Adipose tissue transcriptomic signature highlights the pathological relevance of extracellular matrix in human obesity

Molecular Mechanisms of Increased Heart Rate in Shenxianshengmai-treated Bradycardia Rabbits

Background:

The molecular mechanisms of Shenxianshengmai (SXSM), a traditional Chinese medicine, on bradycardia have been incompletely understood. The study tried to investigate the gene expression profile and proteomics of bradycardia rabbits’ hearts after SXSM treatment.

Methods:

Twenty-four adult rabbits were randomly assigned in four groups: sham, model, model plus SXSM treatment, and sham plus SXSM treatment groups. Heart rate was recorded in all rabbits. Then, total RNA of atria and proteins of ventricle were isolated and quantified, respectively. Gene expression profiling was conducted by gene expression chip, and quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) was performed to confirm the results of gene expression chip. We used isobaric tags for elative and absolute quantitation and Western blotting to identify altered proteins after SXSM treatment.

Results:

There was a constant decrease in the mean heart rate (32%, from 238 ± 6 beats/min to 149 ± 12 beats/min) after six weeks in model compared with that in sham group. This effect was partially reversed by 4-week SXSM treatment. Complementary DNA microarray demonstrated that the increased acetylcholinesterase and reduced nicotinic receptor were take responsibility for the increased heart rate. In addition, proteins involved in calcium handling and signaling were affected by SXSM treatment. Real-time RT-PCR verified the results from gene chip. Results from proteomics demonstrated that SXSM enhanced oxidative phosphorylation and tricarboxylic acid (TCA) cycle in ventricular myocardium to improve ATP generation.

Conclusions:

Long-term SXSM stimulates sympathetic transmission by increasing the expression of acetylcholinesterase and reduces the expression of nicotinic receptor to increase heart rate. SXSM also restored the calcium handling genes and altered genes involved in signaling. In addition, SXSM improves the ATP supply of ventricular myocardium by increasing proteins involved in TCA cycle and oxidation-respiratory chain.

A PDGFRα-Mediated Switch toward CD9high Adipocyte Progenitors Controls Obesity-Induced Adipose Tissue Fibrosis

Obesity-induced white adipose tissue (WAT) fibrosis is believed to accelerate WAT dysfunction. However, the cellular origin of WAT fibrosis remains unclear. Here, we show that adipocyte platelet-derived growth factor receptor-α-positive (PDGFRα⁺) progenitors adopt a fibrogenic phenotype in obese mice prone to visceral WAT fibrosis. More specifically, a subset of PDGFRα⁺ cells with high CD9 expression (CD9^high) originates pro-fibrotic cells whereas their CD9^low counterparts, committed to adipogenesis, are almost completely lost in the fibrotic WAT. PDGFRα pathway activation promotes a phenotypic shift toward PDGFRα⁺CD9^high fibrogenic cells, driving pathological remodeling and altering WAT function in obesity. These findings translated to human obesity as the frequency of CD9^high progenitors in omental WAT (oWAT) correlates with oWAT fibrosis level, insulin-resistance severity, and type 2 diabetes. Collectively, our data demonstrate that in addition to representing a WAT adipogenic niche, different PDGFRα⁺ cell subsets modulate obesity-induced WAT fibrogenesis and are associated with loss of metabolic fitness.

Aberrant Epicardial Adipose Tissue Extracellular Matrix Remodeling in Patients with Severe Ischemic Cardiomyopathy: Insight from Comparative Quantitative Proteomics

There is ample evidence indicating that epicardial adipose tissue (EAT) volume and thickness is positively associated with coronary artery disease (CAD). However, the exact pathological changes in the human EAT after myocardial ischemia remains largely unclear. In the current study, we applied a comparative quantitative proteomics to elucidate the altered biological processes in the EAT of ischemic cardiomyopathy (ICM) patients. A total of 1649 proteins were successfully quantified in our study, among which 165 proteins were significantly changed (ratio <0.8 or >1.2 fold and p < 0.05 in both repetitions) in EAT of ICM individuals. Gene ontology (GO) enrichment analysis revealed that cardiac structure and cellular metabolism were over-represented among these regulated proteins. The hypertrophic cardiomyopathy, adrenergic signaling in cardiomyocytes, extracellular matrix (ECM)-receptor interaction, phagosome, Glycolysis/Gluconeogenesis, and PPAR signaling pathway were highlighted by the KEGG PATHWAY analysis. More importantly, we found that the proteins responsible for extracellular matrix organization were dramatically increased in EAT of ICM patients. In addition, the picrosirius red (PSR) staining results showed that the collagen fiber content was prominently increased, which indicated the EAT of ICM individuals underwent extracellular matrix remodeling and ERK1/2 activation maybe responsible for these pathological changes partially.

Histomorphology, ultrastructure and fatty acid composition of the adipose tissue in pansteatitis, the potentials in understanding the underlying mechanism and diagnosis of pansteatitis in the Nile crocodile

BACKGROUND

In an effort to characterize the fat body and other adipose tissue in the Nile crocodile and the effects of pansteatitis on the structure and composition of the adipose tissue, we evaluated the regional variation in structure and fatty acid composition of healthy farmed crocodiles and those affected by pansteatitis.

METHODS

Adipose tissue samples were collected from the subcutaneous, visceral and intramuscular fat and the abdominal fat body of ten 4-year old juvenile crocodiles from Izinthaba Crocodile Farm, Pretoria, South Africa while pansteatitis samples were collected from visceral and intramuscular fat of crocodiles that had died of pansteatitis at the Olifant River, Mpumalanga, also in South Africa. Histomorphology, ultrastrustucture and fatty acid composition by fatty acid methyl ester (FAME) analysis were conducted.

RESULTS

Histological examination showed regional variations in the adipose tissue especially in the collagen content of the ECM, tissue perfusion and division into lobes and lobules by fibrous capsule. Considerable fibrosis, mononuclear cell infiltration especially by macrophages and lymphocytes and toxic changes in the nucleus were observed in the pansteatitis samples. Regional variation in lipid composition especially in Myristoleic (C14:1), Erucic acid (C22:1n9), and Docosadienoic acid (C22:2n6) was observed. Most of the saturated and trans fatty acids were found in significant quantities in the pansteatitis samples, but had very low levels of the cis fatty acid and the essential fatty acids with C18 backbone.

CONCLUSION

This study demonstrates that there exists some regional variation in histomorphology and fatty acid composition in the healthy adipose tissue of the Nile crocodile. It also showed that pansteatitis in the Nile crocodile might have been triggered by sudden change in energy balance from consumption of dead fish; and probable exposure to toxic environmental conditions with the evidence of up scaled monounsaturated long chain fatty acids composition and toxic changes in the leucocytes observed in pansteatitis in the present study.

FAK signalling controls insulin sensitivity through regulation of adipocyte survival

Focal adhesion kinase (FAK) plays a central role in integrin signalling, which regulates growth and survival of tumours. Here we show that FAK protein levels are increased in adipose tissue of insulin-resistant obese mice and humans. Disruption of adipocyte FAK in mice or in 3T3 L1 cells decreases adipocyte survival. Adipocyte-specific FAK knockout mice display impaired adipose tissue expansion and insulin resistance on prolonged metabolic stress from a high-fat diet or when crossed on an obese db/db or ob/ob genetic background. Treatment of these mice with a PPARγ agonist does not restore adiposity or improve insulin sensitivity. In contrast, inhibition of apoptosis, either genetically or pharmacologically, attenuates adipocyte death, restores normal adiposity and improves insulin sensitivity. Together, these results demonstrate that FAK is required for adipocyte survival and maintenance of insulin sensitivity, particularly in the context of adipose tissue expansion as a result of caloric excess.

The kinase FAK is important for integrin signalling and promotes cell survival. Here, the authors demonstrate FAK regulates adipocyte survival, and is particularly important for maintaining insulin sensitivity during adipose tissue expansion in the context of a calorie-rich diet.

PCR arrays indicate that the expression of extracellular matrix and cell adhesion genes in human adipocytes is regulated by IL-1β (interleukin-1β)

The role of IL-1β in regulating the expression of extracellular matrix (ECM) and cell adhesion genes in human adipocytes has been examined. Adipocytes differentiated in culture were incubated with IL-1β for 4 or 24 h and RNA probed with PCR arrays for 84 ECM and cell adhesion genes. Treatment with IL-1β resulted in changes in the expression at one or both time points of ∼50% of the genes probed by the arrays, the majority being down-regulated. Genes whose expression was down-regulated by IL-1β included those encoding several collagen chains and integrin subunits. In contrast, IL-1β induced substantial increases (>10-fold) in the expression of ICAM1, VCAM1, MMP1 and MMP3; the secretion of the encoded proteins was also markedly stimulated. IL-1β has a pervasive effect on the expression of ECM and cell adhesion genes in human adipocytes, consistent with the derangement of tissue structure during inflammation in white fat.

