Thyroid Hormones Play Role in Sarcopenia and Myopathies

Progesterone may be a regulator and B12 could be an indicator of the proximal D4Z4 repeat methylation status on 4q35ter

Facioscapulohumeral dystrophy (FSHD) has a hypomethylation-related epigenetic background and exhibits a different course in male and female patients. The differences between males and females have been linked to the levels of sex hormones. This study is the first to investigate the possible effect of these hormones on methylation status. We hypothesized that the levels of sex-related hormones, estradiol, testosterone, progesterone, and prolactin might be associated with the methylation status of the proximal part of the D4Z4. We also investigated the effect of fT3, folic acid, and vitamin B12 levels. We collected blood from 28 FSHD patients and 28 controls. DNA was extracted from each individual for bisulfite methylation analysis and serum was separated for biochemical analysis of estradiol, testosterone, progesterone, prolactin, fT3, folic acid, and B12 analysis. Methylation analysis was specified to the DR1, 5P regions and the proximal region covering both DR1 and 5P. Methylation levels were compared between FSHD patients and controls. The correlation of methylation levels with estradiol, testosterone, progesterone, prolactin, fT3, folic acid, and B12 was investigated. We found that the 5P region and the proximal region were significantly hypomethylated in FSHD patients compared to the controls, but not the DR1 region. Male patients exhibited a significant reduction in DNA methylation compared to male controls. Older FSHD patients exhibited a notable decrease in fT3 levels and hypomethylation of the 5P region. Analyses of each CpG revealed seven hypomethylated positions that were significantly different from the control group. Two of the positions demonstrated a correlation with progesterone in the control group. With the exception of one position, the methylation levels were inversely correlated with vitamin B12 in FSHD patients. The results of our study indicate that the methylation of the proximal D4Z4 region, particularly at specific positions, may be associated with progesterone. In addition, vitamin B12 may be an indicator of hypomethylation. We suggest that examining position-specific methylations may be a useful approach for the development of epigenetic treatment modalities.

Correlation of subclinical hypothyroidism with sarcopenia and its components in the Chinese older adults

OBJECTIVE

To identify the correlation of thyroid function and subclinical hypothyroidism (SCH) with sarcopenia and its components in the older Chinese adults.

METHODS

Older adults were recruited and divided into SCH group and non-SCH group. Free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) were measured by electrochemiluminescence. Appendicular skeletal muscle mass (ASM) was measured, and skeletal muscle index (SMI) was further calculated. Grip strength was measured. Physical performance was graded by the Short Physical Performance Battery (SPPB) scores of the gait speed test, chair stand test and balance test.

RESULTS

Of the 240 older adults included, 48 (20.00%) presented with SCH. The prevalence of sarcopenia in SCH group was higher than that in non-SCH group (33.33% v.s. 18.75%). Grip strength was significantly lower in patients with SCH than those without sarcopenia. In terms of physical performance, 6-meter gait speed and SPPB score were lower in subjects with SCH than those without SCH, while 5 sit-to-stand movements was longer score in subjects with SCH than those without SCH. SCH was significantly correlated with sarcopenia, while FT3, FT4, and TSH levels were not. SCH was significantly correlated with low muscle strength and low muscle mass, but not with low physical performance. FT3 level was positively correlated with grip strength and SMI. TSH level was negatively correlated with grip strength, 6-meter gait speed, and SPPB score, but positively correlated with the time of 5 sit-to-stand movements.

CONCLUSION

SCH is a risk factor for sarcopenia in the older adults and correlated with low muscle strength and low muscle mass, but not with low physical performance. FT3, FT4 and TSH levels are associated with sarcopenia components, but not with sarcopenia.

Are resting metabolic rate and clinical symptoms affected by variation of serum thyroid stimulating hormone levels within the normal range in healthy and women with hypothyroidism? A case-control study

BACKGROUND

It is unclear whether variation in thyroid stimulating hormone (TSH) levels within the reference range affect energy expenditure and clinical symptoms and even within the normal range of TSH levels, resting energy expenditure may alter. The aim of the present study was to determine whether treated hypothyroid subjects and healthy subjects with a low-normal TSH range (0.3-2.3 mIU/L) have better clinical outcomes and increased energy expenditure than those with a high-normal TSH range (2.3-4.3 mIU/L).

METHODS

This was a case-control study of 160 overweight/obese women with TSH levels across the reference range of 0.3-4.3 mU/l. Subjects were paired in four groups: healthy subjects with low-normal target TSH (n = 40), healthy subjects with high-normal target TSH (n = 40), subjects with treated hypothyroidism with low-normal target TSH (n = 40), and subjects with treated hypothyroidism with high-normal target TSH (n = 40). Resting energy expenditure (RMR), dietary intake, body composition, physical activity, and biochemical markers were assessed.

RESULTS

Subjects with low-normal (≤2.3 mU/L) and high-normal (>2.3 mU/L) TSH levels did not differ in terms of RMR, serum T3 levels, and clinical symptoms except fatigue (P = 0.013). However, serum fT4 levels were found to be significantly different between the study groups (P = 0.002). Serum fT4 concentration was the highest in subjects with treated hypothyroidism with low-normal target TSH.

CONCLUSION

Variation in serum TSH levels within the reference range did not significantly affect REE and clinical symptoms except fatigue in healthy and women with hypothyroidism.

Triiodothyronine hormone supplementation therapy in septic shock patients with euthyroid sick syndrome: two pilot, placebo-controlled, randomized trials

BACKGROUND

To assess 28-day survival in two pilot groups of septic shock patients with euthyroid sick syndrome (ESS) supplemented with triiodothyronine (T3).

METHODS

A total of 95 septic shock patients with ESS were divided according to values of the thyroid hormones into low T3 and low T3T4 groups. Among 48 patients with low T3, 24 (50%) were randomized to T3 for 4 days and 24 (50%) to placebo. Among 47 patients with low T3T4, 24 (51%) were randomized to T3 for 4 days and 23 (49%) to placebo. The analysis included 28-day survival as the primary outcome and laboratory with hemodynamics as the secondary outcomes. Laboratory data were analyzed on the day of admission (T0), on the first (T1), third (T2) and seventh day (T3) with hemodynamics analyzed for the first four days.

