Intestinal cholesterol transport proteins: an update and beyond

C1orf115 interacts with clathrin adaptors to undergo endocytosis and induces ABCA1 to promote enteric cholesterol efflux

C1orf115 has been identified in high-throughput screens as a regulator of multidrug resistance possibly mediated through an interaction with ATP-dependent membrane transporter ABCB1. Here we show that C1orf115 not only shares structural similarities with FACI/C11orf86 to interact with clathrin adaptors to undergo endocytosis, but also induces ABCA1 transcription to promote cholesterol efflux. C1orf115 consists of an N-terminal intrinsically disordered region and a C-terminal α-helix. Its α-helix binds to phosphoinositides, and mediates C1orf115 localization to the plasma membrane, nucleolus and nuclear speckles. An acidic dileucine-like motif "ExxxIL" within C1orf115 binds with the AP2 complex and mediates its localization to clathrin-coating pits. The positively charged amphipathic α-helix undergoes acetylation, which redistributes C1orf115 from the plasma membrane and nucleolus to nuclear speckles. C1orf115 is widely expressed and most abundant in the small intestine. The ability of C1orf115 in clathrin-mediated endocytosis is required for its regulation of drug resistance, which is modulated by acetylation. RNA-seq analysis reveals that C1orf115 induces intestinal transcription of another ATP-dependent transporter ABCA1 and consequently promotes ABCA1-mediated cholesterol efflux in enterocytes. Our study provides mechanistic insight into how C1orf115 modulates drug resistance and cholesterol efflux through clathrin-mediated endocytosis and ABCA1 expression.

Unraveling Ferroptosis: A New Frontier in Combating Renal Fibrosis and CKD Progression

Chronic kidney disease (CKD) is a global health concern caused by conditions such as hypertension, diabetes, hyperlipidemia, and chronic nephritis, leading to structural and functional kidney injury. Kidney fibrosis is a common outcome of CKD progression, with abnormal fatty acid oxidation (FAO) disrupting renal energy homeostasis and leading to functional impairments. This results in maladaptive repair mechanisms and the secretion of profibrotic factors, and exacerbates renal fibrosis. Understanding the molecular mechanisms of renal fibrosis is crucial for delaying CKD progression. Ferroptosis is a type of discovered an iron-dependent lipid peroxidation-regulated cell death. Notably, Ferroptosis contributes to tissue and organ fibrosis, which is correlated with the degree of renal fibrosis. This study aims to clarify the complex mechanisms of ferroptosis in renal parenchymal cells and explore how ferroptosis intervention may help alleviate renal fibrosis, particularly by addressing the gap in CKD mechanisms related to abnormal lipid metabolism under the ferroptosis context. The goal is to provide a new theoretical basis for clinically delaying CKD progression.

Bioinformatic characterization of ENPEP, the gene encoding a potential cofactor for SARS-CoV-2 infection

Research on SARS-CoV-2, the viral pathogen that causes COVID-19, has identified angiotensin converting enzyme 2 (ACE2) as the primary viral receptor. Several genes that encode viral cofactors, such as TMPRSS2, NRP1, CTSL, and possibly KIM1, have since been discovered. Glutamyl aminopeptidase (APA), encoded by the gene ENPEP, is another cofactor candidate due to similarities in its biological role and high correlation with ACE2 and other human coronavirus receptors, such as aminopeptidase N (APN) and dipeptidyl peptidase 4 (DPP4). Recent studies have proposed a role for ENPEP as a viral receptor in humans, and ENPEP and ACE2 are both closely involved in the renin-angiotensin-aldosterone system proposed to play an important role in SARS-CoV-2 pathophysiology. We performed bioinformatic analyses using publicly available bulk (>17,000 samples from 49 distinct tissues) and single-cell (>2.5 million cells) RNA-Seq gene expression datasets to evaluate the expression and function of the ENPEP gene. We also investigated age- and sex-related changes in ENPEP expression. Overall, expression of ENPEP was highest in the small intestine enterocyte brush border and the kidney cortex. ENPEP is widely expressed in a subset of vascular smooth muscle cells (likely pericytes) in systemic vasculature, the heart, and the brain. ENPEP is expressed at low levels in the lower respiratory epithelium. In the lung, ENPEP is most highly expressed in para-alveolar fibroblasts. Single-cell data revealed ENPEP expression in a substantial fraction of ependymal cells, a finding not reported before in humans. Age increases ENPEP expression in skeletal muscle and the prostate, while decreasing it in the heart and aorta. Angiogenesis was found to be a central biological function associated with the ENPEP gene. Tissue-specific roles, such as protein digestion and fat metabolism, were also identified in the intestine. In the liver, the gene is linked to the complement system, a connection that has not yet been thoroughly investigated. Expression of ENPEP and ACE2 is strongly correlated in the small intestine and renal cortex. Both overall and in blood vessels, ENPEP and ACE2 have a stronger correlation than many other genes associated with SARS-CoV-2, such as TMPRSS2, CTSL, and NRP1. Possible interaction between glutamyl aminopeptidase and SARS-CoV-2 should be investigated experimentally.

The Molecular and Functional Characterization of Sensory Neuron Membrane Protein 1b (SNMP1b) from Cyrtotrachelus buqueti (Coleoptera: Curculionidae)

Sensory neuron membrane proteins (SNMPs) play important roles in insect chemoreception and SNMP1s have been reported to be essential in detecting sex pheromones in Drosophila and some lepidopteran species. However, SNMPs for Cyrtotrachelus buqueti (Coleoptera: Curculionidae), a major insect pest of bamboo plantations, remain uncharacterized. In this study, a novel SNMP gene, CbuqSNMP1b, from C. buqueti was functionally characterized. The expression of CbuqSNMP1b was significantly higher in antennae than in other tissues of both sexes and the expression level was significantly male-biased. Additionally, CbuqSNMP1b showed significantly higher transcription levels in the adult stage and very low transcription levels in other stages, suggesting that CbuqSNMP1b is involved in the process of olfaction. Fluorescence binding assays indicated that CbuqSNMP1b displayed the strongest binding affinity to dibutyl phthalate (Ki = 9.03 μM) followed by benzothiazole (Ki = 11.59 μM) and phenol (Ki = 20.95 μM) among fourteen C. buqueti volatiles. Furthermore, molecular docking revealed key residues in CbuqSNMP1b that interact with dibutyl phthalate, benzothiazole, and phenol. In conclusion, these findings will lay a foundation to further understand the olfactory mechanisms of C. buqueti and promote the development of novel methods for controlling this pest.

Pancreatic lipase and its related proteins: where are we now?

Obesity is a disease of epidemic proportions, with a worrisome upward trend. The high consumption of lipids, a major energy source, leads to obesity because of their high calorific value. Pancreatic lipase (PTL), produced by pancreatic acinar cells, hydrolyzes 50-70% of triacylglycerol (TAG) from food. PTL-related protein 1 (PLRP1) and 2 (PLRP2) are also produced by these cells. In vertebrates, PLRP1 has relatively less lipolytic activity, whereas PLRP2 has an essential role in lipid digestion, especially in infants. In this review, we summarize the structure and function of PTL, PLRP1, and PLRP2, and the metabolic fate of PTL inhibitors. We also discuss the current status of clinical trials on orlistat and its combinations for obesity treatment.

