Systematic review of bariatric surgery liver biopsies clarifies the natural history of liver disease in patients with severe obesity

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD) is a frequent complication of morbid obesity, but its severity varies greatly and thus there is a strong need to better define its natural history in these patients.

DESIGN

Liver biopsies were systematically performed in 798 consecutive patients with severe obesity undergoing bariatric surgery. Histology was compared with clinical, biological, anthropometrical and body composition characteristics.

RESULTS

Patients with presumably normal liver (n=179, 22%) were significantly younger at bariatric surgery than patients with NAFLD (37.0 vs 44.4 years, p<0.0001). However, both groups showed quite similar obesity duration, since patients with presumably normal liver reported the onset of obesity at a significantly younger age than those with NAFLD (14.8 vs 20.0 year, p<0.0001). The trunk/limb fat mass ratio increased according to liver disease severity (presumably normal liver: 1.00, steatosis: 1.21, non-alcoholic steatohepatitis (NASH): 1.34, p<0.0001), although the total body fat mass decreased (presumably normal liver: 50%, steatosis: 49.1%, NASH: 47.4%, p<0.0001). The volume of subcutaneous adipocytes increased according to severity of liver disease but only in female patients (presumably normal liver: 8543 picolitres, steatosis: 9156 picolitres, NASH: 9996 picolitres).

CONCLUSIONS

These results suggest that young adults are more prone to store fat in subcutaneous tissue and reach the threshold of bariatric surgery indication before their liver is damaged. A shift of fat storage from subcutaneous to visceral adipose tissue compartment is associated with liver damages. Liver might also be targeted by subcutaneous hypertrophic adipocytes in females since hypertrophic adipocytes are more exposed to lipolysis and to the production of inflammatory mediators.

The FAT Score, a Fibrosis Score of Adipose Tissue: Predicting Weight-Loss Outcome After Gastric Bypass

CONTEXT

Bariatric surgery (BS) induces major and sustainable weight loss in many patients. Factors predicting poor weight-loss response (PR) need to be identified to improve patient care. Quantification of subcutaneous adipose tissue (scAT) fibrosis is negatively associated with post-BS weight loss, but whether it could constitute a predictor applicable in clinical routine remains to be demonstrated.

OBJECTIVE

To create a semiquantitative score evaluating scAT fibrosis and test its predictive value on weight-loss response after Roux-en-Y gastric bypass (RYGB).

METHODS

We created a fibrosis score of adipose tissue (FAT score) integrating perilobular and pericellular fibrosis. Using this score, we characterized 183 perioperative scAT biopsy specimens from severely obese patients who underwent RYGB (n = 85 from a training cohort; n = 98 from a confirmation cohort). PR to RYGB was defined as <28% of total weight loss at 1 year (lowest tertile). The link between FAT score and PR was tested in univariate and multivariate models.

RESULTS

FAT score was directly associated with increasing scAT fibrosis measured by a standard quantification method (P for trend <0.001). FAT score interobserver agreement was good (κ = 0.76). FAT score ≥2 was significantly associated with PR. The association remained significant after adjustment for age, diabetes status, hypertension, percent fat mass, and interleukin-6 level (adjusted odds ratio, 3.6; 95% confidence interval, 1.8 to 7.2; P = 0.003).

CONCLUSION

The FAT score is a new, simple, semiquantitative evaluation of human scAT fibrosis that may help identify patients with a potential limited weight-loss response to RYGB.

Knee and hip intra-articular adipose tissues (IAATs) compared with autologous subcutaneous adipose tissue: a specific phenotype for a central player in osteoarthritis

Objectives

Compared with subcutaneous adipose tissue (SCAT), infrapatellar fat pad (IFP), the main knee intra-articular adipose tissue (IAAT), has an inflammatory phenotype in patients with osteoarthritis (OA). We phenotyped suprapatellar fat pad (SPFP) and hip acetabular fat pad (AFP), two other IAATs, to determinate the unique signature of IAATs compared with SCAT.

Methods

IFP, SPFP, AFP and autologous SCAT were obtained from patients with OA during total knee (n=38) or hip replacement (n=5). Fibrosis and adipocyte area were analysed by histology and vascularisation, leucocyte and mast cell infiltration were analysed by immunohistochemistry for von Willebrand factor, leucocytes and tryptase, respectively. Secretion of interleukin (IL)-6, IL-8 and prostaglandin E2 (PGE2) was assessed by ELISA. The mRNA expression of adipocyte-associated genes (ATGL, LPL, PPAR-γ, FABP4 and CD36) and developmental genes (SFRP2, HoxC9 and EN1) was determined. The inflammatory response of isolated fibroblast-like synoviocytes (FLS) to autologous IFP and SPFP conditioned media was examined.

Results

Fibrosis, vascularisation and leucocyte and mast cell infiltration were greater in IAATs than SCAT, and levels of IL-6, IL-8 and PGE2 were greater in all IAATs than SCAT. IFP and SPFP induced a similar inflammatory response to FLS. Adipocyte area was smaller in IAATs than SCAT. Adipocyte-associated and developmental genes showed a similar gene expression pattern in all IAATs, different from SCAT.

Conclusions

IFP but also SPFP and AFP (gathered under the term ‘IAAT’) may play a deleterious role in OA by affecting joint homeostasis because of their inflammatory phenotype and their close interaction with synovium in the same functional unit.

Prospective assessment and histological analysis of adherent perinephric fat in partial nephrectomies

OBJECTIVES

The complexity of partial nephrectomy (PN) is partly anticipated by morphometric tumor-based scores that do not consider patient-related issues such as adherent perinephric fat (APF). Also, the objective is to prospectively assess the predictive factors of APF during PN, its effect on complications, and to correlate it to the histological reality.

METHODS

A total of 125 consecutive patients undergoing robotic or open PN were prospectively included. The Mayo adhesive probability score (MAP score) was compared to the peroperative presence of APF defined by a score≥2. Adipose tissue was analyzed histologically for fibrosis and inflammatory infiltrate of CD68+macrophages. Univariate and multivariate logistic regression analyses were performed to evaluate predictive factors of APF, and outcomes were compared using chi-square and Kruskal-Wallis tests.

RESULTS

APF was present in 51 patients (40.8%) and associated with slight longer operating time and increased blood loss. Warm ischemia time, margins, transfusion, and the Clavien-Dindo score were not different. In multivariate analysis, only male sex, age, waist circumference, fat density on computed tomography, and MAP score were significant predictors of APF. A radioclinical score was more predictive of APF than MAP score alone. Histologically, there was no macrophage infiltration but larger adipocytes in APF without significant differences in fibrosis.

CONCLUSIONS

APF can be accurately predicted using radioclinical data as the MAP score, combined with sex, age, and waist circumference. APF is associated with increased operative time and blood loss without postoperative complications. Histological analysis finds larger adipocytes in APF without inflammatory infiltrate, and no difference in fibrosis.

AdipoScan: A Novel Transient Elastography-Based Tool Used to Non-Invasively Assess Subcutaneous Adipose Tissue Shear Wave Speed in Obesity

We describe a novel device called the AdipoScan that was adapted from the FibroScan to specifically assess shear wave speed (SWS) in human abdominal subcutaneous adipose tissue (scAT). Measurement reproducibility was assessed on tissue-mimicking phantoms with and without repositioning, with resultant coefficients of variation of 1% and 0%, respectively, as well as in vivo (14% and 7%, respectively). The applicability of the AdipoScan was tested on 19 non-obese volunteers, and a scAT thickness >2 cm was found to be mandatory to perform a valid measurement. Abdominal scAT SWS was assessed in 73 severely obese subjects, all candidates for bariatric surgery. Subcutaneous AT SWS was positively associated with scAT fibrosis and obesity-related co-morbidities such as hypertension, glycemic status, dyslipidemia and liver dysfunction. These results suggest that the AdipoScan could be a useful non-invasive tool to evaluate scAT fibrosis and metabolic complications in obesity. Further investigation is required to evaluate the relevance of using the AdipoScan to predict patient weight trajectories and metabolic outcomes after bariatric surgery.

Increased Basement Membrane Components in Adipose Tissue During Obesity: Links With TGFβ and Metabolic Phenotypes

CONTEXT

Collagen accumulation around adipocytes and vessels (ie, pericellular fibrosis) is a hallmark of obese adipose tissue associated with altered metabolism.

OBJECTIVE

Our objective was to evaluate components of basement membrane (BM) in adipose tissue, including collagen IV, a major BM component, and its relationships with metabolic parameters and TGFβ isoforms.

DESIGN AND SETTING

We used immuno-techniques and gene expression approaches to detect BM components in subcutaneous and visceral adipose tissue samples. Adipocytes and endothelial cells were isolated from lean and obese adipose tissue. We also focused on the expression of COL4A1 correlated to metabolic variables in moderate obesity and, in severe obesity before and after bariatric surgery. Using in vitro analysis, we explored the impact of TGFβ isoforms on the expression of inflammatory and extracellular matrix genes in adipocytes and endothelial cells.

