Hyperthyroxinemia and Hypercortisolemia due to Familial Dysalbuminemia.

A 23-year-old man and his grandmother with hyperthyroxinemia and hypercortisolemia were heterozygous for an ALB mutation (p. Arg218Pro), known to cause familial dysalbuminemic hyperthyroxinemia (FDH). However, serum-free cortisol levels in these individuals were normal and total cortisol concentrations fell markedly after depletion of albumin from their serum. We conclude that binding of steroid as well as iodothyronines to mutant albumin causes raised circulating cortisol as well as thyroid hormones in euthyroid euadrenal individuals with R218P FDH, with potential for misdiagnosis, unnecessary investigation, and inappropriate treatment.

Thyroid Hormone Analogues: An Update.

The development of thyroid hormone (TH) analogues was prompted by the attempt to exploit the effects of TH on lipid metabolism, avoiding cardiac thyrotoxicosis. Analysis of the relative distribution of the α and ß subtypes of nuclear TH receptors (TRα and TRß) showed that TRα and TRß are responsible for cardiac and metabolic responses, respectively. Therefore, analogues with TRß selectivity were developed, and four different compounds have been used in clinical trials: GC-1 (sobetirome), KB-2115 (eprotirome), MB07344/VK2809, and MGL-3196 (resmetirom). Each of these compounds was able to reduce low-density lipoprotein cholesterol, but a phase 3 trial with eprotirome was interrupted because of a significant increase in liver enzymes and the contemporary report of cartilage side effects in animals. As a consequence, the other projects were terminated as well. However, in recent years, TRß agonists have raised new interest for the treatment of nonalcoholic fatty liver disease (NAFLD). After obtaining excellent results in experimental models, clinical trials have been started with MGL-3196 and VK2809, and the initial reports are encouraging. Sobetirome turned out to be effective also in experimental models of demyelinating disease. Aside TRß agonists, TH analogues include some TH metabolites that are biologically active on their own, and their synthetic analogues. 3,5,3'-triiodothyroacetic acid has already found clinical use in the treatment of some cases of TH resistance due to TRß mutations, and interesting results have recently been reported in patients with the Allan-Herndon-Dudley syndrome, a rare disease caused by mutations in the TH transporter MCT8. 3,5-diiodothyronine (T2) has been used with success in rat models of dyslipidemia and NAFLD, but the outcome of a clinical trial with a synthetic T2 analogue was disappointing. 3-iodothyronamine (T1AM) is the last entry in the group of active TH metabolites. Promising results have been obtained in animal models of neurological injury induced by ß-amyloid or by convulsive agents, but no clinical data are available so far.

A combined LC-MS/MS and LC-MS3 multi-method for the quantification of iodothyronines in human blood serum.

We report here a novel approach for the extraction and analysis of thyroid hormones (TH) and their metabolites (THM) from human serum samples. Our method features a compact, 96-well micro-titre plate-based pre-analytic extraction/clean-up workflow combined with an isotope dilution LC-MS/MS-MS3 analytical method. In particular, these features make possible the detection of iodothyronines at their endogenous concentrations in serum differing by a factor of ca. 104, with potential to semi-automate the pre-analytics. The method was validated by the assessment of linearity, lower limits of quantification and detection (LLOQ and LLOD respectively), intra- and inter-day accuracy, precision, process efficiency (PE), matrix effect (ME) and relative recovery (RE). Calibration curves were linear in the concentration range in sample matrix from 0.1-250 nM for T3, rT3, T4 and 3-T1AM and from 0.005-1 nM for 3,5-T2 and 3,3'-T2. Using a 200-µL sample volume, the analyte dependant LLOQ were in the range 0.005 (3,5-T2) to 0.25 (T4) nM and LLOD were between 0.002 (3,5-T2) and 0.052 nM (T4). We applied the LC-MS/MS-MS3 method to the analysis of a cross section of patients with disorders of the thyroid hormone axis. T4, T3 and rT3 concentrations (± standard deviation) were 120 ± 18, 1.9 ± 0.4 and 0.45 ± 0.09 nM respectively. 3,3'-T2 concentrations (± standard deviation) were 0.079 ± 0.022 nM; 3,5-T2 concentrations were below the LLOQ and/or LLOD in all but a single sample (0.013 nM). This method expands the analytical spectrum to endogenous thyroid hormone metabolites such as 3,5-T2 which exert biological actions and rT3 which may act as surrogate markers for disturbed thyroid hormone metabolism. Graphical abstract.

