creatinine; Cr and blood urea nitrogen; BUN) and urine (Glucose, protein, gamma-glutamyl transferase; γ-GT, and alkaline phosphatase; ALP) biomarkers of renal injury, as well as serum electrolytes disturbances (hypokalemia and hypophosphatemia), were evident in imatinib-treated animals. On the other hand, imatinib (100 mg/kg) caused an increase in kidney ROS and LPO. Renal tubular interstitial nephritis, tissue necrosis, and atrophy were evident as tissue histopathological changes in imatinib-treated rats. Mitochondrial parameters were also adversely affected by imatinib administration. These data represent mitochondrial impairment, renal tissue energy crisis, and oxidative stress as possible mechanisms involved in the pathogenesis of imatinib-induced renal injury and serum electrolytes disturbances.

Impact of Supplementary Amino Acids, Micronutrients, and Overall Diet on Glutathione Homeostasis

Glutathione (GSH) is a critical endogenous antioxidant found in all eukaryotic cells. Higher GSH concentrations protect against cellular damage, tissue degeneration, and disease progression in various models, so there is considerable interest in developing interventions that augment GSH biosynthesis. Oral GSH supplementation is not the most efficient option due to the enzymatic degradation of ingested GSH within the intestine by γ-glutamyltransferase, but supplementation of its component amino acids-cysteine, glycine, and glutamate-enhances tissue GSH synthesis. Furthermore, supplementation with some non-precursor amino acids and micronutrients appears to influence the redox status of GSH and related antioxidants, such as vitamins C and E, lowering systemic oxidative stress and slowing the rate of tissue deterioration. In this review, the effects of oral supplementation of amino acids and micronutrients on GSH metabolism are evaluated. And since specific dietary patterns and diets are being prescribed as first-line therapeutics for conditions such as hypertension and diabetes, the impact of overall diets on GSH homeostasis is also assessed.

Ameliorative effects of taurine against diabetes: a review

Diets in rats and humans have shown promising results. Taurine improved glucagon activity, promoted glycemic stability, modified glucose levels, successfully addressed hyperglycemia via advanced glycation end-product control, improved insulin secretion and had a beneficial effect on insulin resistance. Taurine treatment performed well against oxidative stress in brain, increased the secretion of required hormones and protected against neuropathy, retinopathy and nephropathy in diabetes compared with the control. Taurine has been observed to be effective in treatments against diabetic hepatotoxicity, vascular problems and heart injury in diabetes. Taurine was shown to be effective against oxidative stress. The mechanism of action of taurine cannot be explained by one pathway, as it has many effects. Several of the pathways are the advanced glycation end-product pathway, PI3-kinase/AKT pathway and mitochondrial apoptosis pathway. The worldwide threat of diabetes underscores the urgent need for novel therapeutic measures against this disorder. Taurine (2-aminoethane sulfonic acid) is a natural compound that has been studied in diabetes and diabetes-induced complications.

Prophylactic role of taurine and its derivatives against diabetes mellitus and its related complications

Taurine is a conditionally essential amino acid present in the body in free form. Mammalian taurine is synthesized in the pancreas via the cysteine sulfinic acid pathway. Anti-oxidation and anti-inflammation are two main properties through which it exerts its therapeutic effects. Many studies have shown its excellent therapeutic potential against diabetes mellitus and related complications like diabetic neuropathy, retinopathy, nephropathy, hematological dysfunctions, reproductive dysfunctions, liver and pancreas related complications etc. Not only taurine, a number of its derivatives have also been reported to be important in ameliorating diabetic complications. The present review has been aimed to describe the importance of taurine and its derivatives against diabetic metabolic syndrome and related complications.

Antidiabetic and antioxidant effects of saponarin from Gypsophila trichotoma on streptozotocin-induced diabetic normotensive and hypertensive rats

BACKGROUND

Diabetes and hypertension are diseases that often coexist, which increases the risk of chronic organ damages and cardiovascular complications.

PURPOSE

To evaluate the effects of saponarin, isolated from Gypsophila trichotoma Wend, on blood pressure, glycemia, body weight, and liver biochemical parameters related to oxidative stress in diabetic normotensive Wistar Kyoto rats (NTR) and spontaneously hypertensive rats (SHR).

