CTRP9 knockout exaggerates lipotoxicity in cardiac myocytes and high-fat diet-induced cardiac hypertrophy through inhibiting the LKB1/AMPK pathway

Mesenchymal stem cell-derived extracellular vesicles relieve endothelial cell senescence via recovering CTRP9 upon repressing miR-674-5p in atherosclerosis

Background

The senescence of endothelial cells is of great importance involving in atherosclerosis (AS) development. Recent studies have proved the protective role of mesenchymal stem cell-derived extracellular vesicles in AS, herein, we further desired to unvei their potential regulatory mechanisms in endothelial cell senescence.

Methods

Senescence induced by H2O2 in primary mouse aortic endothelial cells (MAECs) was evaluated by SA-β-gal staining. Targeted molecule expression was detected by qRT-PCR and Western blotting. The biological functions of MAECs were determined by CCK-8, flow cytometry, transwell, and tube formation assays. Oxidative injury was assessed by LDH, total and lipid ROS, LPO and MDA levels. The proliferation of adipose-derived mesenchymal stem cell (ADSCs) was analyzed by EdU assay. Effect of ADSCs-derived extracellular vesicles (ADSC-EVs) on AS was investigated in HFD-fed ApoE-/- mice.

Results

miR-674-5p was up-regulated, while C1q/TNF-related protein 9 (CTRP9) was down-regulated in H2O2-induced senescent MAECs. CTRP9 was demonstrated as a target gene of miR-674-5p. miR-674-5p inhibition restrained senescence, oxidative stress, promoted proliferation, migration, and angiogenesis of H2O2-stimulated MAECs via enhancing CTRP9 expression. Moreover, treatment with ADSC-EVs inhibited H2O2-induced senescence and dysfunction of MAECs through regulating miR-674-5p/CTRP9 axis. In the in vivo AS mouse model, ADSC-EVs combination with miR-674-5p silencing slowed down AS progression via up-regulation of CTRP9.

Conclusion

ADSC-EVs repressed endothelial cell senescence and improved dysfunction via promotion of CTRP9 expression upon miR-674-5p deficiency during AS progression, which might provide vital evidence for ADSC-EVs as a promising therapy for AS.

Effects of 12-weeks resistance training and vitamin E supplementation on aminotransferases, CTRP-2, and CTRP-9 levels in males with nonalcoholic fatty liver disease: a double-blind, randomized trial

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) involves excessive liver fat accumulation and is closely linked to oxidative stress, which contributes to liver inflammation and damage. This study aimed to evaluate how interventions such as resistance training (RT) and vitamin E supplementation (VES) can modulate markers of NAFLD and key proteins regulating glucose and lipid metabolism, such as C1Q/TNF-related proteins (CTRPs).

METHODS

Forty participants with NAFLD (mean age: 32.4 ± 8.2 years) were randomly assigned to one of four groups for 12 weeks: placebo (PLB), VES, PLB + RT, and VES + RT. VES was administered at 800 IU/day in a double-blind manner. The RT regimen included eight exercises at 60-80% of one-repetition maximum (1RM), with three sets of 8-12 repetitions, performed three times per week. Pre- and post-intervention assessments included body composition, aspartate aminotransferase (AST), alanine aminotransferase (ALT), lipid profile, glycemic control, CTRP-2, CTRP-9, and 1RM evaluations.

RESULTS

Following the interventions, there was a significant improvement in body composition, lipid profile, glycemic control, and 1RM indices in the exercise groups compared to non-exercise groups (p < 0.05). AST and ALT levels decreased in all groups (p < 0.05) compared to the PLB group. There was also a significant difference between the VES + RT group and both the VES and PLB + RT groups (p < 0.05). CTRP-2 and CTRP-9 levels decreased in the exercise groups compared to non-exercise groups (p < 0.05), and their changes showed a marked correlation with body composition, lipid profile, and glycemic control indices (p < 0.05).

CONCLUSIONS

This study highlights the benefits of RT on various health parameters among NAFLD patients. While adding VES to RT resulted in greater decreases in aminotransferases, it did not provide further improvements in other variables. Additionally, enhancements in body composition, lipid profile, and glycemic control indices were possibly associated with decreased levels of CTRPs.

TRIAL REGISTRATION

Registered retrospectively in the Iranian Registry of Clinical Trials (IRCT20220601055056N1) on December 21, 2023. Access at https://irct.behdasht.gov.ir/trial/69231 .

LKB1 delays atherosclerosis by inhibiting phenotypic transformation of vascular smooth muscle cells

BACKGROUND AND OBJECTIVE

Although liver kinase B1 (LKB1) is a well-known tumor suppressor gene, and its encoded protein has important biological functions, it is not clear whether LKB1 can inhibit atherosclerosis by regulating vascular smooth muscle cells (VSMCs). The purpose of this study is to explore the relationship among LKB1, VSMCs and atherosclerosis.

METHODS AND RESULTS

ApoE-/- mice with VSMCs-specific overexpression of LKB1 were constructed by adeno-associated virus transfection technique, and then fed with high-fat diet for eight weeks. The effect of LKB1 overexpression on atherosclerosis in mice was investigated by oil red O staining, HE staining, immunofluorescence and Western Blot. The results showed that the expression of LKB1 mRNA and protein in arterial tissue of mice increased significantly after overexpression of LKB1. The degree of atherosclerosis, smooth muscle fiber proliferation and lipid accumulation were significantly alleviated in the overexpression group. The results of Western Blot showed that the expression of α-SMA was increased, while the expression of OPN and CD68 was significantly decreased in the overexpression group (P < 0.05). The Immunofluorescence results of Image Pro Plus software analysis showed that the co-localization relationship between α-SMA and CD68 was more obvious in the control group (P < 0.01).

CONCLUSION

Our results suggested that LKB1 can delay the progression of atherosclerosis by inhibiting the phenotypic transition of VSMCs.

Tiaogan Jiejiu Tongluo Formula attenuated alcohol-induced chronic liver injury by regulating lipid metabolism in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Tiaogan Jiejiu Tongluo Formula (TJTF), a traditional Chinese medicine formula, is modified from the well-known ancient prescription Danzhi-Xiaoyao Powder (DXP). Owing to its ability to regulate liver, strengthen spleen, detoxicating, and dredge collaterals in Chinese medicine, TJTF is usually used to treat anxiety, hypertension, alcoholic fatty liver disease in clinical application. However, the protective effect and potential molecular mechanism of TJTF on alcoholic liver injury has not fully been clarified.

AIM OF THE STUDY

To explore the effect of TJTF on chronic alcoholic liver injury and figure out whether its effects were due to the regulation of lipid metabolism.

