Insertion/deletion polymorphism of the angiotensin I-converting enzyme gene and arterial oxygen saturation at high altitude

ACE Genotype May Have an Effect on Single versus Multiple Set Preferences in Strength Training

A polymorphic variant of the human angiotensin converting enzyme (ACE) gene was identified. The 'D' (rather than 'I') variant was associated with improvements in strength related to physical training. We set out to determine whether the response to different patterns of strength training might also differ. Ninty-nine Caucasian male non-elite athletes were randomly allocated into one of three groups: 31 non-training/control (CG: 31), single-set (SSG: 35) and multiple-set (MSG: 33). SSG and MSG trained three times a week for 6 weeks. Both training groups were underwent a strength-training program with two mesocycles (12-15 repetition maximum (RM) and 8-12 RM mesocycles). One RM loads in half squat and bench press were assessed before training and after the first and second mesocycles. ACE polymorphisms analysed by polymerase chain reaction (PCR) methods. Subjects with ACE II genotype in the MST group had improved strength development in 12-15 RM, while SST and MST groups had similar gains in 8-12 RM. Subjects with ACE DD genotype in both the SSG and the MSG had similar benefits from both 12-15 RM and 8-12 RM. Strength gains for subjects with ACE ID genotype in the SSG were similar to MSG gains in response to 8-12 RM loads but not with 12-15 RM loads. Additionally, subjects with DD genotype had superior strength gains in both strength training groups. Tailoring strength training programmes (single-set vs. multiple set) according to the athlete's ACE genotype may be advantageous.

Saturación arterial de oxígeno a gran altitud. Estudio en montañeros no aclimatados y en habitantes de alta montaña

BACKGROUND AND OBJECTIVE

We decided to determine how arterial oxygen saturation (SaO2) diminishes with altitude in unacclimatized mountaineers and in mountain dwellers.

SUBJECTS AND METHOD

Pulseoximetric measurements in unacclimatized mountaineers (214 measurements in several Spanish mountains and in the Alps up to 4,164 m) and in mountain dwellers (209 measurements in several Spanish and Bolivian villages up to 4,230 m). We performed pulseoximetric measurements for three consecutive days in eight mountaineers on the summit of Aneto (3,404 m) to ascertain whether SaO2 increases or not during early acclimatization.

RESULTS

Equations describing the SaO2 reduction with altitude are as follows: a) for unacclimatized mountaineers, SaO2 = 98.8183 - 0.0001.h - 0.000001.h2, b) for mountain dwellers, SaO2 = 98.2171 + 0.0012.h - 0.0000008.h2. (SaO2 in %; h: altitude in m. Lower limit of 95% confidence intervals given in the text). SaO2 of mountain dwellers is higher than that of unacclimatized mountaineers studied at the same altitude (p < 0.05 for any altitude over 1,692 m). SaO2 of mountaineers increased during early acclimatization (p < 0.05) to reach in few days the SaO2 of mountain dwellers. Unacclimatized mountaineers who spent the previous night over 2,000 m had higher SaO2 in altitude than those who slept under 2,000 m (p < 0.05). Mountaineers who performed any high-mountain activity (i.e. over 2,500 m) in the previous 12 months had higher SaO2 on the summit of Aneto than those who have never been over 2,500 m before (p < 0.05).

CONCLUSION

SaO2 increases during the acclimatization process. Our equations serve to calculate the SaO2 which can be considered normal for healthy people for every altitude below 4,200 m, both before and after the acclimatization process.

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.

Polymorphisms of renin-angiotensin system genes with high-altitude pulmonary edema in Japanese subjects

STUDY OBJECTIVES

The renin-angiotensin system (RAS), including angiotensin-converting enzyme (ACE) and angiotensin II type 1 receptor (AT(1)R), plays an important role in the pathogenesis of pulmonary hypertension, which is suggested to be critical in the development of high-altitude pulmonary edema (HAPE). Investigating the associations of the polymorphisms in the genes of RAS with HAPE is to elucidate the genetic background underlying this disease.

DESIGN

A cross-sectional, case-control study.

SETTING

Shinshu University Hospital, Matsumoto, Japan.

PARTICIPANTS

Forty-nine HAPE-susceptible (HAPE-s) subjects with a history of HAPE, and 55 healthy climbers with HAPE resistance (HAPE-r).

INTERVENTIONS

Twenty-one of 49 HAPE-s subjects underwent right cardiac catheterization.

MEASUREMENTS AND RESULTS

The insertion/deletion polymorphism in the ACE gene (ACE-I/D) was investigated by polymerase chain reaction (PCR). There was no significant difference of the distribution of the ACE-I/D polymorphism between the HAPE-s and HAPE-r groups. The A(1166)C and G(1517)T single-nucleotide polymorphisms (SNPs) in AT(1)R gene were investigated by the PCR following digested by corresponding restricted endonuclease enzymes. The distribution of the G(1517)T SNP was significantly different between the two groups (p = 0.012). The pulmonary hemodynamics of the 21 HAPE-s subjects were retrospectively examined. The pulmonary artery pressure (PAP), pulmonary vascular resistance (PVR), and PVR index (PVRI) were all significantly increased on hospital admission. Moreover, the PVR and PVRI were significantly higher in the HAPE-s subjects with D positivity than in the HAPE-s subjects with I positivity (PVR, p = 0.015; PVRI, p = 0.028), while the PAP did not show any significant difference between the two subgroups.

