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Oxidative stress has been related increasingly to the onset and/or progression of a growing number of human diseases. However, large studies on supplementation with anti-oxidants for prevention or treatment of different pathologies have yielded contradictory and mostly negative results, as documented by numerous meta-analyses and clinical trials. Here we analyze in detail the findings of these studies and discuss major aspects that, in our opinion, are likely to be responsible for these confounding data. With the belief that a clear correlation between disease and oxidative stress is far from being proven for most pathological conditions, our argument focuses on the following points: i) choice of biomarker(s) and/or the biological system(s) for the analyses; ii) pitfalls in pre-analytical and analytical methods for assessing oxidative stress; and iii) scientific misconduct. Eventually, suggestions aiming to obtain more convergent results on this topic are provided.

Peripartum cardiomyopathy (PPCM) is a life-threatening heart disease developing towards the end of pregnancy or in the months following delivery in previously healthy women in terms of cardiac disease. Enhanced oxidative stress and the subsequent cleavage of the nursing hormone Prolactin into an anti-angiogenic 16 kDa subfragment emerged as a potential causal factor of the disease. We established a prospective registry with confirmed PPCM present in 115 patients (mean baseline left ventricular ejection fraction, LVEF: 27 ± 9 %). Follow-up data (6 ± 3 months) showed LVEF improvement in 85 % and full recovery in 47 % while 15 % failed to recover with death in 2 % of patients. A positive family history of cardiomyopathy was present in 16.5 %. Pregnancy-associated hypertension was associated with a better outcome while a baseline LVEF ≤ 25 % was associated with a worse outcome. A high recovery rate (96 %) was observed in patients obtaining combination therapy with beta-blocker, angiotensin-converting enzyme (ACE) inhibitors/angiotensin-receptor-blockers (ARBs) and bromocriptine. Increased serum levels of Cathepsin D, the enzyme that generates 16 kDa Prolactin, miR-146a, a direct target of 16 kDa Prolactin, N-terminal-pro-brain-natriuretic peptide (NT-proBNP) and asymmetric dimethylarginine (ADMA) emerged as biomarkers for PPCM. In conclusion, low baseline LVEF is a predictor for poor outcome while pregnancy-induced hypertensive disorders are associated with a better outcome in this European PPCM cohort. The high recovery rate in this collective is associated with a treatment concept using beta-blockers, ACE inhibitors/ARBs and bromocriptine. Increased levels of Cathepsin D activity, miR-146a and ADMA in serum of PPCM patients support the pathophysiological role of 16 kDa Prolactin for PPCM and may be used as a specific diagnostic marker profile.Electronic supplementary materialThe online version of this article (doi:10.1007/s00395-013-0366-9) contains supplementary material, which is available to authorized users.