Diabetes-induced Cardiac Dysfunction Research Articles

Cardioprotective Potentials of Anacardium occidentale Nuts Methanolic Extract in Diabetes-Induced Cardiac Dysfunction in Rats

Background: The unwanted adverse toxicity displayed by synthetic antidiabetic medicine leads to the search for effective natural medicine to combat diabetes complications. This study investigated the cardioprotective of Anacardium occidentale nuts methanolic in high-fat diet (HFD)/streptozotocin (STZ)-induced diabetic rats. Materials and methods: Forty male adult Wistar were used and fed with HFD for 6 weeks before diabetes induction. The rats were grouped into 5 groups, 8 rats/group. Group I: normal control; Group II: diabetic control; Group III & IV: diabetic rats + 100 mg/kgb.wt & 200 mg/kgb.wt Anacardium occidentale nuts methanolic extract; Group V: diabetic rats + 200 mg/kgb.wt metformin. The rats were sacrificed on the experiment’s last day, blood samples were collected and the hearts were isolated for biochemical parameters estimation. Results: Food intake, water intake, plasmas insulin, Fasting Blood Glucose (FBG), glycosylated hemoglobin (HbA1c), cardiac enzymes, lipid profile, inflammatory cytokines, malondialdehyde, fibrotic marker, caspase-3 in cardiac of diabetic rats were elevated (p < 0.05) significantly. Body weight, cardiac antioxidant, and anti-apoptotic marker levels diminished (p < 0.05) significantly in diabetic rats. 100 mg/kgb.wt & 200 mg/kgb.wt of Anacardium occidentale nuts methanolic extract administration significantly suppressed the plasma insulin, FBG, HbA1c, cardiac lipid profile, cardiac enzymes biomarker, cardiac inflammatory cytokines, cardiac malondialdehyde, cardiac fibrotic marker, cardiac caspase-3, food intake & water intake and increased the body weight, cardiac antioxidant & cardiac anti-apoptotic marker in the diabetic rats. Conclusion: Anacardium occidentale nuts attenuate cardiac injury in diabetes. It could be a natural medicine to manage diabetes-cardiovascular complications.

Patchouli Alcohol Protects the Heart against Diabetes-Related Cardiomyopathy through the JAK2/STAT3 Signaling Pathway.

Diabetic cardiomyopathy (DCM) represents a common pathological state brought about by diabetes mellitus (DM). Patchouli alcohol (PatA) is known for its diverse advantageous effects, notably its anti-inflammatory properties and protective role against metabolic disorders. Despite this, the influence of PatA on DCM remains relatively unexplored. To explore the effect of PatA on diabetes-induced cardiac injury and dysfunction in mice, streptozotocin (STZ) was used to mimic type 1 diabetes in mice. Serological markers and echocardiography show that PatA treatment protects the heart against cardiomyopathy by controlling myocardial fibrosis but not by reducing hyperglycemia in diabetic mice. Discovery Studio 2017 software was used to perform reverse target screening of PatA, and we found that JAK2 may be a potential target of PatA. RNA-seq analysis of heart tissues revealed that PatA activity in the myocardium was primarily associated with the inflammatory fibrosis through the Janus tyrosine kinase 2 (JAK2)/signal transducer and activator of the transcription 3 (STAT3) pathway. In vitro, we also found that PatA alleviates high glucose (HG) + palmitic acid (PA)-induced fibrotic and inflammatory responses via inhibiting the JAK2/STAT3 signaling pathway in H9C2 cells. Our findings illustrate that PatA mitigates the effects of HG + PA- or STZ-induced cardiomyopathy by acting on the JAK2/STAT3 signaling pathway. These insights indicate that PatA could potentially serve as a therapeutic agent for DCM treatment.

Combination of ADAM17 knockdown with eplerenone is more effective than single therapy in ameliorating diabetic cardiomyopathy.