The relationship between thyroid dysfunction and nephrotic syndrome: a clinicopathological study.

Abnormalities of thyroid function are common in patients with nephrotic syndrome (NS). However, a limited number of studies have reported on the association between clinicopathologic features and thyroid dysfunction in patients with NS. We retrospectively studied 317 patients who had been definitively diagnosed with NS. The NS patients with thyroid dysfunction showed higher urine protein, creatinine and lipid levels and lower albumin and hemoglobin than those with normal thyroid function, with no significant differences of pathological types. After dividing thyroid dysfunction groups into five subgroups, interestingly, membranous nephropathy was the most common pathologic type, both in normal thyroid group and in subclinical hypothyroidism group (40.4% and 46.7%, respectively), followed by minimal change disease (28.1% and 21.7%, respectively); while in the hypothyroid, low T3, and low T3T4 groups minimal change disease is now the leading type (48.8%, 33.3% and 38.6%, respectively). High levels of urinary protein, creatinine, cholesterol, and platelets were independent risk factors predicting thyroid dysfunction, while higher albumin and hemoglobin were protective factors. We demonstrated that the type of renal pathology was different among NS patients in different thyroid dysfunction subgroups. Interpretation of the interactions between thyroid and renal function is a challenge for clinicians involved in the treatment of patients with NS.

Association Between 3-Iodothyronamine (T1am) Concentrations and Left Ventricular Function in Chronic Heart Failure.

CONTEXT: Thyroid hormone metabolites might affect the heart. The endogenous aminergic metabolite 3-iodothyronamine (T1am) reduces left ventricular ejection fraction (LVEF) in rodents. OBJECTIVE: To investigate concentration of T1am and its association with LVEF and biomarkers of heart function in patients with chronic heart failure (CHF) without thyroid disease, including patients with cardiac cachexia (nonedematous weight loss >5% over 6 months). METHODS: Cross-sectional study. CHF was characterized by LVEF <45% and symptoms. Three groups were included (n = 19 in each group, matched on age, sex, and kidney function): patients with cachexia (CAC), patients without (non-CAC), and control (C) patients with prior myocardial infarction and LVEF >45%. T1am was measured by a monoclonal antibody-based chemiluminescence immunoassay. N-amino terminal pro-BNP (NT-proBNP) concentrations were also analyzed. RESULTS: Mean (SD) LVEF: CAC, 32 ± 9%; non-CAC, 38 ± 8%; and C, 60 ± 8% (P < 0.0001). TSH, T4, and T3 levels did not differ between groups and did not correlate to T1am. Serum T1am (nmol/L) concentrations were higher in CHF: CAC (mean ± SD), 12.4 ± 6.6; non-CAC, 9.1 ± 5; and C, 7.3 ± 2.9. A negative association between T1am and LVEF was present after adjusting for sex, age, T3, and estimated glomerular filtration rate (P = 0.03). Further, serum T1am levels tended to be associated with NT-proBNP (P = 0.053). CONCLUSION: Serum T1am levels were increased in patients with CHF and numerically highest (although nonsignificant) in patients with cardiac cachexia. Increasing T1am concentrations were independently associated with reduced LVEF, suggesting a direct effect on the human heart.

Thyronamines and Derivatives: Physiological Relevance, Pharmacological Actions, and Future Research Directions.

