Masatsuna Tasaka

BACKGROUND: The accumulation of quinolinic acid (QUIN) in cerebrospinal fluid and serum may be used as a biomarker for various neuropsychiatric and inflammatory diseases. In this study, we developed a highly sensitive method to measure QUIN. METHODS: A reverse-phase high-performance liquid chromatography (HPLC) with fluorescence detection was established based on the enzymatic conversion of QUIN to nicotinic acid mononucleotide by recombinant quinolinic acid phosphoribosyltransferase, followed by the formation of fluorescent (BODIPY)-labeled deamido-NAD by recombinant nicotinic acid mononucleotide adenyltransferase. RESULTS: BODIPY-deamido-NAD was isocratically eluted within 6 minutes using reverse-phase chromatography and its chromatographic peak was resolved. The calibration range, precision, and analytical recovery of the QUIN assay are suitable for the analysis of biological fluids. Compared with published quantitation limits for QUIN measurement by HPLC, this method is at least 30-fold more sensitive and has a lower limit of detection of 5.0 nmol/L. The sensitivity was comparable to that previously reported for gas chromatography/mass spectrometry (GC/MS) and the quantitation results of QUIN from samples of cerebrospinal fluid correlated well with that of the GC/MS method. CONCLUSIONS: We established a novel method to quantify QUIN in biological samples. Due to its high sensitivity and the fact that it does not rely on MS instrumentation, this method has the potential for widespread adoption in research laboratories.

1. Gemfibrozil (Lopid) is extensively used as lipid-regulating agent in the Western World, and its beneficial effect is demonstrated in human studies such as the Helsinki Heart Study. However, the mechanism of its hypolipidaemic action is not fully understood. In the present paper, to elucidate the hypolipidaemic mechanism, we examined the effects of gemfibrozil on lipid metabolism in the normocholesterolaemic and hypercholesterolaemic stroke-prone spontaneously hypersensitive rat (SHRSP). 2. Gemfibrozil effectively increased high density lipoprotein (HDL) subfraction rich in apoE (apoE-HDL) and significantly decreased very low density lipoprotein (VLDL) in normocholesterolaemic SHRSP. In the liver of normocholesterolaemic SHRSP, gemfibrozil significantly reduced the activity of microsomal acyl-CoA:cholesterol acyltransferase. 3. Gemfibrozil markedly reduced atherogenic beta-very low density lipoprotein (beta-VLDL) and low density lipoprotein (LDL) in hypercholesterolaemic SHRSP fed a high-fat and high-cholesterol diet (HFC diet). On the other hand, it significantly increased the contents of apoA-I, A-IV and E in the HDL fraction compared with the control group, suggesting that gemfibrozil effectively increases anti-atherogenic HDL subfractions rich in apoA-I, A-IV or E. In the liver of hypercholesterolaemic SHRSP, gemfibrozil markedly prevented lipid accumulation.