RESULTS

BM components were detected around adipocytes and endothelial cells, and were increased in obese adipocytes. COL4A1 expression was positively correlated with insulin-resistance indices in obese subjects and showed less reduction in severely obese subjects with poorer insulin-resistance outcomes 6 months after gastric bypass. COL4A1 expression also correlated with TGFβ1 and TGFβ3 gene expressions in subcutaneous adipose tissue. Stimulating isolated adipocytes and endothelial cells in vitro with these TGFβ isoforms showed an inflammatory and pro-fibrotic phenotype. However, TGFβ1 and TGFβ3 exposure only provoked COL4A1 overexpression in endothelial cells and not in adipocytes.

CONCLUSION

The disorganization of several BM components, including collagen IV, could contribute to pathological alterations of obese adipose tissue and cells.

Statins, antidiabetic medications and liver histology in patients with diabetes with non-alcoholic fatty liver disease

Background

Type-2 diabetes mellitus (T2DM) is a risk factor for progressive non-alcoholic fatty liver disease (NAFLD). Drugs commonly prescribed in patients with T2DM may affect liver histology by interfering with lipid metabolism and insulin resistance/secretion.

Aim

We studied if statins or antidiabetic agents were associated with non-alcoholic steatohepatitis (NASH) and significant fibrosis (SF).

Methods

We performed a cross-sectional study of 346 diabetics with biopsy-proven NAFLD. T2DM was defined as fasting glucose ≥7 mmol/L or glycated haemoglobin ≥6.5% and/or use of antidiabetics. NASH was defined according to the FLIP algorithm and SF as F2–4 Kleiner's stages.

Results

84% of patients were on antidiabetic therapy and 45% on statins. NASH and SF were present in 57% and 48% of patients. Statin-treated patients were older, more frequently male and with poorer glycaemic control despite more frequent antidiabetic therapy than those without statins; however, the prevalence of NASH (57%vs56%, p=0.868) and SF (48%vs48%, p=0.943) was not different between statin users and non-users. NASH was more common in patients on metformin or insulin than in those not treated with these drugs (60%vs47%, p=0.026; 68%vs53%, p=0.017). SF was more common in those treated with sulfonylureas (57%vs44%, p=0.030). Multivariate analyses confirmed that use of statins was independently and negatively associated with both NASH (OR (95% CI) 0.57 (0.32 to 1.01), p=0.055) and SF (OR (95% CI) 0.47 (0.26 to 0.84), p=0.011). Moreover, we found independent associations between insulin use and NASH (OR (95% CI) 2.24 (1.11 to 4.54), p=0.025) and sulfonylureas use and SF (OR (95% CI) 2.04 (1.11 to 3.74), p=0.022).

Conclusions

Several medications used in patients with diabetes are differently associated with NAFLD histology. Statin use is negatively associated, while insulin and sulfonylureas are positively associated with NASH and SF. A wider use of statins may be warranted in this high-risk population.

Prospective assessment of the adherent perinephric fat in partial nephrectomies: Predictors and impact on peri-operative outcomes

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Background: The surgical complexity of partial nephrectomy (PN) can be partly anticipated using renal morphometric scores that do not consider patient related issues such as obesity or perirenal fat. Our primary objective was to prospectively assess the predictive factors for adherent perinephric fat (APF) and its impact on the onset of complications. The secondary objective was to correlate the surgical appraising with the histological reality of APF. Methods: Fifty consecutive patients undergoing robotic or open PN were prospectively included from November 2014 to March 2015. The previously published Mayo adhesive probability score (MAP score) was calculated and compared to the per-operative surgical assessment of APF using a 0 to 3 scale (APF being defined by a score ≥ 2). Fat was analyzed histologically for fibrosis (HES staining and picrosirius red) and inflammatory infiltrate of macrophages (immunohistochemistry using anti-CD68 antibody). Results: APF was present in 18 patients (36%), with no impact on surgical approach (31.3% vs 38.9 robotic way, without surgical conversion). APF was associated with longer operating time (169 min vs. 146 min, p = 0.036) and increased blood loss (469 mL vs 179 mL, p = 0.014). Duration of clamping, rate of positive margins, blood transfusion and the Clavien-Dindo score were not different (Table 1). In multivariate analysis, only male gender (p = 0.044), age (p = 0.014) and MAP score (p = 0.00057) were significant predictors of APF. Histologically, APF was characterized by a marked fibrosis but no macrophage infiltrate. Conclusions: APF can be accurately predicted using radio-clinical data as the MAP score, combined with age and gender. APF is associated with increased operative time and blood loss without impacting the rate of complications. Histological analysis of APF demonstrates significant fibrosis without inflammatory infiltrate. [Table: see text]

Accumulation and Changes in Composition of Collagens in Subcutaneous Adipose Tissue After Bariatric Surgery

CONTEXT

Extracellular matrix (ECM) in sc adipose tissue (scAT) undergoes pathological remodeling during obesity. However, its evolution during weight loss remains poorly explored.

OBJECTIVE

The objective of the investigation was to study the histological, transcriptomic, and physical characteristics of scAT ECM remodeling during the first year of bariatric surgery (BS)-induced weight loss and their relationships with metabolic and bioclinical improvements.

DESIGN, SETTING, PATIENTS, AND INTERVENTIONS

A total of 118 morbidly obese candidates for BS were recruited and followed up during 1 year after BS.

MAIN OUTCOME MEASURES

scAT surgical biopsy and needle aspiration as well as scAT stiffness measurement were performed in three subgroups before and after BS. Fourteen nonobese, nondiabetic subjects served as controls.

RESULTS

Significantly increased picrosirius-red-stained collagen accumulation in scAT after BS was observed along with fat mass loss, despite metabolic and inflammatory improvements and undetectable changes of scAT stiffness. Collagen accumulation positively associated with M2-macrophages (CD163(+) cells) before BS but negatively afterward. Expression levels of genes encoding ECM components (eg, COL3A1, COL6A1, COL6A2, ELN), cross-linking enzymes (eg, lysyl oxidase [LOX], LOXL4, transglutaminase), metalloproteinases, and their inhibitors were modified 1 year after BS. LOX expression and protein were significantly decreased and associated with decreased fat mass as well as other cross-linking enzymes. Although total collagen I and VI staining decreased 1 year after BS, we found increased degraded collagen I and III in scAT, suggesting increased degradation.

CONCLUSIONS

After BS-induced weight loss and related metabolic improvements, scAT displays major collagen remodeling with an increased picrosirius-red staining that relates to increased collagen degradation and importantly decreased cross-linking. These features are in agreement with adequate ECM adaptation during fat mass loss.

Leptin Deficiency Shifts Mast Cells toward Anti-Inflammatory Actions and Protects Mice from Obesity and Diabetes by Polarizing M2 Macrophages

Mast cells (MCs) contribute to the pathogenesis of obesity and diabetes. This study demonstrates that leptin deficiency slants MCs toward anti-inflammatory functions. MCs in the white adipose tissue (WAT) of lean humans and mice express negligible leptin. Adoptive transfer of leptin-deficient MCs expanded ex vivo mitigates diet-induced and pre-established obesity and diabetes in mice. Mechanistic studies show that leptin-deficient MCs polarize macrophages from M1 to M2 functions because of impaired cell signaling and an altered balance between pro- and anti-inflammatory cytokines, but do not affect T cell differentiation. Rampant body weight gain in ob/ob mice, a strain that lacks leptin, associates with reduced MC content in WAT. In ob/ob mice, genetic depletion of MCs exacerbates obesity and diabetes, and repopulation of ex vivo expanded ob/ob MCs ameliorates these diseases.

Macrophage activation marker soluble CD163 and non-alcoholic fatty liver disease in morbidly obese patients undergoing bariatric surgery

BACKGROUND AND AIMS

Macrophages play an important role in non-alcoholic fatty liver disease (NAFLD). Soluble CD163 (sCD163) is a specific marker of macrophage activation. We aimed to measure sCD163 in morbidly obese patients with varying degrees of NAFLD before and after bariatric surgery (BS).

METHODS

Demographic, clinical, and biochemical data, and plasma sCD163 measured by enzyme-linked immunosorbent assay, of 196 patients were collected preoperatively and 3, 6, and 12 months after BS leading to significant weight loss. Peroperative liver biopsies were assessed for the NAFLD Activity Score (NAS), Kleiner fibrosis score, and the fatty liver inhibition of progression (FLIP) algorithm. In a subset, CD163 immunohistochemistry and real-time quantitative polymerase chain reaction for CD163 mRNA were performed.

RESULTS

sCD163 was higher in patients with NAS ≥ 5 compared with those with NAS < 5 (2.4(2.0-3.1) vs 1.9(1.5-2.3) mg/L, P < 0.001) and in patients with bridging fibrosis (F ≥ 3) compared with lower fibrosis stages (2.6(2.0-4.9) vs 2.0(1.5-2.4) mg/L, P = 0.001). Preoperative sCD163 was independently associated with both the NAS (P = 0.002) and the fibrosis score (P = 0.024). sCD163 decreased after BS and was greatly reduced after 12 months, more rapidly so in patients with NAS ≥ 5 (P < 0.001) and non-alcoholic steatohepatitis (NASH) according to the FLIP algorithm (P = 0.03). Immunohistochemistry showed CD163-positive macrophages aligning fat-laden hepatocytes and forming microgranulomas in patients with NASH. CD163 mRNA expression did not vary with NAS.

