Search

BACKGROUND: Diabetic cardiomyopathy (DbCM) is characterized by asymptomatic stage B heart failure (SBHF) caused by diabetes-related metabolic alterations. DbCM is associated with an increased risk of progression to overt heart failure (HF). The prevalence of DbCM in patients with type 2 diabetes (T2D) is not well established. This study aims to determine prevalence of DbCM in adult T2D patients in real-world clinical practice. METHODS: Retrospective multi-step review of electronic medical records of patients with the diagnosis of T2D who had echocardiogram at UC San Diego Medical Center (UCSD) within 2010-2019 was conducted to identify T2D patients with SBHF. We defined pure DbCM when SBHF is associated solely with T2D and mixed SBHF when other medical conditions can contribute to SBHF. Pure DbCM was diagnosed in T2D patients with echocardiographic demonstration of SBHF defined as left atrial (LA) enlargement (LAE), as evidenced by LA volume index ≥ 34 mL/m2, in the presence of left ventricular ejection fraction (LVEF) ≥ 45%, while excluding overt HF and comorbidities that can contribute to SBHF. RESULTS: Of 778,314 UCSD patients in 2010-2019, 45,600 (5.9%) had T2D diagnosis. In this group, 15,182 T2D patients (33.3%) had echocardiogram and, among them, 13,680 (90.1%) had LVEF ≥ 45%. Out of 13,680 patients, 4,790 patients had LAE. Of them, 1,070 patients were excluded due to incomplete data and/or a lack of confirmed T2D according to the American Diabetes Association recommendations. Thus, 3,720 T2D patients with LVEF ≥ 45% and LAE were identified, regardless of HF symptoms. In this group, 1,604 patients (43.1%) had overt HF and were excluded. Thus, 2,116 T2D patients (56.9% of T2D patients with LVEF ≥ 45% and LAE) with asymptomatic SBHF were identified. Out of them, 1,773 patients (83.8%) were diagnosed with mixed SBHF due to comorbidities such as hypertension (58%), coronary artery disease (36%), and valvular heart disease (17%). Finally, 343 patients met the diagnostic criteria of pure DbCM, which represents 16.2% of T2D patients with SBHF, i.e., at least 2.9% of the entire T2D population in this study. CONCLUSIONS: Our findings provide insights into prevalence of DbCM in real-world clinical practice and indicate that DbCM affects a significant portion of T2D patients.

Background Diabetes-induced cardiac fibrosis is one of the main mechanisms of diabetic cardiomyopathy. As a common histone methyltransferase, enhancer of zeste homolog 2 (EZH2) has been implicated in fibrosis progression in multiple organs. However, the mechanism of EZH2 in diabetic myocardial fibrosis has not been clarified. Methods In the current study, rat and mouse diabetic model were established, the left ventricular function of rat and mouse were evaluated by echocardiography and the fibrosis of rat ventricle was evaluated by Masson staining. Primary rat ventricular fibroblasts were cultured and stimulated with high glucose (HG) in vitro. The expression of histone H3 lysine 27 (H3K27) trimethylation, EZH2, and myocardial fibrosis proteins were assayed. Results In STZ-induced diabetic ventricular tissues and HG-induced primary ventricular fibroblasts in vitro, H3K27 trimethylation was increased and the phosphorylation of EZH2 was reduced. Inhibition of EZH2 with GSK126 suppressed the activation, differentiation, and migration of cardiac fibroblasts as well as the overexpression of the fibrotic proteins induced by HG. Mechanical study demonstrated that HG reduced phosphorylation of EZH2 on Thr311 by inactivating AMP-activated protein kinase (AMPK), which transcriptionally inhibited peroxisome proliferator-activated receptor γ (PPAR-γ) expression to promote the fibroblasts activation and differentiation. Conclusion Our data revealed an AMPK/EZH2/PPAR-γ signal pathway is involved in HG-induced cardiac fibrosis.

Background: Diabetes-induced cardiac fibrosis is one of the main mechanisms of diabetic cardiomyopathy. As a common histone methyltransferase, enhancer of zeste homolog 2 (EZH2) has been implicated in fibrosis progression in multiple organs. However, the mechanism of EZH2 in diabetic myocardial fibrosis has not been clarified. Methods: In the current study, rat and mouse diabetic model were established, the left ventricular function of rat and mouse were evaluated by echocardiography and the fibrosis of rat ventricle was evaluated by Masson staining. Primary rat ventricular fibroblasts were cultured and stimulated with high glucose (HG) in vitro. The expression of histone H3 lysine 27 (H3K27) trimethylation, EZH2, and myocardial fibrosis proteins were assayed. Results: In STZ-induced diabetic ventricular tissues and HG-induced primary ventricular fibroblasts in vitro, H3K27 trimethylation was increased and the phosphorylation of EZH2 was reduced. Inhibition of EZH2 with GSK126 suppressed the activation, differentiation, and migration of cardiac fibroblasts as well as the overexpression of the fibrotic proteins induced by HG. Mechanical study demonstrated that HG reduced phosphorylation of EZH2 on Thr311 by inactivating AMP-activated protein kinase (AMPK), which transcriptionally inhibited peroxisome proliferator-activated receptor γ (PPAR-γ) expression to promote the fibroblasts activation and differentiation. Conclusion: Our data revealed an AMPK/EZH2/PPAR-γ signal pathway is involved in HG-induced cardiac fibrosis. [ABSTRACT FROM AUTHOR]

