Thyroid hormones in the pathogenesis and treatment of obesity

Synthesis and preclinical testing of a selective beta-subtype agonist of thyroid hormone receptor ZTA-261

BACKGROUND

Thyroid hormones (TH) regulate the basal metabolic rate through their receptors THRα and THRβ. TH activates lipid metabolism via THRβ, however, an excess amount of TH can lead to tachycardia, bone loss, and muscle wasting through THRα. In recent years, TH analogs that selectively bind to THRβ have gained attention as new agents for treating dyslipidemia and obesity, which continue to pose major challenges to public health worldwide.

METHODS

We developed a TH analog, ZTA-261, by modifying the existing THRβ-selective agonists GC-1 and GC-24. To determine the THRβ-selectivity of ZTA-261, an in vitro radiolabeled TH displacement assay was conducted. ZTA-261 was intraperitoneally injected into a mouse model of high-fat diet-induced obesity, and its effectiveness in reducing body weight and visceral fat, and improving lipid metabolism was assessed. In addition, its toxicity in the liver, heart, and bone was evaluated.

RESULTS

ZTA-261 is more selective towards THRβ than GC-1. Although ZTA-261 is less effective in reducing body weight and visceral fat than GC-1, it is as effective as GC-1 in reducing the levels of serum and liver lipids. These effects are mediated by the same pathway as that of T3, a natural TH, as evidenced by similar changes in the expression of TH-induced and lipid metabolism-related genes. The bone, cardiac, and hepatotoxicity of ZTA-261 are significantly lower than those of GC-1.

CONCLUSIONS

ZTA-261, a highly selective and less toxic THRβ agonist, has the potential to be used as a drug for treating diseases related to lipid metabolism.

Multifaceted physiological and therapeutical impact of curcumin on hormone-related endocrine dysfunctions: A comprehensive review

Over the past five decades, Curcumin (Cur), derived from turmeric (Curcuma longa), has gained considerable attention for its potential therapeutic applications. Synthesizing insights from clinical trials conducted over the last 25 years, this review delves into diseases where Cur has demonstrated promise, offering a nuanced understanding of its pharmacokinetics, safety, and effectiveness. Focusing on specific examples, the impact of Cur on various human diseases is explored. Endocrine glands and associated signaling pathways are highlighted, elucidating how Cur influences cellular signaling. The article underscores molecular mechanisms such as hormone level alteration, receptor interaction, cytokine and adipokine expression inhibition, antioxidant enzyme activity, and modulation of transcription factors. Cur showcases diverse protective mechanisms against inflammation and oxidative damage by suppressing antiapoptotic genes and impeding tumor promotion. This comprehensive overview emphasizes the potential of Cur as a natural agent for countering aging and degenerative diseases, calling for further dedicated research in this realm.

Effects of laparoscopic sleeve gastrectomy on thyroid hormones and relationship between metabolic parameters and long-term total weight loss

BACKGROUND

Bariatric surgery has significant effects on metabolic parameters and hormone levels. However, the specific impact of laparoscopic sleeve gastrectomy (LSG) on thyroid hormones and other metabolic parameters remains unclear. This study aimed to investigate the short and long-term effects of LSG on thyroid hormone levels, HbA1c, and other metabolic parameters.

METHODS

A total of 619 euthyroid patients without a history of thyroid disease or thyroid hormone replacement therapy were included in the study. Patients with diabetes were excluded from the study. Preoperative, 1-year postoperative, and 5-year postoperative levels of thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4), HbA1c, and other metabolic parameters were recorded and analyzed.

RESULTS

LSG resulted in significant weight loss and improvements in metabolic parameters. At 1 year postoperatively, there were significant reductions in BMI, HbA1c, TSH, fT3, and triglyceride levels, while fT4 levels increased. A statistically significant negative correlation was found between preoperative HbA1c level and percentage of total weight loss (%TWL) value at the fifth postoperative year. Additionally, a statistically significant negative correlation was found between the 5-year change in TSH and %TWL.

CONCLUSION

Being the first study to predict long-term total weight loss based on preoperative HbA1c, it is significant. This finding has important implications for personalized patient management and could aid clinicians in identifying individuals who may benefit most from sleeve gastrectomy as a treatment modality. This is valuable in that it emphasizes multidisciplinary work, including the endocrinologist and dietician.

Assessment of Metabolic Parameters in Female Triathletes with Hashimoto’s Thyroiditis in Poland

Background: Hypothyroidism is a complex disorder characterized by an increase in body weight. About 15–30% of hypothyroid patients are reported to be overweight. The triathlon is an endurance combination sport that comprises a sequential swim, cycle, and run. Triathletes must withstand high training loads with various combinations of intensity and volume. Adequate body structure, the ratio of fat and muscle tissue, and adequate hydration play a huge role. The aim of our study was to show the potential differences in metabolic parameters assessed by medical Body Composition Analyzer before the initiation of treatment with L-thyroxine and after 3 and 6 months of treatment in females who practiced triathlon and who were newly diagnosed with Hashimoto’s thyroiditis. Methods: The study group included 32 females practicing triathlon. They were recruited for 10 months from March to December 2021. Analysis of anthropometric measurements was performed using a seca device mBCA 515 medical Body Composition Analyzer. Results: We observed significant differences in FM and VAT before and after L-thyroxine treatment. We also noticed lower BMI levels after treatment, along with significant differences in thyroid function tests (TSH and fT4) carried out during the recruitment period and after 3 and 6 months of treatment. Conclusion: Due to their higher daily energy consumption, further research is needed into the treatment of Hashimoto’s thyroiditis in athletes who practice triathlon. Frequent bioelectrical impedance analysis of body composition during treatment can be very helpful.

Risk of carotid plaques according to triglyceride-glucose index stratified by thyroid function: A cross-sectional study

BACKGROUND

Recent studies have indicated that the triglyceride-glucose (TyG) index or subclinical thyroid dysfunction is associated with carotid plaques, a predictor of cardiovascular disease risk. However, evidence for this association is limited and inconsistent. This study aimed to evaluate the risk of carotid plaques according to TyG index and thyroid function status in the general population.

METHODS

A total of 2,931 individuals who underwent carotid ultrasound as part of a comprehensive health examination at the Health Promotion Center of Soonchunhyang University Hospital were retrospectively reviewed. Based on the TyG index and thyroid function status, the participants were divided into six groups: LoTyG-SHyper (low TyG index with subclinical hyperthyroidism), LoTyG-Eu (low TyG index with euthyroidism), LoTyG-SHypo (low TyG index with subclinical hypothyroidism), HiTyG-SHyper (high TyG index with subclinical hyperthyroidism), HiTyG-Eu (high TyG index with euthyroidism), and HiTyG-SHypo (high TyG index with subclinical hypothyroidism). A multivariate logistic regression analysis was conducted to determine the risk of carotid plaques.

RESULTS

The proportion of participants with significant carotid plaques was significantly different among the six groups (p<0.001, p for trend<0.001). The odds ratio (OR) and 95% confidence interval (CI) for significant carotid plaques were significantly higher in the HiTyG-SHypo group than in the LoTyG-Eu group, even after adjusting for confounding variables including sex, age, smoking, obesity, hypertension and diabetes mellitus (OR 1.506, 95% CI 1.045-2.170, p = 0.028). The OR of significant carotid plaques was higher in the HiTyG-Eu group than in the LoTyG-Eu group; however no associations were observed after additional adjustment for confounding variables.

CONCLUSION

The TyG index and thyroid function status are important predictors of the risk of carotid plaques in healthy individuals. Early evaluation of carotid plaques may be necessary for subjects with high insulin resistance and subclinical hypothyroidism.

Retrospective cohort analysis comparing changes in blood glucose level and body composition according to changes in thyroid-stimulating hormone level

BACKGROUND

In the euthyroid state, the risk of developing diabetes according to changes in thyroid-stimulating hormone (TSH) levels remains controversial. Additionally, the correlation of various body indices affecting blood glucose levels according to changes in TSH levels over a certain period is not well known.

METHODS

Patients who underwent health check-ups twice at a 2 year interval at a tertiary university hospital between 2009 and 2018 were included. By dividing baseline TSH levels into quartiles (TSH_Q1, Q2, Q3, and Q4), various variables were compared, and their changes after 2 years (∆TSH_Q1, Q2, Q3, and Q4) were confirmed.

