Goitrogenic/antithyroidal potential of green tea extract in relation to catechin in rats

The relationship between dietary total flavonoids and thyroid function in U.S.adults, NHANES 2007-2010

BACKGROUND

Although small studies have shown that flavonoids can affect thyroid disease, few epidemiological studies have explored the relationship between dietary total flavonoids (TFs) intake and serum thyroid function. The aim of this research was to evaluate the relationship between TFs and serum thyroid function.

METHODS

Our study included 4,949 adults from the National Health and Nutrition Examination Survey (NHANES) 2007-2010. Multivariable linear regression, subgroup analyses, and interaction terms were used to explore the relationships between TFs and thyroid function. And we also used restricted cubic splines (RCS) to investigate possible nonlinear relationships.

RESULTS

After adjusting for covariates, we found that log10-transformated dietary total flavonoids intake (LgTFs) was negatively associated with total thyroxine (TT4) (β = -0.153, 95% CI = -0.222 to -0.084, P<0.001). Subgroup analyses revealed a stronger and statistically supported association in subjects with high annual family income (β = -0.367, P<0.001, P for interaction = 0.026) and subjects with high poverty to income ratio (PIR) (β = -0.622, P<0.001, P for interaction = 0.042). And we found a U-shaped curve association between LgTFs and free triiodothyronine (FT3) (inflection point for LgTFs: 2.063).

CONCLUSION

The results of our study demonstrated that a higher intake of total flavonoids in the diet was negatively associated with a lower TT4. Furthermore, the associations were more pronounced in high annual family income and high PIR adults. And we found a U-shaped relationship between LgTFs and FT3. These findings provided guidance for future thyroid dysfunction diet guidelines.

Long-Term Consumption of Green Tea Can Reduce the Degree of Depression in Postmenopausal Women by Increasing Estradiol

Postmenopausal women face a higher risk of depression due to a combination of social and physiological factors. As a beverage rich in a variety of bioactive substances, green tea has significant effects on metabolism, inflammation and endocrine, and may reduce the risk of depression, but few studies have looked at the effects of green tea on postmenopausal women. Therefore, we designed this study to investigate the effects of long-term green tea consumption on inflammation, endocrine and depression levels in postmenopausal women. We investigated a tea-producing village and eventually included 386 postmenopausal women, both in the tea drinking and control groups. The results showed that there were significant differences in the degree of insomnia, degree of depression, BMI, SII and estradiol between the two groups. And, green tea consumption may reduce the risk of depression through the mediating pathway of sleep, SII and estradiol. In summary, long-term green tea consumption can reduce the risk of depression in postmenopausal women by reducing inflammation and increasing estradiol. This kind of living habit deserves further promotion.

Comparison of antithyroid effects and hepatic complications of methimazole with catechin and its nanoencapsulation form in adult male rats

OBJECTIVES

Methimazole is an antithyroid drug and is used clinically in hyperthyroidism. Liver dysfunction is one of the side effects of methimazole. Catechins are natural flavonoids and have antioxidant, antithyroid, and liver protection effects. Despite the wide range of biological properties of catechins, their effective use is limited due to poor water solubility, low stability, and low bioavailability. Catechin niosomal nanoencapsulation improves the properties of catechin and increases its antioxidant activities.

METHODS

Niosomal vesicles were synthesized by the Thin Film Hydration method and their physicochemical characteristics, morphology, and percentage of trapped catechin in them were determined by dynamic light scattering (DLS), transmission electron microscopy (TEM), and spectrophotometry, respectively. In this study, 32 adult male rats were divided into 4 groups: control, 50 mg/kg methimazole, 100 mg/kg catechin, and 100 mg/kg nanocapsule niosomal form of catechin. The drugs were administered orally and the duration of treatment was 8 weeks. Then, the serum concentration of thyroid hormones and thyroid stimulating hormone (TSH) by enzyme-linked immunosorbent assay (ELISA) method, and serum liver function tests were performed using an autoanalyzer. The activities of hepatic oxidative enzymes were measured spectrophotometrically.

RESULTS

Our study showed that the percentage of catechin encapsulation in the niosome was calculated to be 51%. A significant difference was observed in the catechin and encapsulated catechin treatment groups compared to the methimazole group (p <0.0001). In all three treatment groups of methimazole, catechin, and niosomal nanocapsule catechin, serum levels of TT3, TT4, FT3, FT4, body weight and daily consumption of water and food were significantly reduced compared to the control group (p <0.0001).

CONCLUSIONS

The antithyroid effects of catechin and its encapsulated form were comparable to methimazole. Also, the encapsulation improved the hepatoprotective effects of catechin.

