Targeting Rab7-Rilp Mediated Microlipophagy Alleviates Lipid Toxicity in Diabetic Cardiomyopathy.

Diabetic cardiomyopathy (DbCM) is characterized by diastolic dysfunction, which progresses into heart failure and aberrant electrophysiology in diabetic patients. Dyslipidemia in type 2 diabetic patients leads to the accumulation of lipid droplets (LDs) in cardiomyocytes and results in lipid toxicity which has been suggested to drive DbCM. It is aimed to explore potential pathways that may boost LDs degradation in DbCM and restore cardiac function. LDs accumulation resulted in an increase in lipid toxicity in DbCM hearts is confirmed. Microlipophagy pathway, rather than traditional macrolipophagy, is activated in DbCM hearts. RNA-Seq data and Rab7-CKO mice implicate that Rab7 is a major modulator of the microlipophagy pathway. Mechanistically, Rab7 is phosphorylated at Tyrosine 183, which allows the recruitment of Rab-interacting lysosome protein (Rilp) to proceed LDs degradation by lysosome. Treating DbCM mice with Rab7 activator ML-098 enhanced Rilp level and rescued the observed cardiac dysfunction. Overall, Rab7-Rilp-mediated microlipophagy may be a promising target in the treatment of lipid toxicity in DbCM is suggested.

Uric acid-lowering therapy with benzbromarone in hypertension with asymptomatic hyperuricemia: a randomized study focusing left ventricular diastolic function.

BACKGROUND: Both hypertension and hyperuricemia are closely associated with the morbidity and mortality of heart failure with preserved ejection fraction (HFpEF). However, there is limited evidence on the effect of uric acid-lowering therapy on left ventricular (LV) diastolic function in this population. In this randomized study, we prescribed benzbromarone, a uric acid-lowering drug, to those with hypertension and asymptomatic hyperuricemia to investigate its clinical benefits by evaluating LV diastolic function, incidence of HFpEF and hospitalization for heart failure and cardiovascular death. METHODS: 230 participants were randomly assigned into two groups: uric acid-lowering group (benzbromarone) and control groups (without uric acid-lowering drug). The primary endpoint was LV diastolic function evaluated by echocardiography. The secondary endpoint of composite endpoints is the combination of new-onset HFpEF, hospitalization for heart failure and cardiovascular death. RESULTS: After a median of 23.5 months' follow-up (16-30 months), the primary endpoint reflected by E/e' in benzbromarone group reached a significant improvement when compared to control group (p <.001). Composite endpoints occurred in 11 patients of the control group while only 3 patients occurred in the benzbromarone group (p = .027). We also presented the favorable trend of freedom from the composite endpoints or new-onset HFpEF using Kaplan-Meier curve by log-rank test in benzbromarone group (p = .037 and p = .054). CONCLUSIONS: Our study demonstrated the efficiency of benzbromarone in hypertensive patients with concomitant asymptomatic hyperuricemia, including the benefits on ameliorating LV diastolic dysfunction as well as improving composite endpoints.

Hydrogen sulfide alleviates heart failure with preserved ejection fraction in mice by targeting mitochondrial abnormalities via PGC-1α.

AIM: Increasing evidence has proposed that mitochondrial abnormalities may be an important factor contributing to the development of heart failure with preserved ejection fraction (HFpEF). Hydrogen sulfide (H2S) has been suggested to play a pivotal role in regulating mitochondrial function. Therefore, the present study was designed to explore the protective effect of H2S on mitochondrial dysfunction in a multifactorial mouse model of HFpEF. METHODS: Wild type, 8-week-old, male C57BL/6J mice or cardiomyocyte specific-Cse (Cystathionine γ-lyase, a major H2S-producing enzyme) knockout mice (CSEcko) were given high-fat diet (HFD) and l-NAME (an inhibitor of constitutive nitric oxide synthases) or standardized chow. After 4 weeks, mice were randomly administered with NaHS (a conventional H2S donor), ZLN005 (a potent transcriptional activator of PGC-1α) or vehicle. After additional 4 weeks, echocardiogram and mitochondrial function were evaluated. Expression of PGC-1α, NRF1 and TFAM in cardiomyocytes was assayed by Western blot. RESULTS: Challenging with HFD and l-NAME in mice not only caused HFpEF but also inhibited the production of endogenous H2S in a time-dependent manner. Meanwhile the expression of PGC-1α and mitochondrial function in cardiomyocytes were impaired. Supplementation with NaHS not only upregulated the expression of PGC-1α, NRF1 and TFAM in cardiomyocytes but also restored mitochondrial function and ultrastructure, conferring an obvious improvement in cardiac diastolic function. In contrast, cardiac deletion of CSE gene aggravated the inhibition of PGC-1α-NRF1-TFAM pathway, mitochondrial abnormalities and diastolic dysfunction. The deleterious effect observed in CSEcko HFpEF mice was partially counteracted by pre-treatment with ZLN005 or supplementation with NaHS. CONCLUSION: Our findings have demonstrated that H2S ameliorates left ventricular diastolic dysfunction by restoring mitochondrial abnormalities via upregulating PGC-1α and its downstream targets NRF1 and TFAM, suggesting the therapeutic potential of H2S supplementation in multifactorial HFpEF.