Kidney lipid dysmetabolism and lipid droplet accumulation in chronic kidney disease

Chronic kidney disease (CKD) is a global health problem with rising incidence and prevalence. Among several pathogenetic mechanisms responsible for disease progression, lipid accumulation in the kidney parenchyma might drive inflammation and fibrosis, as has been described in fatty liver diseases. Lipids and their metabolites have several important structural and functional roles, as they are constituents of cell and organelle membranes, serve as signalling molecules and are used for energy production. However, although lipids can be stored in lipid droplets to maintain lipid homeostasis, lipid accumulation can become pathogenic. Understanding the mechanisms linking kidney parenchymal lipid accumulation to CKD of metabolic or non-metabolic origin is challenging, owing to the tremendous variety of lipid species and their functional diversity across different parenchymal cells. Nonetheless, multiple research reports have begun to emphasize the effect of dysregulated kidney lipid metabolism in CKD progression. For example, altered cholesterol and fatty acid metabolism contribute to glomerular and tubular cell injury. Newly developed lipid-targeting agents are being tested in clinical trials in CKD, raising expectations for further therapeutic development in this field.

Impact of (intestinal) LAL deficiency on lipid metabolism and macrophage infiltration

OBJECTIVE

To date, the only enzyme known to be responsible for the hydrolysis of cholesteryl esters and triacylglycerols in the lysosome at acidic pH is lysosomal acid lipase (LAL). Lipid malabsorption in the small intestine (SI), accompanied by macrophage infiltration, is one of the most common pathological features of LAL deficiency. However, the exact role of LAL in intestinal lipid metabolism is still unknown.

METHODS

We collected three parts of the SI (duodenum, jejunum, ileum) from mice with a global (LAL KO) or intestine-specific deletion of LAL (iLAL KO) and corresponding controls.

RESULTS

We observed infiltration of lipid-associated macrophages into the lamina propria, where neutral lipids accumulate massively in the SI of LAL KO mice. In addition, LAL KO mice absorb less dietary lipids but have accelerated basolateral lipid uptake, secrete fewer chylomicrons, and have increased fecal lipid loss. Inflammatory markers and genes involved in lipid metabolism were overexpressed in the duodenum of old but not in younger LAL KO mice. Despite the significant reduction of LAL activity in enterocytes of enterocyte-specific (iLAL) KO mice, villous morphology, intestinal lipid concentrations, expression of lipid transporters and inflammatory genes, as well as lipoprotein secretion were comparable to control mice.

CONCLUSIONS

We conclude that loss of LAL only in enterocytes is insufficient to cause lipid deposition in the SI, suggesting that infiltrating macrophages are the key players in this process.

Proteomics, dietary intake, and changes in cardiometabolic health within a behavioral weight-loss intervention: A pilot study

OBJECTIVE

Identifying associations among circulating proteins, dietary intakes, and clinically relevant indicators of cardiometabolic health during weight loss may elucidate biologically relevant pathways affected by diet, allowing for an incorporation of precision nutrition approaches when designing future interventions. This study hypothesized that plasma proteins would be associated with diet and cardiometabolic health indicators within a behavioral weight-loss intervention.

METHODS

This secondary data analysis included participants (n = 20, mean [SD], age: 40.1 [9.5] years, BMI: 34.2 [4.0] kg/m2 ) who completed a 1-year behavioral weight-loss intervention. Cardiovascular disease-related plasma proteins, diet, and cardiometabolic health indicators were evaluated at baseline and 3 months. Associations were determined via linear regression and integrated networks created using Visualization Of LineAr Regression Elements (VOLARE).

RESULTS

A total of 16 plasma proteins were associated with ≥1 diet or health indicator at baseline (p < 0.001); changes in 42 proteins were associated with changes in diet or health indicators from baseline to 3 months (p < 0.005). Baseline tumor necrosis factor receptor superfamily member 10C (TNFRSF10C) was associated with intakes of dark green vegetables (r = -0.712), and fatty acid-binding protein 4 (FABP4) was associated with intakes of unsweetened coffee (r = -0.689). Changes in refined-grain intakes were associated with changes in scavenger receptor cysteine-rich type 1 protein M130 (CD163; r = 0.725), interleukin-1 receptor type 1 (IL1R-T1; r = 0.624), insulin (r = 0.656), and triglycerides (r = 0.648).

CONCLUSIONS

Circulating cardiovascular disease-related proteins were associated with diet and cardiometabolic health indicators prior to and in response to weight loss.

Non-Pharmacological Therapeutic Options for the Treatment of Alzheimer's Disease

Alzheimer's disease is a growing global crisis in need of urgent diagnostic and therapeutic strategies. The current treatment strategy mostly involves immunotherapeutic medications that have had little success in halting disease progress. Hypotheses for pathogenesis and development of AD have been expanded to implicate both organ systems as well as cellular reactions. Non-pharmacologic interventions ranging from minimally to deeply invasive have attempted to address these diverse contributors to AD. In this review, we aim to delineate mechanisms underlying such interventions while attempting to provide explanatory links between the observed differences in disease states and postulated metabolic or structural mechanisms of change. The techniques discussed are not an exhaustive list of non-pharmacological interventions against AD but provide a foundation to facilitate a deeper understanding of the area of study.

Efficacy of Polyphenols in the Management of Dyslipidemia: A Focus on Clinical Studies

Polyphenols (PLPs), phytochemicals found in a wide range of plant-based foods, have gained extensive attention in view of their antioxidant, anti-inflammatory, immunomodulatory and several additional beneficial activities. The health-promoting effects noted in animal models of various non-communicable diseases explain the growing interest in these molecules. In particular, in vitro and animal studies reported an attenuation of lipid disorders in response to PLPs. However, despite promising preclinical investigations, the effectiveness of PLPs in human dyslipidemia (DLP) is less clear and necessitates revision of available literature. Therefore, the present review analyzes the role of PLPs in managing clinical DLP, notably by dissecting their potential in ameliorating lipid/lipoprotein metabolism and alleviating hyperlipidemia, both postprandially and in long-term interventions. To this end, PubMed was used for article search. The search terms included polyphenols, lipids, triglycerides, cholesterol, LDL-cholesterol and /or HDL-cholesterol. The critical examination of the trials published to date illustrates certain benefits on blood lipids along with co-morbidities in participant’s health status. However, inconsistent results document significant research gaps, potentially owing to study heterogeneity and lack of rigor in establishing PLP bioavailability during supplementation. This underlines the need for further efforts in order to elucidate and support a potential role of PLPs in fighting DLP.

