Rapid disease progression in a patient with mismatch repair-deficient and cortisol secreting adrenocortical carcinoma treated with pembrolizumab.

CONTEXT: Metastatic adrenocortical carcinoma (ACC) is an aggressive malignancy with a poor prognosis and limited therapeutic options. A subset of ACC is due to Lynch syndrome, an inherited tumor syndrome resulting from germline mutations in mismatch repair (MMR) genes. It has been demonstrated that several cancers characterized by MMR deficiency are sensitive to immune checkpoint inhibitors that target PD-1. Here, we provide the first report of PD-1 blockade with pembrolizumab in a patient with Lynch syndrome and progressive cortisol-secreting metastatic ACC. CASE REPORT: A 58-year-old female with known Lynch syndrome presented with severe Cushing's syndrome and was diagnosed with a cortisol-secreting ACC. Three months following surgical resection and adjuvant mitotane therapy the patient developed metastatic disease and persistent hypercortisolemia. She commenced pembrolizumab, but her second cycle was delayed due to a transient transaminitis. Computed tomography performed after 12 weeks and 2 cycles of pembrolizumab administration revealed significant disease progression and treatment was discontinued. After 7 weeks, the patient became jaundiced and soon died due to fulminant liver failure. CONCLUSION: Treatment of MMR-deficient cortisol-secreting ACC with pembrolizumab may be ineffective due to supraphysiological levels of circulating corticosteroids, which may in turn mask severe drug-induced organ damage.

Molecular spectrum of TSHß subunit gene defects in central hypothyroidism in the UK and Ireland.

OBJECTIVE: Homozygous mutations in the TSH beta subunit gene (TSHB) result in severe, isolated, central congenital hypothyroidism (CCH). This entity evades diagnosis in TSH-based congenital hypothyroidism (CH) screening programmes in the UK and Ireland. Accordingly, genetic diagnosis, enabling ascertainment of affected relatives in families, is critical for prompt diagnosis and treatment of the disorder. DESIGN, PATIENTS AND MEASUREMENTS: Four cases of isolated TSH deficiency from three unrelated families in the UK and Ireland were investigated for mutations or deletions in TSHB. Haplotype analysis, to investigate a founder effect, was undertaken in cases with identical mutations (c.373delT). RESULTS: Two siblings in kindred 1 were homozygous for a previously described TSHB mutation (c.373delT). In kindreds 2 and 3, the affected individuals were compound heterozygous for TSHB c.373delT and either a 5·4-kB TSHB deletion (kindred 2, c.1-4389_417*195delinsCTCA) or a novel TSHB missense mutation (kindred 3, c.2T>C, p.Met1?). Neurodevelopmental retardation, following delayed diagnosis and treatment, was present in 3 cases. In contrast, the younger sibling in kindred 1 developed normally following genetic diagnosis and treatment from birth. CONCLUSIONS: This study, including the identification of a second, novel, TSHB deletion, expands the molecular spectrum of TSHB defects and suggests that allele loss may be a commoner basis for TSH deficiency than previously suspected. Delayed diagnosis and treatment of profound central hypothyroidism in such cases result in neurodevelopmental retardation. Inclusion of thyroxine (T4) plus thyroxine-binding globulin (TBG), or free thyroxine (FT4) in CH screening, together with genetic case ascertainment enabling earlier therapeutic intervention, could prevent such adverse sequelae.

Mild cold effects on hunger, food intake, satiety and skin temperature in humans.

BACKGROUND: Mild cold exposure increases energy expenditure and can influence energy balance, but at the same time it does not increase appetite and energy intake. OBJECTIVE: To quantify dermal insulative cold response, we assessed thermal comfort and skin temperatures changes by infrared thermography. METHODS: We exposed healthy volunteers to either a single episode of environmental mild cold or thermoneutrality. We measured hunger sensation and actual free food intake. After a thermoneutral overnight stay, five males and five females were exposed to either 18°C (mild cold) or 24°C (thermoneutrality) for 2.5 h. Metabolic rate, vital signs, skin temperature, blood biochemistry, cold and hunger scores were measured at baseline and for every 30 min during the temperature intervention. This was followed by an ad libitum meal to obtain the actual desired energy intake after cold exposure. RESULTS: We could replicate the cold-induced increase in REE. But no differences were detected in hunger, food intake, or satiety after mild cold exposure compared with thermoneutrality. After long-term cold exposure, high cold sensation scores were reported, which were negatively correlated with thermogenesis. Skin temperature in the sternal area was tightly correlated with the increase in energy expenditure. CONCLUSIONS: It is concluded that short-term mild cold exposure increases energy expenditure without changes in food intake. Mild cold exposure resulted in significant thermal discomfort, which was negatively correlated with the increase in energy expenditure. Moreover, there is a great between-subject variability in cold response. These data provide further insights on cold exposure as an anti-obesity measure.

