Regulation Of Lipid Transport Research Articles

Direct evidence of lipid transport by the Drs2-Cdc50 flippase upon truncation of its terminal regions.

P4-ATPases in complex with Cdc50 subunits are lipid flippases that couple ATP hydrolysis with lipid transport to the cytoplasmic leaflet of membranes to create lipid asymmetry. Such vectorial transport has been shown to contribute to vesicle formation in the late secretory pathway. Some flippases are regulated by autoinhibitory regions that can be destabilized by protein kinase-mediated phosphorylation and possibly by binding of cytosolic proteins. In addition, the binding of lipids to flippases may also induce conformational changes required for the activity of these transporters. Here, we address the role of phosphatidylinositol-4-phosphate (PI4P) and the terminal autoinhibitory tails on the lipid flipping activity of the yeast lipid flippase Drs2-Cdc50. By functionally reconstituting the full-length and truncated forms of Drs2 in a 1:1 complex with the Cdc50 subunit, we provide compelling evidence that lipid flippase activity is exclusively detected for the truncated Drs2 variant and is dependent on the presence of the phosphoinositide PI4P. These findings highlight the critical role of phosphoinositides as lipid co-factors in the regulation of lipid transport by the Drs2-Cdc50 flippase.

Milk and plasma proteomes from cows facing diet-induced milk fat depression are related to immunity, lipid metabolism and inflammation

Milk proteins are a source of bioactive molecules for calves and humans that may also reflect the physiology and metabolism of dairy cows. Dietary lipid supplements are classically used to modulate the lipid content and composition of bovine milk, with potential impacts on the nutrient’s homeostasis and the systemic inflammation of cows that remains to be more explored. This study aimed at identifying discriminant proteins and their associated pathways in twelve Holstein cows (87 ± 7 days in milk), multiparous and non-pregnant, fed for 28 d a diet either, supplemented with 5% DM intake of corn oil and with 50% additional starch from wheat in the concentrate (COS, n = 6) chosen to induce a milk fat depression, or with 3% DM intake of hydrogenated palm oil (HPO, n = 6) known to increase milk fat content. Intake, milk yield and milk composition were measured. On d 27 of the experimental periods, milk and blood samples were collected and label-free quantitative proteomics was performed on proteins extracted from plasma, milk fat globule membrane (MFGM) and skimmed milk (SM). The proteomes from COS and HPO samples were composed of 98, 158 and 70 unique proteins, respectively, in plasma, MFGM and SM. Of these, the combination of a univariate and a multivariate partial least square discriminant analyses reveals that 15 proteins in plasma, 24 in MFGM and 14 in SM signed the differences between COS and HPO diets. The 15 plasma proteins were related to the immune system, acute-phase response, regulation of lipid transport and insulin sensitivity. The 24 MFGM proteins were related to the lipid biosynthetic process and secretion. The 14 SM proteins were linked mainly to immune response, inflammation and lipid transport. This study proposes discriminant milk and plasma proteomes, depending on diet-induced divergence in milk fat secretion, that are related to nutrient homeostasis, inflammation, immunity and lipid metabolism. The present results also suggest a higher state of inflammation with the COS diet.

Blood Proteomics-Based Detection of Upregulated Lipid Metabolism and Immune Dysfunction in an Elite Adventure Athlete Trekking Across Antarctica

