Influence of green tea polyphenol in rats with arginine-induced renal failure

Beneficial effects of phenolic compounds: native phenolic compounds vs metabolites and catabolites

In the human body, the positive effects of phenolic compounds are increasingly observed through their presence in tissues and organs in their native form or in the form of metabolites or catabolites formed during digestion, microbial metabolism, and host biotransformation. The full extent of these effects is still unclear. The aim of this paper is to review the current knowledge of beneficial effects of native phenolic compounds or their metabolites and catabolites focusing on their role in the health of the digestive system, including disorders of the gastrointestinal and urinary tracts and liver. Studies are mostly connecting beneficial effects in the gastrointestinal and urinary tract to the whole food rich in phenolics, or to the amount of phenolic compounds/antioxidants in food. Indeed, the bioactivity of parent phenolic compounds should not be ignored due to their presence in the digestive tract, and the impact on the gut microbiota. However, the influence of their metabolites and catabolites might be more important for the liver and urinary tract. Distinguishing between the effects of parent phenolics vs metabolites and catabolites at the site of action are important for novel areas of food industry, nutrition and medicine.

Hormesis and Ginseng: Ginseng Mixtures and Individual Constituents Commonly Display Hormesis Dose Responses, Especially for Neuroprotective Effects

This paper demonstrates that ginseng mixtures and individual ginseng chemical constituents commonly induce hormetic dose responses in numerous biological models for endpoints of biomedical and clinical relevance, typically providing a mechanistic framework. The principal focus of ginseng hormesis-related research has been directed toward enhancing neuroprotection against conditions such as Alzheimer's and Parkinson's Diseases, stroke damage, as well as enhancing spinal cord and peripheral neuronal damage repair and reducing pain. Ginseng was also shown to reduce symptoms of diabetes, prevent cardiovascular system damage, protect the kidney from toxicities due to immune suppressant drugs, and prevent corneal damage, amongst other examples. These findings complement similar hormetic-based chemoprotective reports for other widely used dietary-type supplements such as curcumin, ginkgo biloba, and green tea. These findings, which provide further support for the generality of the hormetic dose response in the biomedical literature, have potentially important public health and clinical implications.

Effects of Dietary Arginine, Ornithine, and Zeolite Supplementation on Uremic Toxins in Cats

To test if arginine and ornithine, both components of the Krebs-Henseleit cycle, or zeolite, a potential ammonium absorber, can modulate the excretion of harmful bacterial metabolites, intestinal microbial protein fermentation was stimulated by feeding a high-protein (60.3%) diet as a single daily meal to 10 adult cats. The diet was supplemented without or with arginine (+50, 75, 100% compared to arginine in the basal diet), ornithine (+100, 150, 200% compared to arginine in the basal diet), or zeolite (0.125, 0.25, 0.375 g/kg body weight/day). The cats received each diet for 11 days. Urine, feces, and blood were collected during the last 4 days. Arginine and ornithine enhanced the postprandial increase of blood urea, but renal urea excretion was not increased. Zeolite decreased renal ammonium excretion and fecal biogenic amines. The data indicate an increased detoxification rate of ammonia by arginine and ornithine supplementation. However, as urea was not increasingly excreted, detrimental effects on renal function cannot be excluded. Zeolite had beneficial effects on the intestinal nitrogen metabolism, which should be further evaluated in diseased cats. Clinical studies should investigate whether dietary arginine and ornithine might improve hepatic ammonia detoxification or could be detrimental for renal function.

A discovery-driven approach to elucidate urinary metabolome changes after a regular and moderate consumption of beer and nonalcoholic beer in subjects at high cardiovascular risk

SCOPE

The aim of this work was to study the urinary metabolomics changes of participants that consumed beer, nonalcoholic beer (na-beer), and gin.

METHODS AND RESULTS

Thirty-three males at high cardiovascular risk between 55 and 75 years old participated in an open, randomized, crossover, controlled trial with three nutritional interventions consisting of beer, na-beer, and gin for 4 wk. Diet and physical activity was monitored throughout the study and compliance was assessed by measurement of urinary isoxanthohumol. Metabolomic analysis was performed in urine samples by LC coupled to an LTQ-Orbitrap mass spectrometer combined with univariate and multivariate statistical analysis. Ten metabolites were identified. Eight were exogenous metabolites related to beer, na-beer, or gin consumption, but two of them were related to endogenic changes: hydroxyadipic acid linked to fatty acid oxidation, and 4-guanidinobutanoic acid, which correlated with a decrease in urinary creatinine. Plasmatic acylcarnitines were quantified by targeted MS. A regular and moderate consumption of beer and na-beer decreased stearoylcarnitine concentrations.

