Adipose tissue macrophages inhibit adipogenesis of mesenchymal precursor cells via wnt-5a in humans

Adipose tissue macrophages as potential targets for obesity and metabolic diseases

Macrophage infiltration into adipose tissue is a key pathological factor inducing adipose tissue dysfunction and contributing to obesity-induced inflammation and metabolic disorders. In this review, we aim to present the most recent research on macrophage heterogeneity in adipose tissue, with a focus on the molecular targets applied to macrophages as potential therapeutics for metabolic diseases. We begin by discussing the recruitment of macrophages and their roles in adipose tissue. While resident adipose tissue macrophages display an anti-inflammatory phenotype and promote the development of metabolically favorable beige adipose tissue, an increase in pro-inflammatory macrophages in adipose tissue has negative effects on adipose tissue function, including inhibition of adipogenesis, promotion of inflammation, insulin resistance, and fibrosis. Then, we presented the identities of the newly discovered adipose tissue macrophage subtypes (e.g. metabolically activated macrophages, CD9+ macrophages, lipid-associated macrophages, DARC+ macrophages, and MFehi macrophages), the majority of which are located in crown-like structures within adipose tissue during obesity. Finally, we discussed macrophage-targeting strategies to ameliorate obesity-related inflammation and metabolic abnormalities, with a focus on transcriptional factors such as PPARγ, KLF4, NFATc3, and HoxA5, which promote macrophage anti-inflammatory M2 polarization, as well as TLR4/NF-κB-mediated inflammatory pathways that activate pro-inflammatory M1 macrophages. In addition, a number of intracellular metabolic pathways closely associated with glucose metabolism, oxidative stress, nutrient sensing, and circadian clock regulation were examined. Understanding the complexities of macrophage plasticity and functionality may open up new avenues for the development of macrophage-based treatments for obesity and other metabolic diseases.

Human RSPO1 Mutation Represses Beige Adipocyte Thermogenesis and Contributes to Diet-Induced Adiposity

Recent genetic evidence has linked WNT downstream mutations to fat distribution. However, the roles of WNTs in human obesity remain unclear. Here, the authors screen all Wnt-related paracrine factors in 1994 obese cases and 2161 controls using whole-exome sequencing (WES) and identify that 12 obese patients harbor the same mutations in RSPO1 (p.R219W/Q) predisposing to human obesity. RSPO1 is predominantly expressed in visceral fat, primarily in the fibroblast cluster, and is increased with adiposity. Mice overexpressing human RSPO1 in adipose tissues develop obesity under a high-fat diet (HFD) due to reduced brown/beige fat thermogenesis. In contrast, Rspo1 ablation resists HFD-induced adiposity by increasing thermogenesis. Mechanistically, RSPO1 overexpression or administration significantly inhibits adipocyte mitochondrial respiration and thermogenesis via LGR4-Wnt/β-catenin signaling pathway. Importantly, humanized knockin mice carrying the hotspot mutation (p.R219W) display suppressed thermogenesis and recapitulate the adiposity feature of obese carriers. The mutation disrupts RSPO1's electrostatic interaction with the extracellular matrix, leading to excessive RSPO1 release that activates LGR4-Wnt/β-catenin signaling and attenuates thermogenic capacity in differentiated beige adipocytes. Therefore, these findings identify that gain-of-function mutations and excessive expression of RSPO1, acting as a paracrine Wnt activator, suppress fat thermogenesis and contribute to obesity in humans.

Reciprocal signaling between adipose tissue depots and the central nervous system

In humans, various dietary and social factors led to the development of increased brain sizes alongside large adipose tissue stores. Complex reciprocal signaling mechanisms allow for a fine-tuned interaction between the two organs to regulate energy homeostasis of the organism. As an endocrine organ, adipose tissue secretes various hormones, cytokines, and metabolites that signal energy availability to the central nervous system (CNS). Vice versa, the CNS is a critical regulator of adipose tissue function through neural networks that integrate information from the periphery and regulate sympathetic nerve outflow. This review discusses the various reciprocal signaling mechanisms in the CNS and adipose tissue to maintain organismal energy homeostasis. We are focusing on the integration of afferent signals from the periphery in neuronal populations of the mediobasal hypothalamus as well as the efferent signals from the CNS to adipose tissue and its implications for adipose tissue function. Furthermore, we are discussing central mechanisms that fine-tune the immune system in adipose tissue depots and contribute to organ homeostasis. Elucidating this complex signaling network that integrates peripheral signals to generate physiological outputs to maintain the optimal energy balance of the organism is crucial for understanding the pathophysiology of obesity and metabolic diseases such as type 2 diabetes.

Cell fate determining molecular switches and signaling pathways in Pax7-expressing somitic mesoderm

During development, different cell types originate from a common progenitor at well-defined time points. Previous lineage-tracing of Pax7⁺ progenitors from the somitic mesoderm has established its developmental trajectory towards the dermis, brown adipocytes, and skeletal muscle in the dorsal trunk; yet the molecular switches and mechanisms guiding the differentiation into different lineages remain unknown. We performed lineage-tracing of Pax7-expressing cells in mouse embryos at E9.5 and profiled the transcriptomes of Pax7-progenies on E12.5, E14.5, and E16.5 at single-cell level. Analysis of single-cell transcriptomic data at multiple time points showed temporal-specific differentiation events toward muscle, dermis, and brown adipocyte, identified marker genes for putative progenitors and revealed transcription factors that could drive lineage-specific differentiation. We then utilized a combination of surface markers identified in the single-cell data, Pdgfra, Thy1, and Cd36, to enrich brown adipocytes, dermal fibroblasts, and progenitors specific for these two cell types at E14.5 and E16.5. These enriched cell populations were then used for further culture and functional assays in vitro, in which Wnt5a and Rgcc are shown to be important factors that could alter lineage decisions during embryogenesis. Notably, we found a bipotent progenitor population at E14.5, having lineage potentials towards both dermal fibroblasts and brown adipocytes. They were termed eFAPs (embryonic fibro/adipogenic progenitors) as they functionally resemble adult fibro/adipogenic progenitors. Overall, this study provides further understanding of the Pax7 lineage during embryonic development using a combination of lineage tracing with temporally sampled single-cell transcriptomics.

The Role of Anti-Inflammatory Adipokines in Cardiometabolic Disorders: Moving beyond Adiponectin

The global burden of obesity has multiplied owing to its rapidly growing prevalence and obesity-related morbidity and mortality. In addition to the classic role of depositing extra energy, adipose tissue actively interferes with the metabolic balance by means of secreting bioactive compounds called adipokines. While most adipokines give rise to inflammatory conditions, the others with anti-inflammatory properties have been the novel focus of attention for the amelioration of cardiometabolic complications. This review compiles the current evidence on the roles of anti-inflammatory adipokines, namely, adiponectin, vaspin, the C1q/TNF-related protein (CTRP) family, secreted frizzled-related protein 5 (SFRP5), and omentin-1 on cardiometabolic health. Further investigations on the mechanism of action and prospective human trials may pave the way to their clinical application as innovative biomarkers and therapeutic targets for cardiovascular and metabolic disorders.

Serum secreted frizzled-related protein 5 in relation to insulin sensitivity and its regulation by insulin and free fatty acids

PURPOSE

Secreted frizzled-related protein 5 (SFRP5) is an adipokine, which acts as an inhibitor of noncanonical WNT signaling pathway. It has been suggested to exert anti-inflammatory and insulin-sensitizing effects, however, contradictory data has also been reported. The aim of this study was to assess serum SFRP5 concentration in a young healthy population in relation to insulin sensitivity and its regulation by hyperinsulinemia and/or serum free fatty acids (FFA) elevation.

METHODS

We examined 150 healthy subjects (83 normal-weight and 67 overweight/obese). Insulin sensitivity (M) was measured with hyperinsulinemic-euglycemic clamp. In 20 male subjects, clamp was prolonged to 6 h and after 1 week another clamp with the concurrent Intralipid/heparin infusion was performed. Independent group of 10 male subjects received infusions of Intralipid/heparin or saline in 1-week interval.

RESULTS

Baseline SFRP5 was lower in the overweight/obese group (p = 0.01) and was positively associated with M (r = 0.23, p = 0.006) and serum adiponectin (r = 0.55, p < 0.001) and negatively with BMI (r = -0.18, p = 0.03). In multiple regression analysis, adiponectin was independently associated with SFRP5. Insulin infusion resulted in a decrease in serum SFRP5, both at 120' (p = 0.02) and 360' (p = 0.031). This effect was not observed during the clamp with Intralipid/heparin as well as during Intralipid/heparin alone or saline infusions.