Abstract Objectives Proteomics when combined with psychological, nutrition, and performance measures may serve as a useful monitoring system for immune dysfunction, training distress, and exercise-induced muscle damage and exhaustion in athletes. Global proteomics monitoring of an elite adventure athlete (age 33 years) was conducted over a 28-week period that culminated in the successful, unassisted 2-month trek across Antarctica (1500 km). Methods Training distress was monitored weekly using the 19-item, validated Training Distress Scale (TDS). Weekly dried blood spot (DBS) specimens were collected via fingerprick blood drops onto standard blood spot cards. DBS proteins were measured with nano-electrospray ionization liquid chromatography tandem mass spectrometry (nanoLC-MS/MS) in data-independent acquisition (DIA) mode, and 712 proteins were identified and quantified. Results The participant experienced a decrease of 11.4 kg in body mass during the Antarctica trek. The 28-week period was divided into time segments based on TDS scores, and a contrast analysis between weeks 5–8 (low TDS) and weeks 20–23 (high TDS, last month of Antarctica trek) showed that 31 proteins (n = 20 immune related, n = 14 nutrition related with n = 8 in dual roles) were upregulated and 35 (n = 17 immune related) were downregulated. Protein-protein interaction (PPI) networks and gene ontology (GO) biological process analysis supported an increase in plasma lipoprotein particle remodeling, regulation of lipid transport, retinoid metabolic process, and vitamin transport due to high energy intake (7048 kcal/d). PPI networks also supported a dichotomous immune response. GO terms for the upregulated immune proteins showed an increase in regulation of the immune system process, especially inflammation, complement activation, and leukocyte mediated immunity. GO terms for the downregulated immune-related proteins indicated a decrease in several aspects of the overall immune system process including neutrophil degranulation and the antimicrobial humoral response. Conclusions These proteomics data support a dysfunctional immune response in an elite adventure athlete during a sustained period of mental and physical distress, high energy intake, and significant loss of body mass while trekking solo across Antarctica. Funding Sources Standard Process, Inc., Palmyra, WI.

Hepatocyte peroxisome proliferator-activated receptor α regulates bile acid synthesis and transport

Peroxisome proliferator-activated receptor alpha (PPARα) controls lipid homeostasis through regulation of lipid transport and catabolism. PPARα activators are clinically used for hyperlipidemia treatment. The role of PPARα in bile acid (BA) homeostasis is beginning to emerge. Herein, Ppara-null and hepatocyte-specific Ppara-null (Ppara∆Hep) as well as the respective wild-type mice were treated with the potent PPARα agonist Wy-14,643 (Wy) and global metabolomics performed to clarify the role of hepatocyte PPARα in the regulation of BA homeostasis. Levels of all serum BAs were markedly elevated in Wy-treated wild-type mice but not in Ppara-null and Ppara∆Hep mice. Gene expression analysis showed that PPARα activation (1) down-regulated the expression of sodium-taurocholate acid transporting polypeptide and organic ion transporting polypeptide 1 and 4, responsible for the uptake of BAs into the liver; (2) decreased the expression of bile salt export pump transporting BA from hepatocytes into the bile canaliculus; (3) upregulated the expression of multidrug resistance-associated protein 3 and 4 transporting BA from hepatocytes into the portal vein. Moreover, there was a notable increase in the compositions of serum, hepatic and biliary cholic acid and taurocholic acid following Wy treatment, which correlated with the upregulated expression of the Cyp8b1 gene encoding sterol 12α-hydroxylase. The effects of Wy were identical between the Ppara∆Hep and Ppara-null mice. Hepatocyte PPARα controlled BA synthesis and transport not only via direct transcriptional regulation but also via crosstalk with hepatic farnesoid X receptor signaling. These findings underscore a key role for hepatocyte PPARα in the control of BA homeostasis.

In Silico Prediction of the Anti-Depression Mechanism of a Herbal Formula (Tiansi Liquid) Containing Morinda officinalis and Cuscuta chinensis.

