Strong association of serum- and glucocorticoid-regulated kinase 1 with peripheral and adipose tissue inflammation in obesity.

OBJECTIVE: The serum- and glucocorticoid-regulated kinase 1 (SGK1) is an early transcriptional target of glucocorticoids and is activated via insulin. Here we investigate the regulation of SGK1 expression in human obesity, diet-induced murine obesity and human monocytic cell line THP-1 monocytes. SUBJECTS AND METHODS: SGK1 expression was studied in subcutaneous and omental adipose tissue (AT) of 20 morbidly obese and 20 age- and gender-matched non-obese controls in murine diet-induced obesity and the THP-1 cell line. The regulation of SGK1 by inflammatory signals was tested in THP-1 cells. RESULTS: Murine diet-induced obesity is associated with a significant upregulation of Sgk1 in gonadal AT. Sgk1 expression is highest in the macrophage-rich stromal vascular fraction and lower in adipocytes. In humans, AT SGK1 is predominantly expressed in CD14(+) macrophages and significantly upregulated in omental and subcutaneous AT of obese subjects. SGK1 mRNA expression in both omental and subcutaneous AT correlates with body mass index, circulating leptin and C-reactive protein, and the local expression of inflammatory markers including monocyte chemotactic protein-1 and macrophage inflammatory protein-1α. The expression of SGK1 in THP-1 cells is upregulated by inflammatory signals, such as lipopolysaccharide and tumour necrosis factor-α, as well as during the induction of monocyte-to-macrophage maturation. CONCLUSIONS: Our data present the first link between SGK1 and obesity-associated inflammation. SGK1 expression is stimulated in response to inflammatory signals and increased in AT macrophages. The characterisation of SGK1 functions in obesity and immunity may help identify potential therapeutic targets in the treatment of obesity.

Effect of a low-fat diet enriched either with rapeseed oil or sunflower oil on plasma lipoproteins in children and adolescents with familial hypercholesterolaemia. Results of a pilot study.

BACKGROUND/OBJECTIVES: There is convincing evidence that unsaturated fatty acids exert favourable effects on plasma cholesterol levels. However, it is not clear which type of oil has the most pronounced effect, especially not in paediatric patients. The aim was to compare two low-fat diet regimes enriched with either monounsaturated fatty acids by rapeseed oil (RO) or polyunsaturated fatty acids by sunflower oil (SO) in children affected with familial hypercholesterolaemia (FH). SUBJECTS/METHODS: Twenty-one children aged 6-18 years affected with FH were enrolled in this randomized and double-blind pilot trial. The subjects and their families were trained to adhere to a low-fat/low-cholesterol diet. All visible fats were to be replaced by either RO or SO (14-27 g/day) for 13 weeks. Dietary adherence was controlled by repeated 4-day dietary records; plasma lipids, lipoproteins and risk markers were assessed at baseline and post-intervention. Out of 21 subjects, 16 could be followed-up after 6 months. RESULTS: Both fat-modified diets resulted in significant reduction in total cholesterol concentrations of 9.4% (RO P<0.005 vs SO P<0.05) and low-density lipoprotein (LDL) cholesterol concentrations of 12.7% (P<0.005) for RO and 11.3% (P<0.05) for SO. The reduction of the LDL/high-density lipoprotein (HDL) cholesterol ratio (RO 9% vs SO 3.5%) and high-sensitivity C-reactive protein (RO 16.8% vs SO 1.7%) were not statistically significant, respectively. In most participating families, a change in eating habits could be observed. CONCLUSIONS: A fat-modified diet enriched with RO seems to have very similar effects on cholesterol levels as with SO. However, our study suggests that RO has possibly more favourable effects concerning cardiovascular risk profile. Both diets appear to be feasible and were well accepted among our subjects. Although these results are promising, larger trials will be required to validate our findings.

Newly identified adipose tissue macrophage populations in obesity with distinct chemokine and chemokine receptor expression.

