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 3

miR-200a is transported from adipocytes to cardiomyocytes in exosomes.

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miR-200a is transported from adipocytes to cardiomyocytes in exosomes. (...
(A) An in vitro coculture system was used in which cardiomyocytes are seeded in the top compartment, which is separated by a porous membrane from adipocytes that are cultured in the bottom of the plate. (B) Adipocytes were transfected with Cy3-miR-200a and cocultured with cardiomyocytes. After 24 hours, cardiomyocytes were fixed and imaged. DAPI is depicted in blue; Cy3-miR-200a in red. Note that the cardiomyocytes were able to take up the Cy3-conjugated miR-200a. The experiment was replicated 3 times. Scale bar: 20 μm. (C) Adipocytes were transfected with cel-miR-39 or not transfected (control) and subsequently seeded in the bottom compartment, as shown in A. RNA was isolated from cardiomyocytes at the indicated times after the start of the coculture. The levels of cel-miR-39 were quantified using quantitative real-time PCR (qRT-PCR). Note that cel-miR-39 was found in cardiomyocytes at 1 hour and 24 hours after coculture, and levels of cel-miR-39 were decreased when exosome biogenesis was inhibited by GW4869. The experiment was replicated 3 times. (D and E) Primary adipocytes were treated with rosiglitazone (RSG) alone, RSG and GW9662, or RSG and GW4869. Cardiomyocytes were subsequently cocultured in the presence or absence of the primary adipocytes for 48 hours. Expression levels of miR-200a (D) and pri-miR-200a (E) in cardiomyocytes were quantified using qRT-PCR. Note that mature miR-200a levels were increased only in cardiomyocytes that were cocultured in the presence of adipocytes. Pretreatment of adipocytes with RSG further augmented the levels of mature miR-200a. Importantly, this effect was rescued by treating cells with either PPARγ antagonist or exosome biogenesis inhibitor. The experiment was replicated 3 times. (F) Primary adipocytes were treated with RSG alone, RSG and GW9662, or RSG and GW4869. H9C2 cells were transfected with a miR-200a luciferase reporter construct and subsequently seeded in the upper compartment of the plate, as depicted in A. Luciferase activity of H9C2 cells was quantified after 48 hours of coculture. Note that luciferase levels were reduced in H9C2 cells when cocultured with adipocytes. This effect was exacerbated when adipocytes were pretreated with RSG and was rescued by treating cells with the PPARγ antagonist GW9662 and exosome biogenesis inhibitor GW4869. The experiment was replicated 3 times. snoRNA 202 was used as internal controls for qRT-PCR experiments. Data are represented as mean ± SEM; *P < 0.05 according to 1-way ANOVA.