The thyroid hormone mediated effects of insulin on serum leptin levels of diabetic rats

Effects of hypothyroidism on the female pancreas involve the regulation of estrogen receptors

This study aimed to investigate the impact of short-time hypothyroidism on the expression of aromatase, estrogen receptors (ERα, β), and GPR30 in the pancreas of female rabbits. The formation of new islets and the expression of insulin, GLUT4, and lactate dehydrogenase (LDH) were also analyzed. This purpose is based on actions that thyroid hormones and estrogens have on β-cells differentiation, acinar cell function, and insulin secretion. Twelve Chinchilla-breed adult virgin female rabbits were divided into control (n = 6) and hypothyroid (n = 6; methimazole 10 mg/kg for 30 days) groups. In the complete pancreas, expressions of aromatase and estrogen receptors, as well as proinsulin, GLUT4, and LDH were determined by western blot. Characteristics of islets were measured in slices of the pancreas with immunohistochemistry for insulin. Islet and acinar cells express aromatase, ERα, ERβ, and GPR30. Hypothyroidism increased the expression of ERα and diminished that for aromatase, ERβ, and GPR30 in the pancreas. It also promoted a high number of extra small islets (new islets) and increased the expression of proinsulin and GLUT4 in the pancreas. Our results show that actions of thyroid hormones and estrogens on β-cells neogenesis, acinar cell function, and synthesis and secretion of insulin are linked. Thus, the effects of hypothyroidism on the pancreas could include summatory actions of thyroid hormones plus estrogens. Our findings indicate the importance of monitoring estrogen levels and actions on the pancreas of hypothyroid women, particularly when serum estrogen concentrations are affected such as menopausal, pregnant, and those with contraceptive use.

Hypothyroidism Reduces the Size of Ovarian Follicles and Promotes Hypertrophy of Periovarian Fat with Infiltration of Macrophages in Adult Rabbits

Ovarian failure is related to dyslipidemias and inflammation, as well as to hypertrophy and dysfunction of the visceral adipose tissue (VAT). Although hypothyroidism has been associated with obesity, dyslipidemias, and inflammation in humans and animals, its influence on the characteristics of ovarian follicles in adulthood is scarcely known. Control and hypothyroid rabbits were used to analyze the ovarian follicles, expression of aromatase in the ovary, serum concentration of lipids, leptin, and uric acid, size of adipocytes, and infiltration of macrophages in the periovarian VAT. Hypothyroidism did not affect the percentage of functional or atretic follicles. However, it reduced the size of primary, secondary, and tertiary follicles considered as large and the expression of aromatase in the ovary. This effect was associated with high serum concentrations of total cholesterol and low-density lipoprotein cholesterol (LDL-C). In addition, hypothyroidism induced hypertrophy of adipocytes and a major infiltration of CD68+ macrophages into the periovarian VAT. Our results suggest that the reduced size of ovarian follicles promoted by hypothyroidism could be associated with dyslipidemias, hypertrophy, and inflammation of the periovarian VAT. Present findings may be useful to understand the influence of hypothyroidism in the ovary function in adulthood.

Effect of Diabetes Mellitus and Its Control on Myocardial Contractile Function in Rats

AIM: This work was done to study the effect of both types of diabetes mellitus (DM) on myocardial contractility in rats. Also, we investigated the role of treatment of DM with insulin and rosiglitazone (used as treatment for type 1 and type 2 DM respectively) in improvement of myocardial dysfunction in diabetic rats.METHODS: The study included 50 male Wistar albino rats, divided into 5 groups: control (group I), streptozotocin induced type 1 DM (group II), fructose induced type 2 DM (group III), insulin treated type 1 diabetic rats (group IV) and rosiglitazone treated type 2 diabetic rats (group V). At the end of the study, retro-orbital blood samples were withdrawn and blood glucose, plasma triglyceride (TG), total cholesterol (TC) and thyroid hormones levels were measured. Rats were then anesthetized and their hearts were excised and connected to Langendorff apparatus to perform mechanical cardiac performance tests including heart rate (HR), left ventricular developed pressure (LVDP) and maximum rate of pressure rise (+dp/dt).RESULTS: Data of the study showed that relative to control group, there was significant increase in blood glucose, plasma TG and TC levels while, thyroid hormones and myocardial performance parameters showed significant decrease in both type 1 and type 2 diabetic rats. Treatment of type 1 diabetic rats with insulin and type 2 with rosiglitazone resulted in significant decrease in blood glucose, plasma TG and TC levels associated with significant improvement in thyroid hormones and myocardial performance parameters. The results also showed that insulin treatment of type 1 was more effective in ameliorating all parameters than treatment of type 2 by rosiglitazone.CONCLUSION: We concluded that the induction of both types of diabetes resulted in decreased myocardial performance parameters. The  treatment of type 1 and type 2 diabetes by insulin and oral rosiglitazone respectively improved to a great extent the altered metabolism and  mechanical myocardial parameters, with more improving effect of  insulin in type 1 than rosiglitazone in type 2 DM.