Effects of Exendin-4 on human adipose tissue inflammation and ECM remodelling

BACKGROUND/OBJECTIVES:

Subjects with type-2 diabetes are typically obese with dysfunctional adipose tissue (AT). Glucagon-like peptide-1 (GLP-1) analogues are routinely used to improve glycaemia. Although, they also aid weight loss that improves AT function, their direct effect on AT function is unclear. To explore GLP-1 analogues' influence on human AT's cytokine and extracellular matrix (ECM) regulation, we therefore obtained and treated omental (OMAT) and subcutaneous (SCAT) AT samples with Exendin-4, an agonist of the GLP-1 receptor (GLP-1R).

SUBJECTS/METHODS:

OMAT and abdominal SCAT samples obtained from women during elective surgery at the Royal Devon & Exeter Hospital (UK) were treated with increasing doses of Exendin-4. Changes in RNA expression of adipokines, inflammatory cytokines, ECM components and their regulators were assessed and protein secretion analysed by ELISA. GLP-1R protein accumulation was compared in paired AT depot samples.

RESULTS:

Exendin-4 induced an increase in OMAT adiponectin (P=0.02) and decrease in elastin expression (P=0.03) in parallel with reduced elastin secretion (P=0.04). In contrast to OMAT, we did not observe an effect on SCAT. There was no change in the expression of inflammatory markers (CD14, TNFA, MCP-1), collagens, TGFB1 or CTGF. GLP-1R accumulation was higher in SCAT.

CONCLUSIONS:

Independently of weight loss, which may bias findings of in vivo studies, GLP-1 analogues modify human OMAT physiology favourably by increasing the insulin-sensitising cytokine adiponectin. However, the reduction of elastin and no apparent effect on AT's inflammatory cytokines suggest that GLP-1 analogues may be less beneficial to AT function, especially if there is no associated weight loss.

Extracellular matrix remodeling and transforming growth factor-β signaling abnormalities induced by lamin A/C variants that cause lipodystrophy

Mutations in the lamin A/C gene encoding nuclear lamins A and C (lamin A/C) cause familial partial lipodystrophy type 2 (FPLD2) and related lipodystrophy syndromes. These are mainly characterized by redistribution of adipose tissue associated with insulin resistance. Several reports suggest that alterations in the extracellular matrix of adipose tissue leading to fibrosis play a role in the pathophysiology of lipodystrophy syndromes. However, the extent of extracellular matrix alterations in FPLD2 remains unknown. We show significantly increased fibrosis and altered expression of genes encoding extracellular matrix proteins in cervical subcutaneous adipose tissue from a human subject with FLPD2. Similar extracellular matrix alterations occur in adipose tissue of transgenic mice expressing an FPLD2-causing human lamin A variant and in cultured fibroblasts from human subjects with FPLD2 and related lipodystrophies. These abnormalities are associated with increased transforming growth factor-β signaling and defects in matrix metalloproteinase 9 activity. Our data demonstrate that lamin A/C gene mutations responsible for FPLD2 and related lipodystrophies are associated with transforming growth factor-β activation and an extracellular matrix imbalance in adipose tissue, suggesting that targeting these alterations could be the basis of novel therapies.

Adipose tissue gene expression is differentially regulated with different rates of weight loss in overweight and obese humans

BACKGROUND/OBJECTIVES

Moderate weight loss (WL) can ameliorate adverse health effects associated with obesity, reflected by an improved adipose tissue (AT) gene expression profile. However, the effect of rate of WL on the AT transcriptome is unknown. We investigated the global AT gene expression profile before and after two different rates of WL that resulted in similar total WL, and after a subsequent weight stabilization period.

SUBJECTS/METHODS

In this randomized controlled trial, 25 male and 28 female individuals (body mass index (BMI): 28-35 kg m^-2) followed either a low-calorie diet (LCD; 1250 kcal day^-1) for 12 weeks or a very-low-calorie diet (VLCD; 500 kcal day^-1) for 5 weeks (WL period) and a subsequent weight stable (WS) period of 4 weeks. The WL period and WS period together is termed dietary intervention (DI) period. Abdominal subcutaneous AT biopsies were collected for microarray analysis and gene expression changes were calculated for all three periods in the LCD group, VLCD group and between diets (ΔVLCD-ΔLCD).

RESULTS

WL was similar between groups during the WL period (LCD: -8.1±0.5 kg, VLCD: -8.9±0.4 kg, difference P=0.25). Overall, more genes were significantly regulated and changes in gene expression appeared more pronounced in the VLCD group compared with the LCD group. Gene sets related to mitochondrial function, adipogenesis and immunity/inflammation were more strongly upregulated on a VLCD compared with a LCD during the DI period (positive ΔVLCD-ΔLCD). Neuronal and olfactory-related gene sets were decreased during the WL period and DI period in the VLCD group.

CONCLUSIONS

The rate of WL (LCD vs VLCD), with similar total WL, strongly regulates AT gene expression. Increased mitochondrial function, angiogenesis and adipogenesis on a VLCD compared with a LCD reflect potential beneficial diet-induced changes in AT, whereas differential neuronal and olfactory regulation suggest functions of these genes beyond the current paradigm.

Mfge8 regulates enterocyte lipid storage by promoting enterocyte triglyceride hydrolase activity

The small intestine has an underappreciated role as a lipid storage organ. Under conditions of high dietary fat intake, enterocytes can minimize the extent of postprandial lipemia by storing newly absorbed dietary fat in cytoplasmic lipid droplets. Lipid droplets can be subsequently mobilized for the production of chylomicrons. The mechanisms that regulate this process are poorly understood. We report here that the milk protein Mfge8 regulates hydrolysis of cytoplasmic lipid droplets in enterocytes after interacting with the αvβ3 and αvβ5 integrins. Mice deficient in Mfge8 or the αvβ3 and αvβ5 integrins accumulate excess cytoplasmic lipid droplets after a fat challenge. Mechanistically, interruption of the Mfge8-integrin axis leads to impaired enterocyte intracellular triglyceride hydrolase activity in vitro and in vivo. Furthermore, Mfge8 increases triglyceride hydrolase activity through a PI3 kinase/mTORC2-dependent signaling pathway. These data identify a key role for Mfge8 and the αvβ3 and αvβ5 integrins in regulating enterocyte lipid processing.

The epigenetic signature of systemic insulin resistance in obese women

AIMS/HYPOTHESIS

Insulin resistance (IR) links obesity to type 2 diabetes. The aim of this study was to explore whether white adipose tissue (WAT) epigenetic dysregulation is associated with systemic IR by genome-wide CG dinucleotide (CpG) methylation and gene expression profiling in WAT from insulin-resistant and insulin-sensitive women. A secondary aim was to determine whether the DNA methylation signature in peripheral blood mononuclear cells (PBMCs) reflects WAT methylation and, if so, can be used as a marker for systemic IR.

METHODS

From 220 obese women, we selected a total of 80 individuals from either of the extreme ends of the distribution curve of HOMA-IR, an indirect measure of systemic insulin sensitivity. Genome-wide transcriptome and DNA CpG methylation profiling by array was performed on subcutaneous (SAT) and visceral (omental) adipose tissue (VAT). CpG methylation in PBMCs was assayed in the same cohort.

RESULTS

There were 647 differentially expressed genes (false discovery rate [FDR] 10%) in SAT, all of which displayed directionally consistent associations in VAT. This suggests that IR is associated with dysregulated expression of a common set of genes in SAT and VAT. The average degree of DNA methylation did not differ between the insulin-resistant and insulin-sensitive group in any of the analysed tissues/cells. There were 223 IR-associated genes in SAT containing a total of 336 nominally significant differentially methylated sites (DMS). The 223 IR-associated genes were over-represented in pathways related to integrin cell surface interactions and insulin signalling and included COL5A1, GAB1, IRS2, PFKFB3 and PTPRJ. In VAT there were a total of 51 differentially expressed genes (FDR 10%); 18 IR-associated genes contained a total of 29 DMS.

CONCLUSIONS/INTERPRETATION

In individuals discordant for insulin sensitivity, the average DNA CpG methylation in SAT and VAT is similar, although specific genes, particularly in SAT, display significantly altered expression and DMS in IR, possibly indicating that epigenetic regulation of these genes influences metabolism.

