Mitochondrial energy metabolism in diabetic cardiomyopathy: Physiological adaption, pathogenesis, and therapeutic targets.

ABSTRACT: Diabetic cardiomyopathy is defined as abnormal structure and function of the heart in the setting of diabetes, which could eventually develop heart failure and leads to the death of the patients. Although blood glucose control and medications to heart failure show beneficial effects on this disease, there is currently no specific treatment for diabetic cardiomyopathy. Over the past few decades, the pathophysiology of diabetic cardiomyopathy has been extensively studied, and an increasing number of studies pinpoint that impaired mitochondrial energy metabolism is a key mediator as well as a therapeutic target. In this review, we summarize the latest research in the field of diabetic cardiomyopathy, focusing on mitochondrial damage and adaptation, altered energy substrates, and potential therapeutic targets. A better understanding of the mitochondrial energy metabolism in diabetic cardiomyopathy may help to gain more mechanistic insights and generate more precise mitochondria-oriented therapies to treat this disease.

[Effect of Pp2cm Gene Silencing on Mouse Macrophage Resistance Against Staphylococcus aureus Infection via TLR Pathway].

Objective: To investigate the effect of silencing protein phosphatase 2cm ( Pp2cm) gene on the expression of inflammatory factors in macrophages infected with Staphylococcus aureus ( S. aureus) and the mechanisms involved. Methods: The effects of Pp2cm knockdown on inflammatory factors, proliferation, apoptosis, and Toll-like receptor (TLR) signaling were analyzed in RAW 264.7 cells, a murine macrophage cell line, transfected with adenovirus (Ad). The cells were divided into four groups, including Ad-Ctrl group, Ad- Pp2cm group, Ad-Ctrl+ S. aureus group and Ad- Pp2cm+ S. aureus group. Cell transfection was achieved by separately introducing control adenovirus (Ad-Ctrl) or adenovirus targeting the Pp2cm gene (Ad- Pp2cm) and inflammation or the absence of inflammation was induced by applying or not applying S. aureus. The expression of tumor necrosis factor-alpha ( TNF-α), interleukin-1ß ( IL-1 ß), TLR2, TLR4, Toll-like receptor adaptor protein ( Tirap) and myeloid differentiation factor 88 ( Myd88) was determined by real-time fluorescent quantitative polymerase chain reaction (RT-qPCR). PP2Cm protein expression was determined by Western blot. Cell proliferation was determined by cell counting kit-8 (CCK-8) assay and cell apoptosis was measured by flow cytometry. Results: The expression of Pp2cmgene and PP2Cm protein was downregulated in the Ad- Pp2cm group when compared to the Ad-Ctrl group, with the diference showing statistical significance ( P<0.05). When compared to those of the Ad-Ctrl+ S. aureus group, macrophages in the Ad- Pp2cm+ S. aureus group showed significantly increase in the TNF- α and IL-1 ß gene levels ( P<0.01). Furthermore, the Ad- Pp2cm group demonstrated elevated gene expression levels of TLR2, TLR4, Tirap and Myd88 in macrophages when compared to the Ad-Ctrl group, with the difference showing statistical significance ( P<0.05). There were no statistically significant differences in cell apoptosis and proliferation between the Ad-Ctrl and Ad- Pp2cm groups. Conclusions: Silencing Pp2cm gene promotes the inflammatory response of macrophages to S. aureus infection. Moreover, the TLR pathway plays an important role in the inflammatory activation of macrophages.

Tyrosine phosphorylation of band 3 impairs the storage quality of suspended red blood cells in the Tibetan high-altitude polycythemia population.

