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Am J Physiol Heart Circ Physiol 291: H459-H466, 2006. First published February 24, 2006; doi:10.1152/ajpheart.01193.2005
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Heart rate recovery after maximal exercise is associated with acetylcholine receptor M2 (CHRM2) gene polymorphism

Arto J. Hautala,1,2 Tuomo Rankinen,1 Antti M. Kiviniemi,2,3 Timo H. Mäkikallio,3,4 Heikki V. Huikuri,3 Claude Bouchard,1 and Mikko P. Tulppo2,3

1Pennington Biomedical Research Center, Human Genomics Laboratory, Louisiana State University System, Baton Rouge, Louisiana; 2Merikoski Rehabilitation and Research Center, Oulu; 3Division of Cardiology, Department of Medicine, University of Oulu, Oulu; and 4Lapland Central Hospital, Rovaniemi, Finland

Submitted 11 November 2005 ; accepted in final form 19 February 2006


   ABSTRACT
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 ABSTRACT
METHODS
 RESULTS
 DISCUSSION
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The determinants of heart rate (HR) recovery after exercise are not well known, although attenuated HR recovery is associated with an increased risk of cardiovascular mortality. Because acetylcholine receptor subtype M2 (CHRM2) plays a key role in the cardiac chronotropic response, we tested the hypothesis that, in healthy individuals, the CHRM2 gene polymorphisms might be associated with HR recovery 1 min after the termination of a maximal exercise test, both before and after endurance training. The study population consisted of sedentary men and women (n = 95, 42 ± 5 yr) assigned to a training (n = 80) or control group (n = 15). The study subjects underwent a 2-wk laboratory-controlled endurance training program, which included five 40-min sessions/wk at 70–80% of maximal HR. HR recovery differed between the intron 5 rs324640 genotypes at baseline (C/C, –33 ± 10; C/T, –33 ± 7; and T/T, –40 ± 11 beats/min, P = 0.008). Endurance training further strengthened the association: the less common C/C homozygotes showed 6 and 12 beats/min lower HR recovery than the C/T heterozygotes or the T/T homozygotes (P = 0.001), respectively. A similar association was found between A/T transversion at the 3'-untranslated region of the CHRM2 gene and HR recovery at baseline (P = 0.025) and after endurance training (P = 0.005). These data suggest that DNA sequence variation at the CHRM2 locus is a potential modifier of HR recovery in the sedentary state and after short-term endurance training in healthy individuals.

genotype; exercise training; cardiovascular autonomic function

DELAYED HEART RATE (HR) recovery after physical exercise has been shown to be a powerful independent predictor of mortality in healthy subjects and in different patient populations (9–11, 25, 33, 49). The balance between the vagal and sympathetic activities mediates the changes in HR during recovery from physical exercise. Acetylcholine released from cardiac vagal nerve endings triggers a chronotropic effect by decreasing HR (6, 8). It is well established that attenuated vagal reactivation after the termination of exercise is involved in slow HR recovery (4, 11, 12, 24, 35). However, marked interindividual differences have been observed in HR recovery rates even in healthy subjects, suggesting a possibility of a genetically determined background for postexercise HR behavior (39, 40).

Regular endurance training shifts the cardiac autonomic balance toward vagal dominance (3, 7, 13, 17, 19, 47). Cardiac vagal activity increases markedly even after 2 wk of regular training (30, 50). Previous studies have also shown that postexercise HR recovery improves after endurance training in sedentary healthy males (46) and in patients with coronary artery disease (18). However, a substantial heritable component may also be involved in the regulation of HR behavior in response to training (40, 41), and this may partly explain the large interindividual variation in HR recovery.

Muscarinic acetylcholine receptors play a fundamental role in cardiac function via vagally mediated regulation of the autonomic nervous system. The human heart expresses predominantly muscarinic acetylcholine receptor subtype M2 (CHRM2) (6, 8). Fisher et al. (14) showed that vagally induced bradycardiac responses were totally abolished in CHRM2-deficient mice in vivo, suggesting the exclusive role of CHRM2 in HR regulation (14). Therefore, we tested the hypothesis that, among healthy individuals, the CHRM2 gene polymorphisms are associated with 1-min HR recovery after peak exercise in the sedentary state and after endurance training.


   METHODS
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 METHODS
RESULTS
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Subjects

