Angiotensin-converting enzyme in skeletal muscle: sentinel of blood pressure control and glucose homeostasis

Angiotensin II and post-streptococcal glomerulonephritis

BACKGROUND

Post-streptococcal glomerulonephritis (PSGN) is a consequence of the infection by group A beta-hemolytic streptococcus. During this infection, various immunological processes generated by streptococcal antigens are triggered, such as the induction of antibodies and immune complexes. This activation of the immune system involves both innate and acquired immunity. The immunological events that occur at the renal level lead to kidney damage with chronic renal failure as well as resolution of the pathological process (in most cases). Angiotensin II (Ang II) is a molecule with vasopressor and pro-inflammatory capacities, being an important factor in various inflammatory processes. During PSGN some events are defined that make Ang II conceivable as a molecule involved in the inflammatory processes during the disease.

CONCLUSION

This review is focused on defining which reported events would be related to the presence of this hormone in PSGN.

Characterization of differential distribution patterns between mitofusin isoforms and their interaction in developing skeletal muscles of rat

Skeletal muscle during postnatal development undergoes several structural and biochemical modifications. It is proposed that these changes are closely intertwined with the increase in load-bearing capacity of the muscle (i.e., myofibrils) and molecular machinery to support the energy demand (i.e., mitochondria). Concomitant establishment of the sarcoplasmic reticulum (SR) and mitochondrial network seems to be a major developmental adjustment of skeletal muscle leading to adult phenotype. Here, we have studied oxidativeness, vascularization, and the changes in mitofusins (Mfn) 1-Mfn 2 expression and interaction in the due course of muscle development. Toward this, we used a series of histochemical techniques to compare neonatal and adult limb muscles (Gastrocnemius and Quadriceps) of Wistar rat (Rattus norvegicus). Additionally, we probed the proximity between Mfn 1 and Mfn 2 using a highly sensitive antibody-based proximity ligation assay indicating the change in mitochondrial fusion pattern or mitochondria-SR interaction. The results show that neonatal fibers bear a uniform distribution of mitochondria while a differential pattern of distribution is seen in adults. The distribution of the blood vessels is also quite distinct in adult muscles with a well-formed capillary network but in neonates, only central blood vessels are seen. Interestingly, our Mfn 1-Mfn 2 interaction data show that this interaction is uniformly distributed throughout the neonatal fibers, while it becomes peripherally localized in fibers of adult muscles. This peripheralization of Mfn 1-Mfn 2 interaction must be an important event of muscle development and might be critical to cater to the metabolic needs of adult muscle.

The Predisposition for Type 2 Diabetes Mellitus and Metabolic Syndrome

Type 2 diabetes mellitus (T2DM) and metabolic syndrome (MetS) are diseases caused by the interaction of genetic and non-genetic factors. Therefore, the aim of our study was to investigate the association between six common genetic polymorphisms and T2DM and MetS in males. A total of 120 T2DM, 75 MetS, and 120 healthy controls (HC) were included in the study. ACE ID, eNOS 4a/b, ATR1 A1166C, OXTR (A>G), SOD1 +35A/C, CAT-21A/T gene polymorphisms were genotyped by PCR or PCR-RFLP techniques. T2DM was diagnosed at an earlier age compared to MetS (54 vs 55 years old, p=0.0003) and the difference was greater in carriers of the OXTR G allele (54 vs 56 years old, p=0.0002) or both OXTR G and eNOS b alleles (54 vs 56, p=0.00016). The SOD1 AA genotype (O.R.=0.11, p=0.0006) and the presence of both ACE I and OXTR1 A (O.R.=0.39, p=0.0005) alleles revealed to be protective for T2DM. SOD1 AA and AC genotypes were protective factors for triglyceride (p=0.0002 and p=0.0005, respectively) and HDL cholesterol (p=0.0002 and p=0.0004, respectively) levels in T2DM patients. ACE DD was identified more frequently in hypertensive T2DM patients (O.R.=3.77, p=0.0005) and in those who reported drinking alcohol (p=0.0001) comparing to HC and T2DM patients who did not drink alcohol, respectively. We observed that T2DM patients who reported drinking alcohol had an increased frequency of ACE DD and eNOS bb (p<0.0001), or ACE DD and OXTR G (p<0.0001) compared to non-drinkers. No gene polymorphisms were associated with MetS.

Investigation of Serum Angiotensin-Converting Enzyme (ACE) Concentration and ACE Gene Polymorphism in Patients With SARS-CoV-2 Pneumonia Admitted to the Emergency Department

Background This study seeks to investigate the distribution of the angiotensin-converting enzyme (ACE) gene polymorphism and serum levels in patients with viral pneumonia and predict which polymorphism will lead to severe progression of the disease. Methodology The serum ACE levels and ACE gene polymorphisms were successfully evaluated with respect to subsequent viral pneumonia using records of 100 patients with viral pneumonia and 100 healthy controls. Results ACE serum concentration was statistically significantly elevated. ACE serum concentration with a cut-off value of ≥5,256.05 pg/mL had 85.3% sensitivity and 83.2% selectivity. In addition, patients with ACE genotype D/D were 0.08 times more likely to manifest severe lung involvement than those with I/I, and patients with the I/D genotype were 0.02 times more likely than their counterparts with I/I. The computed tomography findings of the patients revealed that ACE serum concentration was significantly effective in discriminating between mild and moderate-to-severe lung involvement. No significant difference was observed between the blood parameters and ACE genotype distributions. Conclusions I/D polymorphism likely affects the expression of the ACE gene and/or the function of the angiotensin I converting enzyme. The D/D genotype is associated with vessel wall thickness and higher blood pressure. Strong evidence was found between D/D and I/D genotypes in the patient cohort concerning genotypes and ACE serum concentration. Further analysis showed that ACE serum levels were more elevated in the D/D genotype compared to the I/D genotype in the patient cohort.

Cardio-sarcopenia: A syndrome of concern in aging

Cardiac alterations in structure and function, namely, the left ventricle, have been intensely studied for decades, in association with aging. In recent times, there has been keen interest in describing myocardial changes that accompany skeletal muscle changes in older adults. Initially described as a cardio-sarcopenia syndrome where alterations in myocardial structure were observed particularly among older adults with skeletal muscle sarcopenia, investigations into this syndrome have spurred a fresh level of interest in the cardiac-skeletal muscle axis. The purpose of this perspective is to summarize the background for this "syndrome of concern," review the body of work generated by various human aging cohorts, and to explore future directions and opportunities for understanding this syndrome.

The effect of dietary supplementation with blueberry, cyanidin-3-O-β-glucoside, yoghurt and its peptides on gene expression associated with glucose metabolism in skeletal muscle obtained from a high-fat-high-carbohydrate diet induced obesity model

Obesity is a leading global health problem contributing to various chronic diseases, including type II diabetes mellitus (T2DM). The aim of this study was to investigate whether blueberries, yoghurt, and their respective bioactive components, Cyanidin-3-O-β-glucoside (C3G) and peptides alone or in combinations, alter the expression of genes related to glucose metabolism in skeletal muscles from diet-induced obese mice. In extensor digitorum longus (EDL), yoghurt up-regulated the expression of activation of 5’adenosine monophosphate-activated protein kinase (AMPK), insulin receptor substrate-1 (IRS-1), phosphatidylinositol-3 kinase (PI3K) and glucose transporter 4 (GLUT4), and down-regulated the expression of angiotensin II receptor type 1 (AGTR-1). The combination of blueberries and yoghurt down-regulated the mRNA expression of AGTR-1 and Forkhead box protein O1 (FoxO1) in the EDL. Whereas the combination of C3G and peptides down-regulated AGTR-1 and up-regulated GLUT4 mRNA expression in the EDL. In the soleus, blueberries and yoghurt alone, and their combination down-regulated AGTR-1 and up-regulated GLUT4 mRNA expression. In summary blueberries and yoghurt, regulated multiple genes associated with glucose metabolism in skeletal muscles, and therefore may play a role in the management and prevention of T2DM.

