Objective

Adipogenesis is critical for adipose tissue remodeling during the development of obesity. While the role of transcription factors in the orchestration of adipogenic pathways is already established, the involvement of coregulators that transduce regulatory signals into epigenome alterations and transcriptional responses remains poorly understood. The aim of our study was to investigate which pathways are controlled by G protein pathway suppressor 2 (GPS2) during the differentiation of human adipocytes.

Methods

We generated a unique loss-of-function model by RNAi depletion of GPS2 in human multipotent adipose-derived stem (hMADS) cells. We thoroughly characterized the coregulator depletion-dependent pathway alterations during adipocyte differentiation at the level of transcriptome (RNA-seq), epigenome (ChIP-seq H3K27ac), cistrome (ChIP-seq GPS2), and lipidome. We validated the in vivo relevance of the identified pathways in non-diabetic and diabetic obese patients.

Results

The loss of GPS2 triggers the reprogramming of cellular processes related to adipocyte differentiation by increasing the responses to the adipogenic cocktail. In particular, GPS2 depletion increases the expression of BMP4, an important trigger for the commitment of fibroblast-like progenitors toward the adipogenic lineage and increases the expression of inflammatory and metabolic genes. GPS2-depleted human adipocytes are characterized by hypertrophy, triglyceride and phospholipid accumulation, and sphingomyelin depletion. These changes are likely a consequence of the increased expression of ATP-binding cassette subfamily G member 1 (ABCG1) that mediates sphingomyelin efflux from adipocytes and modulates lipoprotein lipase (LPL) activity. We identify ABCG1 as a direct transcriptional target, as GPS2 depletion leads to coordinated changes of transcription and H3K27 acetylation at promoters and enhancers that are occupied by GPS2 in wild-type adipocytes. We find that in omental adipose tissue of obese humans, GPS2 levels correlate with ABCG1 levels, type 2 diabetic status, and lipid metabolic status, supporting the in vivo relevance of the hMADS cell-derived in vitro data.

Conclusion

Our study reveals a dual regulatory role of GPS2 in epigenetically modulating the chromatin landscape and gene expression during human adipocyte differentiation and identifies a hitherto unknown GPS2-ABCG1 pathway potentially linked to adipocyte hypertrophy in humans.

中文翻译：

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人脂肪细胞中 G 蛋白通路抑制因子 2 的缺失通过上调 ATP 结合盒亚家族 G 成员 1 触发脂质重塑。

客观的

脂肪生成对于肥胖发展过程中的脂肪组织重塑至关重要。虽然转录因子在脂肪生成途径协调中的作用已经确立，但将调节信号转导为表观基因组改变和转录反应的共调节因子的参与仍然知之甚少。我们研究的目的是研究在人类脂肪细胞分化过程中哪些通路受 G 蛋白通路抑制因子 2 (GPS2) 控制。

方法

我们通过 RNAi 耗尽人类多能脂肪来源干 (hMADS) 细胞中的 GPS2，生成了一个独特的功能丧失模型。我们在转录组 (RNA-seq)、表观基因组 (ChIP-seq H3K27ac)、逆转录组 (ChIP-seq GPS2) 和脂质组水平上彻底表征了脂肪细胞分化过程中的共调节因子消耗依赖性途径改变。我们在非糖尿病和糖尿病肥胖患者中验证了已识别途径的体内相关性。

结果

GPS2 的缺失通过增加对脂肪形成混合物的反应来触发与脂肪细胞分化相关的细胞过程的重新编程。特别是，GPS2 耗竭增加了BMP4的表达，这是成纤维细胞样祖细胞向成脂谱系定向的重要触发因素，并增加了炎症和代谢基因的表达。GPS2 耗尽的人类脂肪细胞的特征是肥大、甘油三酯和磷脂积累以及鞘磷脂耗尽。这些变化可能是 ATP 结合盒亚家族 G 成员 1 ( ABCG1 )表达增加的结果，该成员介导鞘磷脂从脂肪细胞流出并调节脂蛋白脂肪酶 (LPL) 活性。我们识别ABCG1作为直接转录目标，因为 GPS2 耗竭导致野生型脂肪细胞中 GPS2 占据的启动子和增强子的转录和 H3K27 乙酰化的协调变化。我们发现在肥胖人的网膜脂肪组织中，GPS2水平与ABCG1水平、2 型糖尿病状态和脂质代谢状态相关，支持hMADS 细胞衍生的体外数据的体内相关性。

结论

我们的研究揭示了 GPS2 在表观遗传调节人类脂肪细胞分化过程中的染色质景观和基因表达中的双重调节作用，并确定了迄今为止未知的 GPS2-ABCG1 通路，该通路可能与人类脂肪细胞肥大有关。