The reduced endothelial-dependent vasodilation in untreated patients with OSA acutely improves by the free radical scavenger vitamin C. These results are in favor of oxidative stress being responsible for the endothelial dysfunction in OSA. Antioxidant strategies should be explored for the treatment of OSA-related cardiovascular disease.

No abstract

SUMMAR Y Adrenomedullin (AM) is a potent endothelial-derived vasodilator secreted under the influence of various stimuli such as hypoxia, shear stress and cytokines. As all of these stimuli might be active under the conditions of obstructive sleep apnoea (OSA), we hypothesized that vascular AM production is increased in these patients. The study included 41 consecutive OSA patients and 28 control subjects without sleep-disordered breathing who were recruited from a pool of patients hospitalized for other reasons. Both groups were matched for anthropometric and comorbid factors. In all patients, i.e. OSA and controls, peripheral venous blood samples were taken at 07:00 hours after diagnostic polysomnography. In subsets of OSA patients, this was repeated after two nights of continuous positive airway pressure (CPAP) therapy (n ¼ 28) and after several months of constant CPAP use (n ¼ 11). The controls and the untreated OSA patients did not have serial blood sampling. In all blood samples, plasma AM levels were measured by an enzyme immunoassay kit. At baseline, the OSA patients had markedly elevated AM concentrations when compared to the controls. There were no differences between normo-and hypertensive OSA patients. After two nights of CPAP therapy, AM levels significantly decreased. Patients on long-term CPAP treatment showed complete normalization of plasma AM concentrations. In conclusion, this pilot study suggests that circulating AM is increased in untreated OSA irrespective of coexistent arterial hypertension and declines after CPAP therapy. AM upregulation might be considered as an adaptive mechanism to counteract the emergence of OSArelated cardiovascular disease.k e y w o r d s adrenomedullin, cardiovascular disease, obstructive sleep apnoea

No abstract

Metabolic syndrome, i. e., the combined occurrence of obesity, arterial hypertension, insulin resistance and dyslipidaemia (increased triglycerides, reduced HDL cholesterol), is associated with a marked increase in cardiovascular risk. The prevalence of metabolic syndrome in patients with obstructive sleep apnoea (OSA) is very high. Obesity is the main risk factor for OSA and OSA itself is now considered to be the most frequent cause of secondary arterial hypertension. Due to the confounding influence of obesity, the causal connection between OSA and metabolic disturbances is less well established, however, epidemiological data are at least in favour of an independent link between OSA and insulin resistance. It is known that CPAP therapy can ameliorate OSA-associated hypertension. In contrast, the effects of CPAP treatment on insulin resistance and dyslipidaemia have to be further elucidated by large, randomised interventional trials.