Due to environmental hypoxia on the Tibetan Plateau, local residents often exhibit a compensative increase in hemoglobin concentration to maintain the body's oxygen supply. However, increases in hemoglobin and hematocrit (Hct) pose a serious challenge to the quality of stored suspended red blood cells (SRBCs) prepared from the blood of high-hemoglobin populations, especially populations at high altitude with polycythemia in Tibet. To explore the difference in storage quality of SRBCs prepared from plateau residents with a high hemoglobin concentration, blood donors were recruited from Tibet (> 3600 m) and Chengdu (≈ 500 m) and divided into a high-altitude control (HAC) group, high-altitude polycythemia (HAPC) group and lowland control (LLC) group according to their hemoglobin concentration and altitude of residence. The extracellular acidification rate (ECAR), pyruvate kinase (PK) activity and band 3 tyrosine phosphorylation were analyzed on the day of blood collection. Then, whole-blood samples were processed into SRBCs, and storage quality parameters were analyzed aseptically on days 1, 14, 21 and 35 of storage. Overall, we found that tyrosine 21 phosphorylation activated glycolysis by releasing glycolytic enzymes from the cytosolic domain of band 3, thus increasing glucose consumption and lactate accumulation during storage, in the HAPC group. In addition, band 3 tyrosine phosphorylation impaired erythrocyte deformability, accompanied by the highest hemolysis rate in the HAPC group, during storage. We believe that these results will stimulate new ideas to further optimize current additive solutions for the high-hemoglobin population in Tibet and reveal new therapeutic targets for the treatment of HAPC populations.

Upper-critical solution temperature (UCST) polymer functionalized nanomedicine for controlled drug release and hypoxia alleviation in hepatocellular carcinoma therapy.

Recently, bioinspired material such as nanoparticle has been successfully applied in the cancer therapy. However, how to precisely control the drug release from nanomedicine in tumor tissue and overcome the hypoxic microenvironment of tumor tissue is still an important challenge in the development of nanomedicine. In this work, a new type of drug-loaded nanoparticles P(AAm-co-AN)-AuNRs@CeO2-DOX (PA-DOX) was prepared by combining high-efficiency photothermal reagents, critical up-conversion temperature polymer layer and anti-cancer drug doxorubicin (DOX) for the treatment of hepatocellular carcinoma (HCC). In this system, CeO2 can decompose hydrogen peroxide to H2O and O2 alleviate the anaerobic microenvironment of liver cancer cells. As a photothermal reagent, AuNRs@CeO2 can convert near-infrared light into heat energy to achieve local heat to kill cancer cells and ablate solid tumors. In addition, the elevated temperature would enable the polymer layer to undergo a phase transition to release more DOX to achieve a controlled release mechanism, which will open up a new horizon for clinical cancer treatment.

Obesity Enables NLRP3 Activation and Induces Myocardial Fibrosis via Hyperacetylation of HADHa.

Obesity increases the risk of myocardial fibrosis, a pathological change in most heart diseases, but the mechanism has not been fully elucidated. Here, we found that mice with high-fat diet-induced obesity had more severe myocardial fibrosis than control mice under normal and ischemia/reperfusion (I/R) conditions, which could be alleviated by neutralizing antibodies against interleukin (IL)-1ß and IL-18, downstream products of the nucleotide-binding oligomerization-like receptor protein 3 (NLRP3) inflammasome, and the NLRP3 inhibitor MCC950. Mechanistically, mitochondrial hyperacetylation in obese mouse hearts recruited apoptosis-associated speck-like protein containing a CARD (ASC) to mitochondria and thus facilitated NLRP3 inflammasome assembly. Acetylation of K255 on hydroxyl-CoA dehydrogenase α subunit (HADHa) was identified to trigger the mitochondrial localization of ASC. Blockade of HADHa-K255 acetylation downregulated mitochondrial ASC, suppressed the NLRP3 inflammasome, and attenuated post-I/R myocardial fibrosis in obese mouse hearts. In obese human patients, the extent of myocardial fibrosis according to T1 MRI was positively correlated with the plasma levels of IL-1ß and IL-18, supporting the connection of NLRP3 inflammation to obesity-induced myocardial fibrosis. In conclusion, our study demonstrates that the heart is susceptible to fibrosis under obesity through hyperacetylated HADHa-mediated activation of the NLRP3 inflammasome.

Circulating metabolic signatures of heart failure in precision cardiology.

