Relationship of thyroid function with obesity and type 2 diabetes in euthyroid Tunisian subjects.

OBJECTIVES: Although a relationship between obesity and metabolic consequences with thyroid function has been reported, the underlying pathogenesis is not completely known. In the current study, we evaluated the thyroid function in obese and/or diabetic patients compared to healthy normal weight peers, exploring the possible association between components of metabolic syndrome and thyroid function parameters. METHODS: We recruited 108 subjects (56 male and 52 female). In all subjects, thyroid stimulating hormone (TSH), free thyroxine (FT4), fasting plasma levels of insulin and glucose, homeostasis model assessment for insulin resistance, and obesity parameters were assessed. RESULTS: We found that circulating levels of TSH and FT4 were significantly increased in overweight and obese subjects. However, the data do not reveal any change of these hormones in diabetics. Multivariate linear regression analysis showed that TSH was directly associated with both obesity and insulin resistance parameters (p < 0.05). FT4 was negatively associated only with obesity parameters (p < 0.05). CONCLUSIONS: Our data strongly support that the changes of thyroid hormones may be influenced by adiposity and its metabolic consequences, such as insulin resistance. This relationship can be explained by a cross talk between adipose tissue release and thyroid function. Nevertheless, metformin treatment seems to affect thyroid function in diabetic patients by maintaining plasma thyrotropin levels to subnormal levels.

Human subcutaneous adipose tissue Glut 4 mRNA expression in obesity and type 2 diabetes.

Cellular resistance to insulin caused by reduced glucose transport and metabolism is a primary defect leading to the development of metabolic disease. While the etiology of insulin resistance is multifactorial, reduced insulin action is associated with impaired activity of the glucose transporter GLUT4 in insulin-sensitive tissues. Yet, the role of adipose tissue GLUT4 deregulation in the pathogenesis of insulin resistance, obesity, and diabetes is still unclear. In this study, we assessed the relative GLUT4 level in human subcutaneous adipose tissue from obese, diabetic, and diabetic obese versus control subjects, using a real-time PCR method. GLUT4 mRNA levels were considerably decreased among type 2 diabetic patients compared with those of the controls (P < 0.01), whereas no such difference was found between obese and normal-weight controls. Multiple linear regressions analysis in both diabetic non-obese and diabetic obese groups showed a negative correlation between GLUT4 mRNA expression and both markers of obesity or insulin resistance (P < 0.01). However, in obese group, GLUT4 was inversely associated only with HOMA-IR (P < 0.01). Our findings showed that adipose GLUT4 gene expression changes were more related to insulin resistance and type 2 diabetes rather than to obesity.