Activation of Protein Kinase A and Exchange Protein Directly Activated by cAMP Promotes Adipocyte Differentiation of Human Mesenchymal Stem Cells

Bingbing Jia,Karsten Kristiansen,Gérard Ailhaud,Nathalie Techer,Ez-Zoubir Amri,Rasmus Koefoed Petersen,Stein Ove Døskeland,Jinfu Wang,Lise Madsen,Tao Ma,Reidun Kopperud

doi:10.1371/journal.pone.0034114

Abstract

Human mesenchymal stem cells are primary multipotent cells capable of differentiating into several cell types including adipocytes when cultured under defined in vitro conditions. In the present study we investigated the role of cAMP signaling and its downstream effectors, protein kinase A (PKA) and exchange protein directly activated by cAMP (Epac) in adipocyte conversion of human mesenchymal stem cells derived from adipose tissue (hMADS). We show that cAMP signaling involving the simultaneous activation of both PKA- and Epac-dependent signaling is critical for this process even in the presence of the strong adipogenic inducers insulin, dexamethasone, and rosiglitazone, thereby clearly distinguishing the hMADS cells from murine preadipocytes cell lines, where rosiglitazone together with dexamethasone and insulin strongly promotes adipocyte differentiation. We further show that prostaglandin I2 (PGI2) may fully substitute for the cAMP-elevating agent isobutylmethylxanthine (IBMX). Moreover, selective activation of Epac-dependent signaling promoted adipocyte differentiation when the Rho-associated kinase (ROCK) was inhibited. Unlike the case for murine preadipocytes cell lines, long-chain fatty acids, like arachidonic acid, did not promote adipocyte differentiation of hMADS cells in the absence of a PPARγ agonist. However, prolonged treatment with the synthetic PPARδ agonist L165041 promoted adipocyte differentiation of hMADS cells in the presence of IBMX. Taken together our results emphasize the need for cAMP signaling in concert with treatment with a PPARγ or PPARδ agonist to secure efficient adipocyte differentiation of human hMADS mesenchymal stem cells.

Highlights

Obesity is a prevalent condition frequently associated with metabolic disorders such as dyslipidemia, diabetes, hypertension and cardiovascular diseases
In the present study we demonstrate that adipocyte differentiation in vitro of human mesenchymal stem cells derived from adipose tissue, is critically dependent of cAMP signaling requiring activation of both the protein kinase A (PKA) and the exchange protein directly activated by cAMP (Epac) branch of signaling
Elevated levels of cAMP promote adipocyte differentiation of hMADS cells To determine whether elevated levels of intracellular cAMP are required to promote adipocyte differentiation of hMADS cells, two-days-post-confluent hMADS cells were treated with the adipogenic cocktail with or without a cAMP elevating agent

Summary

Introduction

Obesity is a prevalent condition frequently associated with metabolic disorders such as dyslipidemia, diabetes, hypertension and cardiovascular diseases. In vivo studies in both human and rodents have illustrated that high fat diets, especially when combined with carbohydrates, promote both hyperplasic and hypertrophic development of adipose tissue [3,4,5,6,7,8]. Results from animal feeding studies have indicated that the effect of dietary fat on adipose tissue mass, at least in part, depends on the source and nature of the fatty acids. We have recently shown that the background diet, in particular the ratio between carbohydrate and protein, acts on insulin secretion and cAMP signaling determine the adipogenic action of both n-3 and n-6 PUFAs, explaining at least in part the apparently discrepant reports on the effect of PUFA supplementation [6,7,8,14]

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Results

Conclusion