The need for the GREAT+ score to predict relapse in Graves' disease: a questionnaire among patients and internal medicine specialists.

PURPOSE: Graves' disease (GD) is an auto-immune cause of hyperthyroidism. First-line treatment often consists of a 12-18 month course of antithyroid drugs (ATD). After discontinuation of ATD, GD relapses in approximately 50% of patients. The 'Graves recurrent event after therapy+ ' (GREAT+) score may predict individual relapse chances after ATD discontinuation more accurately based on clinical and laboratory parameters at diagnosis. We investigated the need for the GREAT+ score through an online questionnaire among GD patients and physicians treating GD. METHODS: An anonymous online questionnaire was distributed to patients and physicians between June 2022 and August 2023. RESULTS: The questionnaire was completed by 532 patients and 44 physicians. Results showed that 94% of patients were interested in knowing their GREAT+ score at the start of treatment. 55% would consider definite treatment (radioiodine/thyroidectomy) as first-line treatment in case of a high relapse chance. 98% of the physicians indicated the GREAT + score would support patient counseling. 84% may change their advice for first-line treatment if a patient has a high relapse chance based on the score. CONCLUSION: Patients and physicians considered the GREAT+ score as a valuable addition to the current available information which could change treatment decisions. Therefore, external validation of the GREAT+ score is justified to implement this score in clinical practice.

Maleic acid is a biomarker for maleylacetoacetate isomerase deficiency; implications for newborn screening of tyrosinemia type 1.

Dried blood spot succinylacetone (SA) is often used as a biomarker for newborn screening (NBS) for tyrosinemia type 1 (TT1). However, false-positive SA results are often observed. Elevated SA may also be due to maleylacetoacetate isomerase deficiency (MAAI-D), which appears to be clinically insignificant. This study investigated whether urine organic acid (uOA) and quantitative urine maleic acid (Q-uMA) analyses can distinguish between TT1 and MAAI-D. We reevaluated/measured uOA (GC-MS) and/or Q-uMA (LC-MS/MS) in available urine samples of nine referred newborns (2 TT1, 7 false-positive), eight genetically confirmed MAAI-D children, and 66 controls. Maleic acid was elevated in uOA of 5/7 false-positive newborns and in the three available samples of confirmed MAAI-D children, but not in TT1 patients. Q-uMA ranged from not detectable to 1.16 mmol/mol creatinine in controls (n = 66) and from 0.95 to 192.06 mmol/mol creatinine in false-positive newborns and MAAI-D children (n = 10). MAAI-D was genetically confirmed in 4/7 false-positive newborns, all with elevated Q-uMA, and rejected in the two newborns with normal Q-uMA. No sample was available for genetic analysis of the last false-positive infant with elevated Q-uMA. Our study shows that MAAI-D is a recognizable cause of false-positive TT1 NBS results. Elevated urine maleic acid excretion seems highly effective in discriminating MAAI-D from TT1.

An update on non-thyroidal illness syndrome.

The non-thyroidal illness syndrome (NTIS) was first reported in the 1970s as a remarkable ensemble of changes in serum TH (TH) concentrations occurring in probably any severe illness. Ever since, NTIS has remained an intriguing phenomenon not only because of the robustness of the decrease in serum triiodothyronine (T3), but also by its clear correlation with morbidity and mortality. In recent years, it has become clear that (parenteral) feeding in patients with critical illness should be taken into account as a major determinant not only of NTIS but also of clinical outcome. Moreover, both experimental animal and clinical studies have shown that tissue TH concentrations during NTIS do not necessarily reflect serum low TH concentrations and may decrease, remain unaltered, or even increase according to the organ and type of illness studied. These differential changes now have a solid basis in molecular studies on organ-specific TH transporters, receptors and deiodinases. Finally, the role of inflammatory pathways in these non-systemic changes has begun to be clarified. A fascinating role for TH metabolism in innate immune cells, including neutrophils and monocytes/macrophages, was reported in recent years, but there is no evidence at this early stage that this may be a determinant of susceptibility to infections. Although endocrinologists have been tempted to correct NTIS by TH supplementation, there is at present insufficient evidence that this is beneficial. Thus, there is a clear need for adequately powered randomized clinical trials (RCT) with clinically relevant endpoints to fill this knowledge gap.

