Adipocyte-specific loss of PPARγ attenuates cardiac hypertrophy
Xi Fang, … , Ju Chen, Nanping Wang
Xi Fang, … , Ju Chen, Nanping Wang
Published October 6, 2016
Citation Information: JCI Insight. 2016;1(16):e89908. https://doi.org/10.1172/jci.insight.89908.
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Research Article Cardiology Cell biology

Adipocyte-specific loss of PPARγ attenuates cardiac hypertrophy

Abstract

Adipose tissue is a key endocrine organ that governs systemic homeostasis. PPARγ is a master regulator of adipose tissue signaling that plays an essential role in insulin sensitivity, making it an important therapeutic target. The selective PPARγ agonist rosiglitazone (RSG) has been used to treat diabetes. However, adverse cardiovascular effects have seriously hindered its clinical application. Experimental models have revealed that PPARγ activation increases cardiac hypertrophy. RSG stimulates cardiac hypertrophy and oxidative stress in cardiomyocyte-specific PPARγ knockout mice, implying that RSG might stimulate cardiac hypertrophy independently of cardiomyocyte PPARγ. However, candidate cell types responsible for RSG-induced cardiomyocyte hypertrophy remain unexplored. Utilizing cocultures of adipocytes and cardiomyocytes, we found that stimulation of PPARγ signaling in adipocytes increased miR-200a expression and secretion. Delivery of miR-200a in adipocyte-derived exosomes to cardiomyocytes resulted in decreased TSC1 and subsequent mTOR activation, leading to cardiomyocyte hypertrophy. Treatment with an antagomir to miR-200a blunted this hypertrophic response in cardiomyocytes. In vivo, specific ablation of PPARγ in adipocytes was sufficient to blunt hypertrophy induced by RSG treatment. By delineating mechanisms by which RSG elicits cardiac hypertrophy, we have identified pathways that mediate the crosstalk between adipocytes and cardiomyocytes to regulate cardiac remodeling.

Authors

Xi Fang, Matthew J. Stroud, Kunfu Ouyang, Li Fang, Jianlin Zhang, Nancy D. Dalton, Yusu Gu, Tongbin Wu, Kirk L. Peterson, Hsien-Da Huang, Ju Chen, Nanping Wang

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Figure 2

Exosome-dependent miR-200a secretion from adipocytes.

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Exosome-dependent miR-200a secretion from adipocytes. (A) The levels of ...
(A) The levels of miR-200a were quantified using quantitative real-time PCR (qRT-PCR) in sera from mice treated with rosiglitazone (RSG) or vehicle (control). Note that miR-200a was increased after RSG treatment, but not in the vehicle control. n = 5 mice. (B) Expression levels of miR-200a were quantified using qRT-PCR in culture media from either 3T3-L1–induced adipocytes or mouse primary adipocytes treated with RSG alone, RSG and GW9662 (PPARγ antagonist), RSG and GW4869 (exosome biogenesis inhibitor), or DMSO (control). Note that RSG increased miR-200a levels in the culture media, but this effect was ablated when cells were treated with either PPARγ antagonist or exosome biogenesis inhibitor. The experiment was replicated 3–6 times. (C) Representative transmission electron micrographs of adipocyte-derived exosomes. The experiment was replicated 3 times. Scale bar: 50 nm. (D) Levels of miR-200a in exosomes were quantified using qRT-PCR from culture media of adipocytes treated with RSG alone, RSG and GW9662 (PPARγ antagonist), or DMSO (control). Note the increase in exosomal miR-200a levels when adipocytes were treated with RSG, but this effect was ablated when adipocytes were treated with PPARγ antagonist. The experiment was replicated 3 times. (E) Cardiomyocytes were incubated with exosomes derived from 3T3-L1 cells transfected with Cy3-conjugated miR-200a and were subsequently fixed and imaged. DAPI is depicted in blue; Cy3-miR-200a in red. Note that cardiomyocytes took up the miR-200a–containing exosomes. The experiment was replicated 3 times. Scale bar: 20 μm. (F) Levels of miR-200a were quantified using qRT-PCR of cardiomyocytes that were incubated with exosomes derived from treated adipocytes, as in D. Note that levels of miR-200a in cardiomyocytes increased after incubation with exosomes derived from RSG-treated adipocytes, but levels were not increased after incubation with exosomes derived from adipocytes treated with RSG and PPARγ antagonist. The experiment was replicated 3 times. snoRNA 202 and cel-miR-39 were used as internal controls for qRT-PCR experiments. Data are represented as mean ± SEM; *P < 0.05 according to 2-tailed Student’s t test for A and 1-way ANOVA for B, D, and F.