Development of a small animal model replicating core characteristics of takotsubo syndrome in humans.

Aims: Adequate animal models are necessary to understand human conditions, such as takotsubo syndrome (TS) characterized by the heart's transient regional wall motion abnormalities. This study aims to develop a reproducible, low-mortality TS model that closely mimics the human condition and addresses the limitations of existing models. Methods and results: We conducted six experiments using 309 Sprague Dawley rats, each approximately 300 g and aged 7-8 weeks. Initially, we replicated an established model using intraperitoneal isoprenaline injections. Subsequent experiments varied the doses and infusion durations of intravenous isoprenaline and assessed the effects of sex, strain, and breeder on the development of reversible akinetic segments. High-resolution echocardiography monitored the regional wall motion over 30 days to correlate with histological changes. Increasing the isoprenaline dose and the infusion time significantly enhanced akinesia (P < 0.01), resulting in pronounced apical ballooning observed in three-dimensional imaging. Akinesia peaked at 6 h post-infusion, with recovery observed at 24 h; most rats recovered from akinetic segments within 48-72 h. Optimizing the mode of administration, dose, and duration achieved a TS-like phenotype in 90% of cases, with a 16.7% mortality rate. Histological examinations confirmed that myocardial injury occurred, independent of apical ballooning. Conclusion: This study presents a refined TS model that reliably replicates the syndrome's key features, including morphological and electrocardiographic changes, demonstrating its transient nature with high fidelity and reduced mortality. The model's reproducibility, evidenced by consistent results across trials, suggests its potential for broader application pending further validation.

Ischemic preconditioning affects phosphosites and accentuates myocardial stunning while reducing infarction size in rats.

Background and aims: Ischemic preconditioning (IPC), i.e., brief periods of ischemia, protect the heart from subsequent prolonged ischemic injury, and reduces infarction size. Myocardial stunning refers to transient loss of contractility in the heart after myocardial ischemia that recovers without permanent damage. The relationship between IPC and myocardial stunning remains incompletely understood. This study aimed primarily to examine the effects of IPC on the relationship between ischemia duration, stunning, and infarct size in an ischemia-reperfusion injury model. Secondarily, this study aimed to examine to which extent the phosphoproteomic changes induced by IPC relate to myocardial contractile function. Methods and results: Rats were subjected to different durations of left anterior descending artery (LAD) occlusion, with or without preceding IPC. Echocardiograms were acquired to assess cardiac contraction in the affected myocardial segment. Infarction size was evaluated using triphenyl tetrazolium chloride staining. Phosphoproteomic analysis was performed in heart tissue from preconditioned and non-preconditioned animals. In contrast to rats without IPC, reversible akinesia was observed in a majority of the rats that were subjected to IPC and subsequently exposed to ischemia of 13.5 or 15 min of ischemia. Phosphoproteomic analysis revealed significant differential regulation of 786 phosphopeptides between IPC and non-IPC groups, with significant associations with the sarcomere, Z-disc, and actin binding. Conclusion: IPC induces changes in phosphosites of proteins involved in myocardial contraction; and both accentuates post-ischemic myocardial stunning and reduces infarct size.

Repressive H3K27me3 drives hyperglycemia-induced oxidative and inflammatory transcriptional programs in human endothelium.

BACKGROUND: Histone modifications play a critical role in chromatin remodelling and regulate gene expression in health and disease. Histone methyltransferases EZH1, EZH2, and demethylases UTX, JMJD3, and UTY catalyse trimethylation of lysine 27 on histone H3 (H3K27me3). This study was designed to investigate whether H3K27me3 triggers hyperglycemia-induced oxidative and inflammatory transcriptional programs in the endothelium. METHODS: We studied human aortic endothelial cells exposed to high glucose (HAEC) or isolated from individuals with diabetes (D-HAEC). RT-qPCR, immunoblotting, chromatin immunoprecipitation (ChIP-qPCR), and confocal microscopy were performed to investigate the role of H3K27me3. We determined superoxide anion (O2-) production by ESR spectroscopy, NF-κB binding activity, and monocyte adhesion. Silencing/overexpression and pharmacological inhibition of chromatin modifying enzymes were used to modulate H3K27me3 levels. Furthermore, isometric tension studies and immunohistochemistry were performed in aorta from wild-type and db/db mice. RESULTS: Incubation of HAEC to high glucose showed that upregulation of EZH2 coupled to reduced demethylase UTX and JMJD3 was responsible for the increased H3K27me3. ChIP-qPCR revealed that repressive H3K27me3 binding to superoxide dismutase and transcription factor JunD promoters is involved in glucose-induced O2- generation. Indeed, loss of JunD transcriptional inhibition favours NOX4 expression. Furthermore, H3K27me3-driven oxidative stress increased NF-κB p65 activity and downstream inflammatory genes. Interestingly, EZH2 inhibitor GSK126 rescued these endothelial derangements by reducing H3K27me3. We also found that H3K27me3 epigenetic signature alters transcriptional programs in D-HAEC and aortas from db/db mice. CONCLUSIONS: EZH2-mediated H3K27me3 represents a key epigenetic driver of hyperglycemia-induced endothelial dysfunction. Targeting EZH2 may attenuate oxidative stress and inflammation and, hence, prevent vascular disease in diabetes.

