Effect of lipopolysaccharides on adipogenic potential and premature senescence of adipocyte progenitors

Cardioprotective response and senescence in aged sEH null female mice exposed to LPS

Deterioration of physiological systems, like the cardiovascular system, occurs progressively with age impacting an individual's health and increasing susceptibility to injury and disease. Cellular senescence has an underlying role in age-related alterations and can be triggered by natural aging or prematurely by stressors such as the bacterial toxin lipopolysaccharide (LPS). The metabolism of polyunsaturated fatty acids by CYP450 enzymes produces numerous bioactive lipid mediators that can be further metabolized by soluble epoxide hydrolase (sEH) into diol metabolites, often with reduced biological effects. In our study, we observed age-related cardiac differences in female mice, where young mice demonstrated resistance to LPS injury, and genetic deletion or pharmacological inhibition of sEH using trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid attenuated LPS-induced cardiac dysfunction in aged female mice. Bulk RNA-sequencing analyses revealed transcriptomics differences in aged female hearts. The confirmatory analysis demonstrated changes to inflammatory and senescence gene markers such as Il-6, Mcp1, Il-1β, Nlrp3, p21, p16, SA-β-gal, and Gdf15 were attenuated in the hearts of aged female mice where sEH was deleted or inhibited. Collectively, these findings highlight the role of sEH in modulating the aging process of the heart, whereby targeting sEH is cardioprotective.NEW & NOTEWORTHY Soluble epoxide hydrolase (sEH) is an essential enzyme for converting epoxy fatty acids to their less bioactive diols. Our study suggests deletion or inhibition of sEH impacts the aging process in the hearts of female mice resulting in cardioprotection. Data indicate targeting sEH limits inflammation, preserves mitochondria, and alters cellular senescence in the aged female heart.

Endotoxin-induced alterations of adipose tissue function: a pathway to bovine metabolic stress

During the periparturient period, dairy cows exhibit negative energy balance due to limited appetite and increased energy requirements for lactogenesis. The delicate equilibrium between energy availability and expenditure puts cows in a state of metabolic stress characterized by excessive lipolysis in white adipose tissues (AT), increased production of reactive oxygen species, and immune cell dysfunction. Metabolic stress, especially in AT, increases the risk for metabolic and inflammatory diseases. Around parturition, cows are also susceptible to endotoxemia. Bacterial-derived toxins cause endotoxemia by promoting inflammatory processes and immune cell infiltration in different organs and systems while impacting metabolic function by altering lipolysis, mitochondrial activity, and insulin sensitivity. In dairy cows, endotoxins enter the bloodstream after overcoming the defense mechanisms of the epithelial barriers, particularly during common periparturient conditions such as mastitis, metritis, and pneumonia, or after abrupt changes in the gut microbiome. In the bovine AT, endotoxins induce a pro-inflammatory response and stimulate lipolysis in AT, leading to the release of free fatty acids into the bloodstream. When excessive and protracted, endotoxin-induced lipolysis can impair adipocyte's insulin signaling pathways and lipid synthesis. Endotoxin exposure can also induce oxidative stress in AT through the production of reactive oxygen species by inflammatory cells and other cellular components. This review provides insights into endotoxins' impact on AT function, highlighting the gaps in our knowledge of the mechanisms underlying AT dysfunction, its connection with periparturient cows' disease risk, and the need to develop effective interventions to prevent and treat endotoxemia-related inflammatory conditions in dairy cattle.

The effect of quercetin on adipogenesis, lipolysis, and apoptosis in 3T3-L1 adipocytes: The role of SIRT1 pathways

Background

Lipotoxicity, caused by adipocyte triglyceride over-accumulation, contributes to obesity-related comorbidities such as hypertension, type 2 diabetes, coronary heart disease, respiratory dysfunction, and osteoarthritis. This study focuses on determining how sirtuin-1 (SIRT-1) mediates quercetin's (QCT) effect on 3T3-L1 adipocytes. Key aspects of this study include preventing adipogenesis, inducing lipolysis, and stimulating adipocyte apoptosis.

Methods

3T3-L1 adipocytes underwent treatment with varying QCT doses, lipopolysaccharide (LPS), and the SIRT-1 inhibitor EX-527, followed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide [MTT] assay for cell viability assessment. Furthermore, quantitative real-time polymerase chain reaction measured mRNA expression levels of adipogenesis markers (fatty acid synthase [FASN] and peroxisome proliferator-activated receptor gamma [PPARγ]), lipolysis markers (adipose triglyceride lipase [ATGL] and hormone-sensitive lipase [HSL]), and apoptosis markers (B-cell lymphoma2 [Bcl-2], Bcl-2 Associated -X-protein [BAX] and Caspase-3).

Results

The data showed that LPS + QCT significantly reduced cell viability in a dose- and time-dependent manner, unaffected by LPS + QCT + EX-527. Treatment with LPS + QCT did not affect FASN and PPARγ expression but significantly increased ATGL and HSL mRNA expression compared with LPS alone. Interestingly, EX-527 reversed the effects of LPS + QCT on lipogenesis and lipolysis markers completely. QCT enhanced apoptosis in a SIRT-1 independent pattern.

Conclusion

The data suggest that QCT suppresses adipogenesis while increasing lipolysis via SIRT-1. However, QCT's effects on apoptosis appear to be independent of SIRT-1. These findings provide further evidence for QCT's effects on adipocytes, particularly its interaction with SIRT-1.

