Mitochondrial-Derived Peptide MOTS-c Attenuates Vascular Calcification and Secondary Myocardial Remodeling via Adenosine Monophosphate-Activated Protein Kinase Signaling Pathway

Mitochondria‑derived peptides: Promising microproteins in cardiovascular diseases (Review)

Mitochondria‑derived peptides (MDPs) are a unique class of peptides encoded by short open reading frames in mitochondrial DNA, including the mitochondrial open reading frame of the 12S ribosomal RNA type‑c (MOTS‑c). Recent studies suggest that MDPs offer therapeutic benefits in various diseases, including neurodegenerative disorders and types of cancer, due to their ability to increase cellular resilience. Mitochondrial dysfunction is a key factor in the onset and progression of cardiovascular diseases (CVDs), such as atherosclerosis and heart failure, as it disrupts energy metabolism, increases oxidative stress and promotes inflammation. MDPs such as humanin and MOTS‑c have emerged as important regulators of mitochondrial health, as they show protective effects against these processes. Recent studies have shown that MDPs can restore mitochondrial function, reduce oxidative damage and alleviate inflammation, thus counteracting the pathological mechanisms that drive CVDs. Therefore, MDPs hold promise as therapeutic agents that are capable of slowing, stopping, or even reversing CVD progression and their use presents a promising strategy for future treatments. However, the clinical application of MDPs remains challenging due to their low bioavailability, poor stability and high synthesis costs. Thus, it is necessary to improve drug delivery systems to enhance the bioavailability of MDPs. Moreover, integrating basic research with clinical trials is essential to bridge the gap between experimental findings and clinical applications.

Novel therapeutic targets for cardiorenal syndrome

Cardiorenal syndrome (CRS) is an interdependent dysfunction of the heart and kidneys, where failure in one organ precipitates failure in the other. The pathophysiology involves sustained renin-angiotensin-aldosterone-system (RAAS) activation, mitochondrial dysfunction, inflammation, fibrosis, oxidative stress and tissue remodeling, culminating in organ dysfunction. Existing therapies targeting the RAAS, diuretics and other agents have limitations, including diuretic resistance and compensatory sodium reabsorption. Therefore, there is a pressing need for novel druggable targets involved in CRS pathogenesis. This review addresses the challenges of existing treatments and emphasizes the importance of discovering new therapeutic targets. It highlights emerging targets such as Klotho, sex-determining region Y box 9 (SOX9), receptor-interacting protein kinase 3 (RIPK3), β-amino-isobutyric acid (BAIBA), thrombospondin-1 (TSP-1), among others, with their potential roles in CRS.

The Human Mitochondrial Genome Encodes for an Interferon-Responsive Host Defense Peptide

The mitochondrial DNA (mtDNA) can trigger immune responses and directly entrap pathogens, but it is not known to encode for active immune factors. The immune system is traditionally thought to be exclusively nuclear-encoded. Here, we report the identification of a mitochondrial-encoded host defense peptide (HDP) that presumably derives from the primordial proto-mitochondrial bacteria. We demonstrate that MOTS-c (mitochondrial open reading frame from the twelve S rRNA type-c) is a mitochondrial-encoded amphipathic and cationic peptide with direct antibacterial and immunomodulatory functions, consistent with the peptide chemistry and functions of known HDPs. MOTS-c targeted E. coli and methicillin-resistant S. aureus (MRSA), in part, by targeting their membranes using its hydrophobic and cationic domains. In monocytes, IFNγ, LPS, and differentiation signals each induced the expression of endogenous MOTS-c. Notably, MOTS-c translocated to the nucleus to regulate gene expression during monocyte differentiation and programmed them into macrophages with unique transcriptomic signatures related to antigen presentation and IFN signaling. MOTS-c-programmed macrophages exhibited enhanced bacterial clearance and shifted metabolism. Our findings support MOTS-c as a first-in-class mitochondrial-encoded HDP and indicates that our immune system is not only encoded by the nuclear genome, but also by the co-evolved mitochondrial genome.

Mitochondrial-derived peptides in cardiovascular disease: Novel insights and therapeutic opportunities

BACKGROUND

Mitochondria-derived peptides (MDPs) represent a recently discovered family of peptides encoded by short open reading frames (ORFs) found within mitochondrial genes. This group includes notable members including humanin (HN), mitochondrial ORF of the 12S rDNA type-c (MOTS-c), and small humanin-like peptides 1-6 (SHLP1-6). MDPs assume pivotal roles in the regulation of diverse cellular processes, encompassing apoptosis, inflammation, and oxidative stress, which are all essential for sustaining cellular viability and normal physiological functions. Their emerging significance extends beyond this, prompting a deeper exploration into their multifaceted roles and potential applications.

AIM OF REVIEW

This review aims to comprehensively explore the biogenesis, various types, and diverse functions of MDPs. It seeks to elucidate the central roles and underlying mechanisms by which MDPs participate in the onset and development of cardiovascular diseases (CVDs), bridging the connections between cell apoptosis, inflammation, and oxidative stress. Furthermore, the review highlights recent advancements in clinical research related to the utilization of MDPs in CVD diagnosis and treatment.

KEY SCIENTIFIC CONCEPTS OF REVIEW

MDPs levels are diminished with aging and in the presence of CVDs, rendering them potential new indicators for the diagnosis of CVDs. Also, MDPs may represent a novel and promising strategy for CVD therapy. In this review, we delve into the biogenesis, various types, and diverse functions of MDPs. We aim to shed light on the pivotal roles and the underlying mechanisms through which MDPs contribute to the onset and advancement of CVDs connecting cell apoptosis, inflammation, and oxidative stress. We also provide insights into the current advancements in clinical research related to the utilization of MDPs in the treatment of CVDs. This review may provide valuable information with MDPs for CVD diagnosis and treatment.

Renin-angiotensin system inhibitors positively impact on multiple aging regulatory pathways: Could they be used to protect against human aging?