Green Tea (Camellia sinensis): A Review of Its Phytochemistry, Pharmacology, and Toxicology

Objectives Green tea (Camellia sinensis) is a kind of unfermented tea that retains the natural substance in fresh leaves to a great extent. It is regarded as the second most popular drink in the world besides water. In this paper, the phytochemistry, pharmacology, and toxicology of green tea are reviewed systematically and comprehensively. Key findings Green tea has been demonstrated to be good for human health. Nowadays, multiple pharmacologically active components have been isolated and identified from green tea, including tea polyphenols, alkaloids, amino acids, polysaccharides, and volatile components. Recent studies have demonstrated that green tea shows versatile pharmacological activities, such as antioxidant, anticancer, hypoglycemic, antibacterial, antiviral, and neuroprotective. Studies on the toxic effects of green tea extract and its main ingredients have also raised concerns including hepatotoxicity and DNA damage. Summary Green tea can be used to assist the treatment of diabetes, Alzheimer’s disease, oral cancer, and dermatitis. Consequently, green tea has shown promising practical prospects in health care and disease prevention.

Endocrine disorders and fertility and pregnancy: An update

It is estimated that more and more couples suffer from fertility and pregnancy maintenance disorders. It is associated with impaired androgen secretion, which is influenced by many factors, ranging from genetic to environmental. It is also important to remember that fertility disorders can also result from abnormal anatomy of the reproductive male and female organ (congenital uterine anomalies - septate, unicornuate, bicornuate uterus; acquired defects of the uterus structure - fibroids, polyps, hypertrophy), disturbed hormonal cycle and obstruction of the fallopian tubes resulting from the presence of adhesions due to inflammation, endometriosis, and surgery, abnormal rhythm of menstrual bleeding, the abnormal concentration of hormones. There are many relationships between the endocrine organs, leading to a chain reaction when one of them fails to function properly. Conditions in which the immune system is involved, including infections and autoimmune diseases, also affect fertility. The form of treatment depends on infertility duration and the patient's age. It includes ovulation stimulation with clomiphene citrate or gonadotropins, metformin use, and weight loss interventions. Since so many different factors affect fertility, it is important to correctly diagnose what is causing the problem and to modify the treatment regimen if necessary. This review describes disturbances in the hormone secretion of individual endocrine organs in the context of fertility and the maintenance of pregnancy.

Multifunctional Therapeutic Potential of Phytocomplexes and Natural Extracts for Antimicrobial Properties

Natural products have been known for their antimicrobial factors since time immemorial. Infectious diseases are a worldwide burden that have been deteriorating because of the improvement of species impervious to various anti-infection agents. Hence, the distinguishing proof of antimicrobial specialists with high-power dynamic against MDR microorganisms is central to conquer this issue. Successful treatment of infection involves the improvement of new drugs or some common source of novel medications. Numerous naturally occurring antimicrobial agents can be of plant origin, animal origin, microbial origin, etc. Many plant and animal products have antimicrobial activities due to various active principles, secondary metabolites, or phytochemicals like alkaloids, tannins, terpenoids, essential oils, flavonoids, lectins, phagocytic cells, and many other organic constituents. Phytocomplexes’ antimicrobial movement frequently results from a few particles acting in cooperative energy, and the clinical impacts might be because of the direct effects against microorganisms. The restorative plants that may furnish novel medication lead the antimicrobial movement. The purpose of this study is to investigate the antimicrobial properties of the phytocomplexes and natural extracts of the plants that are ordinarily being utilized as conventional medications and then recommended the chance of utilizing them in drugs for the treatment of multiple drug-resistant disease.

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Thyroid hormones are necessary for the normal functioning of physiological systems. Therefore, knowledge of any factor (whether genetic, environmental or intrinsic) that alters the levels of thyroid-stimulating hormone (TSH) and thyroid hormones is crucial. Genetic factors contribute up to 65% of interindividual variations in TSH and thyroid hormone levels, but many environmental factors can also affect thyroid function. This review discusses studies that have analyzed the impact of environmental factors on TSH and thyroid hormone levels in healthy adults. We included lifestyle factors (smoking, alcohol consumption, diet and exercise) and pollutants (chemicals and heavy metals). Many inconsistencies in the results have been observed between studies, making it difficult to draw a general conclusion about how a particular environmental factor influences TSH and thyroid hormone levels. However, lifestyle factors that showed the clearest association with TSH and thyroid hormones were smoking, body mass index (BMI) and iodine (micronutrient taken from the diet). Smoking mainly led to a decrease in TSH levels and an increase in triiodothyronine (T3) and thyroxine (T4) levels, while BMI levels were positively correlated with TSH and free T3 levels. Excess iodine led to an increase in TSH levels and a decrease in thyroid hormone levels. Among the pollutants analyzed, most studies observed a decrease in thyroid hormone levels after exposure to perchlorate. Future studies should continue to analyze the impact of environmental factors on thyroid function as they could contribute to understanding the complex background of gene-environment interactions underlying the pathology of thyroid diseases.

