YAP and TAZ protect against white adipocyte cell death during obesity

Enhancing adipose tissue plasticity: progenitor cell roles in metabolic health

Adipose tissue demonstrates considerable plasticity and heterogeneity, enabling metabolic, cellular and structural adaptations to environmental signals. This adaptability is key for maintaining metabolic homeostasis. Impaired adipose tissue plasticity can lead to abnormal adipose tissue responses to metabolic cues, which contributes to the development of cardiometabolic diseases. In chronic obesity, white adipose tissue undergoes pathological remodelling marked by adipocyte hypertrophy, chronic inflammation and fibrosis, which are linked to local and systemic insulin resistance. Research data suggest that the capacity for healthy or unhealthy white adipose tissue remodelling might depend on the intrinsic diversity of adipose progenitor cells (APCs), which sense and respond to metabolic cues. This Review highlights studies on APCs as key determinants of adipose tissue plasticity, discussing differences between subcutaneous and visceral adipose tissue depots during development, growth and obesity. Modulating APC functions could improve strategies for treating adipose tissue dysfunction and metabolic diseases in obesity.

PIEZO1-mediated mechanotransduction regulates collagen synthesis on nanostructured 2D and 3D models of fibrosis

Progressive fibrosis can lead to tissue malfunction and organ failure due to the pathologic accumulation of a collagen-rich extracellular matrix. In vitro models provide useful tools for deconstructing the roles of specific biomechanical or biological mechanisms, such as substrate micro- and nanoscale architecture, in these processes for identifying potential therapeutic targets. Here, we investigated how the mechanosensitive ion channel PIEZO1 influences fibrotic gene and protein expression in adipose-derived stem cells (hASCs). Specifically, we examined the role of PIEZO1 and the mechanosensitive transcription factors YAP/TAZ in sensing aligned or non-aligned substrate architecture to regulate collagen formation. We utilized both 2D microphotopatterned substrates and 3D electrospun polycaprolactone (PCL) substrates to study the role of culture dimensionality. We found that PIEZO1 regulates collagen synthesis in hASCs in a manner that is sensitive to substrate architecture. Activation of PIEZO1 induced significant morphological changes in hASCs, particularly when cultured on aligned substrates, leading to a 30-40 % reduction in cell spreading area and increased cell elongation, in 3D-aligned cultures. Picrosirius Red staining and immunoblotting revealed that PIEZO1 activation reduced collagen accumulation in 3D culture. While YAP translocated to the cytoplasm following PIEZO1 activation, depleting YAP and TAZ did not change collagen expression significantly downstream of PIEZO1 activation, implying that YAP/TAZ translocation from the nucleus and decreased collagen synthesis may be independent consequences of PIEZO1 activation. Our studies demonstrate a role for PIEZO1 in cellular mechanosensing of substrate architecture and provide targetable pathways for treating fibrosis and for enhancing tissue-engineered and regenerative approaches for fibrous tissue repair. STATEMENT OF SIGNIFICANCE: This study examines how cells sense and respond to their physical environment via PIEZO1 mechanotransduction. We discovered that cells use PIEZO1 to detect the alignment of surrounding structures, influencing the production of collagen - a key component in fibrosis. Our study used both 2D and 3D models to mimic different tissue environments, providing new insights into how cellular responses change in more complex settings. Importantly, we found that activating PIEZO1 alters cell shape and collagen production, especially on aligned surfaces. Interestingly, while PIEZO1 activation caused YAP translocation to the cytoplasm, this translocation did not directly affect collagen production. This work advances our understanding of fibrosis development and identifies PIEZO1 as a potential target for new therapies.

Inhibition of AHCY impedes proliferation and differentiation of mouse and human adipocyte progenitor cells

S-adenosyl-homocysteine-hydrolase (AHCY) plays an important role in the methionine cycle regulating cellular methylation levels. AHCY has been reported to influence proliferation and differentiation processes in different cell types, e.g. in cancer cells and mouse embryonic stem cells. In the development of adipose tissue, both the proliferation and differentiation of adipocyte progenitor cells (APCs) are important processes, which in the context of obesity are often dysregulated. To assess whether AHCY might also be involved in cell proliferation and differentiation of APCs, we investigated the effect of reduced AHCY activity on human and mouse APCs in vitro. We show that the inhibition of AHCY using adenosine dialdehyde (AdOx) and the knockdown of AHCY using gene-specific siRNAs reduced APC proliferation and number. Inhibition of AHCY further reduced APC differentiation into mature adipocytes and the expression of adipogenic differentiation markers. Global DNA methylation profiling in human APCs revealed that inhibition of AHCY is associated with alterations in CpG methylation levels of genes involved in fat cell differentiation and pathways related to cellular growth. Our findings suggest that AHCY is necessary for the maintenance of APC proliferation and differentiation and inhibition of AHCY alters DNA methylation processes leading to a dysregulation of the expression of genes involved in the regulation of these processes.

A key role of PIEZO2 mechanosensitive ion channel in adipose sensory innervation

Compared to the well-established functions of sympathetic innervation, the role of sensory afferents in adipose tissues remains less understood. Recent work revealed the anatomical and physiological significance of adipose sensory innervation; however, its molecular underpinning remains unclear. Here, using organ-targeted single-cell RNA sequencing, we identified the mechanoreceptor PIEZO2 as one of the most prevalent receptors in fat-innervating dorsal root ganglia (DRG) neurons. We found that selective PIEZO2 deletion in fat-innervating neurons phenocopied the molecular alternations in adipose tissue caused by DRG ablation. Conversely, a gain-of-function PIEZO2 mutant shifted the adipose phenotypes in the opposite direction. These results indicate that PIEZO2 plays a major role in the sensory regulation of adipose tissues. This discovery opens new avenues for exploring mechanosensation in organs not traditionally considered mechanically active, such as the adipose tissues, and therefore sheds light on the broader significance of mechanosensation in regulating organ function and homeostasis.

Tissue adaptation to metabolic stress: insights from SUMOylation

Post-translational modification (PTM) plays a crucial role in adaptation of mammals to environmental changes, enabling them to survive in stressful situations. One such PTM is SUMO modification, which is evolutionarily conserved. It involves the covalent and reversible attachment of a small ubiquitin-like modifier (SUMO) to lysine (Lys) residues in the target protein. SUMOylation regulates various functions, including cell proliferation, differentiation, apoptosis, senescence, and maintenance of specific cellular activities. It achieves this by influencing protein-protein interactions, subcellular localization, protein stability, and DNA binding activity. Mounting evidence suggests that SUMOylation is implicated in the pathogenesis of metabolic disorders such as obesity, insulin resistance, and fatty liver. This review aims to provide an overview of the role of SUMOylation in regulating tissue adaptation to metabolic stress. Recent advancements in spectroscopic techniques have shed light on potential targets of SUMOylation and the underlying regulatory mechanisms have been elucidated, laying the theoretical foundation for the development of targeted SUMOylation interventions for metabolic syndrome while minimizing side effects.

