Serum metabolomic data, dietary lipids and hepatic phospholipids from a study of the effects of cheese feeding in rats.

We hypothesize that inclusion of cheese in the diet would improve indices of glucoregulation. We made rats insulin resistant with high fat diet, then included either low fat (LOW) or regular fat (REG) cheese in the diets for an additional 8 weeks. The notable findings were that both LOW and REG improved insulin sensitivity as assesssed using an insulin tolerance test. In tissues harvested from the rats, we found mild decreases in the hepatic abundance of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase. We subjected serum samples to metabolomic analysis. Notably, 21 species of lysophosphatidylcholine (LPC) or phosphatidylcholine (PC) differed between groups. The general trend was that HFD lowered LPC and PC and that cheese (both LOW and REG) tended to increase these phospholipids towards the concentrations seen in low-fat diet-fed controls. In the tables, the groups and their abbreviations are: LFD - rats fed low fat diet for the entire 12 week study. HFD - rats fed high fat diet (20% fat w/w, from lard, corn oil and flaxseed oil) for the entire 12 week period. LOW - rats fed high fat diet for 4 weeks. In the 5th week, the diet was changed so that of the 20% fat, 7.5% was from low-fat cheddar cheese. REG - rats fed high fat diet for 4 weeks. In the 5th week, the diet was changed so that of the 20% fat, 10% was from low-fat cheddar cheese. Other abbreviations: SFA - saturated fatty acids MUFA - monounsaturated fatty acids PUFA - polyunsaturated fatty acids ND - not detected PC - phosphatidylcholine PE - phosphatidylethanolamine Table 1 - fatty acid profiles of the 4 diets analysed by gas chromatography Table 2 - metabolomic analysis of serum by either direct ionization -mass spectrometry or nuclear magnetic resonance by the Metabolomics Innovation Centre, University of Alberta Table 3 - Hepatic phosphatidylcholine and phosphatidylethanolamine isolated by thin-layer chromatography and and quantified by a phosphorous assay.

我们提出假说：膳食中添加奶酪可改善糖调节相关指标。本研究通过高脂饮食构建胰岛素抵抗大鼠模型，随后在饲料中分别添加低脂（LOW）或常规脂肪（REG）奶酪，持续干预8周。核心研究结果显示，LOW与REG两组大鼠的胰岛素敏感性均通过胰岛素耐量试验得到改善。在采集的大鼠组织中，我们观察到肝脏内葡萄糖-6-磷酸酶（glucose-6-phosphatase）与磷酸烯醇式丙酮酸羧激酶（phosphoenolpyruvate carboxykinase）的表达丰度出现轻度下调。我们对血清样本开展代谢组学分析，值得关注的是，两组间共有21种溶血磷脂酰胆碱（lysophosphatidylcholine, LPC）或磷脂酰胆碱（phosphatidylcholine, PC）存在显著差异。整体变化趋势为：高脂饮食（HFD）会降低血清中LPC与PC的水平，而添加奶酪（LOW与REG两组）则可使这些磷脂的浓度回升至低脂饮食对照组的水平。

各组及其缩写说明如下：
LFD：在整个12周研究周期内均饲喂低脂饲料的大鼠。
HFD：在整个12周研究周期内均饲喂高脂饲料（脂肪含量为20%重量比，脂肪来源为猪油、玉米油及亚麻籽油）的大鼠。
LOW：前4周饲喂高脂饲料，第5周起调整饲料配方：原20%总脂肪中，7.5%由低脂切达干酪提供。
REG：前4周饲喂高脂饲料，第5周起调整饲料配方：原20%总脂肪中，10%由低脂切达干酪提供。

其他缩写说明：
SFA：饱和脂肪酸（saturated fatty acids）
MUFA：单不饱和脂肪酸（monounsaturated fatty acids）
PUFA：多不饱和脂肪酸（polyunsaturated fatty acids）
ND：未检出（not detected）
PC：磷脂酰胆碱（phosphatidylcholine）
PE：磷脂酰乙醇胺（phosphatidylethanolamine）

表1：通过气相色谱法分析的4种饲料的脂肪酸谱
表2：由阿尔伯塔大学代谢组学创新中心采用直接电离质谱法或核磁共振法开展的血清代谢组学分析结果
表3：经薄层色谱法分离、磷含量测定法定量的肝脏磷脂酰胆碱与磷脂酰乙醇胺含量。