Gut microbiota in overweight and obesity: crosstalk with adipose tissue

Overweight and obesity are characterized by excessive fat mass accumulation produced when energy intake exceeds energy expenditure. One plausible way to control energy expenditure is to modulate thermogenic pathways in white adipose tissue (WAT) and/or brown adipose tissue (BAT). Among the different environmental factors capable of influencing host metabolism and energy balance, the gut microbiota is now considered a key player. Following pioneering studies showing that mice lacking gut microbes (that is, germ-free mice) or depleted of their gut microbiota (that is, using antibiotics) developed less adipose tissue, numerous studies have investigated the complex interactions existing between gut bacteria, some of their membrane components (that is, lipopolysaccharides), and their metabolites (that is, short-chain fatty acids, endocannabinoids, bile acids, aryl hydrocarbon receptor ligands and tryptophan derivatives) as well as their contribution to the browning and/or beiging of WAT and changes in BAT activity. In this Review, we discuss the general physiology of both WAT and BAT. Subsequently, we introduce how gut bacteria and different microbiota-derived metabolites, their receptors and signalling pathways can regulate the development of adipose tissue and its metabolic capacities. Finally, we describe the key challenges in moving from bench to bedside by presenting specific key examples.

The potential use of ascorbic acid to recover the cellular senescence of lipopolysaccharide-induced human apical papilla cells: an in vitro study

OBJECTIVES

To examine the effect of lipopolysaccharide (LPS) on cellular senescence induction of human apical papilla cells (hAPCs) and evaluate the potential use of 50 μg/ml ascorbic acid to recover cellular senescence and regenerative functions.

MATERIALS AND METHODS

hAPCs were treated with LPS at 1 and 10 μg/ml either with or without 50 μg/ml ascorbic acid for 48 h. The cellular senescence biomarkers were analyzed by senescence-associated β-galactosidase (SA-β-gal) staining and senescence-related gene expression, p16 and p21. Cell migration, at 12 h and 24 h, was evaluated using a scratch wound assay. Mineralization potential was assessed at 21 days using Alizarin red S staining and dentine sialophosphoprotein (DSPP) and bone sialoprotein (BSP) gene expression.

RESULTS

1 μg/ml and 10 μg/ml LPS stimulation for 48 h induced cellular senescence, as shown by remarkable SA-β-gal staining and p16 and p21 gene expression. The percentage of wound closure and mineralized formation was reduced. The co-incubation with ascorbic acid significantly down-regulated the level of SA-β-gal staining. The reduction of senescence-associated gene expressions was observed. Ascorbic acid improved cell migration, mineralized nodule formation, and the expression of DSPP and BSP genes in LPS-treated hAPCs.

CONCLUSIONS

LPS significantly promoted cellular senescence on hAPCs and diminished the cell function capacity. Co-presence of ascorbic acid could impede cellular senescence and possibly improve the regenerative capacity of LPS-induced senescent hAPCs in vitro.

CLINICAL RELEVANCE

The data support the in vitro potential benefit of ascorbic acid on cellular senescence recovery of apical papilla cells.

Inflammatory response to bacterial lipopolysaccharide drives iron accumulation in human adipocytes

The association among increased inflammation, disrupted iron homeostasis, and adipose tissue dysfunction in obesity has been widely recognized. However, the specific impact of inflammation on iron homeostasis during human adipogenesis and in adipocytes remains poorly understood. In this study, we investigated the effects of bacterial lipopolysaccharide (LPS) on iron homeostasis during human adipocyte differentiation, in fully differentiated adipocytes, and in human adipose tissue. We found that LPS-induced inflammation hindered adipogenesis and led to a gene expression profile indicative of intracellular iron accumulation. This was accompanied by increased expression of iron importers (TFRC and SLC11A2), markers of intracellular iron accumulation (FTH, CYBA, FTL, and LCN2), and decreased expression of iron exporter-related genes (SLC40A1), concomitant with elevated intracellular iron levels. Mechanistically, RNA-seq analysis and gene knockdown experiments revealed the significant involvement of iron importers SLC39A14, SLC39A8, and STEAP4 in LPS-induced intracellular iron accumulation in human adipocytes. Notably, markers of LPS signaling pathway-related inflammation were also associated with a gene expression pattern indicative of intracellular iron accumulation in human adipose tissue, corroborating the link between LPS-induced inflammation and iron accumulation at the tissue level. In conclusion, our findings demonstrate that induction of adipocyte inflammation disrupts iron homeostasis, resulting in adipocyte iron overload.

Physiological Approaches Targeting Cellular and Mitochondrial Pathways Underlying Adipose Organ Senescence

The adipose organ is involved in many metabolic functions, ranging from the production of endocrine factors to the regulation of thermogenic processes. Aging is a natural process that affects the physiology of the adipose organ, leading to metabolic disorders, thus strongly impacting healthy aging. Cellular senescence modifies many functional aspects of adipose tissue, leading to metabolic alterations through defective adipogenesis, inflammation, and aberrant adipocytokine production, and in turn, it triggers systemic inflammation and senescence, as well as insulin resistance in metabolically active tissues, leading to premature declined physiological features. In the various aging fat depots, senescence involves a multiplicity of cell types, including mature adipocytes and immune, endothelial, and progenitor cells that are aging, highlighting their involvement in the loss of metabolic flexibility, one of the common features of aging-related metabolic disorders. Since mitochondrial stress represents a key trigger of cellular senescence, and senescence leads to the accumulation of abnormal mitochondria with impaired dynamics and hindered homeostasis, this review focuses on the beneficial potential of targeting mitochondria, so that strategies can be developed to manage adipose tissue senescence for the treatment of age-related metabolic disorders.

ERBB2-PTGS2 axis promotes intervertebral disc degeneration by regulating senescence of nucleus pulposus cells

Intervertebral disc degeneration (IDD) is considered one of the main causes of low back pain and lumbar disc herniation. Various studies have shown that disc cell senescence plays a critical role in this process. however, its role in IDD is yet unclear. In this study, we explored the role of senescence-related genes (SR-DEGs) and its underlying mechanism in IDD. A total of 1325 differentially expressed genes (DEGs) were identified using Gene Expression Omnibus (GEO) database GSE41883. 30 SR-DEGs were identified for further functional enrichment and pathway analysis, and two hub SR-DEGs (ERBB2 and PTGS2) were selected to construct transcription factor (TF)-gene interaction and TF-miRNA coregulatory networks, and 10 candidate drugs were screened for the treatment of IDD. Last but not least, in vitro experiments show that ERBB2 expression decreased and PTGS2 expression increased in human nucleus pulposus (NP) cell senescence model treated with TNF-α. After lentivirus-mediated overexpression of ERBB2, the expression of PTGS2 decreased and the senescence level of NP cells decreased. Overexpression of PTGS2 reversed the anti-senescence effects of ERBB2. The findings in this study suggested that ERBB2 overexpression further reduced NP cell senescence by inhibiting PTGS2 levels, which ultimately alleviated IDD. Taken together, our findings provide new insights into the roles of senescence-related genes in IDD and highlight a novel target of ERBB2-PTGS2 axis for therapeutic strategies.