METHODS

Diabetes was induced by administration of streptozotocin (40 mg/kg, i.p.). The following biochemical parameters: reduced glutathione (GSH), malondialdehyde (MDA), total cytochrome P450, aniline hydroxylase (AH) activity, as well as the activities of antioxidant enzymes such as glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) were measured in the livers of euthanized rats.

RESULTS

Saponarin exerted slight antihypertensive activity in non-diabetic SHR, judged by 19% (p<0.05) decrease of the initial blood pressure. However, such effect was not observed in streptozotocin-induced diabetic SHR (SHR-D). Streptozotocin-induced diabetes was evidenced by 78% (p<0.05) and by 171% (p<0.05) increase in blood glucose level in NTR and SHR, respectively. In non-diabetic SHR the initial MDA quantity was by 36% (p<0.05) higher and the initial GSH levels were by 28% (p<0.05) lower in comparison to non-diabetic NTR. Significant decrease in the activities of GPx, GR, and GST was measured in the livers of all diabetic rats. Treatment with saponarin ameliorated the above mentioned liver parameters in both diabetic strains, however its effects were less pronounced in the diabetic SHR group.

CONCLUSION

Taken together our data indicate that diabetes and hypertension in combination are more difficult to be modulated by saponarin.

Effect of taurine on chronic and acute liver injury: Focus on blood and brain ammonia

Hyperammonemia is associated with chronic and acute liver injury. There is no promising therapeutic agent against ammonia-induced complications. Hence, finding therapeutic molecules with safe profile of administration has clinical value. The present study was conducted to evaluate the role of taurine (TA) administration on plasma and brain ammonia and its consequent events in different models of chronic and acute liver injury and hyperammonemia. Bile duct ligated (BDL) rats were used as a model of chronic liver injury. Thioacetamide and acetaminophen-induced acute liver failure were used as acute liver injury models. A high level of ammonia was detected in blood and brain of experimental groups. An increase in brain ammonia level coincided with a decreased total locomotor activity of animals and significant changes in the biochemistry of blood and also liver tissue. TA administration (500 and 1000 mg/kg, i.p), effectively alleviated liver injury and its consequent events including rise in plasma and brain ammonia and brain edema. The data suggested that TA is not only a useful and safe agent to preserve liver function, but also prevented hyperammonemia as a deleterious consequence of acute and chronic liver injury.

Octaphlorethol A isolated from Ishige foliacea prevents and protects against high glucose-induced oxidative damage in vitro and in vivo

We investigated the protective effect of octaphlorethol A (OPA) isolated from Ishige foliacea against high-glucose-induced oxidative damage, as indicated by reactive oxygen species (ROS) generation, lipid peroxidation, and cell death, in human umbilical vein endothelial cells (HUVECs) and in a zebrafish model. OPA treatment significantly and dose-dependently decreased ROS generation, lipid peroxidation, and cell death in HUVECs and in a zebrafish model. Our results show that OPA can protect HUVECs and zebrafish against high glucose by suppressing intracellular ROS generation, lipid peroxidation, and cell death.

The role of antioxidants and other agents in alleviating hyperglycemia mediated oxidative stress and injury in liver

Several antioxidants and agents having similar antioxidant effects are known to exert beneficial effects in ameliorating the injurious effects of hyperglycemia on liver in different diabetic in vitro and in vivo models. The review deals with some of the agents which have been shown to exert protective effects on liver against hyperglycemic insult and the various mechanisms involved. The different classes of agents which protect the diabetic liver or decrease the severity of hyperglycemia mediated injury include flavonoids, catechins, and other polyphenolic compounds, curcumin and its derivatives, certain vitamins, hormones and drugs, trace elements, prototypical antioxidants and amino acids. Some of the pronounced changes mediated by the antioxidants in liver exposed to hyperglycemia include decreased oxidative stress, and alterations in carbohydrate and lipid metabolism. Other mechanisms through which the agents ameliorate hyperglycemia mediated liver injury include decrease in oxidative DNA and protein damage, restoration of mitochondrial structural and functional integrity, decrease in inflammation and improved insulin signaling. Thus, antioxidants may prove to be an important mode of defense in maintaining normal hepatic functions in diabetes.