The subjects were recruited by newspaper ads, which attracted 355 replies. All smokers, subjects with body mass index (BMI) > 32 kg/m2, subjects who did regular physical training more than two times per week, and subjects with diabetes mellitus, asthma, or cardiovascular disorders were excluded. We invited 108 subjects to our laboratory (Dept. of Exercise and Medical Physiology, Merikoski Rehabilitation and Research Centre, Oulu, Finland) for more specific assessment. The number of subjects was selected on the basis of a priori power analysis to give 80% power to the responsiveness of maximal aerobic power [peak oxygen consumption (VO2 peak)] after 2 wk of endurance training. According the previous studies (16, 30, 31, 50), 8% improvement in VO2 peak can be expected after short-term endurance training with SD of approximately ±7%, giving the estimate of needing at least 10 subjects for both the intervention and the control group. The subjects were randomized into a training group (n = 90) and a control group (n = 18). The unbalanced study design was used to particularly assess the contribution of genotypes to actual training effect. The average heterozygosity and allele frequencies of DNA sequence variation of interest are available from the National Center for Biotechnology Information (NCBI) database. These frequencies were used to estimate the hypothetical number of subjects of each genotype group at the present population. During the study, 13 subjects dropped out (10 from the training group and 3 from the control group) because of personal or health-related problems. Finally, 80 subjects (36 men and 44 women) performed the endurance training program. The control group consisted of 15 subjects (9 men and 6 women). The Ethical Committee of the Northern Ostrobothnia Hospital District, Oulu, Finland, approved the protocol.

Experimental Design

Sequence of tests. On their first laboratory day, the subjects completed a health status questionnaire, gave written informed consent, and were assessed for BMI. Resting electrocardiogram (12-lead ECG) was recorded to confirm their cardiac health status, and overnight R-R intervals were recorded to evaluate autonomic regulation by the HR variability method. On the second day, blood pressure was recorded and maximal exercise testing performed. Use of alcohol or strenuous physical activity was not allowed during the test days and on the two preceding days.

The endurance training period was 2 wk, including five consecutive sessions per week (Monday–Friday). The short intervention period was chosen on the basis of the previous studies, which shows that a well-controlled, short-term training intervention increased significantly VO2 peak (16, 20, 30, 31, 45, 50) and cardiac vagal activity (30, 50). At the end of the training intervention, all measures were repeated 48 h after the last training session. The control group was tested similarly to the training group, and they were asked to maintain their habitual physical activity level during the 2-wk period. Finally, blood samples were collected 2 days after the last exercise testing in the laboratory of Internal Medicine at the University Hospital of Oulu.

Assessment of VO2 peak, maximal HR, and HR recovery. The subjects performed a graded maximal exercise test on an 839E Monark cycle ergometer (Stockholm, Sweden). The test was started at 25 W, and work rate was increased by 25 W every 2 min until exhaustion. Pedaling was started at 50 rpm and increased by 5 rpm up to 90 rpm, to achieve maximal effort. The subjects were encouraged to continue cycling until they could no longer maintain the required pace, at which time the test was terminated. After the termination of the test, the subjects were asked to remain seated on the bicycle, and HR recording was continued for 6 min. They were not allowed to talk or move during the first minute after the test, which was followed by a 5-min cool-down period at a work rate of 25 W. HR recovery was determined as maximal HR (mean of 10 s) – HR at 1 min after exercise (mean of 5 s). Ventilation, gas exchange (M909 Ergospirometer, Medikro, Kuopio, Finland), and HR (Cardiolife TEC-7721K, Nihon Kohden, Tokyo) were monitored continuously during the protocol. The highest oxygen uptake value measured during the test (1-min collection) was taken as the VO2 peak. All subjects fulfilled the criteria for VO2 peak given in the literature (i.e., respiratory exchange ratio >1.1 or maximal HR within ±10 beats of the age-appropriate reference value) (21). HR was recorded during the exercise test and recovery with a Polar R-R Recorder (Polar Electro, Kempele, Finland) and saved in a computer for further analysis with the HEARTS software (Heart Signal, Kempele, Finland).

Assessment of resting blood pressure. Resting systolic (SBP) and diastolic blood pressures (DBP) were assessed by using an electronic sphygmomanometer (Omron M4, Omron Healthcare). The subjects lay in the supine position in a quiet room for at least 10 min before the blood pressure measurements. The blood pressure measurements were performed in a supine position at the same time of the day before and after the training program.

Assessment of HR variability. The R-R intervals were recorded overnight (from midnight to 6 AM) with a Polar R-R Recorder at an accuracy of 1 ms and saved in a computer for further analysis of HR variability with the Hearts software. All R-R intervals were edited by visual inspection on the basis of ECG portions to exclude all undesirable beats, which accounted for <2% in every subject's recording. The details of this analysis and the filtering technique have been described previously (22). The subjects were asked to go to bed before midnight and to stay in bed until 6 AM on the R-R interval recording days.

The mean HR and the SD of all R-R intervals were used as time-domain measures of HR variability. An autoregressive model was used to estimate the power spectrum densities of R-R interval variability. Low-frequency power (LF, 0.04–0.15 Hz) and high-frequency power (HF, 0.15–0.4 Hz) were calculated from the segments of the 512 R-R interval overnight recording (36). A logarithmic transformation to the natural base was performed on both spectral components of HR variability.

Exercise training. The endurance training program consisted of cycling on an 818E Monark cycle ergometer for 40 min (Stockholm, Sweden). Each exercise session consisted of a 5-min warm-up period (cycling at 50-W and 75-W resistance for women and men, respectively), followed by 30 min of cycling at a resistance that elicited a HR of 70–80% of maximal HR, and ended with a 5-min cool-down period (cycling at 50-W and 75-W resistance for women and men, respectively). Exercise intensity was closely monitored using a Polar Electro HR monitor A1, and the mean HR of each training session was recorded. Endurance exercise training was planned on the basis of the recommendations of American College of Sports Medicine (2). A professional instructor supervised each training session.

