ACE2, angiotensin 1-7 and skeletal muscle: review in the era of COVID-19

Cardiovascular diseases as risk factors of post-COVID syndrome: a systematic review

BACKGROUND

A growing proportion of people experience incomplete recovery months after contracting coronavirus disease 2019 (COVID-19). These COVID-19 survivors develop a condition known as post-COVID syndrome (PCS), where COVID-19 symptoms persist for > 12 weeks after acute infection. Limited studies have investigated PCS risk factors that notably include pre-existing cardiovascular diseases (CVD), which should be examined considering the most recent PCS data. This review aims to identify CVD as a risk factor for PCS development in COVID-19 survivors.

METHODS

Following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) checklist, systematic literature searches were performed in the PubMed, Scopus, and Web of Science databases from the earliest date available to June 2023. Data from observational studies in English that described the association between CVD and PCS in adults (≥ 18 years old) were included. A minimum of two authors independently performed the screening, study selection, data extraction, data synthesis, and quality assessment (Newcastle-Ottawa Scale). The protocol of this review was registered under PROSPERO (ID: CRD42023440834).

RESULTS

In total, 594 studies were screened after duplicates and non-original articles had been removed. Of the 11 included studies, CVD including hypertension (six studies), heart failure (three studies), and others (two studies) were significantly associated with PCS development with different factors considered. The included studies were of moderate to high methodological quality.

CONCLUSION

Our review highlighted that COVID-19 survivors with pre-existing CVD have a significantly greater risk of developing PCS symptomology than survivors without pre-existing CVD. As heart failure, hypertension and other CVD are associated with a higher risk of developing PCS, comprehensive screening and thorough examinations are essential to minimise the impact of PCS and improve patients' disease progression.

Levels of circulating angiotensin-converting enzyme 2 are affected by acute exercise and correlate with markers of physical fitness in male athletes

While under physiological conditions angiotensin-converting enzyme 2 (ACE2) is an antagonist of vasoconstrictive agents in the renin-angiotensin-aldosterone system (RAAS), in the context of SARS coronavirus 2 (SARS-CoV-2) ACE2 serves as the gateway into cells. Furthermore, RAAS has previously been shown to be influenced by exercise training and is suggested to be involved in skeletal muscle mass maintenance. Given this connection, the investigation of circulating ACE2 plasma protein concentration before and following acute and chronic endurance and resistance exercise could increase the understanding of the implications of the exposure of athletes to SARS-CoV-2. Therefore, this study investigated levels of circulating ACE2 in lifelong high-level trained endurance and resistance athletes and control subjects in response to either acute endurance or resistance exercise. Results show no baseline differences in absolute ACE2 concentration between groups, but a strong negative correlation with levels of fitness and positive correlation with BMI in control subjects. Furthermore, acute endurance exercise significantly increased ACE2 levels across all groups, but only in the strength group in response to resistance exercise. This indicates that circulating ACE2 plasma levels are influenced by levels of fitness and health, and that acute endurance exercise has a stronger effect on plasma ACE2 levels than resistance exercise.

Alternative Renin-Angiotensin System

The renin-angiotensin system is the most important peptide hormone system in the regulation of cardiovascular homeostasis. Its classical arm consists of the enzymes, renin, and angiotensin-converting enzyme, generating angiotensin II from angiotensinogen, which activates its AT1 receptor, thereby increasing blood pressure, retaining salt and water, and inducing cardiovascular hypertrophy and fibrosis. However, angiotensin II can also activate a second receptor, the AT2 receptor. Moreover, the removal of the C-terminal phenylalanine from angiotensin II by ACE2 (angiotensin-converting enzyme 2) yields angiotensin-(1-7), and this peptide interacts with its receptor Mas. When the aminoterminal Asp of angiotensin-(1-7) is decarboxylated, alamandine is generated, which activates the Mas-related G-protein-coupled receptor D, MrgD (Mas-related G-protein-coupled receptor type D). Since Mas, MrgD, and the AT2 receptor have opposing effects to the classical AT1 receptor, they and the enzymes and peptides activating them are called the alternative or protective arm of the renin-angiotensin system. This review will cover the historical aspects and the current standing of this recent addition to the biology of the renin-angiotensin system.

Hypertension facilitates age-related diseases. ~ Is hypertension associated with a wide variety of diseases?~

Hypertension, a disease whose prevalence increases with age, induces pathological conditions of ischemic vascular disorders such as cerebral infarction and myocardial infarction due to accelerated arteriosclerosis and circulatory insufficiency of small arteries and sometimes causes hemorrhagic conditions such as cerebral hemorrhage and ruptured aortic aneurysm. On the other hand, as it is said that aging starts with the blood vessels, impaired blood flow associated with vascular aging is the basis for the development of many pathological conditions, and ischemic changes in target organs associated with vascular disorders result in tissue dysfunction and degeneration, inducing organ hypofunction and dysfunction. Therefore, we hypothesized that hypertension is associated with all age-related vascular diseases, and attempted to review the relationship between hypertension and diseases for which a relationship has not been previously well reported. Following our review, we hope that a collaborative effort to unravel age-related diseases from the perspective of hypertension will be undertaken together with experts in various specialties regarding the relationship of hypertension to all pathological conditions.

RNA m5C methylation modification: a potential therapeutic target for SARS-CoV-2-associated myocarditis

The Corona Virus Disease (COVID-19), caused by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), has quickly spread worldwide and resulted in significant morbidity and mortality. Although most infections are mild, some patients can also develop severe and fatal myocarditis. In eukaryotic RNAs, 5-methylcytosine (m5C) is a common kind of post-transcriptional modification, which is involved in regulating various biological processes (such as RNA export, translation, and stability maintenance). With the rapid development of m5C modification detection technology, studies related to viral m5C modification are ever-increasing. These studies have revealed that m5C modification plays an important role in various stages of viral replication, including transcription and translation. According to recent studies, m5C methylation modification can regulate SARS-CoV-2 infection by modulating innate immune signaling pathways. However, the specific role of m5C modification in SARS-CoV-2-induced myocarditis remains unclear. Therefore, this review aims to provide insights into the molecular mechanisms of m5C methylation in SARS-CoV-2 infection. Moreover, the regulatory role of NSUN2 in viral infection and host innate immune response was also highlighted. This review may provide new directions for developing therapeutic strategies for SARS-CoV-2-associated myocarditis.