MATERIAL AND METHODS

75 male SD rats were divided into the following five groups, control group, EtOH group, TJTF high dose group, TJTF low dose group and silybin group. Then a chronic alcoholic liver injury model was established by increasing concentration of 56% ethanol in rats. The rats in each TJTF group were given the corresponding dose of TJTF, the rats in the silybin group were given silybin, the rats in the control group and the EtOH group were given distilled water by gavage, once a day for 8 consecutive weeks. The components of TJTF were analyzed by UPLC-Q-TOF-MS. Hematoxylin and Eosin (H&E) was used to assess the severity of liver injury. in the pathological examination. Periodic acid-Schiff (PAS) and oil red O staining were used to evaluate the degree of the liver glycogen accumulation and lipid deposition, respectively. The serum ALT, AST, T-CHO, TG, LDL-C, ADH, HDL-C, and ALDH levels as well as liver tissue GSH, MDA, and SOD levels were analyzed in rats. Immunohistochemistry and western blotting were used to detect lipid metabolism-related proteins expressed in rat liver.

RESULTS

TJTF significantly alleviated the chronic liver injury caused by alcohol in rats, and enhanced liver function. TJTF significantly decreased AST, ALT, ADH levels and increased ALDH level of serum, and increased GSH, SOD levels and decreased MDA level of liver tissue. In addition, TJTF significantly decreased the serum T-CHO, TG and LDL-C levels and increased HDL-C level in chronic alcoholic liver injury rats by regulating the expression of lipid metabolism associated proteins including p-LKB1, p-AMPKα, p-ACC, FAS, HMGCR, SREBP-1c, PPARα and CPT-1A. The results of western blot and immunohistochemical staining confirmed that TJTF can inhibit lipid production and promote fatty acid oxidation in the liver tissue of chronic alcoholic liver injury rats by activating the LKB1-AMPKα axis and then downregulating the protein expressions of p-ACC, FAS, HMGCR and SREBP-1c, as well as promoting the protein expressions of PPARα and CPT-1A. Meanwhile, TJTF also increased the glycogen content of liver and alleviated the liver damage.

CONCLUSION

According to current research, TJTF is effective in treating chronic liver damage induced by alcohol in rats. Additionally, TJTF exhibits the protective benefits by modulating LKB1-AMPKα signal axis, which in turn inhibits the synthesis of lipids and promotes the oxidation of fatty acids.

Cardioprotective effect of the quercetin on cardiovascular remodeling and atherosclerosis in rodents fed a high-fat diet: A systematic review

Cardiovascular diseases (CVD) are the leading cause of death globally, estimated at 17.9 million premature deaths. Several risk factors contribute to the development of CVD, including unhealthy diet rich in saturated fat. Quercetin (Q) is a important natural flavonoid with cardioprotective effect. However, it is crucial to understand and clarify which dosages and intervention times quercetin promotes better cardioprotective effects when exposed to a High-Fat Diet (HFD). We aim was to carry out a review to identify and compare experimental studies that investigated the quercetin effect on cardiac parameters in rodents fed a HFD. This literature search was performed through the specialized databases PubMed, Embase, Web of Science and Lilacs in May 2022. The following information was collected and assessed: Species of animals, dietary fat content, intervention protocol (quercetin), and main results of alterations associated with cardiac change. A total of 116 articles were selected from the database and 30 articles were included in this study. The administration form of quercetin was used in the diet supplemented in 73.4% (n = 22) of the studies. The dosage ranged between 10 and 100 mg/kg, 0.01%-0.36%, and 4-8 g/kg diet. The treatment time ranged between 14 and 63 days in 48.4% studies and most of the selected studies observed changes in the: Serum concentrations of lipids (60%, n = 18) mainly decrease in TC and TG, left ventricle (LV) (16.13%, n = 5) includes attenuation of the cardiac hypertrophy; inhibition of atherosclerotic progression (32%, n = 10) with decrease in lesions and plaque formation; improvement in the expression of gene and protein associated with cardiac functionality and oxidative stress (51.6%; n = 16). Quercetin supplementation at different concentrations/doses promotes important cardioprotective effects in experimental models exposed to a HFD. The supplemented diet was shown to be the better administration option. The methodological variation presented in the articles selected in this review proves that the most appropriate intervention protocol, as well as the most effective route of administration, promotes these effects.

Research progress of AMP-activated protein kinase and cardiac aging

The process of aging is marked by a gradual deterioration in the physiological functions and functional reserves of various tissues and organs, leading to an increased susceptibility to diseases and even death. Aging manifests in a tissue- and organ-specific manner, and is characterized by varying rates and direct and indirect interactions among different tissues and organs. Cardiovascular disease (CVD) is the leading cause of death globally, with older adults (aged >70 years) accounting for approximately two-thirds of CVD-related deaths. The prevalence of CVD increases exponentially with an individual's age. Aging is a critical independent risk factor for the development of CVD. AMP-activated protein kinase (AMPK) activation exerts cardioprotective effects in the heart and restores cellular metabolic functions by modulating gene expression and regulating protein levels through its interaction with multiple target proteins. Additionally, AMPK enhances mitochondrial function and cellular energy status by facilitating the utilization of energy substrates. This review focuses on the role of AMPK in the process of cardiac aging and maintaining normal metabolic levels and redox homeostasis in the heart, particularly in the presence of oxidative stress and the invasion of inflammatory factors.

The role of adiponectin in cardiovascular disease

Cardiovascular disease (CVD) is a common disease that seriously threatens the health of human beings, especially middle-aged and elderly people over 50 years old. It has the characteristics of high prevalence, high disability rate and high mortality rate. Previous studies have shown that adiponectin has therapeutic effects on a variety of CVDs. As a key adipokine, adiponectin, is an abundant peptide-regulated hormone that is mainly released by adipocytes and cardiomyocytes, as well as endothelial and skeletal cells. Adiponectin can protect against CVD by improving lipid metabolism, protecting vascular endothelial cells and inhibiting foam cell formation and vascular smooth muscle cell proliferation. Further investigation of the molecular and cellular mechanisms underlying the adiponectin system may provide new ideas for the treatment of CVD. Herein, this review aims to describe the structure and function of adiponectin and adiponectin receptors, introduce the function of adiponectin in the protection of cardiovascular disease and analyze the potential use and clinical significance of this hormone in the protection and treatment of cardiovascular disease, which shows that adiponectin can be expected to become a new therapeutic target and biomarker for the diagnosis and treatment of CVD.