The renin-angiotensin-aldosterone system (RAAS) members, especially Ang II and aldosterone, play key roles in the pathogenesis of diabetic cardiomyopathy (DCM). Angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers combined with aldosterone receptor antagonists (mineralocorticoid receptor antagonists) have substantially improved clinical outcomes in patients with DCM. However, the use of the combination has been limited due to its high risk of inducing hyperkalemia. Type 1 diabetes was induced in 8-week-old male C57BL/6J mice by intraperitoneal injection of streptozotocin at a dose of 55mg/kg for 5 consecutive days. Adeno-associated virus 9-mediated short-hairpin RNA (shRNA) was used to knock down the expression of ADAM17 in mice hearts. Eplerenone was administered via gavage at 200mg/kg daily for 4weeks. Primary cardiac fibroblasts were exposed to high glucose (HG) in vitro for 24h to examine the cardiac fibroblasts to myofibroblasts transformation (CMT). Cardiac collagen deposition and CMT increased in diabetic mice, leading to cardiac fibrosis and dysfunction. In addition, ADAM17 expression and activity increased in the hearts of diabetic mice. ADAM17 inhibition and eplerenone treatment both improved diabetes-induced cardiac fibrosis, cardiac hypertrophy and cardiac dysfunction, ADAM17 deficiency combined with eplerenone further reduced the effects of cardiac fibrosis, cardiac hypertrophy and cardiac dysfunction compared with single therapy in vivo. High-glucose stimulation promotes CMT in vitro and leads to increased ADAM17 expression and activity. ADAM17 knockdown and eplerenone pretreatment can reduce the CMT of fibroblasts that is induced by high glucose levels by inhibiting TGFβ1/Smad3 activation; the combination of the two can further reduce CMT compared with single therapy in vitro. Our findings indicated that ADAM17 knockout could improve diabetes-induced cardiac dysfunction and remodeling through the inhibition of RAAS overactivation when combined with eplerenone treatment, which reduced TGF-β1/Smad3 pathway activation-mediated CMT. The combined intervention of ADAM17 deficiency and eplerenone therapy provided additional cardiac protection compared with a single therapy alone without disturbing potassium level. Therefore, the combination of ADAM17 inhibition and eplerenone is a potential therapeutic strategy for human DCM.

MSC exosomes attenuate sterile inflammation and necroptosis associated with TAK1-pJNK-NFKB mediated cardiomyopathy in diabetic ApoE KO mice.

Diabetes is a debilitating disease that leads to complications like cardiac dysfunction and heart failure. In this study, we investigated the pathophysiology of diabetes-induced cardiac dysfunction in mice with dyslipidemia. We hypothesize diabetes in ApoE knockout (ApoE-/-) mice induces cardiac dysfunction by increasing inflammation and necroptosis. ApoE-/- mice were divided into experimental groups: Control, Streptozotocin (STZ), STZ + MSC-Exo (mesenchymal stem cell-derived exosomes), and STZ+MEF-Exo (Mouse embryonic fibroblast derived exosomes). At Day 42, we assessed cardiac function, collected blood and heart tissues. Heart tissue samples were analyzed for inflammation, necroptosis, signaling mechanism, hypertrophy and adverse structural remodeling using histology, immunohistochemistry, western blotting, RT-PCR, cytokine array and TF array. STZ treated ApoE-/- mice developed diabetes, with significantly (p<0.05) increased blood glucose and body weight loss. These mice developed cardiac dysfunction with significantly (p<0.05) increased left ventricular internal diameter end diastole and end systole, and decreased ejection fraction, and fractional shortening. We found significant (p<0.05) increased expression of inflammatory cytokines TNF- a, IL-6, IL-1a, IL-33 and decreased IL-10 expression. Diabetic mice also exhibited significantly (p<0.05) increased necroptosis marker expression and infiltration of inflammatory monocytes and macrophages. MSC-Exos treated mice showed recovery of diabetes associated pathologies with significantly reduced blood glucose, recovered body weight, increased IL-10 secretion and M2 polarized macrophages in the heart. These mice showed reduced TAK1-pJNK-NFKB inflammation associated expression and improved cardiac function with significantly reduced cardiac hypertrophy and fibrosis compared to diabetic mice. Treatment with MEF-Exos did not play a significant role in attenuating diabetes-induced cardiomyopathy as these treatment mice presented with cardiac dysfunction and underlying pathologies observed in STZ mice. Thus, we conclude that cardiac dysfunction develops in diabetic ApoE-/- mice, arising from inflammation, necroptosis, and adverse tissue remodeling, which is ameliorated by MSC-Exos, a potential therapeutic for diabetes-induced cardiomyopathy.

AGO2 Protects Against Diabetic Cardiomyopathy by Activating Mitochondrial Gene Translation.

Diabetes is associated with cardiovascular complications. microRNAs translocate into subcellular organelles to modify genes involved in diabetic cardiomyopathy. However, functional properties of subcellular AGO2 (Argonaute2), a core member of miRNA machinery, remain elusive. We elucidated the function and mechanism of subcellular localized AGO2 on mouse models for diabetes and diabetic cardiomyopathy. Recombinant adeno-associated virus type 9 was used to deliver AGO2 to mice through the tail vein. Cardiac structure and functions were assessed by echocardiography and catheter manometer system. AGO2 was decreased in mitochondria of diabetic cardiomyocytes. Overexpression of mitochondrial AGO2 attenuated diabetes-induced cardiac dysfunction. AGO2 recruited TUFM, a mitochondria translation elongation factor, to activate translation of electron transport chain subunits and decrease reactive oxygen species. Malonylation, a posttranslational modification of AGO2, reduced the importing of AGO2 into mitochondria in diabetic cardiomyopathy. AGO2 malonylation was regulated by a cytoplasmic-localized short isoform of SIRT3 through a previously unknown demalonylase function. Our findings reveal that the SIRT3-AGO2-CYTB axis links glucotoxicity to cardiac electron transport chain imbalance, providing new mechanistic insights and the basis to develop mitochondria targeting therapies for diabetic cardiomyopathy.