Precision cardiology aims to implement personalized health care and precise medical decisions based on the specific characteristics of individuals. Metabolic remodeling plays a causal role in the pathogenesis of heart failure (HF). Changes in metabolic pathways such as substrate preference, high-energy phosphate metabolism and amino acid metabolism, are involved in pathological structural remodeling and functional impairment. These metabolic alterations are usually not restricted in the cardiac tissue, but also manifest in circulation. In clinical practice, blood sample is routinely used for HF screening. Metabolomics is an emerging omics technology that provides an efficient way to acquire dynamic metabolic profiles in circulation. An increasing number of metabolic biomarkers have been implicated in disease progression, making it possible to fight HF in a more effective and precise way. This review summarizes the modern analytical techniques in metabolomics as well as emerging circulating metabolites during the pathogenesis of HF, aiming to provide new insights into the prevention, diagnosis and treatment of HF in the era of precision medicine.

Nanomedicine-Based Therapeutics for Myocardial Ischemic/Reperfusion Injury.

Myocardial ischemic/reperfusion (IR) injury is a global cardiovascular disease with high mortality and morbidity. Therapeutic interventions for myocardial ischemia involve restoring the occluded coronary artery. However, reactive oxygen species (ROS) inevitably impair the cardiomyocytes during the ischemic and reperfusion phases. Antioxidant therapy holds great promise against myocardial IR injury. The current therapeutic methodologies for ROS scavenging depend predominantly on administering antioxidants. Nevertheless, the intrinsic drawbacks of antioxidants limit their further clinical transformation. The use of nanoplatforms with versatile characteristics greatly benefits drug delivery in myocardial ischemic therapy. Nanoplatform-mediated drug delivery significantly improves drug bioavailability, increases therapeutic index, and reduces systemic toxicity. Nanoplatforms can be specifically and reasonably designed to enhance molecule accumulation at the myocardial site. The present review initially summarizes the mechanism of ROS generation during the process of myocardial ischemia. The understanding of this phenomenon will facilitate the advancement of innovative therapeutic strategies against myocardial IR injury. The latest developments in nanomedicine for treating myocardial ischemic injury are then discussed. Finally, the current challenges and perspectives in antioxidant therapy for myocardial IR injury are addressed.

Gold-based nanoparticles realize photothermal and photodynamic synergistic treatment of liver cancer and improve the anaerobic tumor microenvironment under near-infrared light.

In order to solve the different pains caused by traditional cancer treatment methods such as surgical treatment, the nano-drug delivery system provides new ideas for cancer treatment. In this paper, a novel anti-tumor therapy nanoparticle, P(AAm-co-AN)-AuNRs@CeO2-Ce6(PA/Ce6), is prepared, which provides a novel idea for liver cancer treatment. The CeO2-coated gold nanorods were grafted onto the surface of the temperature-sensitive polymer P(AAm-co-AN)-CTPD. The photosensitizer Ce6 is loaded on the surface of the nanoparticles and the polymer layer. CeO2 can effectively alleviate the tumor anaerobic microenvironment, and under 808 nm near-infrared (NIR) excitation, the gold nanorods achieve photothermal conversion to induce local heating, which leads to the phase transition of the polymer layer and realizes a controllable release mechanism. In addition, 660 nm NIR light can effectively induce Ce6 to produce singlet oxygen, thereby effectively killing cancer cells. Under the 808 nm laser irradiation within 600 s, the PA/Ce6 solution can heat up to about 60°C, which was enough to ablate both cancer cells and tumor tissues. When the temperature was 50°C, the cumulative release rate of Ce6 was 95.31%. Under the 808 nm laser irradiation, oxygen production capacity of PA/Ce6 was higher and can effectively reduce the content of hydrogen peroxide in cancer cells. Compared to free Ce6, the reactive oxygen species-mediated fluorescence of PA/Ce6 nanoparticles was greater. The cell viability and migration of HepG2 cells were decreased after the 660 and 880 nm lasers were irradiated at the same time. The cancer cells were further inhibited, showing a good in vitro anti-tumor effect. PA-DOX showed the best tumor growth inhibitory effect under NIR laser irradiation and had no acute toxicity in vivo. Due to the existence of AuNRs, nanoparticles had high-efficiency photothermal conversion ability to achieve photothermal therapy. Ce6 can generate singlet oxygen under the excitation of 660 nm laser to realize photodynamic therapy. The experimental results also showed that PA/Ce6 can effectively decompose hydrogen peroxide under laser irradiation, aiming to effectively alleviate the anaerobic microenvironment of tumors. These indicate that PA/Ce6 plays a promising role for hepatocellular carcinoma treatment.