CONCLUSION

Humulinone and 2,3-dihydroxy-3-methylvaleric acid showed to be potential biomarkers of beer and na-beer consumption. Moreover, the results of this trial provide new evidence that the nonalcoholic fraction of beer may increase fatty oxidation.

The effect of green tea on opposing toxicity of acrylamide on kidney function

Purpose

The purpose of this paper is to investigate the effects of green tea extract on kidney function tests, in male rats that received different doses of acrylamide (AA).

Design/methodology/approach

Animals were dispensed at random to one of the following treatments: group 1 served as control, whereas groups 2, 3 received seven, 14 mg/100 g B.W/day of AA, respectively, in drinking water for 15 and 30 days. Group 4 received green tea 1.5 percent concentration and groups 5, 6 received seven, 14 mg/100 g B.W/day in a mixture with green tea for 15 and 30 days.

Findings

Serum urea and creatinine significantly increase with AA. However, Total protein, albumin and A/G ratio showed significant drop in all treated groups when compared with control. Supplementation of rats with antioxidant (green tea) enhanced the general health condition, reduced the severity of genotoxic effect and the alteration in blood and serum parameters produced by AA.

Practical implications

The authors suggest that green tea may deliver a cushion for long therapeutic option against toxins-induced nephrotoxicity without damaging side effects.

Originality/value

The study uses green tea as a natural antioxidant source. Epigallocatechin-3 gallate is the most plentiful catechin preserved in green tea and a high source of flavonoids. Flavonoids are a group of phenolic products of plant metabolism with high antioxidant properties to reduce nephrotoxicity without side effects.

EGCG inhibit chemical reactivity of iron through forming an Ngal-EGCG-iron complex

Accumulated evidence indicates that the interconversion of iron between ferric (Fe(3+)) and ferrous (Fe(2+)) can be realized through interaction with reactive oxygen species in the Fenton and Haber-Weiss reactions and thereby physiologically effects redox cycling. The imbalance of iron and ROS may eventually cause tissue damage such as renal proximal tubule injury and necrosis. Many approaches were exploited to ameliorate the oxidative stress caused by the imbalance. (-)-Epigallocatechin-3-gallate, the most active and most abundant catechin in tea, was found to be involved in the protection of a spectrum of renal injuries caused by oxidative stress. Most of studies suggested that EGCG works as an antioxidant. In this paper, Multivariate analysis of the LC-MS data of tea extracts and binding assays showed that the tea polyphenol EGCG can form stable complex with iron through the protein Ngal, a biomarker of acute kidney injury. UV-Vis and Luminescence spectrum methods showed that Ngal can inhibit the chemical reactivity of iron and EGCG through forming an Ngal-EGCG-iron complex. In thinking of the interaction of iron and ROS, we proposed that EGCG may work as both antioxidant and Ngal binding siderphore in protection of kidney from injuries.

The protective effects of green tea extract against L-arginine toxicity to cultured human mesangial cells

The aim of this study was to investigate whether green tea extract (GTE) has the protective effects on excess L-arginine induced toxicity in human mesangial cell. Human mesangial cells treated with L-arginine were cultured on Dulbecco's modified eagle medium in the presence and absence of inducible nitric oxide synthase (iNOS) inhibitor and GTE. The cell proliferation was determined by 3 (4,5-dimethylthiazol-2-yl)-2, 5-diphengltetrqzolium bromide, a tetrazole assay. The iNOS mRNA and its protein expression were detected by reverse transcription polymerase chain reaction and Western blot, respectively. The concentration of nitric oxide (NO) was measured by NO enzyme-linced immuno sorbent assay kit. L-arginine significantly inhibited the proliferation of human mesangial cells, and induced the secretion of NO to the media. NO production by L-arginine was significantly suppressed by GTE and iNOS inhibitor (p<0.01). The expression level of iNOS mRNA and its protein that was significantly increased by L-arginine was decreased by iNOS inhibitor but not by GTE. GTE protected the mesangial cells from the NO-mediated cytotoxicity by scavenging the NO rather than by iNOS gene expression. Therefore, we conclude that GTE has some protective effect for renal cells against oxidative injury possibly by polyphenols contained in GTE.

