Search

We previously reported on the development of left ventricular (LV) structural and functional changes in an aged, female rat model where the effects of ovariectomy and excess weight (stimulated by fructose in water) were also explored. Ovariectomy and/or excess weight led to a prolongation of active relaxation, loss of cardiac output, and LV fibrosis in the setting of preserved ejection fraction. In this follow-up study, we wished to characterize the possible role of LV inflammation, oxidative stress (OS), and cell death in inducing such changes. Four experimental groups were studied: young (3 months old), aged (18 months old), aged + ovariectomy (OVX), and aged + ovariectomy + 10% fructose (OVF). Using conventional histology and immunohistochemistry of myocardium as well as biochemical assays of plasma samples, we document the presence of inflammatory cell aggregates in LV myocardium which are associated to high levels of plasma inflammatory cytokines (IL-1β, TNF-α, IFN-γ, TGF-β1) and OS (carbonyl proteins) in aged, OVX, and OVF vs. young animals. In the inflammatory areas, normal cardiac tissue was substituted by replacement and interstitial fibrosis and M1 macrophages, (as per by CD68 immunostaining) as we all as by co-localization with TGF-β1. We also document increases in plasma troponin I levels, loss of capillary density, cardiomyocyte hypertrophy, and death. Select changes were further aggravated by ovariectomy and/or excess weight. In conclusion, aging in the female rat heart, when compounded with estrogen depletion and excess weight promotes the development of greater levels inflammation, OS, fibrosis, capillary rarefaction, cardiomyocyte hypertrophy, and injury/death. These factors likely play an important role in the development of LV remodeling that leads to the development of a “pre-HFpEF” phenotype. Impact statement The incidence of HFpEF continues to increase and ∼2/3 of the patient population are post-menopausal women. Unfortunately, most studies focus on the use of male animal models of remodeling. In this study, however, using female rats to set a model of pre-HFpEF, we provide insights to possible mechanisms that contribute to HFpEF development in humans that will lead us to a better understanding of the underlying pathophysiology of HFpEF.

Endothelial dysfunction (EnD) occurs with aging and endothelial nitric oxide (NO) production by NO synthase (NOS) can be impaired. Low NO levels have been linked to increased arginase (Ar) activity as Ar competes with NOS for L-arginine. The inhibition of Ar activity can reverse EnD and (−)-epicatechin (Epi) inhibits myocardial Ar activity. In this study, through in silico modeling we demonstrate that Epi interacts with Ar similarly to its inhibitor Norvaline (Norv). Using in vitro and in vivo models of aging, we examined Epi and Norv-inhibition of Ar activity and its endothelium-protective effects. Bovine coronary artery endothelial cells (BCAEC) were treated with Norv (10 μM), Epi (1 μM) or the combination (Epi + Norv) for 48 h. Ar activity increased in aged BCAEC, with decreased NO generation. Treatment decreased Ar activity to levels seen in young cells. Epi and Epi + Norv decreased nitrosylated Ar levels by ∼25% in aged cells with lower oxidative stress (∼25%) (dihydroethidium) levels. In aged cells, Epi and Epi + Norv restored the eNOS monomer/dimer ratio, protein expression levels and NO production to those of young cells. Furthermore, using 18 month old rats 15 days of treatment with either Epi (1 mg/kg), Norv (10 mg/kg) or combo, decreased hypertension and improved aorta vasorelaxation to acetylcholine, blood NO levels and tetra/dihydribiopterin ratios in cultured rat aortic endothelial cells. In conclusion, results provide evidence that inhibiting Ar with Epi reverses aged-related loss of eNOS function and improves vascular function through the modulation of Ar and eNOS protein levels and activity., Highlights • In aged endothelium, arginase (Ar) activity is increased, leading to a reduction in NO production. • (−)-Epicatechin (Epi) inhibits Ar activity and modulates L-arginine availability. • Inhibition of Ar with Epi reverses aged-related loss of eNOS function. • Epi and Epi plus Norvaline improves endothelial and vascular function in aged endothelium.