Kaempferol alleviates adipose tissue inflammation and insulin resistance in db/db mice by inhibiting the STING/NLRP3 signaling pathway

Chronic inflammation induced by obesity plays a crucial role in the pathogenesis of insulin resistance. The infiltration of macrophages into adipose tissues contributes to adipose tissue inflammation and insulin resistance. Kaempferol, a flavonoid present in various vegetables and fruits, has been shown to possess remarkable anti-inflammatory properties. In this study, we used leptin receptor-deficient obese mice (db/db) as an insulin-resistant model and investigated the effects of kaempferol treatment on obesity-induced insulin resistance. Our findings revealed that the administration of kaempferol (50 mg/kg/day, for 6 weeks) significantly reduced body weight, fat mass, and adipocyte size. Moreover, it effectively ameliorated abnormal glucose tolerance and insulin resistance in db/db mice. In the adipose tissue of obese mice treated with kaempferol, we observed a reduction in macrophage infiltration and a downregulation of mRNA expression of M1 marker genes TNF-α and IL-1β, accompanied by an upregulation of Arg1 and IL-10 mRNA expression. Additionally, kaempferol treatment significantly inhibited the STING/NLRP3 signaling pathway in adipose tissue. In vitro experiments, we further discovered that kaempferol treatment suppressed LPS-induced inflammation through the activation of NLRP3/caspase 1 signaling in RAW 264.7 macrophages. Our results suggest that kaempferol may effectively alleviate inflammation and insulin resistance in the adipose tissue of db/db mice by modulating the STING/NLRP3 signaling pathway.

Adipose stem cells control obesity-induced T cell infiltration into adipose tissue

T cell infiltration into white adipose tissue (WAT) drives obesity-induced adipose inflammation, but the mechanisms of obesity-induced T cell infiltration into WAT remain unclear. Our single-cell RNA sequencing reveals a significant impact of adipose stem cells (ASCs) on T cells. Transplanting ASCs from obese mice into WAT enhances T cell accumulation. C-C motif chemokine ligand 5 (CCL5) is upregulated in ASCs as early as 4 weeks of high-fat diet feeding, coinciding with the onset of T cell infiltration into WAT during obesity. ASCs and bone marrow transplantation experiments demonstrate that CCL5 from ASCs plays a crucial role in T cell accumulation during obesity. The production of CCL5 in ASCs is induced by tumor necrosis factor alpha via the nuclear factor κB pathway. Overall, our findings underscore the pivotal role of ASCs in regulating T cell accumulation in WAT during the early phases of obesity, emphasizing their importance in modulating adaptive immunity in obesity-induced adipose inflammation.

IL-6 signaling drives self-renewal and alternative activation of adipose tissue macrophages

Introduction

Obesity is associated with chronic low-grade inflammation of adipose tissue (AT) and an increase of AT macrophages (ATMs) that is linked to the onset of type 2 diabetes. We have recently shown that neutralization of interleukin (IL)-6 in obese AT organ cultures inhibits proliferation of ATMs, which occurs preferentially in alternatively activated macrophage phenotype.

Methods

In this study, we investigated AT biology and the metabolic phenotype of mice with myeloid cell-specific IL-6Rα deficiency (Il6ra Δmyel) after normal chow and 20 weeks of high-fat diet focusing on AT inflammation, ATM polarization and proliferation. Using organotypical AT culture and bone marrow derived macrophages (BMDMs) of IL-4Rα knockout mice (Il4ra -/-) we studied IL-6 signaling.

Results

Obese Il6ra Δmyel mice exhibited no differences in insulin sensitivity or histological markers of AT inflammation. Notably, we found a reduction of ATMs expressing the mannose receptor 1 (CD206), as well as a decrease of the proliferation marker Ki67 in ATMs of Il6ra Δmyel mice. Importantly, organotypical AT culture and BMDM data of Il4ra -/- mice revealed that IL-6 mediates a shift towards the M2 phenotype independent from the IL-6/IL-4Rα axis.

Discussion

Our results demonstrate IL-4Rα-independent anti-inflammatory effects of IL-6 on macrophages and the ability of IL-6 to maintain proliferation rates in obese AT.

Contribution of NKT cells and CD1d-expressing cells in obesity-associated adipose tissue inflammation

Natural killer T (NKT) cell are members of the innate-like T lymphocytes and recognizes lipid antigens presented by CD1d-expressing cells. Obesity-associated inflammation in adipose tissue (AT) leads to metabolic dysfunction, including insulin resistance. When cellular communication is properly regulated among AT-residing immune cells and adipocytes during inflammation, a favorable balance of Th1 and Th2 immune responses is achieved. NKT cells play crucial roles in AT inflammation, influencing the development of diet-induced obesity and insulin resistance. NKT cells interact with CD1d-expressing cells in AT, such as adipocytes, macrophages, and dendritic cells, shaping pro-inflammatory or anti-inflammatory microenvironments with distinct characteristics depending on the antigen-presenting cells. Additionally, CD1d may be involved in the inflammatory process independently of NKT cells. In this mini-review, we provide a brief overview of the current understanding of the interaction between immune cells, focusing on NKT cells and CD1d signaling, which control AT inflammation both in the presence and absence of NKT cells. We aim to enhance our understanding of the mechanisms of obesity-associated diseases.

Apocynin alleviates weight gain and obesity-induced adipose tissue inflammation in high-fat diet-fed C57BL/6 mice

Obesity involves chronic low-grade inflammation within adipose tissue. Apocynin (APO) is a therapeutic agent for the treatment of inflammatory diseases. Therefore, the present study aimed to investigate whether APO can reduce weight gain and obesity-induced adipose tissue inflammation. C57BL/6 mice were administered APO or orlistat (Orli) as a positive control with a high-fat diet (HFD) for 12 weeks. Lipopolysaccharide-stimulated 3T3-L1 adipocytes were used for the in vitro study. Our results showed a significantly lower white adipose tissue (WAT) mass index in 10 mg/kg APO-treated mice than in 20 mg/kg Orli-treated mice. Moreover, the protein expression of adipose triglyceride lipase, fatty acid synthase, sterol regulatory element-binding transcription factor 1, and peroxisome proliferator-activated receptor γ was reversed in the WAT of 10 mg/kg APO-treated mice. Furthermore, APO reduced the expression of the macrophage marker F4/80, decreased the mRNA levels of tumor necrosis factor-α and monocyte chemoattractant protein-1, and increased the mRNA levels of interleukin-10 in WAT. APO decreased the phosphorylation of c-Jun N-terminal kinase, extracellular signal-regulated kinase, and p65 in vivo and in vitro. Notably, APO had a stronger effect on the amelioration of adipose tissue inflammation than Orli did. Our findings lay the foundation for research on the use of APO as an agent to ameliorate weight gain and obesity-induced inflammatory diseases.

Enhancing de novo ceramide synthesis induced by bisphenol A exposure aggravates metabolic derangement during obesity

Exposure to bisphenol A (BPA) has been shown to increase the prevalence of obesity and its related insulin resistance (IR). Ceramide is a sphingolipid known to facilitate the production of proinflammatory cytokines and subsequently exacerbate inflammation and IR during the progression of obesity. Here, we investigated the effects of BPA exposure on ceramide de novo synthesis and whether increased ceramides aggravate adipose tissue (AT) inflammation and obesity-related IR. A population-based case-control study was conducted to explore the relationship between BPA exposure and IR and the potential role of ceramide in AT in obesity. Next, we used mice reared on a normal chow diet (NCD) or a high-fat diet (HFD) to verify the results from the population study and then investigated the role of ceramides in low-level BPA exposure with HFD-induced IR and AT inflammation in mice treated with or without myriocin (an inhibitor of the rate-limiting enzyme in de novo ceramide synthesis). BPA levels are higher in obese individuals and are significantly associated with AT inflammation and IR. Specific subtypes of ceramides mediated the associations between BPA and obesity, obesity-related IR and AT inflammation in the obesity group. In animal experiments, BPA exposure facilitated ceramide accumulation in AT, activated PKCζ, promoted AT inflammation, increased the expression and secretion of proinflammatory cytokines via the JNK/NF-κB pathway, and lowered insulin sensitivity by disrupting IRS1-PI3K-AKT signaling in mice fed a HFD. Myriocin suppressed BPA-induced AT inflammation and IR. These findings indicate that BPA aggravates obesity-induced IR, which is partly via increased de novo synthesis of ceramides and subsequent promotion of AT inflammation. Ceramide synthesis could be a potential target for the prevention of environmental BPA exposure-related metabolic diseases.

Adipose tissue metabolic changes in chronic kidney disease

Adipose tissue is a complex organ whose functions go beyond being an energy reservoir to sustain proper body energy homeostasis. Functioning as an endocrine organ, the adipose tissue has an active role in the body's metabolic balance regulation through several secreted factors generally termed as adipokines. Thus, adipose tissue dysregulation in chronic kidney disease (CKD) can have a deep impact in the pathophysiology of diseases associated with metabolic dysregulation including metabolic syndrome, insulin resistance (IR), atherosclerosis, and even cachexia. CKD is a progressive disorder linked to increased morbidity and mortality. Despite being characterized by renal function loss, CKD is accompanied by metabolic disturbances such as dyslipidemia, protein energy wasting, chronic low-grade inflammation, IR, and lipid redistribution. Thus far, the mechanisms by which these changes occur and the role of adipose tissue in CKD development and progression are unclear. Further understanding of how these factors develop could have implications for the management of CKD by helping identify pharmacological targets to improve CKD outcomes.