CONCLUSION

sCD163 increased in parallel with the severity of NAFLD in morbid obesity, indicating macrophage activation. BS reduced sCD163 even in patients with severe liver injury and fibrosis, suggesting full reversibility of macrophage activation associated with improved insulin sensitivity.

Jejunal T Cell Inflammation in Human Obesity Correlates with Decreased Enterocyte Insulin Signaling

In obesity, insulin resistance is linked to inflammation in several tissues. Although the gut is a very large lymphoid tissue, inflammation in the absorptive small intestine, the jejunum, where insulin regulates lipid and sugar absorption is unknown. We analyzed jejunal samples of 185 obese subjects stratified in three metabolic groups: without comorbidity, suffering from obesity-related comorbidity, and diabetic, versus 33 lean controls. Obesity increased both mucosa surface due to lower cell apoptosis and innate and adaptive immune cell populations. The preferential CD8αβ T cell location in epithelium over lamina propria appears a hallmark of obesity. Cytokine secretion by T cells from obese, but not lean, subjects blunted insulin signaling in enterocytes relevant to apical GLUT2 mislocation. Statistical links between T cell densities and BMI, NAFLD, or lipid metabolism suggest tissue crosstalk. Obesity triggers T-cell-mediated inflammation and enterocyte insulin resistance in the jejunum with potential broader systemic implications.

Circulating phospholipid profiling identifies portal contribution to NASH signature in obesity

BACKGROUND & AIMS

Non-alcoholic steatohepatitis (NASH) is characterized by steatosis, lobular inflammation, hepatocyte ballooning with fibrosis in severe cases, and high prevalence in obesity. We aimed at defining NASH signature in morbid obesity by mass spectrometry-based lipidomic analysis.

METHODS

We analyzed systemic blood before and 12 months after bariatric surgery, along with portal blood and adipose tissue lipid efflux collected from obese women at the time of surgery (9 structural classes, 150 species).

RESULTS

Increased concentrations of several glycerophosphocholines (PC), glycerophosphoethanolamines (PE), glycerophosphoinositols (PI), glycerophosphoglycerols (PG), lyso-glycerophosphocholines (LPC), and ceramides (Cer) were detected in systemic circulation of NASH subjects. Post-surgery weight loss (12 months) improved the levels of liver enzymes, as well as several lipids, but most PG and Cer species remained elevated. Analysis of lipids from hepatic portal system at the time of surgery revealed limited lipid alterations compared to systemic circulation, but PG and PE classes were found significantly increased in NASH subjects. We evaluated the contribution of visceral adipose tissue to lipid alterations in portal circulation by measuring adipose tissue lipid efflux ex vivo, and observed only minor alterations in NASH subjects. Interestingly, integration of clinical and lipidomic data (portal and systemic) led us to define a NASH signature in which lipids and clinical parameters are equal contributors.

CONCLUSIONS

Circulatory (portal and systemic) phospholipid profiling and clinical data defines NASH signature in morbid obesity. We report weak contribution of visceral adipose tissue to NASH-related portal lipid alterations, suggesting possible contribution from other organs draining into hepatic portal system.

Adipocyte ATP-binding cassette G1 promotes triglyceride storage, fat mass growth, and human obesity

The role of the ATP-binding cassette G1 (ABCG1) transporter in human pathophysiology is still largely unknown. Indeed, beyond its role in mediating free cholesterol efflux to HDL, the ABCG1 transporter equally promotes lipid accumulation in a triglyceride (TG)-rich environment through regulation of the bioavailability of lipoprotein lipase (LPL). Because both ABCG1 and LPL are expressed in adipose tissue, we hypothesized that ABCG1 is implicated in adipocyte TG storage and therefore could be a major actor in adipose tissue fat accumulation. Silencing of Abcg1 expression by RNA interference in 3T3-L1 preadipocytes compromised LPL-dependent TG accumulation during the initial phase of differentiation. Generation of stable Abcg1 knockdown 3T3-L1 adipocytes revealed that Abcg1 deficiency reduces TG storage and diminishes lipid droplet size through inhibition of Pparγ expression. Strikingly, local inhibition of adipocyte Abcg1 in adipose tissue from mice fed a high-fat diet led to a rapid decrease of adiposity and weight gain. Analysis of two frequent ABCG1 single nucleotide polymorphisms (rs1893590 [A/C] and rs1378577 [T/G]) in morbidly obese individuals indicated that elevated ABCG1 expression in adipose tissue was associated with increased PPARγ expression and adiposity concomitant to increased fat mass and BMI (haplotype AT>GC). The critical role of ABCG1 in obesity was further confirmed in independent populations of severe obese and diabetic obese individuals. This study identifies for the first time a major role of adipocyte ABCG1 in adiposity and fat mass growth and suggests that adipose ABCG1 might represent a potential therapeutic target in obesity.

Muscle ectopic fat deposition contributes to anabolic resistance in obese sarcopenic old rats through eIF2α activation

Obesity and aging are characterized by decreased insulin sensitivity (IS) and muscle protein synthesis. Intramuscular ceramide accumulation has been implicated in insulin resistance during obesity. We aimed to measure IS, muscle ceramide level, protein synthesis, and activation of intracellular signaling pathways involved in translation initiation in male Wistar young (YR, 6-month) and old (OR, 25-month) rats receiving a low- (LFD) or a high-fat diet (HFD) for 10 weeks. A corresponding cellular approach using C2C12 myotubes treated with palmitate to induce intracellular ceramide deposition was taken. A decreased ability of adipose tissue to store lipids together with a reduced adipocyte diameter and a development of fibrosis were observed in OR after the HFD. Consequently, OR fed the HFD were insulin resistant, showed a strong increase in intramuscular ceramide level and a decrease in muscle protein synthesis associated with increased eIF2α phosphorylation. The accumulation of intramuscular lipids placed a lipid burden on mitochondria and created a disconnect between metabolic and regulating pathways in skeletal muscles of OR. In C2C12 cells, palmitate-induced ceramide accumulation was associated with a decreased protein synthesis together with upregulated eIF2α phosphorylation. In conclusion, a reduced ability to expand adipose tissues was found in OR, reflecting a lower lipid buffering capacity. Muscle mitochondrial activity was affected in OR conferring a reduced ability to oxidize fatty acids entering the muscle cell. Hence, OR were more prone to ectopic muscle lipid accumulation than YR, leading to decreased muscle protein anabolism. This metabolic change is a potential therapeutic target to counter sarcopenic obesity.

Association of adipose tissue and liver fibrosis with tissue stiffness in morbid obesity: links with diabetes and BMI loss after gastric bypass

CONTEXT

Liver and white adipose tissue (WAT) develop inflammation and fibrosis.

OBJECTIVE

The aim of the study was to evaluate the bioclinical relevance of WAT fibrosis in morbid obesity and diabetes and the relationships with tissue stiffness measured using a novel device.

DESIGN AND SETTING

Observational and longitudinal studies were conducted in a hospital nutrition department.

PATIENTS

Biopsies of liver and subcutaneous WAT (scWAT) and omental adipose tissue were collected from 404 obese bariatric surgery candidates, of whom 243 were clinically characterized before surgery and 3, 6, and 12 months after surgery. In 123 subjects, liver and scWAT stiffness was assessed noninvasively using vibration-controlled transient elastography (VCTE).

INTERVENTIONS

Bariatric surgery was performed for some patients.

MAIN OUTCOME MEASURE

Adipose tissue fibrosis and stiffness and their link to obesity phenotypes were measured.

RESULTS

scWAT fibrosis was positively associated with liver fibrosis (fibrosis score ≥2) (ϱ= 0.14; P = .01). VCTE-evaluated liver and scWAT stiffness was positively correlated with immunohistochemistry-determined liver (ϱ= 0.46; P = .0009) and scWAT fibrosis (ϱ= 0.48; P = .0001). VCTE-evaluated scWAT stiffness measures negatively associated with dual-energy x-ray absorptiometry-evaluated body fat mass (R = -0.25; P = .009) and were correlated with metabolic variables. Diabetic subjects showed increased scWAT stiffness. Participants less responsive to gastric bypass were older and more frequently diabetic, and they had increased body mass index, serum IL-6, and scWAT and liver fibrosis. Subjects with no diabetes and normal liver had higher fat mass and lower tissue fibrosis and stiffness.

CONCLUSION

scWAT stiffness was associated with tissue fibrosis, obesity, and diabetes-related traits. Noninvasive evaluation of scWAT stiffness might be useful in clinical practice.

Macrophage gene expression in adipose tissue is associated with insulin sensitivity and serum lipid levels independent of obesity

OBJECTIVE

Obesity is linked to both increased metabolic disturbances and increased adipose tissue macrophage infiltration. However, whether macrophage infiltration directly influences human metabolism is unclear. The aim of this study was to investigate if there are obesity-independent links between adipose tissue macrophages and metabolic disturbances.

DESIGN AND METHODS

Expression of macrophage markers in adipose tissue was analyzed by DNA microarrays in the SOS Sib Pair study and in patients with type 2 diabetes and a BMI-matched healthy control group.