Heart disease is a worldwide health menace. Both intractable primary and secondary cardiomyopathies contribute to malignant cardiac dysfunction and mortality. One of the key cellular processes associated with cardiomyopathy is cardiomyocyte death. Cardiomyocytes are terminally differentiated cells with very limited regenerative capacity. Various insults can lead to irreversible damage of cardiomyocytes, contributing to progression of cardiac dysfunction. Accumulating evidence indicates that majority of cardiomyocyte death is executed by regulating molecular pathways, including apoptosis, ferroptosis, autophagy, pyroptosis, and necroptosis. Importantly, these forms of regulated cell death (RCD) are cardinal features in the pathogenesis of various cardiomyopathies, including dilated cardiomyopathy, diabetic cardiomyopathy, sepsis-induced cardiomyopathy, and drug-induced cardiomyopathy. The relevance between abnormity of RCD with adverse outcome of cardiomyopathy has been unequivocally evident. Therefore, there is an urgent need to uncover the molecular and cellular mechanisms for RCD in order to better understand the pathogenesis of cardiomyopathies. In this review, we summarize the latest progress from studies on RCD pathways in cardiomyocytes in context of the pathogenesis of cardiomyopathies, with particular emphasis on apoptosis, necroptosis, ferroptosis, autophagy, and pyroptosis. We also elaborate the crosstalk among various forms of RCD in pathologically stressed myocardium and the prospects of therapeutic applications targeted to various cell death pathways.

Diabetic cardiomyopathy (DCM) is a complication of type 2 diabetes mellitus (T2DM) capable of progressing to the development of symptomatic heart failure (HF), independently of traditional risk factors for it, such as coronary artery disease and hypertension. There is no specific treatment for DCM; however, sodium-glucose cotransporter 2 inhibitors (SGLT2i) are hypoglycemic drugs that act on SGLT2 channels, inhibiting glucose reabsorption in the kidney. In addition, they have cardioprotective effects, which is why their mechanisms at the cardiac level have been studied. According to the results of preclinical studies, SGLT2i act by interfering in the pathophysiology of DCM. Their main effects are: improvement in diastolic function and left ventricular ejection fraction (LVEF), attenuation in the progress of cardiac fibrosis, reduction of oxidative stress and proinflammatory markers. The clinical trials in humans specifically with DCM that have been carried out are limited; however, randomized clinical trials in patients with HF have shown benefits with SGLT2i, regardless of glycemic control in the reduction of hospitalization for HF and mortality from cardiovascular causes. In summary, SGLT2i suggest a treatment in DCM due to their cardiovascular benefits, in preclinical and clinical models of DCM and in the glycemic control of T2DM. [ABSTRACT FROM AUTHOR]

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. [ABSTRACT FROM AUTHOR]

Diabetic cardiomyopathy (DCM) is one of the most serious cardiovascular complications in diabetic patients, and it is also the main cause of increased mortality in diabetic patients, which has become a major global public health problem. As an important intracellular regulatory protein in body, sirtuin 1 (SIRT1) plays an important role in many biological processes, including reducing oxidative stress in cardiomyocytes, maintaining Ca2+ homeostasis in myocardial mitochondria, reducing myocardial endoplasmic reticulum stress, improving myocardial mitochondrial dysfunction, and inhibiting the activation of renin-angiotensin-aldosterone system. SIRT1 may be a potential therapeutic target for DCM. Further research targeting SIRT1 can provide a new theoretical basis for the clinical treatment of DCM. This article reviews the specific role of SIRT1 in the pathogenesis and treatment strategies of DCM. [ABSTRACT FROM AUTHOR]

Abstract Diabetic cardiomyopathy (DCM) is a significant cause of heart failure in patients with diabetes, and its pathogenesis is closely related to myocardial mitochondrial injury and functional disability. Studies have shown that the development of diabetic cardiomyopathy is related to disorders in mitochondrial metabolic substrates, changes in mitochondrial dynamics, an imbalance in mitochondrial Ca2+ regulation, defects in the regulation of microRNAs, and mitochondrial oxidative stress. Physical activity may play a role in resistance to the development of diabetic cardiomyopathy by improving myocardial mitochondrial biogenesis, the level of autophagy and dynamic changes in fusion and division; enhancing the ability to cope with oxidative stress; and optimising the metabolic substrates of the myocardium. This paper puts forward a new idea for further understanding the specific mitochondrial mechanism of the occurrence and development of diabetic cardiomyopathy and clarifying the role of exercise‐mediated myocardial mitochondrial changes in the prevention and treatment of diabetic cardiomyopathy. This is expected to provide a new theoretical basis for exercise to reduce diabetic cardiomyopathy symptoms.

Insulin resistance has been regarded as a hallmark of diabetes heart disease (DHD). Numerous studies have shown that insulin resistance can affect blood circulation and myocardium, which indirectly cause cardiac hypertrophy and ventricular remodeling, participating in the pathogenesis of DHD. Meanwhile, hyperinsulinemia, hyperglycemia, and hyperlipidemia associated with insulin resistance can directly impair the metabolism and function of the heart. Targeting insulin resistance is a potential therapeutic strategy for the prevention of DHD. Currently, the role of insulin resistance in the pathogenic development of DHD is still under active research, as the pathological roles involved are complex and not yet fully understood, and the related therapeutic approaches are not well developed. In this review, we describe insulin resistance and add recent advances in the major pathological and physiological changes and underlying mechanisms by which insulin resistance leads to myocardial remodeling and dysfunction in the diabetic heart, including exosomal dysfunction, ferroptosis, and epigenetic factors. In addition, we discuss potential therapeutic approaches to improve insulin resistance and accelerate the development of cardiovascular protection drugs.