RESULTS

In the low T3 population, 18 (75%) patients receiving T3 died at day 28 compared with 8 (33.3%) patients receiving placebo (p = 0.004). In the low T3T4 population, 6 (25%) patients receiving T3 died in ICU compared with 12 (52.1%) patients receiving placebo (p = 0.039). Oral T3 treatment increased mean arterial pressure values at day 1, day 3 and day 7 in the low T3T4 population, (p = 0.015, =0.005 and =0.042 respectively), and had no significant effect on these values in the low T3 population.

CONCLUSION

T3 supplementation was associated with a low 28-day mortality rate in patients with low T3T4 but with increased mortality in patients with low T3 ESS. These results suggest caution before initiating thyroid supplementation in septic patients.

REGISTRATION

ClinTrials.gov (NCT05270798).

Integration of ATAC-Seq and RNA-Seq Analysis to Identify Key Genes in the Longissimus Dorsi Muscle Development of the Tianzhu White Yak

During the postnatal stages, skeletal muscle development undergoes a series of meticulously regulated alterations in gene expression. However, limited studies have employed chromatin accessibility to unravel the underlying molecular mechanisms governing muscle development in yak species. Therefore, we conducted an analysis of both gene expression levels and chromatin accessibility to comprehensively characterize the dynamic genome-wide chromatin accessibility during muscle growth and development in the Tianzhu white yak, thereby elucidating the features of accessible chromatin regions throughout this process. Initially, we compared the differences in chromatin accessibility between two groups and observed that calves exhibited higher levels of chromatin accessibility compared to adult cattle, particularly within ±2 kb of the transcription start site (TSS). In order to investigate the correlation between alterations in chromatin accessible regions and variations in gene expression levels, we employed a combination of ATAC-seq and RNA-seq techniques, leading to the identification of 18 central transcriptional factors (TFs) and 110 key genes with significant effects. Through further analysis, we successfully identified several TFs, including Sp1, YY1, MyoG, MEF2A and MEF2C, as well as a number of candidate genes (ANKRD2, ANKRD1, BTG2 and LMOD3) which may be closely associated with muscle growth and development. Moreover, we constructed an interactive network program encompassing hub TFs and key genes related to muscle growth and development. This innovative approach provided valuable insights into the molecular mechanism underlying skeletal muscle development in the postnatal stages of Tianzhu white yaks while also establishing a solid theoretical foundation for future research on yak muscle development.

Pathophysiology of sarcopenia: Genetic factors and their interplay with environmental factors

Sarcopenia is a geriatric disorder characterized by a progressive decline in muscle mass and function. This disorder has been associated with a range of adverse health outcomes, including fractures, functional deterioration, and increased mortality. The pathophysiology of sarcopenia is highly complex and multifactorial, involving both genetic and environmental factors as key contributors. This review consolidates current knowledge on the genetic factors influencing the pathogenesis of sarcopenia, particularly focusing on the altered gene expression of structural and metabolic proteins, growth factors, hormones, and inflammatory cytokines. While the influence of environmental factors such as physical inactivity, chronic diseases, smoking, alcohol consumption, and sleep disturbances on sarcopenia is relatively well understood, there is a dearth of studies examining their mechanistic roles. Therefore, this review emphasizes the interplay between genetic and environmental factors, elucidating their cumulative role in exacerbating the progression of sarcopenia beyond their individual effects. The unique contribution of this review lies in synthesizing the latest evidence on the genetic factors and their interaction with environmental factors, aiming to inform the development of novel therapeutic or preventive interventions for sarcopenia.

Development of a predictive score for post-hemithyroidectomy hypothyroidism using skeletal muscle index, remnant thyroid index, and thyroid-stimulating hormone levels: a retrospective cohort study

Background

Hypothyroidism is a major complication of hemithyroidectomy. Low remnant thyroid volume and high serum thyroid-stimulating hormone (TSH) levels are suggested as risk factors for post-hemithyroidectomy hypothyroidism. Reduced skeletal muscle mass is associated with a variety of postoperative complications. However, its impact on post-hemithyroidectomy hypothyroidism has not yet been studied. This study aimed to evaluate the association between skeletal muscle mass and the onset of post-hemithyroidectomy hypothyroidism and develop a predictive score using skeletal muscle mass in combination with previously reported risk factors.

Methods

This study retrospectively analyzed 226 consecutive patients who underwent hemithyroidectomy at Shinshu University Hospital between January 2011 and December 2020. The skeletal muscle area at the fourth thoracic vertebral level and maximal remnant thyroid area were quantified using preoperative computed tomography and standardized by dividing them by the square of the patient's height, designated as the skeletal muscle index (SMI) and remnant thyroid volume index (RTI). Subclinical hypothyroidism was defined as a postoperative elevated serum TSH level (>5 µU/mL) with a normal free thyroxine (FT4) level (≥0.9 ng/dL), overt hypothyroidism as a postoperative increase in serum TSH level (>5 µU/mL) and a decrease in serum FT4 level (<0.9 ng/dL), and symptomatic hypothyroidism as an elevated serum TSH level (>5 µU/mL) with hypothyroidism-related symptoms. Logistic regression analysis was used to determine the factors associated with the onset of hypothyroidism.

Results

Patients with euthyroid status had significantly higher SMI and RTI than those who developed post-hemithyroidectomy hypothyroidism (SMI, euthyroid: 12.0±2.4 vs. subclinical hypothyroid: 10.2±1.7, P<0.001, euthyroid vs. overt or symptomatic hypothyroid: 10.1±1.7, P<0.001, RTI, euthyroid: 1.19±0.41 vs. subclinical hypothyroid: 0.92±0.35, P<0.001, euthyroid vs. overt or symptomatic hypothyroid: 0.84±0.30, P<0.001). Multivariable analysis demonstrated that low SMI, low RTI [hazard ratio (HR): 3.35, P<0.001], and preoperative high serum TSH levels (HR: 2.54, P=0.003) were independent predictive factors for hypothyroidism. Patients who had low SMI, low RTI, and preoperative high serum TSH levels were more likely to develop hypothyroidism (68.8%) than those with either one (25.3%), two (47.8%), or none (15.2%) of these three factors.

Conclusions

Preoperative evaluation of the SMI, RTI, and serum TSH levels may be useful in predicting the development of post-hemithyroidectomy hypothyroidism.