The Hippo Signaling Pathway, Reactive Oxygen Species Production, and Oxidative Stress: A Two-Way Traffic Regulation

The Hippo signaling pathway is recognized for its significant role in cell differentiation, proliferation, survival, and tissue regeneration. Recently, the Hippo signaling pathway was also found to be associated with oxidative stress and reactive oxygen species (ROS) regulation, which are important in the regulation of cell survival. Studies indicate a correlation between components of the Hippo signaling pathway, including MST1, YAP, and TAZ, and the generation of ROS. On the other hand, ROS and oxidative stress can activate key components of the Hippo signaling pathway. For example, ROS production activates MST1, which subsequently phosphorylates FOXO3, leading to apoptotic cell death. ROS was also found to regulate YAP, in addition to MST1/2. Oxidative stress and ROS formation can impair lipids, proteins, and DNA, leading to many disorders, including aging, neurodegeneration, atherosclerosis, and diabetes. Consequently, understanding the interplay between the Hippo signaling pathway, ROS, and oxidative stress is crucial for developing future disease management strategies. This paper aimed to review the association between the Hippo signaling pathway, regulation of ROS production, and oxidative stress to provide beneficial information in understanding cell function and pathological processes.

miR-10a regulates cell death and inflammation in adipose tissue of male mice with diet-induced obesity

OBJECTIVE

Adipose tissue remodeling plays a critical role in obesity-induced metabolic dysfunction, but the underlying molecular mechanisms remain incompletely understood. This study investigates the role of miR-10a-5p in adipose tissue inflammation and metabolic dysfunction induced by a high-fat diet (HFD).

METHODS

Male miR-10a knockout (KO) mice were fed a HFD to induce obesity for up to 16 weeks. RNA sequencing (RNA-seq) analysis was performed to profile mRNA expression and assess the effects of miR-10a-5p KO in gonadal white adipose tissue (gWAT). Additional analyses included immunoblotting, qPCR, histological examination, and validation of the miR-10a-5p target sequence using a dual-luciferase reporter assay.

RESULTS

miR-10a-5p was highly expressed in gWAT but decreased after 8 weeks of HFD feeding. Over the 16-week HFD period, miR-10a KO mice exhibited greater weight gain and reduced energy expenditure compared to wild-type (WT) controls. gWAT of miR-10a KO mice on a HFD showed an increased population of proinflammatory macrophages, elevated inflammation, and increased cell death, characterized by upregulated apoptosis and necrosis markers. This was also associated with increased triglyceride accumulation in liver. Mechanistically, the proapoptotic gene Bcl2l11 was identified as a direct target of miR-10a-5p. Loss of miR-10a-5p led to BIM-mediated adipocyte death and inflammation, contributing to mitochondrial metabolic dysregulation, increased fibrosis marker expression, and the onset of inflammation in adipose tissue.

CONCLUSIONS

This study demonstrates the significant role of miR-10a-5p and its downstream target BIM in regulating adipocyte death during diet-induced obesity. This signaling pathway presents a potential therapeutic target for modulating obesity-induced inflammation and cell death in adipose tissue.

Biomaterials Mimicking Mechanobiology: A Specific Design for a Specific Biological Application

Mechanosensing and mechanotransduction pathways between the Extracellular Matrix (ECM) and cells form the essential crosstalk that regulates cell homeostasis, tissue development, morphology, maintenance, and function. Understanding these mechanisms involves creating an appropriate cell support that elicits signals to guide cellular functions. In this context, polymers can serve as ideal molecules for producing biomaterials designed to mimic the characteristics of the ECM, thereby triggering responsive mechanisms that closely resemble those induced by a natural physiological system. The generated specific stimuli depend on the different natural or synthetic origins of the polymers, the chemical composition, the assembly structure, and the physical and surface properties of biomaterials. This review discusses the most widely used polymers and their customization to develop biomaterials with tailored properties. It examines how the characteristics of biomaterials-based polymers can be harnessed to replicate the functions of biological cells, making them suitable for biomedical and biotechnological applications.

Directly targeting PRDM16 in thermogenic adipose tissue to treat obesity and its related metabolic diseases

Obesity is increasing globally and is closely associated with a range of metabolic disorders, including metabolic associated fatty liver disease, diabetes, and cardiovascular diseases. An effective strategy to combat obesity involves stimulating brown and beige adipocyte thermogenesis, which significantly enhances energy expenditure. Recent research has underscored the vital role of PRDM16 in the development and functionality of thermogenic adipocytes. Consequently, PRDM16 has been identified as a potential therapeutic target for obesity and its related metabolic disorders. This review comprehensively examines various studies that focus on combating obesity by directly targeting PRDM16 in adipose tissue.

Hepatocyte-Specific Yap1 Knockout Maintained the Liver Homeostasis of Lipid Metabolism in Mice

Introduction

Yes-associated protein 1 (YAP1) is a crucial molecule in the Hippo pathway. The impact of hepatocyte-specific Yap1 knockout (Yap1 LKO) on hepatic lipid droplets (LD) and pePLIN2 in metabolic fatty liver has not been reported. This study aims to explore whether Yap1 LKO could offer a protective effect in a liver injury model.

Methods

Three-week-old Yap1 LKO and Yap1 Flox mice were given aristolochic acid I (AAI) combined carbon tetrachloride (CCL4) establish liver injury model. Eight-week-old Yap1 LKO and Yap1 Flox mice were fed with a high-fat diet for 18 weeks to establish obesity-related liver injury model. Further biochemical, histomorphological, immunohistochemical, and lipidomic analyses were performed on serum and liver tissues of these mice to elucidate the effects of hepatocyte-specific Yap1 knockout on hepatic lipid metabolism.

Results

Yap1 LKO reduced triglyceride (TG) content and PLIN2 expression level in the liver during the intervention of AAI combined CCl4. Moreover, Yap1 LKO improved lipid metabolism homeostasis in the liver by increasing the beneficial lipid molecules and reducing the harmful lipid molecules through lipidomics. Finally, Yap1 LKO reduced TG content in the serum and liver, hepatic vacuolar degeneration, and hepatic PLIN2 expression level in mice fed with a high-fat diet (HFD).

Conclusion

Yap1 LKO is protective in regulating liver and blood TG when induced with toxic substances AAI combined CCl4 and a high-fat diet.

