Logistic regression as to risk for prediabetes of SNPs per allele (2a) or sum score (2b).

<p>Logistic regression as to risk for prediabetes of SNPs per allele (2a) or sum score (2b).</p

Number of total homozygous or heterozygous risk alleles.

<p>Values are given as mean ±1 standard deviation.</p

Baseline characteristics of normoglycemic versus prediabetic participants.

<p>Values are given as mean ±1 standard deviation or as absolute or relative frequencies.</p>*<p>males / ^#females;</p>§<p>t-test,</p>†<p>chi-square test;</p>‡<p>estimated by the Friedewald formula.</p

Relevance of markers as to prediabetic status of 100 runs in a random forest analysis.

<p>Relevance of markers as to prediabetic status of 100 runs in a random forest analysis.</p

Effect of Sfrp5 on Cytokine Release and Insulin Action in Primary Human Adipocytes and Skeletal Muscle Cells

<div><p>Secreted frizzled-related protein 5 (Sfrp5) is an adipokine with anti-inflammatory and insulin-sensitizing properties in mice. However, the mechanism of Sfrp5 action, especially in humans, is largely unknown. Therefore, cytokine release and insulin signaling were analyzed to investigate the impact of Sfrp5 on inflammation and insulin signaling in primary human adipocytes and skeletal muscle cells (hSkMC). Sfrp5 neither affected interleukin (IL)-6, monocyte chemoattractant protein-1 (MCP-1) and adiponectin release from human adipocytes, nor IL-6 and IL-8 release from hSkMC. In tumor necrosis factor (TNF) α-treated adipocytes, Sfrp5 reduced IL-6 release by 49% (p<0.05), but did not affect MCP-1 and adiponectin release. In MCP-1-treated hSkMC, Sfrp5 did not affect cytokine secretion. In untreated adipocytes, Sfrp5 decreased the insulin-mediated phosphorylation of Akt-Ser473, Akt-Thr308, GSK3α-Ser21 and PRAS40-Thr246 by 34% (p<0.01), 31% (p<0.05), 37% (p<0.05) and 34% (p<0.01), respectively, and the stimulation of glucose uptake by 25% (p<0.05). Incubation with TNFα increased the phosphorylation of JNK and NFκB, and impaired insulin signaling. When Sfrp5 and TNFα were combined, there was no additional effect on insulin signaling and JNK phosphorylation, but phosphorylation of NFκB was reversed to basal levels. Sfrp5 had no effect on insulin signaling in untreated or in MCP-1 treated hSkMC. Thus, Sfrp5 lowered IL-6 release and NFκB phosphorylation in cytokine-treated human adipocytes, but not under normal conditions, and decreased insulin signaling in untreated human adipocytes. Sfrp5 did not act on hSkMC. Therefore, the cellular actions of Sfrp5 seem to depend on the type of tissue as well as its inflammatory and metabolic state.</p></div

Additional file 1 of Chronic air pollution-induced subclinical airway inflammation and polygenic susceptibility

Additional file 1. Air pollution assignment within the European Study of Cohorts for Air Pollution Effects. Details of air pollution measurements. Genotyping, quality control and imputation. Details of genotyping, quality control and imputation

Effect of Sfrp5 on glucose uptake in primary human adipocytes.

<p>Mature adipocytes were kept untreated, exposed to 100/ml Sfrp5 for 24 h, when indicated (+) stimulated with insulin (30 min; 100 nM), whereafter glucose uptake was determined. The incorporated amount of 2-deoxy-D-[1-³H]glucose was normalized for protein content and expressed as mean ± standard error of the mean of four independent experiments using cells from different donors. The values obtained for Sfrp5-untreated, insulin-treated cells were considered as control and set at 100%. Differences among groups were calculated by two-way ANOVA followed by Bonferroni multiple comparison analysis. #, indicates <i>p</i><0.05 for the effect of insulin stimulation; *, <i>p</i><0.05 for the effect of Sfrp5.</p

Effect of Sfrp5 on adipokine and myokine release (unstimulated conditions).

<p>Primary human adipocytes (A–C) and primary human skeletal muscle cells (D–E) were exposed to increasing amounts of Sfrp5 for 24 h. Cytokine release by the adipocytes and myotubes was quantified by ELISA, and expressed as mean ± standard error of the mean (A–C: n = 5; D–E: n = 4).</p

Effect of Sfrp5 on adipokine and myokine release from cytokine-stimulated cells.

<p>Primary human adipocytes (A–C) and primary human skeletal muscle cells (D–E) were exposed to Sfrp5 (4 h; 100 ng/ml) prior to incubation with TNFα (24 h; 5 nmol/l) or MCP-1 (18 h; 2 ng/ml). Cytokine release by the adipocytes and myotubes was quantified by ELISA, and expressed as mean ± standard error of the mean (A–C: n = 5; D–E: n = 4). Differences among the various conditions were analyzed by Friedman's test followed by Dunn's multiple comparison test; ### indicates <i>P</i><0.001; ##, <i>P</i><0.01 versus cells kept untreated (basal); *, <i>P</i><0.05 for the effect of the additional Sfrp5 incubation versus TNFα alone.</p

Effect of Sfrp5 on insulin signaling in primary human adipocytes.

<p>Primary human adipocytes were kept untreated, exposed to Sfrp5 for 24/ml TNFα for 24 h with or without a 4 h preincubation with Sfrp5. Then, when indicated (+) cells were stimulated with insulin (10 min; 100 nM). Cell lysates were analyzed for phosphorylation of Akt-Thr308 (A), Akt-Ser473 (B), GSK3α-Ser21 (C) and PRAS40-Thr246 (D) by Western blotting. Phosphorylation signals were normalized for GAPDH protein abundance and expressed as mean ± standard error of the mean of five independent experiments using cells from different donors. The values obtained for Sfrp5-untreated, insulin-treated cells were considered as control and set at 100%. Differences among groups were calculated by two-way ANOVA followed by Bonferroni multiple comparison analysis. #, indicates <i>p</i><0.05 for the effect of insulin stimulation; ***, <i>p</i><0.001; **, <i>p</i><0.01; *, <i>p</i><0.05 versus untreated cells.</p