The Role of Zinc in Thyroid Hormones Metabolism.

Thyroid hormones play an important role in body homeostasis by facilitating metabolism of lipids and glucose, regulating metabolic adaptations, responding to changes in energy intake, and controlling thermogenesis. Proper metabolism and action of these hormones requires the participation of various nutrients. Among them is zinc, whose interaction with thyroid hormones is complex. It is known to regulate both the synthesis and mechanism of action of these hormones. In the present review, we aim to shed light on the regulatory effects of zinc on thyroid hormones. Scientific evidence shows that zinc plays a key role in the metabolism of thyroid hormones, specifically by regulating deiodinases enzymes activity, thyrotropin releasing hormone (TRH) and thyroid stimulating hormone (TSH) synthesis, as well as by modulating the structures of essential transcription factors involved in the synthesis of thyroid hormones. Serum concentrations of zinc also appear to influence the levels of serum T3, T4 and TSH. In addition, studies have shown that Zinc transporters (ZnTs) are present in the hypothalamus, pituitary and thyroid, but their functions remain unknown. Therefore, it is important to further investigate the roles of zinc in regulation of thyroid hormones metabolism, and their importance in the treatment of several diseases associated with thyroid gland dysfunction.

Selenium status and its relationship with thyroid hormones in obese women.

BACKGROUND AND AIMS: Studies have been conducted with the purpose of elucidating thyroid gland dysfunction in obesity, however the contributing factors for such dysfunction are not yet fully understood. Selenium is notable for its role in thyrocyte protection against oxidative damage and control of thyroid hormone synthesis. In addition, subjects with obesity may exhibit alterations in the selenium homeostasis. Therefore, the present study aimed to examine the selenium status and its relationship with serum thyroid hormone levels in obese women. METHODS: This cross-sectional study included 69 euthyroid women, aged between 18 and 50 years, who were divided in two groups: an obese group (n = 35) and a control group with women of normal weight (n = 34). Selenium intake was assessed by three-day diet records and analyzed using NutWin software version 1.5. Plasma, erythrocyte, and urinary selenium levels were determined using inductively coupled plasma optical emission spectrometry. Testing for thyroid hormones and thyroid autoantibodies was performed based on chemiluminescence. RESULTS: The median dietary selenium content was adequate according to the recommendations, with no statistical difference between groups. Obese women had reduced plasma and erythrocyte selenium levels compared to the control group, although selenium concentration in erythrocytes was adequate within the normal range for both groups. There was no significant difference between the urinary selenium concentrations in the subjects; however, the mineral clearance was higher in the obese group. Free triiodothyronine (fT3) and free thyroxine (fT4) levels were higher in obese women with class II obesity when compared to the control group. There was a negative correlation between plasma selenium and serum fT4 levels. CONCLUSIONS: Obese women showed impairment in selenium homeostasis, however, this fact did not seem to adversely affect thyroid metabolism.

The role of selenium in insulin resistance

ABSTRACT In recent years, there has been growing interest in clarifying the pathogenesis of some chronic diseases, such as obesity and type 2 diabetes mellitus. Metabolic alterations in these diseases are characterized by chronic hyperglycemia and insulin resistance. Studies have demonstrated the participation of minerals in the pathogenesis of insulin resistance, more specifically their involvement in the synthesis and regulation of insulin. Selenium is an anti-inflammatory and antioxidant micronutrient that is essential for the activity of selenoproteins. Two selenoproteins (glutathione peroxidase and selenoprotein P) are known to be involved in the insulin signaling pathway. The aim of this review is to provide an update on the role of selenium in insulin resistance mechanisms. Evidence shows that adequate concentrations of selenium play a key role in the secretion and action of insulin, but an excess of selenium in the body is associated with the pathogenesis of insulin resistance and the development of diabetes mellitus.

