Subcutaneous Metabolites Involving Acupoint Sensitization Induced by Myocardial Ischemia and Acupuncture Stimulation in Rabbits

Abstract

The present study aimed at observing the profile of metabolites in sensitized acupoints induced by myocardial ischemia (MI) and the effect of acupuncture intervention on the changes of the metabolites so as to explore the material basis of acupoint sensitization. A total of 20 New Zealand rabbits were randomly and equally divided into a control group and a model group. The MI model was established by occlusion of the anterior descending branch of the left coronary artery with a controllable air balloon inflation method for 5 min/time, twice a day (4-hours' interval) for continuous 5 days (the first stage of MI). After one day's rest, another 5 days' occlusion was conducted again (the second stage of MI) in the same way. The rabbits of the control group were treated with the same procedures but without occlusion. Subcutaneous microdialysis fluid samples were collected from "Neiguan" (PC 6), "Shenmen" (HT 7), "Xinshu" (BL 15), and "Taixi" (KI 3) regions on day 8(after recovery from operation), 14 (the first stage of MI), and 20 (the second stage of MI), as well as collected from PC 6 region during and post-acupuncture stimulation of PC 6, respectively. Manual acupuncture stimulation was applied to the right PC 6 for 30 min. Partial least squares -linear discriminant analysis (PLS-DA) was used to identify different metabolism patterns of the microdialysis fluid sample between groups and at different time-points in the same one group, and the distinct metabolites as the potential markers between groups were weighted via the values of variable importance in the projection (VIP) in combination with t-test analysis. An area under the curve (AUC) >1.0 indicated a test exhibiting good discrimination between groups. Six metabolites identified to be significantly different between the control and model groups were L-glutamic acid, phenylalanine and 3-hydroxyisobutyric acid (which were significantly increased relevant to the control group), and L-histidine, octadecanedioic acid and 9-keto palmitic acid (significantly decreased relevant to the control group) in the microdialysate of PC 6, HT 7 and BL 15 regions. In the microdialysate of PC 6, 4 metabolites including L-glutamic acid, octadecanedioic acid and 8-isohydroxy PGF 2 α (significantly increased), as well as L-histidine (markedly decreased) were identified to be considerably different between the model and control groups. After acupuncture for 30 min, the AUC level of L-glutamic acid was further significantly increased (P<0.05), that of L-histidine obviously decreased, and those of octadecanedioic acid and 8-isohydroxy PGF 2 α turned back nearly to the level of pre-MI. L-glutamic acid, phenylalanine, 3-hydroxyisobutyric acid, L-histidine, octadecanedioic acid and 9-keto palmitic acid from PC 6, HT 7 and BL 15 regions may be used as the material biomarker for MI-induced sensitization of these acupoints. Manual acupuncture intervention of PC 6 induces a significant change of L-histidine and L-glutamic acid in the local subcutaneous tissues.