Obese adipocytes show ultrastructural features of stressed cells and die of pyroptosis

Lycopene Ameliorates Di(2-ethylhexyl) Phthalate-Induced Pyroptosis in Spleen via Suppression of Classic Caspase-1/NLRP3 Pathway

Lycopene (Lyc) as a natural antioxidant has attracted widespread attention. Di(2-ethylhexyl) phthalate (DEHP) can cause serious spleen injury in animals via the environment and food chain. For investigation of whether Lyc could alleviate DEHP-exerted pyroptosis in spleen through inhibiting the Caspase-1/NLRP3 pathway activation, 140 male mice were randomly divided into 7 groups: control group, vehicle control group, Lyc group (5 mg/kg BW/day), DEHP-exposed group (500 or 1000 mg/kg BW/day, respectively), and DEHP + Lyc groups by daily administration for 28 days. Pathological results showed that the supplementation of Lyc alleviated DEHP-induced inflammatory infiltration. Moreover, the addition of Lyc inhibited DEHP-induced Caspase-1, NLRP3, ASC, NF-κB, IL-1β, and IL-18 overexpression and GSDMD down-expression. These results indicate that Lyc could inhibit DEHP-induced Caspase-1-dependent pyroptosis and the inflammatory response. Taken together, the study provided new evidence that Lyc may be a strategy to mitigate spleen injury induced by DEHP.

Adipose tissue plasticity and the pleiotropic roles of BMP signaling

Adipose tissues, including white, beige, and brown adipose tissue, have evolved to be highly dynamic organs. Adipose tissues undergo profound changes during development and regeneration and readily undergo remodeling to meet the demands of an everchanging metabolic landscape. The dynamics are determined by the high plasticity of adipose tissues, which contain various cell types: adipocytes, immune cells, endothelial cells, nerves, and fibroblasts. There are numerous proteins that participate in regulating the plasticity of adipose tissues. Among these, bone morphogenetic proteins (BMPs) were initially found to regulate the differentiation of adipocytes, and they are being reported to have pleiotropic functions by emerging studies. Here, in the first half of the article, we summarize the plasticity of adipocytes and macrophages, which are two groups of cells targeted by BMP signaling in adipose tissues. We then review how BMPs regulate the differentiation, death, and lipid metabolism of adipocytes. In addition, the potential role of BMPs in regulating adipose tissue macrophages is considered. Finally, the expression of BMPs in adipose tissues and their metabolic relevance are discussed.

Adipose tissue remodelling in obese subjects is a determinant of presence and severity of fatty liver disease

AIMS

Experimental data suggest that visceral adipose tissue (VAT) dysfunction contributes to non-alcoholic fatty liver disease (NAFLD) development in obesity, however, data on humans are limited. Aims of this study were to investigate the relationship between NAFLD and VAT morphofunctional impairment and to determine whether the extent of VAT remodelling is associated with liver damage and metabolic alterations in obesity.

METHODS

We analysed data from 40 obese individuals candidate to bariatric surgery in whom paired intraoperative liver and omental biopsies were performed for diagnosing NAFLD and VAT inflammation by immunohistochemistry and mRNA expression studies.

RESULTS

Within our study population, NAFLD was significantly associated with greater VAT CD68⁺ macrophages infiltration (P = .04), fibrosis (P = .04) and impaired microvascular density (P = .03) as well as increased expression of markers of local hypoxia, apoptosis and inflammation (UNC5B, CASP7, HIF1-α, IL-8, MIP2, WISP-1, all P < .01). The degree of VAT inflammation correlated with the severity of hepatic injury (steatosis, inflammation, fibrosis; all P < .01) and impaired gluco-metabolic profile.

CONCLUSIONS

In obese patients, NAFLD is associated in a dose-dependent manner with signs of VAT remodelling, which reflect more severe clinical metabolic impairment. Our study depicts morphological alterations and novel mediators of VAT dysfunction, adding knowledge for future therapeutic approaches to NAFLD and its metabolic complications.

Lipodistrophy: a paradigm for understanding the consequences of "overloading" adipose tissue

Lipodystrophies have been recognized since at least the nineteenth century and, despite their rarity, tended to attract considerable medical attention because of the severity and somewhat paradoxical nature of the associated metabolic disease that so closely mimics that of obesity. Within the last 20 yr most of the monogenic subtypes have been characterized, facilitating family genetic screening and earlier disease detection as well as providing important insights into adipocyte biology and the systemic consequences of impaired adipocyte function. Even more recently, compelling genetic studies have suggested that subtle partial lipodystrophy is likely to be a major factor in prevalent insulin-resistant type 2 diabetes mellitus (T2DM), justifying the longstanding interest in these disorders. This progress has also underpinned novel approaches to treatment that, in at least some patients, can be of considerable therapeutic benefit.

Ginsenoside Rb2 improves insulin resistance by inhibiting adipocyte pyroptosis

Pyroptosis plays a critical role in the development of obesity-associated inflammation and insulin resistantance (IR). Ginsenoside Rb2 (Rb2), the main component of ginsenosides has drawn appreciable interest in the context of glucose metabolism. In the present study, we investigated Rb2-mediated protection against obesity-induced IR and the related mechanisms. Rb2 could significantly reduce high-fat diet (HFD)-induced body weight changes, fat accumulation and IR. In addition, Rb2 treatment inhibited pyroptosis-related genes and proteins, such as caspase-1, ASC, NLRP3, IL-1β and GSDMD in HFD-fed mice. The above results were recapitulated in 3T3-L1 adipocytes and demonstrated that Rb2 improved TNF-α induced IR and pyroptosis in 3T3-L1 adipocytes. Furthermore, Rb2 reduced the phosphorylation levels of p65 and IκBα both in vitro and in vivo. The present study showed that Rb2, which could serve as a promising agent for the treatment of IR and obesity, ameliorated IR by inhibiting pyroptosis in adipocytes in vivo and in vitro through the NF-κB pathway.

Fibroblast growth factor 2 exacerbates inflammation in adipocytes through NLRP3 inflammasome activation

Chronic inflammation in adipose tissue is the hallmark of obesity and a major risk factor for the development of obesity-induced insulin resistance. NLRP3 inflammasome regulates the maturation and secretion of pro-inflammatory cytokines, such as IL-1β and IL-18, and was recently discovered to be involved in obesity-related metabolic diseases. Fibroblast growth factors (FGFs) such as FGF1, FGF10, and FGF21 are adipokines that regulate adipocyte development and metabolism, but reports on the effect of other FGFs on adipocytes are lacking. In the present study, the novel role of FGF2 in NLRP3 inflammasome activation was elucidated. Our results showed that FGF2 levels were increased during adipocyte differentiation and in the adipose tissue of high-fat diet (HFD)-induced obese mice. Recombinant FGF2 treatment upregulated inflammasome markers such as NLRP3, which was further exaggerated by TNF-ɑ treatment. Interestingly, β-Klotho, a co-receptor of FGF21, was significantly decreased by FGF2 treatment. Results from mice confirmed the positive correlation between FGF2 and NLRP3 expression in epididymal and subcutaneous adipose tissue, while exercise training effectively reversed HFD-induced NLRP3 expression as well as FGF2 levels in both adipose depots. Our results suggest that FGF2 is an adipokine that may exacerbate the inflammatory response in adipocytes through NLRP3 inflammasome activation.

How does adipose tissue contribute to inflammageing?

Across aging, white adipose tissue (WAT) undergoes significant changes in quantity and distribution, with an increase in visceral adipose tissue, ectopic fat deposition and a decline in gluteofemoral subcutaneous depot. In particular, WAT becomes dysfunctional with an increase in production of inflammatory peptides and a decline of those with anti-inflammatory activity and infiltration of inflammatory cells. Moreover, dysfunction of WAT is characterized by preadipocyte differentiation decline, increased oxidative stress and mitochondrial dysfunction, reduction in vascularization and hypoxia, increased fibrosis and senescent cell accumulation. WAT changes represent an important hallmark of the aging process and may be responsible for the systemic pro-inflammatory state ("inflammageing") typical of aging itself, leading to age-related metabolic alterations. This review focuses on mechanisms linking age-related WAT changes to inflammageing.