From Congenital Disorders of Fat Malabsorption to Understanding Intra-Enterocyte Mechanisms Behind Chylomicron Assembly and Secretion

During the last two decades, a large body of information on the events responsible for intestinal fat digestion and absorption has been accumulated. In particular, many groups have extensively focused on the absorptive phase in order to highlight the critical "players" and the main mechanisms orchestrating the assembly and secretion of chylomicrons (CM) as essential vehicles of alimentary lipids. The major aim of this article is to review understanding derived from basic science and clinical conditions associated with impaired packaging and export of CM. We have particularly insisted on inborn metabolic pathways in humans as well as on genetically modified animal models (recapitulating pathological features). The ultimate goal of this approach is that "experiments of nature" and in vivo model strategy collectively allow gaining novel mechanistic insight and filling the gap between the underlying genetic defect and the apparent clinical phenotype. Thus, uncovering the cause of disease contributes not only to understanding normal physiologic pathway, but also to capturing disorder onset, progression, treatment and prognosis.

The role of SNMPs in insect olfaction

The sense of smell enables insects to recognize olfactory signals crucial for survival and reproduction. In insects, odorant detection highly depends on the interplay of distinct proteins expressed by specialized olfactory sensory neurons (OSNs) and associated support cells which are housed together in chemosensory units, named sensilla, mainly located on the antenna. Besides odorant-binding proteins (OBPs) and olfactory receptors, so-called sensory neuron membrane proteins (SNMPs) are indicated to play a critical role in the detection of certain odorants. SNMPs are insect-specific membrane proteins initially identified in pheromone-sensitive OSNs of Lepidoptera and are indispensable for a proper detection of pheromones. In the last decades, genome and transcriptome analyses have revealed a wide distribution of SNMP-encoding genes in holometabolous and hemimetabolous insects, with a given species expressing multiple subtypes in distinct cells of the olfactory system. Besides SNMPs having a neuronal expression in subpopulations of OSNs, certain SNMP types were found expressed in OSN-associated support cells suggesting different decisive roles of SNMPs in the peripheral olfactory system. In this review, we will report the state of knowledge of neuronal and non-neuronal members of the SNMP family and discuss their possible functions in insect olfaction.

Identification and Characterization of Two Sensory Neuron Membrane Proteins From Onion Maggot (Diptera: Anthomyiidae)

Sensory neuron membrane proteins (SNMPs) in insects are critical peripheral olfactory proteins and act as markers for pheromone detection. However, the SNMPs for onion maggot, Delia antiqua Meigen, a world-wide subterranean pest, have not been previously characterized. In this study, we first report the cloning and characterization of two novel SNMPs from D. antiqua, DantSNMP1 and DantSNMP2. Sequence alignment and phylogenetic analysis showed that DantSNMP1 and DantSNMP2 are very similar to the previously reported SNMP1 and SNMP2 isolated from other dipteran insects but they share low identity with each other. Further expression profile experiments showed that DantSNMP1 is antenna-specific, while DantSNMP2 is expressed both in antennae and nonantennal tissues. Immunocytochemical localization experiments showed that DantSNMP1 was expressed only in sensilla trichodae, which suggests that this protein is involved in pheromone reception in insect olfaction.

Xanthohumol Suppresses NPC1L1 Gene Expression through Downregulation of HNF-4α and Inhibits Cholesterol Uptake in Caco-2 Cells

Xanthohumol (Xan) is a prenylated chalcone mainly found in hops; it has been demonstrated to function against hypercholesterolemia, hyperlipidemia, and atherosclerosis. In this study, we focused on the hypocholesterolemic effect of Xan on cholesterol uptake and the underlying molecular mechanisms of Xan in human intestinal Caco-2 cells. The microarray data showed that Niemann-Pick C1-like 1 (NPC1L1), an essential transporter for dietary cholesterol absorption, was significantly downregulated in Xan-treated Caco-2 cells. We demonstrated that Xan (10 and 20 μM) suppressed the mRNA and protein expression of NPC1L1 by 0.65 ± 0.12-fold and 0.54 ± 0.15-fold and 0.72 ± 0.04-fold and 0.44 ± 0.12-fold, respectively, compared to that of the vehicle-treated Caco-2 cells. Moreover, Xan (10 and 20 μM) significantly inhibited cholesterol uptake by approximately 12 and 32% in Caco-2 cells. NPC1L1 promoter activity was significantly suppressed by Xan, and a DNA element within the NPC1L1 promoter involved in Xan-mediated NPC1L1 reduction located between the -120 and -20 positions was identified. Moreover, Xan markedly decreased the mRNA and protein levels of hepatocyte nuclear factor 4α (HNF-4α), a critical activator of NPC1L1 transcription, and subsequently attenuated HNF-4α/NPC1L1 promoter complex formation, resulting in the suppression of NPC1L1 gene expression. Finally, we demonstrated that Xan markedly abolished lovastatin-induced NPC1L1 overexpression in Caco-2 cells. These findings reveal that Xan suppresses NPC1L1 expression via downregulation of HNF-4α and exerts inhibitory effects on cholesterol uptake in the intestinal Caco-2 cells. Our findings suggest Xan could serve as a potential cholesterol-lowering agent and supplement for statin therapy.

The expression patterns of SNMP1 and SNMP2 underline distinct functions of two CD36-related proteins in the olfactory system of the tobacco budworm Heliothis virescens

In insects, male and female pheromone signals are detected by olfactory sensory neurons (OSNs) expressing the "sensory neuron membrane protein type 1". SNMP1 is supposed to function as a co-receptor involved in the transfer of pheromones to adjacent pheromone receptors. In the moth Heliothis virescens, we previously found OSNs that project their dendrites into pheromone-responsive trichoid sensilla and are associated with cells containing transcripts for the HvirSNMP1-related protein HvirSNMP2. Like HvirSNMP1, HvirSNMP2 belongs to the CD36-family of two-transmembrane domain receptors and transporters for lipophilic compounds, but its role in the olfactory system is unknown. Here, we generated polyclonal anti-peptide antibodies against HvirSNMP2 as well as HvirSNMP1 and conducted an in-depth immunohistochemical analysis of their subcellular localization in the antenna of both sexes. In line with a function in pheromone detection, HvirSNMP1 was immunodetected in the somata and the dendrites of distinct OSNs in subsets of trichoid sensilla. These trichoid sensilla contained only one α-SNMP1-positive OSN in males and clusters of 2-3 labeled cells in females. In contrast, experiments with α-SNMP2-antibodies revealed a broad labeling of non-neuronal support cells (SCs) that are associated with OSNs in likely all trichoid and basiconic sensilla of the antenna with no differences between sexes. Detailed confocal microscope examinations of olfactory sensilla revealed SNMP2-like immunoreactivity close to the apical membrane of SCs and interestingly inside the sensillum. Together, these findings indicate a potential function of SNMP2 in pheromone- as well as general odorant-responsive sensilla and a role fundamentally different from SNMP1.