Thyronamines (3-T1AM, T0AM) are endogenous compounds probably derived from L-thyroxine or its intermediate metabolites. Combined activities of intestinal deiodinases and ornithine decarboxylase generate 3-T1AM in vitro. Alternatively, 3-T1AM might be formed by the thyroid gland and secreted into the blood. 3-T1AM and T0AM concentrations have been determined by liquid chromatography-tandem mass spectrometry analysis (LC-MS/MS) in tissues, serum, and cell lines. However, large variations of 3-T1AM concentrations in human serum were reported by LC-MS/MS compared with a monoclonal antibody-based immunoassay. These differences might be caused by strong binding of the highly hydrophobic 3-T1AM to apolipoprotein B100. Pharmacological administration of 3-T1AM results in dose-dependent reversible effects on body temperature, cardiac function, energy metabolism, and neurological functions. The physiological relevance of these actions is unclear, but may occur at tissue concentrations close to the estimated endogenous concentrations of 3-T1AM or its metabolites T0AM or thyroacetic acid (TA1). A number of putative receptors, binding sites, and cellular target molecules mediating actions of the multi-target ligand 3-T1AM have been proposed. Among those are members of the trace amine associated receptor family, the adrenergic receptor ADRα2a, and the thermosensitive transient receptor potential melastatin 8 channel. Preclinical studies employing various animal experimental models are in progress, and more stable receptor-selective agonistic and antagonistic analogues of 3-T1AM are now available for testing. The potent endogenous thyroid hormone-derived biogenic amine 3-T1AM exerts marked cryogenic, metabolic, cardiac and central actions and represents a valuable lead compound linking endocrine, metabolic, and neuroscience research to advance development of new drugs.

Circulating 3-T1AM and 3,5-T2 in Critically Ill Patients: A Cross-Sectional Observational Study.

BACKGROUND: Critical illness is hallmarked by low circulating thyroxine (T4) and triiodothyronine (T3) concentrations, in the presence of elevated reverse T3 (rT3) and low-normal thyrotropin (TSH), referred to as nonthyroidal illness (NTI). Thyroid hormone (TH) metabolism is substantially increased during NTI, in part explained by enhanced deiodinase 3 (D3) activity. T4- and T3-sulfate concentrations are elevated, due to suppressed D1 activity in the presence of unaltered sulfotransferase activity, and 3,3'-diiodothyronine (3,3'-T2) concentrations are normal. To elucidate further the driving forces behind increased TH metabolism during NTI, two other potential T4 metabolites-3,5-diiodothyronine (3,5-T2) and 3-iodothyronamine (3-T1AM)-were measured and related to their potential TH precursors. METHODS: Morning blood samples were collected cross-sectionally from 83 critically ill patients on a University Hospital intensive care unit and from 38 demographically matched healthy volunteers. Serum TH and binding proteins were quantified with commercial assays, and 3,5-T2 and 3-T1AM with in-house developed immunoassays. RESULTS: Critically ill patients revealed, besides the NTI, a median 44% lower serum 3-T1AM concentration (p < 0.0001) and a 30% higher serum 3,5-T2 concentration (p = 0.01) than healthy volunteers did. Non-survivors and patients diagnosed with sepsis upon admission to the intensive-care unit had significantly higher 3,5-T2 (p ≤ 0.01) but comparable 3-T1AM (p > 0.2) concentrations than other patients did. Multivariable linear regression analysis adjusted for potential precursors revealed that the reduced serum 3-T1AM was positively correlated with the low serum T3 (p < 0.001) but unrelated to serum T4 or rT3. The elevated 3,5-T2 concentration did not independently correlate with TH. CONCLUSIONS: Increased TH metabolism during NTI could not be explained by increased conversion to 3-T1AM, as circulating 3-T1AM was suppressed in proportion to the concomitantly low T3 concentrations. Increased conversion of T4 and/or T3 to 3,5-T2 could be possible, as serum 3,5-T2 concentrations were elevated. Whether 3-T1AM or 3,5-T2 plays a functional role during critical illness needs further investigation.

Serum Metabonomics of Mild Acute Pancreatitis.

BACKGROUND: Mild acute pancreatitis (MAP) is a common acute abdominal disease, and exhibits rising incidence in recent decades. As an important component of systemic biology, metabonomics is a new discipline developed following genomics and proteomics. In this study, the objective was to analyze the serum metabonomics of patients with MAP, aiming to screen metabolic markers with potential diagnostic values. METHODS: An analysis platform with ultra performance liquid chromatography-high-resolution mass spectrometry was used to screen the difference metabolites related to MAP diagnosis and disease course monitoring. RESULTS: A total of 432 endogenous metabolites were screened out from 122 serum samples, and 49 difference metabolites were verified, among which 12 difference metabolites were identified by nonparametric test. After material identification, eight metabolites exhibited reliable results, and their levels in MAP serum were higher than those in healthy serum. Four metabolites exhibited gradual downward trend with treatment process going on, and the differences were statistically significant (P < 0.05). CONCLUSION: Metabonomic analysis has revealed eight metabolites with potential diagnostic values toward MAP, among which four metabolites can be used to monitor the disease course.