S-allylcysteine Improves Streptozotocin-Induced Alterations of Blood Glucose, Liver Cytochrome P450 2E1, Plasma Antioxidant System, and Adipocytes Hormones in Diabetic Rats

BACKGROUND

S-allylcysteine, a garlic derivative, could have a protective effect against pathogenesis of diabetes mellitus.

OBJECTIVES

Sustained free radical generation and oxidative damage to system leads to the final conclusion phase of diabetes and also it coexists with a constant diminution in the antioxidant status.The present study aims to evaluate the therapeutic effects of S-allylcysteine (SAC) against adipocytes hormones and antioxidant defense systems of plasma and erythrocytes of treptozotocin (STZ) induced diabetes in rats.

MATERIALS AND METHODS

Diabetic rats were administered SAC (150 mg/kg b.w) orally for 45 days. At 46(th) day, the rats were anesthetized, and blood and liver sample were collected for analyzing glucose, plasma insulin, CYP2E1 activity, Thiobarbituric acid reactive substances (TBARS), hydroperoxide, enzymatic and nonenzymatic antioxidants, reduced glutathione (GSH), ceruloplasmin, plasma leptin, and adiponectin.

RESULTS

The levels of glucose, CYP2E1 activity, Thiobarbituric acid reactive substances (TBARS), hydroperoxide, and ceruloplasmin were increased significantly; whereas, the levels of plasma insulin, reduced glutathione, enzymatic and nonenzymatic antioxidants, leptin and adiponectin were decreased in experimental diabetic rats. Administration of SAC to diabetic rats led to a decrease in the levels of glucose, CYP2E1 activity, TBARS, and ceruloplasmin. In addition, the levels of plasma insulin, enzymatic and nonenzymatic antioxidants leptin and adiponectin were increased in SAC treated diabetic rats. Gliclazide, a standard drug for diabetes, was used for the comparative purpose.

CONCLUSIONS

The results of the present investigation suggest that SAC could be used as a food supplement in the treatment of diabetes characterized by provoked antioxidant status, altered blood glucose, and hormones level.

Isothiocyanates protect against oxidized LDL-induced endothelial dysfunction by upregulating Nrf2-dependent antioxidation and suppressing NFκB activation

SCOPE

Oxidative stress plays a pivotal role in the pathophysiology of cardiovascular diseases. Oxidized low-density lipoprotein (oxLDL) is a key contributor to atherogenesis through multiple mechanisms. In this study, we investigated the protection by three structurally related isothiocyanates, i.e., sulforaphane (SFN), benzyl isothiocyanate (BITC), and phenethyl isocyanate (PEITC), against oxLDL-induced leukocyte adhesion to vascular endothelium and the mechanism involved.

METHODS AND RESULTS

The protection against oxLDL-induced endothelial dysfunction by isothiocyanates was studied in human umbilical vein endothelial cells (HUVECs). oxLDL increased reactive oxygen species (ROS) production, stimulated nuclear factor-kappaB (NFκB) activation, and enhanced intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and E-selectin expression in HUVECs, which led to promotion of monocyte adhesion to HUVECs. Treatment with SFN, BITC, and PEITC (0-10 μM) dose-dependently induced heme oxygenase (HO)-1, glutamate cysteine ligase (GCL) catalytic and modifier subunit expression, intracellular glutathione content, and antioxidant response element (ARE)-luciferase reporter activity. SFN, BITC, and PEITC pretreatment reversed oxLDL-induced ROS production, NFκB nuclear translocation, κB-reporter activity, ICAM-1, VCAM-1, and E-selectin expression, and monocyte adhesion to endothelial cells. Both heme oxygenase 1 (HO-1) and nuclear factor erythroid 2-related factor 2 (Nrf2) knockdown attenuated the isothiocyanate inhibition of oxLDL-induced ROS production, κB-reporter activity, and adhesion molecule expression.

CONCLUSION

SFN, BITC, and PEITC protect against oxLDL-induced endothelial damage by upregulating Nrf2-dependent HO-1 and GCL expression, which leads to inhibition of NFκB activation and ICAM-1, VCAM-1, and E-selectin expression.

