A novel method for the analysis of clinical biomarkers to investigate the effect of diet on health in a rat model.

K Hopes,H Macqueen,M Cauchi,W Wassif,C Walton,C Turner

doi:10.1039/c5an00182j

Abstract

Experiments into the relationship between diet and health have been an area of high interest for a long time. In this study, we investigate the application of multivariate data analysis to differentiate between rat populations fed on two different diets: normal rat diet (control) and Western affluent diet (WAD). Two sets of data were acquired and analysed: one from a biochemical clinical analyser, taking measurements of blood-based biochemical markers; the other from the analysis of the volatile organic compounds (VOCs) emitted from faecal samples from the same animals using selected ion flow tube mass spectrometry (SIFT-MS). Five classes were considered: weanlings, 12 month controls, 12 month WADs, 18 month controls, and 18 month WADs. Data from the biochemical analyser, weanlings and 18 month WAD fed rats showed significant differences from the other measurement classes. This was shown in both the exploratory analysis and through multivariate classification. Classification of control diet versus WAD diets suggested there are differences between classes with 92% accuracy for the 12 month classes and 91% for the 18 month classes. Cholesterol markers, especially as low density lipoprotein-cholesterol (LDL), were the main factor in influencing WAD samples. The data from the SIFT-MS analysis also produced very good classification accuracies. Classification of control diet versus WAD diets using the H3O(+) precursor ion data suggested there are differences between classes with 71% accuracy for the 12 month classes and 100% for the 18 month classes. These findings confirm that total cholesterol and LDL-cholesterol are elevated in the 18 month WAD-fed rats. We therefore suggest that the analysis of VOCs from faecal samples in conjunction with multivariate data analysis may be a useful alternative to blood analysis for the detection of parameters of health.

Highlights

There are recommended daily amounts of nutrients for the human body to ensure maintenance and repair of key systems and functions.[1,2] For optimum performance, macronutrients should contribute to the diet in an appropriate balance, and micronutrients should be present in sufficient – but not excessive – quantities
The circles represent the weanlings (WEAN); inverse triangles are the 12 month control diet rats (12M C); the filled triangles are 12 month old Western affluent diet (WAD) (12M W); the squares are 18 month old Application of partial least squares discriminant analysis (PLS-DA) to distinguish between the 12 month controls and 12 month WADs produced an overall accuracy of 92% with a specificity of 100% and a sensitivity of 89%
PLS-DA distinguished between the 18 month controls and 18 month WADs producing an overall accuracy of 91% with a specificity of 100% and a sensitivity of 86%

Summary

Introduction

There are recommended daily amounts of nutrients for the human body to ensure maintenance and repair of key systems and functions.[1,2] For optimum performance, macronutrients (in the form of carbohydrates, proteins and fats) should contribute to the diet in an appropriate balance, and micronutrients should be present in sufficient – but not excessive – quantities. The quantities of certain nutrients taken in by an individual significantly affect what happens internally and can vary the probability of developing certain illnesses/diseases. Many nutritional imbalances have been linked to disease in human and rat models.[3] High plasma sodium and low plasma potassium are linked to hypertension,[4] and there is a wealth of information linking diet with cardiovascular function.[5] Liver and kidney function are compromised by a high fat, high carbohydrate diet,[6] and the immune system is significantly affected by sub-optimal diets.[7]

Results

Discussion

Conclusion