Therapeutic potential of green tea: a new horizon in drug discovery

Worldwide, tea is one of the most widely consumed beverages. Green tea consumption is especially popular in China, Japan and other Asian countries. It has been found to be rich in polyphenolic compounds, of which catechins are the major constituents. A large number of clinical and preclinical studies have explored its pharmacologic activities. It holds promise as an antioxidant, anti-inflammatory, antibacterial, antiarteriosclerotic, cardioprotective, neuroprotective and anticarcinogenic agent, to name a few. This review summarizes the pharmacodynamics and pharmacokinetics of green tea polyphenols and explores their future as novel drugs for both health and disease conditions.

Protective Effect of Green Tea Extract and Tea Polyphenols against FK506-Induced Cytotoxicity in Renal Cells

The nephrotoxicity induced by the immunosuppressive drug FK506 (tacrolimus or fujimycin), limits its usefulness in widespread application, and the underlying mechanism has not been completely understood. The primary targets of FK506 in the kidney are the proximal tubular epithelial cells. In this study, the protection of green tea extract against FK506-induced cell death of LLC-PK1 cells was investigated. FK506 caused a significant decrease in survival of the cells, but the addition of green tea extract reduced this effect in a dose-dependent manner. Treatment of the cells with 50 microM (41.1 microg/ml) FK506 induced a significant increase in annexin V-positive/propidium iodide-negative cells from 2.68 to 14.5%, whereas the addition of 6.25, 12.5, and 25 microg/ml of green tea extract caused a significant protective effect in apoptotic cells from 14.5 to 6.51, 3.20 and 3.02%, respectively. The effect of five different constituent tea polyphenols was also examined. Epigallocatechin-gallate and epigallocatechin significantly reduced FK506-induced cytotoxicity but epicatechin and catechin had no effect on cell viability. Furthermore, changes in cytochrome c release and caspase activation, which characterize apoptosis, were studied. Epigallocatechin-gallate and epigallocatechin suppressed a significant release of cytochrome c and activation of caspase-3 in FK506-treated LLC-PK1 cells.

Adjuvant strategies for prevention of glomerulosclerosis

The glomerulosclerosis which frequently complicates diabetes and severe hypertension is mediated primarily by increased mesangial production and activation of transforming growth factor-beta (TGF-beta), which acts on mesangial cells to boost their production of matrix proteins while suppressing extracellular proteolytic activity. Hyperglycemia and glomerular hypertension work in various complementary ways to stimulate superoxide production via NADPH oxidase in mesangial cells; the resulting oxidant stress results in the induction and activation of TFG-beta. Nitric oxide, generated by glomerular capillaries and by mesangial cells themselves, functions physiologically to oppose mesangial TGF-beta overproduction; however, NO bioactivity is compromised by oxidant stress. In addition to low-protein diets and drugs that suppress angiotensin II activity, a variety of other agents and measures may have potential for impeding the process of glomerulosclerosis. These include vitamin E, which blunts the rise in mesangial diacylglycerol levels induced by hyperglycemia; statins and (possibly) policosanol, which down-regulate NADPH oxidase activity by diminishing isoprenylation of Rac1; lipoic acid, whose potent antioxidant activity antagonizes the impact of oxidant stress on TGF-beta expression; pyridoxamine, which inhibits production of advanced glycation endproducts; arginine, high-dose folate, vitamin C, and salt restriction, which may support glomerular production of nitric oxide; and estrogen and soy isoflavones, which may induce nitric oxide synthase in glomerular capillaries while also interfering with TGF-beta signaling. Further research along these lines may enable the development of complex nutraceuticals which have important clinical utility for controlling and preventing glomerulosclerosis and renal failure. Most of these measures may likewise reduce risk for left ventricular hypertrophy in hypertensives, inasmuch as the signaling mechanisms which mediate this disorder appear similar to those involved in glomerulosclerosis.