Angiotensin II Blood Serum Levels in Piglets, after Intra-Dermal or Intra-Muscular Vaccination against PRRSV

Simple Summary

Porcine reproductive and respiratory syndrome virus (PRRSV) infection causes massive financial losses in pig production worldwide. Vaccination is still the most cost-effective tool to handle PRRSV infection. PRRSV induces apoptosis in different organs. Angiotensin II (Ang II) participates in the inflammatory response, cell proliferation, migration, and apoptosis. The objective of the current study was to assess the concentration of Ang II in the serum of piglets following immunization against PRRSV through intradermal (ID) or intramuscular (IM) vaccination with a commercial PRRS modified live virus (MLV) vaccine. The results indicated differences in viremia of tested piglets at 7 weeks of age, while piglets at 10 weeks of age were all found qRT-PCR positive for PRRSV. Moreover, significant differences were noticed in Ang II in 7-week-old piglets. In conclusion, our study provides evidence that ID vaccination induces less tissue damage, based on the lower measurements of Ang II in the serum of ID vaccinated piglets.

Abstract

The Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) induces apoptosis in different organs. Angiotensin II (Ang II) is the main effector of the renin-angiotensin system and participates in apoptosis. Thus, this study aimed to investigate changes in piglet serum Ang II levels following intradermal (ID) and intramuscular (IM) vaccination with a commercial PRRS modified live virus (MLV) vaccine. The trial was conducted in a commercial pig farm, including 104 piglets which were randomly allocated to four groups: Group A—Porcilis PRRS ID, Group B—Porcilis PRRS IM, Group C—Diluvac ID and Group D—Diluvac IM. The study piglets were either vaccinated or injected at 2 weeks of age and they were tested by qRT-PCR for PRRSV and by ELISA for Ang II. The results indicated differences in viremia of tested piglets at 7 weeks of age, while piglets at 10 weeks of age were all found qRT-PCR positive for PRRSV. In addition, significant differences were noticed in Ang II in 7-week-old piglets. In conclusion, the present study provides evidence that ID vaccination induces less tissue damage, based on the lower measurements of Ang II in the serum of ID vaccinated piglets.

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.

Characterization of the Skeletal Muscle Proteome in Undernourished Old Rats

Aging is associated with a progressive loss of skeletal muscle mass and function termed sarcopenia. Various metabolic alterations that occur with aging also increase the risk of undernutrition, which can worsen age-related sarcopenia. However, the impact of undernutrition on aged skeletal muscle remains largely under-researched. To build a deeper understanding of the cellular and molecular mechanisms underlying age-related sarcopenia, we characterized the undernutrition-induced changes in the skeletal muscle proteome in old rats. For this study, 20-month-old male rats were fed 50% or 100% of their spontaneous intake for 12 weeks, and proteomic analysis was performed on both slow- and fast-twitch muscles. Proteomic profiling of undernourished aged skeletal muscle revealed that undernutrition has profound effects on muscle proteome independently of its effect on muscle mass. Undernutrition-induced changes in muscle proteome appear to be muscle-type-specific: slow-twitch muscle showed a broad pattern of differential expression in proteins important for energy metabolism, whereas fast-twitch muscle mainly showed changes in protein turnover between undernourished and control rats. This first proteomic analysis of undernourished aged skeletal muscle provides new molecular-level insight to explain phenotypic changes in undernourished aged muscle. We anticipate this work as a starting point to define new biomarkers associated with undernutrition-induced muscle loss in the elderly.

The angiotensin-converting enzyme gene insertion/deletion polymorphism interacts with fear of falling in relation to stepping speed in community-dwelling older adults

BACKGROUND

Despite the association of genetic factors with falls, balance, and lower extremity functioning, interaction of the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism with fear of falling (FOF) in relation to stepping performance has, to the best of our knowledge, not been investigated in older adults.

OBJECTIVE

The purpose of this study was to examine the interaction effects of the ACE I/D polymorphism with FOF in relation to stepping performance in older adults.

METHODS

Eighty-eight community-dwelling adults 60 years or older participated in a cross-sectional observational study. Participants completed tests of rapid and distance stepping, and self-reported FOF (yes/no). Participants provided saliva for ACE genotyping. General linear models evaluated ACE genotype × FOF interaction effects in relation to stepping performance. The α level was set at 0.05.

RESULTS

The ACE I/D polymorphism exhibited significant interaction effects (p for interactions 0.002 ≤ p ≤ .04) with FOF in relation to stepping speed. Relationships between FOF and stepping speed varied among ACE genotypes. The insertion/insertion (II) genotype was significantly associated (p = .01) with slow stepping in individuals with, but not without FOF (p > .05).

CONCLUSION

Variation in relationships between FOF and stepping speed among ACE genotypes suggests a role for the ACE I/D polymorphism in modifying relationships between FOF and stepping speed in older adults. The association of the ACE II genotype with slow stepping performance in individuals with, but not without FOF, suggests that older adults with the ACE II genotype and FOF may be at increased risk for poor stepping performance and associated functional declines.

Sarcopenia: An Age-Related Multifactorial Disorder

Sarcopenia is an emerging clinical entity characterized by a gradual decline in skeletal muscle mass and strength that accompanies the normal aging process. It has been noted that sarcopenia is associated with various adverse health outcomes in the geriatric population like prolonged hospital admission, disability, poor quality of life, frailty, and mortality. Factors involved in the development of age-related sarcopenia include anorexia, alteration in the hormone levels, decreased neural innervation, low blood flow to the muscles, cytokine dysregulation, altered mitochondrial activity, genomic instability, intracellular proteolysis, and insulin resistance. Understanding the mechanism may help develop efficient preventive and therapeutic strategies which can improve the quality of life in elderly individuals. Thus, the objective of the present article is to review the literature regarding the mechanism involved in the development of sarcopenia in aged individuals.

Role of hormones in sarcopenia

Aging involves numerous changes in body composition that include a decrease in skeletal muscle mass. The gradual reduction in muscle mass is associated with a simultaneous decrease in muscle strength, which leads to reduced mobility, fragility and loss of independence. This process called sarcopenia is secondary to several factors such as sedentary lifestyle, inadequate nutrition, chronic inflammatory state and neurological alterations. However, the endocrine changes associated with aging seem to be of special importance in the development of sarcopenia. On one hand, advancing age is associated with a decreased secretion of the main hormones that stimulate skeletal muscle mass and function (growth hormone, insulin-like growth factor 1 (IGFI), testosterone and estradiol). On the other hand, the alteration of the IGF-I signaling along with decreased insulin sensitivity also have an important impact on myogenesis. Other hormones that decline with aging such as the adrenal-derived dehydroepiandrosterone, thyroid hormones and vitamin D seem to also be involved in sarcopenia. Adipokines released by adipose tissue show important changes during aging and can affect muscle physiology and metabolism. In addition, catabolic hormones such as cortisol and angiotensin II can accelerate aged-induced muscle atrophy, as they are involved in muscle wasting and their levels increase with age. The role played by all of these hormones and the possible use of some of them as therapeutic tools for treating sarcopenia will be discussed.

