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Journal of Colloid and Interface Science May 2024Understanding the digestion of lipid-based pharmaceutical formulations and food systems is necessary for optimising drug and nutrient delivery and has been extensively...
HYPOTHESIS
Understanding the digestion of lipid-based pharmaceutical formulations and food systems is necessary for optimising drug and nutrient delivery and has been extensively studied in bulk emulsion systems using the pH-stat method [1]. However, this approach is not suitable for investigation of individual lipid droplets, in particular the interface where the lipase acts. Microfluidic approaches to study digestion at lipid-water interfaces using droplet trapping have been proposed, however the aqueous phase in that case washes over the interface presenting uncertainty over the stoichiometry of interactions [2]. The internal interface of a Janus-like droplet, containing distinct aqueous and lipid compartments, mimics the interface of a lipid droplet in aqueous solution with controlled stoichiometry [3]. Hence, it was hypothesised that the internal interface of Janus droplets can offer a precise way to study the enzymatic digestion of lipids formulations.
EXPERIMENTS
Using microfluidic methods, Janus-like droplets were formed by coalescing emulsion droplets containing lipid formulation and pancreatic lipase. Polarised light microscopy (PLM) and in-situ small-angle X-ray scattering (SAXS) were used to investigate the droplets.
FINDINGS
PLM revealed the growth of an aligned inverse hexagonal phase (H), and with SAXS showed that this phase transformation and alignment resulted from enzymatic digestion. A subsequent partial transformation from H to inverse bicontinuous cubic phase occurred when simulated intestinal fluid was used instead of Tris buffer. Suggesting that phospholipids and bile salts could diffuse across the internal interface to locally affect their surroundings.
PubMed: 38838633
DOI: 10.1016/j.jcis.2024.05.087 -
Frontiers in Veterinary Science 2024The suppressor of cytokine signaling 3 (SOCS3) is a key signaling molecule that regulates milk synthesis in dairy livestock. However, the molecular mechanism by which...
The suppressor of cytokine signaling 3 (SOCS3) is a key signaling molecule that regulates milk synthesis in dairy livestock. However, the molecular mechanism by which regulates lipid synthesis in goat milk remains unclear. This study aimed to screen for key downstream genes associated with lipid synthesis regulated by in goat mammary epithelial cells (GMECs) using RNA sequencing (RNA-seq). Goat overexpression vector (PC-SOCS3) and negative control (PCDNA3.1) were transfected into GMECs. Total RNA from cells after overexpression was used for RNA-seq, followed by differentially expressed gene (DEG) analysis, functional enrichment analysis, and network prediction. overexpression significantly inhibited the synthesis of triacylglycerol, total cholesterol, non-esterified fatty acids, and accumulated lipid droplets. In total, 430 DEGs were identified, including 226 downregulated and 204 upregulated genes, following overexpression. Functional annotation revealed that the DEGs were mainly associated with lipid metabolism, cell proliferation, and apoptosis. We found that the lipid synthesis-related genes, , were downregulated. In addition, the proliferation-related genes , , and were upregulated, and the apoptosis-related gene was downregulated. In conclusion, six DEGs were identified as key regulators of milk lipid synthesis following overexpression in GMECs. Our results provide new candidate genes and insights into the molecular mechanisms involved in milk lipid synthesis regulated by in goats.
PubMed: 38835896
DOI: 10.3389/fvets.2024.1392152 -
BioRxiv : the Preprint Server For... May 2024The physical characteristics of brown adipose tissue (BAT) are defined by the presence of multilocular lipid droplets (LD) within the brown adipocytes and a high...
The physical characteristics of brown adipose tissue (BAT) are defined by the presence of multilocular lipid droplets (LD) within the brown adipocytes and a high abundance of iron-containing mitochondria, which give it its characteristic color. Normal mitochondrial function is, in part, regulated by organelle-to-organelle contacts. Particularly, the contact sites that mediate mitochondria-LD interactions are thought to have various physiological roles, such as the synthesis and metabolism of lipids. Aging is associated with mitochondrial dysfunction, and previous studies show that there are changes in mitochondrial structure and proteins that modulate organelle contact sites. However, how mitochondria-LD interactions change with aging has yet to be fully clarified. Therefore, we sought to define age-related changes in LD morphology and mitochondria-lipid interactions in BAT. We examined the three-dimensional morphology of mitochondria and LDs in young (3-month) and aged (2-year) murine BAT using serial block face-scanning electron microscopy and the Amira program for segmentation, analysis, and quantification. Analysis showed reductions in LD volume, area, and perimeter in aged samples compared to young samples. Additionally, we observed changes in LD appearance and type in aged samples compared to young samples. Notably, we found differences in mitochondrial interactions with LDs, which could implicate that these contacts may be important for energetics in aging. Upon further investigation, we also found changes in mitochondrial and cristae structure for mitochondria interacting with LD lipids. Overall, these data define the nature of LD morphology and organelle-organelle contacts during aging and provide insight into LD contact site changes that interconnect biogerontology and mitochondrial functionality, metabolism, and bioactivity in aged BAT.
