Alterations in adiponectin concentration in hyper- and hypothyroid patients; possible underlying mechanisms and role of metformin treatment in experimental animals
N. Ramadan, H. Shawky, N. Ghanem & M. Gamal
Recent reports on the interplay between adiponectin, thyroid hormones and metformin have given conflicting results. Our study aimed to investigate adiponectin concentration in thyroid disorders and to assess the possibility of involvement of adiponectin in the regulation of thyroid hormone production, also to clarify the role of pituitary-thyroid axis in the modulation of adiponectin production and to assess the interplay between metformin treatment, thyroid function and adiponectin. The study was designed on 2 modules; In the human 30 study females were included in 3 groups; control, hyperthyroid and hypothyroid. Body mass index (BMI), serum adiponectin, thyroid profile, total cholesterol (TC), high density lipoprotein(HDL) and HOMA-IR were measured. In the animal study, female albino rats divided into control, experimentally-induced hyperthyroid, experimentally-induced hypothyroid, hyperthyroid+metformin, hypothyroid + metformin groups. gC1q gene expression (in thyroid tissue), adiponectin, TSHr, PPARγ in adipose tissue were measured. Results: increased serum adiponectin, decreased BMI, unchanged HOMA-IR or lipid profile in hyperthyroid patients. Decreased serum adiponectin and HDL, increased TC and HOMA-IR in hypothyroid patients. increased adiponectin expression in hyperthyroidism rats and its decrease in hypothyroidism without observed weight changes with unchanged TSHr expression in different thyroid states. In hypothyroidism decreased PPARγ expression which was improved by metformin, which also improved thyroid function and adiponcectin expression. Decreased gC1q expression in thyroid disorders and its increase by metformin. Conclusion: increased adiponectin concentration and expression in hyperthyroidism and their decrease in hypothyroidism. These observed changes in adiponectin could contribute to changes in HOMA-IR and lipid profile detected hyper and hypothyroidism. Adipose tissue TSH receptors are not involved in the modulation of adiponectin production. In case of hypothyroidism, there is a link between decreased adiponectin secretion and expression, decreased PPARγ receptors and dyslipidemia. Metformin improved thyroid function in hypothyroidism and has an antiapoptotic effect in both thyroid disorders.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.