Combination of exercise and calorie restriction exerts greater efficacy on cardioprotection than monotherapy in obese-insulin resistant rats through the improvement of cardiac calcium regulation

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.

Effects of dietary intervention on human diseases: molecular mechanisms and therapeutic potential

Diet, serving as a vital source of nutrients, exerts a profound influence on human health and disease progression. Recently, dietary interventions have emerged as promising adjunctive treatment strategies not only for cancer but also for neurodegenerative diseases, autoimmune diseases, cardiovascular diseases, and metabolic disorders. These interventions have demonstrated substantial potential in modulating metabolism, disease trajectory, and therapeutic responses. Metabolic reprogramming is a hallmark of malignant progression, and a deeper understanding of this phenomenon in tumors and its effects on immune regulation is a significant challenge that impedes cancer eradication. Dietary intake, as a key environmental factor, can influence tumor metabolism. Emerging evidence indicates that dietary interventions might affect the nutrient availability in tumors, thereby increasing the efficacy of cancer treatments. However, the intricate interplay between dietary interventions and the pathogenesis of cancer and other diseases is complex. Despite encouraging results, the mechanisms underlying diet-based therapeutic strategies remain largely unexplored, often resulting in underutilization in disease management. In this review, we aim to illuminate the potential effects of various dietary interventions, including calorie restriction, fasting-mimicking diet, ketogenic diet, protein restriction diet, high-salt diet, high-fat diet, and high-fiber diet, on cancer and the aforementioned diseases. We explore the multifaceted impacts of these dietary interventions, encompassing their immunomodulatory effects, other biological impacts, and underlying molecular mechanisms. This review offers valuable insights into the potential application of these dietary interventions as adjunctive therapies in disease management.

So close, yet so far away: the relationship between MAM and cardiac disease

Mitochondria-associated membrane (MAM) serve as crucial contact sites between mitochondria and the endoplasmic reticulum (ER). Recent research has highlighted the significance of MAM, which serve as a platform for various protein molecules, in processes such as calcium signaling, ATP production, mitochondrial structure and function, and autophagy. Cardiac diseases caused by any reason can lead to changes in myocardial structure and function, significantly impacting human health. Notably, MAM exhibits various regulatory effects to maintain cellular balance in several cardiac diseases conditions, such as obesity, diabetes mellitus, and cardiotoxicity. MAM proteins independently or interact with their counterparts, forming essential tethers between the ER and mitochondria in cardiomyocytes. This review provides an overview of key MAM regulators, detailing their structure and functions. Additionally, it explores the connection between MAM and various cardiac injuries, suggesting that precise genetic, pharmacological, and physical regulation of MAM may be a promising strategy for preventing and treating heart failure.

Acute aerobic exercise regulation of myocardial calcium homeostasis involves CASQ1, CASQ2, and TRDN

Exercise maintains cardiac calcium homeostasis and promotes cardiovascular health. This study explored temporal changes of calcium-related myocardial transcriptome changes during the recovery phase following a single bout of moderate-intensity aerobic exercise. Healthy male Sprague-Dawley rats were anesthetized with sodium pentobarbital after moderate-intensity aerobic exercise at four time points (0, 12, 24, and 72 h postexercise). The hearts were removed and RNA-seq and bioinformatics analyses were used to examine temporal transcriptional changes in the myocardium. Casq1, Casq2, and Trdn were identified as key genes in the regulation of calcium homeostasis during myocardial recovery. The highest expression of Casq1, Casq2, and Trdn genes and the proteins they encode occurred 24 h after exercise. An in vitro calcium overload heart model using the Langendorff heart perfusion method was used to examine myocardial calcium buffering capacity. Calcium overload caused the least changes in left ventricular developed pressure, infarct area, Lactate dehydrogenase release, and extent of morphological damage to myocardial cells, with the highest protein expressions of CASQ1, CASQ2, and TRDN at 24 h after acute exercise. This study indicates that maximal myocardial Ca2+ buffering capacity occurs 24 h postexercise in rats. Our study provides insights into exercise-mediated improvements in cardiovascular function and exercise preconditioning.NEW & NOTEWORTHY Acute aerobic exercise upregulates myocardial Casq1, Casq2, and Trdn genes and the proteins they encode in rats. Higher protein levels of CASQ1, CASQ2, and TRDN conferred an improved ability of the myocardium to resist calcium overload. Furthermore, 24 h postexercise is the time point with optimal myocardial calcium buffer capacity.

