The ACE gene and muscle performance

Angiotensin-Converting Enzyme Genotype Predicts Cardiac and Autonomic Responses to Prolonged Exercise

OBJECTIVES

The purpose of this study was to investigate the phenomenon of left ventricular (LV) dysfunction after ultraendurance exercise.

BACKGROUND

Subclinical LV dysfunction in response to endurance exercise up to 24 h duration has been described, but its mechanism remains elusive.

METHODS

We tested 86 athletes before and after the Adrenalin Rush Adventure Race using echocardiography, impedance cardiography, and plasma immunoassay.

RESULTS

At baseline, athletes demonstrated physiology characteristic of extreme endurance training. After 90 to 120 h of almost-continuous exercise, LV systolic and diastolic function declined (fractional shortening before the race, 39.6 +/- 0.65%; after, 32.2 +/- 0.84%, p < 0.001; mitral inflow E-wave deceleration time before the race, 133 +/- 5 ms; after, 160 +/- 5 ms, n = 48, p < 0.001) without change in loading conditions as defined by LV end-diastolic dimension and total peripheral resistance estimated by thoracic impedance. There was a compensatory increase in heart rate (before, 55 +/- 1.3 beats/min; after, 59 +/- 1.5 beats/min, p = 0.05), which left cardiac output unchanged, as well as significant-but-subclinical increases in brain natriuretic peptide and troponin I. In addition, we found that athletes who were homozygous for the intron-16 insertion polymorphism of the angiotensin-converting enzyme (ACE) gene exhibited a significantly greater decrease in fractional shortening than athletes who were homozygous for the deletion allele. Heterozygotes showed an intermediate phenotype. In addition, the deletion group manifest an enhanced sympathovagal balance after the race, as evidenced by greater power in the low-frequency component of blood pressure variability.

CONCLUSIONS

The ACE genotype predicts the extent of reversible subclinical LV dysfunction after prolonged exercise and is associated with a differential postactivity augmentation of sympathetic nervous system function that may explain it.

Sarcopenia – A Potential Target for Angiotensin-Converting Enzyme Inhibition?

Society is ageing. There has been a steady increase in the number of people aged 65 years and over throughout the 20th century and this trend is predicted to continue worldwide. This has resulted in an increase in the incidence of sarcopenia, which is a loss of muscle mass and function with age. Maintenance of muscular function into old age is critical to sustaining normal daily activity and functional independence. Sarcopenia is associated with increased morbidity and mortality. Till now most efforts to counteract sarcopenia have met with limited success. We postulate that targeting the renin-angiotensin system through angiotensin-converting enzyme (ACE) inhibition could play a role in countering sarcopenia. ACE inhibitors could work by preventing mitochondrial decline and improving endothelial function and muscle metabolism. We describe the literature to support our hypothesis that sarcopenia may be a potential therapeutic target for ACE inhibitors.

The bradykinin beta 2 receptor (BDKRB2) and endothelial nitric oxide synthase 3 (NOS3) genes and endurance performance during Ironman Triathlons

We have previously shown that the insertion allele of the angiotensin-converting enzyme (ACE) gene was over-represented in the fastest South-African-born finishers of the South African Ironman Triathlons. As ACE is a component of the skeletal muscle kallikrein-kinin system (KKS), the aim of this study is to determine if there are any further associations between polymorphisms within the BDKRB2 and NOS3 genes, which encode for the KKS components, bradykinin beta(2) receptor and nitric oxide synthase, respectively, and ultra-endurance performance during the Ironman Triathlons. Four-hundred and forty-three male Caucasian triathletes who completed the 2000 and/or 2001 South African Ironman Triathlons and 203 healthy Caucasian male control subjects were genotyped for the functional -9/+9 polymorphism within exon 1 of the BDKRB2 gene and the G894T NOS3 gene polymorphisms. The BDKRB2 -9/-9 genotype occurred at a significantly higher frequency when the triathlete group (27.0%) was compared with the control group (19.3%, P=0.035). When divided into tertiles, there was also a significant linear trend for the NOS3 GG genotype distribution among the fastest (35.0%), middle (40.4%) and slowest (46.9%) finishers (P=0.039). The overall finishing times of the triathletes with an NOS3 GG genotype together with a BDKRB2 +9 allele were significantly slower than those with other genotype combinations (P=0.001). The NOS3/BDKRB2 genotype (beta=-0.150, B=-31.48, P=0.002), together with body mass index and age, accounted for 14.6% of the variance in the overall race time for the triathlon. In conclusion, both the NOS3 and BDKRB2 genes are associated with the actual performance during the Ironman Triathlons.

Histochemical characteristics of soleus muscle in angiotensin-converting enzyme gene knockout mice

We examined the histochemical characteristics of soleus muscle in the angiotensin-converting enzyme (ACE) gene (Ace in mice, ACE in humans) knockout mice. Serial sections of soleus muscle of wild-type (Ace+/+, n=20) and heterozygous mutant (Ace+/-, n=24) mice were stained for myosin adenosine triphosphatase activity to identify different muscle fiber types. Capillaries were visualized by amylase-periodic acid-Schiff staining. ACE activity in the serum and gastrocnemius muscle was higher in male mice than in female mice. Female and male Ace+/- mice had markedly lower ACE activity in the serum and the gastrocnemius muscle than did female and male Ace+/+ mice, respectively. In both male and female mice, the composition of fiber types (type I and IIa) did not differ significantly between Ace+/+ and Ace+/- mice. There was no significant gender difference in capillary density. Ace+/- mice had significantly more capillaries around type IIa fibers (5.44 +/- 0.18 vs. 5.01 +/- 0.13, p<0.05) than Ace+/+ mice. The differences in the number of capillaries around type I fibers and in the number of capillaries around per fiber (capillary:fiber ratio) between Ace+/- and Ace+/+ mice were not significant (p<0.1). There was no significant difference in the mean cross-sectional area occupied by one capillary and the number of capillaries per fiber area between Ace+/+ and Ace+/- mice. In conclusion, knockout of the Ace gene in mice increased capillary density, as expressed by the mean number of capillaries around type IIa fibers. This finding suggests a possible mechanism for the cardioprotective effects of ACE inhibitors.