Determination of genotypes. EDTA blood samples were obtained from all subjects, and DNA was isolated by using simple salting-out procedure. Six single-nucleotide polymorphisms (SNPs) were selected from the NCBI dbSNP database: rs2278098 in intron 3 (1780 bp downstream from exon 3), rs2061174 in intron 4 (25,573 from exon 4), rs324640 and rs324650 in intron 5 (10,571 and 5,906 bp, respectively, upstream of exon 6), rs8191992 in the 3'-untranslated region of exon 6, and rs1378650 located 152 bp downstream of exon 6. These SNPs were chosen on the basis of their clinical relevance (48) and their capturing role of common genetic variation at the CHRM2 locus. The SNPs were genotyped by using template-directed dye-terminator incorporation with the fluorescence polarization detection (FP-TDI) method. A DNA sequence containing the SNP was amplified with PCR, and after cleaning with shrimp alkaline phosphatase and exonuclease I, the PCR product was used as a template in the AcycloPrime-FP reaction. The SNP detection primers were designed so as to locate their 3'-end immediately upstream of the polymorphic (SNP) site. The SNP detection PCR reaction utilized a mutant thermostable polymerase and a pair of AcycloTerminators labeled with R110 and TAMRA (AcycloPrime-FP SNP kit, PerkinElmer Life Sciences, Boston, MA), representing the possible alleles for the SNP of interest. Allele detection was done by measuring the changes in fluorescence polarization after excitation of the samples by plane-polarized light by using a Victor2 FP Plate Reader (PerkinElmer Life Sciences) on a 384-well plate format. Allele calling was done by using the SNPscorer genotyping software (PerkinElmer Life Sciences). Haplotypes were constructed using the SHEsis software package (38).

Statistical Analyses

Chi-square test was used to verify whether the observed genotype frequencies were in Hardy-Weinberg equilibrium, and pairwise linkage disequilibrium (LD) between the SNPs was assessed using the ldmax program available in the GOLD software package (1). The normal Gaussian distribution of the data was verified by the Kolmogorov-Smirnov goodness-of-fit test. The difference in change in VO2 peak after training within the training and control group was analyzed by a two-factor ANOVA for repeated measures with time and interventions followed by post hoc analysis (Student's paired t-test). The associations between the CHRM2 gene polymorphisms, the end-point phenotypes, and the associations with the haplotypes were tested with an analysis of covariance by using the general linear model procedure of the SAS software package. The phenotypes were adjusted for age, sex, and BMI. The training response phenotypes were adjusted in addition to the baseline value of the phenotype. Pearson's correlation coefficients were calculated to study the associations between the HR phenotypes, HR variability phenotypes, physical performance phenotypes, and resting blood pressure before and after the training program. Pearson's correlation analysis was also used to test the relationships between HR recovery and the other measured phenotypes separately within the three genotype groups (rs324640 in Intron 5; C/C, C/T, T/T). Values are given as means ± SD. The SAS statistical software package (SAS Institute) was used for the analyses.


   RESULTS
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The baseline characteristics of the subjects are shown in Table 1, and a summary of the minor allele frequencies, as well as the pairwise LD of the CHRM2 SNPs, is shown in Table 2. The minor allele frequencies were similar between men and women in all CHRM2 SNPs (e.g., for rs324640 C:0.40 for men and C:0.39 for women). SNPs rs2278098 and rs2061174 showed low LDs with other CHRM2 SNPs, whereas moderate to high pairwise LDs were observed between the SNPs located in the vicinity of the coding exon 6 of the CHRM2 gene. Because the intron 5 SNPs rs324640 and rs324650 were in complete LD (r2 = 1.0), they yielded identical results. Therefore, only the results for rs324640 are presented. All genotype frequencies were in Hardy-Weinberg equilibrium.


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  		Table 1. Baseline characteristics of subjects

 

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  		Table 2. Allele frequencies and pairwise linkage disequilibriums of CHRM2 SNPs

 
Training

All the subjects in the training group maintained the training frequency of 10 times during 2 wk. The intensity of training was 74 ± 3% of maximal HR, and the mean duration of exercise was 40 ± 3 min/session. The change in VO2 peak was +8.1 ± 5.7% (P < 0.001) for the training group and –0.5 ± 7.0% (P = 0.941) for the control group. There were no differences in the change of VO2 peak between the genotypes in the CHRM2 SNPs (e.g., for rs324640 SNP the improvement of VO2 peak was 7.5 ± 7.2% for C/C, 8.2 ± 7.2% for C/T, and 8.0 ± 5.7% for T/T, P = 0.924).

