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Effect of different doses of un-fractionated green and black tea extracts on thyroid physiology
Abstract
Tea is a rich source of polyphenolic flavonoids including catechins, which are thought to contribute to the health benefits of it. Flavonoids have been reported to have antithyroid and goitrogenic effect. The purpose of this study was to evaluate whether high doses of green and black tea have a harmful effect on thyroid physiology. Un-fractionated green and black tea extracts were administered orally to male rats for 30 days at doses of 1.25 g%, 2.5 g% and 5.0 g%. The results showed that green tea extract at 2.5 g% and 5.0 g% doses and black tea extract only at 5.0 g% dose have the potential to alter the thyroid gland physiology and architecture, that is, enlargement of thyroid gland as well as hypertrophy and/or hyperplasia of the thyroid follicles and inhibition of the activity of thyroid peroxidase and 5(')-deiodinase I with elevated thyroidal Na+, K+-ATPase activity along with significant decrease in serum T3 and T4, and a parallel increase in serum thyroid stimulating hormone (TSH). This study concludes that goitrogenic/antithyroidal potential of un-fractionated green tea extract is much more than black tea extract because of the differences in catechin contents in the tea extracts.
... It is permittable to consume one's desiredquantity of tea and coffee on a daily basis, but overconsumption may disturb the sleep cycle, heart problems, dental erosion, and acidity [8,9]. In some diseases such as diabetes and thyroid disease, consumers should know the dose of tea and coffee in order to control and avoid health consequences [8]. ...
... It is permittable to consume one's desiredquantity of tea and coffee on a daily basis, but overconsumption may disturb the sleep cycle, heart problems, dental erosion, and acidity [8,9]. In some diseases such as diabetes and thyroid disease, consumers should know the dose of tea and coffee in order to control and avoid health consequences [8]. The authors of the paper [8] had discussed the impact of the addition of sugar, lemon, and milk in the tea. ...
... In some diseases such as diabetes and thyroid disease, consumers should know the dose of tea and coffee in order to control and avoid health consequences [8]. The authors of the paper [8] had discussed the impact of the addition of sugar, lemon, and milk in the tea. The addition of sugar in tea can cause dental caries, whereas the addition of lemon with the prescribed quantity is safe. ...
Tea is the most popular hot beverageworldwide. In 2020, the value of the global tea market was almost USD 200 billion, and is estimated to reach up to USD 318 billion by the year 2025. Tea has been included as part ofa regular diet for centuries because of its various health benefits. However, tea is acidic, and over-consumption causes heat problems, disturbance of the sleep cycle, tooth erosion, and low calcium absorption in the body. Strong tea concentration is very harmful and toxic. The safe consumption of tea should be guaranteed. The treatment applied in this research work is on sensory mechanisms and Arduino UNO. The objective of this paper is to find out community interest in a particular tea species and inform them about tea overdose.The acidity is mapped with tea taste in terms of strong, medium, and low flavors. Based on the data analysis, the results differentiatethe acidity level of black tea (pH: 3.89–4.08) as very high, green tea (pH: 4.68–4.70) is in the 2nd position, and the energy drink Herbalife Nutrition (pH: 5.59–5.64) is the least acidic comparatively, with a proportion ratio 1:10 of tea to water. Experimental analysis reveals that in the additives, lemon is most acidic, followed byginger, lemongrass, and Tulasi.
... Flavonoids can inhibit various enzymatic activities such as protein tyrosine kinase and DNA topoisomerase I and II which are crucial for cellular proliferation 11,12 . Apart from these effects flavonoids inhibit thyroid peroxidase (TPO) in in vitro and in vivo in experimental animals and humans [13][14][15][16] and also 5'deiodinase activity in vitro 11,12 . Certain plant foods contain both the naturally occurring goitrogenic/antithyroidal agents' viz. ...
... Antithyroid effects of feeding goitrogenic foods containing thiocyanate precursor are well established 8,10,27,28 . It has been also reported that tea extracts, both green and black, have potent antithyroidal activity for the presence of flavonoids 15,16 . In different goitre endemic regions people are exposed to thiocyanate (SCN), polyphenols or both for the consumption of goitrogenic foods that are used as common vegetables and beverage. ...
... As a consequence, SCN ultimately results in an Ideficient thyroid and there occurs a decrease in thyroid hormone synthesis 28 . Some of the natural flavonoids inhibit TPO in vitro 16,32 . It seems to be competitive; since the enzyme Vmax was unchanged and Km for iodide was significantly increased, it likely is able to scavenge H2O2, an essential TPO cofactor 32 . ...
In adequate iodine intake including and a number of environmental agents can affect thyroid gland functions in man and animals. Thiocyanate and catechin that arise for the consumption of cyanogenic and flavonoids containing foods respectively, affect thyroid hormone synthesis but the data comparing the goitrogenic/ antithyroid potentiality of thiocyanate and catechin when act individually or synergistically on thyroid function found scanty. Experimental animals were divided into groups and orally administered either thiocyanate or catechin or both in combination for 30 days followed by analysis of thyroid gland weight, histology, thyroid peroxidase, sodium potassium ATPase, 5’-deiodinase- I activities, thyroid hormone profiles, urinary iodine and urinary thiocyanate of each group of animals. Enlarged thyroid showing hypertrophic and hyperplastic changes, decreased thyroid peroxidase, sodium potassium ATPase, 5’-deiodinase- I activities activities and thyroid hormone profiles were observed in the treated groups. Overall results reveal that goitrogenic/ antithyroid potentiality found highest after concomitant exposure of thiocyanate and catechin followed by thiocyanate and least after catechin. © 2015, International Journal of Pharmaceutical and Clinical Research. All rights reserved.
... The content of the goitrogenic substances in the same foods grown in different regions is not uniform; the same foodstuff may show large differences in goitrogen content from region to region due to genetic and ecologic factors 17 . Tea extracts, both green and black, have also shown potent anti-thyroidal activity possibly due to the presence of flavonoids 20,21 . ...
... More pronounced inhibition in TPO activity was found after chronic exposure. Some of the natural flavonoids inhibit TPO in vitro 21,27 . Flavonoids from Kalanchoe brasiliensis, a popular medicinal plant used in Brazil, have been reported to cause competitive in vitro TPO inhibition, competitive, since the enzyme V max remians unchanged while K m for iodide significantly increases, and thereby scavenges H 2 O 2 , an essential TPO cofactor 36 . ...
... Decreased circulating hormone levels were associated with decreased thyroid hormone synthesis due to inhibition of TPO activity of the thyroid gland under the influence of goitrogens present in PSC. As discussed earlier, it is also known that the flavonoids cause in vitro TPO activity inhibition 20,21 and scavenge H 2 O 2 , an essential TPO cofactor 36 . Inhibition of both iodide uptake and thyroidal iodide efflux due to excess thiocyanate 23 and flavonoids might be another reason for the decreased synthesis of thyroid hormones. ...
In animals, long-term feeding with peanut (Arachis hypogaea) seed coats causes hypertrophy and hyperplasia of the thyroid gland. However, to date there have been no detailed studies. Here, we explored the thyroidal effects of dietary peanut seed coats (PSC) in rats. The PSC has high levels of pro-goitrogenic substances including phenolic and other cyanogenic constituents. The PSC was mixed with a standard diet and fed to rats for 30 and 60 days, respectively. Animals fed with the PSC-supplemented diet showed a significant increase in urinary excretion of thiocyanate and iodine, thyroid enlargement, and hypertrophy and/or hyperplasia of thyroid follicles. In addition, there was inhibition of thyroid peroxidase (TPO) activity, 5'-deiodinase-I (DIO1) activity, and (Na+-K+)-ATPase activity in the experimental groups of rats as compared to controls. Furthermore, the PSC fed animals exhibited decreased serum circulating total T4 and T3 levels, severe in the group treated for longer duration. These data indicate that PSC could be a novel disruptor of thyroid function, due to synergistic actions of phenolic as well as cyanogenic constituents.
... Bentvena et al. 52 found that caffeine blocks the uptake of levothyroxine in hypothyroid patients, thereby affecting thyroid function. Chandra et al. 53 revealed the potential antithyroid activity of black and green tea extracts. These components are very important factors in DII calculations. ...
Objective
Researchers have developed the Dietary Inflammatory Index (DII) as a tool to quantify the inflammatory potential of a given diet. Higher DII scores indicated a more proinflammatory diet. While inflammation is known to have a strong impact on thyroid function, the precise nature of the association between DII scores and thyroid function has yet to be clarified. This study was conducted with the goal of exploring this relationship in a representative population of adults from the United States.
Methods
For this study, we used data from the National Health and Nutrition Examination Survey (NHANES). Standardized questionnaires were used to collect demographic and dietary data from the participants, and laboratory tests were used to collect data on the participants' thyroid parameters and other relevant data. Linear regression models and smoothed curve fitting were used to assess the relationship between DII scores and thyroid function, with weighted data analyses and subgroup analyses being conducted as appropriate.
Results
In total, 7712 subjects were recruited from the NHANES 2007–2012 cohort. Their weighted mean age was 44.87 (0.47) years, mean DII score was 1.41 (0.05). Mean FT3 was 3.20 (0.01) pg/mL and mean TT4 was 7.81 (0.03) µg/dL. In adjusted analyses, higher DII values were related to increases in FT3 ( β = .007; p = .027) and TT4 ( β = .050; p = .005) levels. Subgroup analyses showed a negative correlation between FT3 levels and DII scores in a population with high urinary iodine concentrations.
Conclusion
These data indicate that the consumption of a more proinflammatory diet, as evidenced by elevated DII scores, is correlated with significant increases in FT3 and TT4 levels. However, for people with high urinary iodine concentrations, a more proinflammatory diet was associated with lower FT3 levels. Additional research will be vital to clarify the mechanistic basis for these findings.
... Tea. Chandra et al., showed that green and black tea extracts have antithyroid potential [151,152]. It has been shown that catechins (flavonoids found in abundance in tea) have a goitrogenic effect in rats [151,153,154]. ...
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.
