Maria L. Pita

Effects of dietary nucleotides on the fatty acid composition of erythrocyte membrane lipids in term infants

Human milk contains relatively high amounts of acid-soluble nucleotides, mainly CMP, AMP, UMP, IMP, and UDP sugars, and lacks orotate. On the contrary, cows milk and adapted formulas contain high amounts of orotate and very low amounts of CMP and AMP. Nucleotides may be modulators of metabolic functions in gut and liver. To evaluate the possible role of dietary nucleotides in newborn fatty acid metabolism, we studied the polyunsaturated fatty acid (PUFA) composition of erythrocyte membrane phospholipids in 58 term infants at 30 days of age. Twenty of them were fed human milk (HM), 19 an adapted formula (MF), and 19 with the same formula supplemented with nucleotides (NMF) in an amount similar to that present in HM. Relative content of omega 6 and 3 PUFA greater than 18 carbon atoms was significantly reduced especially in phosphatidylethanolamine and phosphatidylserine for infants fed regular MF compared with those fed HM or NMF. Unsaturation index of red blood cell phospholipids showed a similar effect. These results suggest that dietary nucleotides play a role in the in vivo desaturation and elongation of essential fatty acids to long chain PUFA during early life for the human newborn.

Changes in the fatty acids pattern of red blood cell phospholipids induced by type of milk, dietary nucleotide supplementation, and postnatal age in preterm infants

The fatty acid profile of red blood cell phospholipids and the total phospholipid and cholesterol contents of erythrocyte membrane in preterm infants in the first month of life were studied. Influences of human milk and adapted formula and dietary nucleotides supplementation at a level similar to that found in human milk were evaluated. Nineteen preterm newborn infants with adequate weight for gestational age were fed their own mothers preterm human milk, 18 with a standard milk formula and 18 with the same formula supplemented with nucleotides. Blood samples were obtained at birth from cord blood, and at 30 days of age. At 1 month of life, linoleic acid rose in formula fed infants compared to those fed human milk (p less than 0.05) and relative amounts of 20:3w6, 20:4w6, 22:4w6, 22:5w6, and total polyunsaturates of the w6 series greater than 18 carbon atoms were significantly decreased in standard milk formula fed infants (p less than 0.05-0.01). No significant differences for these fatty acids were found between human milk and nucleotide milk formula infants. Docosahexaenoic acid (22:6w3) decreased from birth to 1 month of age in formula fed infants (p less than 0.01) but not in human milk fed infants. Infants fed nucleotide milk formula showed intermediate values for 20:3w6 and 20:4w6 (p less than 0.1) between infants fed human milk and those fed standard milk formula.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the Protein Fractions of Human Milk during Lactation

The changes in the absolute and relative contents of alpha- and kappa-caseins, lactoferrin, alpha-lactalbumin, serum albumin and lysozyme in human milk have been studied through the period of lactation. Protein fractions of 209 samples were analyzed by a discontinuous polyacrylamide gel electrophoresis method. beta- and kappa-caseins decreased from colostrum to mature milk although their relative percentages remained constant. They accounted for 12-15 and 9-13% of the total protein in human milk, respectively. Lactoferrin decreased in absolute and relative amounts with advancing lactation. This protein represented 32-19% of the human milk proteins. alpha-Lactalbumin slightly decreased from colostrum to transitional milk but there was an increase in mature milk by 16-30 days. The percentages of this protein in colostrum and mature milk were approximately 23 and 30%, respectively. Serum albumin also decreased with advancing lactation, but the differences between transitional and mature milk were not statistically significant. Lysozyme increased from colostrum to mature milk both in relative and absolute amounts. Colostrum contained about 262 micrograms/ml, and mature milk 1,246 micrograms/ml, representing 1.5 and 12.1% of total milk proteins.

The n-3 polyunsaturated fatty acid levels in rat tissue lipids increase in response to dietary olive oil relative to sunflower oil.

In the present study, changes in phospholipid compositions of liver microsomes, erythrocyte membranes, platelets, aorta, cardiac muscle and brain of rats fed olive oil were compared with those of rats fed sunflower oil. Four groups of rats starting at weaning were fed for four weeks a basal diet containing 5 or 25% olive oil or sunflower oil. We found that oleic acid was higher and linoleic acid was lower in membrane phospholipids of olive oil fed rats compared to sunflower oil fed rats. Polyunsaturated fatty acids of the n−3 series were markedly elevated in all tissues of rats on the olive oil diets relative to those on the sunflower oil diets. The results are consistent with a lower linoleic/linolenic acid ratio induced by the olive oil diets, suggesting a positive correlation between olive oil ingestion and n−3 polyunsaturated fatty acid levels in cell and tissue lipids. The study suggests that an adequate intake of olive oil may enhance the conversion of n−3 fatty acids.

Influences of Diet and Postnatal Age on the Lipid Composition of Red Blood Cell Membrane in Newborn Infants

The fatty acid and cholesterol contents of tissue membranes are determinants of their stability and functionality. This study was designed to evaluate the influences of diet and postnatal age on the polyunsaturated fatty acid (PUFA) composition of erythrocyte membrane phospholipid fractions and on the red blood cell membrane cholesterol and phosphorus contents in newborn infants during the 1st month of life. A group of infants was fed on human milk and another group on adapted milk formula. Blood samples were obtained at birth, from cord blood, and at 7 and 30 days of age. Long-chain w6 PUFA declined with advancing age in all membrane phosphoglycerides and sphingomyelin (SM) in those infants fed formula. w6 PUFA also decreased in phosphatidylcholine (PC) and phosphatidylserine (PS) in infants fed human milk and were maintained constant in phosphatidylethanolamine (PE) and SM. w3 PUFA were less affected by postnatal age. PE and SM showed significantly higher percentages of w6 and w3 long-chain PUFA in infants fed human milk than in those fed formula. Membrane cholesterol content increased in all infants from birth to 1 month of life but phosphorus levels were unaffected by diet and postnatal age. These results suggest that diets with a low content of long-chain PUFA, such as adapted cows milk formulas, may induce changes in membrane functionality and that incorporation of PUFA to the diet in amounts similar to those found in human milk should be considered at least in early life.