Association Between CHRM2 SNPs and HR Recovery

Maximal HR was not significantly associated with the CHRM2 SNPs. However, HR recovery differed significantly between the rs324640 genotypes at baseline (C/C, –33 ± 10; C/T, –33 ± 7; and T/T, –40 ± 11 beats/min, P = 0.008, Fig. 1A, Table 3). The association was even stronger (P = 0.001) after the 2-wk endurance training period: the C/C homozygotes showed 6 and 12 beats/min lower HR recovery than the C/T heterozygotes and the T/T homozygotes, respectively (Fig. 1B). The change in HR recovery after the training program also differed between the rs324640 genotypes (C/C, –3 ± 7; C/T, 2 ± 7; and T/T, 2 ± 8 beats/min, P = 0.038). Moreover, rs8191992 SNP was associated with HR recovery: the A/A homozygotes and the A/T heterozygotes showed lower HR recovery values than the T/T homozygotes both at baseline (P = 0.025, Table 4) and after the endurance training program (P = 0.005, Table 4). The SNPs rs2278098, rs2061174, and rs1378650 were not associated with HR recovery.


Figure 1
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  		Fig. 1. Individual and mean values of heart rate recovery before (baseline; A) and after (posttraining; B) 2 wk of controlled endurance training program according to the acetylcholine receptor subtype M2 (CHRM2) gene rs324640 polymorphism in healthy subjects. The association tests between the rs324640 genotype and heart rate recovery are adjusted for age, sex, and body mass index. bpm, Beats/min.

 

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  		Table 3. Associations between CHRM2 rs324640 genotype and hemodynamic phenotypes, VO2peak, and HR variability overnight (from midnight to 6 AM) before and after a 2-wk endurance training program

 

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  		Table 4. Associations between the CHRM2 rs8191992 genotype and the hemodynamic phenotypes, VO2peak, and HR variability overnight (from midnight to 6 AM) before and after a 2-wk endurance training program

 
Association Between CHRM2 SNPs and HR Variability

Overnight HR was not significantly associated with CHRM2 SNPs. However, the LF-to-HF ratio showed significantly higher values in the rs8191992 A/A homozygotes than in the other genotypes both before (P = 0.036) and after (P = 0.046) endurance training (Table 4). The rs324640 C/C homozygotes showed a similar trend (P = 0.064 and P = 0.063, respectively), but the difference was not statistically significant (Table 3).

Association Between CHRM2 SNPs and Blood Pressure

Resting DBP was significantly higher in the rs324640 C/C homozygotes than in the other genotypes both before (P = 0.049) and after (P = 0.045) the training program (Table 3). Similar trends were also observed for SBP, but the differences did not reach statistical significance.

Correlation Between SBP and HR Recovery Between rs324640 Genotypes

There were no statistically significant correlations between HR recovery, HR variability, and the other hemodynamic phenotypes before (e.g., HR recovery vs. HF power, r = 0.016; and HR recovery vs. LF-to-HF ratio, r = –0.064) or after the training program (e.g., HR recovery vs. HF power, r = –0.033; and HR recovery vs. LF-to-HF ratio, r = –0.135). However, the relationship between resting SBP and HR recovery varied considerably between the rs324640 genotypes, especially in the trained state (Fig. 2): the common T/T homozygotes (Fig. 2F) showed a strong positive correlation [r = 0.517, 95% confidence interval (CI) from 0.20 to 0.74], whereas the C/C homozygotes (Fig. 2B) showed a negative correlation (r = –0.353, CI from –0.72 to 0.17) and the C/T heterozygotes (Fig. 2D) an intermediate correlation (r = 0.087, CI from –0.22 to 0.38).


Figure 2
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  		Fig. 2. Associations between heart rate recovery and resting systolic blood pressure before (baseline; A, C, and E) and after (posttraining; B, D, and F) 2 wk of controlled endurance training program in the CHRM2 rs324640 genotypes: C/C homozygotes (A and B), C/T heterozygotes (C and D), and T/T homozygotes (E and F). CI, confidence interval.

 
Haplotype Analysis

The CHRM2 haplotypes were constructed by using the "best" option of the SHEsis software haplotyping function. The haplotype analyses confirmed the associations detected with individual SNPs. The haplotype consisting of the minor alleles of the rs324640 and rs8191992 variants (CA) was associated with lower HR recovery values in the trained state (P = 0.007). The minor allele haplotype also showed a stronger association with the LF-to-HF ratio both at baseline (P = 0.004) and after the training period (P = 0.007) compared with the association detected in rs8191992 alone. The common allele (TT) haplotype of the rs324640 and rs8191992 variants was associated with higher HR recovery both before (P = 0.003) and after the training program (P = 0.003). Furthermore, the TT haplotype showed lower values of resting DBP at the baseline (P = 0.037) and after the training (P = 0.011).


   DISCUSSION
TOP
 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
GRANTS
 REFERENCES
 
The novel finding of the present study was the association of the CHRM2 gene polymorphism with HR recovery after maximal exercise. These data suggest that, among healthy individuals, DNA sequence variation at the CHRM2 locus is a potential modifier of HR recovery both in the sedentary state and after a short-term endurance training program. Because postexercise HR recovery has been shown to be an independent predictor of mortality both in healthy subjects and in various patient groups, the present results may provide important clues to understanding the molecular mechanisms underlying the regulation of HR recovery and its association with adverse cardiovascular events.

