Analysis of micellar and vesicular lecithin and cholesterol in model bile using1H- and31P-NMR

The distribution of phospholipid and cholesterol between the vesicular and micellar phases in bile plays an important role in the formation of cholesterol gallstones. Conventional analytical procedures to determine the distribution are potentially unreliable because they disturb the distribution of these compounds between the two phases. In this work, we circumvent this problem by using NMR.³¹P-NMR is used to quantify directly the micellar and the vesicular amount of lecithin. The previously described¹H-NMR method to determine directly the micellar lecithin (Groen et al.,J Lipid Res 31: 1315–1321) has been optimized by the implementation of a spectral quantification method. The agreement between the³¹P and¹H methods was excellent.In our hands, the method of Ellul et al. (FEBS Lett 300: 30–32) did not allow quantification of micellar cholesterol, although our fitting procedure offered the possibility of quantifying overlapping spectral peaks by the use of prior knowledge about all the parameters of the compounds visible in the spectrum. The micellar cholesterol concentration was so low compared to the overlapping lecithin peaks that no reliable quantification was possible. The same problem was encountered when using other characteristic cholesterol resonances for quantification. Our data suggest that cholesterol present in the vesicular phases is too immobile to give rise to high-resolution peaks and the amount of cholesterol present in the micellar phase is too low to allow quantitation by NMR. We conclude that¹H-NMR can be used to determine micellar lecithin, and³¹P-NMR to determine micellar as well as vesicular lecithin in model bile.     

胆结石有序结构的红外光谱研究

胆石病是徐州地区的多发病之一,利用傅里叶变换红外光谱（FTIR）针对胆结石的组成及生物矿化有序结构形成进行研究,初步探索该地区胆结石的形成过程。红外光谱分析表明：蛋白质为胆结石的形成提供沉淀基质,对于胆结石成核及有序结构的行程具有重要意义;在胆结石难溶物中胆固醇和羟基碳酸磷灰石相伴而生,推测羟基碳酸磷灰石可与胆固醇相互作用,促使其结晶析出,从而加速胆结石的形成。     

Common Variants of <Emphasis Type="Italic">ABCB4</Emphasis> and <Emphasis Type="Italic">ABCB11</Emphasis> and Plasma Lipid Levels: A Study in Sib Pairs with Gallstones,and Controls

Most epidemiological surveys have confirmed the association of low HDL-cholesterol and high triglyceride levels with cholesterol gallstones. Our objective was to analyze the relationship between plasma lipid levels and common polymorphisms of ABCB11 (encoding the bile salt export pump, BSEP) and ABCB4 (encoding the phospholipid transporter into bile, MDR3) genes. Plasma lipids were measured in 108 index patients of sib pairs with gallstones and in 260 controls. Using PCR-based assays with 5′-nuclease and fluorescence detection (TaqMan), the ABCB11 coding SNP p.A444V and four haplotype-tagging SNPs covering the ABCB4 gene (c.504C > T, c.711T > A, p.R652G, rs31653 in intron 26) were genotyped. Plasma lipids were compared in carriers of the common versus rare allele of these polymorphisms using Student’s t test and Pearson’s correlation. BMI and triglyceride levels were higher and HDL-cholesterol levels were lower in affected siblings than in controls. Among cases, triglyceride and cholesterol levels were higher in carriers of the common versus rare (hetero/homozygous carriers) allele of the SNPs p.A444V of ABCB11 and C.504C > T of ABCB4. HDL-cholesterol was lower in carriers of the common allele of rs31653. In controls, significant differences of cholesterol and HDL-cholesterol levels were found in carriers of ABCB4 polymorphisms. Our results do not support the hypothesis of a link between ABCB4 and ABCB11 polymorphisms, lithogenic dyslipidemia, and gallstone risk.