Diabetes Mellitus, Energy Metabolism, and COVID-19

Obesity, diabetes mellitus (mostly type 2), and COVID-19 show mutual interactions because they are not only risk factors for both acute and chronic COVID-19 manifestations, but also because COVID-19 alters energy metabolism. Such metabolic alterations can lead to dysglycemia and long-lasting effects. Thus, the COVID-19 pandemic has the potential for a further rise of the diabetes pandemic. This review outlines how preexisting metabolic alterations spanning from excess visceral adipose tissue to hyperglycemia and overt diabetes may exacerbate COVID-19 severity. We also summarize the different effects of SARS-CoV-2 infection on the key organs and tissues orchestrating energy metabolism, including adipose tissue, liver, skeletal muscle, and pancreas. Last, we provide an integrative view of the metabolic derangements that occur during COVID-19. Altogether, this review allows for better understanding of the metabolic derangements occurring when a fire starts from a small flame, and thereby help reducing the impact of the COVID-19 pandemic.

Novel Insights into the Cardioprotective Effects of the Peptides of the Counter-Regulatory Renin-Angiotensin System

Currently, cardiovascular diseases are a major contributor to morbidity and mortality worldwide, having a significant negative impact on both the economy and public health. The renin-angiotensin system contributes to a high spectrum of cardiovascular disorders and is essential for maintaining normal cardiovascular homeostasis. Overactivation of the classical renin-angiotensin system is one of the most important pathophysiological mechanisms in the progression of cardiovascular diseases. The counter-regulatory renin-angiotensin system is an alternate pathway which favors the synthesis of different peptides, including Angiotensin-(1-7), Angiotensin-(1-9), and Alamandine. These peptides, via the angiotensin type 2 receptor (AT2R), MasR, and MrgD, initiate multiple downstream signaling pathways that culminate in the activation of various cardioprotective mechanisms, such as decreased cardiac fibrosis, decreased myocardial hypertrophy, vasodilation, decreased blood pressure, natriuresis, and nitric oxide synthesis. These cardioprotective effects position them as therapeutic alternatives for reducing the progression of cardiovascular diseases. This review aims to show the latest findings on the cardioprotective effects of the main peptides of the counter-regulatory renin-angiotensin system.

Deciphering the crosstalk of immune dysregulation between COVID-19 and idiopathic inflammatory myopathy

Background

The coronavirus disease (COVID-19) pandemic is a serious threat to public health worldwide. Growing evidence reveals that there are certain links between COVID-19 and autoimmune diseases; in particular, COVID-19 and idiopathic inflammatory myopathies (IIM) have been observed to be clinically comorbid. Hence, this study aimed to elucidate the molecular mechanisms of COVID-19 and IIM from a genomic perspective.

Methods

We obtained transcriptome data of patients with COVID-19 and IIM separately from the GEO database and identified common differentially expressed genes (DEGs) by intersection. We then performed functional enrichment, PPI, machine learning, gene expression regulatory network, and immune infiltration analyses of co-expressed genes.

Results

A total of 91 common genes were identified between COVID-19 and IIM. Functional enrichment analysis revealed that these genes were mainly involved in immune dysregulation, response to external stimuli, and MAPK signaling pathways. The MCODE algorithm recognized two densely linked clusters in the common genes, which were related to inflammatory factors and interferon signaling. Subsequently, three key genes (CDKN1A, IFI27, and STAB1) were screened using machine learning to predict the occurrence of COVID-19 related IIM. These key genes exhibited excellent diagnostic performance in both training and validation cohorts. Moreover, we created TF-gene and miRNA-gene networks to reveal the regulation of key genes. Finally, we estimated the relationship between key genes and immune cell infiltration, of which IFI27 was positively associated with M1 macrophages.

Conclusion

Our work revealed common molecular mechanisms, core genes, potential targets, and therapeutic approaches for COVID-19 and IIM from a genomic perspective. This provides new ideas for the diagnosis and treatment of COVID-19 related IIM in the future.

Novel Potential Targets for Function-Promoting Therapies: Orphan Nuclear Receptors, Anti-inflammatory Drugs, Troponin Activators, Mas Receptor Agonists, and Urolithin A

In recent years, several new classes of therapies have been investigated with their potential for restoring or improving physical functioning in older adults. These have included Mas receptor agonists, regulators of mitophagy, skeletal muscle troponin activators, anti-inflammatory compounds, and targets of orphan nuclear receptors. The present article summarizes recent developments of the function-promoting effects of these exciting new compounds and shares relevant preclinical and clinical data related to their safety and efficacy. The development of novel compounds in this area is expanding and likely will need the advent of a new treatment paradigm for age-associated mobility loss and disability.

Exploration of multifaceted molecular mechanism of angiotensin-converting enzyme 2 (ACE2) in pathogenesis of various diseases

Angiotensin converting enzyme 2 (ACE2) is a homolog of ACE (a transmembrane bound dipeptidyl peptidase enzyme). ACE2 converts angiotensinogen to the heptapeptide angiotensin-(1-7). ACE2 and its product, angiotensin-(1-7), have counteracting effects against the adverse actions of other members of renin-angiotensin system (RAS). ACE2 and its principal product, angiotensin-(1-7), were considered an under recognized arm of the RAS. The COVID-19 pandemic brought to light this arm of RAS with special focus on ACE2. Membrane bound ACE2 serves as a receptor for SARS-CoV-2 viral entry through spike proteins. Apart from that, ACE2 is also involved in the pathogenesis of various other diseases like cardiovascular disease, cancer, respiratory diseases, neurodegenerative diseases and infertility. The present review focuses on the molecular mechanism of ACE2 in neurodegenerative diseases, cancer, cardiovascular disease, infertility and respiratory diseases, including SARS-CoV-2. This review summarizes unveiled roles of ACE2 in the pathogenesis of various diseases which further provides intriguing possibilities for the use of ACE2 activators and RAS modulating agents for various diseases.