Collagen Peptide Exerts an Anti-Obesity Effect by Influencing the Firmicutes/Bacteroidetes Ratio in the Gut

Alterations in the intestinal microbial flora are known to cause various diseases, and many people routinely consume probiotics or prebiotics to balance intestinal microorganisms and the growth of beneficial bacteria. In this study, we selected a peptide from fish (tilapia) skin that induces significant changes in the intestinal microflora of mice and reduces the Firmicutes/Bacteroidetes ratio, which is linked to obesity. We attempted to verify the anti-obesity effect of selected fish collagen peptides in a high-fat-diet-based obese mouse model. As anticipated, the collagen peptide co-administered with a high-fat diet significantly inhibited the increase in the Firmicutes/Bacteroidetes ratio. It increased specific bacterial taxa, including Clostridium_sensu_stricto_1, Faecalibaculum, Bacteroides, and Streptococcus, known for their anti-obesity effects. Consequently, alterations in the gut microbiota resulted in the activation of metabolic pathways, such as polysaccharide degradation and essential amino acid synthesis, which are associated with obesity inhibition. In addition, collagen peptide also effectively reduced all obesity signs caused by a high-fat diet, such as abdominal fat accumulation, high blood glucose levels, and weight gain. Ingestion of collagen peptides derived from fish skin induced significant changes in the intestinal microflora and is a potential auxiliary therapeutic agent to suppress the onset of obesity.

Types of cell culture inserts affect cell crosstalk between co-cultured macrophages and adipocytes

Cell culture inserts offer an in vivo-like microenvironment to investigate cell-cell interactions between co-cultivated cells. However, it is unclear if types of inserts affect cell crosstalk. Here, we developed an environment-friendly cell culture insert, XL-insert, which can reduce plastic waste with lower cost. We compared XL insert with two types of commercial disposable culture inserts, Koken® insert with atelocollagen membrane (Col-inserts) and Falcon® inserts with plastic membrane (PET-inserts) on cell-cell interactions in co-cultivated THP-1 macrophages and OP9 adipocytes. Scanning electron microscope, immunoassay and imaging analysis showed that among three types of inserts, XL-inserts allowed cytokines from co-cultivated macrophages and adipocytes to diffuse freely and offered preferable in vivo-like microenvironment for cell-cell interactions. PET-inserts showed limitations for intercellular communication due to some pores being blocked by somas on the membrane that caused much lower permeability for cytokines passing through. Col-inserts blocked large sized cytokines but allowed small sized molecules to permeate resulting in improved lipid accumulation and adiponectin secretion in OP9 adipocytes. Taken together, our data demonstrated that membrane type and pore size on the membrane affect the cross-talk between co-cultivated cells very differently. Some previous co-culture studies might have different results if the inserts were changed.

Lipopolysaccharides and Cellular Senescence: Involvement in Atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the vascular walls related to aging. Thus far, the roles of cellular senescence and bacterial infection in the pathogenesis of atherosclerosis have been speculated to be independent of each other. Some types of macrophages, vascular endothelial cells, and vascular smooth muscle cells are in a senescent state at the sites of atherosclerotic lesions. Likewise, bacterial infections and accumulations of lipopolysaccharide (LPS), an outer-membrane component of Gram-negative bacteria, have also been observed in the atherosclerotic lesions of patients. This review introduces the integration of these two potential pathways in atherosclerosis. Previous studies have suggested that LPS directly induces cellular senescence in cultured monocytes/macrophages and vascular cells. In addition, LPS enhances the inflammatory properties (senescence-associated secretory phenotype [SASP]) of senescent endothelial cells. Thus, LPS derived from Gram-negative bacteria could exaggerate the pathogenesis of atherosclerosis by inducing and enhancing cellular senescence and the SASP-associated inflammatory properties of specific vascular cells in atherosclerotic lesions. This proposed mechanism can provide novel approaches to preventing and treating this common age-related disease.

MDM2 Aggravates Adipose Tissue Dysfunction through Ubiquitin-mediated STEAP4 Degradation

Healthy adipose tissue is crucial to maintain normal energy homeostasis. Little is known about the role of murine double minute 2 (MDM2), an E3 ubiquitin ligase and has been highlighted in oncopathology, in adipose tissue. Our results indicated that MDM2 expression was associated with nutritional status. Mdm2 adipocyte-specific knock-in (Mdm2-AKI) mice exhibited exacerbated weight gain, insulin resistance, and decreased energy expenditure. Meanwhile, chronic high-fat diet (HFD) exposure caused obvious epididymal white adipose tissue (eWAT) dysfunction, such as senescence, apoptosis, and chronic inflammation, thereby leading to hepatic steatosis in Mdm2-AKI mice. Mechanically, MDM2 could interact with six-transmembrane epithelial antigen of prostate 4 (STEAP4) and inhibit STEAP4 expression through ubiquitin-mediated STEAP4 degradation. Thereinto, the K18 and K161 sites of STEAP4 were ubiquitin-modificated by MDM2. Finally, STEAP4 restoration in eWAT of Mdm2-AKI mice on a HFD rescued MDM2-induced adipose dysfunction, insulin resistance, and hepatic steatosis. Summary, the MDM2-STEAP4 axis in eWAT plays an important role in maintaining healthy adipose tissue function and improving hepatic steatosis.