RESULTS

The expression of macrophage markers in adipose tissue was increased in obesity and associated with several metabolic and anthropometric measurements. After adjustment for BMI, the expression remained associated with insulin sensitivity, serum levels of insulin, C-peptide, high density lipoprotein cholesterol (HDL-cholesterol) and triglycerides. In addition, the expression of most macrophage markers was significantly increased in patients with type 2 diabetes compared to the control group.

CONCLUSION

Our study shows that infiltration of macrophages in human adipose tissue, estimated by the expression of macrophage markers, is increased in subjects with obesity and diabetes and associated with insulin sensitivity and serum lipid levels independent of BMI. This indicates that adipose tissue macrophages may contribute to the development of insulin resistance and dyslipidemia.

Fibrosis and adipose tissue dysfunction

Fibrosis is increasingly appreciated as a major player in adipose tissue dysfunction. In rapidly expanding adipose tissue, pervasive hypoxia leads to an induction of HIF1α that in turn leads to a potent profibrotic transcriptional program. The pathophysiological impact of adipose tissue fibrosis is likely to play an equally important role on systemic metabolic alterations as fibrotic conditions play in the liver, heart, and kidney. Here, we discuss recent advances in our understanding of the genesis, modulation, and systemic impact of excessive extracellular matrix (ECM) accumulation in adipose tissue of both rodents and humans and the ensuing impact on metabolic dysfunction.

Semaphorin 3C is a novel adipokine linked to extracellular matrix composition

AIMS/HYPOTHESIS

Alterations in white adipose tissue (WAT) function, including changes in protein (adipokine) secretion and extracellular matrix (ECM) composition, promote an insulin-resistant state. We set out to identify novel adipokines regulated by body fat mass in human subcutaneous WAT with potential roles in adipose function.

METHODS

Adipose transcriptome data and secretome profiles from conditions with increased/decreased WAT mass were combined. WAT donors were predominantly women. In vitro effects were assessed using recombinant protein. Results were confirmed by quantitative PCR/ELISA, metabolic assays and immunochemistry in human WAT and adipocytes.

RESULTS

We identified a hitherto uncharacterised adipokine, semaphorin 3C (SEMA3C), the expression of which correlated significantly with body weight, insulin resistance (HOMA of insulin resistance [HOMAIR], and the rate constant for the insulin tolerance test [KITT]) and adipose tissue morphology (hypertrophy vs hyperplasia). SEMA3C was primarily found in mature adipocytes and had no direct effect on human adipocyte differentiation, lipolysis, glucose transport or the expression of β-oxidation genes. This could in part be explained by the significant downregulation of its cognate receptors during adipogenesis. In contrast, in pre-adipocytes, SEMA3C increased the production/secretion of several ECM components (fibronectin, elastin and collagen I) and matricellular factors (connective tissue growth factor, IL6 and transforming growth factor-β1). Furthermore, the expression of SEMA3C in human WAT correlated positively with the degree of fibrosis in WAT.

CONCLUSIONS/INTERPRETATION

SEMA3C is a novel adipokine regulated by weight changes. The correlation with WAT hypertrophy and fibrosis in vivo, as well as its effects on ECM production in human pre-adipocytes in vitro, together suggest that SEMA3C constitutes an adipocyte-derived paracrine signal that influences ECM composition and may play a pathophysiological role in human WAT.

Plasma NOV/CCN3 levels are closely associated with obesity in patients with metabolic disorders

OBJECTIVE

Evidence points to a founder of the multifunctional CCN family, NOV/CCN3, as a circulating molecule involved in cardiac development, vascular homeostasis and inflammation. No data are available on the relationship between plasma NOV/CCN3 levels and cardiovascular risk factors in humans. This study investigated the possible relationship between plasma NOV levels and cardiovascular risk factors in humans.

METHODS

NOV levels were measured in the plasma from 594 adults with a hyperlipidemia history and/or with lipid-lowering therapy and/or a body mass index (BMI) >30 kg/m(2). Correlations were measured between NOV plasma levels and various parameters, including BMI, fat mass, and plasma triglycerides, cholesterol, glucose, and C-reactive protein. NOV expression was also evaluated in adipose tissue from obese patients and rodents and in primary cultures of adipocytes and macrophages.

RESULTS

After full multivariate adjustment, we detected a strong positive correlation between plasma NOV and BMI (r = 0.36 p<0.0001) and fat mass (r = 0.33 p<0.0005). According to quintiles, this relationship appeared to be linear. NOV levels were also positively correlated with C-reactive protein but not with total cholesterol, LDL-C or blood glucose. In patients with drastic weight loss induced by Roux-en-Y bariatric surgery, circulating NOV levels decreased by 28% (p<0.02) and 48% (p<0.0001) after 3 and 6 months, respectively, following surgery. In adipose tissue from obese patients, and in human primary cultures NOV protein was detected in adipocytes and macrophages. In mice fed a high fat diet NOV plasma levels and its expression in adipose tissue were also significantly increased compared to controls fed a standard diet.

CONCLUSION

Our results strongly suggest that in obese humans and mice plasma NOV levels positively correlated with NOV expression in adipose tissue, and support a possible contribution of NOV to obesity-related inflammation.

Roles of chemokine ligand-2 (CXCL2) and neutrophils in influencing endothelial cell function and inflammation of human adipose tissue

The hypertrophied white adipose tissue (WAT) during human obesity produces inflammatory mediators, including cytokines (IL-6 and TNFα) and chemokines ([C-C motif] chemokine ligand 2 and IL-8). These inflammatory factors are preferentially produced by the nonadipose cells, particularly the adipose tissue infiltrating macrophages. We identified the chemokine (C-X-C motif) ligand 2 (CXCL2) by a transcriptomic approach. Because CXCL2 could represent a WAT-produced chemokine, we explored its role in obesity-associated inflammation. CXCL2 levels in serum and mRNA in WAT were higher in obese subjects compared with lean ones. CXCL2 secretions were higher in sc and visceral (vis) WAT from obese compared with lean subjects. In vis WAT, CXCL2 mRNA expression was higher in macrophages compared with other WAT cells and positively correlated with the inflammatory macrophage markers TNFα and IL-6. CXCL2 triggered the in vitro adhesion of the neutrophils, its selective cell targets, to endothelial cells (ECs) of vis WAT (vis WAT-ECs). Immunohistological analysis indicated that activated neutrophils were adherent to the endothelium of vis WAT from human obese subjects. Blood neutrophils from obese subjects released high levels of proinflammatory mediators (IL-8, chemokine motif ligand 2 [CCL2], matrix metalloproteinase [MMP] 9, and myeloperoxidase [MPO]). Visceral WAT-ECs, treated by neutrophil-conditioned media prepared from obese subjects, displayed an increase of the expression of inflammatory molecules associated with senescence and angiogenic capacities. To conclude, CXCL2, a WAT-produced chemokine being up-regulated in obesity, stimulates neutrophil adhesion to vis WAT-ECs. Activated neutrophils in obesity may influence vis WAT-ECs functions and contribute to WAT inflammation.

Solute carrier family 2 member 1 is involved in the development of nonalcoholic fatty liver disease

Susceptibility to develop nonalcoholic fatty liver disease (NAFLD) has genetic bases, but the associated variants are uncertain. The aim of the present study was to identify genetic variants that could help to prognose and further understand the genetics and development of NAFLD. Allele frequencies of 3,072 single-nucleotide polymorphisms (SNPs) in 92 genes were characterized in 69 NAFLD patients and 217 healthy individuals. The markers that showed significant allele-frequency differences in the pilot groups were subsequently studied in 451 NAFLD patients and 304 healthy controls. Besides this, 4,414 type 2 diabetes mellitus (T2DM) cases and 4,567 controls were genotyped. Liver expression of the associated gene was measured and the effect of its potential role was studied by silencing the gene in vitro. Whole genome expression, oxidative stress (OS), and the consequences of oleic acid (OA)-enriched medium on lipid accumulation in siSLC2A1-THLE2 cells were studied by gene-expression analysis, dihydroethidium staining, BODIPY, and quantification of intracellular triglyceride content, respectively. Several SNPs of SLC2A1 (solute carrier family 2 [facilitated glucose transporter] member 1) showed association with NAFLD, but not with T2DM, being the haplotype containing the minor allele of SLC2A1 sequence related to the susceptibility to develop NAFLD. Gene-expression analysis demonstrated a significant down-regulation of SLC2A1 in NAFLD livers. Enrichment functional analyses of transcriptome profiles drove us to demonstrate that in vitro silencing of SLC2A1 induces an increased OS activity and a higher lipid accumulation under OA treatment.

CONCLUSIONS

Genetic variants of SLC2A1 are associated with NAFLD, and in vitro down-regulation of this gene promotes lipid accumulation. Moreover, the oxidative response detected in siSLC2A1-THLE2 cells corroborated the antioxidant properties previously related to this gene and linked the most representative clinical characteristics of NAFLD patients: oxidative injury and increased lipid storage.