Multiomics profiling of the impact of an angiotensin (1-7)-expressing probiotic combined with exercise training in aged male rats

Angiotensin (1-7) [Ang (1-7)] is an active heptapeptide of the noncanonical arm of the renin-angiotensin system that modulates molecular signaling pathways associated with vascular and cellular inflammation, vasoconstriction, and fibrosis. Preclinical evidence suggests that Ang (1-7) is a promising therapeutic target that may ameliorate physical and cognitive function in late life. However, treatment pharmacodynamics limits its clinical applicability. Therefore, this study explored the underlying mechanisms altered by a genetically modified probiotic (GMP) that expresses Ang (1-7) combined with and without exercise training in an aging male rat model as a potential adjunct strategy to exercise training to counteract the decline of physical and cognitive function. We evaluated cross-tissue (prefrontal cortex, hippocampus, colon, liver, and skeletal muscle) multi-omics responses. After 12 wk of intervention, the 16S mRNA microbiome analysis revealed a main effect of probiotic treatment within- and between groups. The probiotic treatment enhanced α diversity (Inverse Simpson (F[2,56] = 4.44; P = 0.02); Shannon-Wiener (F[2,56] = 4.27; P = 0.02)) and β-diversity (F[2,56] = 2.66; P = 0.01) among rats receiving our GMP. The analysis of microbes' composition revealed three genera altered by our GMP (Enterorhabdus, Muribaculaceae unclassified, and Faecalitalea). The mRNA multi-tissue data analysis showed that our combined intervention upregulated neuroremodeling pathways on prefrontal cortex (i.e., 140 genes), inflammation gene expression in the liver (i.e., 63 genes), and circadian rhythm signaling on skeletal muscle. Finally, the integrative network analysis detected different communities of tightly (|r| > 0.8 and P < 0.05) correlated metabolites, genera, and genes in these tissues.NEW & NOTEWORTHY This manuscript uses a multiomics approach (i.e., microbiome, metabolomics, and transcriptomics) to explore the underlying mechanisms driven by a genetically modified probiotic (GMP) designed to express angiotensin (1-7) combined with moderate exercise training in an aged male rat model. After 12 wk of intervention, our findings suggest that our GMP enhanced gut microbial diversity while exercise training altered the transcriptional response in relevant neuroremodeling genes, inflammation, and circadian rhythm signaling pathways in an aging animal model.

Changes in intestinal morphology, number of mucus-producing cells and expression of coronavirus receptors APN, DPP4, ACE2 and TMPRSS2 in pigs with aging

Porcine enteric viral infections cause high morbidity and mortality in young piglets (<3 weeks). Later, these rates decrease with age. This age-dependent infectivity remains largely unexplored. This study investigated the changes in intestinal morphology, number of mucus-producing cells and expression level of coronavirus receptors in three age groups of pigs. Villus height and crypt depth increased with age from 3 days to 3 months in duodenum and ileum but not in mid-jejunum, where the villus height decreased from 580 µm at 3 days to 430 µm at 3 months. Enterocyte length-to-width ratio increased from 3 days to 3 months in all intestinal regions. The number of mucus-producing cells increased with age in the intestinal villi and crypts. The Brunner's glands of the duodenum contained the highest concentration of mucus-producing cells. The expression of coronavirus receptor APN was highest in the small intestinal villi at all ages. DPP4 expression slightly decreased over time in jejunum and ileum; it was highest in the ileal villi of 3-day-old piglets (70.2% of cells). ACE2 and TMPRSS2 positive cells increased with age in jejunal and ileal crypts and were particularly dominant in the ileal crypts (> 45% of cells). Except for the expression of DPP4 in the jejunum and ileum of young pigs, the expression pattern of the selected coronavirus receptors was very different and not correlated with the age-dependent susceptibility to viral infections. In contrast, the number of mucus-producing cells increased over time and may play an essential role in protecting enteric mucosae against intestinal viruses.

Shared genetic architecture between type 2 diabetes and COVID-19 severity

PURPOSE

Patients with type 2 diabetes (T2D) have demonstrated a higher risk for developing more severe cases of COVID-19, but the complex genetic mechanism between them is still unknown. The aim of the present study was to untangle this relationship using genetically based approaches.

METHODS

By leveraging large-scale genome-wide association study (GWAS) summary statistics of T2D and COVID-19 severity, linkage disequilibrium score regression and Mendelian randomization (MR) analyses were utilized to quantify the genetic correlations and causal relationships between the two traits. Gene-based association and enrichment analysis were further applied to identify putative functional pathways shared between T2D and COVID-19 severity.

RESULTS

Significant, moderate genetic correlations were detected between T2D and COVID-19 hospitalization (r_g = 0.156, SE = 0.057, p = 0.005) or severe disease (r_g = 0.155, SE = 0.057, p = 0.006). MR analysis did not support evidence for a causal effect of T2D on COVID-19 hospitalization (OR 1.030, 95% CI 0.979, 1.084, p = 0.259) or severe disease (OR 0.999, 95% CI 0.934, 1.069, p = 0.982). Genes having p_gene < 0.05 for both T2D and COVID-19 severe were significantly enriched for biological pathways, such as response to type I interferon, glutathione derivative metabolic process and glutathione derivative biosynthetic process.

CONCLUSIONS

Our findings further confirm the comorbidity of T2D and COVID-19 severity, but a non-causal impact of T2D on severe COVID-19. Shared genetically modulated molecular mechanisms underlying the co-occurrence of the two disorders are crucial for identifying therapeutic targets.

Graphene Oxide Decreases Pro-Inflammatory Proteins Production in Skeletal Muscle Cells Exposed to SARS-CoV-2 Spike Protein

Aim

The experiments aimed to document the presence of the ACE2 receptor on human muscle cells and the effects of the interaction of these cells with the spike protein of the SARS-CoV-2 virus in terms of induction of pro-inflammatory proteins, as well as to assess the possibility of reducing the pool of these proteins with the use of graphene oxide (GO) flakes.