C1q/tumor necrosis factor-related protein-9 exerts antioxidant and anti-inflammatory effects on oxygen-glucose deprivation/reoxygenation-stimulated neurons by modulating the Akt-GSK-3β-Nrf2 cascade via AdipoR1

C1q/tumor necrosis factor-related protein-9 (CTRP9) is linked to diverse pathological conditions via the effects on cell apoptosis, inflammatory response, and oxidative stress. However, its functional relevance in ischemic brain injury is not well determined. The present work aimed to evaluate the role of CTRP9 in ischemia/reperfusion-associated neuronal injury using an in vitro model. The cultured cortical neurons were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) to simulate ischemia/reperfusion in vitro. CTRP9 level was lowered in cultured neurons exposed to OGD/R. Neurons with overexpressed CTRP9 were resistant to OGD/R-elicited injuries, including neuronal apoptosis, oxidative stress, and pro-inflammatory response. Mechanism research revealed that CTRP9 could boost the activation of the nuclear factor erythroid 2-related factor (Nrf2) pathway associated with modulation of the Akt-glycogen synthase kinase-3β (GSK-3β) axis. CTRP9 regulated the transduction of the Akt-GSK-3β-Nrf2 cascade via adiponectin receptor 1 (AdipoR1). Restraining Nrf2 could diminish CTRP9-mediated neuroprotective effects in OGD/R-injured neurons. Altogether, these results confirmed that CTRP9 exerts a protective effect on OGD/R-injured neurons by modulating Akt-GSK-3β-Nrf2 cascade via AdipoR1. This work suggests a possible link between CTRP9 and ischemic brain injury.

Effect of voluntary wheel running on autophagy status in lung tissue of high-fat diet-fed rats

Here, we aimed to explore the therapeutic effect of voluntary wheel running (VWR) in high-fat diet-fed rats on pulmonary tissue injury via the modulation of autophagic response. Thirty-two rats were allocated into four groups; normal diet (Control); VWR; high-fat-diet (HFD), and HFD + VWR. After three months, pathological effect of HFD on pulmonary tissue was investigated. The levels of tumour necrosis factor (TNF)-α were detected in the bronchoalveolar lavage fluid (BALF). We monitored the expression of interleukin (IL)-6 and autophagy-related genes in lung tissues. H&E staining showed pathological changes in HFD group coincided with the increase of TNF-α levels in the bronchoalveolar fluid compared to the normal rats. Our results showed the up-regulation of IL-6, becline-1, LC3 and P62 in the HFD group compared to the Control group. VWR inhibited HFD-induced changes and could decrease HFD-induced changes via the regulation of autophagy status.

C1q and Tumor Necrosis Factor Related Protein 9 Protects from Diabetic Cardiomyopathy by Alleviating Cardiac Insulin Resistance and Inflammation

(1) Background: Diabetic cardiomyopathy is a major health problem worldwide. CTRP9, a secreted glycoprotein, is mainly expressed in cardiac endothelial cells and becomes downregulated in mouse models of diabetes mellitus; (2) Methods: In this study, we investigated the impact of CTRP9 on early stages of diabetic cardiomyopathy induced by 12 weeks of high-fat diet; (3) Results: While the lack of CTRP9 in knock-out mice aggravated insulin resistance and triggered diastolic left ventricular dysfunction, AAV9-mediated cardiac CTRP9 overexpression ameliorated cardiomyopathy under these conditions. At this early disease state upon high-fat diet, no fibrosis, no oxidative damage and no lipid deposition were identified in the myocardium of any of the experimental groups. Mechanistically, we found that CTRP9 is required for insulin-dependent signaling, cardiac glucose uptake in vivo and oxidative energy production in cardiomyocytes. Extensive RNA sequencing from myocardial tissue of CTRP9-overexpressing and knock-out as well as respective control mice revealed that CTRP9 acts as an anti-inflammatory mediator in the myocardium. Hence, CTRP9 knock-out exerted more, while CTRP9-overexpressing mice showed less leukocytes accumulation in the heart during high-fat diet; (4) Conclusions: In summary, endothelial-derived CTRP9 plays a prominent paracrine role to protect against diabetic cardiomyopathy and might constitute a therapeutic target.

The multifaceted roles of ER and Golgi in metabolic cardiomyopathy

Metabolic cardiomyopathy is a significant global financial and health challenge; however, pathophysiological mechanisms governing this entity remain poorly understood. Among the main features of metabolic cardiomyopathy, the changes to cellular lipid metabolism have been studied and targeted for the discovery of novel treatment strategies obtaining contrasting results. The endoplasmic reticulum (ER) and Golgi apparatus (GA) carry out protein modification, sorting, and secretion activities that are more commonly studied from the perspective of protein quality control; however, they also drive the maintenance of lipid homeostasis. In response to metabolic stress, ER and GA regulate the expression of genes involved in cardiac lipid biogenesis and participate in lipid droplet formation and degradation. Due to the varied roles these organelles play, this review will focus on recapitulating the alterations and crosstalk between ER, GA, and lipid metabolism in cardiac metabolic syndrome.

The AMPK pathway in fatty liver disease

Lipid metabolism disorders are the primary causes for the occurrence and progression of various liver diseases, including non-alcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (AFLD) caused by a high-fat diet and ethanol. AMPK signaling pathway plays an important role in ameliorating lipid metabolism disorders. Progressive research has clarified that AMPK signal axes are involved in the prevention and reduction of liver injury. Upregulation of AMK can alleviate FLD in mice induced by alcohol or insulin resistance, type 2 diabetes, and obesity, and most natural AMPK agonists can regulate lipid metabolism, inflammation, and oxidative stress in hepatocytes, consequently regulating FLD in mice. In NAFLD and AFLD, increasing the activity of AMPK can inhibit the synthesis of fatty acids and cholesterol by down-regulating the expression of adipogenesis gene (FAS, SREBP-1c, ACC and HMGCR); Simultaneously, by increasing the expression of fatty acid oxidation and lipid decomposition genes (CPT1, PGC1, and HSL, ATGL) involved in fatty acid oxidation and lipid decomposition, the body’s natural lipid balance can be maintained. At present, some AMPK activators are thought to be beneficial during therapeutic treatment. Therefore, activation of AMPK signaling pathway is a potential therapeutic target for disorders of the liver. We summarized the most recent research on the role of the AMPK pathway in FLD in this review. Simultaneously, we performed a detailed description of each signaling axis of the AMPK pathway, as well as a discussion of its mechanism of action and therapeutic significance.

Anti-Diabetic Therapy, Heart Failure and Oxidative Stress: An Update

Diabetes mellitus (DM) and heart failure (HF) are two chronic disorders that affect millions worldwide. Hyperglycemia can induce excessive generation of highly reactive free radicals that promote oxidative stress and further exacerbate diabetes progression and its complications. Vascular dysfunction and damage to cellular proteins, membrane lipids and nucleic acids can stem from overproduction and/or insufficient removal of free radicals. The aim of this article is to review the literature regarding the use of antidiabetic drugs and their role in glycemic control in patients with heart failure and oxidative stress. Metformin exerts a minor benefit to these patients. Thiazolidinediones are not recommended in diabetic patients, as they increase the risk of HF. There is a lack of robust evidence on the use of meglinitides and acarbose. Insulin and dipeptidyl peptidase-4 (DPP-4) inhibitors may have a neutral cardiovascular effect on diabetic patients. The majority of current research focuses on sodium glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide 1 (GLP-1) receptor agonists. SGLT2 inhibitors induce positive cardiovascular effects in diabetic patients, leading to a reduction in cardiovascular mortality and HF hospitalization. GLP-1 receptor agonists may also be used in HF patients, but in the case of chronic kidney disease, SLGT2 inhibitors should be preferred.