14-Deoxygarcinol improves insulin sensitivity in high-fat diet-induced obese mice via mitigating NF-κB/Sirtuin 2-NLRP3-mediated adipose tissue remodeling

Interleukin (IL)-1β is a culprit of adipose tissue inflammation, which in turn causes systematic inflammation and insulin resistance in obese individuals. IL-1β is mainly produced in monocytes and macrophages and marginally in adipocytes, through cleavage of the inactive pro-IL-1β precursor by caspase-1, which is activated via the NLRP3 inflammasome complex. The nuclear factor-κB (NF-κB) transcription factor is the master regulator of inflammatory responses. Brindle berry (Garcinia cambogia) has been widely used as health products for treating obesity and related metabolic disorders, but its active principles remain unclear. We previously found a series of polyisoprenylated benzophenones from brindle berry with anti-inflammatory activities. In this study we investigated whether 14-deoxygarcinol (DOG), a major polyisoprenylated benzophenone from brindle berry, alleviated adipose tissue inflammation and insulin sensitivity in high-fat diet fed mice. The mice were administered DOG (2.5, 5 mg · kg-1 · d-1, i.p.) for 4 weeks. We showed that DOG injection dose-dependently improved insulin resistance and hyperlipidemia, but not adiposity in high-fat diet-fed mice. We found that DOG injection significantly alleviated adipose tissue inflammation via preventing macrophage infiltration and pro-inflammatory polarization of macrophages, and adipose tissue fibrosis via reducing the abnormal deposition of extracellular matrix. In LPS plus nigericin-stimulated THP-1 macrophages, DOG (1.25, 2.5, 5 μM) dose-dependently suppressed the activation of NLRP3 inflammasome and NF-κB signaling pathway. We demonstrated that DOG bound to and activated the deacetylase Sirtuin 2, which in turn deacetylated and inactivated NLRP3 inflammasome to reduce IL-1β secretion. Moreover, DOG (1.25, 2.5, 5 μM) dose-dependently mitigated inflammatory responses in macrophage conditioned media-treated adipocytes and suppressed macrophage migration toward adipocytes. Taken together, DOG might be a drug candidate to treat metabolic disorders through modulation of adipose tissue remodeling.

Phenotypic diversity of human adipose tissue-resident NK cells in obesity

Natural killer (NK) cells have emerged as key mediators of obesity-related adipose tissue inflammation. However, the phenotype of NK cell subsets residing in human adipose tissue are poorly defined, preventing a detailed understanding of their role in metabolic disorders. In this study, we applied multicolor flow cytometry to characterize CD56^bright and CD56^dim NK cells in blood and adipose tissue depots in individuals with obesity and identified surface proteins enriched on adipose tissue-resident CD56^bright NK cells. Particularly, we found that adipose tissue harbored clusters of tissue-resident CD56^bright NK cells signatured by the expression of CD26, CCR5 and CD63, possibly reflecting an adaptation to the microenvironment. Together, our findings provide broad insights into the identity of NK cells in blood and adipose tissue in relation to obesity.

Adipose Tissue-Derived CCL5 Enhances Local Pro-Inflammatory Monocytic MDSCs Accumulation and Inflammation via CCR5 Receptor in High-Fat Diet-Fed Mice

The C-C chemokine motif ligand 5 (CCL5) and its receptors have recently been thought to be substantially involved in the development of obesity-associated adipose tissue inflammation and insulin resistance. However, the respective contributions of tissue-derived and myeloid-derived CCL5 to the etiology of obesity-induced adipose tissue inflammation and insulin resistance, and the involvement of monocytic myeloid-derived suppressor cells (MDSCs), remain unclear. This study used CCL5-knockout mice combined with bone marrow transplantation (BMT) and mice with local injections of shCCL5/shCCR5 or CCL5/CCR5 lentivirus into bilateral epididymal white adipose tissue (eWAT). CCL5 gene deletion significantly ameliorated HFD-induced inflammatory reactions in eWAT and protected against the development of obesity and insulin resistance. In addition, tissue (non-hematopoietic) deletion of CCL5 using the BMT method not only ameliorated adipose tissue inflammation by suppressing pro-inflammatory M-MDSC (CD11b⁺Ly6G^-Ly6C^hi) accumulation and skewing local M1 macrophage polarization, but also recruited reparative M-MDSCs (CD11b⁺Ly6G^-Ly6C^low) and M2 macrophages to the eWAT of HFD-induced obese mice, as shown by flow cytometry. Furthermore, modulation of tissue-derived CCL5/CCR5 expression by local injection of shCCL5/shCCR5 or CCL5/CCR5 lentivirus substantially impacted the distribution of pro-inflammatory and reparative M-MDSCs as well as macrophage polarization in bilateral eWAT. These findings suggest that an obesity-induced increase in adipose tissue CCL5-mediated signaling is crucial in the recruitment of tissue M-MDSCs and their trans-differentiation to tissue pro-inflammatory macrophages, resulting in adipose tissue inflammation and insulin resistance.

Vitamin D and Visceral Obesity in Humans: What Should Clinicians Know?

The extraskeletal effect of vitamin D on adipose tissue biology and modulation in human obesity is of great interest and has been extensively investigated. Current evidence from preclinical and clinical studies in human adipose tissue suggests that the anti-inflammatory effects of vitamin D are evident and consistent, whereas the effects of vitamin D on adipocyte differentiation, adipogenesis, and energy metabolism and the effects of vitamin D supplementation on adipokine levels are inconclusive. Interventional studies related to medical and surgical weight loss in humans have shown small or no improvement in vitamin D status. Additionally, the benefit of vitamin D supplementation for the reduction in visceral adipose tissue has only been demonstrated in a few studies. Overall, the findings on the relationship between vitamin D and visceral adipose tissue in humans are still inconclusive. Further studies are required to confirm the beneficial effects of vitamin D on ameliorating adipose tissue dysfunction.

Ainsliadimer C, a disesquiterpenoid isolated from Ainsliaea macrocephala, ameliorates inflammatory responses in adipose tissue via Sirtuin 1-NLRP3 inflammasome axis

Interleukin-1β (IL-1β), a key pro-inflammatory cytokine, is majorly produced by macrophages through NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome, which has been identified as the culprit to deteriorate the inflammatory crosstalk between macrophages and adipocytes. Ainsliadimer C (AC) is a disesquiterpenoid isolated from Ainsliaea macrocephala. In the current study, we investigated the effects of AC on adipose tissue inflammation in co-culture of macrophages and adipocytes in vitro as well as in LPS-treated mice in vivo. We showed that AC (20-80 µM) dose-dependently inhibited the secretion of IL-1β from LPS plus ATP-stimulated THP-1 macrophages by inhibiting the activation of NLRP3 inflammasome. Furthermore, we found that AC treatment activated NAD⁺-dependent deacetylase Sirtuin 1 (SIRT1), resulting in reduced acetylation level of NLRP3. Molecular modeling analysis revealed that binding of AC to sirtuin-activating compound-binding domain increased the affinity of the substrate to the catalytic domain of SIRT1. Moreover, AC (80 µM) significantly attenuated macrophage-conditioned medium-induced inflammatory responses in 3T3-L1 adipocytes. In LPS-induced acute inflammatory mice, administration of AC (20, 60 mg·kg^-1·d^-1, ip) for 5 days significantly suppressed the pro-inflammatory cytokine levels in serum and epididymal white adipose tissue (eWAT), attenuated macrophage infiltration into eWAT, and mitigated adipose tissue inflammation. The beneficial effects of AC were blocked by co-administration of a selective SIRT1 inhibitor EX-527 (10 mg·kg^-1·d^-1). Taken together, AC suppresses NLRP3-mediated IL-1β secretion through activating SIRT1, leading to attenuated inflammation in macrophages and adipose tissue, which might be a candidate to treat obesity-associated metabolic diseases.

SREBP1c-PARP1 axis tunes anti-senescence activity of adipocytes and ameliorates metabolic imbalance in obesity

Emerging evidence indicates that the accretion of senescent cells is linked to metabolic disorders. However, the underlying mechanisms and metabolic consequences of cellular senescence in obesity remain obscure. In this study, we found that obese adipocytes are senescence-susceptible cells accompanied with genome instability. Additionally, we discovered that SREBP1c may play a key role in genome stability and senescence in adipocytes by modulating DNA-damage responses. Unexpectedly, SREBP1c interacted with PARP1 and potentiated PARP1 activity during DNA repair, independent of its canonical lipogenic function. The genetic depletion of SREBP1c accelerated adipocyte senescence, leading to immune cell recruitment into obese adipose tissue. These deleterious effects provoked unhealthy adipose tissue remodeling and insulin resistance in obesity. In contrast, the elimination of senescent adipocytes alleviated adipose tissue inflammation and improved insulin resistance. These findings revealed distinctive roles of SREBP1c-PARP1 axis in the regulation of adipocyte senescence and will help decipher the metabolic significance of senescence in obesity.

