Do mammalian NPC1 and NPC2 play a role in intestinal cholesterol absorption?
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ABSTRACT:
SUBMITTER: Dixit SS
PROVIDER: S-EPMC2049080 | biostudies-other | 2007 Nov
REPOSITORIES: biostudies-other
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Project description:Dietary and biliary cholesterol are taken up by intestinal epithelial cells and transported to the endoplasmic reticulum. At the endoplasmic reticulum, cholesterol is esterified, packaged into chylomicrons and secreted into the lymph for delivery to the bloodstream. NPC1L1 (Niemann-Pick C1-like 1) is a protein on the enterocyte brush-border membrane that facilitates cholesterol absorption. Cholesterol's itinerary as it moves to the endoplasmic reticulum is unknown, as is the identity of any cellular proteins that facilitate the movement. Two proteins that play an important role in intracellular cholesterol transport and could potentially influence NPC1L1-mediated cholesterol uptake are NPC1 and NPC2 (Niemann-Pick type C disease proteins 1 and 2). In this issue of the Biochemical Journal, Dixit and colleagues show that the absence or presence of NPC1 and NPC2 has no effect on intestinal cholesterol absorption in the mouse. Thus neither protein fills the gap in our knowledge of intra-enterocyte cholesterol transport. Furthermore, the NPC1/NPC2 pathway would not be a good target for limiting the uptake of dietary cholesterol.
| S-EPMC2049072 | biostudies-other
Project description:1. Short-term incubation of the everted intestinal sacs of rats in media containing cholesterol oleate or cholesterol plus oleic acid resulted in rapid hydrolysis, but no synthesis, of the sterol ester. 2. On separation of the brush border from the rest of the mucosal cell, almost all of the hydrolytic activity and appreciable amounts of the synthetic activity of the whole cell were found to be present in the brush-border fraction. 3. The isolated brush-border fraction contained considerable amounts of cholesterol, which was always present in the unesterified state; the rest of the cell contained about an equal amount of unesterified cholesterol, but, in addition, small but definite amounts of the esterified sterol were also found in this fraction. 4. On feeding rats with [4-(14)C]cholesterol, which was diluted with 3mg. of cholesterol, it was found that the brush border very rapidly took up the fed sterol without changing its net content of cholesterol. No traces of radioactive cholesterol ester could ever be detected in the isolated brush border after feeding with (14)C-labelled esterified or unesterified cholesterol. 5. The appearance of the labelled sterol was quite rapid in the rest of the cell also, where small proportions were found in the esterified state. 6. Therefore the sequence of events in the absorption of cholesterol appears to be: the dietary cholesterol esters are hydrolysed by the cholesterol ester hydrolase of pancreas or of the mucosal brush border or both, after which the brush border rapidly absorbs the de-esterified sterol and transfers it into the mucosal cell, by a mechanism of displacement, where it is slowly re-esterified for transport through the lymph.
| S-EPMC1264904 | biostudies-other
Project description:Single nucleotide polymorphisms (SNPs) have been associated with cholesterol metabolism and may partly explain large inter-individual variability in intestinal cholesterol absorption and endogenous cholesterol synthesis rates. This cross-sectional study therefore examined whether SNPs in genes encoding for proteins involved in intestinal cholesterol absorption (ABCG5, ABCG8, and NPC1L1) and endogenous cholesterol synthesis (CYP51A1, DHCR7, DHCR24, HMGCR, HSD17B7, LBR, and MSMO1) were associated with intestinal cholesterol absorption markers (total cholesterol (TC) standardized campesterol and sitosterol levels), an endogenous cholesterol synthesis marker (TC-standardized lathosterol levels), and serum low-density lipoprotein cholesterol (LDL-C) concentrations in a European cohort. ABCG5 (rs4245786) and the tag SNP ABCG8 (rs4245791) were significantly associated with serum campesterol and/or sitosterol levels. In contrast, NPC1L1 (rs217429 and rs217416) were significantly associated with serum lathosterol levels. The tag SNP in HMGCR (rs12916) and a SNP in LBR (rs12141732) were significantly associated with serum LDL-C concentrations. SNPs in the cholesterol absorption genes were not associated with serum LDL-C concentrations. SNPs in CYP51A1, DHCR24, HSD17B7, and MSMO1 were not associated with the serum non-cholesterol sterols and LDL-C concentrations. Given the variable efficiency of cholesterol-lowering interventions, the identification of SNPs associated with cholesterol metabolism could be a step forward towards personalized approaches.