Role of AMP-activated protein kinase on cardio-metabolic abnormalities in the development of diabetic cardiomyopathy: A molecular landscape

Cardiovascular complications associated with diabetes mellitus remains a leading cause of morbidity and mortality across the world. Diabetic cardiomyopathy is a descriptive pathology that in absence of co-morbidities such as hypertension, dyslipidemia initially characterized by cardiac stiffness, myocardial fibrosis, ventricular hypertrophy, and remodeling. These abnormalities further contribute to diastolic dysfunctions followed by systolic dysfunctions and eventually results in clinical heart failure (HF). The clinical outcomes associated with HF are considerably worse in patients with diabetes. The complexity of the pathogenesis and clinical features of diabetic cardiomyopathy raises serious questions in developing a therapeutic strategy to manage cardio-metabolic abnormalities. Despite extensive research in the past decade the compelling approaches to manage and treat diabetic cardiomyopathy are limited. AMP-Activated Protein Kinase (AMPK), a serine-threonine kinase, often referred to as cellular "metabolic master switch". During the development and progression of diabetic cardiomyopathy, a plethora of evidence demonstrate the beneficial role of AMPK on cardio-metabolic abnormalities including altered substrate utilization, impaired cardiac insulin metabolic signaling, mitochondrial dysfunction and oxidative stress, myocardial inflammation, increased accumulation of advanced glycation end-products, impaired cardiac calcium handling, maladaptive activation of the renin-angiotensin-aldosterone system, endoplasmic reticulum stress, myocardial fibrosis, ventricular hypertrophy, cardiac apoptosis, and impaired autophagy. Therefore, in this review, we have summarized the findings from pre-clinical and clinical studies and provided a collective overview of the pathophysiological mechanism and the regulatory role of AMPK on cardio-metabolic abnormalities during the development of diabetic cardiomyopathy.

Interindividual Variation in Cardiorespiratory Fitness: A Candidate Gene Study in Han Chinese People

Cardiorespiratory fitness, as assessed through peak oxygen uptake (VO2peak), is a powerful health indicator. We aimed to evaluate the influence of several candidate causal genetic variants on VO2peak level in untrained Han Chinese people. A total of 1009 participants (566 women; age [mean ± SD] 40 ± 14 years, VO2peak 29.9 ± 7.1 mL/kg/min) performed a maximal incremental cycling test for VO2peak determination. Genomic DNA was extracted from peripheral whole blood, and genotyping analysis was performed on 125 gene variants. Using age, sex, and body mass as covariates, and setting a stringent threshold p-value of 0.0004, only one single nucleotide polymorphism (SNP), located in the gene encoding angiotensin-converting enzyme (rs4295), was associated with VO2peak (β = 0.87; p < 2.9 × 10-4). Stepwise multiple regression analysis identified a panel of three SNPs (rs4295 = 1.1%, angiotensin II receptor type 1 rs275652 = 0.6%, and myostatin rs7570532 = 0.5%) that together accounted for 2.2% (p = 0.0007) of the interindividual variance in VO2peak. Participants carrying six 'favorable' alleles had a higher VO2peak (32.3 ± 8.1 mL/kg/min) than those carrying only one favorable allele (24.6 ± 5.2 mL/kg/min, p < 0.0001). In summary, VO2peak at the pre-trained state is partly influenced by several polymorphic variations in candidate genes, but they represent a minor portion of the variance.

Lisinopril Preserves Physical Resilience and Extends Life Span in a Genotype-Specific Manner in Drosophila melanogaster

Physical resiliency declines with age and comorbid conditions. In humans, angiotensin-converting enzyme (ACE) has been associated with attenuation of the decline in physical performance with age. ACE-inhibitor compounds, commonly prescribed for hypertension, often have beneficial effects on physical performance however the generality of these effects are unclear. Here, we tested the effects of the ACE-inhibitor Lisinopril on life span, and age-specific speed, endurance, and strength using three genotypes of the Drosophila melanogaster Genetic Reference Panel. We show that age-related decline in physical performance and survivorship varies with genetic background. Lisinopril treatment increased mean life span in all Drosophila Genetic Reference Panel lines, but its effects on life span, speed, endurance, and strength depended on genotype. We show that genotypes with increased physical performance on Lisinopril treatment experienced reduced age-related protein aggregation in muscle. Knockdown of skeletal muscle-specific Ance, the Drosophila ortholog of ACE, abolished the effects of Lisinopril on life span, implying a role for skeletal muscle Ance in survivorship. Using transcriptome profiling, we identified genes involved in stress response that showed expression changes associated with genotype and age-dependent responsiveness to Lisinopril. Our results demonstrate that Ance is involved in physical decline and demonstrate genetic variation in phenotypic responses to an ACE inhibitor.

Angiotensin-Converting Enzyme Related-Polymorphisms on Inflammation, Muscle and Myocardial Damage After a Marathon Race

Muscle damage is one of the most important factors that affect muscle fatigue during endurance exercise. Recent evidence suggests that the renin–angiotensin system impacts on skeletal muscle wasting. The aim of this study was to determine association between the AGT Met235Thr, ACE I/D and BDKRB2 −9/+9 polymorphisms with inflammation, myocardial and muscle injury induced by endurance exercise. Eighty-one Brazilian male runners participated in this study and completed the International Marathon of Sao Paulo. Muscle and myocardial damage markers (alanine transaminase, ALT, aspartate transaminase, AST, lactic dehydrogenase, LDH, creatine kinase, CK, Troponin, pro BNP, myoglobin, and CK-MB) and inflammatory mediators (IL-6, IL-8, IL-10, IL12p70, IL1β, and TNF-α) were determined one day before, immediately after, one day after, and three days after the event. Muscle damage was also determined fifteen days after race and angiotensinogen (AGT) Met235Thr, angiotensin-converting enzyme (ACE) I/D, and Bradykinin B2 receptor (BDKRB2) −9/+9 polymorphisms were determined. Marathon race participation induced an increase in all muscle damage and inflammatory markers evaluated (p < 0.0001). The muscle damage markers, troponin and pro BNP, CK and LDH and inflammatory markers, IL-6, IL-8, IL-1β and IL-10 were also higher in ACE II genotype immediately after race, compared to DD genotype. The percentage of runners higher responders (>500U/I) to CK levels was higher for II genotypes (69%) compared to DD and ID genotypes (38% and 40%, respectively) immediately after. Troponin, pro BNP and IL-1β, IL-8 levels were also elevated in AGT MM genotype compared to TT genotype athletes after and/or one day after race. BDKRB2 −9/−9 had pronounced response to LDH, CK, CK-MB and ALT and AST activities, myoglobin, troponin, IL-6, IL-8 levels immediately, one day and/or three days after race. The percentage of runners higher responders (>500U/I) to CK levels was greater for −9−9 and −9+9 genotypes (46 and 48%, respectively) compared to +9+9 genotypes (31%) immediately after. ACE II, AGT MM, and BDKRB2 −9−9 genotypes may increase the susceptibility to inflammation, muscle injury after endurance exercise and could be used to predict the development of clinical conditions associated with muscle damage and myocardial injury.