Disrupted cardiac fibroblast BCAA catabolism contributes to diabetic cardiomyopathy via a periostin/NAP1L2/SIRT3 axis

BackgroundPeriostin is an extracellular matrix protein that plays a critical role in cell fate determination and tissue remodeling, but the underlying role and mechanism of periostin in diabetic cardiomyopathy (DCM) are far from clear. Thus, we aimed to clarify the mechanistic participation of periostin in DCM.MethodsThe expression of periostin was examined in DCM patients, diabetic mice and high glucose (HG)-exposed cardiac fibroblasts (CF). Gain- and loss-of-function experiments assessed the potential role of periostin in DCM pathogenesis. RNA sequencing was used to investigate the underlying mechanisms of periostin in DCM.ResultsA mouse cytokine antibody array showed that the protein expression of periostin was most significantly upregulated in diabetic mouse heart, and this increase was also observed in patients with DCM or HG-incubated CF. Periostin-deficient mice were protected from diabetes-induced cardiac dysfunction and myocardial damage, while overexpression of periostin held the opposite effects. Hyperglycemia stimulated the expression of periostin in a TGF-β/Smad-dependent manner. RNA sequencing results showed that periostin upregulated the expression of nucleosome assembly protein 1-like 2 (NAP1L2) which recruited SIRT3 to deacetylate H3K27ac on the promoters of the branched-chain amino acid (BCAA) catabolism-related enzymes BCAT2 and PP2Cm, resulting in BCAA catabolism impairment. Additionally, CF-derived periostin induced hypertrophy, oxidative injury and inflammation in primary cardiomyocytes. Finally, we identified that glucosyringic acid (GA) specifically targeted and inhibited periostin to ameliorate DCM.ConclusionOverall, manipulating periostin expression may function as a promising strategy in the treatment of DCM.

Moderate- and High-Intensity Endurance Training Alleviate Diabetes-Induced Cardiac Dysfunction in Rats.

Exercise training is an encouraging approach to treat cardiac dysfunction in type 2 diabetes (T2DM), but the impact of its intensity is not understood. We aim to investigate whether and, if so, how moderate-intensity training (MIT) and high-intensity interval training (HIIT) alleviate adverse cardiac remodeling and dysfunction in rats with T2DM. Male rats received standard chow (n = 10) or Western diet (WD) to induce T2DM. Hereafter, WD rats were subjected to a 12-week sedentary lifestyle (n = 8), running MIT (n = 7) or HIIT (n = 7). Insulin resistance and glucose tolerance were assessed during the oral glucose tolerance test. Plasma advanced glycation end-products (AGEs) were evaluated. Echocardiography and hemodynamic measurements evaluated cardiac function. Underlying cardiac mechanisms were investigated by histology, western blot and colorimetry. We found that MIT and HIIT lowered insulin resistance and blood glucose levels compared to sedentary WD rats. MIT decreased harmful plasma AGE levels. In the heart, MIT and HIIT lowered end-diastolic pressure, left ventricular wall thickness and interstitial collagen deposition. Cardiac citrate synthase activity, mitochondrial oxidative capacity marker, raised after both exercise training modalities. We conclude that MIT and HIIT are effective in alleviating diastolic dysfunction and pathological cardiac remodeling in T2DM, by lowering fibrosis and optimizing mitochondrial capacity.

CD226 deficiency attenuates cardiac early pathological remodeling and dysfunction via decreasing inflammatory macrophage proportion and macrophage glycolysis in STZ-induced diabetic mice.

Diabetic cardiomyopathy (DCM) is one of the main complications in type I diabetic patients. Activated macrophage is critical for directing the process of inflammation during the development of DCM. The present study focused on the roles of CD226 on macrophage function during the DCM progression. It has been found that the number of cardiac macrophages in the hearts of streptozocin (STZ)-induced diabetes mice was significantly increased compared with that in non-diabetes mice, and the expression level of CD226on cardiac macrophages in STZ-induced diabetes mice was higher than that in non-diabetes mice. CD226 deficiency attenuated the diabetes-induced cardiac dysfunction and decreased the proportion of CD86+ F4/80+ macrophages in the diabetic hearts. Notably, adoptive transfer of Cd226-/- - bone marrow derived macrophages (BMDMs) alleviated diabetes-induced cardiac dysfunction, which may be due to the attenuated migration capacity of Cd226-/- -BMDM under high glucose stimulation. Furthermore, CD226 deficiency decreased the macrophage glycolysis accompanying by the downregulated hexokinase 2 (HK2) and lactate dehydrogenase A (LDH-A) expression. Taken together, these findings revealed the pathogenic roles of CD226 played in the process of DCM and provided a basis for the treatment of DCM.

