Persistent Organic Pollutant Exposure Leads to Insulin Resistance Syndrome

International audienceBackground: the incidence of the insulin resistance syndrome has increased at an alarming rate worldwide, creating a serious challenge to public health care in the 21st century. Recently, epide-miological studies have associated the prevalence of type 2 diabetes with elevated body burdens of persistent organic pollutants (POPs). However, experimental evidence demonstrating a causal link between POPs and the development of insulin resistance is lacking. Objective: We investigated whether exposure to POPs contributes to insulin resistance and meta-bolic disorders. Methods: Sprague-Dawley rats were exposed for 28 days to lipophilic POPs through the con-sumption of a high-fat diet containing either refined or crude fish oil obtained from farmed Atlantic salmon. In addition, differentiated adipocytes were exposed to several POP mixtures that mimicked the relative abundance of organic pollutants present in crude salmon oil. We measured body weight, whole-body insulin sensitivity, POP accumulation, lipid and glucose homeostasis, and gene expres-sion and we performed micro array analysis. Results: Adult male rats exposed to crude, but not refined, salmon oil developed insulin resis-tance, abdominal obesity, and hepatosteatosis. The contribution of POPs to insulin resistance was confirmed in cultured adipocytes where POPs, especially organochlorine pesticides, led to robust inhibition of insulin action. Moreover, POPs induced down-regulation of insulin-induced gene-1 (Insig-1) and Lpin1, two master regulators of lipid homeostasis. Conclusion: Our findings provide evidence that exposure to POPs commonly present in food chains leads to insulin resistance and associated metabolic disorder

The genome landscape of ER{alpha}- and ER{beta}-binding DNA regions.

In this article, we have applied the ChIP-on-chip approach to pursue a large scale identification of ERα- and ERβ-binding DNA regions in intact chromatin. We show that there is a high degree of overlap between the regions identified as bound by ERα and ERβ, respectively, but there are also regions that are bound by ERα only in the presence of ERβ, as well as regions that are selectively bound by either receptor. Analysis of bound regions shows that regions bound by ERα have distinct properties in terms of genome landscape, sequence features, and conservation compared with regions that are bound by ERβ. ERβ-bound regions are, as a group, located more closely to transcription start sites. ERα- and ERβ-bound regions differ in sequence properties, with ERα-bound regions having an overrepresentation of TA-rich motifs including forkhead binding sites and ERβ-bound regions having a predominance of classical estrogen response elements (EREs) and GC-rich motifs. Differences in the properties of ER bound regions might explain some of the differences in gene expression programs and physiological effects shown by the respective estrogen receptors

Genome-wide detection and analysis of hippocampus core promoters using DeepCAGE

Finding and characterizing mRNAs, their transcription start sites (TSS), and their associated promoters is a major focus in post-genome biology. Mammalian cells have at least 5–10 magnitudes more TSS than previously believed, and deeper sequencing is necessary to detect all active promoters in a given tissue. Here, we present a new method for high-throughput sequencing of 5′ cDNA tags—DeepCAGE: merging the Cap Analysis of Gene Expression method with ultra-high-throughput sequence technology. We apply DeepCAGE to characterize 1.4 million sequenced TSS from mouse hippocampus and reveal a wealth of novel core promoters that are preferentially used in hippocampus: This is the most comprehensive promoter data set for any tissue to date. Using these data, we present evidence indicating a key role for the Arnt2 transcription factor in hippocampus gene regulation. DeepCAGE can also detect promoters used only in a small subset of cells within the complex tissue