Physiological Background of HR Recovery

CHRM2 plays a fundamental role in cardiac autonomic regulation (14). Activation of cardiac vagal efferents leads to release of acetylcholine, which acts on cardiac CHRM2 to decrease HR (6, 8). Several studies have shown that the main physiological mechanism underlying postexercise cardiodeceleration is vagal reactivation (4, 10, 24, 25, 35). A recent study by Smith and colleagues (43) showed that mongrel dogs vulnerable to ventricular fibrillation had reduced HR recovery compared with dogs resistant to malignant arrhythmias. The differences in HR recovery and cardiac vagal activity were eliminated by administration of atropine, which confirmed the dominant role of vagal activity in the control of HR after exercise (43). Furthermore, acetylcholine receptor resistance in rats resulted in reduced cardiac muscarinic receptor function, leading to cardiovagal insufficiency (34). As a novel finding of the present study, we found that genetic variation at the CHRM2 locus is associated with interindividual variability in the modulation of HR after maximal exercise.

The role of HR recovery as a clean index of cardiac vagal function has been questioned because the sympathetic withdrawal is also involved (37). In the present study, HR recovery did not associate with HF power of R-R intervals, which is the most commonly used index of cardiac vagal outflow. Analysis of HF power from ambulatory R-R interval recordings includes also some methodological problems, e.g., the saturation of HF power during the very high vagal outflow (26). This may be one reason for the low association between HR recovery and ambulatory measured HF power. Second, the CHRM2 gene polymorphisms were slightly but significantly associated with LF-to-HF ratio, known as an index of sympathovagal balance. Taken together, it is possible that both branches of autonomic regulation contribute to the magnitude of HR recovery after maximal exercise.

Association Between CHRM2 SNPs and Central Nervous System

The central nervous system plays an important role in cardiovascular regulation (15). Locally released acetylcholine acts through CHRM2 within the ventrolateral medulla in the brain, increasing the activity of sympathetic preganglionic neurons and consequently elevating blood pressure and HR (15, 27, 28). It was previously observed that the same SNPs of the CHRM2 gene as reported in the present study showed a strong association with alcohol dependence, depressive disorder, and various biopotential waves, some of which are also associated with cardiovascular dysfunctions (48). Our subjects were healthy but were not assessed for alcohol dependence or depressive disorders. However, we were able to confirm the association between the CHRM2 polymorphisms and early cardiovascular dysfunction in various autonomic markers by, for instance, verifying slow HR recovery in untrained and trained states and an elevated LF-to-HF ratio in long-term R-R interval recording.

Effects of Training on HR Recovery

Endurance training has been suggested to protect the heart against harmful cardiac events by increasing vagal tone (5). Cardiac vagal activity has been shown to increase after 2 wk of regular endurance training (30, 50). Previous studies on sedentary healthy men and patients with severe coronary artery disease have reported endurance training induced improvement in cardiac autonomic regulation, quantified as improved postexercise HR recovery (18, 46). In the present study, the minor allele homozygotes of the rs324640 and rs8191992 variants showed less optimal HR recovery than the common allele homozygotes, both in the sedentary state and especially after the 2-wk training program. Furthermore, the determinant of sympathovagal balance, i.e., LF-to-HF ratio, showed an association with the minor allele (CA) haplotype of the rs324640 and rs8191992 variants, confirming the contribution of the CHRM2 gene locus to the autonomic regulation of the heart.

Role of Acetylcholine Receptors in Blood Pressure Regulation

Altered autonomic modulation of HR has been shown to be associated with elevated blood pressure (23) and early stage of hypertension among normotensive men (42). Systemic administration of acetylcholine and other muscarinic agonists lowers blood pressure, presumably because of vasodilatation caused by the activation of muscarinic acetylcholine receptors located on vascular endothelial cells (14). Fisher et al. (14) reported recently that the blood pressure response in CHRM3-deficient mice was greatly attenuated after the administration of muscarinic agonist compared with wild-type control mice. Furthermore, they observed that the CHRM2-mediated decrease in HR was the major factor responsible for the pronounced reduction in blood pressure after the administration of muscarinic agonist, suggesting a dominant role of CHRM receptors in the control of blood pressure level (14). In our healthy normotensive series, we observed that rs324640 C/C homozygotes also tended to have higher resting blood pressure values before and after endurance training. Furthermore, the relationship between resting blood pressure and postexercise HR recovery varied markedly across the rs324640 genotypes, especially after endurance training. Taken together, these results suggest that the CHRM2 gene locus may contribute to interindividual variation in blood pressure levels. However, this hypothesis should be confirmed in larger populations.

Limitations

The present study was limited by the fact that a relatively small number of subjects were examined, which may emphasize the preliminary nature of the results. Therefore, the results must obviously be confirmed in other populations. Second, to date, there is no functional evidence of the associated CHRM2 SNPs, although the role of CHRM2 in the regulation of human HR is evident at the receptor level.

