Elsevier

Experimental Cell Research

Volume 331, Issue 1, 1 February 2015, Pages 82-96
Experimental Cell Research

Research Article
Involvement of IGF-1 and MEOX2 in PI3K/Akt1/2 and ERK1/2 pathways mediated proliferation and differentiation of perivascular adipocytes

https://doi.org/10.1016/j.yexcr.2014.09.011Get rights and content

Highlights

  • IGF-1 activated PI3K/Akt2 and ERK1/2 pathways to mediate PVAC proliferation and differentiation.

  • The expression of ERK1, ERK 2, PI3K, Akt1 and Akt2 showed different change trends between PVAC proliferation and differentiation.

  • MEOX2 effectively expressed in PVAC, increased early and late cellular apoptosis, and inhibited its proliferation.

  • MEOX2 depressed PVAC differentiation and FAS expression, and decreased lipid content in PVAC.

  • MEOX2 repressed the effects of IGF-1 on PVAC by restraining the activation of PI3K/Akt1/2 and ERK1/2 signaling pathways.

Abstract

Perivascular adipocyte (PVAC) proliferation and differentiation were closely involved in cardiovascular disease. We aimed to investigate whether phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signaling pathways enhance PVAC functions activated by insulin-like growth factor 1(IGF-1) and suppressed by mesenchyme homeobox 2 (MEOX2). In this study, PVACs from primary culture were cultured and induced to differentiate. Cell viability assays demonstrated that IGF-1 promoted PVAC proliferation and differentiation. However MEOX2 counteracted these IGF-1-mediated actions. Flow Cytometry revealed that IGF-1 increased S phase cells and decreased apoptosis; however, MEOX2 decreased S phase cells, increased G0–G1 phase cells, and promoted apoptosis. During PVAC proliferation and differentiation, IGF-1 activated PI3K/Akt1/2 and ERK1/2 signaling pathways, upregulated the expression of these signaling proteins and FAS, and increased PVAC lipid content. In contrast, MEOX2 constrained the phosphorylation of ERK1/2 and Akt1/2 protein, down-regulated these signaling molecules and FAS, and decreased PVAC lipid content. Instead, MEOX2 knockdown enhanced the ERK1/2 and Akt1/2 phosphorylation, augmented the expression of these signaling molecules and FAS, and increased PVAC lipid content. Our findings suggested that PI3K/Akt1/2 and ERK1/2 activation mediated by IGF-1 is essential for PVAC proliferation and differentiation, and MEOX2 is a promising therapeutic gene to intervene in the signaling pathways and inhibit PVAC functions.

Section snippets

Background

Traditionally, adipocytes and adipose tissue were primarily considered as fat depots and calory preservers. More recently, they are recognized as actively metabolic endocrine cells and organs that synthesize, store, and secrete adipokines, free fatty acids and steroid hormones [1], [2], [3]. Especially, visceral obesity is related with an incremental risk for insulin resistance and cardiovascular disease [1], [2], [4], [5], and its perivascular adipose tissue (PVAT) and perivascular adipocytes

Materials

The Rattus norvegicus rat MEOX2 plasmid was kind gift of Dr. Kenneth Walsh (St. Elizabeth׳s Medical Center, Boston, MA) and Dr. Bert Vogelstein (The Howard Hughes Medical Institute and The Sidney Kimmel Comprehensive Cancer Center, USA) [19]. pAdxsi was obtained from Nosai Genome Research Center Co., Ltd. (Beijing, China). All restriction enzymes were purchased from New England Biolabs (Beverly, MA, USA). Cell culture reagents were obtained from GibcoBRL (Life Technologies, Grand Island, NY).

PVAC dedifferentiation and differentiation

Morphological changes of PVACs in the ceiling culture are shown in Fig. 1. When lipid-filled mature cells (Fig. 1A) isolated from PVAT were applied into culture flasks filled completely with media, the cells got attached to upper surface of flasks and extend cytoplasm after 1 week of culture (Fig. 1B). The adhered unilocular cells flattened and lost a round contour and the dominant lipid droplets were broken into several smaller parts to exhibit a multi-ocular outlook. Approximately 70% of the

Discussion

Our investigations identify a unique role for IGF-1 mediated PI3K/Akt1/2 and ERK1/2 signaling pathways in regulating PVAC proliferation and adipogenesis. Thus this study may provide new insights into an understanding of the pro-growth and anti-apoptosis role of IGF-1 affecting PVAC functions. IGF-1 is a critical regulator of adipose tissue through its regulation of proliferation and adipogenesis by activating two downstream pathways, ERK of the MAPK family and PI3K, in vivo and in vitro [10],

Disclosures

None.

Acknowledgments

This study was supported by Grants from Shandong Provincial Natural Science Foundation (No. 2009ZRB019BS) and the National Natural Science Foundation of China (No. 81170274).

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