Myristate is selectively incorporated into surfactant and decreases dipalmitoylphosphatidylcholine without functional impairment.
Lung surfactant mainly comprises phosphatidylcholines (PC), together with phosphatidylglycerols and surfactant proteins SP-A to SP-D. Dipalmitoyl-PC (PC16:0/16:0), palmitoylmyristoyl-PC (PC16:0/14:0), and palmitoylpalmitoleoyl-PC (PC16:0/16:1) together comprise 75-80% of surfactant PC. During alveolarization, which occurs postnatally in the rat, PC16:0/14:0 reversibly increases at the expense of PC16:0/16:0. As lipoproteins modify surfactant metabolism, we postulated an extrapulmonary origin of PC16:0/14:0 enrichment in surfactant. We, therefore, fed rats (d19-26) with trilaurin (C12:0(3)), trimyristin (C14:0(3)), tripalmitin (C16:0(3)), triolein (C18:1(3)) or trilinolein (C18:2(3)) vs. carbohydrate diet to assess their effects on surfactant PC composition and surface tension function using a captive bubble surfactometer. Metabolism was assessed with deuterated C12:0 (ω-d(3)-C12:0) and ω-d(3)-C14:0. C14:0(3) increased PC16:0/14:0 in surfactant from 12 ± 1 to 45 ± 3% and decreased PC16:0/16:0 from 47 ± 1 to 29 ± 2%, with no impairment of surface tension function. Combined phospholipase A(2) assay and mass spectrometry revealed that 50% of the PC16:0/14:0 peak comprised its isomer 1-myristoyl-2-palmitoyl-PC (PC14:0/16:0). While C12:0(3) was excluded from incorporation into PC, it increased PC16:0/14:0 as well. C16:0(3), C18:1(3), and C18:2(3) had no significant effect on PC16:0/16:0 or PC16:0/14:0. d(3)-C14:0 was enriched in lung PC, either via direct supply or via d(3)-C12:0 elongation. Enrichment of d(3)-C14:0 in surfactant PC contrasted its rapid turnover in plasma and liver PC, where its elongation product d(3)-C16:0 surmounted d(3)-C14:0. In summary, high surfactant PC16:0/14:0 during lung development correlates with C14:0 and C12:0 supply via specific C14:0 enrichment into lung PC. Surfactant that is high in PC16:0/14:0 but low in PC16:0/16:0 is compatible with normal respiration and surfactant function in vitro.
Pynn
Christopher J
CJ
Department of Neonatology, Faculty of Medicine, Eberhard-Karls-University, Tübingen, Germany.
Picardi
M Victoria
MV
Nicholson
Tim
T
Wistuba
Dorothee
D
Poets
Christian F
CF
Schleicher
Erwin
E
Perez-Gil
Jesus
J
Bernhard
Wolfgang
W
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism*; D000818:Animals; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D003903:Deuterium; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage / Q000378:metabolism*; D005260:Female; D008168:Lung / Q000254:growth & development / Q000378:metabolism*; D008297:Male; D019814:Myristic Acid / Q000008:administration & dosage / Q000378:metabolism*; D054467:Phospholipases A2 / Q000378:metabolism; D011663:Pulmonary Surfactants / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012119:Respiration; D021241:Spectrometry, Mass, Electrospray Ionization; D013500:Surface Tension; D053719:Tandem Mass Spectrometry; D013997:Time Factors; D014280:Triglycerides / Q000008:administration & dosage / Q000378:metabolism; D014304:Triolein / Q000008:administration & dosage / Q000378:metabolism
D004040:Dietary Carbohydrates; D004041:Dietary Fats; D011663:Pulmonary Surfactants; D014280:Triglycerides; D019814:Myristic Acid; D014304:Triolein; C036694:trimyristin; D015060:1,2-Dipalmitoylphosphatidylcholine; C004565:trilaurin; D003903:Deuterium; C005859:tripalmitin; D054467:Phospholipases A2; C009564:trilinolein