Molecular mechanisms underlying the beneficial effects of exercise and dietary interventions in the prevention of cardiometabolic diseases

Cardiometabolic diseases still represent a major cause of mortality worldwide. In addition to pharmacological approaches, lifestyle interventions can also be adopted for the prevention of these morbid conditions. Lifestyle changes include exercise and dietary restriction protocols, such as calorie restriction and intermittent fasting, which were shown to delay cardiovascular ageing and elicit health-promoting effects in preclinical models of cardiometabolic diseases. Beneficial effects are mediated by the restoration of multiple molecular mechanisms in heart and vessels that are compromised by metabolic stress. Exercise and dietary restriction rescue mitochondrial dysfunction, oxidative stress and inflammation. They also improve autophagy. The result of these effects is a marked improvement of vascular and heart function. In this review, we provide a comprehensive overview of the molecular mechanisms involved in the beneficial effects of exercise and dietary restriction in models of diabetes and obesity. We also discuss clinical studies and gap in animal-to-human translation.

Compositions and Functions of Mitochondria-Associated Endoplasmic Reticulum Membranes and Their Contribution to Cardioprotection by Exercise Preconditioning

Mitochondria-associated endoplasmic reticulum membranes (MAMs) are important components of intracellular signaling and contribute to the regulation of intracellular Ca²⁺/lipid homeostasis, mitochondrial dynamics, autophagy/mitophagy, apoptosis, and inflammation. Multiple studies have shown that proteins located on MAMs mediate cardioprotection. Exercise preconditioning (EP) has been shown to protect the myocardium from adverse stimuli, but these mechanisms are still being explored. Recently, a growing body of evidence points to MAMs, suggesting that exercise or EP may be involved in cardioprotection by modulating proteins on MAMs and subsequently affecting MAMs. In this review, we summarize the latest findings on MAMs, analyzing the structure and function of MAMs and the role of MAM-related proteins in cardioprotection. We focused on the possible mechanisms by which exercise or EP can modulate the involvement of MAMs in cardioprotection. We found that EP may affect MAMs by regulating changes in MFN2, MFN1, AMPK, FUNDC1, BECN1, VDAC1, GRP75, IP3R, CYPD, GSK3β, AKT, NLRP3, GRP78, and LC3, thus playing a cardioprotective role. We also provided direction for future studies that may be of interest so that more in-depth studies can be conducted to elucidate the relationship between EP and cardioprotection.

AMPK Activation Is Indispensable for the Protective Effects of Caloric Restriction on Left Ventricular Function in Postinfarct Myocardium

Background: Caloric restriction (CR) extends lifespan in many species, including mammals. CR is cardioprotective in senescent myocardium by correcting pre-existing mitochondrial dysfunction and apoptotic activation. Furthermore, it confers cardioprotection against acute ischemia-reperfusion injury. Here, we investigated the role of AMP-activated protein kinase (AMPK) in mediating the cardioprotective CR effects in failing, postinfarct myocardium. Methods: Ligation of the left coronary artery or sham operation was performed in rats and mice. Four weeks after surgery, left ventricular (LV) function was analyzed by echocardiography, and animals were assigned to different feeding groups (control diet or 40% CR, 8 weeks) as matched pairs. The role of AMPK was investigated with an AMPK inhibitor in rats or the use of alpha 2 AMPK knock-out mice. Results: CR resulted in a significant improvement in LV function, compared to postinfarct animals receiving control diet in both species. The improvement in LV function was accompanied by a reduction in serum BNP, decrease in LV proapoptotic activation, and increase in mitochondrial biogenesis in the LV. Inhibition or loss of AMPK prevented most of these changes. Conclusions: The failing, postischemic heart is protected from progressive loss of LV systolic function by CR. AMPK activation is indispensable for these protective effects.

