TAK1-AMPK Pathway in Macrophages Regulates Hypothyroid Atherosclerosis

Targeting of AMPK/MTOR signaling in the management of atherosclerosis: Outmost leveraging

Atherosclerosis (AS) is a chronic vascular disorder that is characterized by the thickening and narrowing of arteries due to the development of atherosclerotic plaques. The traditional risk factors involved in AS are obesity, type 2 diabetes (T2D), dyslipidemia, hypertension, and smoking. Furthermore, non-traditional risk factors for AS, such as inflammation, sleep disturbances, physical inactivity, air pollution, and alterations of gut microbiota, gained attention in relation to the pathogenesis of AS. Interestingly, the pathogenesis of AS, is complex and related to different abnormalities of cellular and sub-cellular signaling pathways. It has been illustrated that AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (MTOR) pathways are involved in AS pathogenesis. Mounting evidence indicated that AMPK plays a critical role in attenuating the development of AS by activating autophagy, which is impaired during atherogenesis. AMPK has a vasculoprotective effect by reducing lipid accumulation, inflammatory cell proliferation, and the release of pro-inflammatory cytokines, as well as decreasing inflammatory cell adhesion to the vascular endothelium. AMPK activation by metformin inhibits the migration of vascular smooth muscle cells (VSMCs) and AS development. However, the MTOR pathway contributes to AS by inhibiting autophagy, highlighting autophagy as a crucial link between the AMPK and MTOR pathways in AS pathogenesis. The MTOR is a key inducer of endothelial dysfunction and is involved in the development of AS. Therefore, both the AMPK and MTOR pathways play a crucial role in the pathogenesis of AS. However, the exact role of AMPK and MTOR pathways in the pathogenesis of AS is not fully clarified. Therefore, this review aims to discuss the potential role of the AMPK/MTOR signaling pathway in AS, and how AMPK activators and MTOR inhibitors influence the development and progression of AS. In conclusion, AMPK activators and MTOR inhibitors have vasculoprotective effects against the development and progression of AS.

Biomarkers of endothelial dysfunction and cytokine levels in hypothyroidism: a series of meta-analyses

BACKGROUND

Hypothyroidism (HT) is associated with different comorbidities comprising increased arterial stiffness and decreased flow-mediated dilatation. The exact pathological mechanism of endothelial activation and dysfunction (ED) in HT remains unknown. We conducted a systematic review and meta-analyses to provide an overview of the pathogenesis of ED in HT.

METHODS

The literature search was done in February 2024 for studies analyzing traditional and novel circulating biomarkers of ED in patients with HT, including cytokines and chemokines. Random-effect models were used except when no heterogeneity was found. Protocol was registered under the number PROSPERO CRD42024540560.

RESULTS

25 macromolecules and 66 studies were entered into analyses. HT was associated with increased levels of E-selectin, soluble intercellular adhesion molecule-1, osteoprotegerin, and oxidized-LDL (p < 0.02). Results were not conclusive for endothelin-1. Interleukin (IL)-6, IL-12 and CXCL10 were higher in HT (p < 0.05). Subjects with overt HT may display a proinflammatory tendency with increased levels of IL-6 and interferon-γ, and decreased levels of TGF-β (p < 0.05).

CONCLUSIONS

The data presented and discussed here highlights the association between HT and soluble biomarkers of ED. Inflammatory mediators released by activated T-cells and macrophages may aggravate local and systemic inflammation, which arouses more inflammation, forming a vicious circle leading to ED.

Systematic review and meta-analyses of adipokine levels in hypothyroidism: a role for retinol-binding protein 4

BACKGROUND

Hypothyroidism (HT) is associated with numerous well-characterized comorbidities and established biomarkers for subclinical atherosclerosis which may lead to an elevated risk of cardiovascular disease; however, the precise molecular mechanism underlying these pathological features remains elusive. Increased levels of adipokines may have adverse effects on multiple atherosclerotic risk factors in HT. Different studies have evaluated the association between HT and adipokines with conflicting results.

