Dietary triacylglycerol structure and saturated fat alter plasma and tissue fatty acids in piglets

Human and pig milk triacylglycerols contain a large proportion of palmitic acid (16:0) which is predominately esterified in the 2-position. Other dietary fats contain variable amounts of 16:0, with unsaturated fatty acids predominantly esterified in the 2-position. These studies determined if the amount or position of 16:0 in dietary fat influences the composition or distribution of liver, adipose tissue, lung, or plasma fatty acids in developing piglets. Piglets were fed to 18 d with sow milk or formula with saturated fat from medium-chain triglyceride (MCT), coconut or palm oil, or synthesized triacylglycerols (synthesized to specifically direct 16:0 to the 2-position) with, in total fatty acids, 30.7, 4.3, 6.5, 27.0, and 29.6% 16:0, and in 2-position fatty acids, 55.3, 0.4, 1.3, 4.4, and 69.9% 16:0, respectively. The percentage of 16:0 in the 2-position of adipose fat from piglets fed sow milk, palm oil, and synthesized triacylglycerols were similar and higher than in piglets fed MCT or coconut oil. Thus, the amount, not the position, of dietary 16:0 determines piglet adipose tissue 16:0 content. The effects of the diets on the plasma and liver triacylglycerols were similar, with significantly lower 16:0 in total and 2-position fatty acids of the MCT and coconut oil groups, and significantly higher 16:0 in the plasma and liver triacylglycerol 2-position of piglets fed the synthesized triacylglycerols rather than sow milk or palm oil. The lung phospholipid total and 2-position 16:0 was significantly lower in the MCT, coconut, and palm oil groups, but similar in the synthesized triacylglycerol group and sow milk group. The lung phospholipid total and 2-position percentage of arachidonic acid (20:4n-6) was significantly lower in all of the formula-fed piglets than in milk-fed piglets. The physiological significance of this is not known.

Palmitic acid is absorbed as sn-2 monopalmitin from milk and formula with rearranged triacylglycerols and results in increased plasma triglyceride sn-2 and cholesteryl ester palmitate in piglets

Milk fatty acids contain 20-30% palmitic acid (16:0), with approximately 70% of the 16:0 esterified to the sn-2 position of the milk triacylglycerol. Formulae containing vegetable and oleo oils contain different amounts of 16:0, but all have unsaturated fatty acids esterified to the triacylglycerol sn-2 position. Intraluminal triacylglycerol hydrolysis by endogenous lipases produces sn-2 monoacylglycerols and free fatty acids, which are absorbed and re-esterified in the enterocyte for secretion to plasma. The extent of absorption and re-esterification of sn-2 monoacylglycerols from milk or formula fats in infants is unknown. This was studied by feeding piglets sow milk or formulae containing similar total saturated fat, 18:1, 18:2(n-6) and 18:3(n-3) with unsaturated fatty acids at the sn-2 position or with rearranged triacylglycerols containing approximately 30% 16:0, with 70% 16:0 in fatty acids at the sn-2 position. Feeding milk or 16:0 on the sn-2 position of formula with rearranged triacylglycerols resulted in higher 16:0 esterified to the plasma triacylglycerol sn-2 position and in cholesteryl esters than feeding formulae with 0.4 to 4.4% 16:0 in the sn-2 position fatty acids. The absorption of 16:0 as monopalmitin from milk and any metabolic importance in human infants has yet to be determined.

Plasma and tissue lipids of piglets fed formula containing saturated fatty acids from medium-chain triglycerides with or without fish oil

Addition of fish oil (FO) with carbon chain 20 and 22 (long-chain polyunsaturated fatty acids; LCPs) n-3 fatty acids to formula has been considered as a method to provide 22:6n-3 to preterm infants. These studies determined the effects of including 0.73% n-3 LCPs from FO in formula containing saturated fatty acids as medium-chain triglyceride (MCT) oil on plasma and organ triglyceride (TG), phospholipid (PL), and cholesterol ester (CE) contents and compositions in piglets. Reference piglets were fed their own mother's milk. Piglets fed the formula with FO had significantly lower liver and kidney, but not plasma, TG concentrations; lower liver PL 20:4n-6; and higher plasma, liver, and kidney TG, PL, and CEn-3 LCPs than piglets fed the formula without FO. The increase in liver and kidney lipid n-3 LCPs and the decrease in kidney lipid content shows that inclusion of FO in formula with a high content of MCTs and 18:2n-6 does not promote tissue lipid metabolism similar to natural milk feeding. Piglets fed formula with FO had similar brain 20:4n-6 and 20:5n-3 but higher 22:6n-3 than did piglets fed sow milk. Diet-related differences in plasma and red blood cell PL were not reliable predictors of differences in brain LCP.