Effectiveness of high cardiorespiratory fitness in cardiometabolic protection in prediabetic rats

Background

Caloric restriction and exercise are lifestyle interventions that effectively attenuate cardiometabolic impairment. However, cardioprotective effects of long-term lifestyle interventions and short-term lifestyle interventions followed by weight maintenance in prediabetes have never been compared. High cardiorespiratory fitness (CRF) has been shown to provide protection against prediabetes and cardiovascular diseases, however, the interactions between CRF, prediabetes, caloric restriction, and exercise on cardiometabolic health has never been investigated.

Methods

Seven-week-old male Wistar rats were fed with either a normal diet (ND; n = 6) or a high-fat diet (HFD; n = 30) to induce prediabetes for 12 weeks. Baseline CRF and cardiometabolic parameters were determined at this timepoint. The ND-fed rats were fed continuously with a ND for 16 more weeks. The HFD-fed rats were divided into 5 groups (n = 6/group) to receive one of the following: (1) a HFD without any intervention for 16 weeks, (2) 40% caloric restriction for 6 weeks followed by an ad libitum ND for 10 weeks, (3) 40% caloric restriction for 16 weeks, (4) a HFD plus an exercise training program for 6 weeks followed by a ND without exercise for 10 weeks, or (5) a HFD plus an exercise training program for 16 weeks. At the end of the interventions, CRF and cardiometabolic parameters were re-assessed. Then, all rats were euthanized and heart tissues were collected.

Results

Either short-term caloric restriction or exercise followed by weight maintenance ameliorated cardiometabolic impairment in prediabetes, as indicated by increased insulin sensitivity, improved blood lipid profile, improved mitochondrial function and oxidative phosphorylation, reduced oxidative stress and inflammation, and improved cardiac function. However, these benefits were not as effective as those of either long-term caloric restriction or exercise. Interestingly, high-level baseline CRF was correlated with favorable cardiac and metabolic profiles at follow-up in prediabetic rats, both with and without lifestyle interventions.

Conclusions

Short-term lifestyle modification followed by weight maintenance improves cardiometabolic health in prediabetes. High CRF exerted protection against cardiometabolic impairment in prediabetes, both with and without lifestyle modification. These findings suggest that targeting the enhancement of CRF may contribute to the more effective treatment of prediabetes-induced cardiometabolic impairment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00458-9.

Inhibition of myeloid differentiation factor 2 attenuates cardiometabolic impairments via reducing cardiac mitochondrial dysfunction, inflammation, apoptosis and ferroptosis in prediabetic rats

Systemic inflammation is a key mediator of left ventricular dysfunction (LV) in prediabetes via the activation of myeloid differentiation factor 2 (MD2)/toll-like receptor 4 complex. The MD2 inhibitor L6H21 effectively reduced systemic and cardiac inflammation in obese mice. However, its effects on cardiac function and regulated cell death pathways in the heart in prediabetes are still unknown. The prediabetic rats were divided into 3 subgroups to receive vehicle, L6H21 (10, 20, 40 mg/kg) or metformin (300 mg/kg) for 1, 2 and 4 weeks. Then, metabolic parameters, cardiac sympathovagal balance, LV function, cardiac mitochondrial function, oxidative stress, inflammation, apoptosis, necroptosis, and ferroptosis were determined. All prediabetic rats exhibited cardiac sympathovagal imbalance, LV dysfunction, and cardiac mitochondrial dysfunction. All doses of L6H21 treatment for 2- and 4-weeks attenuated insulin resistance. L6H21 at 40 mg/kg attenuated cardiac autonomic imbalance and LV dysfunction after 1 week of treatment. Both 10 and 20 mg/kg of L6H21 required longer treatment duration to show these benefits. Mechanistically, all doses of L6H21 reduced cardiac mitochondrial dysfunction after 1 week of treatment, resulting in alleviated oxidative stress and inflammation. L6H21 also effectively suppressed cardiac apoptosis and ferroptosis, but it did not affect necroptosis in prediabetic rats. L6H21 provided the cardioprotective efficacy in dose- and time-dependent manners in prediabetic rats via reduction in apoptosis and ferroptosis.