CONCLUSIONS

The relation between SFRP5 and insulin sensitivity is mainly dependent on adiponectin. FFA abolish a decrease in circulating SFRP5 caused by insulin, but Intralipid/heparin infusion alone does not regulate SFRP5 concentration. Insulin seems to be more important factor in the regulation of circulating SFRP5 levels than FFA.

Overview of the molecular mechanisms contributing to the formation of cancer‑associated adipocytes (Review)

Adipocytes are the main stromal cells in the tumor microenvironment. In addition to serving as energy stores for triglycerides, adipocytes may function as an active endocrine organ. The crosstalk between adipocytes and cancer cells was shown to promote the migration, invasion and proliferation of cancer cells and to cause phenotypic and functional changes in adipocytes. Tumor-derived soluble factors, such as TNF-α, plasminogen activator inhibitor 1, Wnt3a, IL-6, and exosomal microRNAs (miRNA/miRs), including miR-144, miR-126, miR-155, as well as other miRNAs, have been shown to act on adipocytes at the tumor invasion front, resulting in the formation of cancer-associated adipocytes (CAAs) with diminished reduced terminal differentiation markers and a dedifferentiated phenotype. In addition, the number and size of CAA lipid droplets have been found to be significantly reduced compared with those of mature adipocytes, whereas inflammatory cytokines and proteases are overexpressed. The aim of the present review was to summarize the latest findings on the biological changes of CAAs and the potential role of tumor-adipocyte crosstalk in the formation of CAAs, in the hope of providing novel perspectives for breast cancer treatment.

Adipose Extracellular Vesicles: Messengers From and to Macrophages in Regulating Immunometabolic Homeostasis or Disorders

Adipose tissue is comprised of heterogenous cell populations that regulate both energy metabolism and immune reactions. Macrophages play critical roles in regulating immunometabolic homeostasis or disorders through cooperation with adipocytes, adipose tissue-derived stem cells (ADSCs) or other cells in adipose tissue. Extracellular vesicles (EVs) are recently recognized as efficient messengers for intercellular communication. Emerging evidences have demonstrated that adipose EVs are actively involved in the mutual interactions of macrophages, adipocytes and ADSCs, which produce considerable influences on immunometabolism under healthy or obese conditions. Here, we will elaborate the production and the characteristics of adipose EVs that are related to macrophages under different metabolic demands or stresses, whilst discuss the roles of these EVs in regulating local or systemic immunometabolic homeostasis or disorders in the context of adipocyte-macrophage dialogue and ADSC-macrophage interaction. Particularly, we provide a profile of dynamic adipose microenvironments based on macrophages. Adipose EVs act as the messengers between ADSCs and macrophages to maintain the balance of metabolism and immunity, while drive a vicious cycle between hypertrophic adipocytes and inflammatory macrophages to cause immunometabolic imbalance. This review may provide valuable information about the physio- or pathological roles of adipose EVs and the application of adipose EVs in the diagnosis and treatment of metabolic diseases.

Circulating Wnt Ligands Activate the Wnt Signaling Pathway in Mature Erythrocytes

[Figure: see text].

Dysmetabolic adipose tissue in obesity: morphological and functional characteristics of adipose stem cells and mature adipocytes in healthy and unhealthy obese subjects

The way by which subcutaneous adipose tissue (SAT) expands and undergoes remodeling by storing excess lipids through expansion of adipocytes (hypertrophy) or recruitment of new precursor cells (hyperplasia) impacts the risk of developing cardiometabolic and respiratory diseases. In unhealthy obese subjects, insulin resistance, type 2 diabetes, hypertension, and obstructive sleep apnoea are typically associated with pathologic SAT remodeling characterized by adipocyte hypertrophy, as well as chronic inflammation, hypoxia, increased visceral adipose tissue (VAT), and fatty liver. In contrast, metabolically healthy obese individuals are generally associated with SAT development characterized by the presence of smaller and numerous mature adipocytes, and a lower degree of VAT inflammation and ectopic fat accumulation. The remodeling of SAT and VAT is under genetic regulation and influenced by inherent depot-specific differences of adipose tissue-derived stem cells (ASCs). ASCs have multiple functions such as cell renewal, adipogenic capacity, and angiogenic properties, and secrete a variety of bioactive molecules involved in vascular and extracellular matrix remodeling. Understanding the mechanisms regulating the proliferative and adipogenic capacity of ASCs from SAT and VAT in response to excess calorie intake has become a focus of interest over recent decades. Here, we summarize current knowledge about the biological mechanisms able to foster or impair the recruitment and adipogenic differentiation of ASCs during SAT and VAT development, which regulate body fat distribution and favorable or unfavorable metabolic responses.

Role of Wnt signaling pathways in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) has become a major global public health issue in the twenty-first century and its incidence has increased each year. Wnt signaling pathways are a set of multi-downstream signaling pathways activated by the binding of Wnt ligands to membrane protein receptors. Wnt signaling pathways regulate protein expression and play important roles in protecting the body's normal physiological metabolism. This review describes Wnt signaling pathways, and then aims to reveal how Wnt signaling pathways participate in the occurrence and development of T2DM. We found that Wnt/c-Jun N-terminal kinase signaling was closely associated with insulin resistance, inflammatory response, and pancreatic β-cell and endothelial dysfunction. β-catenin/transcription factor 7-like 2 (TCF7L2)-mediated and calcineurin/nuclear factor of activated T cells-mediated target genes were involved in insulin synthesis and secretion, insulin degradation, pancreatic β-cell growth and regeneration, and functional application of pancreatic β-cells. In addition, polymorphisms in the TCF7L2 gene could increase risk of T2DM according to previous and the most current results, and the T allele of its variants was a more adverse factor for abnormal pancreatic β-cell function and impaired glucose tolerance in patients with T2DM. These findings indicate a strong correlation between Wnt signaling pathways and T2DM, particularly in terms of pancreatic islet dysfunction and insulin resistance, and new therapeutic targets for T2DM may be identified.

Circulating sDPP-4 is Increased in Obesity and Insulin Resistance but Is Not Related to Systemic Metabolic Inflammation

CONTEXT

Dipeptidylpeptidase (DPP)-4 is a key regulator of the incretin system. It exists in a membrane-bound form and a soluble form (sDPP-4). Initial human studies suggested sDPP-4 to be an adipokine involved in metabolic inflammation. However, recent mechanistic data in genetically modified mice has questioned these findings.

OBJECTIVES

We examined circulating sDPP-4 in a cohort of n = 451 humans with different metabolic phenotypes and during 3 different weight loss interventions (n = 101) to further clarify its role in human physiology and metabolic diseases.

DESIGN

sDPP-4 serum concentrations were measured by enzyme-linked immunosorbent assay and related to several phenotyping data including gut microbiome analysis.

RESULTS

sDPP-4 increased with age and body weight and was positively associated with insulin resistance and hypertriglyceridemia but was reduced in manifest type 2 diabetes. In addition, we found reduced serum concentrations of sDPP-4 in subjects with arterial hypertension. In contrast to earlier reports, we did not identify an association with systemic markers of inflammation. Impaired kidney and liver functions significantly altered sDPP-4 concentrations while no relation to biomarkers for heart failure was observed. Having found increased levels of sDPP-4 in obesity, we studied surgical (gastric bypass and sleeve gastrectomy) and nonsurgical interventions, revealing a significant association of sDPP-4 with improvement of liver function tests but not with changes in body weight.

CONCLUSIONS

Our data suggest that sDPP-4 is related to hepatic abnormalities in obesity rather than primarily functioning as an adipokine and that sDPP-4 is implicated both in glucose and in lipid metabolism, but not fundamentally in systemic inflammation.

Adipose Tissue Epigenetic Profile in Obesity-Related Dysglycemia - A Systematic Review

BACKGROUND

Obesity is a major risk factor for dysglycemic disorders, including type 2 diabetes (T2D). However, there is wide phenotypic variation in metabolic profiles. Tissue-specific epigenetic modifications could be partially accountable for the observed phenotypic variability.

SCOPE

The aim of this systematic review was to summarize the available data on epigenetic signatures in human adipose tissue (AT) that characterize overweight or obesity-related insulin resistance (IR) and dysglycemia states and to identify potential underlying mechanisms through the use of unbiased bioinformatics approaches.

METHODS

Original data published in the last decade concerning the comparison of epigenetic marks in human AT of individuals with metabolically unhealthy overweight/obesity (MUHO) versus normal weight individuals or individuals with metabolically healthy overweight/obesity (MHO) was assessed. Furthermore, association of these epigenetic marks with IR/dysglycemic traits, including T2D, was compiled.