Investigating the Link Between Abdominal Pain, Weight Loss, and IgG4-Related Pancreatitis: A Case Report.

This case report describes a 55-year-old male who presented with a two-year history of abdominal pain and weight loss, along with recent onset nausea, vomiting, and anorexia. Laboratory tests revealed elevated serum IgG4 levels and anemia, and abdominal CT showed diffuse pancreatic enlargement and multiple retroperitoneal lymphadenopathy. Endoscopic ultrasound-guided fine-needle aspiration of the pancreatic mass revealed dense lymphoplasmacytic infiltration with fibrosis and increased numbers of IgG4-positive plasma cells, consistent with the diagnosis of IgG4-related pancreatitis. Treatment with prednisone led to a significant improvement in the patient's symptoms and laboratory values, with subsequent reduction in the size of the pancreatic mass and retroperitoneal lymphadenopathy. The patient remained asymptomatic at the six-month follow-up visit, and serum IgG4 levels remained within the normal range. This case highlights the importance of considering IgG4-related disease (IgG4-RD) in patients presenting with abdominal pain and weight loss and the potential effectiveness of corticosteroid therapy in managing this condition.

Differences between cardiac troponin I vs. T according to the duration of myocardial ischaemia.

AIMS: Cardiac troponin T (cTnT) and troponin I (cTnI) are expressed as an obligate 1:1 complex in the myocardium. However, blood levels of cTnI often rise much higher than that of cTnT in myocardial infarction (MI), whereas cTnT is often higher in patients with stable conditions such as atrial fibrillation. Here we examine high-sensitive (hs) cTnI and hs-cTnT after different durations of experimental cardiac ischaemia. METHODS AND RESULTS: hs-cTnI, hs-cTnT, and the hs-cTnT/hs-cTnI ratio were measured in plasma samples from rats before and at 30 and 120 min after 5, 10, 15, and 30 min of myocardial ischaemia. The animals were killed after 120 min of reperfusion, and the infarct volume and volume at risk were measured. hs-cTnI, hs-cTnT, and the hs-cTnT/hs-cTnI ratio were also measured in plasma samples collected from patients with ST-elevation myocardial infarction (STEMI). hs-cTnT and hs-cTnI increased over 10-fold in all rats subjected to ischaemia. The increase of hs-cTnI and hs-cTnT after 30 min was similar, resulting in a hs-cTnI/hs-cTnT ratio around 1. The hs-cTnI/hs-cTnT ratio was also around 1 in blood samples collected at 120 min in rats subjected to 5 or 10 min of ischaemia where no localized necrosis was observed. In contrast, the hs-cTnI/hs-cTnT ratio at 2 h was 3.6-5.5 after longer ischaemia that induced cardiac necrosis. The large hs-cTnI/hs-cTnT ratio was confirmed in patients with anterior STEMI. CONCLUSION: Both hs-cTnI and hs-cTnT increased similarly after brief periods of ischaemia that did not cause overt necrosis, whereas the hs-cTnI/hs-cTnT ratio tended to increase following longer ischaemia that induced substantial necrosis. A low hs-cTnI/hs-cTnT ratio around 1 may signify non-necrotic cTn release.

Dehydro-Tocotrienol-ß Counteracts Oxidative-Stress-Induced Diabetes Complications in db/db Mice.

