Relationship between fatty acid accretion, membrane composition, and biologic functions.

Dietary fat affects metabolic pathways for phospholipid biosynthesis in tissues in a coordinated fashion. This may be important to aspects of development that concern phosphatidylcholine metabolism or regulatory processes that depend on signals from a changing milieu in the microenvironment of the membrane. Dietary fat influences the phosphatidylethanolamine (PE) composition in many membranes of the brain and retina and may by altered by small changes in the content of 20:4(6) and 22:6(3). Membrane PE fatty acids that contain one, four, or six double bonds and the ratio of 22:5(6) to 22:6(3) in PE that contains four to six double bonds are also affected. An increase in the omega 6 fatty acid content of membranes is associated with increased PE methyltransferase activity and decreased phosphocholine transferase activity, thus indicating a mechanism by which change in an exogenous factor (e.g., dietary fat intake) may alter neural phospholipid biosynthesis. Small changes in the composition of dietary fat intake change the composition of brain membranes during development. It is provocative to ponder whether diet could be used to induce formation of membrane structures that are more resistant to specific insults that cause degeneration of brain structural material, to ensure optimal functional compositions, or to reverse degenerative changes that occur in neural membrane structure and function.

Fatty acid balance studies in premature infants fed human milk or formula: effect of calcium supplementation.

During the first 4 neonatal weeks, serial total fatty acid and individual fatty acid balance studies were completed in 35 healthy premature infants with appropriate weight for gestational age. Infants weighed less than 1500 gm at birth, were descriptively similar, and were receiving similar volumes of either preterm mothers' milk (PTM) or formula (S-M-A 20). Total fatty acid and major fatty acid contents of the two feeding regimens were similar. Total fecal output and total fatty acid excretion were higher, whereas subsequent total fat absorption and coefficient of absorption were significantly lower, in the group fed S-M-A 20 (P less than 0.001). Administration of oral calcium supplements fed as calcium lactate (1.5 to 2.0 mmol/kg/day) decreased total fatty acid absorption in both the PTM (P less than 0.01) and S-M-A 20 (P less than 0.001) groups. Furthermore, the effect of feeding (P less than 0.0001) and oral calcium (P less than 0.001) independently influenced coefficients of absorption for major fatty acids fed (C12:0, C14:0, C16:0, C18:0, and C18:1). Although the main indices for growth were similar in both feeding groups, infants with inefficient rates of total fatty acid absorption attained slower rates of weight gain and increased skinfold thickness. We conclude that oral calcium supplements significantly alter the efficiency of lipid absorption in enterally fed preterm infants.