The role of cardiopulmonary fitness and its genetic influences on surgical outcomes

Background

Outcome after major surgery remains poor in some patients. There is an increasing need to identify this cohort and develop strategies to reduce postsurgical morbidity and mortality. Central to outcome is the ability to mount cardiovascular output in response to the increased oxygen demand associated with major surgery.

Methods

A medline search was performed using keywords to identify factors that affect, and genetic influences in, disease and outcome from surgery, and all relevant English language articles published between 1980 and 2005 were retrieved. Secondary references were obtained from key articles.

Results

Preoperative cardiopulmonary exercise testing assesses patient fitness, highlights those at particular risk and, combined with triage to critical care, facilitates significant improvement in surgical outcome. However, genetic factors also influence responses to increased oxygen demand, and some patients are genetically predisposed to mounting increased inflammatory responses, which raise oxygen demand further. Polymorphisms in genes influencing fitness (angiotensin converting enzyme) and immune and inflammatory responses (such as interleukin 6) may associate with surgical outcome.

Conclusions

Development of preoperative screening methods like cardiopulmonary exercise testing and genotype analysis to identify index factors may permit better patient stratification, provide targets for future tailored treatments and so improve surgical outcome.

Does angiotensin-1 converting enzyme genotype influence motor or cognitive development after pre-term birth?

Background

Raised activity of the renin-angiotensin system (RAS) may both amplify inflammatory and free radical responses and decrease tissue metabolic efficiency and thus enhance cerebral injury in the preterm infant. The angiotensin-converting enzyme (ACE) DD genotype is associated with raised ACE and RAS activity as well as potentially adverse stimuli such as inflammation. The DD genotype has been associated with neurological impairments in the elderly, and thus may be also associated with poorer motor or cognitive development amongst children born preterm prematurely.

Methods

The association of DD genotype with developmental progress amongst 176 Caucasian children born at less than 33 weeks gestation (median birthweight 1475 g, range 645–2480 g; gestation 30 weeks, range 22–32; 108 male) was examined at 2 and 5 1/2 years of age. Measured neuro-cognitive outcomes were cranial ultrasound abnormalities, cerebral palsy, disability, Griffiths Developmental Quotient [DQ] at 2 yrs, and General Cognitive Ability [British Ability Scales-11] and motor performance [ABC Movement], both performed at 5 1/2 yrs. All outcomes were correlated with ACE genotype.

Results

The DD genotype was not associated with lower developmental quotients even after accounting for important social variables.

Conclusion

These data do not support either a role for ACE in the development of cognitive or motor function in surviving infants born preterm or inhibition of ACE as a neuroprotective therapy.

Genes and human elite athletic performance

Physical fitness is a complex phenotype influenced by a myriad of environmental and genetic factors, and variation in human physical performance and athletic ability has long been recognised as having a strong heritable component. Recently, the development of technology for rapid DNA sequencing and genotyping has allowed the identification of some of the individual genetic variations that contribute to athletic performance. This review will examine the evidence that has accumulated over the last three decades for a strong genetic influence on human physical performance, with an emphasis on two sets of physical traits, viz. cardiorespiratory and skeletal muscle function, which are particularly important for performance in a variety of sports. We will then review recent studies that have identified individual genetic variants associated with variation in these traits and the polymorphisms that have been directly associated with elite athlete status. Finally, we explore the scientific implications of our rapidly growing understanding of the genetic basis of variation in performance.

The human gene map for performance and health-related fitness phenotypes: the 2003 update

This review presents the 2003 update of the human gene map for physical performance and health-related fitness phenotypes. It is based on peer-reviewed papers published by the end of 2003 and includes association studies with candidate genes, genome-wide scans with polymorphic markers, and single-gene defects causing exercise intolerance to variable degrees. The genes and markers with evidence of association or linkage with a performance or fitness phenotype in sedentary or active people, in adaptation to acute exercise, or for training-induced changes are positioned on the genetic map of all autosomes and the X chromosome. Negative studies are reviewed but a gene or locus must be supported by at least one positive study before being inserted on the map. By the end of 2000, 29 loci were depicted on the first edition of the map. In contrast, the 2003 human gene map for physical performance and health-related phenotypes includes 109 autosomal gene entries and QTL, plus two on the X chromosome. Moreover, there are 15 mitochondrial genes in which sequence variants have been shown to influence relevant fitness and performance phenotypes.

Performance at altitude and angiotensin I-converting enzyme genotype

The "insertion" (I) rather than "deletion" (D) variant of the human angiotensin-converting enzyme (ACE) gene is associated with both lower tissue ACE activity and elite performance at high altitude. We examined whether the onset of acute mountain sickness (AMS), and further performance on reaching the summit of Mt. Blanc are influenced by the ACE I/D polymorphism. Two hundred and eighty-four climbers (235 males, [37.0 (11.0 years], (86 DD, 142 ID, 56 II)) had assessment of their AMS status upon arrival to the Gouter hut (3,807 m) on day 1, and again on day 2 after an attempted ascent to the summit of Mt. Blanc (4,807 m). Success in reaching the summit was genotype dependent (87.7% of DD, 94.9% of ID and 100% of II individuals; P=0.048); I allele frequency for those reaching the summit was 0.47 compared to 0.21 for those who did not (P=0.01). The onset of AMS on day 1 appeared to be dependent on genotype (P=0.003), but with those heterozygous being less affected. ACE genotype was not associated either with AMS onset or severity on day 2. Thus, ACE I/D genotype is associated with successful high altitude ascent in this prospective study-an association not explicable by genotype-dependence of AMS onset or severity. Values are given as mean (SD) unless otherwise stated.

Association of medically unexplained fatigue with ACE insertion/deletion polymorphism in Gulf War veterans

Genes associated with muscle metabolism and physical endurance were evaluated for variants that may contribute to the etiology of medically unexplained severe and chronic fatigue. Subjects included 49 Gulf War veterans and 61 nonveterans with chronic fatigue syndrome (CFS) or idiopathic chronic fatigue (ICF) and 30 veterans and 45 nonveterans who served as healthy controls. Increased risk for CFS/ICF was associated with alterations of the insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme gene within the Gulf War veteran sample only. The I allele frequency was decreased in affected versus unaffected veterans (0.15 versus 0.48; odds ratio [OR], 5.08; 95% confidence interval [CI], 1.97-13.35; P < 0.0001). Correspondingly, the II genotype was decreased fourfold in affected veterans (0.08 versus 0.35; OR = 5.87; 95% CI: 1.21-28.36; P = 0.02), and the DD genotype was increased twofold (0.78 versus 0.39; OR, 5.4; 95% CI, 1.6-18.4; P = 0.007). Veterans with the DD genotype were eight times more likely to develop CFS/ICF than were those with the II genotype (OR, 8.30; 95% CI, 1.50-56.09; P = 0.009).