RESULTS

We catalogued more than two thousand differentially methylated regions (DMRs; above the cut-off of 5%) in the AT of individuals with MUHO compared to individuals with MHO. These DNA methylation changes were less likely to occur around the promoter regions and were enriched at loci implicated in intracellular signaling (signal transduction mediated by small GTPases, ERK1/2 signaling and intracellular trafficking). We also identified a network of seven transcription factors that may play an important role in targeting DNA methylation changes to specific genes in the AT of subjects with MUHO, contributing to the pathogeny of obesity-related IR/T2D. Furthermore, we found differentially methylated CpG sites at 8 genes that were present in AT and whole blood, suggesting that DMRs in whole blood could be potentially used as accessible biomarkers of MUHO.

CONCLUSIONS

The overall evidence linking epigenetic alterations in key tissues such AT to metabolic complications in human obesity is still very limited, highlighting the need for further studies, particularly those focusing on epigenetic marks other than DNA methylation. Our initial analysis suggests that DNA methylation patterns can potentially discriminate between MUHO from MHO and provide new clues into why some people with obesity are less susceptible to dysglycemia. Identifying AT-specific epigenetic targets could also lead to novel approaches to modify the progression of individuals with obesity towards metabolic disease.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, identifier CRD42021227237.

Weight Regain in Formerly Obese Mice Hastens Development of Hepatic Steatosis Due to Impaired Adipose Tissue Function

OBJECTIVE

Weight regain after weight loss is common, and there is evidence to suggest negative effects on health because of weight cycling. This study sought to investigate the impact of weight regain in formerly obese mice on adipose tissue architecture and stromal cell function.

METHODS

A diet-switch model was employed for obesity induction, weight loss, and weight regain in mice. Flow cytometry quantified adipose tissue leukocytes in adipose tissue. Liver and adipose tissue depots were compared to determine tissue-specific effects of weight cycling.

RESULTS

Epididymal white adipose tissue of formerly obese mice failed to expand in response to repeat exposure to high-fat diet and retained elevated numbers of macrophages and T cells. Weight regain was associated with disproportionally elevated liver mass, hepatic triglyceride content, serum insulin concentration, and serum transaminase concentration. These effects occurred despite an extended 6-month weight loss cycle and they demonstrate that formerly obese mice maintain durable alterations in their physiological response to weight regain. Conditioned media from epididymal adipose tissue of formerly obese mice inhibited adipogenesis of 3T3-L1 preadipocytes, suggesting a potential mechanism to explain failed epididymal adipose tissue expansion during weight regain.

CONCLUSIONS

Metabolic abnormalities related to defects in adipose tissue expansion and ongoing dysfunction manifest in formerly obese mice during weight regain.

Association of serum levels of secreted frizzled-related protein 5 and Wnt member 5a with glomerular filtration rate in patients with type 2 diabetes mellitus and chronic renal disease: a cross-sectional study

BACKGROUND

Diabetic nephropathy is a common complication of chronic kidney disease (CKD). -Inflammation in the kidneys is crucial for promoting development and progression of this complication. Wnt member 5a (Wnt5a) and secreted frizzled-related protein 5 (Sfrp5) are proinflammatory proteins associated with insulin resistance and chronic low-grade adipose tissue inflammation.

OBJECTIVE

To determine the correlation between serum Sfrp5 and Wnt5a concentrations and glomerular filtration rate in patients with type 2 diabetes mellitus and CKD.

DESIGN AND SETTING

Cross-sectional, comparative and observational study in the Department of Endocrinology, Civil Hospital, Culiacán, Sinaloa, Mexico.

METHODS

Eighty individuals with chronic kidney disease were recruited. Their serum Sfrp5 and Wnt5a concentrations were quantified using the enzyme-linked immunosorbent assay (ELISA) test. The statistical analysis consisted of the Mann-Whitney U test for independent samples and Spearman correlation, with statistical significance of P < 0.05.

RESULTS

Serum Sfrp5 concentration continually increased through the stages of CKD progression, whereas serum Wnt5a concentration presented its highest levels in stage 3 CKD. Negative correlations between estimated glomerular filtration rate (eGFR) and serum concentrations of Sfrp5 (r = -0434, P = 0.001) and Wnt5a (r = -0481, P = 0.001) were found.

CONCLUSIONS

There were negative correlations between serum Sfrp5 and Wnt5a concentrations and eGFR at each stage of CKD, with higher levels in female patients. This phenomenon suggests that Sfrp5 and Wnt5a might be involved in development and evolution towards end-stage renal disease.

Macrophages as an Emerging Source of Wnt Ligands: Relevance in Mucosal Integrity

The Wnt signaling pathway is a conserved pathway involved in important cellular processes such as the control of embryonic development, cellular polarity, cellular migration, and cell proliferation. In addition to playing a central role during embryogenesis, this pathway is also an essential part of adult homeostasis. Indeed, it controls the proliferation of epithelial cells in different organs such as intestine, lung, and kidney, and guarantees the maintenance of the mucosa in physiological conditions. The origin of this molecular pathway is the binding between Wnt ligands (belonging to a family of 19 different homologous secreted glycoproteins) and their specific membrane receptors, from the Frizzled receptor family. This specific interaction triggers the activation of the signaling cascade, which in turn activates or suppresses the expression of different genes in order to change the behavior of the cell. On the other hand, alterations of this pathway have been described in pathological conditions such as inflammation, fibrosis, and cancer. In recent years, macrophages-among other cell types-have emerged as a potential source of Wnt ligands. Due to their high plasticity, macrophages, which are central to the innate immune response, are capable of adopting different phenotypes depending on their microenvironment. In the past, two different phenotypes were described: a proinflammatory phenotype-M1 macrophages-and an anti-inflammatory phenotype-M2 macrophages-and a selective expression of Wnt ligands has been associated with said phenotypes. However, nowadays it is assumed that macrophages in vivo move through a continual spectrum of functional phenotypes. In both physiological and pathological (inflammation, fibrosis and cancer) conditions, the accumulation and polarization of macrophages conditions the future of the tissue, facilitating various scenarios, such as resolution of inflammation, activation of fibrosis, and cancer development due to the modulation of the Wnt signaling pathway, in autocrine and paracrine manner. In this work, we provide an overview of studies that have explored the role of macrophages and how they act as a source of Wnt ligands and as mediators of mucosal integrity.

Raloxifene inhibits adipose tissue inflammation and adipogenesis through Wnt regulation in ovariectomized rats and 3 T3-L1 cells

BACKGROUND

Loss of ovarian function, as in menopause or after ovariectomy (OVX), is closely associated with obesity and white adipose tissue (WAT) inflammation. Estrogen replacement protects against postmenopausal obesity but increases the risks of carcinogenesis. In the present study, we investigated the effects of long-term treatment of raloxifene (RAL), a selective estrogen receptor modulator, on the features of estrogen deficiency-induced obesity and explored the involvement of canonical and non-canonical Wnt regulation in vivo and in vitro.

METHODS

Adult female rats received bilateral OVX and divided into 5 groups: (1) Sham, (2) OVX, (3) OVX + E₂: OVX rats were administered with E₂ (50 μg/kg, s.c., 3 times/week), (4) OVX + RAL: OVX rats were treated with RAL (gavage, 1 mg/kg/day) suspended in 0.8% carboxymethylcellulose (CMC), (5) OVX + CMC: 0.8% CMC as vehicle control. All treatments were given for 8 weeks beginning at 1 week after OVX. In 3 T3-L1 cells, the effects of RAL on adipogenesis and lipopolysaccharide (LPS)-induced inflammation were evaluated.

RESULTS

Treatment with RAL significantly decreased body weight, visceral fat pad mass, adipocyte size and plasma levels of glucose but increased plasma adiponectin. RAL reduced the elevation of HIF-1α, VEGF-A and proinflammatory cytokines (MCP-1 and TNF-α) expression by inhibition of NF-κB p65 and JNK cascades in retroperitoneal WAT. This anti-inflammatory capacity of RAL may result from upregulation of secreted frizzle-related protein 5 (SFRP5), an adipokine that repressed Wnt5a signaling. Furthermore, RAL inhibited adipogenic factors such as PPAR-γ, C/EBP-α, and FABP4, and preserved canonical Wnt10b/β-catenin protein expression. In 3 T3-L1 adipocytes, RAL (20 μM) diminished lipid accumulation and inhibited adipogenic factors accompanied with the induction of β-catenin, which were effectively reversed by the β-catenin inhibitor IWR-1-endo. In addition, RAL reduced LPS-induced NF-κB p65 and p-IκB expression as well as TNF-α secretion. Suppression of SFRP5 by small interfering RNA significantly abrogated the anti-inflammatory effects of RAL.

CONCLUSIONS

Distinct activation of canonical β-catenin on inhibition of adipogenesis and non-canonical SFRP5 on suppression of WAT inflammation may contribute to the beneficial effects of RAL. Therefore, this study provides a rationale for the therapeutic potential of RAL for postmenopausal obesity.