Angiotensin-Converting Enzyme Insertion/Deletion Polymorphism, Lower Extremity Strength, and Physical Performance in Older Adults

BACKGROUND

Evidence for associations between the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene and physical performance is conflicting. Furthermore, investigations of relationships between lower extremity strength and physical performance have usually not considered the role of the ACE genotype, and it is unclear whether there are variations in relationships between lower extremity strength and physical performance among ACE genotypes in older adults.

OBJECTIVE

The objectives of this study were to investigate associations between the ACE I/D polymorphism and physical performance and to determine whether relationships between lower extremity strength and physical performance vary among ACE genotypes in older adults.

DESIGN

This was a cross-sectional observational study.

METHODS

Community-dwelling adults (N = 88) who were at least 60 years old completed physical performance and lower extremity strength tests. After DNA was extracted from saliva, ACE I/D polymorphism genotyping was done. The Spearman rank order correlation coefficient was used to examine associations between lower extremity strength and physical performance within ACE genotype subgroups. Analysis of covariance and linear regression were used to examine ACE genotype and ACE genotype × lower extremity strength interaction effects in relation to physical performance.

RESULTS

Genotype-specific correlation coefficients exhibited substantial variation among ACE genotype subgroups; however, differences did not attain statistical significance. Statistically significant genotype × lower extremity strength interaction effects in relation to physical performance were detected.

LIMITATIONS

The cross-sectional design precludes inferring causal relationships between strength and performance. The small sample size contributed to limited power to detect additional interaction effects and to detect statistically significant differences between correlation coefficients among ACE genotype subgroups.

CONCLUSIONS

The ACE I/D polymorphism is, interactively with lower extremity strength, associated with physical performance. Genotype-specific correlation coefficients and ACE genotype × lower extremity strength interaction effects on physical performance are consistent with variations in relationships between lower extremity strength and performance among ACE genotype subgroups.

Egg white hydrolysate enhances insulin sensitivity in high-fat diet-induced insulin-resistant rats via Akt activation

Agents that block the renin-angiotensin system (RAS) improve glucoregulation in the metabolic syndrome disorder. We evaluated the effects of egg white hydrolysate (EWH), previously shown to modulate the protein abundance of RAS component in vivo, on glucose homeostasis in diet-induced insulin-resistant rats. Sprague-Dawley rats were fed a high-fat diet (HFD) for 6 weeks to induce insulin resistance. They were then randomly divided into four groups receiving HFD or HFD supplemented with different concentrations of EWH (1, 2 and 4 %) for another 6 weeks in the first trial. In the second trial, insulin-resistant rats were divided into two groups receiving only HFD or HFD+4 % EWH for 6 weeks. Glucose homeostasis was assessed by oral glucose tolerance and insulin tolerance tests. Insulin signalling and protein abundance of RAS components, gluconeogenesis enzymes and PPARγ were evaluated in muscle, fat and liver. Adipocyte morphology and inflammatory markers were evaluated. In vivo administration of EWH increased insulin sensitivity, improved oral glucose tolerance (P < 0·0001) and reduced systemic inflammation (P < 0·05). EWH potentiated insulin-induced Akt phosphorylation in muscle (P = 0·0341) and adipose tissue (P = 0·0276), but minimal differences in the protein abundance of tissue RAS components between the EWH and control groups were observed. EWH treatment also reduced adipocyte size (P = 0·0383) and increased PPARγ2 protein abundance (P = 0·0237). EWH treatment yielded positive effects on the inflammatory profile, glucose tolerance, insulin sensitivity and adipocyte differentiation in HFD-induced insulin resistance rats. The involvement of local RAS activity requires further investigation.

ACE Insertion/Deletion Polymorphism (rs4646994) Is Associated With the Increased Risk of Multiple Myeloma

Introduction: The insertion (I allele) deletion (D allele) polymorphism of ACE gene (rs4646994) may influence the etiopathogenesis of multiple myeloma (MM). ACE gene is expressed in bone marrow cells and encodes angiotensin converting enzyme (ACE). It converts angiotensin I to active peptide angiotensin II, which stimulates proliferation of hematopoietic stem cells. This suggests possible association of ACE I/D gene polymorphism with MM. The aim of our study was to check possible impact of this polymorphism on risk of development and outcome of MM, as well as, sensitivity to bortezomib in cell cultures derived from MM patients.

Objects and Methods: Genomic DNA from 98 newly diagnosed MM patients and 100 healthy blood donors were analyzed by PCR method. Chromosomal aberrations were detected by use of cIg-FISH. In a subgroup of 40 MM patients nucleated bone marrow cells were treated with bortezomib in vitro.

Results: The Hardy-Weinberg equilibrium test showed that genotypic frequencies diverged significantly from the equilibrium. The differences between I and D allele frequencies in control and study population were significant (p = 0.046). We observed the association between DD genotype and more than 2-fold risk of MM - OR = 2.69; p < 0.0001. We did not detect any significant differences among studied genotypes regarding clinical and laboratory parameters. Moreover, we did not observe the association between survival of MM patients and I/D genotypes. Bortezomib increased number of apoptotic and necrotic cells, but the only statistically significant differences were observed in the number of viable cells at 1 nM between ID and DD genotypes (p = 0.026).

Conclusion: Presented results confirmed the significant relationship between ACE (I/D) polymorphism and risk of MM development. We did not observe the association of ACE I/D polymorphism with disease outcome and bortezomib in vitro sensitivity.

ACE I/D gene variant predicts ACE enzyme content in blood but not the ACE, UCP2, and UCP3 protein content in human skeletal muscle in the Gene SMART study

Angiotensin-converting enzyme (ACE) is expressed in human skeletal muscle. The ACE I/D polymorphism has been associated with athletic performance in some studies. Studies have suggested that the ACE I/D gene variant is associated with ACE enzyme content in serum, and there is an interaction between ACE and uncoupling proteins 2 and 3 (UCP2 and UCP3). However, no studies have explored the effect of ACE I/D on ACE, UCP2, and UCP3 protein content in human skeletal muscle. Utilizing the Gene SMART cohort ( n = 81), we investigated whether the ACE I/D gene variant is associated with ACE enzyme content in blood and ACE, UCP2, and UCP3 protein content in skeletal muscle at baseline and following a session of high-intensity interval exercise (HIIE). Using a stringent and robust statistical analyses, we found that the ACE I/D gene variant was associated with ACE enzyme content in blood ( P < 0.005) at baseline but not the ACE, UCP2, and UCP3 protein content in muscle at baseline. A single session of HIIE tended (0.005 < P < 0.05) to increase blood ACE content immediately postexercise, whereas muscle ACE protein content was lower 3 h after a single session of HIIE ( P < 0.005). Muscle UCP3 protein content decreased immediately after a single session of HIIE ( P < 0.005) and remained low 3 h postexercise. However, those changes in the muscle were not genotype dependent. In conclusion, The ACE I/D gene variant predicts ACE enzyme content in blood but not the ACE, UCP2, and UCP3 protein content of human skeletal muscle. NEW & NOTEWORTHY This paper describes the association between ACE I/D gene variant and ACE protein content in blood and ACE, UCP2, and UCP3 protein content in skeletal muscle at baseline and after exercise in a large cohort of healthy males. Our data suggest that ACE I/D is a strong predictor of blood ACE content but not muscle ACE content.