Noninvasive diagnosis of nonalcoholic steatohepatitis disease based on clinical decision support system

Non-alcoholic fatty liver disease (NAFLD) is a hepatic disease associated with metabolic syndrome. NAFLD covers a spectrum of liver disease from steatosis to non-alcoholic steatohepatitis (NASH) and cirrhosis. NASH is a disease evolving under the influence of various stimuli still poorly understood. In this paper we present new clinical decision support system (CDSS) for the diagnosis of NASH and the comparison of this system with machine learning algorithms.

Histopathological algorithm and scoring system for evaluation of liver lesions in morbidly obese patients

Nonalcoholic fatty liver disease (NAFLD) is highly prevalent and being overweight is a significant risk factor. The aim was to build an algorithm along with a scoring system for histopathologic classification of liver lesions that covers the entire spectrum of lesions in morbidly obese patients. A cohort of 679 obese patients undergoing liver biopsy at the time of bariatric surgery was studied. An algorithm for segregating lesions into normal liver, NAFLD, or nonalcoholic steatohepatitis (NASH) was built based on semiquantitative evaluation of steatosis, hepatocellular ballooning, and lobular inflammation. For each case, the SAF score was created including the semiquantitative scoring of steatosis (S), activity (A), and fibrosis (F). Based on the algorithm, 230 obese patients (34%) were categorized as NASH, 291 (43%) as NAFLD without NASH, and 158 (23%) as not NAFLD. The activity score (ballooning + lobular inflammation) enabled discriminating NASH because all patients with NASH had A ≥ 2, whereas no patients with A < 2 had NASH. This score was closely correlated with both alanine aminotransferase (ALT) and aspartate aminotransferase (AST) (P < 0.0001, analysis of variance [ANOVA]). Comparison of transaminase levels between patients with normal liver and pure steatosis did not reveal significant differences, thus lending support to the proposal not to include steatosis in the activity score but to report it separately in the SAF score. In the validation series, the interobserver agreement for the diagnosis of NASH was excellent (κ = 0.80) between liver pathologists. There was no discrepancy between the initial diagnosis and the diagnosis proposed using the algorithm.

CONCLUSION

We propose a simple but robust algorithm for categorizing liver lesions in NAFLD patients. Because liver lesions in obese patients may display a continuous spectrum of histologic lesions, we suggest describing liver lesions using the SAF score.

Structural and inflammatory heterogeneity in subcutaneous adipose tissue: relation with liver histopathology in morbid obesity

BACKGROUND & AIMS

In addition to total body fat, the regional distribution and inflammatory status of enlarged adipose tissue are strongly associated with metabolic co-morbidities of obesity. We recently showed that the severity of histological liver lesions related to obesity increases with the amount of macrophage accumulation in visceral adipose tissue (VAT), while no association was found with the subcutaneous adipose tissue (SAT). In the abdominal region, SAT is anatomically divided into two layers, i.e. superficial (sSAT) and deep (dSAT). The aim of the present study was to test the hypothesis that these distinct compartments differentially contribute to hepatic alterations in obesity.

METHODS

Biopsies of the liver, sSAT, dSAT, and VAT were collected in 45 subjects with morbid obesity (age 43.7±1.6 years; BMI 48.5±1.2kg/m(2)) during bariatric surgery. Large scale gene expression analysis was performed to identify the pathways that discriminate sSAT from dSAT. Adipose tissue macrophages were quantified by immunohistochemistry using HAM56 antibody in subjects scored for liver histopathology.

RESULTS

An inflammatory gene pattern discriminates between sSAT and dSAT. dSAT displayed an intermediate level of macrophage accumulation between sSAT and VAT. The abundance of macrophages in dSAT, but not in sSAT, was significantly increased in patients with non-alcoholic steatohepatitis (NASH) and/or fibroinflammatory hepatic lesions.

CONCLUSIONS

These data show distinct gene signature and macrophage abundance in the two compartments of SAT, with dSAT more closely related to VAT than to sSAT in terms of inflammation and relation with the severity of liver diseases in morbid obesity.

Adipose tissue remodeling in children: the link between collagen deposition and age-related adipocyte growth

CONTEXT

Extracellular matrix (ECM) remodeling is essential for adipose tissue growth and expansion in high fat-fed mice, and there is evidence of fibrosis in adipose tissue in human obesity.

OBJECTIVE

The aim of the study was to explore the role of ECM remodeling in adipose tissue in healthy, growing children. RESEARCH DESIGN, SETTING, AND PARTICIPANTS: Abdominal sc adipose biopsies were obtained from 65 otherwise healthy children [57 boys; age, 5.3 ± 3.8 yr (mean ± sd)] having elective surgery (cross-sectional study). Twenty percent of the participants were classified as overweight/obese based on body mass index (BMI) z score.

MAIN OUTCOME MEASURES

We examined collagen (total and pericellular), HAM56+ macrophages, CD206+ M2 phenotype macrophages, and CD3+ T cells measured by immunohistochemistry and ECM gene expression markers.

RESULTS

Overweight children had significantly less total collagen compared to normal weight children (median, 3.4 vs. 9.1%; P = 0.001). However, collagen areas were not positive for COL6 and showed little evidence of collagen surrounding adipocytes. Fat cell size was negatively correlated with the percentage of total (r = -0.398; P = 0.003) and pericellular collagen (r = -0.462; P < 0.001) but positively correlated with HAM56+ macrophages (r = 0.541; P < 0.001). The percentage of total collagen was inversely associated with BMI z score (r = -0.345; P = 0.01) and age (r = -0.348; P = 0.005), with older (>11 yr old) children in the top BMI z tertile having less collagen (3.8%) than younger (2-5 yr old) children in the bottom BMI z tertile (12.6%). Adipose tissue in overweight children showed little evidence of crown-like structures or T cells.

CONCLUSION

In healthy, growing children, increased collagen in adipose tissue is associated with decreased fat cell size and BMI z score and increased M2+ phenotype macrophages, suggesting dynamic interaction between ECM remodeling and immune cells even at an early age.

Obesity-dependent metabolic signatures associated with nonalcoholic fatty liver disease progression

Our understanding of the mechanisms by which nonalcoholic fatty liver disease (NAFLD) progresses from simple steatosis to steatohepatitis (NASH) is still very limited. Despite the growing number of studies linking the disease with altered serum metabolite levels, an obstacle to the development of metabolome-based NAFLD predictors has been the lack of large cohort data from biopsy-proven patients matched for key metabolic features such as obesity. We studied 467 biopsied individuals with normal liver histology (n=90) or diagnosed with NAFLD (steatosis, n=246; NASH, n=131), randomly divided into estimation (80% of all patients) and validation (20% of all patients) groups. Qualitative determinations of 540 serum metabolite variables were performed using ultraperformance liquid chromatography coupled to mass spectrometry (UPLC-MS). The metabolic profile was dependent on patient body-mass index (BMI), suggesting that the NAFLD pathogenesis mechanism may be quite different depending on an individual's level of obesity. A BMI-stratified multivariate model based on the NAFLD serum metabolic profile was used to separate patients with and without NASH. The area under the receiver operating characteristic curve was 0.87 in the estimation and 0.85 in the validation group. The cutoff (0.54) corresponding to maximum average diagnostic accuracy (0.82) predicted NASH with a sensitivity of 0.71 and a specificity of 0.92 (negative/positive predictive values=0.82/0.84). The present data, indicating that a BMI-dependent serum metabolic profile may be able to reliably distinguish NASH from steatosis patients, have significant implications for the development of NASH biomarkers and potential novel targets for therapeutic intervention.

Performance of biomarkers FibroTest, ActiTest, SteatoTest, and NashTest in patients with severe obesity: meta analysis of individual patient data

BACKGROUND

Liver biopsy is considered as the gold standard for assessing non-alcoholic fatty liver disease (NAFLD) histologic lesions in patients with severe obesity. The aim of this study was to perform an overview of 3 studies which assessed the performance of non-invasive markers of fibrosis (FibroTest), steatosis (SteatoTest) and steato-hepatitis (NashTest, ActiTest) in these patients.

METHODS

494 patients with interpretable biopsy and biomarkers using of three prospective cohorts of patients with severe obesity (BMI >35 kg/m2) were included. Histology (NAS score) and the biochemical measurements were blinded to any other characteristics. The area under the ROC curves (AUROC), sensitivity, specificity, positive and negative predictive values were assessed. Weighted AUROC (wAUROC Obuchowski method) was used to prevent multiple testing and spectrum effect. Two meta-analyses were performed; one used the individual patient, and the other a classical meta-analysis.

RESULTS

Prevalence of advanced fibrosis (bridging) was 9.9%, advanced steatosis (>33%) 54.2%, and steato-hepatitis (NAS score >4) 17.2%. The mean wAUROCs were: FibroTest for advanced fibrosis (95%CI; significance)  =  0.85 (0.83-0.87; P<0.0001); SteatoTest for advanced steatosis = 0.80 (0.79-0.83); and ActiTest for steato-hepatitis = 0.84 (0.82-0.86; P<0.0001). Using the classical meta-analysis (random effect model) the mean AUROCs were: FibroTest = 0.72 (0.63-0.79; P<0.0001); SteatoTest = 0.71 (0.66-0.75; P<0.0001); and ActiTest = 0.74 (0.68-0.79; P<0.0001). Despite more metabolic risk factors in one cohort, results were similar according to gender, presence of diabetes and between the 3 cohorts.

