The impact of DRP1 on myocardial fibrosis in the obese minipig

Mitochondrial dysfunction is a key link involved in the pathogenesis of sick sinus syndrome: a review

Sick sinus syndrome (SSS) is a grave medical condition that can precipitate sudden death. The pathogenesis of SSS remains incompletely understood. Existing research postulates that the fundamental mechanism involves increased fibrosis of the sinoatrial node and its surrounding tissues, as well as disturbances in the coupled-clock system, comprising the membrane clock and the Ca2+ clock. Mitochondrial dysfunction exacerbates regional tissue fibrosis and disrupts the functioning of both the membrane and calcium clocks. This plays a crucial role in the underlying pathophysiology of SSS, including mitochondrial energy metabolism disorders, mitochondrial oxidative stress damage, calcium overload, and mitochondrial quality control disorders. Elucidating the mitochondrial mechanisms involved in the pathophysiology of SSS and further investigating the disease's mechanisms is of great significance.

The DNA methyltransferase inhibitor decitabine blunts the response to a high-animal fat and protein diet in mice

Increasing evidence hints that DNA hypermethylation may mediate the pathogenic response to cardiovascular risk factors. Here, we tested a corollary of that hypothesis, that is, that the DNA methyltransferase inhibitor decitabine (Dec) ameliorates the metabolic profile of mice fed a moderately high-animal fat and protein diet (HAFPD), a proxy of cardiovascular risk-associated Western-type diet. HAFPD-fed mice were exposed to Dec or vehicle for eight weeks (8W set, 4-32/group). To assess any memory of past exposure to Dec, we surveyed a second mice set treated as 8W but HAFPD-fed for further eight weeks without any Dec (16W set, 4-20/group). In 8W, Dec markedly reduced HAFPD-induced body weight gain in females, but marginally in males. Characterization of females revealed that Dec augmented skeletal muscle lipid content, while decreasing liver fat content and increasing plasma nonesterified fatty acids, adipose insulin resistance, and-although marginally-whole blood acylcarnitines, compared to HAFPD alone. Skeletal muscle mitochondrial DNA copy number was higher in 8W mice exposed to HAFPD and Dec, or in 16W mice fed HAFPD only, relative to 8W mice fed HAFPD only, but Dec induced a transcriptional profile indicative of ameliorated mitochondrial function. Memory of past Dec exposure was tissue-specific and sensitive to both duration of exposure to HAFPD and age. In conclusion, Dec redirected HAFPD-induced lipid accumulation toward the skeletal muscle, likely due to augmented mitochondrial functionality and increased lipid demand. As caveat, Dec induced adipose insulin resistance. Our findings may help identifying strategies for prevention and treatment of lipid dysmetabolism.

Future perspectives on the roles of mitochondrial dynamics in the heart in obesity and aging

Increasing global obesity rates and an aging population are independently linked to cardiac complications. Consequently, it is crucial to comprehensively understand the mechanisms behind these conditions to advance innovative therapies for age-related diseases. Mitochondrial dysfunction, specifically defects in mitochondrial fission/fusion processes, has emerged as a central regulator of cardiac complications in aging and age-related diseases (e.g., obesity). Since excessive fission and impaired fusion of cardiac mitochondria lead to disruptions in mitochondrial dynamics and cellular metabolism in aging and obesity, modulating mitochondrial dynamics with either fission inhibitors or fusion promoters has offered cardioprotection against these pathological conditions in preclinical models. This review explores the molecular mechanisms governing mitochondrial dynamics as well as the disturbances observed in aging and obesity. Additionally, pharmaceutical interventions that specifically target the processes of mitochondrial fission and fusion are presented and discussed. By establishing a connection between mitochondrial dynamism through fission and fusion and the advancement or mitigation of age-related diseases, particularly obesity, this review provides valuable insights into the progression and potential prevention strategies for such conditions.