A Novel Thyrotropin-Releasing Hormone Receptor Missense Mutation (P81R) in Central Congenital Hypothyroidism.

CONTEXT: Isolated central congenital hypothyroidism (CCH) is rare and evades diagnosis on TSH-based congenital hypothyroidism (CH) screening programs in the United Kingdom. Accordingly, genetic ascertainment facilitates diagnosis and treatment of familial cases. Recognized causes include TSH ß subunit (TSHB) and Ig superfamily member 1 (IGSF1) mutations, with only two previous reports of biallelic, highly disruptive mutations in the TRH receptor (TRHR) gene. CASE DESCRIPTION: A female infant presenting with prolonged neonatal jaundice was found to have isolated CCH, with TSH of 2.2 mU/L (Reference range, 0.4-3.5) and free T4 of 7.9 pmol/L (0.61 ng/dL) (Reference range, 10.7-21.8 pmol/L). Because TSHB or IGSF1 mutations are usually associated with profound or X-linked CCH, TRHR was sequenced, and a homozygous mutation (p.P81R) was identified, substituting arginine for a highly conserved proline residue in transmembrane helix 2. Functional studies demonstrated normal cell membrane expression and localization of the mutant TRHR; however, its ability to bind radio-labelled TRH and signal via Gqα was markedly impaired, likely due to structural distortion of transmembrane helix 2. CONCLUSIONS: Two previously reported biallelic, highly disruptive (nonsense; R17*, in-frame deletion and single amino acid substitution; p.[S115-T117del; A118T]) TRHR mutations have been associated with CCH; however, we describe the first deleterious, missense TRHR defect associated with this phenotype. Importantly, the location of the mutated amino acid (proline 81) highlights the functional importance of the second transmembrane helix in mediating hormone binding and receptor activation. Future identification of other naturally occurring TRHR mutations will likely offer important insights into the molecular basis of ligand binding and activation of TRHR, which are still poorly understood.

An approach to quantifying abnormalities in energy expenditure and lean mass in metabolic disease.

BACKGROUND/OBJECTIVES: The objective of this study was to develop approaches to expressing resting energy expenditure (REE) and lean body mass (LM) phenotypes of metabolic disorders in terms of Z-scores relative to their predicted healthy values. SUBJECTS/METHODS: Body composition and REE were measured in 135 healthy participants. Prediction equations for LM and REE were obtained from linear regression and the range of normality by the standard deviation of residuals. Application is demonstrated in patients from three metabolic disorder groups (lipodystrophy, n=7; thyrotoxicosis, n=16; and resistance to thyroid hormone (RTH), n=46) in which altered REE and/or LM were characterised by departure from the predicted healthy values, expressed as a Z-score. RESULTS: REE (kJ/min) = -0.010 × age (years)+0.016 × FM (kg)+0.054 × fat-free mass (kg)+1.736 (R2 = 0.732, RSD = 0.36 kJ/min). LM (kg)=5.30 × bone mineral content (kg)+10.66 × height2 (m)+6.40 (male). LM (kg)=0.20 × fat (kg)+14.08 × height2 (m)-2.93 (female).(male R2=0.55, RSD = 3.90 kg; female R2 = 0.59, RSD=3.85 kg).We found average Z-scores for REE and LM of 1.77 kJ/min and -0.17 kg in the RTH group, 5.82 kJ/min and -1.23 kg in the thyrotoxic group and 2.97 kJ/min and 4.20 kg in the LD group. CONCLUSION: This approach enables comparison of data from individuals with metabolic disorders with those of healthy individuals, describing their departure from the healthy mean by a Z-score.

