PROTECTIVE FUNCTION OF MILK LIPIDS AND LIPID CONJUGATES IN THE NEWBORN. 22

Most nutrients in human milk have multiple functions, among them the protection of the infant from invading micro-organisms (1). This symposium will address the topic of immune protection, i.e. specific antibody-mediated protection against micro-organisms and the much broader non specific protection which, contrary to the former, is independent of prior maternal exposure to micro-organisms. In this category there are milk components that act as analogs or homologues to host cell surface pathogen receptors(glycoproteins, gangliosides, proteins) have specific bactericidal and antiviral activity (lactoferrin) or are able to lyse micro-organisms(lysozyme, fatty acids and monoglycerides) (2). Lipid conjugates such as gangliosides in the milk fat globule membrane inhibit the action of the heat stable enterotoxins of V-cholerae and E coli. Milk lipids acquire the potential to lyse micro-organisms after their partial digestion to free fatty acids and monoglycerides (3). The fat contained in the core of milk fat globules is more accessible to gastric lipolysis than the fat in infant formula. Indeed hydrolysis of dietary fat is 1.7 to 2.5 fold higher in human milk-fed than in formula-fed infants (4). The free fatty acids and monoglycerides released cause rapid lysis of enveloped viruses, protozoa and certain bacteria. Highest lytic activity is associated with lauric and (C 12:0) and monolaurin and with long chain unsaturated fatty acids (C 18:2). Storage of milk, even at -20 C, releases large amounts of free fatty acids(5),that might lower viral and bacterial counts during frozen storage of human milk. The milk fat globule is an important protective factor through its core triglyceride (after lipolysis) and through the globule membrane gangliosides and glycoproteins (6).