Determination of mitochondrial functions and damage in kidney in female LeeSung minipigs with a high-fat diet-induced obesity

The purpose of this study was to investigate the nexus between mitochondrial function and kidney injury by using a dietary-induced obese minipig model. Female Lee-Sung minipigs feeding a high-fat diet (HFD) for 6 months exhibited obesity, hyperglycaemia and dyslipidemia. HFD elevated the levels of plasma biomarkers related to renal injury, including symmetric dimethylarginine, creatinine and urea nitrogen. An extensive structural change in tubules and glomeruli was observed in HFD-fed pigs. A great amount of triacylglycerol was accumulated in HFD kidney compared to control kidney, whereas a reduction of ATP level and antioxidant capacity were exhibited in HFD kidney. Moreover, HFD altered the expressions of mitochondrial-related protein in renal cortex. To conclude, long-term HFD feeding to Lee-Sung minipigs induced obesity and kidney injury accompanied by abnormal mitochondrial functions in the renal cortex, suggesting an interrelationship with renal disease progression.

The link between obesity and aging - insights into cardiac energy metabolism

Obesity and aging are well-established risk factors for a range of diseases, including cardiovascular diseases and type 2 diabetes. Given the escalating prevalence of obesity, the aging population, and the subsequent increase in cardiovascular diseases, it is crucial to investigate the underlying mechanisms involved. Both aging and obesity have profound effects on the energy metabolism through various mechanisms, including metabolic inflexibility, altered substrate utilization for energy production, deregulated nutrient sensing, and mitochondrial dysfunction. In this review, we aim to present and discuss the hypothesis that obesity, due to its similarity in changes observed in the aging heart, may accelerate the process of cardiac aging and exacerbate the clinical outcomes of elderly individuals with obesity.

Enrofloxacin (ENR) exposure induces lipotoxicity by promoting mitochondrial fragmentation via dephosphorylation of DRP1 at S627 site

Enrofloxacin (ENR) is a kind of widespread hazardous pollutant on aquatic ecosystems and causes toxic effects, such as disorders of metabolism, on aquatic animals. However, its potential mechanisms at an environmental concentration on metabolic disorders of aquatic organisms remain unclear. Herin, we found that hepatic lipotoxicity was induced by ENR exposure, which led to ENR accumulation, oxidative stress, mitochondrial fragmentation, and fatty acid transfer blockage from lipid droplets into fragmented mitochondria. ENR-induced lipotoxicity and mitochondrial β-oxidation down-regulation were mediated by reactive oxygen species (ROS). Moreover, dynamin-like protein 1 (DRP1) mediated ENR-induced mitochondrial fragmentation and changes of lipid metabolism. Mechanistically, ENR induced increment of DRP1 mitochondrial localization via dephosphorylating DRP1 at S627 and promoted its interaction with mitochondrial fission factor (MFF), leading to mitochondria fragmentation. For the first time, our study provides an innovative mechanistic link between hepatic lipotoxicity and mitochondrial fragmentation under ENR exposure, and thus identifies previously unknown mechanisms for the direct relationship between environmental ENR concentration and lipotoxicity in aquatic animals. Our study provides innovative insights for toxicological mechanisms and environmental risk assessments of antibiotics in aquatic environment.

The impact of microbiota-derived short-chain fatty acids on macrophage activities in disease: Mechanisms and therapeutic potentials