... Rats injected with pure green tea intra-pretonialy were studied for acute effects on endocrine systems, significantly reduction in food intake, body weight gain, testosterone blood level as well as there has been a growth in the prostate and uterus in lean and obese male zucker rats (Yung et al., 2000). Green tea extract at dose level of 5.0% has the potential to alter the thyroid gland physiology and architecture that is an enlargement of thyroid gland as well as hypertrophy and/or hyperplasia of the thyroid follicles and significant decrease in serum T3 and T4 and a parallel increase in serum thyroid stimulating hormone (TSH) (Chandra et al., 2010). The level of estrogen, progesterone and testosterone in the serum was not affected by the treatment of L-Carnitine as dairy supplementation in cats following ovariohysterectomy, since, long-term study is recommended (Tavakoli et al., 2017). ...
This work was designed to study the effect of daily oral administration for two groups of male albino rats suffering from weight gain (obese rats) with both 10% aqueous extract of green tea and 21 mg L-Carnitine/kg body weight for 9 weeks. Green tea (GT) and L-Carnitine (LC) cause significant body weight reduction in overweight rats with low thyroid hormone levels (triiodothyronin T3 and thyroxin T4) as well as testosterone. Treatment of obese male rats with GT caused decrease in count of red blood cells and blood haemoglobin and elevate in both count of white blood cells WBCs and haematocrit PCV%, while LC caused elevate in blood haemoglobin levels Hb, RBCs, WBCs and (PCV) % compared with both negative and positive groups of control while haematocrit PCV% in rats of positive contrl group was reduced compared with rats of (C-ve) group and all treatment groups.
... It is found that thyroid peroxidase activity and DI activity were decreased in treated group of rats. Flavonoids inhibit TPO activity in vitro (Chandra, De, Choudhury, 2011) which seems to be competitive and it might be able to scavenge H 2 O 2 , an essential TPO cofactor (Divi, Doerge, 1996). A high concentration of thiocyanate is also responsible for inhibition of TPOcatalysed oxidation (Ileads to I 2 ) (Virion et al., 1980). ...
Moringa leaves and spinach used as vegetables containing cyanogens and polyphenols having suspected antithyroidal activity; however, detailed studies in this aspect found unavailable. Goitrogenic/antithyroid potentiality of those plant foods of Indian origin was evaluated. To explore the goitrogenic/antithyroid effect of those plant foods cyanogenic glucosides, glucosinolates, thiocyanate and polyphenol content were measured. These plant foods were fed with diet regularly to adult male albino rats for 30 and 60 days respectively, followed by evaluation of morphological and functional status of thyroid,as thyroid gland weight, the activity status of thyroid hormone synthesizing enzymes viz. TPO, Na+-K+-ATPase, deiodinase I, thyroid hormone profiles, thyroid histoarchitecture as well as urinary iodine and thiocyanate. In moringa leaves and spinach fed diet, there was a significant increase in urinary excretion of thiocyanate and iodine, enlargement of thyroid gland along with hypertrophy of thyroid follicles and altered in the activities of thyroid hormone synthesizing enzymes with concomitant changes of thyroid hormone profiles. Effects were more severe in moringa leaves treated group than that of spinach. Biochemical analysis moringa leaves and spinach reveal that those are rich sources of goitrogens and their prolonged consumption gradually developed a relative state of biochemical and morphological hypothyroidism.
... Tea shows goitrogenic effect due to its flavonoids. The goitrogenic potential of green tea is higher than black tea because of the differences in catechin concentration (Chandra et al., 2010). ...
... However, due to non-availability of control values it is difficult to indicate whether their activity statuses in vitro as observed from the surgical specimens were within normal ranges, or to assign any physiologic and/or clinical significance to these findings. Contextual references can be discussed here from the observations of our earlier studies involving human as well as animal models that looked for the effects of excess iodine, various goitrogenic plants foods and community food habits on the biochemical and morphological patterns of goitrous thyroid and it wa s f o un d th at pr ol on ge d ex pos ur e of t ho s e substances resulted in a state of hypothyroidism (2, 3,7,[33][34][35][36][37][38][39][40]. In such conditions, the activity of Na + -K + -ATPase was enhanced while that of TPO and 5'-DI was decreased. ...
Background and Objective: Endemic goitre is the most important clinical manifestation of iodine deficiency
disorders (IDDs). To prevent IDDs, universal salt iodisation (USI) has been implemented, irrespective of the
environmental iodine content of the region that might not necessarily be iodine-deficient, like the Gangetic
plains of West Bengal (WB), India. In this study, surgical specimens of goitrous thyroids from patients of
the Gangetic plains of WB were investigated with the objective to explore the aetiology of large goitres.
Materials and Methods: Seven specimens of thyroid tissue of large goitrous subjects after their thyroidectomy
were collected during June 2014 - May 2015. To know their thyroid functional status, serum total thyroxine
(TT4), total triiodothyronine (TT3) and thyroid stimulating hormone (TSH) were assayed prior to their surgery
; to understand their thyroid gland status, histology of thyroid as well as the activity of thyroid hormone
synthesizing enzymes as sodium-potassium adenosine triphosphatase (Na-K-ATPase), thyroid peroxidase
(TPO) and deiodinase (5’DI) from excised specimen were assayed.
Results: The pre-operative serum TT3, TT4 and TSH levels were within normal range in all patients. In thyroid
tissue specimen, activities of enzymes (Na+-K+-ATPase, TPO, 5’-DI) were noted. The follicles were distended
with colloids as found in colloid goitre, with flattened lining epithelial cells. Further involution was almost
complete. However, there were areas having smaller follicles with peripheral vacuolations and scalloping
within the thin colloids, showing that resorption of colloid continued to occur as found in Graves’ disease.
Conclusion: Large goitres in patients belonging to iodine replete Gangetic plains of West Bengal histologically
mimic Graves’ disease apparently developed for the consumption of dietary goitrogens, including excess
iodine for USI programme.
... However, due to non-availability of control values it is difficult to indicate whether their activity statuses in vitro as observed from the surgical specimens were within normal ranges, or to assign any physiologic and/or clinical significance to these findings. Contextual references can be discussed here from the observations of our earlier studies involving human as well as animal models that looked for the effects of excess iodine, various goitrogenic plants foods and community food habits on the biochemical and morphological patterns of goitrous thyroid and it wa s f o un d th at pr ol on ge d ex pos ur e of t ho s e substances resulted in a state of hypothyroidism (2, 3,7,[33][34][35][36][37][38][39][40]. In such conditions, the activity of Na + -K + -ATPase was enhanced while that of TPO and 5'-DI was decreased. ...
Background and Objective: Endemic goitre is the most important clinical manifestation of iodine deficiencydisorders (IDDs). To prevent IDDs, universal salt iodisation (USI) has been implemented, irrespective of theenvironmental iodine content of the region that might not necessarily be iodine-deficient, like the Gangeticplains of W est Bengal (W B), India. In this study, surgical specimens of goitrous thyroids from patients ofthe Gangetic plains of W B were investigated with the objective to explore the aetiology of large goitres.Materials and Methods: Seven specimens of thyroid tissue of large goitrous subjects after their thyroidectomywere collected during June 2014 - May 2015. To know their thyroid functional status, serum total thyroxine(TT4), total triiodothyronine (TT3) and thyroid stimulating hormone (TSH) were assayed prior to their surgery; to understand their thyroid gland status, histology of thyroid as well as the activity of thyroid hormonesynthesizing enzymes as sodium-potassium adenosine triphosphatase (Na-K-ATPase), thyroid peroxidase(TPO) and deiodinase (5’DI) from excised specimen were assayed.Results: The pre-operative serum TT3, TT4 and TSH levels were within normal range in all patients. In thyroidtissue specimen, activities of enzymes (Na+-K+-ATPase, TPO, 5’-DI) were noted. The follicles were distendedwith colloids as found in colloid goitre, with flattened lining epithelial cells. Further involution was almostcomplete. However, there were areas having smaller follicles with peripheral vacuolations and scallopingwithin the thin colloids, showing that resorption of colloid continued to occur as found in Graves’ disease.Conclusion: Large goitres in patients belonging to iodine replete Gangetic plains of West Bengal histologicallymimic Graves’ disease apparently developed for the consumption of dietary goitrogens, including excessiodine for USI programme.
... However, due to non-availability of control values it is difficult to indicate whether their activity statuses in vitro as observed from the surgical specimens were within normal ranges, or to assign any physiologic and/or clinical significance to these findings. Contextual references can be discussed here from the observations of our earlier studies involving human as well as animal models that looked for the effects of excess iodine, various goitrogenic plants foods and community food habits on the biochemical and morphological patterns of goitrous thyroid and it wa s f o un d th at pr ol on ge d ex pos ur e of t ho s e substances resulted in a state of hypothyroidism (2, 3,7,[33][34][35][36][37][38][39][40]. In such conditions, the activity of Na + -K + -ATPase was enhanced while that of TPO and 5'-DI was decreased. ...
Background and Objective: Endemic goitre is the most important clinical manifestation of iodine deficiencydisorders (IDDs). To prevent IDDs, universal salt iodisation (USI) has been implemented, irrespective of theenvironmental iodine content of the region that might not necessarily be iodine-deficient, like the Gangeticplains of W est Bengal (W B), India. In this study, surgical specimens of goitrous thyroids from patients ofthe Gangetic plains of W B were investigated with the objective to explore the aetiology of large goitres.Materials and Methods: Seven specimens of thyroid tissue of large goitrous subjects after their thyroidectomywere collected during June 2014 - May 2015. To know their thyroid functional status, serum total thyroxine(TT4), total triiodothyronine (TT3) and thyroid stimulating hormone (TSH) were assayed prior to their surgery; to understand their thyroid gland status, histology of thyroid as well as the activity of thyroid hormonesynthesizing enzymes as sodium-potassium adenosine triphosphatase (Na-K-ATPase), thyroid peroxidase(TPO) and deiodinase (5’DI) from excised specimen were assayed.Results: The pre-operative serum TT3, TT4 and TSH levels were within normal range in all patients. In thyroidtissue specimen, activities of enzymes (Na+-K+-ATPase, TPO, 5’-DI) were noted. The follicles were distendedwith colloids as found in colloid goitre, with flattened lining epithelial cells. Further involution was almostcomplete. However, there were areas having smaller follicles with peripheral vacuolations and scallopingwithin the thin colloids, showing that resorption of colloid continued to occur as found in Graves’ disease.Conclusion: Large goitres in patients belonging to iodine replete Gangetic plains of West Bengal histologicallymimic Graves’ disease apparently developed for the consumption of dietary goitrogens, including excessiodine for USI programme.