THYROTOXICOSIS AND ITS RELATION TO SARCOPENIA, MUSCLE STRENGTH, MUSCLE MASS AND PHYSICAL PERFORMANCE

Background

Sarcopenia is a syndrome, considered one of the main risk factors for morbidity and mortality among adults. Thyrotoxicosis may contribute to its development.

Aim

To assess the physical well-being among women with thyrotoxicosis and to determine the risk of sarcopenia among them; 13 women over 40 years of age with thyrotoxicosis took part in this study.

Materials and Methods

Grip strength was used to assess muscle strength. Appendicular skeletal muscle mass, adjusted for body size was used to asses muscle quantity. Physical performance was measured by gait speed test. We divided women in groups: group A - patients with newly diagnosed thyrotoxicosis and group B - patients who had started treatment.

Results

The values of muscle strength, muscle mass and gait speed were lower in group A compared to group B. Three of the patients in group A were diagnosed with severe sarcopenia. Thus the frequency of sarcopenia was 50% in this group. None of the women in group B met the criteria for sarcopenia.Despite the small number of women in this study, we can conclude that untreated thyrotoxicosis is a risk factor for decreased muscle strength, quantity and physical performance and could cause secondary sarcopenia.

Systemic Factors in Temporomandibular Disorder Pain

The science of temporomandibular disorder (TMD) pain and its management has gone through significant changes during the last several decades. The authors strongly feel that the effect of systemic factors influencing TMD pain has been largely overlooked and poorly accounted for, even in established pain-management programs and protocols. The hope is that this article will act as a wake-up call for the pain management community to consider the importance of adequate knowledge of the systemic factors that affect the experience of TMD pain by the patient.

Lower serum FT3 within the reference range is associated with mortality for older adults over 80 years of age with sarcopenia

OBJECTIVE

Thyroid hormones stimulate myogenesis and muscle contraction and regulate skeletal muscle cell metabolism. However, the association between thyroid hormone levels and mortality in sarcopenic older adults remains elusive. The aim of this study was to investigate the relationship between thyroid hormones and all-cause mortality in people over 80 years of age with sarcopenia.

METHODS

This study was performed on 264 sarcopenic patients aged 80 years and older. Serum levels of thyroid hormone, including free triiodothyronine (FT3), free thyroxine (FT4), and thyroid stimulating hormone (TSH) were tested to evaluate thyroid status. Sarcopenia was defined using the criteria of the European Working Group on Sarcopenia in Older People. Mortality data were available for up to 38 months of follow-up. The correlation between FT3 and calf circumference (CC) or handgrip strength (HGS) was determined by Pearson correlation analysis. Kaplan-Meier analysis was used to compare the differences between FT3 tertile groups. Cox regression was used to analyze the mortality risk ratio of patients with different FT3 tertiles.

RESULTS

During the follow-up period, 88 older adults died. Non-Survivors had lower serum FT3 levels (3.7 ± 0.5 vs. 3.9 ± 0.7, P = 0.001) than the Survivor. Serum FT3 was positively associated with CC and HGS (r = 0.29, P < 0.001, r = 0.21, P = 0.002, respectively). The Kaplan-Meier curve analysis demonstrated a difference in mortality among the FT3 tertile groups (log-rank test, χ² = 11.83, P = 0.003). The high FT3 group had lower mortality compared with the low FT3 group (the adjusted HRs were 0.63 (95%CI: 0.41-0.96 P = 0.031).

CONCLUSION

Lower FT3 within the reference range is associated with higher mortality in adults over 80 years with sarcopenia and euthyroid. Routine assessment of FT3 may be an easy way to identify high-risk older adults with sarcopenia.

Organotypic cultures as aging associated disease models

Aging remains a primary risk factor for a host of diseases, including leading causes of death. Aging and associated diseases are inherently multifactorial, with numerous contributing factors and phenotypes at the molecular, cellular, tissue, and organismal scales. Despite the complexity of aging phenomena, models currently used in aging research possess limitations. Frequently used in vivo models often have important physiological differences, age at different rates, or are genetically engineered to match late disease phenotypes rather than early causes. Conversely, routinely used in vitro models lack the complex tissue-scale and systemic cues that are disrupted in aging. To fill in gaps between in vivo and traditional in vitro models, researchers have increasingly been turning to organotypic models, which provide increased physiological relevance with the accessibility and control of in vitro context. While powerful tools, the development of these models is a field of its own, and many aging researchers may be unaware of recent progress in organotypic models, or hesitant to include these models in their own work. In this review, we describe recent progress in tissue engineering applied to organotypic models, highlighting examples explicitly linked to aging and associated disease, as well as examples of models that are relevant to aging. We specifically highlight progress made in skin, gut, and skeletal muscle, and describe how recently demonstrated models have been used for aging studies or similar phenotypes. Throughout, this review emphasizes the accessibility of these models and aims to provide a resource for researchers seeking to leverage these powerful tools.

Low Inflammatory Stimulus Increases D2 Activity and Modulates Thyroid Hormone Metabolism during Myogenesis In Vitro

Thyroid hormone (TH) signaling controls muscle progenitor cells differentiation. However, inflammation can alter muscle TH signaling by modulating the expression of TH transporters (Slc16a2), receptors (Thra1), and deiodinase enzymes (Dio2 and Dio3). Thus, a proinflammatory environment could affect myogenesis. The role of a low-grade inflammatory milieu in TH signaling during myogenesis needs further investigation. Herein, we aimed to study the impact of the bacterial lipopolysaccharide (LPS)-induced inflammatory stimulus on the TH signaling during myogenesis. C2C12 myoblasts differentiation was induced without (CTR) or with 10 ng/mL LPS presence. The myoblasts under LPS stimulus release the proinflammatory cytokines (IL-6 and IL-1β) and chemokines (CCL2 and CXCL-1). LPS decreases Myod1 expression by 28% during the initial myogenesis, thus reducing the myogenic stimulus. At the same time, LPS reduced the expression of Dio2 by 41% but doubled the D2 enzymatic activity. The late differentiation was not affected by inflammatory milieu, which only increased the Slc16a2 gene expression by 38%. LPS altered the intracellular metabolism of TH and reduced the initial myogenic stimulus. However, it did not affect late differentiation. Increased intracellular TH activation may be the compensatory pathway involved in the recovery of myogenic differentiation under a low-grade inflammatory milieu.

