Ruthie Amir

The ACE deletion allele is associated with Israeli elite endurance athletes

An Alu insertion (I)/deletion (D) polymorphism in the angiotensin I converting enzyme (ACE) gene has been associated with ACE activity. Opposing effects on elite athletic performance have been proposed for the I and D alleles; while the D allele favours improved endurance ability, the I allele promotes more power‐orientated events. We tested this hypothesis by determining the frequency of ACE ID alleles amongst 121 Israeli top‐level athletes classified by their sporting discipline (marathon runners or sprinters). Genotyping for ACE ID was performed using polymerase chain reaction on DNA from leucocytes. The ACE genotype and allele frequencies were compared with those of 247 healthy individuals. Allele and genotype frequencies differed significantly between the groups. The frequency of the D allele was 0.77 in the marathon runners, 0.66 in the control subjects (P= 0.01) and 0.57 in the sprinters (P= 0.002). The ACE DD genotype was more prevalent among the endurance athletes (0.62) than among the control subjects (0.43, P= 0.004) and the power athletes (0.34, P= 0.004). In the group of elite athletes, the odds ratio of ACE DD genotype being an endurance athlete was 3.26 (95% confidence interval 1.49–7.11), and of ACE II genotype was 0.41 (95% confidence interval 0.14–1.19). We conclude that in Israeli elite marathon runners the frequency of the ACE D allele and ACE DD genotype seems to be higher than in sprinters, suggesting a positive association between the D allele and the likelihood of being an elite endurance athlete in some ethnic groups.

Mechanism of processing of the NF-κB2 p100 precursor: identification of the specific polyubiquitin chain-anchoring lysine residue and analysis of the role of NEDD8-modification on the SCFβ-TrCP ubiquitin ligase

Processing of the NF-κB2 precursor p100 to the mature p52 subunit is regulated via a unique pathway. NF-κB-inducing kinase (NIK) induces IκB kinase α (IKKα)-mediated phosphorylation of specific serine residues in the C-terminal domain of p100, leading to recruitment of the SCFβ-TrCP ubiquitin ligase. We identified a single lysine residue, K855, that serves as the ubiquitin-anchoring residue required for signal-induced processing of p100. In a reconstituted system containing purified components, p100-K855R could not be ubiquitinated. In a crude extract and cells, only residual, signal-independent ubiquitination and processing were retained. Importantly, K855 is located in a site homologous to K22 that serves as an ubiquitination site in IκBα. This suggests a common recognition mechanism for the two molecules. In contrast, p105, the p100 homologue, lacks a similar Lys residue. We also demonstrate that the NEDD8 pathway is essential for the SCFβ-TrCP activity. In a reconstituted system, efficient ubiquitination of p100 required all three components of the pathway – E1, the UBC12 E2 and NEDD8. Experiments in reconstituted systems and in cells demonstrated that SCFβ-TrCP, which contains a mutant Cul-1 that cannot be NEDDylated, cannot stimulate ubiquitination and processing. Similarly, dominant negative UBC12 inhibits, in a reversible manner, both ubiquitination and processing of p100.

The NEDD8 Pathway Is Essential for SCFβ-TrCP-mediated Ubiquitination and Processing of the NF-κB Precursor p105

The p50 subunit of NF-κB is generated by limited processing of the precursor p105. IκB kinase-mediated phosphorylation of the C-terminal domain of p105 recruits the SCFβ-TrCP ubiquitin ligase, resulting in rapid ubiquitination and subsequent processing/degradation of p105. NEDD8 is known to activate SCF ligases following modification of their cullin component. Here we show that NEDDylation is required for conjugation and processing of p105 by SCFβ-TrCP following phosphorylation of the molecule. In a crude extract, a dominant negative E2 enzyme, UBC12, inhibits both conjugation and processing of p105, and inhibition is alleviated by an excess of WT- UBC12. In a reconstituted cell-free system, ubiquitination of p105 was stimulated only in the presence of all three components of the NEDD8 pathway, E1, E2, and NEDD8. A Cul-1 mutant that cannot be NEDDylated could not stimulate ubiquitination and processing of p105. Similar findings were observed also in cells. It should be noted that NEDDylation is required only for the stimulated but not for basal processing of p105. Although the mechanisms that underlie processing of p105 are largely obscure, it is clear that NEDDylation and the coordinated activity of SCFβ-TrCP on both p105 and IκBα serve as an important regulatory mechanism controlling NF-κB activity.