The renin-angiotensin system (RAS)-a classical blood pressure regulator-largely contributes to healthy organ development and function. Besides, RAS activation promotes age-related changes and age-associated diseases, which are attenuated/abolished by RAS-blockade in several mammalian species. RAS-blockers also increase rodent lifespan. In previous work, we discussed how RAS-blockade downregulates mTOR and growth hormone/IGF-1 signaling, and stimulates AMPK activity (together with klotho, sirtuin, and vitamin D-receptor upregulation), and proposed that at least some of RAS-blockade's aging benefits are mediated through regulation of these intermediaries and their signaling to mitochondria. Here, we included RAS-blockade's impact on other aging regulatory pathways, that is, TGF-ß, NF-kB, PI3K, MAPK, PKC, Notch, and Wnt, all of which affect mitochondria. No direct evidence is available on RAS/RAS-blockade-aging regulatory pathway-mitochondria interactions. However, existing results allow to conjecture that RAS-blockers neutralize mitochondrial dysfunction by acting on the discussed pathways. The reviewed evidence led us to propose that the foundation is laid for conducting clinical trials aimed at testing whether angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB)-even at subclinical doses-offer the possibility to live longer and in better health. As ACEi and ARB are low cost and well-tolerated anti-hypertension therapies in use for over 35 years, investigating their administration to attenuate/prevent aging effects seems simple to implement.

Beneficial Effects of Low-Grade Mitochondrial Stress on Metabolic Diseases and Aging

Mitochondria function as platforms for bioenergetics, nutrient metabolism, intracellular signaling, innate immunity regulators, and modulators of stem cell activity. Thus, the decline in mitochondrial functions causes or correlates with diabetes mellitus and many aging-related diseases. Upon stress or damage, the mitochondria elicit a series of adaptive responses to overcome stress and restore their structural integrity and functional homeostasis. These adaptive responses to low-level or transient mitochondrial stress promote health and resilience to upcoming stress. Beneficial effects of low-grade mitochondrial stress, termed mitohormesis, have been observed in various organisms, including mammals. Accumulated evidence indicates that treatments boosting mitohormesis have therapeutic potential in various human diseases accompanied by mitochondrial stress. Here, we review multiple cellular signaling pathways and interorgan communication mechanisms through which mitochondrial stress leads to advantageous outcomes. We also discuss the relevance of mitohormesis in obesity, diabetes, metabolic liver disease, aging, and exercise.

The role of MOTS-c-mediated antioxidant defense in aerobic exercise alleviating diabetic myocardial injury

Myocardial remodeling and dysfunction are commonly observed in type 2 diabetes mellitus (T2DM). Aerobic exercise can partly alleviate diabetes-induced myocardial dysfunction through its antioxidant actions. MOTS-c is a potential exercise mimic. This study aimed to investigate the effects of MOTS-c on improving diabetic heart function and its mechanism and to identify whether MOTS-c improved antioxidant defenses due to aerobic exercise. Herein, we established a rat model of T2DM induced by high-fat diet combined with a low-dose streptozotocin injection. Interventions were performed using intraperitoneal injections of MOTS-c (i.p. 0.5 mg/kg/day, 7 days/week) or aerobic exercise training (treadmill, 20 m/min, 60 min/day, 5 days/week) for 8 weeks. Myocardial ultrastructure was assessed using transmission electron microscopy (TEM), myocardial lipid peroxidation levels (MDA), superoxide dismutase (SOD), glutathione (GSH), and catalase (CAT) levels were assessed using colorimetric methods, and molecular analyses including MOTS-c, Kelch-like ECH-associated protein 1 (Keap1), Nuclear factor E2-related factor 2 (Nrf2), adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)and phospho-AMPK (p-AMPK) were examined using Western blot. The results showed that MOTS-c, with or without exercise, reduced myocardial ultrastructural damage and improved glucolipid metabolism and cardiac function in T2DM. Furthermore, MOTS-c increased antioxidant markers such as SOD, CAT, and the protein expression of myocardial MOTS-c, Keap1, Nrf2, and p-AMPK. MOTS-c with exercise treatment reduced myocardial MDA and increased p-AMPK significantly comparing to only exercise or MOTS-c alone. Our findings suggest that MOTS-c may be a helpful supplement for overcoming exercise insufficiency and improving myocardial structure and function in diabetes.

mTOR Signaling: New Insights into Cancer, Cardiovascular Diseases, Diabetes and Aging

The mechanistic/mammalian target of rapamycin (mTOR), a member of the phosphoinositide 3-kinase (PI3K) related kinase family, integrates intracellular and environmental cues that coordinate a diverse set of cellular/tissue functions, such as cell growth, proliferation, metabolism, autophagy, apoptosis, longevity, protein/lipid/nucleotide synthesis, and tissue regeneration and repair [...].

MOTS-c: A potential anti-pulmonary fibrosis factor derived by mitochondria

Pulmonary fibrosis (PF) is a serious lung disease characterized by diffuse alveolitis and disruption of alveolar structure, with a poor prognosis and unclear etiopathogenesis. While ageing, oxidative stress, metabolic disorders, and mitochondrial dysfunction have been proposed as potential contributors to the development of PF, effective treatments for this condition remain elusive. However, Mitochondrial open reading frame of the 12S rRNA-c (MOTS-c), a peptide encoded by the mitochondrial genome, has shown promising effects on glucose and lipid metabolism, cellular and mitochondrial homeostasis, as well as the reduction of systemic inflammatory responses, and is being investigated as a potential exercise mimetic. Additionally, dynamic expression changes of MOTS-c have been closely linked to ageing and ageing-related diseases, indicating its potential as an exercise mimetic. Therefore, the review aims to comprehensively analyze the available literature on the potential role of MOTS-c in improving PF development and to identify specific therapeutic targets for future treatment strategies.

Exercise and vascular function in sedentary lifestyles in humans

People with sedentary lifestyles engage in minimal or no physical activity. A sedentary lifestyle promotes dysregulation of cellular redox balance, diminishes mitochondrial function, and increases NADPH oxidase activity. These changes collectively increase cellular oxidative stress, which alters endothelial function by oxidizing LDL-C, reducing NO production, and causing eNOS uncoupling. Reduced levels of nitric oxide (NO) leads to vasoconstriction, vascular remodeling, and vascular inflammation. Exercise modulates reactive oxygen species (ROS) to modify NRF2-KEAP signaling, leading to the activation of NRF2 to alleviate oxidative stress. While regular moderate exercise activates NRF2 through ROS production, high-intensity intermittent exercise stimulates NRF2 activation to a greater degree by reducing KEAP levels, which can be more beneficial for sedentary individuals. We review the damaging effects of a sedentary lifestyle on the vascular system and the health benefits of regular and intermittent exercise.