Sarcopenia: An Age-Related Multifactorial Disorder

Sarcopenia is an emerging clinical entity characterized by a gradual decline in skeletal muscle mass and strength that accompanies the normal aging process. It has been noted that sarcopenia is associated with various adverse health outcomes in the geriatric population like prolonged hospital admission, disability, poor quality of life, frailty, and mortality. Factors involved in the development of age-related sarcopenia include anorexia, alteration in the hormone levels, decreased neural innervation, low blood flow to the muscles, cytokine dysregulation, altered mitochondrial activity, genomic instability, intracellular proteolysis, and insulin resistance. Understanding the mechanism may help develop efficient preventive and therapeutic strategies which can improve the quality of life in elderly individuals. Thus, the objective of the present article is to review the literature regarding the mechanism involved in the development of sarcopenia in aged individuals.

Thyroid hormone regulates glutamine metabolism and anaplerotic fluxes by inducing mitochondrial glutamate aminotransferase GPT2

Thyroid hormones (THs) are key metabolic regulators coordinating short- and long-term energy needs. In skeletal muscle, THs modulate energy metabolism in pathophysiological conditions. Indeed, hypo- and hyperthyroidism are leading causes of muscle weakness and strength; however, the metabolic pathways underlying these effects are still poorly understood. Using molecular, biochemical, and isotope-tracing approaches combined with mass spectrometry and denervation experiments, we find that THs regulate glutamine metabolism and anaplerotic fluxes by up-regulating the glutamate pyruvate transaminase 2 (GPT2) gene. In humans, GPT2 autosomal recessive mutations cause a neurological syndrome characterized by intellectual disability, microcephaly, and progressive motor symptoms. Here, we demonstrate a role of the TH/GPT2 axis in skeletal muscle in which it regulates muscle weight and fiber diameter in resting and atrophic conditions and results in protection from muscle loss during atrophy. These results describe an anabolic route by which THs rewire glutamine metabolism toward the maintenance of muscle mass.

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THs induce the expression of the mitochondrial GPT2 gene in skeletal muscle

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The GPT2 up-regulation by THs enhances anaplerotic cycles and α-KG production

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GPT2 is reduced during muscle atrophy and is reactivated by THs treatment

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GPT2 KO^+/– mice undergo muscle loss that is partially attenuated by THs

High Serum AST/ALT Ratio and Low Serum INS*PA Product Are Risk Factors and Can Diagnose Sarcopenia in Middle-Aged and Older Adults

BACKGROUND

Sarcopenia is an age-related clinical condition and associated with an increased risk of adverse outcomes. However, to date, there is no global standard for the diagnosis of sarcopenia, and fewer serum biomarkers have been suggested for the diagnosis of sarcopenia. It is, thus, important that sarcopenia-related serological diagnostic markers be explored. The present study was based on the Asian Working Group on Sarcopenia 2019 (AWGS 2019) criteria to assess whether aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio and fasting insulin*prealbumin (INS*PA) product are diagnostic markers associated with sarcopenia in various ethnic groups in western China.

METHODS

This cross-sectional study included 4,099 adults (1,471 men and 2,628 women) from the West China Health and Aging Trend (WCHAT) study. The value of serum biomarkers was based on laboratory data. The accompanying metabolic disorders and the associated parameters were evaluated. Logistic regression analysis was used to explore the association between markers and sarcopenia. Receiver operating characteristic curve (ROC) analysis was used to evaluate the diagnostic efficacy of the test in differentiating sarcopenia.

RESULTS

Binary regression analysis showed that high serum AST/ALT (OR = 2.247) and adrenal cortisol (PTC, OR = 1.511), low serum INS*PA (OR = 2.970), free triiodothyronine (FT3, OR = 1.313), 25-OH-VitD (VitD, in male participants, OR = 1.817), and diastolic blood pressure (DBP, in female subjects, OR = 1.250) were independent risk factors for sarcopenia (P < 0.05). AST/ALT and INS*PA were not affected by metabolic factors and had better diagnostic efficacy for sarcopenia. The AUC of the INS*PA was the highest (0.705, 0.706, and 0.701, respectively, P < 0.05), followed by that of the AST/ALT (0.680, 0.675, and 0.695, respectively, P < 0.05). The AUC of the AST/ALT/(INS*PA)*10,000 used to diagnose sarcopenia was 0.727.

CONCLUSION

Among middle-aged and older adults of multiple ethnicities in western China, we found that higher AST/ALT and lower INS*PA levels are associated with an increased prevalence of sarcopenia. Since these serum biomarkers are inexpensive and can be obtained easily from biochemical routine, regular follow-up of AST/ALT and INS*PA may be an effective strategy in sarcopenia screening and management.

Association of subtle alterations in thyroid function with presarcopenia in patients with type 2 diabetes mellitus

Aims/Introduction

To investigate the association of subtle alterations in thyroid function with presarcopenia among patients with type 2 diabetes mellitus.

Materials and Methods

A total of 1,865 adult patients with type 2 diabetes mellitus were enrolled in this cross‐sectional study, excluding patients with overt thyroid dysfunction. Skeletal muscle mass measured by dual energy X‐ray absorptiometry was used to assess presarcopenia. Logistic regression models were used to estimate the effects of thyroid hormones on presarcopenia, and subgroup analyses were carried out in different strata of age, sex and body mass index, respectively.

Results

Compared with the euthyroid group (Euthy), the subclinical hyperthyroidism group had an increased odds of presarcopenia (multivariate‐adjusted odds ratio 1.99, 95% confidence interval 1.09–3.63), but the subclinical hypothyroidism group did not (P > 0.05). In the subclinical hyperthyroidism group, age and body mass index <24 kg/m² were independent risk factors for presarcopenia. In the overall Euthy group, an increased odds of presarcopenia was correlated with the elevated free thyroxine : free triiodothyronine ratio (all P for trend <0.05), whereas not with increment in free triiodothyronine level (P for trend >0.05). Additionally, in Euthy subgroup analyses stratified by middle‐age, sex and body mass index, a similar association was noted (all P for trend <0.05), but not in the older‐aged patients (P for trend >0.05).

Conclusions

Subclinical hyperthyroidism was an independent risk factor for presarcopenia in patients with type 2 diabetes mellitus, but subclinical hypothyroidism was not. In the Euthy group with type 2 diabetes mellitus, a high free thyroxine : free triiodothyronine ratio was a good index of presarcopenia in addition to older age.