Quercetin suppressed CYP2E1-dependent ethanol hepatotoxicity via depleting heme pool and releasing CO

Naturally occuring quercetin protects hepatocytes from ethanol-induced oxidative stress, and heme oxygenase-1 (HO-1) induction and carbon monoxide (CO) metabolite may be implicated in the beneficial effect. However, the precise mechanism by which quercetin counteracts CYP2E1-mediated ethanol hepatotoxicity through HO-1 system is still remained unclear. To explore the potential mechanism, herein, ethanol (4.0 g/kg.bw.) was administrated to rats for 90 days. Our data showed that chronic ethanol over-activated CYP2E1 but suppressed HO-1 with concurrent hepatic oxidative damage, which was partially normalized by quercetin (100mg/kg.bw.). Quercetin (100 μM) induced HO-1 and depleted heme pool when incubated to human hepatocytes. Ethanol-stimulated (100mM) CYP2E1 upregulation was suppressed by quercetin but further enhanced by HO-1 inhibition with resultant heme accumulation. CO scavenging blocked the suppression of quercetin only on CYP2E1 activity. CO donor dose-dependently inactivated CYP2E1 of ethanol-incubated microsome, which was mimicked by HO-1 substrate but abolished by CO scavenger. Thus, CYP2E1-mediated ethanol hepatotoxicity was alleviated by quercetin through HO-1 induction. Depleted heme pool and CO releasing limited protein synthesis and inhibited enzymatic activity of CYP2E1, respectively.

Mechanism of the protective action of taurine in toxin and drug induced organ pathophysiology and diabetic complications: a review

Taurine (2-aminoethanesulfonic acid), a conditionally essential amino acid, is found in large concentrations in all mammalian tissues and is particularly abundant in aquatic foods. Taurine exhibits membrane stabilizing, osmoregulatory and cytoprotective effects, antioxidative properties, regulates intracellular Ca(2+) concentration, modulates ion movement and neurotransmitters, reduce the levels of pro-inflammatory cytokines in various organs and controls blood pressure. Recently, emerging evidence from the literature shows the effectiveness of taurine as a protective agent against several environmental toxins and drug-induced multiple organ injuries as the outcome of hepatotoxicity, nephrotoxicity, neurotoxicity, testicular toxicity and cardiotoxicity in several animal models. Besides, taurine is also effective in combating diabetes and its associated complications, including cardiomyopathy, nephropathy, neuropathy, retinopathy and atherosclerosis. These beneficial effects appear to be due to the multiple actions of taurine on cellular functions. This review summarizes the mechanism of the prophylactic role of taurine against several environmental toxins and drug-induced organ pathophysiology and diabetes.

Effect of vanillin and ethyl vanillin on cytochrome P450 activity in vitro and in vivo

Food safety is of extreme importance to human health. Vanillin and ethyl vanillin are the widely used food additives and spices in foods, beverages, cosmetics and drugs. The objective of the present work was to evaluate the impact of vanillin and ethyl vanillin on the activities of CYP2C9, CYP2E1, CYP3A4, CYP2B6 and CYP1A2 in human liver microsomes (HLM) in vitro, and impact on the activities of CYP1A2, CYP2C, CYP3A and CYP2E1 in rat liver microsomes (RLM) in vivo. The in vitro results demonstrated that vanillin and ethyl vanillin had no significant effect on the activity of five human CYP450 enzymes with concentration ranged from 8 to 128 μM. However, after rats were orally administered vanillin or ethyl vanillin once a day for seven consecutive days, CYP2E1 activity was increased and CYP1A2 activity was decreased in RLM. The in vivo results revealed that drug interaction between vanillin/ethyl vanillin and the CYP2E1/CYP1A2-metabolizing drugs might be possible, and also suggested that the application of the above additives in foods and drugs should not be unlimited so as to avoid the adverse interaction.

Induction of glutathione synthesis and heme oxygenase 1 by the flavonoids butein and phloretin is mediated through the ERK/Nrf2 pathway and protects against oxidative stress