Implications

The importance of HR recovery after both maximal (10, 25) and submaximal exercise (11) as a predictor of mortality has been well established in large population-based cohorts. The independent predictive value is evident both in healthy subjects (25) and in different patient groups (10, 32, 33, 44). Indeed, the American Heart Association has proposed that HR recovery could be used to assess the risk for developing clinical coronary disease among asymptomatic subjects (29). In this respect, the findings of the present study may have clinical relevance and contribute to our understanding of the genetic background of HR recovery after exercise. In summary, DNA sequence variation in the CHRM2 gene locus is a potential modifier of postexercise HR recovery in healthy individuals. Whether the same findings apply to other ethnic groups and to cardiac patients remains to be confirmed in future studies.


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 ABSTRACT
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This research was funded by grants from the Finnish Ministry of Education (Helsinki, Finland), the Medical Council of the Academy of Finland (Helsinki, Finland), the Seppo Säynäjäkangas Foundation, the Juho Vainio Foundation, and the Olga and Vilho Linnamo Foundation. We appreciate the technical and financial support received from Polar Electro (Kempele, Finland) and the generous help from Heart Signal (Kempele, Finland).


   FOOTNOTES
 

Address for reprint requests and other correspondence: A. J. Hautala, Dept. of Exercise and Medical Physiology, Merikoski Rehabilitation and Research Centre, P.O. Box 404, Kasarmintie 13, FIN-90101, Oulu, Finland (e-mail: arto.hautala{at}merikoski.fi)

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.