RESULTS

Among 15 557 patients, the incidence of diabetes mellitus after 2 years was 2.4% (377/15 557 patients). There was no statistically significant difference in the incidence of diabetes according to TSH_Q (p = 0.243) or ∆TSH_Q (p = 0.131). However, as TSH levels increased, skeletal muscle mass decreased (p < 0.001), and body fat mass and percent body fat significantly increased (p < 0.001). As ∆TSH increased, ∆fasting blood glucose and ∆body mass index also significantly increased (all p < 0.001). The incidence of diabetes decreased significantly as skeletal muscle mass increased (odds ratio 0.734, p < 0.001).

CONCLUSIONS

Owing to the short study period, it was not possible to prove a statistical relationship between the incidence of diabetes mellitus and TSH levels in the euthyroid state. Significant decreases in skeletal muscle mass and increases in body mass index and body fat mass according to baseline TSH levels were demonstrated. Therefore, a focus on improving physical functions, such as increasing muscle mass and decreasing fat, is required in this case.

Application of metabolomics and network analysis to reveal the ameliorating effect of four typical “hot” property herbs on hypothyroidism rats

Herbs with a “hot” properties are frequently used to treat cold symptoms in TCM. However, the underlying mechanisms of the herbs with “hot” properties on hypothyroidism have not been investigated. This study aimed to explore four typical “hot” and “cold” property herb on hypothyroidism. Firstly, the difference efficacy between the four typical “hot” property herbs and the four typical “cold” property herbs was assessed by physical signs, thyroid function, and the metabolic profile using multivariate statistical analysis. The influence of the four typical “hot” property herbs on hypothyroidism was validated pathologically. The impact mechanism of the four typical “hot” property herbs on hypothyroidism was investigated through a metabolomics method combined with network analysis. Na⁺/K⁺-ATP, ACC1 enzyme, UCP-1, and the PI3K-Akt pathway were used to confirm the metabolite pathways and target-associated metabolites. The results showed that the four typical “hot” property herbs could significantly improve physical signs, thyroid function, and the metabolic profile in hypothyroidism rats, the four typical “cold” property herbs did not show any benefit. Moreover, the four typical “hot” property herbs could improve lipid metabolism, energy metabolism, and thyroid hormone levels by the PI3K-Akt signaling pathway, Ca²⁺- AMPK signaling pathways, purine metabolism, and tryptophan metabolism. Additionally, the levels of UCP-1, Na+/K + -ATP enzyme, and ACC1 were ameliorated by the four typical “hot” property herbs in hypothyroidism rats. Therefore, a metabolomics strategy combined with network analysis was successfully performed and interpreted the mechanism of the four typical “hot” property herbs on hypothyroidism based on the theory of “cold and hot” properties of TCM well.

Peripubertal Bisphenol A Exposure Imparts Detrimental Age-Related Changes in Body Composition, Cognition, and Hydrogen Sulfide Production Capacities

Aims: Peripubertal endocrine disruption has immediate and lifelong consequences on health, cognition, and lifespan. Disruption comes from dietary, environmental, and pharmaceutical sources. The plasticizer Bisphenol A (BPA) is one such endocrine disrupting chemical. However, it is unclear whether peripubertal BPA exposure incites long-lasting physiological, neuro-cognitive, and/or longevity-related metabolic impairments. Catabolism of cysteine via transsulfuration enzymes produces hydrogen sulfide (H2S), a redox-modulating gasotransmitter causative to endocrine and metabolic homeostasis and improved cognitive function with age. As thyroid hormone (TH) regulates hepatic H2S production and BPA is a TH receptor antagonist, we hypothesized that BPA exposure during peripubertal development impairs metabolic and neuro-cognitive/behavioral endpoints in aged mice, in part, due to altered peripheral and/or localized H2S production and redox status. Results: To test this, male C57BL/6J mice at 5 weeks of age were orally exposed daily for 5 weeks to 250 μg BPA/kg, defined as low dose group (LD BPA), or 250 mg BPA/kg, defined as high dose group (HD BPA). Both LD and HD BPA exposure decreased lean mass and increased fat mass accompanied by decreased serum total TH at advanced ages. In addition, LD BPA had an anxiogenic effect whereas HD BPA caused cognitive deficits. Notably, HD BPA disrupted tissue-specific H2S production capacities and/or protein persulfidation, with the former negatively correlated with memory deficits and oxidative stress. Innovation and Conclusion: These findings provide a potential mechanism of action for acute and long-term health impacts of BPA-induced peripubertal endocrine disruption and bolster the need for improved monitoring and limitation of adolescent BPA exposure.

The possible hormetic effects of fluorene-9-bisphenol on regulating hypothalamic-pituitary-thyroid axis in zebrafish

Fluorene-9-bisphenol (BHPF) is a bisphenol A substitute, which has been introduced for the production of so-called 'bisphenol A (BPA)-free' plastics. However, it has been reported that BHPF can enter living organisms through using commercial plastic bottles and cause adverse effects. To date, the majority of the toxicologic study of BHPF focused on investigating its doses above the toxicological threshold. Here, we studied the effects of BHPF on development, locomotion, neuron differentiation of the central nervous system (CNS), and the expression of genes in the hypothalamic-pituitary-thyroid (HPT) axis in zebrafish exposed to different doses of BHPF ranging from 1/5 of LD1 to LD50 (300, 500, 750, 1500, 3000, and 4500 nM). As a result, the possible hormetic effects of BHPF on regulating the HPT axis were revealed, in which low-dose BHPF positively affected the HPT axis while this regulation was inhibited as the dose increased. Underlying mechanism investigation suggested that BHPF disrupted myelination through affecting HPT axis including related genes expression and TH levels, thus causing neurotoxic characteristics. Collectively, this study provides the full understanding of the environmental impact of BHPF and its toxicity on living organisms, highlighting a substantial and generalized ongoing dose-response relationship with great implications for the usage and risk assessment of BHPF.

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Thyroid hormones are necessary for the normal functioning of physiological systems. Therefore, knowledge of any factor (whether genetic, environmental or intrinsic) that alters the levels of thyroid-stimulating hormone (TSH) and thyroid hormones is crucial. Genetic factors contribute up to 65% of interindividual variations in TSH and thyroid hormone levels, but many environmental factors can also affect thyroid function. This review discusses studies that have analyzed the impact of environmental factors on TSH and thyroid hormone levels in healthy adults. We included lifestyle factors (smoking, alcohol consumption, diet and exercise) and pollutants (chemicals and heavy metals). Many inconsistencies in the results have been observed between studies, making it difficult to draw a general conclusion about how a particular environmental factor influences TSH and thyroid hormone levels. However, lifestyle factors that showed the clearest association with TSH and thyroid hormones were smoking, body mass index (BMI) and iodine (micronutrient taken from the diet). Smoking mainly led to a decrease in TSH levels and an increase in triiodothyronine (T3) and thyroxine (T4) levels, while BMI levels were positively correlated with TSH and free T3 levels. Excess iodine led to an increase in TSH levels and a decrease in thyroid hormone levels. Among the pollutants analyzed, most studies observed a decrease in thyroid hormone levels after exposure to perchlorate. Future studies should continue to analyze the impact of environmental factors on thyroid function as they could contribute to understanding the complex background of gene-environment interactions underlying the pathology of thyroid diseases.

Analysis of metabolomics profile in hypothyroid patients before and after thyroid hormone replacement

PURPOSE

The serum metabolic changes occurring during the transition from hypothyroidism to euthyroidism are not known. This study aimed to determine the metabolomic profile in hypothyroid patients before (HypoT₀) and after (HypoT₁) euthyroidism achieved through levothyroxine (L-T4) treatment.

METHODS

Eighteen patients with overt primary hypothyroidism were recruited for the study. All patients were treated with L-T4 to achieve euthyroidism. Thyrotropin (TSH), free thyroxine (FT4), free triiodothyronine (FT3) and metabolomics profiles were measured before and after 3 months of treatment. The euthyroid control group consisted of 28 healthy volunteers. Metabolomics analysis was performed using Nuclear Magnetic Resonance (NMR) spectroscopy.