Ketogenic diet as a potential intervention for lipedema

Lipedema (LI) is a common yet misdiagnosed condition, often misconstrued with obesity. LI affects women almost exclusively, and its painful and life-changing symptoms have long been thought to be resistant to the lifestyle interventions such as diet and exercise. In this paper, we discuss possible mechanisms by which patients adopting a ketogenic diet (KD) can alleviate many of the unwanted clinical features of LI. This paper is also an effort to provide evidence for the hypothesis of the potency of this dietary intervention for addressing the symptoms of LI. Specifically, we examine the scientific evidence of effectiveness of adopting a KD by patients to alleviate clinical features associated with LI, including excessive and disproportionate lower body adipose tissue (AT) deposition, pain, and reduction in quality of life (QoL). We also explore several clinical features of LI currently under debate, including the potential existence and nature of edema, metabolic and hormonal dysfunction, inflammation, and fibrosis. The effectiveness of a KD on addressing clinical features of LI has been demonstrated in human studies, and shows promise as an intervention for LI. We hope this paper leads to an improved understanding of optimal nutritional management for patients with LI and stimulates future research in this area of study.

Galectin-3 gene deletion results in defective adipose tissue maturation and impaired insulin sensitivity and glucose homeostasis

Adiposopathy is a pathological adipose tissue (AT) response to overfeeding characterized by reduced AT expandability due to impaired adipogenesis, which favors inflammation, insulin resistance (IR), and abnormal glucose regulation. However, it is unclear whether defective adipogenesis causes metabolic derangement also independently of an increased demand for fat storage. As galectin-3 has been implicated in both adipocyte differentiation and glucose homeostasis, we tested this hypothesis in galectin-3 knockout (Lgal3-/-) mice fed a standard chow. In vitro, Lgal3-/- adipocyte precursors showed impaired terminal differentiation (maturation). Two-month-old Lgal3-/- mice showed impaired AT maturation, with reduced adipocyte size and expression of adipogenic genes, but unchanged fat mass and no sign of adipocyte degeneration/death or ectopic fat accumulation. AT immaturity was associated with AT and whole-body inflammation and IR, glucose intolerance, and hyperglycemia. Five-month-old Lgal3-/- mice exhibited a more mature AT phenotype, with no difference in insulin sensitivity and expression of inflammatory cytokines versus WT animals, though abnormal glucose homeostasis persisted and was associated with reduced β-cell function. These data show that adipogenesis capacity per se affects AT function, insulin sensitivity, and glucose homeostasis independently of increased fat intake, accumulation and redistribution, thus uncovering a direct link between defective adipogenesis, IR and susceptibility to diabetes.

NLRP3 Inflammasome: The Stormy Link Between Obesity and COVID-19

Several countries around the world have faced an important obesity challenge for the past four decades as the result of an obesogenic environment. This disease has a multifactorial origin and it is associated with multiple comorbidities including type 2 diabetes, hypertension, osteoarthritis, metabolic syndrome, cancer, and dyslipidemia. With regard to dyslipidemia, hypertriglyceridemia is a well-known activator of the NLRP3 inflammasome, triggering adipokines and cytokines secretion which in addition induce a systemic inflammatory state that provides an adequate scenario for infections, particularly those mediated by viruses such as HIV, H1N1 influenza, and SARS-CoV-2. The SARS-CoV-2 infection causes the coronavirus disease 2019 (COVID-19) and it is responsible for the pandemic that we are currently living. COVID-19 causes an aggressive immune response known as cytokine release syndrome or cytokine storm that causes multiorgan failure and in most cases leads to death. In the present work, we aimed to review the molecular mechanisms by which obesity-associated systemic inflammation could cause a more severe clinical presentation of COVID-19. The SARS-CoV-2 infection could potentiate or accelerate the pre-existing systemic inflammatory state of individuals with obesity, via the NLRP3 inflammasome activation and the release of pro-inflammatory cytokines from cells trough Gasdermin-pores commonly found in cell death by pyroptosis.

The NLRP3 inflammasome regulates adipose tissue metabolism

Adipose tissue regulates metabolic homeostasis by participating in endocrine and immune responses in addition to storing and releasing lipids from adipocytes. Obesity skews adipose tissue adipokine responses and degrades the coordination of adipocyte lipogenesis and lipolysis. These defects in adipose tissue metabolism can promote ectopic lipid deposition and inflammation in insulin-sensitive tissues such as skeletal muscle and liver. Sustained caloric excess can expand white adipose tissue to a point of maladaptation exacerbating both local and systemic inflammation. Multiple sources, instigators and propagators of adipose tissue inflammation occur during obesity. Cross-talk between professional immune cells (i.e. macrophages) and metabolic cells (i.e. adipocytes) promote adipose tissue inflammation during metabolic stress (i.e. metaflammation). Metabolic stress and endogenous danger signals can engage pathogen recognition receptors (PRRs) of the innate immune system thereby activating pro-inflammatory and stress pathways in adipose tissue. The Nod-like receptor protein 3 (NLRP3) inflammasome can act as a metabolic danger sensor to a wide range of pathogen- and damage-associated molecular patterns (PAMPs and DAMPs). Activation of the NLRP3 inflammasome facilitates caspase-1 dependent production of the pro-inflammatory cytokines IL-1β and IL-18. Activation of the NLRP3 inflammasome can promote inflammation and pyroptotic cell death, but caspase-1 is also involved in adipogenesis. This review discusses the role of the NLRP3 inflammasome in adipose tissue immunometabolism responses relevant to metabolic disease. Understanding the potential sources of NLRP3 activation and consequences of NLRP3 effectors may reveal therapeutic opportunities to break or fine-tune the connection between metabolism and inflammation in adipose tissue during obesity.

Expansion and inflammation of white adipose tissue - focusing on adipocyte progenitors

Adipose tissue is an important organ in our body, participating not only in energy metabolism but also immune regulation. It is broadly classified as white (WAT) and brown (BAT) adipose tissues. WAT is highly heterogeneous, composed of adipocytes, various immune, progenitor and stem cells, as well as the stromal vascular populations. The expansion and inflammation of WAT are hallmarks of obesity and play a causal role in the development of metabolic and cardiovascular diseases. The primary event triggering the inflammatory expansion of WAT remains unclear. The present review focuses on the role of adipocyte progenitors (APS), which give rise to specialized adipocytes, in obesity-associated WAT expansion, inflammation and fibrosis.

Stoking the Fire: How Dying Cells Propagate Inflammatory Signalling through Extracellular Vesicle Trafficking

Communication between dying cells and their environment is a critical process that promotes tissue homeostasis during normal cellular turnover, whilst during disease settings, it can contribute to inflammation through the release of intracellular factors. Extracellular vesicles (EVs) are a heterogeneous class of membrane-bound cell-derived structures that can engage in intercellular communication via the trafficking of bioactive molecules between cells and tissues. In addition to the well-described functions of EVs derived from living cells, the ability of dying cells to release EVs capable of mediating functions on target cells or tissues is also of significant interest. In particular, during inflammatory settings such as acute tissue injury, infection and autoimmunity, the EV-mediated transfer of proinflammatory cargo from dying cells is an important process that can elicit profound proinflammatory effects in recipient cells and tissues. Furthermore, the biogenesis of EVs via unique cell-death-associated pathways has also been recently described, highlighting an emerging niche in EV biology. This review outlines the mechanisms and functions of dying-cell-derived EVs and their ability to drive inflammation during various modes of cell death, whilst reflecting on the challenges and knowledge gaps in investigating this subgenre of extracellular vesicles research.

