Green tea decoction improves glucose tolerance and reduces weight gain of rats fed normal and high-fat diet.

Green tea containing polyphenols exerts antidiabetic and antiobesity effects, but the mechanisms involved are not fully understood. In this study, we first analyzed and compared polyphenol compounds [epigallocatechin gallate (EGCG), epigallocatechin (EGC)] in decoction of green tea leaves versus usual green tea extracts. Second, the effects of acute (30 min) or chronic (6 weeks) oral administration of green tea decoction (GTD) on intestinal glucose absorption were studied in vitro in Ussing chamber, ex vivo using isolated jejunal loops and in vivo through glucose tolerance tests. Finally, we explore in rat model fed normal or high-fat diet the effects of GTD on body weight, blood parameters and on the relative expression of glucose transporters SGLT-1, GLUT2 and GLUT4. GTD cooked for 15 min contained the highest amounts of phenolic compounds. In fasted rats, acute administration of GTD inhibited SGLT-1 activity, increased GLUT2 activity and improved glucose tolerance. Similarly to GTD, acute administration of synthetic phenolic compounds (2/3 EGCG+1/3 EGC) inhibited SGLT-1 activity. Chronic administration of GTD in rat fed high-fat diet reduced body weight gain, circulating triglycerides and cholesterol and improved glucose tolerance. GTD-treated rats for 6 weeks display significantly reduced SGLT-1 and increased GLUT2 mRNA levels in the jejunum mucosa. Moreover, adipose tissue GLUT4 mRNA levels were increased. These results indicate that GTD, a traditional beverage rich in EGCG and EGC reduces intestinal SGLT-1/GLUT2 ratio, a hallmark of regulation of glucose absorption in enterocyte, and enhances adipose GLUT4 providing new insights in its possible role in the control of glucose homeostasis.

Protective effects of crude garlic by reducing iron-mediated oxidative stress, proliferation and autophagy in rats.

The impact of garlic, known for its antioxidant activities, on iron metabolism has been poorly investigated. The aim of this work was to study the effect of crude garlic pre-treatment on iron-mediated lipid peroxidation, proliferation and autophagy for 5 weeks. Rats were fed distilled water or garlic solution (1 g/kg body weight) by gavage for the first 3 weeks as pre-treatment and received a basal diet supplemented or not with ferrous sulfate (650 mg Fe/kg diet) for the last 2 weeks of treatment. Immunohistochemistry labeling and ultrastuctural observations were used to evaluate the iron deleterious effects in the liver. Iron supplementation induced cell proliferation predominantly in non parenchymal cells comparing to hepatocytes, but not apoptosis. In addition, iron was accumulated within the hepatic lysosomes where it triggers autophagy as evidenced by the formation of autophagic vesicles detected by LC3-II staining. It also induced morphologic alterations of the mitochondrial membranes due to increased lipid peroxidation as shown by elevated iron and malondialdehyde concentrations in serum and tissues. Garlic pre-treatment reduced iron-catalyzed lipid peroxidation by decreasing the malondialdehyde level in the liver and colon and by enhancing the status of antioxidants. In addition, garlic reduced the iron-mediated cell proliferation and autophagy by lowering iron storage in the liver and protected mitochondrial membrane. Based on these results, garlic treatment significantly prevented iron-induced oxidative stress, proliferation and autophagy at both biochemical and histological levels due to its potent free radical scavenging and antioxidant properties.

Influence of garlic or its main active component diallyl disulfide on iron bioavailability and toxicity.

Garlic is regularly consumed and is known to have diverse biologic activities, particularly due to its antioxidant properties. In this study, we hypothesized that crude garlic can prevent iron-mediated oxidative stress in a rat model of nutritional iron overload, and we used an in vitro model to confirm the results. For the in vivo studies, rats received a basal diet supplemented with or without carbonyl iron (3%) and were fed distilled water or garlic solution (1g/kg body weight) by gavage for 3 weeks. The presence of both garlic and iron led to a 2-fold increase in plasma iron and a 50% increase in liver iron as compared with iron alone. However, garlic did not offer any protection against iron-induced oxidative stress. Duodenal divalent metal transporter-1 mRNA expression was fully repressed by iron and by the combined treatments but was also reduced by garlic alone. To confirm these data, we tested the effect of diallyl disulfide, one of the active components in garlic, in vitro on polarized Caco-2 cells. A 24-hour treatment decreased iron uptake at the apical side of Caco-2 cells but increased the percentage of iron transfer at the basolateral side. This probably resulted from a modest induction of ferroportin mRNA and protein expression. These results suggest that garlic, when given in the presence of iron, enhances iron absorption by increasing ferroportin expression. The presence of garlic in the diet at the dose studied does not seem to protect against iron-mediated oxidative stress.