Improving the comprehension of sarcopenic state determinants: An multivariate approach involving hormonal, nutritional, lifestyle and genetic variables

It is known that sarcopenia is a multifaceted phenomenon, which involves genetic, nutritional, hormonal and living habits aspects. Then, an integrated analysis, as a multivariate approach, could improve the comprehension about the determinants of sarcopenic state in old adults. The present study aimed to investigate the interaction among serum vitamin D, daily caloric and protein intake, lifestyle habits, ACE I/D gene polymorphism and sarcopenic state in community-dwelling old adults. One hundred one community-dwelling old adults were clinically stratified as sarcopenic or non-sarcopenic. Serum vitamin D, daily caloric and protein intake, lifestyle habits (smoking, physical activity level and sedentary behavior) and ACE I/D gene polymorphism were recorded. A multivariate logistic regression technique was applied to investigate the interaction among the selected independent variables and the sarcopenic state. The independent variables age, smoking, serum Vitamin D and ACE I/D polymorphism achieved the statistical criteria to be inserted in the multivariate analysis. After a stepwise procedure from the multivariate logistic regression, the variables age, serum Vitamin D and ACE I/D polymorphism remained, together, in the final model. Sarcopenic state was significantly associated to older age, II-genotype and low serum Vitamin D in old adults from 60 years old.

Leucine and ACE inhibitors as therapies for sarcopenia (LACE trial): study protocol for a randomised controlled trial

BACKGROUND

Sarcopenia (the age-related loss of muscle mass and function) is a major contributor to loss of mobility, falls, loss of independence, morbidity and mortality in older people. Although resistance training is effective in preventing and reversing sarcopenia, many older people are sedentary and either cannot or do not want to exercise. This trial examines the efficacy of supplementation with the amino acid leucine and/or angiotensin converting enzyme inhibition to potentially improve muscle mass and function in people with sarcopenia. Promising preliminary data exist from small studies for both interventions, but neither has yet been tested in adequately powered randomised trials in patients with sarcopenia.

METHODS

Leucine and ACE inhibitors in sarcopenia (LACE) is a multicentre, masked, placebo-controlled, 2 × 2 factorial randomised trial evaluating the efficacy of leucine and perindopril (angiotensin converting enzyme inhibitor (ACEi)) in patients with sarcopenia. The trial will recruit 440 patients from primary and secondary care services across the UK. Male and female patients aged 70 years and over with sarcopenia as defined by the European Working Group on Sarcopenia (based on low total skeletal muscle mass on bioimpedance analysis and either low gait speed or low handgrip strength) will be eligible for participation. Participants will be excluded if they have a contraindication to, or are already taking, an ACEi, angiotensin receptor blocker or leucine. The primary clinical outcome for the trial is the between-group difference in the Short Physical Performance Battery score at all points between baseline and 12 months. Secondary outcomes include appendicular muscle mass measured using dual-energy X-ray absorptiometry, muscle strength, activities of daily living, quality of life, activity using pedometer step counts and falls. Participants, clinical teams, outcomes assessors and trial analysts are masked to treatment allocation. A panel of biomarkers including microRNAs, neurohormones, genetic polymorphisms and markers of inflammation relevant to muscle pathophysiology will be measured to explore predictors of response and further elucidate mechanisms underlying sarcopenia. Participants will receive a total of 12 months of either perindopril or placebo and either leucine or placebo.

DISCUSSION

The results will provide the first robust test of the overall clinical and cost-effectiveness of these novel therapies for older patients with sarcopenia.

TRIAL REGISTRATION

ISRCTN, ISRCTN90094835 . Registered on 18 February 2015.

The Metabolic Response of Skeletal Muscle to Endurance Exercise Is Modified by the ACE-I/D Gene Polymorphism and Training State

The insertion/deletion polymorphism in the gene for the regulator of vascular tone, angiotensin-converting enzyme (ACE), is the prototype of a genetic influence on physical fitness and this involves an influence on capillary supply lines and dependent aerobic metabolism in skeletal muscle. The respective interaction of ACE-I/D genotype and training status on local metabolic and angiogenic reactions in exercised muscle is not known. Toward this end we characterized the metabolomic and angiogenic response in knee extensor muscle, m. vastus lateralis, in 18 untrained and 34 endurance-trained (physically active, [Formula: see text]O2max > 50 mL min^-1 kg^-1) white British men to an exhaustive bout of one-legged cycling exercise. We hypothesized that training status and ACE-I/D genotype affect supply-related muscle characteristics of exercise performance in correspondence to ACE expression and angiotensin 2 levels. ACE-I/D genotype and training status developed an interaction effect on the cross-sectional area (CSA) of m. vastus lateralis and mean CSA of slow type fibers, which correlated with peak power output (r ≥ 0.44). Genotype × training interactions in muscle also resolved for exercise-induced alterations of 22 metabolites, 8 lipids, glycogen concentration (p = 0.016), ACE transcript levels (p = 0.037), and by trend for the pro-angiogenic factor tenascin-C post exercise (p = 0.064). Capillary density (p = 0.001), capillary-to-fiber ratio (p = 0.010), systolic blood pressure (p = 0.014), and exercise-induced alterations in the pro-angiogenic protein VEGF (p = 0.043) depended on the ACE-I/D genotype alone. Our observations indicate that variability in aerobic performance in the studied subjects was in part reflected by an ACE-I/D-genotype-modulated metabolic phenotype of a major locomotor muscle. Repeated endurance exercise appeared to override this genetic influence in skeletal muscle by altering the ACE-related metabolic response and molecular aspects of the angiogenic response to endurance exercise.

Oxidative stress in adipose tissue as a primary link in pathogenesis of insulin resistance

Obesity is a leading risk factor of diabetes mellitus type 2, impairments of lipid metabolism and cardiovascular diseases. Dysfunctions of the accumulating weight of the visceral fat are primarily linked to pathogenesis of systemic insulin resistance. The review considers modern views about biochemical mechanisms underlying formation of oxidative stress in adipocytes at obesity, as one of key elements of impairments of their metabolism triggering formation of systemic insulin resistance.

Heterogeneity of Physical Function Responses to Exercise in Older Adults: Possible Contribution of Variation in the Angiotensin-1 Converting Enzyme (ACE) Gene?

Behavioral exercise interventions, aimed at improving either aerobic endurance or muscular strength, are currently the only therapy found, on average, to consistently retard loss of physical function in aging adults. However, not all individuals experience the same magnitude of benefit from a given exercise treatment, and certain persons may respond more favorably to a particular mode of exercise than another. Research now shows that genetic predisposition is one of the factors accounting for interindividual differences in responses to exercise as well as differences in the propensity to engage in exercise. This article discusses how a common variant in a single gene (the angiotensin-1 converting enzyme gene) could emerge as a prospective tool to identify older individuals more likely to benefit from and adhere to a specific type of exercise activity over another type.