Augmentation index in resistance to thyroid hormone (RTH).

OBJECTIVE: Resistance to thyroid hormone (RTH) is associated with a varied clinical presentation. The cardiac effects of RTH have been described but vascular function has yet to be fully evaluated in this condition. We have measured the arterial function of those with RTH to assess any vascular changes. DESIGN: An observational study. PATIENTS: Twelve RTH patients were recruited from the thyroid clinic (mean value +/- SD), age 40.8 +/- 18.7 years; BMI 27.2 +/- 4.2 kg/m(2) and compared with 12 healthy, euthyroid, age-matched controls (age 41.4 +/- 19.3; BMI 24.8 +/- 4.4 kg/m(2)) with no history of cardiovascular disease. No interventional measures were instituted. MEASUREMENTS: Arterial stiffness was measured using pulse wave analysis at the radial artery. Thyroid function, fasting lipids and glucose were also measured on the same occasion in both patients and controls. Results The corrected augmentation index, a surrogate marker of arterial stiffness was significantly higher in patients compared with controls (21.0% +/- 14.1%vs. 5.4% +/- 18.2%, P < 0.03). Low density lipoprotein cholesterol (LDL-cholesterol) levels were also significantly elevated in patients compared with controls (3.0 +/- 0.6 vs. 2.1 +/- 0.5 mmol/l; P < 0.002). CONCLUSION: RTH patients show evidence in this study of increased augmentation index consistent with an increase in arterial stiffness compared with euthyroid controls. They also demonstrate elevated LDL-cholesterol levels. Both these measures may lead to increased cardiovascular risk.

Influences of age, gender, smoking, and family history on autoimmune thyroid disease phenotype.

CONTEXT: Both genetic and environmental factors contribute to susceptibility to Graves' disease (GD) and Hashimoto's thyroiditis (HT), as well as disease manifestations. OBJECTIVE: The objective of the study was to define how endogenous/environmental factors contribute to variation in phenotype. DESIGN/SETTING: This was a multicenter cohort study. PATIENTS/OUTCOME MEASURES: We prospectively collected clinical/biochemical data as part of the protocol for a United Kingdom DNA collection for GD and HT. We investigated, in 2805 Caucasian subjects, whether age at diagnosis, gender, family history (FH), smoking history, and presence of goiter influenced disease manifestations. RESULTS: For 2405 subjects with GD, the presence of goiter was independently associated with disease severity (serum free T4 at diagnosis) (P < 0.001). Free T4 (P < 0.05) and current smoking (P < 0.001) were both independent predictors of the presence of ophthalmopathy. Approximately half of those with GD (47.4% of females, 40.0% of males) and HT (n = 400) (56.4% of females, 51.7% of males) reported a FH of thyroid dysfunction. In GD, a FH of hyperthyroidism in any relative was more frequent than hypothyroidism (30.1 vs. 24.4% in affected females, P < 0.001). In HT, a FH of hypothyroidism was more common than hyperthyroidism (42.1 vs. 22.8% in affected females, P < 0.001). For GD (P < 0.001) and HT (P < 0.05), a FH was more common in maternal than paternal relatives. The reporting of a parent with thyroid dysfunction (hyper or hypo) was associated with lower median age at diagnosis of both GD (mother with hyperthyroidism, P < 0.001) and HT (father with hypothyroidism, P < 0.05). In GD and HT, there was an inverse relationship between the number of relatives with thyroid dysfunction and age at diagnosis (P < 0.01). CONCLUSIONS: Marked associations among age at diagnosis, disease severity, goiter, ophthalmopathy, smoking, and FH provide evidence for interactions between genetic and environmental/endogenous factors; understanding these may allow preventive measures or better tailoring of therapies.

A novel missense mutation in human TTF-2 (FKHL15) gene associated with congenital hypothyroidism but not athyreosis.