BACKGROUND: The majority of people with diabetes are susceptible to cardiac dysfunction and heart failure, and conventional drug therapy cannot correct diabetic cardiomyopathy progression. Herein, we assessed the potential role and therapeutic value of USP28 (ubiquitin-specific protease 28) on the metabolic vulnerability of diabetic cardiomyopathy. METHODS: The type 2 diabetes mouse model was established using db/db leptin receptor–deficient mice and high-fat diet/streptozotocin–induced mice. Cardiac-specific knockout of USP28 in the db/db background mice was generated by crossbreeding db/m and Myh6-Cre+/USP28fl/fl mice. Recombinant adeno-associated virus serotype 9 carrying USP28 under cardiac troponin T promoter was injected into db/db mice. High glucose plus palmitic acid–incubated neonatal rat ventricular myocytes and human induced pluripotent stem cell-derived cardiomyocytes were used to imitate diabetic cardiomyopathy in vitro. The molecular mechanism was explored through RNA sequencing, immunoprecipitation and mass spectrometry analysis, protein pull-down, chromatin immunoprecipitation sequencing, and chromatin immunoprecipitation assay. RESULTS: Microarray profiling of the UPS (ubiquitin-proteasome system) on the basis of db/db mouse hearts and diabetic patients' hearts demonstrated that the diabetic ventricle presented a significant reduction in USP28 expression. Diabetic Myh6-Cre+/USP28fl/fl mice exhibited more severe progressive cardiac dysfunction, lipid accumulation, and mitochondrial disarrangement, compared with their controls. On the other hand, USP28 overexpression improved systolic and diastolic dysfunction and ameliorated cardiac hypertrophy and fibrosis in the diabetic heart. Adeno-associated virus serotype 9-USP28 diabetic mice also exhibited less lipid storage, reduced reactive oxygen species formation, and mitochondrial impairment in heart tissues than adeno-associated virus serotype 9-null diabetic mice. As a result, USP28 overexpression attenuated cardiac remodeling and dysfunction, lipid accumulation, and mitochondrial impairment in high-fat diet/streptozotocin–induced type 2 diabetes mice. These results were also confirmed in neonatal rat ventricular myocytes and human induced pluripotent stem cell–derived cardiomyocytes. RNA sequencing, immunoprecipitation and mass spectrometry analysis, chromatin immunoprecipitation assays, chromatin immunoprecipitation sequencing, and protein pull-down assay mechanistically revealed that USP28 directly interacted with PPARα (peroxisome proliferator–activated receptor α), deubiquitinating and stabilizing PPARα (Lys152) to promote Mfn2 (mitofusin 2) transcription, thereby impeding mitochondrial morphofunctional defects. However, such cardioprotective benefits of USP28 were largely abrogated in db/db mice with PPARα deletion and conditional loss-of-function of Mfn2. CONCLUSIONS: Our findings provide a USP28-modulated mitochondria homeostasis mechanism that involves the PPARα-Mfn2 axis in diabetic hearts, suggesting that USP28 activation or adeno-associated virus therapy targeting USP28 represents a potential therapeutic strategy for diabetic cardiomyopathy. [ABSTRACT FROM AUTHOR]

Diabetic cardiomyopathy (DCM) is a significant cause of heart failure in patients with diabetes, and its pathogenesis is closely related to myocardial mitochondrial injury and functional disability. Studies have shown that the development of diabetic cardiomyopathy is related to disorders in mitochondrial metabolic substrates, changes in mitochondrial dynamics, an imbalance in mitochondrial Ca2+ regulation, defects in the regulation of microRNAs, and mitochondrial oxidative stress. Physical activity may play a role in resistance to the development of diabetic cardiomyopathy by improving myocardial mitochondrial biogenesis, the level of autophagy and dynamic changes in fusion and division; enhancing the ability to cope with oxidative stress; and optimising the metabolic substrates of the myocardium. This paper puts forward a new idea for further understanding the specific mitochondrial mechanism of the occurrence and development of diabetic cardiomyopathy and clarifying the role of exercise‐mediated myocardial mitochondrial changes in the prevention and treatment of diabetic cardiomyopathy. This is expected to provide a new theoretical basis for exercise to reduce diabetic cardiomyopathy symptoms. What is the topic of this review?The mechanism of exercise decrease diabetic cardiomyopathy by improving the mitochondrial homeostasis of the myocardium, and new insights for the treatment of diabetic cardiomyopathy with exercise.What advances does it highlight?Mitochondrial dysfunction induced by a high‐glucose environment is one of the main causes of diabetic cardiomyopathy. The mitochondrial mechanism is mainly mitochondrial metabolic substrate disorder, mitochondrial dynamics change, mitochondrial Ca2+ regulation imbalance, and so on. Exercise can improve the function of myocardial mitochondria in multiple ways, so as to achieve the effect of decreasing diabetic cardiomyopathy. [ABSTRACT FROM AUTHOR]

BACKGROUND: Diabetes is an important risk factor for heart failure (HF) and is associated with left ventricular (LV) diastolic dysfunction. However, diabetic comorbid conditions, such as nocturnal hypertension, as predictors of diastolic dysfunction are not known in the absence of an HF period. The present study was conducted as the longitudinal examination of the predictive value of nocturnal hypertension profiles on the progression of LV diastolic dysfunction in patients with and without diabetes without HF. METHODS: The subjects (154 diabetes and 268 nondiabetes) in the absence of HF were followed for 36.8±18.2 months. The relationships among the patterns of nocturnal hypertension and the outcome of LV diastolic dysfunction, defined as an increase in E/e'>14, were investigated in the patients with and without diabetes. RESULTS: The interaction effect of the diabetes status and the patterns of nocturnal hypertension on the hazard rate of the occurrence of E/e'>14 was statistically significant (P=0.017). Kaplan-Meier analysis results revealed that patients with diabetes with nondipper (P=0.021 versus dipper) and riser (P=0.006 versus dipper) had a greater risk for a diastolic dysfunction event. Furthermore, multivariable Cox proportional hazards analysis revealed that nondipper (hazard ratio, 4.56 [95% CI, 1.49-13.96]; P=0.007) and riser (hazard ratio, 3.89 [95% CI, 1.31-11.57]; P=0.014) patterns were associated with elevated risk of the outcome of LV diastolic dysfunction. In contrast, no similar significant associations were found in patients without diabetes. CONCLUSIONS: During the absence of HF periods, nocturnal hypertension is an important predictor for the progression of LV diastolic dysfunction in patients with diabetes. [ABSTRACT FROM AUTHOR]

