RESUMEN
One of the major survival challenges of premature birth is production of lung surfactant. The lipid component of surfactant, dipalmitoyl PC (DPPC), increases in concentration in the period before normal term birth via a net shift in FA composition away from unsaturates. We investigated the influence of dietary DHA and arachidonic acid (AA) on lung FA composition and DPPC concentration in term and preterm baboons. Pregnant animals/neonates were randomized to one of four groups: breast-fed (B), term formula-fed (T-, preterm formula-fed (P-, and preterm fed formula supplemented with DHA-AA (P+). Breast milk contained 0.68%wt DHA and the P+ group formula contained 0.61%wt DHA. In the preterm groups (P- and P+), pregnant females received a course of antenatal corticosteroids. At the adjusted age of 4 wk, neonate lung tissue was harvested, and FA composition and DPPC were analyzed. Palmitate was approximately 28%wt of lung total FA and no significant differences were found among the four treatment groups. In contrast, DPPC in the B group lung tissue was significantly greater than DPPC in the unsupplemented groups, but not compared with the P+ group. The B and P+ groups were not significantly different in DHA and AA, but were different compared with the unsupplemented (T, P-) groups. These results indicate that LCP supplementation increases lung DHA and AA, without compromising overall lung 16:0 or DPPC. The shift in FA composition toward greater unsaturation in the groups consuming LCP supported improved surfactant lipid concentration in preterm neonate lungs.
Asunto(s)
1,2-Dipalmitoilfosfatidilcolina/metabolismo , Grasas Insaturadas en la Dieta/metabolismo , Ácidos Grasos Insaturados/metabolismo , Pulmón/metabolismo , Papio/metabolismo , Animales , Animales Recién Nacidos , Grasas Insaturadas en la Dieta/administración & dosificación , Ácidos Grasos/análisis , Ácidos Grasos/metabolismo , Ácidos Grasos Insaturados/administración & dosificación , Femenino , Leche/química , EmbarazoRESUMEN
We present a rapid and selective method to increase the volatility of tyrosine and phenylalanine without adding derivative C for high-precision gas chromatography-continuous-flow isotope ratio mass spectrometry (GCC-IRMS) based on enzymatic decarboxylation to yield alkylamines and evaluated for 15N isotopic integrity. Purified tyrosine and phenylalanine were converted to tyramine and phenethylamine by tyrosine and phenylalanine decarboxylases, respectively. GC separation was achieved using a thick stationary phase (5-microm) capillary column. Recoveries were 95 +/- 2%. The reproducibility of delta15N of tyramine and phenethylamine measured by GCC-IRMS averaged SD(delta15N) = 0.33 per thousand. The absolute differences between delta15N of amino acids measured by elemental analyzer-IRMS and the alkylamines measured by GCC-IRMS was not significant. Phenethylamine and tyramine prepared from a mixture of 18 amino acids were extracted by ethanol with 95% recovery, and analysis yielded clean chromatograms and equivalent precision. These data indicate that enzymatic decarboxylation of phenylalanine and tyrosine is a convenient method to increase their volatility for continuous-flow isotopic analysis without introducing extraneous C or significant isotopic fractionation.