RESULTS

¹H NMR-based metabolomics profiling of patients with newly diagnosed hypothyroidism (HypoT₀) showed significantly higher levels of citrate, creatinine, glycerol, myo-inositol and serine, and lower levels of proline and taurine compared to controls. Interestingly, some metabolic changes were persistent three months after pharmacological treatments, despite normal serum TSH and thyroid hormone concentrations (HypoT₁). When an Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) model was built to evaluate possible differences in the metabolic profile between HypoT₀ and HypoT₁, the data obtained were not significantly different.

CONCLUSION

These results suggest that metabolic changes in the patients with hypothyroidism may persist after normalization of serum levels of FT3, FT4, and TSH, which currently represent the gold standard in laboratory testing for diagnosis and evaluation of thyroid pathology. So, the metabolomics approach may contribute to integrate classical hormone assays and to determine the euthyroid status achievement with greater efficacy.

3-Iodothyronamine and Derivatives: New Allies Against Metabolic Syndrome?

In the two decades since its discovery, a large body of evidence has amassed to highlight the potential of 3-iodothyronamine (T1AM) as an antiobesity drug, whose pleiotropic signaling actions profoundly impact energy metabolism. In the present review, we recapitulate the most relevant properties of T1AM, including its structural and functional relationship to thyroid hormone, its endogenous levels, molecular targets, as well as its genomic and non-genomic effects on metabolism elicited in experimental models after exogenous administration. The physiological and pathophysiological relevance of T1AM in the regulation of energy homeostasis and metabolism is also discussed, along with its potential therapeutic applications in metabolic disturbances. Finally, we examine a number of T1AM analogs that have been recently developed with the aim of designing novel pharmacological agents for the treatment of interlinked diseases, such as metabolic and neurodegenerative disorders, as well as additional synthetic tools that can be exploited to further explore T1AM-dependent mechanisms and the physiological roles of trace amine-associated receptor 1 (TAAR1)-mediated effects.

Hypothalamic-Pituitary-Thyroid Axis Perturbations in Male Mice by CNS-Penetrating Thyromimetics

Thyromimetics represent a class of experimental drugs that can stimulate tissue-selective thyroid hormone action. As such, thyromimetics should have effects on the hypothalamic-pituitary-thyroid (HPT) axis, but details of this action and the subsequent effects on systemic thyroid hormone levels have not been reported to date. Here, we compare the HPT-axis effects of sobetirome, a well-studied thyromimetic, with Sob-AM2, a newly developed prodrug of sobetirome that targets sobetirome distribution to the central nervous system (CNS). Similar to endogenous thyroid hormone, administration of sobetirome and Sob-AM2 suppress HPT-axis gene transcript levels in a manner that correlates to their specific tissue distribution properties (periphery vs CNS, respectively). Dosing male C57BL/6 mice with sobetirome and Sob-AM2 at concentrations ≥10 μg/kg/d for 29 days induces a state similar to central hypothyroidism characterized by depleted circulating T4 and T3 and normal TSH levels. However, despite the systemic T4 and T3 depletion, the sobetirome- and Sob-AM2-treated mice do not show signs of hypothyroidism, which may result from the presence of the thyromimetic in the thyroid hormone-depleted background.

Preoperative thyroid function and weight loss after bariatric surgery

Thyroid function has an important role on body weight regulation. However, the impact of thyroid function on weight loss after bariatric surgery is still largely unknown. We evaluated the association between preoperative thyroid function and the excess weight loss 1 year after surgery, in 641 patients with morbid obesity who underwent bariatric surgery. Patients with a history of thyroid disease, treatment with thyroid hormone or antithyroid drugs and those with preoperative evaluation consistent with overt hypothyroidism or hyperthyroidism were excluded. The preoperative levels of TSH and FT4 were not associated with weight loss after bariatric surgery. The variation of FT3 within the reference range was also not associated with weight loss. In contrast, the subgroup with FT3 above the reference range (12.3% of patients) had a significantly higher excess weight loss than patients with normal FT3. This difference remained significant after adjustment for age, sex, BMI, type of surgery, TSH and FT4. In conclusion, we observed an association between high FT3 and a greater weight loss after bariatric surgery, highlighting a group of patients with an increased benefit from this intervention. Our results also suggest a novel hypothesis: the pharmacological modulation of thyroid function may be a potential therapeutic target in patients undergoing bariatric surgery.

Serum agouti-related protein (AgRP) levels in bipolar disorder: Could AgRP be a state marker for mania?

Orexigenic and anorexigenic peptides, especially agouti-related protein (AgRP) and leptin, play important roles in the regulation of energy homeostasis in bipolar disorder. AgRP regulates energy metabolism by increasing appetite and decreasing energy expenditure. The resting energy expenditures of patients with manic bipolar disorder are higher than those of controls. Due to the effects of AgRP on energy expenditure and the increased physical activity of manic patients, we hypothesised that serum AgRP levels may be lower in manic patients than in euthymic patients and controls. There was a total of 112 participants, including 47 patients in the manic group, 35 patients in the euthymic group and 30 healthy controls. For this study, serum AgRP, leptin, cholesterol, and cortisol levels were measured and compared between the groups. The serum AgRP, leptin, and cholesterol levels were significantly different between the groups. The serum AgRP levels of manic group were significantly lower than those of euthymic and control groups. The lower serum AgRP levels of manic patients could be indicators of impaired energy homeostasis during manic episodes. Since the serum AgRP levels of manic patients are lower than those of euthymic patients and controls, AgRP could be a state marker for manic episodes.

Variations of Adipokines and Insulin Resistance in Primary Hypothyroidism

INTRODUCTION

Hypothyroidism is a common concern in endocrinology practice, which plays a significant role in metabolic and development processes. Obesity, hyperlipidaemia and hypertension may complicate hypothyroidism. Recent studies have shown that cytokines like leptin and adiponectin, secreted by adipose tissue and exert their endocrinal functions by modulating appetite, obesity and insulin sensitivity in conjunction with thyroid hormones. Interrelation between thyroid hormone, insulin resistance and adipokines are not yet clear.

AIM

To estimate serum leptin, adiponectin and insulin resistance in patients with hypothyroidism and to compare with control subjects and measure the relation between the mean value of one variable with others.

MATERIALS AND METHODS

Forty primary hypothyroidism patients and forty age and sex matched controls were selected for the study with informed consent. Fasting serum Thyroid Stimulating Hormone (TSH), leptin, adiponectin, glucose and insulin were estimated. Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) was evaluated from fasting plasma glucose and serum insulin levels. Statistical analysis was carried out using SPSS version 17.0. Unpaired t-test and regression analysis were used to compare and determine the dependence, p<0.05 was considered significant.

RESULTS

Serum TSH, leptin, adiponectin HOMA-IR were significantly higher (p<0.05) in patients with hypothyroidism (10.37±4.10, 10.97±0.60, 31.09±4.07, 3.64±0.40) than controls (2.41±2.09, 10.37±0.12, 33.32±1.44, 2.36±0.35). Regression analysis showed that leptin was significantly (p=0.054) dependent on adiponectin but not on others.

CONCLUSION

Increased oxidative stress by hypothyroid mediated leptin secretion and increased insulin resistance can down-regulate the adiponectin secretion and future complications. Serum estimation and correction of imbalance of adipokines in hypothyroidism can prevent severe consequences.

High Thyroid-stimulating Hormone Levels Increase Proinflammatory and Cardiovascular Markers in Patients with Extreme Obesity

BACKGROUND AND AIMS

Obesity is an important health problem worldwide and many studies have suggested a relationship between obesity and thyroid function, with controversial results. Interestingly, high TSH levels have been involved with the presence of inflammatory state and risk for developing cardiovascular diseases in hypothyroid and obese patients. The aim in this work was to determine the prevalence of hypothyroidism in patients with extreme obesity and to determine whether their TSH levels were related to increased serum levels of inflammatory and cardiovascular markers.

METHODS

A cross-sectional study in 101 patients with extreme obesity (BMI ≥40) was performed. Anthropometric (weight, height and waist circumference) and biochemical (fasting glucose, glycosylated hemoglobin, triglycerides, total cholesterol, LDL-C, HDL-C and insulin) parameters were measured. TSH and FT4 levels as well as clinical exploration for diagnosis of hypothyroidism were carried out. Serum concentration of IL-10, IL-6, adiponectin, resistin, leptin, ICAM-1, VCAM-1 and E-selectin were determined.