METHODS

A systematic review and meta-analyses were conducted to provide an overview of adipokine levels in HT. The last literature search was done in February 2024 for studies analyzing traditional and novel circulating adipokines levels (excluding resistin and irisin) in patients with HT. The standard mean differences and 95% confidence intervals (CI) were calculated using random-effect models except if no heterogeneity was found.

RESULTS

HT was not associated with leptin, adiponectin, omentin-1, visfatin, or apelin levels; however, increased retinol-binding protein 4 (RPB4) levels were found in both overall and subclinical HT (p-values = 0.0002 and 0.004 respectively).

CONCLUSION

While pooled analysis suggested a role for RBP4 in hypothyroid patients, associations do not imply cause-effect relationships, and therefore the potential clinical implications of these findings should await further mechanistic studies.

REGISTRATION

The protocol has been registered in the Prospective Register of Systematic Reviews (PROSPERO) under the identification number CRD42024537717.

AMPK, a hub for the microenvironmental regulation of bone homeostasis and diseases

AMP-activated protein kinase (AMPK), a crucial regulatory kinase, monitors energy levels, conserving ATP and boosting synthesis in low-nutrition, low-energy states. Its sensitivity links microenvironmental changes to cellular responses. As the primary support structure and endocrine organ, the maintenance, and repair of bones are closely associated with the microenvironment. While a series of studies have explored the effects of specific microenvironments on bone, there is lack of angles to comprehensively evaluate the interactions between microenvironment and bone cells, especially for bone marrow mesenchymal stem cells (BMMSCs) which mediate the differentiation of osteogenic lineage. It is noteworthy that accumulating evidence has indicated that AMPK may serve as a hub between BMMSCs and microenvironment factors, thus providing a new perspective for us to understand the biology and pathophysiology of stem cells and bone. In this review, we emphasize AMPK's pivotal role in bone microenvironment modulation via ATP, inflammation, reactive oxygen species (ROS), calcium, and glucose, particularly in BMMSCs. We further explore the use of AMPK-activating drugs in the context of osteoarthritis and osteoporosis. Moreover, building upon the foundation of AMPK, we elucidate a viewpoint that facilitates a comprehensive understanding of the dynamic relationship between the microenvironment and bone homeostasis, offering valuable insights for prospective investigations into stem cell biology and the treatment of bone diseases.

Research Advancements in the Interplay between T3 and Macrophages

3,3',5-Triiodo-L-thyronine (T3) is a key endocrine hormone in the human body that plays crucial roles in growth, development, metabolism, and immune function. Macrophages, the key regulatory cells within the immune system, exhibit marked "heterogeneity" and "plasticity", with their phenotype and function subject to modulation by local environmental signals. The interplay between the endocrine and immune systems is well documented. Numerous studies have shown that T3 significantly target macrophages, highlighting them as key cellular components in this interaction. Through the regulation of macrophage function and phenotype, T3 influences immune function and tissue repair in the body. This review comprehensively summarizes the regulatory actions and mechanisms of T3 on macrophages, offering valuable insights into further research of the immunoregulatory effects of T3.

Increased thyroid stimulating hormone (TSH) as a possible risk factor for atherosclerosis in subclinical hypothyroidism

Primary hypothyroidism (PHT) is associated with an increased risk for the development of atherosclerosis (AS) and other cardiovascular disorders. PHT induces atherosclerosis (AS) through the induction of endothelial dysfunction, and insulin resistance (IR). PHT promotes vasoconstriction and the development of hypertension. However, patients with subclinical PHT with normal thyroid hormones (THs) are also at risk for cardiovascular complications. In subclinical PHT, increasing thyroid stimulating hormone (TSH) levels could be one of the causative factors intricate in the progression of cardiovascular complications including AS. Nevertheless, the mechanistic role of PHT in AS has not been fully clarified in relation to increased TSH. Therefore, in this review, we discuss the association between increased TSH and AS, and how increased TSH may be involved in the pathogenesis of AS. In addition, we also discuss how L-thyroxine treatment affects the development of AS.