Methods

Human Skeletal Myoblast (HSkM), purchased from Gibco were maintained in standard condition according to the manufacturer's instruction. The cells were divided into 4 groups; 1. C-control, 2. S-with addition of spike protein, 3. GO-with the addition of graphene oxide, 4. GO-S-with addition of GO followed by the addition of S protein. Protein S (PX-COV-P049) was purchased from ProteoGenix (France). GO was obtained from Advanced Graphene Products (Zielona Gora, Poland). The influence of all the factors on the morphology of cells was investigated using light and confocal microscopy. ACE2 protein expression on muscle cells was visualized and 40 pro-inflammatory cytokines were investigated using the membrane antibody array method. The protein profile of the lysate of cells from individual groups was also analyzed by mass spectrometry.

Conclusion

The experiments confirmed the presence of the ACE2 receptor in human skeletal muscle cells. It has also been documented that the SARS-CoV-2 virus spike protein influences the activation of selected pro-inflammatory proteins that promote cytokine storm and oxidative stress in muscle cells. The use of low levels of graphene oxide does not adversely affect muscle cells, reducing the levels of most proteins, including pro-inflammatory proteins. It can be assumed that GO may support anti-inflammatory therapy in muscles by scavenging proteins that activate cytokine storm.

Determinants of 1-Year Adverse Event Requiring Re-Hospitalization in COVID-19 Oldest Old Survivors

The incidence of "Long COVID" syndrome appears to be increasing, particularly in the geriatric population. At present, there are few data regarding the relationship between long COVID and the risk of re-hospitalization in the oldest old survivors. Patients older than 80 years consecutively hospitalized for COVID-19 in our tertiary care hospital were enrolled and followed after discharge in a 12-month ambulatory program. A comprehensive geriatric assessment (CGA), including functional capabilities and physical and cognitive performances, was performed at 6-month follow-up. Frailty degree was assessed using a 30-item frailty index. The re-hospitalization rate was assessed at 12-month follow-up through a computerized archive and phone interviews. Out of 100 patients discharged after hospitalization for COVID-19 (mean [SD] age 85 [4.0] years), 24 reported serious adverse events requiring re-hospitalization within 12 months. The most frequent causes of re-hospitalization were acute heart failure (HF), pneumonia and bone fracture (15.3% each). By multivariate logistic analysis, after adjustment for potential confounders, history of chronic HF [aOR: 3.00 (CI 95%: 1.10-8.16), p = 0.031] or chronic renal failure [aOR: 3.83 (CI 95%: 1.09-13.43), p = 0.036], the burden of comorbidity [(CIRSc) aOR: 1.95 (CI 95%: 1.28-2.97), p = 0.002] and frailty [aOR: 7.77 (CI 95%: 2.13-28.27), p = 0.002] resulted as independent predictors of re-hospitalization. One-fourth of the oldest old patients previously hospitalized for COVID-19 suffered from adverse events requiring re-hospitalization, two-thirds of them within three months after discharge. Frailty, the burden of comorbidity, history of chronic HF or chronic renal failure, but not COVID-19 disease severity, independently predicted re-hospitalization.

Long COVID: The latest manifestations, mechanisms, and potential therapeutic interventions

COVID-19 caused by SARS-CoV-2 infection affects humans not only during the acute phase of the infection, but also several weeks to 2 years after the recovery. SARS-CoV-2 infects a variety of cells in the human body, including lung cells, intestinal cells, vascular endothelial cells, olfactory epithelial cells, etc. The damages caused by the infections of these cells and enduring immune response are the basis of long COVID. Notably, the changes in gene expression caused by viral infection can also indirectly contribute to long COVID. We summarized the occurrences of both common and uncommon long COVID, including damages to lung and respiratory system, olfactory and taste deficiency, damages to myocardial, renal, muscle, and enduring inflammation. Moreover, we provided potential treatments for long COVID symptoms manifested in different organs and systems, which were based on the pathogenesis and the associations between symptoms in different organs. Importantly, we compared the differences in symptoms and frequency of long COVID caused by breakthrough infection after vaccination and infection with different variants of concern, in order to provide a comprehensive understanding of the characteristics of long COVID and propose improvement for tackling COVID-19.

The RAAS Axis and SARS-CoV-2: From Oral to Systemic Manifestations

One of the essential regulators of arterial blood pressure, the renin-angiotensin-aldosterone system (RAAS) seems to be one of the most complex mechanisms in the human body. Since the discovery of its key components and their actions, new substances and functions are still being unraveled. The main pathway begins with the secretion of renin in the kidney and culminates with the synthesis of angiotensin II (Ang II)-a strong vasoconstrictor-thanks to the angiotensin-converting enzyme (ACE). Research conducted in 2000 identified another enzyme, named ACE2, that converts Ang II into Ang-(1-7), a heptapeptide with opposing effects to those of Ang II: vasodilation and anti-inflammatory properties. This particular enzyme became of paramount importance during the last two decades, as a result of the confrontation of the human race with life-threatening epidemics. Multiple studies have been performed in order to uncover the link between ACE2 and human coronaviruses, the results of which we systemized in order to create an overview of the pathogenic mechanism. Human coronaviruses, such as SARS-CoV and SARS-CoV-2, attach to ACE2 via their spike proteins (S), causing the destruction of the enzyme. Because ACE2 limits the production of Ang II (by converting it into Ang-(1-7)), its destruction leads to a dysregulated inflammatory response. The purpose of this review is to decipher the complex pathophysiological mechanisms underlying the multiorgan complications (oral, cardiac, pulmonary, systemic) that appear as a result of the interaction of the SARS CoV-2 virus with the angiotensin-converting enzyme type 2.