LKB1: An emerging therapeutic target for cardiovascular diseases

Cardiovascular diseases (CVDs) are currently the most common cause of morbidity and mortality worldwide. Experimental studies suggest that liver kinase B1 (LKB1) plays an important role in the heart. Several studies have shown that cardiomyocyte-specific LKB1 deletion leads to hypertrophic cardiomyopathy, left ventricular contractile dysfunction, and an increased risk of atrial fibrillation. In addition, the cardioprotective effects of several medicines and natural compounds, including metformin, empagliflozin, bexarotene, and resveratrol, have been reported to be associated with LKB1 activity. LKB1 limits the size of the damaged myocardial area by modifying cellular metabolism, enhancing the antioxidant system, suppressing hypertrophic signals, and inducing mild autophagy, which are all primarily mediated by the AMP-activated protein kinase (AMPK) energy sensor. LKB1 also improves myocardial efficiency by modulating the function of contractile proteins, regulating the expression of electrical channels, and increasing vascular dilatation. Considering these properties, stimulation of LKB1 signaling offers a promising approach in the prevention and treatment of heart diseases.

Liquiritin Attenuates Pathological Cardiac Hypertrophy by Activating the PKA/LKB1/AMPK Pathway

Background: Liquiritin (LQ) is one of the main flavonoids extracted from the roots of Glycyrrhiza spp., which are widely used in traditional Chinese medicine. Studies in both cellular and animal disease models have shown that LQ attenuates or prevents oxidative stress, inflammation, and apoptosis. However, the potential therapeutic effects of LQ on pressure overload-induced cardiac hypertrophy have not been so far explored. Therefore, we investigated the cardioprotective role of LQ and its underlying mechanisms in the aortic banding (AB)-induced cardiac hypertrophy mouse model.

Methods and Results: Starting 3 days after AB surgery, LQ (80 mg/kg/day) was administered daily over 4 weeks. Echocardiography and pressure-volume loop analysis indicated that LQ treatment markedly improved hypertrophy-related cardiac dysfunction. Moreover, hematoxylin and eosin, picrosirius red, and TUNEL staining showed that LQ significantly inhibited cardiomyocyte hypertrophy, interstitial fibrosis, and apoptosis. Western blot assays further showed that LQ activated LKB1/AMPKα2/ACC signaling and inhibited mTORC1 phosphorylation in cardiomyocytes. Notably, LQ treatment failed to prevent cardiac dysfunction, hypertrophy, and fibrosis in AMPKα2 knockout (AMPKα2^−/−) mice. However, LQ still induced LKB1 phosphorylation in AMPKα2^−/− mouse hearts. In vitro experiments further demonstrated that LQ inhibited Ang II-induced hypertrophy in neonatal rat cardiomyocytes (NRCMs) by increasing cAMP levels and PKA activity. Supporting the central involvement of the cAMP/PKA/LKB1/AMPKα2 signaling pathway in the cardioprotective effects of LQ, inhibition of Ang II-induced hypertrophy and induction of LKB1 and AMPKα phosphorylation were no longer observed after inhibiting PKA activity.

Conclusion: This study revealed that LQ alleviates pressure overload-induced cardiac hypertrophy in vivo and inhibits Ang II-induced cardiomyocyte hypertrophy in vitro via activating cAMP/PKA/LKB1/AMPKα2 signaling. These findings suggest that LQ might be a valuable adjunct to therapeutic approaches for treating pathological cardiac remodeling.

CTRP9 overexpression attenuates palmitic acid‑induced inflammation, apoptosis and impaired migration in HTR8/SVneo cells through AMPK/SREBP1c signaling

Obesity in pregnant mothers often leads to a range of obstetric complications, including miscarriage, pre-eclampsia, gestational hypertension and diabetes. C1q/TNF-related protein 9 (CTRP9) is an adipokine with an anti-inflammatory effect. The aim of the present study was to identify the role of CTRP9 in the pathogenesis of maternal obesity during pregnancy. Following treatment with palmitic acid (PA), HTR8/SVneo cell viability and CTRP9 expression were analyzed using Cell Counting Kit-8 (CCK-8), reverse transcription-quantitative PCR (RT-qPCR) and western blot analyses. The effects of CTRP9 overexpression on cell viability, apoptosis, pro-inflammatory cytokine levels and migration were assessed using CCK-8, TUNEL, RT-qPCR and Transwell assays, respectively. Subsequently, sterol-regulatory element binding protein 1c (SREBP1c) overexpression efficiency was verified using RT-qPCR, and its effects on cell viability, apoptosis, pro-inflammatory cytokines and migration damage were then examined in HTR8/SVneo cells. The results showed that CTRP9 overexpression attenuated the inhibition of cell viability and apoptosis caused by PA in HTR8/SVneo cells, reduced pro-inflammatory cytokine release, improved cell migration and regulated the protein expression level of AMP-activated protein kinase (AMPK)/SREBP1c signaling. In addition, CTRP9 inhibited SREBP1c expression through AMPK signaling, thereby attenuating the inflammation, apoptosis and inhibited migration caused by PA in HTR8/SVneo cells. In brief, CTRP9 protected against inflammation, apoptosis and migration defects in HTR8/SVneo cells exposed to PA treatment through AMPK/SREBP1c signaling, which suggested the potential role of CTRP9 in alleviating the toxicity of PA.