Secreted frizzled-related protein 5 serum levels in human periodontitis-A nested case-control study

AIM

Recombinant secreted frizzled-related protein 5 (sFRP5) improved periodontal status in mice. Thus, this study aimed to investigate this finding in human periodontitis using an epidemiological approach.

MATERIALS AND METHODS

sFRP5 and wnt5a concentrations were determined in human serum from the Food Chain Plus cohort using ELISAs. A total of 128 patients with periodontitis and tooth loss and 245 patients with periodontitis without tooth loss were compared to 373 sex-, smoker-, age- and BMI-matched individuals in a nested case-control design.

RESULTS

Systemic sFRP5 serum levels were significantly lower in patients with periodontitis and tooth loss (2.5 [0.0-10.4] ng/ml, median [IQR]) compared to patients with periodontitis without tooth loss (6.0 [2.5-15.8] ng/ml, median [IQR], p = 0.04] and matched controls (7.0 [2.5-18.3] ng/ml, median [IQR], p = 0.02). No significant differences in sFRP5 serum levels were found among patients with periodontitis without tooth loss (6.0 [2.5-15.8] ng/ml, median [IQR]) and controls (3.1 [0.0-10.6] ng/ml, median [IQR], p = 0.06).

CONCLUSIONS

sFRP5 might serve as a novel biomarker for periodontitis severity. Modulating the inflammatory background of severe forms of periodontitis, in the time of precision medicine, needs to be revealed in further studies.

Adipose-derived stromal/stem cells from different adipose depots in obesity development

The increasing prevalence of obesity is alarming because it is a risk factor for cardiovascular and metabolic diseases (such as type 2 diabetes). The occurrence of these comorbidities in obese patients can arise from white adipose tissue (WAT) dysfunctions, which affect metabolism, insulin sensitivity and promote local and systemic inflammation. In mammals, WAT depots at different anatomical locations (subcutaneous, preperitoneal and visceral) are highly heterogeneous in their morpho-phenotypic profiles and contribute differently to homeostasis and obesity development, depending on their ability to trigger and modulate WAT inflammation. This heterogeneity is likely due to the differential behavior of cells from each depot. Numerous studies suggest that adipose-derived stem/stromal cells (ASC; referred to as adipose progenitor cells, in vivo) with depot-specific gene expression profiles and adipogenic and immunomodulatory potentials are keys for the establishment of the morpho-functional heterogeneity between WAT depots, as well as for the development of depot-specific responses to metabolic challenges. In this review, we discuss depot-specific ASC properties and how they can contribute to the pathophysiology of obesity and metabolic disorders, to provide guidance for researchers and clinicians in the development of ASC-based therapeutic approaches.

Role of wnt5a in Metabolic Inflammation in Humans

CONTEXT

Common nutrition-associated diseases like obesity and type 2 diabetes are linked to chronic low-grade inflammation. The secreted glycopeptide wingless-type mouse mammary tumor virus integration site family member 5a (wnt5a) has been implicated in metabolic inflammation in rodent models, suggesting a potential treatment target. Data on the role of wnt5a in human physiology have yielded conflicting results.

OBJECTIVE

Serum concentrations of wnt5a were measured in a cross-sectional cohort of 896 people to gain deeper insights into wnt5a physiology.

DESIGN

Serum concentrations of wnt5a were measured by ELISA and related to several phenotyping and genotyping data. In vitro experiments were performed in THP-1 macrophages to examine potential molecular mechanisms.

RESULTS

Wnt5a levels were significantly positively correlated to IL-6 and triglyceride levels. In subjects with diabetes, wnt5a levels were elevated and significantly correlated with fasting plasma glucose concentrations. Although wnt5a levels were not influenced by common single-nucleotide polymorphisms in the human wnt5a gene, environmental factors significantly altered wnt5a concentrations, as follows: (1) wnt5a levels were reduced in subjects with high nutritional load of the long-chain eicosatetraenoic acid independent of the total caloric intake and overall composition of the macronutrients, and (2) wnt5a levels were lower in humans with a high gut microbiome α diversity. In vitro experiments revealed that stimulation of the IL-6 receptor or the long-chain fatty acid receptor GPR40 directly affected wnt5a expression in human macrophages.

CONCLUSION

Our data suggest that wnt5a is important in linking inflammation to metabolism. The nutrition and the microbiome might be interesting targets to prevent and/or treat wnt5a-mediated metabolic inflammation.

Insight into the development of obesity: functional alterations of adipose-derived mesenchymal stem cells

Obesity is associated with a variety of disorders including cardiovascular diseases, diabetes mellitus and cancer. Obesity changes the composition and structure of adipose tissue, linked to pro-inflammatory environment, endocrine/metabolic dysfunction, insulin resistance and oxidative stress. Adipose-derived mesenchymal stem cells (ASCs) have multiple functions like cell renewal, spontaneous repair and homeostasis in adipose tissue. In this review article, we have summarized the recent data highlighting that ASCs in obesity are defective in various functionalities and properties including differentiation, angiogenesis, motility, multipotent state, metabolism and immunomodulation. Inflammatory milieu, hypoxia and abnormal metabolites in obese tissue are crucial for impairing the functions of ASCs. Further work is required to explore the precise molecular mechanisms underlying its alterations and impairments. Based on these data, we suggest that deregulated ASCs, possibly also other mesenchymal stem cells, are important in promoting the development of obesity. Restoration of ASCs/mesenchymal stem cells might be an additional strategy to combat obesity and its associated diseases.

The role of infiltrating immune cells in dysfunctional adipose tissue

Adipose tissue (AT) dysfunction, characterized by loss of its homeostatic functions, is a hallmark of non-communicable diseases. It is characterized by chronic low-grade inflammation and is observed in obesity, metabolic disorders such as insulin resistance and diabetes. While classically it has been identified by increased cytokine or chemokine expression, such as increased MCP-1, RANTES, IL-6, interferon (IFN) gamma or TNFα, mechanistically, immune cell infiltration is a prominent feature of the dysfunctional AT. These immune cells include M1 and M2 macrophages, effector and memory T cells, IL-10 producing FoxP3+ T regulatory cells, natural killer and NKT cells and granulocytes. Immune composition varies, depending on the stage and the type of pathology. Infiltrating immune cells not only produce cytokines but also metalloproteinases, reactive oxygen species, and chemokines that participate in tissue remodelling, cell signalling, and regulation of immunity. The presence of inflammatory cells in AT affects adjacent tissues and organs. In blood vessels, perivascular AT inflammation leads to vascular remodelling, superoxide production, endothelial dysfunction with loss of nitric oxide (NO) bioavailability, contributing to vascular disease, atherosclerosis, and plaque instability. Dysfunctional AT also releases adipokines such as leptin, resistin, and visfatin that promote metabolic dysfunction, alter systemic homeostasis, sympathetic outflow, glucose handling, and insulin sensitivity. Anti-inflammatory and protective adiponectin is reduced. AT may also serve as an important reservoir and possible site of activation in autoimmune-mediated and inflammatory diseases. Thus, reciprocal regulation between immune cell infiltration and AT dysfunction is a promising future therapeutic target.

Circulating secreted frizzled-related protein 5 and chronic kidney disease in patients with acute ST-segment elevation myocardial infarction

Secreted frizzled-related protein-5 (Sfrp5) known as secreted antagonist binds to Wnt protein. It has been shown to be downregulated by histone acetylation and promoter methylation, and to function as a tumor suppressor gene by inducing apoptosis in renal cell cancer cells. However, its relationship with chronic kidney disease (CKD) has not been well studied. Our objective was to investigate the effect of plasma Sfrp5 levels in subjects with and without CKD. Plasma Sfrp5 levels were determined by enzyme-linked immunosorbent assays in 196 consecutive patients with acute ST-segment elevation myocardial infarction (STEMI). CKD was defined as an estimated glomerular filtration rate (eGFR) <60 ml/min per 1.73 m². For the purpose of this study, stage 1 or 2 CKD patients (eGFR ≥ 60 ml/min per 1.73 m²) were classified as not having CKD. With increasing Sfrp5 tertiles, the patients had higher frequencies of hypertension, stage 4 or 5 CKD, and waist-to-hip ratio, incrementally lower eGFRs and serum hemoglobin levels, and higher levels of blood urine nitrogen (BUN), creatinine, and adiponectin. Multivariate logistic regression analysis showed that an increased plasma Sfrp5 level was independently associated with CKD for all subjects (adjusted odds ratio (OR), 1.08; 95% confidence interval (CI), 1.02-1.14; p = 0.011). Sfrp5 was also significantly positively related to BUN, creatinine, and adiponectin, and significantly negatively related to eGFR and hemoglobin. When the patients were stratified by age, plasma Sfrp5 level was independently related to CKD for patients >65 years old (adjusted OR, 1.10; 95% CI, 1.00-1.20; p = 0.045), however, the association was not significant for those <65 years old. In addition, Sfrp5 was significantly positively related to BUN, creatinine, and adiponectin, and significantly negatively related to eGFR and hemoglobin in patients >65 years old. Our results suggest that Sfrp5 may play a role in the pathogenesis of CKD in acute STEMI patients who are older than 65 years.