Efficacy of Dietary Supplementation with Capsicum Annum L on Performance, Hematology, Blood Biochemistry and Hepatic Antioxidant Status of Growing Rabbits

Simple Summary

The inclusion of phytochemicals in animal diets is a strategy that has been used to improve animal productivity by increasing the production yield. The addition of red-hot pepper (RHP) powder enhances productive rabbit performance and immunological, biochemical, and antioxidant statuses. Rabbits fed 2% RHP powder had higher weights. Thus, adding 1 or 2% RHP powder to rabbit diets is an easy, simple, and safe option for producers. The slaughter index and physical blood characteristics red blood cells (RBC’s), packed cell volume (PCV), hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscle hemoglobin (MCH) and mean corpuscle hemoglobin concentration (MCHC) were significantly improved by feeding growing rabbits on RHP levels. Low-density lipoprotein-cholesterol (LDL-C) and very-low were distinctly (VLDL-C) decreased (p < 0.05) when feeding rabbits either 1 or 2% RHP supplemented diets. Furthermore, supplementing the rabbit’s diet with 1% RHP led to a significant increase (p < 0.001) in the total antioxidant capacity when compared to the rabbits fed with the basal diet. Additionally, the thyroxin concentration was increased with RHP supplementation. A remarkably significant effect on serum and hepatic oxidative stress responses was observed with RHP supplementation.

Abstract

Animals fed with a high amount of a wide range of antioxidants in their diet are significantly protected against oxidative stress. Powerful antioxidant substances such as vitamin E, vitamin C, and carotenoids are present naturally in red-hot pepper (RHP). This study hypothesized that using RHP may provide protection against oxidative stress and enhance animal physiological responses. Thus, this study aimed to investigate the effect of feeding New Zealand white rabbits with RHP-supplemented diets on their physiological and biochemical responses. New Zealand White rabbits (age = 6 weeks, n = 48) were split equally into three groups (n = 16 in each group). One group was fed a basal diet only (control group), with the other two groups fed a basal diet along with 1 and 2% RHP. Mass spectrometric analysis for the RHP methanolic extract showed some phenolic compounds, such as p-coumaric, sinapinic acids, vanillic, and luteolin, as well as catechin and its isomers. Hepatic antioxidant enzymes (SOD, GSH, GSH-Px, and CAT) were significantly elevated (p < 0.05) by feeding rabbits diets supplemented with 1 or 2% RHP. The addition of RHP significantly enhanced immune-responses; phagocytic activity, chemotaxis, TIg, IgG, IgM, and IgA increased when growing rabbits were fed RHP compared with the control group. In conclusion, dietary supplementation of 1 or 2% RHP may play a role as an enhancer of growth and immune response in growing rabbits.

Nutraceuticals in Thyroidology: A Review of in Vitro, and in Vivo Animal Studies

Nutraceuticals are defined as a food, or parts of a food, that provide medical or health benefits, including the prevention of different pathological conditions, and thyroid diseases, or the treatment of them. Nutraceuticals have a place in complementary medicines, being positioned in an area among food, food supplements, and pharmaceuticals. The market of certain nutraceuticals such as thyroid supplements has been growing in the last years. In addition, iodine is a fundamental micronutrient for thyroid function, but also other dietary components can have a key role in clinical thyroidology. Here, we have summarized the in vitro, and in vivo animal studies present in literature, focusing on the commonest nutraceuticals generally encountered in the clinical practice (such as carnitine, flavonoids, melatonin, omega-3, resveratrol, selenium, vitamins, zinc, and inositol), highlighting conflicting results. These experimental studies are expected to improve clinicians’ knowledge about the main supplements being used, in order to clarify the potential risks or side effects and support patients in their use.

Apigenin-mediated Alterations in Viability and Senescence of SW480 Colorectal Cancer Cells Persist in The Presence of L-thyroxine

INTRODUCTION

Deregulation of Thyroid Hormones (THs) system in Colorectal Cancer (CRC) suggests that these hormones may play roles in CRC pathogenesis. Flavonoids are polyphenolic compounds, which possess potent antitumor activities and interfere, albeit some of them, with all aspects of THs physiology. Whether the antitumor actions of flavonoids are affected by THs is unknown. Therefore, we investigated the effects of apigenin (Api), a well-known flavone, on some tumorigenic properties of SW480 CRC cells in the presence and absence of L-thyroxine (T4).

METHODS

Cell viability was assessed by MTT assay. Flow cytometry and DNA electrophoresis were used to evaluate cell death. Cell senescence was examined by in situ detection of β-galactosidase activity. Protein expression was assessed by antibody array technique.