Thyroid hormone receptors in health and disease.

Thyroid hormones (TH) play a key role in energy homeostasis throughout life. Thyroid hormone production and secretion by the thyroid gland is regulated via the hypothalamus-pituitary-thyroid (HPT)-axis. Thyroid hormone has to be transported into the cell, where it can bind to the thyroid hormone receptor (TR) in the nucleus to exert its effect on cellular gene-transcription. Mutations in both the THRA and THRB gene have been described, each inducing a characteristic phenotype clearly showing the selective effect of an excess or shortage of thyroid hormone in specific TRα and TRß regulated organs. Profound changes in thyroid hormone metabolism occur during a variety of non-thyroidal illnesses, each associated with reduced TR expression in a tissue-specific manner. However, thyroid hormone action at the tissue level during illness is not a simple reflection of the extent of TR expression as illness has additional differential effects on local thyroid hormone availability in various organs.

Determination of thyroid hormones and their metabolites in tissue using SPE UPLC-tandem MS.

A solid-phase liquid chromatography tandem mass spectrometry (SPE LC-MS/MS) method was developed to determine thyroid hormones and their metabolites in tissue samples. The separation was achieved using reversed-phase ultra-performance liquid chromatography (UPLC); the mass spectrometric detection was achieved by positive electrospray ionization and multiple reaction monitoring. Prior to the UPLC separation a sample cleanup with a cation exchange was performed. ¹³C6 labeled internal standards were used for the thyroid hormones and their metabolites. The method was linear over a range from 0.23 to 90 nmol/L for thyroxine and from 0.23 to 9 nmol/L for the metabolites. The lower limit of quantification ranged from 0.98 to 1.73 pg on column. Intra- and total assay variation were <10 and <15%, respectively. This method enables us to link thyroid hormone tissue concentrations to local iodothyronine deiodinase expressions, which will enhance our understanding of the regulation of thyroid hormone metabolism on the tissue level.

Interleukin-1beta modulates endogenous thyroid hormone receptor alpha gene transcription in liver cells.

One of the main characteristics of nonthyroidal illness (NTI) is a decrease in serum triiodothyronine, partly caused by a decrease in liver deiodinase type 1 (D1) mRNA and activity. Proinflammatory cytokines have been associated with NTI in view of their capability to decrease D1 and thyroid hormone receptor (TR)beta1 mRNA expression in hepatoma cells. Proinflammatory cytokine induction leads to activation of the inflammatory pathways nuclear factor (NF)kappaB and activator protein (AP)-1. The proinflammatory cytokine interleukin (IL)-1beta decreases thyroid hormone receptor (TR)beta1 mRNA in an NFkappaB-dependent way. The aim of this study was to unravel the effects of IL-1beta on endogenous TRalpha gene expression in an animal model and in a liver cell line. The TRalpha gene product is alternatively spliced in TRalpha1 and TRalpha2, TRalpha2 is capable of inhibiting TRalpha1-induced gene transcription. We showed that both TRalpha1 and TRalpha2 mRNA decreased not only after lipopolysaccharide administration in liver of mice, but also after IL-1beta stimulation of hepatoma cells (HepG2). Using the NFkappaB inhibitor sulfasalazine and the AP-1 inhibitor SP600125, it became clear that the IL-1beta-induced decrease in TRalpha mRNA expression in HepG2 cells can only be abolished by simultaneous inhibition of NFkappaB and AP-1. The IL-1beta-induced TRalpha1 and TRalpha2 mRNA decrease in HepG2 cells is the result of decreased TRalpha gene promoter activity, as evident from actinomycin D experiments. Cycloheximide experiments showed that the decreased promoter activity is independent of de novo protein synthesis and therefore most likely due to posttranslational modifications such as phosphorylation or subcellular relocalization.