Hypoxia-triggered O-GlcNAcylation in the brain drives the glutamate-glutamine cycle and reduces sensitivity to sevoflurane in mice.

BACKGROUND: Hypersensitivity to general anaesthetics predicts adverse postoperative outcomes in patients. Hypoxia exerts extensive pathophysiological effects on the brain; however, whether hypoxia influences sevoflurane sensitivity and its underlying mechanisms remain poorly understood. METHODS: Mice were acclimated to hypoxia (oxygen 10% for 8 h day-1) for 28 days and anaesthetised with sevoflurane; the effective concentrations for 50% of the animals (EC50) showing loss of righting reflex (LORR) and loss of tail-pinch withdrawal response (LTWR) were determined. Positron emission tomography-computed tomography, O-glycoproteomics, seahorse analysis, carbon-13 tracing, site-specific mutagenesis, and electrophysiological techniques were performed to explore the underlying mechanisms. RESULTS: Compared with the control group, the hypoxia-acclimated mice required higher concentrations of sevoflurane to present LORR and LTWR (EC50LORR: 1.61 [0.03]% vs 1.46 [0.04]%, P<0.01; EC50LTWR: 2.46 [0.14]% vs 2.22 [0.06]%, P<0.01). Hypoxia-induced reduction in sevoflurane sensitivity was correlated with elevation of protein O-linked N-acetylglucosamine (O-GlcNAc) modification in brain, especially in the thalamus, and could be abolished by 6-diazo-5-oxo-l-norleucine, a glutamine fructose-6-phosphate amidotransferase inhibitor, and mimicked by thiamet-G, a selective O-GlcNAcase inhibitor. Mechanistically, O-GlcNAcylation drives de novo synthesis of glutamine from glucose in astrocytes and promotes the glutamate-glutamine cycle, partially via glycolytic flux and activation of glutamine synthetase. CONCLUSIONS: Intermittent hypoxia exposure decreased mouse sensitivity to sevoflurane anaesthesia through enhanced O-GlcNAc-dependent modulation of the glutamate-glutamine cycle in the brain.

Ketone Body ß-Hydroxybutyrate Prevents Myocardial Oxidative Stress in Septic Cardiomyopathy.

Septic cardiomyopathy is a life-threatening complication of severe sepsis and septic shock. Oxidative stress and mitochondrial dysfunction have been identified as significant abnormalities in septic cardiomyopathy. However, specific treatments are rare. This study aims to investigate the impact of ß-hydroxybutyrate (ß-OHB) on septic cardiomyopathy and explore the underlying mechanism(s). We found that pretreatment of D-ß-hydroxybutyrate-(R)-1,3 butanediol monoester (ketone ester, 3 mg/g body weight, once daily) by gavage for three days elevated the levels of ketone bodies, especially that of ß-hydroxybutyrate (ß-OHB) in the circulation and mouse hearts, which exerted a protective effect against lipopolysaccharide (LPS, 20 mg/kg)-induced septic cardiomyopathy in mice. In addition, an LPS-stimulated macrophage-conditioned medium (MCM) was used to mimic the pathological process of septic cardiomyopathy. Mechanistically, ß-OHB alleviated myocardial oxidative stress and improved mitochondrial respiratory function through the antioxidant FoxO3a/MT2 pathway activated via histone deacetylase (HDAC) inhibition, which ultimately enhanced heart performance in septic cardiomyopathy. Our results, therefore, suggested an unappreciated critical role of ß-OHB in septic heart protection as well as highlighted the potential of ß-OHB as a simple remedy for the septic cardiomyopathy population.

Mitochondrial protein hyperacetylation underpins heart failure with preserved ejection fraction in mice.