CONCLUSION

In patients with severe obesity, a significant diagnostic performance of FibroTest, SteatoTest and ActiTest was observed for liver lesions.

Chronic intermittent hypoxia is a major trigger for non-alcoholic fatty liver disease in morbid obese

BACKGROUND & AIMS

Morbid obesity is frequently associated with low grade systemic inflammation, increased macrophage accumulation in adipose tissue (AT), obstructive sleep apnea (OSA), and nonalcoholic fatty liver disease (NAFLD). It has been suggested that chronic intermittent hypoxia (CIH) resulting from OSA could be an independent factor for early stage of NAFLD in addition to other well-recognized factors (dyslipidemia or insulin resistance). Moreover, macrophage accumulation in AT is associated with local hypoxia in fat tissue. We hypothesized that the association between CIH and morbid obesity could exert additional specific deleterious effects both in the liver and adipose tissues.

METHODS

One hundred and one morbidly obese subjects were prospectively recruited and underwent bariatric surgery during which a liver needle biopsy as well as surgical subcutaneous and omental AT biopsies were obtained. Oxygen desaturation index (ODI) quantified the severity of nocturnal CIH.

RESULTS

Histopathologic analysis of liver biopsies demonstrated that NAFLD lesions (ballooning of hepatocytes, lobular inflammation), NAFLD activity score (NAS), and fibrosis were significantly more severe in patients with the highest ODI tertile (p values ≤0.001 for all hepatic lesions). In multivariate analysis, after adjustment for age, obesity, and insulin resistance status, CIH remained independently associated with hepatic fibrosis, fibroinflammation, and NAS. By contrast, no association was found between CIH, macrophage accumulation, and adipocytes size in both subcutaneous and omental adipose tissue.

CONCLUSIONS

In morbidly obese patients, CIH was strongly associated with more severe liver injuries but did not worsen obesity induced macrophage accumulation in adipose tissue depots.

GLUT2 accumulation in enterocyte apical and intracellular membranes: a study in morbidly obese human subjects and ob/ob and high fat-fed mice

OBJECTIVE

In healthy rodents, intestinal sugar absorption in response to sugar-rich meals and insulin is regulated by GLUT2 in enterocyte plasma membranes. Loss of insulin action maintains apical GLUT2 location. In human enterocytes, apical GLUT2 location has not been reported but may be revealed under conditions of insulin resistance.

RESEARCH DESIGN AND METHODS

Subcellular location of GLUT2 in jejunal enterocytes was analyzed by confocal and electron microscopy imaging and Western blot in 62 well-phenotyped morbidly obese subjects and 7 lean human subjects. GLUT2 locations were assayed in ob/ob and ob/+ mice receiving oral metformin or in high-fat low-carbohydrate diet-fed C57Bl/6 mice. Glucose absorption and secretion were respectively estimated by oral glucose tolerance test and secretion of [U-(14)C]-3-O-methyl glucose into lumen.

RESULTS

In human enterocytes, GLUT2 was consistently located in basolateral membranes. Apical GLUT2 location was absent in lean subjects but was observed in 76% of obese subjects and correlated with insulin resistance and glycemia. In addition, intracellular accumulation of GLUT2 with early endosome antigen 1 (EEA1) was associated with reduced MGAT4a activity (glycosylation) in 39% of obese subjects on a low-carbohydrate/high-fat diet. Mice on a low-carbohydrate/high-fat diet for 12 months also exhibited endosomal GLUT2 accumulation and reduced glucose absorption. In ob/ob mice, metformin promoted apical GLUT2 and improved glucose homeostasis. Apical GLUT2 in fasting hyperglycemic ob/ob mice tripled glucose release into intestinal lumen.

CONCLUSIONS

In morbidly obese insulin-resistant subjects, GLUT2 was accumulated in apical and/or endosomal membranes of enterocytes. Functionally, apical GLUT2 favored and endosomal GLUT2 reduced glucose transepithelial exchanges. Thus, altered GLUT2 locations in enterocytes are a sign of intestinal adaptations to human metabolic pathology.

Liquid chromatography-mass spectrometry-based parallel metabolic profiling of human and mouse model serum reveals putative biomarkers associated with the progression of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease in most western countries. Current NAFLD diagnosis methods (e.g., liver biopsy analysis or imaging techniques) are poorly suited as tests for such a prevalent condition, from both a clinical and financial point of view. The present work aims to demonstrate the potential utility of serum metabolic profiling in defining phenotypic biomarkers that could be useful in NAFLD management. A parallel animal model/human NAFLD exploratory metabolomics approach was employed, using ultra performance liquid chromatography-mass spectrometry (UPLC-MS) to analyze 42 serum samples collected from nondiabetic, morbidly obese, biopsy-proven NAFLD patients, and 17 animals belonging to the glycine N-methyltransferase knockout (GNMT-KO) NAFLD mouse model. Multivariate statistical analysis of the data revealed a series of common biomarkers that were significantly altered in the NAFLD (GNMT-KO) subjects in comparison to their normal liver counterparts (WT). Many of the compounds observed could be associated with biochemical perturbations associated with liver dysfunction (e.g., reduced Creatine) and inflammation (e.g., eicosanoid signaling). This differential metabolic phenotyping approach may have a future role as a supplement for clinical decision making in NAFLD and in the adaption to more individualized treatment protocols.

Urokinase plasminogen activator receptor in adipose tissue macrophages of morbidly obese subjects

OBJECTIVE

At present, circulating markers characterizing the inflammatory infiltration of white adipose tissue (WAT) in human obesity are not well known. We previously identified, by a pangenomic approach (microarrays), the urokinase plasminogen activator receptor (PLAUR or CD87) as a potential marker of subcutaneous adipose tissue macrophage infiltration (ATM).

METHOD

We studied i) the presence of PLAUR protein in WAT; ii) the PLAUR amount in plasma of obese patients; iii) the circulating variations during surgery-induced weight loss, and iv) the correlations between PLAUR circulating levels and bioclinical parameters.

RESULTS

We observed that PLAUR is preferentially expressed by infiltrating ATMs, with a typical localization on macrophage membrane. Circulating soluble PLAUR levels were significantly elevated in obese patients compared to lean controls. However, despite a trend towards a decrease 3 months after weight loss, PLAUR plasma levels were not modulated during a 1-year weight loss follow-up, suggesting the contribution of secretion sites other than subcutaneous WAT in obese patients.

CONCLUSIONS

These findings indicate that PLAUR mRNA expression could be used for the estimation of local subcutaneous ATMs infiltration in obese patients, but it cannot be used as a systemic marker of this inflammatory infiltration in dynamic phases of weight loss.

Fibrosis in human adipose tissue: composition, distribution, and link with lipid metabolism and fat mass loss

OBJECTIVE

Fibrosis is a newly appreciated hallmark of the pathological alteration of human white adipose tissue (WAT). We investigated the composition of subcutaneous (scWAT) and omental WAT (oWAT) fibrosis in obesity and its relationship with metabolic alterations and surgery-induced weight loss.

RESEARCH DESIGN AND METHODS

Surgical biopsies for scWAT and oWAT were obtained in 65 obese (BMI 48.2 ± 0.8 kg/m(2)) and 9 lean subjects (BMI 22.8 ± 0.7 kg/m(2)). Obese subjects who were candidates for bariatric surgery were clinically characterized before, 3, 6, and 12 months after surgery, including fat mass evaluation by dual energy X-ray absorptiometry. WAT fibrosis was quantified and characterized using quantitative PCR, microscopic observation, and immunohistochemistry.

RESULTS

Fibrosis amount, distribution and collagen types (I, III, and VI) present distinct characteristics in lean and obese subjects and with WAT depots localization (subcutaneous or omental). Obese subjects had more total fibrosis in oWAT and had more pericellular fibrosis around adipocytes than lean subjects in both depots. Macrophages and mastocytes were highly represented in fibrotic bundles in oWAT, whereas scWAT was more frequently characterized by hypocellular fibrosis. The oWAT fibrosis negatively correlated with omental adipocyte diameters (R = -0.30, P = 0.02), and with triglyceride levels (R = -0.42, P < 0.01), and positively with apoA1 (R = 0.25, P = 0.05). Importantly, scWAT fibrosis correlated negatively with fat mass loss measured at the three time points after surgery.

CONCLUSIONS

Our data suggest differential clinical consequences of fibrosis in human WAT. In oWAT, fibrosis could contribute to limit adipocyte hypertrophy and is associated with a better lipid profile, whereas scWAT fibrosis may hamper fat mass loss induced by surgery.

Short-term overfeeding may induce peripheral insulin resistance without altering subcutaneous adipose tissue macrophages in humans

OBJECTIVE

Chronic low-grade inflammation is a feature of obesity and is postulated to be causal in the development of insulin resistance and type 2 diabetes. The aim of this study was to assess whether overfeeding induces peripheral insulin resistance in lean and overweight humans, and, if so, whether it is associated with increased systemic and adipose tissue inflammation.

