Liver X Receptor Agonist AZ876 Induces Beneficial Endogenous Cardiac Lipid Reprogramming and Protects Against Isoproterenol-Induced Cardiac Damage

Baicalin Prevents Chronic β-AR Agonist-Induced Heart Failure via Preventing Oxidative Stress and Overactivation of the NADPH Oxidase NOX2

Heart failure (HF) remains the leading cause of mortality worldwide. Although various drugs are currently used in the treatment of HF, including angiotensin receptor blockers, angiotensin-converting enzyme inhibitors and beta blockers, none of these drugs can reverse the physiological remodelling of the heart associated with HF. Therefore, discovering novel drugs that can limit the extent of HF or prevent the structural dysfunction of the heart during HF progression is urgently needed. Baicalin is a natural flavonoid widely used in Traditional Chinese Medicine for its anti-inflammatory and anti-oxidative effects; however, the role of baicalin in chronic HF, in particular its underlying mechanisms of action, remains largely unelucidated. Murine models of beta-adrenergic receptor agonist (β-AR)-induced HF were induced via chronic induction with isoproterenol (ISO) for 4 weeks. Furthermore, we examined the effects and mechanisms of baicalin in protecting against ISO-induced cardiac impairment and HF. Daily administrations of baicalin robustly protected against chronic ISO-induced pathophysiological changes of the heart, including cardiac hypertrophy, reduced ejection fraction, fibrosis and remodelling. Baicalin also strongly inhibited the production of reactive oxygen and nitrogen species in the heart by preventing overactivation of the NADPH oxidase NOX2. Hence, the cardioprotective effects of baicalin in preventing chronic β-AR-induced HF were due to preventing the overactivation of NOX2 and generation of excessive oxidative stress. Our findings provide new mechanistic insight and suggest the therapeutic potential of baicalin as a novel drug in the treatment of chronic HF.

Liver X Receptor Agonist 4β-Hydroxycholesterol as a Prognostic Factor in Coronary Artery Disease

BACKGROUND

Regardless of progress in treatment of coronary artery disease (CAD), there is still a significant residual risk of death in patients with CAD, highlighting the need for additional risk stratification markers. Our previous study provided evidence for a novel blood pressure-regulating mechanism involving 4β-hydroxycholesterol (4βHC), an agonist for liver X receptors, as a hypotensive factor. The aim was to determine the role of 4βHC as a prognostic factor in CAD.

METHODS AND RESULTS

The ARTEMIS (Innovation to Reduce Cardiovascular Complications of Diabetes at the Intersection) cohort consists of 1946 patients with CAD. Men and women were analyzed separately in quartiles according to plasma 4βHC. Basic characteristics, medications, ECG, and echocardiography parameters as well as mortality rate were analyzed. At baseline, subjects with a beneficial cardiovascular profile, as assessed with traditional markers such as body mass index, exercise capacity, prevalence of diabetes, and use of antihypertensives, had the highest plasma 4βHC concentrations. However, in men, high plasma 4βHC was associated with all-cause death, cardiac death, and especially sudden cardiac death (SCD) in a median follow-up of 8.8 years. Univariate and comprehensively adjusted hazard ratios for SCD in the highest quartile were 3.76 (95% CI, 1.6-8.7; P=0.002) and 4.18 (95% CI, 1.5-11.4; P=0.005), respectively. In contrast, the association of cardiac death and SCD in women showed the lowest risk in the highest 4βHC quartile.

CONCLUSIONS

High plasma 4βHC concentration was associated with death and especially SCD in men, while an inverse association was detected in women. Our results suggest 4βHC as a novel sex-specific risk marker of cardiac death and especially SCD in chronic CAD.

REGISTRATION INFORMATION

clinicaltrials.gov. Identifier NCT01426685.

Cardioprotective Effects of Palmitoleic Acid (C16:1n7) in a Mouse Model of Catecholamine-Induced Cardiac Damage Are Mediated by PPAR Activation

Palmitoleic acid (C16:1n7) has been identified as a regulator of physiological cardiac hypertrophy. In the present study, we aimed to investigate the molecular pathways involved in C16:1n7 responses in primary murine cardiomyocytes (PCM) and a mouse model of isoproterenol (ISO)-induced cardiac damage. PCMs were stimulated with C16:1n7 or a vehicle. Afterwards, RNA sequencing was performed using an Illumina HiSeq sequencer. Confirmatory analysis was performed in PCMs and HL-1 cardiomyocytes. For an in vivo study, 129 sv mice were orally treated with a vehicle or C16:1n7 for 22 days. After 5 days of pre-treatment, the mice were injected with ISO (25 mg/kg/d s. c.) for 4 consecutive days. Cardiac phenotyping was performed using echocardiography. In total, 129 genes were differentially expressed in PCMs stimulated with C16:1n7, including Angiopoietin-like factor 4 (Angptl4) and Pyruvate Dehydrogenase Kinase 4 (Pdk4). Both Angptl4 and Pdk4 are proxisome proliferator-activated receptor α/δ (PPARα/δ) target genes. Our in vivo results indicated cardioprotective and anti-fibrotic effects of C16:1n7 application in mice. This was associated with the C16:1n7-dependent regulation of the cardiac PPAR-specific signaling pathways. In conclusion, our experiments demonstrated that C16:1n7 might have protective effects on cardiac fibrosis and inflammation. Our study may help to develop future lipid-based therapies for catecholamine-induced cardiac damage.