OBJECTIVE: Infiltration by macrophages is a hallmark of obesity-related adipose tissue (AT) inflammation that is tightly linked to insulin resistance. Although CD11c+ AT macrophages (ATMs) have recently been shown to promote inflammation in obese mice, the knowledge on phenotype and function of different ATM populations is still very limited. This study aimed at identifying and characterizing ATM populations in obesity. METHODS: Isolation of ATM populations defined by CD11c and mannose receptor (MR) expression and analysis of gene expression in high-fat diet-induced obese mice. RESULTS: Obesity provoked a shift from a predominant MR+CD11c⁻ population ('MR-ATM') to two MR⁻ populations, namely MR⁻CD11c+ ('CD11c-ATM') and MR⁻CD11c⁻ (double negative, 'DN-ATM'). Although CD11c-ATMs were of a clear inflammatory M1 phenotype, DN-ATMs expressed few inflammatory mediators and highly expressed genes for alternative activation (M2) markers involved in tissue repair, such as arginase and YM1. In contrast, MR-ATMs marginally expressed M1 and M2 markers but highly expressed chemokines, including Mcp-1 (Ccl2) and Mcp-3 (Ccl7). Both CD11c-ATMs and DN-ATMs, but not MR-ATM, highly expressed a panel of chemokine receptors (namely Ccr2, Ccr5, Ccr3 and Cx3cr1), whereas the expression of Ccr7 and Ccr9 was selective for CD11c-ATMs and DN-ATMs, respectively. Notably, stressed adipocytes upregulated various chemokines capable of attracting CD11c-ATM and DN-ATM. CONCLUSION: This study identifies a novel ATM population with a putatively beneficial role in AT inflammation. This DN-ATM population could be attracted to the obese AT by similar chemokines such as inflammatory CD11c-ATM, on which only Ccr7 is uniquely expressed.

Diminished upregulation of visceral adipose heme oxygenase-1 correlates with waist-to-hip ratio and insulin resistance.

OBJECTIVE: Insulin resistance in visceral obesity is substantially driven by adipose tissue inflammation, particularly by macrophages accumulating in obese adipose tissue. In contrast, adipose tissue macrophages express the hemoglobin scavenger receptor (CD163) and heme oxygenase-1 (gene: HMOX1) that together protect from oxidative stress. Our aim was to evaluate the expression of CD163 and HMOX1 in intra-abdominal visceral (omental) and subcutaneous adipose tissue as well as circulating soluble CD163 concentrations in human obesity and its association with adipose tissue inflammation, body fat distribution and insulin resistance. METHODS: CD163, HMOX1 and CD68 mRNA expression in visceral and subcutaneous adipose tissue, serum concentration of soluble CD163 in morbidly obese patients (body mass index (BMI) >40 kg m(-2)), who underwent laparoscopic surgery for gastric banding (n=20), matched for age and sex to controls (BMI<30 kg m(-2); n=20) was analyzed. RESULTS: CD163 expression was highly upregulated in human adipose tissue and soluble CD163 serum concentration was elevated in obese vs lean subjects. HMOX1 was upregulated in adipose tissue by obesity as well and expressed predominantly in macrophages. Although CD163 expression strictly correlated with macrophage abundance, HMOX1 was additionally upregulated within macrophages. This upregulation was significantly lower in visceral compared with subcutaneous adipose tissue. Strikingly, relative visceral adipose tissue expression of HMOX1 negatively correlated with waist-to-hip ratio and the homeostasis model assessment of insulin resistance (both P=0.024). CONCLUSIONS: Visceral obesity is associated with defective upregulation of heme oxygenase-1 in visceral adipose tissue. A lack of this antioxidative and anti-inflammatory enzyme in visceral adipose tissue could contribute to the development of insulin resistance.

Human adipose tissue macrophages are of an anti-inflammatory phenotype but capable of excessive pro-inflammatory mediator production.

OBJECTIVE: Obesity is associated with a chronic low-grade inflammation and an increased abundance of macrophages in adipose tissue. Adipose tissue macrophages (ATMs) are assumed to interfere with adipocyte function leading to insulin resistance, thereby contributing to the pathogenesis of type 2 diabetes mellitus. Macrophages exist in separate types of differentiation, but the nature of ATMs is largely unknown. DESIGN AND MEASUREMENTS: Stromal vascular cells (SVCs) and ATMs were isolated from human adipose tissues from different locations. We characterized ATMs phenotypically and functionally by flow cytometry, endocytosis assay and determination of secreted cytokines. For comparison, we used macrophages of the 'classical' (M1) and the 'alternative', anti-inflammatory (M2) type differentiated in vitro from peripheral blood monocytes. RESULTS: Like prototypic M2 macrophages, ATMs expressed considerable amounts of mannose receptor, haemoglobin scavenger receptor CD163 and integrin alphavbeta5. The number of cells expressing these molecules correlated significantly with the donors' body mass indices (BMIs). Notably, SVCs positive for the common monocyte/macrophage marker CD14 contained a considerable fraction of blood monocytes, the abundance of which did not correlate with the BMIs, pointing to the requirement of the surface markers identified here for the identification of ATMs. ATMs showed endocytic activities similar to M2 macrophages and accordingly secreted high amounts of IL-10 and IL-1 receptor antagonist. However, basal and induced secretion of pro-inflammatory mediators TNF-alpha, IL-6, IL-1, MCP-1 and MIP-1alpha was even higher in ATMs than in pro-inflammatory M1 macrophages. CONCLUSION: ATMs comprise a particular macrophage type that is M2-like by surface marker expression, but they are competent to produce extensive amounts of inflammatory cytokines, which could considerably contribute to the development of insulin resistance.