Expression patterns and colocalization of two sensory neurone membrane proteins in Ectropis obliqua Prout, a geometrid moth pest that uses Type-II sex pheromones

Sensory neurone membrane proteins (SNMPs) function as essential cofactors for insect sex pheromone detection. In this study, we report two SNMPs in Ectropis obliqua Prout, a serious geometrid pest that produces typical Type-II sex pheromones. Sequence alignments and phylogenetic analyses showed that EoblSNMP1 and EoblSNMP2 belong to two distinct SNMP subfamilies. Quantitative real-time PCR suggested that EoblSNMP1 was male antennae-biased, whereas EoblSNMP2 was highly expressed on male antennae but was also expressed on female antennae and other chemosensory tissues. Additionally, EoblSNMP1 and EoblSNMP2 differed in their developmental expression profiles. In situ hybridization revealed that EoblSNMP1 was sensilla trichodea I specific, whereas EoblSNMP2 was expressed in sensilla trichodea I and the sensilla basiconica; furthermore, EoblSNMP1 and EoblSNMP2 were co-expressed in sensilla trichodea I but in different cells. This study suggests that EoblSNMP1 is functionally distinct from EoblSNMP2 in E. obliqua; EoblSNMP1 may specifically contribute to the recognition of sex pheromones, whereas EoblSNMP2 exhibits multiple olfactory roles. Our findings comprehensively reveal the expression patterns of SNMPs in a lepidopteran species that uses Type-II sex pheromones, providing new insights into the functional evolution of SNMPs from lepidopteran moths with Type-I sex pheromones to those with Type-II sex pheromones.

Gastrointestinal factors regulating lipid droplet formation in the intestine

Cytoplasmic lipid droplets (CLD) are considered as neutral lipid reservoirs, which protect cells from lipotoxicity. It became clear that these fascinating dynamic organelles play a role not only in energy storage and metabolism, but also in cellular lipid and protein handling, inter-organelle communication, and signaling among diverse functions. Their dysregulation is associated with multiple disorders, including obesity, liver steatosis and cardiovascular diseases. The central aim of this review is to highlight the link between intra-enterocyte CLD dynamics and the formation of chylomicrons, the main intestinal dietary lipid vehicle, after overviewing the morphology, molecular composition, biogenesis and functions of CLD.

Dietary lipid content reorganizes gut microbiota and probiotic L. rhamnosus attenuates obesity and enhances catabolic hormonal milieu in zebrafish

In the present study, we explored whether dietary lipid content influences the gut microbiome in adult zebrafish. Diets containing three different lipid levels (high [HFD], medium [MFD], and low [LFD]) were administered with or without the supplementation of Lactobacillus rhamnosus (P) to zebrafish in order to explore how the dietary lipid content may influence the gut microbiome. Dietary lipid content shifted the gut microbiome structure. The addition of L. rhamnosus in the diets, induced transcriptional reduction of orexigenic genes, upregulation of anorexigenic genes, and transcriptional decrease of genes involved in cholesterol and triglyceride (TAG) metabolism, concomitantly with lower content of cholesterol and TAG. Probiotic feeding also decreased nesfatin-1 peptide in HFD-P and attenuated weight gain in HFD-P and MFD-P fed zebrafish, but not in LFD-P group. Intestinal ultrastructure was not affected by dietary fat level or probiotic inclusion. In conclusion, these findings underline the role of fat content in the diet in altering gut microbiota community by shifting phylotype composition and highlight the potential of probiotics to attenuate high-fat diet-related metabolic disorder.

Ezetimibe increases intestinal expression of the LDL receptor gene in dyslipidaemic men with insulin resistance

AIM

To gain further insight into intestinal cholesterol homeostasis in dyslipidaemic men with insulin resistance (IR) by examining the impact of treatment with ezetimibe on the expression of key genes involved in cholesterol synthesis and LDL receptor (R)-mediated uptake of lipoproteins.

METHODS

A total of 25 men with dyslipidaemia and IR were recruited to participate in this double-blind, randomized, crossover, placebo-controlled trial. Participants received 10 mg/day ezetimibe or placebo for periods of 12 weeks each. Intestinal gene expression was measured by quantitative PCR in duodenal biopsy samples collected by gastroduodenoscopy at the end of each treatment.

RESULTS

A total of 20 participants completed the protocol. Treatment with ezetimibe significantly increased intestinal LDLR (+16.2%; P = .01), 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG-CoAR; +14.0%; P = .04) and acetyl-Coenzyme A acetyltransferase 2 (ACAT-2) mRNA expression (+12.5%; P = .03). Changes in sterol regulatory element-binding transcription factor 2 (SREBP-2) expression were significantly correlated with changes in HMG-CoAR (r = 0.55; P < .05), ACAT-2 (r = 0.69; P < .001) and proprotein convertase substilisin/kexin type 9 (PCSK9) expression (r = 0.45; P < .05).

CONCLUSIONS

These results show that inhibition of intestinal cholesterol absorption by ezetimibe increases expression of the LDLR gene, supporting the concept that increased LDL clearance with ezetimibe treatment occurs not only in the liver but also in the small intestine.

Using fluorescent lipids in live zebrafish larvae: From imaging whole animal physiology to subcellular lipid trafficking

Lipids serve essential functions in cells as signaling molecules, membrane components, and sources of energy. Defects in lipid metabolism are implicated in a number of pandemic human diseases, including diabetes, obesity, and hypercholesterolemia. Many aspects of how fatty acids and cholesterol are absorbed and processed by intestinal cells remain unclear and present a hurdle to developing approaches for disease prevention and treatment. Numerous studies have shown that the zebrafish is an excellent model for vertebrate lipid metabolism. In this chapter, we review commercially available fluorescent lipids that can be deployed in live zebrafish to better understand lipid signaling and metabolism. In this chapter, we present criteria one should consider when selecting specific fluorescent lipids for the study of digestive physiology or lipid metabolism in larval zebrafish.

Identification of nonabsorbable inhibitors of the scavenger receptor-BI (SR-BI) for tissue-specific administration

The identification of a low-permeability scavenger receptor BI (SR-BI) inhibitor starting from the ITX-5061 template is described. Structure-activity and structure-permeability relationships were assessed for analogs leading to the identification of compound 8 as a potent and nonabsorbable SR-BI inhibitor.

Cholesterol Absorption and Metabolism

Inhibitors of cholesterol absorption have been sought for decades as a means to treat and prevent cardiovascular diseases (CVDs) associated with hypercholesterolemia. Ezetimibe is the one clear success story in this regard, and other compounds with similar efficacy continue to be sought. In the last decade, the laboratory mouse, with all its genetic power, has become the premier experimental model for discovering the mechanisms underlying cholesterol absorption and has become a critical tool for preclinical testing of potential pharmaceutical entities. This chapter briefly reviews the history of cholesterol absorption research and the various gene candidates that have come under consideration as drug targets. The most common and versatile method of measuring cholesterol absorption is described in detail along with important considerations when interpreting results, and an alternative method is also presented. In recent years, reverse cholesterol transport (RCT) has become an area of intense new interest for drug discovery since this process is now considered another key to reducing CVD risk. The ultimate measure of RCT is sterol excretion and a detailed description is given for measuring neutral and acidic fecal sterols and interpreting the results.

Biomarkers of cholesterol homeostasis in a clinical laboratory database sample comprising 667,718 patients

BACKGROUND

Circulating noncholesterol sterols/stanols (NCS) are used in clinical lipidology as surrogate measures of cholesterol synthesis and absorption, where they can be valuable tools in assessing cholesterol metabolism and personalizing therapies in patients with dyslipidemia.