[Analysis of influencing factors of transient hypothyroxinemia and low T3 syndrome in premature infants].

OBJECTIVE: To investigate the influencing factors of transient hypothyroxinemia (THT) and low T3 syndrome (LT3S) in premature infants. METHOD: We have studied 418 premature infants whose gestational age was between 26 and 36 weeks.Serum thyronine (T4), triiodothyronine (T3) and thyrotropin (TSH) of them were detected on the fourteenth day approximately after birth. The patients were divided according to their serum T4, T3 and TSH into 3 groups (transient hypothyroxinemia, low T3 syndrome and normal). Then 20 Perinatal factors which may be associated with THT and LT3S were collected. The factors were analyzed by using Chi-square test and Logistic regression. RESULT: Forty-nine infants were found suffering from THT, 35 infants suffering from LT3S, and 334 infants in normal group. The prevalence rate of THT was 11.7%, and the prevalence rate of LT3S was 8.4%. Among the 20 factors, the factors related to the incidence of THT were male gender (OR = 1.863, 95%CI 0.966-3.594), albumin (OR = 2.401, 95%CI 1.294-4.455), dopamine (OR = 3.295, 95%CI 1.110-9.783) and those related to the incidence of LT3S were male gender (OR = 2.592, 95%CI 1.171-5.736), gestational age ≤ 28 wk (OR = 3.503, 95%CI 1.275-9.627). CONCLUSION: Male gender, albumin and dopamine are perinatal risk factors of THT, meanwhile, male gender and gestational age ≤ 28 wk are perinatal risk factors of LT3S.With the use of risk factors identified in our study, it may be possible to separate infants having the highest risk of THT and LT3S, so as to form optimizing treatment strategies.

Qualitative and quantitative changes in saliva among patients with thyroid dysfunction prior to and following the treatment of the dysfunction.

OBJECTIVE: Animal studies have shown thyroid dysfunction affects salivary gland functioning, however conclusive human studies are lacking. We sought to assess the qualitative and quantitative changes in saliva among subjects with thyroid dysfunction prior to and following treatment. MATERIAL AND METHODS: A longitudinal observational study of 153 newly diagnosed subjects who had hypothyroidism (n = 107) or hyperthyroidism (n = 46), aged 18-45 years, fulfilling the inclusion/exclusion criteria was conducted. Analysis of salivary parameters (stimulated salivary flow rate (SSFR), pH and buffering capacity) was performed at diagnosis (baseline), on attaining euthyroid state and 3 months thereafter. RESULTS: Subjects were 86% females, and at baseline 13% of subjects had hyposalivation. Mean SSFR, pH, buffering capacity as well as percentage of hypothyroid subjects having normal salivation increased following thyroid treatment. CONCLUSIONS: Thyroid dysfunction affects salivary gland function. Subjects with chronic hyposalivation should have thyroid function assessment if the known established causes are excluded.

Identification and quantification of 3-iodothyronamine metabolites in mouse serum using liquid chromatography-tandem mass spectrometry.

3-Iodothyronamine (T(1)AM) is an endogenous derivative of thyroxine. Recently there have been numerous reports of analytical methods to quantify endogenous T(1)AM levels, but substantial discrepancies in concentration depending on the method of analysis (LC-MS/MS or immunoassay) suggest endogenous T(1)AM may be covalently modified in vivo. Using information dependent acquisition methods to perform unbiased scans for T(1)AM metabolites following a single IP injection in mice, we have identified O-sulfonate-T(1)AM, N-acetyl-T(1)AM and T(1)AM-glucuronide as conjugates occurring in vivo, as well as the oxidatively deaminated 3-iodothyroacetic acid and non-iodinated thyroacetic acid. 3-iodothyroacetic acid, O-sulfonate-T(1)AM and T(1)AM-glucuronide are present in serum at greater concentrations that unmodified T(1)AM and all metabolites are extensively distributed to tissues. These results suggest covalent modifications of T(1)AM may play a critical role in regulating distribution and biological activity of T(1)AM, and analytical methods to quantify endogenous T(1)AM should be able to account for these metabolites as well.

