Gas chromatography/time-of-flight mass spectrometry based metabonomic approach to differentiating hypertension- and age-related metabolic variation in spontaneously hypertensive rats

Abstract

Metabonomics is a systematic approach to the study of in vivo metabolic profiles and therefore allows deep insight into and a better understanding of the pathogenesis of disease. To characterize the development of hypertension, a hypertensive animal model, the spontaneously hypertensive rat (SHR), and its normotensive control, the Wistar Kyoto (WKY) rat, were investigated and their blood plasma analyzed using the high-throughput metabolomic tool, gas chromatography/time-of-flight mass spectrometry (GC/TOFMS). A total of 187 peaks were quantitatively determined after deconvolution, and 78 of them were identified. Principal components analysis (PCA) and projection to latent structure partial least-squares discriminant analysis (PLS-DA) were used to process the GC/TOFMS data. The resulting mathematical models were further validated by cross-validation. Plasma compositional differences of many identified compounds showed hypertension-related variation between SHR and WKY rats, and age-related changes from 10 to 18 weeks for both the SHR and WKY rats. These compositional changes involved compounds such as hexadecanoic acid, linoleic acid, oleic acid, stearic acid, 3-hydroxybutyric acid, citric acid, threonic acid, tyrosine, tryptophan, threonine, phenylalanine, serine, ornithine, methionine, 3-hydroxyproline, creatinine, erythrose, myo-inositol, D-methylglucopyranoside, tocopherol, sitosterol, and nonesterified cholesterol. Significantly elevated free fatty acids (FFA) were observed in SHR relative to those in WKY rats, and their levels increased as the SHR aged from 10 to 18 weeks. The close correlation between FFA and hypertension suggests that FFA are potential biomarker candidates for hypertension and they may play an important role in the development of hypertension in SHR. It is also indicated that GC/TOFMS-based metabonomics is a powerful approach to identifying potential biomarkers and investigating the pathological processes of hypertension and the physiological developments of aging.