Short-chain fatty acids (SCFAs) derived from the fermentation of carbohydrates by gut microbiota play a crucial role in regulating host physiology. Among them, acetate, propionate, and butyrate are key players in various biological processes. Recent research has revealed their significant functions in immune and inflammatory responses. For instance, butyrate reduces the development of interferon-gamma (IFN-γ) generating cells while promoting the development of regulatory T (Treg) cells. Propionate inhibits the initiation of a Th2 immune response by dendritic cells (DCs). Notably, SCFAs have an inhibitory impact on the polarization of M2 macrophages, emphasizing their immunomodulatory properties and potential for therapeutics. In animal models of asthma, both butyrate and propionate suppress the M2 polarization pathway, thus reducing allergic airway inflammation. Moreover, dysbiosis of gut microbiota leading to altered SCFA production has been implicated in prostate cancer progression. SCFAs trigger autophagy in cancer cells and promote M2 polarization in macrophages, accelerating tumor advancement. Manipulating microbiota- producing SCFAs holds promise for cancer treatment. Additionally, SCFAs enhance the expression of hypoxia-inducible factor 1 (HIF-1) by blocking histone deacetylase, resulting in increased production of antibacterial effectors and improved macrophage-mediated elimination of microorganisms. This highlights the antimicrobial potential of SCFAs and their role in host defense mechanisms. This comprehensive review provides an in-depth analysis of the latest research on the functional aspects and underlying mechanisms of SCFAs in relation to macrophage activities in a wide range of diseases, including infectious diseases and cancers. By elucidating the intricate interplay between SCFAs and macrophage functions, this review aims to contribute to the understanding of their therapeutic potential and pave the way for future interventions targeting SCFAs in disease management.

High-fat diet causes mitochondrial damage and downregulation of mitofusin-2 and optic atrophy-1 in multiple organs

High-fat consumption promotes the development of obesity, which is associated with various chronic illnesses. Mitochondria are the energy factories of eukaryotic cells, maintaining self-stability through a fine-tuned quality-control network. In the present study, we evaluated high-fat diet (HFD)-induced changes in mitochondrial ultrastructure and dynamics protein expression in multiple organs. C57BL/6J male mice were fed HFD or normal diet (ND) for 24 weeks. Compared with ND-fed mice, HFD-fed mice exhibited increased body weight, cardiomyocyte enlargement, pulmonary fibrosis, hepatic steatosis, renal and splenic structural abnormalities. The cellular apoptosis of the heart, liver, and kidney increased. Cellular lipid droplet deposition and mitochondrial deformations were observed. The proteins related to mitochondrial biogenesis (TFAM), fission (DRP1), autophagy (LC3 and LC3-II: LC3-I ratio), and mitophagy (PINK1) presented different changes in different organs. The mitochondrial fusion regulators mitofusin-2 (MFN2) and optic atrophy-1 (OPA1) were consistently downregulated in multiple organs, even the spleen. TOMM20 and ATP5A protein were enhanced in the heart, skeletal muscle, and spleen, and attenuated in the kidney. These results indicated that high-fat feeding caused pathological changes in multiple organs, accompanied by mitochondrial ultrastructural damage, and MFN2 and OPA1 downregulation. The mitochondrial fusion proteins may become promising targets and/or markers for treating metabolic disease.

The role of circadian clock-controlled mitochondrial dynamics in diabetic cardiomyopathy

Diabetes mellitus is a metabolic disease with a high prevalence worldwide, and cardiovascular complications are the leading cause of mortality in patients with diabetes. Diabetic cardiomyopathy (DCM), which is prone to heart failure with preserved ejection fraction, is defined as a cardiac dysfunction without conventional cardiac risk factors such as coronary heart disease and hypertension. Mitochondria are the centers of energy metabolism that are very important for maintaining the function of the heart. They are highly dynamic in response to environmental changes through mitochondrial dynamics. The disruption of mitochondrial dynamics is closely related to the occurrence and development of DCM. Mitochondrial dynamics are controlled by circadian clock and show oscillation rhythm. This rhythm enables mitochondria to respond to changing energy demands in different environments, but it is disordered in diabetes. In this review, we summarize the significant role of circadian clock-controlled mitochondrial dynamics in the etiology of DCM and hope to play a certain enlightening role in the treatment of DCM.

Butyric Acid Ameliorates Myocardial Fibrosis by Regulating M1/M2 Polarization of Macrophages and Promoting Recovery of Mitochondrial Function

Background

We aimed to investigate the effect and mechanism of butyric acid on rat myocardial fibrosis (MF).

