Effects of Sodium Selenate Treatment on Altered Responses of Left and Right Atria from Streptozotocin-Induced Diabetic Rats

Supplementation of Micronutrient Selenium in Metabolic Diseases: Its Role as an Antioxidant

Selenium is an essential mineral naturally found in soil, water, and some of the food. As an antioxidant, it is one of the necessary trace elements in human body and has been suggested as a dietary supplement for health benefit. Although the human body only needs a trace amount of selenium every day, plenty of recent studies have revealed that selenium is indispensable for maintaining normal functions of metabolism. In this study, we reviewed the antioxidant role of nutritional supplementation of selenium in the management of major chronic metabolic disorders, including hyperlipidaemia, hyperglycaemia, and hyperphenylalaninemia. Clinical significance of selenium deficiency in chronic metabolic diseases was elaborated, while clinical and experimental observations of dietary supplementation of selenium in treating chronic metabolic diseases, such as diabetes, arteriosclerosis, and phenylketonuria, were summarized. Toxicity and recommended dose of selenium were discussed. The mechanism of action was also proposed via inspecting the interaction of molecular networks and predicting target protein such as xanthine dehydrogenase in various diseases. Future direction in studying the role of selenium in metabolic disorders was also highlighted. In conclusion, highlighting the beneficial role of selenium in this review would advance our knowledge of the dietary management of chronic metabolic diseases.

Alteration of purinergic neurotransmission in isolated atria of streptozotocin-induced diabetic rats

Cardiac dysfunctions are described in diabetes. However, the role of purinergic neurotransmission in diabetes-related cardiovascular diseases is unknown. The purpose of this study was to evaluate the purinergic neurotransmission in isolated atria from streptozotocin-induced diabetic rats. The animals were grouped as control and diabetic with 30 days (D30) and 60 days (D60) after streptozotocin-induced diabetes. The isolated left and right atria were used in functional experiments. The effects of adenosine triphosphate, uridine diphosphate, and adenosine were evaluated on atrial inotropism and chronotropism. The antagonists 8-cyclopentyl-1,3-dipropylxanthine and pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate were also used, as blockers of P1 and P2 receptors, respectively. A negative inotropic effect followed by a positive inotropic effect was induced by adenosine triphosphate in isolated atria. This negative inotropic effect was decreased by 25% in left atria of D30. Additionally, the apparent affinity for adenosine was diminished in left atria of D30, suggesting changes in P1 receptor function. No changes were found in the right atria of D30 stimulated by adenosine. The left atria and right atria stimulated by uridine diphosphate showed an increased inotropic effect of 92% and 17%, respectively. No changes were observed in left and right atria of D30 stimulated by uridine diphosphate. Our data showed the involvement of purinergic neurotransmission in diabetes-related cardiovascular changes.

Selenium, the thyroid, and the endocrine system

Recent identification of new selenocysteine-containing proteins has revealed relationships between the two trace elements selenium (Se) and iodine and the hormone network. Several selenoproteins participate in the protection of thyrocytes from damage by H(2)O(2) produced for thyroid hormone biosynthesis. Iodothyronine deiodinases are selenoproteins contributing to systemic or local thyroid hormone homeostasis. The Se content in endocrine tissues (thyroid, adrenals, pituitary, testes, ovary) is higher than in many other organs. Nutritional Se depletion results in retention, whereas Se repletion is followed by a rapid accumulation of Se in endocrine tissues, reproductive organs, and the brain. Selenoproteins such as thioredoxin reductases constitute the link between the Se metabolism and the regulation of transcription by redox sensitive ligand-modulated nuclear hormone receptors. Hormones and growth factors regulate the expression of selenoproteins and, conversely, Se supply modulates hormone actions. Selenoproteins are involved in bone metabolism as well as functions of the endocrine pancreas and adrenal glands. Furthermore, spermatogenesis depends on adequate Se supply, whereas Se excess may impair ovarian function. Comparative analysis of the genomes of several life forms reveals that higher mammals contain a limited number of identical genes encoding newly detected selenocysteine-containing proteins.