| S-EPMC8533139 | biostudies-literature
Project description:Background/objectivesConsumption of cholesterol-rich foods, such as eggs, has a minimal effect on circulating cholesterol levels in healthy humans. To gain insight, we investigated whether phospholipids rich in eggs (EPL) interfere with intestinal cholesterol absorption in vivo.Materials/methodsTo investigate the acute effect of EPL on intestinal cholesterol absorption, male C57BL/6J mice were orally administered with 6, 11, or 19 mg of EPL for three days. We also tested the effect of chronic EPL consumption on cholesterol metabolism in the small intestine and the liver in mice with diet-induced hypercholesterolemia. Male C57BL/6J mice were fed a high fat/high cholesterol (HF/HC; 35% fat, 0.25% cholesterol, w/w) diet for 4 weeks to induce hypercholesterolemia, and subsequently the mice were either fed 0, 0.4 or 0.8% (w/w) of EPL for 6 weeks.ResultsIntestinal cholesterol absorption was significantly decreased by the highest dose of acute EPL administration compared to control. Chronic EPL supplementation did not significantly alter intestinal cholesterol absorption nor plasma levels of total cholesterol and low-density lipoprotein cholesterol. In the small intestine and the liver, EPL supplementation minimally altered the expression of genes which regulate cellular cholesterol levels.ConclusionAlthough chronic EPL consumption was not able to counteract hypercholesterolemia in HF/HC-fed mice, acute EPL administration decreased intestinal cholesterol absorption. This study provides in vivo evidence that acute administration of PLs in eggs prevent cholesterol absorption in the intestine, suggesting a mechanism for a minimal effect of egg consumption on circulating cholesterol levels.
| S-EPMC6669065 | biostudies-literature
Project description:The release of a toxicant from a food matrix during the gastrointestinal digestion is a crucial determinant of the toxicant's oral bioavailability. We present a modified setup of the human simulator of the gut microbial ecosystem (SHIME), with four sequential gastrointestinal reactors (oral, stomach, small intestine, and colon), including the salivary and colonic microbiomes. Naturally arsenic-containing rice, mussels, and nori seaweed were digested in the presence of microorganisms and in vitro oral bioaccessibility, bioavailability, and metabolism of arsenic species were evaluated following analysis by using HPLC/mass spectrometry. When food matrices were digested with salivary bacteria, the soluble arsenic in the gastric digestion stage increased for mussel and nori samples, but no coincidence impact was found in the small intestinal and colonic digestion stages. However, the simulated small intestinal absorption of arsenic was increased in all food matrices (1.2-2.7 fold higher) following digestion with salivary microorganisms. No significant transformation of the arsenic species occurred except for the arsenosugars present in mussels and nori. In those samples, conversions between the oxo arsenosugars were observed in the small intestinal digestion stage whereupon the thioxo analogs became major metabolites. These results expand our knowledge on the likely metabolism and oral bioavailabiltiy of arsenic during human digestion, and provide valuable information for future risk assessments of dietary arsenic.
| S-EPMC6300781 | biostudies-literature
Project description:The hypothesis tested in this study was that cholesterol esterification by ACAT2 would increase cholesterol absorption efficiency by providing cholesteryl ester (CE) for incorporation into chylomicrons. The assumption was that absorption would be proportional to Acat2 gene dosage. Male ACAT2?/?, ACAT2?/?, and ACAT2?/? mice were fed a diet containing 20% of energy as palm oil with 0.2% (w/w) cholesterol. Cholesterol absorption efficiency was measured by fecal dual-isotope and thoracic lymph duct cannulation (TLDC) methods using [³H]sitosterol and [¹?C]cholesterol tracers. Excellent agreement among individual mice was found for cholesterol absorption measured by both techniques. Cholesterol absorption efficiency in ACAT2?/? mice was 16% compared with 46-47% in ACAT2?/? and ACAT2?/? mice. Chylomicrons from ACAT2?/? and ACAT2?/? mice carried ?80% of total sterol mass as CE, whereas ACAT2?/? chylomicrons carried >90% of sterol mass in the unesterified form. The total percentage of chylomicron mass as CE was reduced from 12% in the presence of ACAT2 to ?1% in ACAT2?/? mice. Altogether, the data demonstrate that ACAT2 increases cholesterol absorption efficiency by providing CE for chylomicron transport, but one copy of the Acat2 gene, providing ?50% of ACAT2 mRNA and enzyme activity, was as effective as two copies in promoting cholesterol absorption.
| S-EPMC3243485 | biostudies-literature
Project description:Small Heterodimer Partner (SHP/NR0B2) is an unusual orphan nuclear receptor that does not have a DNA binding domain and acts as a co-repressor for many transcriptional factors, including LRH-1, SREBPs, FOXA1, and AhR, which inhibits expression of its target genes. To explore global intestinal functions of SHP, WT and SHP-KO mice were fed for 6 h after fasting overnight. In SHP-KO mice, 1,707 genes were upregulated, and 1,055 genes downregulated by 2-fold or more compared to WT mice. In GO analysis, intestinal genes upregulated with the highest significance were involved in the transport of ions, lipids, and hormones, and in cholesterol metabolic processes; whereas genes downregulated were involved in the cell cycle, the immune response, and apoptosis. Remarkably, expression of genes important for cholesterol absorption, including Npc1l1, sterol biosynthetic genes, including Hmgcr, and key intestinal bile acid transporters, Asbt and Ost-alpha/beta, was altered in SHP-KO mice compared to WT mice. Overall, in this study, SHP was shown to be a gene-specific transcriptional partner of SREBP-2 to epigenetically inhibit cholesterol-regulating genes, including Npc1l1, in the late-fed state.
