Thyroid Hormone Actions and Bone Remodeling – The Role of the Wnt Signaling Pathway

Hair and Serum Trace Element and Mineral Levels Profiles in Women with Premenopausal and Postmenopausal Osteoporosis

The objective of the present study was to evaluate serum and hair trace element and mineral levels in women with osteoporosis, as well as to estimate the impact of menopausal status on the profile of trace element and mineral status in women with osteoporosis. 207 women with diagnosed osteoporosis 22-85 years-of-age, and 197 healthy women of the respective age participated in the present study. Analysis of the levels of mineral and trace element in hair and serum samples was performed by inductively-coupled plasma mass-spectrometry (ICP-MS). Women with osteoporosis were characterized by significantly lower hair Ca, Mg, Co, I, Li, and Mn levels, as well as serum Ca, Mg, Co, Fe, V, and Zn concentrations compared to women in the control group. After additional grouping according to menopausal status, the lowest hair Ca and Mg content was observed in postmenopausal osteoporotic women, whereas serum Ca and Mg concentrations were the lowest in premenopausal osteoporotic women. Hair Co, Mn, and Zn levels in postmenopausal osteoporotic women were lower than in healthy postmenopausal women. The lowest circulating Zn levels were observed in osteoporotic postmenopausal women. Taken together, decreased hair and serum levels in osteoporotic women are indicative of increased risk of Ca, Mg, Co, and Zn deficiency in women with osteoporosis. In turn, alterations in hair trace element and mineral levels in osteoporosis are more profound in postmenopausal women. Hypothetically, improvement in trace element and mineral metabolism especially in postmenopausal women may be considered as a potential strategy for mitigating osteoporosis.

Bone Marrow Adipose Tissue as a Critical Regulator of Postmenopausal Osteoporosis - A Concise Review

Postmenopausal osteoporosis (PMOP) is a major health problem affecting millions of women worldwide. PMOP patients are often accompanied by abnormal accumulation of bone marrow adipose tissue (BMAT). BMAT is a critical regulator of bone homeostasis, and an increasing BMAT volume is negatively associated with bone mass reduction or fracture. BMAT regulates bone metabolism via adipokines, cytokines and the immune system, but the specific mechanisms are largely unknown. This review emphasizes the impact of estrogen deficiency on bone homeostasis and BMAT expansion, and the mechanism by which BMAT regulates PMOP, providing a promising strategy for targeting BMAT in preventing and treating PMOP.

Bridging the Gap in Understanding Bone Metastasis: A Multifaceted Perspective

The treatment of patients with advanced cancer poses clinical problems due to the complications that arise as the disease progresses. Bone metastases are a common problem that cancer patients may face, and currently, there are no effective drugs to treat these individuals. Prostate, breast, and lung cancers often spread to the bone, causing significant and disabling health conditions. The bone is a highly active and dynamic tissue and is considered a favorable environment for the growth of cancer. The role of osteoblasts and osteoclasts in the process of bone remodeling and the way in which their interactions change during the progression of metastasis is critical to understanding the pathophysiology of this disease. These interactions create a self-perpetuating loop that stimulates the growth of metastatic cells in the bone. The metabolic reprogramming of both cancer cells and cells in the bone microenvironment has serious implications for the development and progression of metastasis. Insight into the process of bone remodeling and the systemic elements that regulate this process, as well as the cellular changes that occur during the progression of bone metastases, is critical to the discovery of a cure for this disease. It is crucial to explore different therapeutic options that focus specifically on malignancy in the bone microenvironment in order to effectively treat this disease. This review will focus on the bone remodeling process and the effects of metabolic disorders as well as systemic factors like hormones and cytokines on the development of bone metastases. We will also examine the various therapeutic alternatives available today and the upcoming advances in novel treatments.

Endocrine Disruptor-Induced Bone Damage Due to Hormone Dysregulation: A Review

Hormones are indispensable for bone development, growth, and maintenance. While many of the genes associated with osteogenesis are well established, it is the recent findings in endocrinology that are advancing the fields of bone biology and toxicology. Endocrine-disrupting chemicals (EDCs) are defined as chemicals that interfere with the function of the endocrine system. Here, we report recent discoveries describing key hormone pathways involved in osteogenesis and the EDCs that alter these pathways. EDCs can lead to bone morphological changes via altering hormone receptors, signaling pathways, and gene expression. The objective of this review is to highlight the recent discoveries of the harmful effects of environmental toxicants on bone formation and the pathways impacted. Understanding the mechanisms of how EDCs interfere with bone formation contributes to providing a comprehensive toxicological profile of a chemical.

