Danielle Hugol

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/m2). 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 γ-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.

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/m2) and 9 lean subjects (BMI 22.8 ± 0.7 kg/m2). 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.

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.

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-14C]-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.

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.

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.