Citrate is widely used as a food additive being part of virtually all processed foods. Although considered inert by most of the regulatory agencies in the world, plasma citrate has been proposed to play immunometabolic functions in multiple tissues through altering a plethora of cellular pathways. Here, we used a short-term alimentary intervention (24 hours) with standard chow supplemented with citrate in amount corresponding to that found in processed foods to evaluate its effects on glucose homeostasis and liver physiology in C57BL/6J mice. Animals supplemented with dietary citrate showed glucose intolerance and insulin resistance as revealed by glucose and insulin tolerance tests. Moreover, animals supplemented with citrate in their food displayed fed and fasted hyperinsulinemia and enhanced insulin secretion during an oral glucose tolerance test. Citrate treatment also amplified glucose-induced insulin secretion in vitro in INS1-E cells. Citrate supplemented animals had increased liver PKCα activity and altered phosphorylation at serine or threonine residues of components of insulin signaling including IRS-1, Akt, GSK-3 and FoxO1. Furthermore, citrate supplementation enhanced the hepatic expression of lipogenic genes suggesting increased de novo lipogenesis, a finding that was reproduced after citrate treatment of hepatic FAO cells. Finally, liver inflammation markers were higher in citrate supplemented animals. Overall, the results demonstrate that dietary citrate supplementation in mice causes hyperinsulinemia and insulin resistance both in vivo and in vitro, and therefore call for a note of caution on the use of citrate as a food additive given its potential role in metabolic dysregulation.

柠檬酸盐被广泛用作食品添加剂，几乎是所有加工食品的一部分。尽管世界上大多数监管机构认为是惰性的，但血浆柠檬酸盐已被提议通过改变过多的细胞途径在多种组织中发挥免疫代谢功能。在这里，我们使用标准食物进行短期消化干预（24 小时），并添加与加工食品中相应量的柠檬酸盐，以评估其对 C57BL/6J 小鼠的葡萄糖稳态和肝脏生理学的影响。通过葡萄糖和胰岛素耐量测试显示，补充饮食柠檬酸盐的动物表现出葡萄糖不耐症和胰岛素抵抗。而且，在食物中补充柠檬酸盐的动物在口服葡萄糖耐量试验中表现出进食和禁食高胰岛素血症和胰岛素分泌增加。柠檬酸盐处理也放大了葡萄糖诱导的胰岛素分泌在INS1-E 细胞中进行体外试验。柠檬酸盐补充的动物肝脏 PKCα 活性增加，并改变了胰岛素信号成分（包括 IRS-1、Akt、GSK-3 和 FoxO1）的丝氨酸或苏氨酸残基的磷酸化。此外，柠檬酸盐补充增强了脂肪生成基因的肝脏表达，表明从头脂肪生成增加，这一发现在柠檬酸盐处理肝FAO细胞后重现。最后，柠檬酸盐补充动物的肝脏炎症标志物较高。总体而言，结果表明，在小鼠体内和体外膳食中补充柠檬酸盐会导致高胰岛素血症和胰岛素抵抗，因此，鉴于柠檬酸盐在代谢失调中的潜在作用，因此呼吁谨慎使用柠檬酸盐作为食品添加剂。