Exercise Induced-Cytokines Response in Marathon Runners: Role of ACE I/D and BDKRB2 +9/-9 Polymorphisms

Renin-angiotensin system (RAS) and kallikrein-kinin system (KKS) have a different site of interaction and modulate vascular tone and inflammatory response as well on exercise adaptation, which is modulated by exercise-induced cytokines. The aim of the study was to evaluate the role of ACE I/D and BDKRB2 +9/−9 polymorphism on exercise-induced cytokine response. Seventy-four male marathon finishers, aged 30 to 55 years, participated in this study. Plasma levels of exercise-induced cytokines were determined 24 h before, immediately after, and 24 h and 72 h after the São Paulo International Marathon. Plasma concentrations of MCP-1, IL-6 and FGF-21 increased after marathon in all genotypes of BDKRB2. IL-10, FSTL and BDNF increased significantly after marathon in the genotypes with the presence of the −9 allele. FSTL and BDNF concentrations were higher in the −9/−9 genotype compared to the +9/+9 genotype before (p = 0.006) and after the race (p = 0.023), respectively. Apelin, IL-15, musclin and myostatin concentrations were significantly reduced after the race only in the presence of −9 allele. Marathon increased plasma concentrations of MCP1, IL-6, BDNF and FGF-21 in all genotypes of ACE I/D polymorphism. Plasma concentrations of IL-8 and MIP-1alpha before the race (p = 0.015 and p = 0.031, respectively), of MIP-1alpha and IL-10 after the race (p = 0.033 and p = 0.047, respectively) and VEGF 72 h after the race (p = 0.018) were lower in II homozygotes compared to runners with the presence of D allele. One day after the race we also observed lower levels of MIP-1alpha in runners with II homozygotes compared to DD homozygotes (p = 0.026). Before the marathon race myostatin concentrations were higher in DD compared to II genotypes (p = 0.009). Myostatin, musclin, IL-15, IL-6 and apelin levels decreased after race in genotypes with the presence of D allele. After the race ACE activity was negatively correlated with MCP1 (r = −56, p < 0.016) and positively correlated with IL-8, IL-10 and MIP1-alpha (r = 0.72, p < 0.0007, r = 0.72, p < 0.0007, r = 0.47, p < 0.048, respectively). The runners with the −9/−9 genotype have greater response in exercise-induced cytokines related to muscle repair and cardioprotection indicating that BDKRB2 participate on exercise adaptations and runners with DD genotype have greater inflammatory response as well as ACE activity was positively correlated with inflammatory mediators. DD homozygotes also had higher myostatin levels which modulates protein homeostasis.

Soluble angiotensin-converting enzyme 2 association with lipid metabolism

Increased expression of angiotensin-converting enzyme 2 (ACE2) is one of the likely explanations for disease severity in patients with coronavirus disease 2019 (COVID-19). In this study, we aimed to test whether soluble ACE2 (sACE2) levels are correlated to known risk factors of severe COVID-19 including biochemical parameters, body mass index and smoking habits. We cross-sectionally evaluated serum sACE2 levels in obese or tobacco-smoking populations and compared them to those in non-obese and non-smoking healthy participants. Additionally, fibroblast growth factor-21 (FGF21) was investigated as a candidate regulator of sACE2. A total of 220 male participants aged 30–59 years undergoing an annual health checkup were enrolled in this study: 59 obese, 80 smokers, and 81 healthy. Serum sACE2 levels were significantly higher in obese participants but not in tobacco-smoking participants when compared to healthy participants. sACE2 levels were significantly correlated with total cholesterol and triglycerides but not with body mass index. Furthermore, no regulatory relationship was found between FGF21 and sACE2. Lipid metabolism disorders accompanied by upregulation of serum sACE2 may be underlying mechanisms of COVID-19 aggravation and might be a novel breakthrough treatment target.

The pathobiological harmony between the local pulmonary/ bone marrow RAS and its management via tissue-RAS modulating agents in COVID-19

Coronavirus disease 2019 (COVID-19) outbreak, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), poses an unprecedented threat to public health and healthcare systems. It presents unusual pathophysiological effects mainly characterized by immune-inflammatory response and prothrombotic state causing acute respiratory distress syndrome and multiple organ failure. SARS-CoV-2 enters target cells after binding to the angiotensin-converting enzyme 2 (ACE2) receptor and therefore has a direct effect on the renin-angiotensin system (RAS). Apart from affecting numerous organs including lungs, heart, gastrointestinal system, spleen, brain and kidneys, the spike protein of SARS-CoV-2 could attack hematopoietic stem cells and hematopoietic progenitor cells in bone marrow (BM) microenvironment together with the precursor and mature blood cells. Within this hematopoietic viral spread context, it is crucial to search the clinicopathological correlations of COVID-19 in order to develop specific potential therapeutics against pleiotropic SARS-CoV-2 actions. Therefore, pharmacological disruption of the pathological cross-talk of local BM RAS and pulmonary RAS via administration of the tissue-RAS modulating agents such as soluble ACE2, angiotensin (1-7), TXA127 and MAS receptor agonists may prevent the clinical progression of the COVID-19 syndrome via reducing the hematopoietic virus propagation and systemic multi-organ spread.

Myokine Response to Blood-Flow Restricted Resistance Exercise in Younger and Older Males in an Untrained and Resistance-Trained State: A Pilot Study

Purpose

The purpose of this study was to examine the response of myokines to blood-flow restricted resistance-exercise (BFR-RE) in younger and older males before and after completing a 12-week resistance-training program.

Methods

There were 8 younger (24.8 ± 3.9 yrs) and 7 older (68.3 ± 5.0 yrs) untrained male participants completed this study. Anthropometric and maximal strength (1RM) measurements were collected before and after a 12-week, supervised, progressive full-body resistance-training program. As well, an acute bout of full-body BFR-RE was performed with venipuncture blood samples collected before and immediately following the BFR-RE, followed by sampling at 3, 6, 24 and 48 h.

Results

The 12-week training program stimulated a 32.2% increase in average strength and 30% increase in strength per kg of fat free mass. The response of particular myokines to the acute bout of BFR-RE was influenced training status (IL-4, untrained = 78.1 ± 133.2 pg/mL vs. trained = 59.8 ± 121.6 pg/mL, P = 0.019; IL-7, untrained = 3.46 ± 1.8 pg/mL vs. trained = 2.66 ± 1.3 pg/mL, P = 0.047) or both training and age (irisin, P = 0.04; leukemia inhibitory factor, P < 0.001). As well, changes in strength per kg of fat free mass were correlated with area under the curve for IL-4 (r = 0.537; P = 0.039), IL-6 (r = 0. 525; P = 0.044) and LIF (r = − 0.548; P = 0.035) in the untrained condition.