Endoplasmic reticulum stress related factor IRE1α regulates TXNIP/NLRP3-mediated pyroptosis in diabetic nephropathy

The nod-like receptor protein-3 (NLRP3)-mediated pyroptosis is involved in kidney diseases. Thioredoxin interacting protein (TXNIP) directly interacts with NLRP3. This study aimed to probe the mechanism of TXNIP and NLRP3 pathway in diabetic nephropathy (DN). Marker detection and histological staining indicated that in DN rats, the renal function was destroyed, and the TXNIP/NLRP3 axis was activated to induce inflammatory generation and pyroptosis. The protein levels of TXNIP, NLRP3 inflammatory components and endoplasmic reticulum stress (ERS)-related factors (ATF4, CHOP and IRE1α) were measured. DN rats were injected with LV-TXNIP-shRNA or IRE1α RNase specific inhibitor (STF-083010) to examine ERS- and pyroptosis-related proteins, and renal injury. Silencing TXNIP inhibited the NLRP3 axis and reduced renal damage in DN rats. ERS was activated in DN rats, and miR-200a expression was degraded by IRE1α. miR-200a bound to TXNIP. NRK-52E cells were induced by high glucose (HG) to simulate DN in vitro. The damage and pyroptosis of NRK-52E cells were analyzed. After inhibiting IRE1α, miR-200a expression increased and TXNIP expression decreased. miR-200a inhibition in HG-induced NRK-52E cells partially reversed the reduced pyroptosis by STF-083010. Overall, IRE1α upregulates miR-200a degradation in DN rats, and stimulates the TXINP/NLRP3 pathway-mediated pyroptosis and renal damage.

NLRP3 Inflammasome in Inflammation and Metabolism: Identifying Novel Roles in Postburn Adipose Dysfunction

Inflammasomes are multiprotein complexes that respond to pathogen or host associated damage markers, leading to caspase-1 maturation and processing of pro-inflammatory cytokines. Initially, inflammasomes were implicated primarily in inflammatory and infectious conditions. However, increasing evidence demonstrates broader roles beyond inflammation, including regulation of adipose tissue metabolism after burns. Here, we conducted a search for articles on PubMed, Web of Science, Embase, Scopus, and UpToDate with applied search strategies including a combination of "burns," "trauma," "(NLRP3) inflammasome," "metabolic conditions," "white adipose tissue," "macrophages," "browning," and "lipolysis" and included papers from 2000 to 2020. We discuss unexpected roles for NLRP3, the most characterized inflammasome to date, as a key metabolic driver in a variety of conditions. In particular, we highlight the function of NLRP3 inflammasome in burn trauma, which is characterized by both hyperinflammation and hypermetabolism. We identify a critical part for NLRP3 activation in macrophage dynamics and delineate a novel role in postburn white adipose tissue remodeling, a pathological response associated with hypermetabolism and poor clinical outcomes. Mechanistically, how inflammation and inflammasome activation is linked to postburn hypermetabolism is a novel concept to contemplate, and herein we provide evidence of an immunometabolic crosstalk between adipocytes and infiltrating macrophages.

Adipose Tissue Fibrosis: Mechanisms, Models, and Importance

Increases in adipocyte volume and tissue mass due to obesity can result in inflammation, further dysregulation in adipose tissue function, and eventually adipose tissue fibrosis. Like other fibrotic diseases, adipose tissue fibrosis is the accumulation and increased production of extracellular matrix (ECM) proteins. Adipose tissue fibrosis has been linked to decreased insulin sensitivity, poor bariatric surgery outcomes, and difficulty in weight loss. With the rising rates of obesity, it is important to create accurate models for adipose tissue fibrosis to gain mechanistic insights and develop targeted treatments. This article discusses recent research in modeling adipose tissue fibrosis using in vivo and in vitro (2D and 3D) methods with considerations for biomaterial selections. Additionally, this article outlines the importance of adipose tissue in treating other fibrotic diseases and methods used to detect and characterize adipose tissue fibrosis.

Lipids, inflammasomes, metabolism, and disease

Inflammasomes are multi-protein complexes that regulate the cleavage of cysteine protease caspase-1, secretion of inflammatory cytokines, and induction of inflammatory cell death, pyroptosis. Several members of the nod-like receptor family assemble inflammasome in response to specific ligands. An exception to this is the NLRP3 inflammasome which is activated by structurally diverse entities. Recent studies have suggested that NLRP3 might be a sensor of cellular homeostasis, and any perturbation in distinct metabolic pathways results in the activation of this inflammasome. Lipid metabolism is exceedingly important in maintaining cellular homeostasis, and it is recognized that cells and tissues undergo extensive lipid remodeling during activation and disease. Some lipids are involved in instigating chronic inflammatory diseases, and new studies have highlighted critical upstream roles for lipids, particularly cholesterol, in regulating inflammasome activation implying key functions for inflammasomes in diseases with defective lipid metabolism. The focus of this review is to highlight how lipids regulate inflammasome activation and how this leads to the progression of inflammatory diseases. The key roles of cholesterol metabolism in the activation of inflammasomes have been comprehensively discussed. Besides, the roles of oxysterols, fatty acids, phospholipids, and lipid second messengers are also summarized in the context of inflammasomes. The overriding theme is that lipid metabolism has numerous but complex functions in inflammasome activation. A detailed understanding of this area will help us develop therapeutic interventions for diseases where dysregulated lipid metabolism is the underlying cause.

Deciphering the cellular interplays underlying obesity-induced adipose tissue fibrosis

Obesity originates from an imbalance between caloric intake and energy expenditure that promotes adipose tissue expansion, which is necessary to buffer nutrient excess. Patients with higher visceral fat mass are at a higher risk of developing severe complications such as type 2 diabetes and cardiovascular and liver diseases. However, increased fat mass does not fully explain obesity's propensity to promote metabolic diseases. With chronic obesity, adipose tissue undergoes major remodeling, which can ultimately result in unresolved chronic inflammation leading to fibrosis accumulation. These features drive local tissue damage and initiate and/or maintain multiorgan dysfunction. Here, we review the current understanding of adipose tissue remodeling with a focus on obesity-induced adipose tissue fibrosis and its relevance to clinical manifestations.

Weighing the Risk: effects of Obesity on the Mammary Gland and Breast Cancer Risk

Obesity is a preventable risk factor for breast cancer following menopause. Regardless of menopausal status, obese women who develop breast cancer have a worsened prognosis. Breast tissue is comprised of mammary epithelial cells organized into ducts and lobules and surrounded by adipose-rich connective tissue. Studies utilizing multiple in vivo models of obesity as well as human breast tissue have contributed to our understanding of how obesity alters mammary tissue. Localized changes in mammary epithelial cell populations, elevated secretion of adipokines and angiogenic mediators, inflammation within mammary adipose tissue, and remodeling of the extracellular matrix may result in an environment conducive to breast cancer growth. Despite these significant alterations caused by obesity within breast tissue, studies have suggested that some, but not all, obesity-induced changes may be mitigated with weight loss. Here, we review our current understanding regarding the impact of obesity on the breast microenvironment, how obesity-induced changes may contribute to breast tumor progression, and the impact of weight loss on the breast microenvironment.

Obesity and Breast Cancer: The Role of Crown-Like Structures in Breast Adipose Tissue in Tumor Progression, Prognosis, and Therapy

Obesity is associated with increased risk and aggressiveness of many types of cancer. Women with obesity and breast cancer are more likely to be diagnosed with larger and higher-grade tumors and have higher incidence of metastases than lean individuals. Increasing evidence indicates that obesity includes systemic, chronic low-grade inflammation, and that adipose tissue can act as an important endocrine site, secreting a variety of substances that may regulate inflammation, immune response, and cancer predisposition. Obesity-associated inflammation appears to be initially mediated by macrophage infiltration into adipose tissue. Macrophages can surround damaged or necrotic adipocytes, forming "crown-like" structures (CLS). CLS are increased in breast adipose tissue from breast cancer patients and are more abundant in patients with obesity conditions. Moreover, the CLS index-ratio from individuals with obesity seems to influence breast cancer recurrence rates and survival. In this review, we discuss the most recent cellular and molecular mechanisms involved in CLS establishment in the white adipose tissue of women with obesity and their implications for breast cancer biology. We also explain how CLS influence the tumor microenvironment and affect breast cancer behavior. Targeting breast adipose tissue CLS can be a crucial therapeutic tool in cancer treatment, especially in patients with obesity.