Human, Environmental & Exercise: The ACE deletion allele is associated with Israeli elite endurance athletes

An Alu insertion (I)/deletion (D) polymorphism in the angiotensin I converting enzyme (ACE) gene has been associated with ACE activity. Opposing effects on elite athletic performance have been proposed for the I and D alleles; while the D allele favours improved endurance ability, the I allele promotes more power‐orientated events. We tested this hypothesis by determining the frequency of ACE ID alleles amongst 121 Israeli top‐level athletes classified by their sporting discipline (marathon runners or sprinters). Genotyping for ACE ID was performed using polymerase chain reaction on DNA from leucocytes. The ACE genotype and allele frequencies were compared with those of 247 healthy individuals. Allele and genotype frequencies differed significantly between the groups. The frequency of the D allele was 0.77 in the marathon runners, 0.66 in the control subjects (P= 0.01) and 0.57 in the sprinters (P= 0.002). The ACE DD genotype was more prevalent among the endurance athletes (0.62) than among the control subjects (0.43, P= 0.004) and the power athletes (0.34, P= 0.004). In the group of elite athletes, the odds ratio of ACE DD genotype being an endurance athlete was 3.26 (95% confidence interval 1.49–7.11), and of ACE II genotype was 0.41 (95% confidence interval 0.14–1.19). We conclude that in Israeli elite marathon runners the frequency of the ACE D allele and ACE DD genotype seems to be higher than in sprinters, suggesting a positive association between the D allele and the likelihood of being an elite endurance athlete in some ethnic groups.

Aldosterone Synthase Gene Polymorphism as a Determinant of Atrial Fibrillation in Patients With Heart Failure

We analyzed the possible association between aldosterone synthase (CYP11B2) T-344C polymorphism, which is associated with increased aldosterone activity, and the prevalence of atrial fibrillation (AF) in 196 consecutive patients who had symptomatic systolic heart failure (HF; left ventricular ejection fraction <40%) for > or =3 months before recruitment. Genomic DNA was extracted from peripheral blood leukocytes using a standard protocol. Subjects were genotyped for the CYP11B2 polymorphism using the polymerase chain reaction/restriction fragment length polymorphism approach. AF was present in 63 patients (33%) with HF. We found the -344 CC genotype to be a strong independent marker for AF. Almost 1/2 (45%) of patients with this genotype had AF compared with 1/4 (27%) with -344 TT and TC genotypes (p = 0.01). A multivariate stepwise logistic regression model that included age, gender, New York Heart Association class, CYP11B2 -344CC genotype, and echocardiographic measurements of left ventricular ejection fraction, left atrial dimension, left ventricular end-diastolic diameter, and mitral regurgitation severity showed that the CYP11B2 CC genotype (adjusted for age and left atrial size) was an independent predictor of AF (adjusted odds ratio 2.35, 95% confidence interval 1.57 to 3.51, p = 0.03). In conclusion, CYP11B2 T-344C promoter polymorphism predisposes to clinical AF in patients with HF.

Serum Oxidative Stress Level Correlates with Clinical Parameters in Chronic Systolic Heart Failure Patients

Serum oxidative stress (OS) level has an important role in the inflammatory process of heart failure.

The guanine nucleotide binding protein β polypeptide 3 gene C825T polymorphism is associated with elite endurance athletes

A functional C825T polymorphism in the human guanine nucleotide binding protein β polypeptide 3 (GNB3) gene has been associated with enhanced G protein activation. Since reports regarding the interaction between physical activity and the GNB3 C825T polymorphism are limited and inconsistent, the aim of this study was to determine the frequency of C825T alleles among 155 elite Israeli athletes (endurance athletes and sprinters) and 234 healthy control subjects. Genotyping for GNB3 C825T was performed using polymerase chain reaction on DNA from leucocytes. Results showed that there was a significant difference in GNB3 C825T polymorphism genotype frequencies between endurance athletes and sprinters (P= 0.045) as well as between endurance athletes and control subjects (P= 0.046). We also observed a significantly higher proportion of the GNB3 TT genotype in the group of endurance athletes (19%) compared with the sprinters (5%, P= 0.014) and the control subjects (8.5%, P= 0.026). In the group of athletes, the odds ratio of GNB3 TT genotype being an endurance athlete was 4.49 (95% confidence interval 1.4–14.3) and of GNB3 CC genotype was 0.91 (95% confidence interval 0.47–1.77). These results were even more pronounced when we compared between the subgroups of 20 top‐level endurance athletes and 24 top‐level sprinters. We conclude that in Israeli athletes the GNB3 TT genotype is higher in elite endurance athletes than it is in sprinters, and within the endurance group it is higher in top‐level athletes, suggesting a positive association between the TT genotype and the likelihood of being an elite endurance athlete.

The effect of long-term beta-adrenergic receptor blockade on the oxygen delivery and extraction relationship in patients with coronary artery disease.