RESEARCH DESIGN AND METHODS

Thirty-six healthy individuals undertook 28 days of overfeeding by +1,250 kcal/day (45% fat). Weight, body composition, insulin sensitivity (hyperinsulinemic-euglycemic clamp), serum and gene expression of inflammation markers, immune cell activation, fat cell size, macrophage and T-cell numbers in abdominal subcutaneous adipose tissue (flow cytometry and immunohistochemistry) were assessed at baseline and after 28 days.

RESULTS

Subjects gained 2.7 +/- 1.6 kg (P < 0.001) and increased fat mass by 1.1 +/- 1.6% (P < 0.001). Insulin sensitivity decreased by 11% from 54.6 +/- 18.7 to 48.9 +/- 15.7 micromol/(kg of FFM)/min (P = 0.01). There was a significant increase in circulating C-reactive protein (P = 0.002) and monocyte chemoattractant protein-1 (P = 0.01), but no change in interleukin-6 and intercellular adhesion molecule-1. There were no changes in fat cell size, the number of adipose tissue macrophages or T-cells, or inflammatory gene expression and no change in circulating immune cell number or expression of their surface activation markers after overfeeding.

CONCLUSIONS

Weight gain-induced insulin resistance was observed in the absence of a significant inflammatory state, suggesting that inflammation in subcutaneous adipose tissue occurs subsequent to peripheral insulin resistance in humans.

Chemerin correlates with markers for fatty liver in morbidly obese patients and strongly decreases after weight loss induced by bariatric surgery

CONTEXT

Chemerin is a new adipokine involved in in vitro adipogenesis and insulin resistance and associates with body mass index (BMI) in vivo.

OBJECTIVE

We investigated the role of chemerin in morbid obesity, associated metabolic diseases (insulin resistance, hepatic diseases), and postsurgery-induced weight loss.

SETTING

This was a prospective study performed at a university hospital.

SUBJECTS

Subjects included 60 obese female patients (BMI 50.0 +/- 1.0 kg/m(-2)) being candidates for gastric bypass.

STUDY DESIGN

Patients were examined before and 3, 6, and 12 months after surgery. In 27 patients, chemerin was measured after 2 yr.

MAIN OUTCOME

Outcomes included chemerin, anthropometric parameters, homeostasis model assessment for insulin resistance index (HOMA-IR), cholesterol, high-density lipoprotein, triglycerides, C-reactive protein, adipokines at all time points; and liver histology and macrophage content in fat at baseline.

RESULTS

Chemerin was substantially elevated in obese patients compared with nonobese persons (353.8 +/- 18.0 vs. 191 +/- 14 ng/ml, P < 0.001). Preoperatively, chemerin concentrations correlated positively with BMI, C-reactive protein, IL-6, HOMA-IR, and the amount of omental macrophages and negatively with high-density lipoprotein levels. Baseline chemerin was elevated in patients with a significant activity score for nonalcoholic fatty liver disease, portal inflammation, fibrosis, and fibroinflammation. After surgery, chemerin decreased significantly to 253.0 +/- 14.9 ng/ml after 1 yr and pursued its decrease in patients studied for 2 yr. After surgery, chemerin concentrations positively correlated with triglycerides. The strong decrease of chemerin in the 3 months after surgery was associated with the decrease in HOMA-IR and blood glucose.

CONCLUSIONS

Chemerin concentrations are elevated in morbidly obese patients and correlated with insulin resistance and markers of liver pathology. Chemerin plasma concentrations decreased after bariatric surgery. This study suggests that chemerin might mediate metabolic alterations in obesity, drastically improving after gastric bypass.

Obesity and low-grade inflammation: a paediatric perspective

Childhood obesity is a major public health problem. Low-grade inflammation, a hallmark characterizing adult obesity, may be a pivotal mechanism linking obesity to its numerous systemic complications, with adipose tissue depots secreting and producing inflammatory mediators and visceral fat displaying an increased inflammatory profile. While knowledge is relatively scarce regarding the importance of the adipose tissue inflammation process in children, identifying its contribution in childhood obesity and the associated influences of age, sex, weight status, growth, and adipose depot phenotypes are crucial for understanding physiopathology and implementing early intervention strategies. We review the latest research linking obesity and inflammation in childhood focusing on serum inflammatory markers and the effectiveness of lifestyle interventions in improving systemic inflammation. Generally, there are significant correlations between body mass index and increased c-reactive protein and decreased adiponectin levels in children; these levels tend to be improved in interventions resulting in approximately 5% weight loss, regardless of the type or length of intervention. There is a need for further research measuring other inflammatory mediators (e.g. tumour necrosis factor (TNF)-alpha, IL-6, IL-8) and histological studies examining immune cell infiltration in adipose tissue depots in obese children.

Human adipose tissue macrophages: m1 and m2 cell surface markers in subcutaneous and omental depots and after weight loss

CONTEXT

Macrophages accumulate in adipose tissue and possibly participate in metabolic complications in obesity. Macrophage number varies with adipose tissue site and weight loss, but whether this is accompanied by phenotypic changes is unknown.

OBJECTIVE

The objective of the study was to characterize the activation state of adipose tissue macrophages in human obesity.

DESIGN/SETTING

We performed a single-center prospective study.

PARTICIPANTS/INTERVENTIONS

Paired biopsies of sc and omental adipose tissue were obtained during gastric surgery in 16 premenopausal obese women (aged 41.1 +/- 8.6 yr; body mass index 43.8 +/- 3.4 kg/m(2)). Subcutaneous adipose tissue biopsies were obtained 3 months later in obese subjects and in 10 nonobese women (aged 43.3 +/- 3.5 yr; body mass index 22.5 +/- 0.75 kg/m(2)). The number of macrophages stained with CD40, CD206, and CD163 surface markers was determined by immunochemistry.

MAIN OUTCOMES

The number of CD40(+) macrophages significantly increased with obesity and in omental vs. sc adipose tissue in obese women. No significant changes in CD163(+) and CD206(+) macrophage counts was found with obesity and fat pad anatomical location. Three months after gastric surgery, the ratio of CD40(+) to CD206(+) macrophages was 2-fold lower than before surgery in the sc adipose tissue of obese subjects (P < 0.001) due to a concomitant decrease of CD40(+) and increase of CD206(+) macrophages counts.

CONCLUSION

We suggest that the activation state of adipose tissue macrophages is weighted toward M1 over M2 status in obese subjects and switch to a less proinflammatory profile 3 months after gastric bypass.

Association between omental adipose tissue macrophages and liver histopathology in morbid obesity: influence of glycemic status

BACKGROUND/AIMS

Recently we showed that macrophage accumulation in omental adipose tissue is associated with liver fibro-inflammation in morbidly obese subjects. Here, we evaluated the influence of glycemic status and extended the analysis to the spectrum of obesity-linked liver damage.

METHODS

Liver biopsies, subcutaneous and omental adipose tissue were collected in 132 obese subjects during gastric bypass surgery. HAM56+ adipose tissue macrophages were counted in subjects classified by liver histopathology and by their degree of insulin resistance.

RESULTS

In the whole population, the number of omental macrophages increased with the score of steatosis, the non-alcoholic fatty liver disease activity score, the stage of fibrosis and with fibro-inflammation index. None of these relationships were significant with subcutaneous macrophage count. In insulin-sensitive participants, omental macrophages accumulation was higher in subjects with high indexes of fibro-inflammation (p=0.012 vs. low indexes). In insulin-resistant including type 2 diabetic participants, omental macrophage count was higher both in subjects with high scores of steatosis and in subjects with high indexes of fibro-inflammation (p<0.05 vs. low scores).

CONCLUSIONS

Macrophage accumulation in omental adipose tissue is associated with aggravated steatosis and fibro-inflammation in insulin-resistant obese subjects independently of altered glycemic status.

Role of serum amyloid a in adipocyte-macrophage cross talk and adipocyte cholesterol efflux

CONTEXT

Acute phase serum amyloid A (A-SAA) is secreted by hepatocytes in response to injury and is regulated by proinflammatory cytokines. In obese humans, adipocytes are also a major contributor to circulating A-SAA levels.

OBJECTIVE

We aimed to investigate the role and regulation of A-SAA in human adipose tissue (AT).

DESIGN

An approach combining microarrays and the FunNet bioinformatics tool was applied to human AT fractions (i.e. adipocytes vs. stroma vascular fraction) to hypothesize genes and functions related to A-SAA. Experiments with human AT from 37 obese subjects and human multipotent adipose-derived stem (hMADS) cells were used to confirm the microarray driven hypotheses.

RESULTS

Microarray analysis highlighted the relationship between A-SAA and stroma vascular fraction inflammatory genes, and between A-SAA and adipocyte-expressed ATP-binding cassette (ABC) transporters. We confirmed that serum amyloid A (SAA) protein is expressed in sc AT of obese subjects (n = 37, body mass index = 49.3 +/- 1.5 kg/m(2)) and showed that SAA protein expression correlated with adipocyte size (R = 0.44; P = 6.10(-3)), macrophage infiltration (R = 0.61; P = 10(-4)), and ABC subfamily A1 protein expression (R = 0.43; P = 9.10(-3)). IL-1beta, TNF-alpha, and human AT macrophage-conditioned medium significantly induced A-SAA secretion (from 2.6 to 7.6 fold) in hMADS cells. Recombinant SAA induced cholesterol ABC subfamily A1-dependent efflux from hMADS adipocytes by 4.3-fold in a dose-dependent manner.

