Inhibition of methyltransferase activity of enhancer of zeste 2 leads to enhanced lipid accumulation and altered chromatin status in zebrafish.
抑制 zeste 2 增强子的甲基转移酶活性导致斑马鱼脂质积累增强，染色质状态改变。
- 作者列表："den Broeder MJ","Ballangby J","Kamminga LM","Aleström P","Legler J","Lindeman LC","Kamstra JH
BACKGROUND:Recent studies indicate that exposure to environmental chemicals may increase susceptibility to developing metabolic diseases. This susceptibility may in part be caused by changes to the epigenetic landscape which consequently affect gene expression and lead to changes in lipid metabolism. The epigenetic modifier enhancer of zeste 2 (Ezh2) is a histone H3K27 methyltransferase implicated to play a role in lipid metabolism and adipogenesis. In this study, we used the zebrafish (Danio rerio) to investigate the role of Ezh2 on lipid metabolism and chromatin status following developmental exposure to the Ezh1/2 inhibitor PF-06726304 acetate. We used the environmental chemical tributyltin (TBT) as a positive control, as this chemical is known to act on lipid metabolism via EZH-mediated pathways in mammals. RESULTS:Zebrafish embryos (0-5 days post-fertilization, dpf) exposed to non-toxic concentrations of PF-06726304 acetate (5 μM) and TBT (1 nM) exhibited increased lipid accumulation. Changes in chromatin were analyzed by the assay for transposase-accessible chromatin sequencing (ATAC-seq) at 50% epiboly (5.5 hpf). We observed 349 altered chromatin regions, predominantly located at H3K27me3 loci and mostly more open chromatin in the exposed samples. Genes associated to these loci were linked to metabolic pathways. In addition, a selection of genes involved in lipid homeostasis, adipogenesis and genes specifically targeted by PF-06726304 acetate via altered chromatin accessibility were differentially expressed after TBT and PF-06726304 acetate exposure at 5 dpf, but not at 50% epiboly stage. One gene, cebpa, did not show a change in chromatin, but did show a change in gene expression at 5 dpf. Interestingly, underlying H3K27me3 marks were significantly decreased at this locus at 50% epiboly. CONCLUSIONS:Here, we show for the first time the applicability of ATAC-seq as a tool to investigate toxicological responses in zebrafish. Our analysis indicates that Ezh2 inhibition leads to a partial primed state of chromatin linked to metabolic pathways which results in gene expression changes later in development, leading to enhanced lipid accumulation. Although ATAC-seq seems promising, our in-depth assessment of the cebpa locus indicates that we need to consider underlying epigenetic marks as well.
背景: 最近的研究表明，暴露于环境化学品可能会增加对发展中的代谢性疾病的易感性。这种易感性可能部分是由表观遗传景观的变化引起的，后者因此影响基因表达并导致脂质代谢的变化。Zeste 2 的表观遗传修饰增强子 (Ezh2) 是一种组蛋白 H3K27 甲基转移酶，与脂质代谢和脂肪形成有关。在这项研究中，我们使用斑马鱼 (Danio rerio) 来研究 Ezh2 对发育暴露于 Ezh2/2 抑制剂 PF-06726304 醋酸盐后的脂质代谢和染色质状态的作用。我们用环境化学物质三丁基锡 (TBT) 作为阳性对照，因为已知这种化学物质通过 EZH 介导的途径作用于哺乳动物的脂质代谢。 结果: 暴露于无毒浓度的醋酸 PF-06726304 (5 μ m) 和 TBT (1 nM) 的斑马鱼胚胎 (受精后 0-5 天，dpf) 表现出脂质积累增加。通过 50% epiboly (5.5 hpf) 的转座酶可访问染色质测序 (ATAC-seq) 分析染色质的变化。我们观察到 349 个改变的染色质区域，主要位于 H3K27me3 位点，在暴露的样本中大部分是开放的染色质。与这些位点相关的基因与代谢途径相关。此外，在 5 dpf 条件下，TBT 和醋酸 PF-06726304 暴露后，参与脂质稳态、脂肪形成的一系列基因和醋酸 PF-06726304 通过改变染色质可及性特异性靶向的基因差异表达。但不是在 50% 外包阶段。一个基因 cebpa 没有显示染色质的变化，但在 5 dpf 时确实显示了基因表达的变化。有趣的是，基础 H3K27me3 标记在 50% epiboly 时在该位点显著降低。 结论: 在这里，我们首次展示了 ATAC-seq 作为研究斑马鱼毒理学反应的工具的适用性。我们的分析表明，Ezh2 抑制导致染色质与代谢途径相关的部分致敏状态，导致发育后期基因表达变化，导致脂质积累增强。虽然 ATAC-seq 似乎很有前途，但我们对 cebpa 位点的深入评估表明，我们也需要考虑潜在的表观遗传标记。
METHODS:BACKGROUND:Given the importance of habitual dietary protein intake, distribution patterns and dietary sources in the aetiology of age-related declines of muscle mass and function, the present study examined these factors as a function of sex and age in Irish adults aged 18-90 years comprising The National Adult Nutrition Survey (NANS). METHODS:In total, 1051 (males, n = 523; females, n = 528) undertook a 4-day semi-weighed food diary. Total, body mass relative intake and percentage contribution to total energy intake of dietary protein were determined in addition to protein distribution scores (PDS), as well as the contribution of food groups, animal- and plant-based foods to total protein intake. RESULTS:Total and relative protein intake [mean (SD)] were highest in those aged 18-35 years [96 (3) g day , 1.32 (0.40) g kg day ], with lower protein intakes with increasing age (i.e. in adults aged ≥65 years [82 (22) g, 1.15 (0.34) g kg day , P < 