CTRP11 contributes modestly to systemic metabolism and energy balance

C1q/TNF‐related proteins (CTRP1‐15) constitute a conserved group of secreted proteins of the C1q family with diverse functions. In vitro studies have shown that CTRP11/C1QL4 can inhibit adipogenesis, antagonize myoblast fusion, and promote testosterone synthesis and secretion. Whether CTRP11 is required for these processes in vivo remains unknown. Here, we show that knockout (KO) mice lacking CTRP11 have normal skeletal muscle mass and function, and testosterone level, suggesting that CTRP11 is dispensable for skeletal muscle development and testosterone production. We focused our analysis on whether this nutrient‐responsive secreted protein plays a role in controlling sugar and fat metabolism. At baseline when mice are fed a standard chow, CTRP11 deficiency affects metabolic parameters in a sexually dimorphic manner. Only Ctrp11‐KO female mice have significantly higher fasting serum ketones and reduced physical activity. In the refeeding phase following food withdrawal, Ctrp11‐KO female mice have reduced food intake and increased metabolic rate and energy expenditure, highlighting CTRP11’s role in fasting–refeeding response. When challenged with a high‐fat diet to induce obesity and metabolic dysfunction, CTRP11 deficiency modestly exacerbates obesity‐induced glucose intolerance, with more pronounced effects seen in Ctrp11‐KO male mice. Switching to a low‐fat diet after obesity induction results in greater fat loss in wild type relative to KO male mice, suggesting impaired response to obesity reversal and reduced metabolic flexibility in the absence of CTRP11. Collectively, our data provide genetic evidence for novel sex‐dependent metabolic regulation by CTRP11, but note the overall modest contribution of CTRP11 to systemic energy homeostasis.

CTRP9 decreases high glucose‑induced trophoblast cell damage by reducing endoplasmic reticulum stress

C1q/TNF-α-related protein 9 (CTRP9) is downregulated in gestational diabetes mellitus (GDM) and may exert a protective effect against GDM, although its mechanism of action is yet to be elucidated. To investigate the specific role of CTRP9 in GDM, the human placental trophoblast cell line HTR8/SVneo was treated with high glucose (HG) to simulate the environment of GDM in vitro. The effects of CTRP9 on the HTR8/SVneo cells and endoplasmic reticulum (ER) stress were analyzed before and after CTRP9 overexpression using reverse transcription-quantitative PCR and western blotting. The results obtained demonstrated that CTRP9 alleviated ER stress in the trophoblast cell line. After treating with the ER-stress inducer tunicamycin, cell viability was investigated by performing Cell Counting Kit-8, TUNEL and western blotting assays, which revealed that CTRP9 increased the activity of HTR8/SVneo cells induced by HG through the alleviation of ER stress. Subsequently, ELISA and western blotting assay results demonstrated that CTRP9 inhibited HG-induced inflammation of the HTR8/SVneo cells by the reduction in ER stress. Finally, the detection of reactive oxygen species, nitric oxide (NO) synthase and NO levels confirmed that CTRP9 inhibited the oxidative stress of HTR8/SVneo cells induced by HG through the reduction of ER stress. Collectively, the results of the present study suggested that CTRP9 may decrease trophoblast cell damage caused by HG through the suppression of ER stress, and therefore, CTRP9 may potentially be a therapeutic target in the treatment of GDM.

C1q/Tumor Necrosis Factor-Related Protein 9: Basics and Therapeutic Potentials

C1q/tumor necrosis factor-related protein 9 (CTRP9) is a newly discovered adipokine that is the closest paralog of adiponectin. Proteolytic cleavage of CTRP9 leads to the release of the globular domain (gCTRP9), which serves as the major circulating subtype. After binding with adiponectin receptor 1 (AdipoR1) and N-cadherin, CTRP9 activates various signaling pathways to regulate glucose and lipid metabolism, vasodilation and cell differentiation. Throughout human development and adult life, CTRP9 controls many biological phenomena. simultaneously, abnormal gene or protein expression of CTRP9 is accompanied by a wide range of human pathological phenomena. In this review, we briefly introduce CTRP9 and its associated signaling pathways and physiological functions, which may be helpful in the understanding of the occurrence of diseases. Moreover, we summarize the broader research prospects of CTRP9 and advances in therapeutic intervention. In recent years, CTRP9 has attracted extensive attention due to its role in the pathogenesis of various diseases, providing further avenues for its exploitation as a potential biomarker or therapeutic target.

Notoginsenoside R1 Ameliorates Cardiac Lipotoxicity Through AMPK Signaling Pathway

Aims: Cardiac lipotoxicity is the common consequence of lipid metabolism disorders in cardiomyocytes during development of heart failure (HF). Adenosine 5'monophosphate-activated protein kinase (AMPK) acts as an energy sensor and has a beneficial effect in reducing lipotoxicity. Notoginsenoside R1 (NGR1) is extracted from the traditional Chinese medicine Panax notoginseng (Burkill) F.H.Chen (P. notoginseng) and has definite cardioprotective effects. However, whether NGR1 can attenuate HF by mitigating lipotoxicity has not been elucidated yet. This study aimed to explore whether NGR1 plays a protective role against HF by ameliorating cardiac lipotoxicity via the AMPK pathway. Methods: In this study, HF mice model was established by left anterior descending (LAD) ligation. palmitic acid (PA) stimulated H9C2 cell model was applied to clarify the effects and potential mechanism of NGR1 on lipotoxicity. In vivo, NGR1 (7.14 mg/kg/days) and positive drug (simvastatin: 2.9 mg/kg/days) were orally administered for 14 days. Echocardiography was applied to assess heart functions. Lipid levels were measured by Enzyme-linked immunosorbent assay (ELISA) and key proteins in the AMPK pathway were detected by western blots. In vitro, NGR1 (40 μmol/L) or Compound C (an inhibitor of AMPK, 10 μmol/L) was co-cultured with PA stimulation for 24 h in H9C2 cells. CCK-8 assay was used to detect cell viability. Key lipotoxicity-related proteins were detected by western blots and the LipidTOX™ neutral lipid stains were used to assess lipid accumulation. In addition, Apoptosis was assessed by Hoechst/PI staining. Results: NGR1 could significantly improve the cardiac function and myocardial injury in mice with HF and up-regulate the expression of p-AMPK. Impressively, NGR1 inhibited the synthesis of diacylglycerol (DAG) and ceramide and promoted fatty acid oxidation (FAO) in vivo. Moreover, NGR1 significantly promoted expression of CPT-1A, the key enzyme in FAO pathway, and down-regulated the expression of GPAT and SPT, which were the key enzymes catalyzing production of DAG and ceramide. In vitro experiments showed that NGR1 could significantly attenuate lipid accumulation in PA-induced H9C2 cells and the Hoechst/PI staining results showed that NGR1 ameliorated lipotoxicity-induced apoptosis in PA-stimulated H9C2 cell model. Furthermore, co-treatment with inhibitor of AMPK abrogated the protective effects of NGR1. The regulative effects of NGR1 on lipid metabolism were also reversed by AMPK inhibitor. Conclusion: NGR1 could significantly improve the heart function of mice with HF and reduce cardiac lipotoxicity. The cardio-protective effects of NGR1 are mediated by the activation of AMPK pathway.