PubMed: 38826465
DOI: 10.1101/2023.09.23.559135 -
Research Square May 2024Despite genome-wide association studies of late-onset Alzheimer's disease (LOAD) having identified many genetic risk loci, the underlying disease mechanisms remain...
Despite genome-wide association studies of late-onset Alzheimer's disease (LOAD) having identified many genetic risk loci, the underlying disease mechanisms remain largely unknown. Determining causal disease variants and their LOAD-relevant cellular phenotypes has been a challenge. Leveraging our approach for identifying functional GWAS risk variants showing allele-specific open chromatin (ASoC), we systematically identified putative causal LOAD risk variants in human induced pluripotent stem cells (iPSC)-derived neurons, astrocytes, and microglia (MG) and linked risk allele to a previously unappreciated MG-specific role of in lipid droplet (LD) accumulation. ASoC mapping uncovered functional risk variants for 26 LOAD risk loci, mostly MG-specific. At the MG-specific locus, the LOAD risk allele of rs10792832 reduced transcription factor (PU.1) binding and expression, impairing the uptake of amyloid beta (Aβ) and myelin debris. Interestingly, MG with risk allele showed transcriptional enrichment of pathways for cholesterol synthesis and LD formation. Genetic and pharmacological perturbations of MG further established a causal link between the reduced expression, LD accumulation, and phagocytosis deficits. Our work elucidates the selective LOAD vulnerability in microglia for the locus through detrimental LD accumulation, providing a neurobiological basis that can be exploited for developing novel clinical interventions.
PubMed: 38826437
DOI: 10.21203/rs.3.rs-4407146/v1 -
Journal of Dairy Science May 2024Products of lipolysis released during digestion positively affect the metabolism of newborns. In contrast to the 3-layer biological membranes covering human milk (HM)...
Products of lipolysis released during digestion positively affect the metabolism of newborns. In contrast to the 3-layer biological membranes covering human milk (HM) fat, the lipid droplets in infant milk formula (IMF) are covered by a single membrane composed of casein and whey proteins. To reduce the differences in lipid structure between IMF and HM, studies have used milk fat globule membrane (MFGM) components such as milk polar lipids (MPL) to prepare emulsions mimicking HM fat globules However, few studies have elucidated the effect of membrane proteins (MP) on lipid digestion in infants. In this study, 3 kinds of emulsions were prepared: One with MPL as the interfaced of lipid droplets (RE-1), one with membrane protein concentrate (MPC) (RE-2) as the interface of lipid droplets, and one with both MPL and MPC (1:2) as the co-interface of lipid droplets (RE-3). The interfacial coverage of the emulsions was confirmed by measuring the contents of MPL and MPC at the lipid droplet interface, and by confocal laser scanning microscopy analyzed. By controlling the homogenization intensity, the specific surface area of lipid droplets was controlled at the same level among the 3 emulsions. The stability constants of the emulsions varied, and RE-1 was the most stable. During simulated in vitro infant gastrointestinal digestion, the amount of free fatty acids (FFA) released from the lipid droplets was significantly higher from those with MPC at the interface (RE-2, RE-3) than from that with MPL at the interface (RE-1). The amount of FFA released at the end of intestinal digestion of RE-1, RE-2, and RE-3 was 255.00 ± 3.54 µmol,328.75 ± 5.30 µmol, 298.50 ± 9.19 µmol, respectively. Compared with the lipid droplets in RE-2, those with MPL at the interface (RE-1, RE-3) released more unsaturated fatty acids (USFAs) during digestion. The emulsifying activity index was highest in RE-3 (MPL and MPC co-interface). The presence of MPL at the emulsion interface increased the release of USFAs, while the presence of MPC increased the release of FFA. These results show that both MPL and MP are indispensable in the construction of MFGM. Understanding their effects on digestion can provide new strategies for the development of infant foods.