Integrative network analysis of nineteen brain regions identifies molecular signatures and networks underlying selective regional vulnerability to Alzheimer's disease

Background

Alzheimer’s disease (AD) is the most common form of dementia, characterized by progressive cognitive impairment and neurodegeneration. However, despite extensive clinical and genomic studies, the molecular basis of AD development and progression remains elusive.

Methods

To elucidate molecular systems associated with AD, we developed a large scale gene expression dataset from 1053 postmortem brain samples across 19 cortical regions of 125 individuals with a severity spectrum of dementia and neuropathology of AD. We excluded brain specimens that evidenced neuropathology other than that characteristic of AD. For the first time, we performed a pan-cortical brain region genomic analysis, characterizing the gene expression changes associated with a measure of dementia severity and multiple measures of the severity of neuropathological lesions associated with AD (neuritic plaques and neurofibrillary tangles) and constructing region-specific co-expression networks. We rank-ordered 44,692 gene probesets, 1558 co-expressed gene modules and 19 brain regions based upon their association with the disease traits.

Results

The neurobiological pathways identified through these analyses included actin cytoskeleton, axon guidance, and nervous system development. Using public human brain single-cell RNA-sequencing data, we computed brain cell type-specific marker genes for human and determined that many of the abnormally expressed gene signatures and network modules were specific to oligodendrocytes, astrocytes, and neurons. Analysis based on disease severity suggested that: many of the gene expression changes, including those of oligodendrocytes, occurred early in the progression of disease, making them potential translational/treatment development targets and unlikely to be mere bystander result of degeneration; several modules were closely linked to cognitive compromise with lesser association with traditional measures of neuropathology. The brain regional analyses identified temporal lobe gyri as sites associated with the greatest and earliest gene expression abnormalities.

Conclusions

This transcriptomic network analysis of 19 brain regions provides a comprehensive assessment of the critical molecular pathways associated with AD pathology and offers new insights into molecular mechanisms underlying selective regional vulnerability to AD at different stages of the progression of cognitive compromise and development of the canonical neuropathological lesions of AD.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-016-0355-3) contains supplementary material, which is available to authorized users.

Adipose and Circulating CCL18 Levels Associate With Metabolic Risk Factors in Women

CONTEXT

Cardiometabolic complications in obesity may be linked to white adipose tissue (WAT) dysfunction. Transcriptomic studies of Sc WAT have reported that CCL18, encoding the CC chemokine ligand 18 (CCL18), is increased in obesity/insulin resistance but its functional role is unknown.

OBJECTIVE

Our objectives were to determine if CCL18 is secreted from Sc WAT and if secreted and/or serum levels associate with metabolic phenotypes. We also planned to define the primary cellular source and if CCL18 exerts effects on adipocytes.

DESIGN

This is a cohort study.

SETTING

The study took place in an outpatient academic clinic.

PARTICIPANTS

A total of 130 obese women scheduled for bariatric surgery and 35 nonobese controls were included.

METHODS

Insulin sensitivity was assessed by hyperinsulinemic euglycemic clamp or homeostasis model assessment. CCL18 was analyzed in serum/WAT incubates by ELISA. Effects of recombinant CCL18 was determined in cultures of primary human adipocytes and the monocyte cell line THP-1 differentiated into M0/M1/M2 macrophages.

MAIN OUTCOME MEASURE

Association with metabolic risk factors was measured.

RESULTS

CCL18 was secreted from WAT and the levels correlated positively with insulin resistance, Adult Treatment Panel III risk score and plasma triglycerides, independent of body mass index and better than other established adipocytokines. In 80 obese women, S-CCL18 levels were significantly higher in insulin resistant compared with insulin sensitive subjects. In WAT CCL18 mRNA was expressed in macrophages and correlated positively with immune-related genes, particularly those enriched in M2 macrophages. While CCL18 increased cyto-/chemokine expression in M0/M2-THP-1 cells, human adipocytes showed no responses in vitro.

CONCLUSIONS

Circulating and WAT-secreted CCL18 correlates with insulin resistance and metabolic risk score. Because CCL18 is macrophage-specific and associates with adipose immune gene expression, it may constitute a marker of WAT inflammation.

Lymphatic pumping: mechanics, mechanisms and malfunction

A combination of extrinsic (passive) and intrinsic (active) forces move lymph against a hydrostatic pressure gradient in most regions of the body. The effectiveness of the lymph pump system impacts not only interstitial fluid balance but other aspects of overall homeostasis. This review focuses on the mechanisms that regulate the intrinsic, active contractions of collecting lymphatic vessels in relation to their ability to actively transport lymph. Lymph propulsion requires not only robust contractions of lymphatic muscle cells, but contraction waves that are synchronized over the length of a lymphangion as well as properly functioning intraluminal valves. Normal lymphatic pump function is determined by the intrinsic properties of lymphatic muscle and the regulation of pumping by lymphatic preload, afterload, spontaneous contraction rate, contractility and neural influences. Lymphatic contractile dysfunction, barrier dysfunction and valve defects are common themes among pathologies that directly involve the lymphatic system, such as inherited and acquired forms of lymphoedema, and pathologies that indirectly involve the lymphatic system, such as inflammation, obesity and metabolic syndrome, and inflammatory bowel disease.

Relevance of omental pericellular adipose tissue collagen in the pathophysiology of human abdominal obesity and related cardiometabolic risk

BACKGROUND

Adipose tissue fibrosis is a relatively new notion and its relationship with visceral obesity and cardiometabolic alterations remains unclear, particularly in moderate obesity.

OBJECTIVE

Our objective was to examine if total and pericellular collagen accumulation are relevant for the pathophysiology of visceral obesity and related cardiometabolic risk.

SUBJECTS AND METHODS

Surgical omental (OM) and subcutaneous (SC) fat samples were obtained in 56 women (age: 47.2±5.8 years; body mass index (BMI): 27.1±4.4 kg/m²). Body composition and fat distribution were measured by dual-energy X-ray absorptiometry and computed tomography, respectively. Total and pericellular collagen were measured using picrosirius red staining. CD68+ cells (total macrophages) and CD163+ cells (M2-macrophages) were identified using immunohistochemistry.

RESULTS

We found that only pericellular collagen percentage, especially in OM fat, was associated with higher BMI, body fat mass and adipose tissue areas as well as lower radiologic attenuation of visceral adipose tissue and altered cardiometabolic risk variables. Strong correlations between peri-adipocyte collagen percentage and total or M2-macrophage percentages were observed in both depots. Total collagen percentage in either compartment was not related to adiposity, fat distribution or cardiometabolic risk.

CONCLUSIONS

As opposed to whole tissue-based assessments of adipose tissue fibrosis, collagen deposition around the adipocyte, especially in the OM fat compartment is related to total and regional adiposity as well as altered cardiometabolic risk profile.

Enhanced biglycan gene expression in the adipose tissues of obese women and its association with obesity-related genes and metabolic parameters

Extracellular matrix (ECM) remodeling dynamically occurs to accommodate adipose tissue expansion during obesity. One non-fibrillar component of ECM, biglycan, is released from the matrix in response to tissue stress; the soluble form of biglycan binds to toll-like receptor 2/4 on macrophages, causing proinflammatory cytokine secretion. To investigate the pattern and regulatory properties of biglycan expression in human adipose tissues in the context of obesity and its related diseases, we recruited 21 non-diabetic obese women, 11 type 2 diabetic obese women, and 59 normal-weight women. Regardless of the presence of diabetes, obese patients had significantly higher biglycan mRNA in both visceral and subcutaneous adipose tissue. Biglycan mRNA was noticeably higher in non-adipocytes than adipocytes and significantly decreased during adipogenesis. Adipose tissue biglycan mRNA positively correlated with adiposity indices and insulin resistance parameters; however, this relationship disappeared after adjusting for BMI. In both fat depots, biglycan mRNA strongly correlated with the expression of genes related to inflammation and endoplasmic reticulum stress. In addition, culture of human preadipocytes and differentiated adipocytes under conditions mimicking the local microenvironments of obese adipose tissues significantly increased biglycan mRNA expression. Our data indicate that biglycan gene expression is increased in obese adipose tissues by altered local conditions.