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Murine double minute 2 (MDM2) overexpression intensifies high-fat diet-induced adipose tissue dysfunction

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Adipocyte MDM2 overexpression aggravates insulin resistance and hepatosteatosis

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MDM2 decreases six-transmembrane epithelial antigen of prostate 4 (STEAP4) expression by ubiquitin-dependent STEAP4 degradation

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STEAP4 overexpression in eWAT alleviates MDM2-induced metabolic disorder

Enzyme-digested Colla Corii Asini (E'jiao) suppresses lipopolysaccharide-induced inflammatory changes in THP-1 macrophages and OP9 adipocytes

Gut microbial lipopolysaccharides (LPS)-induced inflammatory responses in adipose tissue are associated with the dysfunction of adipocytes, insulin resistance and the development of metabolic syndrome. The aim of this study is to investigate (1) the effects of LPS on the differentiation and inflammatory responses of THP-1 monocytes and OP9 preadipocytes under serum free conditions and (2) the repressive effects of enzyme-digested Colla Corii Asini (CCAD) and fish gelatin (FGD) on LPS-induced inflammatory responses in THP-1 macrophages and OP9 adipocytes. Immunofluorescence and oil red O staining showed that a serum free medium supplied with phorbol 12-myristate 13-acetate (PMA) could induce differentiation and lipid accumulation in THP-1 cells as well as OP9 cells. ELISA showed that LPS significantly increased interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) secretions in PMA-differentiated THP-1 macrophages in a dose-dependent manner. LPS significantly suppressed lipid accumulation and adiponectin secretions, and enhanced IL-6 secretions in OP9 adipocytes. Both CCAD and FGD significantly reduced the levels of both macrophages- and adipocytes-derived inflammatory cytokines and increased the level of OP9-secreted adiponectin. In conclusion, LPS could induce inflammatory responses in both THP-1 and OP9 cells and cause dysfunction of OP9 adipocytes under the serum free conditions. CCAD and FGD can repress LPS-induced inflammatory responses in both THP-1 macrophages and OP9 adipocytes, and increase the secretion of adiponectin in OP9 adipocytes. They could be used as health care supplements for improving metabolic syndrome.

Long-term cardiovascular complications following sepsis: is senescence the missing link?

Among the long-term consequences of sepsis (also termed “post-sepsis syndrome”) the increased risk of unexplained cardiovascular complications, such as myocardial infarction, acute heart failure or stroke, is one of the emerging specific health concerns. The vascular accelerated ageing also named premature senescence is a potential mechanism contributing to atherothrombosis, consequently leading to cardiovascular events. Indeed, vascular senescence-associated major adverse cardiovascular events (MACE) are a potential feature in sepsis survivors and of the elderly at cardiovascular risk. In these patients, accelerated vascular senescence could be one of the potential facilitating mechanisms. This review will focus on premature senescence in sepsis regardless of age. It will highlight and refine the potential relationships between sepsis and accelerated vascular senescence. In particular, key cellular mechanisms contributing to cardiovascular events in post-sepsis syndrome will be highlighted, and potential therapeutic strategies to reduce the cardiovascular risk will be further discussed.

With improved management of patients, sepsis survivors are increasing each year.

Early cardiovascular complications, of yet undeciphered mechanisms, are an emerging health issue in post-sepsis syndrome.

Premature senescence of endothelium and vascular tissue is proven an accelerated process of atherogenesis in young septic rats.

An increasing body of clinical evidence point at endothelial senescence in the initiation and development of atherosclerosis.

Prevention of premature senescence by senotherapy and cardiological follow-up could improve long-term septic patients’ outcomes.

The Interplay of Vitamin D Deficiency and Cellular Senescence in The Pathogenesis of Obesity-Related Co-Morbidities

This scoping review aims to clarify the interplay between obesity, vitamin D deficiency, cellular senescence, and obesity-related metabolic consequences, mainly subclinical atherosclerosis, and non-alcoholic fatty liver disease (NAFLD). Obesity is a significant global health problem that involves cellular, environmental, behavioral, and genetic elements. The fundamental cause of obesity throughout all life stages is an energy imbalance, and its consequences are countless and, foremost, very common. Obesity has been comprehensively studied in the literature given its association with low serum vitamin D, with many proposed mechanisms linking the two conditions. Moreover, markers of exaggerated cellular senescence have been proven to accumulate in obese individuals. Subclinical atherosclerosis initiates an early stage that ends in serious cardiac events, and obesity, low vitamin D, and senescent cells largely contribute to its associated chronic low-grade inflammation. Furthermore, NAFLD signifies the hepatic manifestation of metabolic syndrome, and studies have highlighted the important role of obesity, vitamin D deficiency, and cellular senescence in its development. Therefore, we outlined the most important mechanisms tying these conditions to one another.

Exploring the endocannabinoidome in genetically obese (ob/ob) and diabetic (db/db) mice: Links with inflammation and gut microbiota

BACKGROUND

Obesity and type 2 diabetes are two interrelated metabolic disorders characterized by insulin resistance and a mild chronic inflammatory state. We previously observed that leptin (ob/ob) and leptin receptor (db/db) knockout mice display a distinct inflammatory tone in the liver and adipose tissue. The present study aimed at investigating whether alterations in these tissues of the molecules belonging to the endocannabinoidome (eCBome), an extension of the endocannabinoid (eCB) signaling system, whose functions are important in the context of metabolic disorders and inflammation, could reflect their different inflammatory phenotypes.

RESULTS

The basal eCBome lipid and gene expression profiles, measured by targeted lipidomics and qPCR transcriptomics, respectively, in the liver and subcutaneous or visceral adipose tissues, highlighted a differentially altered eCBome tone, which may explain the impaired hepatic function and more pronounced liver inflammation remarked in the ob/ob mice, as well as the more pronounced inflammatory state observed in the subcutaneous adipose tissue of db/db mice. In particular, the levels of linoleic acid-derived endocannabinoid-like molecules, of one of their 12-lipoxygenase metabolites and of Trpv2 expression, were always altered in tissues exhibiting the highest inflammation. Correlation studies suggested the possible interactions with some gut microbiota bacterial taxa, whose respective absolute abundances were significantly different between ob/ob and the db/db mice.