Concentrações de cobre em mulheres obesas e sua relação com marcador da peroxidação lipídica / Copper concentrations in obese women and their relationship to lipid peroxidation marker

Introdução: Estudos atuais têm mostrado relação entre minerais antioxidantes e desordens bioquímicas envolvidas na patogênese da obesidade, em especial, a peroxidação lipídica. Nesse sentido, a literatura revela importância da atuação de elementos traços, a exemplo do cobre, na proteção contra a produção excessiva de radicais livres em indivíduos obesos. Objetivo: deste estudo foi avaliar as concentrações de cobre em mulheres obesas e sua relação com marcador da peroxidação lipídica. Metodologia: Estudo de natureza transversal, analítico e experimental envolveu 89 mulheres, com idade entre 20 e 50 anos, distribuídas em dois grupos: grupo controle (mulheres eutróficas, n=45) e grupo caso (obesas, n=44). As concentrações plasmáticas e eritrocitárias do cobre foram determinadas por espectrometria de absorção atômica. As concentrações plasmáticas das TBARS foram determinadas seguindo-se método descrito por Ohkawa, Ohishi e Yagi (1979), com adaptações. Resultados: A concentração das substâncias reativas ao ácido tiobarbitúrico foi significativamente maior no grupo caso em comparação com o grupo controle (p=0,001). O grupo caso apresentou concentrações inferiores de cobre plasmático e eritrocitário (p<0,05). Ambos os grupos apresentaram concentrações adequadas de cobre eritrocitário e plasmático. Não foi verificada correlação significativa entre o cobre plasmático e eritrocitário e parâmetros de adiposidade (p>0,05). Conclusão: Os resultados deste estudo indicam concentrações plasmáticas e eritrocitárias de cobre dentro da faixa de adequação, sendo que o grupo caso apresenta concentrações inferiores comparado ao grupo controle. O estudo não revelou correlação significativa entre o marcador de peroxidação lipídica e as concentrações de cobre plasmático e eritrocitário

Background: Current studies have shown a relationship between antioxidant minerals and biochemical disorders involved in the pathogenesis of obesity, especially lipid peroxidation. In this sense, the literature reveals importance of the performance of trace elements, such as copper, in the protection against the excessive production of free radicals in obese individuals. Objective: was to evaluate how the associations of obese women and their interface with lipid peroxidation. Methods: Cross-sectional, analytical and experimental involved 89 women, aged between 20 and 50 years, divided into two groups: control group (eutrophic women, n = 45) and case group (obese, n = 44). As plasma and erythrocyte concentrations of copper and determined by atomic absorption spectrometry. Plasma concentrations of TBARS were determined following the method described by Ohkawa, Ohishi and Yagi (1979), with adaptations. Results: The concentration of the reactive substances to thiobarbituric acid was significantly higher in the case group compared to the control group (p = 0,001). The case group had lower concentrations of plasma and erythrocyte copper (p <0,05). Both groups had adequate concentrations of erythrocyte and plasma copper. There was no significant correlation between plasma and erythrocyte copper and adiposity parameters (p> 0,05). Conclusion: From the results of this study, it can be concluded that the participants of the study have plasma and erythrocyte copper concentrations within the adequacy range, and the case group presents lower concentrations compared to the control group. In addition, no significant correlation was found between the lipid peroxidation marker and the plasma and erythrocyte copper concentrations

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Participação do selênio no diabetes mellitus tipo 2 / Participation of selenium in type 2 diabetes mellitus

OBJECTIVE: This review aims to bring updated information on the relationship between oxidative stress and the role of selenium as antioxidant nutrient in mechanisms involved in the pathogenesis of type 2 diabetes mellitus. Data source: The bibliographic survey was conducted in PubMed, SciELO and Lilacs, considering the 2002-2014 period, and included the following types of studies: randomized or quasi-randomized controlled trials, cohort, case-control study, case series and case report. Forty-nine pertinent scientific studies were selected. Data synthesis: Several studies have demonstrated the contribution of acute and/or chronic hyperglycemia to the manifestation of oxidative stress in type 2 diabetic patients. Accordingly, selenium has an important participation in controlling this disease due to its antioxidant role in the elimination of free radicals, present in excess, and because it blocks the activation of nuclear transcription factor kappa B, a regulator sensitive to oxidants that stimulates the production of inflammatory mediators (cytokines) and adhesion molecules. CONCLUSIONS: There is convincing experimental evidence demonstrating the involvement of selenium in glycemic control. However, current information is still scarce and inconsistent, and it is necessary to conduct further studies on the subject to determine the selenium intake safety range as well as clarify the influence of this mineral on the manifestation of type 2 diabetes mellitus and its associated disorders