Methods

16S rRNA sequencing was used to analyze the gut microbiota characteristics of the Sham group and MF group. HPLC was applied to measure butyric acid in the feces and serum. In vitro, rat macrophages RMa-bm were stimulated with LPS and IL-4, respectively, and then butyrate was added to study the influences of butyrate on M1/M2 polarization and mitochondrial function of rat macrophages. The rat macrophages and rat myocardial fibroblasts were co-cultured to explore the effect of butyrate on rat myocardial fibroblasts. In addition, MF rats were fed with butyric acid diet.

Results

Compared with the Sham group, collagen deposition in the MF group was increased, and fibrosis was serious. The abundance of Desulfovibrionaceae and Helicobacteraceae in the MF group was increased compared with the Sham group. Gut epithelial cells were destroyed in the MF group compared with the Sham group. Compared with the Sham group, LPS content in the MF group was increased and butyric acid was decreased. Butyrate inhibited M1 and promoted M2. Furthermore, butyrate may promote mitochondrial function recovery by regulating M1/M2 polarization of macrophages. After adding butyrate, cell proliferation ability was decreased, and aging and apoptosis were increased, which indicated that butyrate inhibited rat myocardial fibroblasts activity. Moreover, butyric acid could protect mitochondria and improve the symptoms of rats with MF.

Conclusions

Butyric acid ameliorated MF by regulating M1/M2 polarization of macrophages and promoting recovery of mitochondrial function.

Traditional Chinese Medicine Ginseng Dingzhi Decoction Ameliorates Myocardial Fibrosis and High Glucose-Induced Cardiomyocyte Injury by Regulating Intestinal Flora and Mitochondrial Dysfunction

Myocardial fibrosis refers to the pathological changes of heart structure and morphology caused by various reasons of myocardial damage. It has become an important challenge in the later clinical treatment of acute myocardial infarction/ischemic cardiomyopathy or diabetes complicated with heart failure. Ginseng Dingzhi Decoction (GN), a Chinese herbal medicine, can reduce heart failure and protect cardiomyocytes. We infer that this may be related to the interaction with intestinal microbiota and mitochondrial homeostasis. The regulatory mechanism of GN on gut microbiota and mitochondria has not yet been elucidated. The intestinal microbiota was analyzed by the 16S rRNA gene; the fecal samples were sequenced and statistically analyzed to determine the changes of microbiota in the phenotype of heart failure rats. In addition, GN can regulate the microbial population that increases the proportion of short-chain fatty acids and anti-inflammatory bacteria and reduces the proportion of conditional pathogens to diabetic phenotype. The results suggest that GN may improve myocardial injury by regulating intestinal flora. Our data also show that stress-type heart failure caused by TAC (transverse aortic constriction) is accompanied by severe cardiac hypertrophy, reduced cardiac function, redox imbalance, and mitochondrial dysfunction. However, the use of GN intervention can significantly reduce heart failure and myocardial hypertrophy, improve heart function and improve myocardial damage, and maintain the mitochondrial homeostasis and redox of myocardial cells under high glucose stimulation. Interestingly, through in vitro experiments after TMBIM6 siRNA treatment, the improvement effect of GN on cell damage and the regulation of mitochondrial homeostasis were eliminated. TMBIM6 can indirectly regulate mitophagy and mitochondrial homeostasis to attenuate myocardial damage and confirms the regulatory effect of GN on mitophagy and mitochondrial homeostasis. We further intervened cardiomyocytes in high glucose through metformin (MET) and GN combination therapy. Research data show that MET and GN combination therapy can improve the level of mitophagy and protect cardiomyocytes. Our findings provide novel mechanistic insights for the treatment of diabetes combined with myocardial injury (myocardial fibrosis) and provide a pharmacological basis for the study of the combination of Chinese medicine and conventional diabetes treatment drugs.