Diabetic cardiomyopathy is a serious complication of diabetes mellitus (DM). Aim. Therefore, we aimed to study myocardial changes in adult rats with streptozotocin (STZ)-induced DM exposed to chronic immobilization stress (CIS). Materials and methods. A total of 26 adult albino male rats weighing 180–200 g were examined. All the animals were divided into three groups: Group I included 10 rats with STZ-induced DM exposed to CIS; Group II comprised 10 rats with STZ-induced DM; Group III included 6 intact animals. The samples were collected on the 14th and 56th days of the experiment. Histological, histochemical, electron microscopy, and biochemical methods were used. Results. On the 14th day of the experiment, in Group I and Group II, increased blood flow was observed in the capillaries, venules, and veins, while an arteriolar spasm in the microcirculation was found. In addition, cardiomyocyte surface area in different myocardial regions reduced due to low glycogen content as confirmed by histochemical and ultrastructural studies. On the 56th day of the experiment, in Group I and Group II, hyperemia occurred due to red blood cell aggregation and microthrombi. The surface area of all microcirculatory vessels increased as compared to that of intact animals, as evidenced by an increase in their wall surface area leading to an increase in their wall-to-lumen ratio. Such morphometric changes in the microcirculatory vessels were indicative of decreased vascular permeability and impaired myocardial blood flow. At the histological level, in Group I and Group II, focal cardiomyocyte lysis, moderate to diffuse stromal edema, lymphohistiocytic infiltration were seen. Such changes pointed to sterile inflammation, probably due to myocardial infraction secondary to diabetic microangiopathy. In cardiomyocytes, karyolysis, vacuolar degeneration, apical ballooning, subsarcolemmic edema, fibrosis and lysis of myofibrils, colliquative necrosis were observed. Conclusions. STZ-induced DM and stress resulted in pronounced destructive changes in the myocardium of rats, including interstitial edema, focal cardiosclerosis, myolysis. Such changes occurred on the background developing diabetic microangiopathy. The most pronounced myocardial changes were recorded in animals with a comorbidity.

Diabetes mellitus is the most common metabolic disorder during pregnancy. The International Diabetes Federation estimates that one in six pregnant women (16.8 %) has diabetes. The prevalence of this disease in the human population is striking and, according to various sources, accounts for 14–25 % of all pregnant women. Most cases of hyperglycemia during pregnancy (75–90 %) is due to gestational diabetes mellitus (GDM). Risk factors, etiology and pathophysiology of GDM are being actively studied, but there are still some controversial issues. For example, the development of GDM in the aspect of circadian rhythm disorders. This problem is especially relevant in connection with pregnancy. After all, there is a two-way relationship here – circadian rhythm disorders affect the course of pregnancy, and pregnancy can be the cause of these disorders. In addition, this problem is relevant for women with a history of endocrine disorders, including diabetes mellitus, as there is a clear link between circadian rhythms and the production of hormones, including insulin. The aim of this review was to show the relationship between the development of GDM, its complications, and circadian rhythm disorders in women. Pregnancy complicated by GDM can have a negative effect on the myocardium and liver. Moreover, this disease has a significant impact on the myocardium of the offspring. GDM also can cause other complications for the mother’s health and fetus or newborn. Scientists have identified a fairly significant number of risk factors for GDM. However, circadian rhythm disorders accompanying pregnancy are often underestimated as a risk factor. In general, there are many controversies regarding the relationship between long / short sleep duration and quality and the risk of developing diabetes, as well as how melatonin and its precursor serotonin affect metabolism in critical organs. Thus, the role of circadian rhythm disorders in the development of diabetes and its consequences is not yet fully understood. It is likely that solving the problem of circadian rhythm disorders will be the key to overcoming a significant proportion of cases of GDM. Therefore, there is an urgent need for further, larger-scale studies to investigate the causal links between circadian rhythm disorders, diabetes mellitus, and pregnancy.

Background Diabetes mellitus is one of the most common chronic diseases worldwide, and cardiovascular disease is the leading cause of morbidity and mortality in diabetic patients. Diabetic cardiomyopathy (DCM) is a phenomenon characterized by a deterioration in cardiac function and structure, independent of vascular complications. Among many possible causes, the renin-angiotensin-aldosterone system and angiotensin II have been proposed as major drivers of DCM development. In the current study, we aimed to investigate the effects of pharmacological activation of angiotensin-converting enzyme 2 (ACE2) on DCM. Methods The ACE2 activator diminazene aceturate (DIZE) was administered intraperitoneally to male db/db mice (8 weeks old) for 8 weeks. Transthoracic echocardiography was used to assess cardiac mass and function in mice. Cardiac structure and fibrotic changes were examined using histology and immunohistochemistry. Gene and protein expression levels were examined using quantitative reverse transcription polymerase chain reaction and Western blotting, respectively. Additionally, RNA sequencing was performed to investigate the underlying mechanisms of the effects of DIZE and identify novel potential therapeutic targets for DCM. Results Echocardiography revealed that in DCM, the administration of DIZE significantly improved cardiac function as well as reduced cardiac hypertrophy and fibrosis. Transcriptome analysis revealed that DIZE treatment suppresses oxidative stress and several pathways related to cardiac hypertrophy. Conclusion DIZE prevented the diabetes mellitus-mediated structural and functional deterioration of mouse hearts. Our findings suggest that the pharmacological activation of ACE2 could be a novel treatment strategy for DCM.

