24-OR: Augmented Heparanase Secretion in Diabetes Regulates Development of Cardiac Hypertrophy

Abstract

HSPG consist of a core protein to which several linear heparan sulphate (HS) side chains are linked. Heparanase (Hpa) is exceptional in its ability to degrade HS. This property is used to regulate cardiac metabolism by releasing LPL, for its onward movement to the vascular lumen to hydrolyze lipoprotein-TG for FA provision to the heart. We hypothesized that another function of Hpa is its ability to promote cardiac hypertrophy. Hearts from mice with global overexpression of Hpa appeared larger, had higher heart weight/tibia length ratios, and exhibited posterior wall thickening. This evidence of cardiac hypertrophy was not reflected in alterations in cardiac function; ejection fraction, fractional shortening, and stroke volume were largely unaffected. This suggested a physiological rather than pathological hypertrophy, and is linked to a role for Hpa in regulation of arterial structure and mechanics. Hearts from animals with cardiac-specific overexpression of VEGFB also released greater amounts of Hpa, and this coincided with a hypertrophic phenotype. Heart function in these VEGFB-Tg rats remained similar to wild-type, and was likely a consequence of the expanded coronary vasculature and metabolic reprogramming that favoured glucose utilization. Rats made diabetic with STZ did not show any changes in cardiac Hpa gene or protein expression. Nevertheless, immediately after retrograde perfusion, the diabetic hearts released significantly greater amounts of Hpa with evidence of relative cardiac hypertrophy. This cardiac hypertrophy in diabetic rats was pathological with ventricular wall thinning and reduced cardiac function. Our data imply that Hpa can stimulate cardiac hypertrophy that remains physiological when there is associated development of coronary vasculature with metabolic flexibility. With diabetes and the occurrence of microangiopathy along with metabolic inflexibility, hypertrophy progresses towards being pathological, leading to heart failure. Disclosure C.Lee: None. R.Shang: None. B.Hussein: None. B.Rodrigues: None. Funding Canadian Institutes of Health Research (PJT178134); Heart and Stroke Foundation of Canada (G190026493)