Backstage players of fibrosis: NOX4, mTOR, HDAC, and S1P; companions of TGF-β

The fibrotic process could be easily defined as a pathological excess of extracellular matrix deposition, leading to disruption of tissue architecture and eventually loss of function; however, this process involves a complex network of several signal transduction pathways. Virtually almost all organs could be affected by fibrosis, the most affected are the liver, lung, skin, kidney, heart, and eyes; in all of them, the transforming growth factor-beta (TGF-β) has a central role. The canonical and non-canonical signal pathways of TGF-β impact the fibrotic process at the cellular and molecular levels, inducing the epithelial-mesenchymal transition (EMT) and the induction of profibrotic gene expression with the consequent increase in proteins such as alpha-smooth actin (α-SMA), fibronectin, collagen, and other extracellular matrix proteins. Recently, it has been reported that some molecules that have not been typically associated with the fibrotic process, such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4), mammalian target of rapamycin (mTOR), histone deacetylases (HDAC), and sphingosine-1 phosphate (S1P); are critical in its development. In this review, we describe and discuss the role of these new players of fibrosis and the convergence with TGF-β signaling pathways, unveiling new insights into the panorama of fibrosis that could be useful for future therapeutic targets.

Mitochondrial Homeostasis Mediates Lipotoxicity in the Failing Myocardium

Heart failure remains the most common cause of death in the industrialized world. In spite of new therapeutic interventions that are constantly being developed, it is still not possible to completely protect against heart failure development and progression. This shows how much more research is necessary to understand the underlying mechanisms of this process. In this review, we give a detailed overview of the contribution of impaired mitochondrial dynamics and energy homeostasis during heart failure progression. In particular, we focus on the regulation of fatty acid metabolism and the effects of fatty acid accumulation on mitochondrial structural and functional homeostasis.

Mitochondrial Fission and Mitophagy Reciprocally Orchestrate Cardiac Fibroblasts Activation

Although mitochondrial fission has been reported to increase proliferative capacity and collagen production, it can also contribute to mitochondrial impairment, which is detrimental to cell survival. The aim of the present study was to investigate the role of mitochondrial fission in cardiac fibroblasts (CF) activation and explore the mechanisms involved in the maintenance of mitochondrial health under this condition. For this, changes in the levels of mitochondrial fission/fusion-related proteins were assessed in transforming growth factor beta 1 (TGF-β1)-activated CF, whereas the role of mitochondrial fission during this process was also elucidated, as were the underlying mechanisms. The interaction between mitochondrial fission and mitophagy, the main defense mechanism against mitochondrial impairment, was also explored. The results showed that the mitochondria in TGF-β1-treated CF were noticeably more fragmented than those of controls. The expression of several mitochondrial fission-related proteins was markedly upregulated, and the levels of fusion-related proteins were also altered, but to a lesser extent. Inhibiting mitochondrial fission resulted in a marked attenuation of TGF-β1-induced CF activation. The TGF-β1-induced increase in glycolysis was greatly suppressed in the presence of a mitochondrial inhibitor, whereas a glycolysis-specific antagonist exerted little additional antifibrotic effects. TGF-β1 treatment increased cellular levels of reactive oxygen species (ROS) and triggered mitophagy, but this effect was reversed following the application of ROS scavengers. For the signals mediating mitophagy, the expression of Pink1, but not Bnip3l/Nix or Fundc1, exhibited the most significant changes, which could be counteracted by treatment with a mitochondrial fission inhibitor. Pink1 knockdown suppressed CF activation and mitochondrial fission, which was accompanied by increased CF apoptosis. In conclusion, mitochondrial fission resulted in increased glycolysis and played a crucial role in CF activation. Moreover, mitochondrial fission promoted reactive oxygen species (ROS) production, leading to mitophagy and the consequent degradation of the impaired mitochondria, thus promoting CF survival and maintaining their activation.