Recent advances in the effect of adipose tissue inflammation on insulin resistance

Obesity is one of the major risk factors for diabetes. Excessive accumulation of fat leads to inflammation of adipose tissue, which can increase the risk of developing diabetes. Obesity-related chronic inflammation can result in anomalies in glucose-lipid metabolism and insulin resistance, and it is a major cause of β-cell dysfunction in diabetes mellitus. Thus, a long-term tissue inflammatory response is crucial for metabolic diseases, particularly type 2 diabetes. Chronic inflammation associated with obesity increases oxidative stress, secretes inflammatory factors, modifies endocrine variables, and interferes with insulin signalling pathways, all of which contribute to insulin resistance and glucose tolerance. Insulin resistance and diabetes are ultimately caused by chronic inflammation in the stomach, pancreas, liver, muscle, and fat tissues. In this article, we systematically summarize the latest research progress on the mechanisms of adipose tissue inflammation and insulin resistance, as well as the mechanisms of cross-talk between adipose tissue inflammation and insulin resistance, with a view to providing some meaningful therapeutic strategies for the treatment of insulin resistance by controlling adipose tissue inflammation.

Mechanobiology in Metabolic Dysfunction-Associated Steatotic Liver Disease and Obesity

With the ongoing obesity epidemic, the prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) is expected to rise and necessitates a greater understanding of how the disease proceeds from benign excess lipid in hepatocytes to liver fibrosis and eventually to liver cancer. MASLD is caused, at least in part, by hepatocytes' storage of free fatty acids (FAs) that dysfunctional adipocytes are no longer able to store, and therefore, MASLD is a disease that involves both the liver and adipose tissues. The disease progression is not only facilitated by biochemical signals, but also by mechanical cues such as the increase in stiffness often seen with fibrotic fatty livers. The change in stiffness and accumulation of excess lipid droplets impact the ability of a cell to mechanosense and mechanotranduce, which perpetuates the disease. A mechanosensitive protein that is largely unexplored and could serve as a potential therapeutic target is the intermediate filament vimentin. In this review, we briefly summarize the recent research on hepatocyte and adipocyte mechanobiology and provide a synopsis of studies on the varied, and sometimes contradictory, roles of vimentin. This review is intended to benefit and encourage future studies on hepatocyte and adipocyte mechanobiology in the context of MASLD and obesity.

Hippo-YAP/TAZ signalling coordinates adipose plasticity and energy balance by uncoupling leptin expression from fat mass

Adipose tissues serve as an energy reservoir and endocrine organ, yet the mechanisms that coordinate these functions remain elusive. Here, we show that the transcriptional coregulators, YAP and TAZ, uncouple fat mass from leptin levels and regulate adipocyte plasticity to maintain metabolic homeostasis. Activating YAP/TAZ signalling in adipocytes by deletion of the upstream regulators Lats1 and Lats2 results in a profound reduction in fat mass by converting mature adipocytes into delipidated progenitor-like cells, but does not cause lipodystrophy-related metabolic dysfunction, due to a paradoxical increase in circulating leptin levels. Mechanistically, we demonstrate that YAP/TAZ-TEAD signalling upregulates leptin expression by directly binding to an upstream enhancer site of the leptin gene. We further show that YAP/TAZ activity is associated with, and functionally required for, leptin regulation during fasting and refeeding. These results suggest that adipocyte Hippo-YAP/TAZ signalling constitutes a nexus for coordinating adipose tissue lipid storage capacity and systemic energy balance through the regulation of adipocyte plasticity and leptin gene transcription.

CSN6-SPOP-HMGCS1 Axis Promotes Hepatocellular Carcinoma Progression via YAP1 Activation

Cholesterol metabolism has important roles in maintaining membrane integrity and countering the development of diseases such as obesity and cancers. Cancer cells sustain cholesterol biogenesis for their proliferation and microenvironment reprograming even when sterols are abundant. However, efficacy of targeting cholesterol metabolism for cancer treatment is always compromised. Here it is shown that CSN6 is elevated in HCC and is a positive regulator of hydroxymethylglutaryl-CoA synthase 1 (HMGCS1) of mevalonate (MVA) pathway to promote tumorigenesis. Mechanistically, CSN6 antagonizes speckle-type POZ protein (SPOP) ubiquitin ligase to stabilize HMGCS1, which in turn activates YAP1 to promote tumor growth. In orthotopic liver cancer models, targeting CSN6 and HMGCS1 hinders tumor growth in both normal and high fat diet. Significantly, HMGCS1 depletion improves YAP inhibitor efficacy in patient derived xenograft models. The results identify a CSN6-HMGCS1-YAP1 axis mediating tumor outgrowth in HCC and propose a therapeutic strategy of targeting non-alcoholic fatty liver diseases- associated HCC.

High-Titer Anti-ZSCAN1 Antibodies in a Toddler Clinically Diagnosed with Apparent Rapid-Onset Obesity with Hypothalamic Dysfunction, Hypoventilation, and Autonomic Dysregulation Syndrome

Severe obesity in young children prompts for a differential diagnosis that includes syndromic conditions. Rapid-Onset Obesity with Hypothalamic Dysfunction, Hypoventilation, and Autonomic Dysregulation (ROHHAD) syndrome is a potentially fatal disorder characterized by rapid-onset obesity associated with hypoventilation, neural crest tumors, and endocrine and behavioral abnormalities. The etiology of ROHHAD syndrome remains to be established, but recent research has been focusing on autoimmunity. We report on a 2-year-old girl with rapid-onset obesity during the first year of life who progressed to hypoventilation and encephalitis in less than four months since the start of accelerated weight gain. The patient had a high titer of anti-ZSCAN1 antibodies (348; reference range < 40), and the increased values did not decline after acute phase treatment. Other encephalitis-related antibodies, such as the anti-NDMA antibody, were not detected. The rapid progression from obesity onset to central hypoventilation with encephalitis warns about the severe consequences of early-onset ROHHAD syndrome. These data indicate that serial measurements of anti-ZSCAN1 antibodies might be useful for the diagnosis and estimation of disease severity. Further research is needed to determine whether it can predict the clinical course of ROHHAD syndrome and whether there is any difference in antibody production between patients with and without tumors.

Beneficial effects of Apelin-13 on metabolic diseases and exercise

Apelin, a novel endogenous ligand of the G-protein-coupled receptor APJ, is encoded by the APLN gene and can be hydrolyzed into multiple subtypes, with Apelin-13 being one of the most active subtypes of the Apelin family. Recent studies have revealed that Apelin-13 functions as an adipokine that participates in the regulation of different biological processes, such as oxidative stress, inflammation, apoptosis, and energy metabolism, thereby playing an important role in the prevention and treatment of various metabolic diseases. However, the results of recent studies on the association between Apelin-13 and various metabolic states remain controversial. Furthermore, Apelin-13 is regulated or influenced by various forms of exercise and could therefore be categorized as a new type of exercise-sensitive factor that attenuates metabolic diseases. Thus, in this review, our purpose was to focus on the relationship between Apelin-13 and related metabolic diseases and the regulation of response movements, with particular reference to the establishment of a theoretical basis for improving and treating metabolic diseases.