The ACE Gene and Endurance Performance during the South African Ironman Triathlons

PURPOSE

Several studies have suggested that the insertion (I) variant rather than the deletion (D) variant of the human angiotensin-converting enzyme (ACE) gene is associated with elite endurance performance. The aim of this study was to determine whether the ID polymorphism is associated with the performance of the fastest finishers of the South African Ironman Triathlons.

METHODS

A total of 447 Caucasian male triathletes of a variety of nationalities and athletic ability who completed either the 2000 or 2001 South African Ironman Triathlons and 199 Caucasian male control subjects were genotyped for the ACE ID polymorphism.

RESULTS

There was a significantly higher frequency of the I allele in the fastest 100 South African-born finishers (103 I, 51.5% and 97 D, 48.5%) compared with the 166 South African-born control subjects (140 I, 42.2% and 192 D, 57.8%) (P = 0.036). There was also a significant linear trend for the allele distribution among the fastest 100 finishers (I allele = 51.5%), slowest 100 finishers (I allele = 47.5%), and control (I allele = 42.2%) South African-born subjects (P = 0.033). There was, however, no significant difference in the ACE genotype or allele frequencies when athletes born outside South Africa were analyzed.

CONCLUSION

To our knowledge this is the first study that has examined the effect of an athlete's ACE genotype on their actual performance during an ultra-endurance race. The I allele of the ACE gene was associated with the endurance performance of the fastest 100 South African-born finishers in these triathlons.

Bradykinin receptor gene variant and human physical performance

Accumulating evidence suggests that athletic performance is strongly influenced by genetic variation. One such locus of influence is the gene for angiotensin-I converting enzyme (ACE), which exhibits a common variant [ACE insertion (I)/deletion (D)]. ACE can drive formation of vasoconstrictor ANG II but preferentially degrades vasodilator bradykinin. The ACE I allele is associated with higher kinin activity. A common gene variant in the kinin β2 receptor (B2R) exists: the -9 as opposed to +9 allele is associated with higher receptor mRNA expression. We tested whether this variant was associated with the efficiency of muscular contraction [delta efficiency (DE)] in 115 healthy men and women, or with running distance among 81 Olympic standard track athletes. We further sought evidence of biological interaction with ACE I/D genotype. DE was highly significantly associated with B2R genotype (23.84 ± 2.41 vs. 24.25 ± 2.81 vs. 26.05 ± 2.26% for those of +9/+9 vs. +9/-9 vs. -9/-9 genotype; n = 25, 61, and 29, respectively; P = 0.0008 for ANOVA adjusted for sex). There was evidence for interaction with ACE I/D genotype, with individuals who were ACE II, with B2R -9/-9 having the highest DE at baseline. The ACE I/B2R -9 “high kinin receptor activity” haplotype was significantly associated with endurance (predominantly aerobic) event among elite athletes ( P = 0.003). These data suggest that common genetic variation in the B2R is associated with efficiency of skeletal muscle contraction and with distance event of elite track athletes and that at least part of the associations of ACE and fitness phenotypes is through elevation of kinin activity.

Does ACE inhibition enhance endurance performance and muscle energy metabolism in rats?

The renin-angiotensin-aldosterone system plays an important role in the hydroelectrolytic balance, blood pressure regulation, and cell growth. In some studies, the insertion (I) allele of the angiotensin-converting enzyme (ACE) gene, associated with a lower ACE activity, has been found in excess frequency in elite endurance athletes, suggesting that decreased ACE activity could be involved in endurance performance (Myerson S, Hemingway H, Budget R, Martin J, Humphries S, and Montgomery H. J Appl Physiol 87: 1313-1316, 1999). To test this hypothesis, we evaluated whether ACE inhibition could be associated with improved endurance performance and muscle oxidative capacity in rats. Eight male Wistar rats were treated for 10-12 wk with an ACE inhibitor, perindopril (2 mg.kg-1.day-1), and compared with eight control rats. Endurance time was measured on a treadmill, and oxidative capacity and regulation of mitochondrial respiration by substrates were evaluated in saponin-permeabilized fibers of slow soleus and fast gastrocnemius muscles. Endurance time did not differ between groups (57 +/- 5 min for perindopril vs. 55 +/- 6 min for control). Absolute and relative (to body weight) left ventricular weight was 20% (P < 0.01) and 12% (P < 0.01) lower, respectively, in the treated group. No difference in oxidative capacity, mitochondrial enzyme activities, or mitochondrial regulation by ADP was observed in soleus or gastrocnemius. Mitochondrial respiration with glycerol 3-phosphate was 17% higher in gastrocnemius (P < 0.03) and with octanoylcarnitine 14% greater in soleus (P < 0.01) of treated rats. These results demonstrate that ACE inhibition was not associated with improved endurance time and maximal oxidative capacity of skeletal muscles. This suggests that ACE activity has no implication in endurance capacity and only minor effects on mitochondrial function in sedentary animals.

Angiotensin-converting enzyme gene polymorphisms in patients with pulmonary sarcoidosis: impact on disease severity

Angiotensin converting enzyme (ACE) is a metallopeptidase with a key function in the regulation of blood pressure and volume. The ACE1 gene, on chromosome 17, contains a insertion/deletion (I/D) polymorphism in intron 16. The D allele of this polymorphism is linked with raised serum ACE (sACE) levels. Sarcoidosis is a systemic disease of granulomatous inflammation that primarily affects the lung and lymph system. It is often accompanied by elevated sACE related to ACE production from granuloma cells. The ACE I/D polymorphism has been tested for association or linkage with the risk of sarcoidosis. Though published results are conflicting, there seems to be suggestive evidence of a minor pro-inflammatory influence of the ACE D allele in sarcoidosis. At present, a more accurate interpretation of sACE levels in diagnosis and monitoring of sarcoidosis seems to be the main value of ACE I/D genotyping.

