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Relative utilization of fatty acids for synthesis of ketone bodies and complex lipids in the liver of developing rats
Author(s) -
Yeh Y. Y.,
Streuli V. L.,
Zee P.
Publication year - 1977
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02533640
Subject(s) - ketogenesis , ketone bodies , clinical chemistry , medicine , fatty acid , lipidology , fatty acid synthesis , endocrinology , chemistry , palmitic acid , biochemistry , metabolism , de novo synthesis , biology , enzyme
Abstract The regulation of hepatic ketogenesis, as related to the metabolism of fatty acids through oxidative and synthetic pathways, was studied in developing rats. [1‐ 14 C] palmitate was used as a substrate to determine the proportions of free fatty acids utilized for the production of ketone bodies, CO 2 and complex lipids. Similar developmental patterns of hepatic ketogenesis were obtained by measuring the production of either [ 14 C]acetoacetate from exogenous [1‐ 14 C] palmitate or the sum of unlabeled acetoacetate and β‐hydroxybutyrate from endogenous fatty acids. The production of total ketone bodies was low during the late fetal stage and at birth, but increased rapidly to a maximum value within 24 hr after birth. The maximal ketogenic capacity appeared to be maintained for the first 10 days of life. 14 CO 2 production from [1‐ 14 C] palmitate increased by two‐ to fourfold during the suckling period, from its initial low rate seen at birth. The capacity for synthesis of total complex lipids was low at birth and had increased by day 3 to a maximal value, which was comparable to that of adult fed rats. The high lipogenic capacity lasted throughout the remaining suckling period. When ketogenesis was inhibited by 4‐pentenoic acid, the rate of synthesis of complex lipids did not increase despite an increase in unutilized fatty acids. During the mid‐suckling period, approximately equal amounts of [1‐ 14 C] palmitate were utilized for the synthesis of ketone plus CO 2 and for complex lipid synthesis. By contrast, in adult fed rats, the incorporation of fatty acids into complex lipids was four times higher than that of ketone plus CO 2 . These observations suggest that stimulated hepatic ketogenesis in suckling rats results from the rapid oxidation of fatty acids and consequent increased production of acetyl CoA, but not from impaired capacity for synthsis of complex lipids.