RESULTS

While T4 had minimal effects, Api reduced cell growth and senescence by induction of apoptosis. Expression of anti-apoptotic and pro-apoptotic proteins were differentially affected by Api and T4. Survivin, HSP60 and HTRA were the most expressed proteins by the cells. Almost all Api-induced effects persisted in the presence of T4.

CONCLUSION

These data suggest that Api may inhibit CRC cell growth and progression through induction of apoptosis rather than cell necrosis or senescence. In addition, they suggest that T4 has minimal effects on CRC cell growth, and is not able to antagonize the anti-growth effects of Api. Regardless of the treatments, cells expressed high levels of survivin, HSP60 and HTRA, indicating that these proteins may play central roles in SW480 CRC cell immortality.

Impact of Antioxidant Natural Compounds on the Thyroid Gland and Implication of the Keap1/Nrf2 Signaling Pathway

BACKGROUND

Natural compounds with potential antioxidant properties have been used in the form of food supplements or extracts with the intent to prevent or treat various diseases. Many of these compounds can activate the cytoprotective Nrf2 pathway. Besides, some of them are known to impact the thyroid gland, often with potential side-effects, but in other instances, with potential utility in the treatment of thyroid disorders.

OBJECTIVE

In view of recent data regarding the multiple roles of Nrf2 in the thyroid, this review summarizes the current bibliography on natural compounds that can have an effect on thyroid gland physiology and pathophysiology, and it discusses the potential implication of the Nrf2 system in the respective mechanisms.

METHODS & RESULTS

Literature searches for articles from 1950 to 2018 were performed in PubMed and Google Scholar using relevant keywords about phytochemicals, Nrf2 and thyroid. Natural substances were categorized into phenolic compounds, sulfur-containing compounds, quinones, terpenoids, or under the general category of plant extracts. For individual compounds in each category, respective data were summarized, as derived from in vitro (cell lines), preclinical (animal models) and clinical studies. The main emerging themes were as follows: phenolic compounds often showed potential to affect the production of thyroid hormones; sulfur-containing compounds impacted the pathogenesis of goiter and the proliferation of thyroid cancer cells; while quinones and terpenoids modified Nrf2 signaling in thyroid cell lines.

CONCLUSION

Natural compounds that modify the activity of the Nrf2 pathway should be evaluated carefully, not only for their potential to be used as therapeutic agents for thyroid disorders, but also for their thyroidal safety when used for the prevention and treatment of non-thyroidal diseases.

Chavibetol corrects thyrotoxicosis through alterations in thyroid peroxidase

Thyrotoxicosis is a clinical syndrome that commonly results from excess secretion and/or release of thyroid hormones in the circulation. It affects most of the body systems and if not treated properly may lead to serious health problems. In this investigation, we isolated a phenolic compound, chavibetol (CHV) from Piper betel leaf and evaluated its possible ameliorative effects in thyrotoxicosis of rats. Adult female rats were rendered thyrotoxic by the administration of L-thyroxine (L-T₄) at 500 μg/kg/day, i.p., for 12 days, and then chavibetol (20.0 mg/kg, p.o.) was administered for 2 weeks. L-T₄ administration elevated the concentration of serum thyroxine and triiodothyronine, activities of alanineaminotransferase and aspartate aminotransferase, and decreased the thyrotropin level as well as the expression of thyroid peroxidase (TPO). Further, it increased the activities of hepatic 5'mono-deiodinase-I, glucose-6--phosphatase, sodium-potasium-ATPase, and lipid peroxidation, and depleted the cellular antioxidants. However, chavibetol treatment to thyrotoxic rats normalized almost all these indices including TPO and also preserved the integrity of thyroid tissues suggesting its potential to correct thyrotoxicosis. Effects of CHV were more or less similar to a conventional antithyroid drug, propylthiouracil (PTU).

Iodine intake and chronic autoimmune thyroiditis: a comparative study between coastal and mainland regions in Greece

INTRODUCTION

The purpose of this study was to evaluate the relationship between iodine intake and autoimmune thyroiditis in Chios, an island located in the North East Aegean Sea, in comparison to mainland regions in South Western Greece (SWG).

MATERIALS AND METHODS

Urine iodine concentration (UIC), thyroid function (serum TSH, thyroid autoantibodies: anti-TPO and anti-Tg), and thyroid U/S were assessed in 200 subjects (150 females and 50 males) from Chios and 322 subjects (255 females and 67 males) from several mainland regions in SWG. All participants were recruited from outpatient clinics and were diagnosed as euthyroid.

