A Polyphenolic Compound Amelirotates Mitochondrial Dysfunction in Human Cardiomyocyte Like Cells Subjected to Insulin-Resistant Senescence or β-Adrenergic Stress

Purpose: Metabolic and β-adrenergic stress are major contributors to cardiac dysfunction and may converge on mitochondrial dysfunction and oxidative stress. A Canadian pine bark extract (CPBE), a polyphenol-rich formulation, has been associated with beneficial cardioprotective effects. However, its direct effects on mitochondrial function in human cardiomyocytes exposed to distinct pathological stressors remain incompletely understood. We hypothesized that CPBE exerts cardioprotective effects by restoring mitochondrial redox homeostasis in AC16 cells subjected to aging combined with metabolic stress or a direct β-adrenergic stress. Methods: Human AC16 cardiomyocyte-like cells were used to establish two distinct models of cardiac stress. Cells were treated with palmitic acid (PA) and D-galactose (D-gal) to mimic an insulin-resistant senescent heart (IRSH), or with isoproterenol (ISO) to model an ISO-induced hypertrophic heart (IIHH), followed by CPBE treatment. Mitochondrial function, cellular morphology, and redox status were comprehensively evaluated by assessing mitochondrial membrane potential (MMP), reactive oxygen species (ROS) production, antioxidant defense parameters, intracellular pH, ATP levels, and inflammatory and apoptotic markers using complementary electrophysiological, histological, and biochemical analyses. Results were compared with those obtained from untreated control cells. Results: CPBE treatment significantly improved mitochondrial membrane potential and normalized mitochondrial fission markers in both the IRSH and IIHH models. It also reduced elevated ROS levels, restored intracellular ATP content, and attenuated inflammatory and apoptotic responses, parallel to improved cell morphology by reducing cell area, decreasing phagocytic vacuole accumulation, and restoring the cellular aspect ratio. Also, CPBE enhanced the balance between oxidative stress and the antioxidant defense system, and restored intracellular pH, indicating improved cellular metabolic and mitochondrial homeostasis. Conclusions: These findings suggest that aging combined with either metabolic or β-adrenergic stress converges on a common pathway of mitochondrial redox dysfunction in human cardiomyocyte-like cells. CPBE appears to counteract these pathological alterations through multifaceted mitochondrial and redox-modulating mechanisms. Collectively, these results provide a mechanistic rationale for further investigation of CPBE as a potential mitochondria-targeted therapeutic strategy for cardiometabolic and stress-related cardiac dysfunction.