S-allylcysteine Improves Streptozotocin-Induced Alterations of Blood Glucose, Liver Cytochrome P450 2E1, Plasma Antioxidant System, and Adipocytes Hormones in Diabetic Rats

BACKGROUND

S-allylcysteine, a garlic derivative, could have a protective effect against pathogenesis of diabetes mellitus.

OBJECTIVES

Sustained free radical generation and oxidative damage to system leads to the final conclusion phase of diabetes and also it coexists with a constant diminution in the antioxidant status.The present study aims to evaluate the therapeutic effects of S-allylcysteine (SAC) against adipocytes hormones and antioxidant defense systems of plasma and erythrocytes of treptozotocin (STZ) induced diabetes in rats.

MATERIALS AND METHODS

Diabetic rats were administered SAC (150 mg/kg b.w) orally for 45 days. At 46(th) day, the rats were anesthetized, and blood and liver sample were collected for analyzing glucose, plasma insulin, CYP2E1 activity, Thiobarbituric acid reactive substances (TBARS), hydroperoxide, enzymatic and nonenzymatic antioxidants, reduced glutathione (GSH), ceruloplasmin, plasma leptin, and adiponectin.

RESULTS

The levels of glucose, CYP2E1 activity, Thiobarbituric acid reactive substances (TBARS), hydroperoxide, and ceruloplasmin were increased significantly; whereas, the levels of plasma insulin, reduced glutathione, enzymatic and nonenzymatic antioxidants, leptin and adiponectin were decreased in experimental diabetic rats. Administration of SAC to diabetic rats led to a decrease in the levels of glucose, CYP2E1 activity, TBARS, and ceruloplasmin. In addition, the levels of plasma insulin, enzymatic and nonenzymatic antioxidants leptin and adiponectin were increased in SAC treated diabetic rats. Gliclazide, a standard drug for diabetes, was used for the comparative purpose.

CONCLUSIONS

The results of the present investigation suggest that SAC could be used as a food supplement in the treatment of diabetes characterized by provoked antioxidant status, altered blood glucose, and hormones level.

Visfatin, Leptin, and TNF-α: Interrelated Adipokines in Insulin-Resistant Clinical and Subclinical Hypothyroidism

PURPOSE

This study is designed to evaluate the interrelationships among adipokines-visfatin, leptin, and tumor necrosis factor-α (TNF-α)- and insulin resistance (IR) in overt (n = 40) and subclinic hypothyroid (n = 25) patients and compare our findings with sex and body mass index-matched healthy controls (n = 25).

METHODS

Serum visfatin, leptin, and TNF-α levels were measured by enzyme-linked immunosorbent assay and C-reactive protein by immunoturbidimetry. Thyroid status (TSH, FT3, FT4) and lipid status (triglyceride, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, total cholesterol) parameters were measured. IR was determined by homeostatic model assessment (HOMA-IR) and McAuley (McA) indices.

RESULTS

HOMA-IR (p < 0.05) and McA indices (p < 0.01) revealed the presence of IR in overt hypothyroid patients. C-reactive protein, TNF-α, leptin, and visfatin levels were significantly higher (p < 0.01, p < 0.01, p < 0.001, and p < 0.001) in overt hypothyroid patients than euthyroid control group. Subclinic hypothyroid patients were observed to have significantly higher leptin and visfatin levels (p < 0.05) than euthyroid control group. In overt hypothyroid patients, we found plasma visfatin to be significantly positively correlated with HOMA-IR index (r = 0.336, p < 0.05) and body mass index (r = 0.445, p < 0.01) and negatively correlated with McA index (r = -0.574, p < 0.01).

CONCLUSION

This study demonstrates the presence of IR in overt hypothyroid patients by HOMA and McA indices. Increased levels of visfatin, leptin, and TNF-α in overt and subclinic hypothyroid patients and the correlations among these adipokines highlighten their crucial role in the IR-associated disorders.

Impacts of the coexistence of diabetes and hypothyroidism on body weight gain, leptin and various metabolic aspects in albino rats