Interrelationship of canonical and non-canonical Wnt signalling pathways in chronic metabolic diseases

Chronic diseases account for approximately 45% of all deaths in developed countries and are particularly prevalent in countries with the most sophisticated and robust public health systems. Chronic metabolic diseases, specifically lifestyle-related diseases pertaining to diet and exercise, continue to be difficult to treat clinically. The most prevalent of these chronic metabolic diseases include obesity, diabetes, non-alcoholic fatty liver disease, chronic kidney disease and cardiovascular disease and will be the focus of this review. Wnt proteins are highly conserved glycoproteins best known for their role in development and homeostasis of tissues. Given the importance of Wnt signalling in homeostasis, aberrant Wnt signalling likely regulates metabolic processes and may contribute to the development of chronic metabolic diseases. Expression of Wnt proteins and dysfunctional Wnt signalling has been reported in multiple chronic diseases. It is interesting to speculate about an interrelationship between the Wnt signalling pathways as a potential pathological mechanism in chronic metabolic diseases. The aim of this review is to summarize reported findings on the contrasting roles of Wnt signalling in lifestyle-related chronic metabolic diseases; specifically, the contribution of Wnt signalling to lipid accumulation, fibrosis and chronic low-grade inflammation.

Hypothalamic Inflammation in Human Obesity Is Mediated by Environmental and Genetic Factors

Obesity is associated with hypothalamic inflammation (HI) in animal models. In the current study, we examined the mediobasal hypothalamus (MBH) of 57 obese human subjects and 54 age- and sex- matched nonobese control subjects by MRI and analyzed the T2 hyperintensity as a measure of HI. Obese subjects exhibited T2 hyperintensity in the left but not the right MBH, which was strongly associated with systemic low-grade inflammation. MRS revealed the number of neurons in the left hypothalamic region to be similar in obese versus control subjects, suggesting functional but not structural impairment due to the inflammatory process. To gain mechanistic insights, we performed nutritional analysis and 16S rDNA microbiome sequencing, which showed that high-fat diet induces reduction of Parasutterella sp. in the gut, which is significantly correlated with MBH T2 hyperintensity. In addition to these environmental factors, we found subjects carrying common polymorphisms in the JNK or the MC4R gene to be more susceptible to HI. Finally, in a subgroup analysis, bariatric surgery had no effect on MBH T2 hyperintensity despite inducing significant weight loss and improvement of peripheral insulin sensitivity. In conclusion, obesity in humans is associated with HI and disturbances in the gut-brain axis, which are influenced by both environmental and genetic factors.

The adipose tissue-derived stromal vascular fraction cells from lipedema patients: Are they different?

BACKGROUND AIMS

Lipedema is a hormone-related disease of women characterized by enlargement of the extremities caused by subcutaneous deposition of adipose tissue. In healthy patients application of autologous adipose tissue-derived cells has shown great potential in several clinical studies for engrafting of soft tissue reconstruction in recent decades. The majority of these studies have used the stromal vascular fraction (SVF), a heterogeneous cell population containing adipose-derived stromal/stem cells (ASC), among others. Because cell identity and regenerative properties might be affected by the health condition of patients, we characterized the SVF cells of 30 lipedema patients in comparison to 22 healthy patients.

METHODS

SVF cells were analyzed regarding cell yield, viability, adenosine triphosphate content, colony forming units and proliferative capacity, as well as surface marker profile and differentiation potential in vitro.

RESULTS

Our results demonstrated a significantly enhanced SVF cell yield isolated from lipedema compared with healthy patients. In contrast, the adipogenic differentiation potential of SVF cells isolated from lipedema patients was significantly reduced compared with healthy patients. Interestingly, expression of the mesenchymal marker CD90 and the endothelial/pericytic marker CD146 was significantly enhanced when isolated from lipedema patients.

DISCUSSION

The enhanced number of CD90⁺ and CD146⁺ cells could explain the increased cell yield because the other tested surface marker were not reduced in lipedema patients. Because the cellular mechanism and composition in lipedema is largely unknown, our findings might contribute to a better understanding of its etiology.

SNP-SNP interactions between WNT4 and WNT5A were associated with obesity related traits in Han Chinese Population

Considering the biological roles of WNT4 and WNT5A involved in adipogenesis, we aimed to investigate whether SNPs in WNT4 and WNT5A contribute to obesity related traits in Han Chinese population. Targeted genomic sequence for WNT4 and WNT5A was determined in 100 Han Chinese subjects and tag SNPs were selected. Both single SNP and SNP × SNP interaction association analyses with body mass index (BMI) were evaluated in the 100 subjects and another independent sample of 1,627 Han Chinese subjects. Meta-analyses were performed and multiple testing corrections were carried out using the Bonferroni method. Consistent with the Genetic Investigation of ANthropometric Traits (GIANT) dataset results, we didn’t detect significant association signals in single SNP association analyses. However, the interaction between rs2072920 and rs11918967, was associated with BMI after multiple testing corrections (combined P = 2.20 × 10⁻⁴). The signal was also significant in each contributing data set. SNP rs2072920 is located in the 3′-UTR of WNT4 and SNP rs11918967 is located in the intron of WNT5A. Functional annotation results revealed that both SNPs might be involved in transcriptional regulation of gene expression. Our results suggest that a combined effect of SNPs via WNT4-WNT5A interaction may affect the variation of BMI in Han Chinese population.

Metabolic Adaptation in Obesity and Type II Diabetes: Myokines, Adipokines and Hepatokines

Obesity and type II diabetes are characterized by insulin resistance in peripheral tissues. A high caloric intake combined with a sedentary lifestyle is the leading cause of these conditions. Whole-body insulin resistance and its improvement are the result of the combined actions of each insulin-sensitive organ. Among the fundamental molecular mechanisms by which each organ is able to communicate and engage in cross-talk are cytokines or peptides which stem from secretory organs. Recently, it was reported that several cytokines or peptides are secreted from muscle (myokines), adipose tissue (adipokines) and liver (hepatokines) in response to certain nutrition and/or physical activity conditions. Cytokines exert autocrine, paracrine or endocrine effects for the maintenance of energy homeostasis. The present review is focused on the relationship and cross-talk amongst muscle, adipose tissue and the liver as secretory organs in metabolic diseases.

Adipose tissue macrophages: going off track during obesity

Inflammation originating from the adipose tissue is considered to be one of the main driving forces for the development of insulin resistance and type 2 diabetes in obese individuals. Although a plethora of different immune cells shapes adipose tissue inflammation, this review is specifically focused on the contribution of macrophages that reside in adipose tissue in lean and obese conditions. Both conventional and tissue-specific functions of adipose tissue macrophages (ATMs) in lean and obese adipose tissue are discussed and linked with metabolic and inflammatory changes that occur during the development of obesity. Furthermore, we will address various circulating and adipose tissue-derived triggers that may be involved in shaping the ATM phenotype and underlie ATM function in lean and obese conditions. Finally, we will highlight how these changes affect adipose tissue inflammation and may be targeted for therapeutic interventions to improve insulin sensitivity in obese individuals.

Revisiting the adipocyte: a model for integration of cytokine signaling in the regulation of energy metabolism

Adipose tissue constitutes an extremely active endocrine organ with a network of signaling pathways enabling the organism to adapt to a wide range of different metabolic challenges, such as starvation, stress, infection, and short periods of gross energy excess. The functional pleiotropism of adipose tissue relies on its ability to synthesize and release a huge variety of hormones, cytokines, complement and growth factors, extracellular matrix proteins, and vasoactive factors, collectively termed adipokines. Obesity is associated with adipose tissue dysfunction leading to the onset of several pathologies including type 2 diabetes, dyslipidemia, nonalcoholic fatty liver, or hypertension, among others. The mechanisms underlying the development of obesity and its associated comorbidities include the hypertrophy and/or hyperplasia of adipocytes, adipose tissue inflammation, impaired extracellular matrix remodeling, and fibrosis together with an altered secretion of adipokines. Recently, the potential role of brown and beige adipose tissue in the protection against obesity has been also recognized. In contrast to white adipocytes, which store energy in the form of fat, brown and beige fat cells display energy-dissipating capacity through the promotion of triacylglycerol clearance, glucose disposal, and generation of heat for thermogenesis. Identification of the morphological and molecular changes in white, beige, and brown adipose tissue during weight gain is of utmost relevance for the identification of pharmacological targets for the treatment of obesity and its associated metabolic diseases.