RESULTS

A high prevalence for diabetes (37.6%), prediabetes (50.5%), dyslipidemia (74.3%), hypertension (61.4%) and hypothyroidism (48.5%) was observed in patients with extreme obesity. The presence of hypothyroidism increased serum concentration of proinflammatory cytokines IL-6 and leptin and decreased the antiinflammatory cytokine adiponectin. In addition, serum TSH levels showed a correlation for waist circumference, weight, BMI, A1c, insulin, IL-6, leptin, ICAM-1 and E-selectin.

CONCLUSION

There is a high prevalence for hypothyroidism in patients with extreme obesity. High levels of TSH contribute to elevate proinflammatory and cardiovascular risk markers, increasing the risk for development of cardiovascular diseases.

Association of triiodothyronine levels with future development of metabolic syndrome in euthyroid middle-aged subjects: a 6-year retrospective longitudinal study

BACKGROUND

Several cross-sectional studies have reported that thyroid hormone levels are associated with cardiovascular risk markers and metabolic syndrome (MetS) even in euthyroid subjects. However, the prognostic role of serum thyroid hormone levels in the risk of incident MetS has not been elucidated.

AIM

We aimed to investigate the associations of baseline serum thyroid hormone levels with the development of MetS in healthy subjects.

METHODS

This 6-year, cross-sectional, longitudinal and follow-up study was conducted in 12 037 euthyroid middle-aged subjects without MetS subjected to comprehensive health examinations. Subjects were grouped according to total triiodothyronine (T3) quartiles. The hazard ratio (HR) for the development of MetS according to T3 quartiles was estimated using Cox proportional hazards model.

RESULTS

During the 6-year period, 3544 incident cases of MetS (29%) were identified. The proportion of subjects with incident MetS increased across the T3 quartiles (P for trend <0.001). The HR and 95% confidence interval (CI) for the development of MetS were significantly higher in the highest T3 quartile compared with the lowest T3 quartile even after adjusting for confounding variables including gender, age and smoking (HR: 1.238, 95% CI: 1.128-1.358, P < 0.001).

CONCLUSION

In euthyroid middle-aged subjects, serum T3 levels are associated with increased risk for future development of MetS.

Thyroid Allostasis-Adaptive Responses of Thyrotropic Feedback Control to Conditions of Strain, Stress, and Developmental Programming

The hypothalamus-pituitary-thyroid feedback control is a dynamic, adaptive system. In situations of illness and deprivation of energy representing type 1 allostasis, the stress response operates to alter both its set point and peripheral transfer parameters. In contrast, type 2 allostatic load, typically effective in psychosocial stress, pregnancy, metabolic syndrome, and adaptation to cold, produces a nearly opposite phenotype of predictive plasticity. The non-thyroidal illness syndrome (NTIS) or thyroid allostasis in critical illness, tumors, uremia, and starvation (TACITUS), commonly observed in hospitalized patients, displays a historically well-studied pattern of allostatic thyroid response. This is characterized by decreased total and free thyroid hormone concentrations and varying levels of thyroid-stimulating hormone (TSH) ranging from decreased (in severe cases) to normal or even elevated (mainly in the recovery phase) TSH concentrations. An acute versus chronic stage (wasting syndrome) of TACITUS can be discerned. The two types differ in molecular mechanisms and prognosis. The acute adaptation of thyroid hormone metabolism to critical illness may prove beneficial to the organism, whereas the far more complex molecular alterations associated with chronic illness frequently lead to allostatic overload. The latter is associated with poor outcome, independently of the underlying disease. Adaptive responses of thyroid homeostasis extend to alterations in thyroid hormone concentrations during fetal life, periods of weight gain or loss, thermoregulation, physical exercise, and psychiatric diseases. The various forms of thyroid allostasis pose serious problems in differential diagnosis of thyroid disease. This review article provides an overview of physiological mechanisms as well as major diagnostic and therapeutic implications of thyroid allostasis under a variety of developmental and straining conditions.

Identifying changes in punitive transcriptional factor binding sites from regulatory single nucleotide polymorphisms that are significantly associated with disease or sickness

AIM

To identify punitive transcriptional factor binding sites (TFBS) from regulatory single nucleotide polymorphisms (rSNPs) that are significantly associated with disease.

METHODS

The genome-wide association studies have provided us with nearly 6500 disease or trait-predisposing SNPs where 93% are located within non-coding regions such as gene regulatory or intergenic areas of the genome. In the regulatory region of a gene, a SNP can change the DNA sequence of a transcriptional factor (TF) motif and in turn may affect the process of gene regulation. SNP changes that affect gene expression and impact gene regulatory sequences such as promoters, enhancers, and silencers are known as rSNPs. Computational tools can be used to identify unique punitive TFBS created by rSNPs that are associated with disease or sickness. Computational analysis was used to identify punitive TFBS generated by the alleles of these rSNPs.

RESULTS

rSNPs within nine genes that have been significantly associated with disease or sickness were used to illustrate the tremendous diversity of punitive unique TFBS that can be generated by their alleles. The genes studied are the adrenergic, beta, receptor kinase 1, the v-akt murine thymoma viral oncogene homolog 3, the activating transcription factor 3, the type 2 demodkinase gene, the endothetal Per-Arnt-Sim domain protein 1, the lysosomal acid lipase A, the signal Transducer and Activator of Transcription 4, the thromboxane A2 receptor and the vascular endothelial growth factor A. From this sampling of SNPs among the nine genes, there are 73 potential unique TFBS generated by the common alleles compared to 124 generated by the minor alleles indicating the tremendous diversity of potential TFs that are capable of regulating these genes.

CONCLUSION

From the diversity of unique punitive binding sites for TFs, it was found that some TFs play a role in the disease or sickness being studied.

Changes in profile of lipids and adipokines in patients with newly diagnosed hypothyroidism and hyperthyroidism

Changes in profile of lipids and adipokines have been reported in patients with thyroid dysfunction. But the evidence is controversial. The present study aimed to explore the relationships between thyroid function and the profile of lipids and adipokines. A cross-sectional study was conducted in 197 newly diagnosed hypothyroid patients, 230 newly diagnosed hyperthyroid patients and 355 control subjects. Hypothyroid patients presented with significantly higher serum levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol (LDLC), fasting insulin, resistin and leptin than control (p < 0.05). Hyperthyroid patients presented with significantly lower serum levels of high-density lipoprotein cholesterol, LDLC and leptin, as well as higher levels of fasting insulin, resistin, adiponectin and homeostasis model insulin resistance index (HOMA-IR) than control (p < 0.05). Nonlinear regression and multivariable linear regression models all showed significant associations of resistin or adiponectin with free thyroxine and association of leptin with thyroid-stimulating hormone (p < 0.001). Furthermore, significant correlation between resistin and HOMA-IR was observed in the patients (p < 0.001). Thus, thyroid dysfunction affects the profile of lipids and adipokines. Resistin may serve as a link between thyroid dysfunction and insulin resistance.

Thyroid hormonal status among children with obesity

BACKGROUND

It is presumed that free T4 and thyroid-stimulating hormone (TSH) levels are related to obesity, but the findings are inconsistent. In this study we evaluated T4 and TSH concentrations between normal children and those with obesity and possible correlations between body mass index (BMI) and these markers.

METHODS

In this prospective study, 190 children who were overweight and obese and 133 children without obesity of the same age and sex were evaluated. Thyroid function tests (TSH, total T4, free T4 and free T3) were measured in all subjects in both groups. Thyroid antibodies (thyroid peroxidase and thyroglobulin) were determined among those with elevated TSH levels.

RESULTS

Levels of TSH and total T4 were significantly higher in children with obesity compared with the control group. Subclinical hypothyroidism was significantly higher in children with obesity (14.7%) compared with normal subjects (6.8%, p = 0.02). Among children with obesity and increased TSH levels, 10.7% had positive thyroid peroxidase and thyroglobulin antibodies. There was significantly positive correlation between BMI z score and TSH level (r = 0.198, p < 0.001) and T4 level (r = 0.18, p = 0.001).

CONCLUSION

TSH and total T4 levels are increased in children who are overweight or obese and are a common finding in these children, but the incidence of thyroid antibodies is low in these patients and so could not be accounted for by thyroid autoimmunity. Due to these findings it is possible that increased TSH and total T4 levels are a consequence of obesity and could be reduced by decreasing BMI.