MOTS-c and aerobic exercise induce cardiac physiological adaptation via NRG1/ErbB4/CEBPβ modification in rats

AIMS

To determine the effects of the mitochondrial open reading frame of the 12S ribosomal RNA type-c (MOTS-c) and aerobic exercise on cardiac structure and function and explore the role of neuregulin-1 (NRG1)- ErbB2 receptor tyrosine kinase 4(ErbB4)- CCAAT-enhancer binding protein β (C/EBPβ) in cardiac physiological adaptation induced by MOTS-c and aerobic training.

MAIN METHODS

We used Hematoxylin-Eosin staining(HE)and Transmission Electron Microscope (TEM) to observe the cardiac myocardial structure, carotid artery catheterization to test cardiac function, and real-time quantitative polymerase chain reaction (qRT-PCR) and Western blotting to describe the changes of NRG1, ErbB4, C/EBPβ, and Gata in cardiac physiological adaptation.

KEY FINDINGS

MOTS-c and aerobic training significantly increased heart weight and heart weight index (HWI) (all p < 0.05). Aerobic exercise and MOTS-c treatment thickened myocardial fibers, with a tendency of hypertrophy. Heart rate (HR) (p < 0.001, p = 0.010, p = 0.011), the isovolumic diastolic time constant (Tau) (p < 0.001, p < 0.001, p < 0.001) in exercised (E), MOST-c treated (M) and their combination (ME) decreased significantly, while the dP/dt_max (p < 0.001, p < 0.001, p = 0.039) and dP/dt_min (p < 0.001, p < 0.001, p = 0.001) in groups E, M and ME were significantly higher than those in group C, but EDP (p = 0.903, p = 0.708, p = 0.744) remained unchanged. Moreover, C/EBPβ gene levels were significantly decreased in the differential gene expression between groups C and M transcriptomics sequencing. The levels of ErbB4 mRNA (p < 0.001, p < 0.001, p < 0.001) and Gata4 mRNA (p < 0.001, p < 0.001, p = 0.001) in groups E, M and ME increased significantly, while C/EBPβ mRNA expression decreased significantly (p < 0.001, p = 0.002, p = 0.001), which was consistent with the results of transcriptome sequencing. NRG1 mRNA in group E was significantly higher than that in group C (p = 0.003), but there was no significant difference between groups M and ME (p = 0.804, p = 0.320). The protein expression of NRG1 (p = 0.026, p < 0.001, p < 0.001), ErbB4 (p < 0.001, p < 0.001, p < 0.001) and Gata4 (p = 0.014, p < 0.001, p = 0.006) in groups E, M and ME increased significantly, while C/EBPβ decreased significantly (p < 0.001, p = 0.001, p = 0.002).

SIGNIFICANCE

Our findings suggest that MOTS-c and aerobic exercise had similar effects, improving myocardial morphology and structure and enhancing cardiac function through activation of the NRG1-ErbB4-C/EBPβ pathway.

Mitochondrial stress and mitokines in aging

Mitokines are signaling molecules that enable communication of local mitochondrial stress to other mitochondria in distant cells and tissues. Among those molecules are FGF21, GDF15 (both expressed in the nucleus) and several mitochondrial-derived peptides, including humanin. Their responsiveness to mitochondrial stress induces mitokine-signaling in response for example to exercise, following mitochondrial challenges in skeletal muscle. Such signaling is emerging as an important mediator of exercise-derived and dietary strategy-related molecular and systemic health benefits, including healthy aging. A compensatory increase in mitokine synthesis and secretion could preserve mitochondrial function and overall cellular vitality. Conversely, resistance against mitokine actions may also develop. Alterations of mitokine-levels, and therefore of mitokine-related inter-tissue cross talk, are associated with general aging processes and could influence the development of age-related chronic metabolic, cardiovascular and neurological diseases; whether these changes contribute to aging or represent "rescue factors" remains to be conclusively shown. The aim of the present review is to summarize the expanding knowledge on mitokines, the potential to modulate them by lifestyle and their involvement in aging and age-related diseases. We highlight the importance of well-balanced mitokine-levels, the preventive and therapeutic properties of maintaining mitokine homeostasis and sensitivity of mitokine signaling but also the risks arising from the dysregulation of mitokines. While reduced mitokine levels may impair inter-organ crosstalk, also excessive mitokine concentrations can have deleterious consequences and are associated with conditions such as cancer and heart failure. Preservation of healthy mitokine signaling levels can be achieved by regular exercise and is associated with an increased lifespan.

Vascular calcification: Molecular mechanisms and therapeutic interventions

Vascular calcification (VC) is recognized as a pathological vascular disorder associated with various diseases, such as atherosclerosis, hypertension, aortic valve stenosis, coronary artery disease, diabetes mellitus, as well as chronic kidney disease. Therefore, it is a life-threatening state for human health. There were several studies targeting mechanisms of VC that revealed the importance of vascular smooth muscle cells transdifferentiating, phosphorous and calcium milieu, as well as matrix vesicles on the progress of VC. However, the underlying molecular mechanisms of VC need to be elucidated. Though there is no acknowledged effective therapeutic strategy to reverse or cure VC clinically, recent evidence has proved that VC is not a passive irreversible comorbidity but an active process regulated by many factors. Some available approaches targeting the underlying molecular mechanism provide promising prospects for the therapy of VC. This review aims to summarize the novel findings on molecular mechanisms and therapeutic interventions of VC, including the role of inflammatory responses, endoplasmic reticulum stress, mitochondrial dysfunction, iron homeostasis, metabolic imbalance, and some related signaling pathways on VC progression. We also conclude some recent studies on controversial interventions in the clinical practice of VC, such as calcium channel blockers, renin-angiotensin system inhibitions, statins, bisphosphonates, denosumab, vitamins, and ion conditioning agents.