CONCLUSIONS

The present findings emphasize the possibility that bioactive lipids and the respective receptors and enzymes belonging to the eCBome may sustain the tissue-dependent inflammatory state that characterizes obesity and diabetes, possibly in relation with gut microbiome alterations.

Septic shock as a trigger of arterial stress-induced premature senescence: A new pathway involved in the post sepsis long-term cardiovascular complications

BACKGROUND

Major adverse cardiovascular events among sepsis survivors is an emerging health issue. Because endothelial senescence leads to vascular dysfunction and atherothrombosis, sepsis could be associated to vascular stress-induced premature senescence and thus with long-term cardiovascular events.

MATERIALS & METHODS

Adult Wistar male rats were submitted to cecal ligation and puncture, or a SHAM operation. Markers of inflammation, oxidative stress and endothelial senescence were assessed at 3, 7 and 90 days (D), and vascular reactivity was assessed in conductance and resistance vessels at D90. Expression of proteins involved in senescence and inflammation was assessed by Western blot analysis and confocal microscopy, oxidative stress by dihydroethidium probing.

RESULTS

Pro-inflammatory endothelial ICAM-1 and VCAM-1 were up-regulated by three-fold in CLP vs. SHAM at D7 and remained elevated at D90. Oxidative stress followed a similar pattern but was detected in the whole vascular wall. Sepsis accelerated premature senescence in aorta vascular tissue as shown by the significant up-regulation of p53 and down-stream p21 and p16 senescent markers at D7, values peaking at D90 whereas the absence of significant variation in activated caspase-3 confirmed p53 as a prime inducer of senescence. In addition, p53 was mainly expressed in the endothelium. Sepsis-induced long-term vascular dysfunction was confirmed in aorta and main mesenteric artery, with a major alteration of the endothelial-dependent nitric oxide pathway.

CONCLUSIONS

Septic shock-induced long-term vascular dysfunction is associated with endothelial and vascular senescence. Our model could prove useful for investigating senotherapies aiming at reducing long-term cardiovascular consequences of septic shock.

Nutrition and cellular senescence in obesity-related disorders

Adequate nutrition is vital for immune homeostasis. However, the incidence of obesity is increasing worldwide due to the adoption of the Western diet and a sedentary lifestyle. Obesity is associated with chronic inflammation which alters the function of adipose tissue, liver, pancreas, and the nervous system. Inflammation is related to cellular senescence, distinguished by irreversible cell cycle arrest. Senescent cells secrete the senescence-associated secretory phenotype (SASP) which contains pro-inflammatory factors. Targeting processes in senescence might have a salutary approach to obesity. The present review highlights the impact of an unhealthy diet on tissues affected by obesity, and the mechanisms that promote the consequent inflammation and senescence.

The Role of Gut Microbiota and Its Produced Metabolites in Obesity, Dyslipidemia, Adipocyte Dysfunction, and Its Interventions

Obesity is becoming an increasing problem worldwide and is often, but not invariably, associated with dyslipidemia. The gut microbiota is increasingly linked to cardiovascular disease, nonalcoholic fatty liver disease, and type 2 diabetes mellitus. However, relatively little focus has been attributed to the role of gut-microbiota-derived metabolites in the development of dyslipidemia and alterations in lipid metabolism. In this review, we discuss current data involved in these processes and point out the therapeutic potentials. We cover the ability of gut microbiota metabolites to alter lipoprotein lipase action, VLDL secretion, and plasma triglyceride levels, and its effects on reverse cholesterol transport, adipocyte dysfunction, and adipose tissue inflammation. Finally, the current intervention strategies for treatment of obesity and dyslipidemia is addressed with emphasis on the role of gut microbiota metabolites and its ability to predict treatment efficacies.

An RNAi Screening of Clinically Relevant Transcription Factors Regulating Human Adipogenesis and Adipocyte Metabolism

CONTEXT

Healthy hyperplasic (many but smaller fat cells) white adipose tissue (WAT) expansion is mediated by recruitment, proliferation and/or differentiation of new fat cells. This process (adipogenesis) is controlled by transcriptional programs that have been mostly identified in rodents.

OBJECTIVE

A systemic investigation of adipogenic human transcription factors (TFs) that are relevant for metabolic conditions has not been revealed previously.

METHODS

TFs regulated in WAT by obesity, adipose morphology, cancer cachexia, and insulin resistance were selected from microarrays. Their role in differentiation of human adipose tissue-derived stem cells (hASC) was investigated by RNA interference (RNAi) screen. Lipid accumulation, cell number, and lipolysis were measured for all screened factors (148 TFs). RNA (RNAseq), protein (Western blot) expression, insulin, and catecholamine responsiveness were examined in hASC following siRNA treatment of selected target TFs.

RESULTS

Analysis of TFs regulated by metabolic conditions in human WAT revealed that many of them belong to adipogenesis-regulating pathways. The RNAi screen identified 39 genes that affected fat cell differentiation in vitro, where 11 genes were novel. Of the latter JARID2 stood out as being necessary for formation of healthy fat cell metabolic phenotype by regulating expression of multiple fat cell phenotype-specific genes.

CONCLUSION

This comprehensive RNAi screening in hASC suggests that a large proportion of WAT TFs that are impacted by metabolic conditions might be important for hyperplastic adipose tissue expansion. The screen also identified JARID2 as a novel TF essential for the development of functional adipocytes.

CD10 marks non-canonical PPARγ-independent adipocyte maturation and browning potential of adipose-derived stem cells

BACKGROUND

Effective stem cell therapy is dependent on the stem cell quality that is determined by their differentiation potential, impairment of which leads to poor engraftment and survival into the target cells. However, limitations in our understanding and the lack of reliable markers that can predict their maturation efficacies have hindered the development of stem cells as an effective therapeutic strategy. Our previous study identified CD10, a pro-adipogenic, depot-specific prospective cell surface marker of human adipose-derived stem cells (ASCs). Here, we aim to determine if CD10 can be used as a prospective marker to predict mature adipocyte quality and play a direct role in adipocyte maturation.