Apple Flavonols Mitigate Adipocyte Inflammation and Promote Angiogenic Factors in LPS- and Cobalt Chloride-Stimulated Adipocytes, in Part by a Peroxisome Proliferator-Activated Receptor-γ-Dependent Mechanism

Adipose tissue (AT) expansion induces local hypoxia, a key contributor to the chronic low-grade inflammation that drives obesity-associated disease. Apple flavonols phloretin (PT) and phlorizin (PZ) are suggested anti-inflammatory molecules but their effectiveness in obese AT is inadequately understood. Using in vitro models designed to reproduce the obese AT microenvironment, 3T3-L1 adipocytes were cultured for 24 h with PT or PZ (100 μM) concurrent with the inflammatory stimulus lipopolysaccharide (LPS; 10 ng/mL) and/or the hypoxia mimetic cobalt chloride (CoCl₂; 100 μM). Within each condition, PT was more potent than PZ and its effects were partially mediated by peroxisome proliferator-activated receptor (PPAR)-γ (p < 0.05), as tested using the PPAR-γ antagonist bisphenol A diglycidyl ether (BADGE). In LPS-, CoCl₂-, or LPS + CoCl₂-stimulated adipocytes, PT reduced mRNA expression and/or secreted protein levels of inflammatory and macrophage chemotactic adipokines, and increased that of anti-inflammatory and angiogenic adipokines, which was consistent with reduced mRNA expression of M1 polarization markers and increased M2 markers in RAW 264.7 macrophages cultured in media collected from LPS + CoCl₂-simulated adipocytes (p < 0.05). Further, within LPS + CoCl₂-stimulated adipocytes, PT reduced reactive oxygen species accumulation, nuclear factor-κB activation, and apoptotic protein expression (p < 0.05). Overall, apple flavonols attenuate critical aspects of the obese AT phenotype.

A large proportion of mediastinal and perirenal visceral fat of Siberian adult people is formed by UCP1 immunoreactive multilocular and paucilocular adipocytes

Many deleterious consequences for health of excessive fat accumulation are due to visceral fat. Browning of visceral fat is mainly cold dependent and has been proposed as a possible tool for future therapies of obesity and related disorders. In this paper, we studied the composition of mediastinal and perirenal visceral fat, collected at necropsy, of human adults that lived in Siberia, one of the coldest regions of the earth. Data showed that a consistent part of the mediastinal and perirenal fat (up to about 40%) had the morphology typical of brown adipocytes and that a relevant percentage of them (up to about 30%) also expressed the functional marker uncoupling protein 1 (UCP1). Patients living mainly outdoor had higher percentage of brown-like adipocytes with more intensely UCP1 immunoreactive cells. The presence of numerous UCP1 immunoreactive paucilocular cells, a transitional stage of transdifferentiating adipocytes, supports the idea that visceral fat can be converted to brown adipose tissue in adult humans in physiological conditions. Tyrosine hydroxylase immunoreactive noradrenergic parenchymal nerve fibers were positively correlated to the number of multilocular adipocytes in mediastinal fat, and a similar trend was also observed in the perirenal fat.

BMPR2 promotes fatty acid oxidation and protects white adipocytes from cell death in mice

Adipocyte cell death is pathologically involved in both obesity and lipodystrophy. Inflammation and pro-inflammatory cytokines are generally regarded as inducers for adipocyte apoptosis, but whether some innate defects affect their susceptibility to cell death has not been extensively studied. Here, we found bone morphogenetic protein receptor type 2 (BMPR2) knockout adipocytes were prone to cell death, which involved both apoptosis and pyroptosis. BMPR2 deficiency in adipocytes inhibited phosphorylation of perilipin, a lipid-droplet-coating protein, and impaired lipolysis when stimulated by tumor necrosis factor (TNFα), which lead to failure of fatty acid oxidation and oxidative phosphorylation. In addition, impaired lipolysis was associated with mitochondria-mediated apoptosis and pyroptosis as well as elevated inflammation. These results suggest that BMPR2 is important for maintaining the functional integrity of adipocytes and their ability to survive when interacting with inflammatory factors, which may explain why adipocytes among individuals show discrepancy for death responses in inflammatory settings.

Trichostatin A alleviated ovarian tissue damage caused by cigarette smoke exposure

Cigarette smoke (CS) has a negative impact on women's health and fertility. Studies have shown that histone deacetylases 1 and 2 (HDAC1/2) were involved in oocyte development. However, the roles of HDAC1/2 in ovarian toxicity caused by CS exposure and the therapeutic potential of trichostatin A (TSA, a HDAC inhibitor) for ovarian tissue damage have not been investigated. In this study, Female C57BL/6 mice were exposed to CS from six cigarettes mixed with indoor air for 120 min (one cigarette for 20 min) using a whole-body mainstream smoke exposure system twice daily for 30 days. TSA (0.6 mg/kg body weight) was injected intraperitoneally into mice in the Control + TSA group and CS + TSA group every two days for 30 days. We found that exposure to CS resulted in ovarian tissue damage and HDAC1/2 over-expression. TSA alleviated the structural changes of ovarian tissue induced by smoking and prevented the activation of HDAC1/2. Exposure to CS caused autophagy inhibition and pyroptosis activation. TSA treatment restored the expression of autophagy-associated proteins and decreased the levels of pyroptosis-related proteins induced by CS exposure. The TSA effect may be mediated by inhibition of HDAC1/2 involved in autophagy and pyroptosis process.

Fumarate and oxidative stress synergize to promote stability of C/EBP homologous protein in the adipocyte

C/EBP homologous protein (CHOP) is a transcription factor that is elevated in adipose tissue across many models of diabetes and metabolic stress. Although increased CHOP levels are associated with the terminal response to endoplasmic reticulum stress and apoptosis, there is no evidence for CHOP mediated apoptosis in the adipose tissue during diabetes. CHOP protein levels increase in parallel with protein succination, a fumarate derived cysteine modification, in the adipocyte during metabolic stress. We investigated the factors contributing to sustained CHOP proteins levels in the adipocyte, with an emphasis on the regulation of CHOP protein turnover by metabolite-driven modification of Keap1 cysteines. CHOP protein stability was investigated in conditions of nutrient stress due to high glucose or elevated fumarate (fumarase knockdown model); where cysteine succination is specifically elevated. CHOP protein turnover is significantly reduced in models of elevated glucose and fumarate with a ~30% increase in CHOP stability (p > 0.01), in part due to decreased CHOP phosphorylation. Sustained CHOP levels occur in parallel with elevated heme-oxygenase-1, a production of increased Nrf2 transcriptional activity and Keap1 modification. While Keap1 is directly succinated in the presence of excess fumarate derived from genetic knockdown of fumarase (fumarate levels are elevated >20-fold), it is the oxidative modification of Keap1 that predominates in adipocytes matured in high glucose (fumarate increases 4-5 fold). Elevated fumarate indirectly regulates CHOP stability through the induction of oxidative stress. The antioxidant N-acetylcysteine (NAC) reduces fumarate levels, protein succination and CHOP levels in adipocytes matured in high glucose. Elevated CHOP does not contribute elevated apoptosis in adipocytes, but plays a redox-dependent role in decreasing the adipocyte secretion of interleukin-13, an anti-inflammatory chemokine. NAC treatment restores adipocyte IL-13 secretion, confirming the redox-dependent regulation of a potent anti-inflammatory eotaxin. This study demonstrates that physiological increases in the metabolite fumarate during high glucose exposure contributes to the presence of oxidative stress and sustained CHOP levels in the adipocyte during diabetes. The results reveal a novel metabolic link between mitochondrial metabolic stress and reduced anti-inflammatory adipocyte signaling as a consequence of reduced CHOP protein turnover.