Modulation of gene expression by 3-iodothyronamine: genetic evidence for a lipolytic pattern

3-Iodothyronamine (T1AM) is an endogenous biogenic amine, structurally related to thyroid hormone, which is regarded as a novel chemical messenger. The molecular mechanisms underlying T1AM effects are not known, but it is possible to envisage changes in gene expression, since delayed and long-lasting phenotypic effects have been reported, particularly with regard to the modulation of lipid metabolism and body weight. To test this hypothesis we analysed gene expression profiles in adipose tissue and liver of eight rats chronically treated with T1AM (10 mg/Kg twice a day for five days) as compared with eight untreated rats. In vivo T1AM administration produced significant transcriptional effects, since 378 genes were differentially expressed in adipose tissue, and 114 in liver. The reported changes in gene expression are expected to stimulate lipolysis and beta-oxidation, while inhibiting adipogenesis. T1AM also influenced the expression of several genes linked to lipoprotein metabolism suggesting that it may play an important role in the regulation of cholesterol homeostasis. No effect on the expression of genes linked to toxicity was observed. The assay of tissue T1AM showed that in treated animals its endogenous concentration increased by about one order of magnitude, without significant changes in tissue thyroid hormone concentration. Therefore, the effects that we observed might have physiological or pathophysiological importance. Our results provide the basis for the reported effectiveness of T1AM as a lipolytic agent and gain importance in view of a possible clinical use of T1AM in obesity and/or dyslipidaemia.

A thyroid hormone challenge in hypothyroid rats identifies T3 regulated genes in the hypothalamus and in models with altered energy balance and glucose homeostasis

BACKGROUND

The thyroid hormone triiodothyronine (T3) is known to affect energy balance. Recent evidence points to an action of T3 in the hypothalamus, a key area of the brain involved in energy homeostasis, but the components and mechanisms are far from understood. The aim of this study was to identify components in the hypothalamus that may be involved in the action of T3 on energy balance regulatory mechanisms.

METHODS

Sprague Dawley rats were made hypothyroid by giving 0.025% methimazole (MMI) in their drinking water for 22 days. On day 21, half the MMI-treated rats received a saline injection, whereas the others were injected with T3. Food intake and body weight measurements were taken daily. Body composition was determined by magnetic resonance imaging, gene expression was analyzed by in situ hybridization, and T3-induced gene expression was determined by microarray analysis of MMI-treated compared to MMI-T3-injected hypothalamic RNA.

RESULTS

Post mortem serum thyroid hormone levels showed that MMI treatment decreased circulating thyroid hormones and increased thyrotropin (TSH). MMI treatment decreased food intake and body weight. Body composition analysis revealed reduced lean and fat mass in thyroidectomized rats from day 14 of the experiment. MMI treatment caused a decrease in circulating triglyceride concentrations, an increase in nonesterified fatty acids, and decreased insulin levels. A glucose tolerance test showed impaired glucose clearance in the thyroidectomized animals. In the brain, in situ hybridization revealed marked changes in gene expression, including genes such as Mct8, a thyroid hormone transporter, and Agrp, a key component in energy balance regulation. Microarray analysis revealed 110 genes to be up- or downregulated with T3 treatment (± 1.3-fold change, p<0.05). Three genes chosen from the differentially expressed genes were verified by in situ hybridization to be activated by T3 in cells located at or close to the hypothalamic ventricular ependymal layer and differentially expressed in animal models of long- and short-term body weight regulation.

CONCLUSION

This study identified genes regulated by T3 in the hypothalamus, a key area of the brain involved in homeostasis and neuroendocrine functions. These include genes hitherto not known to be regulated by thyroid status.

Regulatory SNPs and transcriptional factor binding sites in ADRBK1, AKT3, ATF3, DIO2, TBXA2R and VEGFA

Abstract Regulatory single nucleotide polymorphisms (rSNPs) which change the transcriptional factor binding sites (TFBS) for transcriptional factors (TFs) to bind DNA were reviewed for the ADRBK1 (GRK2), AKT3, ATF3, DIO2, TBXA2R and VEGFA genes. Changes in the TFBS where TFs attach to regulate these genes may result in human sickness and disease. The highlights of this previous work were reviewed for these genes.

Central body fat changes in men affected by post-surgical hypogonadotropic hypogonadism undergoing testosterone replacement therapy are modulated by androgen receptor CAG polymorphism

BACKGROUND AND AIMS

Little is known about the effect of androgen receptor (AR) gene CAG repeat polymorphism in conditioning body composition changes after testosterone replacement therapy (TRT). In this study, we aimed to clarify this aspect by focussing our attention on male post-surgical hypogonadotropic hypogonadism, a condition often associated with partial or total hypopituitarism.

METHODS AND RESULTS

Fourteen men affected by post-surgical hypogonadotropic hypogonadism and undergoing several replacement hormone therapies were evaluated before and after TRT. Dual-energy X-ray absorptiometry (DEXA)-derived body composition measurements, pituitary-dependent hormones and AR gene CAG repeat polymorphism were considered. While testosterone and insulin-like growth factor-1 (IGF-1) levels increased after TRT, cortisol concentration decreased. No anthropometric or body composition parameters varied significantly, except for abdominal fat decrease. The number of CAG triplets was positively and significantly correlated with this abdominal fat decrease, while the opposite occurred between the latter and Δ-testosterone. No correlation of IGF-1 or cortisol variation (Δ-) with Δ-abdominal fat was found. At multiple linear regression, after correction for Δ-testosterone, the positive association between CAG triplet number and abdominal fat change was confirmed.

CONCLUSIONS

In male post-surgical hypogonadotropic hypogonadism, shorter length of AR CAG repeat tract is independently associated with a more marked decrease of abdominal fat after TRT.

Thyroid hormone, thyromimetics, and metabolic efficiency

Thyroid hormone (TH) has long been recognized as a major modulator of metabolic efficiency, energy expenditure, and thermogenesis. TH effects in regulating metabolic efficiency are transduced by controlling the coupling of mitochondrial oxidative phosphorylation and the cycling of extramitochondrial substrate/futile cycles. However, despite our present understanding of the genomic and nongenomic modes of action of TH, its control of mitochondrial coupling still remains elusive. This review summarizes historical and up-to-date findings concerned with TH regulation of metabolic energetics, while integrating its genomic and mitochondrial activities. It underscores the role played by TH-induced gating of the mitochondrial permeability transition pore (PTP) in controlling metabolic efficiency. PTP gating may offer a unified target for some TH pleiotropic activities and may serve as a novel target for synthetic functional thyromimetics designed to modulate metabolic efficiency. PTP gating by long-chain fatty acid analogs may serve as a model for such strategy.

The effect of vitamin A supplementation on thyroid function in premenopausal women

OBJECTIVE

Vitamin A and its retinoid derivates play an important role in regulation of normal growth and development. Vitamin A has been shown to regulate thyroid hormone metabolism and inhibit thyroid-stimulating hormone (TSH) secretion via down regulation of TSH-β gene expression; however, the effect of vitamin A on thyroid function in obese individuals who are at higher risk of subclinical hypothyroidism is still unclear. In the present study we investigate the impact of vitamin A supplementation on thyroid function in obese women.

METHOD

A 4-month randomized, double blind controlled trial was conducted among 84 healthy women aged 17-50 years old: 56 were obese (body mass index [BMI] 30-35 kg/m(2)) and 28 were nonobese (BMI 18.5-24.9 kg/m(2)). Obese women were randomly allocated to receive either vitamin A (25,000 IU/d retinyl palmitate) or placebo. Nonobese women received vitamin A. At baseline and 4 months after intervention, serum concentrations of TSH, total thyroxine (T4), total triiodothyronine (T3), retinol-binding protein (RBP), and transthyretin (TTR) were measured.

RESULTS

Baseline concentrations of thyroid hormones, RBP and TTR were not significantly different between groups. Vitamin A caused a significant reduction in serum TSH concentrations in obese (p = 0.004) and nonobese (p = 0.001) groups. Serum T3 concentrations also increased in both obese and nonobese vitamin A-treated groups (p < 0.001). Serum T4 decreased in all 3 groups after treatment. The results showed a significant reduction in serum RBP in the obese group after vitamin A supplementation (p = 0.007), but no significant change was seen in serum TTR.