Mitochondria-derived peptide MOTS-c: effects and mechanisms related to stress, metabolism and aging

MOTS-c is a peptide encoded by the short open reading frame of the mitochondrial 12S rRNA gene. It is significantly expressed in response to stress or exercise and translocated to the nucleus, where it regulates the expression of stress adaptation-related genes with antioxidant response elements (ARE). MOTS-c mainly acts through the Folate-AICAR-AMPK pathway, thereby influencing energy metabolism, insulin resistance, inflammatory response, exercise, aging and aging-related pathologies. Because of the potential role of MOTS-c in maintaining energy and stress homeostasis to promote healthy aging, especially in view of the increasing aging of the global population, it is highly pertinent to summarize the relevant studies. This review summarizes the retrograde signaling of MOTS-c toward the nucleus, the regulation of energy metabolism, stress homeostasis, and aging-related pathological processes, as well as the underlying molecular mechanisms.

MOTS-c Functionally Prevents Metabolic Disorders

Mitochondrial-derived peptides are a family of peptides encoded by short open reading frames in the mitochondrial genome, which have regulatory effects on mitochondrial functions, gene expression, and metabolic homeostasis of the body. As a new member of the mitochondrial-derived peptide family, mitochondrial open reading frame of the 12S rRNA-c (MOTS-c) is regarding a peptide hormone that could reduce insulin resistance, prevent obesity, improve muscle function, promote bone metabolism, enhance immune regulation, and postpone aging. MOTS-c plays these physiological functions mainly through activating the AICAR-AMPK signaling pathways by disrupting the folate-methionine cycle in cells. Recent studies have shown that the above hormonal effect can be achieved through MOTS-c regulating the expression of genes such as GLUT4, STAT3, and IL-10. However, there is a lack of articles summarizing the genes and pathways involved in the physiological activity of MOTS-c. This article aims to summarize and interpret the interesting and updated findings of MOTS-c-associated genes and pathways involved in pathological metabolic processes. Finally, it is expected to develop novel diagnostic markers and treatment approaches with MOTS-c to prevent and treat metabolic disorders in the future.

Evaluation of Coronary Flow Level with Mots-C in Patients with STEMI Undergoing Primary PCI

BACKGROUND

The protective effects of mitochondrial open reading frame of the 12S rRNA-c (MOTS-C) on cardiovascular diseases have been shown in numerous studies. However, there is little documentation of the relationship between MOTS-C and coronary blood flow in ST-segment elevation myocardial infarction (STEMI).

OBJECTIVE

We aimed to investigate the role of MOTS-C, which is known to have cytoprotective properties in the pathogenesis of the no-reflow phenomenon, by comparing the coronary flow rate and MOTS-C levels in patients with STEMI submitted to primary PCI.

METHODS

52 patients with STEMI and 42 patients without stenosis >50% in the coronary arteries were included in the study. The STEMI group was divided into two groups according to post-PCI TIMI (Thrombolysis In Myocardial Infarction) flow grade:(i) No-reflow: grade 0, 1, and 2 and (ii) grade 3(angiographic success). A p value of <0.05 was considered significant.

RESULTS

MOTS-C levels were significantly lower in the STEMI group compared to the control group (91.9 ± 8.9 pg/mL vs. 171.8±12.5 pg/mL, p<0.001). In addition, the Receiver Operating Characteristics (ROC) curve analysis indicated that serum MOTS-C levels had a diagnostic value in predicting no-reflow (Area Under the ROC curve [AUC]:0.95, 95% CI:0.856-0.993, p<0.001). A MOTS-C ≥84.15 pg/mL measured at admission was shown to have 95.3% sensitivity and 88.9% specificity in predicting no-reflow.

CONCLUSION

MOTS-C is a strong and independent predictor of no-reflow and in-hospital MACE in patients with STEMI. It was also noted that low MOTS-C levels may be an important prognostic marker of and may have a role in the pathogenesis of STEMI.

High Glucose-Induced Cardiomyocyte Damage Involves Interplay between Endothelin ET-1/ETA/ETB Receptor and mTOR Pathway

Patients with type two diabetes mellitus (T2DM) are at increased risk for cardiovascular diseases. Impairments of endothelin-1 (ET-1) signaling and mTOR pathway have been implicated in diabetic cardiomyopathies. However, the molecular interplay between the ET-1 and mTOR pathway under high glucose (HG) conditions in H9c2 cardiomyoblasts has not been investigated. We employed MTT assay, qPCR, western blotting, fluorescence assays, and confocal microscopy to assess the oxidative stress and mitochondrial damage under hyperglycemic conditions in H9c2 cells. Our results showed that HG-induced cellular stress leads to a significant decline in cell survival and an impairment in the activation of ETA-R/ETB-R and the mTOR main components, Raptor and Rictor. These changes induced by HG were accompanied by a reactive oxygen species (ROS) level increase and mitochondrial membrane potential (MMP) loss. In addition, the fragmentation of mitochondria and a decrease in mitochondrial size were observed. However, the inhibition of either ETA-R alone by ambrisentan or ETA-R/ETB-R by bosentan or the partial blockage of the mTOR function by silencing Raptor or Rictor counteracted those adverse effects on the cellular function. Altogether, our findings prove that ET-1 signaling under HG conditions leads to a significant mitochondrial dysfunction involving contributions from the mTOR pathway.

MOTS-c, the Most Recent Mitochondrial Derived Peptide in Human Aging and Age-Related Diseases

MOTS-c, a 16 amino acid mitochondrial derived peptide, is encoded from the 12S rRNA region of the mitochondrial genome. Under stress conditions, MOTS-c translocates to the nucleus where it regulates a wide range of genes in response to metabolic dysfunction. It is colocalized to mitochondria in various tissues and is found in plasma, but the levels decline with age. Since MOTS-c has important cellular functions as well as a possible hormonal role, it has been shown to have beneficial effects on age-related diseases including Diabetes, Cardiovascular diseases, Osteoporosis, postmenopausal obesity and Alzheimer. Aging is characterized by gradual loss of (mitochondrial) metabolic balance, decreased muscle homeostasis and eventual diminished physical capability, which potentially can be reversed with MOTS-c treatment. This review examines the latest findings on biological effects of MOTS-c as a nuclear regulatory peptide and focuses on the role of MOTS-c in aging and age-related disorders, including mechanisms of action and therapeutic potential.

