Effects of acupuncture on the urinary metabolome of spontaneously hypertensive rats

Background The mechanism of action underlying the putative effects of acupuncture in essential hypertension remains unknown but neuronal mechanisms have been explored most extensively to date. We aimed to explore the effects of manual acupuncture (MA) with manual stimulation on blood pressure (BP) and urine metabolites in the spontaneously hypertensive rat (SHR) model of hypertension. Methods After adaptive feeding (with a standard laboratory diet and distilled water) for 1week, five normotensive Wistar Kyoto (WKY) rats with normal BP formed the control group. Ten SHRs were randomised into two groups (n=5each), one of which received MA at ST9 for a total of 14 days (SHR+MA group). The other (SHR group) and the WKY control group underwent needle insertion without manual stimulation. BP was measured pre- and post-acupuncture in all groups and urinary metabolic profiles were investigated using metabonomics methods based on H-1 nuclear magnetic resonance (NMR) spectroscopy coupled with principal component analysis, partial least squares discriminant analysis, and orthogonal to partial least squares discriminant analysis. Results A total of 46 metabolites were clearly separated in the urine by H-1 NMR. Loading plots showed significant changes in urinary metabolite contents after acupuncture treatment as well as significant differences between SHR and WKY rats. Acupuncture at ST9 in SHRs increased urine metabolites including -ketoglutaric acid, N-acetyl glutamic acid, and betaine. Furthermore, systolic and diastolic BP, mean arterial pressure and heart rate were significantly reduced after acupuncture. Conclusions Acupuncture may decrease BP in SHRs by improving the metabolic disorder associated with hypertension.