   REFERENCES
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  1. Abecasis GR and Cookson WO. GOLD—graphical overview of linkage disequilibrium. Bioinformatics 16: 182–183, 2000.[Abstract/Free Full Text]
  2. ACSM. American College of Sports Medicine Position Stand. The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness, and flexibility in healthy adults. Med Sci Sports Exerc 30: 975–991, 1998.[ISI][Medline]
  3. Al-Ani M, Munir SM, White M, Townend J, and Coote JH. Changes in R-R variability before and after endurance training measured by power spectral analysis and by the effect of isometric muscle contraction. Eur J Appl Physiol Occup Physiol 74: 397–403, 1996.[CrossRef][ISI][Medline]
  4. Arai Y, Saul JP, Albrecht P, Hartley LH, Lilly LS, Cohen RJ, and Colucci WS. Modulation of cardiac autonomic activity during and immediately after exercise. Am J Physiol Heart Circ Physiol 256: H132–H141, 1989.[Abstract/Free Full Text]
  5. Billman GE. Aerobic exercise conditioning: a nonpharmacological antiarrhythmic intervention. J Appl Physiol 92: 446–454, 2002.[Abstract/Free Full Text]
  6. Brodde OE and Michel MC. Adrenergic and muscarinic receptors in the human heart. Pharmacol Rev 51: 651–690, 1999.[Abstract/Free Full Text]
  7. Carter JB, Banister EW, and Blaber AP. The effect of age and gender on heart rate variability after endurance training. Med Sci Sports Exerc 35: 1333–1340, 2003.[Medline]
  8. Caulfield MP. Muscarinic receptors—characterization, coupling and function. Pharmacol Ther 58: 319–379, 1993.[CrossRef][ISI][Medline]
  9. Cheng YJ, Lauer MS, Earnest CP, Church TS, Kampert JB, Gibbons LW, and Blair SN. Heart rate recovery following maximal exercise testing as a predictor of cardiovascular disease and all-cause mortality in men with diabetes. Diabetes Care 26: 2052–2057, 2003.[Abstract/Free Full Text]
  10. Cole CR, Blackstone EH, Pashkow FJ, Snader CE, and Lauer MS. Heart-rate recovery immediately after exercise as a predictor of mortality. N Engl J Med 341: 1351–1357, 1999.[Abstract/Free Full Text]
  11. Cole CR, Foody JM, Blackstone EH, and Lauer MS. Heart rate recovery after submaximal exercise testing as a predictor of mortality in a cardiovascularly healthy cohort. Ann Intern Med 132: 552–555, 2000.[Abstract/Free Full Text]
  12. Curfman GD and Hillis LD. A new look at cardiac exercise testing. N Engl J Med 348: 775–776, 2003.[Free Full Text]
  13. De Meersman RE. Respiratory sinus arrhythmia alteration following training in endurance athletes. Eur J Appl Physiol Occup Physiol 64: 434–436, 1992.[Medline]
  14. Fisher JT, Vincent SG, Gomeza J, Yamada M, and Wess J. Loss of vagally mediated bradycardia and bronchoconstriction in mice lacking M2 or M3 muscarinic acetylcholine receptors. FASEB J 18: 711–713, 2004.[Abstract/Free Full Text]
  15. Giuliano R, Ruggiero DA, Morrison S, Ernsberger P, and Reis DJ. Cholinergic regulation of arterial pressure by the C1 area of the rostral ventrolateral medulla. J Neurosci 9: 923–942, 1989.[Abstract]
  16. Goodman JM, Liu PP, and Green HJ. Left ventricular adaptations following short-term endurance training. J Appl Physiol 98: 454–460, 2005.[Abstract/Free Full Text]
  17. Gregoire J, Tuck S, Yamamoto Y, and Hughson RL. Heart rate variability at rest and exercise: influence of age, gender, and physical training. Can J Appl Physiol 21: 455–470, 1996.[Medline]
  18. Hao SC, Chai A, and Kligfield P. Heart rate recovery response to symptom-limited treadmill exercise after cardiac rehabilitation in patients with coronary artery disease with and without recent events. Am J Cardiol 90: 763–765, 2002.[CrossRef][ISI][Medline]
  19. Hautala AJ, Makikallio TH, Kiviniemi A, Laukkanen RT, Nissila S, Huikuri HV, and Tulppo MP. Heart rate dynamics after controlled training followed by a home-based exercise program. Eur J Appl Physiol 92: 289–297, 2004.[ISI][Medline]
  20. Hickson RC, Hagberg JM, Ehsani AA, and Holloszy JO. Time course of the adaptive responses of aerobic power and heart rate to training. Med Sci Sports Exerc 13: 17–20, 1981.[ISI][Medline]
  21. Howley ET, Bassett DR Jr, and Welch HG. Criteria for maximal oxygen uptake: review and commentary. Med Sci Sports Exerc 27: 1292–1301, 1995.[ISI][Medline]
  22. Huikuri HV, Linnaluoto MK, Seppanen T, Airaksinen KE, Kessler KM, Takkunen JT, and Myerburg RJ. Circadian rhythm of heart rate variability in survivors of cardiac arrest. Am J Cardiol 70: 610–615, 1992.[CrossRef][ISI][Medline]
  23. Huikuri HV, Ylitalo A, Pikkujamsa SM, Ikaheimo MJ, Airaksinen KE, Rantala AO, Lilja M, and Kesaniemi YA. Heart rate variability in systemic hypertension. Am J Cardiol 77: 1073–1077, 1996.[CrossRef][ISI][Medline]
  24. Imai K, Sato H, Hori M, Kusuoka H, Ozaki H, Yokoyama H, Takeda H, Inoue M, and Kamada T. Vagally mediated heart rate recovery after exercise is accelerated in athletes but blunted in patients with chronic heart failure. J Am Coll Cardiol 24: 1529–1535, 1994.[Abstract]
  25. Jouven X, Empana JP, Schwartz PJ, Desnos M, Courbon D, and Ducimetiere P. Heart-rate profile during exercise as a predictor of sudden death. N Engl J Med 352: 1951–1958, 2005.[Abstract/Free Full Text]
  26. Kiviniemi AM, Hautala AJ, Seppanen T, Makikallio TH, Huikuri HV, and Tulppo MP. Saturation of high-frequency oscillations of R-R intervals in healthy subjects and patients after acute myocardial infarction during ambulatory conditions. Am J Physiol Heart Circ Physiol 287: H1921–H1927, 2004.[Abstract/Free Full Text]
  27. Kubo T. Cholinergic mechanism and blood pressure regulation in the central nervous system. Brain Res Bull 46: 475–481, 1998.[CrossRef][ISI][Medline]
