[Show abstract][Hide abstract] ABSTRACT: Inflammation and increased ceramide concentrations characterise adipose tissue of obese women with high liver fat content compared to equally obese women with normal liver fat content. The present study characterises enzymes involved in ceramide metabolism in subcutaneous and intra-abdominal adipose tissue.
Pathways leading to increased ceramide concentrations in inflamed versus non-inflamed adipose tissue were investigated by quantifying expression levels of key enzymes involved in ceramide metabolism. Sphingomyelinases (sphingomyelin phosphodiesterases SMPD1-3) were investigated further using immunohistochemistry to establish their location within adipose tissue, and their mRNA expression levels were determined in subcutaneous and intra-abdominal adipose tissue from both non-obese and obese subject.
Gene expression levels of sphingomyelinases, enzymes that hydrolyse sphingomyelin to ceramide, rather than enzymes involved in de novo ceramide synthesis, were higher in inflamed compared to non-inflamed adipose tissue of obese women (with high and normal liver fat contents respectively). Sphingomyelinases were localised to both macrophages and adipocytes, but also to blood vessels and to extracellular regions surrounding vessels within adipose tissue. Expression levels of SMPD3 mRNA correlated significantly with concentrations of different ceramides and sphingomyelins. In both non-obese and obese subjects SMPD3 mRNA levels were higher in the more inflamed intra-abdominal compared to the subcutaneous adipose tissue depot.
Generation of ceramides within adipose tissue as a result of sphingomyelinase action may contribute to inflammation in human adipose tissue.
Full-text · Article · Sep 2012 · Lipids in Health and Disease
[Show abstract][Hide abstract] ABSTRACT: A sedentary lifestyle predisposes to cardiometabolic diseases. Lifestyle changes such as increased physical activity improve a range of cardiometabolic risk factors. The objective of this study was to examine whether functional changes in adipose tissue were related to these improvements.
Seventy-three sedentary, overweight (mean BMI 29.9 ± 3.2 kg/m2) and abdominally obese, but otherwise healthy men and women (67.6 ± 0.5 years) from a randomised controlled trial of physical activity on prescription over a 6-month period were included (control n = 43, intervention n = 30). Detailed examinations were carried out at baseline and at follow-up, including fasting blood samples, a comprehensive questionnaire and subcutaneous adipose tissue biopsies for fatty acid composition analysis (n = 73) and quantification of mRNA expression levels of 13 candidate genes (n = 51), including adiponectin, leptin and inflammatory cytokines.
At follow-up, the intervention group had a greater increase in exercise time (+137 min/week) and a greater decrease in body fat mass (-1.5 kg) compared to the control subjects (changes of 0 min/week and -0.5 kg respectively). Circulating concentrations of adiponectin were unchanged, but those of leptin decreased significantly more in the intervention group (-1.8 vs -1.1 ng/mL for intervention vs control, P < 0.05). The w6-polyunsaturated fatty acid content, in particular linoleic acid (18:2w6), of adipose tissue increased significantly more in the intervention group, but the magnitude of the change was small (+0.17 vs +0.02 percentage points for intervention vs control, P < 0.05). Surprisingly leptin mRNA levels in adipose tissue increased in the intervention group (+107% intervention vs -20% control, P < 0.05), but changes in expression of the remaining genes did not differ between the groups.
After a 6-month period of increased physical activity in overweight elderly individuals, circulating leptin concentrations decreased despite increased levels of leptin mRNA in adipose tissue. Otherwise, only minor changes occurred in adipose tissue, although several improvements in metabolic parameters accompanied the modest increase in physical activity.