Thyroid Hormone Action in Muscle Atrophy

Skeletal muscle atrophy is a condition associated with various physiological and pathophysiological conditions, such as denervation, cachexia, and fasting. It is characterized by an altered protein turnover in which the rate of protein degradation exceeds the rate of protein synthesis, leading to substantial muscle mass loss and weakness. Muscle protein breakdown reflects the activation of multiple proteolytic mechanisms, including lysosomal degradation, apoptosis, and ubiquitin-proteasome. Thyroid hormone (TH) plays a key role in these conditions. Indeed, skeletal muscle is among the principal TH target tissue, where TH regulates proliferation, metabolism, differentiation, homeostasis, and growth. In physiological conditions, TH stimulates both protein synthesis and degradation, and an alteration in TH levels is often responsible for a specific myopathy. Intracellular TH concentrations are modulated in skeletal muscle by a family of enzymes named deiodinases; in particular, in muscle, deiodinases type 2 (D2) and type 3 (D3) are both present. D2 activates the prohormone T4 into the active form triiodothyronine (T3), whereas D3 inactivates both T4 and T3 by the removal of an inner ring iodine. Here we will review the present knowledge of TH action in skeletal muscle atrophy, in particular, on the molecular mechanisms presiding over the control of intracellular T3 concentration in wasting muscle conditions. Finally, we will discuss the possibility of exploiting the modulation of deiodinases as a possible therapeutic approach to treat muscle atrophy.

Association between Thyroid Dysfunction and Intensive Care Unit-Acquired Weakness: A Case-Control Study

Background

Thyroid disorders may decrease the threshold for developing myopathy. Nonthyroidal illness syndrome (NTIS) is a common form of thyroid dysfunction in critically ill patients who are prone to the development of intensive care unit-acquired weakness (ICUAW). We therefore tested the hypothesis that patients with abnormalities in thyroid function are at a higher risk of developing ICUAW.

Methods

We assessed blood samples from patients admitted to the ICU for ≥7 days for thyroid functions. Patients were classified into 4 categories (euthyroid, hyperthyroid, hypothyroid, and NTIS). Patients were then evaluated daily for ICUAW development. Patients with ICUAW were considered as cases, whereas patients who did not develop ICUAW served as controls. We compared demographic and clinical variables, such as APACHE II score; length of ICU stay; free T3 (FT3), free T4, and thyroid-stimulating hormone levels; incidence of the four categories of thyroid function; and other risk factors for ICUAW. Logistic regression was used to determine independent risk factors for ICUAW.

Results

This case-control study included 114 patients: 57 cases (ICUAW) and 57 controls. FT3 levels were significantly lower in the cases (2.13 ± 0.96 mU/L) than in controls (2.69 ± 1.07 mU/L; P=0.004). There were no significant differences between cases and controls regarding the incidence of all categories of thyroid function. In univariate analysis, five independent variables had P < 0.25 (sepsis, vasopressors, mechanical ventilation duration, NTIS, and FT3 levels). Among these variables, multiple regression showed that only FT3 level (CI = 0.157-0.82, P=0.015) was an independent risk factor.

Conclusion

The study revealed an inverse association between ICUAW incidence and FT3 levels.

Smoothelin-Like Protein 1 Regulates Development and Metabolic Transformation of Skeletal Muscle in Hyperthyroidism

Hyperthyroidism triggers a glycolytic shift in skeletal muscle (SKM) by altering the expression of metabolic proteins, which is often accompanied by peripheral insulin resistance. Our previous results show that smoothelin-like protein 1 (SMTNL1), a transcriptional co-regulator, promotes insulin sensitivity in SKM. Our aim was to elucidate the role of SMTNL1 in SKM under physiological and pathological 3,3',5-Triiodo-L-thyronine (T3) concentrations. Human hyper- and euthyroid SKM biopsies were used for microarray analysis and proteome profiler arrays. Expression of genes related to energy production, nucleic acid- and lipid metabolism was changed significantly in hyperthyroid samples. The phosphorylation levels and activity of AMPKα2 and JNK were increased by 15% and 23%, respectively, in the hyperthyroid samples compared to control. Moreover, SMTNL1 expression showed a 6-fold decrease in the hyperthyroid samples and in T3-treated C2C12 cells. Physiological and supraphysiological concentrations of T3 were applied on differentiated C2C12 cells upon SMTNL1 overexpression to assess the activity and expression level of the elements of thyroid hormone signaling, insulin signaling and glucose metabolism. Our results demonstrate that SMTNL1 selectively regulated TRα expression. Overexpression of SMTNL1 induced insulin sensitivity through the inhibition of JNK activity by 40% and hampered the non-genomic effects of T3 by decreasing the activity of ERK1/2 through PKCδ. SMTNL1 overexpression reduced IRS1 Ser307 and Ser612 phosphorylation by 52% and 53%, respectively, in hyperthyroid model to restore the normal responsiveness of glucose transport to insulin. SMTNL1 regulated glucose phosphorylation and balances glycolysis and glycogen synthesis via the downregulation of hexokinase II by 1.3-fold. Additionally, mitochondrial respiration and glycolysis were measured by SeaHorse analysis to determine cellular metabolic function/phenotype of our model system in real-time. T3 overload strongly increased the rate of acidification and a shift to glycolysis, while SMTNL1 overexpression antagonizes the T3 effects. These lines of evidence suggest that SMTNL1 potentially prevents hyperthyroidism-induced changes in SKM, and it holds great promise as a novel therapeutic target in insulin resistance.

Perturbed BMP signaling and denervation promote muscle wasting in cancer cachexia

Most patients with advanced solid cancers exhibit features of cachexia, a debilitating syndrome characterized by progressive loss of skeletal muscle mass and strength. Because the underlying mechanisms of this multifactorial syndrome are incompletely defined, effective therapeutics have yet to be developed. Here, we show that diminished bone morphogenetic protein (BMP) signaling is observed early in the onset of skeletal muscle wasting associated with cancer cachexia in mouse models and in patients with cancer. Cancer-mediated factors including Activin A and IL-6 trigger the expression of the BMP inhibitor Noggin in muscle, which blocks the actions of BMPs on muscle fibers and motor nerves, subsequently causing disruption of the neuromuscular junction (NMJ), denervation, and muscle wasting. Increasing BMP signaling in the muscles of tumor-bearing mice by gene delivery or pharmacological means can prevent muscle wasting and preserve measures of NMJ function. The data identify perturbed BMP signaling and denervation of muscle fibers as important pathogenic mechanisms of muscle wasting associated with tumor growth. Collectively, these findings present interventions that promote BMP-mediated signaling as an attractive strategy to counteract the loss of functional musculature in patients with cancer.