The serum angiotensin-converting enzyme and angiotensin II response to altered posture and acute exercise, and the influence of ACE genotype

The deletion (D) rather than insertion (I) allele of the angiotensin-converting enzyme (ACE) gene is associated with greater ACE activity. We examined: (1) the influence of posture change (recumbent to seated) and acute exercise on serum ACE and angiotensin II (Ang II) activity; (2) the relationship between ACE and Ang II levels; and (3) the influence of ACE genotype on changes in ACE and Ang II levels with posture and exercise. Recreationally active young male Caucasians (10 each of II, ID and DD genotypes) rested for 35 min supine then 15 min upright, took 20 min bicycle ergometric exercise at 70% maximum oxygen uptake, then rested for 40 min. Samples were taken throughout for ACE activity and Ang II levels. Supine ACE levels were dependent upon ACE genotype [24.8 (5.7), 26.9 (4.5), 45.5 (6.4) nmol His-Leu ml(-1) min(-1); II, ID, DD, respectively; P<0.00005] and thereafter. ACE activity rose with assumption of a seated posture [from 32.4 (10.9) nmol His-Leu ml(-1) min(-1) to 35.0 (11.5) nmol His-Leu ml(-1) min(-1), P<0.00001], the absolute rise being independent of genotype [3.22 (1.92), 1.6 (1.6), 2.4 (2.3) nmol His-Leu ml(-1) min(-1); II, ID, DD; P=0.22], unlike percentage change [12.8 (6.8), 5.6 (5.5), 5.3 (5.0)%; II, ID, DD; P<0.01, and P=0.004 for II vs presence of the D allele]. A further genotype-independent rise occurred with exercise [+2.9 (3.7) units, P<0.0003]. An associated rise in Ang II levels [30.3 (15.9), or 2587.9 (489.76)%, P<0.00001] was independent of ACE genotype or activity. Upright posture increases ACE activity, and this may be influenced by ACE genotype. ACE activity and Ang II levels rise independently with exercise in a non-genotype-dependent fashion.

Movement systems as dynamical systems: the functional role of variability and its implications for sports medicine

In recent years, concepts and tools from dynamical systems theory have been successfully applied to the study of movement systems, contradicting traditional views of variability as noise or error. From this perspective, it is apparent that variability in movement systems is omnipresent and unavoidable due to the distinct constraints that shape each individual's behaviour. In this position paper, it is argued that trial-to-trial movement variations within individuals and performance differences observed between individuals may be best interpreted as attempts to exploit the variability that is inherent within and between biological systems. That is, variability in movement systems helps individuals adapt to the unique constraints (personal, task and environmental) impinging on them across different timescales. We examine the implications of these ideas for sports medicine, by: (i) focusing on intra-individual variability in postural control to exemplify within-individual real-time adaptations to changing informational constraints in the performance environment; and (ii) interpreting recent evidence on the role of the angiotensin-converting enzyme gene as a genetic (developmental) constraint on individual differences in physical performance. The implementation of a dynamical systems theoretical interpretation of variability in movement systems signals a need to re-evaluate the ubiquitous influence of the traditional 'medical model' in interpreting motor behaviour and performance constrained by disease or injury to the movement system. Accordingly, there is a need to develop new tools for providing individualised plots of motor behaviour and performance as a function of key constraints. Coordination profiling is proposed as one such alternative approach for interpreting the variability and stability demonstrated by individuals as they attempt to construct functional, goal-directed patterns of motor behaviour during each unique performance. Finally, the relative contribution of genes and training to between-individual performance variation is highlighted, with the conclusion that dynamical systems theory provides an appropriate multidisciplinary theoretical framework to explain their interaction in supporting physical performance.

The human gene map for performance and health-related fitness phenotypes: the 2002 update

This review presents the 2002 update of the human gene map for physical performance and health-related phenotypes. It is based on peer-reviewed papers published by the end of 2002 and includes association studies with candidate genes, genome-wide scans with polymorphic markers, and single gene defects causing exercise intolerance to variable degrees. The genes and markers with evidence of association or linkage with a performance or fitness phenotype in sedentary or active people, in adaptation to acute exercise, or for training-induced changes are positioned on the genetic map of all autosomes and the X chromosome. Negative studies are reviewed, but a gene or locus must be supported by at least one positive study before being inserted on the map. By the end of 2000, 29 loci were depicted on the map. The 2001 map includes 71 loci on the autosomes and two on the X chromosome. In contrast, the 2002 human gene map for physical performance and health-related phenotypes includes 90 gene entries and QTL, plus two on the X chromosome. To all these loci, one must add 14 mitochondrial genes in which sequence variants have been shown to influence relevant fitness and performance phenotypes.

Human and mouse proteases: a comparative genomic approach

The availability of the human and mouse genome sequences has allowed the identification and comparison of their respective degradomes--the complete repertoire of proteases that are produced by these organisms. Because of the essential roles of proteolytic enzymes in the control of cell behaviour, survival and death, degradome analysis provides a useful framework for the global exploration of these protease-mediated functions in normal and pathological conditions.

Phenotype modulators in myophosphorylase deficiency

Myophosphorylase deficiency is characterized by exercise intolerance, muscle cramps, and recurrent myoglobinuria. Some patients are severely affected, whereas others are minimally affected or asymptomatic. The molecular basis of the disease has been elucidated but does not provide an explanation for the clinical variability. In a large cohort of patients with myophosphorylase deficiency, we tested the hypothesis that polymorphic variants in either myoadenylate deaminase (MADA) or angiotensin-converting enzyme (ACE) could act as modulators of phenotype expression. Forty-seven patients were evaluated. Clinical severity was assessed according to a severity scale of four grades. MADA activity was studied by histochemical and biochemical analysis of muscle, and the Q12X mutation in the adenine monophosphate deaminase 1 gene (AMPD1) and the insertion/deletion polymorphism in the ACE gene were assessed genetically. A complete MADA defect together with the Q12X mutation was detected in one severely affected patient. Eleven patients were heterozygous for the Q12X mutation. There was no association between clinical grading and MADA status. In contrast, we found a highly significant (p < 0.01) association between ACE genotype and clinical severity, with strong correlation between severe phenotype and number of D alleles. We show that ACE insertion/deletion polymorphism may play a significant role as phenotype modulator in McArdle's disease.