CONCLUSIONS

The ACE-I/D polymorphism is not associated with HAPE susceptibility in Japanese subjects. The AT(1)R gene polymorphisms may likely associate with HAPE susceptibility. The D allele of the ACE-I/D polymorphism probably contributes to the hyperresponsive PVR and PVRI to acute hypoxia.

The genetic basis of high-altitude pulmonary oedema

High-altitude pulmonary oedema (HAPE) is a potentially fatal condition affecting fit and previously well individuals at altitudes in excess of 3000 m. This article discusses the mechanisms of HAPE, considers the contribution of hypoxic pulmonary vasoconstriction and alterations in sodium transport to the pathological process. It discusses the various biochemical mediators such as nitric oxide (NO), endothelin-1 (ET-1), and the renin-angiotensin-aldosterone system (RAS) that may be involved and considers possible oxygen-sensing mechanisms involved in hypoxic adaptation such as hypoxia-inducible factor-1 (HIF-1). Those who have had HAPE once run an unpredictable but significant risk of recurrence; therefore, there may be a constitutional or genetic component in its aetiology. This paper considers the possible involvement of genes that may be involved in physiological adaptation to hypoxia (e.g., angiotensin-1 [AT(1)]-converting enzyme [ACE], tyrosine hydroxylase, serotonin transporter [5-HTT], and endothelial NO synthase [eNOS] genes). As yet, no formal association has been identified between an identified genetic polymorphism and HAPE, but genetic variation provides a possible mechanism to explain interindividual variation in response to hypoxia and enhanced or reduced performance at altitude.

The effects of flight and altitude

Increasing numbers of infants and children journey by aeroplane, or travel to high altitude destinations, for example, on holiday or as part of a population migration. Most are healthy, although increasingly children may be transported by aeroplane or helicopter specifically to obtain treatment for severe illness or injury. It is therefore useful to review the effects of altitude, and their relevance to children who undertake flights or travel to, or at high altitudes, particularly those with acute and chronic medical conditions.

Angiotensin-converting enzyme DD genotype is associated with worse perinatal cardiorespiratory adaptation in preterm infants

OBJECTIVES

The angiotensin-converting enzyme (ACE) deletion (D) variant is associated with greater ACE activity and perhaps with deleterious cardiorespiratory pathophysiological responses. We determined whether the early health status of the preterm infant was adversely influenced by homozygosity for the D allele (DD genotype) compared with ID or II genotype. Study design Angiotensin-converting enzyme genotype was determined in a cohort of 148 preterm infants born in Bristol, United Kingdom (median gestational age, 31 weeks; range, 28-32). Intensive care data were prospectively obtained. Primary analysis was by Mann-Whitney U and chi(2) tests.

RESULTS

Higher oxygen, circulatory support requirements, and base deficit in the first 12 hours after birth were found in infants with DD genotype (minimum inspired oxygen concentration in first 12 hours, median [interquartile range], DD 0.26 [0.21-0.40], ID/II 0.21 [0.21-0.30], P=.028; blood pressure support in first 12 hours, DD 12 [30%], ID/II 15 [14%], P=.039; worse base deficit in first 12 hours, DD 4.8 [7.7 to 0], ID/II 0 [5.3 to 0], P=.020).

CONCLUSIONS

Angiotensin-converting enzyme polymorphism has a role in the development of preterm cardiorespiratory disease. The DD genotype, encoding higher angiotensin-converting enzyme activity, may adversely influence the early health status of preterm infants.

Regulation of the angiotensin-converting enzyme activity by a time-course hypoxia in the carotid body

Chronic hypoxia activates a local angiotensin-generating system in the carotid body. Here, we test the hypothesis that the activity of the critical enzyme for this system, angiotensin-converting enzyme (ACE), in the carotid body is subject to regulation by a time-course hypoxia. Results from the carotid body assays showed that ACE activity was markedly increased under the hypoxic stress of 7-, 14-, 21-, and 28-day exposures. The changes in ACE activity of 7-day (15.00 vs. 30.95 x 10(-5) nmol.microg(-1).min(-1)), 14-day (8.73 vs. 30.25 x 10(-5) nmol.microg(-1).min(-1)), and 21-day (11.41 vs. 31.83 x 10(-5) nmol.microg(-1).min(-1)) hypoxia treatments were enhanced significantly. However, ACE activity in 28-day (13.18 vs. 24.53 x 10(-5) nmol.microg(-1).min(-1)) hypoxia treatment was observed to increase insignificantly when compared with results in the respective control groups. Captopril inhibited all rises in ACE activity in both the control and experimental groups. Results clearly indicate an activation of the enzymatic activity of ACE, the critical enzyme for determining the conversion of angiotensin I into the physiologically active angiotensin II, by chronic hypoxia in the carotid body. An increase in the ACE activity may increase the local production of angiotensin II in the carotid body and thus its agonist action at the AT1 receptor. This may be important in the modulation of cardiopulmonary adaptation in the hypoxic ventilatory response as well as for electrolyte and water homeostasis during chronic hypoxia.