0.001 for both]. Differences in protein intake between age groups were more pronounced in males compared to females. Protein distribution followed a skewed pattern for all age groups [breakfast, 15 (10) g; lunch, 30 (15) g; dinner, 44 (17) g]. Animal-based foods were the dominant protein source within the diet [63% (11%) versus 37% (11%) plant protein, P < 0.001]. CONCLUSIONS:Protein intake and the number of meals reaching the purported threshold for maximising post-prandial anabolism were highest in young adults, and lower with increasing age. For main meals, breakfast provided the lowest quantity of protein across all age categories and may represent an opportunity for improving protein distribution, whereas, in older adults, increasing the number of meals reaching the anabolic threshold regardless of distribution pattern may be more appropriate.
METHODS:BACKGROUND:Low cardiorespiratory fitness (CRF) increases risk of all-cause mortality and cardiovascular events. Periodic CRF assessment can have an important preventive function. OBJECTIVE:To develop a protocol-free method to estimate CRF in daily life based on heart rate (HR) and body acceleration measurements. METHODS:Acceleration and HR data were collected from 37 subjects (M=49%) while performing a standardized laboratory activity protocol (sitting, walking, running, cycling) and during a 5-days free-living monitoring period. CRF was determined by oxygen uptake (VO2max) during maximal exercise testing. A doubly-labeled water validated equation was used to predict total energy expenditure (TEE) from acceleration data. A fitness index was defined as the ratio between TEE and HR (TEE-pulse). Activity recognition techniques were used to process acceleration features and classify sedentary, ambulatory and other activity types. Regression equations based on TEE-pulse data from each activity type were developed to predict VO2max. RESULTS:TEE-pulse measured within each activity type of the laboratory protocol was highly correlated to VO2max (r from 0.74 to 0.91). Averaging the outcome of each activity-type specific equation based on TEE-pulse from the laboratory data led to accurate estimates of VO2max (RMSE: 300.0 mlO2/min or 10%). The difference between laboratory and free-living determined TEE-pulse was 3.7 ± 11% (r =0.85). The prediction method preserved the prediction accuracy when applied to free-living data (RMSE: 367 mlO2/min or 12%). CONCLUSIONS:Measurements of body acceleration and HR can be used to predict VO2max in daily life. Activity-specific prediction equations are needed to achieve highly accurate estimates of CRF.
METHODS:OBJECTIVE:Postprandial dyslipidemia is a common feature of insulin resistant states and contributes to increased cardiovascular disease risk. Recently, bile acids have been recognized beyond their emulsification properties as important signaling molecules that promote energy expenditure, improve insulin sensitivity, and lower fasting lipemia. While bile acid receptors have become novel pharmaceutical targets, their effects on postprandial lipid metabolism remain unclear. Here we investigated the potential role of bile acids in regulation of postprandial chylomicron production and triglyceride excursion. Approach and Results: Healthy C57BL/6 mice were given an intraduodenal infusion of taurocholic acid (TA) under fat-loaded conditions and circulating lipids were measured. Targeting of bile acid receptors was achieved with GW4064, a synthetic agonist to the farnesoid X receptor (FXR), and with deoxycholic acid (DCA), an activator of the Takeda G-protein-coupled receptor 5. TA, GW4064, and DCA treatments all lowered postprandial lipemia. FXR agonism also reduced intestinal triglyceride content and activity of microsomal triglyceride transfer protein, involved in chylomicron assembly. Importantly, TA effects (but not DCA) were largely lost in FXR knockout mice. These bile acid effects are reminiscent of the anti-diabetic hormone glucagon-like peptide-1 (GLP-1). While the GLP-1 receptor agonist exendin-4 retained its ability to acutely lower postprandial lipemia during bile acid sequestration and FXR deficiency, it did raise hepatic expression of the rate limiting enzyme for bile acid synthesis. CONCLUSIONS:Bile acid signaling may be an important mechanism of controlling dietary lipid absorption and bile acid receptors may constitute novel targets for the treatment of postprandial dyslipidemia.