The miR-181d-regulated metalloproteinase Adamts1 enzymatically impairs adipogenesis via ECM remodeling

The extracellular matrix (ECM) maintenance is crucial to the structural integrity of adipocytes and whole adipose tissue formation. However, the potential impact of the ECM on adipocyte lineage commitment is unclear. Herein, we demonstrate that forced expression of matrix-associated metalloproteinase Adamts1 (a disintegrin and metalloproteinase with thrombospondin motifs 1), which we show is targeted by microRNA-181d (miR-181d) during BMP4-induced adipocytic lineage commitment, markedly impairs adipocyte commitment. Conversely, siRNA-induced inhibition of Adamts1 promotes adipocyte commitment. Adamst1 metalloprotease activity is required for this inhibition and is determined to function via remodeling ECM components followed by activating FAK-ERK signaling pathway during the commitment process. Furthermore, ablation of Adamts1 in adipose tissue increases adipose tissue mass, reduces insulin sensitivity, and disrupts lipid homeostasis. This finding is consistent with Adamts1 decreased expression in the adipose tissue of obese mice and an inverse correlation of Adamts1 expression with body mass index in humans. Collectively, our results indicate that Adamts1 acts as an ECM 'modifier', with miR-181d-induced downregulation, that regulates adipocyte lineage commitment and obesity.

Proteomics analyses of subcutaneous adipocytes reveal novel abnormalities in human insulin resistance

OBJECTIVE

To provide a more global view of adipocyte changes in human insulin resistance by proteomics analyses.

METHODS

Baseline biopsies of abdominal subcutaneous adipose tissue were obtained from 23 subjects without diabetes. Euglycemic clamps were used to divide subjects into an insulin-resistant group (IR, N = 10) and an insulin-sensitive (IS, N = 13) group, which were of similar age and gender but unequal adiposity (greater in IR). Proteins of isolated adipocytes were quantified by mass spectrometry using normalized spectral abundance factors.

RESULTS

Of 1,245 proteins assigned, 30 were detected in at least 12 of the 23 subjects that differed significantly in abundance ≥1.5-fold between IR and IS. IR displayed a pattern of increased cytoskeletal proteins and decreased mitochondrial proteins and FABP4 and FABP5. In subgroup analyses of adiposity-matched subjects, several of these changes were less pronounced in IR, but the abundance of proteins related to lipid metabolism and the unfolded/misfolded protein response were significantly and unfavorably altered.

CONCLUSIONS

These results confirm lower abundance of mitochondrial proteins and suggest increased cytoskeletal proteins and decreased FABP4 and FABP5 in subcutaneous adipocytes of typical IR individuals. Changes in proteins related to lipid metabolism and the unfolded/misfolded protein may discriminate IR and IS individuals of equal adiposity.

Transcriptomic signatures of villous cytotrophoblast and syncytiotrophoblast in term human placenta

During pregnancy, the placenta ensures multiple functions, which are directly involved in the initiation, fetal growth and outcome of gestation. The placental tissue involved in maternal-fetal exchanges and in synthesis of pregnancy hormones is the mononucleated villous cytotrophoblast (VCT) which aggregates and fuses to form and renew the syncytiotrophoblast (ST). Knowledge of the gene expression pattern specific to this endocrine and exchanges tissue of human placenta is of major importance to understand functions of this heterogeneous and complex tissue. Therefore, we undertook a global analysis of the gene expression profiles of primary cultured-VCT (n = 6) and in vitro-differentiated-ST (n = 5) in comparison with whole term placental tissue from which mononucleated VCT were isolated. A total of 880 differentially expressed genes (DEG) were observed between VCT/ST compared to whole placenta, and a total of 37 and 137 genes were significantly up and down-regulated, respectively, in VCT compared to ST. The 37 VCT-genes were involved in cellular processes (assembly, organization, and maintenance), whereas the 137 ST-genes were associated with lipid metabolism and cell morphology. In silico, all networks were linked to 3 transcriptional regulators (PPARγ, RARα and NR2F1) which are known to be essential for trophoblast differentiation. A subset of six DEG was validated by RT-qPCR and four by immunohistochemistry. To conclude, recognition of these pathways is fundamental to increase our understanding of the molecular basis of human trophoblast differentiation. The present study provides for the first time a gene expression signature of the VCT and ST compared to their originated term human placental tissue.

Microenvironmental Control of Adipocyte Fate and Function

The properties of tissue-specific microenvironments vary widely in the human body and demonstrably influence the structure and function of many cell types. Adipocytes are no exception, responding to cues in specialized niches to perform vital metabolic and endocrine functions. The adipose microenvironment is remodeled during tissue expansion to maintain the structural and functional integrity of the tissue and disrupted remodeling in obesity contributes to the progression of metabolic syndrome, breast cancer, and other malignancies. The increasing incidence of these obesity-related diseases and the recent focus on improved in vitro models of human tissue biology underscore growing interest in the regulatory role of adipocyte microenvironments in health and disease.

Obesity-dependent changes in interstitial ECM mechanics promote breast tumorigenesis

Obesity and extracellular matrix (ECM) density are considered independent risk and prognostic factors for breast cancer. Whether they are functionally linked is uncertain. We investigated the hypothesis that obesity enhances local myofibroblast content in mammary adipose tissue and that these stromal changes increase malignant potential by enhancing interstitial ECM stiffness. Indeed, mammary fat of both diet- and genetically induced mouse models of obesity were enriched for myofibroblasts and stiffness-promoting ECM components. These differences were related to varied adipose stromal cell (ASC) characteristics because ASCs isolated from obese mice contained more myofibroblasts and deposited denser and stiffer ECMs relative to ASCs from lean control mice. Accordingly, decellularized matrices from obese ASCs stimulated mechanosignaling and thereby the malignant potential of breast cancer cells. Finally, the clinical relevance and translational potential of our findings were supported by analysis of patient specimens and the observation that caloric restriction in a mouse model reduces myofibroblast content in mammary fat. Collectively, these findings suggest that obesity-induced interstitial fibrosis promotes breast tumorigenesis by altering mammary ECM mechanics with important potential implications for anticancer therapies.

Differential Effect of Electroacupuncture on Inflammatory Adipokines in Two Rat Models of Obesity

Chronic inflammation is known to be associated with visceral obesity and insulin resistance which are characterized by altered levels of production of pro- and anti-inflammatory adipokines. The dysregulation of the production of inflammatory adipokines and their functions in obese individuals leads to a state of chronic low-grade inflammation and may promote obesity-linked metabolic disorders and cardiovascular diseases such as insulin resistance, metabolic syndrome, and atherosclerosis. Electroacupuncture (EA) was tested to see if there was a difference in its effect on pro- and anti-inflammatory adipokine levels in the blood serum and the white adipose tissue of obese Zucker fatty rats and high-fat diet-induced obese Long Evans rats. In the two rat models of obesity, on Day 12 of treatment, repeated applications of EA were seen to have had a significant differential effect for serum tumor necrosis factor-α, adiponectin, the adiponectin:leptin ratio, and blood glucose. For the adipose tissue, there was a differential effect for adiponectin that was on the borderline of significance. To explore these changes further and how they might affect insulin resistance would require a modification to the research design to use larger group sizes for the two models or to give a greater number of EA treatments.

Hypoxia Promotes the Inflammatory Response and Stemness Features in Visceral Fat Stem Cells From Obese Subjects

Low-grade chronic inflammation is a salient feature of obesity and many associated disorders. This condition frequently occurs in central obesity and is connected to alterations of the visceral adipose tissue (AT) microenvironment. Understanding how obesity is related to inflammation may allow the development of therapeutics aimed at improving metabolic parameters in obese patients. To achieve this aim, we compared the features of two subpopulations of adipose-derived stem cells (ASC) isolated from both subcutaneous and visceral AT of obese patients with the features of two subpopulations of ASC from the same isolation sites of non-obese individuals. In particular, the behavior of ASC of obese versus non-obese subjects during hypoxia, which occurs in obese AT and is an inducer of the inflammatory response, was evaluated. Obesity deeply influenced ASC from visceral AT (obV-ASC); these cells appeared to exhibit clearly distinguishable morphology and ultrastructure as well as reduced proliferation, clonogenicity and expression of stemness, differentiation and inflammation-related genes. These cells also exhibited a deregulated response to hypoxia, which induced strong tissue-specific NF-kB activation and an NF-kB-mediated increase in inflammatory and fibrogenic responses. Moreover, obV-ASC, which showed a less stem-like phenotype, recovered stemness features after hypoxia. Our findings demonstrated the peculiar behavior of obV-ASC, their influence on the obese visceral AT microenvironment and the therapeutic potential of NF-kB inhibitors. These novel findings suggest that the deregulated hyper-responsiveness to hypoxic stimulus of ASC from visceral AT of obese subjects may contribute via paracrine mechanisms to low-grade chronic inflammation, which has been implicated in obesity-related morbidity.