Serum ACE predicts severe hypoglycemia in children and adolescents with type 1 diabetes

OBJECTIVE

To investigate whether risk of severe hypoglycemia is related to serum (S) ACE level during intensive treatment in type 1 diabetic children.

RESEARCH DESIGN AND METHODS

A cohort of 86 intensively treated type 1 diabetic patients was studied during 1999-2000. In 1999, the age range was 7-19 years (median 12.8), diabetes duration was 1.2-14.7 years (5.3), insulin dose was 0.4-1.7 units x kg(-1) x 24 h(-1) (1.0), and the HbA(1c) year mean was 4.7-10.2% (6.8). HbA(1c), insulin doses, and events of severe hypoglycemia (needing assistance from another person) were prospectively registered at regular visits, scheduled quarterly. S-ACE was determined once.

RESULTS

Severe hypoglycemia was correlated to S-ACE (r = 0.22, 95% CI 0.01-0.41, P = 0.0093). The square root of severe hypoglycemia was correlated to S-ACE (r = 0.27, 95% CI 0.06-0.45, P = 0.0093). Patients with S-ACE at the median level or above (n = 44) reported a mean of 3.0 yearly events of severe hypoglycemia compared with 0.5 events in patients with S-ACE lower than the median (n = 42) (P = 0.0079). Of the patients with an S-ACE at the median level or above, 27 (61%) reported severe hypoglycemia, compared with 17 (40%) patients with an S-ACE lower than the median (P = 0.0527). Insulin dose, HbA(1c), age, onset age, duration, C-peptide, and sex did not differ between these two groups. S-ACE was negatively correlated with age (r = -0.27, 95% CI -0.46 to 0.07, P = 0.0265) but not with HbA(1c), duration, or blood pressure.

CONCLUSIONS

The elevated rate of severe hypoglycemia among patients with higher S-ACE suggests, among other factors, that a genetic determinant for severe hypoglycemia exists. Further evaluation is needed before the clinical usefulness of this test can be elucidated.

The I allele of the angiotensin-converting enzyme gene is associated with an increased percentage of slow-twitch type I fibers in human skeletal muscle

The insertion (I) allele of the human angiotensin-converting enzyme (ACE) gene is associated with lower serum and tissue ACE activity, and with greater endurance performance and enhanced mechanical efficiency of trained muscle. We tested the hypothesis that the ACE-I allele may be associated with increased slow-twitch fiber, which is more efficient than fast-twitch fiber in low-velocity contraction, by examining the association between the ACE genotype and skeletal muscle fiber (SMF) types in 41 untrained healthy young volunteer subjects (31 males, 10 females, age 24 +/- 3 years). Skeletal muscle samples were taken from the left vastus lateralis using the needle-biopsy method. Slow-twitch type I fibers and fast-twitch type IIa and IIb fibers were classified histochemically based on staining for myosin adenosine triphosphatase (ATPase) activity at different pH values. Amylase-periodic acid-Schiff staining was used to visualize capillaries around fibers. ACE-II subjects had significantly (p < 0.01) higher percentages of type I fibers (50.1 +/- 13.9%vs 30.5 +/- 13.3%) and lower percentages of type IIb fibers (16.2 +/- 6.6%vs 32.9 +/- 7.4%) than ACE-DD subjects. The linear trends for decreases in type I fibers and increases in type IIb fibers from ACE-II --> ID --> DD genotypes were significant as assessed by an analysis of variance. The ratio of type I:II fibers also differed according to the ACE genotype. A multivariate logistic regression analysis showed that the ACE-I allele had significant additive and recessive (codominant) effects on the increased type I fibers and the ratio of type I:II fibers. No specific pattern of capillarization was observed among the three ACE genotypes. In conclusion, the ACE-I allele was associated with increased type I SMF, which may be a mechanism for the association between the ACE genotype and endurance performance.

The influence of genetic factors on physical functioning and exercise in second half of life

During the past decades, a number of studies of families and twins in particular have assessed the relative contribution of genetic and environmental factors to traits reflecting various aspects of physical functioning: maximal O2 uptake, muscular endurance, muscular strength, muscle cross sectional area, flexibility, and trainability. Although the estimate of the size of the genetic component differs between the various studies, they point towards a moderate to substantial genetic influence on these phenotypes. Most of the studies have used only young and healthy study subjects, although in recent years phenotypes of particular importance to the elderly and the oldest-old (e.g., activities-of-daily living abilities) have also been shown to have substantial genetic component. Furthermore, behavioural studies have also revealed a genetic contribution to the disposition to level of leisure time physical activity. At present, there is still a few association studies on specific genetic variants, and the results have either been inconsistent or failed to show an association with physical functioning. Therefore, the mechanisms through which the genetic influence is expressed, is still an enigma. Here, we summarise the evidence currently available for a genetic influence on physical functioning and disposition to leisure time physical activity with a focus on recent Danish twin data.

The pulmonary physician in critical care. 10: difficult weaning

The study of patients being weaned from mechanical ventilation has offered new insights into the physiology of respiratory failure. Assessment of the balance between respiratory muscle strength, work and central drive is essential if difficulty in weaning occurs, and optimisation of these elements may improve the success of weaning. Psychological support of patients and the creation of units specialising in weaning have also resulted in a higher success rate.

Association of angiotensin-converting-enzyme gene polymorphism with the depressor response to mild exercise therapy in patients with mild to moderate essential hypertension

We studied the association of angiotensin I-converting enzyme (ACE) gene polymorphism with the depressor response to exercise therapy in 64 Japanese subjects with mild to moderate essential hypertension. Each subject performed 10 weeks of mild (lactate threshold intensity: approximately 50% maximum oxygen consumption) exercise therapy on a bicycle ergometer. Systolic blood pressure (SPB), diastolic blood pressure (DPB), and mean arterial pressure (MAP) were significantly decreased by exercise therapy in subjects with the ACE-II and ID genotypes but not in DD subjects. The time-by-genotype interaction effects were significant for DBP and MAP. According to a multiple logistic regression analysis, the age- and baseline plasma renin activity-adjusted relative risk (odds ratio) for the lack of a depressor response conferred by the D allele (assuming an additive effect) was 2.72 [95% confidence interval (CI), 1.07-6.91; p = 0.034]; for DD genotypes, as compared with the DI and II genotypes (assuming that the D allele is recessive), it was 11.7 (95% CI, 2.25-60.6; p = 0.003). ACE gene I/D polymorphism is associated with the depressor response of essential hypertensives to mild exercise therapy, which suggests that genetic features may underlie, at least in part, the heterogeneity of the depressor response in essential hypertensives to mild exercise therapy.