BACKGROUND: Thyroid dysgenesis is the most frequent cause of congenital hypothyroidism (CH), and its genetic basis is largely unknown. Hitherto, two mutations in the human thyroid transcription factor 2 (TTF-2) gene have been described in unrelated cases of CH with cleft palate, spiky hair, variable choanal atresia, and complete thyroid agenesis. Here, we describe a novel TTF-2 mutation in a female child resulting in syndromic CH in the absence of thyroid agenesis. RESULTS: The index case is homozygous for an arginine to cysteine mutation (R102C) of a highly conserved residue within the forkhead, DNA binding domain of TTF-2. Her consanguineous, heterozygous parents are unaffected, and the mutation was not detected in 100 control chromosomes. Consonant with its location, the R102C mutant TTF-2 protein showed loss of DNA binding and was transcriptionally inactive. CH in the proposita was associated with cleft palate, spiky hair, and bilateral choanal atresia. However, radiological studies showed the presence of thyroid tissue in a eutopic location. CONCLUSION: Our findings indicate that human thyroid development can occur despite loss of TTF-2 function and suggest that TTF-2 gene defects should also be considered in cases of syndromic CH without total athyreosis.

Elevated plasma adiponectin in humans with genetically defective insulin receptors.

CONTEXT: Adiponectin has been suggested to play a role in the etiopathogenesis of at least some forms of insulin resistance, in part based on a strong correlation between plasma levels of adiponectin and measures of insulin sensitivity. OBJECTIVE: The objective of the study was to establish whether this relationship is maintained at extreme levels of insulin resistance. DESIGN/SETTING: This was a cross-sectional study in a university teaching hospital of subjects recruited from the United Kingdom and the United States. PARTICIPANTS: Participants included 75 subjects with a range of syndromes of severe insulin resistance and 872 nondiabetic controls. OUTCOME MEASURES: Fasting plasma insulin, adiponectin, and leptin were measured. RESULTS: Unexpectedly, subjects with mutations in the insulin receptor, despite having the most severe degree of insulin resistance, had elevated plasma adiponectin [median 24.4 mg/liter; range 6.6-36.6 (normal adult range for body mass index 20 kg/m(2) = 3-19 mg/liter)], whereas all other subjects had low adiponectin levels (median 2.0 mg/liter; range 0.12-11.2). Plasma leptin in all but one subject with an insulin receptoropathy was low or undetectable [median 0.5 ng/ml; range 0-16: normal adult range for body mass index of < 25 kg/m(2) = 2.4-24.4 (female) and 0.4-8.3 ng/ml (male)]. CONCLUSIONS: We conclude that the relationship between plasma adiponectin and insulin sensitivity is complex and dependent on the precise etiology of defective insulin action and that the combination of high plasma adiponectin with low leptin may have clinical utility in patients with severe insulin resistance as a marker of the presence of a genetic defect in the insulin receptor.

Genetics of congenital hypothyroidism.

Congenital hypothyroidism is the most common neonatal metabolic disorder and results in severe neurodevelopmental impairment and infertility if untreated. Congenital hypothyroidism is usually sporadic but up to 2% of thyroid dysgenesis is familial, and congenital hypothyroidism caused by organification defects is often recessively inherited. The candidate genes associated with this genetically heterogeneous disorder form two main groups: those causing thyroid gland dysgenesis and those causing dyshormonogenesis. Genes associated with thyroid gland dysgenesis include the TSH receptor in non-syndromic congenital hypothyroidism, and Gsalpha and the thyroid transcription factors (TTF-1, TTF-2, and Pax-8), associated with different complex syndromes that include congenital hypothyroidism. Among those causing dyshormonogenesis, the thyroid peroxidase and thyroglobulin genes were initially described, and more recently PDS (Pendred syndrome), NIS (sodium iodide symporter), and THOX2 (thyroid oxidase 2) gene defects. There is also early evidence for a third group of congenital hypothyroid conditions associated with iodothyronine transporter defects associated with severe neurological sequelae. This review focuses on the genetic aspects of primary congenital hypothyroidism.

A dominant negative human peroxisome proliferator-activated receptor (PPAR){alpha} is a constitutive transcriptional corepressor and inhibits signaling through all PPAR isoforms.