The Mitochondrial-Derived Peptide MOTS-c Attenuates Oxidative Stress Injury and the Inflammatory Response of H9c2 Cells Through the Nrf2/ARE and NF-κB Pathways

AIM

Oxidative stress and the inflammatory response contribute to the progression of cardiovascular disease. The present study aimed to investigate whether the mitochondrial-derived peptide MOTS-c could alleviate H₂O₂-induced oxidative stress and inflammatory status in H9c2 cells through activation of nuclear factor erythroid 2-related Factor 2 (Nrf2)/antioxidative response element (ARE) and inhibition of the NF-κB pathway.

METHODS

Rat H9c2 cardiomyocytes were obtained, and 10, 20 or 50 μM MOTS-c was pretreated for 24 h before treatment with H₂O_2. Then, the cell was treated with 100 μM H₂O₂ for 1 h to induce oxidative stress. An inhibition model of sh-Nrf2 was constructed via a lentivirus expression system, and an activation model of NF-κB was achieved using phorbol 12-myristate-13-acetate (PMA). Cell viability was determined using a Cell Counting kit-8 assay. Relative measurement of relative protein and mRNA expression used western blotting and qRT-PCR, respectively. Intracellular reactive oxygen species (ROS) levels were detected using dichlorodihydrofluorescein diacetate, and malondialdehyde (MDA) and superoxide dismutase (SOD) levels were determined via commercial kits. The protein expression and distribution in the cells were visualized by immunofluorescence analysis. Enzyme-linked immunosorbent assay was used to detect the levels of inflammatory cytokines, including TNF-α, IL-6 and IL-1β.

RESULTS

We found that H₂O₂ treatment significantly decreased cell viability and the level of SOD, increased the levels of ROS and MDA, and upregulated the expression of inflammatory cytokines, including TNF-α, IL-6 and IL-1β, in H9c2 cells. The expression levels of Nrf2, HO-1 and NQO-1 were significantly downregulated in the H₂O₂, while the phosphorylation of NF-κBp65 was promoted by H₂O₂. However, pretreatment with MOTS-c significantly reversed H₂O₂-induced damage in H9c2 cells. Moreover, both inhibition of the Nrf2/ARE pathway and activation of the NF-κB pathway significantly decreased the effects of MOTS-c, suggesting that MOTS-c might play a role in alleviating oxidative damage via the Nrf2/ARE and NF-κB pathways.

CONCLUSIONS

Our investigation indicated that MOTS-c could protect against H₂O₂-induced inflammation and oxidative stress in H9c2 cells by inhibiting NF-κB and activating the Nrf2/ARE pathways.

Mitochondrial derived peptide MOTS-c prevents the development of heart failure under pressure overload conditions in mice

MOTS-c, a mitochondrial-derived peptide (MDP), has been shown to have multiple biological activities such as antioxidation, anti-inflammation, and anti-apoptosis properties. In the present study, we aimed at evaluating the therapeutic effect of MOTS-c peptide in an animal model of heart failure. The heart failure mouse model was made by transverse aortic constriction (TAC) operations. The MOTS-c peptide was administrated subcutaneously by using an osmotic pump. At the end of the animal experiment, cardiac function was evaluated by echocardiography, and heart tissues were subjected to histological and molecular analysis. In vitro cultured H9C2 cells were used to test the effects of MOTS-c overexpression on cell death in response to H₂ O₂ stimulation. Our study showed that MOTS-c peptide attenuated TAC-induced cardiac dysfunction and remodelling. In addition, the MOTS-c peptide reduced the inflammatory response and upregulated the antioxidant capacity, coupled with the activation of the AMPK pathway in the heart of the TAC mouse model. In in vitro cultured cardiac cells, overexpression of MOTS-c was shown to activate the AMPK pathway and protect cell apoptosis in response to H₂ O₂ stimulation. Taken together, our study suggested that MOTS-c peptides may have therapeutic potential in treating HF.

Mitochondrial-derived peptides as a novel intervention for obesity and cardiac diseases: bench evidence for potential bedside application

Currently, obesity is the most common major health problem for people worldwide. Obesity is known to be a significant risk factor for several diseases, including metabolic syndrome, insulin resistance and type 2 diabetes, eventually leading to the development of chronic systemic disorders. Previous studies showed that mitochondrial dysfunction could be one of the potential mechanisms for obesity progression. Most interventions used for combating obesity have also been reported to modulate mitochondrial function, suggesting the potential role of mitochondria in the pathology of the obese condition. Recent studies have shown that peptides produced by mitochondria, mitochondrial-derived peptides (MDPs), potentially improve metabolic function and exert benefits in obesity-associated diabetes and various heart pathologies. In this review, the roles of MDPs in the metabolic pathways and their use in the treatment of various adverse effects of obesity are comprehensively summarised based on collective evidence from in vitro, in vivo and clinical studies. The roles of MDPs as novel therapeutic interventions for cardiac dysfunction caused by various stresses or toxicities are also presented and discussed. This review aims to summarise the knowledge regarding the effects of MDPs on obesity, with a particular emphasis on their potential protective effects on the impaired cardiac function associated with obesity. The information from this review will also encourage further clinical investigations to warrant the potential application of MDP interventions in the clinical setting in the future.

Comparison of Serum Mitochondrial Open Reading Frame of the 12S rRNA-c (MOTS-c) Levels in Patients With Multiple Sclerosis and Healthy Controls

Background

Multiple sclerosis (MS) is a major global problem, and as its pathogenesis is understood more clearly, therapeutic options expand accordingly. The mitochondrial open reading frame of the 12S rRNA-c (MOTS-c) is a novel mitochondria-derived protein acting on metabolic homeostasis. In this study, we aimed to investigate the role of serum MOTS-c in the pathophysiology of the disease in MS patients and to discuss the mechanism of MOTS-c.

Methodology

In total, 43 patients diagnosed with relapsing-remitting MS and 41 healthy controls were enrolled in the study. MOTS-c, fasting blood glucose, insulin, Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), lipid panel, and body mass index levels were assessed.

Results

The participants’ MOTS-c levels remained significantly lower than that of the control group, while their fasting blood glucose and HOMA-IR values were higher. The multivariate logistic regression analysis established that increased MOTS-c levels could be a protective factor against the development of MS disease. The area under the receiver operating characteristic curve for MOTS-c was calculated as 0.782 (95% confidence interval = 0.684-0.879, p = 0.0001).