Full-text · Article · Jun 2012 · Lipids in Health and Disease
[Show abstract][Hide abstract] ABSTRACT: Adipose tissue (AT) is a store of energy but also an endocrine organ with the capacity to produce and release proinflammatory mediators into the circulation. The mechanism that may trigger human AT inflammation on a cellular level still remains largely unknown. The aim of this study was to investigate whether an acute systemic inflammation increases AT inflammatory activity, focused on innate immunity. Open heart surgery results in an extensive acute systemic inflammation. Therefore, we investigated the in vivo gene expression and production of inflammatory mediators in omental and subcutaneous AT stimulated by surgery. Biopsies from omental and subcutaneous AT were collected before and after cardiopulmonary bypass. Blood samples were collected at the same time as the AT biopsies and plasma IL-6 levels were measured with ELISA. RT-PCR was used for quantification of relative AT gene expression. To verify the gene expression results on a protein level, we used immunohistochemistry and microdialysis. After surgery, in both omental and subcutaneous AT, there was a strong upregulation of nuclear factor-kappaB-regulated genes, e.g., chemokine ligand-2, E-selectin, IL-1beta, IL-6, IL-8, and Toll-like receptor-2. Immunohistochemistry showed staining for E-selectin associated with a high number of macrophages in close contact with and in the vascular wall. Increased levels of IL-6 were detected in microdialysate from subcutaneous AT. In conclusion, we present the novel finding that this model of inflammation induced a strong inflammatory response in both omental and subcutaneous AT including adhesion of macrophages to an activated endothelium and release of IL-6 from AT interstitium. It can be hypothesized that AT exerts a modulatory effect on innate immunity in humans.
Preview · Article · Aug 2010 · AJP Endocrinology and Metabolism
[Show abstract][Hide abstract] ABSTRACT: Despite the high prevalence of nonalcoholic fatty liver disease (NAFLD), little is known of its pathogenesis based on study of human liver samples. By the use of Affymetrix GeneChips (17,601 genes), we investigated gene expression in the human liver of subjects with extreme steatosis due to NAFLD without histological signs of inflammation (liver fat 66.0 +/- 6.8%) and in subjects with low liver fat content (6.4 +/- 2.7%). The data were analyzed by using sequence-based reannotation of Affymetrix probes and a robust model-based normalization method. We identified genes involved in hepatic glucose and lipid metabolism, insulin signaling, inflammation, coagulation, and cell adhesion to be significantly associated with liver fat content. In addition, genes involved in ceramide signaling (MAP2K4) and metabolism (UGCG) were found to be positively associated with liver fat content. Genes involved in lipid metabolism (PLIN, ACADM), fatty acid transport (FABP4, CD36), amino acid catabolism (BCAT1), and inflammation (CCL2) were validated by real-time PCR and were found to be upregulated in subjects with high liver fat content. The data show that multiple changes in gene expression characterize simple steatosis.
Full-text · Article · Jun 2008 · AJP Gastrointestinal and Liver Physiology
[Show abstract][Hide abstract] ABSTRACT: CCL2 (MCP-1, monocyte chemoattractant protein 1) and CCL3 (MIP-1alpha, macrophage inflammatory protein 1alpha) are required for macrophage infiltration in adipose tissue. Insulin increases CCL2 expression in adipose tissue and in serum more in insulin-resistant obese than in insulin-sensitive lean mice, but whether this is true in humans is unknown. We compared basal expression and insulin regulation of CCL2 and CCL3 in adipose tissue and MCP-1 and MIP-1alpha in serum between insulin-resistant and insulin-sensitive human subjects. Subcutaneous adipose tissue biopsies and blood samples were obtained before and at the end of 6 h of in vivo euglycemic hyperinsulinemia (maintained by the insulin clamp technique) in 11 lean insulin-sensitive and 10 obese insulin-resistant women, and before and after a 6-h saline infusion in 8 women. Adipose tissue mRNA concentrations of monocyte/macrophage markers CD68, EMR1, ITGAM, ADAM8, chemokines CCL2 and CCL3, and housekeeping gene ribosomal protein large P0 (RPLP0) were measured by means of real-time PCR at baseline. In addition, mRNA concentrations of CCL2, CCL3, and RPLP0 were measured after insulin infusion. Levels of MCP-1 and MIP-1alpha were determined in serum, and protein concentration of MCP-1 was determined in adipose tissue at baseline and after insulin infusion. Basally, expression of the macrophage markers CD68 and EMR1 were increased in adipose tissue of insulin-resistant subjects. Insulin increased MCP-1 gene and protein expression significantly more in the insulin-resistant than in the insulin-sensitive subjects. Basally expression of CCL2 and CCL3 and expression of macrophage markers CD68 and ITGAM were significantly correlated. In serum, MCP-1 decreased significantly in insulin-sensitive but not insulin-resistant subjects. MIP-1alpha was undetectable in serum. Insulin regulation of CCL2 differs between insulin-sensitive and -resistant subjects in a direction that could exacerbate adipose tissue inflammation.