Human performance: a role for the ACE genotype?

The I allele of the angiotensin I-converting enzyme (ACE) gene is associated with lower ACE activity and endurance performance; an excess occurs in elite distance runners, rowers, and mountaineers, perhaps secondary to enhanced muscle efficiency. Conversely, the D allele is associated with training-related strength gain and elite power-oriented performance secondary to increased ACE and angiotensin II, a growth factor.

The human gene map for performance and health-related fitness phenotypes: the 2001 update

This review presents the 2001 update of the human gene map for physical performance and health-related phenotypes. It is based on scientific papers published by the end of 2001. Association studies with candidate genes, genome-wide scans with polymorphic markers, and single gene defects causing exercise intolerance to variable degrees are included. The genes and markers with evidence of association or linkage with a performance or fitness phenotype in sedentary or active people, in adaptation to acute exercise or for training-induced changes are positioned on the genetic map of all autosomes and the X chromosome. Negative studies are reviewed, but a gene or locus must be supported by at least one positive study before being inserted on the map. By the end of 2000, there were 29 loci depicted on the map. The 2001 map includes 71 loci on the autosomes and two on the X chromosome. Among these genes or markers, 24 are from prior publications on exercise intolerance and four relate to other pathologies. Finally, 13 sequence variants in mitochondrial DNA have been shown to influence relevant fitness and performance phenotypes.

Hand grip strength: a phenotype suitable for identifying genetic variants affecting mid- and late-life physical functioning

Physical functioning late in life has been shown to be affected by genetic factors. Only a few genetic variants have been suggested to be associated with physical functioning, and this only in selected populations (e.g., young healthy males and elite athletes). Declining physical functioning late in life is a major problem in terms of prevalence, morbidity, functional limitations, and quality of life. It is therefore of interest to find a phenotype reflecting physical functioning which has a relatively high heritability and which can be measured in large samples. Hand grip strength is known to be associated with muscular functioning in other muscle groups and with activities of daily living (ADL) functioning, and it predicts incident disability. We studied 1,757 Danish twin pairs aged 45-96 years, and found that this phenotype has a heritability of 52% (95% confidence interval (CI), 48-55%). A powerful design to detect genes associated with a phenotype is obtained using the extreme discordant and concordant sib pairs, of whom 28 and 77 dizygotic twin pairs, respectively, were found in this study. Hence grip strength is a suitable phenotype for identifying genetic variants of importance to mid- and late-life physical functioning.

Cerebrovascular disorders and genetic polymorphisms: mitochondrial DNA5178C is predominant in cerebrovascular disorders

We studied polymorphisms of mitochondrial DNA 5178cytosine/adenine (mt5178C/A) and angiotensin I-converting enzyme (ACE) genes (DCP1) in 127 cerebrovascular disorder (CVD) patients and 294 age-matched normal controls to clarify the genetic background of Japanese patients with CVD. Mt5178C was predominant in CVD patients compared with controls (P<0.01). The frequency of DCP1 insertion (I) and deletion (D) alleles showed no significant difference between the CVD patients and controls or between each CVD subgroup. Although the number of CVD patients in the present study was too small to make a final conclusion, mt5178C might be one of the genetic factors to be considered in Japanese patients with CVD.

ACE gene and physical activity, blood pressure, and hypertension: a population study in Finland

The study evaluated the association of the insertion/deletion polymorphism of the angiotensin-converting enzyme gene (ACE I/D) with self-reported moderate-intensity leisure time physical activity (MILTPA), arterial blood pressure (BP) and history of hypertension (HT). A representative population-based sample of 721 middle-aged adults (358 women) from two areas of Finland was genotyped for the ACE I/D. After exclusion criteria were applied, 455 subjects (288 women) were selected for the analysis. The distribution of the ACE I/D genotypes did not differ significantly among frequent vs. nonfrequent MILTPA groups (chi(2) = 2.556; df = 2; P value = 0.279). The main predictors of BP were male gender, age, body mass index, and arterial pulse. Additionally, tobacco smoking and alcohol consumption also had a significant main effect on diastolic BP. HT was significantly more frequent in subjects with obesity, family history of cardiovascular disease, or lower educational level. As for BP, neither ACE I/D nor MILTPA was associated with HT. The study confirmed recent reports from population-based studies of no association between ACE I/D and physical fitness. The study also confirmed a lack of association between ACE I/D and BP or HT.

No association between DCP1 genotype and late-onset Alzheimer disease

In a study of 261 patients with Alzheimer disease (AD) and 306 cognitively normal control subjects from Germany, Switzerland, and Italy, we found no association between genotype counts or allelic frequencies of DCP1, the gene encoding angiotensin-converting enzyme. In accordance with several other studies, our data could not confirm previous association findings. Critical review about all studies available on DCP1 genotyping and AD, age-associated cognitive decline, longevity, and other conditions revealed remarkable inconsistencies. Several studies showed significant deviations of genotype counts from Hardy Weinberg equilibrium (HWE). Deviations from HWE may limit the comparability of study results and require clarification before drawing conclusions with respect to disease risk, health conditions, or longevity in association with DCP1 genotype.

Relation between use of angiotensin-converting enzyme inhibitors and muscle strength and physical function in older women: an observational study

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors prevent decline in physical function in patients with congestive heart failure (CHF). We aimed to see whether ACE inhibitors also prevent reduction in physical performance and in muscle strength in older women who do not have CHF.

METHODS

We assessed 3-year rates of decline in both knee extensor muscle strength and walking speed in 641 women with hypertension who had participated in the Women's Health and Aging Study. Women were stratified into four groups according to type and duration of antihypertensive drug treatment. 61 had used ACE inhibitors continuously, 133 intermittently, 146 never, and 301 had used other hypertensive drugs either continuously or intermittently.