Conclusions

This study is the first to scrutinize MOTS-c levels in MS patients. We tried to provide clinical evidence that MOTS-c could act as a highly discriminative biomarker between MS patients and control groups, which may hold great promise for future therapeutic options.

Mitochondria-derived peptides in aging and healthspan

The mechanisms that explain mitochondrial dysfunction in aging and healthspan continue to be studied, but one element has been unexplored: microproteins. Small open reading frames in circular mitochondria DNA can encode multiple microproteins, called mitochondria-derived peptides (MDPs). Currently, eight MDPs have been published: humanin, MOTS-c, and SHLPs 1–6. This Review describes recent advances in microprotein discovery with a focus on MDPs. It discusses what is currently known about MDPs in aging and how this new understanding could add to the way we understand age-related diseases including type 2 diabetes, cancer, and neurodegenerative diseases at the genomic, proteomic, and drug-development levels.

Exercise, Mitohormesis, and Mitochondrial ORF of the 12S rRNA Type-C (MOTS-c)

Low levels of mitochondrial stress are beneficial for organismal health and survival through a process known as mitohormesis. Mitohormetic responses occur during or after exercise and may mediate some salutary effects of exercise on metabolism. Exercise-related mitohormesis involves reactive oxygen species production, mitochondrial unfolded protein response (UPRmt), and release of mitochondria-derived peptides (MDPs). MDPs are a group of small peptides encoded by mitochondrial DNA with beneficial metabolic effects. Among MDPs, mitochondrial ORF of the 12S rRNA type-c (MOTS-c) is the most associated with exercise. MOTS-c expression levels increase in skeletal muscles, systemic circulation, and the hypothalamus upon exercise. Systemic MOTS-c administration increases exercise performance by boosting skeletal muscle stress responses and by enhancing metabolic adaptation to exercise. Exogenous MOTS-c also stimulates thermogenesis in subcutaneous white adipose tissues, thereby enhancing energy expenditure and contributing to the anti-obesity effects of exercise training. This review briefly summarizes the mitohormetic mechanisms of exercise with an emphasis on MOTS-c.

Single Nucleotide Polymorphism in the 3' Untranslated Region of PRKAA2 on Cardiometabolic Parameters in Type 2 Diabetes Mellitus Patients Who Received Metformin

Purpose

This study aimed to explore the association of rs857148 A>C as 3'UTR variants with blood pressure, HbA1c profile, and lipid profiles as cardiometabolic parameters among patients with T2DM receiving metformin.

Patients and Methods

This cross-sectional analytic research was conducted with 114 consecutively selected patients with T2DM. Polymerase chain reaction-restriction fragment length polymorphism was conducted to determine rs857148. A total of 108 patients fulfilled inclusion and exclusion criteria.

Results

Genotype distribution agreed with the Hardy Weinberg Equation for Equilibrium (p>0.05) but wildtype allele was found as the minor allele. Subjects with CC genotype and C allele had enhanced HbA1c levels (OR=7.12; 95% CI=1.05-48.26; p=0.04; OR=1.66; 95% CI=1.06-2.60; p=0.03, respectively). It was confirmed by dominant model whereas subjects with AA tended to have reduced HbA1c compared to AC+CC genotype (OR=0.15; 95% CI=0.02-0.97; p=0.047). AC genotype had significant correlation to total cholesterol (OR=1.05; 95% CI=1.01-1.10; p=0.03) compared to AA genotype.

Conclusion

We conclude that polymorphism of rs87148, specifically CC genotype and C allele, has a significant association with HbA1c and total cholesterol after considering oral hypoglycemia agent dose, age, gender, and combination therapy, compared to AA genotype. Future studies that involve a larger sample population and more rigorous selection criteria are required.

Exercise improves vascular health: Role of mitochondria

Vascular mitochondria constantly integrate signals from environment and respond accordingly to match vascular function to metabolic requirements of the organ tissues, while mitochondrial dysfunction contributes to vascular aging and pathologies such as atherosclerosis, stenosis, and hypertension. As an effective lifestyle intervention, exercise induces extensive mitochondrial adaptations through vascular mechanical stress and the increased production and release of reactive oxygen species and nitric oxide that activate multiple intracellular signaling pathways, among which peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) plays a critical role. PGC-1α coordinates mitochondrial quality control mechanisms to maintain a healthy mitochondrial pool and promote endothelial nitric oxide synthase activity in vasculature. The mitochondrial adaptations to exercise improve bioenergetics, balance redox status, protect endothelial cells against detrimental insults, increase vascular plasticity, and ameliorate aging-related vascular dysfunction, thus benefiting vascular health. This review highlights recent findings of mitochondria as a central hub integrating exercise-afforded vascular benefits and its underlying mechanisms. A better understanding of the mitochondrial adaptations to exercise will not only shed light on the mechanisms of exercise-induced cardiovascular protection, but may also provide new clues to mitochondria-oriented precise exercise prescriptions for cardiovascular health.

Novel Insights Into the Role of Mitochondria-Derived Peptides in Myocardial Infarction

Mitochondria-derived peptides (MDPs) are a new class of bioactive peptides encoded by small open reading frames (sORFs) within known mitochondrial DNA (mtDNA) genes. MDPs may affect the expression of nuclear genes and play cytoprotective roles against chronic and age-related diseases by maintaining mitochondrial function and cell viability in the face of metabolic stress and cytotoxic insults. In this review, we summarize clinical and experimental findings indicating that MDPs act as local and systemic regulators of glucose homeostasis, immune and inflammatory responses, mitochondrial function, and adaptive stress responses, and focus on evidence supporting the protective effects of MDPs against myocardial infarction. These insights into MDPs actions suggest their potential in the treatment of cardiovascular diseases and should encourage further research in this field.