Berberine remodels adipose tissue to attenuate metabolic disorders by activating sirtuin 3

Adipose tissue remodelling is considered a critical pathophysiological hallmark of obesity and related metabolic diseases. Berberine (BBR), a natural isoquinoline alkaloid, has potent anti-hyperlipidaemic and anti-hyperglycaemic effects. This study aimed to explore the role of BBR in modulating adipose tissue remodelling and the underlying mechanisms. BBR protected high fat diet (HFD)-fed mice against adiposity, insulin resistance and hyperlipidemia. BBR alleviated adipose tissue inflammation and fibrosis by inhibiting macrophage infiltration, pro-inflammatory macrophage polarization and the abnormal deposition of extracellular matrix, and the effect was mediated by BBR directly binding and activating the deacetylase Sirtuin 3 (SIRT3) and suppressing the activation of the mitogen-activated protein kinases and nuclear factor-κB signalling pathways. Furthermore, BBR decreased microRNA-155-5p secretion by macrophages, which in turn ameliorated liver injury. Moreover, BBR mitigated inflammatory responses in both LPS-stimulated macrophages and TNF-α-treated adipocytes and suppressed macrophage migration towards adipocytes by activating SIRT3. Collectively, this study revealed that BBR improved adipose tissue remodelling, and subsequently inhibited the secretion of microRNA-155-5p by macrophages, which alleviated adiposity, insulin resistance and liver injury in obese mice. The modulation of adipose tissue remodelling by activating SIRT3 could contribute to the anti-hyperlipidemic and anti-hyperglycemic effects of BBR.

Polydextrose Alleviates Adipose Tissue Inflammation and Modulates the Gut Microbiota in High-Fat Diet-Fed Mice

The soluble dietary fiber polydextrose (PDX) is a randomly linked glucose oligomer containing small amounts of sorbitol and citric acid and is widely used in the food industry. However, whether PDX can prevent and treat obesity in high-fat diet (HFD)-fed mice has not been directly investigated, and further studies are needed to better understand the complex interactions among PDX, adipose tissue inflammation and the gut microbiota. In the present study, PDX reduced body weight, fasting blood glucose (FBG), adipose tissue accumulation, adipocyte hypertrophy, serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) levels in HFD-fed mice. Moreover, PDX alleviated serum lipopolysaccharide (LPS) levels and macrophage infiltration in epididymal adipose tissue and resulted in macrophage polarization toward the M2 phenotype. Gut microbiota analysis revealed that PDX promoted the growth of beneficial microbes such as Bacteroides, Parabacteroides, Alloprevotella, Muribaculum, Akkermansia, Ruminococcaceae_UCG-014 and UBA1819 in obese mice, which were negatively correlated with subcutaneous fat, epididymal fat, body weight, FBG, serum TC, HDL-C, LDL-C and LPS levels. Our results indicates that PDX can prevent and treat obesity in HFD-fed mice, specifically in alleviating glucolipid metabolism disorders and adipose tissue inflammation, which may be mediated by modulating the structure of the gut microbiota. Therefore, PDX may become a promising nondrug therapy for obesity.

Organokines and Exosomes: Integrators of Adipose Tissue Macrophage Polarization and Recruitment in Obesity

The prevalence of obesity is escalating and has become a worldwide health challenge coinciding with the development of metabolic diseases. Emerging evidence has shown that obesity is accompanied by the infiltration of macrophages into adipose tissue, contributing to a state of low-grade chronic inflammation and dysregulated metabolism. Moreover, in the state of obesity, the phenotype of adipose tissue macrophages switches from the M2 polarized state to the M1 state, thereby contributing to chronic inflammation. Notably, multiple metabolic organs (adipose tissue, gut, skeletal muscle, and the liver) communicate with adipose tissue macrophages via secreting organokines or exosomes. In this review, we systematically summarize how the organokines (adipokines, gut microbiota and its metabolites, gut cytokines, myokines, and hepatokines) and exosomes (adipocyte-, skeletal muscle-, and hepatocyte-derived exosomes) act as important triggers for macrophage recruitment in adipose tissue and adipose tissue macrophage polarization, thus providing further insight into obesity treatment. In addition, we also highlight the complex interaction of organokines with organokines and organokines with exosomes, revealing new paths in understanding adipose tissue macrophage recruitment and polarization.

Pharmacological inhibition of the lipid phosphatase PTEN ameliorates heart damage and adipose tissue inflammation in stressed rats with metabolic syndrome

Phosphatidylinositol 3-kinase (PI3K) signaling promotes the differentiation and proliferation of regulatory B (Breg) cells, and the lipid phosphatase phosphatase and tensin homolog deleted on chromosome 10 (PTEN) antagonizes the PI3K-Akt signaling pathway. We previously demonstrated that cardiac Akt activity is increased and that restraint stress exacerbates hypertension and both heart and adipose tissue (AT) inflammation in DS/obese rats, an animal model of metabolic syndrome (MetS). We here examined the effects of restraint stress and pharmacological inhibition of PTEN on heart and AT pathology in such rats. Nine-week-old animals were treated with the PTEN inhibitor bisperoxovanadium-pic [bpV(pic)] or vehicle in the absence or presence of restraint stress for 4 weeks. BpV(pic) treatment had no effect on body weight or fat mass but attenuated hypertension in DS/obese rats subjected to restraint stress. BpV(pic) ameliorated left ventricular (LV) inflammation, fibrosis, and diastolic dysfunction as well as AT inflammation in the stressed rats. Restraint stress reduced myocardial capillary density, and this effect was prevented by bpV(pic). In addition, bpV(pic) increased the proportions of Breg and B-1 cells as well as reduced those of CD8+ T and B-2 cells in AT of stressed rats. Our results indicate that inhibition of PTEN by bpV(pic) alleviated heart and AT inflammation in stressed rats with MetS. These positive effects of bpV(pic) are likely due, at least in part, to a reduction in blood pressure, an increase in myocardial capillary formation, and an altered distribution of immune cells in fat tissue that result from the activation of PI3K-Akt signaling.

Butyrate Protects against Diet-Induced NASH and Liver Fibrosis and Suppresses Specific Non-Canonical TGF-β Signaling Pathways in Human Hepatic Stellate Cells

In obesity-associated non-alcoholic steatohepatitis (NASH), persistent hepatocellular damage and inflammation are key drivers of fibrosis, which is the main determinant of NASH-associated mortality. The short-chain fatty acid butyrate can exert metabolic improvements and anti-inflammatory activities in NASH. However, its effects on NASH-associated liver fibrosis remain unclear. Putative antifibrotic effects of butyrate were studied in Ldlr-/-.Leiden mice fed an obesogenic diet (HFD) containing 2.5% (w/w) butyrate for 38 weeks and compared with a HFD-control group. Antifibrotic mechanisms of butyrate were further investigated in TGF-β-stimulated primary human hepatic stellate cells (HSC). HFD-fed mice developed obesity, insulin resistance, increased plasma leptin levels, adipose tissue inflammation, gut permeability, dysbiosis, and NASH-associated fibrosis. Butyrate corrected hyperinsulinemia, lowered plasma leptin levels, and attenuated adipose tissue inflammation, without affecting gut permeability or microbiota composition. Butyrate lowered plasma ALT and CK-18M30 levels and attenuated hepatic steatosis and inflammation. Butyrate inhibited fibrosis development as demonstrated by decreased hepatic collagen content and Sirius-red-positive area. In TGF-β-stimulated HSC, butyrate dose-dependently reduced collagen deposition and decreased procollagen1α1 and PAI1 protein expression. Transcriptomic analysis and subsequent pathway and upstream regulator analysis revealed deactivation of specific non-canonical TGF-β signaling pathways Rho-like GTPases and PI3K/AKT and other important pro-fibrotic regulators (e.g., YAP/TAZ, MYC) by butyrate, providing a potential rationale for its antifibrotic effects. In conclusion, butyrate protects against obesity development, insulin resistance-associated NASH, and liver fibrosis. These antifibrotic effects are at least partly attributable to a direct effect of butyrate on collagen production in hepatic stellate cells, involving inhibition of non-canonical TGF-β signaling pathways.

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.

Adipocyte-Derived Versican and Macrophage-Derived Biglycan Control Adipose Tissue Inflammation in Obesity

Obesity is characterized by adipose tissue inflammation. Because proteoglycans regulate inflammation, here we investigate their role in adipose tissue inflammation in obesity. We find that adipose tissue versican and biglycan increase in obesity. Versican is produced mainly by adipocytes and biglycan by adipose tissue macrophages. Both proteoglycans are also present in adipose tissue from obese human subjects undergoing gastric bypass surgery. Deletion of adipocyte-specific versican or macrophage-specific biglycan in mice reduces macrophage accumulation and chemokine and cytokine expression, although only adipocyte-specific versican deletion leads to sustained improvement in glucose tolerance. Macrophage-derived biglycan activates inflammatory genes in adipocytes. Versican expression increases in cultured adipocytes exposed to excess glucose, and adipocyte-conditioned medium stimulates inflammation in resident peritoneal macrophages, in part because of a versican breakdown product, versikine. These findings provide insights into the role of adipocyte- and macrophage-derived proteoglycans in adipose tissue inflammation in obesity.

