Studies on Fatty Acids Metabolism of Goldthioglucose Obese Mice

II. Metabolism of (U)-¹⁴C-Palmitic Acid, 1-¹⁴C-Linoleic Acid and 1-¹⁴C-γ-Linolenic Acid

Abstract

Fatty acids synthesis from acetate in goldthioglucose obese (GTG) mice was described in part 1.
In this report, the incorporation of ¹⁴C from (U)-¹⁴C-palmitic acid, 1-¹⁴C-linoleic acid and 1-¹⁴C-γlinolenic acid into individual fatty acids and major lipid classes of liver was determined in vivo.
Results were as follows.
1) No significant differences between GTG and control mice were found in the incorporation of ¹⁴C into saponifiable fraction of lipids (total fatty acids) from ¹⁴C-palmitic acid, ¹⁴C-linoleic acid and ¹⁴C-γ-linolenic acid.
2) In the percentage distribution of ¹⁴C in major lipid classes in both groups of mice, it was found that ¹⁴C come from ¹⁴C-palmitic acid was incorporated mainly into triglyceride, ¹⁴C from ¹⁴C-linoleic acid into triglyceride and phospholipids, and ¹⁴C from ¹⁴C-γ-linolenic acid mainly into phospholipids.
A few differences between GTG and control mice were found in the percentage distribution of ¹⁴C from ¹⁴C-palmltic acid, ¹⁴C-linoleic acid and ¹⁴C-γ-linolenic acid in triglyceride and phospholipids.
3) In regard to the study on the incorporation of ¹⁴C into individual fatty acids of saponifiable fraction of lipids, the percentage of ¹⁴C recovered in palmitic acid from ¹⁴C-palmitic acid more increased and that in stearic acid more decreased in GTG mice than in control mice.
When ¹⁴C-linoleic acid was used as precursor, the percentage of ¹⁴C recovered in linoleic acid was 55-62% and that in arachidonic acid was about 12% of ¹⁴C in total fatty acids, in both groups of mice.
However, the percentage distribution of ¹⁴C in γ-linolenic acid from ¹⁴C-γ-linolenic acid was 10% and that in arachidonic acid was 46-58%, in both groups of mice.
The rate of conversion from γ-linolenic acid to arachidonic acid more increased in GTG mice than control mice.
4) In regard to the esterification of individual fatty acids into major lipid classes, it was found in both groups of mice that linoleic acid was more esterified into tryglyceride than into phospholipids, and arachidonic acid was esterified mainly into phospholipids.
From these results, metabolism of palmitic acid and essential fatty acids in GTG mice is characterized by increased palmitic acid pool and increased ratio of the conversion from γ-linolenic acid to arachidonic acid.