RESULTS

Median UIC in Chios was significantly higher compared to SWG (136.1 vs. 104.5 μg/L, p < 0.001), indicating that both regions are iodine sufficient according to World Health Organization (WHO) criteria. The prevalence of thyroid autoimmunity was 66.5% in Chios and 27% in SWG, significantly higher in females (46.7%) than in males (26.5%). Furthermore, individuals with increased levels of thyroid autoantibodies either anti-TPO or anti-Tg (TAbs) showed increased median UIC levels compared to those / subjects / patients with normal levels (126.7 vs. 108.95 μg/L, p < 0.001). Serum TSH mean values (mIU/L) were greater in females (mean = 2.1 ± 1.41) compared to males (mean = 1.82 ± 1.26) (p = 0.04) and decreased with age.

CONCLUSIONS

In conclusion, in the present study, we clearly indicate that increased thyroid autoimmunity is positively associated with increased iodine intake, as well as with the female gender. Moreover, iodine intake and thyroid autoimmunity appear to be significantly higher in a coastal region (Chios) than in mainland Greece (SWG). Additional environmental factors, apart from iodine, should be investigated in future studies. Mean TSH values were increased in females and decreased with age. The latter is probably due to the presence of autonomous goiter in older Greek populations, as a result of long-term status of iodine deficiency in the past.

The safety of green tea and green tea extract consumption in adults - Results of a systematic review

A systematic review of published toxicology and human intervention studies was performed to characterize potential hazards associated with consumption of green tea and its preparations. A review of toxicological evidence from laboratory studies revealed the liver as the target organ and hepatotoxicity as the critical effect, which was strongly associated with certain dosing conditions (e.g. bolus dose via gavage, fasting), and positively correlated with total catechin and epigallocatechingallate (EGCG) content. A review of adverse event (AE) data from 159 human intervention studies yielded findings consistent with toxicological evidence in that a limited range of concentrated, catechin-rich green tea preparations resulted in hepatic AEs in a dose-dependent manner when ingested in large bolus doses, but not when consumed as brewed tea or extracts in beverages or as part of food. Toxico- and pharmacokinetic evidence further suggests internal dose of catechins is a key determinant in the occurrence and severity of hepatotoxicity. A safe intake level of 338 mg EGCG/day for adults was derived from toxicological and human safety data for tea preparations ingested as a solid bolus dose. An Observed Safe Level (OSL) of 704 mg EGCG/day might be considered for tea preparations in beverage form based on human AE data.

Interaction between iodine and glucosinolates in rutabaga sprouts and selected biomarkers of thyroid function in male rats

Rutabaga sprouts belong to the Brassicaceae family and may exert a negative influence on thyroid function, because they are a rich in glucosinolates. These sprouts are also valuable source of iodine (6.5 ± 0.6 μg/100 g of fresh weight). Sprouts were tested in a long-term experiment with young male rats as an element of their diet, combined with two models of hypothyroidism, the first - deficit of iodine and the second - sulfadimethoxine ingestion as a pharmacological agent caused inhibition of thyroid peroxidase. Evaluations were performed for the serum TSH and thyroid hormones together with analyzes of thyroid histopathology, cytosolic glutathione peroxidase (GPX1), thioredoxin reductase in the thyroid, plasma GPX3 and CAT, erythrocyte GPX1. Rutabaga sprouts' intake by healthy rats did not cause any harmful effect on their health, including thyroid function. For animals with hypothyroidism, rutabaga sprouts enhanced the adverse effect of iodine deficiency or ingestion of sulfadimethoxine on the organism. According to the results obtained for young male rats thyroid function, the interpretation of data for human exposure to rutabaga sprouts has to be avoided. Furthermore, unless new scientific data confirms a lack of the negative effect of brassica sprouts on thyroid function in human, they should not be excluded from the group of goitrogenic products.

Flavonoids, Thyroid Iodide Uptake and Thyroid Cancer-A Review

Thyroid cancer is the most common malignant tumor of the endocrine system and the incidence has been increasing in recent years. In a great part of the differentiated carcinomas, thyrocytes are capable of uptaking iodide. In these cases, the main therapeutic approach includes thyroidectomy followed by ablative therapy with radioiodine. However, in part of the patients, the capacity to concentrate iodide is lost due to down-regulation of the sodium-iodide symporter (NIS), the protein responsible for transporting iodide into the thyrocytes. Thus, therapy with radioiodide becomes ineffective, limiting therapeutic options and reducing the life expectancy of the patient. Excessive ingestion of some flavonoids has been associated with thyroid dysfunction and goiter. Nevertheless, studies have shown that some flavonoids can be beneficial for thyroid cancer, by reducing cell proliferation and increasing cell death, besides increasing NIS mRNA levels and iodide uptake. Recent data show that the flavonoids apingenin and rutin are capable of increasing NIS function and expression in vivo. Herein we review literature data regarding the effect of flavonoids on thyroid cancer, besides the effect of these compounds on the expression and function of the sodium-iodide symporter. We will also discuss the possibility of using flavonoids as adjuvants for therapy of thyroid cancer.