Hyperglycemia, hyperlipidemia, and adiposity are the main factors that cause inflammation in type 2 diabetes due to excessive ROS production, leading to late complications. To counteract the effects of increased free radical production, we searched for a compound with effective antioxidant properties that can induce coenzyme Q biosynthesis without affecting normal cellular functions. Tocotrienols are members of the vitamin E family, well-known as efficient antioxidants that are more effective than tocopherols. Deh-T3ß is a modified form of the naturally occurring tocotrienol-ß. The synthesis of this compound involves the sequential modification of geranylgeraniol. In this study, we investigated the effects of this compound in different experimental models of diabetes complications. Deh-T3ß was found to possess multifaceted capacities. In addition to enhanced wound healing, deh-T3ß improved kidney and liver functions, reduced liver steatosis, and improved heart recovery after ischemia and insulin sensitivity in adipose tissue in a mice model of type 2 diabetes. Deh-T3ß exerts these positive effects in several organs of the diabetic mice without reducing the non-fasting blood glucose levels, suggesting that both its antioxidant properties and improvement in mitochondrial function are involved, which are central to reducing diabetes complications.

Hyperglycemia Induces Myocardial Dysfunction via Epigenetic Regulation of JunD.

RATIONALE: Hyperglycemia -induced reactive oxygen species are key mediators of cardiac dysfunction. JunD (Jund proto-oncogene subunit), a member of the AP-1 (activator protein-1) family of transcription factors, is emerging as a major gatekeeper against oxidative stress. However, its contribution to redox state and inflammation in the diabetic heart remains to be elucidated. OBJECTIVE: The present study investigates the role of JunD in hyperglycemia-induced and reactive oxygen species-driven myocardial dysfunction. METHODS AND RESULTS: JunD mRNA and protein expression were reduced in the myocardium of mice with streptozotocin-induced diabetes mellitus as compared to controls. JunD downregulation was associated with oxidative stress and left ventricular dysfunction assessed by electron spin resonance spectroscopy as well as conventional and 2-dimensional speckle-tracking echocardiography. Furthermore, myocardial expression of free radical scavenger superoxide dismutase 1 and aldehyde dehydrogenase 2 was reduced, whereas the NOX2 (NADPH [nicotinamide adenine dinucleotide phosphatase] oxidase subunit 2) and NOX4 (NADPH [nicotinamide adenine dinucleotide phosphatase] oxidase subunit 4) were upregulated. The redox changes were associated with increased NF-κB (nuclear factor kappa B) binding activity and expression of inflammatory mediators. Interestingly, mice with cardiac-specific overexpression of JunD via the α MHC (α- myosin heavy chain) promoter (α MHC JunDtg) were protected against hyperglycemia-induced cardiac dysfunction. We also showed that JunD was epigenetically regulated by promoter hypermethylation, post-translational modification of histone marks, and translational repression by miRNA (microRNA)-673/menin. Reduced JunD mRNA and protein expression were confirmed in left ventricular specimens obtained from patients with type 2 diabetes mellitus as compared to nondiabetic subjects. CONCLUSIONS: Here, we show that a complex epigenetic machinery involving DNA methylation, histone modifications, and microRNAs mediates hyperglycemia-induced JunD downregulation and myocardial dysfunction in experimental and human diabetes mellitus. Our results pave the way for tissue-specific therapeutic modulation of JunD to prevent diabetic cardiomyopathy.

High-intensity interval training modulates retinal microvascular phenotype and DNA methylation of p66Shc gene: a randomized controlled trial (EXAMIN AGE).