High incidence of hypermethioninaemia in a single neonatal intensive care unit detected by a newly introduced neonatal screening programme.

From 1 January 2007 an expanded neonatal screening programme was initiated in the Netherlands, including homocystinuria with methionine as the primary marker. During the first 2 months hypermethioninaemia was detected in 14 newborns who, after proper evaluation, were demonstrated not to have classical homocystinuria. Remarkably, all these children were admitted to a single neonatal intensive care unit (Academic Medical Center, Amsterdam (AMC-NICU)). We evaluated the possible causes for this finding. The cohort of newborns with hypermethioninaemia (group 1) was compared with the cohort of newborns with normal screening results admitted to the AMC-NICU in the same time period (group 2). In addition, parenteral nutrition protocols from all NICUs in the Netherlands were compared. Mean birth weight and gestational age were significantly lower in group 1 than in group 2. All patients in group 1 received parenteral feeding (TPN) at the time of screening and received a higher mean amino acid intake per kilogram body weight than patients receiving TPN in group 2. Also, the AMC-NICU uses a different amino acid mixture for TPN than the other Dutch NICUs, containing more than twice the amount of methionine per gram of amino acids compared with other mixtures. The high incidence of hypermethioninaemia in the AMC-NICU is explained by a combination of low birth weight, low gestational age, and high protein intake supplied by a specific parenteral amino acid mixture containing large amounts of methionine. To prevent hypermethioninaemia, the use of high-methionine containing solutions for TPN should be reconsidered.

Dietary intake in asylum seeker children in The Netherlands, strongly related to age and origin.

OBJECTIVE: To monitor the dietary intake of energy, macro- and micronutrients in asylum seeker children. DESIGN AND SETTING: Cross-sectional study in three asylum seeker centres in The Netherlands. SUBJECTS: Hundred and sixteen children 2-12 years old (86% of the study cohort) provided a dietary history. METHOD: The dietary intake was estimated by 24 h recall, and the origin of the children was classified in three geographic regions: African (n=45), Central Asia (n=34) or Eastern Europe (n=37). RESULTS: The total energy intake from fat was in 24% of the children above 40En%. Seventy per cent of the children above 4 year of age had a saturated fat intake above 10En%. The children from Eastern Europe had a higher intake of fat and disaccharides than the children from the other regions. Among the children, an intake less than 80% of the recommended daily allowances of micronutrients was found for calcium (42%), iron (49%), vitamin A (45%) and vitamin D (80%). An inadequate dietary intake of iron and vitamin D was significantly more seen among the youngest children, whereas an inadequate intake of calcium and vitamin A was found more among the elder children. CONCLUSIONS: The dietary intake of a prominent proportion of these children contains too much fat and insufficient amounts of calcium, iron, vitamin A and vitamin D. The low micronutrient intake of the asylum seeker children can be considered as a nutritional risk. Nutritional education and strategies to improve the macro- and micronutrient intake of asylum seeker children is indicated.

Iron deficiency among children of asylum seekers in the Netherlands.

OBJECTIVES: To investigate, in asylum seekers' children in the Netherlands, biochemical iron status and the prevalence of iron deficiency (ID) and anemia in relation to age, region of origin, length of stay in the Netherlands, body mass index (BMI), and dietary iron intake. PATIENTS AND METHODS: Hemoglobin (Hb) and plasma ferritin concentrations were determined in 122 asylum seekers' children (median age, 7.1 years; range, 2-12 y). ID was defined by plasma ferritin levels <15 microg/L. Anemia was defined by Hb levels <6.8 mmol/L (11 g/dL) for children <6 years of age and Hb levels <7.1 mmol/L (11.5 g/dL) for children between 6 and 12 years of age. Nutritional status of the children was assessed by BMI and dietary intake of iron was estimated by 24-hour recall. RESULTS: Twenty percent of the children had compromised iron status (16% with ID, 4% with ID anemia [IDA]). Another 6% of the children had anemia caused by thalassemia. ID was significantly more prevalent in children <6 years of age and in children of African origin. The iron status was not significantly correlated with the length of stay in the Netherlands (r = 0.6; P = 0.48). Higher BMI z scores were positively correlated with iron status. Adequate or marginal dietary iron intake was not significantly related to the presence of ID (r = 0.02; P = 0.9) or anemia (IDA and thalassemia; r = 0.15; P = 0.9). CONCLUSIONS: Iron deficiency is highly prevalent among the children of asylum seekers in the Netherlands. Our data indicate that systematic biochemical screening for ID is warranted in asylum seekers' children.