Effect of Eurycoma longifolia standardised aqueous root extract-Physta® on testosterone levels and quality of life in ageing male subjects: a randomised, double-blind, placebo-controlled multicentre study

Background

Low testosterone levels cause physiological changes that compromise the quality of life in ageing men. A standardised water extract from the root of Eurycoma longifolia (EL), known as Physta^®, is known to increase testosterone levels.

Objective

To evaluate the safety and efficacy of Physta^® in improving the testosterone levels and quality of life in ageing male subjects.

Design

This randomised, double-blind, placebo-controlled study enrolled 105 male subjects aged 50-70 years with a testosterone level <300 ng/dL, BMI ≥ 18 and ≤30.0 kg/m². The subjects were given either Physta^® 100 mg, 200 mg or placebo daily for 12 weeks. The primary endpoints were changes in serum total and free testosterone levels. The secondary endpoints included changes in the level of sex hormone-binding globulin (SHBG), dihydroepiandrosterone (DHEA), glycated haemoglobin (HbA1c), insulin-like growth factor-1 (IGF-1), thyroid function tests (T3, T4, TSH and Free T3) and cortisol. Changes in Ageing Male Symptoms (AMS) score, Fatigue Severity Scale (FSS) score and muscle strength are other secondary endpoints. The safety of the intervention products was measured by complete blood count, lipid profile, liver and renal function tests.

Results

There was a significant increase in the total testosterone levels at week 12 (P < 0.05) in the Physta^® 100 mg group and at weeks 4 (P < 0.05), 8 (P < 0.01) and 12 (P < 0.001) in the Physta^® 200 mg group compared to placebo. No significant between-group differences in free testosterone levels were observed but a significant within-group increase occurred at weeks 4 (P < 0.01), 8 (P < 0.001) and 12 (P < 0.001) in the Physta^®100 mg group and at weeks 2 (P < 0.01), 4 (P < 0.01), 8 (P < 0.001) and 12 (P < 0.001) in the Physta^® 200 mg group. The AMS and FSS showed significant reduction (P < 0.001) in total scores at all time-points within- and between-group in both Physta^® groups. DHEA levels significantly increased (P < 0.05) within-group in both Physta^® groups from week 2 onwards. Cortisol levels significantly (P < 0.01) decreased in the Physta^® 200 mg group, while muscle strength significantly (P < 0.001) increased in both Physta^® groups at week 12 in the within-group comparison. There were no significant changes in SHBG. No safety related clinically relevant changes were observed.

Conclusion

Supplementation of Physta^® at 200 mg was able to increase the serum total testosterone, reduce fatigue and improve the quality of life in ageing men within 2 weeks' time.

Trial registration

This clinical study has been registered in ctri.nic.in (CTRI/2019/03/017959).

A prolonged hiatus in postmenopausal HRT, does not nullify the therapy's positive impact on ageing related sarcopenia

Background

Previous work suggest a positive skeletal muscle effect of hormone replacement therapy (HRT) on skeletal muscle characteristics This study aimed to quantify any continued positive effect of HRT even after a sustained hiatus in treatment, controlling for two key muscle modulation hormones: Estradiol (E2) and Tri-iodo-thyronine (T3).

Method and findings

In 61 untrained women (18-78yrs) stratified as pre-menopausal, post-menopausal without (No_HRT) and post-menopausal with (Used_HRT) HRT history, body composition, physical activity, serum E2 and T3 were assessed by dual energy x-ray absorptiometry, Baecke questionnaire and ELISA. Gastrocnemius medialis (GM) and tibialis anterior (TA) electromyographic profiles (mean power frequency (mPowerF)), isometric plantar-flexion (PF) and dorsi-flexion (DF) maximum voluntary contraction (MVC), rate of torque development (RTD), isokinetic MVC and muscle volume, were assessed using surface electromyography, dynamometry and ultrasonography. Muscle quality was quantified as MVC per unit muscle size. E2 and E2:T3 ratio were significantly lower in postmenopausal participants, and were positively correlated with RTD even after controlling for adiposity and/or age. Pre-menopausal females had greater MVC in 8/8 PF and 2/5 DF (23.7–98.1%; P<0.001–0.049) strength measures compared to No_HRT, but only 6/8 PF (17.4–42.3%; P<0.001–0.046) strength measures compared to Used_HRT. Notably, Used_HRT had significant higher MVC in 7 PF MVC (30.0%-37.7%; P = 0.006–0.031) measures than No_HRT, while premenopausal and Used_HRT had similar uncorrected muscle size or quality. In addition, this cross-sectional data suggest an annual reduction in GM muscle volume corrected for intra-muscular fat by 1.3% in No_HRT and only 0.5% in Used_HRT.

Conclusion

Even years after cessation of the therapy, a history of HRT is positively associated with negating the expected post-menopausal drop in muscle quantity and quality. Whilst mPowerF did not differ between groups, our work highlights positive associations between RTD against E2 and E2:T3. Notwithstanding our study limitation of single time point for blood sampling, our work is the first to illustrate an HRT attenuation of ageing-related decline in RTD. We infer from these data that high E2, even in the absence of high T3, may help maintain muscle contractile speed and quality. Thus our work is the first to points to markedly larger physiological reserves in women with a past history of HRT.

Fall-Associated Drugs in Community-Dwelling Older Adults: Results from the ActiFE Ulm Study

OBJECTIVES

Many studies describing an association of drugs with falls focus mostly on drugs acting in the central nervous system. We aim to analyze the association of all drugs taken with falls in older adults.

DESIGN

Prospective population-based study (ActiFE study).

SETTING AND PARTICIPANTS

A total of 1377 community-dwelling older adults with complete recording of falls and baseline information on drug intake.

METHODS

Negative binomial regression was used to analyze the association of 34 drug classes with a 12-month incidence rate ratio (IRR) of falls adjusting for age, sex, comorbidities, gait speed, balance, chair rise, kidney function, liver disease, and smoking.

