Lysosomal acid lipase and lipid metabolism: new mechanisms, new questions, and new therapies

New insights into the relationship of mitochondrial metabolism and atherosclerosis

Atherosclerotic cardiovascular and cerebrovascular diseases are the number one killer of human health. In view of the important role of mitochondria in the formation and evolution of atherosclerosis, our manuscript aims to comprehensively elaborate the relationship between mitochondria and the formation and evolution of atherosclerosis from the aspects of mitochondrial dynamics, mitochondria-organelle interaction (communication), mitochondria and cell death, mitochondria and vascular smooth muscle cell phenotypic switch, etc., which is combined with genome, transcriptome and proteome, in order to provide new ideas for the pathogenesis of atherosclerosis and the diagnosis and treatment of related diseases.

Reduced Intra- and Extracellular Circulating Postprandial Lysosomal Acid Lipase Activity in Patients with MASLD

BACKGROUND/OBJECTIVES

Low fasting blood lysosomal acid lipase (LAL) activity is associated with the pathogenesis of metabolic hepatic steatosis. We measured LAL activity in blood and plasma before and after an oral fat tolerance test (OFTT) in patients with metabolic-dysfunction-associated steatotic liver disease (MASLD).

METHODS

Twenty-six controls and seventeen patients with MASLD but without diabetes were genotyped for the patatin-like phospholipase 3 (PNPLA3) rs738409 variant by RT-PCR and subjected to an OFTT, measuring LAL activity in blood and plasma with a fluorimetric method.

RESULTS

LAL activity in blood both under fasting and 4 h after OFTT (0.846 ± 0.309 nmol/spot/h vs. 1.180 ± 0.503 nmol/spot/h p < 0.01) was lower in patients with MASLD compared to controls. These differences were present only in carriers of the PNPLA3 variant. In controls not carrying the PNPLA3 variant, the postprandial increase in blood LAL activity was negatively correlated with that of serum triglycerides (p < 0.05). Extracellular LAL activity in plasma was lower in patients with MASLD (n = 9) compared to controls (n = 8) in the fasting state (p < 0.01) and 4 h post-meal (p < 0.05). The area under the curve up to 6 h of plasma LAL activity was lower in patients with MASLD than in controls (p < 0.05) and correlated negatively with that of triglycerides only in controls (r = -0.841; p < 0.01).

CONCLUSIONS

Patients with MASLD have reduced LAL activity in blood and plasma both before and 4 h after a meal. In patients with MASLD, the physiological negative correlation between circulating LAL levels and postprandial hypertriglyceridemia is lost.

Size of lipid emulsion droplets influences metabolism in human CD4+ T cells

SCOPE

Triglyceride-based lipid emulsions are critical for total parenteral nutrition (TPN), but their long-term use has adverse effects, such as severe liver dysfunction necessitating improved formulations. This study compares the uptake mechanism and intracellular fate of novel glycerol-stabilized nano-sized lipid emulsions with conventional emulsions in CD4+ T cells, focusing on their impact on cellular metabolism.

METHODS AND RESULTS

Nanoemulsions were formulated with increased glycerol content. Uptake of emulsions in primary human CD4+ T cells was investigated using different endocytic blockers, then quantified by flow cytometry, and visualized by confocal microscopy. To investigate emulsion intracellular fate, fatty acids in membrane phospholipids were quantified by GC-MS/MS and cellular metabolism was assessed by Seahorse technology. Results show T cells internalize both conventional and nano-sized emulsions using macropinocytosis. Fatty acids from emulsions are stored as neutral lipids in intracellular vesicles and are incorporated into phospholipids of cellular membranes. However, only nanoemulsions additionally use clathrin-mediated endocytosis and deliver fatty acids to mitochondria for increased β-oxidation.

CONCLUSIONS

Size of lipid emulsion droplets significantly influences their uptake and subsequent metabolism in CD4+ T cells. Our results highlight the potential for improved nutrient utilization with nanoemulsions in TPN formulations possibly leading to less adverse effects.

Endo-Lysosomal Network Disorder Reprograms Energy Metabolism in SorL1-Null Rat Hippocampus

Sortilin-related receptor 1 (SorL1) deficiency is a genetic predisposition to familial Alzheimer's disease (AD), but its pathology is poorly understood. In SorL1-null rats, a disorder of the global endosome-lysosome network (ELN) is found in hippocampal neurons. Deletion of amyloid precursor protein (APP) in SorL1-null rats could not completely rescue the neuronal abnormalities in the ELN of the hippocampus and the impairment of spatial memory in SorL1-null young rats. These in vivo observations indicated that APP is one of the cargoes of SorL1 in the regulation of the ELN, which affects hippocampal-dependent memory. When SorL1 is depleted, the endolysosome takes up more of the lysosome flux and damages lysosomal digestion, leading to pathological lysosomal storage and disturbance of cholesterol and iron homeostasis in the hippocampus. These disturbances disrupt the original homeostasis of the material-energy-subcellular structure and reprogram energy metabolism based on fatty acids in the SorL1-null hippocampus, instead of glucose. Although fatty acid oxidation increases ATP supply, it cannot reduce the levels of the harmful byproduct ROS during oxidative phosphorylation, as it does in glucose catabolism. Therefore, the SorL1-null rats exhibit hippocampal degeneration, and their spatial memory is impaired. Our research sheds light on the pathology of SorL1 deficiency in AD.