Evaluation of Safety and Antioxidant Activity of Yellow Tea (Camellia sinensis) Extract for Application in Food

The article presents an evaluation of the safety of yellow tea (Camellia sinensis) extract consumption and its antioxidant activity in an animal model. Wistar rats were exposed through diet to 2, 6, and 10 g yellow tea extract/kg feed for 90 days. No signs of toxicity and no differences in mean body weight gain in the treated and control rats were recorded throughout the experiment. No statistically significant differences in hematology findings and clinical chemistry parameters were observed between controls and treated groups. Microscopic examination of tissue sections revealed no pathology attributable to yellow tea extract intake. Lipid peroxidation level in the liver was slightly increased in medium-dose males and high-dose females and decreased in two female groups receiving 2 and 6 g/kg of the extract tested. Content of carbonyl groups in protein, as well as the basal level of DNA damage, was not changed. In a majority of rats, the activity of antioxidant enzymes was increased except superoxide dismutase in high-dose groups, glutathione peroxidase in high-dose females, glutathione reductase in low- and mid-dose groups, and glutathione S-transferase in mid-dose females and high-dose males. It could be concluded that rats tolerated well dietary treatment with yellow tea extract up to 0.8 g/kg b.w./day for 90 days. Results showed that yellow tea extract at the doses tested did not demonstrate adverse effects and improved the antioxidant status in the liver of rats.

Acute and Subchronic Oral Toxicity Evaluation of Aqueous Root Extract of Dicoma anomala Sond. in Wistar Rats

The present study evaluated the safety of aqueous root extract of Dicoma anomala (AQRED) through acute and subchronic toxicity studies. Single oral dose of AQRED at the concentration of 0, 5, 300, and 2000 mg/kg as well as 125, 250, and 500 mg/kg/day was administered to rats for 14-day acute and 90-day subchronic oral toxicity studies. The results revealed no mortalities or observed clinical signs of toxicity in all the rats during both investigation periods. In subchronic toxicity testing, administration of AQRED also did not cause any changes in body weight as well as food and water consumption patterns. The haematological parameters and blood chemistry revealed no significant difference (p > 0.05) between the treatment and the control except in platelet count, alkaline phosphatase, and sodium levels where there was a significant increase (p < 0.05), although there was also a significant reduction (p < 0.05) in alanine transaminase, aspartate transaminase, and creatinine when compared to control. However, these changes were not reflecting the results from histology. Conclusively, the obtained results suggested that the LD₅₀ of AQRED is in excess of 2000 mg/kg and its oral administration for 90 days revealed that it is unlikely to be toxic, hence, safe.

Various Possible Toxicants Involved in Thyroid Dysfunction: A Review

About 300 million people across the world suffer from thyroid gland dysfunction. Environmental factors play an important role in causation of autoimmune thyroid diseases in susceptible individuals. Genetics contributes to 70% of the risk. In order to reduce the risk, we need to understand the association of environmental agents with thyroid dysfunction. These factors are especially relevant for those at increased risk due to positive family history. The ideal study to see the impact of a thyroid toxicant consists of directly measuring the degree of exposure to toxicant in an individual with his thyroid status. Knowledge of various factors influencing thyroid dysfunction can help in interpreting the results of such studies in a better way. This article is an attempt to highlight the various possible toxicants affecting thyroid function so that adequate measures can be undertaken to control excessive exposure in future to reduce the prevalence of thyroid disorders.

Bio-refinery of orange peels waste: a new concept based on integrated green and solvent free extraction processes using ultrasound and microwave techniques to obtain essential oil, polyphenols and pectin

In this study, extraction of essential oil, polyphenols and pectin from orange peel has been optimized using microwave and ultrasound technology without adding any solvent but only "in situ" water which was recycled and used as solvent. The essential oil extraction performed by Microwave Hydrodiffusion and Gravity (MHG) was optimized and compared to steam distillation extraction (SD). No significant changes in yield were noticed: 4.22 ± 0.03% and 4.16 ± 0.05% for MHG and SD, respectively. After extraction of essential oil, residual water of plant obtained after MHG extraction was used as solvent for polyphenols and pectin extraction from MHG residues. Polyphenols extraction was performed by ultrasound-assisted extraction (UAE) and conventional extraction (CE). Response surface methodology (RSM) using central composite designs (CCD) approach was launched to investigate the influence of process variables on the ultrasound-assisted extraction (UAE). The statistical analysis revealed that the optimized conditions of ultrasound power and temperature were 0.956 W/cm(2) and 59.83°C giving a polyphenol yield of 50.02 mgGA/100 g dm. Compared with the conventional extraction (CE), the UAE gave an increase of 30% in TPC yield. Pectin was extracted by conventional and microwave assisted extraction. This technique gives a maximal yield of 24.2% for microwave power of 500 W in only 3 min whereas conventional extraction gives 18.32% in 120 min. Combination of microwave, ultrasound and the recycled "in situ" water of citrus peels allow us to obtain high added values compounds in shorter time and managed to make a closed loop using only natural resources provided by the plant which makes the whole process intensified in term of time and energy saving, cleanliness and reduced waste water.