OBJETIVO: Esta revisão visa trazer informações atualizadas sobre a relação entre o estresse oxidativo e o papel do selênio como nutriente antioxidante em mecanismos envolvidos na patogênese do diabetes mellitus tipo 2. Fonte de dados: O levantamento bibliográfico foi realizado nas bases de dados Pubmed, SciELO e Lilacs considerando o período de 2002 a 2014 e abrangeu os seguintes tipos de estudos: ensaios clínicos controlados randomizados ou quase-randomizados, coorte, estudo caso-controle, série de casos e relato de caso. Foram selecionados 49 que se relacionavam com esta pesquisa bibliográfica. Síntese dos dados: Várias pesquisas têm demonstrado a contribuição do estado hiperglicêmico agudo e/ou crônico na manifestação do estresse oxidativo em pacientes diabéticos tipo 2. Nesse sentido, o selênio possui participação importante no controle dessa doença, devido ao seu papel antioxidante na eliminação dos radicais livres, presentes em excesso, e por bloquear a ativação do fator de transcrição nuclear kappa B, um regulador sensível a oxidantes que estimula a produção de mediadores inflamatórios (citocinas) e de moléculas de adesão. CONCLUSÕES: Existem evidências experimentais convincentes que demonstram a participação do selênio no controle glicêmico. No entanto, as informações atuais ainda são bastante escassas e inconsistentes e faz-se necessária a realização de novos estudos sobre o tema a fim de determinar a faixa de segurança de ingestão de selênio, além de obter esclarecimentos acerca da influência do mineral sobre a manifestação do diabetes mellitus tipo 2 e das desordens a ele associadas

Effect of zinc supplementation on superoxide dismutase activity in patients with ulcerative rectocolitis / Efecto de la suplementación de zinc sobre la actividad de la enzima superóxido dismutasa (SOD) en pacientes con colitis ulcerosa

Introduction: Ulcerative rectocolitis is characterized by diffuse mucosal inflammation and oxidative stress. Thus, the organism activates the antioxidant defence system in an attempt to reduce the excessive production of reactive oxygen species or neutralize them. Objective: This study evaluated the effect of zinc supplementation on the activity of the enzyme superoxide dismutase (SOD) in patients with ulcerative rectocolitis. Methods: The study included 24 patients, aged between 20 and 59 years and diagnosed with ulcerative rectocolitis, in the remission stage of the disease, who were divided into two groups: experimental - deficient in zinc (n=12) and control - normal or high zinc (n=12). Only the first group underwent supplement intervention, in the form of zinc gluconate (30 mg Zn/day), taken daily in the morning, fasted for 60 days. Plasma and erythrocyte zinc concentrations were determined by flame atomic absorption spectrophotometer. The erythrocyte SOD activity was determined in vitro according to the methodology recommended by the manufacturer Randox. Results and Discussion: Zinc supplementation caused a significant increase in the plasma concentrations of the mineral, and showed a significant reduction in erythrocyte zinc, remaining within normal limits. The SOD activity was high in patients of both the experimental and control groups, with no difference after supplementation. Conclusion: This study demonstrates that zinc supplementation improves the homeostatic condition of the mineral, with no change in SOD activity, as a marker of oxidative stress in patients with ulcerative rectocolitis (AU)

Introducción: La colitis ulcerosa se caracteriza por la inflamación difusa de la mucosa y el estrés oxidativo. De esta forma, el cuerpo activa el sistema de defensa antioxidante en un intento de reducir la producción excesiva de especies reactivas de oxígeno, así como poder neutralizarlos. Objetivo: Este estudio evaluó el efecto de la suplementación de zinc sobre la actividad de la enzima superóxido dismutasa en pacientes con colitis ulcerosa. Métodos: El estudio incluyó 24 pacientes, con edades comprendidas entre 20 y 59 años y con diagnóstico de colitis ulcerosa en fase de remisión de la enfermedad. Los pacientes fueron divididos en dos grupos: experimental - deficiencia de zinc (n = 12) y control - normales o con altos contenido de zinc (n = 12). El grupo experimental se sometió a tratamiento con suplemento de drogas, en forma de gluconato de zinc (30 mg Zn / día), administrada diariamente por la mañana en ayunas durante 60 días. Las concentraciones en plasma y los eritrocitos de zinc se determinaron por espectrofotometría de absorción atómica de llama. La actividad de la superóxido dismutasa (SOD) se determinó por el método de eritrocitos in vitro utilizando el kit de Randox. Resultados y Discusión: La suplementación de zinc causó un aumento significativo en las concentraciones plasmáticas de mineral y mostró una reducción significativa en los eritrocitos, permaneciendo dentro de los límites normales. La actividad de SOD fue mayor en los pacientes de los grupos experimentales y de control, sin diferencias después de la suplementación. Conclusión: El estudio evidenció que la administración de suplementos de zinc mejora la condición homeostática del mineral, sin ningún cambio en la actividad de SOD, como un marcador de estrés oxidativo en pacientes con colitis ulcerosa (AU)