Several missense mutations in the ligand-binding domain of human peroxisome proliferator-activated receptor (PPAR)gamma have been described in subjects with dominantly inherited severe insulin resistance associated with partial lipodystrophy, hypertension, and dyslipidemia. These mutant receptors behave as dominant-negative inhibitors of PPARgamma signaling when studied in transfected cells. The extent to which such dominant-negative effects extend to signaling through other coexpressed PPAR isoforms has not been evaluated. To examine these issues further, we have created a PPARalpha mutant harboring twin substitutions, Leu459Ala and Glu462Ala, within the ligand binding domain (PPARalpha(mut)), examined its signaling properties, and compared the effects of dominant-negative PPARalpha and PPARgamma mutants on basal and ligand-induced gene transcription in adipocytes and hepatocytes. PPARalpha(mut) was transcriptionally inactive, repressed basal activity from a PPAR response element-containing promoter, inhibited the coactivator function of cotransfected PPAR-gamma coactivator 1alpha, and strongly inhibited the transcriptional response to cotransfected wild-type receptor. In contrast to PPARgamma, wild-type PPARalpha failed to recruit the transcriptional corepressors NCoR and SMRT. However, PPARalpha(mut) avidly recruited these corepressors in a ligand-dissociable manner. In hepatocytes and adipocytes, both PPARalpha(mut) and the corresponding PPARgamma mutant were capable of inhibiting the expression of genes primarily regulated by PPARalpha, -gamma, or -delta ligands, albeit with some differences in potency. Thus, dominant-negative forms of PPARalpha and PPARgamma are capable of interfering with PPAR signaling in a manner that is not wholly restricted to their cognate target genes. These findings may have implications for the pathogenesis of human syndromes resulting from mutations in this family of transcription factors.

Congenital hypothyroidism and apparent athyreosis with compound heterozygosity or compensated hypothyroidism with probable hemizygosity for inactivating mutations of the TSH receptor.

OBJECTIVE: We wished to ascertain whether mutations in the TSH receptor (TSHR) gene were present in two siblings with congenital hypothyroidism with no parental consanguinity. DESIGN: The pituitary-thyroid axis and thyroid gland morphology were investigated in both affected siblings and their parents. The TSHR gene was analysed in each subject. MEASUREMENTS: Basal thyroid function together with circulating thyroglobulin levels were measured in each subject. In addition, a TRH stimulation test was undertaken in each parent. All family members underwent thyroid ultrasonography. The TSHR gene was amplified from genomic DNA using the polymerase chain reaction and receptor mutations were identified by sequence analysis. RESULTS: Two siblings were diagnosed with severe congenital hypothyroidism (total T4 19-21 nmol/l, TSH 160-230 mU/l on neonatal screening). Although radioiodine scanning showed no tracer uptake and ultrasound imaging in both individuals failed to demonstrate thyroid tissue, suggesting complete athyreosis, circulating thyroglobulin levels were measurable. The thyroid status of the parents was discordant: in the father, baseline thyroid function (FT4 13 pmol/l, TSH 4 mU/l), the peak TSH level after TRH stimulation (30 mU/l) were normal and he exhibited an appropriate rise in circulating thyroid hormones in response to the elevated TSH; in contrast, in the mother, baseline thyroid function was abnormal (FT4 10 pmol/l, TSH 15 mU/l), the TSH response to TRH was exaggerated (110 mU/l), with no subsequent rise in circulating thyroid hormones. An eutopic, slightly hypoplastic thyroid gland was visualized on ultrasonography in the mother and her thyroid antibody status was negative. Both children were compound heterozygotes for missense (alanine to threonine at codon 553, A553T) and premature stop (tryptophan at codon 546, W546X) mutations in the fourth transmembrane domain of the TSH receptor. The mother and father were heterozygous for W546X and A553T mutations, respectively. Each mutation is known to abolish the function or cellular surface expression of the TSH receptor. CONCLUSIONS: Inactivating mutations in the TSH receptor can be associated with severe TSH resistance presenting as congenital hypothyroidism with apparent athyreosis. Our observations also suggest that heterozygosity for an inactivating TSHR mutation may be associated with compensated hypothyroidism and thyroid hypoplasia.

Focused parathyroid surgery with intraoperative parathyroid hormone measurement as a day-case procedure.

