High dose of radioactive iodine per se has no effect on glucose metabolism in thyroidectomized rats

Excess Iodine Consumption Induces Oxidative Stress and Pancreatic Damage Independently of Chemical Form in Male Wistar Rats: Participation of PPAR-γ and C/EBP-β

BACKGROUND

Human beings consume different chemical forms of iodine in their diet. These are transported by different mechanisms in the cell. The forms of iodine can be part of thyroid hormones, bind to lipids, be an antioxidant, or be an oxidant, depending on their chemical form. The excessive consumption of iodine has been associated with pancreatic damage and diabetes mellitus type 2, but the association between disease and the chemical form consumed in the diet is unknown. This research analyzes the effect of excessive iodine consumption as Lugol (molecular iodine/potassium iodide solution) and iodate on parameters of pancreatic function, thyroid and lipid profiles, antioxidant and oxidant status, the expression of IR/Akt/P-Akt/GLUT4, and transcription factors PPAR-γ and CEBP-β.

METHODS

Three groups of Wistar rats were treated with 300 μg/L of iodine in drinking water: (1) control, (2) KIO3, and (3) Lugol.

RESULTS

Lugol and KIO3 consumption increased total iodine levels. Only KIO3 increased TSH levels. Both induced high serum glucose levels and increased oxidative stress and pancreatic alpha-amylase activity. Insulin levels and antioxidant status decreased significantly. PPAR-γ and C/EBP-β mRNA expression increased.

CONCLUSION

The pancreatic damage, hypertriglyceridemia, and oxidative stress were independent of the chemical form of iodine consumed. These effects depended on PPAR-γ, C/EBP-β, GLUT-4, and IR.

The Role of Mineral Deficiencies in Insulin Resistance and Obesity

Minerals are critical for maintaining overall health. These tiny chemical compounds are responsible for enzymatic activation, maintaining healthy teeth and bones, regulating energy metabolism, enhancing immunity, and aiding muscle and brain function. However, mineral deficiency in the form of inadequate or under nourished intake affects millions of people throughout the world, with well-documented adverse health consequences of malnutrition. Conversely, mineral deficiency may also be a risk factor for Insulin Resistance (IR) and obesity. This review focuses on another, more "less discussed" form of malnutrition, namely mineral deficiency and its contribution to metabolic disorders. At the cellular level, minerals maintain not only molecular communication but also trigger several key biochemical pathways. Disturbances in these processes due to mineral insufficiency may gradually lead to metabolic disorders such as insulin resistance, pre-diabetes, and central obesity, which might lead to renal failure, cardiac arrest, hepatic carcinoma, and various neurodegenerative diseases. Here we discuss the burden of disease promoted by mineral deficiencies and the medical, social, and economic consequences. Mineral deficiency-mediated IR and obesity have a considerable negative impact on individual well-being, physical consideration, and economic productivity. We discuss possible molecular mechanisms of mineral deficiency that may lead to IR and obesity and suggest strategies to counter these metabolic disorders. To protect mankind from mineral nutrient deficiencies, the key is to take a variety of foods in reasonable quantities, such as organic and pasture-raised eggs, low fat dairy, and grass-fed and finished meats, insecticide, and pesticide-free vegetables and fruits.

Development of a Rat Model for Evaluating Thyroid-Stimulating Hormone Suppression after Total Thyroidectomy

BACKGROUND

We developed an animal model for evaluating thyroid-stimulating hormone (TSH) suppression therapy after total thyroidectomy in rats.

METHODS

Sixty Wistar rats were randomly divided into 6 groups, including a sham-operated group (SO group), a total thyroidectomy group (TD group), and a L-thyroxine (L-T4) treatment I group (TS-I group), II group (TS-II group), III group (TS-III group), and IV group (TS-IV group) (in which rats were treated with 1.4, 1.6, 1.8, and 2.0 μg/100 g body weight, respectively) after total thyroidectomy.

