RNA sequence on the fed and fasted state of kidneys in mice

We studied whether the accumulation of lipids in the fasted kidney are derived from lipoproteins or (non-esterified fatty acids) NEFAs. With overnight fasting, kidneys accumulated triglyceride, but had reduced levels of ceramide and glycosphingolipid species. Fasting led to a nearly 5-fold increase in kidney uptake of plasma [14C]oleic acid. Increasing circulating NEFAs using a ß adrenergic receptor agonist caused a 15-fold greater accumulation of lipid in the kidney, while mice with reduced NEFAs due to adipose tissue deficiency of adipose triglyceride lipase had reduced triglycerides. Cluster of differentiation (Cd)36 mRNA increased 2-fold, and angiopoietin-like 4 (Angptl4), an LPL inhibitor, increased 10-fold. Fasting-induced kidney lipid accumulation was not affected by inhibition of LPL with poloxamer 407 or by use of mice with induced genetic LPL deletion. Despite the increase in CD36 expression with fasting, genetic loss of CD36 did not alter fatty acid uptake or triglyceride accumulation. Our data demonstrate that fasting-induced triglyceride accumulation in the kidney correlates with the plasma concentrations of NEFAs, but is not due to uptake of lipoprotein lipids and does not involve the fatty acid transporter, CD36. Overall design: Mice (n=4-5/group) were either fasted for 16 hours or fed ad libitum. Kidneys were removed and snap frozen. RNA was extracted for sequencing.本研究旨在探讨禁食状态下肾脏内脂质蓄积是否源自脂蛋白或非酯化脂肪酸（non-esterified fatty acids, NEFAs）。经整夜禁食后，小鼠肾脏出现甘油三酯蓄积，但神经酰胺与糖鞘脂类物质水平降低。禁食可使肾脏对血浆[14C]油酸的摄取量提升近5倍。通过β肾上腺素能受体激动剂升高循环NEFAs水平，可导致肾脏脂质蓄积量增加15倍；而因脂肪组织脂肪甘油三酯脂酶缺陷导致循环NEFAs水平降低的小鼠，其肾脏甘油三酯水平下降。分化簇36（Cluster of differentiation 36, CD36）的mRNA表达上调2倍，而作为脂蛋白脂酶（Lipoprotein Lipase, LPL）抑制剂的血管生成素样4（angiopoietin-like 4, Angptl4）的mRNA表达上调10倍。使用泊洛沙姆407抑制LPL，或采用诱导性基因敲除LPL的小鼠模型，均未对禁食诱导的肾脏脂质蓄积产生影响。尽管禁食可上调CD36的表达，但CD36基因敲除并未改变脂肪酸摄取或甘油三酯蓄积水平。本研究数据表明，禁食诱导的肾脏甘油三酯蓄积与循环NEFAs的血浆浓度相关，但并非源自脂蛋白脂质的摄取，且不依赖于脂肪酸转运蛋白CD36。实验整体设计：将小鼠（每组n=4~5）分为两组，一组禁食16小时，另一组自由采食。摘取肾脏并快速冷冻，提取RNA进行测序。