... Four published experiments investigated the effect of green tea catechins on thyroid function in rat models (Supplementary Table 4), and reported that green tea catechins may have a goitrogenic effect (Chandra and De, 2010;Chandra et al., 2011;Sakamoto et al., 2001;Satoh et al., 2002). These studies showed that administration of GTEs or pure catechin at doses above 25 mg catechins/kg/day via oral gavage or 5% in the diet (delivering estimated 2334 mg catechins/kg/day) resulted in an increase in thyroid weight, induced hypertrophy and hyperplasia, decreased T3 and T4 and elevated thyroid-stimulating hormone (TSH) in rats. ...
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 reveals the liver as target organ and hepatotoxicity as 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 yields the findings consistent with toxicological evidence in that a limited range of concentrated, catechin-rich green tea preparations when ingested in large solid bolus doses resulted in hepatic AEs in a dose-dependent manner, but not brewed tea or extracts consumed 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 in 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.
... It has been previously reported that the consumption of flavonoids and some phenolic acids by experimental animals induced goiter and histological changes in the thyroid gland. Chandra and Choudhury (2011) have shown that green tea and to a lesser extent black tea exposure to rats induces a decrease in TPO and DIO1 (key enzymes in TH synthesis and TH bioactivation, respectively). In addition, in this model thyroid gland weight and TSH levels increased while T4 and T3 levels decreased, which suggests a state of hypothyroidism. ...
... One of the main ingredients of green tea is catechins which have antioxidative and anticarcinogenic action. However, catechins seem to also have antithyroid activity, through their influence in thyroid peroxidase, 5 0 -deiodinase I (5 0 -DI), and Na(C), K(C)-ATPase, as evidenced from both in vivo and in vitro studies show [27,28] Another very interesting point that literature has highlighted is a high prevalence of B12 deficiency in hypothyroid patients compared to healthy individuals. Vitamin B12 deficiency may occur as a result of autoimmune pernicious anemia, malabsorption, malnutrition or use of drugs including protonpump inhibitors [29]. ...
Background:
Anxiety combined with nervousness and apprehension consist a focal response to different life conditions. Lifestyle habits, anxiety and biochemical markers are in a constant interaction.
Aim:
To investigate the prevalence of anxiety in healthy adults and its possible association with biochemical factors-lipid profile, liver markers, thyroid hormones-and lifestyle habits.
Methods:
Quantitative descriptive correlation study. A total of 100 healthy adults participated in the research. A specially designed questionnaire and Hamilton's scale were used. Anthropometric and biochemical analyses were performed.
Findings:
Overall, 61% of the participants presented moderate to very serious anxiety. The average score on the Hamilton scale was 13.82 (±9.000), with men exhibiting less stress than women. For p ≤ 0.05: Stress was positively correlated with impaired thyroid and hepatic function. Hepatic function was affected by both sugar products and water melon, which were positively correlated with total bilirubin and AST/SGOT respectively. Tomato, peppers and legumes were negatively correlated with AST/SGOT. Deep fried food was positively correlated with GGT and triglycerides. Legumes and fish were negatively correlated with CPK. Regarding the lipid metabolism, it was found that food cooked with oil was positively associated with uric acid, but non-cooked olive oil was negatively correlated with the risk for CAD. Thyroid function was negatively correlated with non-homemade food and pasta consumption and positively correlated with consumption of whole grains and green tea. Participants with subclinical hypothyroidism seemed to consume less vitamin B12, folic acid and vegetables.
Conclusion:
No direct correlation between lifestyle habits and anxiety was found. Nevertheless, eating habits influenced biochemical markers-especially the thyroid hormones-which may be indirectly responsible for anxiety and related moods.
... As antioxidants, green tea polyphenols either chelate redox-active metal ions, such as iron and copper preventing the formation of metal-catalyzed free radicals or scavenge reactive oxygen/nitrogen species or modulate antioxidant enzymes (Nakagawa & Yokozawa, 2002). On the contrary, prior researches (Chandra et al., 2011;Abulfadle et al., 2015) have declared that excessive and high doses of green tea have the potential to alter the thyroid gland physiology and architecture, that is, enlargement of thyroid gland as well as hypertrophy and/or hyperplasia of the thyroid follicles and inhibition of the activity of thyroid peroxidase and 50-deiodinase I with elevated thyroidal sodium-potassium-ATPase activity along with significant decrease in serum T3 and T4, and a parallel increase in serum thyroid stimulating hormone (TSH). ...
Introduction
Tributyltin is one of the important and wide-spread persistent organic contaminants that accumulate in the food chain. It is suspected to cause endocrine-disrupting effects in mammals, due in part to its possible transfer through marine food chains and to the consumption of contaminated seafood.
Aim of the work
Was to study the possible toxic effect of Tributyltin on thyroid follicular cells of adult male albino rats and to evaluate the possible protective role of green tea.
Material and methods
Forty-five adult male albino rats were included and randomly divided into 3 equal groups: a control group (Group I); Group II: received tributyltin chloride (TBT) dissolved in corn oil orally in a dose of 5 mg/kg for 30 days. Group III: received tributyltin chloride in the same dose with concomitant oral administration of green tea extract for 30 days. At the end of the experiment, the animals were sacrificed and blood samples were subjected to hormonal assay for T3, T4 and TSH levels. Malondialdehyde and reduced glutathione were assessed. The thyroid tissue was processed for histological and ultrastructure examination. The colloid area of thyroid follicles was evaluated morphometrically and statistically analyzed.
Results
A significant decrease in T3 and T4 levels and serum reduced glutathione in the group II when compared with the other groups. Furthermore, a significant increase in serum Malondialdehyde and TSH levels was recorded in group II treated group by comparison to the other two groups. Histopathological and ultrastructural changes of thyroid gland follicles were detected in tributyltin treated rats; the follicular cells appeared swollen and vacuolated. Epithelial stratification was noticed in some foci with excessive vacuolation of the colloid. Dilated rough endoplasmic reticulum filled with flocculent material and increased number of lysosomes were also detected together with variation in shape and size of the nuclei. A marked improvement in the histological features of thyroid follicles was noticed in group III.
Conclusion
Tributyltin induces oxidative stress in rats as well as anti-thyroid effect. The green tea extract is useful in combating tissue injury that is a result of tributyltin toxicity.
... Some studies found that green tea extract induced an enlargement in the thyroid of normal rats (Sakamoto et al., 2001;Satoh et al., 2002). In addition to the enlargement of thyroid gland, Chandra, De, and Choudhury (2011) declared that green tea extract decreased the serum level of both T3 and T4.But, the green tea contains fluoride absorbed from the soil and accumulated in its leaves. (Koblar, Tavčar, & Ponikvar-Svet, 2012) and the green tea beverages contain. ...
Green tea is a worldwide used beverage rich in fluoride and caffeine. To study the effect of excessive green tea intake versus fluoride and caffeine on body weight and serum thyroid hormones in male mice. Also, to confirm the effect of excessive green tea intake on thyroid gland was due to its fluoride and caffeine content or not. Thirty Male albino mice 25-30 gm weight were divided into five groups. Control (C) group (6 mice) receiving distilled water. Green tea (GT) treated group; 6 mice were given a 5 gm% tea hot water extract as their sole water supply. Fluoride (FL) treated group, 6 mice were given fluorine excess solution as their only water supply. Caffeine (Caf) treated group, 6 mice were treated with caffeine (6.25 mg/kg ip). Propylthiouracil (PTU) treated group, 6 mice were treated with PTU (10 mg/kg ip). Each of the five groups is treated with the corresponding substance for 30 days, then sacrificed under ether anesthesia, blood was collected to study serum levels of T3 and T4. There was a significant decrease in serum T3 in PTU treated group (0.72±0.03), GT treated group (0.96±0.04), FL treated group (0.93±0.04) and Caf treated group (1.46±0.08) in comparison to the C group (1.71±0.05).Also, there was a significant decrease in serum T4 in PTU treated group (15.71±1.26), GT treated group (30.07±2.29) and FL treated group (22.03±1.95)in comparison to the C group (51.1±3.15). But, there was an insignificant change in serum T4 in Caf treated group (45.55±2.73) in comparison to the C group (51.1±3.15). Green tea unfractionated aqueous extract decreased serum T3 and T4 and at the same time, increased final total body weight without a significant effect on the relative thyroid weight in comparison to the control group and this may be at least partly due to its content of fluoride and caffeine. Further work should be done on green tea free fluoride and caffeine to confirm this result.
... Thyroid peroxidase activity in thyroid tissue was determined by the CLIA kits according to the method of Kaczur et al. [37]. The enzyme activity was expressed as ΔO.D/min/mg of sample protein. ...
... 2,6 Other reports have demonstrated that flavonoids (such as catechins and rutin), which are polyphenols, can suppress thyroid function, reducing thyroid hormone synthesis and affecting the pituitary-thyroid axis. 27,28 However, in our study, we observed normal T4 and TSH concentrations, suggestive of a lack of major changes in thyroid hormonogenesis despite the presence of polyphenols in cinnamon. However, the low serum T3 level suggests the presence of alterations in the peripheral metabolism of thyroid hormones. ...
BACKGROUND
Cinnamon has several effects on energy metabolism. However, no data exist on the impact of cinnamon intake on thyroid hormone serum concentrations and action, since thyroid hormones (TH) play a major role in metabolism.RESULTSMale rats were treated with cinnamon water extract (400 mg kg−1 body weight, 25 days). Cinnamon supplementation resulted in a lower serum total T3 level accompanied by normal serum T4 and TSH levels. The cinnamon-treated rats did not exhibit significant differences in TSHβ subunit, TRβ or deiodinase type 2 mRNA expression in the pituitary. In the liver, cinnamon did not change the TRβ protein expression or the deiodinase type 1 mRNA expression, suggesting that there were no changes in T3 signaling or metabolism in this organ. However, mitochondrial GPDH, a target gene for T3 in the liver, exhibited no changes in mRNA expression, although its activity level was reduced by cinnamon. In the cardiac ventricle, T3 action was markedly reduced by cinnamon, as demonstrated by the lower TRα mRNA and protein levels, reduced SERCA2a and RyR2 and increased phospholamban mRNA expression.CONCLUSION
This study has revealed that TH action is a novel target of cinnamon, demonstrating impairment of T3 signaling in the cardiac ventricles.