FINDINGS

Participants who had taken ACE inhibitors continuously had a lower mean 3-year decline in muscle strength of -1.0 kg (SE 1.1) compared with -3.7 (0.5) kg in continuous/intermittent users of other antihypertensive drugs (p=0.016) and with -3.9 kg in those who had never used antihypertensives (p=0.026). Muscle strength fell by 3.0 kg in 3 years in both continuous and intermittent users of ACE inhibitors (p=0.096). Mean 3-year decline in walking speed in continuous ACE inhibitor users was -1.7 cm/s compared with -13.6 cm/s in intermittent users of ACE inhibitors (p=0.015), -15.7 cm/s in continuous/intermittent users of other antihypertensive drugs (p=0.002), and -17.9 cm/s in never users of antihypertensive drugs (p=0.001).

INTERPRETATION

ACE inhibitor treatment may halt or slow decline in muscle strength in elderly women with hypertension and without CHF.

Exercise and skeletal muscle gene expression

1. Skeletal muscle is a complex and heterogenous tissue capable of remarkable adaptation in response to exercise training. The role of gene transcription, as an initial target to control protein synthesis, is poorly understood. 2. Mature myofibres contain several hundred nuclei, all of which maintain transcriptional competency, although the localized responsiveness of nuclei is not well known. Myofibres are capable of hypertrophy. These processes require the activation and myogenic differentiation of mononuclear satellite cells that fuse with the enlarging or repairing myofibre. 3. A single bout of exercise in human subjects is capable of activating the expression of many diverse groups of genes. 4. The impact of repeated exercise bouts, typical of exercise training, on gene expression has yet to receive systematic investigation. 5. The molecular programme elicited by resistance exercise and endurance exercise differs markedly. Muscular hypertrophy following resistance exercise is dependent on the activation of satellite cells and their subsequent myogenic maturation. Endurance exercise requires the simultaneous activation of mitochondrial and nuclear genes to enable mitochondrial biogenesis. 6. Future analysis of the regulation of genes by exercise may combine high-throughput technologies, such as gene-chips, enabling the rapid detection and analysis of changes in the expression of many thousands of genes.

The angiotensin converting enzyme I/D polymorphism in Russian athletes

The deletion (D) allele of the human ACE gene is associated with higher ACE activity than the insertion (I) allele. There is controversy as to whether the ACE genotype may be associated with elite athletic status; recent studies have identified no significant associations amongst those drawn from mixed sporting disciplines. However, such lack of association may reflect the mixed nature of such cohorts, given that an excess frequency of the I allele has been reported amongst elite endurance athletes, and an excess of the D allele amongst those engaged in more power-orientated sports. We examined this hypothesis by determining ACE I/D allele frequency amongst 217 Russian athletes (swimmers, skiers, triathletes and track-and-field participants) prospectively stratified by performance ('outstanding' or 'average'), and the duration of their event (SDA (<1 min), MDA (1 to 20 min), and LDA (>20 min): short, middle and long distance athletes respectively). ACE genotype and allele frequencies were compared to 449 controls. ACE genotype frequency amongst the whole cohort, or the outstanding athletes alone, was no different to that amongst sedentary controls. However, there was an excess of the D allele (frequency 0.72, P=0.001) amongst the outstanding SDA group, and an excess of the I allele (frequency 0.63, P=0.032) amongst the outstanding MDA group. These findings were replicated in the outstanding swimmers, with track and field SDA similarly demonstrating an excess of the D allele (P=0.01). There was no association found between the outstanding LDA and ACE genotype (P=0.27). These data not only confirm an excess of the D allele in elite SDA, and I allele in elite MDA, but also offer an explanation as to why any such association may be hard to detect amongst a heterogeneous cohort of mixed athletic ability and discipline.

Angiotensin-converting enzyme genotype and physical performance during US Army basic training

Prior studies have suggested that angiotensin I-converting enzyme (ACE) genotype correlates with superior physical performance in highly selected populations. This study assessed whether such an association exists in a heterogeneous population. Using polymerase chain reaction techniques, we determined the ACE genotypes (insertion/insertion, deletion/insertion, or deletion/deletion) of 62 male and 85 female US Army recruits. Before and after 8 wk of basic training, we determined peak oxygen uptake and performance on the Army Physical Fitness Test (APFT), which includes standardized measures of muscular endurance (sit-ups, push-ups) and a 2-mile run. Subjects of different ACE genotypes had similar peak oxygen uptakes and APFT scores, both before and after training. Subjects with genotype II had higher APFT scores than others, but the differences were not statistically significant. Furthermore, no ACE genotype group had a performance advantage in analyses that adjusted for baseline fitness. We conclude that ACE genotype does not have a strong effect on aerobic power or muscular endurance in healthy, young American adults drawn from an ethnically and geographically diverse population.

The human gene map for performance and health-related fitness phenotypes

The aim of this paper is to describe the first human gene map for physical performance and health-related fitness traits based on the papers published until the end of 2000. Studies of candidate genes using case-control and other designs are reviewed. Quantitative trait loci from the limited evidence reported to date in genomic scans are also incorporated. Performance and fitness phenotypes in the sedentary state as well as their changes during exercise, if applicable, or in response to exercise training are considered. Physical performance traits include cardiorespiratory endurance indicators and muscular strength or muscular performance variables. Health-related fitness phenotypes are grouped under the following categories: hemodynamic traits; anthropometry and body composition; insulin and glucose metabolism; and lipids, lipoproteins, and hemostatic factors. A yearly update of this human gene map will be published.

Activity of angiotensin-converting enzyme and risk of severe hypoglycaemia in type 1 diabetes mellitus

BACKGROUND

The insertion (I) allele of the angiotensin-converting-enzyme (ACE) gene occurs at increased frequency in endurance athletes. This association suggests that low ACE activity is favourable for performance in conditions with limited substrate availability. Such conditions occur in endurance athletes during competition and in diabetic patients during insulin-induced hypoglycaemia. Patients rely on preserved functional capacity to recognise hypoglycaemic episodes and avoid progression by self-treatment. We studied whether ACE activity is related to the risk of severe hypoglycaemia in type 1 diabetes.

METHODS

Consecutive adult outpatients with type 1 diabetes, untreated with ACE inhibitors or angiotensin-II-receptor antagonists (n=207) reported their experience of mild and severe hypoglycaemia during the previous 1 year and 2 years. The patients were further characterised by diabetes history, degree of hypoglycaemia awareness, measurement of C-peptide, haemoglobin A(1c), and serum ACE concentrations, and determination of ACE genotype.

