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.