RESULTS

Participants took a median 3 drugs (interquartile range 1, 5), with 34.5% (n = 469) having ≥5 drugs. The median IRR for a fall per person-year was overall 0.72 [95% confidence interval (CI) 0.60-0.83] and 2.22 (95% CI 1.90-2.53) among those who experienced ≥1 fall. The following drug classes showed significant associations: antiparkinsonian medication [IRR 2.68 (95% CI 1.59-4.51)], thyroid therapy [IRR 1.40 (95% CI 1.08-1.81)], and systemic corticosteroids [IRR 0.33 (95% CI 0.13-0.81)]. Among fall-risk-increasing drugs only antiepileptics [IRR 2.16 (95% CI 1.10-4.24)] and urologicals [IRR 2.47 (95% CI 1.33-4.59)] were associated with falls in those participants without a prior fall history at baseline.

CONCLUSION AND IMPLICATIONS

Additional drug classes, such as antiparkinsonian medication, thyroid therapy, and systemic corticosteroids, might be associated with falls in older adults, possibly representing pharmacological effects on the musculoskeletal and central nervous systems. Further evaluations in larger study populations are recommended.

Role of hormones in sarcopenia

Aging involves numerous changes in body composition that include a decrease in skeletal muscle mass. The gradual reduction in muscle mass is associated with a simultaneous decrease in muscle strength, which leads to reduced mobility, fragility and loss of independence. This process called sarcopenia is secondary to several factors such as sedentary lifestyle, inadequate nutrition, chronic inflammatory state and neurological alterations. However, the endocrine changes associated with aging seem to be of special importance in the development of sarcopenia. On one hand, advancing age is associated with a decreased secretion of the main hormones that stimulate skeletal muscle mass and function (growth hormone, insulin-like growth factor 1 (IGFI), testosterone and estradiol). On the other hand, the alteration of the IGF-I signaling along with decreased insulin sensitivity also have an important impact on myogenesis. Other hormones that decline with aging such as the adrenal-derived dehydroepiandrosterone, thyroid hormones and vitamin D seem to also be involved in sarcopenia. Adipokines released by adipose tissue show important changes during aging and can affect muscle physiology and metabolism. In addition, catabolic hormones such as cortisol and angiotensin II can accelerate aged-induced muscle atrophy, as they are involved in muscle wasting and their levels increase with age. The role played by all of these hormones and the possible use of some of them as therapeutic tools for treating sarcopenia will be discussed.

Characterization of Skeletal Muscle Endocrine Control in an In Vitro Model of Myogenesis

Skeletal muscle has remarkable regenerative abilities regulated by a highly orchestrated process involving the activation of cellular and molecular responses, which are dependent on satellite cells. These cells maintain the stem cell population and provide numerous myogenic cells that proliferate, differentiate, fuse and lead to new myofiber formation for a functional contractile tissue. We have isolated and characterized satellite cells obtained from human biopsies and established an in vitro model of myogenesis, evaluating muscle regeneration, monitoring the dynamic increases of the specific myogenic regulatory factors and the final formation of multinucleated myofibers. As the skeletal muscle is an endocrine tissue able of producing many substances that can act on distant organs, and it can be physiologically modulated by a variety of hormones, we embarked in a project of characterization of muscle cell endocrinology machinery. The expression of a large array of hormone receptors was quantified during the process of myogenesis. The results obtained showed a significant and generalized increase of all the tested hormone receptors along the process of differentiation of human cultured cells from myoblasts to myocytes. Interestingly, also the production of the myokine irisin increased in a parallel manner. These findings point to the human cultured myoblasts as an ideal model to characterize the skeletal muscle endocrine machinery and its hormonal regulation.

Skeletal Muscle Gene Expression in Long-Term Endurance and Resistance Trained Elderly

Physical exercise is deemed the most efficient way of counteracting the age-related decline of skeletal muscle. Here we report a transcriptional study by next-generation sequencing of vastus lateralis biopsies from elderly with a life-long high-level training practice (n = 9) and from age-matched sedentary subjects (n = 5). Unsupervised mixture distribution analysis was able to correctly categorize trained and untrained subjects, whereas it failed to discriminate between individuals who underwent a prevalent endurance (n = 5) or a prevalent resistance (n = 4) training, thus showing that the training mode was not relevant for sarcopenia prevention. KEGG analysis of transcripts showed that physical exercise affected a high number of metabolic and signaling pathways, in particular those related to energy handling and mitochondrial biogenesis, where AMPK and AKT-mTOR signaling pathways are both active and balance each other, concurring to the establishment of an insulin-sensitive phenotype and to the maintenance of a functional muscle mass. Other pathways affected by exercise training increased the efficiency of the proteostatic mechanisms, consolidated the cytoskeletal organization, lowered the inflammation level, and contrasted cellular senescence. This study on extraordinary individuals who trained at high level for at least thirty years suggests that aging processes and exercise training travel the same paths in the opposite direction.

Thyroid Function and Sarcopenia: Results from the ELSA-Brasil Study

OBJECTIVES

We aimed to investigate the association of subclinical thyroid disease and thyroid hormone levels with sarcopenia and its defining components in community-dwelling middle-aged and older adults without overt thyroid dysfunction.

DESIGN

Cross-sectional study.

SETTING

Active and retired employees from public institutions located in six Brazilian cities.

PARTICIPANTS

A total of 6974 participants from the ELSA-Brasil study's second wave, aged 50 years and older, without overt thyroid dysfunction and with complete data for exposure, outcome, and covariates.

METHODS

Serum levels of thyrotropin (TSH), free thyroxine, and free triiodothyronine (FT3) were measured and divided in quintiles for the analyses. Participants were classified with euthyroidism, subclinical hypothyroidism, and subclinical hyperthyroidism. Muscle mass was assessed by bioelectrical impedance analysis and muscle strength by handgrip strength. Sarcopenia was defined according to the Foundation for the National Institutes of Health criteria. Possible confounders included sociodemographic characteristics, clinical conditions, and lifestyle. Analyses were performed separately for middle-aged and older adults (≥65 y).