Progress of Wnt Signaling Pathway in Osteoporosis

Osteoporosis, one of the serious health diseases, involves bone mass loss, bone density diminishing, and degeneration of bone microstructure, which is accompanied by a tendency toward bone fragility and a predisposition to fracture. More than 200 million people worldwide suffer from osteoporosis, and the cost of treating osteoporotic fractures is expected to reach at least $25 billion by 2025. The generation and development of osteoporosis are regulated by genetic factors and regulatory factors such as TGF-β, BMP, and FGF through multiple pathways, including the Wnt signaling pathway, the Notch signaling pathway, and the MAPK signaling pathway. Among them, the Wnt signaling pathway is one of the most important pathways. It is not only involved in bone development and metabolism but also in the differentiation and proliferation of chondrocytes, mesenchymal stem cells, osteoclasts, and osteoblasts. Dkk-1 and SOST are Wnt inhibitory proteins that can inhibit the activation of the canonical Wnt signaling pathway and block the proliferation and differentiation of osteoblasts. Therefore, they may serve as potential targets for the treatment of osteoporosis. In this review, we analyzed the mechanisms of Wnt proteins, β-catenin, and signaling molecules in the process of signal transduction and summarized the relationship between the Wnt signaling pathway and bone-related cells. We hope to attract attention to the role of the Wnt signaling pathway in osteoporosis and offer new perspectives and approaches to making a diagnosis and giving treatment for osteoporosis.

Embryonic thermal manipulation leads growth inhibition and reduced hepatic insulin-like growth factor1 expression due to promoter DNA hypermethylation in broilers

When broilers cannot adapt to a high-temperature environment through self-regulation, it will cause heat stress, resulting in a large number of deaths and substantial economic losses. Studies have shown that thermal manipulation (TM) during the embryonic stage can improve broilers' ability to resist heat stress later. However, different TM strategies produce different results on broilers' growth. In this study, yellow-feathered broiler eggs were selected and randomly divided into 2 groups between E10 and E18, which the control group was incubated at 37.8°C with 56% humidity, and the TM group was subjected to 39°C with 65% humidity. After hatching, all broilers were reared normally until slaughtered at 12 d of age (D12). During D1 to D12, body weight, feed intake, and body temperature were recorded. The results showed that TM significantly decreased (P < 0.05) the final body weight, weight gain, and average daily feed intake of broilers. Meanwhile, the serum levels of Triiodothyronine (T3) and free T3 were significantly decreased in the TM group (P < 0.05). The expressions of hepatic growth regulation-associated genes, growth hormone receptor (GHR), insulin-like growth factor1, and 2 (IGF1 and IGF2) were significantly down-regulated in the TM group (P < 0.05). In addition, TM altered hepatic DNA methylation, resulting in a significant increase (P < 0.05) in the methylation of the IGF1 and GHR promoter regions. The above results indicated that TM during the embryonic stage decreased the serum thyroid hormone level and increased the methylation level of the IGF1 and GHR promoter regions to down-regulate the expression of growth-related genes, resulting in early growth inhibition of broilers.

Hyperthyroidism and Wnt Signaling Pathway: Influence on Bone Remodeling

Graves' disease is an autoimmune disease of the thyroid gland, characterized by increased production of thyroid hormones, which can affect many different organ systems in the body. Among other problems, it can cause disorders of the skeletal system, shortening the bone remodeling cycle and causing a decrease in bone density. The Wnt cascade signaling pathway and the β-catenin, as a part of the canonical Wnt pathway, also play roles in maintaining bone mass. Inhibition of the Wnt pathway can cause bone loss, and its stimulation can increase it. The Wnt signaling pathway influences the effectiveness of thyroid hormones by affecting receptors for thyroid hormones and deiodinase, while thyroid hormones can change levels of β-catenin within the cell cytoplasm. This indicates that the Wnt pathway and thyroid hormone levels, including hyperthyroidism, are linked and may act together to change bone density. In this review article, we attempt to explain the interplay between thyroid hormones and the Wnt pathway on bone density, with a focus on directions for further research and treatment options.