No preview · Article · Jun 2008 · AJP Endocrinology and Metabolism
[Show abstract][Hide abstract] ABSTRACT: Skipping meals is a common practice in our current society; however, it is not clear whether eating meals regularly is associated with the metabolic syndrome.
Our aim was to assess the association of eating meals regularly with parameters of the metabolic syndrome and insulin resistance in a representative population-based cohort of 60-year-old men and women.
A population-based cross-sectional study of 3,607 individuals (1,686 men and 1,921 women), aged 60 years, was conducted in Stockholm County, Sweden. Medical history, socioeconomic factors, and lifestyle data were collected by a questionnaire and a medical examination, which included laboratory tests.
Of the subjects who were regular eaters, 20% fulfilled the criteria for the metabolic syndrome vs. 27% of subjects who were irregular eaters (P < 0.0001). The adjusted odds ratio (OR) for having the greatest number of components of the metabolic syndrome in subjects who were regular eaters was 0.27 (95% confidence interval (CI), 0.13-0.54) using subjects who did not fulfill any criteria for the metabolic syndrome as a reference group. Eating meals regularly was also inversely related to insulin resistance (OR, 0.68 (95% CI, 0.48-0.97)) and to gamma-glutamyl transferase (OR, 0.52 (95% CI, 0.33-83)) after full adjustment.
Eating meals regularly is inversely associated to the metabolic syndrome, insulin resistance and (high) serum concentrations of gamma-glutamyl transferase. These findings suggest that eating meals irregularly may be part of several potential environmental risk factors that are associated with the metabolic syndrome and may have future implications in giving dietary advice to prevent and/or treat the syndrome.
[Show abstract][Hide abstract] ABSTRACT: The objective of this study is to quantitate expression of genes possibly contributing to insulin resistance and fat deposition in the human liver.
A total of 24 subjects who had varying amounts of histologically determined fat in the liver ranging from normal (n = 8) to steatosis due to a nonalcoholic fatty liver (NAFL) (n = 16) were studied. The mRNA concentrations of 21 candidate genes associated with fatty acid metabolism, inflammation, and insulin sensitivity were quantitated in liver biopsies using real-time PCR. In addition, the subjects were characterized with respect to body composition and circulating markers of insulin sensitivity.
The following genes were significantly upregulated in NAFL: peroxisome proliferator-activated receptor (PPAR) gamma 2 (2.8-fold), the monocyte-attracting chemokine CCL2 (monocyte chemoattractant protein [MCP]-1, 1.8-fold), and four genes associated with fatty acid metabolism (acyl-CoA synthetase long-chain family member 4 [ACSL4] [2.8-fold], fatty acid binding protein [FABP]4 [3.9-fold], FABP5 [2.5-fold], and lipoprotein lipase [LPL] [3.6-fold]). PPARgamma coactivator 1 (PGC1) was significantly lower in subjects with NAFL than in those without. Genes significantly associated with obesity included nine genes: plasminogen activator inhibitor 1, PPARgamma, PPARdelta, MCP-1, CCL3 (macrophage inflammatory protein [MIP]-1 alpha), PPAR gamma 2, carnitine palmitoyltransferase (CPT1A), FABP4, and FABP5. The following parameters were associated with liver fat independent of obesity: serum adiponectin, insulin, C-peptide, and HDL cholesterol concentrations and the mRNA concentrations of MCP-1, MIP-1 alpha, ACSL4, FABP4, FABP5, and LPL.
