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Partial characterization of mechanism(s) by which sulphobromophthalein reduces biliary lipid secretion.

ABSTRACT: This study was performed to explore the mechanisms by which sulphobromophthalein (BSP) reduces the secretion of biliary lipid using Sprague-Dawley rats (SDR) and mutant rats with congenital conjugated hyperbilirubinaemia bred from SDR (EHBR). We infused the bile-salt-pool-depleted rats with sodium taurocholate at a constant rate of 160 nmol/min per 100 g body wt. with BSP (12.5, 25 and 50 nmol/min per 100 g body wt.) or BSP-GSH (12.5, 25 and 50 nmol/min per 100 g body wt.). The biliary secretion of BSP and BSP-GSH was markedly impaired in EHBR as compared with that in SDR. BSP reduced the biliary secretion of cholesterol and phospholipids in a dose-dependent manner without affecting the secretion of bile salts and composition of fatty acids in phospholipids in SDR, but had no effect on lipid secretion in EHBR. In contrast, BSP-GSH had no such effect on biliary lipids, either in the SDR or EHBR. In addition, the amount of BSP in the liver of EHBR was in the same range as that of SDR. Therefore it is unlikely that an intracellular mechanism is involved in the phenomenon of uncoupling by BSP. We conclude that the uncoupling of biliary lipids from bile-salt secretion by BSP occurs at the level of the bile canaliculus following the secretion of unconjugated BSP.

SUBMITTER: Yamashita G

PROVIDER: S-EPMC1132498 | biostudies-other | 1993 Apr

REPOSITORIES: biostudies-other

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Project description:Background In randomized trials (SHARP [Study of Heart and Renal Protection], IMPROVE -IT [Improved Reduction of Outcomes: Vytorin Efficacy International Trial]), combination of statin and ezetimibe resulted in additional reduction of cardiovascular events. The reduction was greater in patients with type 2 diabetes mellitus (T2 DM ), where elevated remnant cholesterol and high cardiovascular disease risk is characteristic. To evaluate possible causes behind these results, 40 patients eligible for cholecystectomy, randomized to simvastatin, ezetimibe, combined treatment (simvastatin+ezetimibe), or placebo treatment during 4 weeks before surgery, were studied. Methods and Results Fasting blood samples were taken before treatment start and at the end (just before surgery). Bile samples and liver biopsies were collected during surgery. Hepatic gene expression levels were assessed with qPCR . Lipoprotein, apolipoprotein levels, and content of cholesterol, cholesteryl ester, and triglycerides were measured after lipoprotein fractionation. Lipoprotein subclasses were analyzed by nuclear magnetic resonance. Apolipoprotein affinity for human arterial proteoglycans ( PG ) was measured. Biomarkers of cholesterol biosynthesis and intestinal absorption and bile lipid composition were analyzed using mass spectrometry. Combined treatment caused a statistically significant decrease in plasma remnant particles and apolipoprotein B (ApoB)/lipoprotein content of cholesterol, cholesteryl esters, and triglycerides. All treatments reduced ApoB-lipoprotein PG binding. Simvastatin and combined treatment modified the composition of lipoproteins. Changes in biomarkers of cholesterol synthesis and absorption and bile acid synthesis were as expected. No adverse events were found. Conclusions Combined treatment caused atheroprotective changes on ApoB-lipoproteins, remnant particles, bile components, and in ApoB-lipoprotein affinity for arterial PG . These effects might explain the decrease of cardiovascular events seen in the SHARP and IMPROVE - IT trials. Clinical Trial Registration URL : www.clinicaltrialsregister.eu . Unique identifier: 2006-004839-30).

Project description:ImportanceRisk factors for atherosclerotic cardiovascular disease (ASCVD) are well established in type 2 diabetes (T2D), but not in type 1 diabetes (T1D). The impact of partial clinical remission (PR) on short-term ASCVD risk in T1D is unclear.AimTo investigate the impact of PR on the earliest ASCVD risk phenotype in adult T1D using factor analysis to compare the lipid phenotypes of T1D, T2D and controls after stratifying the T1D cohort into remitters and non-remitters.Subjects and methodsA study of 203 adults subjects consisting of 86 T2D subjects, and 77 T1D subjects stratified into remitters (n=49), and non-remitters (n=28). PR was defined as insulin-dose adjusted HbA1c of ≤9, and obesity as a BMI ≥30 kg/m2. Factor analysis was used to stratify the groups by ASCVD risk by factorizing seven lipid parameters (TC, LDL, HDL, non-HDL, TC/HDL, TG, TG/HDL) into 2 orthogonal factors (factor 1: TC*LDL; factor 2: HDL*TG) that explained 90% of the variance in the original seven parameters.ResultsThe analysis of individual lipid parameters showed that TC/HDL was similar between the controls and remitters (p=NS) but was significantly higher in the non-remitters compared to the remitters (p=0.026). TG/HDL was equally similar between the controls and remitters (p=NS) but was lower in the remitters compared to the non-remitters (p=0.007). TG was significantly lower in the remitters compared to T2D subjects (p<0.0001) but was similar between T2D subjects and non-remitters (p=NS). Non-HDL was significantly lower in the controls versus non-remitters (p=0.0003) but was similar between the controls and remitters (p=NS). Factor analysis showed that the means of factor 1 and factor 2 composite scores for dyslipidemia increased linearly from the controls, remitters, non-remitters to T2D, p value 0.0042 for factor 1, and <0.0001 for factor 2, with remitters having similar lipid phenotype as controls, while non-remitters were similar to T2D.ConclusionsPartial clinical remission of T1D is associated with a favorable early lipid phenotype which could translate to reduced long-term CVD risk in adults.

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Partial characterization of mechanism(s) by which sulphobromophthalein reduces biliary lipid secretion.

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