Establishing New Cut-Off Limits for Galactose 1-Phosphate-Uridyltransferase Deficiency for the Dutch Newborn Screening Programme.

Newborn screening for classical galactosemia in the Netherlands is performed by five laboratories and is based on the measurement of galactose 1-phosphate-uridyltransferase (GALT) activity and total galactose (TGAL) in heel prick blood spots. Unexpected problems with the GALT assay posed a challenge to switch to a new assay. The aim of this study was to make an analytical and clinical evaluation of GALT assays to replace the current assay and to establish new cut-off values (COVs).First, the manual assay from PerkinElmer (NG-1100) and the GSP assay were compared by analyzing 626 anonymous heel prick samples in parallel. Secondly, a manual GSP method was evaluated and 2,052 samples were compared with the automated GSP assay. Finally, a clinical evaluation was performed by collecting data from 93 referred newborns.No satisfactory correlation was observed between GALT activity measured with the manual NG-1100 assay and the automated GSP assay. An acceptable correlation was found between the manual and automated GSP assay. Intra- and inter-assay variation of the automated GSP were 1.8-10.0% and 3.1-13.9%, respectively. Evaluation of clinical data demonstrated that adjusting the COVs for GALT to 2.0 U/dl and TGAL to 1,100 µmol/l improved specificity of screening for classical galactosemia.An assay designed for automated processing to measure GALT activity in heel prick samples works equally well when processed manually. We therefore adopted both methods in the Dutch screening laboratories. As a result of this evaluation new COVs for GALT and TGAL have been introduced and are valid from July 2015.

Effects of meal composition and meal timing on the expression of genes involved in hepatic drug metabolism in rats.

INTRODUCTION: With chronotherapy, drug administration is synchronized with daily rhythms in drug clearance and pharmacokinetics. Daily rhythms in gene expression are centrally mastered by the suprachiasmatic nucleus of the hypothalamus as well as by tissue clocks containing similar molecular mechanisms in peripheral organs. The central timing system is sensitive to changes in the external environment such as those of the light-dark cycle, meal timing and meal composition. We investigated how changes in diet composition and meal timing would affect the daily hepatic expression rhythms of the nuclear receptors PXR and CAR and of enzymes involved in P450 mediated drug metabolism, as such changes could have consequences for the practice of chronotherapy. MATERIALS AND METHODS: Rats were subjected to either a regular chow or a free choice high-fat-high-sugar (fcHFHS) diet. These diets were provided ad libitum, or restricted to either the light phase or the dark phase. In a second experiment, rats had access to chow either ad libitum or in 6 meals equally distributed over 24 hours. RESULTS: Pxr, Alas1 and Por displayed significant day-night rhythms under ad libitum chow fed conditions, which for Pxr was disrupted under fcHFHS diet conditions. Although no daily rhythms were detected in expression of CAR, Cyp2b2 and Cyp3a2, the fcHFHS diet did affect basal expression of these genes. In chow fed rats, dark phase feeding induced a diurnal rhythm in Cyp2b2 expression while light phase feeding induced a diurnal rhythm in Car expression and completely shifted the peak expression of Pxr, Car, Cyp2b2, Alas1 and Por. The 6-meals-a-day feeding only abolished the Pxr rhythm but not the rhythms of the other genes. CONCLUSION: We conclude that although nuclear receptors and enzymes involved in the regulation of hepatic drug metabolism are sensitive to meal composition, changes in meal timing are mainly effectuated via changes in the molecular clock.

