title: Arg16Gly and Gln27Glu β2 adrenergic polymorphisms influence cardiac autonomic modulation and baroreflex sensitivity in healthy young Brazilians.
abstract: The association between functional β2 adrenergic receptor (β2-AR) polymorphisms and cardiac autonomic modulation is still unclear. Thus, two common polymorphisms in the β2-AR gene (Gln27Glu β2 and Arg16Gly β2) were studied to determine whether they might affect tonic and reflex cardiac sympathetic activity in healthy young subjects. A total of 213 healthy young white subjects of both genders (53% female), aged 18-30 years (23.5±3.4 y), had their continuous blood pressure curves noninvasively recorded by Finometer at baseline, and other hemodynamic parameters, as cardiac autonomic modulation, baroreflex sensitivity, and allele, genotype, and diplotype frequencies calculated. Associations were made between Arg16Gly β2 and Gln27Glu β2 polymorphisms and between β2-AR diplotypes and all variables. The heart rate was significantly lower (P<0.001) in the presence of homozygous Arg/Arg alleles (60.9±1.5 bpm) than in that of Arg/Gly heterozygotes (65.9±1.0 bpm) or Gly/Gly homozygotes (66.3±1.2 bpm). Homozygous carriers of Arg16 allele had an alpha index (19.2±1.3) significantly higher (P<0.001) than that of the subjects with the Gly allele Gly/Gly (14.5±0.7) or Arg/Gly (14.6±0.7). Furthermore, the recessive Glu27Glu and the heterozygous Gln27Glu genotypes had a higher percentage of low-frequency components (LF%) than the homozygous Gln27Gln (15.1% vs. 16.0% vs. 8.2%, P=0.03, respectively). In healthy young subjects, the presence of β2-AR Arg16 allele in a recessive model was associated with higher baroreflex sensitivity, and increased parasympathetic modulation in studied individuals.
authors.affiliation: Hypertension Unit, Heart Institute (InCor), Medical School of University of São Paulo (FMUSP) São Paulo, Brazil.
authors.forename: Magda M
authors.initials: MM
authors.lastname: Atala
authors.affiliation: Department of Internal Medicine, Universitary Hospital, Medical School of University of São Paulo (FMUSP) São Paulo, Brazil ; Department of Nefrology, Federal University of São Paulo (UNIFESP) São Paulo, Brazil.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Goulart
authors.affiliation: Hypertension Unit, Heart Institute (InCor), Medical School of University of São Paulo (FMUSP) São Paulo, Brazil.
authors.forename: Grazia M
authors.initials: GM
authors.lastname: Guerra
authors.affiliation: Hospital Materno Infantil, Universidade Federal do Maranhão São Luis, Brazil.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Mostarda
authors.affiliation: Human Movement Laboratory, Universidade São Judas Tadeu (USJT) São Paulo, Brazil.
authors.forename: Bruno
authors.initials: B
authors.lastname: Rodrigues
authors.affiliation: Hypertension Unit, Heart Institute (InCor), Medical School of University of São Paulo (FMUSP) São Paulo, Brazil.
authors.forename: Priscila R
authors.initials: PR
authors.lastname: Mello
authors.affiliation: Department of Nefrology, Federal University of São Paulo (UNIFESP) São Paulo, Brazil.
authors.forename: Dulce E
authors.initials: DE
authors.lastname: Casarine
authors.affiliation: Hypertension Unit, Heart Institute (InCor), Medical School of University of São Paulo (FMUSP) São Paulo, Brazil.
authors.forename: Maria-Claudia
authors.initials: MC
authors.lastname: Irigoyen
authors.affiliation: Molecular Genetics Laboratory, Heart Institute (InCor), Medical School of University of São Paulo (FMUSP) São Paulo, Brazil.
authors.forename: Alexandre C
authors.initials: AC
authors.lastname: Pereira
authors.affiliation: Hypertension Unit, Heart Institute (InCor), Medical School of University of São Paulo (FMUSP) São Paulo, Brazil ; Universidade Nove de Julho (UNINOVE) São Paulo, Brazil.
authors.forename: Fernanda M
authors.initials: FM
authors.lastname: Consolim-Colombo
keywords: autonomic nervous system; cardiac autonomic balance; heart rate variability; β2-adrenergic polymorphism