  28. Kubo T, Taguchi K, Sawai N, Ozaki S, and Hagiwara Y. Cholinergic mechanisms responsible for blood pressure regulation on sympathoexcitatory neurons in the rostral ventrolateral medulla of the rat. Brain Res Bull 42: 199–204, 1997.[CrossRef][ISI][Medline]
  29. Lauer M, Froelicher ES, Williams M, and Kligfield P. Exercise testing in asymptomatic adults: a statement for professionals from the American Heart Association Council on Clinical Cardiology, Subcommittee on Exercise, Cardiac Rehabilitation, and Prevention. Circulation 112: 771–776, 2005.[Abstract/Free Full Text]
  30. Lee CM, Wood RH, and Welsch MA. Influence of short-term endurance exercise training on heart rate variability. Med Sci Sports Exerc 35: 961–969, 2003.[Medline]
  31. Mier CM, Turner MJ, Ehsani AA, and Spina RJ. Cardiovascular adaptations to 10 days of cycle exercise. J Appl Physiol 83: 1900–1906, 1997.[Abstract/Free Full Text]
  32. Nishime EO, Cole CR, Blackstone EH, Pashkow FJ, and Lauer MS. Heart rate recovery and treadmill exercise score as predictors of mortality in patients referred for exercise ECG. JAMA 284: 1392–1398, 2000.[Abstract/Free Full Text]
  33. Nissinen SI, Makikallio TH, Seppanen T, Tapanainen JM, Salo M, Tulppo MP, and Huikuri HV. Heart rate recovery after exercise as a predictor of mortality among survivors of acute myocardial infarction. Am J Cardiol 91: 711–714, 2003.[CrossRef][ISI][Medline]
  34. Padley JR, Overstreet DH, Pilowsky PM, and Goodchild AK. Impaired cardiac and sympathetic autonomic control in rats differing in acetylcholine receptor sensitivity. Am J Physiol Heart Circ Physiol 289: H1985–H1992, 2005.[Abstract/Free Full Text]
  35. Pierpont GL, Stolpman DR, and Gornick CC. Heart rate recovery post-exercise as an index of parasympathetic activity. J Auton Nerv Syst 80: 169–174, 2000.[CrossRef][ISI][Medline]
  36. Pikkujamsa SM, Makikallio TH, Sourander LB, Raiha IJ, Puukka P, Skytta J, Peng CK, Goldberger AL, and Huikuri HV. Cardiac interbeat interval dynamics from childhood to senescence: comparison of conventional and new measures based on fractals and chaos theory. Circulation 100: 393–399, 1999.[Abstract/Free Full Text]
  37. Savin WM, Davidson DM, and Haskell WL. Autonomic contribution to heart rate recovery from exercise in humans. J Appl Physiol 53: 1572–1575, 1982.[Abstract/Free Full Text]
  38. Shi YY and He L. SHEsis, a powerful software platform for analyses of linkage disequilibrium, haplotype construction, and genetic association at polymorphism loci. Cell Res 15: 97–98, 2005.[CrossRef][ISI][Medline]
  39. Singh JP, Larson MG, Manolio TA, O'Donnell CJ, Lauer M, Evans JC, and Levy D. Blood pressure response during treadmill testing as a risk factor for new-onset hypertension. The Framingham Heart Study. Circulation 99: 1831–1836, 1999.[Abstract/Free Full Text]
  40. Singh JP, Larson MG, O'Donnell CJ, Tsuji H, Corey D, and Levy D. Genome scan linkage results for heart rate variability (the Framingham Heart Study). Am J Cardiol 90: 1290–1293, 2002.[CrossRef][ISI][Medline]
  41. Singh JP, Larson MG, O'Donnell CJ, Tsuji H, Evans JC, and Levy D. Heritability of heart rate variability: the Framingham Heart Study. Circulation 99: 2251–2254, 1999.[Abstract/Free Full Text]
  42. Singh JP, Larson MG, Tsuji H, Evans JC, O'Donnell CJ, and Levy D. Reduced heart rate variability and new-onset hypertension: insights into pathogenesis of hypertension: the Framingham Heart Study. Hypertension 32: 293–297, 1998.[Abstract/Free Full Text]
  43. Smith LL, Kukielka M, and Billman GE. Heart rate recovery after exercise: a predictor of ventricular fibrillation susceptibility after myocardial infarction. Am J Physiol Heart Circ Physiol 288: H1763–H1769, 2005.[Abstract/Free Full Text]
  44. Spies C, Otte C, Kanaya A, Pipkin SS, Schiller NB, and Whooley MA. Association of metabolic syndrome with exercise capacity and heart rate recovery in patients with coronary heart disease in the heart and soul study. Am J Cardiol 95: 1175–1179, 2005.[CrossRef][ISI][Medline]
  45. Spina RJ, Chi MM, Hopkins MG, Nemeth PM, Lowry OH, and Holloszy JO. Mitochondrial enzymes increase in muscle in response to 7–10 days of cycle exercise. J Appl Physiol 80: 2250–2254, 1996.[Abstract/Free Full Text]
  46. Sugawara J, Murakami H, Maeda S, Kuno S, and Matsuda M. Change in post-exercise vagal reactivation with exercise training and detraining in young men. Eur J Appl Physiol 85: 259–263, 2001.[CrossRef][ISI][Medline]
  47. Tulppo MP, Hautala AJ, Makikallio TH, Laukkanen RT, Nissila S, Hughson RL, and Huikuri HV. Effects of aerobic training on heart rate dynamics in sedentary subjects. J Appl Physiol 95: 364–372, 2003.[Abstract/Free Full Text]
  48. Wang JC, Hinrichs AL, Stock H, Budde J, Allen R, Bertelsen S, Kwon JM, Wu W, Dick DM, Rice J, Jones K, Nurnberger JI Jr, Tischfield J, Porjesz B, Edenberg HJ, Hesselbrock V, Crowe R, Schuckit M, Begleiter H, Reich T, Goate AM, and Bierut LJ. Evidence of common and specific genetic effects: association of the muscarinic acetylcholine receptor M2 (CHRM2) gene with alcohol dependence and major depressive syndrome. Hum Mol Genet 13: 1903–1911, 2004.[Abstract/Free Full Text]
  49. Watanabe J, Thamilarasan M, Blackstone EH, Thomas JD, and Lauer MS. Heart rate recovery immediately after treadmill exercise and left ventricular systolic dysfunction as predictors of mortality: the case of stress echocardiography. Circulation 104: 1911–1916, 2001.[Abstract/Free Full Text]
  50. Yamamoto K, Miyachi M, Saitoh T, Yoshioka A, and Onodera S. Effects of endurance training on resting and post-exercise cardiac autonomic control. Med Sci Sports Exerc 33: 1496–1502, 2001.[ISI][Medline]



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