CONCLUSIONS

Serum TSH concentrations in vitamin A-treated subjects were significantly reduced; therefore, vitamin A supplementation might reduce the risk of subclinical hypothyroidism in premenopausal women.

Correction of hypothyroidism seems to have no effect on body fat

Aim. We aimed to observe the effects of L-thyroxine replacement therapy on body fat content determined with various anthropometric methods and a bioelectrical impedance analysis method in patients with hypothyroidism. Methods. Forty-two women with naive autoimmune hypothyroidism were included. Also, 40 healthy participants were enrolled as a control group. Weight, body mass index, waist circumference, and subscapulary, suprailiac, femur, biceps, and triceps skin fold thicknesses were measured. Body fat percentages were calculated and body fat measurements were performed. Euthyroidism was maintained with L-thyroxine. At the 6th and 18th month, of therapy, measurements were reperformed. Results. Mean TSH levels were 57.49 ± 36.46 mIU/L in hypothyroid group and 1.94 ± 1.12 mIU/L in control subjects at admission. In hypothyroid patients, calculated body fat percentages were greater than those of the control subjects during follow-up. Body fat percentage of each hypothyroid case decreased at 6- and 18-month controls, but the decrements were statistically insignificant. Although skin fold thicknesses measured from all sites were observed to decline, only those obtained from femur and biceps showed a significant decrease (P = 0.03 and P = 0.01, resp.). Discussion. Correction of hypothyroidism did not cause any improvement in body weight and body fat percentage. The decrease in skin fold thicknesses might probably result from the reduction in subcutaneous mucopolysaccharide deposits.

Association between novel adipocytokines adiponectin, vaspin, visfatin, and thyroid: An experimental and clinical update

Adipose tissue secretes a variety of active biological substances, called adipocytokines, that act in an autocrine, paracrine, and endocrine manner. They have roles in appetite control, thermogenesis, and thyroid and reproductive functions. All these molecules may lead to local and generalized inflammation, mediating obesity-associated vascular disorders including hypertension, diabetes, atherosclerosis, and insulin resistance. Thyroid dysfunction is associated with changes in body weight, thermogenesis, and energy expenditure. The connections between cardiovascular risk factors such as dyslipidemia, impaired glucose tolerance, insulin resistance, atherosclerosis, and thyroid dysfunction have been reported in several studies. The adipocytokines serve as causative or protective factors in the development of these disorders in the states of thyroid dysfunction. Abnormal levels of adipocytokines (adiponectin (ADP), leptin, resistin, vaspin, and visfatin) in hypo- and hyperthyroidism have been reported with controversial results. This review aims to update the implication of novel adipokines ADP, vaspin, and visfatin in thyroid dysfunction.

Inverse association between serum free thyroxine levels and hepatic steatosis: results from the Study of Health in Pomerania

BACKGROUND

Associations between thyroid function and hepatic steatosis defined by enzymatic and sonographic criteria are largely unknown in the general population. Thus, the aim of the present study was to investigate the association between thyroid function tests and sonographic as well as enzymatic criteria of liver status in a large population-based study, the Study of Health in Germany (SHIP).

METHODS

Data from 3661 SHIP participants without a self-reported history of thyroid or liver disease were analyzed. Hepatic steatosis was defined as the presence of a hyperechogenic ultrasound pattern of the liver and increased serum alanine transferase concentrations. Serum thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) concentrations were associated with hepatic steatosis using multinomial regression models adjusted for sex, age, physical activity, alcohol consumption, waist circumference, and food intake pattern.

RESULTS

We detected no consistent association of serum TSH and FT3 concentrations with hepatic steatosis. In contrast, serum FT4 concentrations were inversely associated with hepatic steatosis in men (odds ratio (OR)=0.04 [95% confidence interval (CI)=0.01; 0.17]) and women (OR=0.06 [95% CI=0.01; 0.42]).

CONCLUSIONS

Results from the present cross-sectional study suggest that low FT4 concentrations are associated with hepatic steatosis. Longitudinal and intervention studies are warranted to investigate whether hypothyroidism increases the risk of hepatic steatosis or vice versa.

Experimental hyperthyroidism decreases gene expression and serum levels of adipokines in obesity

Aims. To analyze the influence of hyperthyroidism on the gene expression and serum concentration of leptin, resistin, and adiponectin in obese animals. Main Methods. Male Wistar rats were randomly divided into two groups: control (C)—fed with commercial chow ad libitum—and obese (OB)—fed with a hypercaloric diet. After group characterization, the OB rats continued receiving a hypercaloric diet and were randomized into two groups: obese animals (OB) and obese with 25 μg triiodothyronine (T₃)/100 BW (OT). The T₃ dose was administered every day for the last 2 weeks of the study. After 30 weeks the animals were euthanized. Samples of blood and adipose tissue were collected for biochemical and hormonal analyses as well as gene expression of leptin, resistin, and adiponectin. Results. T₃ treatment was effective, increasing fT₃ levels and decreasing fT₄ and TSH serum concentration. Administration of T₃ promotes weight loss, decreases all fat deposits, and diminishes serum levels of leptin, resistin, and adiponectin by reducing their gene expression. Conclusions. Our results suggest that T₃ modulate serum and gene expression levels of leptin, resistin, and adiponectin in experimental model of obesity, providing new insights regarding the relationship between T₃ and adipokines in obesity.

Association analyses of variants in the DIO2 gene with early-onset type 2 diabetes mellitus in Pima Indians

BACKGROUND

The type 2 deiodinase gene (DIO2) encodes a deiodinase that converts the thyroid prohormone, thyroxine, to the biologically active triiodothyronine. Thyroid hormones regulate energy balance and may also influence glucose metabolism. Therefore, we hypothesized that variations in DIO2 could contribute to obesity or type 2 diabetes mellitus (T2DM) in Pima Indians.

METHODS

Sequencing of the DIO2 gene in DNA from 83 Pima Indians identified 12 single-nucleotide polymorphisms (SNPs). Several of these SNPs were in perfect genotypic concordance among the 83 samples that were sequenced, and all 12 could be divided into five linkage disequilibrium groups. One representative SNP from each group (Thr92Ala, rs225011, rs225015, rs6574549, and a rare 5' flanking SNP) was selected for further genotyping for association analyses. In this study, the five selected variants in DIO2, as described above, were genotyped in three groups of Pima Indians: (i) a case (n=150)/control (n=150) group for early-onset T2DM (onset age <25 years); (ii) a case (n=362)/control (n=127) group for obesity; (iii) a large (n=1,311, cases n=810/controls n=501) family-based group, of which 256 nondiabetic subjects had undergone detailed metabolic phenotyping.

RESULTS

The Thr92Ala variant common in Pima Indians, rs225011, and rs225015 were modestly associated with early-onset T2DM (p=0.01-0.04) in the case-control study, but were not associated with obesity in the obesity case-control study, nor associated with T2DM (at any age) or body-mass index (BMI; as a quantitative trait) in the family-based analysis. Thr92Ala, rs225011, rs225015, and rs6574549 were also nominally associated with hepatic glucose output (p=0.02). rs6574549 was associated with fasting insulin (p=0.02), insulin action (p=0.04), and energy expenditure (p=0.02). None of these nominal associations remained statistically significant after corrections for multiple testing.

CONCLUSIONS

We propose that variation in DIO2 may have a subtle role in altering metabolic processes that lead to early-onset T2DM, but this gene does not have a large impact on T2DM at older ages, nor does DIO2 influence BMI in the Pima Indian population.

Lower free thyroxin associates with a less favorable metabolic phenotype in healthy pregnant women

CONTEXT

A lower free T(4) (fT4), within the euthyroid range, has been shown in adults to associate with an adverse metabolic phenotype. Thyroid physiology changes significantly during gestation and affects maternal and fetal well-being.

OBJECTIVE

The aim of the study was to test the hypothesis that a lower serum fT4 in healthy euthyroid pregnant women is related to a less favorable metabolic phenotype and to fetal or placental weight. DESIGN, SETTING, PATIENTS, AND OUTCOME MEASURES: We examined associations of thyroid function tests (TSH and fT4) and the free T(3) (fT3)-to-fT4 ratio (as a proxy of deiodinase activity) with a metabolic profile [preload and postload glucose, glycosylated hemoglobin (HbA1c), high molecular-weight (HMW)-adiponectin, homeostasis model of assessment for insulin resistance (HOMA-IR), and serum lipids] in 321 healthy pregnant women. All women were euthyroid and had negative anti-thyroid peroxidase antibodies. None received thyroid hormone replacement. Blood tests were performed in women between 24 and 28 wk gestation. Placentas and newborns were weighed at birth.

