FT23, an orally active antifibrotic compound, attenuates structural and functional abnormalities in an experimental model of diabetic cardiomyopathy Sih Min Tan,* ∫ Yuan Zhang,* Bing Wang, † Christina YR Tan,* Steven C Zammit, § Spencer J Williams, § Henry Krum † and Darren J Kelly* ‡ *The University of Melbourne, Department of Medicine, St Vincent’s Hospital, Fitzory, † Centre of Cardiovascular Research and Education in Therapeutics, Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, ‡ Fibrotech Therapeutics Pty Ltd and § School of Chemistry, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Vic., Australia SUMMARY 1. Diabetic cardiomyopathy is characterized by early dia- stolic dysfunction and structural changes, such as interstitial fibrosis and cardiac hypertrophy. Using the Ren-2 rat model, we sought to investigate the effect of FT23 on the structural and functional changes associated with diabetic cardiomyopathy. 2. Heterozygous Ren-2 rats were rendered diabetic with streptozotocin by tail vein injection. Rats were then treated with FT23 (200 mg/kg per day by gavage twice daily) or vehi- cle from Week 8 to Week 16 after the onset of diabetes. Echocardiography was performed to assess heart function before the rats were killed and their hearts collected for histo- logical and molecular biological assessment. The antifibrotic effect of FT23 was compared with that of tranilast in neona- tal cardiac fibroblasts when stimulated with transforming growth factor (TGF)-b (5 ng/mL) at 30, 50 and 100 umol/L. 3. FT23 exhibited greater inhibition of TGF-b-induced col- lagen production in neonatal cardiac fibroblasts, as measured by a [ 3 H]-proline incorporation assay, compared with its parental compound tranilast. In the in vivo study, FT23 sig- nificantly attenuated the increased heart weight : bodyweight ratio in FT23-treated diabetic Ren-2 rats. Diastolic dysfunc- tion, as measured by mitral valve (MV) E/A ratio and MV deceleration time, was also significantly attenuated by FT23. Picrosirius red-stained heart sections revealed that cardiac fibrosis in the diabetic rats was reduced by FT23 compared with that in vehicle-treated rats, with a concomitant reduction in collagen I immunostaining and infiltration of macrophages, as demonstrated by ED1 immunostaining. 4. The results of the present study suggest that FT23 inhibits the activity of TGF-b and attenuates structural and functional manifestations of diastolic dysfunction observed in a model of diabetic cardiomyopathy. Key words: diabetic cardiomyopathy, diastolic dysfunction, fibrosis, transforming growth factor-b. INTRODUCTION Cardiovascular complications are the most common causes of morbidity and mortality in diabetic patients. 1 Diabetic cardio- myopathy is characterized by diastolic dysfunction, cardiac fibrosis and hypertrophy, independent of hypertension or other coronary artery disease. Although the concept of diabetic cardiomyopathy has gained considerable attention since it was first described four decades ago, there is currently no specific therapy recommended for this complication. Conventional thera- pies, such as angiotensin AT 1 receptor blockers and angioten- sin-converting enzyme inhibitors, are associated with the attenuation of some of the cardiovascular complications of dia- betes, but patients often still progress to heart failure. Targeted therapy is therefore being sought for the treatment of diabetic cardiomyopathy. One of the hallmark characteristics of diabetic cardiomyopathy is the accumulation of extracellular matrix (ECM) in the intersti- tial area of the heart. Antifibrotic agents, such as tranilast, have been shown to attenuate aberrant fibrosis and improve kidney and heart function in animal models of diabetic nephropathy 2 and diabetic cardiomyopathy, 3 respectively. However, toxicity issues, including hyperbilirubinaemia and increased alanine transaminase and serum creatinine, have halted the progression of tranilast in clinical trials. 4 More recently, a series of cinnamoyl anthranilate derivatives were synthesised in an effort to optimize the antifibrotic effects of tranilast. 5 Compounds that exhibited higher activity were assessed for their ability to inhibit transforming growth factor (TGF)-b in cultured mesangial cells. Compound FT23 ((E)-2- ([3-(3-(but-2-ynyloxy)-4-methoxyphenyl)-1-oxo-2-propenyl]amino) benzoic acid) was reported to display an inhibitory effect twice that of tranilast in mesangial cells. 5 Correspondence: Darren J Kelly, Department of Medicine, St Vincent’s Hospital, Level 4 Clinical Sciences Building, 29 Regent Street, Fitzroy, Vic. 3065, Australia. Email: dkelly@medstv.unimelb.edu.au ∫ Present address: Baker IDI Heart and Diabetes Institute, Melbourne, Vic., Australia. Received 22 November 2011; revision 3 May 2012; accepted 15 May 2012. © 2012 The Authors Clinical and Experimental Pharmacology and Physiology © 2012 Blackwell Publishing Asia Pty Ltd Clinical and Experimental Pharmacology and Physiology (2012) 39, 650–656 doi: 10.1111/j.1440-1681.2012.05726.x