James J. Schultz

A thyroid hormone receptor α gene mutation (P398H) Is associated with visceral adiposity and impaired catecholamine-stimulated lipolysis in mice

Thyroid hormone has profound effects on metabolic homeostasis, regulating both lipogenesis and lipolysis, primarily by modulating adrenergic activity. We generated mice with a point mutation in the thyroid hormone receptor α (TRα) gene producing a dominant-negative TRα mutant receptor with a proline to histidine substitution (P398H). The heterozygous P398H mutant mice had a 3.4-fold (p < 0.02) increase in serum thyrotropin (TSH) levels. Serum triiodothyronine (T3) and thyroxine (T4) concentrations were slightly elevated compared with wild-type mice. The P398H mice had a 4.4-fold increase in body fat (as a fraction of total body weight) (p < 0.001) and a 5-fold increase in serum leptin levels (p < 0.005) compared with wild-type mice. A 3-fold increase in serum fasting insulin levels (p < 0.002) and a 55% increase in fasting glucose levels (p < 0.01) were observed in P398H compared with wild-type mice. There was a marked reduction in norepinephrine-induced lipolysis, as reflected in reduced glycerol release from white adipose tissue isolated from P398H mice. Heart rate and cold-induced adaptive thermogenesis, mediated by thyroid hormone-catecholamine interaction, were also reduced in P398H mice. In conclusion, the TRα P398H mutation is associated with visceral adiposity and insulin resistance primarily due to a marked reduction in catecholamine-stimulated lipolysis. The observed phenotype in the TRα P398H mouse is likely due to interference with TRα action as well as influence on other metabolic signaling pathways. The physiologic significance of these findings will ultimately depend on understanding the full range of actions of this mutation.

Expression of Uncoupling Protein 1 in Mouse Brown Adipose Tissue Is Thyroid Hormone Receptor-β Isoform Specific and Required for Adaptive Thermogenesis

Cold-induced adaptive (or nonshivering) thermogenesis in small mammals is produced primarily in brown adipose tissue (BAT). BAT has been identified in humans and becomes more active after cold exposure. Heat production from BAT requires sympathetic nervous system stimulation, T(3), and uncoupling protein 1 (UCP1) expression. Our previous studies with a thyroid hormone receptor-beta (TR beta) isoform-selective agonist demonstrated that after TR beta stimulation alone, adaptive thermogenesis was markedly impaired, although UCP-1 expression in BAT was normal. We used mice with a dominant-negative TR beta PV mutation (frameshift mutation in resistance to thyroid hormone patient PV) to determine the role of TR beta in adaptive thermogenesis and UCP1 expression. Wild-type and PV mutant mice were made hypothyroid and replaced with T(3) (7 ng/g x d) for 10 d to produce similar serum thyroid hormone concentration in the wild-type and mutant mice. The thermogenic response of interscapular BAT, as determined by heat production during iv infusions of norepinephrine, was reduced in PV beta heterozygous and homozygous mutant mice. The level of UCP1, the key thermogenic protein in BAT, was progressively reduced in PV beta(+/-) and PV beta(-/-) mutant mice. Brown adipocytes isolated from PV mutant mice had some reduction in cAMP and glycerol production in response to adrenergic stimulation. Defective adaptive thermogenesis in TR beta PV mutant mice is due to reduced UCP1 expression and reduced adrenergic responsiveness. TR beta mediates T(3) regulation of UCP1 in BAT and is required for adaptive thermogenesis.

Systemic Retinoic Acid Treatment Induces Sodium/Iodide Symporter Expression and Radioiodide Uptake in Mouse Breast Cancer Models

Lactating breast tissue and some breast cancers express the sodium/iodide symporter (NIS) and concentrate iodide. We recently demonstrated that all-trans retinoic acid (tRA) induces both NIS gene expression and iodide accumulation in vitro in well-differentiated human breast cancer cells (MCF-7). In the present study, we investigated the in vivo efficacy and specificity of tRA-stimulated iodide accumulation in mouse breast cancer models. Immunodeficient mice with MCF-7 xenograft tumors were treated with systemic tRA for 5 days. Iodide accumulation in the xenograft tumors was markedly increased, ∼15-fold greater than levels without treatment, and the effects were tRA dose dependent. Iodide accumulation in other organs was not significantly influenced by tRA treatment. Significant induction of NIS mRNA and protein in the xenograft tumors was observed after tRA treatment. Iodide accumulation and NIS mRNA expression were also selectively induced in breast cancer tissues in transgenic mice expressing the oncogene, polyoma virus middle T antigen. These data demonstrate selective induction of functional NIS in breast cancer by tRA. Treatment with short-term systemic retinoic acid, followed by radioiodide administration, is a potential tool in the diagnosis and treatment of some differentiated breast cancer.

