title: The lactotripeptides isoleucine-proline-proline and valine-proline-proline do not inhibit the N-terminal or C-terminal angiotensin converting enzyme active sites in humans.
abstract: BACKGROUND
  The potential blood pressure lowering effect of fermented milk may involve inhibition of angiotensin-converting enzyme (ACE) by dairy lactotripeptides generated during milk fermentation, such as isoleucine-proline-proline (IPP) and valine-proline-proline (VPP). These peptides are weak ACE inhibitors in vitro but it remains unclear whether they inhibit ACE in vivo in humans.
  
  
  OBJECTIVE
  To assess in vivo ACE inhibition in individuals given fermented milk over a 7-day period.
  
  
  METHODS
  Twelve healthy normotensive men were given 330 ml of fermented milk once daily from day 1 to day 7 (IPP: 4.5 mg and VPP: 6.6 mg) and a single dose of 50 mg captopril on day 8. ACE inhibition was assessed in vivo by measuring plasma and urine AcSDKP and plasma active renin and in vitro by measuring plasma ACE activity using hippuryl-histidine-leucine. Plasma IPP/VPP concentrations were measured by LC/MS/MS.
  
  
  RESULTS
  Plasma IPP concentrations increased slightly and very transiently after fermented milk administration. Plasma VPP concentrations were below the limit of quantification. Fermented milk had no effect on plasma AcSDKP, ACE activity or active renin concentrations on days 1 or 7. Urine AcSDKP excretion underwent a small transient increase. In contrast, plasma and urine AcSDKP increased 7.7-fold and 70-fold, respectively, and plasma ACE activity decreased by 82.3 +/- 16.1% following captopril administration; plasma active renin concentration increased four-fold.
  
  
  CONCLUSIONS
  IPP and VPP were poorly absorbed and rapidly eliminated. They did not inhibit plasma or endothelial ACE in vivo at the selected doses and had no specific effect on the N-terminal or C-terminal ACE domains.
authors.affiliation: Université Paris Descartes, Paris, France.
authors.forename: Grégoire
authors.initials: G
authors.lastname: Wuerzner
authors.forename: Séverine
authors.initials: S
authors.lastname: Peyrard
authors.forename: Anne
authors.initials: A
authors.lastname: Blanchard
authors.forename: Florent
authors.initials: F
authors.lastname: Lalanne
authors.forename: Michel
authors.initials: M
authors.lastname: Azizi
mesh_terms: D000818:Animals; D020134:Catalytic Domain; D005285:Fermentation; D006801:Humans; D008297:Male; D008892:Milk; D009842:Oligopeptides / Q000097:blood / Q000494:pharmacology*; D007703:Peptidyl-Dipeptidase A / Q000187:drug effects* / Q000378:metabolism; D012016:Reference Values; D012083:Renin / Q000097:blood
chemical_list: D009842:Oligopeptides; C489032:isoleucyl-prolyl-proline; C489031:valyl-prolyl-proline; D007703:Peptidyl-Dipeptidase A; D012083:Renin