Small molecule QF84139 ameliorates cardiac hypertrophy via activating the AMPK signaling pathway

Cardiac hypertrophy is a common adaptive response to a variety of stimuli, but prolonged hypertrophy leads to heart failure. Hence, discovery of agents treating cardiac hypertrophy is urgently needed. In the present study, we investigated the effects of QF84139, a newly synthesized pyrazine derivative, on cardiac hypertrophy and the underlying mechanisms. In neonatal rat cardiomyocytes (NRCMs), pretreatment with QF84139 (1-10 μM) concentration-dependently inhibited phenylephrine-induced hypertrophic responses characterized by fetal genes reactivation, increased ANP protein level and enlarged cardiomyocytes. In adult male mice, administration of QF84139 (5-90 mg·kg^-1·d^-1, i.p., for 2 weeks) dose-dependently reversed transverse aortic constriction (TAC)-induced cardiac hypertrophy displayed by cardiomyocyte size, left ventricular mass, heart weights, and reactivation of fetal genes. We further revealed that QF84139 selectively activated the AMPK signaling pathway without affecting the phosphorylation of CaMKIIδ, ERK1/2, AKT, PKCε, and P38 kinases in phenylephrine-treated NRCMs and in the hearts of TAC-treated mice. In NRCMs, QF84139 did not show additive effects with metformin on the AMPK activation, whereas the anti-hypertrophic effect of QF84139 was abolished by an AMPK inhibitor Compound C or knockdown of AMPKα2. In AMPKα2-deficient mice, the anti-hypertrophic effect of QF84139 was also vanished. These results demonstrate that QF84139 attenuates the PE- and TAC-induced cardiac hypertrophy via activating the AMPK signaling. This structurally novel compound would be a promising lead compound for developing effective agents for the treatment of cardiac hypertrophy.

Acacetin ameliorates cardiac hypertrophy by activating Sirt1/AMPK/PGC-1α pathway

Cardiac hypertrophy is a major risk factor for developing heart failure. This study investigates the effects of the natural flavone acacetin on myocardial hypertrophy in cellular level and whole animals. In cardiomyocytes from neonatal rat with hypertrophy induced by angiotensin II (Ang II), acacetin at 0.3, 1, and 3 μM reduced the increased myocyte surface area, brain natriuretic peptide (BNP), and ROS production by upregulating anti-oxidative molecules (i.e. Nrf2, SOD1, SOD2, HO-1), anti-apoptotic protein Bcl-2, and downregulating the pro-apoptotic protein Bax and the inflammatory cytokine IL-6 in a concentration-dependent manner. In addition, acacetin rescued Ang II-induced impairment of PGC-1α, PPARα and pAMPK. These beneficial effects of acacetin were mediated by activation of Sirt1, which was confirmed in cardiac hypertrophy induced by abdominal aorta constriction (AAC) in SD rats. Acacetin prodrug (10 mg/kg, s.c., b.i.d.) treatment reduced the elevated artery blood pressure, improved the increased heart size and thickness of left ventricular wall and the ventricular fibrosis associated with inhibiting myocardial fibrosis and BNP, and reversed the impaired protective signal molecules including PGC-1α, Nrf2, PPARα, pAMPK and Sirt1 of left ventricular tissue. Our results demonstrate the novel pharmacological effect that acacetin ameliorates cardiac hypertrophy via Sirt1-mediated activation of AMPK/PGC-1α signal molecules followed by reducing oxidation, inflammation and apoptosis.

Intermittent Fasting Improves High-Fat Diet-Induced Obesity Cardiomyopathy via Alleviating Lipid Deposition and Apoptosis and Decreasing m6A Methylation in the Heart

Intermittent fasting (IF) plays an essential role in improving lipid metabolism disorders caused by metabolic cardiomyopathy. Growing evidence revealed that N6-methyladenosine (m6A) RNA methylation is related to obesity and lipid metabolic. Our study aimed to assess the beneficial effects of IF on lipid deposition, apoptosis, and m6A methylation in high-fat diet (HFD)-induced obesity cardiomyopathy. Male C57BL/6J mice were fed a normal diet (ND) or HFD ad libitum for 13 weeks, after which time a subgroup of HFD mice were subjected to IF for 24 h and fed HFD in the other day for 8 weeks. We found that IF intervention significantly improved cardiac functional and structural impairment and serum lipid metabolic disorder induced by HFD. Furthermore, IF intervention decreased the mRNA levels of the fatty acid uptake genes of FABP1, FATP1, and CD36 and the fatty acid synthesis genes of SREBF1, FAS, and ACCα and increased the mRNA levels of the fatty acid catabolism genes of ATGL, HSL, LAL, and LPL in cardiac tissueof HFD-induced obese mice. TUNEL-positive cells, Bax/Bcl-2 ratio, and Cleaved Caspase-3 protein expression in HFD-induced obese mice hearts was down-regulated by IF intervention. In addition, IF intervention decreased the m6A methylation levels and METTL3 expression and increased FTO expression in HFD-induced obesity cardiomyopathy. In conclusion, our findings demonstrate that IF attenuated cardiac lipid deposition and apoptosis, as well as improved cardiac functional and structural impairment in HFD-induced obesity cardiomyopathy, by a mechanism associated with decreased m6A RNA methylation levels.

LKB1 Regulates Vascular Macrophage Functions in Atherosclerosis

Liver kinase B1 (LKB1) is known to shape the regulation of macrophage function by participating in multiple processes including cell metabolism, growth, and polarization. However, whether LKB1 also affects the functional plasticity of macrophages in atherosclerosis has not attracted much attention. Abnormal macrophage function is a pathophysiological hallmark of atherosclerosis, characterized by the formation of foam cells and the maintenance of vascular inflammation. Mounting evidence supports that LKB1 plays a vital role in the regulation of macrophage function in atherosclerosis, including affecting lipid metabolism reprogramming, inflammation, endoplasmic reticulum stress, and autophagy in macrophages. Thus, decreased expression of LKB1 in atherosclerosis aggravates vascular injury by inducing excessive lipid deposition in macrophages and the formation of foam cells. To systematically understand the role and potential mechanism of LKB1 in regulating macrophage functions in atherosclerosis, this review summarizes the relevant data in this regard, hoping to provide new ideas for the prevention and treatment of atherosclerosis.

