Long term effects on human plasma lipoproteins of a formulation enriched in butter milk polar lipid.

BACKGROUND: Sphingolipids (SL), in particular sphingomyelin (SM) are important components of milk fat polar lipids. Dietary SM inhibits cholesterol absorption in rats (Nyberg et al. J Nutr Biochem. 2000) and SLs decrease both cholesterol and TG concentrations in lipid- and cholesterol fed APOE*3Leiden mice (Duivenvoorden et al. Am J Clin Nutr. 2006). This human study examines effects of a butter milk formulation enriched in milk fat globule membrane material, and thereby in SLs, on blood lipids in healthy volunteers. In a four week parallel group study with 33 men and 15 women we examined the effects of an SL-enriched butter milk formulation (A) and an equivalent control formulation (B) on plasma lipid levels. Plasma concentrations of HDL and LDL cholesterol, triacylglycerols (TG), apolipoproteins AI and B, and lipoprotein (a) were measured. The daily dose of SL in A was 975 mg of which 700 mg was SM. The participants registered food and drink intake four days before introducing the test formula and the last four days of the test period. RESULTS: A daily increase of SL intake did not significantly influence fasting plasma lipids or lipoproteins. In group B TG, cholesterol, LDL, HDL and apolipoprotein B concentrations increased, however, but not in group A after four weeks. The difference in LDL cholesterol was seen primarily in women and difference in TG primarily in men. No significant side effects were observed. CONCLUSION: The study did not show any significant decrease on plasma lipids or lipoprotein levels of an SL-enriched formulation containing 2-3 times more SL than the normal dietary intake on cholesterol, other plasma lipids or on energy intake. The formulation A may, however, have counteracted the trend towards increased blood lipid concentrations caused by increased energy intake that was seen with the B formulation.

Thermodynamic characterization of the interactions between the immunoregulatory proteins osteopontin and lactoferrin.

The immunoregulatory proteins osteopontin (OPN) and lactoferrin (LF) are both highly abundant in milk, with a conserved ratio between different mammalian species, suggesting that the role of each protein in infant development may be linked. In this study we used isothermal titration calorimetry and differential scanning calorimetry experiments to demonstrate that LF and OPN interact with each other through a complex mechanism involving multiple cationic LF molecules binding to a single anionic molecule of OPN. At least two classes of thermodynamically distinct LF binding sites were identified, with the higher affinity interactions (dissociation constants 10(-6)M) being in the biologically relevant range. Ca(2+) binding to OPN, or Fe(3+) binding to LF, influenced the enthalpy and entropy of binding, but had little effect on the overall binding affinity. Considering that the regions of electrostatic complementarity between OPN and LF mediate the numerous biological functions of each protein, we suggest that OPN may act as a carrier protein for LF in milk, and modulate the potent antimicrobial and immunostimulatory activities of the LF protein.