The Imbalance of p53-Park7 Signaling Axis Induces Iron Homeostasis Dysfunction in Doxorubicin-Challenged Cardiomyocytes.

Doxorubicin (DOX)-induced cardiotoxicity (DoIC) is a major side effect for cancer patients. Recently, ferroptosis, triggered by iron overload, is demonstrated to play a role in DoIC. How iron homeostasis is dysregulated in DoIC remains to be elucidated. Here, the authors demonstrate that DOX challenge exhibits reduced contractile function and induction of ferroptosis-related phenotype in cardiomyocytes, evidenced by iron overload, lipid peroxide accumulation, and mitochondrial dysfunction. Compared to Ferric ammonium citrate (FAC) induced secondary iron overload, DOX-challenged cardiomyocytes show a dysfunction of iron homeostasis, with decreased cytoplasmic and mitochondrial iron-sulfur (FeS) cluster-mediated aconitase activity and abnormal expression of iron homeostasis-related proteins. Mechanistically, mass spectrometry analysis identified DOX-treatment induces p53-dependent degradation of Parkinsonism associated deglycase (Park7) which results in iron homeostasis dysregulation. Park7 counteracts iron overload by regulating iron regulatory protein family transcription while blocking mitochondrial iron uptake. Knockout of p53 or overexpression of Park7 in cardiomyocytes remarkably restores the activity of FeS cluster and iron homeostasis, inhibits ferroptosis, and rescues cardiac function in DOX treated animals. These results demonstrate that the iron homeostasis plays a key role in DoIC ferroptosis. Targeting of the newly identified p53-Park7 signaling axis may provide a new approach to prevent DoIC.

Diabetic cardiomyopathy: a brief summary on lipid toxicity.

Diabetes mellitus (DM) is a serious epidemic around the globe, and cardiovascular diseases account for the majority of deaths in patients with DM. Diabetic cardiomyopathy (DCM) is defined as a cardiac dysfunction derived from DM without the presence of coronary artery diseases and hypertension. Patients with either type 1 or type 2 DM are at high risk of developing DCM and even heart failure. Metabolic disorders of obesity and insulin resistance in type 2 diabetic environments result in dyslipidaemia and subsequent lipid-induced toxicity (lipotoxicity) in organs including the heart. Although various mechanisms have been proposed underlying DCM, it remains incompletely understood how lipotoxicity alters cardiac function and how DM induces clinical heart syndrome. With recent progress, we here summarize the latest discoveries on lipid-induced cardiac toxicity in diabetic hearts and discuss the underlying therapies and controversies in clinical DCM.

Characteristics, prognosis, and treatment response in HFpEF patients with high vs. normal ejection fraction.

Background: Heart failure with preserved ejection fraction (HFpEF) patients varied by left ventricular ejection fraction (LVEF) have different clinical characteristics, prognosis, and treatment response. With data from our prospective HFpEF cohort, we assessed the possible relationship between clinical characteristics, outcome as well as treatment response and LVEF. Methods: We compared differences in baseline characteristics and clinical outcomes across LVEF categories (50%≤LVEF <60% vs. LVEF≥60%) in 1,502 HFpEF patients, and determined whether LVEF modified the treatment response. During 5-year follow-up, all-cause mortality was used as the primary endpoints, and composite endpoints (all-cause mortality or HF hospitalization) were set as the secondary endpoint. Results: Patients with higher LVEF were statistically older, more likely to be women and have a history of atrial fibrillation. Patients with lower LVEF category were more likely to have a history of coronary artery disease. The incidences of all-cause mortality and composite endpoints were higher in patients with higher LVEF. Also, LVEF modified the spironolactone treatment effect for the primary outcome and secondary endpoint with stronger estimated benefits at the lower LVEF category with respect to all-cause mortality (HR 0.734, 95% CI 0.541-0.997, P = 0.048) and all-cause mortality or HF hospitalization (HR 0.767, 95% CI 0.604-0.972, P = 0.029). Conclusion: The characteristics and outcomes of HFpEF patients varied substantially by LVEF. Patients with higher LVEF encountered more adverse events than those with lower LVEF. The potential efficacy of spironolactone was greatest at the lower category of LVEF spectrum in HFpEF.