2019-02-23 | GSE126939 | GEO
Project description:The pyruvate kinase M2 isoform (PKM2) is preferentially expressed in cancer to regulate anabolic metabolism. However, the metabolic requirements of PKM2 in tumorigenesis have yielded contradictory results. Herein we discovered that this glycolytic enzyme regulates lipid homeostasis in cancer cell autonomous manner and at systemic levels. Transmembrane protein 33 (TMEM33) was identified as a downstream effector of PKM2, whose expression level positively correlates with plasma total cholesterol level in vivo. Loss of PKM2 leads to up-regulation of TMEM33, which recruits ring finger protein 5 (RNF5) to promote SCAP ubiquitination and degradation, thereby inhibiting Golgi translocation and activation of sterol regulatory element binding protein 1 (SREBP1). Moreover, global PKM2 knockout promoted allografted tumor growth, at least partially attributes to the elevated plasma cholesterol level caused by increased intestinal Niemann-Pick C1-Like 1 (NPC1L1) to facilitate cholesterol absorption. Collectively, PKM2-TMEM33 axis modulates cell autonomous lipid metabolism by regulating SREBP activation. PKM2 in small intestine plays critical functions in controlling systemic cholesterol level. Overall, our results underscore unappreciated functions of PKM2 in lipid homeostasis and imply that combining an allosteric activator of PKM2 with NPC1L1 inhibitor represents a therapeutic invention for cancer treatment.
2021-08-06 | PXD026434 | Pride
Project description:BackgroundElevated concentrations of LDL cholesterol are associated with the development of atherosclerosis and therefore are considered an important target for intervention to prevent cardiovascular diseases. The inhibition of cholesterol absorption in the small intestine is an attractive approach to lowering plasma cholesterol, one that is addressed by drug therapy as well as dietary supplementation with plant sterols and plant sterol esters (PSEs).ObjectiveThis study was conducted to test the hypothesis that the cholesterol-lowering effects of PSE require hydrolysis to free sterols (FSs).MethodsMale Syrian hamsters were fed atherogenic diets (AIN-93M purified diet containing 0.12% cholesterol and 8% coconut oil) to which one of the following was added: no PSEs or ethers (control), 5% sterol stearate esters, 5% sterol palmitate esters (PEs), 5% sterol oleate esters (OEs), 5% sterol stearate ethers (STs; to mimic nonhydrolyzable PSE), or 3% FSs plus 2% sunflower oil. The treatments effectively created a spectrum of PSE hydrolysis across which cholesterol metabolism could be compared. Metabolic measurements included cholesterol absorption, plasma and liver lipid concentration, and fecal neutral sterol and bile acid excretion.ResultsThe STs and the PEs and SEs were poorly hydrolyzed (1.69-4.12%). In contrast, OEs were 88.3% hydrolyzed. The percent hydrolysis was negatively correlated with cholesterol absorption (r = -0.85; P < 0.0001) and positively correlated with fecal cholesterol excretion (r = 0.92; P < 0.0001), suggesting that PSE hydrolysis plays a central role in the cholesterol-lowering properties of PSE.ConclusionsOur data on hamsters suggest that PSE hydrolysis and the presence of FSs is necessary to induce an optimum cholesterol-lowering effect and that poorly hydrolyzed PSEs may lower cholesterol through an alternative mechanism than that of competition with cholesterol for micelle incorporation.
| S-EPMC4478947 | biostudies-literature
Project description:The sorting receptor Sortilin functions in the regulation of glucose and lipid metabolism. Dysfunctional lipid uptake, storage, and metabolism contribute to several major human diseases including atherosclerosis and obesity. Sortilin associates with cardiovascular disease; however, the role of Sortilin in adipose tissue and lipid metabolism remains unclear. Here we show that in the low-density lipoprotein receptor-deficient (Ldlr-/-) atherosclerosis model, Sortilin deficiency (Sort1-/-) in female mice suppresses Niemann-Pick type C1-Like 1 (Npc1l1) mRNA levels, reduces body and white adipose tissue weight, and improves brown adipose tissue function partially via transcriptional downregulation of Krüppel-like factor 4 and Liver X receptor. Female Ldlr-/-Sort1-/- mice on a high-fat/cholesterol diet had elevated plasma Fibroblast growth factor 21 and Adiponectin, an adipokine that when reduced is associated with obesity and cardiovascular disease-related factors. Additionally, Sort1 deficiency suppressed cholesterol absorption in both female mice ex vivo intestinal tissue and human colon Caco-2 cells in a similar manner to treatment with the NPC1L1 inhibitor ezetimibe. Together our findings support a novel role of Sortilin in energy regulation and lipid homeostasis in female mice, which may be a potential therapeutic target for obesity and cardiovascular disease.
| S-EPMC5998044 | biostudies-literature