OBJECTIVES

To describe the distributions of plasma NCS concentrations and inter-NCS correlations in a large cohort of American patients constituting a clinical laboratory database, and to investigate the relationship between circulating NCS, age, sex, and apolipoprotein E (APOE) genotype.

METHODS

A total of 667,718 patient blood samples submitted for testing to Health Diagnostic Laboratory, Inc. (Richmond, VA) were analyzed for cholesterol absorption markers (sitosterol, campesterol, and cholestanol) and one cholesterol synthesis marker (desmosterol). NCS percentiles were determined, along with intermarker correlations (Pearson's R). Analysis of variance was used to assess the effect of age and sex on NCS level, and to evaluate the relationship between cholesterol synthesis/absorption status and APOE genotype in a subset of 336,866 patients.

RESULTS

Mean NCS concentrations were: sitosterol, 2.45 μg/mL; campesterol, 3.3 μg/mL; cholestanol, 2.92 μg/mL; and desmosterol 0.99 μg/mL. The correlations between each NCS and its ratio to total cholesterol ranged from 0.72 (cholestanol) to 0.94 (desmosterol). NCS levels were significantly affected by age and sex (P < .0001), and prevalence of cholesterol hyperabsorption was higher in APOE ε4 allele carriers compared with the other APOE genotypes.

CONCLUSIONS

We have described sample distributions of NCS biomarkers and characterized their relationship to age, sex, and APOE genotype. These data may facilitate research into altered cholesterol homeostasis and human disease, and help physicians optimize lipid-lowering therapies.

Lactobacillus rhamnosus lowers zebrafish lipid content by changing gut microbiota and host transcription of genes involved in lipid metabolism

The microbiome plays an important role in lipid metabolism but how the introduction of probiotic communities affects host lipid metabolism is poorly understood. Using a multidisciplinary approach we addressed this knowledge gap using the zebrafish model by coupling high-throughput sequencing with biochemical, molecular and morphological analysis to evaluate the changes in the intestine. Analysis of bacterial 16S libraries revealed that Lactobacillus rhamnosus was able to modulate the gut microbiome of zebrafish larvae, elevating the abundance of Firmicutes sequences and reducing the abundance of Actinobacteria. The gut microbiome changes modulated host lipid processing by inducing transcriptional down-regulation of genes involved in cholesterol and triglycerides metabolism (fit2, agpat4, dgat2, mgll, hnf4α, scap, and cck) concomitantly decreasing total body cholesterol and triglyceride content and increasing fatty acid levels. L. rhamnosus treatment also increased microvilli and enterocyte lengths and decreased lipid droplet size in the intestinal epithelium. These changes resulted in elevated zebrafish larval growth. This integrated system investigation demonstrates probiotic modulation of the gut microbiome, highlights a novel gene network involved in lipid metabolism, provides an insight into how the microbiome regulates molecules involved in lipid metabolism, and reveals a new potential role for L. rhamnosus in the treatment of lipid disorders.

Identification and localization of two sensory neuron membrane proteins from Spodoptera litura (Lepidoptera: Noctuidae)

Sensory neuron membrane proteins (SNMPs), which are located on the dendritic membrane of olfactory sensory neurons (OSNs), are proposed to be associated with odor reception in insects. Recent studies have demonstrated that SNMP1 is essential for electrophysiological responses of OSNs to the sex pheromone, cis-vaccenyl acetate (cVA) in Drosophila melanogaster. To investigate the function of Lepidoptera SNMPs, we cloned two SNMP genes, SlituSNMP1 and SltiuSNMP2, from Spodoptera litura (Lepidoptera: Noctuidae). Sequence alignment and phylogenetic analysis showed that both genes bear the general characteristics of SNMPs, including six conserved cysteine residues and two transmembrane domains. Further expression profile experiments showed that SlituSNMP1 is mainly expressed in the antenna, while SlituSNMP2 is broadly expressed in various tissues. By in situ hybridization experiments, it was found that SlituSNMP1 expressing cells are surrounded by the SlituSNMP2 expressing cells in the pheromone sensitive sensilla, suggesting different functions of the two SNMPs in insect olfaction.

Pheromone reception in moths: from molecules to behaviors

Male moths detect and find their mates using species-specific sex pheromones emitted by conspecific females. Olfaction plays a vital role in this behavior. Since the first discovery of an insect sex pheromone from the silkmoth Bombyx mori, great efforts have been spent on understanding the sensing of the pheromones in vivo. Much progress has been made in elucidating the molecular mechanisms that mediate chemoreception in insects in the past few decades. In this review, we focus on pheromone reception and detection in moths, from the molecular to the behavioral level. We trace the information pathway from the capture of pheromone by male antennae, binding and transportation to olfactory receptor neurons, receptor activation, signal transduction, molecule inactivation, through brain processing and behavioral response. We highlight the impact of recent studies and also provide our insights into pheromone processing.

Dab2, megalin, cubilin and amnionless receptor complex might mediate intestinal endocytosis in the suckling rat

We previously proposed that Dab2 participates in the endocytosis of milk macromolecules in rat small intestine. Here we investigate the receptors that may mediate this endocytosis by studying the effects of age and diet on megalin, VLDLR, and ApoER2 expression, and that of age on the expression of cubilin and amnionless. Of megalin, VLDLR and ApoER2, only the megalin expression pattern resembles that of Dab2 previously reported. Thus the mRNA and protein levels of megalin and Dab2 are high in the intestine of the suckling rat, down-regulated by age and up-regulated by milk diet, mainly in the ileum. Neither age nor diet affect ApoER2 mRNA levels. The effect of age on VLDLR mRNA levels depends on the epithelial cell tested but they are down-regulated by milk diet. In the suckling rat, the intestinal expressions of both cubilin and amnionless are similar to that of megalin and megalin, cubilin, amnionless and Dab2 co-localize at the microvilli and in the apical endocytic apparatus. Co-localization of Dab2 with ApoER2 and VLDLR at the microvilli and in the apical endocytic apparatus is also observed. This is the first report showing intestinal co-localization of: megalin/cubilin/amnionless/Dab2, VLDLR/Dab2 and ApoER2/Dab2. We conclude that the megalin/cubilin/amnionless/Dab2 complex/es participate in intestinal processes, mainly during the lactation period and that Dab2 may act as an adaptor in intestinal processes mediated by ApoER2 and VLDLR.