Deletion of the stress response protein REDD1 prevents impaired cardiac function in diabetic mice

The overwhelming impact of heart failure on morbidity and mortality in obesity and type 2 diabetes requires a deeper understanding of the molecular events that mediate cardiac dysfunction. We recently demonstrated using in vivo and in vitro models of diabetes that upregulation of endoplasmic reticulum stress in cardiomyocytes promoted expression of the stress response protein regulated in development and DNA damage 1 (REDD1). REDD1 has been implicated in diabetes-induced functional deficits in both the retina and kidney; however, a role for REDD1 in diabetes-induced cardiac dysfunction has not been investigated. Thus, we explored the hypothesis that REDD1 contributes to the development of diabetes-induced cardiac dysfunction. To induce diabetes, 6-week old male wild-type and REDD1 knock-out (KO) B6;129 mice were fed a high-fat high-sugar diet (42% kcal fat, 34% sucrose by weight) for 16 weeks; 2 weeks after initiation of the diet, mice were administered low-dose streptozotocin (STZ) for five consecutive days. Non-diabetic control mice were fed a standard rodent diet and received vehicle injections. Mice with a fasting blood glucose level &gt;250mg/dL were defined as diabetic. At 10 weeks of age, transthoracic echocardiogram was evaluated every 2 weeks using a GE Logique small animal echocardiography machine. After 12 weeks of diabetes, left ventricular ejection fraction (EF) was reduced in diabetic wild-type mice as compared to non-diabetic wild-type mice (51.0 +/-9.8% versus 39.5 +/- 5.5%, p = 0.015). Meanwhile, EF in diabetic REDD1 KO mice (47.4 +/- 6.6%) was similar to that observed in non-diabetic REDD1 KO mice (49.6 +/- 6.7%). To investigate a potential cause of the preserved EF in diabetic REDD1 KO mice, tissue homogenates from the left ventricle were examined by PCR analysis. REDD1 mRNA expression in diabetic wild-type mice was enhanced as compared to non-diabetic controls in coordination with increased expression of Tgfb1, as well as expression of the pro-fibrotic genes Fn1, Col1a1, and Col3a1. By contrast, there was no increase in pro-fibrotic mRNA expression in cardiac tissue homogenates from diabetic REDD1 KO mice, as compared to non-diabetic REDD1 KO mice. Overall, the data support a role for REDD1 expression in the development of impaired cardiac function and the pro-fibrotic response of the heart to diabetes. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Tanshinone IIA ameliorates experimental diabetic cardiomyopathy by inhibiting endoplasmic reticulum stress in cardiomyocytes via SIRT1.

Diabetic cardiomyopathy (DCM) is a common complication in patients with diabetes, and ultimately leads to heart failure. Endoplasmic reticulum stress (ERS) induced by abnormal glycolipid metabolism is a critical factor that affects the occurrence and development of DCM. Additionally, the upregulation/activation of silent information regulation 2 homolog-1 (SIRT1) has been shown to protect against DCM. Tanshinone II A (Tan IIA), the main active component of Salviae miltiorrhizae radix et rhizome (a valuable Chinese medicine), has protective effects against cardiovascular disease and diabetes. However, its role and mechanisms in diabetes-induced cardiac dysfunction remain unclear. Therefore, we explored whether Tan IIA alleviates ERS-mediated DCM via SIRT1 and elucidated the underlying mechanism. The results suggested that Tan IIA alleviated the pathological changes in the hearts of diabetic mice, ameliorated the cytopathological morphology of cardiomyocytes, reduced the cell death rate, and inhibited the expression of ERS-related proteins and mRNA. The SIRT1 agonist inhibited the activities of glucose-regulated protein 78 (GRP78). Furthermore, the opposite results under the SIRT1 inhibitor. SIRT1 knockdown was induced by siRNA-SIRT1 transfection, and the degree of GRP78 acetylation was increased. Cumulatively, Tan IIA ameliorated DCM by inhibiting ERS and upregulating SIRT1 expression.

Dectin-1 deficiency alleviates diabetic cardiomyopathy by attenuating macrophage-mediated inflammatory response

Cardiovascular diseases are the primary cause of mortality in patients with diabetes and obesity. Hyperglycemia and hyperlipidemia in diabetes alters cardiac function, which is associated with broader cellular processes such as aberrant inflammatory signaling. Recent studies have shown that a pattern recognition receptor called Dectin-1, expressed on macrophages, mediates pro-inflammatory responses in innate immunity. In the present study, we examined the role of Dectin-1 in the pathogenesis of diabetic cardiomyopathy. We observed increased Dectin-1 expression in heart tissues of diabetic mice and localized the source to macrophages. We then investigated the cardiac function in Dectin-1-deficient mice with STZ-induced type 1 diabetes and high-fat-diet-induced type 2 diabetes. Our results show that Dectin-1 deficient mice are protected against diabetes-induced cardiac dysfunction, cardiomyocyte hypertrophy, tissue fibrosis, and inflammation. Mechanistically, our studies show that Dectin-1 is important for cell activation and induction of inflammatory cytokines in high-concentration glucose and palmitate acid (HG + PA)-challenged macrophages. Deficiency of Dectin-1 generate fewer paracrine inflammatory factors capable of causing cardiomyocyte hypertrophy and fibrotic responses in cardiac fibroblasts. In conclusion, this study provides evidence that Dectin-1 mediates diabetes-induced cardiomyopathy through regulating inflammation. Dectin-1 may be a potential target to combat diabetic cardiomyopathy.