Oxidative stress in cardiac hypertrophy: From molecular mechanisms to novel therapeutic targets

When faced with increased workload the heart undergoes remodelling, where it increases its muscle mass in an attempt to preserve normal function. This is referred to as cardiac hypertrophy and if sustained, can lead to impaired contractile function. Experimental evidence supports oxidative stress as a critical inducer of both genetic and acquired forms of cardiac hypertrophy, a finding which is reinforced by elevated levels of circulating oxidative stress markers in patients with cardiac hypertrophy. These observations formed the basis for using antioxidants as a therapeutic means to attenuate cardiac hypertrophy and improve clinical outcomes. However, the use of antioxidant therapies in the clinical setting has been associated with inconsistent results, despite antioxidants having been shown to exert protection in several animal models of cardiac hypertrophy. This has forced us to revaluate the mechanisms, both upstream and downstream of oxidative stress, where recent studies demonstrate that apart from conventional mediators of oxidative stress, metabolic disturbances, mitochondrial dysfunction and inflammation as well as dysregulated autophagy and protein homeostasis contribute to disease pathophysiology through mechanisms involving oxidative stress. Importantly, novel therapeutic targets have been identified to counteract oxidative stress and attenuate cardiac hypertrophy but more interestingly, the repurposing of drugs commonly used to treat metabolic disorders, hypertension, peripheral vascular disease, sleep disorders and arthritis have also been shown to improve cardiac function through suppression of oxidative stress. Here, we review the latest literature on these novel mechanisms and intervention strategies with the aim of better understanding the complexities of oxidative stress for more precise targeted therapeutic approaches to prevent cardiac hypertrophy.

Quercetin Reverses Cardiac Systolic Dysfunction in Mice Fed with a High-Fat Diet: Role of Angiogenesis

Global consumption of high-fat diets (HFD) is associated with an increased incidence of cardiometabolic syndrome and cardiac injury, warranting identification of cardioprotective strategies. Cardioprotective effects of quercetin (Q) have mostly been evaluated in ischemic heart disease models and attributed to senolysis. We hypothesized that Q could alleviate murine cardiac damage caused by HFD by restoring the myocardial microcirculation. C57BL/6J mice were fed standard chow or HFD for 6 months and then treated with Q (50 mg/kg) or vehicle 5-day biweekly for 10 additional weeks. Left ventricular (LV) cardiac function was studied in vivo using magnetic resonance imaging, and intramyocardial fat deposition, microvascular density, oxidative stress, and senescence were analyzed ex vivo. Additionally, direct angiogenic effects of Q were studied in vitro in HUVECs. HFD increased body weight, heart weight, total cholesterol, and triglyceride levels, whereas Q normalized heart weight and triglycerides. LV ejection fraction was lower in HFD vs. control mice (56.20 ± 15.8% vs. 73.38 ± 5.04%, respectively, P < 0.05), but improved in HFD + Q mice (67.42 ± 7.50%, P < 0.05, vs. HFD). Q also prevented cardiac fat accumulation and reduced HFD-induced cardiac fibrosis, cardiomyocyte hypertrophy, oxidative stress, and vascular rarefaction. Cardiac senescence was not observed in any group. In vitro, ox-LDL reduced HUVEC tube formation activity, which Q effectively improved. Quercetin may directly induce angiogenesis and decrease myocardial oxidative stress, which might account for its cardioprotective effects in the murine HFD-fed murine heart independently from senolytic activity. Furthermore, its beneficial effects might be partly attributed to a decrease in plasma triglycerides and intramyocardial fat deposition.

Impact of PCSK9 on CTRP9-Induced Metabolic Effects in Adult Rat Cardiomyocytes

The adipocytokine adiponectin and its structural homologs, the C1q/TNF-related proteins (CTRPs), increase insulin sensitivity, fatty acid oxidation and mitochondrial biogenesis. Adiponectin- and CTRP-induced signal transduction has been described to involve the adiponectin receptors and a number of co-receptors including the Low density lipoprotein receptor-related protein 1 (LRP1). LRP1 is another target of the proprotein convertase subtilisin/kexin-9 (PCSK9) in addition to the LDL-receptor (LDL-R). Here, we investigated the influence of PCSK9 on the metabolic effects of CTRP9, the CTRP with the highest homology to adiponectin. Knockdown of LRP1 in H9C2 cardiomyoblasts blunts the effects of CTRP9 on signal transduction and mitochondrial biogenesis, suggesting its involvement in CTRP9-induced cellular effects. Treatment of adult rat cardiomyocytes with recombinant PCSK9 but not knockdown of endogenous PCSK9 by siRNA results in a strong reduction in LRP1 protein expression and subsequently reduces the mitochondrial biogenic effect of CTRP9. PCSK9 treatment (24 h) blunts the effects of CTRP9-induced signaling cascade activation (AMP-dependent protein kinase, protein kinase B). In addition, the stimulating effects of CTRP9 on cardiomyocyte mitochondrial biogenesis and glucose metabolism (GLUT-4 translocation, glucose uptake) are largely blunted. Basal fatty acid (FA) uptake is strongly reduced by exogenous PCSK9, although protein expression of the PCSK9 target CD36, the key regulator of FA transport in cardiomyocytes, is not altered. In addition, only minor effects of PCSK9 were observed on CTRP9-induced FA uptake or the expression of genes involved in FA metabolism or uptake. Finally, this CTRP9-induced increase in CD36 expression occurs independent from LRP1 and LDL-R. In conclusion, PCSK9 treatment influences LRP1-mediated signaling pathways in cardiomyocytes. Thus, therapeutic PCSK9 inhibition may provide an additional benefit through stimulation of glucose metabolism and mitochondrial biogenesis in addition to the known lipid-lowering effects. This could be an important beneficial side effect in situations with impaired mitochondrial function and reduced metabolic flexibility thereby influencing cardiac function.

Ferulic acid alleviates lipotoxicity-induced hepatocellular death through the SIRT1-regulated autophagy pathway and independently of AMPK and Akt in AML-12 hepatocytes

Background

Lipotoxicity-induced cell death plays a detrimental role in the pathogenesis of metabolic diseases. Ferulic acid, widespread in plant-based food, is a radical scavenger with multiple bioactivities. However, the benefits of ferulic acid against hepatic lipotoxicity are largely unclear. Here, we investigated the protective effect of ferulic acid against palmitate-induced lipotoxicity and clarified its potential mechanisms in AML-12 hepatocytes.

Methods

AML-12 mouse hepatocytes were exposed to palmitate to mimic lipotoxicity. Different doses (25, 50, and 100 μM) of ferulic acid were added 2 h before palmitate treatment. Cell viability was detected by measuring lactate dehydrogenase release, nuclear staining, and the expression of cleaved-caspase-3. Intracellular reactive oxygen species content and mitochondrial membrane potential were analysed by fluorescent probes. The potential mechanisms were explored by molecular biological methods, including Western blotting and quantitative real-time PCR, and were further verified by siRNA interference.

Results

Our data showed that ferulic acid significantly inhibited palmitate-induced cell death, rescued mitochondrial membrane potential, reduced reactive oxygen species accumulation, and decreased inflammatory factor activation, including IL-6 and IL-1beta. Ferulic acid significantly stimulated autophagy in hepatocytes, whereas autophagy suppression blocked the protective effect of ferulic acid against lipotoxicity. Ferulic acid-activated autophagy, which was triggered by SIRT1 upregulation, was mechanistically involved in its anti-lipotoxicity effects. SIRT1 silencing blocked most beneficial changes induced by ferulic acid.