Dietary saturated, monounsaturated, n-6 and n-3 fatty acids, and cholesterol influence platelet fatty acids in the exclusively formula-fed piglet

Platelet lipid composition is important to normal platelet morphology and function, and is influenced by dietary fatty acids and cholesterol. The fatty acid composition and cholesterol content of infant formulas differs from those of human milk, but the possible effects on platelet lipids in young infants is not known. This was studied in piglets fed from birth to 18 d of age with one of eight formulas differing in saturated fatty acid chain length, or content of 18:1, 20:5n-3 plus 22:6n-3, or cholesterol. A reference group of piglets fed sow milk was also studied. Sow milk has a fatty acid composition and cholesterol content similar to that of human milk. Piglets fed formulas high in 18:1 (34.9-40.8% wt fatty acids) and low in 16.0 (< or = 6.5% wt fatty acids) had lower platelet counts and greater platelet size than piglets fed sow milk (40.4% 18:1, 30.7% 16:0). Piglets fed formulas high in 16:0 (27-29.6%) and 18:1 (40-40.6%), or low in both 16:0 (5.9-6.1%) and 18:1 (10.8-11.2%), had similar platelet counts and size to piglets fed sow milk. Platelet phospholipid % 20:4n-6 was lower in all the groups of piglets fed formula than in the group fed sow milk. Addition of fish oil with 20:5n-3 plus 22:6n-3 to the formula further decreased platelet phospholipid 20:4n-6. Addition of cholesterol to the formula increased the platelet phospholipid % 20:4n-6 and platelet volume.

Saturated fatty acid chain length and positional distribution in infant formula: effects on growth and plasma lipids and ketones in piglets

Human milk contains a large proportion of palmitic acid (16:0) with > 70% esterified to the center sn-2 position of the milk triglyceride. Infant formulas often use 8:0 + 10:0 [medium-chain triglyceride (MCT)] or 12:0 + 14:0 (coconut oil) as the saturated fat. The effect of formula saturated fatty acid composition; 8:0 + 10:0, 12:0 + 14:0, or 16:0 from palm oil or synthesized triglyceride containing predominantly sn-2 16:0 on plasma lipids and fatty acids was studied in piglets. Although the formulas contained similar 18:1 and 18:2n-6, plasma lipid percentages of 18:1 and 18:2n-6 were higher in piglets fed the formula with MCT or coconut oil rather than the formulas with 16:0, or sow milk. The sn-2 16:0 of the synthesized triglyceride had unique properties. Specifically, piglets fed synthesized triglyceride had significantly higher cholesteryl ester 16:0 identical to that in piglets fed sow milk and higher plasma total and high-density-lipoprotein cholesterol than piglets fed the other formulas.

Nonessential fatty acids in formula fat blends influence essential fatty acid metabolism and composition in plasma and organ lipid classes in piglets

The n-6 and n-3 fatty acid status of developing organs is the cumulative result of the diet lipid composition and many complex events of lipid metabolism. Little information is available, however, on the potential effects of the saturated fatty acid chain length (8:0-16:0) or oleic acid (18:1) content of the diet on the subsequent metabolism of the essential fatty acids 18:2n-6 and 18:3n-3 and their elongated/desaturated products. The effects of feeding piglets formulas with fat blends containing either coconut oil (12:0 + 14:0) or medium chain triglycerides (MCT, 8:0 + 10:0) but similar levels of 18:1, 18:2n-6 and 18:3n-3, or MCT with high or low 18:1 but constant 18:2n-6 and 18:3n-3 on the fatty acid composition of plasma, liver and kidney triglycerides, phospholipids and cholesteryl esters, and of brain total lipid, were studied. Diet-induced changes in the fatty acid composition of lipid classes were generally similar for plasma, liver and kidney. Dietary 18:1 content was reflected in tissue lipids and was inversely associated with levels of 18:2n-6. Lower percentage of 18:2n-6, however, was not associated with lower levels of its elongated/desaturated product 20:4n-6 but was associated with higher levels of 22:6n-3. Feeding coconut oil vs. MCT resulted in lower 18:1 levels in all lipids, and higher percentages of 20:4n-6 in tissue phospholipid. Increasing the dietary n-6/n-3 ratio from 5 to 8 significantly increased tissue percentage of 18:2n-6 and decreased phospholipid 22:6n-3.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary saturated fatty acids (12:0, 14:0, 16:0) differ in their impact on plasma cholesterol and lipoproteins in nonhuman primates

Three species of monkey (rhesus, cebus, and squirrel) were rotated through five purified diets containing 31% energy as various fat blends (P:S between 0.1 and 1.0) for 12-wk periods to compare the impact of specific dietary fatty acids on plasma lipids and lipoproteins. As 12:0 + 14:0 was replaced by 16:0, a significant decrease occurred in total and LDL cholesterol, whereas slight increases in total cholesterol and the LDL-HDL ratio occurred when 16:0 replaced 18:2. Hegsted and Keys regression equations provided a good fit for the observed data, but the predicted total cholesterol response was perfect (r = 0.995) for both equations when 16:0 was considered neutral. Thus, under these conditions 16:0 was less cholesterolemic than 12:0 + 14:0 and only slightly cholesterolemic compared with 18:2.