Impact of maternal dietary n-3 and n-6 fatty acids on milk medium-chain fatty acids and the implications for neonatal liver metabolism

Abstract

Levels of n-6, n-3, and medium-chain fatty acids (MCFA) in milk are highly variable. Higher carbohydrate intakes are associated with increased mammary gland MCFA synthesis, but the role of unsaturated fatty acids for milk MCFA secretion is unclear. This study addressed whether n-6 and n-3 fatty acids, which are known to inhibit hepatic fatty acid synthesis, influence MCFA in rat and human milk and the implications of varying MCFA, n-6, and n-3 fatty acids in rat milk for metabolic regulation in the neonatal liver. Rats were fed a low-fat diet or one of six higher-fat diets, varying in 16:0, 18:1n-9, 18:2n-6, 18:3n-3, and long-chain (LC) n-3 fatty acids. Higher maternal dietary 18:2n-6 or 18:3n-3 did not influence milk MCFA, but lower maternal plasma triglycerides, due to either a low-fat or a high-fat high-LC n-3 diet led to higher milk MCFA. MCFA levels were inversely associated with 18:1n-9, 18:2n-6, and 18:3n-3 in human milk, likely reflecting the association between dietary total fat and unsaturated fatty acids. High LC n-3 fatty acid in rat milk was associated with lower hepatic Pklr, Acly, Fasn, and Scd1 and higher Hmgcs2 in the milk-fed rat neonate, with no effect of milk 18:1n-9, 18:2n-6, or MCFA. These studies show that the dietary fatty acid composition does not impact MCFA secretion in milk, but the fatty acid composition of milk, particularly the LC n-3 fatty acid, is relevant to hepatic metabolic regulation in the milk-fed neonate.

Maternal Obesity Reduces Milk Lipid Production in Lactating Mice by Inhibiting Acetyl-CoA Carboxylase and Impairing Fatty Acid Synthesis

“…In humans impaired MCFA oxidation is associated with neonatal metabolic disorders and elevated morbidity [46], and animal model studies have demonstrated that MCFA are more readily absorbed by the gut and transported to the liver for oxidation than long chain fatty acids (LCFA) [47], [48]. These observations indicate that MCFA may be the preferred energy source for growth in the developing neonate, and suggest that reduced MCFA consumption would alter neonatal metabolic properties and lead to impaired growth.…”

The inverse association between relative abundances of oleic acid and arachidonic acid is related to alpha -linolenic acid

“…Fatty acid composition of total lipids of breast muscle and feed was determined by gas chromatography [29]. Fatty acid content is presented as g fatty acid/kg tissue (wet weight), and as weight percentage of the measured fatty acids.…”

Scientific Opinion on the essential composition of infant and follow-on formulae

“…TAGs containing SCFAs, MCFAs and to some extent also lauric acid, with 12 carbon atoms, are more rapidly hydrolysed by gastrointestinal lipases and the hydrolysis products are more easily absorbed and are taken to the liver directly via the portal vein (Novak and Innis, 2011). The ingestion of these fatty acids, therefore, could provide some benefit under conditions where fat absorption is a limiting factor.…”

“…The ingestion of these fatty acids, therefore, could provide some benefit under conditions where fat absorption is a limiting factor. The MCFA content of human milk varies and is increased by a high carbohydrate and low fat intake of the mother (Koletzko et al, 1992;Sauerwald et al, 2001;Novak and Innis, 2011).…”