CONCLUSION

This work provides original insight suggesting that A-SAA is a player in the dialogue between hypertrophied adipocytes and macrophages through its regulation of adipocyte cholesterol efflux.

Adipose tissue inflammation and liver pathology in human obesity

The increase in circulating inflammatory factors found in obese subjects and the recent discovery of macrophage infiltration in white adipose tissue (WAT) have opened up new fields of investigation, allowing a reevaluation of the pathophysiology of human obesity. The so-called 'low-grade' inflammatory state, which characterizes this complex disease, is revealed by the moderate, but chronic, systemic rise of a growing panel of molecules with proinflammatory functions. The qualitative and quantitative alterations in the production of these molecules (free fatty acids, cytokines) by the different WAT cell types, particularly in the omental fat depot, are considered new factors with the potential to modify local WAT biology and to contribute, via the portal system, to liver alteration. The aim of this review is to present the most upto-date knowledge regarding the relationships between inflammatory processes in WAT and non-alcoholic liver disease in human obesity.

Needle and surgical biopsy techniques differentially affect adipose tissue gene expression profiles

BACKGROUND

Adipose tissue gene expression analysis in humans now provides a tremendous means to discover the physiopathologic gene targets critical for our understanding and treatment of obesity. Clinical studies are emerging in which adipose gene expression has been examined in hundreds of subjects, and it will be fundamentally important that these studies can be compared so that a common consensus can be reached and new therapeutic targets for obesity proposed.

OBJECTIVE

We studied the effect of the biopsy sampling methods (needle-aspirated and surgical) used in clinical investigation programs on the functional interpretation of adipose tissue gene expression profiles.

DESIGN

A comparative microarray analysis of the different subcutaneous adipose tissue sampling methods was performed in age-matched lean (n = 19) and obese (n = 18) female subjects. Appropriate statistical (principal components analysis) and bioinformatic (FunNet) functional enrichment software were used to evaluate data. The morphology of adipose tissue samples obtained by needle-aspiration and surgical methods was examined by immunohistochemistry.

RESULTS

Biopsy techniques influence the gene expression underlying the biological themes currently discussed in obesity (eg, inflammation, extracellular matrix, and metabolism). Immunohistochemistry experiments showed that the easier to obtain needle-aspirated biopsies poorly aspirate the fibrotic fraction of subcutaneous adipose tissue, resulting in an underrepresentation of the stroma-vascular fraction.

CONCLUSIONS

The adipose tissue biopsy technique is an important caveat to consider when designing, interpreting, and, most important, comparing microarray experiments. These results will have crucial implications for the clinical and physiopathologic understanding of human obesity and therapeutic approaches.

Elevated expression of osteopontin may be related to adipose tissue macrophage accumulation and liver steatosis in morbid obesity

OBJECTIVE

Osteopontin (OPN) plays an important role in the development of insulin resistance and liver complications in dietary murine models. We aimed to determine the expression pattern of OPN and its receptor CD44 in obese patients and mice according to insulin resistance and liver steatosis.

RESEARCH DESIGN AND METHODS

OPN and CD44 expressions were studied in 52 morbidly obese patients and in mice. Cellular studies were performed in HepG2 cells.

RESULTS

Hepatic OPN and CD44 expressions were strongly correlated with liver steatosis and insulin resistance in obese patients and mice. This increased OPN expression could be due to the accumulation of triglycerides, since fat loading in HepG2 promotes OPN expression. In contrast, OPN expression in adipose tissue (AT) was enhanced independently of insulin resistance and hepatic steatosis in obese patients. The elevated OPN expression in AT was paralleled with the AT macrophage infiltration, and both phenomena were reversed after weight loss. The circulating OPN level was slightly elevated in obese patients and was not related to liver steatosis. Further, AT did not appear to secrete OPN. In contrast, bariatric surgery-induced weight loss induced a strong increase in circulating OPN.

CONCLUSIONS

The modestly elevated circulating OPN levels in morbidly obese patients were not related to liver steatosis and did not appear to result from adipose tissue secretion. In subcutaneous AT, expression of OPN was directly related to macrophage accumulation independently from liver complications. In contrast, hepatic OPN and CD44 expressions were related to insulin resistance and steatosis, suggesting their local implication in the progression of liver injury.

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

Analysis of the transcriptomic signature of white adipose tissue in obese human subjects revealed increased interstitial fibrosis and an infiltration of inflammatory cells into the tissue.

Background

Investigations performed in mice and humans have acknowledged obesity as a low-grade inflammatory disease. Several molecular mechanisms have been convincingly shown to be involved in activating inflammatory processes and altering cell composition in white adipose tissue (WAT). However, the overall importance of these alterations, and their long-term impact on the metabolic functions of the WAT and on its morphology, remain unclear.

Results

Here, we analyzed the transcriptomic signature of the subcutaneous WAT in obese human subjects, in stable weight conditions and after weight loss following bariatric surgery. An original integrative functional genomics approach was applied to quantify relations between relevant structural and functional themes annotating differentially expressed genes in order to construct a comprehensive map of transcriptional interactions defining the obese WAT. These analyses highlighted a significant up-regulation of genes and biological themes related to extracellular matrix (ECM) constituents, including members of the integrin family, and suggested that these elements could play a major mediating role in a chain of interactions that connect local inflammatory phenomena to the alteration of WAT metabolic functions in obese subjects. Tissue and cellular investigations, driven by the analysis of transcriptional interactions, revealed an increased amount of interstitial fibrosis in obese WAT, associated with an infiltration of different types of inflammatory cells, and suggest that phenotypic alterations of human pre-adipocytes, induced by a pro-inflammatory environment, may lead to an excessive synthesis of ECM components.

Conclusion

This study opens new perspectives in understanding the biology of human WAT and its pathologic changes indicative of tissue deterioration associated with the development of obesity.

Cytosolic aspartate aminotransferase, a new partner in adipocyte glyceroneogenesis and an atypical target of thiazolidinedione

We show that cytosolic aspartate aminotransferase (cAspAT) is involved in adipocyte glyceroneogenesis, a regulated pathway that controls fatty acid homeostasis by promoting glycerol 3-phosphate formation for fatty acid re-esterification during fasting. cAspAT activity, as well as the incorporation of [(14)C]aspartate into the neutral lipid fraction of 3T3-F442A adipocytes was stimulated by the thiazolidinedione (TZD) rosiglitazone. Conversely, the ratio of fatty acid to glycerol released into the medium decreased. Regulation of cAspAT gene expression was specific to differentiated adipocytes and did not require any peroxisome proliferator-activated receptor gamma (PPARgamma)/retinoid X receptor-alpha direct binding. Nevertheless, PPARgamma is indirectly necessary for both cAspAT basal expression and TZD responsiveness because they are, respectively, diminished and abolished by ectopic overexpression of a dominant negative PPARgamma. The cAspAT TZD-responsive site was restricted to a single AGGACA hexanucleotide located at -381 to -376 bp whose mutation impaired the specific RORalpha binding. RORalpha ectopic expression activated the cAspAT gene transcription in absence of rosiglitazone, and its protein amount in nuclear extracts is 1.8-fold increased by rosiglitazone treatment of adipocytes. Finally, the amounts of RORalpha and cAspAT mRNAs were similarly increased by TZD treatment of human adipose tissue explants, confirming coordinated regulation. Our data identify cAspAT as a new member of glyceroneogenesis, transcriptionally regulated by TZD via the control of RORalpha expression by PPARgamma in adipocytes.

Increased infiltration of macrophages in omental adipose tissue is associated with marked hepatic lesions in morbid human obesity

In human obesity, white adipose tissue (WAT) is enriched in macrophages. How macrophage infiltration in WAT contributes to the complications of obesity is unknown. This study tested the hypothesis that recruitment of macrophages in omental WAT is associated with hepatic damage in obese patients. Paired biopsies of subcutaneous and omental WAT and a liver biopsy were collected during gastric surgery in 46 obese women and 9 obese men (BMI 47.9 +/- 0.93 kg/m(2)). The number of HAM56+ macrophages in WAT was quantified microscopically, and correlations with clinical and biological parameters and histological liver pathology were investigated. There were twice as many macrophages in omental as in subcutaneous WAT (P<0.0001). After adjustment for age, omental WAT macrophage infiltration was correlated to fasting glucose and insulin, quantitative insulin sensitivity check index, triglycerides, aspartate aminotransferase (AST), and gamma-glutamyltranspeptidase. We propose an easy equation to estimate the amount of macrophages in omental WAT. Increased macrophage accumulation specifically in omental WAT was associated with hepatic fibroinflammatory lesions (P=0.01). The best predictive model for the severity of hepatic damage includes adiponectinemia, AST, and omental WAT macrophages. These data suggest that the presence of macrophages in omental WAT participates in the cellular mechanisms favoring hepatic fibroinflammatory lesions in obese patients.