METHODS

We first generated 14 primary human subject-derived ASCs and stable immortalized CD10 knockdown and overexpression lines for 4 subjects by the lentiviral transduction system. To evaluate the role of CD10 in adipogenesis, the adipogenic potential of the human subject samples were scored against their respective CD10 transcript levels. Assessment of UCP1 expression levels was performed to correlate CD10 levels to the browning potential of mature ASCs. Quantitative polymerase chain reaction (qPCR) and Western blot analysis were performed to determine CD10-dependent regulation of various targets. Seahorse analysis of oxidative metabolism and lipolysis assay were studied. Lastly, as a proof-of-concept study, we used CD10 as a prospective marker for screening nuclear receptor ligands library.

RESULTS

We identified intrinsic CD10 levels as a positive determinant of adipocyte maturation as well as browning potential of ASCs. Interestingly, CD10 regulates ASC's adipogenic maturation non-canonically by modulating endogenous lipolysis without affecting the classical peroxisome proliferator-activated receptor gamma (PPARγ)-dependent adipogenic pathways. Furthermore, our CD10-mediated screening analysis identified dexamethasone and retinoic acid as stimulator and inhibitor of adipogenesis, respectively, indicating CD10 as a useful biomarker for pro-adipogenic drug screening.

CONCLUSION

Overall, we establish CD10 as a functionally relevant ASC biomarker, which may be a prerequisite to identify high-quality cell populations for improving metabolic diseases.

Severe COVID-19 Lung Infection in Older People and Periodontitis

Periodontal bacteria dissemination into the lower respiratory tract may create favorable conditions for severe COVID-19 lung infection. Once lung tissues are colonized, cells that survive persistent bacterial infection can undergo permanent damage and accelerated cellular senescence. Consequently, several morphological and functional features of senescent lung cells facilitate SARS-CoV-2 replication. The higher risk for severe SARS-CoV-2 infection, the virus that causes COVID-19, and death in older patients has generated the question whether basic aging mechanisms could be implicated in such susceptibility. Mounting evidence indicates that cellular senescence, a manifestation of aging at the cellular level, contributes to the development of age-related lung pathologies and facilitates respiratory infections. Apparently, a relationship between life-threatening COVID-19 lung infection and pre-existing periodontal disease seems improbable. However, periodontal pathogens can be inoculated during endotracheal intubation and/or aspirated into the lower respiratory tract. This review focuses on how the dissemination of periodontal bacteria into the lungs could aggravate age-related senescent cell accumulation and facilitate more efficient SARS-CoV-2 cell attachment and replication. We also consider how periodontal bacteria-induced premature senescence could influence the course of COVID-19 lung infection. Finally, we highlight the role of saliva as a reservoir for both pathogenic bacteria and SARS-CoV-2. Therefore, the identification of active severe periodontitis can be an opportune and valid clinical parameter for risk stratification of old patients with COVID-19.

Is Adipose Tissue the Fountain of Youth? The Impact of Adipose Stem Cell Aging on Metabolic Homeostasis, Longevity, and Cell-Based Therapies

Aging is driven by four interlinked processes: (1) low-grade sterile inflammation; (2) macromolecular and organelle dysfunction, including DNA damage, telomere erosion, and mitochondrial dysfunction; (3) stem cell dysfunction; and (4) an accumulation of senescent cells in tissues. Adipose tissue is not immune to the effects of time, and all four of these processes contribute to a decline of adipose tissue function with advanced age. This decline is associated with an increase in metabolic disorders. Conversely, optimally functioning adipose tissue generates signals that promote longevity. As tissue-resident progenitor cells that actively participate in adipose tissue homeostasis and dysregulation, adipose stem cells (ASCs) have emerged as a key feature in the relationship between age and adipose tissue function. This review will give a mechanistic overview of the myriad ways in which age affects ASC function and, conversely, how ASC function contribute to healthspan and lifespan. A central mediator in this relationship is the degree of resilience of ASCs to maintain stemness into advanced age and the consequent preservation of adipose tissue function, in particular subcutaneous fat. The last sections of this review will discuss therapeutic options that target senescent ASCs to extend healthspan and lifespan, as well as ASC-based therapies that can be used to treat age-related pathologies, and collectively, these therapeutic applications may transform the way we age.

Depletion of ASK1 blunts stress-induced senescence in adipocytes

Increasing energy expenditure via induction of browning in white adipose tissue has emerged as a potential strategy to treat obesity and associated metabolic complications. We previously reported that ASK1 inhibition in adipocytes protected from high-fat diet (HFD) or lipopolysaccharide (LPS)-mediated downregulation of UCP1 both in vitro and in vivo. Conversely, adipocyte-specific ASK1 overexpression attenuated cold-induction of UCP-1 in inguinal fat. Herein, we provide evidence that both TNFα-mediated and HFD-induced activation of p38 MAPK in white adipocytes are ASK1-dependent. Moreover, expression of senescence markers was reduced in HFD-fed adipocyte-specific ASK1 knockout mice. Similarly, LPS-induced upregulation of senescence markers was blunted in ASK1-depleted adipocytes. Thus, our study identifies a previously unknown role for ASK1 in the induction of stress-induced senescence.

Role of TLR4 in the induction of inflammatory changes in adipocytes and macrophages

In obesity, high levels of saturated fatty acids (SFAs) contribute to adipose tissue inflammation and dysfunction. Obesity-induced macrophage infiltration leads to insulin resistance, but the adipocyte itself may play a role in generating the inflammatory milieu. Given our recent findings of the role of TLR4 in myeloid biasing in obesity, we next investigated the role of TLR4 in adipocyte generated inflammatory responses to SFAs and lipopolysaccharides. We used WT and Tlr4^-/- ear mesenchymal stem cell derived adipocytes (EMSC Ad) and bone marrow dendritic cells (BMDCs) to evaluate cell specific responses. Our work demonstrates a role for TLR4 in adipocyte- immune cell crosstalk and that SFA derived metabolites from adipocytes may induce proinflammatory stimulation of immune cells in a TLR4 independent manner.

