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Plasma unbound free fatty acid profiles in premature infants before and after intralipid infusion.

ABSTRACT: Background: Unbound free fatty acids (FFAu) are the bioactive fraction of plasma free fatty acids (FFA). Most plasma FFA are bound to albumin. Only when FFA dissociate from albumin, do they become biologically active.Objective: To measure the first FFAu profiles in human infants and to measure these profiles before and during intravenous administration of the soybean lipid, intralipid (IL).Study design: The study population was 16 premature infants, from a parent study of 130 infants with birth weights 500-2000 g and gestational age 23-34 weeks. The infants chosen had plasma samples of ≥120 µL (volume needed for each FFAu profile measurement) in the first day of life. Infants received IL infusions starting in the second day of life at 1 g/kg/day, increasing by 1-g/kg/day daily up to 3 g/kg/day. FFAu profiles were determined during IL infusion when plasma was available. Profiles are the concentrations of the nine most abundant long-chain FFAu and were determined using novel fluorescent probes.Results: Before intralipid infusion unbound myristic acid was the dominant FFAu, as high as 78% of the total FFAu (sum of the 9 FFAu). In contrast, unbound linoleic acid was 0% in all infants. With increasing infusion of IL to 3 g/kg/day, unbound linoleic increased to 26% of the total FFAu, with unbound oleic, myristic, and linolenic acid the second, third and fourth most abundant. The average total FFAu concentration also increased from 4 nM before intralipid to 53 nM at 3 g/kg/day. During IL infusion the FFAu profiles approached the fatty acid composition of intralipid at 3 g/kg/day.Conclusions: This first study of FFAu profiles in neonates revealed that before IL infusion unbound linoleic acid was zero in all 16 infants and levels of myristic acid were exceptionally large, as much as 78% of the total FFAu profile. These results suggest important and previously unrecognized roles of lipid metabolism in early development. Zero unbound linoleic acid before IL infusion may help promote closure of the ductus arteriosus but after IL infusion, synthesis of arachidonic from linoleic acid may tend to promote patency. The high levels of unbound myristate may be needed for immediate neonatal energy needs.

SUBMITTER: Hegyi T

PROVIDER: S-EPMC6579715 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundFree fatty acids (FFAs) are an important source of energy, and also serve as signaling molecules to regulate gene expression. Exercise performed in a post-absorptive state, in contrast to that performed in a postprandial state, increases 24-h fat oxidation under an energy-balanced condition. The primary aim of the present study was to clarify whether the effects of exercise on the concentration and composition of plasma FFAs, which may underlie distinct effects of exercise on 24-h fat oxidation, depend on the nutritional state of the individual when performing the exercise.MethodsTen healthy young men underwent 3 trials of indirect calorimetry in a metabolic chamber. The subjects performed exercise at 60% of VO2max for 60 min in either a post-absorptive or postprandial state, or remained sedentary without an exercise session (control). All trials were designed to be energy balanced over 24 h. Blood samples were collected immediately before and after exercise.ResultsFat oxidation over 24 h was increased only when exercise was performed in a post-absorptive state (control, 531 ± 60; post-absorptive, 779 ± 70; postprandial, 569 ± 37 kcal/24 h). The increase in the 24-h fat oxidation was related to the magnitude of the transient carbohydrate deficit after exercise. The plasma FFA concentration after exercise was higher in the post-absorptive trial (0.38 ± 0.04) than in the control (0.13 ± 0.01) and postprandial (0.15 ± 0.02 mM) trials. The ratio of unsaturated to saturated (U/S) fatty acids after exercise was higher in the post-absorptive trial (1.76 ± 0.06) than in the control (1.56 ± 0.07) and postprandial (1.53 ± 0.08) trials. On the other hand, the plasma FFA concentration after exercise in a postprandial state did not differ significantly from that in the control trial.ConclusionExercise performed in a post-absorptive state effectively increased the plasma FFA concentration and U/S ratio to a greater degree than exercise performed in a postprandial state, underlying the increase in the 24-h fat oxidation. The increase in the plasma FFA concentration was related to the transient carbohydrate deficit after exercise.

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Plasma unbound free fatty acid profiles in premature infants before and after intralipid infusion.

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