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Open Access Highly Accessed Original investigation

High glucose induces Smad activation via the transcriptional coregulator p300 and contributes to cardiac fibrosis and hypertrophy

Antoinette Bugyei-Twum12, Andrew Advani12, Suzanne L Advani1, Yuan Zhang3, Kerri Thai1, Darren J Kelly3 and Kim A Connelly124*

Author Affiliations

1 Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, 209 Victoria Street, Toronto, ON M5B 1T8, Canada

2 Institute of Medical Science, University of Toronto, 1 King’s College Circle, Toronto, ON M5S 1A8, Canada

3 Department of Medicine, University of Melbourne St. Vincent’s Hospital, Melbourne, Victoria, Australia

4 Division of Cardiology, St. Michael’s Hospital, 30 Bond St, Rm 7-052, Toronto, ON M5B 1W8, Canada

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Cardiovascular Diabetology 2014, 13:89  doi:10.1186/1475-2840-13-89

Published: 5 May 2014

Abstract

Background

Despite advances in the treatment of heart failure, mortality remains high, particularly in individuals with diabetes. Activated transforming growth factor beta (TGF-β) contributes to the pathogenesis of the fibrotic interstitium observed in diabetic cardiomyopathy. We hypothesized that high glucose enhances the activity of the transcriptional co-activator p300, leading to the activation of TGF-β via acetylation of Smad2; and that by inhibiting p300, TGF-β activity will be reduced and heart failure prevented in a clinically relevant animal model of diabetic cardiomyopathy.

Methods

p300 activity was assessed in H9c2 cardiomyoblasts under normal glucose (5.6 mmol/L—NG) and high glucose (25 mmol/L—HG) conditions. 3H-proline incorporation in cardiac fibroblasts was also assessed as a marker of collagen synthesis. The role of p300 activity in modifying TGF-β activity was investigated with a known p300 inhibitor, curcumin or p300 siRNA in vitro, and the functional effects of p300 inhibition were assessed using curcumin in a hemodynamically validated model of diabetic cardiomyopathy – the diabetic TG m(Ren-2)27 rat.

Results

In vitro, H9c2 cells exposed to HG demonstrated increased p300 activity, Smad2 acetylation and increased TGF-β activity as assessed by Smad7 induction (all p < 0.05 c/w NG). Furthermore, HG induced 3H-proline incorporation as a marker of collagen synthesis (p < 0.05 c/w NG). p300 inhibition, using either siRNA or curcumin reduced p300 activity, Smad acetylation and TGF-β activity (all p < 0.05 c/w vehicle or scrambled siRNA). Furthermore, curcumin therapy reduced 3H-proline incorporation in HG and TGF-β stimulated fibroblasts (p < 0.05 c/w NG). To determine the functional significance of p300 inhibition, diabetic Ren-2 rats were randomized to receive curcumin or vehicle for 6 weeks. Curcumin treatment reduced cardiac hypertrophy, improved diastolic function and reduced extracellular matrix production, without affecting glycemic control, along with a reduction in TGF-β activity as assessed by Smad7 activation (all p < 0.05 c/w vehicle treated diabetic animals).

Conclusions

These findings suggest that high glucose increases the activity of the transcriptional co-regulator p300, which increases TGF-β activity via Smad2 acetylation. Modulation of p300 may be a novel strategy to treat diabetes induced heart failure.