Conclusions

We demonstrated that the phytochemical ferulic acid, which is found in plant-based food, protected against hepatic lipotoxicity, through the SIRT1/autophagy pathway. Increased intake of ferulic acid-enriched food is a potential strategy to prevent and/or improve metabolic diseases with lipotoxicity as a typical pathological feature.

Cardiac Endocrinology: Heart-Derived Hormones in Physiology and Disease

The heart plays a central role in the circulatory system and provides essential oxygen, nutrients, and growth factors to the whole organism. The heart can synthesize and secrete endocrine signals to communicate with distant target organs. Studies of long-known and recently discovered heart-derived hormones highlight a shared theme and reveal a unified mechanism of heart-derived hormones in coordinating cardiac function and target organ biology. This paper reviews the biochemistry, signaling, function, regulation, and clinical significance of representative heart-derived hormones, with a focus on the cardiovascular system. This review also discusses important and exciting questions that will advance the field of cardiac endocrinology.

AMPK, Mitochondrial Function, and Cardiovascular Disease

Adenosine monophosphate-activated protein kinase (AMPK) is in charge of numerous catabolic and anabolic signaling pathways to sustain appropriate intracellular adenosine triphosphate levels in response to energetic and/or cellular stress. In addition to its conventional roles as an intracellular energy switch or fuel gauge, emerging research has shown that AMPK is also a redox sensor and modulator, playing pivotal roles in maintaining cardiovascular processes and inhibiting disease progression. Pharmacological reagents, including statins, metformin, berberine, polyphenol, and resveratrol, all of which are widely used therapeutics for cardiovascular disorders, appear to deliver their protective/therapeutic effects partially via AMPK signaling modulation. The functions of AMPK during health and disease are far from clear. Accumulating studies have demonstrated crosstalk between AMPK and mitochondria, such as AMPK regulation of mitochondrial homeostasis and mitochondrial dysfunction causing abnormal AMPK activity. In this review, we begin with the description of AMPK structure and regulation, and then focus on the recent advances toward understanding how mitochondrial dysfunction controls AMPK and how AMPK, as a central mediator of the cellular response to energetic stress, maintains mitochondrial homeostasis. Finally, we systemically review how dysfunctional AMPK contributes to the initiation and progression of cardiovascular diseases via the impact on mitochondrial function.

Cardiolipin deficiency elevates susceptibility to a lipotoxic hypertrophic cardiomyopathy

Cardiolipin (CL) is a unique tetra-acyl phospholipid localized to the inner mitochondrial membrane and essential for normal respiratory function. It has been previously reported that the failing human heart and several rodent models of cardiac pathology have a selective loss of CL. A rare genetic disease, Barth syndrome (BTHS), is similarly characterized by a cardiomyopathy due to reduced levels of cardiolipin. A mouse model of cardiolipin deficiency was recently developed by knocking-down the cardiolipin biosynthetic enzyme tafazzin (TAZ KD). These mice develop an age-dependent cardiomyopathy due to mitochondrial dysfunction. Since reduced mitochondrial capacity in the heart may promote the accumulation of lipids, we examined whether cardiolipin deficiency in the TAZ KD mice promotes the development of a lipotoxic cardiomyopathy. In addition, we investigated whether treatment with resveratrol, a small cardioprotective nutraceutical, attenuated the aberrant lipid accumulation and associated cardiomyopathy. Mice deficient in tafazzin and the wildtype littermate controls were fed a low-fat diet, or a high-fat diet with or without resveratrol for 16 weeks. In the absence of obesity, TAZ KD mice developed a hypertrophic cardiomyopathy characterized by reduced left-ventricle (LV) volume (~36%) and 30-50% increases in isovolumetric contraction (IVCT) and relaxation times (IVRT). The progression of cardiac hypertrophy with tafazzin-deficiency was associated with several underlying pathological processes including altered mitochondrial complex I mediated respiration, elevated oxidative damage (~50% increase in reactive oxygen species, ROS), the accumulation of triglyceride (~250%) as well as lipids associated with lipotoxicity (diacylglyceride ~70%, free-cholesterol ~44%, ceramide N:16-35%) compared to the low-fat fed controls. Treatment of TAZ KD mice with resveratrol maintained normal LV volumes and preserved systolic function of the heart. The beneficial effect of resveratrol on cardiac function was accompanied by a significant improvement in mitochondrial respiration, ROS production and oxidative damage to the myocardium. Resveratrol treatment also attenuated the development of cardiac steatosis in tafazzin-deficient mice through reduced de novo fatty acid synthesis. These results indicate for the first time that cardiolipin deficiency promotes the development of a hypertrophic lipotoxic cardiomyopathy. Furthermore, we determined that dietary resveratrol attenuates the cardiomyopathy by reducing ROS, cardiac steatosis and maintaining mitochondrial function.

CTRP9 knockout exaggerates lipotoxicity in cardiac myocytes and high-fat diet-induced cardiac hypertrophy through inhibiting the LKB1/AMPK pathway

CTRP9 has been reported to regulate lipid metabolism and exert cardioprotective effects, yet its role in high‐fat diet (HFD)‐induced cardiac lipotoxicity and the underlying mechanisms remain unclear. In the current study, we established HFD‐induced obesity model in wild‐type (WT) or CTRP9 knockout (CTRP9‐KO) mice and palmitate‐induced lipotoxicity model in neonatal rat cardiac myocytes (NRCMs) to investigate the effects of CTRP9 on cardiac lipotoxicity. Our results demonstrated that the HFD‐fed CTRP9‐KO mice accentuated cardiac hypertrophy, fibrosis, endoplasmic reticulum (ER) stress‐initiated apoptosis and oxidative stress compared with the HFD‐fed WT mice. In vitro, CTRP9 treatment markedly alleviated palmitate‐induced oxidative stress and ER stress‐induced apoptosis in NRCMs in a dose‐dependent manner. Phosphorylated AMPK at Thr172 was reduced, and phosphorylated mammalian target of rapamycin (mTOR) was strengthened in the heart of the HFD‐fed CTRP9‐KO mice compared with the HFD‐fed control mice. In vitro, AMPK inhibitor compound C significantly abolished the effects of CTRP9 on the inhibition of the apoptotic pathway in palmitate‐treated NRCMs. In a further mechanistic study, CTRP9 enhanced expression of phosphorylated LKB1 at Ser428 and promoted LKB1 cytoplasmic localization. Besides, silencing of LKB1 gene by lentivirus significantly prohibited activation of AMPK by CTRP9 and partially eliminated the protective effect of CTRP9 on the cardiac lipotoxicity. These results indicate that CTRP9 exerted anti‐myocardial lipotoxicity properties and inhibited cardiac hypertrophy probably through the LKB1/AMPK signalling pathway.