Purpose: Depression is a sickening psychiatric condition that is prevalent worldwide. To manage depression, the underlying modes of antidepressant effect of herbals are important to be explored for the development of natural drugs. Tiansi Liquid is a traditional Chinese medicine (TCM) that is prescribed for the management of depression, however its underlying mechanism of action is still uncertain. The purpose of this study was to systematically investigate the pharmacological mode of action of a herbal formula used in TCM for the treatment of depression. Methods: Based on literature search, an ingredients-targets database was developed for Tiansi Liquid, followed by the identification of targets related to depression. The interaction between these targets was evaluated on the basis of protein-protein interaction network constructed by STITCH and gene ontology (GO) enrichment analysis using ClueGO plugin. Results: As a result of literature search, 57 components in Tiansi Liquid formula and 106 potential targets of these ingredients were retrieved. A careful screening of these targets led to the identification of 42 potential targets associated with depression. Ultimately, 327 GO terms were found by analysis of gene functional annotation clusters and abundance value of these targets. Most of these terms were found to be closely related to depression. A significant number of protein targets such as IL10, MAPK1, PTGS2, AKT1, APOE, PPARA, MAPK1, MIF, NOS3 and TNF-α were found to be involved in the functioning of Tiansi Liquid against depression. Conclusions: The findings elaborate that Tiansi Liquid can be utilized to manage depression, however, multiple molecular mechanisms of action could be proposed for this effect. The observed core mechanisms could be the sensory perception of pain, regulation of lipid transport and lipopolysaccharide-mediated signaling pathway.

Multilevel systems biology modeling characterized the atheroprotective efficiencies of modified dairy fats in a hamster model.

We assessed the atheroprotective efficiency of modified dairy fats in hyperlipidemic hamsters. A systems biology approach was implemented to reveal and quantify the dietary fat-related components of the disease. Three modified dairy fats (40% energy) were prepared from regular butter by mixing with a plant oil mixture, by removing cholesterol alone, or by removing cholesterol in combination with reducing saturated fatty acids. A plant oil mixture and a regular butter were used as control diets. The atherosclerosis severity (aortic cholesteryl-ester level) was higher in the regular butter-fed hamsters than in the other four groups (P < 0.05). Eighty-seven of the 1,666 variables measured from multiplatform analysis were found to be strongly associated with the disease. When aggregated into 10 biological clusters combined into a multivariate predictive equation, these 87 variables explained 81% of the disease variability. The biological cluster "regulation of lipid transport and metabolism" appeared central to atherogenic development relative to diets. The "vitamin E metabolism" cluster was the main driver of atheroprotection with the best performing transformed dairy fat. Under conditions that promote atherosclerosis, the impact of dairy fats on atherogenesis could be greatly ameliorated by technological modifications. Our modeling approach allowed for identifying and quantifying the contribution of complex factors to atherogenic development in each dietary setup.

Role of ATP‐binding cassette transporters in brain lipid transport and neurological disease

The brain is lipid-rich compared to other organs and although previous studies have highlighted the importance of ATP-binding cassette (ABC) transporters in the regulation of lipid transport across membranes in peripheral tissues, very little is known regarding ABC transporter function in the CNS. In this study, we bring together recent literature focusing on potential roles for ABC transporters in brain lipid transport and, where appropriate, identify possible links between ABC transporters, lipid transport and neurological disease. Of the 48 transcriptionally active ABC transporters in the human genome, we have focused on 13 transporters (ABCA1, ABCA2, ABCA3, ABCA4, ABCA7 and ABCA8; ABCB1 and ABCB4; ABCD1 and ABCD2; ABCG1, ABCG2, and ABCG4) for which there is evidence suggesting they may contribute in some way to brain lipid transport or homeostasis. The transporters are discussed in terms of their location within brain regions and brain cell types and, where possible, in terms of their known functions and established or proposed association with human neurological diseases. Specific examples of novel treatment strategies for diseases, such as Alzheimer's disease and X-linked adrenoleukodystrophy that are based on modulation of ABC transporter function are discussed and we also examine possible functions for specific ABC transporters in human brain development.

Identification of LBM180, a Lamellar Body Limiting Membrane Protein of Alveolar Type II Cells, as the ABC Transporter Protein ABCA3