The role of uncoupling protein 2 in macrophages and its impact on obesity-induced adipose tissue inflammation and insulin resistance

The development of a chronic, low-grade inflammation originating from adipose tissue in obese subjects is widely recognized to induce insulin resistance, leading to the development of type 2 diabetes. The adipose tissue microenvironment drives specific metabolic reprogramming of adipose tissue macrophages, contributing to the induction of tissue inflammation. Uncoupling protein 2 (UCP2), a mitochondrial anion carrier, is thought to separately modulate inflammatory and metabolic processes in macrophages and is up-regulated in macrophages in the context of obesity and diabetes. Here, we investigate the role of UCP2 in macrophage activation in the context of obesity-induced adipose tissue inflammation and insulin resistance. Using a myeloid-specific knockout of UCP2 (Ucp2^ΔLysM), we found that UCP2 deficiency significantly increases glycolysis and oxidative respiration, both unstimulated and after inflammatory conditions. Strikingly, fatty acid loading abolished the metabolic differences between Ucp2^ΔLysM macrophages and their floxed controls. Furthermore, Ucp2^ΔLysM macrophages show attenuated pro-inflammatory responses toward Toll-like receptor-2 and -4 stimulation. To test the relevance of macrophage-specific Ucp2 deletion in vivo, Ucp2^ΔLysM and Ucp2^fl/fl mice were rendered obese and insulin resistant through high-fat feeding. Although no differences in adipose tissue inflammation or insulin resistance was found between the two genotypes, adipose tissue macrophages isolated from diet-induced obese Ucp2^ΔLysM mice showed decreased TNFα secretion after ex vivo lipopolysaccharide stimulation compared with their Ucp2^fl/fl littermates. Together, these results demonstrate that although UCP2 regulates both metabolism and the inflammatory response of macrophages, its activity is not crucial in shaping macrophage activation in the adipose tissue during obesity-induced insulin resistance.

Anthocyanin-Rich Aronia Berry Extract Mitigates High-Fat and High-Sucrose Diet-Induced Adipose Tissue Inflammation by Inhibiting Nuclear Factor-κB Activation

Obesity-induced inflammation in adipose tissue (AT) promotes the development of metabolic dysregulations by increasing macrophage recruitment in the stromal vascular fraction (SVF). The activation of nuclear factor-κB (NF-κB) signaling in macrophages serves as a pivotal mediator of AT inflammatory responses by increasing the expression of proinflammatory genes in obesity. Given the purported anti-inflammatory effects of berry consumption in humans, we evaluated if anthocyanin-rich aronia berry extract (ARN) can prevent obesity-induced AT inflammation in vivo. We also examined whether ARN suppresses lipopolysaccharide (LPS)-induced NF-κB activation in RAW 264.7 macrophages and mouse bone marrow-derived macrophages (BMDMs). Male C57BL/6J mice were fed a low-fat diet, a high-fat (HF), and high-sucrose (HS) diet or HF/HS diet supplemented with 0.2% ARN (HF/HS + ARN) for 14 weeks. Compared to HF-/HS-fed mice, ARN supplementation tended to decrease fasting serum glucose (P = .07). Furthermore, ARN supplementation significantly inhibited the phosphorylation of NF-κB p65 in epididymal AT with a concomitant decrease in the expression of Cd11b and Tnfα mRNAs in epididymal SVF isolated, compared with those from HF-/HS-fed mice. Consistent with these in vivo findings, ARN treatment significantly decreased the phosphorylation of p65 in LPS-stimulated RAW 264.7 macrophages and BMDMs. Moreover, ARN suppressed LPS-induced mRNA expression of inflammation mediators (iNos, Cox-2, Tnfα, Mcp-1, and Il-6) and glycolysis markers (Glut1, G6pdh, and Hk1) in both cell types. Taken together, our in vivo and in vitro results suggest that ARN supplementation may attenuate obesity-induced AT inflammation by inhibiting NF-κB signaling and glycolytic pathway in macrophages.

Adipose tissue inflammation and systemic insulin resistance in mice with diet-induced obesity is possibly associated with disruption of PFKFB3 in hematopoietic cells

Obesity-associated inflammation in white adipose tissue (WAT) is a causal factor of systemic insulin resistance; however, precisely how immune cells regulate WAT inflammation in relation to systemic insulin resistance remains to be elucidated. The present study examined a role for 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) in hematopoietic cells in regulating WAT inflammation and systemic insulin sensitivity. Male C57BL/6J mice were fed a high-fat diet (HFD) or low-fat diet (LFD) for 12 weeks and examined for WAT inducible 6-phosphofructo-2-kinase (iPFK2) content, while additional HFD-fed mice were treated with rosiglitazone and examined for PFKFB3 mRNAs in WAT stromal vascular cells (SVC). Also, chimeric mice in which PFKFB3 was disrupted only in hematopoietic cells and control chimeric mice were also fed an HFD and examined for HFD-induced WAT inflammation and systemic insulin resistance. In vitro, adipocytes were co-cultured with bone marrow-derived macrophages and examined for adipocyte proinflammatory responses and insulin signaling. Compared with their respective levels in controls, WAT iPFK2 amount in HFD-fed mice and WAT SVC PFKFB3 mRNAs in rosiglitazone-treated mice were significantly increased. When the inflammatory responses were analyzed, peritoneal macrophages from PFKFB3-disrputed mice revealed increased proinflammatory activation and decreased anti-inflammatory activation compared with control macrophages. At the whole animal level, hematopoietic cell-specific PFKFB3 disruption enhanced the effects of HFD feeding on promoting WAT inflammation, impairing WAT insulin signaling, and increasing systemic insulin resistance. In vitro, adipocytes co-cultured with PFKFB3-disrupted macrophages revealed increased proinflammatory responses and decreased insulin signaling compared with adipocytes co-cultured with control macrophages. These results suggest that PFKFB3 disruption in hematopoietic cells only exacerbates HFD-induced WAT inflammation and systemic insulin resistance.

Navy Bean Supplementation in Established High-Fat Diet-Induced Obesity Attenuates the Severity of the Obese Inflammatory Phenotype

Cooked common beans (Phaseolus vulgaris) improve intestinal health in lean mice and attenuate intestinal dysbiosis and inflammation when consumed concurrent with obesity development. We determined the effects of a high-fat (HF) bean supplemented diet in mice with established obesity (induced by 12 weeks of HF diet (60% fat as kcal)) compared to obese mice consuming a HF or low-fat (LF) weight loss control diet. Obese C57BL/6 male mice remained consuming HF for eight weeks or were randomly switched from HF to an isocaloric HF with 15.7% cooked navy bean powder diet (HF→HFB) or LF (11% fat as kcal; HF→LF) (n = 12/group). HF→HFB improved the obese phenotype, including (i) fecal microbiome (increased Prevotella, Akkermansia muciniphila, and short-chain fatty acid levels), (ii) intestinal health (increased ZO-1, claudin-2, Muc2, Relmβ, and Reg3γ expression), and (iii) reduced adipose tissue (AT) inflammatory proteins (NFκBp65, STAT3, IL-6, MCP-1, and MIP-1α), versus HF (p < 0.05). Conversely, HF→LF reduced body weight and circulating hormones (leptin, resistin, and PAI-1) versus HF and HF→HFB (p < 0.05); however, AT inflammation and intestinal health markers were not improved to the same degree as HF→HFB (p < 0.05). Despite remaining on a HF obesogenic diet, introducing beans in established obesity improved the obese phenotype (intestinal health and adipose inflammation) more substantially than weight loss alone.

Sarsasapogenin improves adipose tissue inflammation and ameliorates insulin resistance in high-fat diet-fed C57BL/6J mice

Insulin resistance is a major cause of type 2 diabetes and metabolic syndrome. Macrophage infiltration into obese adipose tissue promotes inflammatory responses that contribute to the pathogenesis of insulin resistance. Suppression of adipose tissue inflammatory responses is postulated to increase insulin sensitivity in obese patients and animals. Sarsasapogenin (ZGY) is one of the metabolites of timosaponin AIII in the gut, which has been shown to exert anti-inflammatory action. In this study, we investigated the effects of ZGY treatment on obesity-induced insulin resistance in mice. We showed that pretreatment with ZGY (80 mg·kg^-1·d^-1, ig, for 18 days) significantly inhibited acute adipose tissue inflammatory responses in LPS-treated mice. In high-fat diet (HFD)-fed obese mice, oral administration of ZGY (80 mg·kg^-1·d^-1, for 6 weeks) ameliorated insulin resistance and alleviated inflammation in adipose tissues by reducing the infiltration of macrophages. Furthermore, we demonstrated that ZGY not only directly inhibited inflammatory responses in macrophages and adipocytes, but also interrupts the crosstalk between macrophages and adipocytes in vitro, improving adipocyte insulin resistance. The insulin-sensitizing and anti-inflammatory effects of ZGY may result from inactivation of the IKK /NF-κB and JNK inflammatory signaling pathways in adipocytes. Collectively, our findings suggest that ZGY ameliorates insulin resistance and alleviates the adipose inflammatory state in HFD mice, suggesting that ZGY may be a potential agent for the treatment of insulin resistance and obesity-related metabolic diseases.