Influence of magnesium on biochemical parameters of iron and oxidative stress in patients with type 2 diabetes / Influencia de magnesio en la bioquímica del hierro y el estrés oxidativo en pacientes con diabetes tipo 2

Introduction: Studies have shown that oxidative stress, found in patients with type 2 diabetes, may be due to changes in the metabolism of minerals, such as magnesium and iron. Data related to compartmentalization of these minerals in diabetes are scarce and controversial. Objective: This study assessed the influence of magnesium on biochemical parameters of iron and oxidative stress in patients with type 2 diabetes. Methods: A case-control study in male and female subjects aged 27-59 years, divided into two groups: type 2 diabetes (n=40) and control (n=48). Intake of magnesium and iron was assessed by three-day food record. Plasma, erythrocyte and urinary levels of magnesium, serum iron, ferritin, total iron binding capacity, fasting glucose, glycated hemoglobin, insulin, creatinine clearance and plasma thiobarbituric acid reactive substances (TBARS) were analyzed. Results and Discussion: Magnesium intake and plasma magnesium were lower in diabetic subjects. There was low urinary magnesium excretion, with no difference between groups. Although normal, the diabetic group had lower serum iron and ferritin concentrations compared to control subjects. Plasma TBARS in diabetic patients was higher than control while creatinine clearance was lower. An inverse correlation between erythrocyte magnesium and serum iron and ferritin was observed in the diabetes group. Conclusions: Diabetes induced hypomagnesemia and this, associated with chronic hyperglycemia, may have enhanced oxidative stress. Erythrocyte magnesium may have contributed to prevent iron overload and worsening of oxidative stress and hyperglycemic status (AU)

Introducción: Los estudios han demostrado que el estrés oxidativo, que se encuentra en pacientes con diabetes tipo 2, puede ser debido a cambios en el metabolismo de los minerales, como el magnesio y el hierro. Los datos relacionados con la compartimentación de estos minerales en la diabetes son pocos y cuestionables. Objetivos: Evaluar la influencia del magnesio sobre parámetros bioquímicos de hierro y el estrés oxidativo en pacientes con diabetes tipo 2. Métodos: Estudio caso-control en los sujetos masculinos y femeninos de edad 27 a 59 años, divididos en dos grupos: la diabetes tipo 2 (n = 40) y control (n = 48). La ingesta de magnesio y hierro se evaluó por tres días registro de alimentos. Plasma, eritrocitos y los niveles urinarios de magnesio, hierro sérico, ferritina, capacidad total de fijación del hierro, glucosa en ayunas, hemoglobina glucosilada, la insulina, el aclaramiento de creatinina y el plasma se analizaron tiobarbitúrico sustancias reactivas al ácido (TBARS). Resultados y Discusión: La ingesta de magnesio y el magnesio en plasma fueron más bajos en los pacientes diabéticos. Hubo baja excreción urinaria de magnesio, sin diferencias entre los grupos. Aunque lo normal, el grupo de diabéticos tenían concentraciones de hierro y ferritina sérica inferiores en comparación con los sujetos control. TBARS plasmáticos en los pacientes diabéticos fue mayor que en el control, mientras que la depuración de creatinina fue menor. Se observó una correlación inversa entre el magnesio y el hierro en suero de los eritrocitos y la ferritina en el grupo de diabetes Conclusiones: Diabetes hipomagnesemia inducida y esto, asociado a la hiperglucemia crónica, pueden haber mejorado el estrés oxidativo. Magnesio eritrocitaria puede haber contribuido a evitar la sobrecarga de hierro y el empeoramiento de estrés oxidativo y el estado de hiperglucemia (AU)