Preparation, chemical characterization and determination of the antioxidant, cytotoxicity and therapeutic effects of gold nanoparticles green-synthesized by Calendula officinalis flower extract in diabetes-induced cardiac dysfunction in rat

• Preparation of mono-dispersed gold nanoparticles using the aqueous extract of Calendula officinalis. • Calendula officinalis acted as reducing and stabilizing agent. • COE@AuNPs shown good antioxidant properties. • The results shown therapeutic effects of COE@AuNPs on diabetes-induced cardiac dysfunction in rat. An ultrasound promoted bio-inspired synthesis of mono-dispersed Au nanoparticles (NPs) has been adopted in this article, templated over Calendula officinalis flower extract. The phytochemicals therein were explored as natural and green reducing as well as NP stabilizers. The as-synthesized bio-nanomaterial (COE@AuNPs) was characterized over FT-IR, UV–Vis spectroscopy, TEM, FE-SEM, EDX and XRD studies. Due to plant extract-based synthesis, the material was obtained as highly dispersed, semi-spherical particles of minuscule dimension (20–25 nm). In the in vivo condition, diabetes was induced by a fructose-enriched diet supplemented by streptozotocin. Half of the animals received COE@AuNPs by oral gavage. Compared to the animals receiving standard chow, serum fasting glucose level was increased and glucose tolerance was diminished in diabetic rats. COE@AuNPs affect significantly fasting hyperglycemia and glucose intolerance; also, it attenuated the diabetes-induced deterioration of cardiac output and cardiac work. Moreover, COE@AuNPs prevented the diabetes-induced increase in cardiac STAT3 phosphorylation. The results of this study indicated the therapeutic effects of COE@AuNPs the diabetes-induced cardiac dysfunction in rat.

Abstract P3046: Deletion Of Sarm1 Nad Hydrolase Ameliorates Diabetic Cardiomyopathy

Diabetes is a risk factor for heart disease. NAD depletion has emerged as a hallmark of cardiometabolic diseases, and hence, elevating NAD level alleviates diabetic cardiomyopathy. On the other hand, inhibition of NAD consumption also maintains NAD homeostasis. SARM1 is a novel intracellular NAD hydrolase that contributes to diabetic neuropathy; however, its role in heart disease has never been described. We assayed 243 plasma metabolites from wild-type (WT) and SARM1-KO (KO) mice by quantitative metabolomics, and found that SARM1 deficiency caused changes in more (67) metabolites in male mice than in female mice (28). Only 5 of these metabolites overlapped between male and female, indicating sex-dependent effect of SARM1 deletion on plasma metabolites. SARM1 deficiency may alter susceptibility of male mice to metabolic stress, since metabolites associated with diabetes and impaired metabolism were altered, e.g. pyridoxic acid, alloisoleucine, LPC/PC, ceramide etc. Despite the differences in plasma metabolite levels, KO mice from either sex did not show changes in cardiac structure and function at baseline. We next tested a hypothesis that SARM1 deficiency protects mice against diabetic cardiomyopathy. WT and KO mice were challenged with streptozotocin (STZ) to induce diabetic stress. 16-week diabetes promoted progressive systolic (fractional shortening) and diastolic dysfunction (E’/A’, e/E’) in WT male mice. SARM1 deficiency attenuated diabetes-induced cardiac dysfunction, although fasting glucose levels were similarly elevated in diabetic WT and KO mice. Diabetic WT hearts showed declined NAD level, which was elevated by SARM1 deficiency. The restored NAD level in KO hearts did not change expression of other NAD hydrolases (Bst1 and CD38). Diabetic WT hearts up-regulated cardiomyopathy markers such as nppb and Nox4 mRNAs, and myh7/myh6 ratio, that were normalized by SARM1 deficiency. Chronic diabetes promoted cardiac fibrosis and upregulation of profibrotic gene expression such as ctgf and Inhbb, that were suppressed by SARM1 deficiency. Our data suggest a protective effect of SARM1 deficiency on diabetic cardiomyopathy in male mice. The effects of SARM1 deficiency on diabetic hearts could be sex-dependent and remain to be determined.