Genes involved in fatty acid partitioning and binding, lipolysis, and monocyte/macrophage recruitment and inflammation are overexpressed in the human fatty liver.
[Show abstract][Hide abstract] ABSTRACT: To determine whether increased expression of macrophage markers and of inflammatory markers in subcutaneous adipose tissue is associated with liver fat in human obesity. We also determined whether expression of TNF (gene encoding TNF-alpha), HSD11B1 (gene encoding 11beta-HSD-1) and RETN (gene encoding resistin) in cultured monocyte-derived macrophages differs between obese/overweight and non-obese subjects.
Cross-sectional comparison of obese/overweight and non-obese subjects with respect to adipose tissue gene expression, gene expression in monocyte-derived macrophages, liver fat content and in vivo insulin sensitivity.
Adipose tissue gene expression, gene expression in monocyte-derived macrophages, liver fat content and in vivo insulin sensitivity: 10 healthy non-obese (24.2+/-1.0 kg/m(2)) and 10 healthy obese/overweight (33.1+/-1.7 kg/m(2)) women. Gene expression in monocyte-derived macrophages: seven healthy non-obese (22.1+/-0.7 kg/m(2)) and seven healthy obese/overweight (36.9+/-2.2 kg/m(2)) women.
Adipose tissue biopsies and blood samples for isolation of peripheral mononuclear cells were taken after an overnight fast. Liver fat content was measured using magnetic resonance proton spectroscopy. Whole body insulin sensitivity was measured using the hyperinsulinemic euglycemic clamp technique. Expression levels of TNF, HSD11B1, RETN and the macrophage markers CD68 and ITGAM were determined by real-time PCR.
In adipose tissue, expression of HSD11B1, ITGAM and CD68 was significantly increased in the obese/overweight as compared to the non-obese group. Expression of all these genes was closely positively correlated with liver fat content and inversely correlated with whole body insulin sensitivity. The associations between expression of CD68, ITGAM and HSD11B1 and liver fat were independent of obesity. There were no differences in TNF, HSD11B1, RETN or CD68 gene expression basally or after stimulation with lipopolysaccharide in monocyte-derived macrophages between obese/overweight and non-obese subjects.
Accumulation of fat in the liver is associated with increased adipose tissue inflammation independent of obesity.
Preview · Article · Nov 2007 · International Journal of Obesity
[Show abstract][Hide abstract] ABSTRACT: We sought to determine whether adipose tissue is inflamed in individuals with increased liver fat (LFAT) independently of obesity.
A total of 20 nondiabetic, healthy, obese women were divided into normal and high LFAT groups based on their median LFAT level (2.3 +/- 0.3 vs. 14.4 +/- 2.9%). Surgical subcutaneous adipose tissue biopsies were studied using quantitative PCR, immunohistochemistry, and a lipidomics approach to search for putative mediators of insulin resistance and inflammation. The groups were matched for age and BMI. The high LFAT group had increased insulin (P = 0.0025) and lower HDL cholesterol (P = 0.02) concentrations.
Expression levels of the macrophage marker CD68, the chemokines monocyte chemoattractant protein-1 and macrophage inflammatory protein-1alpha, and plasminogen activator inhibitor-1 were significantly increased, and those of peroxisome proliferator-activated receptor-gamma and adiponectin decreased in the high LFAT group. CD68 expression correlated with the number of macrophages and crown-like structures (multiple macrophages fused around dead adipocytes). Concentrations of 154 lipid species in adipose tissue revealed several differences between the groups, with the most striking being increased concentrations of triacylglycerols, particularly long chain, and ceramides, specifically Cer(d18:1/24:1) (P = 0.01), in the high LFAT group. Expression of sphingomyelinases SMPD1 and SMPD3 were also significantly increased in the high compared with normal LFAT group.
