Folic acid-fortified foods and multi-vitamin supplements containing folic acid (FA) are widely used around the world, but the exact mechanisms/metabolic effects of FA are not precisely identified. We have demonstrated that Ceramide Synthase 6 (CerS6) and C_16:0-ceramide mediate response to folate stress in cultured cells. Here we investigated the dietary FA effects on mouse liver metabolome, with a specific focus on sphingolipids, CerS6 and C_16:0-ceramide.

Wild-type and CerS6^−/− mice were fed FA-deficient, control, or FA over-supplemented diets for 4 weeks. After dietary treatment, liver concentrations of ceramides, sphingomyelins and hexosylceramides were measured by LC-MS/MS and complemented by untargeted metabolomic characterization of mouse livers.

Our study shows that alterations in dietary FA elicit multiple sphingolipid responses mediated by CerS6 in mouse livers. Folic acid-deficient diet elevated C_14:0-, C_18:0- and C_20:0- but not C_16:0-ceramide in WT male and female mice. Additionally, FA over-supplementation increased multiple sphingomyelin species, including total sphingomyelins, in both sexes. Of note, concentrations of C_14:0- and C_16:0-ceramides and hexosylceramides were significantly higher in female livers than in male. The latter were increased by FD diet, with no difference between sexes in total pools of these sphingolipid classes. Untargeted liver metabolomic analysis concurred with the targeted measurements and showed broad effects of dietary FA and CerS6 status on multiple lipid classes including sex-specific effects on phosphatidylethanolamines and diacylglycerols.

Our study demonstrates that both dietary FA and CerS6 status exhibit pleiotropic and sex-dependent effects on liver metabolism, including hepatic sphingolipids, diacylglycerols, long chain fatty acids, and phospholipids.

叶酸强化食品和含叶酸 (FA) 的复合维生素补充剂在世界范围内广泛使用，但 FA 的确切机制/代谢作用尚未明确。我们已经证明，神经酰胺合酶 6 (CerS6) 和 C _16:0神经酰胺介导培养细胞对叶酸应激的反应。在这里，我们研究了膳食 FA 对小鼠肝脏代谢组的影响，特别关注鞘脂、CerS6 和 C _16:0 -神经酰胺。

野生型和 CerS6 ^-/-小鼠被喂食 FA 缺乏、对照或 FA 过度补充的饮食 4 周。饮食治疗后，通过 LC-MS/MS 测量神经酰胺、鞘磷脂和己糖神经酰胺的肝脏浓度，并辅以小鼠肝脏的非靶向代谢组学表征。

我们的研究表明，膳食 FA 的改变会在小鼠肝脏中引发由 CerS6 介导的多种鞘脂反应。在 WT 雄性和雌性小鼠中，叶酸缺乏饮食会升高 C _14:0 -、C _18:0 - 和 C _20:0 - 但不会升高 C _{16:0 - 神经酰胺。}此外，FA 过度补充增加了两种性别的多种鞘磷脂种类，包括总鞘磷脂。值得注意的是，C _14:0和 C _{16:0的浓度}-神经酰胺和己糖神经酰胺在女性肝脏中显着高于男性。后者因 FD 饮食而增加，在这些鞘脂类的总池中性别之间没有差异。非靶向肝脏代谢组学分析与靶向测量结果一致，并显示膳食 FA 和 CerS6 状态对多种脂质类别的广泛影响，包括对磷脂酰乙醇胺和甘油二酯的性别特异性影响。

我们的研究表明，膳食 FA 和 CerS6 状态均对肝脏代谢表现出多效性和性别依赖性影响，包括肝鞘脂、甘油二酯、长链脂肪酸和磷脂。