Lactate production and catecholamine profile during aerobic exercise in normotensive OSAS patients.
OBJECTIVE
The aim of the study was to evaluate the catecholaminergic activity and lactate concentration during exercise in normotensive patients with obstructive sleep apnoea syndrome (OSAS).


METHODS
Thirteen normotensive patients affected by OSAS (mean age+/-standard error (SE), 52.6+/-2.8 yrs; mean apnoea-hypopnea index, 35.7+/-20.3) were enrolled in the study. Night-polysomnography and multiple sleep latency test in the sleep laboratory were performed for every patient. Patients also underwent an incremental workload exercise on a cycloergometer. We evaluated plasma epinephrine and norepinephrine levels in aerobic exercise conditions, relating them to lactate levels.


RESULTS
Analysis of the venous lactate curve showed that exercise lactate levels were significantly higher (peak normalised levels, 782 vs. 270%; P<0.001 ), and an earlier lactate threshold was detected, in the patients compared to normal controls. While plasma catecholamine levels were abnormally high in almost all patients at rest, exercise values were not significantly different from controls. Lactate/norepinephrine and lactate/epinephrine area ratios were significantly higher in OSAS subjects than in controls (2.25 vs. 1.21 and 2.37 vs. 1.03, respectively).


CONCLUSIONS
The results indicate that abnormal production of lactate during exercise occurs in OSAS, possibly due to some muscular metabolic modification. While catecholaminergic activity is abnormally increased at rest, this activity does not seem to play a significant role in lactate concentration during exercise in these patients.
Bonanni
Enrica
E
Neurological Clinic, Department of Neurosciences, University of Pisa, Via Roma 67, Pisa 56126, Italy. e.bonanni@neuro.med.unipi.it
Pasquali
Livia
L
Manca
Maria Laura
ML
Maestri
Michelangelo
M
Prontera
Concetta
C
Fabbrini
Monica
M
Berrettini
Stefano
S
Zucchelli
Giancarlo
G
Siciliano
Gabriele
G
Murri
Luigi
L
D001794:Blood Pressure / Q000502:physiology*; D002395:Catecholamines / Q000378:metabolism*; D004562:Electrocardiography; D004837:Epinephrine / Q000378:metabolism; D015444:Exercise; D005260:Female; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D017286:Polysomnography; D011175:Positive-Pressure Respiration / Q000379:methods; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis / Q000378:metabolism* / Q000628:therapy; D012894:Sleep Stages / Q000502:physiology
D002395:Catecholamines; D019344:Lactic Acid; D009638:Norepinephrine; D004837:Epinephrine