1.
The hemodynamic and neurohumoral phenotype of postural tachycardia syndrome.
Garland, EM, Raj, SR, Black, BK, Harris, PA, Robertson, D
Neurology. 2007;(8):790-8
Abstract
BACKGROUND Previous studies of patients with postural tachycardia syndrome (POTS) have been hampered by relatively small cohorts, failure to control medications and diet, and inconsistent testing procedures. METHODS The Vanderbilt Autonomic Dysfunction Center Database provided results of posture studies performed in 165 patients and 66 normal controls after dietary and medication restrictions. All posture studies were performed after an overnight fast and > or =30 minutes of supine rest. RESULTS In both the supine and standing positions, heart rate (HR) and plasma concentrations of norepinephrine (NE), epinephrine, and dopamine were higher in patients with POTS compared with the healthy controls. Supine diastolic blood pressure (BP) was also elevated in POTS, whereas supine plasma l-3,4-dihydroxyphenyalanine was reduced. In an analysis of patient subgroups with either an upright plasma NE > or = 3.54 nM (high NE) or an upright plasma NE < 3.54 nM (normal NE), HR and BP were greater in the patient subgroup with high NE. In addition to these significant differences in hemodynamic and catechol measurements, we demonstrated that supine and standing plasma aldosterone and the aldosterone/renin ratio were decreased in patients with POTS. Plasma renin activity (PRA) tended to be higher in patients, and standing HR for those in the highest PRA quartile was significantly greater than for those in the lowest PRA quartile. CONCLUSIONS Our results from larger cohorts of patients and controls than previously studied confirm published findings and contribute additional evidence of sympathetic activation in postural tachycardia syndrome (POTS). Abnormalities in the renin-angiotensin-aldosterone system may also contribute to the POTS phenotype.
2.
Is there an association between ACE and CKMM polymorphisms and cycling performance status during 3-week races?
Lucía, A, Gómez-Gallego, F, Chicharro, JL, Hoyos, J, Celaya, K, Córdova, A, Villa, G, Alonso, JM, Barriopedro, M, Pérez, M, et al
International journal of sports medicine. 2005;(6):442-7
Abstract
In this paper, we examine the association between polymorphisms of the angiotensin-converting enzyme (ACE) and muscle-specific creatine kinase (CKMM) genes, and the actual performance status observed in professional cyclists capable of completing a classic tour stage race such as the Giro d'Italia, Tour de France, or Vuelta a España. To accomplish this, we compared the frequencies of the ACE and CKMM genotypes/alleles in 50 top-level Spanish professional cyclists that have completed at least one of these events to 119 sedentary controls, and 27 elite (Olympic-class) Spanish runners. The genetic polymorphism at the CK-MM locus was detected with the NcoI restriction endonuclease. The results of our study showed that the proportion of the DD genotype was higher in cyclists (50.0 %) than in the other two groups (p<0.05), the proportion of the ID genotype was higher in controls (46.2 %) than in the other two groups (p<0.05), and the proportion of the II genotype was higher in runners (40.7 %) than in the other two groups (p<0.05). The proportion of the D allele was higher in both cyclists (65.0 %) and controls (57.6 %) than in runners (46.3 %) (p<0.001), whereas the proportion of the I allele was higher in runners than in the other two groups (p<0.001). No statistical differences were found for CKK-MM- NcoI. We conclude that in top-level professional cyclists capable of completing a classic 3-wk tour race, the frequency distribution of the D allele and the DD genotype seems to be higher than in other endurance athletes such as elite runners (in whom the I allele is especially frequent).