Allopurinol (ALP) attenuates oxidative stress and diabetic cardiomyopathy (DCM), but the mechanism is unclear. Activation of nuclear factor erythroid 2-related factor 2 (Nrf2) following the disassociation with its repressor Keap1 under oxidative stress can maintain inner redox homeostasis and attenuate DCM with concomitant attenuation of autophagy. We postulated that ALP treatment may activate Nrf2 to mitigate autophagy over-activation and consequently attenuate DCM. Streptozotocin-induced type 1 diabetic rats were untreated or treated with ALP (100 mg/kg/d) for 4 weeks and terminated after heart function measurements by echocardiography and pressure-volume conductance system. Cardiomyocyte H9C2 cells infected with Nrf2 siRNA or not were incubated with high glucose (HG, 25 mmol/L) concomitantly with ALP treatment. Cell viability, lactate dehydrogenase, 15-F2t-Isoprostane and superoxide dismutase (SOD) were measured with colorimetric enzyme-linked immunosorbent assays. ROS, apoptosis, was assessed by dihydroethidium staining and TUNEL, respectively. The Western blot and qRT-PCR were used to assess protein and mRNA variations. Diabetic rats showed significant reductions in heart rate (HR), left ventricular eject fraction (LVEF), stroke work (SW) and cardiac output (CO), left ventricular end-systolic volume (LVVs) as compared to non-diabetic control and ALP improved or normalized HR, LVEF, SW, CO and LVVs in diabetic rats (all P

RATIONALE:Diabetes mellitus is often associated with cardiovascular complications, which is the leading cause of morbidity and mortality among patients with diabetes mellitus, but little is known about the mechanism that connects diabetes mellitus to the development of cardiovascular dysfunction. OBJECTIVE:We aim to elucidate the mechanism underlying hyperglycemia-induced cardiac dysfunction on a well-established db/db mouse model for diabetes mellitus and diabetic complications that lead to heart failure. METHODS AND RESULTS:We first profiled the expression of microRNAs (miRNAs) by microarray and quantitative reverse transcription polymerase chain reaction on db/db mice and identified miR-320 as a key miRNA associated with the disease phenotype. We next established the clinical relevance of this finding by showing the upregulation of the same miRNA in the failing heart of patients with diabetes mellitus. We demonstrated the causal role of miR-320 in inducing diabetic cardiomyopathy, showing that miR-320 overexpression exacerbated while its inhibition improved the cardiac phenotype in db/db mice. Unexpectedly, we found that miR-320 acts as a small activating RNA in the nucleus at the level of transcription. By chromatin immunoprecipitation sequencing and chromatin immunoprecipitation quantitive polymerase chain reaction analysis of Ago2 (argonaute RISC catalytic component 2) and RNA polymerase II in response to miR-320 induction, we identified CD36 (fatty acid translocase) as a key target gene for this miRNA and showed that the induced expression of CD36 is responsible for increased fatty acid uptake, thereby causing lipotoxicity in the heart. CONCLUSIONS:These findings uncover a novel mechanism for diabetes mellitus-triggered cardiac dysfunction, provide an endogenous case for small activating RNA that has been demonstrated to date only with synthetic RNAs in transfected cells, and suggest a potential strategy to develop a miRNA-based therapy to treat diabetes mellitus-associated cardiovascular complications.

Diabetes mellitus is the most common metabolic disorder during pregnancy. The International Diabetes Federation estimates that one in six pregnant women (16.8 %) has diabetes. The prevalence of this disease in the human population is striking and, according to various sources, accounts for 14-25 % of all pregnant women. Most cases of hyperglycemia during pregnancy (75-90 %) is due to gestational diabetes mellitus (GDM). Risk factors, etiology and pathophysiology of GDM are being actively studied, but there are still some controversial issues. For example, the development of GDM in the aspect of circadian rhythm disorders. This problem is especially relevant in connection with pregnancy. After all, there is a two-way relationship here - circadian rhythm disorders affect the course of pregnancy, and pregnancy can be the cause of these disorders. In addition, this problem is relevant for women with a history of endocrine disorders, including diabetes mellitus, as there is a clear link between circadian rhythms and the production of hormones, including insulin. The aim of this review was to show the relationship between the development of GDM, its complications, and circadian rhythm disorders in women. Pregnancy complicated by GDM can have a negative effect on the myocardium and liver. Moreover, this disease has a significant impact on the myocardium of the offspring. GDM also can cause other complications for the mother's health and fetus or newborn. Scientists have identified a fairly significant number of risk factors for GDM. However, circadian rhythm disorders accompanying pregnancy are often underestimated as a risk factor. In general, there are many controversies regarding the relationship between long / short sleep duration and quality and the risk of developing diabetes, as well as how melatonin and its precursor serotonin affect metabolism in critical organs. Thus, the role of circadian rhythm disorders in the development of diabetes and its consequences is not yet fully understood. It is likely that solving the problem of circadian rhythm disorders will be the key to overcoming a significant proportion of cases of GDM. Therefore, there is an urgent need for further, larger-scale studies to investigate the causal links between circadian rhythm disorders, diabetes mellitus, and pregnancy. [ABSTRACT FROM AUTHOR]