Angiotensin-dependent autonomic dysregulation precedes dilated cardiomyopathy in a mouse model of muscular dystrophy

NEW FINDINGS

What is the central question of this study? Is autonomic dysregulation in a mouse model of muscular dystrophy dependent on left ventricular systolic dysfunction and/or activation of the renin-angiotensin system (RAS) and does it predict development of dilated cardiomyopathy (DCM)? What is the main finding and its importance? The results demonstrate that autonomic dysregulation precedes and predicts left ventricular dysfunction and DCM in sarcoglycan-δ-deficient (Sgcd-/-) mice. The autonomic dysregulation is prevented by treatment of young Sgcd-/- mice with the angiotensin II type 1 receptor blocker losartan. Measurements of RAS activation and autonomic dysregulation may predict risk of DCM, and therapies targeting the RAS and autonomic dysregulation at a young age may slow disease progression in patients. Sarcoglycan mutations cause muscular dystrophy. Patients with muscular dystrophy develop autonomic dysregulation and dilated cardiomyopathy (DCM), but the temporal relationship and mechanism of autonomic dysregulation are not well understood. We hypothesized that activation of the renin-angiotensin system (RAS) causes autonomic dysregulation prior to development of DCM in sarcoglycan-δ-deficient (Sgcd-/-) mice and that the severity of autonomic dysfunction at a young age predicts the severity of DCM at older ages. At 10-12 weeks of age, when left ventricular function assessed by echocardiography remained normal, Sgcd-/- mice exhibited decreases in arterial pressure, locomotor activity, baroreflex sensitivity and cardiovagal tone and increased sympathetic tone compared with age-matched C57BL/6 control mice (P < 0.05). Systemic and skeletal muscle RAS were activated, and angiotensin II type 1 receptor (AT1 R) expression, superoxide and fibrosis were increased in dystrophic skeletal muscle (P < 0.05). Treatment with the AT1 R blocker losartan for 7-9 weeks beginning at 3 weeks of age prevented or strongly attenuated the abnormalities in Sgcd-/- mice (P < 0.05). Repeated assessment of phenotypes between 10 and 75 weeks of age demonstrated worsening of autonomic function, progressive cardiac dysfunction and DCM and increased mortality in Sgcd-/- mice. High sympathetic tone predicted subsequent left ventricular dysfunction. We conclude that activation of the RAS causes severe autonomic dysregulation in young Sgcd-/- mice, which portends a worse long-term prognosis. Therapeutic targeting of the RAS at a young age may improve autonomic function and slow disease progression in muscular dystrophy.

Genetic influence on exercise-induced changes in physical function among mobility-limited older adults

To date, physical exercise is the only intervention consistently demonstrated to attenuate age-related declines in physical function. However, variability exists in seniors' responsiveness to training. One potential source of variability is the insertion (I allele) or deletion (D allele) of a 287 bp fragment in intron 16 of the angiotensin-converting enzyme (ACE) gene. This polymorphism is known to influence a variety of physiological adaptions to exercise. However, evidence is inconclusive regarding the influence of this polymorphism on older adults' functional responses to exercise. This study aimed to evaluate the association of ACE I/D genotypes with changes in physical function among Caucasian older adults (n = 283) following 12 mo of either structured, multimodal physical activity or health education. Measures of physical function included usual-paced gait speed and performance on the Short Physical Performance Battery (SPPB). After checking Hardy-Weinberg equilibrium, we used using linear regression to evaluate the genotype*treatment interaction for each outcome. Covariates included clinic site, body mass index, age, sex, baseline score, comorbidity, and use of angiotensin receptor blockers or ACE inhibitors. Genotype frequencies [II (19.4%), ID (42.4%), DD (38.2%)] were in Hardy-Weinberg equilibrium (P > 0.05). The genotype*treatment interaction was statistically significant for both gait speed (P = 0.002) and SPPB (P = 0.020). Exercise improved gait speed by 0.06 ± 0.01 m/sec and SPPB score by 0.72 ± 0.16 points among those with at least one D allele (ID/DD carriers), but function was not improved among II carriers. Thus, ACE I/D genotype appears to play a role in modulating functional responses to exercise training in seniors.

Bioactive natural constituents from food sources-potential use in hypertension prevention and treatment

Prevention and management of hypertension are the major public health challenges worldwide. Uncontrolled high blood pressure may lead to a shortened life expectancy and a higher morbidity due to a high risk of cardiovascular complications such as coronary heart disease (which leads to heart attack) and stroke, congestive heart failure, heart rhythm irregularities, and kidney failure etc. In recent years, it has been recognized that many dietary constituents may contribute to human cardiovascular health. There has been an increased focus on identifying these natural components of foods, describing their physiological activities and mechanisms of actions. Grain, vegetables, fruits, milk, cheese, meat, chicken, egg, fish, soybean, tea, wine, mushrooms, and lactic acid bacteria are various food sources with potential antihypertensive effects. Their main bioactive constituents include angiotensin I-converting enzyme (ACE) inhibitory peptides, vitamins C and E, flavonoids, flavanols, cathecins, anthocyanins, phenolic acids, polyphenols, tannins, resveratrol, polysaccharides, fiber, saponin, sterols, as well as K, Ca, and P. They may reduce blood pressure by different mechanisms, such as ACE inhibition effect, antioxidant, vasodilatory, opiate-like, Ca(2+) channel blocking, and chymase inhibitory activities. These functional foods may provide new therapeutic applications for hypertension prevention and treatment, and contribute to a healthy cardiovascular population. The present review summarizes the antihypertensive food sources and their bioactive constituents, as well as physiological mechanisms of dietary products, especially focusing on ACE inhibitory activity.

Ace I/D polymorphism is associated with habitual physical activity in pubertal boys

We investigated the association between the angiotensin I-converting enzyme (ACE) gene insertion (I)/deletion (D) polymorphism and physical activity levels in boys at early pubertal stage (calendar age 12.04 ± 0.77 years). Body composition by DXA, pubertal stage and cardiovascular fitness on cycle ergometer were measured in addition to 7-day accelerometry. DNA was separated from the whole blood. Sedentary behaviour level was significantly lower in DD subjects compared to I allele carriers. A significant main effect of the D allele was found on total physical activity (F 1,256 = 5,453; p = 0.020; η (2) = 0.021] and on light physical activity (F 1,256 = 4.74; p = 0.030; η (2) = 0.018). Adding screen time as a covariate did not change ACE I/D polymorphism effect on total physical activity levels (F 2,256 = 3,326; p = 0.041; η (2) = 0.025). Carriers of the D allele had significantly higher light physical activity (F 1,256 = 4,710; p = 0.031; η (2) = 0.20), with screen time as covariate. In conclusion, ACE gene has a significant effect on sedentary, light and total physical activity levels in healthy 12-year-old boys.