Adipose tissue is infiltrated with macrophages, and its content of long-chain triacylglycerols and ceramides is increased in subjects with increased LFAT compared with equally obese subjects with normal LFAT content. Ceramides or their metabolites could contribute to adverse effects of long-chain fatty acids on insulin resistance and inflammation.
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to compare effects of therapeutic doses of rosiglitazone and metformin on expression of 50 genes in human adipose tissue in vivo.
Twenty patients with diet-treated type 2 diabetes (13 women, seven men) were randomized to receive either rosiglitazone (n = 9; 8 mg/d) or metformin (n = 11; 2 g/d) for 16 wk. Subcutaneous adipose tissue biopsies were performed before and after treatment. Expression of 50 genes, previously shown to be altered by thiazolidinediones in experimental models, was quantified by real-time PCR and normalized to two housekeeping genes.
Rosiglitazone, but not metformin, treatment increased expression of genes involved in triacylglycerol storage [e.g. stearyl-CoA desaturase (3.2-fold), CD36 (1.8-fold)], structural genes [e.g. alpha-1 type-1 procollagen (1.7-fold) and GLUT4 (1.5-fold)], and decreased expression of inflammation-related genes [e.g. IL-6 (0.6-fold), chemokine (C-C motif) ligand 3 (0.4-fold)], 11beta-hydroxysteroid dehydrogenase 1 (0.6-fold), and resistin (0.3-fold) (all P < 0.05).
These results suggest that the insulin-sensitizing action of rosiglitazone involves remodeling of human adipose tissue to reduce inflammation and promote lipid storage. Furthermore, we show some important differences between thiazolidinedione action in human adipose tissue and experimental models.
Preview · Article · Feb 2007 · Journal of Clinical Endocrinology & Metabolism
[Show abstract][Hide abstract] ABSTRACT: We determined the response of selected genes to in vivo insulin in adipose tissue in 21 non-diabetic women.
The women were divided into insulin-sensitive and -resistant groups based on their median whole-body insulin sensitivity (8.7+/-0.4 vs 4.2+/-0.3 mg kg(-1) min(-1) for insulin-sensitive vs -resistant group). Subcutaneous adipose tissue biopsies were obtained before and after 3 and 6 h of i.v. maintained euglycaemic hyperinsulinaemia. Adipose tissue mRNA concentrations of facilitated glucose transporter, member 1 (SLC2A1, previously known as GLUT1), facilitated glucose transporter, member 4 (SLC2A4, previously known as GLUT4), peroxisome proliferator-activated receptor gamma ( PPARG), peroxisome proliferator-activated receptor gamma co-activator 1alpha (PPARGC1A), 11beta-hydroxysteroid dehydrogenase-1 (HSD11B1), TNF, adiponectin (ADIPOQ), IL6 and the macrophage marker CD68 were measured using real-time PCR.
Basal expression of 'insulin-sensitivity genes' SLC2A4 and ADIPOQ was lower while that of 'insulin-resistance genes', HSD11B1 and IL6 was significantly higher in the insulin-resistant than in the insulin-sensitive group. Insulin significantly increased expression of 'insulin-sensitivity genes' SLC2A4, PPARG, PPARGC1A and ADIPOQ in the insulin-sensitive group, while only expression of PPARG and PPARGC1A was increased in the insulin-resistant group. The expression of 'insulin-resistance genes' HSD11B1 and IL6 was increased by insulin in the insulin-resistant group, but insulin failed to increase HSD11B1 expression in the insulin-sensitive group. At 6 h, expression of HSD11B1, TNF and IL6 was significantly higher in the insulin-resistant than in the insulin-sensitive group. IL6 expression increased significantly more in response to insulin in the insulin-resistant than in the insulin-sensitive group. CD68 was overexpressed in the insulin-resistant as compared with the insulin-sensitive group at both 0 and 6 h.
These data suggest that genes adversely affecting insulin sensitivity hyperrespond to insulin, while genes enhancing insulin sensitivity hyporespond to insulin in insulin-resistant human adipose tissue in vivo.