AIMS: Impairments of retinal vessel diameter are associated with major adverse cardiovascular (CV) events. Promoter DNA methylation is a repressor of the mitochondrial adaptor p66Shc gene transcription, a key driver of ageing-induced reactive oxygen species. The study aimed to investigate whether high-intensity interval training (HIIT) affects retinal microvascular phenotype as well as p66Shc expression and oxidative stress in ageing subjects with increased CV risk from the EXAMIN AGE cohort. METHODS AND RESULTS: Eighty-four sedentary subjects (mean age 59.4 ± 7.0 years) with ≥2 CV risk factors were randomized into either a 12-week HIIT or standard physical activity recommendations. Retinal arteriolar and venular diameters were measured by use of a retinal vessel analyser. As a marker of oxidative stress plasma 3-nitrotyrosine (3-NT) level was determined by ELISA. Gene expression of p66Shc and DNA methylation were assessed in mononuclear cells by RT-qPCR and methylated-DNA capture (MethylMiner Enrichment Kit) coupled with qPCR, respectively. High-intensity interval training reduced body mass index, fat mass, low-density lipoprotein and increased muscle mass, as well as maximal oxygen uptake (VO2max). Moreover, HIIT restored microvascular phenotype by inducing retinal arteriolar widening (pre: 175 ± 14 µm vs. post: 181 ± 13 µm, P = 0.001) and venular narrowing (pre: 222 ± 14 µm vs. post: 220 ± 14 µm, P = 0.007). After HIIT, restoration of p66Shc promoter methylation (P = 0.034) reduced p66Shc gene expression (P = 0.037) and, in turn, blunted 3-NT plasma levels (P = 0.002). CONCLUSION: High-intensity interval training rescues microvascular dysfunction in ageing subjects at increased CV risk. Exercise-induced reprogramming of DNA methylation of p66Shc gene may represent a putative mechanistic link whereby exercise protects against age-related oxidative stress. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov: NCT02796976 (https://clinicaltrials.gov/ct2/show/NCT02796976).

Physical activity may drive healthy microvascular ageing via downregulation of p66Shc.

BACKGROUND: Narrower retinal arterioles and wider venules are linked to adverse cardiovascular outcomes. The mitochondrial adaptor p66Shc is a major source of ageing-induced generation of reactive oxygen species. Promoter DNA methylation inhibits p66Shc gene transcription. This cross-sectional study was designed to investigate the link between physical activity, retinal vessel diameters and p66Shc expression in active and sedentary ageing subjects. DESIGN/METHODS: Altogether 158 subjects were included in the study (mean age 59.4 ± 7.0 years). Thirty-eight subjects were healthy active, 36 were healthy sedentary and 84 were sedentary with ≥2 cardiovascular risk factors. Retinal arteriolar and venular diameters were measured by means of a retinal vessel analyser. As a marker of oxidative stress, plasma 3-nitrotyrosine was determined by enzyme-linked immunosorbent assay. Gene expression of p66Shc and DNA methylation were assessed in mononuclear cells by real-time quantitative polymerase chain reaction and methylated-DNA capture (MethylMiner Enrichment kit) coupled with quantitative polymerase chain reaction, respectively. RESULTS: Wider retinal arterioles (179 ± 14 vs 172 ± 11 and 171 ± 14 µm; p < 0.05 and narrower venules (204 ± 17 vs 209 ± 11 and 218 ± 16 µm; p < 0.001) were observed in healthy active subjects compared with healthy sedentary subjects and sedentary subjects with ≥2 cardiovascular risk factors, respectively. Furthermore, healthy active subjects had blunted p66Shc expression and lower 3-nitrotyrosine plasma levels compared with healthy sedentary and sedentary subjects with ≥2 cardiovascular risk factors. Accordingly, hypomethylation of p66Shc promoter observed in healthy sedentary and sedentary subjects with ≥2 cardiovascular risk factors was not found in healthy active subjects. CONCLUSION: Long-term physical activity-induced DNA methylation of p66Shc may represent a putative mechanistic link whereby active lifestyle promotes healthy microvascular ageing.

Interplay among H3K9-editing enzymes SUV39H1, JMJD2C and SRC-1 drives p66Shc transcription and vascular oxidative stress in obesity.