Lamellar bodies are the specialized secretory organelles of alveolar type II (ATII) epithelial cells through which the cell packages pulmonary surfactant and regulates its secretion. Surfactant within lamellar bodies is densely packed as circular arrays of lipid membranes and appears to be the product of several trafficking and biosynthetic processes. To elucidate these processes, we reported previously on the generation of a monoclonal antibody (3C9) that recognizes a unique protein of the lamellar body membrane of 180 kDa, which we named LBM180. We report that mass spectrometry of the protein precipitated by this antibody generated a partial sequence that is identical to the ATP-binding cassette protein, ABCA3. Homology analysis of partial sequences suggests that this protein is highly conserved among species. The ABCA3 gene transcript was found in cell lines of human lung origin, in ATII cells of human, rat, and mouse, as well as different tissues of rat, but the highest expression of ABCA3 was observed in ATII cells. Expression of this transcript was at its maximum prior to birth, and hormonal induction of ABCA3 transcript was observed in human fetal lung at the same time as other surfactant protein transcripts were induced, suggesting that ABCA3 is developmentally regulated. Molecular and biochemical studies show that ABCA3 is targeted to vesicle membranes and is found in the limiting membrane of lamellar bodies. Because ABCA3 is a member of a subfamily of ABC transporters that are predominantly known to be involved in the regulation of lipid transport and membrane trafficking, we speculate that this protein may play a key role in lipid organization during the formation of lamellar bodies.

Crystal Structure and Thermodynamic Analysis of Human Brain Fatty Acid-binding Protein

Crystal Structure and Thermodynamic Analysis of Human Brain Fatty Acid-binding Protein

Fat metabolism during total parenteral nutrition: a biochemical and ultra‐structural study

Background: Before the introduction of Intralipid in 1961, the incidence of adverse reactions to intravenous fat emulsions was quite common. Concurrent with hyperlipidaemia, multiple organ dysfunction could occur, but the most prominent symptoms were high fever and anaemia, and the reaction was called “the fat overloading syndrome”. Although the reports are quite rare today the reaction does still appear, and we have observed that some patients develop severe fever during or after incidental retention of exogenous fat in the blood during total parenteral nutrition (TPN). The pathophysiological background to these adverse reactions, as well as the final destiny and the effects of the retained exogenous fat particles, are largely unknown. These questions initiated the present study, which focuses on two factors of importance for the clearance of infused fat from the circulation: the lipoprotein lipase (LPL) system and the reticluloendo‐thelial system.Methods: An introductory analysis of the clinical course of a head‐injured patient suffering from fat intolerance during TPN implied that observed adverse reactions could be due to influence on macrophages by retained exogenous fat particles.Results: During infusion of lipid emulsions, cholesterol and phospholipids accumulated in non‐high‐density lipoproteins, while high‐density lipoproteins were enriched in triglycerides. Triglycerides also accumulated in hepatic tissue, and the activity of hepatic lipase decreased.Although lipoprotein lipase activity in the heart was up‐regulated and serum levels of triglycerides were normal, suggesting that the total elimination rate of triglycerides was not impaired, ultra‐structural investigations indicated that Kupffer cells were involved in clearing exogenous lipids from the blood during the infusion of long‐chain triglycerides. Furthermore, the Kupffer cells were activated, according to morphological criteria. When high doses of fat were given intravenously, the Kupffer cells were grossly distended by fat vacuoles, and serum levels of lactate dehydrogenase increased.During treatment with fat emulsions containing medium‐chain triglycerides and long‐chain triglycerides in equal amounts, the alterations in lipid transport were less pronounced, and signs of Kupffer cell activation were weaker than during infusion with long‐chain triglycerides only.Conclusion: The experimental studies showed that infusion of exogenous fat particles interfered with the regulation of lipid transport, and there were signs of increased demands on various aspects of lipid metabolism. Although the capacity of the LPL was sufficient in most situations in healthy rats, the Kupffer cells seemed to be involved in the clearance of exogenous lipids. The present investigations identified one factor, LCT fat emulsion, which was necessary for the appearance of fat vacuoles in the Kupffer cells during TPN.To some extent, the experimental findings may be related to clinical observations of a head‐injured patient who developed signs of acute, severe macrophage activation with haemophago‐cytosis during and after accumulation of exogenous fat in the blood after treatment with intravenous fat emulsions. The condition was considered to be a consequence of impaired lipid elimination and altered macrophage function during clearance of fat from the blood, a consideration supported by the morphological changes of rat Kupffer cells after TPN in the present study.