Differential involvement of nuclear factor-kappaB and activator protein-1 pathways in the interleukin-1beta-mediated decrease of deiodinase type 1 and thyroid hormone receptor beta1 mRNA.

One of the hallmarks of the sick euthyroid syndrome or non-thyroidal illness is a decrease of serum triiodothyronine, caused mainly by a decrease in liver deiodinase type 1 (D1) mRNA and activity. Proinflammatory cytokines like interleukin (IL)-1beta are likely involved in this disease, but are also known to inhibit thyroid hormone receptor (TR)-beta1 gene expression, which is of interest as the D1 promoter contains TREs. The aim of the present study was to evaluate whether the IL-1beta-induced decrease of D1 and TRbeta1 mRNA is mediated by the same cytokine signalling pathways in a human hepatoma cell line (HepG2). We observed a downregulation of both D1 and TRbeta1 mRNA after 4 h of incubating the cells with IL-1beta. Sulfasalazine was used to inhibit the nuclear factor-kappaB (NFkappaB) pathway and SP600125, a chemical inhibitor of the c-Jun N-terminal kinase, was used as an inhibitor of the activator protein-1 (AP-1) pathway. AP-1 inhibition did not affect the decrease of D1 and TRbeta1 mRNA, but the TRbeta1 mRNA decrease was completely abolished after inhibiting NFkappaB, while D1 mRNA was unaffected. Only simultaneous inhibition of both the NFkappaB and AP-1 pathways abolished the D1 mRNA decrease. We concluded that IL-1beta stimulation of HepG2 cells results in a marked decrease of D1 and TRbeta1 mRNA. The decrease of TRbeta1 mRNA is exclusively mediated by the NFkappaB pathway, while the decrease of D1 mRNA requires inhibition of both the AP-1 and the NFkappaB pathways.

Chronic local inflammation in mice results in decreased TRH and type 3 deiodinase mRNA expression in the hypothalamic paraventricular nucleus independently of diminished food intake.

During illness, changes in thyroid hormone metabolism occur, known as nonthyroidal illness and characterised by decreased serum triiodothyronine (T3) and thyroxine (T4) without an increase in TSH. A mouse model of chronic illness is local inflammation, induced by a turpentine injection in each hind limb. Although serum T3 and T4 are markedly decreased in this model, it is unknown whether turpentine administration affects the central part of the hypothalamus-pituitary-thyroid axis (HPT-axis). We therefore studied thyroid hormone metabolism in hypothalamus and pituitary of mice during chronic inflammation induced by turpentine injection. Using pair-fed controls, we could differentiate between the effects of chronic inflammation per se and the effects of restricted food intake as a result of illness. Chronic inflammation increased interleukin (IL)-1beta mRNA expression in the hypothalamus more rapidly than in the pituitary. This hypothalamic cytokine response was associated with a rapid increase in local D2 mRNA expression. By contrast, no changes were present in pituitary D2 expression. TSHbeta mRNA expression was altered compared with controls. Comparing chronic inflamed mice with pair-fed controls, both preproTSH releasing hormone (TRH) and D3 mRNA expression in the paraventricular nucleus were significantly lower 48 h after turpentine administration. The timecourse of TSHbeta mRNA expression was completely different in inflamed mice compared with pair-fed mice. Turpentine administration resulted in significantly decreased TSHbeta mRNA expression only after 24 h while later in time it was lower in pair-fed controls. In conclusion, central thyroid hormone metabolism is altered during chronic inflammation and this cannot solely be attributed to diminished food intake.

Differential effects of leptin and refeeding on the fasting-induced decrease of pituitary type 2 deiodinase and thyroid hormone receptor beta2 mRNA expression in mice.