Cytoplasmic Polyadenylation Element Binding Protein 1 and Atherosclerosis: Prospective Target and New Insights

The ribonucleic acid (RNA)-binding protein Cytoplasmic Polyadenylation Element Binding Protein 1 (CPEB1), a key member of the CPEB family, is essential in controlling gene expression involved in both healthy physiological and pathological processes. CPEB1 can bind to the 3'- untranslated regions (UTR) of substrate messenger ribonucleic acid (mRNA) and regulate its translation. There is increasing evidence that CPEB1 is closely related to the pathological basis of atherosclerosis. According to recent investigations, many pathological processes, including inflammation, lipid metabolism, endothelial dysfunction, angiogenesis, oxidative stress, cellular senescence, apoptosis, and insulin resistance, are regulated by CPEB1. This review considers the prevention and treatment of atherosclerotic heart disease in relation to the evolution of the physiological function of CPEB1, recent research breakthroughs, and the potential participation of CPEB1 in atherosclerosis.

The role of AMPK in macrophage metabolism, function and polarisation

AMP-activated protein kinase (AMPK) is a ubiquitous sensor of energy and nutritional status in eukaryotic cells. It plays a key role in regulating cellular energy homeostasis and multiple aspects of cell metabolism. During macrophage polarisation, AMPK not only guides the metabolic programming of macrophages, but also counter-regulates the inflammatory function of macrophages and promotes their polarisation toward the anti-inflammatory phenotype. AMPK is located at the intersection of macrophage metabolism and inflammation. The metabolic characteristics of macrophages are closely related to immune-related diseases, infectious diseases, cancer progression and immunotherapy. This review discusses the structure of AMPK and its role in the metabolism, function and polarisation of macrophages. In addition, it summarises the important role of the AMPK pathway and AMPK activators in the development of macrophage-related diseases.

Thyroid hormones inhibit apoptosis of macrophage induced by oxidized low-density lipoprotein

Increasing evidence suggests that hypothyroidism aggravates atherosclerosis. Macrophage apoptosis plays a significant role in the development of atherosclerotic plaque. We aimed to explore the effect of thyroid hormones on macrophage apoptosis induced by oxidized low-density lipoprotein (oxLDL). Peripheral blood samples from 20 patients (normal group, hypothyroidism group, coronary artery disease [CAD] group, hypothyroidism + CAD group) were collected to perform messenger RNA microarray analysis. Bioinformatics analysis identified apoptosis and mitogen-activated protein kinase (MAPK) signaling as differentially expressed pathways between CAD and hypothyroidism + CAD group. In vitro, thyroid hormones concentration-dependently promoted cell survival and inhibited apoptosis in oxLDL-treated RAW264.7 macrophages, along with elevated extracellular signal-regulated kinases 1 and 2 (Erk1/2) phosphorylation. The STRING database showed an interaction of thyroid hormone receptor alpha1 (TRα1) and MAPK pathway. TRα1 knockdown increased cell apoptosis and decreased Erk1/2 phosphorylation. Erk1/2 inhibitor aggravated macrophage apoptosis. Moreover, thyroid hormones inhibited oxidative stress in oxLDL-treated macrophages. The study indicates that thyroid hormones concentration-dependently attenuate oxLDL-induced macrophage apoptosis through activating TRα1-Erk1/2 pathway and inhibiting oxidative stress, which implies a potential mechanism of hypothyroid-accelerated atherosclerosis.

Long Noncoding RNA 00472: A Novel Biomarker in Human Diseases

Long non-coding RNAs (lncRNAs) play important roles in human diseases. They control gene expression levels and influence various biological processes through multiple mechanisms. Functional abnormalities in lncRNAs are strongly associated with occurrence and development of various diseases. LINC00472, which is located on chromosome 6q13, is involved in several human diseases, particularly cancers of the breast, lung, liver, osteosarcoma, bladder, colorectal, ovarian, pancreatic and stomach. Importantly, LINC00472 can be used as a biomarker for breast cancer cell sensitivity to chemotherapeutic regimens, including doxorubicin. LINC00472 is regulated by microRNAs and several signaling pathways. However, the significance of LINC00472 in human diseases has not been clearly established. In this review, we elucidate on the significance of LINC00472 in various human diseases, indicating that LINC00472 may be a diagnostic, prognostic as well as therapeutic target for these diseases.