Adipocytes Are the Control Tower That Manages Adipose Tissue Immunity by Regulating Lipid Metabolism

Accumulating evidence reveals that adipose tissue is an immunologically active organ that exerts multiple impacts on the regulation of systemic energy metabolism. Adipose tissue immunity is modulated by the interactions between adipocytes and various immune cells. Nevertheless, the underlying mechanisms that control inter-cellular interactions between adipocytes and immune cells in adipose tissue have not been thoroughly elucidated. Recently, it has been demonstrated that adipocytes utilize lipid metabolites as a key mediator to initiate and mediate diverse adipose tissue immune responses. Adipocytes present lipid antigens and secrete lipid metabolites to determine adipose immune tones. In addition, the interactions between adipocytes and adipose immune cells are engaged in the control of adipocyte fate and functions upon metabolic stimuli. In this review, we discuss an integrated view of how adipocytes communicate with adipose immune cells using lipid metabolites. Also, we briefly discuss the newly discovered roles of adipose stem cells in the regulation of adipose tissue immunity.

Perirenal Adipose Tissue Inflammation: Novel Insights Linking Metabolic Dysfunction to Renal Diseases

A healthy adipose tissue (AT) is indispensable to human wellbeing. Among other roles, it contributes to energy homeostasis and provides insulation for internal organs. Adipocytes were previously thought to be a passive store of excess calories, however this view evolved to include an endocrine role. Adipose tissue was shown to synthesize and secrete adipokines that are pertinent to glucose and lipid homeostasis, as well as inflammation. Importantly, the obesity-induced adipose tissue expansion stimulates a plethora of signals capable of triggering an inflammatory response. These inflammatory manifestations of obese AT have been linked to insulin resistance, metabolic syndrome, and type 2 diabetes, and proposed to evoke obesity-induced comorbidities including cardiovascular diseases (CVDs). A growing body of evidence suggests that metabolic disorders, characterized by AT inflammation and accumulation around organs may eventually induce organ dysfunction through a direct local mechanism. Interestingly, perirenal adipose tissue (PRAT), surrounding the kidney, influences renal function and metabolism. In this regard, PRAT emerged as an independent risk factor for chronic kidney disease (CKD) and is even correlated with CVD. Here, we review the available evidence on the impact of PRAT alteration in different metabolic states on the renal and cardiovascular function. We present a broad overview of novel insights linking cardiovascular derangements and CKD with a focus on metabolic disorders affecting PRAT. We also argue that the confluence among these pathways may open several perspectives for future pharmacological therapies against CKD and CVD possibly by modulating PRAT immunometabolism.

Inflammation initiates a vicious cycle between obesity and nonalcoholic fatty liver disease

Low‐level of chronic inflammation activation is characteristic of obesity. Nonalcoholic fatty liver disease (NAFLD) is closely linked to obesity and is an emerging health problem, it originates from abnormal accumulation of triglycerides in the liver, and sometimes causes inflammatory reactions that could contribute to cirrhosis and liver cancer, thus its pathogenesis needs to be clarified for more treatment options. Once NAFLD is established, it contributes to systemic inflammation, the low‐grade inflammation is continuously maintained during NAFLD causing impaired resolution of inflammation in obesity, which subsequently exacerbates its severity. This study focuses on the effects of obesity‐induced inflammations, which are the underlying causes of the disease progression and development of more severe inflammatory and fibrotic stages. Understanding the relationship between obesity and NAFLD could help in establishing attractive therapeutic targets or diagnostic markers in obesity‐induced inflammation response and provides new approaches for the prevention and treatment of NAFLD in obesity.

Exercise Training Reduces Inflammation of Adipose Tissue in the Elderly: Cross-Sectional and Randomized Interventional Trial

CONTEXT

Metabolic disturbances and a pro-inflammatory state associated with aging and obesity may be mitigated by physical activity or nutrition interventions.

OBJECTIVE

The aim of this study is to assess whether physical fitness/exercise training (ET) alleviates inflammation in adipose tissue (AT), particularly in combination with omega-3 supplementation, and whether changes in AT induced by ET can contribute to an improvement of insulin sensitivity and metabolic health in the elderly.

DESIGN, PARTICIPANTS, MAIN OUTCOME MEASURES

The effect of physical fitness was determined in cross-sectional comparison of physically active/physically fit (trained) and sedentary/less physically fit (untrained) older women (71 ± 4 years, n = 48); and in double-blind randomized intervention by 4 months of ET with or without omega-3 (Calanus oil) supplementation (n = 55). Physical fitness was evaluated by spiroergometry (maximum graded exercise test) and senior fitness tests. Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp. Samples of subcutaneous AT were used to analyze mRNA gene expression, cytokine secretion, and immune cell populations.

RESULTS

Trained women had lower mRNA levels of inflammation and oxidative stress markers, lower relative content of CD36+ macrophages, and higher relative content of γδT-cells in AT when compared with untrained women. Similar effects were recapitulated in response to a 4-month ET intervention. Content of CD36+ cells, γδT-cells, and mRNA expression of several inflammatory and oxidative stress markers correlated to insulin sensitivity and cardiorespiratory fitness.

CONCLUSIONS

In older women, physical fitness is associated with less inflammation in AT. This may contribute to beneficial metabolic outcomes achieved by ET. When combined with ET, omega-3 supplementation had no additional beneficial effects on AT inflammatory characteristics.

Flavonoids in adipose tissue inflammation and atherosclerosis: one arrow, two targets

Flavonoids are polyphenolic compounds naturally occurring in fruits and vegetables, in addition to beverages such as tea and coffee. Flavonoids are emerging as potent therapeutic agents for cardiovascular as well as metabolic diseases. Several studies corroborated an inverse relationship between flavonoid consumption and cardiovascular disease (CVD) or adipose tissue inflammation (ATI). Flavonoids exert their anti-atherogenic effects by increasing nitric oxide (NO), reducing reactive oxygen species (ROS), and decreasing pro-inflammatory cytokines. In addition, flavonoids alleviate ATI by decreasing triglyceride and cholesterol levels, as well as by attenuating inflammatory mediators. Furthermore, flavonoids inhibit synthesis of fatty acids and promote their oxidation. In this review, we discuss the effect of the main classes of flavonoids, namely flavones, flavonols, flavanols, flavanones, anthocyanins, and isoflavones, on atherosclerosis and ATI. In addition, we dissect the underlying molecular and cellular mechanisms of action for these flavonoids. We conclude by supporting the potential benefit for flavonoids in the management or treatment of CVD; yet, we call for more robust clinical studies for safety and pharmacokinetic values.

Distinct Influence of Hypercaloric Diets Predominant with Fat or Fat and Sucrose on Adipose Tissue and Liver Inflammation in Mice

Overfeeding of a hypercaloric diet leads to obesity, diabetes, chronic inflammation, and fatty liver disease. Although limiting fat or carbohydrate intake is the cornerstone for obesity management, whether lowering fat or reducing carbohydrate intake is more effective for health management remains controversial. This study used murine models to determine how dietary fat and carbohydrates may influence metabolic disease manifestation. Age-matched C57BL/6J mice were fed 2 hypercaloric diets with similar caloric content, one with very high fat and low carbohydrate content (VHF) and the other with moderately high fat levels with high sucrose content (HFHS) for 12 weeks. Both groups gained more weight and displayed hypercholesterolemia, hyperglycemia, hyperinsulinemia, and liver steatosis compared to mice fed a normal low-fat (LF) diet. Interestingly, the VHF-fed mice showed a more robust adipose tissue inflammation compared to HFHS-fed mice, whereas HFHS-fed mice showed liver fibrosis and inflammation that was not observed in VHF-fed mice. Taken together, these results indicate macronutrient-specific tissue inflammation with excess dietary fat provoking adipose tissue inflammation, whereas moderately high dietary fat with extra sucrose is necessary and sufficient for hepatosteatosis advancement to steatohepatitis. Hence, liver and adipose tissues respond to dietary fat and sucrose in opposite manners, yet both macronutrients are contributing factors to metabolic diseases.

Impact of weight loss and partial weight regain on immune cell and inflammatory markers in adipose tissue in male mice

Weight fluctuations are common among individuals with obesity and are associated with increased morbidity. We examined adipose tissue immune and inflammatory markers in mice following weight loss and partial weight regain. Male C57BL/6 mice were randomized into four groups (n = 8-10/group): low-fat diet for 32 wk (LFD), high-fat diet for 32 wk (HFD), LFD for 28 wk and then changed to a HFD for 4 wk (LFD→H), and HFD for 21 wk and then changed to LFD for 7 wk and then changed to HFD for 4 wk (HFD→L→H). LFD→H and HFD→L→H mice did not differ in body weight, fat mass, or fat percentage; however, these parameters were greater than in LFD (P < 0.05) but lower than in HFD (P < 0.05). HFD→L→H mice had smaller adipocytes than HFD and LFD→H (P < 0.05) but not LFD mice. Expressions of CD11c and CD8a genes were elevated in epididymal fat of HFD→L→H compared with LFD→H and LFD (P < 0.05)mice. However, CD11c was lower in HFD→L→H than in HFD mice (P < 0.05), but there was no difference in CD8a between these groups. TNFα and IFNγ expressions were increased in HFD→L→H compared with LFD and LFD→H mice (P < 0.05), although HFD→L→H had lower expression of these cytokines than HFD (P < 0.05). IL-1β was greater in HFD→L→H compared with LFD (P < 0.05) but was not different from LFD→H or HFD mice. Monocyte chemoattractant protein-1 was lower (P < 0.05) in HFD→L→H than in LFD→H. These data reinforce the importance of maintaining a body weight in the range that is recommended for optimal health to reduce immune and inflammatory perturbations associated with obesity.NEW & NOTEWORTHY We examined the immune and inflammatory status of adipose tissue in mice after they underwent weight loss followed by partial weight regain. We show an increase in selected immune cells and inflammatory mediators, in high-fat diet-fed mice that had prior exposure to a high-fat diet. Although weight fluctuations appear to exacerbate immune cell abundance and inflammation in adipose tissue, severity is less than in mice that were exposed to sustained high-fat diet feedings.