Profound changes in thyroid hormone metabolism occur in the central part of the hypothalamus-pituitary-thyroid (HPT) axis during fasting. Hypothalamic changes are partly reversed by leptin administration, which decreases during fasting. It is unknown to what extent leptin affects the HPT axis at the level of the pituitary. We, therefore, studied fasting-induced alterations in pituitary thyroid hormone metabolism, as well as effects of leptin administration on these changes. Because refeeding rapidly increased serum leptin, the same parameters were studied after fasting followed by refeeding. Fasting for 24 h decreased serum T(3) and T(4) and pituitary TSHbeta, type 2deiodinase (D2), and thyroid hormone receptor beta2 (TRbeta2) mRNA expression. The decrease in D2 and TRbeta2 mRNA expression was prevented when 20 mug leptin was administered twice during fasting. By contrast, the decrease in TSHbeta mRNA expression was unaffected. A single dose of leptin given after 24 h fasting did not affect decreased TSHbeta, D2, and TRbeta2 mRNA expression, while 4 h refeeding resulted in pituitary D2 and TRbeta2 mRNA expression as observed in control mice. Serum leptin, T(3), and T(4) after refeeding were similar compared with leptin administration. We conclude that fasting decreases pituitary TSHbeta, D2, and TRbeta2 mRNA expression, which (with the exception of TSHbeta) can be prevented by leptin administration during fasting. Following 24 h fasting, 4 h refeeding completely restores pituitary D2 and TRbeta2 mRNA expression, while a single leptin dose is ineffective. This indicates that other postingestion signals may be necessary to modulate rapidly the fasting-induced decrease in pituitary D2 and TRbeta2 mRNA expression.

A model for chronic, intrahypothalamic thyroid hormone administration in rats.

In addition to the direct effects of thyroid hormone (TH) on peripheral organs, recent work showed metabolic effects of TH on the liver and brown adipose tissue via neural pathways originating in the hypothalamic paraventricular and ventromedial nucleus (PVN and VMH). So far, these experiments focused on short-term administration of TH. The aim of this study is to develop a technique for chronic and nucleus-specific intrahypothalamic administration of the biologically active TH tri-iodothyronine (T3). We used beeswax pellets loaded with an amount of T3 based on in vitro experiments showing stable T3 release (∼5 nmol l(-1)) for 32 days. Upon stereotactic bilateral implantation, T3 concentrations were increased 90-fold in the PVN region and 50-fold in the VMH region after placing T3-containing pellets in the rat PVN or VMH for 28 days respectively. Increased local T3 concentrations were reflected by selectively increased mRNA expression of the T3-responsive genes Dio3 and Hr in the PVN or in the VMH. After placement of T3-containing pellets in the PVN, Tshb mRNA was significantly decreased in the pituitary, without altered Trh mRNA in the PVN region. Plasma T3 and T4 concentrations decreased without altered plasma TSH. We observed no changes in pituitary Tshb mRNA, plasma TSH, or plasma TH in rats after placement of T3-containing pellets in the VMH. We developed a method to selectively and chronically deliver T3 to specific hypothalamic nuclei. This will enable future studies on the chronic effects of intrahypothalamic T3 on energy metabolism via the PVN or VMH.

The Role of Hypothalamic NF-κB Signaling in the Response of the HPT-Axis to Acute Inflammation in Female Mice.