... Some investigators also provide support for protective effects of fresh fruits and vegetables against cancer, heart diseases and stroke [3,7]. However, on the antithyroidic role of polyphenols containing plants, only few reports are available which include goitrogenic/ antithyroidal potential of un-fractionated green tea extract, inhibition of thyroid peroxidase by Myrcia uniflora flavonoids and antithyroid properties of flavonoids extracted from fonio millet, Digitaria exilis [8][9][10][11]. Particularly, on rutin, hesperidin and naringin, nothing was investigated earlier on their thyroid regulatory role. ...
Background
Investigations are meager on the ameliorative role of plant based active compounds in regulating hyperthyroidism. We have now explored the possible role of three flavonoids in the regulation of L-thyroxine (l-T4)-induced hyperthyroidism in rats. This investigation attempts to reveal whether rutin, naringin and hesperidin supplementation exhibit antithyroid effects in L-T4-induced hyperthyroid rats and to work out the possible involvement of free radicals in their mode of action.
Methods
Either rutin or naringin or hesperidin (50 mg/kg each) was administered to L-T4-induced hyperthyroid rats for two weeks and their effects were evaluated on the alterations in levels of thyroid hormones, 5′-deiodinase I (5′DI) activity, hepatic lipid peroxidation as well as in antioxidants.
Results
l-T4 administration significantly enhanced the serum concentrations of thyroxine and triiodothyronine; the activities of hepatic 5′DI, serum lactate dehydrogenase and serum glutamate pyruvate transaminase along with an increase in content of malondialdehyde in hepatic tissues, but depleted the cellular antioxidants. However, on administration of the test flavonoids, these effects were more or less normalized. Electro paramagnetic resonance (EPR) spectra also indicated the suppression of the hydroxyl radicals (OH
Conclusion
Rutin, naringin and hesperidin have the potential to inhibit thyroid functions without hepatotoxicity and the effects are possibly mediated through their free radical scavenging action as evidenced by EPR study. From the comparative analyses of the results, rutin appeared to be the most effective one suggesting its better antithyroid and antioxidative potential over other two.
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.
Tea (Camellia sinensis) being the most consumed beverage worldwide. The safety evaluation of tea needs to be monitored during pregnancy, prenatal as well as postnatal developmental period beside its beneficial roles toward health and disease. Black Tea extract (BTE) may have an impact on thyroid hormone physiology and reproductive health during pregnancy. The objective of present study was to evaluate the role of BTE on thyroid physiology of pregnant rat during prenatal and postnatal period. Among three experimental groups, Group 1 was the control pregnant female rats respectively treated orally with saline, Group 2 and Group 3 were pregnant female rats treated with 50 mg and 100 mg BTE/kg body weight/day, p.o. respectively throughout prenatal and postnatal periods. All three groups of rats were provided balance diet and drinking water ad libitum. Animals were examined through their T3, T4, TSH, E2 and P4 hormone assay and histology of thyroid, ovary and uterus. All data were expressed as mean ± standard deviation with significance between the controls and the treated groups (n = 6). Experimental data were subjected to the ANOVA and Tukey test; P < 0.05 was considered as statistically significant. BTE treatment significantly increased the levels of T3 and T4 whereas decreased TSH level. BTE also alters the shape of thyroid follicles, follicular epithelium and colloid content in the lumen. This study confirmed BTE induced hyperthyroidism during pregnancy.
Background: Few investigations on the ameliorative role of plant based active compounds in regulating hyperthyroidism. A
previously study was conducted to demonstrate the effect of excessive green tea consumption on euthyroid mice and found
that it decreased thyroid hormones and affected thyroid gland and body weight. Thus, we postulated that green tea has a role
in the regulation of L-thyroxine (L-T4)-induced hyperthyroidism in mice. Objective: This investigation attempts to declare if
green tea extract supplementation exhibits antithyroid effects in L-T4-induced hyperthyroid mice or not. Methods: twenty
four animals were divided into four groups, each with six healthy male mice were established. Group I (control, C) received
distilled water and served as a control. Eighteen mice in Groups (II, III and IV) were rendered hyperthyroid by daily
administration of L-thyroxine at a dose of 2μg /ml, diluted in drinking water for 30 days. From the 30th day to the 40thday,
Groups II mice (hyperthyroid, H) continued to receive L-thyroxine only, Group III mice (hyperthyroid propylthiouracil
treated, H-PTU) were administered L-thyroxine plus propylthiouracil (PTU, 10 mg/kg i.p.) while, Group IV mice
(hyperthyroid green tea treated, H-GT) were administered L-thyroxine plus green tea extract (5 gm% green tea hot water
extract as their sole water supply). Results: There were significant increases in serum levels of T4 (87.77±2.84) and T3
(2.52±0.17) in (H) group in comparison to those of the (C) group (51.66±2.84) and (1.79±0.04) respectively. But, there were
insignificant changes in serum levels of T4 (60.26±2.15) and T3 (1.87±0.04) in (H-GT) group in comparison to those of the
(C) group (51.66±2.84) and (1.79±0.04) respectively. On the other hand, there were significant decreases in serum levels of
T4 (60.26±2.15) and T3 (1.87±0.04) in (H-GT) group in comparison to those of the (H) group (87.77±2.84) and (2.52±0.17)
respectively. Also, there was a significant decrease in serum level of TSH in (H) group (1.89±0.08) in comparison to that of
the (C) group (3.39±0.13), but, a significant increase in its level in (H-GT) group (2.9±0.15) in comparison to that in the (H)
group (1.89±0.08). Moreover, there was a significant decrease in final body weight in (H) group (22.01±0.92) and
insignificant change in final body weight in (H-GT) in comparison to that of the (C) group (29.27±1.33), but, there was a
significant increase in final body weight in (H-GT) group (27.77±0.74) in comparison to that of (H) group (22.01±0.92).
Conclusions: It is concluded that green tea improved biochemical and histopathological features of hyperthyroidism in mice.
Thus, it may be used as a potential source of drug for the treatment of hyperthyroidism. However, further investigations are
required.
Keywords: Thyroid; Green tea; Histopathology; Hyperthyroidism; Mice.
Background Green tea (GT) is one of the most popular beverages with high daily consumption worldwide. It has a rich content of polyphenols, among which catechins predominate. Its extracts are widely used as ingredients in dietary supplements, beverages, and functional foods, which may lead to a higher consumption of GT polyphenols by the general population. Recently, a relationship between GT administration and disruption of thyroid homeostasis was suggested. Aim The goal of the study was to clarify the impact of GT administration on the histological structure of thyroid follicular cells of adult albino rats. Materials and methods Thirty adult male albino rats (140–160 g) were categorized into three equal groups: group I served as the control group; groups II and III received 1.25 and 5.0 g% GT extract orally at a dose of 10 ml/kg body weight, respectively, every day for 30 days. At the end of the experiment, blood samples were collected from all animals for estimation of serum triiodothyronine (T3), thyroxine (T4), and thyroid stimulating hormone. Rats were then euthanized and the thyroid glands were harvested for histological examination of thyroid follicular cells by light and transmission electron microscopy. The follicular epithelial height and colloid area of thyroid follicles were morphometrically evaluated and statistically analyzed. Results GT in small concentrations (in group II) did not induce any significant change in hormonal, histological, and histomorphometric assessments as compared with the control group. However, some follicular cells exhibited mildly dilated rough endoplasmic reticulum and multiple lysosomes. In contrast, GT administration in group III induced hypothyroidism as evidenced by significant reduction in serum T3 and T4 levels along with substantial increase in thyroid stimulating hormone level compared with controls. Histologically, many follicles displayed signs of hyperactivity as evidenced by focal hypertrophy and hyperplasia of the follicular cells along with colloid depletion. Ultrastructurally, dilated rough endoplasmic reticulum and disrupted mitochondria were encountered. Some severely degenerated follicular cells were revealed as well. Histomorphometrically, there was a significant increase in the mean follicular epithelial height, whereas the colloid area was significantly lowered as compared with the respective controls. Conclusion The study clearly indicates that GT in large concentrations has the potential to disrupt thyroid follicular cell structure and function.
Resveratrol (3,4,5-trihydroxystilbene), a polyphenol and well-known natural antioxidant has been evaluated for its protective effect against fluoride-induced metabolic dysfunctions in rat thyroid gland. Fluoride, the most abundant anions present in groundwater throughout the world, creates a major problem in safe drinking water and causes metabolic, structural, and functional injuries in different organ systems. Sub-acute exposure to sodium fluoride at a dose of 20 mg/kg b.w./day orally to rat for 30 days induces thyroidal dysfunction including suppressed synthetic machinery of the thyroid gland to produce nucleic acids and thyroid hormones, mainly T3 and T4. Other functional changes are alteration of certain metabolic enzyme activities like Na(+)-K(+)-ATPase, thyroid peroxidase, and 5,5'-deiodinase. Structural abnormality of thyroid follicles by fluoride intoxication clearly indicates its thyrotoxic manifestation. Resveratrol supplementation in fluoride-exposed animals appreciably prevented metabolic toxicity caused by fluoride and restored both functional status and ultra-structural organization of the thyroid gland towards normalcy. This study first establishes the therapeutic efficacy of resveratrol as a natural antioxidant in thyroprotection against toxic insult caused by fluoride.