PubMed: 38825138
DOI: 10.3168/jds.2024-24707 -
Cell Death & Disease Jun 2024Drusen, the yellow deposits under the retina, are composed of lipids and proteins, and represent a hallmark of age-related macular degeneration (AMD). Lipid droplets are...
Drusen, the yellow deposits under the retina, are composed of lipids and proteins, and represent a hallmark of age-related macular degeneration (AMD). Lipid droplets are also reported in the retinal pigment epithelium (RPE) from AMD donor eyes. However, the mechanisms underlying these disease phenotypes remain elusive. Previously, we showed that Pgc-1α repression, combined with a high-fat diet (HFD), induce drastic AMD-like phenotypes in mice. We also reported increased PGC-1α acetylation and subsequent deactivation in the RPE derived from AMD donor eyes. Here, through a series of in vivo and in vitro experiments, we sought to investigate the molecular mechanisms by which PGC-1α repression could influence RPE and retinal function. We show that PGC-1α plays an important role in RPE and retinal lipid metabolism and function. In mice, repression of Pgc-1α alone induced RPE and retinal degeneration and drusen-like deposits. In vitro inhibition of PGC1A by CRISPR-Cas9 gene editing in human RPE (ARPE19- PGC1A KO) affected the expression of genes responsible for lipid metabolism, fatty acid β-oxidation (FAO), fatty acid transport, low-density lipoprotein (LDL) uptake, cholesterol esterification, cholesterol biosynthesis, and cholesterol efflux. Moreover, inhibition of PGC1A in RPE cells caused lipid droplet accumulation and lipid peroxidation. ARPE19-PGC1A KO cells also showed reduced mitochondrial biosynthesis, impaired mitochondrial dynamics and activity, reduced antioxidant enzymes, decreased mitochondrial membrane potential, loss of cardiolipin, and increased susceptibility to oxidative stress. Our data demonstrate the crucial role of PGC-1α in regulating lipid metabolism. They provide new insights into the mechanisms involved in lipid and drusen accumulation in the RPE and retina during aging and AMD, which may pave the way for developing novel therapeutic strategies targeting PGC-1α.
Topics: Retinal Pigment Epithelium; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; Animals; Lipid Metabolism; Humans; Mice; Lipid Droplets; Macular Degeneration; Mice, Inbred C57BL; Mitochondria; Male; Oxidative Stress
PubMed: 38824126
DOI: 10.1038/s41419-024-06762-y -
Food Research International (Ottawa,... Jul 2024Spatiotemporal assessment of lipid and protein oxidation is key for understanding quality deterioration in emulsified food products containing polyunsaturated fatty...
Spatiotemporal assessment of lipid and protein oxidation is key for understanding quality deterioration in emulsified food products containing polyunsaturated fatty acids. In this work, we first mechanistically validated the use of the lipid oxidation-sensitive fluorophore BODIPY 665/676 as a semi-quantitative marker for local peroxyl radical formation. Next, we assessed the impact of microfluidic and colloid mill emulsification (respectively producing mono- and polydisperse droplets) on local protein and lipid oxidation kinetics in whey protein isolate (WPI)-stabilized emulsions. We further used BODIPY 581/591 C11 and CAMPO-AFDye 647 as colocalisation markers for lipid and protein oxidation. The polydisperse emulsions showed an inverse relation between droplet size and lipid oxidation rate. Further, we observed less protein and lipid oxidation occurring in similar sized droplets in monodisperse emulsions. This observation was linked to more heterogeneous protein packing at the droplet surface during colloid mill emulsification, resulting in larger inter-droplet heterogeneity in both protein and lipid oxidation. Our findings indicate the critical roles of emulsification methods and droplet sizes in understanding and managing lipid oxidation.
Topics: Whey Proteins; Emulsions; Oxidation-Reduction; Particle Size; Boron Compounds; Kinetics; Peroxides; Lipids
PubMed: 38823851
DOI: 10.1016/j.foodres.2024.114341 -
Cell May 2024Dolichol is a lipid critical for N-glycosylation as a carrier for activated sugars and nascent oligosaccharides. It is commonly thought to be directly produced from...