FINDINGS

Patients with the DD genotype had a relative risk of severe hypoglycaemia in the preceding 2 years of 3.2 (95% CI 1.4-7.4) compared with those who had the II genotype. There was a significant relation between serum ACE activity and the rate of severe hypoglycaemia (relative risk per 10 U/L increment 1.4 [1.2-1.6]), corresponding to a 3.5 times higher risk for patients in the highest quartile than for those in the lowest quartile. Multiple regression analysis showed that the effect of the ACE genotype was explained by its influence on serum ACE activity and that the only other significant determinants of the risk of severe hypoglycaemia were the degree of hypoglycaemia awareness, b-cell function, and duration of diabetes of more than 20 years.

INTERPRETATION

ACE activity is a clinically significant marker of the risk of severe hypoglycaemia in patients with type 1 diabetes, especially in those with impaired defence against hypoglycaemia. These findings need to be confirmed in prospective studies.

Specific genetic markers of endurance performance and VO2max

Specific genetic markers of endurance performance and VO2max. Exerc. Sport Sci. Rev., Vol. 29, No. 1, pp 15-19, 2001. Recent advances have revolutionized genetic studies of quantitative traits. Mitochondrial DNA and creatine kinase variations may influence VO2max. Other data strongly suggest that angiotensin-converting enzyme genotype affects VO2max and endurance performance capacity, but the mechanisms are unclear. A recent genome-wide scan study also has provided candidate loci requiring further study.

Loss of renal function following bone marrow transplantation: an analysis of angiotensin converting enzyme D/I polymorphism and other clinical risk factors

Chronic renal failure is an acknowledged late complication of BMT. It is related to the intensive chemotherapy, radiation and supporting medications. Polymorphism in the angiotensin converting enzyme (ACE) gene is associated with progression of nephropathy caused by diabetes and IgA nephropathy. We sought to determine whether ACE genotype and other clinical factors were associated with loss of renal function after BMT. We determined the genotype of 106 adult allogeneic BMT recipients, who received a similar preparative regimen, survived 1 year, and had assessment of renal function up to 3 years after BMT. We found that the distribution of genotypes was similar to the general population; 29%, 51%, and 20% for the DD, DI, and II genotypes, respectively. There was no statistical difference in patient survival between the three groups. Among all patients, the average creatinine clearance declined from 124 (95% CI 117, 131) to 89 (95% CI 78, 100) ml/min over the 36 months after BMT. Decline in renal function over time was less for patients with the DD compared to the II genotype (P = 0.040). Renal function in patients with the DD genotype was also better than those with the DI genotype, but this was of borderline statistical significance (P = 0.055). Renal shielding reduced decline in renal function compared to no shielding (P = 0.026). We conclude that the ACE genotype does not seem to influence survival, but the DD genotype may be protective against renal injury after BMT. Furthermore, we confirm that renal shielding during TBI reduces the renal injury after BMT.

ANG II is required for optimal overload-induced skeletal muscle hypertrophy

ANG II mediates the hypertrophic response of overloaded cardiac muscle, likely via the ANG II type 1 (AT(1)) receptor. To examine the potential role of ANG II in overload-induced skeletal muscle hypertrophy, plantaris and/or soleus muscle overload was produced in female Sprague-Dawley rats (225-250 g) by the bilateral surgical ablation of either the synergistic gastrocnemius muscle (experiment 1) or both the gastrocnemius and plantaris muscles (experiment 2). In experiment 1 (n = 10/group), inhibiting endogenous ANG II production by oral administration of an angiotensin-converting enzyme (ACE) inhibitor during a 28-day overloading protocol attenuated plantaris and soleus muscle hypertrophy by 57 and 96%, respectively (as measured by total muscle protein content). ACE inhibition had no effect on nonoverloaded (sham-operated) muscles. With the use of new animals (experiment 2; n = 8/group), locally perfusing overloaded soleus muscles with exogenous ANG II (via osmotic pump) rescued the lost hypertrophic response in ACE-inhibited animals by 71%. Furthermore, orally administering an AT(1) receptor antagonist instead of an ACE inhibitor produced a 48% attenuation of overload-induced hypertrophy that could not be rescued by ANG II perfusion. Thus ANG II may be necessary for optimal overload-induced skeletal muscle hypertrophy, acting at least in part via an AT(1) receptor-dependent pathway.

Single nucleotide polymorphisms and the future of genetic epidemiology

In this review, we consider the motivation behind contemporary single nucleotide polymorphism (SNP) initiatives. Many of these initiatives are projected to involve large, population-based surveys. We therefore emphasize the utility of SNPs for genetic epidemiology studies. We start by offering an overview of genetic polymorphism and discuss the historical use of polymorphism in the identification of disease-predisposing genes via meiotic mapping. We next consider some of the unique aspects of SNPs, and their relative advantages and disadvantages in human population-based analyses. In this context, we describe and critique the following six different areas of application for SNP technologies: Gene discovery and mapping. Association-based candidate polymorphism testing. Diagnostics and risk profiling. Prediction of response to environmental stimuli, xenobiotics and diet. Homogeneity testing and epidemiological study design. Physiologic genomics. We focus on key issues within each of these areas in an effort to point out potential problems that might plague the use of SNPs (or other forms of polymorphism) within them. However, we make no claim that our list of considerations are exhaustive. Rather, we believe that they may provide a starting point for further dialog about the ultimate utility of SNP technologies. In addition, although our emphasis is placed on applications of SNPs to the understanding of human phenotypes, we acknowledge that SNP maps and technologies applied to other species (e.g. the mouse genome, pathogen genomes, plant genomes, etc.) are also of tremendous interest.

Gene-environment interactions and the response to exercise

Many of the symptoms of heart failure (breathlessness and fatigue) are not primarily due to reduced cardiac output, but relate to an impairment of peripheral muscle performance and metabolic efficiency. With regular training it is possible to increase skeletal muscle performance through improvements in muscle efficiency. Recent data suggest that such improvements may be modulated by local tissue renin-angiotensin systems and, in particular, by the local activity of angiotensin-converting enzyme (ACE). These findings might explain the remarkable benefits of ACE inhibition in the treatment of heart failure.