Blueberry leaves are a prospective source of phenolic compounds which can be obtained by microwave assisted extraction leading to higher yield in shorter period of time and with lower solvent consumption when compared to solvent extraction. During this study, three experiments with microwave assisted extraction, were separately designed and conducted using highbush blueberry (variety Bluetta) leaves collected during the late fall season. The yields of different compounds obtained during these experiments with microwave extraction were compared with ultrasonic extraction for one hour and 24-h room temperature extraction. The first microwave assisted extraction experiment was conducted to streamline the combination of ethanol and citric acid concentration for further analysis of microwave as a potential extraction method for phenolic compounds and anthocyanins from blueberry leaves. During the second experiment the effect of microwave power level (10–20% absolute power level) and time of extraction (4–16 min) on total phenolics, total anthocyanins and chlorogenic acid was studied which was further used to design the third experiment consisting of a face-centred central composite design with varying factors namely power level and time, each at 3 levels. All the experimental combinations for the 2nd and 3rd experiments were conducted with 80 ml of solvent consisting of 30% ethanol and 1.5 M citric acid combination in ratio of 97:3 (v/v). The total anthocyanins and chlorogenic acid extracted during the study were between 2.321–2.636 mg malvidin 3-glucoside/g dry matter and 49.34–52.66 mg chlorogenic acid/g dry matter respectively, not showing a huge variation between highest and lowest yields, however both compounds with a noteworthy yield. For total phenolics extraction, both microwave power and time of microwave application were observed to be statistically significant factors and the yield of total phenolics was found to be much higher (in the range of 92.719–128.76 mg GAE/g dry weight) than for 24-h extraction at room temperature (average 89.164 mg GAE/g dry weight) and 1 h extraction by sonication (average 97.77 mg GAE/g dry weight) with the same solvent combination.
Catechins, the flavonoids found in abundance in green tea, have many beneficial health effects such as antioxidative, anticarcinogenic, anti-inflammatory, antiallergic, and hypotensive properties. However, flavonoids have antithyroid/goitrogenic effect, although less information is available about the effect of pure catechin on thyroid physiology. The present investigation has been undertaken to explore the effect of catechin administration on thyroid physiology in rat model. For the in vivo experiment catechin was injected intraperitoneally (i.p.) at doses of 10, 20 and 30 mg/kg body to male albino rats for 15 and 30 days, respectively, and thyroid activities were evaluated with respect to determination of serum levels of thyroid hormones, thyroid peroxidase, 5'-deiodinase I (5'-DI), and Na(+), K(+)-ATPase activities that are involved in the synthesis of thyroid hormone. Catechin decreased the activities of thyroid peroxidase and thyroidal 5'-deiodinase I, while Na(+), K(+)-ATPase activity significantly increased in dose-dependent manner; substantial decrease in serum T3 and T4 levels coupled with significant elevation of serum TSH were also noted. Histological examinations of the thyroid gland revealed marked hypertrophy and/or hyperplasia of the thyroid follicles with depleted colloid content. In in vitro study, short-term exposure of rat thyroid tissue to catechin at the concentrations of 0.10, 0.20, and 0.30 mg/ml leads to decrease in the activities of thyroid peroxidase and 5'-deiodinase I, while the activity of thyroidal Na(+), K(+)-ATPase remains unaltered even at high concentration of catechin treatment. The present study reinforces the concept that catechin, tea flavonoids possess potent antithyroid activity as evidenced from in vivo and in vitro studies.
Flavonoids are major bioactive compounds known to be beneficial against many chronic diseases such as cancer, cardiovascular
disorders, and inflammation. Food products obtained from plants are key sources of flavonoids for humans. However, during
different food-processing steps, flavonoids are lost in remarkable amounts. Supplementation of flavonoids as a food additive
will help in retaining the required health-beneficial amount of flavonoids in the diet, and extraction is an important step
in the preparation of food additives. Microwave extraction is one of the most advanced extraction methods, which has the potential
of playing a major role in flavonoid extraction and analytical quantification. The present paper reviews the potential application
of microwave extraction for flavonoids and the advantage of microwave-assisted process over the other extraction processes
generally employed for extraction.
KeywordsFlavonoids–Microwave-assisted extraction–Extraction
Green tea, prepared from the steamed and dried leaves of the shrub Camellia sinensis, is known for its antioxidant and anti-carcinogenic effects. However, its effects on male gonadal functions have not been explored adequately and the present investigation has been undertaken to evaluate the effect of green tea extract on gonads of adult male albino rats. Results of in vivo studies showed that green tea extract (GTE) at mild (1.25 g%, identical to 5 cups of tea/day), moderate (2.5 g%, identical to 10 cups of tea/day) and high (5.0 g%, identical to 20 cups of tea/day) doses, for a period of 26 days, altered morphology and histology of testis and accessory sex organs. A significant dose-dependent decrease in the sperm counts, inhibited activities of testicular delta(5)3beta-and 17beta-hydroxysteroid dehydrogenase (delta5-3beta3-HSD and 17beta3-HSD respectively) and decreased serum testosterone level were noticed. Significant increase in serum LH level was observed after moderate and high doses; serum FSH level also increased but not significantly. Histopathological examination showed inhibition of spermatogenesis evidenced by preferential loss of matured and elongated spermatids. Results of this study showed that GTE at relatively high dose may cause impairment of both the morphological and normal functional status of testis in rodents and thus its consumption at relatively high doses raises concern on male reproductive function in spite of its other beneficial effects.
Indian black tea; CTC leaf and dust, produced by Tata Tea Limited, Kolkata, (India) was studiedin vitro as potential scavenger of oxygen free radicals. Super oxide anions were generated in a system containing xanthine-xanthine oxidase (enzymic system) and by NADH- phenozine methosulphate (non enzymic system). Anions were assayed in terms of uric acid formation and reduction of nitroblue tetrazolium salt, which were shown to be suppressed by tea extracts. Extracts from both leaf and dust also inhibted the formation of hydroxyl radicalsin vitro in the enzymic system comprising hypoxanthine-Cu(+2)-sodium ascorbate and xanthine oxidase and in non enzymic system of deoxyribose-Cu(+2)-sodium ascorbate and H(2)O(2) as well as the Cu(+2) induced lipid peroxidation in human low density lipoprotein. Feeding with black tea in normal rats for sixty days increased their antioxidant activity and their liver microsomes were shown to be protected against peroxidation of lipids as stimulated by metal ions with enzymic or non enzymic reactants. Furthermore feeding with tea extracts in normal as well as triton WR-1339 induced hyperlipidemic rats caused decrease in their plasma levels of total cholesterol, phospholipids and triglycerides. The antioxidant and lipid lowering activities of both extracts from CTC leaf and dust tea was comparable and may be due to the presence of natural products like catechin and others.
The medicinal effects of tea have a history dating back almost 5000 years. The chemical components of green tea chiefly include polyphenols, caffeine and amino acids. Tea also contains flavonoids, compounds reported to have anti-oxidant properties having many beneficial effects. Tea flavonoids reduce inflammation, have antimicrobial effects and prevent tooth decay. Consumption of tea may have diuretic effects due to the caffeine. A related compound found in tea is theophylline, a licensed medicine for the treatment of respiratory diseases such as asthma. Today’s computer-driven world can generate complicated lifestyle-related disorders and consumption of certain natural product like tea may very well replace the ill-effects of chemical drugs leading to a safer world with happier life. The paper is an overview of revealing all such ethno medicinal research efforts throughout the world over the times.
Digitaria exilis (fonio) is a tiny variety of millet commonly eaten by inhabitants of semiarid regions. A sample of fonio collected right in the middle of a severely iodine-depleted goitrous endemic was submitted to phytochemical investigations in order to assess the potential contributory roles played by vegetable molecules to the goitrogenic processes. The total content of flavonoids amounts to 500 mg/kg of the edible whole cereal grains. Their extraction and identification fail to detect the C-glycosylflavones described in other millet varieties but point out the presence of apigenin (A = 150 mg/kg) and of luteolin (L1 = 350 mg/kg). Ten percent of A and 80% of L1 are present in free form, whereas the remaining 90% of A and 20% of L1 are bound as O-glycosylflavones. Both A and L1 aglycones manifest strong anti-thyroid peroxidase (TPO) activities, resulting in a significant reduction of the hormonogenic capacity of this enzyme. In addition, L1 significantly depresses the cyclic AMP phosphodiesterase, implying a concomitant overproduction of the thyrotropin-dependent nucleotide. These last unreported data are regarded as counteracting to some extent the TPO-mediated goitrogenic properties of L1. Since fonio is devoid of other molecules likely to interfere with the thyroid function, our results are directly and casually attributed to A and L1 found in the customary diet.
Plant flavonoids are common dietary components that have many potent biological properties. Early studies of these compounds investigated their mutagenic and genotoxic activity in a number of in vitro assays. Recently, a renewed interest in flavonoids has been fueled by the antioxidant and estrogenic effects ascribed to them. This has led to their proposed use as anticarcinogens and cardioprotective agents, prompting a dramatic increase in their consumption as dietary supplements. Unfortunately, the potentially toxic effects of excessive flavonoid intake are largely ignored. At higher doses, flavonoids may act as mutagens, pro-oxidants that generate free radicals, and as inhibitors of key enzymes involved in hormone metabolism. Thus, in high doses, the adverse effects of flavonoids may outweigh their beneficial ones, and caution should be exercised in ingesting them at levels above that which would be obtained from a typical vegetarian diet. The unborn fetus may be especially at risk, since flavonoids readily cross the placenta. More research on the toxicological properties of flavonoids is warranted given their increasing levels of consumption.
Tea is an important dietary source of flavanols and flavonols. In vitro and animal studies provide strong evidence that tea polyphenols may possess the bioactivity to affect the pathogenesis of several chronic diseases, especially cardiovascular disease and cancer. However, the results from epidemiological and clinical studies of the relationship between tea and health are mixed. International correlations do not support this relationship although several, better controlled case-referent and cohort studies suggest an association with a moderate reduction in the risk of chronic disease. Conflicting results between human studies may arise, in part, from confounding by socioeconomic and lifestyle factors as well as by inadequate methodology to define tea preparation and intake. Clinical trials employing putative intermediary indicators of disease, particularly biomarkers of oxidative stress status, suggest tea polyphenols could play a role in the pathogenesis of cancer and heart disease.