Scavenger receptor class B, type I (Scarb1) deficiency promotes osteoblastogenesis but stunts terminal osteocyte differentiation

Scavenger receptor class B type I (SR-BI), the Scarb1 gene product, is a high-density lipoprotein (HDL) receptor which was shown to influence bone metabolism. Its absence in mice is associated with alterations of the glucocorticoid/adrenocorticotropic hormone axis, and translated in high bone mass and enhanced bone formation. Since the cellular alterations underlying the enhanced bone formation remain unknown, we investigated Scarb1-deficient marrow stromal cells (MSC) behavior in vitro. No difference in HDL3, cholesteryl ester (CE) or estradiol (E) association/binding was measured between Scarb1-null and wild-type (WT) cells. Scarb1 genic expression was down-regulated twofold following osteogenic treatment. Neither WT nor null cell proliferation was influenced by HDL3 exposure whereas this condition decreased genic expression of osteoblastic marker osterix (Sp7), and osteocyte markers sclerostin (Sost) and dentin matrix protein 1 (Dmp1) independently of genotype. Sost and Dmp1 basal expression in null cells was 40% and 50% that of WT cells; accordingly, osteocyte density was 20% lower in vertebrae from Scarb1-null mice. Genic expression of co-receptors for Wnt signaling, namely LDL-related protein (Lrp) 5 and Lrp8, was increased, respectively, by two- and threefold, and of transcription target-genes axis inhibition protein 2 (Axin2) and lymphoid enhancer-binding factor 1 (Lef1) over threefold. Gene expression of Wnt signaling agonist Wnt5a and of the antagonist dickkopfs-related protein 1 (Dkk1) were found to be increased 10- to 20-fold in null MSC. These data suggest alterations of Wnt pathways in Scarb1-deficient MSC potentially explaining their enhanced function, hence contributing to the high bone mass observed in these mice.

Lactobacillus acidophilus ATCC 4356 prevents atherosclerosis via inhibition of intestinal cholesterol absorption in apolipoprotein E-knockout mice

The objective of this study was to investigate the effect of Lactobacillus acidophilus ATCC 4356 on the development of atherosclerosis in apolipoprotein E-knockout (ApoE(-/-)) mice. Eight-week-old ApoE(-/-) mice were fed a Western diet with or without L. acidophilus ATCC 4356 daily for 16 weeks. L. acidophilus ATCC 4356 protected ApoE(-/-) mice from atherosclerosis by reducing their plasma cholesterol levels from 923 ± 44 to 581 ± 18 mg/dl, likely via a marked decrease in cholesterol absorption caused by modulation of Niemann-Pick C1-like 1 (NPC1L1). In addition, suppression of cholesterol absorption induced reverse cholesterol transport (RCT) in macrophages through the peroxisome proliferator-activated receptor/liver X receptor (PPAR/LXR) pathway. Fecal lactobacillus and bifidobacterium counts were significantly (P < 0.05) higher in the L. acidophilus ATCC 4356 treatment groups than in the control groups. Furthermore, L. acidophilus ATCC 4356 was detected in the rat small intestine, colon, and feces during the feeding trial. The bacterial levels remained high even after the administration of lactic acid bacteria had been stopped for 2 weeks. These results suggest that administration of L. acidophilus ATCC 4356 can protect against atherosclerosis through the inhibition of intestinal cholesterol absorption. Therefore, L. acidophilus ATCC 4356 may be a potential therapeutic material for preventing the progression of atherosclerosis.

Sequence-specific alterations of epitope production by HIV protease inhibitors

Ag processing by intracellular proteases and peptidases and epitope presentation are critical for recognition of pathogen-infected cells by CD8+ T lymphocytes. First-generation HIV protease inhibitors (PIs) alter proteasome activity, but the effect of first- or second-generation PIs on other cellular peptidases, the underlying mechanism, and impact on Ag processing and epitope presentation to CTL are still unknown. In this article, we demonstrate that several HIV PIs altered not only proteasome but also aminopeptidase activities in PBMCs. Using an in vitro degradation assay involving PBMC cytosolic extracts, we showed that PIs altered the degradation patterns of oligopeptides and peptide production in a sequence-specific manner, enhancing the cleavage of certain residues and reducing others. PIs affected the sensitivity of peptides to intracellular degradation, and altered the kinetics and amount of HIV epitopes produced intracellularly. Accordingly, the endogenous degradation of incoming virions in the presence of PIs led to variations in CTL-mediated killing of HIV-infected cells. By altering host protease activities and the degradation patterns of proteins in a sequence-specific manner, HIV PIs may diversify peptides available for MHC class I presentation to CTL, alter the patterns of CTL responses, and provide a complementary approach to current therapies for the CTL-mediated clearance of abnormal cells in infection, cancer, or other immune disease.

Loss of von Hippel-Lindau protein (VHL) increases systemic cholesterol levels through targeting hypoxia-inducible factor 2α and regulation of bile acid homeostasis

Cholesterol synthesis is a highly oxygen-dependent process. Paradoxically, hypoxia is correlated with an increase in cellular and systemic cholesterol levels and risk of cardiovascular diseases. The mechanism for the increase in cholesterol during hypoxia is unclear. Hypoxia signaling is mediated through hypoxia-inducible factor 1α (HIF-1α) and HIF-2α. The present study demonstrates that activation of HIF signaling in the liver increases hepatic and systemic cholesterol levels due to a decrease in the expression of cholesterol hydroxylase CYP7A1 and other enzymes involved in bile acid synthesis. Specifically, activation of hepatic HIF-2α (but not HIF-1α) led to hypercholesterolemia. HIF-2α repressed the circadian expression of Rev-erbα, resulting in increased expression of E4BP4, a negative regulator of Cyp7a1. To understand if HIF-mediated decrease in bile acid synthesis is a physiologically relevant pathway by which hypoxia maintains or increases systemic cholesterol levels, two hypoxic mouse models were assessed, an acute lung injury model and mice exposed to 10% O2 for 3 weeks. In both models, cholesterol levels increased with a concomitant decrease in expression of genes involved in bile acid synthesis. The present study demonstrates that hypoxic activation of hepatic HIF-2α leads to an adaptive increase in cholesterol levels through inhibition of bile acid synthesis.

Control of cholesterol homeostasis by entero-hepatic bile transport – the role of feedback mechanisms

Cholesterol homeostasis is achieved through a tight regulation between synthesis, dietary absorption, utilization of bile salts, and excretion in the entero-hepatic compartment.

Evaluation of cholesterol absorption and biosynthesis by decoctions of Annona cherimola leaves

ETHNOPHARMACOLOGICAL RELEVANCE

Decoctions of the leaves of Annona cherimola Mill. are traditionally used in Azores to treat hypercholesterolemia. Although they are sold and consumed by people in order to improve their health, these are products that cannot be sold with claims for health benefits as they have never been studied scientifically.

MATERIALS AND METHODS

The activities of decoctions from Annona cherimola leaves were analysed for the two therapeutic approaches currently used to reduce plasma cholesterol: inhibition of dietary cholesterol uptake and inhibition of HMG-CoA reductase activity. Furthermore, the composition of the decoction was elucidated by LC-MS and the permeability of the active components was analysed using Caco-2 cell monolayers as a model of the intestinal barrier (dietary cholesterol uptake).

RESULTS

The chemical composition of the Annona cherimola leaves' extract revealed that rutin was its main component. The in vitro gastrointestinal digestion did not modify the chemical composition of the extract. This extract was able to originate a slight reduction in cholesterol absorption through Caco-2 cells lines and to reduce the HMG-CoA reductase activity in 50% when using 137.3 μg of the extract/mL. Rutin, when used in the same concentration as that found in the extract, was able to reduce cholesterol absorption through Caco-2 cells monolayer in approximately 47%. This flavonoid had an IC50 of 17.85 μM relatively to the HMG-CoA reductase activity.