Small molecule-driven SIRT3-autophagy-mediated NLRP3 inflammasome inhibition ameliorates inflammatory crosstalk between macrophages and adipocytes

BACKGROUND AND PURPOSE

IL-1β produced by macrophages via the NOD-, LRR- and pyrin domain-containing 3 (NLRP3) inflammasome, mediates the inflammatory crosstalk between macrophages and adipocytes. In our previous study, (16S,20S,24R)-12β-acetoxy-16,23-epoxy-24,25-dihydroxy-3β-(β-D-xylopyranosyloxy)-9,19-cyclolanost-22(23)-ene (AEDC), a cycloartane triterpenoid isolated from Actaea vaginata (Ranunculaceae), was found to possess anti-inflammatory effect on LPS-treated RAW264.7 macrophages. This study was designed to investigate whether AEDC modulates macrophage-adipocyte crosstalk to alleviate adipose tissue inflammation.

EXPERIMENTAL APPROACH

The anti-inflammatory effect of AEDC was evaluated on LPS plus ATP-induced THP-1 macrophages and C57BL/6J mice. The expression of autophagy-related and NLRP3 inflammasome complex proteins was analysed by western blots, immunofluorescence staining and co-immunoprecipitation. The pro-inflammatory cytokines levels were determined by ELISA kits. The adipose tissue inflammation was evaluated by histological analysis and immunohistochemical staining.

KEY RESULTS

AEDC (5 and 10 μM) activated autophagy, which in turn suppressed the NLRP3 inflammasome activation and IL-1β secretion in THP-1 macrophages. AEDC increased the expression of SIRT3 deacetylase and enhanced its deacetylating activity to reverse mitochondrial dysfunction and activate AMP-activated protein kinase, which together induced autophagy. Moreover, AEDC (10 μM) attenuated macrophage conditioned medium-induced inflammatory responses in adipocytes and blocked THP-1 macrophages migration towards 3T3-L1 adipocytes. In inflammation mice, AEDC (5 and 20 mg·kg^-1 ) treatment reduced the levels of pro-inflammatory cytokines in serum and epididymal adipose tissue and reduced macrophage infiltration to alleviate adipose tissue inflammation.

CONCLUSION AND IMPLICATIONS

AEDC attenuated the inflammatory crosstalk between macrophages and adipocytes through SIRT3-autophagy-mediated NLRP3 inflammasome inhibition, which might used for the treatment of adipose tissue inflammation-related metabolic disorders.

Adoptive Cell Transfer of Regulatory T Cells Exacerbates Hepatic Steatosis in High-Fat High-Fructose Diet-Fed Mice

Background and Aims: Non-alcoholic steatohepatitis (NASH) is a multisystem condition, involving the liver, adipose tissue, and immune system. Regulatory T (Treg) cells are a subset of T cells that exert an immune-controlling effect. Previously, a reduction of Treg cells in the visceral adipose tissue (VAT) was shown to be associated with a more severe degree of liver disease. We aimed to correct this immune disruption through adoptive cell transfer (ACT) of Treg cells. Methods: Male 8-week-old C57BL/6J mice were fed a high-fat high-fructose diet (HFHFD) for 20 weeks. Treg cells were isolated from the spleens of healthy 8 to 10-week-old C57BL/6J mice and were adoptively transferred to HFHFD-fed mice. PBS-injected mice served as controls. Plasma ALT and lipid levels were determined. Liver and adipose tissue were assessed histologically. Cytotoxic T (Tc), Treg, T helper (Th) 1 and Th17 cells were characterized in VAT, liver, subcutaneous adipose tissue (SAT), blood, and spleen via flow cytometry. Gene expression analysis was performed in SAT and VAT of mice fed either the HFHFD or a control diet for 10-32 weeks. Results: ACT increased Treg cells in SAT, but not in any of the other tissues. Moreover, the ACT induced a decrease in Th1 cells in SAT, liver, blood, and spleen. Higher plasma ALT levels and a higher degree of steatosis were observed in ACT mice, whereas the other HFHFD-induced metabolic and histologic disruptions were unaffected. Expression analysis of genes related to Treg-cell proliferation revealed a HFHFD-induced decrease in all investigated genes in the SAT, while in the VAT the expression of these genes was largely unaffected, except for a decrease in Pparg. Conclusion: ACT of Treg cells in HFHFD-fed mice exacerbated hepatic steatosis, which was possibly related to the increase of Treg cells in the SAT and/or the general decrease in Th1 cells. Moreover, the HFHFD-induced decrease in Pparg expression appeared critical in the decrease of Treg cells at the level of the VAT and the inability to replenish the amount of Treg cells by the ACT, while the mechanism of Treg cell accumulation at the level of the SAT remained unclear.

Insulin resistance is improved in high-fat fed mice by photobiomodulation therapy at 630 nm

Photobiomodulation therapy (PBMT) in the infrared spectrum exerts positive effects on glucose metabolism, but the use of PBMT at the red spectrum has not been assessed. Male Swiss albino mice were divided into low-fat control and high-fat diet (HFD) for 12 weeks and were treated with red (630 nm) PBMT or no treatment (Sham) during weeks 9 to 12. PBMT was delivered at 31.19 J/cm² , 60 J total dose per day for 20 days. In HFD-fed mice, PBMT improved glucose tolerance, insulin resistance and fasting hyperinsulinemia. PBMT also reduced adiposity and inflammatory infiltrate in adipose tissue. Phosphorylation of Akt in epididymal adipose tissue and rectus femoralis muscle was improved by PBMT. In epididymal fat PBMT reversed the reduced phosphorylation of AS160 and the reduced Glut4 content. In addition, PBMT reversed the alterations caused by HFD in rectus femoralis muscle on proteins involved in mitochondrial dynamics and β-oxidation. In conclusion, PBMT at red spectrum improved insulin resistance and glucose metabolism in HFD-fed mice.

Effects of 1,25-dihydroxyvitamin D3 on the Inflammatory Responses of Stromal Vascular Cells and Adipocytes from Lean and Obese Mice

Vitamin D status has been implicated in obesity and adipose tissue inflammation. In the present study, we explored the effects of dietary vitamin D supplementation on adipose tissue inflammation and immune cell population, and the effects of in vitro 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) treatment on pro-inflammatory cytokine production by stromal vascular cells (SVCs) and adipocytes in lean and high-fat diet-induced obese mice. The results show that epididymal fat Mcp-1 and Rantes mRNA levels, which were higher in obese mice compared with lean mice, were significantly down-regulated by vitamin D supplementation. While obese mice had higher numbers of macrophages and natural killer (NK) cells within adipose tissue, these remained unaltered by vitamin D supplementation. In accordance with these in vivo findings, the in vitro 1,25(OH)2D3 treatment decreased IL-6, MCP-1, and IL-1β production by SVCs from obese mice, but not by adipocytes. In addition, 1,25(OH)2D3 treatment significantly decreased Tlr2 expression and increased mRNA levels of Iκba and Dusp1 in SVCs. These findings suggest that vitamin D supplementation attenuates inflammatory response in adipose tissue, especially in SVCs, possibly through inhibiting NF-κB and MAPK signaling pathways in SVCs but not by the inhibition of macrophage infiltration.

Chronic Adipose Tissue Inflammation Linking Obesity to Insulin Resistance and Type 2 Diabetes

Obesity is one of the major health burdens of the 21st century as it contributes to the growing prevalence of its related comorbidities, including insulin resistance and type 2 diabetes. Growing evidence suggests a critical role for overnutrition in the development of low-grade inflammation. Specifically, chronic inflammation in adipose tissue is considered a crucial risk factor for the development of insulin resistance and type 2 diabetes in obese individuals. The triggers for adipose tissue inflammation are still poorly defined. However, obesity-induced adipose tissue expansion provides a plethora of intrinsic signals (e.g., adipocyte death, hypoxia, and mechanical stress) capable of initiating the inflammatory response. Immune dysregulation in adipose tissue of obese subjects results in a chronic low-grade inflammation characterized by increased infiltration and activation of innate and adaptive immune cells. Macrophages are the most abundant innate immune cells infiltrating and accumulating into adipose tissue of obese individuals; they constitute up to 40% of all adipose tissue cells in obesity. In obesity, adipose tissue macrophages are polarized into pro-inflammatory M1 macrophages and secrete many pro-inflammatory cytokines capable of impairing insulin signaling, therefore promoting the progression of insulin resistance. Besides macrophages, many other immune cells (e.g., dendritic cells, mast cells, neutrophils, B cells, and T cells) reside in adipose tissue during obesity, playing a key role in the development of adipose tissue inflammation and insulin resistance. The association of obesity, adipose tissue inflammation, and metabolic diseases makes inflammatory pathways an appealing target for the treatment of obesity-related metabolic complications. In this review, we summarize the molecular mechanisms responsible for the obesity-induced adipose tissue inflammation and progression toward obesity-associated comorbidities and highlight the current therapeutic strategies.