To elucidate the anti-obesity effects of three major components of green tea, catechins, caffeine and theanine, female ICR mice were fed on diets containing 2% green tea powder and diets containing 0.3% catechins, 0.05% caffeine and 0.03% theanine, which correspond, respectively, to their concentrations in a 2% green tea powder diet, singly and in combination for 16 weeks. Body weight and food intake were determined monthly during this period, kidneys, adrenals, liver, spleen, brain, pituitary and intraperitoneal adipose tissues (IPAT) were weighed and lipid levels in the serum and liver were measured at the end of this period. The body weight increase and weight of IPAT were significantly reduced by the diets containing green tea, caffeine, theanine, caffeine + catechins, caffeine + theanine and caffeine + catechins + theanine. Noticeably, the IPAT weight decreased by 76.8% in the caffeine + catechins compared to the control group. Serum concentrations of triglycerides (TG) and non-esterified fatty acids (NEFA) were decreased by green tea, catechins and theanine. Moreover, caffeine + catechins, caffeine + theanine and caffeine + catechins + theanine also decreased NEFA in the serum. The TG level in the liver was significantly reduced by catechins and catechins + theanine in comparison with the control. These results indicated that at least caffeine and theanine were responsible for the suppressive effect of green tea powder (GTP) on body weight increase and fat accumulation. Moreover, it was shown that catechins and caffeine were synergistic in anti-obesity activities.
Thyroid peroxidase (TPO), the key enzyme in thyroid hormone biosynthesis, is inhibited by dietary flavonoids; thus, a high consumption of plants containing inhibitory flavonoids may affect thyroid function and lead to hypothyroidism. In this work, TPO inhibition by the aqueous partition of Myrcia uniflora and its isolated compounds has been evaluated. The aqueous partition of the methanolic extract of M. uniflora is able to inhibit TPO activity in vitro. Two known flavonoids were isolated and characterized by mass spectrometry and (1)H NMR from plant extracts: mearnsitrin and myricitrin. The degree of TPO inhibition produced by the aqueous solution of the flavonoids was very high, with a 50% inhibition of the original TPO activity (IC(50)) obtained at 1.97 microM mearnsitrin and at 2.88 microM myricitrin. These results suggest that the indiscriminated consumption of M. uniflora pharmaceutical products allied to the nutritional deficiency of iodine might contribute to the development of hypothyroidism and goiter.
Cruciferous plants viz. cabbage, cauliflower, turnip, radish, mustard etc. that contain goitrogenic/antithyroid substances, constitute a portion of regular human diet. The effect of chronic feeding of fresh and cooked radish, R. sativus under varying state of iodine intake on morphological and functional status of thyroid in albino rats was evaluated by thyroid gland morphology and histology, thyroid peroxidase activity, serum triiodothyronine, thyroxine and thyrotropin levels. The consumption pattern of iodine and goitrogens of cyanogenic origin was evaluated by measuring urinary iodine and thiocyanate levels respectively. After chronic radish feeding, increased weight of thyroid gland, decreased thyroid peroxidase activity, reduced thyroid hormone profiles and elevated level of thyrotropin were observed resembling a relative state of hypoactive thyroid gland in comparison to control even after supplementation of adequate iodine.
Although studies have documented the regulatory effects of thyroid hormones on the Na,K-ATPase in peripheral tissues, there is little information on the regulation of this transporter in the thyroid gland itself. Accordingly, we investigated the effects of thyroid status on Na,K-ATPase specific activity and the abundance of its constituent subunits in rat thyroid. Exogenous tri-iodothyronine (T3) was administered daily to produce hyperthyroidism. 6n-propyl-2-thiouracil (PTU), an inhibitor of thyroid hormone synthesis, was used to induce hypothyroidism. There was a four-fold increase in Na,K-ATPase specific activity in the follicular membranes from PTU-treated animals after 7 days. Enzymatic activities were not changed in the T3-treated glands. Immunoblotting of membranes from T3-treated rats revealed a 75% reduction in alpha1 subunit abundance and a slight, but nonsignificant reduction in beta1 abundance. On the other hand, the membranes from PTU-treated rats displayed 136 and 567% increases in the abundance of the alpha1 and beta1 subunits respectively. These data demonstrate that thyroid hormone status regulates Na,K-ATPase in the gland, but the effects are in direct contrast to those seen in the periphery.
An investigation was carried out on a newer method for the determination of inorganic phosphate which is applicable to the study of phosphate-splitting enzymes. It offers a unique advantage: after the color reagent has been added any inorganic phosphate formed cannot react with molybdenum, for the latter has been complexed by the addition of a citrate-arsenite solution and phosphate cannot compete successfully for the molybdate.This procedure appears to be quite suitable for the determination of inorganic phosphate, phospholipids, nucleotides or enzyme-hydrolyzed phosphate.
A rapid, sensitive spectrophotometric assay for iodide oxidation by thyroid peroxidase is described. The method depends upon the measurement of periodide at either of its absorption peaks, 353 mμ or 287.5 mμ, and is adequately suited for enzyme purification studies.
Tea is grown in about 30 countries but is consumed worldwide, although at greatly varying levels. It is the most widely consumed beverage aside from water with a per capita worldwide consumption of approximately 0.12 liter per year. Tea is manufactured in three basic forms. Green tea is prepared in such a way as to preclude the oxidation of green leaf polyphenols. During black tea production oxidation is promoted so that most of these substances are oxidized. Oolong tea is a partially oxidized product. Of the approximately 2.5 million metric tons of dried tea manufactured, only 20% is green tea and less than 2% is oolong tea. Green tea is consumed primarily in China, Japan, and a few countries in North Africa and the Middle East. Fresh tea leaf is unusually rich in the flavanol group of polyphenols known as catechins which may constitute up to 30% of the dry leaf weight. Other polyphenols include flavanols and their glycosides, and depsides such as chlorogenic acid, coumarylquinic acid, and one unique to tea, theogallin (3-galloylquinic acid). Caffeine is present at an average level of 3% along with very small amounts of the other common methylxanthines, theobromine and theophylline. The amino acid theanine (5-N-ethylglutamine) is also unique to tea. Tea accumulates aluminum and manganese. In addition to the normal complement of plant cell enzymes, tea leaf contains an active polyphenol oxidase which catalyzes the aerobic oxidation of the catechins when the leaf cell structure is disrupted during black tea manufacture. The various quinones produced by the enzymatic oxidations undergo condensation reactions which result in a series of compounds, including bisflavanols, theaflavins, epitheaflavic acids, and thearubigens, which impart the characteristic taste and color properties of black tea. Most of these compounds readily form complexes with caffeine. There is no tannic acid in tea. Thearubigens constitute the largest mass of the extractable matter in black tea but their composition is not well known. Proanthocyanidins make up part of the complex. Tea peroxidase may be involved in their generation. The catechin quinones also initiate the formation of many of the hundreds of volatile compounds found in the black tea aroma fraction. Green tea composition is very similar to that of the fresh leaf except for a few enzymatically catalyzed changes which occur extremely rapidly following plucking. New volatile substances are produced during the drying stage. Oolong tea is intermediate in composition between green and black teas.
The aim of this chapter is to describe the procedures involved in the characterization of an Na+,K+-ATPase preparation. The first part is concerned with measurement of the overall Na+,K+-ATPase activity and the partial reactions catalyzed by the enzyme. The second part deals with the problem of determining the protein concentration, which must be known accurately for calculation of specific activity. A third section is devoted to the molar activity and the purity of the preparation in terms of the protein components, the α and β peptides. The final section contains some comments on the problem of inactive or partially active enzyme molecules in the preparations.
Pearl millet [Pennisetum millet (L.) leeke] is the main source of food energy for the rural poor in many areas of the semiarid tropics. Epidemiological evidence suggests that millet may play a role in the genesis of endemic goiter in these areas, and sparse experimental data in rats support this suspicion. This study was undertaken to determine in vivo in rats and in vitro using porcine thyroid slices and a thyroid peroxidase (TPO) assay the goitrogenic and antithyroid effects of millet diets, extracts of millet, and certain pure compounds contained therein. For use in these studies, whole grain millet was progressively dehulled to yield successively four bran and four flour fractions in which direct analyses revealed progressively lower concentrations of C-glycosylflavones. In vivo feeding of bran fraction 1, that richest in C-glycosylflavones, led to a significant increase in thyroid weight and antithyroid effects. Feeding of bran fraction 2, the next richest in C-glycosylflavones, produced similar, but less marked, changes. In vitro studies of 125I metabolism using porcine thyroid slices indicated that extracts of bran fractions 1 and 2 were most potent, producing changes similar to those produced by methimazole (MMI). At a concentration of 60 mumol/L, glucosylvitexin, the major C-glycosylflavone present in millet, had effects comparable to those of 1 mumol/L MMI. Similarly, in studies of porcine TPO, extracts of bran fraction 1 caused pronounced (85%) inhibition of enzyme activity, and progressively less inhibition was induced by extracts of bran fractions 2, 3, and 4. Overall, the TPO-inhibiting activities of the various millet fractions closely correlated with their C-glycosylflavone concentrations. Three C-glycosylflavones present concentrations. Three C-glycosylflavones present in millet, glucosylvitexin, glycosylorientin, and vitexin, also inhibited TPO activity. Thus, in vivo and in vitro studies revealed that millet diets rich in C-glycosylflavones produce goitrogenic and antithyroid effects similar to those of certain other antithyroid agents and small doses of MMI. We conclude that in areas of iodine deficiency in which millet is a major component of the diet, its ingestion may contribute to the genesis of endemic goiter.