Prospective randomised cross-over comparison of three LDL-apheresis systems in statin pretreated patients with familial hypercholesterolaemia.

Various LDL-apheresis systems have gained wider clinical acceptance in recent years to treat patients with severe familial hypercholesterolaemia, in particular in patients with coronary artery disease. For each single device data on efficacy have been provided, but up to now no comparative analysis including the novel direct adsorption of lipoproteins from whole blood has been reported. This prospectively designed cross-over comparison of three commercially available LDL-apheresis systems (immunoadsorption, IMAL; dextran sulphate adsorption, DSA; direct adsorption of lipoproteins, DALI) was performed in eight patients with homozygous (n = 3) and heterozygous (n = 5) familial hypercholesterolaemia. Removal of atherogenic lipoproteins was highly effective in all systems, for LDL-cholesterol in particular: DSA: - 84.3 +/- 6.2%; IMAL: -82.1 +/- 8.3%; DALI: -76.6 +/- 7.2% (P < 0.05 as compared DALI versus IMAL and DSA). A reduction in Lp(a) of about 63% was achieved by each device. Loss in HDL-cholesterol was highest with IMAL (-21.3 +/- 4.9%, P < 0.05) as compared to the other two treatment modalities. DSA decreased HDL-cholesterol by - 10.4 +/- 6.1% and the DALI system by -12.7 +/- 5.0%. Remarkable differences were found for the removal of fibrinogen (DSA: -29.8 +/- 14.7%, (P < 0.05 versus DALI/IMAL); IMAL: -21.4 +/- 10.1% (P < 0.05 versus DALI); DALI: -14.8 +/- 8.0%). The shortest duration for treatment was achieved by the DALI system (135 +/- 20 min, P < 0.05 versus IMAL (195 +/- 20 min) and DSA (187 +/- 29 min)). No side effects were recorded in the total of 96 treatments performed during the study. Long-term observations have yet to prove whether these differences in efficacy may be of clinical relevance.

Elevated serum free fatty acid concentrations inhibit T lymphocyte signaling.

Unbound cis-unsaturated free (i.e., nonesterified) fatty acids (FFA) inhibit T lymphocyte activation in vitro and therefore may exert immunosuppressive effects. However, in blood serum the major proportion of FFA is tightly bound to albumin, whereas unbound FFA are hardly detectable. Since serum FFA elevation occurs under pathological conditions like insulin resistance or cancer, which are often associated with a disturbed immune response, we addressed the question of whether increased serum FFA concentrations could affect T lymphocyte activation under in vivo conditions. Our studies revealed that 1) addition of pure long-chain cis-unsaturated FFA in the absence of albumin inhibited calcium response in cultured Jurkat T cells. 2) In healthy volunteers, serum FFA elevation by a lipid/heparin infusion, including predominantly unsaturated fatty acids, decreased calcium response of cultured T cells in contrast to studies without heparin. 3) Most notably, stepwise increasing serum FFA by lipid/heparin infusion also inhibited calcium response of simultaneously isolated autologous peripheral blood T lymphocytes as well as their CD4(+) and CD8(+) subsets. In conclusion, our data emphasize that serum FFA elevation is able to exert immunosuppressive effects in vivo.

Polyunsaturated fatty acids inhibit T cell signal transduction by modification of detergent-insoluble membrane domains.

Polyunsaturated fatty acids (PUFAs) exert immunosuppressive effects, but the molecular alterations leading to T cell inhibition are not yet elucidated. Signal transduction seems to involve detergent-resistant membrane domains (DRMs) acting as functional rafts within the plasma membrane bilayer with Src family protein tyrosine kinases being attached to their cytoplasmic leaflet. Since DRMs include predominantly saturated fatty acyl moieties, we investigated whether PUFAs could affect T cell signaling by remodeling of DRMs. Jurkat T cells cultured in PUFA-supplemented medium showed a markedly diminished calcium response when stimulated via the transmembrane CD3 complex or glycosyl phosphatidylinositol (GPI)- anchored CD59. Immunofluorescence studies indicated that CD59 but not Src family protein tyrosine kinase Lck remained in a punctate pattern after PUFA enrichment. Analysis of DRMs revealed a marked displacement of Src family kinases (Lck, Fyn) from DRMs derived from PUFA-enriched T cells compared with controls, and the presence of Lck in DRMs strictly correlated with calcium signaling. In contrast, GPI-anchored proteins (CD59, CD48) and ganglioside GM1, both residing in the outer membrane leaflet, remained in the DRM fraction. In conclusion, PUFA enrichment selectively modifies the cytoplasmic layer of DRMs and this alteration could underlie the inhibition of T cell signal transduction by PUFAs.