Dickkopf-1 promotes the differentiation and adipocytokines secretion via canonical Wnt signaling pathway in primary cultured human preadipocytes

OBJECTIVE

Dickkopf-1, a newly recognized antagonist for canonical Wnt signaling, is secreted in the early stage of human adipose-derived stem cells (ASCs) adipogenic differentiation. This study was aimed to investigate whether human recombinant DKK-1 (rhDKK-1) could affect the differentiation and metabolism as well as adipocytokines secretion in primary cultured human ASCs.

METHODS

Human ASCs were isolated from omental adipose tissue and induced to adipogenic differentiation in the absence or presence of Wnt signaling antagonist rhDKK-1 and agonist SB216763, respectively. mRNA and protein expression profiles of adipogenic factors during the differentiation process were analyzed using quantitative RT-PCR and Western blotting. Adipocytokines secretion levels in the culture medium were measured by ELISA method.

RESULTS

Our results showed that DKK-1 was already expressed during the early stage of adipogenesis and reached the peak on the 9th day. Exogenous rhDKK-1 exposure accelerated the differentiation by up-regulating PPAR-γ and C/EBP-α, down-regulating Wnt3a, Wnt10b and β-catenin, without affecting non-canonical Wnt signaling marker (Wnt5a). In addition, rhDKK-1 treatment increased the secretion of leptin, RBP4, TNF-α and adiponectin during differentiation. rhDKK-1 treatment also significantly increased the intracellular accumulation of lipids and lipolysis. Thus, Wnt signal pathway agonist SB216763 down-regulated DKK-1 transcriptional and secretion levels during adipogenic process.

CONCLUSIONS

Our results suggest that rhDKK-1 could promote ASCs differentiation and increase adipocytokines secretion via canonical Wnt signaling pathway.

The wingless-related integration site-5a/secreted frizzled-related protein-5 system is dysregulated in human sepsis

Sepsis and type 2 diabetes exhibit insulin resistance as a common phenotype. In type 2 diabetes we and others have recently provided evidence that alterations of the proinflammatory wingless-related integration site (wnt)-5a/anti-inflammatory secreted frizzled-related protein (sFRP)-5 system are involved in the pathogenesis of insulin resistance. The aim of the present study was to investigate whether this novel cytokine system is dysregulated in human sepsis, which may indicate a potential mechanism linking inflammation to metabolism. In this single-centre prospective observational study, critically ill adult septic patients were examined and proinflammatory wnt5a and wnt5a inhibitor sFRP5 were measured in serum samples by enzyme-linked immunosorbent assay (ELISA) at admission to the intensive care unit (ICU) and 5 days later. Sixty sepsis patients were included, and 30 healthy individuals served as controls. Wnt5a levels were found to be increased significantly in septic patients compared to healthy controls (2·21 ± 0·33 versus 0·32 ± 0·03 ng/ml, P < 0·0001). In contrast, sFRP5 was not altered significantly in septic patients (19·72 ± 3·06 versus 17·48 ± 6·38 ng/ml, P = 0·07). On admission to the ICU, wnt5a levels exhibited a significant positive correlation with the leucocyte count (rs  = 0·3797, P = 0·004). Interestingly, in patients recovering from sepsis, wnt5a levels declined significantly within 5 days (2·17 ± 0·38-1·03 ± 0·28 ng/ml, P < 0·01). In contrast, if sepsis was worsening, wnt5a levels increased in the same time-period by trend (2·34 ± 0·59-3·25 ± 1·02 ng/ml, P > 0·05). sFRP5 levels did not change significantly throughout the study period. The wnt5a/sFRP5 system is altered in human sepsis and might therefore be of interest for future studies on molecular pathophysiology of this common human disease.

Granulocyte/Macrophage Colony-stimulating Factor-dependent Dendritic Cells Restrain Lean Adipose Tissue Expansion

The physiological roles of macrophages and dendritic cells (DCs) in lean white adipose tissue homeostasis have received little attention. Because DCs are generated from bone marrow progenitors in the presence of granulocyte/macrophage colony-stimulating factor (GM-CSF), we used GM-CSF-deficient (Csf2(-/-)) mice fed a low fat diet to test the hypothesis that adipose tissue DCs regulate the development of adipose tissue. At 4 weeks of age, Csf2(-/-) mice had 75% fewer CD45(+)Cd11b(+)Cd11c(+)MHCII(+) F4/80(-) DCs in white adipose tissue than did wild-type controls. Furthermore, the Csf2(-/-) mice showed a 30% increase in whole body adiposity, which persisted to adulthood. Adipocytes from Csf2(-/-) mice were 50% larger by volume and contained higher levels of adipogenesis gene transcripts, indicating enhanced adipocyte differentiation. In contrast, adipogenesis/adipocyte lipid accumulation was inhibited when preadipocytes were co-cultured with CD45(+)Cd11b(+)Cd11c(+)MHCII(+)F4/80(-) DCs. Medium conditioned by DCs, but not by macrophages, also inhibited adipocyte lipid accumulation. Proteomic analysis revealed that matrix metalloproteinase 12 and fibronectin 1 were greatly enriched in the medium conditioned by DCs compared with that conditioned by macrophages. Silencing fibronectin or genetic deletion of matrix metalloproteinase 12 in DCs partially reversed the inhibition of adipocyte lipid accumulation. Our observations indicate that DCs residing in adipose tissue play a critical role in suppressing normal adipose tissue expansion.

Stromal-vascular fraction content and adipose stem cell behavior are altered in morbid obese and post bariatric surgery ex-obese women

INTRODUCTION

Subcutaneous adipose tissue is an interesting source of autologous stem cells with a fundamental role in the pathophysiology of obesity, metabolic syndromes and insulin resistance. We hypothesize that obesity could alter the stromal-vascular fraction (SVF) and adipose stem cell (ASCs) functions, which could compromise its regenerative behavior. Furthermore, we aimed to evaluate whether ASCs derived from post bariatric surgery ex-obese women maintain their functions in a similar fashion as do those from individuals who have never been obese.

METHODS

The SVF of subcutaneous adipose tissue from control (n = 6, body mass index - BMI - 27.5 ± 0.5 kg/m(2)), obese (n = 12, BMI 46.2 ± 5.1 kg/m(2)) and post bariatric surgery ex-obese (n = 7, initial BMI 47.8 ± 1.3 kg/m(2); final BMI 28.1 ± 1.1 kg/m(2)) women were isolated and evaluated by flow cytometry. ASCs were tested for lipid accumulation by perilipin, adipose differentiation-related protein (ADRP) and Oil Red O staining after adipogenic stimulus. The cytokines secreted by the ASCs and after lipid accumulation induction were also evaluated.

RESULTS

The subcutaneous adipose tissue of obese and post bariatric surgery ex-obese women was enriched in pericytes (p = 0.0345). The number of supra-adventitial cells was not altered in the obese patients, but it was highly enriched in the post bariatric surgery ex-obese women (p = 0.0099). The ASCs of the post bariatric surgery ex-obese patients secreted more MCP-1 (monocyte chemoattractant protein-1; p = 0.0078). After lipid accumulation induction, the ASCs of the patients in all groups secreted less IL-6 than the ASCs with no adipogenic stimulus (p < 0.0001). Obese ASCs with lipid accumulation secreted the highest amount of IL-6 (p < 0.001) whereas the ASCs from the controls secreted the highest amount of adiponectin (p < 0.0001). The ASCs from the post bariatric surgery ex-obese patients showed the highest levels of lipid accumulation whereas those from the obese women had the lowest levels (p < 0.0001).

CONCLUSIONS

SVF content and ASC behavior are altered in the subcutaneous adipose tissue of morbid obese women; these changes are not completely restored after bariatric surgery-induced weight loss. The cellular alterations described in this study could affect the regenerative effects of adipose stem cells. Further investigations are required to avoid jeopardizing the development of autologous stem cell-based therapies.

Noncanonical Wnt signaling promotes obesity-induced adipose tissue inflammation and metabolic dysfunction independent of adipose tissue expansion

Adipose tissue dysfunction plays a pivotal role in the development of insulin resistance in obese individuals. Cell culture studies and gain-of-function mouse models suggest that canonical Wnt proteins modulate adipose tissue expansion. However, no genetic evidence supports a role for endogenous Wnt proteins in adipose tissue dysfunction, and the role of noncanonical Wnt signaling remains largely unexplored. Here we provide evidence from human, mouse, and cell culture studies showing that Wnt5a-mediated, noncanonical Wnt signaling contributes to obesity-associated metabolic dysfunction by increasing adipose tissue inflammation. Wnt5a expression is significantly upregulated in human visceral fat compared with subcutaneous fat in obese individuals. In obese mice, Wnt5a ablation ameliorates insulin resistance, in parallel with reductions in adipose tissue inflammation. Conversely, Wnt5a overexpression in myeloid cells augments adipose tissue inflammation and leads to greater impairments in glucose homeostasis. Wnt5a ablation or overexpression did not affect fat mass or adipocyte size. Mechanistically, Wnt5a promotes the expression of proinflammatory cytokines by macrophages in a Jun NH2-terminal kinase-dependent manner, leading to defective insulin signaling in adipocytes. Exogenous interleukin-6 administration restores insulin resistance in obese Wnt5a-deficient mice, suggesting a central role for this cytokine in Wnt5a-mediated metabolic dysfunction. Taken together, these results demonstrate that noncanonical Wnt signaling contributes to obesity-induced insulin resistance independent of adipose tissue expansion.