Vitiligo treatment with vitamins, minerals and polyphenol supplementation.

BACKGROUND: Mammalian pigmentation results from the synthesis and accumulation of photo protective epidermal melanin. Melanin was formed from the amino acid precursor L-tyrosine within specialized cells, the melanocytes. Oxidative stress has been suggested to be the initial pathogenetic event in melanocyte degeneration with H(2)O(2) accumulation in the epidermis of patients with active disease. Auto immunity has been also suggested as another hypothesis in the pathogenesis of depigmentation disorders. Topical corticosteroids and phototherapy as common treatment modalities have been prescribed in patients with vitiligo. However, they are often not effective and safe (epidermal atrophy). Therefore, research for alternative therapies continues. AIMS: To evaluate the beneficial effects of a supplementation with antioxidant vitamins (A, C, E) and minerals (zinc, selenium) for vitiligo treatment. METHODS: Forty experimental autoimmune vitiligo mice C57BL6, aged from 5 to 12 months showing visible signs of induced vitiligo, were sequentially randomized into five parallel groups (8 mice per group). Each group mice was allocated an identical pre coded cage. the first group (SZV) received the ED + 1,4 g zinc (Zn) + 0.04 g selenium (Se) + vitamins (A 118 UI, C 8,5 mg, E 5,4 UI) /kg diet, the second group (PSZV) received the ED + 1,4 g zinc (Zn) + 0.04 g selenium (Se) + vitamins (A 118 UI, C 8.5 mg, E 5,4 UI)/kg diet + Polyphenol orally, the group 3 (PSZ) received the ED + green tea decoction prepared from 100 g/l (polyphenol orally) + 1,4 g Zn + 0.04 g Se, the 4 (P) received the ED + green tea decoction prepared green tea decoction prepared from 100 g/l, the control group 5(C) received the ED + distilled water. Cure was defined as repigmentation of treated sites. Photographic and optical techniques were used both at the baseline and on weekly basis. RESULTS: By the end of the study, mice showed visible repigmentation. Using the investigator's global assessment, therapeutic success in terms of a clear repigmentation documented in 70% of treated mice. CONCLUSION: Our findings suggest that an antioxidant supplementation is significantly beneficial in contributing superior clinical efficacy to cure vitiligo.

Both aluminum and polyphenols in green tea decoction (Camellia sinensis) affect iron status and hematological parameters in rats.

BACKGROUND: Green tea leaves naturally contain high levels of polyphenols and aluminum (Al). Polyphenols in green tea decoction are considered to be one of the major factors responsible of low iron status. However, the effects of Al from green tea decoction on iron status and hematological parameters remained unclear. AIM OF THE STUDY: The objective was to investigate the Al absorption from green tea decoction and studied its influence on iron status and hematological parameters in rats. METHODS: During the experiment period, rats were given the experimental diet + a simple dose of Al sulfate with or without graded doses of green tea decoction (25, 50 and 100 g/l). The Al absorption was evaluated in the serum; however, iron status was evaluated by the iron concentration in the liver, kidney, spleen and femur. In addition, the hemoglobin and hematocrit were evaluated. RESULTS: Our results showed that the serum Al significantly increased between 61.5 and 342%, as tea doses-dependant. The Al sulfate significantly decreased the reserve of iron in all studied organs between 21.7 and 17% (P < 0.05). In groups receiving green tea decoction alone or Al + graded doses of tea, the reserve of iron significantly decreased in all studied organs between 59.4 and 18.5% (P < 0.01). Al alone or associated with drinking doses of tea significantly decreased hemoglobin concentration between 23.6 and 9% (P < 0.05) and hematocrit between 12.7 and 7% (P < 0.01). CONCLUSION: Our data showed that Al from green tea decoction was more absorbed in the serum than Al sulfate. Al absorption was associated with low iron status and reduction of hemoglobin and hematocrit. Considering that Al competes with iron in different stage of erythropoiesis including transferrin binding, so we could assume that the negative effect of tea on iron status arises not only from polyphenols iron complexes but also from Al released in tea decoction.

Artemisia herba-alba Asso (Asteraceae) has equivalent effects to green and black tea decoctions on antioxidant processes and some metabolic parameters in rats.