Impact of endocrine-disrupting chemicals on thyroid function and brain development

Endocrine disrupting chemicals (EDCs) are synthetic or natural substances in the environment. EDCs have been shown to disrupt reproductive, developmental and other homeostatic systems by interfering with the synthesis, secretion, transport, metabolism and action of endogenous hormones including the thyroid hormone (TH) system. Since TH plays a critical role in brain development, the exposure to TH-system disrupting EDCs during development may have serious consequences. In this article, representative previous studies showing the effect of representative EDCs on the TH system are summarized. Then, the molecular mechanisms of action of polychlorinated biphenyls and polybrominated diphenyl ethers on the TH system are discussed further. Particularly, the effect of polychlorinated biphenyls and polybrominated diphenyl ethers on TH-mediated brain development is discussed. Our recent studies may provide a novel idea regarding the effect of EDCs on the TH system.

Flavonoid rutin increases thyroid iodide uptake in rats

Thyroid iodide uptake through the sodium-iodide symporter (NIS) is not only an essential step for thyroid hormones biosynthesis, but also fundamental for the diagnosis and treatment of different thyroid diseases. However, part of patients with thyroid cancer is refractory to radioiodine therapy, due to reduced ability to uptake iodide, which greatly reduces the chances of survival. Therefore, compounds able to increase thyroid iodide uptake are of great interest. It has been shown that some flavonoids are able to increase iodide uptake and NIS expression in vitro, however, data in vivo are lacking. Flavonoids are polyhydroxyphenolic compounds, found in vegetables present in human diet, and have been shown not only to modulate NIS, but also thyroperoxidase (TPO), the key enzyme in thyroid hormones biosynthesis, besides having antiproliferative effect in thyroid cancer cell lines. Therefore, we aimed to evaluate the effect of some flavonoids on thyroid iodide uptake in Wistar rats in vivo. Among the flavonoids tested, rutin was the only one able to increase thyroid iodide uptake, so we decided to evaluate the effect of this flavonoid on some aspects of thyroid hormones synthesis and metabolism. Rutin led to a slight reduction of serum T4 and T3 without changes in serum thyrotropin (TSH), and significantly increased hypothalamic, pituitary and brown adipose tissue type 2 deiodinase and decreased liver type 1 deiodinase activities. Moreover, rutin treatment increased thyroid iodide uptake probably due to the increment of NIS expression, which might be secondary to increased response to TSH, since TSH receptor expression was increased. Thus, rutin might be useful as an adjuvant in radioiodine therapy, since this flavonoid increased thyroid iodide uptake without greatly affecting thyroid function.

Effects of green tea polyphenols on iodide-induced autoimmune thyroiditis in nonobese diabetic mice

Because green tea polyphenols (GTPs) possess anti-inflammatory properties and are effective in inhibiting autoimmune diseases in experimental settings, we examined whether GTPs prevented the development of autoimmune thyroiditis in iodide-treated nonobese diabetic (NOD) mice, an animal model of Hashimoto's thyroiditis (HT). Mice were given 0.05% iodide water or iodide water supplemented with 0.2% GTPs for 8 weeks. GTPs administration led to an enhanced production of interleukin-10 by concanavalin A-stimulated splenocytes but did not interfere with thyroiditis development. Serum thyroxine levels were not influenced by GTPs. Our data suggest that administration of GTPs may not be an effective strategy for the prevention of HT.

Evaluation of oral subchronic toxicity of Pu-erh green tea (camellia sinensis var. assamica) extract in Sprague Dawley rats

ETHNOPHARMACOLOGICAL RELEVANCE

Pu-erh green tea, originally produced in the Yunnan province of P.R. China for about 1700 years, is believed to be beneficial to health in Asian countries. The potential toxicity of Pu-erh green tea when administered at high doses via concentrated extract, however, has not been completely investigated.

THE AIM OF THE STUDY

The present study was aimed to evaluate the potential toxicity of Pu-erh green tea extract (PGTE) of sub-chronic administration to Sprague Dawley (SD) rats.

MATERIALS AND METHODS

Growing SD rats were administrated orally by gavage with PGTE at doses of 0, 1250, 2500, and 5000 mg/kg/day for 91 consecutive days. Clinical observations, including survival, hematology, serum biochemistry, urinalysis and histopathological examination were measured to monitor treatment-related adverse effects in rats.

RESULTS

The results showed that oral administration of high dose of PGTE led to body weight gain suppression, liver and calcium deposition dysfunctions.