The role of the renin-angiotensin system in the development of insulin resistance in skeletal muscle

The canonical renin-angiotensin system (RAS) involves the initial action of renin to cleave angiotensinogen to angiotensin I (ANG I), which is then converted to ANG II by the angiotensin converting enzyme (ACE). ANG II plays a critical role in numerous physiological functions, and RAS overactivity underlies many conditions of cardiovascular dysregulation. In addition, ANG II, by acting on both endothelial and myocellular AT1 receptors, can induce insulin resistance by increasing cellular oxidative stress, leading to impaired insulin signaling and insulin-stimulated glucose transport activity. This insulin resistance associated with RAS overactivity, when coupled with progressive ß-cell dysfunction, eventually leads to the development of type 2 diabetes. Interventions that target RAS overactivity, including ACE inhibitors, ANG II receptor blockers, and, most recently, renin inhibitors, are effective both in reducing hypertension and in improving whole-body and skeletal muscle insulin action, due at least in part to enhanced Akt-dependent insulin signaling and insulin-dependent glucose transport activity. ANG-(1-7), which is produced from ANG II by the action of ACE2 and acts via Mas receptors, can counterbalance the deleterious actions of the ACE/ANG II/AT1 receptor axis on the insulin-dependent glucose transport system in skeletal muscle. This beneficial effect of the ACE2/ANG-(1-7)/Mas receptor axis appears to depend on the activation of Akt. Collectively, these findings underscore the importance of RAS overactivity in the multifactorial etiology of insulin resistance in skeletal muscle, and provide support for interventions that target the RAS to ameliorate both cardiovascular dysfunctions and insulin resistance in skeletal muscle tissue.

The angiotensin converting enzyme insertion/deletion polymorphism alters the response of muscle energy supply lines to exercise

The presence of a silencing sequence (the I-allele) in the gene for the upstream regulator of blood flow, angiotensin I-converting enzyme (ACE), is associated with superior endurance performance and its trainability. We tested in a retrospective study with 36 Caucasian men of Swiss descent whether carriers of the ACE I-allele demonstrate a modified adaptive response of energy supply lines in knee extensor muscle, and aerobic fitness, to endurance training based on 6 weeks of supervised bicycle exercise or 6 months of self-regulated running (p value <Bonferroni-corrected 5 %). Body weight related maximal oxygen uptake and capillary density in vastus lateralis muscle before training were 20 and 23 % lower, respectively, in carriers of the I-allele. Bicycle (n = 16) but not running type endurance training (n = 19) increased the volume content of subsarcolemmal mitochondria (2.5-fold) and intramyocellular lipid (2.1-fold). This was specifically amplified in I-allele carriers after 6 weeks of bicycle exercise. The enhanced adjustment in myocellular organelles of aerobic metabolism with bicycle training corresponded to ACE I-allele dependent upregulation of 23 muscle transcripts during recovery from the bicycle stimulus and with training. The majority of affected transcripts were associated with glucose (i.e. ALDOC, Glut2, LDHC) and lipid metabolism (i.e. ACADL, CPTI, CPTII, LIPE, LPL, FATP, CD36/FAT); all demonstrating an enhanced magnitude of change in carriers of the ACE I-allele. Our observations suggest that local improvements in mitochondrial metabolism, through a novel expression pathway, contribute to the varying trainability in endurance performance between subjects with genetically modified expression of the regulator of vascular tone, ACE.

Angiotensin II receptor type 1 blockade decreases CTGF/CCN2-mediated damage and fibrosis in normal and dystrophic skeletal muscles

Connective tissue growth factor (CTGF/CCN-2) is mainly involved in the induction of extracellular matrix (ECM) proteins. The levels of CTGF correlate with the degree and severity of fibrosis in many tissues, including dystrophic skeletal muscle. The CTGF overexpression in tibialis anterior skeletal muscle using an adenoviral vector reproduced many of the features observed in dystrophic muscles including muscle damage and regeneration, fibrotic response and decrease in the skeletal muscle strength. The renin-angiotensin system is involved in the genesis and progression of fibrotic diseases through its main fibrotic components angiotensin-II and its transducer receptor AT-1. The use of AT-1 receptor blockers (ARB) has been shown to decrease fibrosis. In this paper, we show the effect of AT-1 receptor blockade on CTGF-dependent biological activity in skeletal muscle cells as well as the response to CTGF overexpression in normal skeletal muscle. Our results show that in myoblasts ARB decreased CTGF-mediated increase of ECM protein levels, extracellular signal regulated kinases 1/2 (ERK-1/2) phosphorylation and stress fibres formation. In tibialis anterior muscle overexpressing CTGF using an adenovirus, ARB treatment decreased CTGF-mediated increase of ECM molecules, α-SMA and ERK-1/2 phosphorylation levels. Quite remarkable, ARB was able to prevent the loss of contractile force of tibialis anterior muscles overexpressing CTGF. Finally, we show that ARB decreased the levels of fibrotic proteins, CTGF and ERK-1/2 phosphorylation augmented in a dystrophic skeletal muscle from mdx mice. We propose that ARB is a novel pharmacological tool that can be used to decrease the fibrosis induced by CTGF in skeletal muscle associated with muscular dystrophies.

The Impacts of ACE Activity according to ACE I/D Polymorphisms on Muscular Functions of People Aged 65

OBJECTIVE

To investigate associations between angiotensin-converting enzyme (ACE) polymorphisms and muscle fatigability in 65-year-old Koreans.

METHOD

The study participants were 49 Koreans aged 65 years. ACE insertion/deletion (I/D) polymorphisms were determined by polymerase chain reaction and serum ACE activity, by spectrophotometry. Body mass index (BMI), body fat mass (BFM), and lean body mass (LBM) were determined. To evaluate muscle fatigability, dynamic Electromyography was used to measure maximum voluntary isometric contractions (MVICs) of ankle plantar flexor muscles. Patients were seated with their hips flexed at 90°, knees fully extended, and ankles at 0°. Continuous submaximal VICs (40% MVIC) were then performed, and contraction duration and EMG frequency changes during the initial 2 min were measured. A self-reported physical activity questionnaire was used to evaluate effects of ACE activity levels on muscle fatigability.

RESULTS

Among the 49 volunteers, 15 showed II genotype; 22, ID genotype; and 12, DD genotype. Serum ACE activity levels were significantly higher in DD genotype subjects than in II genotype subjects (p<0.05). Furthermore, the duration of submaximal isometric contractions was longer in II and ID genotype subjects than in DD genotype subjects (p<0.05). Dynamic EMG showed significantly lower mean frequency changes in II genotype subjects than in DD genotype subjects (p<0.05). However, LBM, BFM, and BMI were independent of ACE genotypes.

CONCLUSION

ACE II genotype subjects showed significantly higher resistant to muscle fatigue than that by DD genotype subjects. However, body composition and BMI showed no correlations with ACE I/D polymorphisms.

Ramipril modulates circadian gene expression in skeletal muscle

OBJECTIVES

Treatment with angiotensin converting enzyme (ACE)-inhibitors favorably affects glucose metabolism and the development of diabetes mellitus by largely elusive mechanisms. To identify these mechanisms, we studied the effect of ACE-inhibition on gene expression in skeletal muscle, a primary target tissue for insulin in glucose homeostasis.

METHODS

A subject-blinded and analyst-blinded, placebo-controlled study was conducted in nine healthy men. Two consecutive muscle biopsies were conducted before and 9 h after a single dose of either 10-mg ramipril (n=6) or placebo (n=3), (randomly allocated). Muscle ribonucleic acid was subjected to transcriptome profiling.