Adipose tissue fibrosis, hypertrophy, and hyperplasia: Correlations with diabetes in human obesity

OBJECTIVE

The relationship between adipose tissue fibrosis, adipocyte hypertrophy, and preadipocyte hyperplasia in the context of obesity and the correlation of these tissue-based phenomena with systemic metabolic disease are poorly defined. The goal of this study was to clarify the relationship between adipose tissue fibrosis, adipocyte hypertrophy, and preadipocyte hyperplasia in human obesity and determine the correlation of these adipose-tissue based phenomena with diabetes.

METHODS

Visceral and subcutaneous adipose tissues from humans with obesity collected during bariatric surgery were studied with QRTPCR, immunohistochemistry, and flow cytometry for expression of collagens and fibrosis-related proteins, adipocyte size, and preadipocyte frequency. Results were correlated with clinical characteristics including diabetes status.

RESULTS

Fibrosis was decreased, hypertrophy was increased, and preadipocyte frequency and fibrotic gene expression were decreased in adipose tissues from diabetic subjects compared to non-diabetic subjects. These differences were greater in visceral compared to subcutaneous adipose tissue.

CONCLUSIONS

These data are consistent with the hypothesis that adipose tissue fibrosis in the context of human obesity limits adipocyte hypertrophy and is associated with a reciprocal increase in adipocyte hyperplasia, with beneficial effects on systemic metabolism. These findings suggest adipose tissue fibrosis as a potential target for manipulation of adipocyte metabolism.

Cachexia-associated adipose tissue morphological rearrangement in gastrointestinal cancer patients

BACKGROUND AND AIMS

Cachexia is a syndrome characterized by marked involuntary loss of body weight. Recently, adipose tissue (AT) wasting has been shown to occur before the appearance of other classical cachexia markers. We investigated the composition and rearrangement of the extracellular matrix, adipocyte morphology and inflammation in the subcutaneous AT (scAT) pad of gastrointestinal cancer patients.

METHODS

Surgical biopsies for scAT were obtained from gastrointestinal cancer patients, who were signed up into the following groups: cancer cachexia (CC, n = 11), weight-stable cancer (WSC, n = 9) and weight-stable control (non-cancer) (control, n = 7). The stable weight groups were considered as those with no important weight change during the last year and body mass index <25 kg/m(2). Subcutaneous AT fibrosis was quantified and characterized by quantitative PCR, histological analysis and immunohistochemistry.

RESULTS

The degree of fibrosis and the distribution and collagen types (I and III) were different in WSC and CC patients. CC patients showed more pronounced fibrosis in comparison with WSC. Infiltrating macrophages surrounding adipocytes and CD3 Ly were found in the fibrotic areas of scAT. Subcutaneous AT fibrotic areas demonstrated increased monocyte chemotactic protein 1 (MCP-1) and Cluster of Differentiation (CD)68 gene expression in cancer patients.

CONCLUSIONS

Our data indicate architectural modification consisting of fibrosis and inflammatory cell infiltration in scAT as induced by cachexia in gastrointestinal cancer patients. The latter was characterized by the presence of macrophages and lymphocytes, more evident in the fibrotic areas. In addition, increased MCP-1 and CD68 gene expression in scAT from cancer patients may indicate an important role of these markers in the early phases of cancer.

Differences in the Osteogenic Differentiation Capacity of Omental Adipose-Derived Stem Cells in Obese Patients With and Without Metabolic Syndrome

Multiple studies have suggested that the reduced differentiation capacity of multipotent adipose tissue-derived mesenchymal stem cells (ASCs) in obese subjects could compromise their use in cell therapy. Our aim was to assess the osteogenic potential of omental ASCs and to examine the status of the isolated CD34(negative)-enriched fraction of omental-derived ASCs from subjects with different metabolic profiles. Omental ASCs from normal-weight subjects and subjects with or without metabolic syndrome were isolated, and the osteogenic potential of omental ASCs was evaluated. Additionally, osteogenic and clonogenic potential, proliferation rate, mRNA expression levels of proteins involved in redox balance, and fibrotic proteins were examined in the CD34(negative)-enriched fraction of omental-derived ASCs. Both the omental ASCs and the CD34(negative)-enriched fraction of omental ASCs from subjects without metabolic syndrome have a greater osteogenic potential than those from subjects with metabolic syndrome. The alkaline phosphatase and osteonectin mRNA were negatively correlated with nicotinamide adenine dinucleotide phosphate oxidase-2 mRNA and the mRNA expression levels of the fibrotic proteins correlated positively with nicotinamide adenine dinucleotide phosphate oxidase-5 mRNA and the homeostasis model assessment. Although the population doubling time was significantly higher in subjects with a body mass index of 25 kg/m(2) or greater, only the CD34(negative)-enriched omental ASC fraction in the subjects with metabolic syndrome had a higher population doubling time than the normal-weight subjects. The osteogenic, clonogenic, fibrotic potential, and proliferation rate observed in vitro suggest that omental ASCs from subjects without metabolic syndrome are more suitable for therapeutic osteogenic applications than those from subjects with metabolic syndrome.

Variation in extracellular matrix genes is associated with weight regain after weight loss in a sex-specific manner

The extracellular matrix (ECM) of adipocytes is important for body weight regulation. Here, we investigated whether genetic variation in ECM-related genes is associated with weight regain among participants of the European DiOGenes study. Overweight and obese subjects (n = 469, 310 females, 159 males) were on an 8-week low-calorie diet with a 6-month follow-up. Body weight was measured before and after the diet, and after follow-up. Weight maintenance scores (WMS, regained weight as percentage of lost weight) were calculated based on the weight data. Genotype data were retrieved for 2903 SNPs corresponding to 124 ECM-related genes. Regression analyses provided us with six significant SNPs associated with the WMS in males: 3 SNPs in the POSTN gene and a SNP in the LAMB1, COL23A1, and FBLN5 genes. For females, 1 SNP was found in the FN1 gene. The risk of weight regain was increased by: the C/C genotype for POSTN in a co-dominant model (OR 8.25, 95 % CI 2.85–23.88) and the T/C–C/C genotype in a dominant model (OR 4.88, 95 % CI 2.35–10.16); the A/A genotype for LAMB1 both in a co-dominant model (OR 18.43, 95 % CI 2.35–144.63) and in a recessive model (OR 16.36, 95 % CI 2.14–124.9); the G/A genotype for COL23A1 in a co-dominant model (OR 3.94, 95 % CI 1.28–12.10), or the A-allele in a dominant model (OR 2.86, 95 % CI 1.10–7.49); the A/A genotype for FBLN5 in a co-dominant model (OR 13.00, 95 % CI 1.61–104.81); and the A/A genotype for FN1 in a recessive model (OR 2.81, 95 % CI 1.40–5.63). Concluding, variants of ECM genes are associated with weight regain after weight loss in a sex-specific manner.

DNA methylation and gene expression patterns in adipose tissue differ significantly within young adult monozygotic BMI-discordant twin pairs

BACKGROUND

Little is known about epigenetic alterations associated with subcutaneous adipose tissue (SAT) in obesity. Our aim was to study genome-wide DNA methylation and gene expression differences in SAT in monozygotic (MZ) twin pairs who are discordant for body mass index (BMI). This design completely matches lean and obese groups for genetic background, age, gender and shared environment.

METHODS

14We analyzed DNA methylome and gene expression from SAT, together with body composition (magnetic resonance imaging/spectroscopy) and glucose tolerance test, lipids and C-reactive protein from 26 rare BMI-discordant (intrapair difference in BMI ⩾3 kg m(-2)) MZ twin pairs identified from 10 birth cohorts of young adult Finnish twins.

RESULTS

We found 17 novel obesity-associated genes that were differentially methylated across the genome between heavy and lean co-twins. Nine of them were also differentially expressed. Pathway analyses indicated that dysregulation of SAT in obesity includes a paradoxical downregulation of lipo/adipogenesis and upregulation of inflammation and extracellular matrix remodeling. Furthermore, CpG sites whose methylation correlated with metabolically harmful fat depots (intra-abdominal and liver fat) also correlated with measures of insulin resistance, dyslipidemia and low-grade inflammation, thus suggesting that epigenetic alterations in SAT are associated with the development of unhealthy obesity.

CONCLUSION

This is the first study in BMI-discordant MZ twin pairs reporting genome-wide DNA methylation and expression profiles in SAT. We found a number of novel genes and pathways whose methylation and expression patterns differ within the twin pairs, suggesting that the pathological adaptation of SAT to obesity is, at least in part, epigenetically regulated.

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.