PURPOSE We evaluated the effects of long-term β-blocker treatment on the balance between oxygen delivery and extraction at peak oxygen uptake (VO2) and at target heart rate training (anaerobic threshold). METHODS Fifteen patients with coronary artery disease performed paired peak cardiopulmonary and submaximal exercise tests on a cycle ergometer with and without atenolol treatment. Thirty minutes following the submaximal tests, participants pedaled 10 minutes at a workload corresponding to that of the anaerobic threshold attained. Arterial oxygen was defined from echocardiography and venous oxygen content. RESULTS At rest, stroke volume, heart rate, and cardiac output were lower (P < .05), whereas arteriovenous oxygen difference [(a − v)O2] was higher with the use of atenolol (P < .05). At peak exercise, heart rate, lactate, and systolic blood pressure were lower (P < .05), whereas (a − v)O2 was higher (P < .05) with the use of atenolol. At anaerobic threshold, stroke volume, heart rate, cardiac output, and systolic blood pressure were lower (P < .05), whereas (a − v)O2was higher (P < .05) with the use of atenolol. Absolute VO2 and workload during maximal (P = .67 and P = .49, respectively) and submaximal (P = .13 and P = .44, respectively) exercises were similar between conditions. CONCLUSIONS Results demonstrate that atenolol treatment in patients with coronary artery disease does not alter VO2 and workload at the anaerobic threshold and peak exercise because of an increase in oxygen extraction and stroke volume in the face of reduced heart rate. These findings indicate that with long-term β-adrenergic receptor blockade, there is interplay between oxygen delivery and extraction, suggesting a link between cardiac hemodynamic responses and skeletal muscle metabolic adaptations.

Relation between AT1R gene polymorphism and long-term outcome in patients with heart failure.

Objectives: Angiotensin II plays a key role in the pathophysiology of heart failure (HF). This study examined the angiotensin II type 1 receptor (AT1R) polymorphism in patients with systolic HF and its relation to clinical manifestations and patient outcome. Methods: We genotyped 134 patients with HF and reduced systolic function for the AT1R A1166C genotype using polymerase chain reaction and restriction fragment length polymorphism. We analyzed the relationship between the AT1R A1166C polymorphism and clinical, electrocardiographic, echocardiographic and laboratory parameters in patients with ischemic and non-ischemic etiology and examined the relation between the AT1R genotype and long-term (30 months) patient survival. Results: In HF patients, frequency of the AT1R 1166C allele and specifically the CC genotype was similar to the general population, but associated with an ischemic and not a non-ischemic etiology (p = 0.02). The CC genotype was associated with more advanced disease and more severe abnormalities of renal function (p = 0.008). Survival analysis showed that AT1R CC homozygous patients had significantly higher mortality (p = 0.008; adjusted odds ratio for mortality 6.35, 95% confidence interval 1.49–11.21, p = 0.01). Conclusion: The CC AT1R genotype was associated with poor prognostic markers and increased mortality. The findings support the principle of genome-based therapies in the future treatment of HF patients.

What Maintains Energy Supply at Peak Aerobic Exercise in Trained and Untrained Older Men

Background: Aging-related changes occur mainly in the cardiopulmonary system and skeletal muscles, bringing about a reduction in physical performance. Consequently, maximal oxygen uptake (VO2max) decreases. Objectives: The current study investigated exercise oxygen utilization during maximal aerobic exercise in trained and untrained elderly. Methods: Fifteen trained (59.3 ± 1.1 years) and 15 untrained (60.1 ± 1.1 years) elderly underwent a peak cardiopulmonary exercise test on a bicycle ergometer. Arterial O2 was defined from echocardiograph and venous oxygen content. Results: At rest, trained compared to untrained elderly had significantly (p < 0.05) higher values of end diastolic volume (108.1 ± 5.8 and 100.7 ± 6.2 ml, respectively) and stroke volume (68.1 ± 4.3 and 57.3 ± 6.5 ml, respectively), while heart rate (68.7 ± 9.3 and 81.3 ± 8.2 beats · min–1, respectively), and mean arterial blood pressure (90.6 ± 6.9 and 95.4 ± 7.2 mm Hg, respectively) were significantly lower. At peak aerobic test, the trained elderly, compared to the untrained subjects, achieved significantly (p < 0.05) higher values of end diastolic volume (156.1 ± 8.2 and 134.1 ± 7.6 ml, respectively), stroke volume (123.0 ± 7.9 and 96.0 ± 4.8 ml, respectively), cardiac output (20.2 ± 1.5 and 15.0 ± 1.3 liters·min–1, respectively) and oxygen uptake (42.1 ± 2.1 and 31.1 ± 2.4 ml·kg–1·min–1, respectively), while diastolic blood pressure (70.3 ± 5.6 and 77.5 ± 4.2 mm Hg, respectively) and total peripheral resistance [4.3 ± 0.8 and 5.9 ± 1.41 (dyn·s–1·cm–5)·10–1, respectively], were significantly (p < 0.05) lower. Conclusions: The present study suggests that the differences between trained and untrained elderly in absolute oxygen uptake of the working muscles and peak power output at maximal exercise test are due to physical activity status. The higher aerobic capacity in the trained elderly is related to increased cardiovascular function and to a lesser extent to increased muscle mitochondria concentration and capillarity. Although untrained elderly have reduced maximal oxygen uptake at peak aerobic exercise, intrinsic regulation of mitochondrial function does not seem to be significantly altered because of aging associated physical inactivity. Therefore, untrained elderly can partially compensate for their lower cardiac output by increasing oxygen extraction to levels comparable with those of trained elderly.