Secretion of miRNA-326-3p by senescent adipose exacerbates myocardial metabolism in diabetic mice.

BACKGROUND: Adipose tissue homeostasis is at the heart of many metabolic syndromes such as diabetes. Previously it has been demonstrated that adipose tissues from diabetic patients are senescent but whether this contributes to diabetic cardiomyopathy (DCM) remains to be elucidated. METHODS: The streptozotocin (STZ) type 1 diabetic mice were established as animal model, and adult mouse ventricular myocytes (AMVMs) isolated by langendorff perfusion as well as neonatal mouse ventricular myocytes (NMVMs) were used as cell models. Senescent associated ß galactosidase (SA-ß-gal) staining and RT-qPCR were used to identify the presence of adipose senescence in diabetic adipose tissue. Senescent adipose were removed either by surgery or by senolytic treatment. Large extracellular vesicles (LEVs) derived from adipose tissue and circulation were separated by ultracentrifugation. Cardiac systolic and diastolic function was evaluated through cardiac ultrasound. Cardiomyocytes contraction function was evaluated by the Ionoptix HTS system and live cell imaging, mitochondrial morphology and functions were evaluated by transmission electron microscope, live cell fluorescent probe and seahorse analysis. RNA-seq for AMVMs and miRNA-seq for LEVs were performed, and bioinformatic analysis combined with RT-qPCR and Western blot were used to elucidate underlying mechanism that senescent adipose derives LEVs exacerbates myocardial metabolism. RESULTS: SA-ß-gal staining and RT-qPCR identified the presence of adipose tissue senescence in STZ mice. Through surgical as well as pharmacological means we show that senescent adipose tissue participates in the pathogenesis of DCM in STZ mice by exacerbates myocardial metabolism through secretion of LEVs. Specifically, expression of miRNA-326-3p was up-regulated in LEVs isolated from senescent adipose tissue, circulation, and cardiomyocytes of STZ mice. Up-regulation of miRNA-326-3p coincided with myocardial transcriptomic changes in metabolism. Functionally, we demonstrate that miRNA-326-3p inhibited the expression of Rictor and resulted in impaired mitochondrial and contractile function in cardiomyocytes. CONCLUSION: We demonstrate for the first time that senescent adipose derived LEVs exacerbates myocardial metabolism through up-regulated miRNA-326-3p which inhibits Rictor in cardiomyocytes. Furthermore, reducing senescence burden in adipose tissue is capable of relieving myocardial metabolism disorder in diabetes mellitus.

Cationic quaternized chitosan bioconjugates with aggregation-induced emission features for cell imaging.

Fluorescent bioprobs are in urgent demand to monitor important biological events in biomedicine. However, the aggregation-caused quenching character, high toxicity, water-insolubility and easy leakage property of conventional small molecular dyes hinder the development in this area. In this work, an aggregation-induced emission (AIE) bioconjugate was synthesised by labeling tetraphenylethylene (TPE) to quaternized chitosan (QCS). The TPE-QCS bioconjugate emits strong fluorescence even in solid state, and is cationic and water-soluble over a wide range of pH values. The TPE-QCS aqueous solution stained HeLa cells by dose- and time-depent manner and imaged living cells with bright fluorescence. Futhermore, the cationic bioconjugate was readily internalized by cells through endocytosis, and further aggragated to large sizes and adhered to negatively charged organelle membranes inside cells achieving fluorescent cell imaging with fluorescence enhancement and leakage-free staining. The AIE-active TPE-QCS with cationic nature, good water-solubility over a wide pH range and unique cell imaging properties could trace HeLa cells for as long as 23 passages, that was obviously superior to existing commercial cellular tracer, so has promising application prospects as ultra long-term tracer in biomedical field.