BACKGROUND: This study assessed the feasibility, efficacy and safety of focused parathyroidectomy combined with intraoperative parathyroid hormone (IOPTH) measurement in a day-case setting. METHODS: Over 28 months 50 consecutive patients (mean age 63 (range 33-92) years) with clear evidence of unifocal disease on sestamibi scanning or ultrasonography underwent unilateral neck exploration via a small lateral incision. Blood samples for measurement of IOPTH were taken at induction of anaesthesia, before adenoma excision and after adenoma excision (at 5, 10 and 20 min). Ten patients were discharged within 23 h and 40 patients on the day of surgery. RESULTS: A solitary adenoma was identified in all but one patient, with a mean operating time of 30 (range 16-57) min. After parathyroidectomy, IOPTH levels fell appropriately except in one patient with multiglandular hyperplasia. No patient developed symptomatic hypocalcaemia during the 2 weeks after operation, enabling cessation of oral supplements. All patients remained normocalcaemic on follow-up (mean 26 (range 8-84) weeks) and histological examination confirmed parathyroid adenoma (48 patients), hyperplasia (one) or carcinoma (one). CONCLUSION: After accurate preoperative localization of uniglandular disease, patients with primary hyperparathyroidism may be managed successfully and safely by focused parathyroidectomy with IOPTH measurement as a day-case procedure.

Does peroxisome proliferator-activated receptor gamma genotype (Pro12ala) modify the association of physical activity and dietary fat with fasting insulin level?

Peroxisome proliferator-activated receptor gamma (PPARgamma) has a role in controlling adipogenesis and insulin sensitivity. Previous studies have suggested that a common polymorphism (Pro12Ala) in the PPARgamma-2 isoform of this gene may be associated with markers of insulin resistance. We have previously shown that in combination, the relationships with fasting insulin of dietary polyunsaturated to saturated fatty acid ratio (P:S ratio) and physical activity are additive. We have also demonstrated that the association between P:S ratio and fasting insulin level is modified by the Pro12Ala genotype. The purpose of the present study was to investigate whether the Pro12Ala genotype modified the combined relationships of P:S ratio and physical activity level (PAL) on fasting insulin concentration. A population-based cohort of 506 Caucasian men and women aged 31 to 71 years was genotyped for the Pro12Ala polymorphism. P:S ratio was assessed by food-frequency questionnaire (FFQ) and PAL was estimated from 4 days of free-living heart rate monitoring following individual calibration of heart rate against energy expenditure during an exercise stress test. The combined associations of PAL and P:S ratio on fasting insulin level were examined stratified by Pro12Ala genotypes in a dominant model for the Ala allele. Among Pro allele homozygotes, there was no interaction between PAL and P:S ratio on fasting insulin (P =.929). However, in carriers of the Ala allele the association of P:S ratio with fasting insulin was modified by activity level (interaction P = 0.038). In those who were inactive and carried the Ala allele, the age-, sex-, and body mass-adjusted relationship between P:S ratio and log insulin was not significant (beta = -0.03, P =.93). In contrast, in physically active Ala carriers, the association of P:S ratio with log fasting insulin was highly significant (beta = -0.93, P =.004). In conclusion, this study examined the modification by PPARgamma genotype of the association between energy expenditure, P:S ratio, and fasting insulin level, a measure of insulin resistance. These data show that in Pro allele homozygotes the combined associations of P:S ratio and PAL are additive. In contrast, in Ala allele carriers, PAL modifies the association between P:S ratio and fasting insulin level in a multiplicative manner.

Neonatal thyrotoxicosis and maternal infertility in thyroid hormone resistance due to a mutation in the TRbeta gene (M313T).