Conclusion

This study identified that both age and training status influence the myokine response to an acute bout of BFR-RE with the release of IL-4, IL-6 and LIF in the untrained state being associated with changes in strength per kg of fat free mass.

Angiotensin-converting enzyme 2 (ACE2): Two decades of revelations and re-evaluation

Angiotensin-converting enzyme-2, or ACE2, is primarily a zinc-dependent peptidase and ectoenzyme expressed in numerous cell types and functioning as a counterbalance to ACE in the renin-angiotensin system. It was discovered 21 years ago more than 40 years after the discovery of ACE itself. Its primary physiological activity is believed to be in the conversion of angiotensin II to the vasodilatory angiotensin-(1-7) acting through the Mas receptor. As such it has been implicated in numerous pathological conditions, largely in a protective mode which has led to the search for ACE2 activatory mechanisms. ACE2 has a diverse substrate specificity allowing its participation in multiple peptide pathways. It also regulates aspects of amino acid transport through its homology with a membrane protein, collectrin. It also serves as a viral receptor for the SARS virus, and subsequently SARS-CoV2, driving the current COVID-19 pandemic. ACE2 therefore provides a therapeutic target for the treatment of COVID and understanding the biological events following viral binding can provide insight into the multiple pathologies caused by the virus, particularly inflammatory and vascular. In part this may relate to the ability of ACE2, like ACE, to be shed from the cell membrane. The shed form of ACE2 (sACE2) may be a factor in determining susceptibility to certain COVID pathologies. Hence, for just over 20 years, ACE2 has provided numerous surprises in the field of vasoactive peptides with, no doubt, more to come but it is its central role in COVID pathology that is producing the current intense interest in its biology.

Screening of anti-atrophic peptides by using photo-cleavable peptide array and 96-well scale contractile human skeletal muscle atrophy models

Skeletal muscle atrophy is characterized by decreases in protein content, myofiber diameter, and contractile force generation. As muscle atrophy worsens the quality of life, the development of anti-atrophic substances is desirable. In this study, we aimed to demonstrate a screening process for anti-atrophic peptides using photo-cleavable peptide array technology and human contractile atrophic muscle models. We developed a 96-well system, and established a screening process with less variability. Dexamethasone-induced human atrophic tissue was constructed on the system. Eight peptides were selected from the literature and used for the screening of peptides for preventing the decrease of the contractile forces of tissues. The peptide QIGFIW, which showed preventive activity, was selected as the seed sequence. As a result of amino acid substitution, we obtained QIGFIQ as a peptide with higher anti-atrophic activity. These results indicate that the combinatorial use of the photo-cleavable peptide array technology and 96-well screening system could comprise a powerful approach to obtaining anti-atrophic peptides, and suggest that the 96-well screening system and atrophic model represent a practical and powerful tool for the development of drugs/functional food ingredients. This article is protected by copyright. All rights reserved.

The Musculoskeletal Involvement After Mild to Moderate COVID-19 Infection

COVID-19, a disease caused by the novel coronavirus SARS-CoV-2, has been drastically affecting the daily lives of millions of people. COVID-19 is described as a multiorgan disease that affects not only the respiratory tract of infected individuals, but it has considerable effects on the musculoskeletal system, causing excessive fatigue, myalgia, arthralgia, muscle weakness and skeletal muscle damage. These symptoms can persist for months, decreasing the quality of life of numerous individuals. Curiously, most studies in the scientific literature focus on patients who were hospitalized due to SARS-CoV-2 infection and little is known about the mechanism of action of COVID-19 on skeletal muscles, especially of individuals who had the mild to moderate forms of the disease (non-hospitalized patients). In this review, we focus on the current knowledge about the musculoskeletal system in COVID-19, highlighting the lack of researches investigating the mild to moderate cases of infection and pointing out why it is essential to care for these patients. Also, we will comment about the need of more experimental data to assess the musculoskeletal manifestations on COVID-19-positive individuals.

Unraveling Muscle Impairment Associated With COVID-19 and the Role of 3D Culture in Its Investigation

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been considered a public health emergency, extensively investigated by researchers. Accordingly, the respiratory tract has been the main research focus, with some other studies outlining the effects on the neurological, cardiovascular, and renal systems. However, concerning SARS-CoV-2 outcomes on skeletal muscle, scientific evidence is still not sufficiently strong to trace, treat and prevent possible muscle impairment due to the COVID-19. Simultaneously, there has been a considerable amount of studies reporting skeletal muscle damage in the context of COVID-19. Among the detrimental musculoskeletal conditions associated with the viral infection, the most commonly described are sarcopenia, cachexia, myalgia, myositis, rhabdomyolysis, atrophy, peripheral neuropathy, and Guillain-Barré Syndrome. Of note, the risk of developing sarcopenia during or after COVID-19 is relatively high, which poses special importance to the condition amid the SARS-CoV-2 infection. The yet uncovered mechanisms by which musculoskeletal injury takes place in COVID-19 and the lack of published methods tailored to study the correlation between COVID-19 and skeletal muscle hinder the ability of healthcare professionals to provide SARS-CoV-2 infected patients with an adequate treatment plan. The present review aims to minimize this burden by both thoroughly exploring the interaction between COVID-19 and the musculoskeletal system and examining the cutting-edge 3D cell culture techniques capable of revolutionizing the study of muscle dynamics.

Double Trouble-COVID-19 and the Widespread Use of Corticosteroids: Are We Staring at an Osteonecrosis Epidemic?

Background

A combination of immune-mediated vascular damage and routine use of systemic corticosteroid (CS) therapy in COVID-19 may significantly increase the risk and burden of osteonecrosis (ON) after COVID-19. This narrative review explores the pathogenesis, risk factors, and possible preventive and early treatment measures for ON in COVID-19.

Methods

For this narrative review, an extensive literature search was performed using the PubMed, Medline, and Science Direct databases from January 2000 to August 2021 for relevant articles on etiopathogenesis, epidemiology, clinical manifestations, and treatment of severe acute respiratory syndrome coronavirus (SARS-CoV) infection and steroid-induced ON (SION).