Loss of Lipocalin 10 Exacerbates Diabetes-Induced Cardiomyopathy via Disruption of Nr4a1-Mediated Anti-Inflammatory Response in Macrophages.

Metabolic disorders (i.e., hyperglycemia, hyperlipidemia, and hyperinsulinemia) cause increased secretion of inflammatory cytokines/chemokines, leading to gradual loss of cardiac resident macrophage population and increased accumulation of inflammatory monocytes/macrophages in the heart. Such self-perpetuating effect may contribute to the development of cardiomyopathy during diabetes. Recent meta-analysis data reveal that lipocalin 10 (Lcn10) is significantly downregulated in cardiac tissue of patients with heart failure but is increased in the blood of septic patients. However, the functional role of Lcn10 in cardiac inflammation triggered by metabolic disorders has never been investigated. In this study, we demonstrate that the expression of Lcn10 in macrophages was significantly decreased under multiple metabolic stress conditions. Furthermore, Lcn10-null macrophages exhibited pro-inflammatory phenotype in response to inflammation stimuli. Next, using a global Lcn10-knockout (KO) mouse model to induce type-2 diabetes (T2D), we observed that loss of Lcn10 promoted more pro-inflammatory macrophage infiltration into the heart, compared to controls, leading to aggravated insulin resistance and impaired cardiac function. Similarly, adoptive transfer of Lcn10-KO bone marrow cells into X-ray irradiated mice displayed higher ratio of pro-/anti-inflammatory macrophages in the heart and worsened cardiac function than those mice received wild-type (WT) bone marrows upon T2D conditions. Mechanistically, RNA-sequencing analysis showed that Nr4a1, a nuclear receptor known to have potent anti-inflammatory effects, is involved in Lcn10-mediated macrophage activation. Indeed, we found that nuclear translocation of Nr4a1 was disrupted in Lcn10-KO macrophages upon stimulation with LPS + IFNγ. Accordingly, treatment with Cytosporone B (CsnB), an agonist of Nr4a1, attenuated the pro-inflammatory response in Lcn10-null macrophages and partially improved cardiac function in Lcn10-KO diabetic mice. Together, these findings indicate that loss of Lcn10 skews macrophage polarization to pro-inflammatory phenotype and aggravates cardiac dysfunction during type-2 diabetes through the disruption of Nr4a1-mediated anti-inflammatory signaling pathway in macrophages. Therefore, reduction of Lcn10 expression observed in diabetic macrophages may be responsible for the pathogenesis of diabetes-induced cardiac dysfunction. It suggests that Lcn10 might be a potential therapeutic factor for diabetic heart failure.

Cannabinoid receptor 2 activation alleviates diabetes-induced cardiac dysfunction, inflammation, oxidative stress, and fibrosis.

Diabetes mellitus promotes accelerated cardiovascular aging and inflammation, which in turn facilitate the development of cardiomyopathy/heart failure. High glucose-induced oxidative/nitrative stress, activation of various pro-inflammatory, and cell death pathways are critical in the initiation and progression of the changes culminating in diabetic cardiomyopathy. Cannabinoid 2 receptor (CB2R) activation in inflammatory cells and activated endothelium attenuates the pathological changes associated with atherosclerosis, myocardial infarction, stroke, and hepatic cardiomyopathy. In this study, we explored the role of CB2R signaling in myocardial dysfunction, oxidative/nitrative stress, inflammation, cell death, remodeling, and fibrosis associated with diabetic cardiomyopathy in type 1 diabetic mice. Control human heart left ventricles and atrial appendages, similarly to mouse hearts, had negligible CB2R expression determine by RNA sequencing or real-time RT-PCR. Diabetic cardiomyopathy was characterized by impaired diastolic and systolic cardiac function, enhanced myocardial CB2R expression, oxidative/nitrative stress, and pro-inflammatory response (tumor necrosis factor-α, interleukin-1β, intracellular adhesion molecule 1, macrophage inflammatory protein-1, monocyte chemoattractant protein-1), macrophage infiltration, fibrosis, and cell death. Pharmacological activation of CB2R with a selective agonist attenuated diabetes-induced inflammation, oxidative/nitrative stress, fibrosis and cell demise, and consequent cardiac dysfunction without affecting hyperglycemia. In contrast, genetic deletion of CB2R aggravated myocardial pathology. Thus, selective activation of CB2R ameliorates diabetes-induced myocardial tissue injury and preserves the functional contractile capacity of the myocardium in the diabetic milieu. This is particularly encouraging, since unlike CB1R agonists, CB2R agonists do not elicit psychoactive activity and cardiovascular side effects and are potential clinical candidates in the treatment of diabetic cardiovascular and other complications.