Immunometabolism in type 2 diabetes mellitus: tissue-specific interactions

The immune system is frequently described in the context of its protective function against infections and its role in the development of autoimmunity. For more than a decade, the interactions between the immune system and metabolic processes have been reported, in effect creating a new research field, termed immunometabolism. Accumulating evidence supports the hypothesis that the development of metabolic diseases may be linked to inflammation, and reflects, in some cases, the activation of immune responses. As such, immunometabolism is defined by 1) inflammation as a driver of disease development and/or 2) metabolic processes stimulating cellular differentiation of the immune components. In this review, the main factors capable of altering the immuno-metabolic communication leading to the development and establishment of obesity and diabetes are comprehensively presented. Tissue-specific immune responses suggested to impair metabolic processes are described, with an emphasis on the adipose tissue, gut, muscle, liver, and pancreas.

Chinese Medicinal Herbs Targeting the Gut-Liver Axis and Adipose Tissue-Liver Axis for Non-Alcoholic Fatty Liver Disease Treatments: The Ancient Wisdom and Modern Science

Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide. The pathogenesis of NAFLD is complex. Frontline western medicines only ameliorate the symptoms of NAFLD. On the contrary, the uniqueness of Chinese medicine in its interpretation of NAFLD and the holistic therapeutic approach lead to a promising therapeutic efficacy. Recent studies reveal that the gut-liver axis and adipose tissue-liver axis play important roles in the development of NAFLD. Interestingly, with advanced technology, many herbal formulae are found to target the gut-liver axis and adipose tissue-liver axis and resolve the inflammation in NAFLD. This is the first review summarizes the current findings on the Chinese herbal formulae that target the two axes in NAFLD treatment. This review not only demonstrates how the ancient wisdom of Chinese medicine is being interpreted by modern pharmacological studies, but also provides valuable information for the further development of the herbal-based treatment for NAFLD.

Exercise Training Promotes Cardiac Hydrogen Sulfide Biosynthesis and Mitigates Pyroptosis to Prevent High-Fat Diet-Induced Diabetic Cardiomyopathy

Obesity increases the risk of developing diabetes and subsequently, diabetic cardiomyopathy (DMCM). Reduced cardioprotective antioxidant hydrogen sulfide (H₂S) and increased inflammatory cell death via pyroptosis contribute to adverse cardiac remodeling and DMCM. Although exercise training (EX) has cardioprotective effects, it is unclear whether EX mitigates obesity-induced DMCM by increasing H₂S biosynthesis and mitigating pyroptosis in the heart. C57BL6 mice were fed a high-fat diet (HFD) while undergoing treadmill EX for 20 weeks. HFD mice developed obesity, hyperglycemia, and insulin resistance, which were reduced by EX. Left ventricle pressure-volume measurement revealed that obese mice developed reduced diastolic function with preserved ejection fraction, which was improved by EX. Cardiac dysfunction was accompanied by increased cardiac pyroptosis signaling, structural remodeling, and metabolic remodeling, indicated by accumulation of lipid droplets in the heart. Notably, EX increased cardiac H₂S concentration and expression of H₂S biosynthesis enzymes. HFD-induced obesity led to features of type 2 diabetes (T2DM), and subsequently DMCM. EX during the HFD regimen prevented the development of DMCM, possibly by promoting H₂S-mediated cardioprotection and alleviating pyroptosis. This is the first report of EX modulating H₂S and pyroptotic signaling in the heart.

Activation of invariant natural killer T cells stimulates adipose tissue remodeling via adipocyte death and birth in obesity

In this study, Park et al. set out to elucidate the mechanism by which adipose-resident invariant natural killer T cells (iNKT) cells impact adipose tissue remodeling in obesity. Using in vitro and ex vivo approaches, the authors found that, in obesity, adipose iNKT cells can kill hypertrophic and pro-inflammatory adipocytes via FasL-Fas-dependent apoptosis, thus providing new insight into the role adipose iNKT cells play in promoting healthy adipose tissue remodeling.

In obesity, adipose tissue undergoes dynamic remodeling processes such as adipocyte hypertrophy, hypoxia, immune responses, and adipocyte death. However, whether and how invariant natural killer T (iNKT) cells contribute to adipose tissue remodeling are elusive. In this study, we demonstrate that iNKT cells remove unhealthy adipocytes and stimulate the differentiation of healthy adipocytes. In obese adipose tissue, iNKT cells were abundantly found nearby dead adipocytes. FasL-positive adipose iNKT cells exerted cytotoxic effects to eliminate hypertrophic and pro-inflammatory Fas-positive adipocytes. Furthermore, in vivo adipocyte-lineage tracing mice model showed that activation of iNKT cells by alpha-galactosylceramide promoted adipocyte turnover, eventually leading to potentiation of the insulin-dependent glucose uptake ability in adipose tissue. Collectively, our data propose a novel role of adipose iNKT cells in the regulation of adipocyte turnover in obesity.

New System Delivering Microwaves Energy for Inducing Subcutaneous Fat Reduction: In - Vivo Histological and Ultrastructural Evidence

BACKGROUND:

Recently, it has been developed a new technology for the reduction of subcutaneous adipose tissue through a non-invasive treatment by microwaves. The main objective of the present study is to demonstrate the feasibility of utilising a non-invasive, localised microwaves (MW) device to induce thermal modifications into subcutaneous adipose tissue only by a controlled electromagnetic field that heats up fat preferentially. This device is provided with a special handpiece appropriately cooled, directly contacting the cutaneous surface of the body, which provides a calibrated energy transfer by microwaves.

AIM:

In this paper, microscopic and ultrastructural modifications of subcutaneous adipose tissue induced by microwaves irradiation are evaluated.

METHODS:

Our experimental plan was designed for collecting biopsy samples, for each skin region treated with a single irradiation session, 1) before treatment (control), 2) immediately after treatment, 3) after 6 hrs, 4) after 1 month, 5) after 2 months. Bioptic samples from each step were processed for light microscopy and transmission electron microscopy. At the same time, each region where biopsies were collected was subjected to ultrasound examination. Recorded images permitted to evaluate the thickness of different layers as epidermis, dermis, hypodermis, connective fasciae, until to muscle layer, and related modifications induced by treatment.

RESULTS:

In every biopsy collected at different time-steps, epidermis and superficial dermis appeared not modified compared to control. Differently, already in the short-term biopsies, in the deep dermis and superficial hypodermis, fibrillar connective tissue appeared modified, showing reduction and fragmentation of interlobular collagen septa. The most important adipose tissue modifications were detectable following 1 month from treatment, with a significant reduction of subcutaneous fat, participating both the lysis of many adipocytes and the related phagocytic action of monocytes/macrophages on residuals of compromised structures of adipocytes. In the samples collected two months following treatment, the remnants of adipose tissue appeared normal, and macrophages were completely absent.

CONCLUSIONS:

Ultrasound, microscopic and ultrastructural evidence are supporting significant effectiveness of the new device treatment in the reduction of subcutaneous fat. In this paper, the possible mechanisms involved in the activation of the monocytes/macrophages system responsible for the removal of adipocytes residuals have also been discussed.