Extensive weight loss reveals distinct gene expression changes in human subcutaneous and visceral adipose tissue

Weight loss has been shown to significantly improve Adipose tissue (AT) function, however changes in AT gene expression profiles particularly in visceral AT (VAT) have not been systematically studied. Here, we tested the hypothesis that extensive weight loss in response to bariatric surgery (BS) causes AT gene expression changes, which may affect energy and lipid metabolism, inflammation and secretory function of AT. We assessed gene expression changes by whole genome expression chips in AT samples obtained from six morbidly obese individuals, who underwent a two step BS strategy with sleeve gastrectomy as initial and a Roux-en-Y gastric bypass as second step surgery after 12 ± 2 months. Global gene expression differences in VAT and subcutaneous (S)AT were analyzed through the use of genome-scale metabolic model (GEM) for adipocytes. Significantly altered gene expressions were PCR-validated in 16 individuals, which also underwent a two-step surgery intervention. We found increased expression of cell death-inducing DFFA-like effector a (CIDEA), involved in formation of lipid droplets in both fat depots in response to significant weight loss. We observed that expression of the genes associated with metabolic reactions involved in NAD+, glutathione and branched chain amino acid metabolism are significantly increased in AT depots after surgery-induced weight loss.

DAPK2 Downregulation Associates With Attenuated Adipocyte Autophagic Clearance in Human Obesity

Adipose tissue dysfunction in obesity has been linked to low-grade inflammation causing insulin resistance. Transcriptomic studies have identified death-associated protein kinase 2 (DAPK2) among the most strongly downregulated adipose tissue genes in human obesity, but the role of this kinase is unknown. We show that mature adipocytes rather than the stromal vascular cells in adipose tissue mainly expressed DAPK2 and that DAPK2 mRNA in obese patients gradually recovered after bariatric surgery-induced weight loss. DAPK2 mRNA is also downregulated in high-fat diet-induced obese mice. Adenoviral-mediated DAPK2 overexpression in 3T3-L1 adipocytes did not affect lipid droplet size or cell viability but did increase autophagic clearance in nutrient-rich conditions, dependent on protein kinase activity. Conversely, DAPK2 inhibition in human preadipocytes by small interfering RNA decreased LC3-II accumulation rates with lysosome inhibitors. This led us to assess autophagic clearance in adipocytes freshly isolated from subcutaneous adipose tissue of obese patients. Severe reduction in autophagic flux was observed in obese adipocytes compared with control adipocytes, inversely correlated to fat cell lipids. After bariatric surgery, adipocyte autophagic clearance partially recovered proportional to the extent of fat cell size reduction. This study links adipocyte expression of an autophagy-regulating kinase, lysosome-mediated clearance and fat cell lipid accumulation; it demonstrates obesity-related attenuated autophagy in adipocytes, and identifies DAPK2 dependence in this regulation.

HMGA1 overexpression in adipose tissue impairs adipogenesis and prevents diet-induced obesity and insulin resistance

High-Mobility-Group-A1 (HMGA1) proteins are non-histone proteins that regulate chromatin structure and gene expression during embryogenesis, tumourigenesis and immune responses. In vitro studies suggest that HMGA1 proteins may be required to regulate adipogenesis. To examine the role of HMGA1 in vivo, we generated transgenic mice overexpressing HMGA1 in adipose tissues. HMGA1 transgenic mice showed a marked reduction in white and brown adipose tissue mass that was associated with downregulation of genes involved in adipogenesis and concomitant upregulation of preadipocyte markers. Reduced adipogenesis and decreased fat mass were not associated with altered glucose homeostasis since HMGA1 transgenic mice fed a regular-chow diet exhibited normal glucose tolerance and insulin sensitivity. However, when fed a high-fat diet, overexpression of HMGA1 resulted in decreased body-weight gain, reduced fat mass, but improved insulin sensitivity and glucose tolerance. Although HMGA1 transgenic mice exhibited impaired glucose uptake in adipose tissue due to impaired adipogenesis, the increased glucose uptake observed in skeletal muscle may account for the improved glucose homeostasis. Our results indicate that HMGA1 plays an important function in the regulation of white and brown adipogenesis in vivo and suggests that impaired adipocyte differentiation and decreased fat mass is not always associated with impaired whole-body glucose homeostasis.

Human adipose tissue expansion in pregnancy is impaired in gestational diabetes mellitus

AIMS/HYPOTHESIS

During pregnancy, adipose tissue (AT) must expand to support the growing fetus and the future nutritional needs of the offspring. Limited expandability of AT is associated with insulin resistance, attributed to ectopic lipid deposition. This study aimed to investigate human AT expandability during pregnancy and its role in the pathogenesis of gestational diabetes mellitus (GDM).

METHODS

This cross-sectional study of omental (OM) and subcutaneous (SQ) AT collected at Caesarean delivery included 11 pregnant and three non-pregnant women with normal glucose tolerance (NGT), five with GDM, three with type 2 diabetes mellitus. Adipocyte size, capillary density, collagen content and capillary growth were measured. Affymetrix arrays and real-time PCR studies of gene expression were performed.

RESULTS

Mean OM adipocyte size was greater in women with GDM than in those with NGT (p = 0.004). Mean OM and SQ capillary density was lower in GDM compared with NGT (p = 0.015). Capillary growth did not differ significantly between groups. The most differentially expressed AT transcript when comparing non-pregnant and pregnant women corresponded to the IGF binding protein (IGFBP)-5, the expression levels of which was found by subsequent quantitative real-time PCR to be lower in women with GDM vs women with NGT (p < 0.0001).

CONCLUSIONS/INTERPRETATION

The relative OM adipocyte hypertrophy and decreased OM and SQ capillary density are consistent with impaired AT expandability in GDM. The induction of adipose tissue IGFBP5 in pregnancy and its decrease in GDM point to the importance of the IGF-1 signalling pathway in AT expansion in pregnancy and GDM susceptibility.

The mRNA expression of soluble urokinase plasminogen activator surface receptor in human adipose tissue is positively correlated with body mass index

suPLAUR is the transcript variant that encodes the soluble form of the urokinase plasminogen activator surface receptor (suPLAUR). This soluble protein has been shown to enhance leukocyte migration and adhesion, and its circulatory level is increased in inflammatory states. In this pilot study, we used RNA-Seq to examine the splicing pattern of PLAUR in omental adipose tissues from obese and lean individuals. Of the three transcript variants of the PLAUR gene, only the proportion of suPLAUR (transcript variant 2) increases in obesity. After removing the effects of gender and age, the expression of suPLAUR is positively correlated with body mass index. This observation was validated using RT-qPCR with an independent cohort of samples. Additionally, in our RNA-Seq differential expression analysis, we also observed, in obese adipose tissues, an up-regulation of genes encoding other proteins involved in the process of chemotaxis and leukocyte adhesion; of particular interest is the integrin beta 2 (ITGB2) that is known to interact with suPLAUR in leukocyte adhesion. These findings suggest an important role for suPLAUR in the recruitment of immune cells to obese adipose tissue, in the pathogenesis of obesity.

Omental adipose tissue fibrosis and insulin resistance in severe obesity

Background/Objectives:

The unresolved chronic inflammation of white adipose tissue (WAT) in obesity leads to interstitial deposition of fibrogenic proteins as reparative process. The contribution of omental adipose tissue (oWAT) fibrosis to obesity-related complications remains controversial. The aim of our study was to investigate whether oWAT fibrosis may be related to insulin resistance in severely obese population.

Subjects/Methods:

Forty obese subjects were studied by glucose clamp before undergoing bariatric surgery and thus stratified according to insulin resistance severity (M-value). From the first (Group B: n=13; M=1.9±0.7 mg kg⁻¹ min⁻¹) and the highest (Group A: n=14; M=4.5±1.4 mg kg⁻¹ min⁻¹) M-value tertiles, which were age-, waist- and body mass index-matched, oWAT samples were then obtained.

Gene expression of collagen type I, III and VI, interleukin-6, profibrotic mediators (transforming growth factor (TGF)-β1, activin A, connective tissue growth factor), hypoxia inducible factor-1α (HIF-1α) and macrophage (CD68, monocyte chemotactic protein (MCP)-1, CD86, CD206, CD150) markers were analyzed by quantitative reverse transcription PCR. Adipocyte size and total fibrosis were assessed by histomorphometry techniques.

Results:

Fibrosis at morphological level resulted significantly greater in Group B compared with Group A, although collagens gene expression did not differ. Notably, collagen VI messenger RNA significantly correlated with collagen I, collagen III, HIF-1α, TGF-β1, CD68, MCP-1 and CD86 transcription levels, supporting their relation with fibrosis development.

Conclusions:

In conclusion, we show for the first time that human oWAT fibrosis in severe obesity is consistent with a higher degree of insulin resistance measured by glucose clamp. Therefore, collagen deposition could represent a maladaptive mechanism contributing to obesity-related metabolic complications.