Amla (Emblica officinalis Gaertn.) Extracts Reduce Oxidative Stress in Streptozotocin-Induced Diabetic Rats

The antioxidant properties of amla extracts and their effects on the oxidative stress in streptozotocin-induced diabetes were examined in rats. Amla in the form of either the commercial enzymatic extract SunAmla (Taiyo Kagaku Co. Ltd., Yokkaichi, Japan) (20 or 40 mg/kg of body weight/day) or a polyphenol-rich fraction of ethyl acetate extract (10 or 20 mg/kg of body weight/day) was given orally for 20 days to the streptozotocin-induced diabetic rats. Amla extracts showed strong free radical scavenging activity. Amla also showed strong inhibition of the production of advanced glycosylated end products. The oral administration of amla extracts to the diabetic rats slightly improved body weight gain and also significantly alleviated various oxidative stress indices of the serum of the diabetic rats. The elevated serum levels of 5-hydroxymethylfurfural, which is a glycosylated protein that is an indicator of oxidative stress, were significantly reduced dose-dependently in the diabetic rats fed amla. Similarly, the serum level of creatinine, yet another oxidative stress parameter, was also reduced. Furthermore, thiobarbituric acid-reactive substances levels were significantly reduced with amla, indicating a reduction in lipid peroxidation. In addition, the decreased albumin levels in the diabetic rats were significantly improved with amla. Amla also significantly improved the serum adiponectin levels. These results form the scientific basis supporting the efficacy of amla for relieving the oxidative stress and improving glucose metabolism in diabetes.

Oxidative stress is enhanced in correlation with renal dysfunction: examination with the redox state of albumin

BACKGROUND

Cardiovascular disease is known to be the most important complication among patients with renal failure, and oxidative stress has been proposed to play a major role as the source of such complications. Human serum albumin (HSA) is composed of human mercaptoalbumin (HMA) with cysteine residues having reducing powers, of reversibly oxidized human non-mercaptoalbumin-1 (HNA-1), and strongly oxidized human non-mercaptoalbumin-2 (HNA-2).

METHODS

We used the "redox state of HSA" as a marker to investigate the current status of oxidative stress in predialysis patients with renal failure. The subjects were 55 nondialysis patients (31 males and 24 females) with chronic renal diseases, and having various degrees of renal function. The subjects' redox state of HSA was determined by a high-performance liquid chromatographic (HPLC) procedure, and the results presented in terms of the ratios between HNA-total(HNA-1 + HNA-2) and HNA-2.

RESULTS

The values for each fraction of HNA-total (f(HNA-total)) and f(HNA-2) were increased with a decrease of renal functions, and a significant positive correlation with serum creatinine (R= 0.529, P < 0.0001 and R= 0.618, P < 0.0001) was detected. Multiple (forward stepwise) regression analysis using f(HNA-total) and f(HNA-2) as the criterion variables was performed, and creatinine was adopted as significant explanatory variable in both equations.

CONCLUSION

We found that even before dialysis, oxidative stress was enhanced in correlation with the level of renal dysfunction among patients with chronic renal failure. In the future, antioxidant strategies should become part of treatment for predialysis renal failure.

Effect of polyphenolic compounds on the renal Na+,K(+)-ATPase during development and persistence of hypertension in rats

It has been suggested that polyphenolic substances provide protection against the risk factors of cardiovascular diseases. The present study was designed to investigate whether application of red wine polyphenols influences the kinetic properties of the renal Na+,K(+)-ATPase in rats with hypertension (164 +/- 8 mmHg) that was experimentally induced by the NO synthase inhibitor N(G.) -nitro-L- arginine methyl ester (L-NAME). Polyphenols in a dose of 40 mg kg(-1) day(-1) in drinking fluid induced different effects on the properties of the renal Na+,K(+)-ATPase depending on the mode of their administration. Preventive application of polyphenols during the development of hypertension (144 +/- 5 mmHg) partially protected the Na+,K(+)-ATPase molecule against hypertension-induced deterioration via increased capability of the enzyme to bind ATP and/or Na+ as suggested by decrease of Km and KNa, respectively, even to values lower than in controls. However, polyphenols did not prevent the hypertension-induced reduction of the number of active Na+,K(+)-ATPase molecules as shown by similar V(max) values as compared to the hypertensive L-NAME group. The above protection is probably secured by a NO-dependent mechanism as suggested by 150% increase of the NO synthesis. Additional treatment of already hypertensive animals with polyphenols (153 +/- 8 mmHg) resulted in partial restoration of the Na+,K(+)-ATPase affinities especially for sodium as indicated by significant diminution of KNa. However, polyphenols in this mode of application did not slow down the L-NAME-induced decrease in the number of Na+,K(+)-ATPase molecules in the kidney as suggested by additional significant decrease in V(max) values when comparing this group with the control group and also the hypertensive L-NAME group. In this case the polyphenols affected the Na,K-ATPase molecule in a NO-independent way as indicated by the fact that polyphenols failed to restore normal NO synthesis.