Resveratrol-Encapsulated Mitochondria-Targeting Liposome Enhances Mitochondrial Respiratory Capacity in Myocardial Cells

The development of drug delivery systems for use in the treatment of cardiovascular diseases is an area of great interest. We report herein on an evaluation of the therapeutic potential of a myocardial mitochondria-targeting liposome, a multifunctional envelope-type nano device for targeting pancreatic β cells (β-MEND) that was previously developed in our laboratory. Resveratrol (RES), a natural polyphenol compound that has a cardioprotective effect, was encapsulated in the β-MEND (β-MEND (RES)), and its efficacy was evaluated using rat myocardioblasts (H9c2 cells). The β-MEND (RES) was readily taken up by H9c2 cells, as verified by fluorescence-activated cell sorter data, and was observed to be colocalized with intracellular mitochondria by confocal laser scanning microscopy. Myocardial mitochondrial function was evaluated by a Seahorse XF Analyzer and the results showed that the β-MEND (RES) significantly activated cellular maximal respiratory capacity. In addition, the β-MEND (RES) showed no cellular toxicity for H9c2 cells as evidenced by Premix WST-1 assays. This is the first report of the use of a myocardial mitochondria-targeting liposome encapsulating RES for activating mitochondrial function, which was clearly confirmed based on analyses using a Seahorse XF Analyzer.

Succinyl-CoA-based energy metabolism dysfunctions in chronic heart failure

Heart failure (HF) is a leading cause of death and repeated hospitalizations1. HF progression generally involves mitochondrial dysfunction2-4. However, how mitochondria react to chronic HF remains unclear. Here, we show the molecular basis of mitochondrial dysfunction in chronic HF, which is characterized by altered succinyl-CoA metabolism. In myocardial mitochondria of coronary ligated mice, heme synthesis and ketolysis, and enzymes using succinyl-CoA in these events were upregulated, and enzymes synthesizing succinyl-CoA at the tricarboxylic acid (TCA) cycle were also increased. Intriguingly, the ADP-specific, but not the GDP-specific, subunit of succinyl-CoA synthetase, which uses succinyl-CoA in the TCA cycle, was decreased. Myocardial succinyl-CoA levels were significantly reduced in chronic HF, impairing mitochondrial oxidative phosphorylation (OXPHOS). Consequently, the administration of 5-aminolevulinic acid (ALA)5, an intermediate in the pathway from succinyl-CoA to heme synthesis, prevented HF progression in mice. Previous reports also support the presence of succinyl-CoA metabolism abnormalities in HF patients6,7. Our results indicated that changes in succinyl-CoA usage in various energy production systems in myocardial mitochondria is characteristic to chronic HF, and that although similar alterations occur in healthy conditions, such as during strenuous exercise, they may often occur irreversibly in HF. Moreover, nutritional interventions compensating the metabolic changes are likely to provide effective methods to treat HF.

Characterisation of the Myocardial Mitochondria Structural and Functional Phenotype in a Murine Model of Diabetic Cardiomyopathy

People affected by diabetes are at an increased risk of developing heart failure than their non-diabetic counterparts, attributed in part to a distinct cardiac pathology termed diabetic cardiomyopathy. Mitochondrial dysfunction and excess reactive oxygen species (ROS) have been implicated in a range of diabetic complications and are a common feature of the diabetic heart. In this study, we sought to characterise impairments in mitochondrial structure and function in a recently described experimental mouse model of diabetic cardiomyopathy. Diabetes was induced in 6-week-old male FVB/N mice by the combination of three consecutive-daily injections of low-dose streptozotocin (STZ, each 55 mg/kg i.p.) and high-fat diet (42% fat from lipids) for 26 weeks. At study end, diabetic mice exhibited elevated blood glucose levels and impaired glucose tolerance, together with increases in both body weight gain and fat mass, replicating several aspects of human type 2 diabetes. The myocardial phenotype of diabetic mice included increased myocardial fibrosis and left ventricular (LV) diastolic dysfunction. Elevated LV superoxide levels were also evident. Diabetic mice exhibited a spectrum of LV mitochondrial changes, including decreased mitochondria area, increased levels of mitochondrial complex-III and complex-V protein abundance, and reduced complex-II oxygen consumption. In conclusion, these data suggest that the low-dose STZ-high fat experimental model replicates some of the mitochondrial changes seen in diabetes, and as such, this model may be useful to study treatments that target the mitochondria in diabetes.

Effects of Aging on Expression of Mic60 and OPA1 and Mitochondrial Morphology in Myocardium of Tibetan Sheep

In order to investigate the effects of aging on the expression of Mic60 and OPA1 and mitochondrial morphology in plateau animals, the expression of Mic60 and OPA1 genes and proteins, and the morphology of mitochondria in the myocardium of adult and aged Tibetan sheep were investigated. The expression of Mic60 and OPA1 genes and OPA1 protein were higher (p < 0.05) in the myocardium of adult Tibetan sheep than in those of the aged ones. The number of mitochondrial cristae in the myocardium of adult was higher than that in aged (p < 0.05). The density of mitochondria in the myocardium of adult was higher than that in aged (p < 0.01). Compared with the adult Tibetan sheep, the mitochondrial crista of aged were relatively sparse, the crista membrane was wide, and the mitochondria were not closely linked, showing fragmentation. These results suggest that the myocardial mitochondria of the adult have better energy supply ability, indicating that aging can lead to the weakening of oxygen supply in the myocardial mitochondria of Tibetan sheep.

IRF1-mediated downregulation of PGC1α contributes to cardiorenal syndrome type 4

Cardiorenal syndrome type 4 (CRS4) is a common complication of chronic kidney disease (CKD), but the pathogenic mechanisms remain elusive. Here we report that morphological and functional changes in myocardial mitochondria are observed in CKD mice, especially decreases in oxidative phosphorylation and fatty acid metabolism. High phosphate (HP), a hallmark of CKD, contributes to myocardial energy metabolism dysfunction by downregulating peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α). Furthermore, the transcriptional factor interferon regulatory factor 1 (IRF1) is revealed as the key molecule upregulated by HP through histone H3K9 acetylation, and responsible for the HP-mediated transcriptional inhibition of PGC1α by directly binding to its promoter region. Conversely, restoration of PGC1α expression or genetic knockdown of IRF1 significantly attenuates HP-induced alterations in vitro and in vivo. These findings demonstrate that IRF1-PGC1α axis-mediated myocardial energy metabolism remodeling plays a crucial role in the pathogenesis of CRS4.