RESULTS

In both ramipril-treated or placebo-treated individuals, the majority of genes with differential expression between the two time points belonged to the family of diurnally regulated genes, such as the NR1D1 and NR1D2 genes (nuclear receptor subfamily 1, group D, members 1 and 2) or members of the period homolog family (PER1-3). Ramipril significantly modulated the expression of other diurnally regulated genes, such as aryl hydrocarbon receptor nuclear translocator-like (ARNTL), encoding aryl hydrocarbon receptor nuclear translocator-like, a core component of the circadian clock (P=0.02). Concomitant attenuation of NR1D1 downregulation (-2.4-fold compared with -4.1-fold in placebo; P=0.04), a transcriptional repressor of ARNTL, supported the view that ramipril might modulate glucose homeostasis pathways involving the NR1D1 ARNTL axis.

CONCLUSION

As circadian rhythms are deranged in patients who are diabetic, modulated expression of circadian clock genes by ramipril could explain the favorable metabolic effects of therapeutic ACE-inhibition.

Chronic renin inhibition with aliskiren improves glucose tolerance, insulin sensitivity, and skeletal muscle glucose transport activity in obese Zucker rats

We have demonstrated previously that overactivity of the renin-angiotensin system (RAS) is associated with whole body and skeletal muscle insulin resistance in obese Zucker (fa/fa) rats. Moreover, this obesity-associated insulin resistance is reduced by treatment with angiotensin-converting enzyme inhibitors or angiotensin receptor (type 1) blockers. However, it is currently unknown whether specific inhibition of renin itself, the rate-limiting step in RAS functionality, improves insulin action in obesity-associated insulin resistance. Therefore, the present study assessed the effect of chronic, selective renin inhibition using aliskiren on glucose tolerance, whole body insulin sensitivity, and insulin action on the glucose transport system in skeletal muscle of obese Zucker rats. Obese Zucker rats were treated for 21 days with either vehicle or aliskiren (50 mg/kg body wt ip). Renin inhibition was associated with a significant lowering (10%, P < 0.05) of resting systolic blood pressure and induced reductions in fasting plasma glucose (11%) and free fatty acids (46%) and homeostatic model assessment for insulin resistance (13%). Glucose tolerance (glucose area under the curve) and whole body insulin sensitivity (inverse of the glucose-insulin index) during an oral glucose tolerance test were improved by 15% and 16%, respectively, following chronic renin inhibition. Moreover, insulin-stimulated glucose transport activity in isolated soleus muscle of renin inhibitor-treated animals was increased by 36% and was associated with a 2.2-fold greater Akt Ser(473) phosphorylation. These data provide evidence that chronic selective inhibition of renin activity leads to improvements in glucose tolerance and whole body insulin sensitivity in the insulin-resistant obese Zucker rat. Importantly, chronic renin inhibition is associated with upregulation of insulin action on skeletal muscle glucose transport, and it may involve improved Akt signaling. These data support the strategy of targeting the RAS to improve both blood pressure regulation and insulin action in conditions of insulin resistance.

Oxidative stress and the etiology of insulin resistance and type 2 diabetes

The condition of oxidative stress arises when oxidant production exceeds antioxidant activity in cells and plasma. The overabundance of oxidants is mechanistically connected to the multifactorial etiology of insulin resistance, primarily in skeletal muscle tissue, and the subsequent development of type 2 diabetes. Two important mechanisms for this oxidant excess are (1) the mitochondrial overproduction of hydrogen peroxide and superoxide ion under conditions of energy surplus and (2) the enhanced activation of cellular NADPH oxidase via angiotensin II receptors. Several recent studies are reviewed that support the concept that direct exposure of mammalian skeletal muscle to an oxidant stress (including hydrogen peroxide) results in stimulation of the serine kinase p38 mitogen-activated protein kinase (p38 MAPK), and that the engagement of this stress-activated p38 MAPK signaling is mechanistically associated with diminished insulin-dependent stimulation of insulin signaling elements and glucose transport activity. The beneficial interactions between the antioxidant α-lipoic acid and the advanced glycation end-product inhibitor pyridoxamine that ameliorate oxidant stress-associated defects in whole-body and skeletal-muscle insulin action in the obese Zucker rat, a model of prediabetes, are also addressed. Overall, this review highlights the importance of oxidative stress in the development of insulin resistance in mammalian skeletal muscle tissue, at least in part via a p38-MAPK-dependent mechanism, and indicates that interventions that reduce this oxidative stress and oxidative damage can improve insulin action in insulin-resistant animal models. Strategies to prevent and ameliorate oxidative stress remain important in the overall treatment of insulin resistance and type 2 diabetes.

Possible Mechanisms of Local Tissue Renin-Angiotensin System Activation in the Cardiorenal Metabolic Syndrome and Type 2 Diabetes Mellitus

The role of local tissue renin-angiotensin system (tRAS) activation in the cardiorenal metabolic syndrome (CRS) and type 2 diabetes mellitus (T2DM) is not well understood. To this point, we posit that early redox stress-mediated injury to tissues and organs via accumulation of excessive reactive oxygen species (ROS) and associated wound healing responses might serve as a paradigm to better understand how tRAS is involved. There are at least five common categories responsible for generating ROS that may result in a positive feedback ROS-tRAS axis. These mechanisms include metabolic substrate excess, hormonal excess, hypoxia-ischemia/reperfusion, trauma, and inflammation. Because ROS are toxic to proteins, lipids, and nucleic acids they may be the primary instigator, serving as the injury nidus to initiate the wound healing process. Insulin resistance is central to the development of the CRS and T2DM, and there are now thought to be four major organ systems important in their development. In states of overnutrition and tRAS activation, adipose tissue, skeletal muscle (SkM), islet tissues, and liver (the quadrumvirate) are individually and synergistically related to the development of insulin resistance, CRS, and T2DM. The obesity epidemic is thought to be the driving force behind the CRS and T2DM, which results in the impairment of multiple end-organs, including the cardiovascular system, pancreas, kidney, retina, liver, adipose tissue, SkM, and nervous system. A better understanding of the complex mechanisms leading to local tRAS activation and increases in tissue ROS may lead to new therapies emphasizing global risk reduction of ROS resulting in decreased morbidity and mortality.

Streptococcal zymogen type B induces angiotensin II in mesangial cells and leukocytes

Previous reports have shown that angiotensin II and oxidative stress may be important features in acute poststreptococcal glomerulonephritis (APSGN) and that streptococcal erythrogenic toxin type B (ETB) and its precursor (ETBP) may have an important role in the pathogenesis of APSGN. The aim of this study was to determine the effect of ETBP on the production of angiotensin II and oxidative stress in rat mesangial cells and human mononuclear leukocytes. Mesangial cells and leukocytes were isolated from digested glomeruli and by histopaque gradient, respectively, while ETBP was isolated from nephritogenic streptococcus cultures using a cation exchange column. Angiotensin II was determined by an enzyme-linked immunosorbent assay and by cytometrics. Superoxide anion, reduced glutathione, nitrites, lipid peroxidation and catalase activity were determined by cytochemical, biochemical and enzymatic assays. Inducible nitric oxide synthase expression was determined by cytometrics. An increased production of angiotensin II was observed in ETBP-treated mesangial cell and leukocyte cultures. The ETBP induced an elevated production of superoxide anions and nitrites in mesangial cells and superoxide anions in leukocytes, while this streptococcal protein decreased the expression of inducible nitric oxide synthase in leukocytes. The ETBP was capable of inducing an increased production of angiotensin II and increased oxidative stress, both of which may be important mediators of inflammatory events in the renal tissue and during APSGN.