Obesity and kidney disease: differential effects of obesity on adipose tissue and kidney inflammation and fibrosis

PURPOSE OF REVIEW

To provide a perspective by investigating the potential cross-talk between the adipose tissue and the kidney during obesity.

RECENT FINDINGS

It is well established that excessive caloric intake contributes to organ injury. The associated increased adiposity initiates a cascade of cellular events that leads to progressive obesity-associated diseases such as kidney disease. Recent evidence has indicated that adipose tissue produces bioactive substances that contribute to obesity-related kidney disease, altering the renal function and structure. In parallel, proinflammatory processes within the adipose tissue can also lead to pathophysiological changes in the kidney during the obese state.

SUMMARY

Despite considerable efforts to better characterize the pathophysiology of obesity-related metabolic disease, there are still a lack of efficient therapeutic strategies. New strategies focused on regulating adipose function with respect to AMP-activated protein kinase activation, NADPH oxidase function, and TGF-β may contribute to reducing adipose inflammation that may also provide renoprotection.

Human epicardial adipose tissue has a specific transcriptomic signature depending on its anatomical peri-atrial, peri-ventricular, or peri-coronary location

AIMS

Human epicardial adipose tissue (EAT) is a visceral and perivascular fat that has been shown to act locally on myocardium, atria, and coronary arteries. Its abundance has been linked to coronary artery disease (CAD) and atrial fibrillation. However, its physiological function remains highly debated. The aim of this study was to determine a specific EAT transcriptomic signature, depending on its anatomical peri-atrial (PA), peri-ventricular (PV), or peri-coronary location.

METHODS AND RESULTS

Samples of EAT and thoracic subcutaneous fat, obtained from 41 patients paired for cardiovascular risk factors, CAD, and atrial fibrillation were analysed using a pangenomic approach. We found 2728 significantly up-regulated genes in the EAT vs. subcutaneous fat with 400 genes being common between PA, PV, and peri-coronary EAT. These common genes were related to extracellular matrix remodelling, inflammation, infection, and thrombosis pathways. Omentin (ITLN1) was the most up-regulated gene and secreted adipokine in EAT (fold-change >12, P < 0.0001). Among EAT-enriched genes, we observed different patterns depending on adipose tissue location. A beige expression phenotype was found in EAT but PV EAT highly expressed uncoupled protein 1 (P = 0.01). Genes overexpressed in peri-coronary EAT were implicated in proliferation, O-N glycan biosynthesis, and sphingolipid metabolism. PA EAT displayed an atypical pattern with genes implicated in cardiac muscle contraction and intracellular calcium signalling pathway.

CONCLUSION

This study opens new perspectives in understanding the physiology of human EAT and its local interaction with neighbouring structures.

Differential DNA Methylation in Relation to Age and Health Risks of Obesity

The aim of this study was to evaluate whether genome-wide levels of DNA methylation are associated with age and the health risks of obesity (HRO); defined according to BMI categories as "Low HRO" (overweight and class 1 obesity) versus "High HRO" (class 2 and class 3 obesity). Anthropometric measurements were assessed in a subsample of 48 volunteers from the Metabolic Syndrome Reduction in Navarra (RESMENA) study and 24 women from another independent study, Effects of Lipoic Acid and Eicosapentaenoic Acid in Human Obesity (OBEPALIP study). In the pooled population; the methylation levels of 55 CpG sites were significantly associated with age after Benjamini-Hochberg correction. In addition, DNA methylation of three CpG sites located in ELOVL2; HOXC4 and PI4KB were further negatively associated with their mRNA levels. Although no differentially methylated CpG sites were identified in relation to HRO after multiple testing correction; several nominally significant CpG sites were identified in genes related to insulin signaling; energy and lipid metabolism. Moreover, statistically significant associations between BMI or mRNA levels and two HRO-related CpG sites located in GPR133 and ITGB5 are reported. As a conclusion, these findings from two Spanish cohorts add knowledge about the important role of DNA methylation in the age-related regulation of gene expression. In addition; a relevant influence of age on DNA methylation in white blood cells was found, as well as, on a trend level, novel associations between DNA methylation and obesity.

Serum SPARC and matrix metalloproteinase-2 and metalloproteinase-9 concentrations after bariatric surgery in obese adults

BACKGROUND

Remodeling of the extracellular matrix (ECM) of adipose tissue is regarded as part of the pathophysiology of obesity. Secreted protein acidic and rich in cysteine (SPARC) was the first ECM protein described in adipose tissue. Matrix metalloproteinases (MMPs) also play a role in ECM remodeling, and MMP-2 and MMP-9 may be associated with abnormal ECM metabolism. Here, we investigated changes in serum SPARC, MMP-2, and MMP-9 concentrations after bariatric surgery in obese adults.

METHODS

We recruited 34 obese patients who were scheduled to undergo bariatric surgery for weight loss. We analyzed changes in serum SPARC, MMP-2, and MMP-9 concentrations before and 9 months after bariatric surgery and any associations between changes in SPARC, MMP-2, and MMP-9 concentrations and obesity-related parameters.

RESULTS

Serum leptin levels significantly decreased, and the serum adiponectin level significantly increased after bariatric surgery. The serum SPARC concentration decreased significantly from 165.0 ± 18.2 to 68.7 ± 6.7 ng/mL (p < 0.001), and the MMP-2 concentration also decreased significantly from 262.2 ± 15.2 to 235.9 ± 10.5 ng/mL (p < 0.001). Changes in the serum SPARC concentration were significantly correlated with HOMA-IR changes, and changes in the serum MMP-9 concentration were found to inversely correlate with serum adiponectin changes.

CONCLUSION

These findings show that significant decreases in serum SPARC and MMP-2 concentrations occur after bariatric surgery. Our results thus suggest that weight loss via bariatric surgery could alter the ECM environment, and that these changes are related to certain metabolic changes.

MFAP5 is related to obesity-associated adipose tissue and extracellular matrix remodeling and inflammation

OBJECTIVE

Low-grade inflammation is involved in adipose tissue (AT) and extracellular matrix (ECM) remodeling and induces deposition of ECM proteins in AT. We have previously shown that MFAP5 (microfibrillar-associated protein 5) expression decreases in AT after weight loss. The aim of this study was to investigate MFAP5 localization in human AT and gene expression in adipocytes and the role of MFAP5 in adipocyte metabolism and inflammation.

METHODS

MFAP5 protein localization and gene expression were studied with immunohistochemistry and quantitative reverse transcriptase PCR (RT-qPCR) in human subcutaneous AT and cultured Simpson-Golabi-Behmel syndrome (SGBS) adipocytes, respectively. The effect of MFAP5 knock-down by siRNA on gene expression and insulin action was examined with RT-qPCR, western blot, and insulin-stimulated glucose uptake. The effect of different cytokines on MFAP5 gene and protein expression was investigated in cultured human SGBS preadipocytes.

RESULTS

MFAP5 protein was highly expressed in AT, and gene expression decreased during adipocyte differentiation in SGBS cells. Treatment of preadipocytes with TNFα and TGFβ1 increased MFAP5 gene and protein expression. Furthermore, MFAP5 knock-down decreased the expression of genes involved in inflammation.

CONCLUSIONS

Our results demonstrate that factors involving low-grade inflammation modulate MFAP5 expression and that the modified expression of MFAP5 may further regulate AT inflammation.

Irf5 deficiency in macrophages promotes beneficial adipose tissue expansion and insulin sensitivity during obesity

Accumulation of visceral adipose tissue correlates with elevated inflammation and increased risk of metabolic diseases. However, little is known about the molecular mechanisms that control its pathological expansion. Transcription factor interferon regulatory factor 5 (IRF5) has been implicated in polarizing macrophages towards an inflammatory phenotype. Here we demonstrate that mice lacking Irf5, when placed on a high-fat diet, show no difference in the growth of their epididymal white adipose tissue (epiWAT) but they show expansion of their subcutaneous white adipose tissue, as compared to wild-type (WT) mice on the same diet. EpiWAT from Irf5-deficient mice is marked by accumulation of alternatively activated macrophages, higher collagen deposition that restricts adipocyte size, and enhanced insulin sensitivity compared to epiWAT from WT mice. In obese individuals, IRF5 expression is negatively associated with insulin sensitivity and collagen deposition in visceral adipose tissue. Genome-wide analysis of gene expression in adipose tissue macrophages highlights the transforming growth factor β1 (TGFB1) gene itself as a direct target of IRF5-mediated inhibition. This study uncovers a new function for IRF5 in controlling the relative mass of different adipose tissue depots and thus insulin sensitivity in obesity, and it suggests that inhibition of IRF5 may promote a healthy metabolic state during this condition.