CONCLUSIONS

In conclusion, the no-observed-adverse-effect level for Pu-erh green tea extract derived from the results of the present study was 2500 mg/kg/day for both genders.

The safety and regulation of natural products used as foods and food ingredients

The use of botanicals and dietary supplements derived from natural substances as an adjunct to an improved quality of life or for their purported medical benefits has become increasingly common in the United States. This review addresses the safety assessment and regulation of food products containing these substances by the U.S. Food and Drug Administration (FDA). The issue of safety is particularly critical given how little information is available on the toxicity of some of these products. The first section uses case studies for stevia and green tea extracts as examples of how FDA evaluates the safety of botanical and herbal products submitted for consideration as Generally Recognized as Safe under the Federal Food, Drug, and Cosmetics Act. The 1994 Dietary Supplement Health Education Act (DSHEA) created a regulatory framework for dietary supplements. The article also discusses the regulation of this class of dietary supplements under DSHEA and addresses the FDA experience in analyzing the safety of natural ingredients described in pre-market safety submissions. Lastly, we discuss an ongoing interagency collaboration to conduct safety testing of nominated dietary supplements.

Impact of flavonoids on thyroid function

Flavonoids are polyphenolic compounds of natural occurrence produced by plants that are largely consumed both for therapeutic purposes and as food. Experimental data have shown that many flavonoids could inhibit thyroperoxidase activity, decreasing thyroid hormones levels thus increasing TSH and causing goiter. In humans, infants fed with soy formula have been shown to develop goiter. However, in post-menopausal women soy intake did not affect thyroid function. In thyroid tumor cell line, flavonoids were shown to inhibit cell growth, but they can also decrease radioiodine uptake, that could reduce the efficacy of radioiodine therapy. Flavonoids could also affect the availability of thyroid hormones to target tissues, by inhibiting deiodinase activity or displacing T4 from transthyretin. Thus, flavonoids have been shown to interfere with many aspects of the thyroid hormones synthesis and availability in in vivo and in vitro models. In the present article, we review and synthesize the literature on the effects of flavonoids on thyroid and discuss the possible relevance of these effects for humans.

Acute and subchronic oral toxicities of Pu-erh black tea extract in Sprague-Dawley rats

ETHNOPHARMACOLOGICAL RELEVANCE

Pu-erh black tea, which is obtained by first parching crude green tea leaves and then undergoes secondary fermentation with microorganisms, has been believed to be beneficial beverages for health for nearly 2000 years in China, Japan and Taiwan area. But its potential toxicity when administered at a high dose as concentrated extracts has not been completely investigated.

THE AIM OF THE STUDY

The present study was aimed at evaluating potential toxicity of Pu-erh black tea extracts (BTE) from acute and sub-chronic administration to male and female Sprague-Dawley (SD) rats.

MATERIALS AND METHODS

A single BTE dose of 10,000 mg/kg of body weight was administered by oral gavage for acute toxicity in SD rats. Four groups (10 males and 10 females per group) of dose levels of 1250, 2500, and 5,000 mg/kg/day of the test article, as well as controls (distilled water) were tested as the subchronic toxicity study.

RESULTS

No deaths and signs of toxicity occurred during the 14 days of the study. There were no test article related mortalities, body weight gain, feed consumption, clinical observation, organ weight changes, gross finding, clinical or histopathological alterations during the 91-day administration.

CONCLUSIONS

The LD(50) of BTE can be defined as more than 10,000 mg/kg, and a dose of 5,000 mg/kg/day was identified as the no-observed-adverse-effect-level (NOAEL) in this study.

Which sources of flavonoids: complex diets or dietary supplements?

There is increasing interest in the potential health benefits of dietary flavonoids. Fruits and vegetables, tea, and cocoa are rich natural sources of flavonoids. Epidemiological studies have indicated that consumption of these foods is likely to be associated with a reduced risk of cardiovascular disease, but the etiology of this benefit is not yet clearly defined. Furthermore, in some acute interventions, a positive effect of tea and cocoa on vascular function has been reported. An alternative source of flavonoids is dietary supplements, which have become increasingly popular in the recent past. In this context, it needs to be critically evaluated whether vascular health-promoting and other positive properties of flavonoid-rich diets can be replaced by purified flavonoids as dietary supplements. Plant sources of flavonoids contain a complex mixture of secondary plant metabolites and not only flavonoids per se. This complex mixture of secondary plant metabolites cannot be simply exchanged by single purified compounds as dietary supplements. If flavonoids are given as dietary supplements, toxicity issues as well as nutrient drug interactions need to be taken into account. Purified flavonoids given in high doses as dietary supplements may affect trace element, folate, and vitamin C status. Furthermore, they may exhibit antithyroid and goitrogenic activities. In this review article, the available literature on the safety issues surrounding high dose supplemental flavonoid consumption has been summarized.