The Δ337T mutation on the TRβ causes alterations in growth, adiposity, and hepatic glucose homeostasis in mice
| Autor: | Tania M. Ortiga-Carvalho, Aline Cordeiro, Fredric E. Wondisford, Patricia Cristina Lisboa, Diana Aragão Santiago, Letícia Aragão Santiago, Larissa C. Faustino, Carmen C. Pazos-Moura |
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| Rok vydání: | 2011 |
| Předmět: |
Leptin
Male medicine.medical_specialty Endocrinology Diabetes and Metabolism medicine.medical_treatment Growth Biology Eating Mice chemistry.chemical_compound Endocrinology Internal medicine medicine Animals Homeostasis Insulin Adiposity Thyroid hormone receptor Glycogen Wild type Thyroid Hormone Receptors beta Hypoglycemia Mice Mutant Strains Mice Inbred C57BL Glucose Liver Gluconeogenesis chemistry Models Animal Mutation Phosphoenolpyruvate carboxykinase Hormone |
| Zdroj: | Journal of Endocrinology. 211:39-46 |
| ISSN: | 1479-6805 0022-0795 |
| Popis: | Mice bearing the genomic mutation Δ337T on the thyroid hormone receptor β (TRβ) gene present the classical signs of resistance to thyroid hormone (TH), with high serum TH and TSH. This mutant TR is unable to bind TH, remains constitutively bound to co-repressors, and has a dominant negative effect on normal TRs. In this study, we show that homozygous (TRβΔ337T) mice for this mutation have reduced body weight, length, and body fat content, despite augmented relative food intake and relative increase in serum leptin. TRβΔ337T mice exhibited normal glycemia and were more tolerant to an i.p. glucose load accompanied by reduced insulin secretion. Higher insulin sensitivity was observed after single insulin injection, when the TRβΔ337T mice developed a profound hypoglycemia. Impaired hepatic glucose production was confirmed by the reduction in glucose generation after pyruvate administration. In addition, hepatic glycogen content was lower in homozygous TRβΔ337T mice than in wild type. Collectively, the data suggest that TRβΔ337T mice have deficient hepatic glucose production, by reduced gluconeogenesis and lower glycogen deposits. Analysis of liver gluconeogenic gene expression showed a reduction in the mRNA of phosphoenolpyruvate carboxykinase, a rate-limiting enzyme, and of peroxisome proliferator-activated receptor-γ coactivator 1α, a key transcriptional factor essential to gluconeogenesis. Reduction in both gene expressions is consistent with resistance to TH action via TRβ, reproducing a hypothyroid phenotype. In conclusion, mice carrying the Δ337T-dominant negative mutation on the TRβ are leaner, exhibit impaired hepatic glucose production, and are more sensitive to hypoglycemic effects of insulin. |
| Databáze: | OpenAIRE |
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