Transcriptional repression of beige fat innervation via a YAP/TAZ-S100B axis

Sympathetic innervation is essential for the development of functional beige fat that maintains body temperature and metabolic homeostasis, yet the molecular mechanisms controlling this innervation remain largely unknown. Here, we show that adipocyte YAP/TAZ inhibit sympathetic innervation of beige fat by transcriptional repression of neurotropic factor S100B. Adipocyte-specific loss of Yap/Taz induces S100b expression to stimulate sympathetic innervation and biogenesis of functional beige fat both in subcutaneous white adipose tissue (WAT) and browning-resistant visceral WAT. Mechanistically, YAP/TAZ compete with C/EBPβ for binding to the zinc finger-2 domain of PRDM16 to suppress S100b transcription, which is released by adrenergic-stimulated YAP/TAZ phosphorylation and inactivation. Importantly, Yap/Taz loss in adipocytes or AAV-S100B overexpression in visceral WAT restricts both age-associated and diet-induced obesity, and improves metabolic homeostasis by enhancing energy expenditure of mice. Together, our data reveal that YAP/TAZ act as a brake on the beige fat innervation by blocking PRDM16-C/EBPβ-mediated S100b expression.

Bioinformatics and system biology approach to identify the influences of SARS-CoV-2 on metabolic unhealthy obese patients

Introduction: The severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) has posed a significant challenge to individuals' health. Increasing evidence shows that patients with metabolic unhealthy obesity (MUO) and COVID-19 have severer complications and higher mortality rate. However, the molecular mechanisms underlying the association between MUO and COVID-19 are poorly understood. Methods: We sought to reveal the relationship between MUO and COVID-19 using bioinformatics and systems biology analysis approaches. Here, two datasets (GSE196822 and GSE152991) were employed to extract differentially expressed genes (DEGs) to identify common hub genes, shared pathways, transcriptional regulatory networks, gene-disease relationship and candidate drugs. Results: Based on the identified 65 common DEGs, the complement-related pathways and neutrophil degranulation-related functions are found to be mainly affected. The hub genes, which included SPI1, CD163, C1QB, SIGLEC1, C1QA, ITGAM, CD14, FCGR1A, VSIG4 and C1QC, were identified. From the interaction network analysis, 65 transcription factors (TFs) were found to be the regulatory signals. Some infections, inflammation and liver diseases were found to be most coordinated with the hub genes. Importantly, Paricalcitol, 3,3',4,4',5-Pentachlorobiphenyl, PD 98059, Medroxyprogesterone acetate, Dexamethasone and Tretinoin HL60 UP have shown possibility as therapeutic agents against COVID-19 and MUO. Conclusion: This study provides new clues and references to treat both COVID-19 and MUO.

AMPK-Dependent YAP Inhibition Mediates the Protective Effect of Metformin against Obesity-Associated Endothelial Dysfunction and Inflammation

Hyperglycemia is a crucial risk factor for cardiovascular diseases. Chronic inflammation is a central characteristic of obesity, leading to many of its complications. Recent studies have shown that high glucose activates Yes-associated protein 1 (YAP) by suppressing AMPK activity in breast cancer cells. Metformin is a commonly prescribed anti-diabetic drug best known for its AMPK-activating effect. However, the role of YAP in the vasoprotective effect of metformin in diabetic endothelial cell dysfunction is still unknown. The present study aimed to investigate whether YAP activation plays a role in obesity-associated endothelial dysfunction and inflammation and examine whether the vasoprotective effect of metformin is related to YAP inhibition. Reanalysis of the clinical sequencing data revealed YAP signaling, and the YAP target genes CTGF and CYR61 were upregulated in aortic endothelial cells and retinal fibrovascular membranes from diabetic patients. YAP overexpression impaired endothelium-dependent relaxations (EDRs) in isolated mouse aortas and increased the expression of YAP target genes and inflammatory markers in human umbilical vein endothelial cells (HUVECs). High glucose-activated YAP in HUVECs and aortas was accompanied by increased production of oxygen-reactive species. AMPK inhibition was found to induce YAP activation, resulting in increased JNK activity. Metformin activated AMPK and promoted YAP phosphorylation, ultimately improving EDRs and suppressing the JNK activity. Targeting the AMPK-YAP-JNK axis could become a therapeutic strategy for alleviating vascular dysfunction in obesity and diabetes.

Mitochondria-associated programmed cell death as a therapeutic target for age-related disease

Mitochondria, ubiquitous double-membrane-bound organelles, regulate energy production, support cellular activities, harbor metabolic pathways, and, paradoxically, mediate cell fate. Evidence has shown mitochondria as points of convergence for diverse cell death-inducing pathways that trigger the various mechanisms underlying apoptotic and nonapoptotic programmed cell death. Thus, dysfunctional cellular pathways eventually lead or contribute to various age-related diseases, such as neurodegenerative, cardiovascular and metabolic diseases. Thus, mitochondrion-associated programmed cell death-based treatments show great therapeutic potential, providing novel insights in clinical trials. This review discusses mitochondrial quality control networks with activity triggered by stimuli and that maintain cellular homeostasis via mitohormesis, the mitochondrial unfolded protein response, and mitophagy. The review also presents details on various forms of mitochondria-associated programmed cell death, including apoptosis, necroptosis, ferroptosis, pyroptosis, parthanatos, and paraptosis, and highlights their involvement in age-related disease pathogenesis, collectively suggesting therapeutic directions for further research.

Association between interatrial septum adiposity and atrial fibrillation: transesophageal echocardiography imaging and autopsy study

Recent clinical evidence has suggested that interatrial septal (IAS) adiposity contributes to atrial fibrillation (AF). The present study aimed to confirm the usefulness of transesophageal echocardiography (TEE) to estimate IAS adiposity in patients with AF. The histological IAS analysis based on autopsy samples sought to clarify characteristics that underlie the contribution of IAS adiposity to AF. The imaging study analyzed the TEE results in patients with AF (n = 184) in comparison with transthoracic echocardiography (TTE) and computed tomography (CT) results. The autopsy study histologically analyzed IAS in subjects with (n = 5) and without (n = 5) history of AF. In the imaging study, the ratio of interatrial septum adipose tissue (IAS-AT) volume per epicardial adipose tissue (EpAT) volume was greater in patients with persistent AF compared (PerAF) to those with paroxysmal AF (PAF). Multivariable analysis revealed that both TEE-assessed IAS thickness and TTE-assessed left atrial dimension were predicted by CT-assessed IAS-AT volume. In the autopsy study, the histologically-assessed IAS section thickness was greater in the AF group than that in the non-AF group and was positively correlated with the IAS-AT area percentage. In addition, the size of adipocytes in IAS-AT was smaller, compared to EpAT and subcutaneous adipose tissue (SAT). IAS-AT infiltrated into the IAS myocardium, as if adipose tissue split the myocardium (designated as myocardial splitting by IAS-AT). The number of island-like myocardium pieces as a result of myocardial splitting by IAS-AT was greater in the AF group than in the non-AF group and was positively correlated with the IAS-AT area percentage. The present imaging study confirmed the usefulness of TEE to estimate IAS adiposity in patients with AF without radiation exposure. The autopsy study suggested that the myocardial splitting by IAS-AT may contribute to atrial cardiomyopathy leading to AF.