ER-Mitochondria Contacts and Insulin Resistance Modulation through Exercise Intervention

The endoplasmic reticulum (ER) makes physical contacts with mitochondria at specific sites, and the hubs between the two organelles are called mitochondria-associated ER membranes (MAMs). MAMs are known to play key roles in biological processes, such as intracellular Ca²⁺ regulation, lipid trafficking, and metabolism, as well as cell death, etc. Studies demonstrated that dysregulation of MAMs significantly contributed to insulin resistance. Alterations of MAMs’ juxtaposition and integrity, impaired expressions of insulin signaling molecules, disruption of Ca²⁺ homeostasis, and compromised metabolic flexibility are all actively involved in the above processes. In addition, exercise training is considered as an effective stimulus to ameliorate insulin resistance. Although the underlying mechanisms for exercise-induced improvement in insulin resistance are not fully understood, MAMs may be critical for the beneficial effects of exercise.

Metabolic syndrome in children

Despite plenty of currently available information on metabolic syndrome (MetS) in children and adolescents, there are still uncertainties regarding definition, prevention, management and treatment of MetS in children. The first approach to MetS in children consists of lifestyle interventions (nutritional education, physical activity). These recommendations are often difficult to achieve, especially for adolescents, therefore, there is usually a lack of successful outcomes. A pharmacological intervention in obese children may be needed in some cases, with the aim to improve the effects of these primary prevention interventions. Metformin seems to be safe and presents evident positive effects on insulin sensitivity, but long-term and consistent data are still missing to establish its role in the pediatric population and the possible effectiveness of other emergent treatments such as glucagon-like peptide-1 analogues, dipeptidylpeptidase-4 inhibitors, dual inhibitors of SGLT1 and SGLT2 and weight loss drugs. Bariatric surgery might be helpful in selected cases. The aim of this review is to present the most recent available treatments for the main components of metabolic syndrome, with a focus on insulin resistance. A short mention of management of congenital forms of insulin resistance will be included too.

Altered mitochondrial metabolism in the insulin-resistant heart

Obesity-induced insulin resistance and type 2 diabetes mellitus can ultimately result in various complications, including diabetic cardiomyopathy. In this case, cardiac dysfunction is characterized by metabolic disturbances such as impaired glucose oxidation and an increased reliance on fatty acid (FA) oxidation. Mitochondrial dysfunction has often been associated with the altered metabolic function in the diabetic heart, and may result from FA-induced lipotoxicity and uncoupling of oxidative phosphorylation. In this review, we address the metabolic changes in the diabetic heart, focusing on the loss of metabolic flexibility and cardiac mitochondrial function. We consider the alterations observed in mitochondrial substrate utilization, bioenergetics and dynamics, and highlight new areas of research which may improve our understanding of the cause and effect of cardiac mitochondrial dysfunction in diabetes. Finally, we explore how lifestyle (nutrition and exercise) and pharmacological interventions can prevent and treat metabolic and mitochondrial dysfunction in diabetes.

Anti-aging Effects of Calorie Restriction (CR) and CR Mimetics based on the Senoinflammation Concept

Chronic inflammation, a pervasive feature of the aging process, is defined by a continuous, multifarious, low-grade inflammatory response. It is a sustained and systemic phenomenon that aggravates aging and can lead to age-related chronic diseases. In recent years, our understanding of age-related chronic inflammation has advanced through a large number of investigations on aging and calorie restriction (CR). A broader view of age-related inflammation is the concept of senoinflammation, which has an outlook beyond the traditional view, as proposed in our previous work. In this review, we discuss the effects of CR on multiple phases of proinflammatory networks and inflammatory signaling pathways to elucidate the basic mechanism underlying aging. Based on studies on senoinflammation and CR, we recognized that senescence-associated secretory phenotype (SASP), which mainly comprises cytokines and chemokines, was significantly increased during aging, whereas it was suppressed during CR. Further, we recognized that cellular metabolic pathways were also dysregulated in aging; however, CR mimetics reversed these effects. These results further support and enhance our understanding of the novel concept of senoinflammation, which is related to the metabolic changes that occur in the aging process. Furthermore, a thorough elucidation of the effect of CR on senoinflammation will reveal key insights and allow possible interventions in aging mechanisms, thus contributing to the development of new therapies focused on improving health and longevity.