Renal denervation ameliorates cardiac metabolic remodeling in diabetic cardiomyopathy rats by suppressing renal SGLT2 expression

AbstractThis study aimed to investigate the effects of renal denervation (RDN) on diabetic cardiomyopathy (DCM) and explore the related mechanisms. Male Sprague-Dawley rats were fed high-fat chow and injected with low-dose streptozotocin to establish a DCM model. Six rats served as controls. The surviving rats were divided into three groups: control group, DCM group and DCM + RDN group. RDN surgery was performed in the fifth week. At the end of the experiment, all rats were subjected to 18F-FDG PET/CT and metabolic cage studies. Cardiac function and structure were evaluated by echocardiography and histology. Myocardial substrate metabolism and mitochondrial function were assessed by multiple methods. In the 13th week, the DCM rats exhibited cardiac hypertrophy and interstitial fibrosis accompanied by diastolic dysfunction. RDN ameliorated DCM-induced cardiac dysfunction (E/A ratio: RDN 1.07 ± 0.18 vs. DCM 0.93 ± 0.12, P < 0.05; E/E' ratio: RDN 10.74 ± 2.48 vs. DCM 13.25 ± 1.99, P < 0.05) and pathological remodeling (collagen volume fraction: RDN 5.05 ± 2.05% vs. DCM 10.62 ± 2.68%, P < 0.05). Abnormal myocardial metabolism in DCM rats was characterized by suppressed glucose metabolism and elevated lipid metabolism. RDN increased myocardial glucose uptake and oxidation while reducing the absorption and utilization of fatty acids. Meanwhile, DCM decreased mitochondrial ATP content, depolarized the membrane potential and inhibited the activity of respiratory chain complexes, but RDN attenuated this mitochondrial damage (ATP: RDN 30.98 ± 7.33 μmol/gprot vs. DCM 22.89 ± 5.90 μmol/gprot, P < 0.05; complexes I, III and IV activity: RDN vs. DCM, P < 0.05). Furthermore, both SGLT2 inhibitor and the combination treatment produced similar effects as RDN alone. Thus, RDN prevented DCM-induced cardiac dysfunction and pathological remodeling, which is related to the improvement of metabolic disorders and mitochondrial dysfunction.Diabetic cardiomyopathy is a serious diabetes-related cardiovascular complication, which is closely related to myocardial metabolic disorders, but there is no specific therapy currently. Renal denervation (RDN), a novel technique to remove renal sympathetic nerves, can reduce the overexpression of renal SGLT2 in diabetic rats, thereby promoting urinary glucose excretion and maintaining systemic glucose homeostasis. On this basis, RDN ameliorated diabetes-induced cardiac metabolic disorders and mitochondrial damages, ultimately preventing diabetes-induced cardiac dysfunction and pathological remodeling.

Nicotinamide riboside promotes Mfn2-mediated mitochondrial fusion in diabetic hearts through the SIRT1-PGC1α-PPARα pathway

Myocardial dysfunction is associated with an imbalance in mitochondrial fusion/fission dynamics in patients with diabetes. However, effective strategies to regulate mitochondrial dynamics in the diabetic heart are still lacking. Nicotinamide riboside (NR) supplementation ameliorated mitochondrial dysfunction and oxidative stress in both cardiovascular and aging-related diseases. This study investigated whether NR protects against diabetes-induced cardiac dysfunction by regulating mitochondrial fusion/fission and further explored the underlying mechanisms. Here, we showed an evident decrease in NAD+ (nicotinamide adenine dinucleotide) levels and mitochondrial fragmentation in the hearts of leptin receptor-deficient diabetic (db/db) mouse models. NR supplementation significantly increased NAD+ content in the diabetic hearts and promoted mitochondrial fusion by elevating Mfn2 level. Furthermore, NR-induced mitochondrial fusion suppressed mitochondrial H2O2 and O2•− production and reduced cardiomyocyte apoptosis in both db/db mice hearts and neonatal primary cardiomyocytes. Mechanistically, chromatin immunoprecipitation (ChIP) and luciferase reporter assay analyses revealed that PGC1α and PPARα interdependently regulated Mfn2 transcription by binding to its promoter region. NR treatment elevated NAD+ levels and activated SIRT1, resulting in the deacetylation of PGC1α and promoting the transcription of Mfn2. These findings suggested the promotion of mitochondrial fusion via oral supplementation of NR as a potential strategy for delaying cardiac complications in patients with diabetes.

MiR-340-5p Mediates Cardiomyocyte Oxidative Stress in Diabetes-Induced Cardiac Dysfunction by Targeting Mcl-1.