Over 50% of patients with heart failure have preserved ejection fraction (HFpEF), rather than reduced ejection fraction (HFrEF). The prevalence of HFpEF continues to increase, while the pathogenic mechanisms underlying HFpEF remain largely elusive and evidence-based therapies are still lacking. This study was designed to investigate the metabolic signature of HFpEF and test the potential therapeutic intervention in a mouse model. By utilizing a "3-Hit" HFpEF mouse model, we observed a global protein hyperacetylation in the HFpEF hearts as compared to the pressure overload-induced HFrEF and adult/aged non-heart failure (NHF) hearts. Acetylome analysis identified that a large proportion of the hyperacetylated proteins (74%) specific to the HFpEF hearts are in mitochondria, and enriched in tricarboxylic acid (TCA) cycle, oxidative phosphorylation (OXPHOS), and fatty acid oxidation. Further study showed that the elevated protein acetylation in the HFpEF hearts was correlated with reduced NAD+/NADH ratio, impaired mitochondrial function, and depleted TCA cycle metabolites. Normalization of NAD+/NADH ratio by supplementation of nicotinamide riboside (NR) for 30 days downregulated the acetylation level, improved mitochondrial function and ameliorated HFpEF phenotypes. Therefore, our study identified a distinct protein acetylation pattern in the HFpEF hearts, and proposed NR as a promising agent in lowering acetylation and mitigating HFpEF phenotypes in mice.

Tumor-Targeting Multifunctional Nanoprobe for Enhanced Photothermal/Photodynamic Therapy of Liver Cancer.

Numerous researchers have committed to the development of combined therapy strategies for tumors, since their use in the treatment of tumors has more ideal therapeutic outcomes. In the study, we designed and prepared gold nanostars with CD147 modified on the surface and then efficiently loaded a photosensitive drug IR820 to construct a multifunctional nanoprobe. Due to the protection effect of gold, the nanoprobe has oxygen/heat energy generation capability and can also efficiently deliver the loaded drugs inside the tumor cells. Moreover, the nanoprobe has excellent photothermal/photodynamic therapeutic outcomes. The observation by photoacoustic real-time imaging validated the outstanding tumor-targeting characteristics of our nanoprobe. Finally, in the in vivo treatment experiment, the nanoprobe achieved ideal tumor-suppressive effects after the photothermal/photodynamic therapy. In summary, the findings of this experiment are useful in the development of new combined tumor therapy strategies based on nanomaterials.

Hypoxic acclimation improves cardiac redox homeostasis and protects heart against ischemia-reperfusion injury through upregulation of O-GlcNAcylation.

Ischemia-reperfusion (I/R) injury is detrimental to cardiovascular system. Alteration in glucose metabolism has been recognized as an important adaptive response under hypoxic conditions. However, the biological benefits underlying this metabolic phenotype remain to be elucidated. This study was designed to investigate the impact of hypoxic acclimation (HA) on cardiac I/R injury and the antioxidative mechanism(s). Male adult mice were acclimated in a hypoxic chamber (10% oxygen [O2]) for 8 h/day for 14 days, and then subjected to cardiac I/R injury by ligation of left anterior descending coronary artery for 30 min and reperfusion for 24 h or 7 days. Our results showed that HA attenuated oxidative stress and reduced infarct size in the I/R hearts. This cardioprotective effect is coupled with an elevation of protein O-linked N-acetylglucosamine (O-GlcNAc) modification partially due to inflammatory stimulation. Hyperglycosylation activated glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme in the pentose phosphate pathway, resulting in an upregulation of NADPH/NADP+ and GSH/GSSG couples and enhancement of redox homeostasis in the heart. Pharmacological suppression of O-GlcNAcylation totally abolished the influence of HA on the G6PDH activity, redox balance and post-I/R damage in the hearts and cultured cardiomyocytes, whereby augmentation of O-GlcNAcylation further enhanced the benefits, suggesting a central role of O-GlcNAcylation in HA-initiated antioxidative and cardioprotective effects. These findings, therefore, identified HA as a promising anti-I/R strategy for the heart and proposed O-GlcNAc modification of G6PDH as a therapeutic target in ischemic heart disease.

Ultra-small gold nanoparticles self-assembled by gadolinium ions for enhanced photothermal/photodynamic liver cancer therapy.