α-Mangostin remodels visceral adipose tissue inflammation to ameliorate age-related metabolic disorders in mice

Low-grade chronic adipose tissue inflammation contributes to the onset and development of aging-related insulin resistance and type 2 diabetes. In the current study, α-mangostin, a xanthone isolated from mangosteen (Garcinia mangostana), was identified to ameliorate lipopolysaccharides-induced acute adipose tissue inflammation in mice, by reducing the expression of pro-inflammatory cytokines and chemokines. In a cohort of young (3 months) and old (18-20 months) mice, α-mangostin mitigated aging-associated adiposity, hyperlipidemia, and insulin resistance. Further study showed that α-mangostin alleviated aging-related adipose tissue inflammation by reducing macrophage content and shifting pro-inflammatory macrophage polarization. Moreover, α-mangostin protected the old mice against liver injury through suppressing the secretion of microRNA-155-5p from macrophages. The above results demonstrated that α-mangostin represents a new scaffold to alleviate adipose tissue inflammation, which might be a novel candidate to treat aging-related metabolic disorders.

Mechanisms linking the renin-angiotensin system, obesity, and breast cancer

Obesity is a complex disease and a global epidemic. It is a risk factor for other chronic diseases including breast cancer, especially in women after menopause. Diverse etiologies underlie the relationship between obesity and breast cancer. Adipose tissue is in part responsible for these interactions. In obesity, adipose tissue undergoes several metabolic dysregulations resulting in the secretion of many pro-inflammatory cytokines, growth factors, and hormones which in turn, can promote tumor microenvironment (TME) formation and cancer progression within the breast tissue. Angiotensin II (Ang II) is a well-known hypertensive hormone produced systemically and locally by the renin-angiotensin system (RAS). Activation of this system in obesity is a potential contributor to local and systemic inflammation in breast adipose tissue. Ang II actions are primarily mediated through binding to its two receptors, type 1 (AT1R) and type 2 (AT2R). RAS inhibitors include angiotensin-converting enzyme inhibitors (ACE-I) and angiotensin receptor blockers (ARBs) which are currently prescribed as safe antihypertensive therapies. Recent studies have explored the potential use of ACE-I and ARBs in breast cancer patients as anti-tumor agents. Therefore, it is vital to understand the role of RAS in breast cancer and identify mechanisms of Ang II and RAS inhibitors in the TME and in obesity and breast cancer crosstalk. In this review, we performed a detailed analysis and discussed mechanisms of Ang II-AT1R interactions in breast cancer with emphasis on obesity-associated breast cancer. We further summarized recent in vitro, in vivo and human studies that used ACE-I/ARB interventions to improve breast cancer outcomes.

Obesity-Induced Adipose Tissue Inflammation as a Strong Promotional Factor for Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is expected to soon become the second leading cause of cancer related deaths in the United States. This may be due to the rising obesity prevalence, which is a recognized risk factor for PDAC. There is great interest in deciphering the underlying driving mechanisms of the obesity–PDAC link. Visceral adiposity has a strong correlation to certain metabolic diseases and gastrointestinal cancers, including PDAC. In fact, our own data strongly suggest that visceral adipose tissue inflammation is a strong promoter for PDAC growth and progression in a genetically engineered mouse model of PDAC and diet-induced obesity. In this review, we will discuss the relationship between obesity-associated adipose tissue inflammation and PDAC development, with a focus on the key molecular and cellular components in the dysfunctional visceral adipose tissue, which provides a tumor permissive environment.

Heat therapy improves glucose tolerance and adipose tissue insulin signaling in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is associated with high rates of obesity and metabolic dysfunction. Repeated passive heat exposure (termed heat therapy) is a novel lifestyle intervention for improving health in obese women with PCOS. The purpose of this study was to examine changes in metabolic function in obese women with PCOS following heat therapy. Eighteen age- and BMI-matched obese women with PCOS (age: 27 ± 1 yr, BMI: 41.3 ± 1.1 kg/m^-2) were assigned to heat therapy (HT) or time control (CON). HT participants underwent 30 one-hour hot tub sessions over 8-10 wk, while CON participants completed all testing but did not undergo heat therapy. Before (Pre), at the mid-point (Mid), and following (Post) 8-10 wk of heat therapy, metabolic health was assessed using a 2-h oral glucose tolerance test, a subcutaneous abdominal fat biopsy (Pre-Post only), and other blood markers relating to metabolic function. HT participants exhibited improved fasting glucose (Pre: 105 ± 3, Post: 89 ± 5mg/dl; P = 0.001), glucose area under the curve (AUC) (Pre: 18,698 ± 1,045, Post: 16,987 ± 1,017 mg·dl^-1·min^-1; P = 0.028) and insulin AUC (Pre: 126,924 ± 11,730, Post: 91,233 ± 14,429 IU l^-1·min^-1; P = 0.012). Adipocyte insulin signaling (p-AKT at Ser-473 with 1.2 nM insulin) increased in HT (Pre: 0.29 ± 0.14, Post: 0.93 ± 0.29 AU; P = 0.021). Additionally, serum testosterone declined in HT participants (Pre: 51 ± 7, Post: 34 ± 4 ng/dl; P = 0.033). No parameters changed over time in CON, and no change in BMI was observed in either group. HT substantially improved metabolic risk profile in obese women with PCOS. HT also reduced androgen excess and may improve PCOS symptomology.

GC-(4→8)-GCG, A Proanthocyanidin Dimer from Camellia ptilophylla, Modulates Obesity and Adipose Tissue Inflammation in High-Fat Diet Induced Obese Mice

SCOPE

Excessive fat accumulation in adipose tissue leads to obesity and related chronic inflammation. This study aims to examine the effects of gallocatechin -(4→8)-gallocatechin-3-O-gallate (GC-(4→8)-GCG), a main proanthocyanidin dimer from Camellia ptilophylla (Cocoa tea), on adipocyte- and adipose-related inflammation in vivo and in vitro.

METHODS AND RESULTS

C57BL/6 mice are fed a high-fat diet (HFD) and GC-(4→8)-GCG (40 or 80 mg kg^-1 d^-1 ) for 8 weeks. The metabolic profiles, adipose tissue hypertrophy, macrophage infiltration, and inflammatory cytokine production are investigated. Additionally, 3T3-L1 preadipocytes are utilized to investigate the effect of GC-(4→8)-GCG on preadipocyte differentiation and the tumor necrosis factor (TNF)-α-stimulated inflammatory response in vitro. GC-(4→8)-GCG supplementation decreases HFD-induced epididymal white adipose tissue (eWAT) hypertrophy, suppresses proinflammatory cytokine production and macrophage infiltration in eWAT, and improves insulin sensitivity in HFD-induced obese mice. In vitro, GC-(4→8)-GCG shows a strong anti-adipogenic potential in 3T3-L1 preadipocyte by inhibiting the expression of key adipogenic transcription factors and decreasing the production of proinflammatory cytokines by inhibiting the activation of the nuclear factor (NF)-κB, Janus tyrosine kinase/signal transducer and activator of transcription (JAK/STAT3) and mitogen-activated protein kinase (MAPK) signaling pathways.

CONCLUSION

GC-(4→8)-GCG can modulate obesity and improve obesity-related insulin resistance by inhibiting preadipocyte differentiation and the related proinflammatory responses.

Diet-Independent Correlations between Bacteria and Dysfunction of Gut, Adipose Tissue, and Liver: A Comprehensive Microbiota Analysis in Feces and Mucosa of the Ileum and Colon in Obese Mice with NAFLD

Development of non-alcoholic fatty liver disease (NAFLD) is linked to obesity, adipose tissue inflammation, and gut dysfunction, all of which depend on diet. So far, studies have mainly focused on diet-related fecal microbiota changes, but other compartments may be more informative on host health. We present a first systematic analysis of microbiota changes in the ileum and colon using multiple diets and investigating both fecal and mucosal samples. Ldlr−/−.Leiden mice received one of three different energy-dense (ED)-diets (n = 15/group) for 15 weeks. All of the ED diets induced obesity and metabolic risk factors, altered short-chain fatty acids (SCFA), and increased gut permeability and NAFLD to various extents. ED diets reduced the diversity of high-abundant bacteria and increased the diversity of low-abundant bacteria in all of the gut compartments. The ED groups showed highly variable, partially overlapping microbiota compositions that differed significantly from chow. Correlation analyses demonstrated that (1) specific groups of bacteria correlate with metabolic risk factors, organ dysfunction, and NAFLD endpoints, (2) colon mucosa had greater predictive value than other compartments, (3) correlating bacteria differed per compartment, and (4) some bacteria correlated with plasma SCFA levels. In conclusion, this comprehensive microbiota analysis demonstrates correlations between the microbiota and dysfunctions of gut, adipose tissue, and liver, independent of a specific disease-inducing diet.