3-Iodothyronamine: a modulator of the hypothalamus-pancreas-thyroid axes in mice.

BACKGROUND AND PURPOSE Preclinical pharmacology of 3-iodothyronamine (T1AM), an endogenous derivative of thyroid hormones, indicates that it is a rapid modulator of rodent metabolism and behaviour. Since T1AM undergoes rapid enzymatic degradation, particularly by MAO, we hypothesized that the effects of T1AM might be altered by inhibition of MAO. EXPERIMENTAL APPROACH We investigated the effects of injecting T1AM (i.c.v.) on (i) feeding behaviour, hyperglycaemia and plasma levels of thyroid hormones and (ii) T1AM systemic bioavailability, in overnight fasted mice, under control conditions and after pretreatment with the MAO inhibitor clorgyline. T1AM (1.3, 6.6, 13, 20 and 26 µg·kg(-1) ) or vehicle were injected i.c.v. in fasted male mice not pretreated or pretreated i.p. with clorgyline (2.5 mg·kg(-1) ). Glycaemia was measured by a glucorefractometer, plasma triiodothyronine (fT3) by a chemiluminescent immunometric assay, c-fos activation immunohistochemically and plasma T1AM by HPLC coupled to tandem-MS. KEY RESULTS T1AM, 1.3 µg·kg(-1) , produced a hypophagic effect (-24% vs. control) and reduced c-fos activation. This dose showed systemic bioavailability (0.12% of injected dose), raised plasma glucose levels and reduced peripheral insulin sensitivity (-33% vs. control) and plasma fT3 levels. These effects were not linearly related to the dose injected. Clorgyline pretreatment strongly increased the systemic bioavailability of T1AM and prevented the hyperglycaemia and reduction in fT3 induced by T1AM. CONCLUSIONS AND IMPLICATIONS T1AM induces central and peripheral effects including hyperglycaemia and a reduction in plasma fT3 levels in fasted mice. These effects critically depend on the concentration of T1AM or its metabolites in target organs.

Detection of 3-iodothyronamine in human patients: a preliminary study.

CONTEXT AND OBJECTIVE: The primary purpose of this study was to detect and quantify 3-iodothyronamine (T(1)AM), an endogenous biogenic amine related to thyroid hormone, in human blood. DESIGN: T(1)AM, total T(3), and total T(4) were assayed in serum by a novel HPLC tandem mass spectrometry assay, which has already been validated in animal investigations, and the results were related to standard clinical and laboratory variables. SETTING AND PATIENTS: The series included one healthy volunteer, 24 patients admitted to a cardiological ward, and 17 ambulatory patients suspected of thyroid disease, who underwent blood sampling at admission for routine diagnostic purposes. Seven patients were affected by type 2 diabetes, and six patients showed echocardiographic evidence of impaired left ventricular function. INTERVENTIONS: No intervention or any patient selection was performed. MAIN OUTCOME MEASURES: serum T(1)AM, total and free T(3) and T(4), routine chemistry, routine hematology, and echocardiographic parameters were measured. RESULTS: T(1)AM was detected in all samples, and its concentration averaged 0.219 ± 0.012 pmol/ml. The T(1)AM concentration was significantly correlated to total T(4) (r = 0.654, P < 0.001), total T(3) (r = 0.705, P < 0.001), glycated hemoglobin (r = 0.508, P = 0.013), brain natriuretic peptide (r = 0.543, P = 0.016), and γ-glutamyl transpeptidase (r = 0.675, P < 0.001). In diabetic vs. nondiabetic patients T(1)AM concentration was significantly increased (0.232 ± 0.014 vs. 0.203 ± 0.006 pmol/ml, P = 0.044), whereas no significant difference was observed in patients with cardiac dysfunction. CONCLUSIONS: T(1)AM is an endogenous messenger that can be assayed in human blood. Our results are consistent with the hypothesis that circulating T(1)AM is produced from thyroid hormones and encourage further investigations on the potential role of T(1)AM in insulin resistance and heart failure.