Gold nanomaterials are widely used in biomedical research as drug delivery systems, imaging agents and therapeutic materials owing to their unique physicochemical properties and high biocompatibility. In this study, we prepared ultra-small gold nanoparticles (AuNPs) and induced them with gadolinium ions to form a spherical self-assembly. The nanoparticles were coupled with matrix metalloproteinase-2 (MMP-2) and loaded with the photosensitive drug IR820 for photothermal/photodynamic combination therapy of liver cancer. The formed nanoprobes were metabolised in vivo via degradation under dual-mode real-time imaging because of their acid response degradation characteristics. In addition, the nanoprobe showed excellent tumour-targeting ability due to the presence of surface-modified MMP-2. In vivo treatment experiments revealed that the nanoprobes achieved enhanced photodynamic/photothermal combination therapy under laser irradiation and significantly inhibited tumour growth. Therefore, the nanoprobes have great potential for anti-tumour therapy guided by dual-mode real-time imaging of liver cancer.

Targeting Mitochondria-Inflammation Circuit by ß-Hydroxybutyrate Mitigates HFpEF.

RATIONALE: Over 50% of patients with heart failure have preserved ejection fraction (HFpEF), rather than reduced ejection fraction. Complexity of its pathophysiology and the lack of animal models hamper the development of effective therapy for HFpEF. OBJECTIVE: This study was designed to investigate the metabolic mechanisms of HFpEF and test therapeutic interventions using a novel animal model. METHODS AND RESULTS: By combining the age, long-term high-fat diet, and desoxycorticosterone pivalate challenge in a mouse model, we were able to recapture the myriad features of HFpEF. In these mice, mitochondrial hyperacetylation exacerbated while increasing ketone body availability rescued the phenotypes. The HFpEF mice exhibited overproduction of IL (interleukin)-1ß/IL-18 and tissue fibrosis due to increased assembly of NLPR3 inflammasome on hyperacetylated mitochondria. Increasing ß-hydroxybutyrate level attenuated NLPR3 inflammasome formation and antagonized proinflammatory cytokine-triggered mitochondrial dysfunction and fibrosis. Moreover, ß-hydroxybutyrate downregulated the acetyl-CoA pool and mitochondrial acetylation, partially via activation of CS (citrate synthase) and inhibition of fatty acid uptake. CONCLUSIONS: Therefore, we identify the interplay of mitochondrial hyperacetylation and inflammation as a key driver in HFpEF pathogenesis, which can be ameliorated by promoting ß-hydroxybutyrate abundance.

Chronic Alcohol Intake Exacerbates Cardiac Dysfunction After Myocardial Infarction.

AIMS: Alcohol intake is a risk factor for cardiovascular diseases. This study was designed to investigate whether chronic alcohol intake affects myocardial infarction (MI)-induced cardiac remodeling and heart failure. METHODS: Eight-week-old male C57BL/6 mice were randomly divided into four groups: Sham group (Sham), MI plus drinking water group (MI + Vehicle), and MI plus daily alcohol intake for 6 weeks with or without gavage of additional alcohol every 3 days (MI + Alcohol and MI + Alcohol + G). The MI were induced by permanent left anterior descending (LAD) coronary artery ligation surgery before vehicle or alcohol treatment. The blood alcohol concentration (BAC), cardiac function, release of cardiac enzymes, pathological changes and mitochondrial function were measured. RESULTS: As expected, supplementation of alcohol in drinking water significantly increased random BAC in mice. Long-term exposure to alcohol further reduced body weight, ejection fraction and fractional shortening in comparison with the MI + Vehicle group. Histopathological data showed that alcohol increased fibrosis in infarct zone, which was well correlated with the functional decline. Also, as compared to the MI + Vehicle group, the adenosine diphosphate-supported respiratory function of freshly isolated cardiac mitochondria was inhibited in the MI + Alcohol + G group. Besides, upon MI-induced cardiac damage, we did not observe further changes in heart weight, cardiomyocyte enlargement in remote zone, exercise capacity, lung edema and the release of cardiac enzyme after chronic alcohol intake. CONCLUSIONS: Our study demonstrated that chronic daily alcohol exposure exacerbated MI-induced cardiac dysfunction, which is related to promoted myocardial fibrosis and inhibited mitochondrial function.