Butein and phloretin are chalcones that are members of the flavonoid family of polyphenols. Flavonoids have well-known antioxidant and anti-inflammatory activities. In rat primary hepatocytes, we examined whether butein and phloretin affect tert-butylhydroperoxide (tBHP)-induced oxidative damage and the possible mechanism(s) involved. Treatment with butein and phloretin markedly attenuated tBHP-induced peroxide formation, and this amelioration was reversed by l-buthionine-S-sulfoximine [a glutamate cysteine ligase (GCL) inhibitor] and zinc protoporphyrin [a heme oxygenase 1 (HO-1) inhibitor]. Butein and phloretin induced both HO-1 and GCL protein and mRNA expression and increased intracellular glutathione (GSH) and total GSH content. Butein treatment activated the ERK1/2 signaling pathway and increased Nrf2 nuclear translocation, Nrf2 nuclear protein-DNA binding activity, and ARE-luciferase reporter activity. The roles of the ERK signaling pathway and Nrf2 in butein-induced HO-1 and GCL catalytic subunit (GCLC) expression were determined by using RNA interference directed against ERK2 and Nrf2. Both siERK2 and siNrf2 abolished butein-induced HO-1 and GCLC protein expression. These results suggest the involvement of ERK2 and Nrf2 in the induction of HO-1 and GCLC by butein. In an animal study, phloretin was shown to increase GSH content and HO-1 expression in rat liver and decrease carbon tetrachloride-induced hepatotoxicity. In conclusion, we demonstrate that butein and phloretin up-regulate HO-1 and GCL expression through the ERK2/Nrf2 pathway and protect hepatocytes against oxidative stress.

Taurine exerts hypoglycemic effect in alloxan-induced diabetic rats, improves insulin-mediated glucose transport signaling pathway in heart and ameliorates cardiac oxidative stress and apoptosis

Hyperlipidemia, inflammation and altered antioxidant profiles are the usual complications in diabetes mellitus. In the present study, we investigated the therapeutic potential of taurine in diabetes associated cardiac complications using a rat model. Rats were made diabetic by alloxan (ALX) (single i.p. dose of 120mg/kg body weight) and left untreated or treated with taurine (1% w/v, orally, in water) for three weeks either from the day of ALX exposure or after the onset of diabetes. Animals were euthanized after three weeks. ALX-induced diabetes decreased body weight, increased glucose level, decreased insulin content, enhanced the levels of cardiac damage markers and altered lipid profile in the plasma. Moreover, it increased oxidative stress (decreased antioxidant enzyme activities and GSH/GSSG ratio, increased xanthine oxidase enzyme activity, lipid peroxidation, protein carbonylation and ROS generation) and enhanced the proinflammatory cytokines levels, activity of myeloperoxidase and nuclear translocation of NFκB in the cardiac tissue of the experimental animals. Taurine treatment could, however, result to a decrease in the elevated blood glucose and proinflammatory cytokine levels, diabetes-evoked oxidative stress, lipid profiles and NFκB translocation. In addition, taurine increased GLUT 4 translocation to the cardiac membrane by enhanced phosphorylation of IR and IRS1 at tyrosine and Akt at serine residue in the heart. Results also suggest that taurine could protect cardiac tissue from ALX induced apoptosis via the regulation of Bcl2 family and caspase 9/3 proteins. Taken together, taurine supplementation in regular diet could play a beneficial role in regulating diabetes and its associated complications in the heart.

Taurine is more effective than melatonin on cytochrome P450 2E1 and some oxidative stress markers in streptozotocin-induced diabetic rats

Melatonin and taurine have alleviative effects in streptozotocin (STZ)-induced diabetic rats. Male Wistar rats were divided into nondiabetic, diabetic, diabetic melatonin supplemented and diabetic taurine supplemented groups. At the end of the study, both blood and liver were collected for determination of some oxidative stress parameters, and hepatic cytochrome P450 2E1 (CYP2E1) enzyme activity and gene expression. An increased CYP2E1 activity and expression level with a concomitant significant change in oxidative stress parameters were found in STZ-induced diabetic rats. Taurine or melatonin supplementation to the diabetic rats alleviated these experimental parameters with a more significant effect for taurine than that of melatonin. Suppression of β-hydroxybutyrate (β-HB) production by taurine can be one of the mechanisms of a reduction in CYP2E1. Taurine was effective more than melatonin in reducing CYP2E1 activity and expression; therefore antioxidants might prove beneficial in type 1 diabetes associated with manifestations of liver injury.