Signaling pathways and intervention for therapy of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) represents one of the fastest growing epidemic metabolic disorders worldwide and is a strong contributor for a broad range of comorbidities, including vascular, visual, neurological, kidney, and liver diseases. Moreover, recent data suggest a mutual interplay between T2DM and Corona Virus Disease 2019 (COVID-19). T2DM is characterized by insulin resistance (IR) and pancreatic β cell dysfunction. Pioneering discoveries throughout the past few decades have established notable links between signaling pathways and T2DM pathogenesis and therapy. Importantly, a number of signaling pathways substantially control the advancement of core pathological changes in T2DM, including IR and β cell dysfunction, as well as additional pathogenic disturbances. Accordingly, an improved understanding of these signaling pathways sheds light on tractable targets and strategies for developing and repurposing critical therapies to treat T2DM and its complications. In this review, we provide a brief overview of the history of T2DM and signaling pathways, and offer a systematic update on the role and mechanism of key signaling pathways underlying the onset, development, and progression of T2DM. In this content, we also summarize current therapeutic drugs/agents associated with signaling pathways for the treatment of T2DM and its complications, and discuss some implications and directions to the future of this field.

Endothelial FAT1 inhibits angiogenesis by controlling YAP/TAZ protein degradation via E3 ligase MIB2

Activation of endothelial YAP/TAZ signaling is crucial for physiological and pathological angiogenesis. The mechanisms of endothelial YAP/TAZ regulation are, however, incompletely understood. Here we report that the protocadherin FAT1 acts as a critical upstream regulator of endothelial YAP/TAZ which limits the activity of these transcriptional cofactors during developmental and tumor angiogenesis by promoting their degradation. We show that loss of endothelial FAT1 results in increased endothelial cell proliferation in vitro and in various angiogenesis models in vivo. This effect is due to perturbed YAP/TAZ protein degradation, leading to increased YAP/TAZ protein levels and expression of canonical YAP/TAZ target genes. We identify the E3 ubiquitin ligase Mind Bomb-2 (MIB2) as a FAT1-interacting protein mediating FAT1-induced YAP/TAZ ubiquitination and degradation. Loss of MIB2 expression in endothelial cells in vitro and in vivo recapitulates the effects of FAT1 depletion and causes decreased YAP/TAZ degradation and increased YAP/TAZ signaling. Our data identify a pivotal mechanism of YAP/TAZ regulation involving FAT1 and its associated E3 ligase MIB2, which is essential for YAP/TAZ-dependent angiogenesis.

Changes in Adipose Tissue Gene Expression of the Core Components of the Hippo Signaling Pathway in Young Adults with Uncomplicated Overweight or Obesity Following Weight Loss

BACKGROUND

Appropriate adipogenesis leads to the "healthy" expansion of adipose tissue and is a crucial component in maintaining metabolic homeostasis. The Hippo signaling network may balance adipocyte proliferation/differentiation regulating adipogenic footpath.

OBJECTIVES

Our study aimed to assess subcutaneous adipose tissue (SAT) expression of genes involved in Hippo signaling network in subjects with marked overweight or obesity after dietary intervention (DI) in relation to obesity and insulin sensitivity.

METHODS

Forty overweight or obese subjects (O/O) [mean ± SD age 33 ± 7 y, 45% men, BMI (in kg/m²) 32.9 ± 3.1] completed DI [low-calorie diet (20 kcal/kg of proper body weight) for 12 wks]. The control group comprising 20 normal-weight subjects (mean ± SD age: 24 ± 2 y, 40% men, BMI: 22.4 ± 2.3 ) was examined at baseline only. Hyperinsulinemic-euglycemic clamp and SAT biopsy with gene expression analysis were performed. Student's t-test for unpaired and paired samples and Pearson correlation analysis were applied. This is an exploratory analysis of the DI program.

RESULTS

SAT mRNA expression of mammalian sterile 20-like kinase 2 (MST2) encoded by serine/threonine kinase 3 gene (STK3)-->, large tumor suppressor kinase 2 (LATS2), and salvador family WW domain containing protein 1 (SAV1), the upstream members of the Hippo pathway, were decreased (21%, 40%, and 36%, respectively) in O/O in comparison with weight subjects individuals before DI (all P < 0.05). At baseline, positive correlations between SAT SAV1, LATS2 expression and adiponectin (ADIPOQ) (r = 0.50, P < 0.001; r = 0.53, P = 0.004, respectively) and solute carrier family 2 member 4 (SLC2A4) (r = 0.35, P = 0.007; r = 0.28, P = 0.03, respectively) expression were observed in the entire study group. Body weight of the O/O group decreased during DI (11.2 ± 3.8 kg, P < 0.001), and there was an increase in insulin sensitivity (by 27%) and SAT expression of STK3, LATS2 (both by 19%), and SAV1 (by 26%) (all P < 0.05). After DI, SAT SLC2A4 expression was correlated with STK3 (r = 0.47, P = 0.003), LATS2 (r = 0.56, P < 0.001), and yes-associated protein (r = 0.50, P = 0.001) expression.

CONCLUSIONS

Obesity is associated with altered mRNA expression of upstream effectors of the Hippo pathway in SAT in young adults. DI may improve adipogenic capacity. J Nutr 20XX;xx:xx-xx.

Never-in-Mitosis A-Related Kinase 8 (NEK8) Regulates Adipogenesis, Glucose Homeostasis, and Obesity

Background

Adipogenesis is a complex biological process and the leading main cause of obesity. We evaluated the role of never-in-mitosis A-related kinase 8 (NEK8) in adipocyte development and insulin sensitivity in the present study.

Methods

NEK8 expression was manipulated using a specific shRNA or the NEK8-full-length expressing recombinant plasmids. The interaction between NEK8 and Tafazzin (TAZ, an oncogenic transcriptional regulator) was examined by Co-immunoprecipitation (Co-IP) and confocal immunofluorescence staining. Western blot assay was performed to determine the protein expression. The in vivo role of NEK8 was explored in a mouse model of high-fat diet- (HFD-) induced insulin resistance.

Results

During adipogenesis, the expression of NEK8 was elevated while TAZ was downregulated. Overexpression of NEK8 promoted lipid accumulation and expression of markers for adipocyte differentiation. Mechanically, NEK8 interacted with TAZ and suppressed its expression in adipocytes. Functionally, lentiviral-mediated NEK8 inhibition ameliorates HFD-induced insulin resistance in adipocytes.