Expression of the protooncogene bcl-2 in Alzheimer's disease brain

To investigate the role of the apopotosis-related protooncogene bcl-2 in Alzheimers disease (AD), we compared levels of its protein product, designated Bcl-2, in AD and nondemented (ND) age-matched control neocortical samples. The 26 kD Bcl-2 protein is increased in expression by more than three-fold in AD compared to ND samples as detected by immunoblots. Immunohistochemical analyses give similar results. In AD patients Bcl-2 immunoreactivity is dense and profuse and appears to occur on reactive astrocytes, whereas Bcl-2 immunoreactivity of astrocytes in ND patients is light and sparse. Staining of both gray and white matter is observed but is most prominent in the latter. Increased expression of Bcl-2 by astrocytes may partially underlie their resistance to loss in AD. By contrast, neuronal Bcl-2 immunoreactivity is more sparse and equivocal, perhaps reflecting the vulnerability of this cell type to apoptotic mechanisms in AD. High levels of Bcl-2 in glial cells may aid in cell survival of reactive astrocytes resulting in either beneficial or deleterious effects on neuronal viability.

Thyroid hormone receptor isoform-specific modification by small ubiquitin-like modifier (SUMO) modulates thyroid hormone-dependent gene regulation.

Background: Thyroid hormone receptor (TR) isoforms α and β have distinct biological and physiological roles in development and in adult tissues. Results: TRα and β are posttranslationally modified by different SUMO isoforms and require specific SUMO E3 ligases. TR sumoylation influences corepressor and coactivator recruitment. Conclusion: TR-SUMO conjugation is important for thyroid hormone action. Significance: Identifying a mechanism contributing to TR isoform-specific action. Thyroid hormone receptor (TR) α and β mediate thyroid hormone action at target tissues. TR isoforms have specific roles in development and in adult tissues. The mechanisms underlying TR isoform-specific action, however, are not well understood. We demonstrate that posttranslational modification of TR by conjugation of small SUMO to TRα and TRβ plays an important role in triiodothyronine (T3) action and TR isoform specificity. TRα was sumoylated at lysines 283 and 389, and TRβ at lysines 50, 146, and 443. Sumoylation of TRβ was ligand-dependent, and sumoylation of TRα was ligand-independent. TRα-SUMO conjugation utilized the E3 ligase PIASxβ and TRβ-SUMO conjugation utilized predominantly PIAS1. SUMO1 and SUMO3 conjugation to TR was important for T3-dependent gene regulation, as demonstrated in transient transfection assay and studies of endogenous gene regulation. The functional role of SUMO1 and SUMO3 in T3 induction in transient expression assays was closely matched to the pattern of TR and cofactor recruitment to thyroid hormone response elements (TREs) as determined by ChIP assays. SUMO1 was required for the T3-induced recruitment of the co-activator CREB-binding protein (CBP) and release of nuclear receptor co-repressor (NCoR) on a TRE but had no significant effect on TR DNA binding. SUMO1 was required for T3-mediated recruitment of NCoR and release of CBP from the TSHβ-negative TRE. SUMO3 was required for T3-stimulated TR binding to the TSHβ-negative TRE and recruitment of NCoR. These findings demonstrate that conjugation of SUMO to TR has a TR-isoform preference and is important for T3-dependent gene induction and repression.

Effects of ZC plus hormone treatment on a transgenic mouse model of Alzheimer's disease

Background: Alzheimer’s Disease (AD) is the sixth leading cause of death in the United States and comprises about 70% of all dementia cases. Although there is no known cause for AD, memory loss has been linked to amyloid beta (Aß) deposition in the AD brain. AD mouse models have been generated to express this Aß pathology, and are used to study changes in cognitive behavior. In the present study, our group has treated an AD mouse model (R1.40) with a novel drug, zinc plus cyclo(his-pro) (ZC) in conjunction with hormone treatment to test their effects on biomarker levels and cognitive behavior.Methods:Nine to twelve month old huAPP-YAC transgenic mice (R1.40 strain) were treated for six months with 10 ml/L Zn plus 1.9 mg/L cyclo(his-pro) (ZC) in water ad libitum and/or treated with subcutaneous hormone pellets. Non-treated transgenic animals were sham operated and given access to non-treated water. Mice were then tested on a Barnes Maze and analyzed for learning and working memory over a 6 month period of time. At the end of testing, brains were harvested and analyzed by ELISA and for enzyme activity (IDE). Results: Analyses of experimental groups show that the novel formulation ZC and hormone treatment alters learning behavior and AD specific biomarker expression in the R1.40 transgenic mouse model of AD. The animals treated with hormone and with ZC found the target hole of the Barnes maze in a shorter amount of time compared to the untreated, transgenic controls. Hormone and ZC treated animals also had significantly higher IDE enzyme activity compared to the non-treated transgenic controls, suggesting a potential to reduce AD specific pathology.Conclusions:This study shows that the novel drug, ZC in conjunction with hormone treatment, may be beneficial to patients who are in the earlier stages of Alzheimer’s disease.

Effects of zinc plus cyclo(his-pro) on pathology, learning and memory in a transgenic mouse model of Alzheimer's disease

meeting annual recruitment goals. There was no correlation between presence of recruitment staff and 1) preferred method of recruitment or 2) a center’s ability to meet recruitment goals. Furthermore, although all ADRCs have a website, few (35%) see it as an active tool for recruitment. Conclusions: These data suggest that successful recruitment is a result of a comprehensive recruitment plan. The successful ADRC 1) promotes study participation while conducting community educational events, and 2) partners with outside physicians. Those interviewed agreed that without the support of lay community and physicians, recruitment goals are not met. The successful ADRC has built their program using educational seminars, free screenings, and a willingness to serve to the community.