title: Olive (Olea europaea L.) leaf polyphenols improve insulin sensitivity in middle-aged overweight men: a randomized, placebo-controlled, crossover trial.
abstract: BACKGROUND
  Olive plant leaves (Olea europaea L.) have been used for centuries in folk medicine to treat diabetes, but there are very limited data examining the effects of olive polyphenols on glucose homeostasis in humans.
  
  
  OBJECTIVE
  To assess the effects of supplementation with olive leaf polyphenols (51.1 mg oleuropein, 9.7 mg hydroxytyrosol per day) on insulin action and cardiovascular risk factors in middle-aged overweight men.
  
  
  METHODS
  Randomized, double-blinded, placebo-controlled, crossover trial in New Zealand. 46 participants (aged 46.4 ± 5.5 years and BMI 28.0 ± 2.0 kg/m(2)) were randomized to receive capsules with olive leaf extract (OLE) or placebo for 12 weeks, crossing over to other treatment after a 6-week washout. Primary outcome was insulin sensitivity (Matsuda method). Secondary outcomes included glucose and insulin profiles, cytokines, lipid profile, body composition, 24-hour ambulatory blood pressure, and carotid intima-media thickness.
  
  
  RESULTS
  Treatment evaluations were based on the intention-to-treat principle. All participants took >96% of prescribed capsules. OLE supplementation was associated with a 15% improvement in insulin sensitivity (p = 0.024) compared to placebo. There was also a 28% improvement in pancreatic β-cell responsiveness (p = 0.013). OLE supplementation also led to increased fasting interleukin-6 (p = 0.014), IGFBP-1 (p = 0.024), and IGFBP-2 (p = 0.015) concentrations. There were however, no effects on interleukin-8, TNF-α, ultra-sensitive CRP, lipid profile, ambulatory blood pressure, body composition, carotid intima-media thickness, or liver function.
  
  
  CONCLUSIONS
  Supplementation with olive leaf polyphenols for 12 weeks significantly improved insulin sensitivity and pancreatic β-cell secretory capacity in overweight middle-aged men at risk of developing the metabolic syndrome.
authors.affiliation: Liggins Institute, University of Auckland, Auckland, New Zealand.
authors.forename: Martin
authors.initials: M
authors.lastname: de Bock
authors.forename: José G B
authors.initials: JG
authors.lastname: Derraik
authors.forename: Christine M
authors.initials: CM
authors.lastname: Brennan
authors.forename: Janene B
authors.initials: JB
authors.lastname: Biggs
authors.forename: Philip E
authors.initials: PE
authors.lastname: Morgan
authors.forename: Steven C
authors.initials: SC
authors.lastname: Hodgkinson
authors.forename: Paul L
authors.initials: PL
authors.lastname: Hofman
authors.forename: Wayne S
authors.initials: WS
authors.lastname: Cutfield
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000187:drug effects; D015992:Body Mass Index; D018592:Cross-Over Studies; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D006801:Humans; D007333:Insulin Resistance; D008875:Middle Aged; D009520:New Zealand; D031658:Olea / Q000737:chemistry*; D050177:Overweight / Q000188:drug therapy* / Q000378:metabolism*; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry*; D059808:Polyphenols / Q000494:pharmacology* / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D001786:Blood Glucose; D010936:Plant Extracts; D059808:Polyphenols; D005947:Glucose