Conclusion

These findings suggest that NEK8 plays a critical role in adipocyte proliferation, providing novel insight into the link between NEK8 and type 2 diabetes- (T2DM-) related obesity.

Aberrant Mesenteric Adipose Extracellular Matrix Remodelling is Involved in Adipocyte Dysfunction in Crohn's Disease: The Role of TLR-4-mediated Macrophages

BACKGROUND AND AIMS

Hypertrophic mesenteric adipose tissue [htMAT] is involved in the disease progression of Crohn's disease [CD] through expressing proinflammatory adipokines from dysfunctional adipocytes by unknown mechanism. Adipocyte function is affected by dynamic adipose tissue extracellular matrix [ECM] remodelling that is mainly mediated by macrophages, and our study aimed to reveal whether aberrant ECM remodelling was present in CD-htMAT and its effects on adipocyte dysfunction, as well as the mechanism.

METHODS

ECM remodelling was examined in MAT samples from CD patients and controls. Mice with dinitrobenzene sulphonic acid [DNBS]-induced colitis were used in vivo study, and lipopolysaccharide [LPS]-induced remodelling behaviour in macrophages was examined in vitro. Macrophages or TLR4 inhibition were used to analyse ECM remodelling mechanisms and their effects on adipocyte function.

RESULTS

Aberrant ECM remodelling: was observed in CD-htMAT, which was characterised by a widened and deformed ECM structure accompanied by dysregulated matrix synthesis and degradation; served as a reservoir for inflammatory factors/cells dominated by macrophages; and was involved in adipocyte dysfunction. In addition, macrophages were the main source of ECM remodelling regulatory factors with activation of Toll-like receptor 4 [TLR4] in htMAT. In vivo, macrophage depletion or TLR4 inhibition largely attenuated mesenteric ECM remodelling while improving mesenteric adipocyte dysfunction during chronic enteritis. In vitro, antagonizing TLR4 significantly inhibited LPS-induced macrophage ECM remodelling behavior.

CONCLUSIONS

The aberrant ECM remodelling in CD-htMAT contributed to mesenteric adipocyte dysfunction, which may be caused at least partly by TLR4-mediated macrophage remodelling behavior. Inhibiting ECM remodelling may be a potential therapeutic strategy for CD.

Disruption of adipocyte YAP improves glucose homeostasis in mice and decreases adipose tissue fibrosis

OBJECTIVE

Adipose tissue is a very dynamic metabolic organ that plays an essential role in regulating whole-body glucose homeostasis. Dysfunctional adipose tissue hypertrophy with obesity is associated with fibrosis and type 2 diabetes. Yes-associated protein 1 (YAP) is a transcription cofactor important in the Hippo signaling pathway. However, the role of YAP in adipose tissue and glucose homeostasis is unknown.

METHODS

To study the role of YAP with metabolic stress, we assessed how increased weight and insulin resistance impact YAP in humans and mouse models. To further investigate the in vivo role of YAP specifically in adipose tissue and glucose homeostasis, we developed adipose tissue-specific YAP knockout mice and placed them on either chow or high fat diet (HFD) for 12-14 weeks. To further study the direct role of YAP in adipocytes we used 3T3-L1 cells.

RESULTS

We found that YAP protein levels increase in adipose tissue from humans with type 2 diabetes and mouse models of diet-induced obesity and insulin resistance. This suggests that YAP signaling may contribute to adipocyte dysfunction and insulin resistance under metabolic stress conditions. On an HFD, adipose tissue YAP knockout mice had improved glucose tolerance compared to littermate controls. Perigonadal fat pad weight was also decreased in knockout animals, with smaller adipocyte size. Adipose tissue fibrosis and gene expression associated with fibrosis was decreased in vivo and in vitro in 3T3-L1 cells treated with a YAP inhibitor or siRNA.

CONCLUSIONS

We show that YAP is increased in adipose tissue with weight gain and insulin resistance. Disruption of YAP in adipocytes prevents glucose intolerance and adipose tissue fibrosis, suggesting that YAP plays an important role in regulating adipose tissue and glucose homeostasis with metabolic stress.

Mouse models of nonalcoholic fatty liver disease (NAFLD): pathomechanisms and pharmacotherapies

The prevalence of non-alcoholic fatty liver disease (NAFLD) increases year by year, and as a consequence, NAFLD has become one of the most prevalent liver diseases worldwide. Unfortunately, no pharmacotherapies for NAFLD have been approved by the United States Food and Drug Administration despite promising pre-clinical benefits; this situation highlights the urgent need to explore new therapeutic targets for NAFLD and for the discovery of effective therapeutic drugs. The mouse is one of the most commonly used models to study human disease and develop novel pharmacotherapies due to its small size, low-cost and ease in genetic engineering. Different mouse models are used to simulate various stages of NAFLD induced by dietary and/or genetic intervention. In this review, we summarize the newly described patho-mechanisms of NAFLD and review the preclinical mouse models of NAFLD (based on the method of induction) and appraises the use of these models in anti-NAFLD drug discovery. This article will provide a useful resource for researchers to select the appropriate model for research based on the research question being addressed.

Importance of the Microenvironment and Mechanosensing in Adipose Tissue Biology

The expansion of adipose tissue is an adaptive mechanism that increases nutrient buffering capacity in response to an overall positive energy balance. Over the course of expansion, the adipose microenvironment undergoes continual remodeling to maintain its structural and functional integrity. However, in the long run, adipose tissue remodeling, typically characterized by adipocyte hypertrophy, immune cells infiltration, fibrosis and changes in vascular architecture, generates mechanical stress on adipose cells. This mechanical stimulus is then transduced into a biochemical signal that alters adipose function through mechanotransduction. In this review, we describe the physical changes occurring during adipose tissue remodeling, and how they regulate adipose cell physiology and promote obesity-associated dysfunction in adipose tissue.

Effects of age on subcutaneous adipose tissue proteins in Chinese indigenous Ningxiang pig by TMT-labeled quantitative proteomics

Adipose tissue not only affects meat quality and animal productivity, but also participates in inflammation and immunity. Ningxiang pig is famous for their excellent meat quality, disease resistance and tolerance of roughage. It is not yet well known how proteins in adipose tissue is dynamically regulated during the growth of Ningxiang pig. This report studies the proteomic changes in subcutaneous adipose tissue in Ningxiang pigs to gain a better understanding of the molecular mechanism of fat development during the growth period. By TMT-labeled quantitative proteomic analysis of subcutaneous adipose tissue of 9 purebred Ningxiang pigs of different ages, we identified 2533 unique proteins and 716 differentially abundant proteins (DAPs), of which more than half of the DAPs were concentrated in the 90d-210d period. Retrograde endocannabinoid signaling was only significantly enriched in DAPs of N90d vs N30d, Alcoholism and Graft-versus-host disease were only significantly enriched in DAPs of N210d vs N90d. Proteins related to dilated cardiomyopathy was found to be an important pathway in fat development and lipid metabolism. A variety of novel DAPs involved in maintaining mitochondrial function and cell viability, such as NDUFS6, SDHB, COX5A, ATP5D and TNNT1, which play a role in controlling the prediction networks, may indirectly regulate the development and functional maintenance of adipocytes. SIGNIFICANCE: These age-dependent DAPs discovered in this study may help expand the understanding of the molecular mechanisms of the development, function maintenance and transformation of adipose tissue in Ningxiang pig for developing new strategies for improving meat quality and pig breeding in the future.