5-Monodeiodination of T4 and T3 and 5'-monodeiodination of T4 and rT3 were studied in brain homogenates of male Sprague-Dawley rats, aged 1-60 days. Portions of the homogenates were incubated with the substrates at 37 C for 30 min. The reaction products were estimated by specific RIAs. All of the four reactions were dependent upon time, temperature, pH, and upon the concentrations of substrate, thiol, and tissue protein. Maximal reactions were obtained between 40 and 160 mM dithioerythritol. T4 5'-deiodination proceeded optimally at pH 7.4 and 0.4 microM substrate, the other reactions at pH 8.5 and 10 microM substrate. The four reactions were inactivated by heat (56 C, 30 min) and inhibited by 10(-5) M iopanoic acid. Only rT3 5'-deiodination was inhibited by 3 X 10(-4) M propylthiouracil (greater than 95%). In cerebellum, basal ganglia, brainstem, and hypothalamus both T4 and T3 5-deiodinase activity were very high in perinatal rats [up to 5.56 pmol/(min X mg protein) in hypothalamus], and decreased rapidly with age. In cortex and olfactory bulb these enzyme activities were low after birth, followed by an increase during the growth spurt [up to 632 fmol/(min X mg protein) in olfactory bulb]. T4 and rT3 5'-deiodinase activity in all brain regions studied were at their lowest in perinatal rats. During and after the growth spurt an increase was observed [up to 457 fmol/(min X mg protein) in cerebellum]. The reciprocal course of 5- and 5'-deiodination between birth and growth spurt in most of the brain regions studied might lead to a reduced intracellular thyromimetic activity during the perinatal period.
Flavonoids are widely distributed in plant-derived foods and possess a variety of biological activities including antithyroid effects in experimental animals and humans. A structure-activity study of 13 commonly consumed flavonoids was conducted to evaluate inhibition of thyroid peroxidase (TPO), the enzyme that catalyzes thyroid hormone biosynthesis. Most flavonoids tested were potent inhibitors of TPO, with IC50 values ranging from 0.6 to 41 microM. Inhibition by the more potent compounds, fisetin, kaempferol, naringenin, and quercetin, which contain a resorcinol moiety, was consistent with mechanism-based inactivation of TPO as previously observed for resorcinol and derivatives. Other flavonoids inhibited TPO by different mechanisms, such as myricetin and naringin, showed noncompetitive inhibition of tyrosine iodination with respect to iodine ion and linear mixed-type inhibition with respect to hydrogen peroxide. In contrast, biochanin A was found to be an alternate substrate for iodination. The major product, 6,8-diiodo-biochanin A, was characterized by electrospray mass spectrometry and 1H-NMR. These inhibitory mechanisms for flavonoids are consistent with the antithyroid effects observed in experimental animals and, further, predict differences in hazards for antithyroid effects in humans consuming dietary flavonoids. In vivo, suicide substrate inhibition, which could be reversed only by de novo protein synthesis, would be long-lasting. However, the effects of reversible binding inhibitors and alternate substrates would be temporary due to attenuation by metabolism and excretion. The central role of hormonal regulation in growth and proliferation of thyroid tissue suggests that chronic consumption of flavonoids, especially suicide substrates, could play a role in the etiology of thyroid cancer.
Chinese teas with different degrees of fermentation were examined for their effect on diet-induced hypercholesterolemia in rats. The teas tested were Chinese Green tea, Jasmine, Iron Buddha, Oolong and Pu erh. Hypercholesterolemia was induced by feeding rats with a cholesterol-enriched diet for 1 week. They were then treated with different tea extracts together with a cholesterol-enriched diet for another 8 weeks. Chinese Green tea and Jasmine tea, both with a minimum degree of fermentation, were found to have significant serum and liver cholesterol lowering effects. They also reduced the increase in liver weight due to lipid deposition. All tea treatments lowered the atherogenic index and increased the HDL-total cholesterol ratio, while HDL-cholesterol and triglyceride levels were not significantly affected. Analysis of catechin levels in tea extracts showed that the individual catechin component in Chinese Green tea and Jasmine tea were significantly higher than the others. (-)-Epicatechin gallate and (-)-epigallocatechin gallate in the tea extracts may account for their hypocholesterolemic effect.
Although studies have documented the regulatory effects of thyroid hormones on the Na,K-ATPase in peripheral tissues, there is little information on the regulation of this transporter in the thyroid gland itself. Accordingly, we investigated the effects of thyroid status on Na,K-ATPase specific activity and the abundance of its constituent subunits in rat thyroid. Exogenous tri-iodothyronine (T3) was administered daily to produce hyperthyroidism. 6n-propyl-2-thiouracil (PTU), an inhibitor of thyroid hormone synthesis, was used to induce hypothyroidism. There was a four-fold increase in Na,K-ATPase specific activity in the follicular membranes from PTU-treated animals after 7 days. Enzymatic activities were not changed in the T3-treated glands. Immunoblotting of membranes from T3-treated rats revealed a 75% reduction in alpha1 subunit abundance and a slight, but nonsignificant reduction in beta1 abundance. On the other hand, the membranes from PTU-treated rats displayed 136 and 567% increases in the abundance of the alpha1 and beta1 subunits respectively. These data demonstrate that thyroid hormone status regulates Na,K-ATPase in the gland, but the effects are in direct contrast to those seen in the periphery.
Aqueous extracts of green and black teas have been shown to inhibit a variety of experimentally induced animal tumors, particularly ultraviolet (UV) B light-induced skin carcinogenesis. In the present study, we compared the effects of different extractable fractions of green and black teas on scavenging hydrogen peroxide (H2O2), and UV irradiation-induced formation of 8-hydroxy 2'-deoxyguanosine (8-OHdG) in vitro. Green and black teas have been extracted by serial chloroform, ethyl acetate and n-butanol, and divided into four subfractions designated as GT1-4 for green tea and BT1-4 for black tea, respectively. The total extracts from green and black teas exhibited a potent scavenging capacity of exogenous H2O2 in a dose-dependent manner. It appeared that the total extracts from black tea scavenged H2O2 more potently than those from green tea. When tested individually, the potency of scavenging H2O2 by green tea subfractions was: GT2 > GT3 > GT1 > GT4, whereas the order of efficacy for black tea was: BT2 > BT3 > BT4 > BT1. In addition, we demonstrated that total fractions of green and black teas substantially inhibited the induction of 8-OHdG in calf thymus by all three portions of UV spectrum (UVA, B and C). Consistent with the capacity of scavenging H2O2, the subfractions from black tea showed a greater inhibition of UV-induced 8-OHdG than those from green tea. At low concentrations, the order of potency of quenching of 8-OHdG by green tea subfractions was: GT2 > GT3 > GT4 > GT1 and the efficacy of all subfractions became similar at high concentrations. All subfractions of the black tea except BT1 strongly inhibited UV-induced 8-OHdG and the order of potency was: BT2 > BT3 > BT4 > BT1. Addition of (-)-epigallocatechin gallate (EGCG), an ingredient of green tea extract, to low concentration of green and black tea extracts substantially enhanced the scavenging of H2O2 and quenching of 8-OHdG, suggesting the important role of EGCG in the antioxidant activities of tea extracts. The potent scavenging of oxygen species and blocking of UV-induced oxidative DNA damage may, at least in part, explain the mechanism(s) by which green/black teas inhibit photocarcinogenesis.
Tissue-specific activation and inactivation of ligands of nuclear receptors which belong to the steroid retinoid-thyroid hormone superfamily of transcription factors represents an important principle of development- and tissue-specific local modulation of hormone action. Recently, several enzyme families have been identified which act as 'guardians of the gate' of ligand-activated transcription modulation. Three monodeiodinase isoenzymes which are involved in activation the 'prohormone' L-thyroxine (T4), the main secretory product of the thyroid gland, have been identified, characterized, and cloned. Both, type I and type II 5'-deiodinase generate the thyromimetically active hormone 3,3',5-triiodothyronine (T3) by reductive deiodination of the phenolic ring of T4. Inactivation of T4 and its product T3 occurs by deiodination of iodothyronines at the tyrosyl ring. This reaction is catalyzed both the type III 5-deiodinase and also by the type I enzyme, which has a broader substrate specificity. The three deiodinases appear to constitute a newly discovered family of selenocysteine-containing proteins and the presence of selenocysteine in the protein is critical for enzyme activity. Whereas the selenoenzyme characteristics of the type I and type III deiodinases are definitively established some controversy still exists for the type II 5'-deiodinase in mammals. The mRNA probably encoding the type II 5'-deiodinase subunit is markedly longer than those of the two other deiodinases and its selenocysteine-insertion element is located more than 5 kB downstream of the UGA-codon in the 3'-untranslated region. The three deiodinase isoenzymes show a distinct development- and tissue-specific pattern of expression, operate at individual optimal substrate levels, are differently regulated and modulated by hormones, cytokines, signaling pathways, natural factors, and pharmaceuticals. Whereas circulating T3 mainly originates from hepatic production via the type I 5'-deiodinase, the local cellular thyroid hormone concentration in various tissues including the central nervous system is controlled by complex para-, auto-, and intracrine interactions of all three deiodinases. Local thyroid hormone availability is further modulated by conjugation reactions of the phenolic 4'-OH-group of iodothyronines, which also inactivate the thyroid hormones.
The effects of green tea extract catechins on the rat thyroid were examined in a 13-week feeding study and subsequent 2-,4- and 8-week studies. Commercially available polyphenon-60 (P-60) which contains green tea extract catechins at 66.2% was used as a source of catechins. A basic diet containing different concentrations of P-60 was used for experiments. In the 13-week study, 10 rats of each sex were administered diets containing P-60 at 0 (control), 0.625, 1.25, 2.5 and 5.0%. Goiters were observed in the 13-week test. The mean thyroid weight of rats fed a diet containing 5.0% of P-60 (5.0% group) significantly increased to 444% of the control in males and to 304% of the control in females. Histological examinations of the thyroid of the 5.0% group revealed marked hypertrophy and/or hyperplasia of the follicles, some with depletion of colloid and some with rich colloid, and formation of a fibrous capsule. Slight hypertrophy of follicular cells was observed in male rats fed a diet containing 1.25% of P-60 (1.25% group) and female rats fed a diet containing 2.5% of P-60 (2.5% group). Degree and incidence of thyroid lesions were higher in males than in females in the 1.25, 2.5 and 5.0% groups. In the 2-8-week studies, five rats of each sex were given diets containing 0 (control) and 5.0% of P-60. In the 5.0% group, the mean thyroid weight in males significantly increased to 161% of the control as early as 2 weeks and increased to 357% of the control at 8 weeks. Histologically, these goiters were also associated with follicular cell hypertrophy/hyperplasia as in the 13-week study. The degree and incidence of thyroid lesions were higher in males than in females. These results indicate that dietary administration of the green tea extract catechins at high doses induced goiters in rats, and this may be due to antithyroid effects of catechins. In the 13-week study, the no-observed effect level (NOEL) of green tea extract catechins for F344 rats based on histological changes of the thyroid was considered to be 0.625% in males and 1.25% in females in the diet, respectively.