Effects and Mechanisms of Rhus chinensis Mill. Fruits on Suppressing RANKL-Induced Osteoclastogenesis by Network Pharmacology and Validation in RAW264.7 Cells

Rhus chinensis Mill. fruits are a kind of widely distributed edible seasoning, which have been documented to possess a variety of biological activities. However, its inhibitory effect on osteoclast formation has not been determined. The objective of this study was to evaluate the effect of the fruits on osteoclast differentiation of RAW264.7 cells, induced by receptor activator of nuclear factor-κB ligand (RANKL) and to illuminate the potential mechanisms using network pharmacology and western blots. Results showed that the extract containing two organic acids and twelve phenolic substances could effectively inhibit osteoclast differentiation in RANKL-induced RAW264.7 cells. Network pharmacology examination and western blot investigation showed that the concentrate essentially decreased the expression levels of osteoclast-specific proteins, chiefly through nuclear factor kappa-B, protein kinase B, and mitogen-activated protein kinase signaling pathways, particularly protein kinase B α and mitogen-activated protein kinase 1 targets. Moreover, the extract likewise directly down regulated the expression of cellular oncogene Fos and nuclear factor of activated T-cells cytoplasmic 1 proteins. Citric acid, quercetin, myricetin-3-O-galactoside, and quercetin-3-O-rhamnoside were considered as the predominant bioactive ingredients. Results of this work may provide a scientific basis for the development and utilization of R. chinensis fruits as a natural edible material to prevent and/or alleviate osteoporosis-related diseases.

Endocrine Regulation on Bone by Thyroid

BACKGROUND

As an endocrine organ, the thyroid acts on the entire body by secreting a series of hormones, and bone is one of the main target organs of the thyroid.

SUMMARY

This review highlights the roles of thyroid hormones and thyroid diseases in bone homeostasis.

CONCLUSION

Thyroid hormones play significant roles in the growth and development of bone, and imbalance of thyroid hormones can impair bone homeostasis.

The alleviative effect of thyroid hormone on cold stress-induced apotosis via HSP70 and mitochondrial apoptosis signal pathway in bovine Sertoli cells

Thyroid hormone was involved in gene expression and functional regulation in various signal pathways. Cold stress can increase triiodothyronine (T₃) level in the blood. The aim of this study was to investigate the effect of T₃ on HSP70 expression and apoptosis in Sertoli cells (SCs) under cold stress in vitro culture at 26 °C, and provide a theoretical and practical basis for improving the reproductive efficiency of bulls in cold areas. SCs were treated with different cold stress duration and different T₃ concentrations for pre-screening. HSP70 inhibitor was added later, and the apoptotic rate was measured using flow cytometry. The expression of HSP70 and the main genes of mitochondrial apoptosis pathway were determined by means of real-time PCR and western-blot, respectively. The localization of HSP70 was assessed by immunofluorescence. The results showed that cold stress (26 °C, 6 h) played an inductive role in SCs apoptotic rate (P < 0.01) and the transfer of HSP70 into the nucleus. 100 nM T₃ further promoted HSP70 expression and its transfer into the nucleus, which significantly inhibited the expression of vital genes (cyt-c, Caspase-9 and Caspase-3) in mitochondrial pathway (P < 0.05). Subsequently, higher survival and lower apoptotic rates of SCs (P < 0.01) were observed. When T₃ and HSP70 inhibitor were added together, the expression of cyt-c, Caspase-9 and Caspase-3 were inhibited (P < 0.05), and then the declining apoptotic rate increased again (P < 0.01). In conclusion, T₃ can regulate HSP70 expression and translocation to mediate mitochondrial apoptosis pathway to inhibit SCs apoptosis induced by cold stress.

The Association between the Dietary Inflammatory Index and Thyroid Function in U.S. Adult Males

Thyroid function has a close link with inflammation. However, it is still unknown whether the dietary inflammatory potential is associated with thyroid function. We aimed to assess the relationship among them using the data from the National Health and Nutrition Examination Survey (NHANES). This study was a cross-sectional study, where weighted multivariable linear regression, subgroup analyses, and interaction terms were employed. Thyroid function was assessed by eight indexes, including total and free T4 and T3, Tg, TgAb, TPOAb, and TSH. A total of 2346 male participants aged ≥20 years with an average age of 50.74 ± 17.68 years were enrolled. The mean DII score among participants was −0.46 ± 1.73, ranging from −4.12 to 4.41, and mean total thyroxine (T4) was 7.61 ± 1.51 μg/dL. We found a positive association between DII and total T4 (β = 0.07; p = 0.0044). Using subgroup analysis, this association became stronger in both the iodine-deficient and obese group (iodine-deficient group: β = 0.15, p < 0.0001; obese group: β = 0.14, p < 0.0001). In conclusion, men adhering to a more pro-inflammatory diet appeared to have higher total T4 levels. However, these hormone variations were still within the normal clinical range and more well-designed studies are still needed to validate the causal relationship between DII and thyroid function.