CONCLUSIONS

The traditional use of decoctions from the leaves of Annona cherimola may be justified, at least by the inhibition of HMG-CoA reductase activity.

Role of the apical and basolateral domains of the enterocyte in the regulation of cholesterol transport by a high glucose concentration

We have recently shown that a high glucose (HG) concentration raised intestinal cholesterol (CHOL) transport and metabolism in intestinal epithelial cells. The objective of the present work is to determine whether the stimulus for increased CHOL absorption by glucose originates from the apical site (corresponding to the intestinal lumen) or from the basolateral site (related to blood circulation). We tackled this issue by using differentiated Caco-2/15 cells. Only basolateral medium, supplemented with 25 mmol/L glucose, stimulated [(14)C]-CHOL uptake via the up-regulation of the critical CHOL transporter NPC1L1 protein, as confirmed by its specific ezetimibe inhibitor that abolished the rise in glucose-mediated CHOL capture. No significant changes were noted in SR-BI and CD36. Elevated CHOL uptake was associated with an increase in the transcription factors SREBP-2, LXR-β, and ChREBP, along with a fall in RXR-α. Interestingly, although the HG concentration in the apical medium caused modest changes in CHOL processing, its impact was synergetic with that of the basolateral medium. Our results suggest that HG concentration influences positively intestinal CHOL uptake when present in the basolateral medium. In addition, excessive consumption of diets containing high levels of carbohydrates may strengthen intestinal CHOL uptake in metabolic syndrome, thereby contributing to elevated levels of circulating CHOL and, consequently, the risk of developing type 2 diabetes and cardiovascular disease.

Ezetimibe and bile acid sequestrants: impact on lipoprotein metabolism and beyond

PURPOSE OF REVIEW

Several lines of evidence indicate that the enterocyte plays a pivotal role in cholesterol homeostasis. The development of the selective inhibitor of cholesterol absorption ezetimibe and bile acid sequestrants (BAS) interrupting the enterohepatic circulation of bile salts has expanded the options for preventing and treating cardiovascular disease. We discuss here a selection of recently published studies that evaluated the effects of ezetimibe and BAS on lipoprotein metabolism.

RECENT FINDINGS

Although significant progress has been made in recent years in elucidating the impacts of ezetimibe and BAS on lipoprotein metabolism, underlying mechanisms are not completely understood. Important new insights have been provided by using in-vivo kinetic studies of apolipoproteins labelled with a stable isotope. Other reports indicated that ezetimibe and BAS modulate the expression of several key genes involved in intestinal lipoprotein metabolism. Many of these effects have been related to the local effects of ezetimibe and BAS on intestinal cholesterol homeostasis.

SUMMARY

A substantial effort is being made by researchers to fully understand the mechanisms by which ezetimibe and BAS improve lipid profile. The efficacy of combination therapy of statins with ezetimibe or BAS for the prevention of cardiovascular disease remains to be confirmed in clinical endpoint studies.

Molecular identification and differential expression of sensory neuron membrane proteins in the antennae of the black cutworm moth Agrotis ipsilon

The insect sensory neuron membrane proteins (SNMPs) SNMP1 and SNMP2 are transmembrane domain-containing proteins and are homologs of the vertebrate CD36 transmembrane proteins. It has been suggested that SNMPs play a significant role in insect chemoreception. Previous studies have demonstrated that SNMP1 is expressed in the pheromone-sensitive olfactory receptor neurons (ORNs), whereas SNMP2 is expressed in the supporting cells. In this study, we identified two full-length SNMP transcripts, AipsSNMP1 and AipsSNMP2, in the black cutworm moth Agrotis ipsilon (Hufnagel). The qRT-PCR results indicated that the AipsSNMP1 and AipsSNMP2 transcripts were expressed significantly higher in the antennae than in other tissues of both sexes. The expression of AipsSNMP1 and AipsSNMP2 in the antennae from different development stages of both sexes was investigated and was shown to begin to express in the pupae stage from 3days before emergence and then increased dramatically at the day of the emergence, and the high expression levels were maintained during the following 4days after the emergence in both sexes. The mating status had no effect on the expression levels of the AipsSNMP1 and AipsSNMP2 transcripts. Consistent with previous in situ hybridization studies in other Lepidoptera insects, our immunolocalization results at protein level demonstrated that both AipsSNMP1 and AipsSNMP2 were expressed in pheromone-sensitive sensilla trichodea but with a completely different expression profile. AipsSNMP1 is more uniformed and highly expressed along the membrane of the ORN dendrites, whereas AipsSNMP2 is widely distributed at the bottom of the sensilla trichodea and highly localized in the sensillum lymph. Our studies provide further detailed evidence for the involvement and general functional role of insect SNMPs in the detection of sex pheromones and general odorant molecules.

Acute Psychological Stress Accelerates Reverse Cholesterol Transport via Corticosterone-Dependent Inhibition of Intestinal Cholesterol Absorption

Rationale:

Psychological stress is associated with an increased risk of cardiovascular diseases. However, the connecting mechanisms of the stress-inducing activation of the hypothalamic-pituitary-adrenal axis with atherosclerosis are not well-understood.

Objective:

To study the effect of acute psychological stress on reverse cholesterol transport (RCT), which transfers peripheral cholesterol to the liver for its ultimate fecal excretion.

Methods and Results:

C57Bl/6J mice were exposed to restraint stress for 3 hours to induce acute psychological stress. RCT in vivo was quantified by measuring the transfer of [ 3 H]cholesterol from intraperitoneally injected mouse macrophages to the lumen of the small intestine within the stress period. Surprisingly, stress markedly increased the contents of macrophage-derived [ 3 H]cholesterol in the intestinal lumen. In the stressed mice, intestinal absorption of [ 14 C]cholesterol was significantly impaired, the intestinal mRNA expression level of peroxisome proliferator–activated receptor-α increased, and that of the sterol influx transporter Niemann-Pick C1–like 1 decreased. The stress-dependent effects on RCT rate and peroxisome proliferator–activated receptor-α gene expression were fully mimicked by administration of the stress hormone corticosterone (CORT) to nonstressed mice, and they were blocked by the inhibition of CORT synthesis in stressed mice. Moreover, the intestinal expression of Niemann-Pick C1–like 1 protein decreased when circulating levels of CORT increased. Of note, when either peroxisome proliferator-activated receptor α or liver X receptor α knockout mice were exposed to stress, the RCT rate remained unchanged, although plasma CORT increased. This indicates that activities of both transcription factors were required for the RCT-accelerating effect of stress.

Conclusions:

Acute psychological stress accelerated RCT by compromising intestinal cholesterol absorption. The present results uncover a novel functional connection between the hypothalamic-pituitary-adrenal axis and RCT that can be triggered by a stress-induced increase in circulating CORT.

An atherogenic diet decreases liver FXR gene expression and causes severe hepatic steatosis and hepatic cholesterol accumulation: effect of endurance training

PURPOSE

The aim of this study was to determine the effects of an atherogenic diet (AD; 40 % lipid, 1.25 % cholesterol, kcal) on triglyceride (TAG) and cholesterol accumulation in liver and on gene expression of liver X receptor (LXR) and farnesoid X receptor (FXR) and their target genes and to observe if these responses are affected by endurance training.