Diabetic cardiomyopathy is a serious complication of diabetes mellitus (DM). Aim. Therefore, we aimed to study myocardial changes in adult rats with streptozotocin (STZ)-induced DM exposed to chronic immobilization stress (CIS). Materials and methods. A total of 26 adult albino male rats weighing 180-200 g were examined. All the animals were divided into three groups: Group I included 10 rats with STZ-induced DM exposed to CIS; Group II comprised 10 rats with STZ-induced DM; Group III included 6 intact animals. The samples were collected on the 14th and 56th days of the experiment. Histological, histochemical, electron microscopy, and biochemical methods were used. Results. On the 14th day of the experiment, in Group I and Group II, increased blood flow was observed in the capillaries, venules, and veins, while an arteriolar spasm in the microcirculation was found. In addition, cardiomyocyte surface area in different myocardial regions reduced due to low glycogen content as confirmed by histochemical and ultrastructural studies. On the 56th day of the experiment, in Group I and Group II, hyperemia occurred due to red blood cell aggregation and microthrombi. The surface area of all microcirculatory vessels increased as compared to that of intact animals, as evidenced by an increase in their wall surface area leading to an increase in their wall-to-lumen ratio. Such morphometric changes in the microcirculatory vessels were indicative of decreased vascular permeability and impaired myocardial blood flow. At the histological level, in Group I and Group II, focal cardiomyocyte lysis, moderate to diffuse stromal edema, lymphohistiocytic infiltration were seen. Such changes pointed to sterile inflammation, probably due to myocardial infraction secondary to diabetic microangiopathy. In cardiomyocytes, karyolysis, vacuolar degeneration, apical ballooning, subsarcolemmic edema, fibrosis and lysis of myofibrils, colliquative necrosis were observed. Conclusions. STZ-induced DM and stress resulted in pronounced destructive changes in the myocardium of rats, including interstitial edema, focal cardiosclerosis, myolysis. Such changes occurred on the background developing diabetic microangiopathy. The most pronounced myocardial changes were recorded in animals with a comorbidity. [ABSTRACT FROM AUTHOR]

The present study investigated the effect of concurrent or aerobic training on middle-aged patients with T2DM. For this, 36 participants (24 women, 54.6±6.9 yrs.) completed a 12-week intervention program in the following groups: control (CON; n=12), concurrent training (CROS; n=12), and aerobic training (AER; n=12). Body mass, glycosylated hemoglobin (HbA1c), total cholesterol and fractions, rate-pressure product, walking speed test and cardiovascular risk were measured before and after the intervention. The main results indicated that after 12 weeks, the trained groups presented lower rate-pressure product in comparison to the pre-intervention means (α=-544.0 for CROS and α=-998.0mmHg.bpm for AER, p≤0.043). The CROS presented a lower mean for HbA1c (6.8±1.7, 5.2±1.3, 7.8±1.6%, for CON, CROS and AER, respectively; p≤0.049) and total cholesterol (171.8±43.3, 155.2±30.7 and 272.8±24.0 mg/dL, for CON, CROS and AER, respectively; p=0.001) compared to the other groups at the post-intervention moment. The CROS showed a significant difference for low density lipoprotein (LDL) at the post-intervention compared to the pre-intervention moment (α=-20.3 mg/dL, p≤0.001). The AER showed a higher mean for the Walking speed test compared to the other groups (420.2±37.5, 502.4±28.5 and 626.7±39.9 meters, for CON, CROS and AER, respectively; p≤0.001) at the post-intervention moment. In conclusion, the present evidence allows us to conclude that the AER and CROS interventions provide metabolic and cardiovascular improvements after 12 weeks in middle-aged T2DM for both genders. The AER group showed a better response in the rate-pressure product and walking-speed test, whereas the CROS presented a better response to HbA1c, total cholesterol and LDL. [ABSTRACT FROM AUTHOR]

Background In murine heart failure models and in humans with diabetic-related heart hypertrophy, inhibition of phosphodiesterase 5 (PDE5) by sildenafil improves cardiac outcomes. However, the mechanism by which sildenafil improves cardiac function is unclear. We have observed a relationship between PDE5 and β2 adrenergic receptor (β2AR), which is characterized here as a novel mechanistic axis by which sildenafil improves symptoms of diabetic cardiomyopathy. Methods and Results Wild-type and β2AR knockout mice fed a high fat diet (HFD) were treated with sildenafil, and echocardiogram analysis was performed. Cardiomyocytes were isolated for excitation-contraction (E-C) coupling, fluorescence resonant energy transfer, and proximity ligation assays; while heart tissues were implemented for biochemical and histological analyses. PDE5 selectively associates with β2AR, but not β1 adrenergic receptor, and inhibition of PDE5 with sildenafil restores the impaired response to adrenergic stimulation in HFD mice and isolated ventriculomyocytes. Sildenafil enhances β adrenergic receptor (βAR)-stimulated cGMP and cAMP signals in HFD myocytes. Consequently, inhibition of PDE5 leads to protein kinase G-, and to a lesser extent, calcium/calmodulin-dependent kinase II-dependent improvements in adrenergically stimulated E-C coupling. Deletion of β2AR abolishes sildenafil's effect. Although the PDE5-β2AR association is not altered in HFD, phosphodiesterase 3 displays an increased association with the β2AR-PDE5 complex in HFD myocytes. Conclusions This study elucidates mechanisms by which the β2AR-PDE5 axis can be targeted for treating diabetic cardiomyopathy. Inhibition of PDE5 enhances β2AR stimulation of cGMP and cAMP signals, as well as protein kinase G-dependent E-C coupling in HFD myocytes.

