Characterisation, regulation and effects of epicardial adipokines

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Sex differences in human adipose tissues – the biology of pear shape

<p>Abstract</p> <p>Women have more body fat than men, but in contrast to the deleterious metabolic consequences of the central obesity typical of men, the pear-shaped body fat distribution of many women is associated with lower cardiometabolic risk. To understand the mechanisms regulating adiposity and adipose tissue distribution in men and women, significant research attention has focused on comparing adipocyte morphological and metabolic properties, as well as the capacity of preadipocytes derived from different depots for proliferation and differentiation. Available evidence points to possible intrinsic, cell autonomous differences in preadipocytes and adipocytes, as well as modulatory roles for sex steroids, the microenvironment within each adipose tissue, and developmental factors. Gluteal-femoral adipose tissues of women may simply provide a safe lipid reservoir for excess energy, or they may directly regulate systemic metabolism via release of metabolic products or adipokines. We provide a brief overview of the relationship of fat distribution to metabolic health in men and women, and then focus on mechanisms underlying sex differences in adipose tissue biology.</p

Depot Dependent Effects of Dexamethasone on Gene Expression in Human Omental and Abdominal Subcutaneous Adipose Tissues from Obese Women

<div><p>Glucocorticoids promote fat accumulation in visceral compared to subcutaneous depots, but the molecular mechanisms involved remain poorly understood. To identify long-term changes in gene expression that are differentially sensitive or responsive to glucocorticoids in these depots, paired samples of human omental (Om) and abdominal subcutaneous (Abdsc) adipose tissues obtained from obese women during elective surgery were cultured with the glucocorticoid receptor agonist dexamethasone (Dex, 0, 1, 10, 25 and 1000 nM) for 7 days. Dex regulated 32% of the 19,741 genes on the array, while 53% differed by Depot and 2.5% exhibited a Depot*Dex concentration interaction. Gene set enrichment analysis showed Dex regulation of the expected metabolic and inflammatory pathways in both depots. Cluster analysis of the 460 transcripts that exhibited an interaction of Depot and Dex concentration revealed sets of mRNAs for which the responses to Dex differed in magnitude, sensitivity or direction between the two depots as well as mRNAs that responded to Dex only in one depot. These transcripts were also clearly depot different in fresh adipose tissue and are implicated in processes that could affect adipose tissue distribution or functions (e.g. adipogenesis, triacylglycerol synthesis and storage, insulin action). Elucidation of the mechanisms underlying the depot differences in the effect of Dex on the expression of specific genes and pathways that regulate adipose function may offer novel insights into understanding the biology of visceral adipose tissues and their links to metabolic health.</p></div

Parallel plot illustrating the cluster analysis of genes that exhibited a Depot*[Dex] interaction.

<p>460 genes that showed a significant interaction of Depot and [Dex], and expression values above a threshold of 20 for at least one Dex concentration in one depot were included in an unsupervised hierarchical cluster analysis (JMP 10 software), as described in Methods. The analysis with 10 clusters is shown.</p

qPCR verification of selected depot-dependent Dex effects.

<p>Transcripts for verification were selected for biological interest, large depot differences in the baseline values and/or the magnitude of the Dex effects: (A) <i>INHBA</i>, (B) <i>GREM1</i>, (C) <i>PKHD1L1</i>, (D) <i>ITLN1</i>, (E) <i>ITGB8</i>, and (F) <i>NRN1</i>. Depot differences are indicated by asterisks (*p < 0.05, paired t-test at each Dex concentration). Within depot, Dex effects were tested by repeated measures ANOVA on log-transformed data (p values indicated in the box on each graph). Post-hoc comparisons of values at each Dex concentration compared to baseline (0 Dex) were carried out by Dunnett’s tests. Within Abdsc, Dex effects were significant for <i>INHBA</i> at Dex concentrations of 10 nM or higher, <i>ITGB8</i> at 25 and 1000 nM and <i>NRN1</i> at 1, 10, and 25 nM. Within Om, Dex effects were significant for <i>PKHD1L1</i> at Dex concentrations of 10 nM and higher and <i>ITLN1</i> at 25 and 1000 nM. Because of missing values for Om for <i>INHBA</i>, only paired t-tests were used to test the effect of each Dex concentration vs. baseline [p = 0.051 at 1 nM (n = 6), p<0.01 at 10 nM (n = 5), 25 and 1000 nM (n = 6)].</p

Transcripts of interest from the cluster analysis of significant Depot*[Dex] interactions (Fig 2).

<p>Transcripts of interest from the cluster analysis of significant Depot*[Dex] interactions (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0167337#pone.0167337.g002" target="_blank">Fig 2</a>).</p

Characteristics of subjects used in microarray and subsequent studies.

<p>Characteristics of subjects used in microarray and subsequent studies.</p

Depot differences in flash frozen samples of Om and Abdsc reflect patterns observed in tissues cultured with Dex.

<p>(A) <i>INHBA</i>, (B) <i>GREM1</i>, (C) <i>PKHD1L1</i>, (D) <i>ITLN1</i>, (E) <i>ITGB8</i>, and (F) <i>NRN1</i>. *p < 0.05, depot difference (paired t-tests of log transformed values, n = 6). Data presented as mean ± SEM.</p

qPCR verification of concentration- and depot-dependent effects of glucocorticoids on selected, known glucocorticoid target genes.

<p>(A) <i>PCK1</i>, (B) <i>LPL</i>, (C) <i>GILZ</i>, and (D) <i>IL-6</i>. Data are mean ± SEM, n = 5–7 independent subjects. The X-axis is a log scale. Significant depot differences at each [Dex] are indicated by an asterisk (*, p < 0.05, paired t-test of log transformed values). Repeated measures ANOVA verified a significant Dex effect in both depots for each gene (Dex effect, p ≤ 0.002). All doses in both Om and Abdsc were significantly different from 0 nM Dex (p ≤ 0.05, Dunnett’s test).</p