The present study was conducted to assess the interrelationship and the influence of the coexistence of diabetes and hypothyroidism on thyroid hormone levels, insulin levels and biochemical variables related to carbohydrate, lipid and protein metabolism in addition to thyroid gland and Islets of Langerhans histological changes and antioxidant defense system. Diabetes mellitus was induced by intraperitoneal injection of streptozotocin to fasting albino rats at dose level of 45 mg/kg b. w. Hypothyroidism in diabetic and normal rats was induced by adding methimazole in drinking water (0.02% w/v) for 4 weeks. The obtained results revealed that hypothyroidism interacts with diabetes in a way that prevents the progress of the hyperglycemic state. This may be due to the increase in the insulin secretory response in diabetic hypothyroid than diabetic rats. Serum T3 level decreased in order in diabetic (-26.63%), hypothyroid (-61.89%) and diabetic hypothyroid (-65.69%) rats while T4 level was increased in diabetic rats and decreased in hypothyroid ones. The decrease in T3 level in diabetic animals in spite of T4 increase may be attributed to the decrease in conversion of T4 to T3 as a result of hepatic 5'-DI decreased activity. Liver glycogen content was three-fold decreased in diabetic rats and was not significantly altered in both hypothyroid and diabetic hypothyroid rats. The serum leptin level and body weight gain were decreased in diabetic and diabetic hypothyroid rats; the leptin level was more deteriorated in diabetic hypothyroid rats while body weight gain was more affected in diabetic rats. Serum triglycerides level was more increased in diabetic rats than in diabetic hypothyroid ones on one hand, while total lipids, total cholesterol, LDL-cholesterol levels as well as cardiovascular indices were more deteriorated in diabetic hypothyroid rats than diabetic ones on the other hand. Serum total protein and globulin levels were decreased in diabetic rats and were increased in hypothyroid and diabetic hypothyroid rats. Hepatic total thiols and glutathione contents and catalase and peroxidase activity were profoundly decreased in diabetic rats while they (except glutathione) were increased in hypothyroid and diabetic hypothyroid rats. In conclusion, the hypothyroidism may have a counteracting effect on the hyperglycemic state and the elevated serum T4 level as well as the deteriorated antioxidant defense system found in diabetes mellitus, but both experimentally-induced diseases may synergize in inducing more elevation of serum total lipids, total cholesterol and LDL-cholesterol and more decrease in leptin levels.

Oxidative stress-induced endothelial cell damage in thyroidectomized rat

Patients with hypothyroidism are considered to have an increased risk of developing atherosclerosis. Uncoupling of endothelial nitric oxide synthase from tetrahyrobiopterin, an essential cofactor, leads to the decrease of nitric oxide production and increase in reactive oxygen species. Both mechanisms contribute to atherosclerotic vascular disease. The aim of this study was to investigate whether hypothyroidism influences the systemic redox-state and the structure of aortic vascular endothelium in thyroidectomized rats. Twenty-eight Sprague-Dawley rats were randomly assigned to two groups; sham thyroidectomy and near-total thyroidectomy. Three weeks after surgery, nitric oxide in plasma, homocysteine, cysteine, glutathione levels and superoxide dismutase activity were measured in serum, and biopterine and creatinine were measured in urine. Aortic endothelium samples were processed for light and transmission electron microscopy. Although superoxide dismutase activity remained constant, urine biopterin levels and serum nitric oxide levels decreased in hypothyroid rats compared to their euthyroid controls. Aortic endothelium showed early features of atherosclerosis, and transmission electron microscopy revealed budding of caveolae in endothelial cells. It is concluded that hypothyroidism might lead to systemic oxidative stress with resultant endothelial dysfunction, and subsequent occurrence of atherosclerosis.

Oxidative DNA damage: the thyroid hormone-mediated effects of insulin on liver tissue

Thyroid hormone affects glucose homeostasis with its actions between the skeletal muscle and liver and the altered oxidative and non-oxidative glucose metabolism. In our study three chemicals are considered biomarkers associated with oxidative stress for protein modifications were measured; 8-hydroxy-2-deoxyyguanosine (8-OHdG), a major lesion that can be generated by reactive oxygen species for DNA damage, protein carbonyl content (PCO), products of protein oxidation and advanced oxidation protein products (AOPPs) a dithyrosine containing cross-linked protein products. The purpose of the recent study was to determine the effects of insulin and T4 or their combination in diabetic, thyroidectomized, or diabetic-thyroidectomized rats and possible relations with oxidative DNA and protein damages. For this purpose, rats were assigned to eight groups: Group 1; control, Group 2; diabetes, Group 3; diabetes+insulin, Group 4; surgically thyroidectomized control, Group 5; thyroidectomized+diabetes, Group 6; thyroidectomized+diabetes+insulin, Group 7; thyroidectomized+diabetes+insulin+thyroid hormone, levothyroxin sodium, 2.5 μg/kg and Group 8; thyroidectomized+diabetes+insulin+thyroid hormone, levothyroxin sodium, 5.0 μg/kg for 5 weeks. After the genomic DNA of liver tissues was extracted, the ratio of 8-OHdG to deoxyguanosine and liver tissue protein oxidation markers was determined. The main findings of our recent study were the increased 8-OHdG levels during the diabetes, hypothyroidism, and hypothyroidism with diabetes, which can be regulated in different percentages with the treatment of 2.5 and 5.0 μg/kg doses of thyroid hormone and the altered protein carbonyl and AOPP levels of liver tissue. Consequently, it was observed that the DNA and protein damage induced by oxidative stress in diabetes could be regulated by dose-dependent thyroid hormone-mediated effects to insulin treatment.