Dolichol is a lipid critical for N-glycosylation as a carrier for activated sugars and nascent oligosaccharides. It is commonly thought to be directly produced from polyprenol by the enzyme SRD5A3. Instead, we found that dolichol synthesis requires a three-step detour involving additional metabolites, where SRD5A3 catalyzes only the second reaction. The first and third steps are performed by DHRSX, whose gene resides on the pseudoautosomal regions of the X and Y chromosomes. Accordingly, we report a pseudoautosomal-recessive disease presenting as a congenital disorder of glycosylation in patients with missense variants in DHRSX (DHRSX-CDG). Of note, DHRSX has a unique dual substrate and cofactor specificity, allowing it to act as a NAD-dependent dehydrogenase and as a NADPH-dependent reductase in two non-consecutive steps. Thus, our work reveals unexpected complexity in the terminal steps of dolichol biosynthesis. Furthermore, we provide insights into the mechanism by which dolichol metabolism defects contribute to disease.
PubMed: 38821050
DOI: 10.1016/j.cell.2024.04.041 -
Frontiers in Cell and Developmental... 2024Over the past 10 years, the biological role of lipid droplets (LDs) has gained significant attention in the context of both physiological and pathological conditions.... (Review)
Review
Over the past 10 years, the biological role of lipid droplets (LDs) has gained significant attention in the context of both physiological and pathological conditions. Considerable progress has been made in elucidating key aspects of these organelles, yet much remains to be accomplished to fully comprehend the myriad functions they serve in the progression of hepatic tumors. Our current perception is that LDs are complex and active structures managed by a distinct set of cellular processes. This understanding represents a significant paradigm shift from earlier perspectives. In this review, we aim to recapitulate the function of LDs within the liver, highlighting their pivotal role in the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD) (Hsu and Loomba, 2024) and their contribution to the progression towards more advanced pathological stages up to hepatocellular carcinoma (HC) (Farese and Walther, 2009). We are aware of the molecular complexity and changes occurring in the neoplastic evolution of the liver. Our attempt, however, is to summarize the most important and recent roles of LDs across both healthy and all pathological liver states, up to hepatocarcinoma. For more detailed insights, we direct readers to some of the many excellent reviews already available in the literature (Gluchowski et al., 2017; Hu et al., 2020; Seebacher et al., 2020; Paul et al., 2022).
PubMed: 38818407
DOI: 10.3389/fcell.2024.1404006 -
Biomedicine & Pharmacotherapy =... Jul 2024Hyperlipidemia-induced osteoporosis is marked by increased bone marrow adiposity, and treatment with statins for hyperlipidemia often leads to new-onset osteoporosis....
Hyperlipidemia-induced osteoporosis is marked by increased bone marrow adiposity, and treatment with statins for hyperlipidemia often leads to new-onset osteoporosis. Endosome-associated trafficking regulator 1 (ENTR1) has been found to interact with different proteins in pathophysiology, but its exact role in adipogenesis is not yet understood. This research aimed to explore the role of ENTR1 in adipogenesis and to discover a new small molecule that targets ENTR1 for evaluating its effectiveness in treating hyperlipidemia-induced osteoporosis. We found that ENTR1 expression increased during the adipogenesis of bone marrow mesenchymal cells (BMSCs). ENTR1 gain- and loss-of-function assays significantly enhanced lipid droplets formation. Mechanistically, ENTR1 binds peroxisome proliferator-activated receptor γ (PPARγ) and enhances its expression, thereby elevating adipogenic markers including C/EBPα and LDLR. Therapeutically, AN698/40746067 attenuated adipogenesis by targeting ENTR1 to suppress PPARγ. In vivo, AN698/40746067 reduced bone marrow adiposity and bone loss, as well as prevented lipogenesis-related obesity, inflammation, steatohepatitis, and abnormal serum lipid levels during hyperlipidemia. Together, these findings suggest that ENTR1 facilitates adipogenesis by PPARγ involved in BMSCs' differentiation, and targeted inhibition of ENTR1 by AN698/40746067 may offer a promising therapy for addressing lipogenesis-related challenges and alleviating osteoporosis following hyperlipidemia.
Topics: Animals; Hyperlipidemias; Osteoporosis; PPAR gamma; Adipogenesis; Adiposity; Mice, Inbred C57BL; Mice; Mesenchymal Stem Cells; Male; Bone Marrow; Endosomal Sorting Complexes Required for Transport
PubMed: 38810405
DOI: 10.1016/j.biopha.2024.116843