Transcriptomic analysis of human polarized macrophages: more than one role of alternative activation?

BACKGROUND

Macrophages are a heterogeneous cell population which in response to the cytokine milieu polarize in either classically activated macrophages (M1) or alternatively activated macrophages (M2). This plasticity makes macrophages essential in regulating inflammation, immune response and tissue remodeling and a novel therapeutic target in inflammatory diseases such as atherosclerosis. The aim of the study was to describe the transcriptomic profiles of differently polarized human macrophages to generate new hypotheses on the biological function of the different macrophage subtypes.

METHODS AND RESULTS

Polarization of circulating monocytes/macrophages of blood donors was induced in vitro by IFN-γ and LPS (M1), by IL-4 (M2a), and by IL-10 (M2c). Unstimulated cells (RM) served as time controls. Gene expression profile of M1, M2a, M2c and RM was assessed at 6, 12 and 24h after polarization with Whole Human Genome Agilent Microarray technique. When compared to RM, M1 significantly upregulated pathways involved in immunity and inflammation, whereas M2a did the opposite. Conversely, decreased and increased expression of mitochondrial metabolism, consistent with insulin resistant and insulin sensitive patterns, was seen in M1 and M2a, respectively. The time sequence in the expression of some pathways appeared to have some specific bearing on M1 function. Finally, canonical and non-canonical Wnt genes and gene groups, promoting inflammation and tissue remodeling, were upregulated in M2a compared to RM.

CONCLUSION

Our data in in vitro polarized human macrophages: 1. confirm and extend known inflammatory and anti-inflammatory gene expression patterns; 2. demonstrate changes in mitochondrial metabolism associated to insulin resistance and insulin sensitivity in M1 and M2a, respectively; 3. highlight the potential relevance of gene expression timing in M1 function; 4. unveil enhanced expression of Wnt pathways in M2a suggesting a potential dual (pro-inflammatory and anti-inflammatory) role of M2a in inflammatory diseases.

Wnt5a signaling increases IL-12 secretion by human dendritic cells and enhances IFN-γ production by CD4+ T cells

Wnt5a is a secreted pleiotropic glycoprotein produced in an inflammatory state by a wide spectrum of ubiquitous cell populations. Recently, we demonstrated that Wnt5a skews the differentiation of human monocyte derived dendritic cells (moDCs) to a tolerogenic functional state. In this study we focus our interest on the role of this Wnt ligand after DC differentiation, during their maturation and function. We show that the expression of Wnt receptors is tightly regulated during the life cycle of DCs suggesting a differential responsiveness to Wnt signaling conditioned by their differentiation stage and the maturational stimuli. Furthermore, we confirm that Wnt5a is the main non-canonical Wnt protein expressed by DCs and its production increases upon specific stimuli. Exogenous Wnt5a improved the endocytic capacity of immature DCs but it is not a stimulatory signal on its own, slightly affecting the maturation and function of DCs. However, knocking down Wnt5a gene expression in maturing DCs demonstrates that DC-derived Wnt5a is necessary for normal IL-12 secretion and plays a positive role during the development of Th1 responses. Wnt5a acts both in autocrine and paracrine ways. Thus, human naive CD4(+) T cells express Wnt receptors and, the addition of Wnt5a during CD3/CD28 stimulation enhances IL-2 and IFN-γ production. Taken together these results suggest a time-dependent role for Wnt5a during inflammatory responses conditioned by the differentiation stage of cellular targets.

Wnt5a: a player in the pathogenesis of atherosclerosis and other inflammatory disorders

OBJECTIVE

The objective of this article is to review the current literature on Wnt5a and its signaling mechanism, along with its role in atherosclerosis. In addition, the significance of Wnt5a as a diagnostic marker and a potential therapeutic target is reviewed. Wnt5a, a secreted glycoprotein, belongs to a family of highly conserved proteins that regulate important processes such as cell fate specification, embryonic development, cell proliferation, migration, and differentiation in a variety of organisms. The complexity of Wnt5a signaling lies in the fact that Wnt5a can bind to different classes of frizzled receptors, receptor tyrosine kinase-like orphan receptor 2, as well as co-receptors such as low density lipoprotein receptor-related protein 5/6. Wnt5a signals primarily through the non-canonical pathway, where it mediates cell proliferation, adhesion, and movement. However, the role of Wnt5a in canonical signaling is still unresolved. Depending on the receptor availability, Wnt5a can serve to activate or inhibit the canonical Wnt signaling pathway. Due to the promiscuous nature of Wnt5a, it has been extremely difficult to fully understand its signaling mechanism. Wnt5a has recently emerged as a macrophage effector molecule that triggers inflammation. Perturbations in Wnt5a signaling have been reported in several inflammatory diseases, particularly in sepsis, rheumatoid arthritis, and atherosclerosis.

CONCLUSION

Both existing and emerging evidence suggests that the expression of Wnt5a is always up-regulated in these, and possibly other inflammatory disorders. This knowledge can be useful for targeting Wnt5a and/or its receptor and downstream signaling molecules for therapeutic intervention in inflammatory disorders.

Activation of noncanonical Wnt signaling through WNT5A in visceral adipose tissue of obese subjects is related to inflammation

CONTEXT

Wingless-type mouse mammary tumor virus integration site family (WNT)-5A is a glycoprotein involved in the regulation of the inflammatory response by activating the noncanonical Wnt signaling pathway. Secreted frizzled-related protein (SFRP)-5 acts as a decoy receptor that binds and sequesters WNT5A, preventing activation of frizzled receptors and attenuating the noncanonical Wnt signaling.

OBJECTIVE

The aim of the study was to evaluate the involvement of WNT5A and SFRP5 in obesity and obesity-related comorbidities as well as to explore their effect in visceral adipose tissue inflammation.

PATIENTS AND METHODS

Samples obtained from 90 subjects were used. Circulating and gene expression levels of WNT5A and SFRP5 were analyzed in different metabolic tissues. The effect of TNF-α and lipopolysaccharide on the transcript levels of WNT5A and SFRP5 in adipocytes was explored. We also investigated whether WNT5A itself can activate an inflammatory response.

RESULTS

Increased circulating levels of WNT5A in obese patients (P < .05) were decreased (P < .001) after gastric bypass. In this line, WNT5A mRNA in visceral adipose tissue was increased (P < .05) in obese patients with gene expression levels of SFRP5 being down-regulated (P < .05). WNT5A mRNA expression was significantly enhanced (P < .01) by lipopolysaccharide and TNF-α treatment, whereas no effects were found in SFRP5 gene expression levels. Furthermore, exogenous WNT5A induced (P < .05) IL-6, IL1B, MMP2, MMP9, and SSP1 mRNA expression in human adipocyte cultures.

CONCLUSIONS

Activation of noncanonical Wnt signaling through the up-regulation of WNT5A and down-regulation of SFRP5 may promote a proinflammatory state in visceral adipose tissue contributing to the development of obesity-associated comorbidities.

Balanced duo of anti-inflammatory SFRP5 and proinflammatory WNT5A in children

BACKGROUND

Secreted frizzled-related protein 5 (SFRP5) is an adipokine protecting against obesity-related insulin resistance and diabetes. SFRP5 binds to wingless type mouse mammary tumor virus (MMTV) integration site family member 5A (WNT5A) to improve insulin sensitivity. We performed the first study of SFRP5 and WNT5A simultaneously in children.

METHODS

Prepubertal children (n = 342) were assessed for circulating SFRP5 (all subjects) and circulating WNT5A (210 subjects), and associations were sought with metabolic markers. In conditioned media of adipose tissue explants from 12 additional children, SFRP5 and WNT5A were studied further.

RESULTS

The concentrations of SFRP5 and WNT5A correlated positively in serum and in conditioned media (all P < 0.001). Lower level of circulating SFRP5 (lowest quartile) was associated with higher BMI (15% increase, P < 0.0001) and lower level of high-molecular-weight adiponectin (26% decrease, P = 0.002). Circulating WNT5A related closely with insulin resistance assessed by the homeostasis model assessment for insulin resistance and hepatic markers (alanine transaminase and gamma glutamyl transpeptidase), particularly in children with lower circulating SFRP5 levels (all P < 0.004).