YAP-dependent Wnt5a induction in hypertrophic adipocytes restrains adiposity

Wnt5a, a prototypic non-canonical Wnt, is an inflammatory factor elevated in the sera of obese humans and mice. In the present study, fat-specific knockout of Wnt5a (Wnt5a-FKO) prevented HFD-induced increases in serum Wnt5a levels in male C57BL/6 J mice, which suggested adipocytes are primarily responsible for obesity-induced increases in Wnt5a levels. Mouse subcutaneous white adipose tissues (WATs) more sensitively responded to HFD, in terms of cell size increases and Wnt5a levels than epididymal WATs. Furthermore, adipocyte sizes were positively correlated with Wnt5a levels in vitro and in vivo. In hypertrophic adipocytes, enlarged lipid droplets increased cell stiffness and rearranged the f-actin stress fibers from the cytoplasm to the cortical region. The activities of YAP (Yes-associated protein) and TAZ (transcriptional co-activator with PDZ-binding motif) increased in response to these mechanical changes in hypertrophic adipocytes, and inhibition or knock-down of YAP and TAZ reduced Wnt5a expression. ChIP (chromatin immunoprecipitation) analyses revealed that YAP was recruited by Wnt5a-1 gene promoter and increased Wnt5a expression. These results suggested that YAP responds to mechanical stress in hypertrophic adipocytes to induce the expression Wnt5a. When 8-week-old Wnt5a-FKO mice were fed an HFD for 20 weeks, the fat mass increased, especially in subcutaneous WATs, as compared with that observed in floxed mice, without significant changes in food intake or activity. Furthermore, Wnt5a-FKO mice showed impaired glucose tolerance regardless of diet type. Our findings show that hypertrophy/YAP/Wnt5a signaling constitutes a negative-feedback loop that retrains adipose tissue hypertrophy.

Mammalian tumor-like organs. 2. Mammalian adipose has many tumor features and obesity is a tumor-like process

BACKGROUND

In previous publications, the author developed the theory of carcino-evo-devo, which predicts that evolutionarily novel organs should recapitulate some features of tumors in their development.

MAIN TEXT

Mammalian adipose is currently recognized as a multi-depot metabolic and endocrine organ consisting of several adipose tissues. Although lipid-storing cells and proteins are ancient, the adipose organ as a whole is evolutionarily novel to mammals. The adipose expansion has remarkable similarities with the growth of solid tumors. These similarities are the following: (1) The capability to unlimited expansion; (2) Reversible plasticity; (3) Induction of angiogenesis; (4) Chronic inflammation; (5) Remodeling and disfunction; (6) Systemic influence on the organism; (7) Hormone production; (8) Production of miRNAs that influence other tissues; (9) Immunosuppression; (10) DNA damage and resistance to apoptosis; (11) Destructive infiltration in other organs and tissues. These similarities include the majority of "hallmarks of cancer". In addition, lipomas are the most frequent soft tissue tumors, and similar drugs may be used for the treatment of obesity and cancer by preventing infiltration. This raises the possibility that obesity, at least in part, may represent an oncological problem. The existing similarities between adipose and tumors suggest the possible evolutionary origin of mammalian adipose from some ancestral benign mesenchymal hereditary tumors. Indeed, using a transgenic inducible zebrafish tumor model, we described many genes, which originated in fish and were expressed in fish tumors. Their human orthologs LEP, NOTCH1, SPRY1, PPARG, ID2, and CIDEA acquired functions connected with the adipose organ. They are also involved in tumor development in humans.

CONCLUSION

If the hypothesis of the evolutionary origin of the adipose organ from the ancestral hereditary tumor is correct, it may open new opportunities to resolve the oncological problem and the problem of the obesity epidemic. New interventions targeting LEP, NOTCH1, SPRY1, PPARG, ID2, and CIDEA gene network, in addition to what already is going on, can be designed for treatment and prevention of both obesity and tumors.

Mechanotransduction regulates inflammation responses of epicardial adipocytes in cardiovascular diseases

Adipose tissue is a crucial regulator in maintaining cardiovascular homeostasis by secreting various bioactive products to mediate the physiological function of the cardiovascular system. Accumulating evidence shows that adipose tissue disorders contribute to several kinds of cardiovascular disease (CVD). Furthermore, the adipose tissue would present various biological effects depending on its tissue localization and metabolic statuses, deciding the individual cardiometabolic risk. Crosstalk between adipose and myocardial tissue is involved in the pathophysiological process of arrhythmogenic right ventricular cardiomyopathy (ARVC), cardiac fibrosis, heart failure, and myocardial infarction/atherosclerosis. The abnormal distribution of adipose tissue in the heart might yield direct and/or indirect effects on cardiac function. Moreover, mechanical transduction is critical for adipocytes in differentiation, proliferation, functional maturity, and homeostasis maintenance. Therefore, understanding the features of mechanotransduction pathways in the cellular ontogeny of adipose tissue is vital for underlining the development of adipocytes involved in cardiovascular disorders, which would preliminarily contribute positive implications on a novel therapeutic invention for cardiovascular diseases. In this review, we aim to clarify the role of mechanical stress in cardiac adipocyte homeostasis and its interplay with maintaining cardiac function.

Insight Into Rho Kinase Isoforms in Obesity and Energy Homeostasis

Obesity and associated complications increasingly jeopardize global health and contribute to the rapidly rising prevalence of type 2 diabetes mellitus and obesity-related diseases. Developing novel methods for the prevention and treatment of excess body adipose tissue expansion can make a significant contribution to public health. Rho kinase is a Rho-associated coiled-coil-containing protein kinase (Rho kinase or ROCK). The ROCK family including ROCK1 and ROCK2 has recently emerged as a potential therapeutic target for the treatment of metabolic disorders. Up-regulated ROCK activity has been involved in the pathogenesis of all aspects of metabolic syndrome including obesity, insulin resistance, dyslipidemia and hypertension. The RhoA/ROCK-mediated actin cytoskeleton dynamics have been implicated in both white and beige adipogenesis. Studies using ROCK pan-inhibitors in animal models of obesity, diabetes, and associated complications have demonstrated beneficial outcomes. Studies via genetically modified animal models further established isoform-specific roles of ROCK in the pathogenesis of metabolic disorders including obesity. However, most reported studies have been focused on ROCK1 activity during the past decade. Due to the progress in developing ROCK2-selective inhibitors in recent years, a growing body of evidence indicates more attention should be devoted towards understanding ROCK2 isoform function in metabolism. Hence, studying individual ROCK isoforms to reveal their specific roles and principal mechanisms in white and beige adipogenesis, insulin sensitivity, energy balancing regulation, and obesity development will facilitate significant breakthroughs for systemic treatment with isoform-selective inhibitors. In this review, we give an overview of ROCK functions in the pathogenesis of obesity and insulin resistance with a particular focus on the current understanding of ROCK isoform signaling in white and beige adipogenesis, obesity and thermogenesis in adipose tissue and other major metabolic organs involved in energy homeostasis regulation.