We report two unusual cases of resistance to thyroid hormone (RTH) in one family. The first case, a male infant, had clinical features of thyrotoxicosis in the neonatal period. In the fourth week of life weight gain was poor despite a daily intake of standard infant formula almost double the infant's estimated requirements. At this time serum free T4 (fT4) was 60.7 pmol/l (Normal range [NR] 11-25 pmol/l) and TSH was inappropriately normal at 1.8 mU/l (NR 0.3-4.0 mU/l). The infant responded clinically and biochemically to propylthiouracil (PTU) at a dose of 10 mg/kg/day. Following 27 days of treatment serum fT4 was 22.6 pmol/l and TSH had risen to 24.9 mU/l. As the infant was thriving treatment was discontinued. The infant, now aged 6 months old, remains clinically euthyroid and developmentally normal off treatment. The infant's mother, from whom he had inherited a mutation of the thyroid receptor beta (TRbeta) gene (M313T), presented earlier with secondary infertility and clinical features of thyrotoxicosis. Treatment with PTU restored her fertility and she spontaneously conceived. In the subsequent pregnancy, clinical and biochemical features of RTH improved, and she gave birth to a small but healthy female infant. In the next pregnancy, resulting in the birth of the affected male infant, clinical and biochemical features of RTH worsened, and high doses of PTU were required to maintain a clinically euthyroid state. To our knowledge, these are the first case reports of RTH associated with added features of a hypermetabolic state in infancy and secondary infertility.

Potentiation of glucose uptake in 3T3-L1 adipocytes by PPAR gamma agonists is maintained in cells expressing a PPAR gamma dominant-negative mutant: evidence for selectivity in the downstream responses to PPAR gamma activation.

Pharmacological agonists for the nuclear receptor PPAR gamma enhance glucose disposal in a variety of insulin-resistant states in humans and animals. The precise mechanisms whereby activation of PPAR gamma leads to increased glucose uptake in metabolically active cells remain to be determined. Notably, certain novel, synthetic PPAR gamma ligands appear to antagonize thiazolidinedione-induced adipogenesis yet stimulate cellular glucose uptake. We have explored the molecular mechanisms underlying the enhancement of glucose uptake produced by PPAR gamma agonists in 3T3-L1 adipocytes. Rosiglitazone treatment for 48 h significantly increased basal and insulin-stimulated glucose uptake and markedly increased the cellular expression of GLUT1 but not GLUT4. Rosiglitazone increased plasma membrane levels of GLUT1, but not GLUT4, both basally and after insulin stimulation. Surprisingly, adenoviral expression of a dominant-negative mutant PPAR gamma, which was demonstrated to strongly inhibit adipogenesis, completely failed to inhibit rosiglitazone-stimulated glucose uptake. Similar findings were obtained with the non-thiazolidinedione PPAR gamma agonists, GW1929 and GW7845. The insensitivity of PPAR gamma agonist-stimulated glucose uptake to expression of a dominant-negative mutant, compared with the latter's marked inhibitory effects on preadipocyte differentiation, suggests that, as is the case for other nuclear receptors, the precise molecular mechanisms linking PPAR gamma activation to downstream events may differ depending on the nature of the biological response. The growing evidence that the effects of PPAR gamma on adipogenesis and glucose uptake can be dissociated may have important implications for the development of improved antidiabetic drug treatments.

Chromatin remodeling by the thyroid hormone receptor in regulation of the thyroid-stimulating hormone alpha-subunit promoter.

The chromatin architecture of a promoter is an important determinant of its transcriptional response. For most target genes, the thyroid hormone receptor (TR) activates gene expression in response to thyroid hormone (T(3)). In contrast, the thyroid-stimulating hormone alpha-subunit (TSH alpha) gene promoter is down-regulated by TR in the presence of T(3). Here we utilize the capacity for the Xenopus oocyte to chromatinize exogenous nuclear- injected DNA to analyze the chromatin architecture of the TSH alpha promoter and how this changes upon TR-mediated regulation. Interestingly, in the oocyte, the TSH alpha promoter was positively regulated by T(3). In the inactive state, the promoter contained six loosely positioned nucleosomes. The addition of TR/retinoid X receptor together had no effect on the chromatin structure, but the inclusion of T(3) induced strong positioning of a dinucleosome in the TSH alpha proximal promoter that was bordered by regions that were hypersensitive to cleavage by methidiumpropyl EDTA. We identified a novel thyroid response element that coincided with the proximal hypersensitive region. Furthermore, we examined the consequences of mutations in TR that impaired coactivator recruitment. In a comparison with the Xenopus TR beta A promoter, we found that the effects of these mutations on transactivation and chromatin remodeling were significantly more severe on the TSH alpha promoter.