RESULTS

Circulating TSH did not relate to metabolic parameters, but decreasing fT4 and increasing fT3-to-fT4 ratio associated with a less favorable metabolic phenotype, as judged by higher postload glucose, HbA1c, fasting insulin, HOMA-IR, and triglycerides, and by a lower HMW-adiponectinemia (all P ≤ 0.005). In multiple regression analyses, fT4 was independently associated with HbA1c (β = -0.135; P = 0.038), HMW-adiponectin (β = 0.218; P < 0.001), and placental weight (β = -0.185; P < 0.005), whereas the fT3-to-fT4 ratio was independently associated with maternal body mass index (β = 0.265; P < 0.001), HMW-adiponectinemia (β = -0.237; P < 0.002), HOMA-IR (β = 0.194; P = 0.014), and placental weight (β = 0.174; P = 0.020).

CONCLUSION

In pregnant women without a history of thyroid dysfunction, lower concentrations of fT4 and a higher conversion of fT4 to fT3, as inferred by changes in the fT3-to-fT4 ratio, were found to be associated with a less favorable metabolic phenotype and with more placental growth.

The role of hypothalamic tri-iodothyronine availability in seasonal regulation of energy balance and body weight

Seasonal cycles of body weight provide a natural model system to understand the central control of energy balance. Studies of such cycles in Siberian hamsters suggest that a change in the hypothalamic availability of thyroid hormone is the key determinant of annual weight regulation. Uptake of thyroid hormone into the hypothalamus from the peripheral circulation occurs largely through a specific monocarboxylate transporter expressed by tanycyte cells lining the third ventricle. Tanycytes are the principal brain cell type expressing type II and type III deiodinases, so they control the local concentrations of T4, T3, and inactive metabolites. Type III deiodinase mRNA in tanycytes is photoperiodically upregulated in short photoperiod. This would be expected to reduce the availability of T3 in the hypothalamus by promoting the production of inactive metabolites such as rT3. Experimental microimplantation of T3 directly into the hypothalamus during short-days promotes a long-day phenotype by increasing food intake and body weight without affecting the peripheral thyroid axis. Thus, thyroid hormone exerts anabolic actions within the brain that play a key role in the seasonal regulation of body weight. Understanding the precise actions of thyroid hormone in the brain may identify novel targets for long-term pharmacological manipulation of body weight.

Serum TSH related to measures of body mass: longitudinal data from the HUNT Study, Norway

OBJECTIVE

Thyroid function and body mass are related, but the causal relationship remains unclear. Our objective was to investigate the longitudinal relationship between thyroid stimulating hormone (TSH) and body mass measures [body weight, body mass index (BMI), waist circumference (WC) and waist-hip-ratio (WHR)].

DESIGN

We used data from two waves of a population-based study: HUNT 2 (1995-1997) and 3 (2006-2008). Average follow-up time was 10·5 years. Multivariable general linear and logistic regression models were used to assess the relation between TSH and the body mass measures.

PARTICIPANTS

In total 9954 women and 5066 men without self-reported thyroid disease and TSH within the reference range (0·5-3·5 mU/l) at baseline and <10 mU/l at follow-up.

RESULTS

For each mU/l increase in TSH among women, weight increased 0·9 kg (95% CI 0·8, 1·1), BMI 0·3 kg/m(2) (95% CI 0·3, 0·4) and WC 0·6 cm (95% CI 0·3, 0·8). In men, the corresponding figures were 0·8 kg (95% CI 0·5, 1·0), 0·2 kg/m(2) (95% CI 0·2, 0·3) and 0·5 cm (95% CI 0·2, 0·8). In line with this, a weight gain of more than 5 kg was associated with a TSH increase of 0·08 mU/l (95% CI 0·06, 0·11) in women and 0·15 mU/l (95% CI 0·12, 0·18) in men. Women who lost more than 5 kg decreased their TSH by 0·12 mU/l (95% CI 0·09, 0·16) and men by 0·03 mU/l (95% CI -0.02, 0·09).

CONCLUSION

Weight gain is accompanied by increasing TSH, and weight loss in women is related to decreasing TSH.

TRC150094, a novel functional analog of iodothyronines, reduces adiposity by increasing energy expenditure and fatty acid oxidation in rats receiving a high-fat diet

Chronic overnutrition and modern lifestyles are causing a worldwide epidemic of obesity and associated comorbidities, which is creating a demand to identify underlying biological mechanisms and to devise effective treatments. In rats receiving a high-fat diet (HFD), we analyzed the effects of a 4-wk administration of a novel functional analog of iodothyronines, TRC150094 (TRC). HFD-TRC rats exhibited increased energy expenditure (+24% vs. HFD rats; P<0.05) and body weight (BW) gain comparable to that of standard chow-fed (N) rats [N, HFD, and HFD-TRC rats, +97 g, +140 g (P<0.05 vs. N), and +98 g (P<0.05 vs. HFD)]. HFD-TRC rats had significantly less visceral adipose tissue (vs. HFD rats) and exhibited altered metabolism in two major tissues that are very active metabolically. In liver, mitochondrial fatty acid import and oxidation were increased (+56 and +32%, respectively; P<0.05 vs. HFD rats), and consequently the hepatic triglyceride content was lower (-35%; P<0.05 vs. HFD rats). These effects were independent of the AMP-activated protein kinase-acetyl CoA-carboxylase-malonyl CoA pathway but involved sirtuin 1 activation. In skeletal muscle, TRC induced a fiber shift toward the oxidative type in tibialis anterior muscle, increasing its capacity to oxidize fatty acids. HFD-TRC rats had lower (vs. HFD rats) plasma cholesterol and triglyceride concentrations. If reproduced in humans, these results will open interesting possibilities regarding the counteraction of metabolic dysfunction associated with ectopic/visceral fat accumulation.

Regulation of the hypothalamic thyrotropin releasing hormone (TRH) neuron by neuronal and peripheral inputs

The hypothalamic-pituitary-thyroid (HPT) axis plays a critical role in mediating changes in metabolism and thermogenesis. Thus, the central regulation of the thyroid axis by Thyrotropin Releasing Hormone (TRH) neurons in the paraventricular nucleus of the hypothalamus (PVN) is of key importance for the normal function of the axis under different physiological conditions including cold stress and changes in nutritional status. Before the TRH peptide becomes biologically active, a series of tightly regulated processes occur including the proper folding of the prohormone for targeting to the secretory pathway, its post-translational processing, and targeting of the processed peptides to the secretory granules near the plasma membrane of the cell ready for secretion. Multiple inputs coming from the periphery or from neurons present in different areas of the brain including the hypothalamus are responsible for the activation or inhibition of the TRH neuron and in turn affect the output of TRH and the set point of the axis.

Thyroid hormone exerts negative feedback on hypothalamic type 4 melanocortin receptor expression

The type 4 melanocortin receptor MC4R, a key relay in leptin signaling, links central energy control to peripheral reserve status. MC4R activation in different brain areas reduces food intake and increases energy expenditure. Mice lacking Mc4r are obese. Mc4r is expressed by hypothalamic paraventricular Thyrotropin-releasing hormone (TRH) neurons and increases energy usage through activation of Trh and production of the thyroid hormone tri-iodothyronine (T(3)). These facts led us to test the hypothesis that energy homeostasis should require negative feedback by T(3) on Mc4r expression. Quantitative PCR and in situ hybridization showed hyperthyroidism reduces Mc4r mRNA levels in the paraventricular nucleus. Comparative in silico analysis of Mc4r regulatory regions revealed two evolutionarily conserved potential negative thyroid hormone-response elements (nTREs). In vivo ChIP assays on mouse hypothalamus demonstrated association of thyroid hormone receptors (TRs) with a region spanning one nTRE. Further, in vivo gene reporter assays revealed dose-dependent T(3) repression of transcription from the Mc4r promoter in mouse hypothalamus, in parallel with T(3)-dependent Trh repression. Mutagenesis of the nTREs in the Mc4r promoter demonstrated direct regulation by T(3), consolidating the ChIP results. In vivo shRNA knockdown, TR over-expression approaches and use of mutant mice lacking specific TRs showed that both TRalpha and TRbeta contribute to Mc4r regulation. T(3) repression of Mc4r transcription ensures that the energy-saving effects of T(3) feedback on Trh are not overridden by MC4R activation of Trh. Thus parallel repression by T(3) on hypothalamic Mc4r and Trh contributes to energy homeostasis.