Evidence for extrathyroidal formation of 3-iodothyronamine in humans as provided by a novel monoclonal antibody-based chemiluminescent serum immunoassay.

CONTEXT: Thyronamines are thyronergic metabolites of thyroid hormones. Lack of reliable and sensitive detection methods for endogenous 3-iodothyronamine (3-T(1)AM) has so far hampered progress in understanding their physiological action and role in endocrine homeostasis or pathophysiology of diseases. OBJECTIVE: We characterized newly generated mouse monoclonal 3-T(1)AM antibodies and established a monoclonal antibody-based chemiluminescence immunoassay as a powerful tool for monitoring 3-T(1)AM levels in investigations addressing altered serum profiles and potential sites of origin and action of 3-T(1)AM in humans. DESIGN AND SETTING: Our exploratory study on 3-T(1)AM serum levels in humans measured 3-T(1)AM concentrations in comparison with thyroid hormones. PATIENTS OR OTHER PARTICIPANTS: Thirteen adult healthy subjects, 10 patients with pituitary insufficiency, and 105 thyroid cancer patients participated. INTERVENTIONS: INTERVENTIONS included l-T(4) withdrawal in patients with pituitary insufficiency as well as TSH-suppressive T(4) substitution in thyroid cancer patients. RESULTS: 3-T(1)AM was reliably quantified in human serum and stable after storage at room temperature and 4 C overnight as well as after four freeze-thaw cycles. The median serum concentration in healthy subjects was 66 ± 26 nm. 3-T(1)AM was also detected in T(4)-substituted thyroid cancer patients. Although free T(4) and T(3) significantly decreased during T(4) withdrawal, 3-T(1)AM levels remained constant for 6 d. CONCLUSION: Because higher 3-T(1)AM levels are detectable in T(4)-substituted thyroid cancer patients after thyroidectomy/radioiodine treatment compared with healthy controls, we concluded that 3-T(1)AM is mainly produced by extrathyroidal tissues. The serum profile during T(4) withdrawal suggests either a long half-life or persisting 3-T(1)AM release into serum from intracellular thyroid hormone precursors or stores.

Effects of competitive and noncompetitive showjumping on total and free iodothyronines, ß-endorphin, ACTH and cortisol levels of horses.

REASONS FOR PERFORMING STUDY: Limited knowledge exists about the differentiated effects of competitive and noncompetitive showjumping on thyroid function and relationships with hypothalamic-hypophysis-corticoadrenal hormones. OBJECTIVES: To obtain preliminary data about differentiated effects of competitive and noncompetitive showjumping on total and free iodothyronines, ß-endorphin, ACTH and cortisol of horses. MATERIAL AND METHODS: Five trained healthy jumper horses were studied during competitive and noncompetitive showjumping, performed in the same circuit design over 10 fences of 1.10 m. Hormone levels before, 5 and 30 min post exercise were recorded. Serum iodothyronines and cortisol concentrations were measured in duplicate utilising EIA kits. Serum ACTH and plasma ß-endorphin concentrations were analysed in duplicate utilising RIA kits. Two-way RM ANOVA was applied to test for effects of interaction between different type of session and time. Significant differences between post exercise and basal values were established using Bonferroni's multiple comparison test. A linear correlation analysis (Pearson's method) was performed to analyse the relationships between total and free iodothyronines and between iodothyronines and ß-endorphin, ACTH and cortisol. RESULTS: In sampling times adopted no statistical different effects of type of session were recorded on hormone variables. Sampling time affected ACTH (F = 4.25; P < 0.02) and T(4) (F = 4.43; P < 0.02) post exercise changes. During the noncompetitive session, significant correlations existed between T(4) and ß-endorphin (r = -0.56), ACTH (r = -0.65), between ß-endorphin and ACTH (r = 0.52) and between T(3) and fT(3) (r = 0.72); during competition between ß-endorphin and T(3) (r = -0.67), fT(3) (r = -0.59). CONCLUSIONS: These preliminary results could demonstrate correlations between thyroid hormones and ß-endorphin response to showjumping, although no definitive conclusion can be produced concerning the relationships between HPA and thyroid function during exercise.

