▼Obesity is associated with several metabolic and endocrine disorders; and changes in plasma concentrations, secretion patterns, and clearance of various hormones are observed in obese patients. In this context, recent research has shown that overweight can influence the function of the thyroid gland, usually leading to increased thyrotropin concentrations and changes in the ratio between the hormones triiodothyronine and thyroxine, though within the normal range. The etiology of these changes is still unclear; how-
Abstract. 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.
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.
Background: Selenium deficiency appears to limit antioxidant defense in obese individuals. This study evaluated the association between adiposity indices, selenium status, and oxidative stress in obese women. Methods: This was a cross-sectional study involving 139 women who were divided into the following two groups: the case group (obese women, n = 63) and the control group (normal-weight women, n = 76). Plasma, erythrocyte, and urinary selenium levels were determined using inductively coupled plasma optical emission spectrometry. Body weight, height, waist circumference, hip circumference and neck circumference were measured. Body mass index, waist/height ratio, conicity index, body fat index, body adiposity index, body circularity index, and visceral adiposity index were calculated. Plasma levels of thiobarbituric acid reactive substances were determined. The erythrocyte glutathione peroxidase activity was determined using an automatic biochemical analyzer and Ransel kit. Results: Obese women had selenium deficiency characterized by reduction in plasma and erythrocyte concentrations (P < .001). The urinary selenium excretion was higher in the case group compared to the control group (P < .001).Adiposity indices values and plasma concentrations of thiobarbituric acid reactive substances were significantly elevated in obese women (P < .001). There was a significant association between adiposity indices and selenium status (P < .001), and between erythrocyte selenium and erythrocyte glutathione peroxidase activity (P < .001). Conclusion:Obese women evaluated in the study have reduced plasma and erythrocyte concentrations of selenium and an increased urinary excretion of selenium. The correlation analysis reveals an association between intra-abdominal fat accumulation and selenium metabolism and oxidative stress.
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