We orally administered polyphenone-60 (P-60), green tea extract catechins, in the diet (0, 1.25 and 5%) to male rats for 2, 4 and 8 weeks initiated at 5 weeks old. It was found that a 5% dose to male rats for 2-8 weeks induced goiters and decreased weights of the body, testis and prostate gland. Endocrinologically, elevating plasma thyroid stimulating hormone (TSH), luteinizing hormone (LH) and testosterone levels and decreasing tri-iodothyronine (T(3)) and thyroxine (T(4)) levels were induced by this treatment. We also found that P-60 as a whole and some of its constituents exhibited inhibitory effects on human placental aromatase activity by in vitro assay. The concentration of P-60 that required producing 50% inhibition of the aromatase activity (IC(50) value) was 28 microg/ml. The IC(50) values of (-)-catechin gallate (Cg), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCg) and (-)-gallocatechin gallate (GCg) were 5.5 x 10(-6), 1.0 x 10(-4), 6.0 x 10(-5) and 1.5 x 10(-5) M, respectively. (-)- Epicatechin gallate (ECg) at 1.0 x 10(-4) M produced 20% inhibition. (-)-Epicatechin (EC) and (+)-catechin (CT) exhibited no effects on aromatase activity. The endocrinological changes observed in vivo were in conformity with antithyroid effects and aromatase inhibition effects of P-60 and its constituents.
Some dietary flavonoids inhibit thyroperoxidase and hepatic deiodinase activity, indicating that these compounds could be classified as anti-thyroid agents. In this study, we evaluated the in vitro effect of various flavonoids on thyroid type 1 iodothyronine deiodinase activity (D1). D1 activity was measured in murine thyroid microsome fractions by the release of 125I from 125I-reverse T3. D1 activity was significantly inhibited by all the flavonoids tested; however, the inhibitory potencies on thyroid D1 activity differed greatly among them. A 50% inhibition of D1 activity (IC(50)) was obtained at 11 microM baicalein, 13 microM quercetin, 17 microM catechin, 55 microM morin, 68 microM rutin, 70 microM fisetin, 72 microM kaempferol and 77 microM biochanin A. Our data reinforce the concept that dietary flavonoids might behave as antithyroid agents, and possibly their chronic consumption could alter thyroid function.
A simple and rapid method is presented for the preparation of I/sup 131/- labeled human growth hormone of high specific radioactivity (240-300 mu C/ mu g). Low amounts of carrierfree I/sup 131/ iodide (2 mC) are allowed to react, without prior treatment, with small quantities of protein (5 mu g) in a highyield reaction (approx. 70% transfer of I/sup 131/ to protein). The degree of chemical substitution is minimized (0.5- 1.0 atom of iodine/molecule of protein) by the use of carrier-free I/sup 131/ iodide. The I/sup 131/-labeled hormone (up to 300 mu C/ mu g) contains no detectable degradation products and is immunologically identical with the unlabeled hormone. The loss of immunological reactivity at high specific radioactivities or at high levels of chemical substitution with STAI/sup 127/!iodine is demonstrated. (auth)
The effects of three natural phenolic acids (caffeic, ferulic, and p-coumaric) on the rat thyroid gland were examined in a 3-week oral-treatment study. Forty male Wistar albino rats, divided into groups of 10 rats each and fed iodine-rich diet, were administered by gastrointestinal tube saline (control), caffeic acid, ferulic acid, or p-coumaric acid at a dose level of 0.25 micromol/kg/day for 3 weeks. The mean absolute and relative thyroid weights in caffeic, ferulic, or p-coumaric acid groups were significantly increased to 127 and 132%, 146 and 153%, or 189 and 201% compared to control value, respectively. Histological examination of the thyroids of p-coumaric acid group revealed marked hypertrophy and/or hyperplasia of the follicles. Caffeic or ferulic groups showed slight to moderate thyroid gland enlargement. Thyroid lesions in p-coumaric acid group were associated with significant increases in cellular proliferation as indicated by [(3)H]thymidine incorporation. In addition, the goitrogenic effect of p-coumaric acid was further confirmed by significant decreases (50%) in serum tri-iodothyronine (T(3)) and thyroxine (T(4)), and a parallel increase (90%) in serum thyroid stimulating hormone (TSH) compared to control group. These results indicate that administration of p-coumaric acid at relatively high doses induces goiter in rats.
Consumption of cyanogenic foods has been considered as one of the etiological factors in certain instances for the persistence of endemic goitre. The present study was undertaken to study the cyanogenic glucosides, glucosinolates and thiocyanate content in edible portion of certain selected plant foods of Indian origin. Further in vitro anti-thyroidal activity using raw, boiled and cooked extracts of these plants with and without excess iodide was also studied.
Cyanogenic plant foods generally vegetables were collected from different areas of West Bengal and Tripura. Cassava was obtained from Meghalaya and Kerala and their cyanogenic glucosides, glucosinolates and thiocyanate were estimated. Thyroid peroxidase activity (TPO) of human thyroid was assayed from microsomal fraction following I3- from iodide. The anti-TPO activities of the plants were assayed after adding raw, boiled and cooked extracts in the assay medium with and without extra iodide. Relative antithyroidal potency of the plant extracts was also evaluated in terms of the concentration (IC50) necessary to produce 50 per cent inhibition of TPO activity. PTU equivalence of the plant foods was also determined.
Cabbage and cauliflower were rich in glucosinolates, bamboo shoot and cassava were rich in cyanogenic glucosides, mustard, turnip and radish were relatively rich in thiocyanate however all the constituents were present in each plant. Boiled extracts showed maximum inhibition of TPO activity followed by cooked and raw extracts. Excess iodide was found relatively effective for raw extract but less effective for boiled and cooked extracts in reversing anti-TPO activity. Inhibition constant (IC50) was found highest with bamboo shoot and least with cabbage.
Raw, boiled and cooked extracts of the plants showed anti-thyroidal activity in vitro. Excess iodide reversed the anti-TPO activity to same extent but could not neutralise it.
Green tea is rich in polyphenolic compounds, with catechins as its major component. Studies have shown that catechins possess diverse pharmacological properties that include anti-oxidative, anti-inflammatory, anti-carcinogenic, anti-arteriosclerotic and anti-bacterial effects. In the gastrointestinal tract, green tea was found to activate intracellular antioxidants, inhibit procarcinogen formation, suppress angiogenesis and cancer cell proliferation. Studies on the preventive effect of green tea in esophageal cancer have produced inconsistent results; however, inverse relationships of tea consumption with cancers of the stomach and colon have been widely reported. Green tea is effective to prevent dental caries and reduce cholesterols and lipids absorption in the gastrointestinal tract, thus benefits subjects with cardiovascular disorders. As tea catechins are well absorbed in the gastrointestinal tract and they interact synergistically in their disease-modifying actions, thus drinking unfractionated green tea is the most simple and beneficial way to prevent gastrointestinal disorders.
Vanadium has been recognized as industrial hazards that adversely affect male reproductive systems of humans and animals. However, less information is available concerning the underlying mechanism in the pathogenesis of male reproductive dysfunction. The present study investigated the possible involvement of oxidative stress to induce oxidative deterioration of testicular functions in adult rats. The results of in vitro and in vivo studies demonstrate that vanadium treatment resulted in a significant dose- and time-dependent increase in the testicular lipid peroxidation, marked inhibition in the level of superoxide dismutase and catalase activities, decreased sperm counts, and substantially inhibited the activities of Delta(5)3beta- and 17beta-hydroxysteroid dehydrogenase as well as serum testosterone level. Histopathological examination revealed inhibition of spermatogenesis and the preferential loss of maturing and elongated spermatids along with increased percent of abnormal sperm. Taken together, the results suggest that an increase in free radical formation relative to loss of antioxidant defense system during vanadium exposure may render testis more susceptible to oxidative damage leading to their functional inactivation. Thus the toxic effects of vanadium are cumulative and that vanadium produced damages in testes are dose- and time-dependent.
People have been consuming brewed tea from the leaves of the Camellia sinensis plant for almost 50 centuries. Although health benefits have been attributed to tea, especially green tea consumption since the beginning of its history, scientific investigations of this beverage and its constituents have been underway for less than three decades. Currently, tea, in the form of green or black tea, next to water, is the most widely consumed beverage in the world. In vitro and animal studies provide strong evidence that polyphenols derived from tea may possess the bioactivity to affect the pathogenesis of several chronic diseases. Among all tea polyphenols, epigallocatechin-3-gallate has been shown to be responsible for much of the health promoting ability of green tea. Tea and tea preparations have been shown to inhibit tumorigenesis in a variety of animal models of carcinogenesis. However, with increasing interest in the health promoting properties of tea and a significant rise in scientific investigation, this review covers recent findings on the medicinal properties and health benefits of tea with special reference to cancer and cardiovascular diseases.
Although it is known that tea catechins exert potent effects in obese subjects, there is scant information concerning these effects on body weight gain and body fat accumulation in the non-obese. We studied normal rats fed a normal diet and water containing either 0.1% or 0.5% tea catechins to examine the effects on body fat content and serum cholesterol levels, as well as evaluating whether the effect is related to bile acids, which in recent years have emerged as an inducer of energy expenditure. The administration of 0.5% catechins decreased the accumulation of body fat and the serum levels of cholesterol and bile acids. These results indicate that tea catechins modulate lipid metabolism not only in obese subjects, but also in the non-obese.
Pharmacoki-netics and intra-thyroidal effects of flavonoids (eds) Environmental goitrogenesis
- Lindsay R E Gaitan
- Cooksey
Lindsay R, Gaitan E, and Cooksey R. Pharmacoki-netics and intra-thyroidal effects of flavonoids. In: Gaitan E (eds) Environmental goitrogenesis. Boca Roton: CRC Press, 1989, p.43–56.
Pharmacokinetics and intra-thyroidal effects of flavonoids
- R Lindsay
- E Gaitan
- R Cooksey