[Factors associated with low cardiometabolic risk in obese women]

OBJECTIVE

To identify factors associated with low cardiometabolic risk (CMR) in obese women (O(b)W) seen at outpatient specialty clinics of SUS (Brazilian Social Security Health System), in the City of Salvador, Bahia, Brazil.

SUBJECTS AND METHODS

Case-control study, matched by age, of 306 O(b)W (BMI > or = 30 kg/m(2)), including 66 (21. 6%) cases - normotensive, normolipidemic and nondiabetic patients - and 240 (78.4%) controls. Secondary data were obtained from clinical records, and primary data were collected by means of a household survey and laboratory assays. Descriptive, bivariate, and conditional logistic regression analyses were conducted.

RESULTS

A positive, statistically significant association was found between low CMR and a diet containing the desirable ingestion of fruit (AOR = 20. 1, CI 95% 5.6-71.9); 1st CRP quartile (AOR = 4. 1, CI 95% 2.0-8. 3), and 3rd and 4th AdipoQ quartiles (AOR = 2.3, CI 95% 1.1-4. 8).

CONCLUSION

This study suggests that a diet rich in soluble fibers as well as lower levels of CRP, and higher levels of AdipoQ, encumber, retard or impede the emergence of other metabolic risk factors or metabolic diseases in O(b)W.

Circulating adiponectin concentrations were related to free thyroxine levels in thyroid cancer patients after thyroid hormone withdrawal

Because it is unclear whether adipose-derived hormones are related to thyroid hormone metabolism, this study evaluated the relationship between adiponectin concentrations and changes in the thyroid hormones in athyreotic patients after thyroid hormone withdrawal. Twenty-eight athyreotic thyroid cancer patients (4 male and 24 female; mean age, 52.2 +/- 11.3 years) were analyzed on the final day of levothyroxine treatment and 1 day before serum thyroglobulin and radioiodine scanning examinations after an average of 4 weeks of thyroid hormone withdrawal. Evaluations included analysis of thyroid function test, serum adiponectin, body composition by bioimpedance analysis, and insulin sensitivity index as determined by the homeostasis model assessment of insulin resistance (HOMA-IR). Discontinuation of thyroid hormone treatment resulted in a significant change in thyroid-stimulating hormone (82.1 +/- 9.8 vs 1.0 +/- 0.4 mL/L, P < .05), free thyroxine (FT4) (5.7 +/- 0.4 vs 18.7 +/- 2.3 pmol/L, P < .05), and free triiodothyronine levels (1.8 +/- 0.2 vs 3.4 +/- 0.2 pmol/L, P < .05) as compared with the prewithdrawal values, whereas circulating adiponectin levels (5.7 +/- 0.6 vs 5.4 +/- 0.6 mg/L), body fat mass (20.3 +/- 1.2 vs 19.4 +/- 1.2 kg), and insulin sensitivity index (1.8 +/- 0.2 vs 2.2 +/- 0.3) remained unaltered. A positive correlation between adiponectin and FT4 (r = 0.61, P < .01) independent of age, sex, fat body mass, HOMA-IR, and other potential covariates known to affect thyroid hormone metabolism, such as renal and liver functions, was observed after thyroid hormone withdrawal. In addition, baseline circulating adiponectin levels were correlated with a diminished postwithdrawal reduction of FT4 concentrations after adjusting for baseline FT4 levels and changes in body mass index, fat body mass, and HOMA-IR (r = 0.71, P < .01). In conclusion, adiponectin concentrations were associated with FT4 levels in the athyreotic patients after thyroid hormone withdrawal. The relevant roles of adiponectin in the regulation of thyroid hormone metabolism require further investigation.

Reimbursed drugs in patients with sleep-disordered breathing: A static-charge-sensitive bed study

BACKGROUND

Co-morbidities in men and women with sleep-disordered breathing (SDB) were compared retrospectively to an age-standardized, general Finnish population. The prevalence of diseases was based on the reimbursement refunds of medications.

METHODS

Two hundred thirty-three age- and BMI-matched male-female pairs and 368 consecutive women identified from our sleep recording database were included. Data on medication were gathered from the National Agency for Medicines and Social Insurance Institution database.

RESULTS

Men with SDB had three-fold prevalence of reimbursed medication for diabetes and two-fold prevalence of reimbursed medication for chronic arrhythmia. Women with SDB had three-fold prevalence of reimbursed medication for thyroid insufficiency, and postmenopausal women had two-fold prevalence of reimbursed medication for psychosis. BMI and age did not explain prevalence of reimbursed medications for chronic arrhythmia or psychosis. In both genders with SDB, prevalence of reimbursed medications compared to the general population was two-fold for hypertension and seven-fold for asthma and/or chronic obstructive pulmonary disease (COPD). Partial upper airway obstruction was associated with three-fold prevalence of reimbursed medication for asthma and/or COPD in both genders and 60% reduced prevalence of reimbursed medication for hypertension in females matched for age and BMI.

CONCLUSIONS

Co-morbidity profile differed between genders. Our results emphasize the importance of diagnosis and treatment of co-morbidities and partial upper airway obstruction.

T3 and the thyroid hormone beta-receptor agonist GC-1 differentially affect metabolic capacity and oxidative damage in rat tissues

We compared the changes in tissue aerobic metabolism and oxidative damage elicited by hypothyroid rat treatment with T3 and its analog GC-1. Aerobic capacities, evaluated by cytochrome oxidase activities, were increased more by T3 than by GC-1. Furthermore, the response of the tissues to T3 was similar, whereas the response to GC-1 was high in liver, low in muscle and scarce in heart. Both treatments induced increases in ADP-stimulated O2 consumption, which were consistent with those in aerobic capacities. However, unlike T3, GC-1 differentially affected pyruvate/malate- and succinate-supported respiration, suggesting that respiratory chain components do not respond as a unit to GC-1 stimulation. According to the positive relationship between electron carrier levels and rates of mitochondrial generation of oxidative species, the most extensive damage to lipids and proteins was found in T3-treated rats. Examination of antioxidant enzyme activities and scavenger levels did not clarify whether oxidative damage extent also depended on different antioxidant system effectiveness. Conversely, the analysis of parameters determining tissue susceptibility to oxidants showed that pro-oxidant capacity was lower in GC-1- than in T3-treated rats, while antioxidant capacity was similar in treatment groups. Interestingly, both agonists decreased serum cholesterol levels, but only GC-1 restored euthyroid values of heart rate and indices of tissue oxidative damage, indicating that GC-1 is able to lower cholesterolemia, bypassing detrimental effects of T3.

Regulation of visceral adipose tissue-derived serine protease inhibitor by nutritional status, metformin, gender and pituitary factors in rat white adipose tissue

Visceral adipose tissue-derived serine protease inhibitor (vaspin) is a recently discovered adipocytokine mainly secreted from visceral adipose tissue, which plays a main role in insulin sensitivity. In this study, we have investigated the regulation of vaspin gene expression in rat white adipose tissue (WAT) in different physiological (nutritional status, pregnancy, age and gender) and pathophysiological (gonadectomy, thyroid status and growth hormone deficiency) settings known to be associated with energy homeostasis and alterations in insulin sensitivity. We have determined vaspin gene expression by real-time PCR. Vaspin was decreased after fasting and its levels were partially recovered after leptin treatment. Chronic treatment with metformin increased vaspin gene expression. Vaspin mRNA expression reached the highest peak at 45 days in both sexes after birth and its expression was higher in females than males, but its levels did not change throughout pregnancy. Finally, decreased levels of growth hormone and thyroid hormones suppressed vaspin expression. These findings suggest that WAT vaspin mRNA expression is regulated by nutritional status, and leptin seems to be the nutrient signal responsible for those changes. Vaspin is influenced by age and gender, and its expression is increased after treatment with insulin sensitizers. Finally, alterations in pituitary functions modify vaspin levels. Understanding the molecular mechanisms regulating vaspin will provide new insights into the pathogenesis of the metabolic syndrome.