Regulation of adipose tissue inflammation by adenosine 2A receptor in obese mice

Adenosine 2A receptor (A2AR) exerts anti-inflammatory effects. However, the role of A2AR in obesity-associated adipose tissue inflammation remains to be elucidated. The present study examined the expression of A2AR in adipose tissue of mice with diet-induced obesity and determined the effect of A2AR disruption on the status of obesity-associated adipose tissue inflammation. WT C57BL/6J mice and A2AR-disrupted mice were fed a high-fat diet (HFD) for 12 weeks to induce obesity and adipose tissue inflammation. In vitro, bone marrow-derived macrophages from A2AR-disrupted mice and WT control mice were treated with palmitate and examined for macrophage proinflammatory activation. Compared with that of low-fat diet (LFD)-fed WT mice, A2AR expression in adipose tissue of HFD-fed WT mice was increased significantly and was present predominantly in adipose tissue macrophages. The increase in adipose tissue A2AR expression in HFD-fed mice was accompanied with increased phosphorylation states of c-Jun N-terminal kinase 1 p46 and nuclear factor kappa B p65 and mRNA levels of interleukin (Il)-1beta, Il6 and tumor necrosis factor alpha. In A2AR-disrupted mice, HFD feeding induced significant increases in adipose tissue inflammation, indicated by enhanced proinflammatory signaling and increased proinflammatory cytokine expression, and adipose tissue insulin resistance, indicated by a decrease in insulin-stimulated Akt phosphorylation relative to those in WT mice. Lastly, A2AR disruption enhanced palmitate-induced macrophage proinflammatory activation. Taken together, these results suggest that A2AR plays a protective role in obesity-associated adipose tissue inflammation, which is attributable to, in large part, A2AR suppression of macrophage proinflammatory activation.

NFATc3 deficiency reduces the classical activation of adipose tissue macrophages

Nuclear factors of activated T cells (NFAT) c3 have a prominent role in the regulation of proinflammatory factors in immune cells. The classically activated M1 macrophages are key players in the initiation and maintenance of adipose tissue (AT) inflammation. The role of NFATc3 in obesity and AT inflammation is unknown. We set out to determine how deficiency of NFATc3 effected macrophage polarization, inflammation and insulin resistance in visceral AT of high-fat diet (HFD)-fed mice. Nfatc3−/− and WT mice were fed a HFD for 8–17 weeks. Epididymal white AT (eWAT) F4/80(+) cells were characterized by fluorescence-activated cell sorting and quantitative RT-PCR. Results showed that Nfatc3−/− mice developed HFD-induced obesity similar to WT mice, but insulin sensitivity and glucose tolerance were improved, and liver fat accumulation was reduced in Nfatc3−/− mice compared to WT control mice. Moreover, M1 macrophage content and proinflammatory factors were reduced, whereas the alternatively activated M2 macrophage content was increased in eWAT of HFD-fed Nfatc3−/− mice compared to that of WT mice. In addition, eWAT insulin signaling was improved in HFD-fed Nfatc3−/− mice. Importantly, after bone-marrow-derived macrophages had been isolated from Nfatc3−/− mice and cultured in vitro, treatment of these cells with interferon-γ and lipopolysaccharide resulted in reduction of M1 inflammatory markers, suggesting that NFATc3 promoted M1 polarization by a cell-autonomous mechanism. The results demonstrated that NFATc3 played an important role in M1 macrophage polarization, AT inflammation and insulin resistance in response to obesity through transcriptional activation of proinflammatory genes.

Peripheral cannabinoid 1 receptor blockade mitigates adipose tissue inflammation via NLRP3 inflammasome in mouse models of obesity

AIM

To analyze the metabolic parameters and adipose tissue inflammation via NLRP3 inflammasome following chronic treatment of mouse models of obesity with AJ5018 as the peripherally restricted cannabinoid 1 receptor (CB1R) antagonist.

MATERIALS AND METHODS

The selectivity for CB1R over CB2R, brain/plasma concentration ratio, and centrally mediated neurobehavioural effects of AJ5018, were assessed. The long-term effects of AJ5018 and rimonabant on the metabolic parameters and adipose tissue inflammation were analyzed in diet-induced obese (DIO) mice and diabetic db/db mice.

RESULTS

AJ5018 had a higher degree of selectivity for CB1R over CB2R and markedly reduced brain penetrance, as reflected by the lower brain/plasma concentration ratio and the attenuated centrally mediated neurobehavioural effects, compared with its brain-penetrant parent compound rimonabant. In DIO and db/db mice, AJ5018 exhibited comparable effects to rimonabant in improving metabolic abnormalities and suppressing macrophage infiltration into white adipose tissue, activation of the NLRP3 inflammasome, and production of proinflammatory cytokines.

CONCLUSIONS

These results suggest that peripheral CB1R blockade improves obesity-induced insulin resistance by suppressing adipose tissue inflammation via the NLRP3 inflammasome.

Perilipin 1 (Plin1) deficiency promotes inflammatory responses in lean adipose tissue through lipid dysregulation

Lipid droplets are specialized cellular organelles that contain neutral lipid metabolites and play dynamic roles in energy homeostasis. Perilipin 1 (Plin1), one of the major lipid droplet-binding proteins, is highly expressed in adipocytes. In mice, Plin1 deficiency impairs peripheral insulin sensitivity, accompanied with reduced fat mass. However, the mechanisms underlying insulin resistance in lean Plin1 knockout (Plin1^-/-) mice are largely unknown. The current study demonstrates that Plin1 deficiency promotes inflammatory responses and lipolysis in adipose tissue, resulting in insulin resistance. M1-type adipose tissue macrophages (ATMs) were higher in Plin1^-/- than in Plin1^+/+ mice on normal chow diet. Moreover, using lipidomics analysis, we discovered that Plin1^-/- adipocytes promoted secretion of pro-inflammatory lipid metabolites such as prostaglandins, which potentiated monocyte migration. In lean Plin1^-/- mice, insulin resistance was relieved by macrophage depletion with clodronate, implying that elevated pro-inflammatory ATMs might be attributable for insulin resistance under Plin1 deficiency. Together, these data suggest that Plin1 is required to restrain fat loss and pro-inflammatory responses in adipose tissue by reducing futile lipolysis to maintain metabolic homeostasis.

Absence of Carbohydrate Response Element Binding Protein in Adipocytes Causes Systemic Insulin Resistance and Impairs Glucose Transport

Lower adipose-ChREBP and de novo lipogenesis (DNL) are associated with insulin resistance in humans. Here, we generated adipose-specific ChREBP knockout (AdChREBP KO) mice with negligible sucrose-induced DNL in adipose tissue (AT). Chow-fed AdChREBP KO mice are insulin resistant with impaired insulin action in the liver, muscle, and AT and increased AT inflammation. HFD-fed AdChREBP KO mice are also more insulin resistant than controls. Surprisingly, adipocytes lacking ChREBP display a cell-autonomous reduction in insulin-stimulated glucose transport that is mediated by impaired Glut4 translocation and exocytosis, not lower Glut4 levels. AdChREBP KO mice have lower levels of palmitic acid esters of hydroxy stearic acids (PAHSAs) in serum, and AT. 9-PAHSA supplementation completely rescues their insulin resistance and AT inflammation. 9-PAHSA also normalizes impaired glucose transport and Glut4 exocytosis in ChREBP KO adipocytes. Thus, loss of adipose-ChREBP is sufficient to cause insulin resistance, potentially by regulating AT glucose transport and flux through specific lipogenic pathways.

Role of Natural Killer T Cells in the Development of Obesity and Insulin Resistance: Insights From Recent Progress

Natural killer T (NKT) cells play important roles in adipose tissue inflammation, and thus influence the development of diet-induced obesity and insulin resistance. The interactions between cluster of differentiation (CD)1d and NKT T cell receptor are thought to be critical in this process, as demonstrated in two NKT cell-deficient mouse models-systemic CD1d gene knockout (KO) and prototypic Jα18 KO mice. The latter lacks some repertoires besides invariant (i)NKT cells due to manipulation of the Jα18 gene segment; therefore, the role of iNKT vs. variant NKT cells must be reinterpreted considering the availability of new Jα18 KO mice. NKT cells have varied roles in the development of obesity; indeed, studies have reported contradictory results depending on the mouse model, diet, and rearing conditions, all of which could affect the microbiome. In this mini-review, we discuss these points considering recent findings from our laboratory and others as well as the role of NKT cells in the development of obesity and insulin resistance based on data obtained from studies on conditional CD1d1 KO and new Jα18 KO mice generated through gene editing.

Neurotensin Is a Lipid-Induced Gastrointestinal Peptide Associated with Visceral Adipose Tissue Inflammation in Obesity

Neurotensin (NT) is a 13-amino acid peptide localized in the neuroendocrine cells of the small intestine, which promotes fat absorption and fatty acids translocation in response to lipid ingestion. NT-knock-out mice fed with a high-fat diet are protected from obesity, fatty liver, and the development of insulin-resistance. In humans, higher plasma levels of pro-NT, which is the stable circulating precursor of NT, predict obesity, type 2 diabetes (T2D), and cardiovascular disease. In obesity, the presence of visceral adipose tissue (VAT) inflammation leads to unfavorable metabolic outcomes and is associated with the development of T2D and non-alcoholic fatty liver disease (NAFLD). In this study, we investigated the relationship between plasma pro-NT levels and the presence of VAT inflammation in biopsies from 40 morbidly obese subjects undergoing bariatric surgery. We demonstrated that higher proNT levels are significantly associated with greater macrophages infiltration, HIF-1α, WISP-1, and UNC5B expression in VAT (all p < 0.01) due to the diagnosis of T2D and NAFLD. The overall results show that, in obesity, pro-NT is a biomarker of VAT inflammation and insulin-resistance. Additionally, NT may be involved in the development of dysmetabolic conditions likely mediated by increased gut fat absorption and the presence of a proinflammatory milieu in the adipose tissue.