title: Muscle Metaboreflex Control of Sympathetic Activity in Obstructive Sleep Apnea.
abstract: Previous studies report abnormal muscle metaboreflex control of muscle sympathetic nerve activity (MSNA) in obesity, hypertension, and heart failure. We hypothesized that obstructive sleep apnea (OSA) is associated with augmented metaboreflex control of MSNA.
  
  
  
  Thirty-one sedentary individuals with no comorbidities (age = 52 ± 1 yr, body mass index = 28 ± 1 kg·m) without (control, n = 14) and with OSA (n = 17) defined by polysomnography, underwent echocardiography. HR, blood pressure (BP), MSNA (microneurography), and forearm blood flow measured by venous occlusion plethysmography were continuously measured 4 min at baseline, during 3 min of 30% handgrip static exercise, and during 2 min of post-handgrip muscle ischemia (PHMI).
  
  
  
  Control and OSA groups were similar in age, body mass index, and ejection fraction. Baseline HR, BP, and forearm blood flow increased similarly during handgrip exercise. Blood pressure remained significantly elevated in relation to baseline during PHMI, but HR and forearm blood flow returned toward baseline during PHMI in both groups. Baseline MSNA was significantly higher in the OSA group than in controls (P < 0.05). During peak 30% static handgrip exercise, MSNA increased significantly in both control and OSA groups, but MSNA responses were higher in patients with OSA. During PHMI, MSNA in control subjects remained significantly elevated compared with that at baseline. In contrast, in patients with OSA, MSNA decreased to baseline values. A significant correlation was found between changes in MSNA due to PHMI and apnea-hypopnea index (r = -0.61, P < 0.001), and with minimum O2 saturation (r = 0.70, P < 0.001).
  
  
  
  These findings suggest an association between OSA and decreased metaboreflex control of MSNA. Muscle vasodilation during handgrip static exercise is preserved in patients with OSA.
authors.affiliation: 1School of Arts, Sciences, and Humanities, University of São Paulo, São Paulo, BRAZIL; 2InCor-HCFMUSP, São Paulo, BRAZIL; 3Master Program in Experimental Physiopathology, HCFMUSP, São Paulo, BRAZIL; and 4Universidade Nove de Julho, São Paulo, BRAZIL.
authors.forename: Linda M
authors.initials: LM
authors.lastname: Ueno-Pardi
authors.forename: Renan S
authors.initials: RS
authors.lastname: Guerra
authors.forename: Thiago T
authors.initials: TT
authors.lastname: Goya
authors.forename: Rosyvaldo F
authors.initials: RF
authors.lastname: Silva
authors.forename: Elisangela M
authors.initials: EM
authors.lastname: Gara
authors.forename: Marta F
authors.initials: MF
authors.lastname: Lima
authors.forename: Thais S
authors.initials: TS
authors.lastname: Nobre
authors.forename: Maria J N N
authors.initials: MJNN
authors.lastname: Alves
authors.forename: Ivani C
authors.initials: IC
authors.lastname: Trombetta
authors.forename: Geraldo
authors.initials: G
authors.lastname: Lorenzi-Filho
mesh_terms: D000328:Adult; D000368:Aged; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D015444:Exercise / Q000502:physiology; D005260:Female; D005542:Forearm / Q000098:blood supply; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply / Q000294:innervation* / Q000503:physiopathology*; D012039:Regional Blood Flow; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014664:Vasodilation / Q000502:physiology