CONCLUSION

SFRP5 and WNT5A comprise a balanced duo that may regulate metabolic homeostasis in prepubertal children.

Macrophages and the regulation of adipose tissue remodeling

The ability of adipose tissue to adapt to a changing nutrient environment is critical to the maintenance of metabolic control. Nutrient excess and deficiency alter the shape of adipose tissue drastically and trigger many events that are collectively known as adipose tissue remodeling. Remodeling of adipose tissue involves more than adipocytes and is controlled by an extensive network of stromal cells and extracellular matrix proteins. Prominent players in this process are adipose tissue macrophages, which are a specialized leukocyte present in lean and obese states that contributes to adipose tissue inflammation. The interest in adipose tissue remodeling has been accelerated by the current epidemic of obesity and the chronic generation of signals that lead to expansion of adipose tissue. It is clear that evidence of dysfunctional remodeling events is a hallmark of obesity associated with metabolic disease. This review summarizes and highlights the recent work in this area and provides a framework in which to consider how adipose tissue macrophages contribute to the remodeling events in lean and obese states. Advancing our understanding of the involvement of macrophages in adipose tissue remodeling will promote one aspect of the new field of "immunometabolism," which connects control systems developed for regulation of immunity with those that control metabolism. It will also provide insight into how physiologic and pathophysiologic remodeling differs in adipose tissue and identify potential nodes for intervention to break the link between obesity and disease.

B Lymphocyte Stimulator (BLyS) is expressed in human adipocytes in vivo and is related to obesity but not to insulin resistance

Inflammation and metabolism have been shown to be evolutionary linked and increasing evidence exists that pro-inflammatory factors are involved in the pathogenesis of obesity and type 2 diabetes. Until now, most data suggest that within adipose tissue these factors are secreted by cells of the innate immune system, e. g. macrophages. In the present study we demonstrate that B lymphocyte stimulator (BLyS) is increased in human obesity. In contrast to several pro-inflammatory factors, we found the source of BLyS in human adipose tissue to be the adipocytes rather than immune cells. In grade 3 obese human subjects, expression of BLyS in vivo in adipose tissue is significantly increased (p<0.001). Furthermore, BLyS serum levels are elevated in grade 3 human obesity (862.5+222.0 pg/ml vs. 543.7+60.7 pg/ml in lean controls, p<0.001) and are positively correlated to the BMI (r = 0.43, p<0.0002). In the present study, bariatric surgery significantly altered serum BLyS concentrations. In contrast, weight loss due to a very-low-calorie-formula-diet (800 kcal/d) had no such effect. To examine metabolic activity of BLyS, in a translational research approach, insulin sensitivity was measured in human subjects in vivo before and after treatment with the human recombinant anti-BLyS antibody belimumab. Since BLyS is known to promote B-cell proliferation and immunoglobulin secretion, the present data suggest that adipocytes of grade 3 obese human subjects are able to activate the adaptive immune system, suggesting that in metabolic inflammation in humans both, innate and adaptive immunity, are of pathophysiological relevance.

Adipose tissue and its role in organ crosstalk

The discovery of adipokines has revealed adipose tissue as a central node in the interorgan crosstalk network, which mediates the regulation of multiple organs and tissues. Adipose tissue is a true endocrine organ that produces and secretes a wide range of mediators regulating adipose tissue function in an auto-/paracrine manner and important distant targets, such as the liver, skeletal muscle, the pancreas and the cardiovascular system. In metabolic disorders such as obesity, enlargement of adipocytes leads to adipose tissue dysfunction and a shift in the secretory profile with an increased release of pro-inflammatory adipokines. Adipose tissue dysfunction has a central role in the development of insulin resistance, type 2 diabetes, and cardiovascular diseases. Besides the well-acknowledged role of adipokines in metabolic diseases, and the increasing number of adipokines being discovered in the last years, the mechanisms underlying the release of many adipokines from adipose tissue remain largely unknown. To combat metabolic diseases, it is crucial to better understand how adipokines can modulate adipose tissue growth and function. Therefore, we will focus on adipokines with a prominent role in auto-/paracrine crosstalk within the adipose tissue such as RBP4, HO-1, WISP2, SFRPs and chemerin. To depict the endocrine crosstalk between adipose tissue with skeletal muscle, the cardiovascular system and the pancreas, we will report the main findings regarding the direct effects of adiponectin, leptin, DPP4 and visfatin on skeletal muscle insulin resistance, cardiovascular function and β-cell growth and function.

Low serum level of secreted frizzled-related protein 5, an anti-inflammatory adipokine, is associated with coronary artery disease

OBJECTIVE

Secreted frizzled-related protein 5 (SFRP5) is an anti-inflammatory adipokine that is associated with insulin resistance in animals. To extend these observations to humans, we investigated the association of serum SFRP5 levels in subjects with and without coronary artery disease (CAD).

METHODS

Subjects (n=185, 68±11 years, 79% male) suspected of having CAD were enrolled in the study and were divided into two groups, CAD and non-CAD subjects, according to the results of their coronary angiographies. Serum SFRP5 levels of the subjects were measured by an enzyme-linked immunosorbent assay.

RESULTS

The serum SFRP5 levels in the subjects with CAD were significantly lower than those in the non-CAD subjects (median [interquartile range]: 47.7 [26.6] vs. 52.4 [29.6] ng/mL, respectively; p=0.02). The serum SFRP5 levels significantly correlated with body mass index, the homeostasis model of assessment of insulin resistance, adiponectin levels, and CAD severity. Multivariate logistic regression analysis revealed that a decreased serum SFRP5 level (log transformed) was independently associated with CAD for all subjects (adjusted odds ratio, 0.36; 95% confidence interval, 0.14-0.94; p=0.03).

CONCLUSION

Serum SFRP5 levels are significantly associated with CAD in humans, suggesting that low SFRP5 levels may contribute to CAD.

Functional analysis LRP6 novel mutations in patients with coronary artery disease

Background

Genetic architecture of coronary artery disease (CAD) is still to be defined. Since low density lipoprotein receptor-related protein 6 (LRP6) gene play critical roles in Wnt signal transduction which are important for vascular development and endodermis specification, we therefore resequenced it to search for mutations in CAD patients.

Methods

We systemically sequenced all the exons and promoter region of LRP6 gene in a sample of 380 early onset CAD patients and 380 control subjects in Chinese.

Results

In total, we identified 5 patient-specific mutations including K82N (two patients), S488Y (one patient), P1066T (two patients), P1206H (two patients) and I1264V (one patient) All these mutations located at the extracellular domain of LRP6 gene. In vitro functional analysis of patient-specific mutations demonstrated that these mutations resulted in a significant reduction in both protein level transporting to cell membrane and downstream Wnt signal activity. Furthermore, we found that LRP6 novel mutations attenuated proliferation and migration of human umbilical vein endothelial cells (HUVECs) when compared with wild type (WT) LRP6.

Conclusion

Our results demonstrated that these loss-of-function variants might contribute to disease liability in a subset of CAD and defects in Wnt signal activation might be important contributing factors for the onset of CAD.

Wnt5a, TLR2 and TLR4 are elevated in advanced human atherosclerotic lesions

Objective and design

Atherosclerosis (ATH) is a chronic inflammatory disease that involves cascades of signaling events mediated by various effector proteins. Here we sought to determine if the expression of Wnt5a, a secreted glycoprotein, is altered in discrete regions of the arterial plaque.

Methods

Atherosclerotic plaque tissues from 14 human subjects undergoing elective carotid endarterectomy were used in this study. Immunohistochemistry and laser capture microdissection combined with quantitative real-time PCR were used to determine the expression of Wnt5a and Toll-like receptors (TLRs) in different sections of the arterial lesions. Atherosclerotic serum samples (n = 30) and serum from healthy subjects (n = 16) were quantified for Wnt5a using an enzyme-linked immunosorbent assay (ELISA).

Results

The data analysis revealed that Wnt5a transcripts and protein were elevated in advanced arterial lesions relative to less advanced arterial lesions; that Wnt5a expression correlated with the presence of TLR4 and TLR2 transcripts; and that the average amount of Wnt5a protein present in atherosclerotic patient serum was significantly higher compared to healthy controls.

Conclusions

This study is the first to provide evidence that the expression of Wnt5a increases as the disease progresses to a more advanced stage, and that this expression is coincident with that of TLR2 and TLR4. In addition, we found that the average Wnt5a levels in the serum of atherosclerotic patients are elevated relative to healthy controls, which is consistent with the hypothesis that Wnt5a plays a role in ATH.