The mitochondrial signaling peptide MOTS-c improves myocardial performance during exercise training in rats

Cardiac remodeling is a physiological adaptation to aerobic exercise and which is characterized by increases in ventricular volume and the number of cardiomyocytes. The mitochondrial derived peptide MOTS-c functions as an important regulator in physical capacity and performance. Exercise elevates levels of endogenous MOTS-c in circulation and in myocardium, while MOTS-c can significantly enhance exercise capacity. However, the effects of aerobic exercise combined with MOTS-c on cardiac structure and function are unclear. We used pressure–volume conductance catheter technique to examine cardiac function in exercised rats with and without treatment with MOTS-c. Surprisingly, MOTS-c improved myocardial mechanical efficiency, enhanced cardiac systolic function, and had a tendency to improve the diastolic function. The findings suggest that using exercise supplements could be used to modulate the cardiovascular benefits of athletic training.

The Role of Mitochondria-Derived Peptides in Cardiovascular Diseases and Their Potential as Therapeutic Targets

Mitochondria-derived peptides (MDPs) are small peptides hidden in the mitochondrial DNA, maintaining mitochondrial function and protecting cells under different stresses. Currently, three types of MDPs have been identified: Humanin, MOTS-c and SHLP1-6. MDPs have demonstrated anti-apoptotic and anti-inflammatory activities, reactive oxygen species and oxidative stress-protecting properties both in vitro and in vivo. Recent research suggests that MDPs have a significant cardioprotective role, affecting CVDs (cardiovascular diseases) development and progression. CVDs are the leading cause of death globally; this term combines disorders of the blood vessels and heart. In this review, we focus on the recent progress in understanding the relationships between MDPs and the main cardiovascular risk factors (atherosclerosis, insulin resistance, hyperlipidaemia and ageing). We also will discuss the therapeutic application of MDPs, modified and synthetic MDPs, and their potential as novel biomarkers and therapeutic targets.

Mitochondrial-encoded MOTS-c prevents pancreatic islet destruction in autoimmune diabetes

Mitochondria are principal metabolic organelles that are increasingly unveiled as immune regulators. However, it is currently not known whether mitochondrial-encoded peptides modulate T cells to induce changes in phenotype and function. In this study, we found that MOTS-c (mitochondrial open reading frame of the 12S rRNA type-c) prevented autoimmune β cell destruction by targeting T cells in non-obese diabetic (NOD) mice. MOTS-c ameliorated the development of hyperglycemia and reduced islet-infiltrating immune cells. Furthermore, adoptive transfer of T cells from MOTS-c-treated NOD mice significantly decreased the incidence of diabetes in NOD-severe combined immunodeficiency (SCID) mice. Metabolic and genomic analyses revealed that MOTS-c modulated T cell phenotype and function by regulating T cell receptor (TCR)/mTOR complex 1 (mTORC1) signaling. Type 1 diabetes (T1D) patients had a lower serum MOTS-c level than did healthy controls. Furthermore, MOTS-c reduced T cell activation by alleviating T cells from the glycolytic stress in T1D patients, suggesting therapeutic potential. Our findings indicate that MOTS-c regulates the T cell phenotype and suppresses autoimmune diabetes.

Impact of an MT-RNR1 Gene Polymorphism on Hepatocellular Carcinoma Progression and Clinical Characteristics

Mitochondrial DNA (mtDNA) mutations are highly associated with cancer progression. The poor prognosis of hepatocellular carcinoma (HCC) is largely due to high rates of tumor metastasis. This emphasizes the urgency of identifying these patients in advance and developing new therapeutic targets for successful intervention. However, the issue of whether mtDNA influences tumor metastasis in hepatoma remains unclear. In the current study, multiple mutations in mtDNA were identified by sequencing HCC samples. Among these mutations, mitochondrially encoded 12S rRNA (MT-RNR1) G709A was identified as a novel potential candidate. The MT-RNR1 G709A polymorphism was an independent risk factor for overall survival and distant metastasis-free survival. Subgroup analysis showed that in patients with cirrhosis, HBV-related HCC, α-fetoprotein ≥ 400 ng/mL, aspartate transaminase ≥ 31 IU/L, tumor number > 1, tumor size ≥ 5 cm, and histology grade 3-4, MT-RNR1 G709A was associated with both shorter overall survival and distant metastasis-free survival. Mechanistically, MT-RNR1 G709A was clearly associated with hexokinase 2 (HK2) expression and unfavorable prognosis in HCC patients. Our data collectively highlight that novel associations among MT-RNR1 G709A and HK2 are an important risk factor in HCC patients.

MOTS-c is an exercise-induced mitochondrial-encoded regulator of age-dependent physical decline and muscle homeostasis

Healthy aging can be promoted by enhanced metabolic fitness and physical capacity. Mitochondria are chief metabolic organelles with strong implications in aging that also coordinate broad physiological functions, in part, using peptides that are encoded within their independent genome. However, mitochondrial-encoded factors that actively regulate aging are unknown. Here, we report that mitochondrial-encoded MOTS-c can significantly enhance physical performance in young (2 mo.), middle-age (12 mo.), and old (22 mo.) mice. MOTS-c can regulate (i) nuclear genes, including those related to metabolism and proteostasis, (ii) skeletal muscle metabolism, and (iii) myoblast adaptation to metabolic stress. We provide evidence that late-life (23.5 mo.) initiated intermittent MOTS-c treatment (3x/week) can increase physical capacity and healthspan in mice. In humans, exercise induces endogenous MOTS-c expression in skeletal muscle and in circulation. Our data indicate that aging is regulated by genes encoded in both of our co-evolved mitochondrial and nuclear genomes.

Exercise has beneficial effects on metabolism and overall physiologic fitness in aged organisms. Here the authors show that MOTS-c is a mitochondrial-encoded exercise-induced peptide that regulates skeletal muscle metabolism and improves healthspan of older mice.

The Protective Effects of the Autophagic and Lysosomal Machinery in Vascular and Valvular Calcification: A Systematic Review

BACKGROUND

Autophagy is a highly conserved catabolic homeostatic process, crucial for cell survival. It has been shown that autophagy can modulate different cardiovascular pathologies, including vascular calcification (VCN).

OBJECTIVE

To assess how modulation of autophagy, either through induction or inhibition, affects vascular and valvular calcification and to determine the therapeutic applicability of inducing autophagy.