Periodontal Disease and Senescent Cells: New Players for an Old Oral Health Problem?

The recent identification of senescent cells in periodontal tissues has the potential to provide new insights into the underlying mechanisms of periodontal disease etiology. DNA damage-driven senescence is perhaps one of the most underappreciated delayed consequences of persistent Gram-negative bacterial infection and inflammation. Although the host immune response rapidly protects against bacterial invasion, oxidative stress generated during inflammation can indirectly deteriorate periodontal tissues through the damage to vital cell macromolecules, including DNA. What happens to those healthy cells that reside in this harmful environment? Emerging evidence indicates that cells that survive irreparable genomic damage undergo cellular senescence, a crucial intermediate mechanism connecting DNA damage and the immune response. In this review, we hypothesize that sustained Gram-negative bacterial challenge, chronic inflammation itself, and the constant renewal of damaged tissues create a permissive environment for the abnormal accumulation of senescent cells. Based on emerging data we propose a model in which the dysfunctional presence of senescent cells may aggravate the initial immune reaction against pathogens. Further understanding of the role of senescent cells in periodontal disease pathogenesis may have clinical implications by providing more sophisticated therapeutic strategies to combat tissue destruction.

The role of adipose tissue senescence in obesity- and ageing-related metabolic disorders

Adipose tissue as the largest energy reservoir and endocrine organ is essential for maintenance of systemic glucose, lipid and energy homeostasis, but these metabolic functions decline with ageing and obesity. Adipose tissue senescence is one of the common features in obesity and ageing. Although cellular senescence is a defensive mechanism preventing tumorigenesis, its occurrence in adipose tissue causatively induces defective adipogenesis, inflammation, aberrant adipocytokines production and insulin resistance, leading to adipose tissue dysfunction. In addition to these paracrine effects, adipose tissue senescence also triggers systemic inflammation and senescence as well as insulin resistance in the distal metabolic organs, resulting in Type 2 diabetes and other premature physiological declines. Multiple cell types including mature adipocytes, immune cells, endothelial cells and progenitor cells gradually senesce at different levels in different fat depots with ageing and obesity, highlighting the heterogeneity and complexity of adipose tissue senescence. In this review, we discuss the causes and consequences of adipose tissue senescence, and the major cell types responsible for adipose tissue senescence in ageing and obesity. In addition, we summarize the pharmacological approaches and lifestyle intervention targeting adipose tissue senescence for the treatment of obesity- and ageing-related metabolic diseases.

LPS-induced premature osteocyte senescence: Implications in inflammatory alveolar bone loss and periodontal disease pathogenesis

Cellular senescence is associated with inflammation and extracellular matrix tissue remodeling through the secretion of proteins termed the senescence-associated secretory phenotype (SASP). Although osteocyte senescence in older individuals in the skeleton is well recognized, whether young alveolar osteocytes can also become senescent is unknown. This is potentially important in the context of periodontal disease, which is an inflammatory condition caused by a gradual change from symbiotic to pathogenic oral microflora that can lead to tooth loss. Our aim was to identify whether senescent osteocytes accumulate in young alveolar bone and whether bacterial-derived lipopolysaccharide (LPS) can influence cellular senescence in alveolar bone. An osteocyte-enriched cell population isolated from alveolar bone expressed increased levels of the known senescence marker p16^Ink4a, as well as select SASP markers known to be implicated alveolar bone resorption (Icam1, Il6, Il17, Mmp13 and Tnfα), compared to ramus control cells. Increased senescence of alveolar bone osteocytes was also observed in vivo using the senescence-associated distension of satellites (SADS) assay and increased γH2AX, a marker of DNA damage associated with senescent cells. To approximate a bacterial infection in vitro, alveolar osteocytes were treated with LPS. We found increased expression of various senescence and SASP markers, increased γH2AX staining, increased SA-β-Gal activity and the redistribution of F-actin leading to a larger and flattened cell morphology, all hallmarks of cellular senescence. In conclusion, our data suggests a model whereby bacterial-derived LPS stimulates premature alveolar osteocyte senescence, which in combination with the resultant SASP, could potentially contribute to the onset of alveolar bone loss.

The Transcription Factor ATF7 Controls Adipocyte Differentiation and Thermogenic Gene Programming

Adipocytes function as major players in the regulation of metabolic homeostasis, and factors contributing to adipocyte differentiation and function are promising targets for combatting obesity and associated metabolic disorders. Activating transcription factor 7 (ATF7), a stress-responsive chromatin regulator, is involved in energy metabolism, but the underlying mechanisms remain unknown. Herein, we showed that ATF7 is required for adipocyte differentiation and interacts with histone dimethyltransferase G9a in adipocytes to repress the expression of interferon-stimulated genes, which in turn suppress adipogenesis. Ablation of ATF7 promotes beige fat biogenesis in inguinal white adipose tissue. ATF7 binds to transcriptional regulatory regions of the gene encoding uncoupling protein 1, silencing it by controlling histone H3K9 dimethylation. Our findings demonstrate that ATF7 is a multifunctional adipocyte protein involved in the epigenetic control of development and function in adipose tissues.

