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Interference of a Mutant Thyroid Hormone Receptor 1 with Hepatic Glucose Metabolism

Karolinska Institutet (M.V., K.N., B.V., J.M.), Department of Cell and Molecular Biology, 17177 Stockholm, Sweden; Institut de Génomique Fonctionnelle de Lyon (K.G., F.F.), Université de Lyon, Université Lyon 1, Centre National de la Recherche Scientifique, Institut National de la Recherche Agonomique, Ecole Normale Supérieure de Lyon, 69007 Lyon, France; and Erasmus Medical Center (T.J.V.), Department of Internal Medicine, 3000 DR Rotterdam, The Netherlands

Address all correspondence and requests for reprints to: Dr. Jens Mittag, Karolinska Institutet, Department of Cell and Molecular Biology, von Eulers väg 3, 17177 Stockholm, Sweden. E-mail: jens.mittag{at}ki.se.

Mice expressing the mutant thyroid hormone receptor TR1R384C, which has a 10-fold reduced affinity to the ligand T₃, exhibit hypermetabolism due to an overactivation of the sympathetic nervous system. To define the consequences in the liver, we analyzed hepatic metabolism and the regulation of liver genes in the mutant mice. Our results showed that hepatic phosphoenolpyruvate-carboxykinase was up-regulated and pyruvate kinase mRNA down-regulated, contrary to what observed after T₃ treatment. In contrast, mice expressing a mutant TR1L400R specifically in the liver did not show a dysregulation of these genes; however, when the TR1L400R was expressed ubiquitously, the hepatic phenotype differed from TR1R384C animals, suggesting that the localization of the mutation plays an important role for its consequences on glucose metabolism. Furthermore, we observed that glycogen stores were completely depleted in TR1R384C animals, despite increased gluconeogenesis and decreased glycolysis. Exposure of the mutant mice to high maternal levels of thyroid hormone during fetal development leads to a normal liver phenotype in the adult. Our results show how genetic and maternal factors interact to determine the metabolic setpoint of the offspring and indicate an important role for maternal thyroid hormone in the susceptibility to metabolic disorders in adulthood.