Effect of dietary olive and sunflower oils on the lipid composition of the aorta and platelets and on blood eicosanoids in rats.

The effects on aortic and platelet fatty acid compositions and on blood levels of prostacyclin and thromboxane A2 of low- and high-fat diets containing olive oil or sunflower oil were studied. For 4 weeks, four groups of weanling rats were fed a basal diet containing 5% or 25% olive oil or sunflower oil. Rats fed olive oil diets showed higher levels of 18:1(n-9) and polyunsaturated fatty acids of the n-3 series and lower percentages of 18:0 and 18:2(n-6) in aortic and platelet phosphatidylcholine and phosphatidylethanolamine than those fed the sunflower oil diets. Arachidonic acid increased in platelet phosphatidylethanolamine and aortic phosphatidylcholine of rats fed the diet containing 5% sunflower oil compared with those fed 5% olive oil. Plasma 6-ketoprostaglandin F1 alpha increased in both groups of animals fed olive oil while these rats also showed the lowest levels of serum thromboxane B2 and plasma cholesterol. Olive oil feeding leads to changes in lipid metabolism of the vascular compartment that could be favorable in the prevention of thrombosis and atherosclerosis.

Changes in lipid composition of liver microsomes and fatty acyl-CoA desaturase activities induced by medium chain triglyceride feeding

Changes in fatty acid composition, microsomal Δ9- and Δ6-desaturase activities and liver contents of cholesterol and phospholipids were studied in rats fed medium chain triglyceride-supplemented diets. Weanling rats were divided into four groups and fed for three weeks a basal diet with different 10%-fat supplements: corn oil, medium chain triglyceride-corn oil, olive oil and medium chain triglyceride-olive oil. The highest relative content of saturated fatty acids corresponded to corn oil-fed animals. Both monounsaturated fatty acid content and Δ9-desaturase activity were higher in the animals fed olive oil diets than in corn oil-fed rats. The long chain polyunsaturated fatty acids of the n−3 series were increased in the olive oil and medium chain triglyceride-olive oil-fed groups probably due to the lower linoleic/α-linolenic ratios found in these two diets. The cholesterol/phospholipid molar ratio was unaffected by diet and the unsaturation index was only slightly changed in the four groups. Thus, some mechanism may be operative under these conditions to maintain the homeostasis of the membrane.

Hormonal effects on the liver glucose metabolism in rainbow trout (Salmo gairdneri).

1. Glucagon, adrenaline and dibutyril cyclic AMP increased the release of glucose to the medium during incubation of liver slices from rainbow trout (Salmo gairdneri) while insulin had no effect. 2. Glycogen content decreased only slightly after cyclic AMP addition and even increased in the presence of glucagon and adrenaline. Consequently, the release of glucose was due mainly to gluconeogenesis. 3. This is corroborated by the reduction of glucose liberation in presence of alpha-cyanocinnamate, an inhibitor of gluconeogenesis.

Involvement of gluconeogenesis in the hyperglycemia induced by glucagon, adrenaline and cyclic AMP in rainbow trout (Salmo gairdneri)

Abstract 1. 1. The injection of adrenaline or dibutyril cyclic AMP to rainbow trout, Salmo gairdneri was followed by an increase in blood glucose and lactate. 2. 2. The injection of glucagon was followed by hyperglycemia without increase in blood lactate. 3. 3. None of these treatments produced significant alterations in liver glycogen. 4. 4. The simultaneous injection of dibutyril cyclic AMP and α-cyano-hydroxy-cinnamate resulted in a substantially smaller increase in blood glucose concentration than the injection of dibutyril cyclic AMP alone. 5. 5. These results show that hyperglycemia was due to gluconeogenesis under these circumstances, confirming the key role of this process in the trout.

Changes in the fatty acid composition of plasma and red blood cell membrane during the first hours of life in human neonates.

The objective of this work was to examine the changes in the fatty acid profiles of plasma lipid fractions and red blood cell membrane phospholipids in newborn infants during the first 6-8 h of life. Methyl esters of fatty acids from plasma free fatty acids and phospholipids and from membrane phosphatidylethanolamine, phosphatidylcholine and sphingomyelin for cord blood (n = 20) and venous blood (n = 19) were analyzed by GLC. Important changes were observed in plasma fatty acids. Palmitic and palmitoleic acid increased from birth to 6-8 h of age for both free fatty acids and phospholipids. Palmitic acid also increased in membrane phosphatidylcholine and phosphatidylethanolamine. In the former, stearic acid declined whereas oleic and docosatetraenoic acids increased. Phosphatidylethanolamine and sphingomyelin were less affected than phosphatidylcholine probably because the internal location of the two first fractions in erythrocyte membrane. Polyunsaturated fatty acids dropped slightly during the first hours of life in most lipid fractions. This may be a consequence of the interruption of placental fatty acid supply and the limited capacity of the newborn to desaturate their essential fatty acid tissue stores.