RESULTS

HE staining in the TD group and all L-T4-treated rats showed that the resected tissue was normal thyroid gland. No residual thyroid tissue was found in neck tissue of the cross-section of the thyroid gland. Serum T3 levels in the TS-II group were not significantly different from those in the SO group, whereas serum T4 levels were slightly higher than those in the SO group, and serum TSH levels were slightly lower.

CONCLUSIONS

Rats subcutaneously injected with L-T4 1.6 μg/100 g body weight for 15 days after total thyroidectomy were suitable as an animal model for TSH suppression therapy.

Altered gene expression of hydrogen sulfide-producing enzymes in the liver and muscles tissues of hyperthyroid rats

Thyroid hormones have a role in the regulation of hydrogen sulfide (H₂ S) biosynthesis. In this study, we determined the effects of hyperthyroidism on H₂ S levels in various tissues and messenger RNA (mRNA) expression of cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST) in the liver and muscles of the rat. Sixteen male Wistar rats were divided into the hyperthyroid and the control groups. Hyperthyroidism was induced by adding l-thyroxine (12 mg/L) to drinking water for a period of 21 days. H₂ S concentrations in serum, liver, aorta, heart, and soleus muscles, as well as mRNA expressions of CBS, CSE, and 3-MST in these tissues were measured at Day 21. Hyperthyroid rats had lower H₂ S levels in the serum compared with controls (14.7 ± 1.4 vs. 25.7 ± 1.6 µmol/L, p < 0.001). Compared with controls, hyperthyroid rats had lower levels of H₂ S in the aorta (89%), heart (80%), and soleus (103%) muscles, but higher levels in the liver (35%). Hyperthyroidism decreased the ratio of CBS/CSE mRNA expression in the liver and the CSE/CBS mRNA expression in the muscles by decreasing CBS levels in liver (34% cf. controls) and CSE levels in the aorta, heart, and soleus muscles (respectively, 51%, 7%, and 52% cf.). In addition, hyperthyroidism decreased the mRNA expression of 3-MST in the liver (51%) and aorta (33%), and increased it in the heart (300%) and soleus muscle (182%). In conclusion, hyperthyroidism increased H₂ S levels in the liver and decreased it in muscles; these effects are at least in part due to increases and decreases in expression of CSE in the liver and muscles, respectively. These data indicate an association between thyroid hormone status and gene expression of the H₂ S-producing enzymes in the rat.

Effect of fetal hypothyroidism on MyomiR network and its target gene expression profiles in heart of offspring rats

Thyroid hormone deficiency during fetal life (fetal hypothyroidism) causes intrauterine growth restriction (IUGR). Fetal hypothyroidism (FH) could attenuate normal cardiac functions in the later life of the offspring rats. The aim of this study was to evaluate the contribution of myomiR network and its target gene expression in cardiac dysfunction in fetal hypothyroid rats. Six Pregnant female rats were divided into two groups: Control consumed tap water, and the hypothyroid group received water containing 0.025% 6-propyl-2-thiouracil during gestation. Hearts from male offspring rats in adulthood (month 3) were tested with Langendorff apparatus for measuring hemodynamic parameters. Expressions of miR-208a, -208b, and -499 and its target genes including thyroid hormone receptor 1 (Thrap1), sex-determining region Y-box 6 (Sox6), and purine-rich element-binding protein β (Purβ) were measured by qPCR. FH rats had lower LVDP (%20), +dp/dt (%26), -dp/dt (%20), and heart rate (%21) than controls. FH rats at month 3 had a higher expression of β-MHC (190%), Myh7b (298%), and lower expression of α-MHC (36%) genes in comparison with controls. FH rats at month 3 had a higher expression of miR-499 (520%) and miR-208b (439%) and had lower expression of miR-208a (74%), Thrap1 (47%), Sox6 (49%), and Purβ (45%) compared with controls. Our results showed that thyroid hormone deficiency during fetal life changes the pattern of gene expression of myomiR network and its target genes in fetal heart, which, in turn, resulted in increased β-MHC expression and associated cardiac dysfunction in adulthood.