DATA SOURCES

A systematic review of English language articles using MEDLINE/PubMed, Web of Science (WoS) and the Cochrane library. The search terms included autophagy, autolysosome, mitophagy, endoplasmic reticulum (ER)-phagy, lysosomal, calcification and calcinosis. Study characteristics: Thirty-seven articles were selected based on pre-defined eligibility criteria. Thirty-three studies (89%) studied vascular smooth muscle cell (VSMC) calcification of which 27 (82%) studies investigated autophagy and six (18%) studies lysosomal function in VCN. Four studies (11%) studied aortic valve calcification (AVCN). Thirty-four studies were published in the time period 2015-2020 (92%).

CONCLUSION

There is compelling evidence that both autophagy and lysosomal function are critical regulators of VCN, which opens new perspectives for treatment strategies. However, there are still challenges to overcome, such as the development of more selective pharmacological agents and standardization of methods to measure autophagic flux.

Mitochondrial-derived peptides in energy metabolism

Mitochondrial-derived peptides (MDPs) are small bioactive peptides encoded by short open-reading frames (sORF) in mitochondrial DNA that do not necessarily have traditional hallmarks of protein-coding genes. To date, eight MDPs have been identified, all of which have been shown to have various cyto- or metaboloprotective properties. The 12S ribosomal RNA (MT-RNR1) gene harbors the sequence for MOTS-c, whereas the other seven MDPs [humanin and small humanin-like peptides (SHLP) 1-6] are encoded by the 16S ribosomal RNA gene. Here, we review the evidence that endogenous MDPs are sensitive to changes in metabolism, showing that metabolic conditions like obesity, diabetes, and aging are associated with lower circulating MDPs, whereas in humans muscle MDP expression is upregulated in response to stress that perturbs the mitochondria like exercise, some mtDNA mutation-associated diseases, and healthy aging, which potentially suggests a tissue-specific response aimed at restoring cellular or mitochondrial homeostasis. Consistent with this, treatment of rodents with humanin, MOTS-c, and SHLP2 can enhance insulin sensitivity and offer protection against a range of age-associated metabolic disorders. Furthermore, assessing how mtDNA variants alter the functions of MDPs is beginning to provide evidence that MDPs are metabolic signal transducers in humans. Taken together, MDPs appear to form an important aspect of a retrograde signaling network that communicates mitochondrial status with the wider cell and to distal tissues to modulate adaptative responses to metabolic stress. It remains to be fully determined whether the metaboloprotective properties of MDPs can be harnessed into therapies for metabolic disease.

AMPK, Mitochondrial Function, and Cardiovascular Disease

Adenosine monophosphate-activated protein kinase (AMPK) is in charge of numerous catabolic and anabolic signaling pathways to sustain appropriate intracellular adenosine triphosphate levels in response to energetic and/or cellular stress. In addition to its conventional roles as an intracellular energy switch or fuel gauge, emerging research has shown that AMPK is also a redox sensor and modulator, playing pivotal roles in maintaining cardiovascular processes and inhibiting disease progression. Pharmacological reagents, including statins, metformin, berberine, polyphenol, and resveratrol, all of which are widely used therapeutics for cardiovascular disorders, appear to deliver their protective/therapeutic effects partially via AMPK signaling modulation. The functions of AMPK during health and disease are far from clear. Accumulating studies have demonstrated crosstalk between AMPK and mitochondria, such as AMPK regulation of mitochondrial homeostasis and mitochondrial dysfunction causing abnormal AMPK activity. In this review, we begin with the description of AMPK structure and regulation, and then focus on the recent advances toward understanding how mitochondrial dysfunction controls AMPK and how AMPK, as a central mediator of the cellular response to energetic stress, maintains mitochondrial homeostasis. Finally, we systemically review how dysfunctional AMPK contributes to the initiation and progression of cardiovascular diseases via the impact on mitochondrial function.

Nϵ-Carboxymethyl-Lysine Deteriorates Vascular Calcification in Diabetic Atherosclerosis Induced by Vascular Smooth Muscle Cell-Derived Foam Cells

Nϵ-carboxymethyl-lysine (CML), an advanced glycation end product, is involved in vascular calcification (VC) in diabetic atherosclerosis. This study aimed to investigate the effects of CML on VC in diabetic atherosclerosis induced by vascular smooth muscle cell (VSMC)–derived foam cells. Human studies, animal studies and cell studies were performed. The human study results from 100 patients revealed a poor blood glucose and lipid status and more severe coronary lesions and stenosis in patients with coronary artery disease and diabetes mellitus. Intraperitoneal injection of streptozotocin combined with a high-fat diet was used to build a diabetic atherosclerosis model in ApoE^−/− mice. The animal study results indicated that CML accelerated VC progression in diabetic atherosclerosis by accelerating the accumulation of VSMC-derived foam cells in ApoE^−/− mice. The cell study results illustrated that CML induced VSMC-derived foam cells apoptosis and aggravated foam cells calcification. Consistent with this finding, calcium content and the expression levels of alkaline phosphatase, bone morphogenetic protein 2 and runt-related transcription factor 2 were significantly elevated in A7r5 cells treated with oxidation-low-density lipoprotein and CML. Thus, we concluded that CML promoted VSMC-derived foam cells calcification to aggravate VC in diabetic atherosclerosis, providing evidence for the contribution of foam cells to diabetic VC.

Vascular Calcification-New Insights Into Its Mechanism

Vascular calcification (VC), which is categorized by intimal and medial calcification, depending on the site(s) involved within the vessel, is closely related to cardiovascular disease. Specifically, medial calcification is prevalent in certain medical situations, including chronic kidney disease and diabetes. The past few decades have seen extensive research into VC, revealing that the mechanism of VC is not merely a consequence of a high-phosphorous and -calcium milieu, but also occurs via delicate and well-organized biologic processes, including an imbalance between osteochondrogenic signaling and anticalcific events. In addition to traditionally established osteogenic signaling, dysfunctional calcium homeostasis is prerequisite in the development of VC. Moreover, loss of defensive mechanisms, by microorganelle dysfunction, including hyper-fragmented mitochondria, mitochondrial oxidative stress, defective autophagy or mitophagy, and endoplasmic reticulum (ER) stress, may all contribute to VC. To facilitate the understanding of vascular calcification, across any number of bioscientific disciplines, we provide this review of a detailed updated molecular mechanism of VC. This encompasses a vascular smooth muscle phenotypic of osteogenic differentiation, and multiple signaling pathways of VC induction, including the roles of inflammation and cellular microorganelle genesis.