Bariatric Surgery Induces Disruption in Inflammatory Signaling Pathways Mediated by Immune Cells in Adipose Tissue: A RNA-Seq Study

Background

Bariatric surgery is associated to improvements in obesity-associated comorbidities thought to be mediated by a decrease of adipose inflammation. However, the molecular mechanisms behind these beneficial effects are poorly understood.

Methodology/Principal Findings

We analyzed RNA-seq expression profiles in adipose tissue from 22 obese women before and 3 months after surgery. Of 15,972 detected genes, 1214 were differentially expressed after surgery at a 5% false discovery rate. Upregulated genes were mostly involved in the basal cellular machinery. Downregulated genes were enriched in metabolic functions of adipose tissue. At baseline, 26 modules of coexpressed genes were identified. The four most stable modules reflected the innate and adaptive immune responses of adipose tissue. A first module reflecting a non-specific signature of innate immune cells, mainly macrophages, was highly conserved after surgery with the exception of DUSP2 and CD300C. A second module reflected the adaptive immune response elicited by T lymphocytes; after surgery, a disconnection was observed between genes involved in T-cell signaling and mediators of the signal transduction such as CXCR1, CXCR2, GPR97, CCR7 and IL7R. A third module reflected neutrophil-mediated inflammation; after surgery, several genes were dissociated from the module, including S100A8, S100A12, CD300E, VNN2, TUBB1 and FAM65B. We also identified a dense network of 19 genes involved in the interferon-signaling pathway which was strongly preserved after surgery, with the exception of DDX60, an antiviral factor involved in RIG-I-mediated interferon signaling. A similar loss of connection was observed in lean mice compared to their obese counterparts.

Conclusions/Significance

These results suggest that improvements of the inflammatory state following surgery might be explained by a disruption of immuno-inflammatory cascades involving a few crucial molecules which could serve as potential therapeutic targets.

The cell biology of fat expansion

Adipose tissue is a complex, multicellular organ that profoundly influences the function of nearly all other organ systems through its diverse metabolite and adipokine secretome. Adipocytes are the primary cell type of adipose tissue and play a key role in maintaining energy homeostasis. The efficiency with which adipose tissue responds to whole-body energetic demands reflects the ability of adipocytes to adapt to an altered nutrient environment, and has profound systemic implications. Deciphering adipocyte cell biology is an important component of understanding how the aberrant physiology of expanding adipose tissue contributes to the metabolic dysregulation associated with obesity.

Genome-wide expression in visceral adipose tissue from obese prepubertal children

Characterization of the genes expressed in adipose tissue (AT) is key to understanding the pathogenesis of obesity and to developing treatments for this condition. Our objective was to compare the gene expression in visceral AT (VAT) between obese and normal-weight prepubertal children. A total of fifteen obese and sixteen normal-weight children undergoing abdominal elective surgery were selected. RNA was extracted from VAT biopsies. Microarray experiments were independently performed for each sample (six obese and five normal-weight samples). Validation by quantitative PCR (qPCR) was performed on an additional 10 obese and 10 normal-weight VAT samples. Of 1276 differentially expressed genes (p < 0.05), 245 were more than two-fold higher in obese children than in normal-weight children. As validated by qPCR, expression was upregulated in genes involved in lipid and amino acid metabolism (CES1, NPRR3 and BHMT2), oxidative stress and extracellular matrix regulation (TNMD and NQO1), adipogenesis (CRYAB and AFF1) and inflammation (ANXA1); by contrast, only CALCRL gene expression was confirmed to be downregulated. In conclusion, this study in prepubertal children demonstrates the up- and down-regulation of genes that encode molecules that were previously proposed to influence the pathogenesis of adulthood obesity, as well as previously unreported dysregulated genes that may be candidate genes in the aetiology of obesity.

The lysyl oxidase inhibitor β-aminopropionitrile reduces body weight gain and improves the metabolic profile in diet-induced obesity in rats

Extracellular matrix (ECM) remodelling of the adipose tissue plays a pivotal role in the pathophysiology of obesity. The lysyl oxidase (LOX) family of amine oxidases, including LOX and LOX-like (LOXL) isoenzymes, controls ECM maturation, and upregulation of LOX activity is essential in fibrosis; however, its involvement in adipose tissue dysfunction in obesity is unclear. In this study, we observed that LOX is the main isoenzyme expressed in human adipose tissue and that its expression is strongly upregulated in samples from obese individuals that had been referred to bariatric surgery. LOX expression was also induced in the adipose tissue from male Wistar rats fed a high-fat diet (HFD). Interestingly, treatment with β-aminopropionitrile (BAPN), a specific and irreversible inhibitor of LOX activity, attenuated the increase in body weight and fat mass that was observed in obese animals and shifted adipocyte size toward smaller adipocytes. BAPN also ameliorated the increase in collagen content that was observed in adipose tissue from obese animals and improved several metabolic parameters – it ameliorated glucose and insulin levels, decreased homeostasis model assessment (HOMA) index and reduced plasma triglyceride levels. Furthermore, in white adipose tissue from obese animals, BAPN prevented the downregulation of adiponectin and glucose transporter 4 (GLUT4), as well as the increase in suppressor of cytokine signaling 3 (SOCS3) and dipeptidyl peptidase 4 (DPP4) levels, triggered by the HFD. Likewise, in the TNFα-induced insulin-resistant 3T3-L1 adipocyte model, BAPN prevented the downregulation of adiponectin and GLUT4 and the increase in SOCS3 levels, and consequently normalised insulin-stimulated glucose uptake. Therefore, our data provide evidence that LOX plays a pathologically relevant role in the metabolic dysfunction induced by obesity and emphasise the interest of novel pharmacological interventions that target adipose tissue fibrosis and LOX activity for the clinical management of this disease.

Highlighted Article: Lysyl oxidase (LOX) could play a role in the metabolic dysfunction induced by obesity, and consequently the inhibition of LOX activity could be a valuable strategy to ameliorate obesity-related metabolic disturbances.

Interaction of differentiated human adipocytes with macrophages leads to trogocytosis and selective IL-6 secretion

Obesity leads to adipose tissue inflammation that is characterized by increased release of proinflammatory molecules and the recruitment of activated immune cells. Although macrophages are present in the highest number among the immune cells in obese adipose tissue, not much is known about their direct interaction with adipocytes. We have introduced an ex vivo experimental system to characterize the cellular interactions and the profile of secreted cytokines in cocultures of macrophages and human adipocytes differentiated from either mesenchymal stem cells or a preadipocyte cell line. As observed by time-lapse microscopy, flow, and laser-scanning cytometry, macrophages phagocytosed bites of adipocytes (trogocytosis), which led to their de novo, phagocytosis and NF-κB-dependent synthesis, then release of interleukin (IL)-6 and monocyte chemoattractant protein (MCP)-1. IL-6 secretion was not accompanied by secretion of other proinflammatory cytokines, such as tumor necrosis factor (TNF)-α and IL-8, except MCP-1. LPS-induced release of TNF-α, IL-8 and MCP-1 was decreased in the presence of the differentiated adipocytes but the IL-6 level did not subside suggesting that phagocytosis-dependent IL-6 secretion may have significant regulatory function in the inflamed adipose tissue.

Global correlation analysis for microRNA and gene expression profiles in human obesity

Obesity is an increasing health problem associated with major adverse consequences for human health. MicroRNAs (miRNAs), small endogenous non-coding RNAs, regulate the expression of genes that play roles in human body via posttranscriptional inhibition. To identify the miRNAs and their target genes involved in obesity, we downloaded the miRNA and gene expression profiles from gene expression omnibus (GEO) database and analyzed the differentially expressed miRNAs (DEMs) and differentially expressed genes (DEGs) in adipose tissues from obese subjects compared to those from non-obese subjects. Then, we constructed the miRNA-target interaction network and conducted functional enrichment analysis of DEGs, and the targets negatively correlated with DEMs. We identified a total of 16 miRNAs and 192 genes that showed a significantly different expression and 3002 miRNA-target interaction pairs, including 182 regulatory pairs in obesity. Target genes of DEMs were found mainly enriched in several functions, such as collagen fibril organization, extracellular matrix part, and extracellular matrix structural constituent. Moreover, hsa-miR-425 and hsa-miR-126 had a significant number of target genes and hsa-miR-16/COL12A1 and hsa-miR-634/SLC4A4 interaction pairs are significantly co-expressed, suggesting that they might play important roles in the pathogenesis of obesity. Our study provides a bioinformatic basis for further research of molecular mechanism in obesity.