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ATF7 is required for adipocyte differentiation

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ATF7 represses the expression of interferon-stimulated genes (ISGs) in adipocytes

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Loss of ATF7 promotes the browning of inguinal white adipose tissue

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ATF7 associates with C/EBPβ and G9a to silence Ucp1 expression

Fat depot-specific differences of macrophage infiltration and cellular senescence in obese bovine adipose tissues

Obesity is associated with the chronic inflammation and senescence of adipose tissues. Macrophage is a key mediator of chronic inflammation that infiltrates obese adipose tissue and stimulates metabolic disorders. However, the fat depot-specific differences of macrophage infiltration and senescence, especially the influence on intramuscular adipose tissue, have remained unclear. We investigated the fat depot-specific differences of macrophage infiltration and senescence in obese bovine adipose tissue from three different anatomical sites (subcutaneous, intramuscular and visceral). Macrophage infiltrations and crown-like structures were observed in visceral adipose tissue, although there were few macrophages in subcutaneous and intramuscular adipose tissues. The positive reaction of senescence marker SA-βgal activity was observed in visceral adipose tissue. In contrast, the activity of SA-βgal in subcutaneous and intramuscular adipose tissues were low. The expression of p53 gene, the master regulator of cellular senescence, in visceral adipose tissue was higher than that of subcutaneous and intramuscular adipose tissue. At the cellular level, p53 gene expression was negatively correlated with the size of subcutaneous adipocytes. In contrast, p53 gene expressions were positively correlated with the size of intramuscular and visceral adipocytes. These results indicate that anatomical sites of obese adipose tissue affect macrophage infiltration and the senescent state in a fat depot-specific manner.

Obesity and type-2 diabetes as inducers of premature cellular senescence and ageing

Cellular senescence is now considered as a major mechanism in the development and progression of various diseases and this may include metabolic diseases such as obesity and type-2 diabetes. The presence of obesity and diabetes is a major risk factor in the development of additional health conditions, such as cardiovascular disease, kidney disease and cancer. Since senescent cells can drive disease development, obesity and diabetes can potentially create an environment that accelerates cell senescence within other tissues of the body. This can consequently manifest as age-related biological impairments and secondary diseases. Cell senescence in cell types linked with obesity and diabetes, namely adipocytes and pancreatic beta cells will be explored, followed by a discussion on the role of obesity and diabetes in accelerating ageing through induction of premature cell senescence mediated by high glucose levels and oxidised low-density lipoproteins. Particular emphasis will be placed on accelerated cell senescence in endothelial progenitor cells, endothelial cells and vascular smooth muscle cells with relation to cardiovascular disease and proximal tubular cells with relation to kidney disease. A summary of the potential strategies for therapeutically targeting senescent cells for improving health is also presented.

Role of microbiota-derived lipopolysaccharide in adipose tissue inflammation, adipocyte size and pyroptosis during obesity

It has been established that ingestion of a high-fat diet increases the blood levels of lipopolysaccharides (LPS) from Gram-negative bacteria in the gut. Obesity is characterised by low-grade systemic and adipose tissue inflammation. This is suggested to be implicated in the metabolic syndrome and obesity. In the present review, we hypothesise that LPS directly and indirectly participates in the inflammatory reaction in adipose tissue during obesity. The experimental evidence shows that LPS is involved in the transition of macrophages from the M2 to the M1 phenotype. In addition, LPS inside adipocytes may activate caspase-4/5/11. This may induce a highly inflammatory type of programmed cell death (i.e. pyroptosis), which also occurs after infection with intracellular pathogens. Lipoproteins with or without LPS are taken up by adipocytes. Large adipocytes are more metabolically active and potentially more exposed to LPS than small adipocytes are. Thus, LPS might be involved in defining the adipocyte death size and the formation of crown-like structures. The adipocyte death size is reached when the intracellular concentration of LPS initiates pyroptosis. The mechanistic details remain to be elucidated, but the observations indicate that adipocytes are stimulated to cell death by processes that involve LPS from the gut microbiota. There is a complex interplay between the composition of the diet and microbiota. This influences the amount of LPS that is translocated from the gut. In particular, the lipid content of a meal may correlate with the amount of LPS built in to chylomicrons.

Long-term culture with lipopolysaccharide induces dose-dependent cytostatic and cytotoxic effects in THP-1 monocytes

Monocytes act as a first line of defence against invading pathogens and their dysfunctions seem to be a key factor in many immune disorders. However, the data on mechanisms underlying these dysfunctions remain elusive. In this study, we evaluated the effects of long-term (168h) lipopolysaccharide exposure on monocytes at low density cultures (1×10⁵cells/ml). Treatment with low dose LPS (≤5μg/ml) resulted in oxidative stress induction followed by p21 pathway activation, permanent cell cycle arrest and SASP development. Furthermore, high dose LPS (≥10μg/ml) induced cell death involving mitochondrial pathways, death receptors as well as p21-dependent DNA damage response activation mediated by ROS generation and TNF-α release. Additionally, exposure to high dose of LPS resulted in THP-1 monocytes differentiation to macrophages. In conclusion, long-term culture with LPS exerts in low density monocytes cytostatic/cytotoxic effects in a dose-dependent manner by inducing senescence associated with chronic inflammation at low doses and initiation of cell death at higher doses. These findings shed new light on understanding of monocytes dysfunction, an issue relevant to chronic inflammation and many immune disorders.

A Randomized Controlled Trial to Increase Navy Bean or Rice Bran Consumption in Colorectal Cancer Survivors

Consumption of navy beans (NB) and rice bran (RB) have been shown to inhibit colon carcinogenesis. Given the overall poor diet quality in colorectal cancer (CRC) survivors and low reported intake of whole grains and legumes, practical strategies to increase consumption merit attention. This study determined feasibility of increasing NB or RB intake in CRC survivors to increase dietary fiber and examined serum inflammatory biomarkers and telomere lengths. Twenty-nine subjects completed a randomized controlled trial with foods that included cooked NB powder (35 g/day), heat-stabilized RB (30 g/day), or no additional ingredient. Fasting blood, food logs, and gastrointestinal health questionnaires were collected. The amount of NB or RB consumed equated to 4-9% of subjects' daily caloric intake and no major gastrointestinal issues were reported with increased consumption. Dietary fiber amounts increased in NB and RB groups at Weeks 2 and 4 compared to baseline and to control (P ≤ 0.01). Telomere length correlated with age and HDL cholesterol at baseline, and with improved serum amyloid A (SAA) levels at Week 4 (P ≤ 0.05). This study concludes feasibility of increased dietary NB and RB consumption to levels associated with CRC chemoprevention and warrants longer-term investigations with both foods in high-risk populations that include cancer prevention and control outcomes.