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Mitochondrial medicine is increasingly discussed as a promising therapeutic approach, given that mitochondrial defects are thought to contribute to many prevalent diseases and their complications. In individuals with diabetes mellitus (DM), defects in mitochondrial structure and function occur in many organs throughout the body, contributing both to the pathogenesis of DM and complications of DM. Diabetic cardiomyopathy (DbCM) is increasingly recognized as an underlying cause of increased heart failure in DM, and several mitochondrial mechanisms have been proposed to contribute to the development of DbCM. Well established mechanisms include myocardial energy depletion due to impaired adenosine triphosphate (ATP) synthesis and mitochondrial uncoupling, and increased mitochondrial oxidative stress. A variety of upstream mechanisms of impaired ATP regeneration and increased mitochondrial reactive oxygen species have been proposed, and recent studies now also suggest alterations in mitochondrial dynamics and autophagy, impaired mitochondrial Ca2+ uptake, decreased cardiac adiponectin action, increased O-GlcNAcylation, and impaired activity of sirtuins to contribute to mitochondrial defects in DbCM, among others. In the current review, we present and discuss the evidence that underlies both established and recently proposed mechanisms that are thought to contribute to mitochondrial dysfunction in DbCM.
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Recent studies have shown that microRNAs (miRNAs) are involved in the process of cardiomyocyte apoptosis. We have previously reported that granulocyte-colony stimulating factor (G-CSF) ameliorated diastolic dysfunction and attenuated cardiomyocyte apoptosis in a rat model of diabetic cardiomyopathy. In this study, we hypothesized a regulatory role of cardiac miRNAs in the mechanism of the anti-apoptotic effect of G-CSF in a diabetic cardiomyopathy rat model.
Rats were given a high-fat diet and low-dose streptozotocin injection and then randomly allocated to receive treatment with either G-CSF or saline. H9c2 rat cardiomyocytes were cultured under a high glucose (HG) condition to induce diabetic cardiomyopathy
G-CSF treatment significantly decreased apoptosis and reduced miR-34a expression in diabetic myocardium and H9c2 cells under the HG condition. G-CSF treatment also significantly increased B-cell lymphoma 2 (Bcl-2) protein expression as a target for miR-34a. In addition, transfection with an miR-34a mimic significantly increased apoptosis and decreased Bcl-2 luciferase activity in H9c2 cells.
Our results indicate that G-CSF might have an anti-apoptotic effect through down-regulation of miR-34a in a diabetic cardiomyopathy rat model.
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Impaired diastolic heart function has been observed in persons with non-alcoholic fatty liver disease (NAFLD) and/or with type 2 diabetes mellitus (T2DM). However, it is unclear whether NAFLD fibrotic progression, i.e., non-alcoholic steatohepatitis, poses an independent risk for diastolic dysfunction in T2DM. We investigated the association between liver fibrosis and left ventricular (LV) diastolic dysfunction in T2DM.
We analyzed 606 patients with T2DM, aged ≥50 years, who had undergone liver ultrasonography and pulsed-wave Doppler echocardiography. Insulin sensitivity was measured by short insulin tolerance test. Presence of NAFLD and/or advanced liver fibrosis was determined by abdominal ultrasonography and NAFLD fibrosis score (NFS). LV diastolic dysfunction was defined according to transmitral peak early to late ventricular filling (E/A) ratio and deceleration time, using echocardiography.
LV diastolic dysfunction was significantly more prevalent in the NAFLD versus non-NAFLD group (59.7% vs. 49.0%,
Liver fibrosis was associated with LV diastolic dysfunction in patients with T2DM and may be an independent risk factor for diastolic dysfunction, especially in patients without systemic insulin resistance.
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Diabetic cardiomyopathy (DCM), as one of the major cardiac complications in diabetic patients, is known to related with oxidative stress that is due to a severe imbalance between reactive oxygen species (ROS) and/or reactive nitrogen species (RNS) generation and their clearance by antioxidant defense systems. Transcription factor nuclear factor NF-E2-related factor 2 (Nrf2) plays an important role in maintaining the oxidative homeostasis by regulating multiple downstream antioxidants. Diabetes may up-regulate several antioxidants in the heart as a compensative mechanism at early stage, but at late stage, diabetes not only generates extra ROS and/or RNS but also impairs antioxidant capacity in the heart, including Nrf2. In an early study, we have established that Nrf2 protect the cardiac cells and heart from high level of glucose
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