Results

Pathogenesis of COVID-19, utility of corticosteroids in the treatment of COVID-19, pathogenesis of SION vis-a-vis SARS-CoV infection, associated risk factors, and early diagnosis and treatment of ON following CS therapy of SARS-CoV infection were discussed.

Conclusion

Preliminary data of COVID-19 and similar trends from the SARS 2003 epidemic indicate that the "angiocentric" pathogenesis of SARS-CoV-2 and treatment with high-dose CS may increase the risk of ON in COVID-19 patients. Risk stratification based on CS intake during COVID-19 treatment can help identify subjects at moderate to high-risk for ON where early preventive and follow-up plans can be initiated.

[Thoracolumbar back pain as the leading symptom of a marked COVID-19 pneumonia]

HISTORY

 A 49-year-old male patient visited the surgical outpatient clinic with new onset low back pain. The pain was increasing for nine days and he did not have any signs of a respiratory infection, in particular neither fever nor cough.

INVESTIGATIONS

 During the further examination and unclothing, mild dyspnea was apparent. According to the patient, the dyspnea was also progressive in the last days but would not affect everyday life. Furthermore, the patient reported a significant and unintended weight loss. Outpatient chest X-ray revealed bilateral, peripheral, fine-speckled infiltrates that became increasingly confluent. Polymerase chain reaction analysis of the nasopharyngeal swab was positive for SARS-CoV-2 (wild type).

TREATMENT AND COURSE

 Due to progressive dyspnea, the patient was referred to inpatient treatment within the day, where he rapidly developed severe acute respiratory failure. To provide respiratory support, a combined intermittent non-invasive ventilation and nasal high flow-therapy was started. Moreover, a probatory antiviral therapy with remdesivir was initiated. Since a bacterial superinfection was suspected, additional antibiotic therapy was ordered. After 13 days of inpatient treatment, the patient was discharged. The low back pain receded completely during inpatient treatment without any specific therapy.

CONCLUSIONS

 Low back pain can be a symptom of COVID-19. In our case report, it was the only complain that led to the outpatient consultation. Even though back pain is a very common symptom in everyday practice, one should keep unusual causes in mind.

Temporal changes in soluble angiotensin-converting enzyme 2 associated with metabolic health, body composition, and proteome dynamics during a weight loss diet intervention: a randomized trial with implications for the COVID-19 pandemic

BACKGROUND

Angiotensin-converting enzyme 2 (ACE2) serves protective functions in metabolic, cardiovascular, renal, and pulmonary diseases and is linked to COVID-19 pathology. The correlates of temporal changes in soluble ACE2 (sACE2) remain understudied.

OBJECTIVES

We explored the associations of sACE2 with metabolic health and proteome dynamics during a weight loss diet intervention.

METHODS

We analyzed 457 healthy individuals (mean ± SD age: 39.8 ± 6.6 y) with BMI 28-40 kg/m2 in the DIETFITS (Diet Intervention Examining the Factors Interacting with Treatment Success) study. Biochemical markers of metabolic health and 236 proteins were measured by Olink CVDII, CVDIII, and Inflammation I arrays at baseline and at 6 mo during the dietary intervention. We determined clinical and routine biochemical correlates of the diet-induced change in sACE2 (ΔsACE2) using stepwise linear regression. We combined feature selection models and multivariable-adjusted linear regression to identify protein dynamics associated with ΔsACE2.

RESULTS

sACE2 decreased on average at 6 mo during the diet intervention. Stronger decline in sACE2 during the diet intervention was independently associated with female sex, lower HOMA-IR and LDL cholesterol at baseline, and a stronger decline in HOMA-IR, triglycerides, HDL cholesterol, and fat mass. Participants with decreasing HOMA-IR (OR: 1.97; 95% CI: 1.28, 3.03) and triglycerides (OR: 2.71; 95% CI: 1.72, 4.26) had significantly higher odds for a decrease in sACE2 during the diet intervention than those without (P ≤ 0.0073). Feature selection models linked ΔsACE2 to changes in α-1-microglobulin/bikunin precursor, E-selectin, hydroxyacid oxidase 1, kidney injury molecule 1, tyrosine-protein kinase Mer, placental growth factor, thrombomodulin, and TNF receptor superfamily member 10B. ΔsACE2 remained associated with these protein changes in multivariable-adjusted linear regression.

CONCLUSIONS

Decrease in sACE2 during a weight loss diet intervention was associated with improvements in metabolic health, fat mass, and markers of angiotensin peptide metabolism, hepatic and vascular injury, renal function, chronic inflammation, and oxidative stress. Our findings may improve the risk stratification, prevention, and management of cardiometabolic complications.This trial was registered at clinicaltrials.gov as NCT01826591.

Factors regulating dynamics of angiotensin-converting enzyme-2 (ACE2), the gateway of SARS-CoV-2: Epigenetic modifications and therapeutic interventions by epidrugs

Angiotensin-converting enzyme-2 (ACE2) is one of the major components of the renin-angiotensin system (RAS) and participates in the physiological functions of the cardiovascular system and lungs. Recent studies identified ACE2 as the receptor for the S-protein of the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and thus acts as the gateway for viral entry into the human body. Virus infection causes an imbalance in the RAS axis and induces acute lungs injury and fibrosis. Various factors regulate ACE2 expression patterns as well as control its epigenetic status at both transcription and translational levels. This review is mainly focused on the impact of environmental toxicants, drugs, endocrine disruptors, and hypoxia as controlling parameters for ACE2 expression and its possible modulation by epigenetic changes which are marked by DNA methylation, histone modifications, and micro-RNAs (miRNAs) profile. Furthermore, we have emphasized on interventions of various phytochemicals and bioactive compounds as epidrugs that regulate ACE2-S-protein interaction and thereby curb viral infection. Since ACE2 is an important component of the RAAS axis and a crucial entry point of SARS-CoV-2, the dynamics of ACE2 expression in response to various extrinsic and intrinsic factors are of contemporary relevance. We have collated updated information on ACE2 expression modulated by epidrugs, and urge to take over further studies on these important physiological regulators to unravel many more systemic linkages related to both metabolic and infectious diseases, in general and SARS-CoV-2 in particular for further development of targeted interventions.