Background: Diabetic heart dysfunction is a common complication of diabetes. Cell death is a core event that leads to diabetic heart dysfunction. However, the time sequence of cell death pathways and the precise time to intervene of particular cell death type remain largely unknown in the diabetic heart. This study aims to identify the particular cell death type that is responsible for diabetic heart dysfunction and to propose a promising therapeutic strategy by intervening in the cell death pathway.Methods: Type 2 diabetes models were established using db/db leptin receptor-deficient mice and high-fat diet/streptozotocin-induced mice. The type 1 diabetes model was established in streptozotocin-induced mice. Apoptosis and programmed cell necrosis (necroptosis) were detected in diabetic mouse hearts at different ages. G protein-coupled receptor-targeted drug library was searched to identify potential receptors regulating the key cell death pathway. Pharmacological and genetic approaches that modulate the expression of targets were used. Stable cell lines and a homemade phosphorylation antibody were prepared to conduct mechanistic studies.Results: Necroptosis was activated after apoptosis at later stages of diabetes and was functionally responsible for cardiac dysfunction. Cannabinoid receptor 2 (CB2R) was a key regulator of necroptosis. Mechanically, during normal glucose levels, CB2R inhibited S6 kinase-mediated phosphorylation of BACH2 at serine 520, thereby leading to BACH2 translocation to the nucleus, where BACH2 transcriptionally repressed the necroptosis genes Rip1, Rip3, and Mlkl. Under hyperglycemic conditions, high glucose induced CB2R internalization in a β-arrestin 2-dependent manner; thereafter, MLKL (mixed lineage kinase domain-like), but not receptor-interacting protein kinase 1 or 3, phosphorylated CB2R at serine 352 and promoted CB2R degradation by ubiquitin modification. Cardiac re-expression of CB2R rescued diabetes-induced cardiomyocyte necroptosis and heart dysfunction, whereas cardiac knockout of Bach2 diminished CB2R-mediated beneficial effects. In human diabetic hearts, both CB2R and BACH2 were negatively associated with diabetes-induced myocardial injuries.Conclusions: CB2R transcriptionally repressed necroptosis through interaction with BACH2; in turn, MLKL formed a negative feedback to phosphorylate CB2R. Our study provides the integrative view of a novel molecular mechanism loop for regulation of necroptosis centered by CB2R, which represents a promising alternative strategy for controlling diabetic heart dysfunction. [ABSTRACT FROM AUTHOR]

BackgroundType 2 resistant starch (RS2) has been shown to improve glycemic control and some cardiovascular endpoints in rodent and human studies.ObjectiveThe aim of this study was to perform one of the first randomized clinical trials in adults with prediabetes and one of the longest trials to test whether RS2 can improve cardiometabolic health.Design68 overweight [body mass index (BMI) ≥27 kg/m2] adults aged 35-75 y with prediabetes were randomized to consume 45 g/d of high-amylose maize (RS2) or an isocaloric amount of the rapidly digestible starch amylopectin (control) for 12 wk. At baseline and postintervention, ectopic fat depots (visceral adipose tissue, intrahepatic lipids, and intramyocellular lipids) were measured by magnetic resonance imaging/spectroscopy, energy metabolism by respiratory chamber, and carbohydrate metabolism by glycated hemoglobin (HbA1c), an intravenous glucose tolerance test, and a meal tolerance test. Cardiovascular risk factors-serum lipids, blood pressure, heart rate, and inflammatory markers (high-sensitivity C-reactive protein [hs-CRP], interleukin-6, and tumor necrosis factor [TNF]-α)-were also measured. The primary endpoints were insulin sensitivity, insulin secretion, ectopic fat, and markers of inflammation. Data were primarily analyzed as treatment effects via a linear mixed model both with and without the addition of covariates.ResultsRelative to the control group, RS2 lowered HbA1c by a clinically insignificant 0.1 ± 0.2% (Δ = -1 ± 2 mmol/mol; P = 0.05) but did not affect insulin secretion, insulin sensitivity, the disposition index, or glucose or insulin areas under the curve relative to baseline (P ≥ 0.23). RS2 decreased heart rate by 5 ± 9 beats/min (P = 0.02) and TNF-α concentrations by 2.1 ± 2.7 pg/mL (P = 0.004), relative to the control group. Ectopic fat, energy expenditure, substrate oxidation, and all other cardiovascular risk factors were unaffected (P ≥ 0.06).Conclusions12 wk of supplementation with resistant starch reduced the inflammatory marker TNF-α and heart rate, but it did not significantly improve glycemic control and other cardiovascular disease risk factors, in adults with prediabetes. This trial was registered at clinicaltrials.gov as NCT01708694.

Amylin is a pancreatic β-cell hormone co-secreted with insulin, plays a role in normal glucose homeostasis, and forms amyloid in the pancreatic islets of individuals with type-2 diabetes. Aggregated amylin is also found in blood and extra-pancreatic tissues, including myocardium. Myocardial amylin accumulation is associated with myocyte Ca2+ dysregulation in diabetic rats expressing human amylin. Whether deposition of amylin in the heart is a consequence of or a contributor to diabetic cardiomyopathy remains unknown. We used amylin knockout (AKO) mice intravenously infused with either human amylin (i.e, the aggregated form) or non-amyloidogenic (i.e., monomeric) rodent amylin to test the hypothesis that aggregated amylin accumulates in the heart in the absence of diabetes. AKO mice infused with human amylin, but not rodent amylin, showed amylin deposits in the myocardium. Cardiac amylin level was larger in males compared to females. Sarcolemmal Ca2+ leak and Ca2+ transients were increased in myocytes isolated from males infused with human amylin while no significant changes occurred in either females injected with human amylin or in rat amylin-infused mice. In isolated cardiac myocytes, the amylin receptor antagonist AC-187 did not effectively block the interaction of amylin with the sarcolemma. In conclusion, circulating aggregated amylin accumulates preferentially in male vs. female hearts and its effects on myocyte Ca2+ cycling do not require diabetic remodeling of the myocardium. This article is part of a Special issue entitled Cardiac adaptations to obesity, diabetes and insulin resistance, edited by Professors Jan F.C. Glatz, Jason R.B. Dyck and Christine Des Rosiers.