Diabetic cardiomyopathy (DCM) is initially characterized by early diastolic dysfunction, left ventricular remodeling, hypertrophy, and myocardial fibrosis, and it is eventually characterized by clinical heart failure. MicroRNAs (miRNAs), endogenous small noncoding RNAs, play significant roles in diabetes mellitus (DM). However, it is still largely unknown about the mechanism that links miRNAs and the development of DCM. Here, we aimed to elucidate the mechanism underlying the potential role of microRNA-340-5p in DCM in db/db mouse, which is a commonly used model of type 2 DM and diabetic complications that lead to heart failure. We first demonstrated that miR-340-5p expression was dramatically increased in heart tissues of mice and cardiomyocytes under diabetic conditions. Overexpression of miR-340-5p exacerbated DCM, which was reflected by extensive myocardial fibrosis and more serious dysfunction in db/db mice as represented by increased apoptotic cardiomyocytes, elevated ROS production, and impaired mitochondrial function. Inhibition of miR-340-5p by a tough decoy (TUD) vector was beneficial for preventing ROS production and apoptosis, thus rescuing diabetic cardiomyopathy. We identified myeloid cell leukemia 1 (Mcl-1) as a major target gene for miR-340-5p and showed that the inhibition of Mcl-1 was responsible for increased functional loss of mitochondria, oxidative stress, and cardiomyocyte apoptosis, thereby caused cardiac dysfunction in diabetic mice. In conclusion, our results showed that miR-340-5p plays a crucial role in the development of DCM and can be targeted for therapeutic intervention.

Nuclear miR-320 in Diabetes-induced Cardiac Dysfunction

Cardiovascular complications, especially heart failure, are leading causes of morbidity and mortality in diabetes mellitus. We found the upregulation of the micro (mi)RNA miR-320 occurred in the heart of db/db mice relative to the wild type (wt) and in the failing heart of patients with diabetes. A high-fat diet increased blood glucose and body weight and caused cardiac dysfunction in miR-320-overexpressing mice as compared to controls. MiR-320 overexpression in the heart had no effect on body weight or fasting glucose, but worsened cardiac function in db/db mice, which was rescued by miR-320 inhibition. MiR-320 was predominantly expressed in the nucleus and enhanced cluster of differentiation 36 (CD36) transcription, resulting in increased fatty acid (FA) uptake, lipotoxicity, and cardiomyocyte apoptosis and subsequent diabetic cardiomyopathy. Our findings provide a basis for developing miRNA-based therapeutics for the treatment of diabetic cardiomyopathy. Cardiovascular complications, especially heart failure, are leading causes of morbidity and mortality in diabetes mellitus. We found the upregulation of the micro (mi)RNA miR-320 occurred in the heart of db/db mice relative to the wild type (wt) and in the failing heart of patients with diabetes. A high-fat diet increased blood glucose and body weight and caused cardiac dysfunction in miR-320-overexpressing mice as compared to controls. MiR-320 overexpression in the heart had no effect on body weight or fasting glucose, but worsened cardiac function in db/db mice, which was rescued by miR-320 inhibition. MiR-320 was predominantly expressed in the nucleus and enhanced cluster of differentiation 36 (CD36) transcription, resulting in increased fatty acid (FA) uptake, lipotoxicity, and cardiomyocyte apoptosis and subsequent diabetic cardiomyopathy. Our findings provide a basis for developing miRNA-based therapeutics for the treatment of diabetic cardiomyopathy.

PGAM5-Mediated PHB2 Dephosphorylation Contributes to Diabetic Cardiomyopathy by Disrupting Mitochondrial Quality Surveillance

Disruption of the mitochondrial quality surveillance (MQS) system contributes to mitochondrial dysfunction in diabetic cardiomyopathy (DCM). In this study, we observed that cardiac expression of phosphoglycerate mutase 5 (PGAM5), a mitochondrial Ser/Thr protein phosphatase, is upregulated in mice with streptozotocin-induced DCM. Notably, DCM-related cardiac structural and functional deficits were negated in cardiomyocyte-specific Pgam5 knockout ( Pgam5 CKO ) mice. Hyperglycemic stress impaired adenosine triphosphate production, reduced respiratory activity, and prolonged mitochondrial permeability transition pore opening in acutely isolated neonatal cardiomyocytes from control Pgam5 f/f mice, and these effects were markedly prevented in cardiomyocytes from Pgam5 CKO mice. Likewise, three main MQS-governed processes—namely, mitochondrial fission/fusion cycling, mitophagy, and biogenesis—were disrupted by hyperglycemia in Pgam5 f/f , but not in Pgam5 CKO , cardiomyocytes. On the basis of bioinformatics prediction of interaction between PGAM5 and prohibitin 2 (PHB2), an inner mitochondrial membrane-associated scaffolding protein, co-immunoprecipitation, and immunoblot assays demonstrated that PGAM5 dephosphorylates PHB2 on Ser91. Transfection of cardiomyocytes with phosphodefective or phosphomimetic Ser91 mutants of PHB2 confirmed a critical role for PGAM5-mediated dephosphorylation of PHB2 in mitochondrial dysfunction associated with hyperglycemic stress. Furthermore, knockin mice expressing phosphomimetic PHB2 S91D were resistant to diabetes-induced cardiac dysfunction. Our findings highlight the PGAM-PHB2 axis as a novel and critical regulator of mitochondrial dysfunction in DCM.