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Keywords:

  • Adults;
  • Hypercholesterolemia;
  • Lipoprotein-associated phospholipase A2;
  • Lyso-PAF acetyltransferase;
  • Milk

Abstract

Hypercholesterolemia is associated with subclinical inflammation, characterised by elevated proinflammatory mediators. Lyso-platelet-activating factor acetyltransferase (lyso-PAF AT) and lipoprotein-associated phospholipase A2 (Lp-PLA2) are two key metabolic enzymes of platelet-activating factor (PAF), a potent inflammatory lipid mediator. Little information is available concerning the efficacy of a dietary intervention on the metabolism of PAF. The objective of the study was to evaluate the effect of fortified milk on the activity of these enzymes. Forty-three adults (mean age 49.8 ± 8.1 years) with body mass index <35 kg/m2, and total cholesterol >200 but <310 mg/dL were randomised to two groups; (i) intervention group received 500 mL/day (two glasses) of a low-fat milk fortified with phytosterols, linoleic and alpha linolenic acids, vitamin C, vitamin E, vitamin A, vitamin B6, vitamin B12, folic acid, magnesium and selenium (n = 22), and (ii) placebo group received 500 mL/day of a conventional low-fat milk (n = 21) for 3 months. Outcome measures were the activities of lyso-PAF AT from leukocytes and serum Lp-PLA2 determined with established methods. None of the activities changed significantly during the study in the intervention group, lyso-PAF AT (95% confidence interval: −1.7, 2.3 nmol/min/mg; p = 0.246), and Lp-PLA2 (−7.8, 5.8 nmol/min/mL, p = 0.591). No difference was observed between the two groups. In conclusion, daily intake of two glasses of phytosterols, antioxidants, linoleic and linolenic acids via fortified milk for three months had no effect on the activity of either lyso-PAF AT or Lp-PLA2.

Practical applications: Platelet-activating factor (PAF) was the first intact phospholipid known to have messenger functions in which the signaling results from the molecule binding to specific receptors on the plasma membrane or other membranes of the cell. It has a number of pro-inflammatory properties, and affects several critical points of atherogenesis including thrombosis, inflammation, and oxidation. Fortification of milk with nutrients that possess anti-inflammatory properties and administration to adults with elevated blood cholesterol could provide a means to controlling inflammatory process through the synthesis and degradation of PAF in a population group at risk for cardiovascular morbidity and mortality.