T his study intended to explore the hypoglycemic and cardioprotective effects of 8-week aerobic interval training combined with liraglutide and elucidate the underlying mechanisms. Male Wistar rats were randomly divided into 5 groups - normal control group (CON), diabetic cardiomyopathy group (DCM), high-dose liraglutide group (DH), low-dose liraglutide group (DL), and aerobic interval training combined with liraglutide group (DLE). High-fat diet and streptozotocin (STZ) were used to induce the DCM model, and both the liraglutide administration group and combination therapy group allocated to 8 weeks of either liraglutide or liraglutide and exercise intervention. Cardiac functions were analyzed by electrocardiography. Blood biochemical parameters were measured to judge glycemic control conditions. Hematoxylin and eosin (HE) staining and Sirus red staining was used to identify cardiac morphology and collagen accumulation, respectively. Advanced glycation end products (AGEs) were determined by enzymatic methods. The mRNA expression of myocardial remodeling genes (BNP, GSK3β, α-MHC, β-MHC and PPARα) and the protein expression of GLP-1, GLP-1R were analyzed. DCM rats developed hyperglycemia, impaired cardiac function with accumulation of AGEs and collagen (P < 0.05). The development of hyperglycemia and cardiac dysfunction was significantly attenuated with all interventions, as reduced cardiac fibrosis and improved cardiac function (P < 0.05). Cardiac remodeling genes were normalized after all interventions, these positive modifications were due to increased GLP-1 and GLP-1R expression in DCM heart (P < 0.05). Liraglutide combined with AIT significantly increased the diameters of cardiomyocytes, increased the α-MHC expressionx, reduced PPARαexpression and reduced the fluctuation of blood glucose level, which showed the safety and effective of medicine combined with exercise. Liraglutide combined with AIT intervention normalized blood glucose alleviates myocardial fibrosis and improves cardiac contractile function in DCM rats, supporting the efficacy and safety of the combination therapy. • Combination therapy is beneficial to maintain the stability of blood glucose level. • Combination therapy can significantly remove AGEs in DCM heart and maintain the stability of ECM. • Liraglutide alone and in combination with AIT reduced the expression of myocardial GSK3β and inhibited the accumulation of myocardial collagen fibers, thereby alleviating myocardial fibrosis and protecting the diabetic. • Liraglutide, alone and in combination with AIT,significantly decreased the relative expression of β-MHC mRNA and increased that of α-MHC mRNA. • 8 weeks of liraglutide intervention significantly reduced the level of BNP in the myocardium of diabetic rats, liraglutide alone or combination therapy reduced the level of BNP. [ABSTRACT FROM AUTHOR]

Introduction: Prolonged hyperglycaemia leads to several disadvantageous effects including hyperglycaemia-induced cardiac apoptosis in the diabetic cardiomyopathy. Previously, we have reported that olmesartan gave benefits in diabetic nephropathy by attenuating endoplasmic reticulum (ER) stress. However, the roles that olmesartan play in diabetic cardiomyopathy are not confirmed yet. Methods: The role of 6 weeks olmesartan medoxomil 10 mg/kg BW in the streptozotocin-induced C57/BL-6 mice were evaluated by measuring blood glucose level and body weight. Protein expression of glucose-regulated protein (GRP)-78 –an ER stress sensor-, cleaved caspase12 and C-EBP homologous protein (CHOP) –ER stress apoptosis initiating factors- were analysed using western blot. Cardiac apoptosis was measured by TUNEL staining. Results: GRP-78, caspase12 and CHOP protein expressions were significantly increased in the diabetic mice. Daily decoction of olmesartan for 6 weeks significantly reduced not only the ER stress chaperone GRP-78 but also the ER stress key initiating factors for apoptosis, caspase12 and CHOP. Constantly, diabetic mice receiving olmesartan suffered from lesser levels of cardiac apoptosis than diabetic mice receiving vehicle treatment. Conclusion: Olmesartan support a beneficial function in the diabetic cardiomyopathy not only by its original properties as an ARB but also as an ER stress inhibitor partly by inhibiting the initiation of pro-apoptotic pathway of GRP78/CHOP/caspase12. [ABSTRACT FROM AUTHOR]

Cardiovascular disease, predominantly ischemic heart disease (IHD), is the leading cause of death in diabetes mellitus (DM). In addition to eliciting cardiomyopathy, DM induces a 'wicked triumvirate': (i) increasing the risk and incidence of IHD and myocardial ischemia; (ii) decreasing myocardial tolerance to ischemia-reperfusion (I-R) injury; and (iii) inhibiting or eliminating responses to cardioprotective stimuli. Changes in ischemic tolerance and cardioprotective signaling may contribute to substantially higher mortality and morbidity following ischemic insult in DM patients. Among the diverse mechanisms implicated in diabetic impairment of ischemic tolerance and cardioprotection, changes in sarcolemmal makeup may play an overarching role and are considered in detail in the current review. Observations predominantly in animal models reveal DM-dependent changes in membrane lipid composition (cholesterol and triglyceride accumulation, fatty acid saturation vs. reduced desaturation, phospholipid remodeling) that contribute to modulation of caveolar domains, gap junctions and T-tubules. These modifications influence sarcolemmal biophysical properties, receptor and phospholipid signaling, ion channel and transporter functions, contributing to contractile and electrophysiological dysfunction, cardiomyopathy, ischemic intolerance and suppression of protective signaling. A better understanding of these sarcolemmal abnormalities in types I and II DM (T1DM, T2DM) can inform approaches to limiting cardiomyopathy, associated IHD and their consequences. Key knowledge gaps include details of sarcolemmal changes in models of T2DM, temporal patterns of lipid, microdomain and T-tubule changes during disease development, and the precise impacts of these diverse sarcolemmal modifications. Importantly, exercise, dietary, pharmacological and gene approaches have potential for improving sarcolemmal makeup, and thus myocyte function and stress-resistance in this ubiquitous metabolic disorder.