Exogenous tetrahydrobiopterin supplementation ameliorates heart failure with preserved ejection fraction by attenuating metabolic dysregulation and cardiac oxidative stress
Y Cai, W S QiAbstract
Background
Heart failure with preserved ejection fraction (HFpEF) is a complex clinical syndrome with limited effective therapies, characterized by diastolic dysfunction, metabolic abnormalities, and systemic inflammation. Oxidative stress is a pivotal pathological driver. Tetrahydrobiopterin (BH4) is an essential cofactor for nitric oxide synthases and a known modulator of redox homeostasis. Our preliminary study demonstrates that upstream enhancement of BH4 synthesis via cardiomyocyte-specific GTP cyclohydrolase 1 (GCH1) overexpression is protective in HFpEF. However, it remains unknown whether direct BH4 replenishment is sufficient to confer therapeutic benefits.
Purpose
This study aimed to determine whether exogenous BH4 administration mitigates HFpEF phenotypes and to investigate its effects on systemic metabolism and cardiac oxidative injury.
Methods
A murine HFpEF model was induced in wild-type C57BL/6J mice with a 16-week high-fat diet (HFD) plus 4 weeks of angiotensin-II (AngII, 1.25 mg/kg/day) infusion. BH4 (20 mg/kg/day) or vehicle was administered via intraperitoneal injection during the final two weeks of AngII infusion. In vivo assessments included echocardiography, exercise capacity, glucose/insulin tolerance tests (GTT/ITT), and plasma analysis (NT-proBNP, lipids). Cardiac tissues were analyzed for hypertrophy (WGA staining), fibrosis (Sirius Red), and oxidative stress (DHE staining, 4-HNE). In vitro, neonatal mouse cardiomyocytes were subjected to a 7-day HFpEF-simulating cytokine/hormonal milieu; BH4 (5 µg/mL) was added for the final 48 hours to assess ROS generation and cell size.
Results
Exogenous BH4 supplementation significantly alleviated HFpEF pathophysiology. Treated mice exhibited improved diastolic function (reduced GLS and E/E’), lower plasma NT-proBNP, enhanced exercise capacity, and reduced pulmonary congestion. Systemically, BH4 reduced body weight and adipose mass, improved glucose tolerance and insulin sensitivity, and attenuated plasma levels of total cholesterol, triglycerides, and free fatty acids. In the heart, BH4 treatment diminished cardiac hypertrophy, fibrosis, and markers of oxidative stress (reduced DHE and 4-HNE). In vitro, BH4 directly reduced ROS accumulation and cellular hypertrophy in cardiomyocytes under simulated HFpEF conditions.
Conclusion
Direct supplementation with BH4 is sufficient to ameliorate HFpEF by mitigating systemic metabolic dysfunction and directly attenuating cardiac oxidative stress, hypertrophy, and fibrosis. These findings establish BH4 as a critical mediator of cardioprotection in HFpEF and highlight its potential as a therapeutic target.