@article{HoeggerKurlbaumMuelek2013,
  author    = {H{\"o}gger, Petra and Kurlbaum, Max and M{\"u}lek, Melanie},
  title     = {Facilitated Uptake of a Bioactive Metabolite of Maritime Pine Bark Extract (Pycnogenol) into Human Erythrocytes},
  series = {PLoS ONE},
  journal   = {PLoS ONE},
  doi       = {10.1371/journal.pone.0063197},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-96656},
  year      = {2013},
  abstract  = {Many plant secondary metabolites exhibit some degree of biological activity in humans. It is a common observation that individual plant-derived compounds in vivo are present in the nanomolar concentration range at which they usually fail to display measurable activity in vitro. While it is debatable that compounds detected in plasma are not the key effectors of bioactivity, an alternative hypothesis may take into consideration that measurable concentrations also reside in compartments other than plasma. We analysed the binding of constituents and the metabolite δ-(3,4-dihydroxy-phenyl)-γ-valerolactone (M1), that had been previously detected in plasma samples of human consumers of pine bark extract Pycnogenol, to human erythrocytes. We found that caffeic acid, taxifolin, and ferulic acid passively bind to red blood cells, but only the bioactive metabolite M1 revealed pronounced accumulation. The partitioning of M1 into erythrocytes was significantly diminished at higher concentrations of M1 and in the presence of glucose, suggesting a facilitated transport of M1 via GLUT-1 transporter. This concept was further supported by structural similarities between the natural substrate α-D-glucose and the S-isomer of M1. After cellular uptake, M1 underwent further metabolism by conjugation with glutathione. We present strong indication for a transporter-mediated accumulation of a flavonoid metabolite in human erythrocytes and subsequent formation of a novel glutathione adduct. The physiologic role of the adduct remains to be elucidated.},
  language  = {en}
}
@article{HaringWylervonBallmoosAppeletal.2014,
  author    = {Haring, Bernhard and Wyler von Ballmoos, Moritz C. and Appel, Lawrence J. and Sacks, Frank M.},
  title     = {Healthy Dietary Interventions and Lipoprotein (a) Plasma Levels: Results from the Omni Heart Trial},
  doi       = {10.1371/journal.pone.0114859},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-111005},
  year      = {2014},
  abstract  = {Background: Increased lipoprotein(a) [Lp(a)] levels are associated with atherosclerotic cardiovascular disease. Studies of dietary interventions on changes in Lp(a) are sparse. We aimed to compare the effects of three healthy dietary interventions differing in macronutrient content on Lp(a) concentration. Methods: Secondary analysis of a randomized, 3-period crossover feeding study including 155 (89 blacks; 66 whites) individuals. Participants were given DASHtype healthy diets rich in carbohydrates [Carb], in protein [Prot] or in unsaturated fat [Unsat Fat] for 6 weeks each. Plasma Lp(a) concentration was assessed at baseline and after each diet. Results: Compared to baseline, all interventional diets increased mean Lp(a) by 2 to 5 mg/dl. Unsat Fat increased Lp(a) less than Prot with a difference of 1.0 mg/dl (95\% CI, -0.5, 2.5; p=0.196) in whites and 3.7 mg/dl (95\% CI, 2.4, 5.0; p<0.001) in blacks (p-value between races=0.008); Unsat Fat increased Lp(a) less than Carb with a difference of 20.6 mg/dl, 95\% CI, -2.1, 0.9; p=0.441) in whites and 21.5 mg/dl (95\% CI, -0.2, -2.8; p=0.021) in blacks (p-value between races=0.354). Prot increased Lp(a) more than Carb with a difference of 0.4 mg/dl (95\% CI, -1.1, 1.9; p=0.597) in whites and 2.2 mg/dl (95\%CI, 0.9, 3.5; p=0.001) in blacks (p-value between races=0.082). Conclusion: Diets high in unsaturated fat increased Lp(a) levels less than diets rich in carbohydrate or protein with greater changes in blacks than whites. Our results suggest that substitutions with dietary mono- and polyunsaturated fatty acids in healthy diets may be preferable over protein or carbohydrates with regards to Lp(a).},
  language  = {en}
}