METHODS

Sprague-Dawley rats (n = 32) were divided into two groups and randomly assigned to an AD or a standard diet (SD) for 7 weeks. Half of the rats in each group were assigned to an exercise training program for 5 days/week.

RESULTS

The AD resulted in a large (P < 0.01) accumulation in liver TAG (4×) along with elevated liver and plasma cholesterol without any gain in peripheral fat mass. The liver TAG and cholesterol accumulations were associated with an important reduction (P < 0.01; 60 %) in FXR, but no change in LXR transcripts. Accompanying the reduction in FXR gene expression, we found an increase (P < 0.001) in SREBP-1c and a decrease (P < 0.01) in MTP mRNAs suggesting an increased lipogenesis and a reduced VLDL production, respectively. The AD was also associated with lower HMG-CoA-r, squalene synthase, and ABCG8 transcripts (P < 0.001). In the intestine, exercise training resulted in higher NPC1L1, ABCG5, and ABCG8 in SD-fed animals, while all these increases were suppressed under the AD feeding.

CONCLUSIONS

It is concluded that dietary cholesterol favors liver TAG and cholesterol accumulations associated with an important reduction in FXR transcripts.

Milk phospholipid and plant sterol-dependent modulation of plasma lipids in healthy volunteers

PURPOSE

Hypolipidemic and/or hypocholesterolemic effects are presumed for dietary milk phospholipid (PL) as well as plant sterol (PSt) supplementation. The aim was to induce changes in plasma lipid profile by giving different doses of milk PL and a combination of milk PL with PSt to healthy volunteers.

METHODS

In an open-label intervention study, 14 women received dairy products enriched with moderate (3 g PL/day) or high (6 g PL/day) dose of milk PL or a high dose of milk PL combined with PSt (6 g PL/day + 2 g PSt/day) during 3 periods each lasting 10 days.

RESULTS

Total cholesterol concentration and HDL cholesterol concentration were reduced following supplementation with 3 g PL/day. No significant change in LDL cholesterol concentration was found compared with baseline. High PL dose resulted in an increase of LDL cholesterol and unchanged HDL cholesterol compared with moderate PL dose. The LDL/HDL ratio and triglyceride concentration remained constant within the study. Except for increased phosphatidyl ethanolamine concentrations, plasma PL concentrations were not altered during exclusive PL supplementations. A combined high-dose PL and PSt supplementation led to decreased plasma LDL cholesterol concentration, decreased PL excretion, increased plasma sphingomyelin/phosphatidyl choline ratio, and significant changes in plasma fatty acid distribution compared with exclusive high-dose PL supplementation.

CONCLUSION

Milk PL supplementations influence plasma cholesterol concentrations, but without changes of LDL/HDL ratio. A combined high-dose milk PL and PSt supplementation decreases plasma LDL cholesterol concentration, but it probably enforces absorption of fatty acids or fatty acid-containing hydrolysis products that originated during lipid digestion.

Recent advances in small bowel diseases: Part II

As is the case in all areas of gastroenterology and hepatology, in 2009 and 2010 there were many advances in our knowledge and understanding of small intestinal diseases. Over 1000 publications were reviewed, and the important advances in basic science as well as clinical applications were considered. In Part II we review six topics: absorption, short bowel syndrome, smooth muscle function and intestinal motility, tumors, diagnostic imaging, and cystic fibrosis.

Perinatal undernutrition alters intestinal alkaline phosphatase and its main transcription factors KLF4 and Cdx1 in adult offspring fed a high-fat diet

Nutrient restriction during gestation and/or suckling is associated with an increased risk of developing inflammation, obesity and metabolic diseases in adulthood. However, the underlying mechanisms, including the role of the small intestine, are unclear. We hypothesized that intestinal adaptation to the diet in adulthood is modulated by perinatal nutrition. This hypothesis was tested using a split-plot design experiment with 20 controls and 20 intrauterine growth-retarded (IUGR) rats aged 240 days and randomly assigned to be fed a standard chow or a high-fat (HF) diet for 10 days. Jejunal tissue was collected at necropsy and analyzed for anatomy, digestive enzymes, goblet cells and mRNA levels. Cecal contents and blood serum were analyzed for alkaline phosphatase (AP). IUGR rats failed to adapt to HF by increasing AP activity in jejunal tissue and cecal content as observed in controls. mRNA levels of transcription factors KLF4 and Cdx1 were blunted in jejunal epithelial cell of IUGR rats fed HF. mRNA levels of TNF-α were lower in IUGR rats. They also displayed exacerbated aminopeptidase N response and reduced jejunal goblet cell density. Villus and crypt architecture and epithelial cell proliferation increased with HF in both control and IUGR rats. Serum AP tended to be lower, and serum levamisole inhibition-resistant AP fraction was lower, in IUGR than controls with HF. Serum fatty acids and triglycerides were higher in IUGR rats and higher with HF. In conclusion, the adult intestine adapts to an HF diet differentially depending on early nutrition, jejunal AP and transcription factors being blunted in IUGR individuals fed HF.

Intestinal lymphatic transport for drug delivery

Intestinal lymphatic transport has been shown to be an absorptive pathway following oral administration of lipids and an increasing number of lipophilic drugs, which once absorbed, diffuse across the intestinal enterocyte and while in transit associate with secretable enterocyte lipoproteins. The chylomicron-associated drug is then secreted from the enterocyte into the lymphatic circulation, rather than the portal circulation, thus avoiding the metabolically-active liver, but still ultimately returning to the systemic circulation. Because of this parallel and potentially alternative absorptive pathway, first-pass metabolism can be reduced while increasing lymphatic drug exposure, which opens the potential for novel therapeutic modalities and allows the implementation of lipid-based drug delivery systems. This review discusses the physiological features of the lymphatics, enterocyte uptake and metabolism, links between drug transport and lipid digestion/re-acylation, experimental model (in vivo, in vitro, and in silico) of lymphatic transport, and the design of lipid- or prodrug-based drug delivery systems for enhancing lymphatic drug transport.

Patterns of cholesterol metabolism: pathophysiological and therapeutic implications for dyslipidemias and the metabolic syndrome

Investigating cholesterol metabolism, which derives from balancing cholesterol synthesis and absorption, opens new perspectives in the pathogenesis of dyslipidemias and the metabolic syndrome (MS). Cholesterol metabolism is studied by measuring plasma levels of campesterol, sitosterol and cholestanol, that is, plant sterols which are recognised as surrogate cholesterol-absorption markers and lathosterol or squalene, that is, cholesterol precursors, which are considered surrogate cholesterol-synthesis markers. This article presents current knowledge on cholesterol synthesis and absorption, as evaluated by means of cholesterol precursors and plant sterols, and discusses patterns of cholesterol balance in the main forms of primary hyperlipidaemia and MS. Understanding the mechanism(s) underlying these patterns of cholesterol synthesis and absorption will help to predict the response to hypolipidemic treatment, which can then be tailored to ensure the maximum clinical benefit for patients.