Suppressive effect of the ethanolic extract of adlay bran on cytochrome P-450 enzymes in rat liver and lungs

Adlay ( Coix lachryma-jobi L. var. ma-yuen Stapf) is a grass crop and is reported to protect against various diseases such as cancer. To investigate the effect of the ethanolic extract of adlay bran (ABE) on drug-metabolizing enzymes and glutathione-related antioxidant enzymes in rats, three groups of eight male Sprague-Dawley rats each were fed a control diet or a diet containing 5 or 10% ABE for 4 weeks. Significant decreases in microsomal cytochrome P-450 (CYP) 1A1-catalyzed ethoxyresorufin O-deethylation, CYP2C-catalyzed diclofenac 4-hydroxylation, CYP2D-catalyzed dextromethorphan O-demethylation, and CYP3A-catalyzed testosterone 6β-hydroxylation in the liver and CYP1A1-catalyzed ethoxyresorufin O-deethylation in the lungs of rats fed ABE were observed. Immunoblot analyses also showed decreases of CYP1A1, 1A2, 2C6, 2C11, 2D1, 2E1, 3A1, and 3A2 in the liver and CYP1A1 in the lungs. Furthermore, rats fed the 10% ABE diet had a higher glutathione content and glutathione peroxidase, glutathione reductase, and glutathione S-transferase activities in the lungs, but such an increase was not noted in the liver. Inhibition of various CYP-catalyzed enzyme reactions by ABE in rat and human liver microsomes had also been shown. The results of this study indicate that ABE feeding may suppress CYP enzyme activities and CYP protein expression in the liver and lungs of rats. Moreover, the increase of the antioxidant potential by ABE is tissue-specific.

Cytochrome P450 2E1 and hyperglycemia-induced liver injury

Cytochrome P450 2E1 (CYP2E1), a microsomal enzyme involved in xenobiotic metabolism and generation of oxidative stress, has been implicated in promoting liver injury. The review deals with the changes in various cellular pathways in liver linked with the changes in regulation of CYP2E1 under hyperglycemic conditions. Some of the hepatic abnormalities associated with hyperglycemia-mediated induction of CYP2E1 include increased oxidative stress, changes in mitochondrial structure and function, apoptosis, nitrosative stress, and increased ketone body accumulation. Thus, changes in regulation of CYP2E1 are associated with the injurious effects of hyperglycemia in liver.

The potential usefulness of taurine on diabetes mellitus and its complications

Taurine (2-aminoethanesulfonic acid) is a free amino acid found ubiquitously in millimolar concentrations in all mammalian tissues. Taurine exerts a variety of biological actions, including antioxidation, modulation of ion movement, osmoregulation, modulation of neurotransmitters, and conjugation of bile acids, which may maintain physiological homeostasis. Recently, data is accumulating that show the effectiveness of taurine against diabetes mellitus, insulin resistance and its complications, including retinopathy, nephropathy, neuropathy, atherosclerosis and cardiomyopathy, independent of hypoglycemic effect in several animal models. The useful effects appear due to the multiple actions of taurine on cellular functions. This review summarizes the beneficial effects of taurine supplementation on diabetes mellitus and the molecular mechanisms underlying its effectiveness.

Effect of chitosan on hepatic drug-metabolizing enzymes and oxidative stress in rats fed low- and high-fat diets

Chitosan is sold worldwide as a lipid-lowering functional food and may be taken with certain medications. To investigate the effect of chitosan on drug-metabolizing enzymes and oxidative stress in the liver, male Wistar rats were fed a low- or high-fat diet with cellulose or chitosan for 4 weeks. A significant decrease in cytochrome P450 (CYP) 3A-catalyzed testosterone 6beta-hydroxylation in liver microsomes was observed in rats fed the chitosan with low- and high-fat diets. The expression of CYP 3A1 and 3A2, however, was suppressed by chitosan in rats fed the low-fat diet only. Furthermore, rats fed the low-fat diet with chitosan had lower hepatic glutathione S-transferase (GST) activity and superoxide dismutase activity and higher total tissue and microsomal lipid hydroperoxides. Hepatic alpha-tocopherol was lower in rats fed the chitosan-containing diet. The results suggest that chitosan is likely to modulate CYP 3A activity and protein expression and GST activity partially in a dietary fat-dependent manner. This change may cause a decrease in the metabolism of drugs catalyzed by these enzymes in liver tissues. Moreover, decrease of alpha-tocopherol level and SOD activity by chitosan partly accounts for the increase of hepatic lipid peroxidation.