A large proportion of critically ill patients have alterations in the hypothalamus-pituitary-thyroid (HPT) axis, collectively known as the nonthyroidal illness syndrome. Nonthyroidal illness syndrome is characterized by low serum thyroid hormone (TH) concentrations accompanied by a suppressed central component of the HPT axis and persistent low serum TSH. In hypothalamic tanycytes, the expression of type 2 deiodinase (D2) is increased in several animal models of inflammation. Because D2 is a major source of T3 in the brain, this response is thought to suppress TRH expression in the paraventricular nucleus via increased local bioavailability of T3. The inflammatory pathway component RelA (the p65 subunit of nuclear factor-κB) can bind the Dio2 promoter and increases D2 expression after lipopolysaccharide (LPS) stimulation in vitro. We aimed to determine whether RelA signaling in tanycytes is essential for the LPS-induced D2 increase in vivo by conditional elimination of RelA in tanycytes of mice (RelA(ASTKO)). Dio2 and Trh mRNA expression were assessed by quantitative in situ hybridization 8 or 24 hours after saline or LPS injection. At the same time points, we measured pituitary Tshß mRNA expression and serum T3 and T4 concentrations. In RelA(ASTKO) mice the LPS-induced increase in Dio2 and decrease in Trh mRNA levels in the hypothalamus were reduced compared with the wild-type littermates, whereas the drop in pituitary Tshß expression and in serum TH concentrations persisted. In conclusion, RelA is essential for the LPS-induced hypothalamic D2 increase and TRH decrease. The central changes in the HPT axis are, however, not required for the down-regulation of Tshß expression and serum TH concentrations.

Fasting-Induced Changes in Hepatic P450 Mediated Drug Metabolism Are Largely Independent of the Constitutive Androstane Receptor CAR.

INTRODUCTION: Hepatic drug metabolism by cytochrome P450 enzymes is altered by the nutritional status of patients. The expression of P450 enzymes is partly regulated by the constitutive androstane receptor (CAR). Fasting regulates the expression of both P450 enzymes and CAR and affects hepatic drug clearance. We hypothesized that the fasting-induced alterations in P450 mediated drug clearance are mediated by CAR. METHODS: To investigate this we used a drug cocktail validated in humans consisting of five widely prescribed drugs as probes for specific P450 enzymes: caffeine (CYP1A2), metoprolol (CYP2D6), omeprazole (CYP2C19), midazolam (CYP3A4) and s-warfarin (CYP2C9). This cocktail was administered to wild type (WT, C57Bl/6) mice or mice deficient for CAR (CAR-/-) that were either fed ad libitum or fasted for 24 hours. Blood was sampled at predefined intervals and drug concentrations were measured as well as hepatic mRNA expression of homologous/orthologous P450 enzymes (Cyp1a2, Cyp2d22, Cyp3a11, Cyp2c37, Cyp2c38 and Cyp2c65). RESULTS: Fasting decreased Cyp1a2 and Cyp2d22 expression and increased Cyp3a11 and Cyp2c38 expression in both WT and CAR-/- mice. The decrease in Cyp1a2 was diminished in CAR-/- in comparison with WT mice. Basal Cyp2c37 expression was lower in CAR-/- compared to WT mice. Fasting decreased the clearance of all drugs tested in both WT and CAR-/- mice. The absence of CAR was associated with an decrease in the clearance of omeprazole, metoprolol and midazolam in fed mice. The fasting-induced reduction in clearance of s-warfarin was greater in WT than in CAR-/-. The changes in drug clearance correlated with the expression pattern of the specific P450 enzymes in case of Cyp1a2-caffeine and Cyp2c37-omeprazole. CONCLUSION: We conclude that CAR is important for hepatic clearance of several widely prescribed drugs metabolized by P450 enzymes. However the fasting-induced alterations in P450 mediated drug clearance are largely independent of CAR.

Effects of Chronic Estrogen Administration in the Ventromedial Nucleus of the Hypothalamus (VMH) on Fat and Bone Metabolism in Ovariectomized Rats.