Moderate exercise may prevent the development of severe forms of COVID-19, whereas high-intensity exercise may result in the opposite

Sedentary lifestyle increases the risk of hospitalization for COVID-19 independently of other factors. There is enough statistics to show that exercise prevents severe forms of COVID-19, but current recommendations do not set an upper limit for exercise intensity. The hypothesis presented in the paper states that intense exercise, through blood hypoxia, increases the expression of transmembrane angiotensin-converting enzyme 2 (tACE2) in the vascular endothelium, increasing the risk of developing serious forms of disease, especially in the untrained. On the other hand, moderate-intensity exercise increases the blood concentration of soluble angiotensin-converting enzyme 2 (ACE2) which has a protective role for SARS-CoV-2 infection and may prevent complications. The importance of this hypothesis consists in the revision of COVID-19 prophylaxis programs through physical exercises, with the possibility of administration of antioxidants to speed up the adaptation of vascular endothelial cells to exertion.

Hand grip strength before and after SARS-CoV-2 infection in community-dwelling older adults

Objective

To assess the association between SARS‐CoV‐2 infection and decreased hand grip strength (HGS).

Design

Longitudinal population‐based study.

Setting

Community‐dwelling older adults (aged ≥60 years) living in a rural Ecuadorian village struck by the SARS‐CoV‐2 pandemic.

Participants

Of 282 enrolled individuals, 254 (90%) finished the study.

Measurements

HGS was measured 3 months before (January 2020) and 9 months after the introduction of the virus into the population (January 2021). SARS‐CoV‐2 antibody testing was performed in two rounds: in May–June (early) and September–November (late), 2020. An independent association between SARS‐CoV‐2 infection and HGS decline was assessed by fitting linear mixed models for longitudinal data. Changes in HGS scores in SARS‐CoV‐2 seropositive subjects, according to the time elapsed since seroconversion, were compared with those who remained seronegative.

Results

Overall, 149 (59%) individuals became seropositive for SARS‐CoV‐2. The mean HGS (in kg) was 25.3 ± 8.3 at baseline and 23.7 ± 8.1 at follow‐up (p = 0.028), with 140 individuals having >5% HGS decline between both measurements. The follow‐up HGS measurement decreased by 1.72 kg in seropositive individuals, and by 0.57 kg in their seronegative counterparts (p < 0.001). SARS‐CoV‐2 seropositive individuals were 2.27 times more likely (95% CI: 1.33–3.87) to have a lower HGS measurement at the time of follow‐up than those who remained seronegative. When compared with seronegative subjects, seropositive patients with early seroconversion were 3.41 times (95% CI: 1.73–6.74) more likely to have >5% HGS decline at the time of the follow‐up than those with later, i.e., more recent, infections.

Conclusions

This study shows an independent deleterious impact of SARS‐CoV‐2 on HGS that is more marked among individuals with infections that occurred more than 8 months before follow‐up HGS. Results suggest the possibility of chronic damage to skeletal muscles by SARS‐CoV‐2.

Hyperactivated RAGE in Comorbidities as a Risk Factor for Severe COVID-19-The Role of RAGE-RAS Crosstalk

The receptor for advanced glycation-end products (RAGE) is a multiligand receptor with a role in inflammatory and pulmonary pathologies. Hyperactivation of RAGE by its ligands has been reported to sustain inflammation and oxidative stress in common comorbidities of severe COVID-19. RAGE is essential to the deleterious effects of the renin-angiotensin system (RAS), which participates in infection and multiorgan injury in COVID-19 patients. Thus, RAGE might be a major player in severe COVID-19, and appears to be a useful therapeutic molecular target in infections by SARS-CoV-2. The role of RAGE gene polymorphisms in predisposing patients to severe COVID-19 is discussed.&nbsp.

The Tissue Renin-Angiotensin System and Its Role in the Pathogenesis of Major Human Diseases: Quo Vadis?

Evidence has arisen in recent years suggesting that a tissue renin-angiotensin system (tRAS) is involved in the progression of various human diseases. This system contains two regulatory pathways: a pathological pro-inflammatory pathway containing the Angiotensin Converting Enzyme (ACE)/Angiotensin II (AngII)/Angiotensin II receptor type 1 (AGTR1) axis and a protective anti-inflammatory pathway involving the Angiotensin II receptor type 2 (AGTR2)/ACE2/Ang1–7/MasReceptor axis. Numerous studies reported the positive effects of pathologic tRAS pathway inhibition and protective tRAS pathway stimulation on the treatment of cardiovascular, inflammatory, and autoimmune disease and the progression of neuropathic pain. Cell senescence and aging are known to be related to RAS pathways. Further, this system directly interacts with SARS-CoV 2 and seems to be an important target of interest in the COVID-19 pandemic. This review focuses on the involvement of tRAS in the progression of the mentioned diseases from an interdisciplinary clinical perspective and highlights therapeutic strategies that might be of major clinical importance in the future.

Developing new drugs that activate the protective arm of the renin-angiotensin system as a potential treatment for respiratory failure in COVID-19 patients

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has reached pandemic proportions with negative impacts on global health, the world economy and human society. The clinical picture of COVID-19, and the fact that Angiotensin converting enzyme 2 (ACE2) is a receptor of SARS-CoV-2, suggests that SARS-CoV-2 infection induces an imbalance in the renin–angiotensin system (RAS). We review clinical strategies that are attempting to rebalance the RAS in COVID-19 patients by using ACE inhibitors, angiotensin receptor blockers, or agonists of angiotensin-II receptor type 2 or Mas receptor (MasR). We also propose that the new MasR activator BIO101, a pharmaceutical grade formulation of 20-hydroxyecdysone that has anti-inflammatory, anti-fibrotic and cardioprotective properties, could restore RAS balance and improve the health of COVID-19 patients who have severe pneumonia.

ACE2, a multifunctional protein - from cardiovascular regulation to COVID-19

This Editorial, written by Guest Editors Professor Michael Bader, Professor Anthony J. Turner and Dr Natalia Alenina, proudly introduces the Clinical Science-themed collection on angiotensin-converting enzyme 2 (ACE2), a multifunctional protein - from cardiovascular regulation to coronavirus disease 2019 (COVID-19).