Thyroid hormone and thyroid hormone nuclear receptors: History and present state of art

The present review traces the road leading to discovery of L-thyroxine, thyroid hormone (3,5,3´-triiodo-L-thyronine, T₃) and its cognate nuclear receptors. Thyroid hormone is a pleio-tropic regulator of growth, differentiation, and tissue homeostasis in higher organisms. The major site of the thyroid hormone action is predominantly a cell nucleus. T₃ specific binding sites in the cell nuclei have opened a new era in the field of the thyroid hormone receptors (TRs) discovery. T₃ actions are mediated by high affinity nuclear TRs, TRalpha and TRbeta, which function as T₃-activated transcription factors playing an essential role as transcription-modulating proteins affecting the transcriptional responses in target genes. Discovery and characterization of nuclear retinoid X receptors (RXRs), which form with TRs a heterodimer RXR/TR, positioned RXRs at the epicenter of molecular endocrinology. Transcriptional control via nuclear RXR/TR heterodimer represents a direct action of thyroid hormone. T₃ plays a crucial role in the development of brain, it exerts significant effects on the cardiovascular system, skeletal muscle contractile function, bone development and growth, both female and male reproductive systems, and skin. It plays an important role in maintaining the hepatic, kidney and intestine homeostasis and in pancreas, it stimulates the beta-cell proliferation and survival. The TRs cross-talk with other signaling pathways intensifies the T₃ action at cellular level. The role of thyroid hormone in human cancers, acting via its cognate nuclear receptors, has not been fully elucidated yet. This review is aimed to describe the history of T₃ receptors, starting from discovery of T3 binding sites in the cell nuclei to revelation of T₃ receptors as T₃-inducible transcription factors in relation to T₃ action at cellular level. It also focuses on milestones of investigation, comprising RXR/TR dimerization, cross-talk between T₃ receptors, and other regulatory pathways within the cell and mainly on genomic action of T₃. This review also focuses on novel directions of investigation on relationships between T₃ receptors and cancer. Based on the update of available literature and the author's experimental experience, it is devoted to clinicians and medical students.

The Role of Osteoclast Energy Metabolism in the Occurrence and Development of Osteoporosis

In recent decades, the mechanism underlying bone metabolic disorders based on energy metabolism has been heavily researched. Bone resorption by osteoclasts plays an important role in the occurrence and development of osteoporosis. However, the mechanism underlying the osteoclast energy metabolism disorder that interferes with bone homeostasis has not been determined. Bone resorption by osteoclasts is a process that consumes large amounts of adenosine triphosphate (ATP) produced by glycolysis and oxidative phosphorylation. In addition to glucose, fatty acids and amino acids can also be used as substrates to produce energy through oxidative phosphorylation. In this review, we summarize and analyze the energy-based phenotypic changes, epigenetic regulation, and coupling with systemic energy metabolism of osteoclasts during the development and progression of osteoporosis. At the same time, we propose a hypothesis, the compensatory recovery mechanism (involving the balance between osteoclast survival and functional activation), which may provide a new approach for the treatment of osteoporosis.

Influence of Low Total Triiodothyronine Levels on Bone Turnover Markers in Type 2 Diabetes Mellitus

PURPOSE

The aim of this study was to investigate whether low total triiodothyronine (TT3) could affect bone turnover in patients with type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

This is a cross-sectional study that recruited 577 patients with T2DM, 141 patients formed the low TT3 group (TT3<1.30nmol/L) and 436 patients formed the control group (TT3≥1.30nmol/L), and the low TT3 group was further subdivided into four groups based on the TT3 level. To investigate whether TT3 level is associated with poor glycemic control, all participants were divided into high glycosylated hemoglobin (HbA1c) group and low HbA1c group using HbA1c 10.5% as the boundary.

RESULTS

The levels of OC and PINP were significantly lower in the low TT3 group compared with the control group (P < 0.05). TT3 positively correlated with OC and PINP (r = 0.219, P = 0.009; r = 0.208, P = 0.019) in the low TT3 group, and this positive correlation still existed after adjusting for other factors in multilinear regression analysis. Next, we want to find a cut-off point to prevent osteoporosis, we divided the patients in the low TT3 group into four groups based on the TT3 level, the levels of OC and PINP were significantly lower in the TT3 < 1.00 nmol/L group than in the TT3 ≥ 1.00 nmol/L groups.

CONCLUSION

In patients with T2DM, low TT3 levels are associated with impaired bone formation. What's more, bone formation was significantly impaired when TT3 was <1.00 nmol/L.