Estrogen deficiency after ovariectomy (OVX) results in increased adiposity and bone loss, which can be prevented by systemic 17-ß estradiol (E2) replacement. Studies in transgenic mice suggested that in addition to direct actions of estrogen in peripheral tissues, also estrogen signaling in the hypothalamus regulates fat distribution and bone metabolism. We hypothesized that the protective effect of systemic E2 on fat and bone metabolism in the OVX model is partly mediated through the ventromedial nucleus of the hypothalamus (VMH). To test this hypothesis, we determined the effect of systemic, central, and targeted VMH administration of E2 on fat and bone metabolism in OVX rats. Subcutaneous administration of E2 for 4 weeks decreased body weight, gonadal and perirenal fat, and bone formation rate in OVX rats. This effect was completely mimicked by intracerebroventricular injections of E2, once every 4 days for 4 weeks. Administration of E2 locally in the VMH by retromicrodialysis (3 h) acutely increased expression of the lipolytic gene hormone-sensitive lipase in gonadal and perirenal fat. Finally, chronic administration of E2 in the VMH for 8 weeks decreased perirenal fat but did not affect body weight, trabecular bone volume, or cortical thickness. In conclusion, we demonstrated that intracerebroventricular E2 replacement reduces body weight gain, ameliorates intraabdominal fat accumulation, and reduces bone formation in the OVX rats. E2 administration selectively in the VMH also reduced intraabdominal fat but did not affect bone metabolism.

Induction of type 3 deiodinase activity in inflammatory cells of mice with chronic local inflammation.

During illness, changes in thyroid hormone metabolism occur, so-called nonthyroidal illness (NTI). NTI has been characterized by a fall of serum T(3) due to decreased extrathyroidal conversion of T(4) into T(3) by liver type 1 deiodinase (D1), without an increase in serum TSH. Type 3 deiodinase (D3) was thought not to play an important role during NTI, but recently it has been shown that D3 activity is up-regulated in liver and skeletal muscle of critically ill patients related to hypoxia. We studied D3 gene expression and activity in liver and muscle/subcutis of mice during illness, which was induced by two different stimuli: bacterial endotoxin (lipopolysaccharide) administration, resulting in an acute systemic response, and a turpentine injection in each hindlimb, resulting in a local sc abscess. Lipopolysaccharide induced a rapid decrease in liver D1 and D3 activity but not skeletal muscle of hindlimb. In contrast, local inflammation induced by turpentine did not decrease liver D1 and D3 activity but increased markedly D3 activity in the muscle/subcutis sample containing the abscess, associated with strongly increased IL-1beta and IL-6 mRNA expression. Inflammatory cells, surrounding the abscess showed D3 and T(3)-transporter monocarboxylate transporter-8 immunoreactivity, whereas muscle cells did not show any immunoreactivity. In conclusion, local inflammation strongly induces D3 activity in inflammatory cells, especially in invading polymorphonuclear granulocytes, suggesting enhanced local degradation of T(3).

Differential effects of fasting vs food restriction on liver thyroid hormone metabolism in male rats.

A variety of illnesses that leads to profound changes in the hypothalamus-pituitary-thyroid (HPT) are axis collectively known as the nonthyroidal illness syndrome (NTIS). NTIS is characterized by decreased tri-iodothyronine (T3) and thyroxine (T4) and inappropriately low TSH serum concentrations, as well as altered hepatic thyroid hormone (TH) metabolism. Spontaneous caloric restriction often occurs during illness and may contribute to NTIS, but it is currently unknown to what extent. The role of diminished food intake is often studied using experimental fasting models, but partial food restriction might be a more physiologically relevant model. In this comparative study, we characterized hepatic TH metabolism in two models for caloric restriction: 36 h of complete fasting and 21 days of 50% food restriction. Both fasting and food restriction decreased serum T4 concentration, while after 36-h fasting serum T3 also decreased. Fasting decreased hepatic T3 but not T4 concentrations, while food restriction decreased both hepatic T3 and T4 concentrations. Fasting and food restriction both induced an upregulation of liver D3 expression and activity, D1 was not affected. A differential effect was seen in Mct10 mRNA expression, which was upregulated in the fasted rats but not in food-restricted rats. Other metabolic pathways of TH, such as sulfation and UDP-glucuronidation, were also differentially affected. The changes in hepatic TH concentrations were reflected by the expression of T3-responsive genes Fas and Spot14 only in the 36-h fasted rats. In conclusion, limited food intake induced marked changes in hepatic TH metabolism, which are likely to contribute to the changes observed during NTIS.