Annexins in Adipose Tissue: Novel Players in Obesity

Obesity and the associated comorbidities are a growing health threat worldwide. Adipose tissue dysfunction, impaired adipokine activity, and inflammation are central to metabolic diseases related to obesity. In particular, the excess storage of lipids in adipose tissues disturbs cellular homeostasis. Amongst others, organelle function and cell signaling, often related to the altered composition of specialized membrane microdomains (lipid rafts), are affected. Within this context, the conserved family of annexins are well known to associate with membranes in a calcium (Ca²⁺)- and phospholipid-dependent manner in order to regulate membrane-related events, such as trafficking in endo- and exocytosis and membrane microdomain organization. These multiple activities of annexins are facilitated through their diverse interactions with a plethora of lipids and proteins, often in different cellular locations and with consequences for the activity of receptors, transporters, metabolic enzymes, and signaling complexes. While increasing evidence points at the function of annexins in lipid homeostasis and cell metabolism in various cells and organs, their role in adipose tissue, obesity and related metabolic diseases is still not well understood. Annexin A1 (AnxA1) is a potent pro-resolving mediator affecting the regulation of body weight and metabolic health. Relevant for glucose metabolism and fatty acid uptake in adipose tissue, several studies suggest AnxA2 to contribute to coordinate glucose transporter type 4 (GLUT4) translocation and to associate with the fatty acid transporter CD36. On the other hand, AnxA6 has been linked to the control of adipocyte lipolysis and adiponectin release. In addition, several other annexins are expressed in fat tissues, yet their roles in adipocytes are less well examined. The current review article summarizes studies on the expression of annexins in adipocytes and in obesity. Research efforts investigating the potential role of annexins in fat tissue relevant to health and metabolic disease are discussed.

Estradiol and NADPH oxidase crosstalk regulates responses to high fat feeding in female mice

We previously demonstrated protection against high fat-induced obesity in female but not male p47phox−/− mice lacking NADPH oxidase NOX1/2 activity. To test the role of estradiol (E2)-NOX crosstalk in development of this sexually dimorphic phenotype, we fed diets containing 42% fat/0.5% cholesterol to intact and ovariectomized wild type female C57BL/6 mice and female p47phox−/− mice and to ovariectomized mice where the diet was supplemented with an 1 mg/kg 17β estradiol (E2) for 12 weeks from PND28. Weight gain, gonadal fat pad weight, serum leptin and adiponectin, and adipose tissue inflammation were greater in intact wild type vs. p47 mice ( P < 0.05). Genotype effects on body weight/fat mass were abolished after ovariectomized and restored in OVX + E2 mice ( P < 0.05). The mRNA of downstream PPARγ targets CD36, lipoprotein lipase, and leptin was higher in intact wild type vs. p47phox−/− mice mice ( P < 0.05). Likewise, intact high fat-fed wild type mice had higher expression of the cytokine Mcp1; the pyroptosis marker Nirp3 and matrix remodeling and fibrosis markers Mmp2, Col1A1, and Col6a3 mRNAs ( P < 0.05). These genotype effects were reversed and restored by ovariectomized and OVX + E2, respectively ( P < 0.05). These data suggest that triglyceride accumulation in adipose tissue and development of adipose tissue injury in response to feeding diets high in fat and cholesterol is regulated by the balance between NOX-dependent reactive oxygen species signaling and E2-signaling during development. Loss of estrogens post menopause may increase the risk of obesity and metabolic syndrome as the result disinhibition of reactive oxygen species signaling.

Impact statement

Estrogens are known to regulate body composition. In addition, reactive oxygen species (ROS) produced by the action of NADPH oxidase (NOX) enzymes have been linked to obesity development. We examined development of obesity and adipose tissue injury in response to feeding “Western” diets high in fat and cholesterol in intact, ovariectomized (OVX), and estrogen-replaced (OVX + E2) wild type and p47phox−/− female mice where NOX2 activity is inhibited. Weight gain, gonadal fat pad weight, and adipose tissue inflammation were greater in intact WT vs. p47phox−/− mice. Genotype effects on body weight/fat mass were abolished after OVX and restored in OVX + E2 mice. These data indicate adipose tissue responses to feeding the “Western” diet is regulated by negative cross-talk between NOX-dependent ROS signaling and E2-signaling during development. Loss of estrogens post menopause may increase the risk of obesity and metabolic syndrome as the result disinhibition of ROS signaling.

Acute high-fat feeding leads to disruptions in glucose homeostasis and worsens stroke outcome

Chronic consumption of diets high in fat leads to obesity and can negatively affect brain function. Rodents made obese by long-term maintenance on a high-fat diet have worse outcome after experimental stroke. High-fat consumption for only three days does not induce obesity but has rapid effects on the brain including memory impairment. However, the effect of brief periods of high-fat feeding or high-fat consumption in the absence of obesity on stroke is unknown. We therefore tested the effect of an acute period of high-fat feeding (three days) in C57B/6 mice on outcome after middle cerebral artery occlusion (MCAo). In contrast to a chronic high-fat diet (7.5 months), an acute high-fat diet had no effect on body weight, adipose tissue, lipid profile or inflammatory markers (in periphery and the brain). Three days of high-fat feeding impaired glucose tolerance, increased plasma glucose and insulin and brain expression of the glucose transporter GLUT-1. Ischaemic damage was increased (48%) in mice fed an acute high-fat diet, and was associated with a further reduction in GLUT-1 in the ischaemic hemisphere. These data demonstrate that only a brief period of high-fat consumption has a negative effect on glucose homeostasis and worsens outcome after ischaemic stroke.

Role of Pyroptosis in Cardiovascular Diseases and its Therapeutic Implications

Pyroptotic cell death or pyroptosis is characterized by caspase-1-dependent formation of plasma membrane pores, leading to the release of pro-inflammatory cytokines and cell lysis. Pyroptosis tightly controls the inflammatory responses and coordinates antimicrobial host defenses by releasing pro-inflammatory cellular contents, such as interleukin (IL)-1β and IL-18, and consequently expands or sustains inflammation. It is recognized as an important innate immune effector mechanism against intracellular pathogens. The induction of pyroptosis is closely associated with the activation of the NOD-like receptor 3 (NLRP3) inflammasome which has been linked to key cardiovascular risk factors including hyperlipidemia, diabetes, hypertension, obesity, and hyperhomocysteinemia. Emerging evidence has indicated pyroptosis as an important trigger and endogenous regulator of cardiovascular inflammation. Thus, pyroptosis may play an important role in the pathogenesis of cardiovascular diseases. Design of therapeutic strategies targeting the activation of NLRP3 inflammasome and pyroptosis holds promise for the treatment of cardiovascular diseases.

Melatonin as a master regulator of cell death and inflammation: molecular mechanisms and clinical implications for newborn care

Melatonin, more commonly known as the sleep hormone, is mainly secreted by the pineal gland in dark conditions and regulates the circadian rhythm of the organism. Its intrinsic properties, including high cell permeability, the ability to easily cross both the blood–brain and placenta barriers, and its role as an endogenous reservoir of free radical scavengers (with indirect extra activities), confer it beneficial uses as an adjuvant in the biomedical field. Melatonin can exert its effects by acting through specific cellular receptors on the plasma membrane, similar to other hormones, or through receptor-independent mechanisms that involve complex molecular cross talk with other players. There is increasing evidence regarding the extraordinary beneficial effects of melatonin, also via exogenous administration. Here, we summarize molecular pathways in which melatonin is considered a master regulator, with attention to cell death and inflammation mechanisms from basic, translational and clinical points of view in the context of newborn care.

A comparison between the abdominal and femoral adipose tissue proteome of overweight and obese women

Body fat distribution is an important determinant of cardiometabolic health. Lower-body adipose tissue (AT) has protective characteristics as compared to upper-body fat, but the underlying depot-differences remain to be elucidated. Here, we compared the proteome and morphology of abdominal and femoral AT. Paired biopsies from abdominal and femoral subcutaneous AT were taken from eight overweight/obese (BMI ≥ 28 kg/m²) women with impaired glucose metabolism after an overnight fast. Proteins were isolated and quantified using liquid chromatography-mass spectrometry, and protein expression in abdominal and femoral subcutaneous AT was compared. Moreover, correlations between fat cell size and the proteome of both AT depots were determined. In total, 651 proteins were identified, of which 22 proteins tended to be differentially expressed between abdominal and femoral AT after removal of blood protein signals (p < 0.05). Proteins involved in cell structure organization and energy metabolism were differently expressed between AT depots. Fat cell size, which was higher in femoral AT, was significantly correlated with ADH1B, POSTN and LCP1. These findings suggest that there are only slight differences in protein expression between abdominal and femoral subcutaneous AT. It remains to be determined whether these differences, as well as differences in protein activity, contribute to functional and/or morphological differences between these fat depots.