Tissue distribution and cardiac metabolism of 3-iodothyronamine.

3-iodothyronamine (T1AM) is a novel relative of thyroid hormone, able to interact with specific G protein-coupled receptors, known as trace amine-associated receptors. Significant functional effects are produced by exogenous T1AM, including a negative inotropic and chronotropic effect in cardiac preparations. This work was aimed at estimating endogenous T1AM concentration in different tissues and determining its cardiac metabolism. A novel HPLC tandem mass spectrometry assay was developed, allowing detection of T1AM, thyronamine, 3-iodothyroacetic acid, and thyroacetic acid. T1AM was detected in rat serum, at the concentration of 0.3±0.03 pmol/ml, and in all tested organs (heart, liver, kidney, skeletal muscle, stomach, lung, and brain), at concentrations significantly higher than the serum concentration, ranging from 5.6±1.5 pmol/g in lung to 92.9±28.5 pmol/g in liver. T1AM was also identified for the first time in human blood. In H9c2 cardiomyocytes and isolated perfused rat hearts, significant Na+-dependent uptake of exogenous T1AM was observed, and at the steady state total cellular or tissue T1AM concentration exceeded extracellular concentration by more than 20-fold. In both preparations T1AM underwent oxidative deamination to 3-iodothyroacetic acid. T1AM deamination was inhibited by iproniazid but not pargyline or semicarbazide, suggesting the involvement of both monoamine oxidase and semicarbazide-sensitive amine oxidase. Thyronamine and thyroacetic acid were not detected in heart. Finally, evidence of T1AM production was observed in cardiomyocytes exposed to exogenous thyroid hormone, although the activity of this pathway was very low.

Validation of a liquid chromatography-tandem mass spectrometry method to enable quantification of 3-iodothyronamine from serum.

There is great interest lately in the availability of analytical methods for quantification of 3-iodothyronamine from blood and tissues. To date, no validated method for determination of 3-iodothyronamine from biological matrices has been described. Detailed in this report is an LC-MS/MS method that permits accurate and reproducible quantification of pharmacological concentrations of 3-iodothyronamine from rat serum, with a 0.0008 M lower limit of quantification. Endogenous 3-iodothyronamine was observed from rodent and human serum (0.2 mL) at the method limit of detection. In summary, the LC-MS/MS method enables quantification of circulating 3-iodothyronamine to allow examination of a relationship with biological activity.

Effect of early feed restriction on myofibre types and expression of growth-related genes in the gastrocnemius muscle of crossbred broiler chickens.

The purpose of this study was to investigate the immediate and long-term effects of early feed restriction (ER) on morphology and gene expression of lateral gastrocnemius muscle. Newly hatched crossbred broiler chickens were allocated into control and ER groups, the latter being free-fed on alternate days from hatch to 14 days of age (14 d), followed by ad libitum feeding as the control group until 63 d. The lateral gastrocnemius muscle was taken at 14 and 63 d, respectively for myofibre typing by both myosin ATPase staining and relative quantification of myosin heavy chain (MyHC) mRNA for slow-twitch (SM), red fast-twitch (FRM) and white fast-twitch (FWM) myofibres. The body weight and lateral gastrocnemius weight were significantly lower in the ER group, accompanied by significantly reduced serum triiodothyronine. The ER group exhibited significantly higher SM and FRM MyHC expression at 14 d, but lower SM expression at 63 d. Myosin ATPase staining revealed a similar pattern. The percentage of SM was higher at 14 d while lower at 63 d in the ER group. These morphological changes were accompanied by changes of mRNA expression for growth-related genes. The ER group expressed lower insulin-like growth factor I (IGF-I) and higher IGF-I receptor (IGF-IR) at 14 d, yet significantly increased growth hormone receptor and IGF-IR mRNA at 63 d. These results indicate that ER may delay the slow to fast myofibre conversion as an immediate effect, but would result in a lower percentage of slow fibres owing to compensatory growth in the long term, which involves changes of mRNA expression for the growth-related genes in the muscle.