Beta-2 Adrenergic Receptor Genotype Influences Power Output in Healthy Subjects

Abstract

The purpose of this study was to determine the effects of ADRB2 genotypes on muscle function (absolute power and relative power) in healthy subjects. We performed genotyping of the ADRB2 (amino acid 16) and high-intensity, steady-state exercise on 77 healthy subjects (AA = 18, AG = 25, GG = 34). There were no differences between genotype groups in age, height, weight, or BMI (age = 28.9 ± 5.7yrs, 27.9 ± 5.7yrs, 29.2 ± 5.9yrs, height = 170.7 ± 8.6cm, 174.9 ± 8.7cm, 173.4 ± 9.6cm, weight = 68.5 ± 13.0kg, 75.0 ± 12.9kg, 74.4 ± 12.9kg, and BMI = 23.4 ± 3.9, 24.4 ± 2.9, 24.7 ± 3.4, for AA, AG, and GG, respectively). The genotype groups differed significantly in watts, and watts/VO2 with heavy exercise (watts = 186.3± 54.6, 237.8 ± 54.4, 219.4 ± 79.5, watts/VO2 = 0.08 ± 0.006, 0.09 ± 0.005, 0.08 ± 0.006). There was a trend towards significance (p=0.058) for watts/kg (2.7 ± 0.4, 3.2 ± 0.5, 2.9 ± 0.8, for AA, AG, and GG, respectively). These data suggest that genetic variation of the ADRB2 may influence relative strength in healthy subjects and may become an important genetic determinant of muscular strength and functional capacity in patients with diseases that result in a loss of muscle strength.

Influence of β2 adrenergic receptor genotype on risk of nocturnal ventilation in patients with Duchenne muscular dystrophy

“…homozygous for Arg at amino acid spot 16 (henceforth named “Arg16 group”, n = 26) vs. homozygous or heterozygous for Gly at amino acid 16 (“Gly16 group”, n = 149) because preliminary analyses of the data demonstrated phenotypic similarity of heterozygotes with Gly homozygotes. Furthermore, this dominant model is consistent with previous literature [32, 33, 36]. For all covariates entered into the Kaplan-Meier and Cox PH analyses, outliers were identified as observations above or below the 95th percentile for residual deviance score.…”

“…Type II fibers have an increased peak contractile strength compared with type I fibers [39]. Indeed, healthy adults expressing the Gly16 polymorphism often display increased muscular strength and power relative to their Arg16 counterparts [36]. While it may seem at first that increased strength is beneficial for respiratory muscle fatigue and weakness, the augmentation of contractile force likely increases the number, and rate of contraction-induced injury in DMD patients.…”

“…A Cox proportional hazard (PH) model was used to examine the effects of genotype variant on the risk of NV in DMD patients, after adjusting for patient age, weight, ambulatory status, corticosteroid use, and FVC. Time dependence of the covariates was ruled out after inspection of the Schoenfeld residuals scores [36]. We chose to group ADRB2 genotypes according to a dominant model for the Gly allele, i.e.…”

Influence of Beta-1 Adrenergic Receptor Genotype on Cardiovascular Response to Exercise in Healthy Subjects

“…Data analyzed for this article were part of a larger study on adrenergic receptor genotypes and cardiopulmonary function at rest and during exercise but the data have not been assessed as presented in this study [18, 19]. This study received approval by the appropriate ethics committee and has therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.…”

Influence of β2 adrenergic receptor genotype on longitudinal measures of forced vital capacity in patients with Duchenne muscular dystrophy

“…Firstly, ADRB2 stimulation is known to increase myofibril peak contractile strength [52] . Indeed, healthy adults expressing the Gly16 polymorphism often display increased muscular strength and power relative to their Arg16 counterparts [53] . While the increased myofibril contraction strength associated with the Gly16 polymorphism may seem beneficial for DMD patients, dystrophin-deficient muscle fibers lack the membrane stability to distribute the mechanical forces of myofibril contraction across the sarcolemma [ 54 , 55 ].…”