The obese adipose tissue microenvironment in cancer development and progression

Obesity is associated with both increased cancer incidence and progression in multiple tumour types, and is estimated to contribute to up to 20% of cancer-related deaths. These associations are driven, in part, by metabolic and inflammatory changes in adipose tissue that disrupt physiological homeostasis both within local tissues and systemically. However, the mechanisms underlying the obesity-cancer relationship are poorly understood. In this Review, we describe how the adipose tissue microenvironment (ATME) evolves during body-weight gain, and how these changes might influence tumour initiation and progression. We focus on multiple facets of ATME physiology, including inflammation, vascularity and fibrosis, and discuss therapeutic interventions that have the potential to normalize the ATME, which might be translationally relevant for cancer prevention and therapy. Given that the prevalence of obesity is increasing on an international scale, translational research initiatives are urgently needed to provide mechanistic explanations for the obesity-cancer relationship, and how to best identify high-risk individuals without relying on crude measures, such as BMI.

Targeting chronic innate inflammatory pathways, the main road to prevention of osteoarthritis progression

Osteoarthritis (OA) is a chronic joint disease characterized by cartilage degradation, osteophyte formation, subchondral bone sclerosis, and synovitis. Systemic factors such as obesity and the components of the metabolic syndrome seem to contribute to its progression. Breakdown of cartilage ensues from an altered balance between mechanical overload and its absorption by this tissue. There is in this context a status of persistent local inflammation by means of the chronic activation of innate immunity. A broad variety of danger-associated molecular patterns inside OA joint are able to activate pattern recognition receptors, mainly TLR (toll-like receptor) 2 and 4, which are overexpressed in the OA cartilage. Chronic activation of innate immune responses in chondrocytes results in a robust production of pro-inflammatory cytokines and chemokines, as well as of tissue-destructive enzymes, downstream of NF-κB and MAPK (mitogen activated protein kinase) dependent pathways. Besides, the toxic effects of an excess of glucose and/or fatty acids, which share the same pro-inflammatory intracellular signalling pathways, may add fuel to the fire. Not only high concentrations of glucose can render cells prone to inflammation, but also AGEs (advanced glycation end products) are integrated into the TLR signalling network through their own innate immune receptors. Considering these mechanisms, we argue for the control of both primary inflammation and proteolytic catabolism as a preventive strategy in OA, instead of focusing treatment on the enhancement of anabolic responses. Even though this approach would not return to normal already degraded cartilage, it nonetheless might avoid damage extension to the surrounding tissue.

ALDH2 Overexpression Alleviates High Glucose-Induced Cardiotoxicity by Inhibiting NLRP3 Inflammasome Activation

Although the underlying mechanisms of diabetes-induced myocardial injury have not been fully illuminated, the inflammation reaction has been reported intently linked with diabetes. The nucleotide binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome, the key component of pyroptosis, is involved in inflammation reaction, which may be one of the important mechanisms in diabetes-induced myocardial injury. The purpose of this study was to investigate the changes of NLRP3 inflammasome and pyroptosis in high glucose-induced H9C2 cardiac cell injury and investigate whether overexpression of mitochondrial aldehyde dehydrogenase 2 (ALDH2) can reduce the occurrence of pyroptosis. The H9C2 cardiac cells were exposed to 35 mM glucose for 24 h to induce cytotoxicity. Mitochondrial ALDH2 overexpression cardiac cell line was constructed. The results showed in high glucose condition that ALDH2 overexpression significantly increased H9C2 cardiac cell viability, increased mitochondrial ALDH2 activity and protein expression, and reduced mitochondrial reactive oxygen species (ROS) production, 4-hydroxynonenal (4-HNE), and lactate dehydrogenase (LDH) levels; meanwhile, the pyroptosis key components-NLRP3 inflammasome-related proteins, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), cysteine-containing aspartate specific protease 1 (Caspase-1), and interleukin-18 (IL-18) protein expressions-were significantly decreased, and IL-18 and interleukin-1β (IL-1β) levels were also decreased. In high glucose-induced cardiac cell injury, ALDH2 overexpression may reduce ROS production, thereby inhibiting the activation of NLRP3 inflammation and cell pyroptosis. ALDH2 gene might play the potential role in the treatment of high glucose-induced H9C2 cardiac cell injury.

Endothelial-specific FoxO1 depletion prevents obesity-related disorders by increasing vascular metabolism and growth

Impaired angiogenesis is a hallmark of metabolically dysfunctional adipose tissue in obesity. However, the underlying mechanisms restricting angiogenesis within this context remain ill-defined. Here, we demonstrate that induced endothelial-specific depletion of the transcription factor Forkhead Box O1 (FoxO1) in male mice led to increased vascular density in adipose tissue. Upon high-fat diet feeding, endothelial cell FoxO1-deficient mice exhibited even greater vascular remodeling in the visceral adipose depot, which was paralleled with a healthier adipose tissue expansion, higher glucose tolerance and lower fasting glycemia concomitant with enhanced lactate levels. Mechanistically, FoxO1 depletion increased endothelial proliferative and glycolytic capacities by upregulating the expression of glycolytic markers, which may account for the improvements at the tissue level ultimately impacting whole-body glucose metabolism. Altogether, these findings reveal the pivotal role of FoxO1 in controlling endothelial metabolic and angiogenic adaptations in response to high-fat diet and a contribution of the endothelium to whole-body energy homeostasis.

In the body, thread-like blood vessels called capillaries weave their way through our tissues to deliver oxygen and nutrients to every cell. When a tissue becomes bigger, existing vessels remodel to create new capillaries that can reach far away cells. However, in obesity, this process does not happen the way it should: when fat tissues expand, new blood vessels do not always grow to match. The starved fat cells can start to dysfunction, which causes a range of issues, from inflammation and scarring of the tissues to problems with how the body processes sugar and even diabetes. Yet, it is still unclear why exactly new capillaries fail to form in obesity.

What we know is that a protein called FoxO (short for Forkhead box O) is present in the cells that line the inside of blood vessels, and that it can stop the development of new capillaries. FoxO controls how cells spend their energy, and it can force them to go into a resting state. During obesity, the levels of FoxO actually increase in capillary cells. Therefore, it may be possible that FoxO prevents new blood vessels from growing in the fat tissues of obese individuals.

To find out, Rudnicki et al. created mice that lack the FoxO protein in the cells lining the capillaries, and then fed the animals a high-fat diet. These mutant mice had more blood vessels in their fat tissue, and their fat cells looked healthier. They also stored less fat than normal mice on the same diet, and their blood sugar levels were normal. This was because the FoxO-deprived cells inside capillaries were burning more energy, which they may have obtained by pulling sugar from the blood.

These results show that targeting the cells that line capillaries helps new blood vessels to grow, and that this could mitigate the health problems that arise with obesity, such as high levels of sugar (diabetes) and fat in the blood. However, more work is needed to confirm that the same cellular processes can be targeted to obtain positive health outcomes in humans.