Pinch Loss Ameliorates Obesity, Glucose Intolerance, and Fatty Liver by Modulating Adipocyte Apoptosis in Mice

The mammalian focal adhesion proteins Pinch1/2 activate integrins and promote cell-extracellular matrix adhesion and migration; however, their roles in adipose tissue and metabolism are unclear. Here we find that high-fat diet (HFD) feeding dramatically increases expression of Pinch1/2 proteins in white adipose tissue (WAT) in mice. Furthermore, expression of Pinch1 is largely upregulated in WAT in leptin-deficient ob/ob type 2 diabetic mice and obese humans. While mice with loss of Pinch1 in adipocytes or global Pinch2 do not display any notable phenotypes, deleting Pinch1 in adipocytes and Pinch2 globally significantly decreases body weight and WAT mass, but not brown adipose tissue mass, in HFD-fed, but not normal chow diet-fed, mice. Pinch loss ameliorates HFD-induced glucose intolerance and fatty liver. After HFD challenge, Pinch loss slightly but significantly accelerates energy expenditure. While Pinch loss decreases adipocyte size and alters adipocyte size distribution, it greatly accelerates cell apoptosis primarily in epididymal WAT and to a lesser extent in subcutaneous WAT. In vitro studies demonstrate that Pinch loss accelerates adipocyte apoptosis by activating the Bim/Caspase-8 pathway. In vivo, genetic ablation of Caspase-8 expression in adipocytes essentially abolishes the ameliorating effects of Pinch deficiency on obesity, glucose intolerance, and fatty liver in mice. Thus, we demonstrate a previously unknown function of Pinch in control of adipose mass, glucose, and fat metabolism via modulation of adipocyte apoptosis. We may define a novel target for the prevention and treatment of metabolic diseases, such as obesity and diabetes.

Towards an understanding of the mechanoreciprocity process in adipocytes and its perturbation with aging

Adipose tissue (AT) is a complex organ, with multiple functions that are essential for maintaining metabolic health. A feature of AT is its capability to expand in response to physiological challenges, such as pregnancy and aging, and during chronic states of positive energy balance occurring throughout life. AT grows through adipogenesis and/or an increase in the size of existing adipocytes. One process that is required for healthy AT growth is the remodeling of the extracellular matrix (ECM), which is a necessary step to restore mechanical homeostasis and maintain tissue integrity and functionality. While the relationship between mechanobiology and adipogenesis is now well recognized, less is known about the role of adipocyte mechanosignaling pathways in AT growth. In this review article, we first summarize evidence linking ECM remodelling to AT expansion and how its perturbation is associated to a metabolically unhealthy phenotype. Subsequently, we highlight findings suggesting that molecules involved in the dynamic, bidirectional process (mechanoreciprocity) enabling adipocytes to sense changes in the mechanical properties of the ECM are interconnected to pathways regulating lipid metabolism. Finally, we discuss processes through which aging may influence the ability of adipocytes to appropriately respond to alterations in ECM composition.

S1P Lyase Regulates Intestinal Stem Cell Quiescence via Ki-67 and FOXO3

Background: Reduction of the Sphingosine-1-phosphate (S1P) degrading enzyme S1P lyase 1 (SGPL1) initiates colorectal cancer progression with parallel loss of colon function in mice. We aimed to investigate the effect of SGPL1 knockout on the stem cell niche in these mice. Methods: We performed immunohistochemical and multi-fluorescence imaging on tissue sections of wildtype and SGPL1 knockout colons under disease conditions. Furthermore, we generated SGPL1 knockout DLD-1 cells (SGPL1^−/−M.Ex1) using CRISPR/Cas9 and characterized cell cycle and AKT signaling pathway via Western blot, immunofluorescence, and FACS analysis. Results: SGPL1 knockout mice were absent of anti-Ki-67 staining in the stem cell niche under disease conditions. This was accompanied by an increase of the negative cell cycle regulator FOXO3 and attenuation of CDK2 activity. SGPL1^−/−M.Ex1 cells show a similar FOXO3 increase but no arrest of proliferation, although we found a suppression of the PDK1/AKT signaling pathway, a prolonged G1-phase, and reduced stem cell markers. Conclusions: While already established colon cancer cells find escape mechanisms from cell cycle arrest, in vivo SGPL1 knockout in the colon stem cell niche during progression of colorectal cancer can contribute to cell cycle quiescence. Thus, we propose a new function of the S1P lyase 1 in stemness.

Bromodomain-containing protein 7 regulates matrix metabolism and apoptosis in human nucleus pulposus cells through the BRD7-PI3K-YAP1 signaling axis

Intervertebral disc degeneration (IDD) results from dysregulated metabolism of the extracellular matrix of the nucleus pulposus (NP) and involves the participation of inflammatory factors such as TNF-α. Bromodomain-containing protein 7 (BRD7) shows considerable potential for anti-inflammatory applications. Herein, we investigated the role of BRD7 in IDD. The immunohistochemistry results demonstrated decreased BRD7 expression in severely degenerated human NP tissues compared to those showing mild degeneration. Lentiviruses and adenoviruses were used to knock down or overexpress BRD7 and YAP1, respectively. Our results revealed that BRD7 knockdown promoted matrix degradation and suppressed PI3K and YAP1 expression, while BRD7 overexpression alleviated matrix degradation and promoted YAP1 and PI3K expression. In addition, PI3K inhibition augmented matrix degradation, enhanced apoptosis, and reduced YAP1 expression, whereas YAP1 overexpression promoted matrix synthesis, suppressed apoptosis and promoted PI3K expression. Besides, BRD7 overexpression reversed the reductions in sulfated glycosaminoglycan levels induced by TNF-α, but this effect was blocked by PI3K or YAP1 inhibitors. Moreover, YAP1 and PI3K were shown to interact through coimmunoprecipitation analysis. In summary, our results demonstrate that BRD7 can regulate matrix metabolism and apoptosis in human NP cells through the BRD7-PI3K-YAP1 signaling axis. This study might provide new insights into the prevention and treatment of IDD.