RESULTS

The frequencies of sarcopenia, low muscle mass, low muscle strength, subclinical hypothyroidism, and subclinical hyperthyroidism were 1.5%, 20.8%, 3.8%, 9.1%, and .9%, respectively. Subclinical thyroid dysfunction was not associated with sarcopenia and its defining components. Among older adults, TSH had a U-shaped association with sarcopenia and low muscle strength. The odds ratios (ORs) (95% confidence intervals [CIs]) for the associations of the first, second, fourth, and fifth quintile with sarcopenia, respectively, were 5.18 (1.47-18.28), 6.28 (1.82-21.73), 4.12 (1.15-14.76), and 4.81 (1.35-17.10), and with low muscle strength was (OR (95% CI) for the first, second, and fifth quintiles, respectively: 1.43 (1.16-5.07), 2.07 (1.24-4.70), and 2.18 (1.03-4.60). Additionally, FT3 had a negative association with muscle mass in both age strata.

CONCLUSION

Subtle thyroid hormone alterations are associated with sarcopenia or its defining components in middle-aged and older adults without overt thyroid dysfunction. J Am Geriatr Soc 68:1545-1553, 2020.

Clinical and biological characterization of skeletal muscle tissue biopsies of surgical cancer patients

BACKGROUND

Researchers increasingly use intraoperative muscle biopsy to investigate mechanisms of skeletal muscle atrophy in patients with cancer. Muscles have been assessed for morphological, cellular, and biochemical features. The aim of this study was to conduct a state-of-the-science review of this literature and, secondly, to evaluate clinical and biological variation in biopsies of rectus abdominis (RA) muscle from a cohort of patients with malignancies.

METHODS

Literature was searched for reports on muscle biopsies from patients with a cancer diagnosis. Quality of reports and risk of bias were assessed. Data abstracted included patient characteristics and diagnoses, sample size, tissue collection and biobanking procedures, and results. A cohort of cancer patients (n = 190, 88% gastrointestinal malignancies), who underwent open abdominal surgery as part of their clinical care, consented to RA biopsy from the site of incision. Computed tomography (CT) scans were used to quantify total abdominal muscle and RA cross-sectional areas and radiodensity. Biopsies were assessed for muscle fibre area (μm² ), fibre types, myosin heavy chain isoforms, and expression of genes selected for their involvement in catabolic pathways of muscle.

RESULTS

Muscle biopsy occurred in 59 studies (total N = 1585 participants). RA was biopsied intraoperatively in 40 studies (67%), followed by quadriceps (26%; percutaneous biopsy) and other muscles (7%). Cancer site and stage, % of male participants, and age were highly variable between studies. Details regarding patient medical history and biopsy procedures were frequently absent. Lack of description of the population(s) sampled and low sample size contributed to low quality and risk of bias. Weight-losing cases were compared with weight stable cancer or healthy controls without considering a measure of muscle mass in 21 out of 44 studies. In the cohort of patients providing biopsy for this study, 78% of patients had preoperative CT scans and a high proportion (64%) met published criteria for sarcopenia. Fibre type distribution in RA was type I (46% ± 13), hybrid type I/IIA (1% ± 1), type IIA (36% ± 10), hybrid type IIA/D (15% ± 14), and type IID (2% ± 5). Sexual dimorphism was prominent in RA CT cross-sectional area, mean fibre cross-sectional area, and in expression of genes associated with muscle growth, apoptosis, and inflammation (P < 0.05). Medical history revealed multiple co-morbid conditions and medications.

CONCLUSIONS

Continued collaboration between researchers and cancer surgeons enables a more complete understanding of mechanisms of cancer-associated muscle atrophy. Standardization of biobanking practices, tissue manipulation, patient characterization, and classification will enhance the consistency, reliability, and comparability of future studies.

Osteosarcopenia: A case of geroscience

Many older persons lose their mobility and independence due to multiple diseases occurring simultaneously. Geroscience is aimed at developing innovative approaches to better identify relationships among the biological processes of aging. Osteoporosis and sarcopenia are two of the most prevalent chronic diseases in older people, with both conditions sharing overlapping risk factors and pathogenesis. When occurring together, these diseases form a geriatric syndrome termed "osteosarcopenia," which increases the risk of frailty, hospitalizations, and death. Findings from basic and clinical sciences aiming to understand osteosarcopenia have provided evidence of this syndrome as a case of geroscience. Genetic, endocrine, and mechanical stimuli, in addition to fat infiltration, sedentarism, and nutritional deficiencies, affect muscle and bone homeostasis to characterize this syndrome. However, research is in its infancy regarding accurate diagnostic markers and effective treatments with dual effects on muscle and bone. To date, resistance exercise remains the most promising strategy to increase muscle and bone mass, while sufficient quantities of protein, vitamin D, calcium, and creatine may preserve these tissues with aging. More recent findings, from rodent models, suggest treating ectopic fat in muscle and bone marrow as a possible avenue to curb osteosarcopenia, although this needs testing in human clinical trials.

A Global Loss of Dio2 Leads to Unexpected Changes in Function and Fiber Types of Slow Skeletal Muscle in Male Mice

The type 2 iodothyronine-deiodinase (D2) enzyme converts T4 to T3, and mice deficient in this enzyme [D2 knockout (D2KO) mice] have decreased T3 derived from T4 in skeletal muscle despite normal circulating T3 levels. Because slow skeletal muscle is particularly susceptible to changes in T3 levels, we expected D2 inactivation to result in more pronounced slow-muscle characteristics in the soleus muscle, mirroring hypothyroidism. However, ex vivo studies of D2KO soleus revealed higher rates of twitch contraction and relaxation and reduced resistance to fatigue. Immunostaining of D2KO soleus showed that these properties were associated with changes in muscle fiber type composition, including a marked increase in the number of fast, glycolytic type IIB fibers. D2KO soleus muscle fibers had a larger cross-sectional area, and this correlated with increased myonuclear accretion in myotubes formed from D2KO skeletal muscle precursor cells differentiated in vitro. Consistent with our functional findings, D2KO soleus gene expression was markedly different from that in hypothyroid wild-type (WT) mice. Comparison of gene expression between euthyroid WT and D2KO mice indicated that PGC-1α, a T3-dependent regulator of slow muscle fiber type, was decreased by ∼50% in D2KO soleus. Disruption of Dio2 in the C2C12 myoblast cell line led to a significant decrease in PGC-1α expression and a faster muscle phenotype upon differentiation. These results indicate that D2 loss leads to significant changes in soleus contractile function and fiber type composition that are inconsistent with local hypothyroidism and suggest that reduced levels of PCG-1α may contribute to the observed phenotypical changes.