Inflammaging: a new immune-metabolic viewpoint for age-related diseases

Ageing and age-related diseases share some basic mechanistic pillars that largely converge on inflammation. During ageing, chronic, sterile, low-grade inflammation - called inflammaging - develops, which contributes to the pathogenesis of age-related diseases. From an evolutionary perspective, a variety of stimuli sustain inflammaging, including pathogens (non-self), endogenous cell debris and misplaced molecules (self) and nutrients and gut microbiota (quasi-self). A limited number of receptors, whose degeneracy allows them to recognize many signals and to activate the innate immune responses, sense these stimuli. In this situation, metaflammation (the metabolic inflammation accompanying metabolic diseases) is thought to be the form of chronic inflammation that is driven by nutrient excess or overnutrition; metaflammation is characterized by the same mechanisms underpinning inflammaging. The gut microbiota has a central role in both metaflammation and inflammaging owing to its ability to release inflammatory products, contribute to circadian rhythms and crosstalk with other organs and systems. We argue that chronic diseases are not only the result of ageing and inflammaging; these diseases also accelerate the ageing process and can be considered a manifestation of accelerated ageing. Finally, we propose the use of new biomarkers (DNA methylation, glycomics, metabolomics and lipidomics) that are capable of assessing biological versus chronological age in metabolic diseases.

Adipose Organ Development and Remodeling

During the last decades, research on adipose tissues has spread in parallel with the extension of obesity. Several observations converged on the idea that adipose tissues are organized in a large organ with endocrine and plastic properties. Two parenchymal components: white (WATs) and brown adipose tissues (BATs) are contained in subcutaneous and visceral compartments. Although both have endocrine properties, their function differs: WAT store lipids to allow intervals between meals, BAT burns lipids for thermogenesis. In spite of these opposite functions, they share the ability for reciprocal reversible transdifferentiation to tackle special physiologic needs. Thus, chronic need for thermogenesis induces browning and chronic positive energy balance induce whitening. Lineage tracing and data from explant studies strongly suggest other remodeling properties of this organ. During pregnancy and lactation breast WAT transdifferentiates into milk-secreting glands, composed by cells with abundant cytoplasmic lipids (pink adipocytes) and in the postlactation period pink adipocytes transdifferentiate back into WAT and BAT. The plastic properties of mature adipocytes are supported also by a liposecretion process in vitro where adult cell in culture transdifferentiate to differentiated fibroblast-like elements able to give rise to different phenotypes (rainbow adipocytes). In addition, the inflammasome system is activated in stressed adipocytes from obese adipose tissue. These adipocytes die and debris are reabsorbed by macrophages inducing a chronic low-grade inflammation, potentially contributing to insulin resistance and T2 diabetes. Thus, the plastic properties of this organ could open new therapeutic perspectives in the obesity-related metabolic disease and in breast pathologies. © 2018 American Physiological Society. Compr Physiol 8:1357-1431, 2018.

Connecting homocysteine and obesity through pyroptosis, gut microbiome, epigenetics, peroxisome proliferator-activated receptor γ, and zinc finger protein 407

Although homocysteine (Hcy), a part of the epigenome, contributes to cell death by pyroptosis and decreases peroxisome proliferator-activated receptor γ (PPARγ) levels, the mechanisms are unclear. Hcy is found in high concentrations in the sera of obese individuals, which can elicit an immune response as well by hypermethylating CpG islands of specific gene promoters, a marker of epigenetics. Hcy has also been established to chelate divalent metal ions like Cu²⁺ and Zn²⁺, but this role of Hcy has not been established in relationship with obesity. It has been known for a while that PPARγ dysregulation results in various metabolic disorders including glucose and lipid metabolism. Recently, zinc finger protein 407 (Zfp407) is reported to regulate PPARγ target gene expression without affecting PPARγ transcript and protein levels by synergistically working with PPARγ. However, the mechanism(s) of this synergy, as well as other factors contributing to or inhibiting this synergism, have not been proven. This review suggests that Hcy contributes to pyroptosis, changes gut microbiome, and alters PPARγ-dependent mechanism(s) via Zfp407-mediated upregulated adipogenesis and misbalanced fatty acid metabolism, which can predispose to obesity and, consequently, obesity-related metabolic disorders.

Caspases in metabolic disease and their therapeutic potential

Caspases, a family of cysteine-dependent aspartate-specific proteases, are central to the maintenance of cellular and organismal homoeostasis by functioning as key mediators of the inflammatory response and/or apoptosis. Both metabolic inflammation and apoptosis play a central role in the pathogenesis of metabolic disease such as obesity and the progression of nonalcoholic steatohepatisis (NASH) to more severe liver disease. Obesity and nonalcoholic fatty liver disease (NAFLD) are the leading global health challenges associated with the development of numerous comorbidities including insulin resistance, type-2 diabetes and early mortality. Despite the high prevalence, current treatment strategies including lifestyle, dietary, pharmaceutical and surgical interventions, are often limited in their efficacy to manage or treat obesity, and there are currently no clinical therapies for NAFLD/NASH. As mediators of inflammation and cell death, caspases are attractive therapeutic targets for the treatment of these metabolic diseases. As such, pan-caspase inhibitors that act by blocking apoptosis have reached phase I/II clinical trials in severe liver disease. However, there is still a lack of knowledge of the specific and differential functions of individual caspases. In addition, cross-talk between alternate cell death pathways is a growing concern for long-term caspase inhibition. Evidence is emerging of the important cell-death-independent, non-apoptotic functions of caspases in metabolic homoeostasis that may be of therapeutic value. Here, we review the current evidence for roles of caspases in metabolic disease and discuss their potential targeting as a therapeutic strategy.

Enterobacter cloacae administration induces hepatic damage and subcutaneous fat accumulation in high-fat diet fed mice

Accumulating evidence indicates that gut microbiota plays a significant role in obesity, insulin resistance and associated liver disorders. Family Enterobacteriaceae and especially Enterobacter cloacae strain B29 have been previously linked to obesity and hepatic damage. The underlying mechanisms, however, remain unclear. Therefore, we comprehensively examined the effects of E. cloacae subsp. cloacae (ATCC® 13047™) administration on host metabolism of mice fed with high-fat diet (HFD). C57BL/6N mice were randomly divided into HFD control, chow control, and E. cloacae treatment groups. The E. cloacae treatment group received live bacterial cells in PBS intragastrically twice a week, every other week for 13 weeks. Both control groups received PBS intragastrically. After the 13-week treatment period, the mice were sacrificed for gene and protein expression and functional analyses. Our results show that E. cloacae administration increased subcutaneous fat mass and the relative proportion of hypertrophic adipocytes. Both subcutaneous and visceral fat had signs of decreased insulin signaling and elevated lipolysis that was reflected in higher serum glycerol levels. In addition, E. cloacae -treated mice had significantly higher hepatic AST and AST/ALT ratio, and their liver histology indicated fibrosis, demonstrating that E. cloacae subsp. cloacae administration promotes hepatic damage in HFD fed mice.

Anti-Inflammatory Effects of Melatonin in Obesity and Hypertension

PURPOSE OF REVIEW

Here, we review the known relations between hypertension and obesity to inflammation and postulate the endogenous protective effect of melatonin and its potential as a therapeutic agent. We will describe the multiple effects of melatonin on blood pressure, adiposity, body weight, and focus on mitochondrial-related anti-inflammatory and antioxidant protective effects.

RECENT FINDINGS

Hypertension and obesity are usually associated with systemic and tissular inflammation. The progressive affection of target-organs involves multiple mediators of inflammation, most of them redundant, which make anti-inflammatory strategies ineffective. Melatonin reduces blood pressure, body weight, and inflammation. The mechanisms of action of this ancient molecule of protection involve multiple levels of action, from subcellular to intercellular. Mitochondria is a key inflammatory element in vascular and adipose tissue and a potential pharmacological target. Melatonin protects against mitochondrial dysfunction. Melatonin reduces blood pressure and adipose tissue dysfunction by multiple anti-inflammatory/antioxidant actions and provides potent protection against mitochondria-mediated injury in hypertension and obesity. This inexpensive and multitarget molecule has great therapeutic potential against both epidemic diseases.