Aims: Accumulation of reactive oxygen species (ROS) promotes vascular disease in obesity, but the underlying molecular mechanisms remain poorly understood. The adaptor p66Shc is emerging as a key molecule responsible for ROS generation and vascular damage. This study investigates whether epigenetic regulation of p66Shc contributes to obesity-related vascular disease. Methods and results: ROS-driven endothelial dysfunction was observed in visceral fat arteries (VFAs) isolated from obese subjects when compared with normal weight controls. Gene profiling of chromatin-modifying enzymes in VFA revealed a significant dysregulation of methyltransferase SUV39H1 (fold change, -6.9, P < 0.01), demethylase JMJD2C (fold change, 3.2, P < 0.01), and acetyltransferase SRC-1 (fold change, 5.8, P < 0.01) in obese vs. control VFA. These changes were associated with reduced di-(H3K9me2) and trimethylation (H3K9me3) as well as acetylation (H3K9ac) of histone 3 lysine 9 (H3K9) on p66Shc promoter. Reprogramming SUV39H1, JMJD2C, and SRC-1 in isolated endothelial cells as well as in aortas from obese mice (LepOb/Ob) suppressed p66Shc-derived ROS, restored nitric oxide levels, and rescued endothelial dysfunction. Consistently, in vivo editing of chromatin remodellers blunted obesity-related vascular p66Shc expression. We show that SUV39H1 is the upstream effector orchestrating JMJD2C/SRC-1 recruitment to p66Shc promoter. Indeed, SUV39H1 overexpression in obese mice erased H3K9-related changes on p66Shc promoter, while SUV39H1 genetic deletion in lean mice recapitulated obesity-induced H3K9 remodelling and p66Shc transcription. Conclusion: These results uncover a novel epigenetic mechanism underlying endothelial dysfunction in obesity. Targeting SUV39H1 may attenuate oxidative transcriptional programmes and thus prevent vascular disease in obese individuals.

Hyperglycaemia-induced epigenetic changes drive persistent cardiac dysfunction via the adaptor p66Shc.

AIMS: Hyperglycaemia-induced reactive oxygen species (ROS) are key mediators of cardiac dysfunction. Intensive glycaemic control (IGC) has failed to reduce risk of heart failure in patients with diabetes but the underlying mechanisms remain to be elucidated. The present study investigates whether epigenetic regulation of the pro-oxidant adaptor p66Shc contributes to persistent myocardial dysfunction despite IGC. METHODS AND RESULTS: p66Shc expression was increased in the heart of diabetic mice, and 3-week IGC by slow-release insulin implants did not revert this phenomenon. Sustained p66Shc upregulation was associated with oxidative stress, myocardial inflammation and left ventricular dysfunction, as assessed by conventional and 2D speckle-tracking echocardiography. In vivo gene silencing of p66Shc, performed during IGC, inhibited ROS production and restored cardiac function. Furthermore, we show that dysregulation of methyltransferase DNMT3b and deacetylase SIRT1 causes CpG demethylation and histone 3 acetylation on p66Shc promoter, leading to persistent transcription of the adaptor. Altered DNMT3b/SIRT1 axis in the diabetic heart was explained by upregulation of miR-218 and miR-34a. Indeed, in human cardiomyocytes exposed to high glucose, inhibition of these miRNAs restored the expression of DNMT3b and SIRT1 and erased the adverse epigenetic signatures on p66Shc promoter. Consistently, reprogramming miR-218 and miR-34a attenuated persistent p66Shc expression and ROS generation. CONCLUSIONS: In diabetic left ventricular dysfunction, a complex epigenetic mechanism linking miRNAs and chromatin modifying enzymes drives persistent p66Shc transcription and ROS generation. Our results set the stage for pharmacological targeting of epigenetic networks to alleviate the clinical burden of diabetic cardiomyopathy.

Evidence for cortical neuronal loss in male type 2 diabetic Goto-Kakizaki rats.

Type 2 diabetes (T2D) is strongly associated with early cognitive decline and may facilitate the development of neurodegenerative diseases. Despite the overwhelming amount of indirect evidence pointing toward the presence of cerebral neurodegeneration in T2D, no hard proof of it on histological and quantitative levels exists. This warrants more research to investigate whether T2D can lead to neurodegeneration in the central nervous system and to study the precise nature and temporal dynamics of such changes. We performed a comprehensive quantitative assessment of T2D-induced changes in neuronal and glial numbers in the cerebral cortex using stereological methods. We compared the cellular composition of 3- and 13-month-old male type 2 diabetic Goto-Kakizaki (GK) rat brains. Age and sex-matched Wistar rats served as healthy controls. Our results show a significant decrease in neuron numbers (≈11%) in the cerebral cortex of 13-month-old GK rats compared to young, or Wistar rats, while astroglia numbers were unchanged. We also recorded increased microglia activation in aged diabetic rat brains as indicated by significantly increased average microglia cell volume. Our observations provide quantitative evidence of T2D-induced changes in brain's cellular composition during aging. These findings may facilitate the mechanistic understanding of cognitive dysfunction and other neurodegenerative disorders in T2D.