AIMS: The objective was to compare the long-term effects of Artemisia herba-alba Asso decoction with a green or black tea decoction, prepared without sugar, on the antioxidant processes in rats. METHODS: The direct parameters used in the control of antioxidant processes were total antioxidant status, glutathione peroxidase activity and conjugated dienes, as early markers of lipid peroxidation. However, the indirect parameters used in this control were the body weight gains, plasma glucose and lipid concentrations, iron, copper and zinc status. RESULTS: After 9 weeks, artemisia or tea decoctions did not influence the daily food intake of the groups; however, they significantly decreased the weight gains. They significantly increased the total antioxidant status between 83.5 and 111% and the whole blood glutathione peroxidase activity between 23 and 38%. However, only the green tea and artemisia decoctions significantly decreased the plasma conjugated diene levels by 35 and 55.5%, respectively. Regarding the trace element status, artemisia, green or black tea decoctions significantly reduced the blood Fe by 28, 30 and 17%, respectively. Also, liver Fe tended to be lower in all treated groups as compared to the control group. In contrast, artemisia significantly increased both blood and liver Cu by 50 and 28% as compared to the control group. Moreover, they significantly decreased the plasma glucose and triglyceride levels between 29 and 40%. For the cholesterol, only the artemisia decoction significantly reduced the total blood cholesterol by 17%. CONCLUSION: Artemisia as well as green tea decoctions increased the total antioxidant status, whole blood glutathione peroxidase activity and zinc and copper status, and prevented weight gains and increases in conjugated dienes, plasma glucose, lipids and iron status. The beneficial antioxidant effects were in descending order: artemisia decoction > or = green tea decoction > black tea decoction. So, artemisia could constitute a good adjuvant to combat obesity, hyperglycemia, hypertriglyceridemia, hypercholesterolemia and particularly oxidative stress.

Effect of green tea decoction on long-term iron, zinc and selenium status of rats.

AIMS: The objective was to examine the effect of green tea decoction given at two different concentrations on the long-term (6 weeks) iron, zinc and selenium status of rats. METHODS: During the experimental period, the rats were given ad libitum a basic diet + ultra pure water (control group), a basic diet + green tea decoction prepared from 50 g/l (tea 50 group), or a basic diet + green tea decoction prepared from 100 g/l (tea 100 group). The zinc and iron status was evaluated by determining their concentrations in the serum, blood precipitate, liver, spleen, femur, heart and kidney. Selenium status was evaluated by the serum selenium concentration and whole blood glutathione peroxidase activity. RESULTS: Green tea decoction significantly reduced serum iron by 26% in the tea groups (p < 0.01). The blood precipitate of iron was significantly decreased by 25 and 41% in the tea 50 and tea 100 groups (p < 0.01), respectively. The reserve of iron stored in the liver, spleen and femur was significantly reduced in the tea 100 group by 32% (p < 0.02), 20% (p < 0.04) and 35% (p < 0.005), respectively. Moreover, the two concentrations of green tea significantly decreased the reserve of iron stored in the kidney (p < 0.005) and heart (p < 0.02). In contrast with its effects on iron status, green tea decoction significantly increased the serum zinc in the tea 100 group by 24% (p < 0.001). It also increased the blood precipitate of zinc by 50 (p < 0.01) and 75% (p < 0.0001) in tea 50 and tea 100 groups, respectively. In the kidney, heart and femur, zinc significantly increased in the tea groups dependent on the tea dose. Similarly, the high concentration of green tea decoction significantly increased the serum selenium concentration by 16% (p < 0.004). In addition, both concentrations of green tea decoction significantly increased the whole blood glutathione peroxidase activity by 102 and 130% (p < 0.01). CONCLUSION: Green tea decoction reduced the iron status and improved the zinc and selenium status of rats. These effects may constitute another beneficial effect of the green tea decoction which could play an important role in the antioxidant processes.

Iron bioavailability and weight gains to iron-deficient rats fed a commonly consumed Tunisian meal 'bean seeds ragout' with or without beef and with green or black tea decoction.

The Fe bioavailability and the weight gains were evaluated in rats fed a commonly consumed Tunisian meal 'bean seeds ragout' (BSR), with or without beef and with black or green tea decoction. The Fe bioavailability was evaluated in Fe-deficient rats by the hemoglobin repletion method and the Fe stored in the liver. The addition of beef to the BSR significantly increased the Fe bioavailability from this meal by 147% and the reserve of Fe stored in the liver by 77% (P < 0.001). In contrast, both black and green tea decoctions caused a significant decrease of the Fe bioavailability from BSR meal (-19.6 +/- 4.9% and -14.9 +/- 4.1%, respectively). The reserve of Fe stored in the liver was significantly lower in the BSR, the black and the green tea groups than in the positive control group (FeSO4). The weight gains were significantly lower in the black and the green tea groups (3.9 +/- 5.7 g, 13 +/- 1.9 g, respectively) than in the BSR group (24.9 +/- 6 g). The addition of beef to BSR meal counteracted the inhibitory effect of the kidney bean and considerably improved the Fe bioavailability and the Fe stored in the liver of rats. The green tea decoction, which constitutes an important source of antioxidant factors, had the same inhibitory effect as the black tea decoction on the Fe bioavailability from BSR meal. In addition, both black and green teas significantly reduced the weight gains, where the black tea decoction has the most effect.