Endolysosomal trapping of therapeutics and endosomal escape strategies

Internalizing therapeutic molecules or genes into cells and safely delivering them to the target tissue where they can perform the intended tasks is one of the key characteristics of the smart gene/drug delivery vector. Despite much research in this field, endosomal escape continues to be a significant obstacle to the development of effective gene/drug delivery systems. In this review, we discuss in depth the several types of endocytic pathways involved in the endolysosomal trapping of therapeutic agents. In addition, we describe numerous mechanisms involved in nanoparticle endosomal escape. Furthermore, many other techniques are employed to increase endosomal escape to minimize entrapment of therapeutic compounds within endolysosomes, which have been reviewed at length in this study.

Twice weekly dosing with Sebelipase alfa (Kanuma®) rescues severely ill infants with Wolman disease

BACKGROUND

Sebelipase alfa (Kanuma®) is approved for patients with Wolman disease (WD) at a dosage of 3-5 mg/kg once weekly. Survival rates in the second of two clinical trials was greater, despite recruiting more severely ill patients, probably related to higher initial and maximal doses. We aimed to evaluate the effective pharmacokinetics and pharmacodynamics of Sebelipase alfa when administered to patients with severe WD at 5 mg/kg twice weekly, an intensive regimen which was not assessed in the trials.

METHODS

We recruited 3 patients receiving Sebelipase alfa 5 mg/kg twice weekly. We measured LAL activity in leukocytes and plasma oxysterol concentration in two patients and LAL activity in fibroblasts in one patient. Clinical follow up was also assessed.

RESULTS

Analyses of LAL activity and oxysterols demonstrate that there is short-lived enzyme activity post-dosing which is associated with the release of stored lipids. Clinical data demonstrate that 5 mg/kg twice weekly dosing is well tolerated and effective.

CONCLUSION

5 mg/kg twice weekly dosing with Sebelipase alfa rescues severely ill infants with WD by increasing substrate clearance. There is biologically relevant lipid accumulation in the 'trough' periods before the next dosing, even with this intensive regimen.

Pedigree Analysis of Nonclassical Cholesteryl Ester Storage Disease with Dominant Inheritance in a LIPA I378T Heterozygous Carrier

BACKGROUND

Cholesterol ester storage disorder (CESD; OMIM: 278,000) was formerly assumed to be an autosomal recessive allelic genetic condition connected to diminished lysosomal acid lipase (LAL) activity due to LIPA gene abnormalities. CESD is characterized by abnormal liver function and lipid metabolism, and in severe cases, liver failure can occur leading to death. In this study, one Chinese nonclassical CESD pedigree with dominant inheritance was phenotyped and analyzed for the corresponding gene alterations.

METHODS

Seven males and eight females from nonclassical CESD pedigree were recruited. Clinical features and LAL activities were documented. Whole genome Next-generation sequencing (NGS) was used to screen candidate genes and mutations, Sanger sequencing confirmed predicted mutations, and qPCR detected LIPA mRNA expression.

RESULTS

Eight individuals of the pedigree were speculatively thought to have CESD. LAL activity was discovered to be lowered in four living members of the pedigree, but undetectable in the other four deceased members who died of probable hepatic failure. Three of the four living relatives had abnormal lipid metabolism and all four had liver dysfunctions. By liver biopsy, the proband exhibited diffuse vesicular fatty changes in noticeably enlarged hepatocytes and Kupffer cell hyperplasia. Surprisingly, only a newly discovered heterozygous mutation, c.1133T>C (p. Ile378Thr) on LIPA, was found by gene sequencing in the proband. All living family members who carried the p.I378T variant displayed reduced LAL activity.

CONCLUSIONS

Phenotypic analyses indicate that this may be an autosomal dominant nonclassical CESD pedigree with a LIPA gene mutation.

LINC317.5 as a novel biomarker for hypertriglyceridemia in normal glucose metabolism

The global rise in prediabetes and diabetes, with type 2 diabetes (T2DM) being predominant, highlights the association between T2DM and hypertriglyceridemia (HTG). Patients with both abnormal glucose levels and HTG require increased attention due to higher risks of complications and mortality. Therefore, this study aimed to find the key long non-coding RNA (lncRNA) of HTG in the abnormal glucose metabolism patients. We collected blood samples for RNA sequencing experiments and blood samples for validation in population. We have conducted RNA sequencing, weighted gene co-expression network analysis (WGCNA), quantitative real-time polymerase chain reaction (qRT-PCR) in a 82-vs-82-sample-size population and insulin induced HepG2, RNA- Fluorescence in situ hybridization (FISH) and Cell Counting Kit-8 (CCK-8). We also explored lipid metabolism related transcription factor and the related protein expression and processed key lncRNA by both interference expression and overexpression, and the related consequences were rescued by its target mRNA. ENST00000540317.5 (LINC317.5) was lower in HTG with abnormal glucose metabolism and was found in both cytoplasm and nucleus in HepG2, inversely regulating the accumulation of TG and its target mRNA TKFC. Relative expression of peroxisome proliferator-activated receptor alpha (PPARα) and peroxisome proliferator-activated receptor gamma (PPARγ) were decreasing, and SREBP-1c (sterol regulatory element-binding protein-1c) was increasing of the interference expression of LINC317.5. Interference expression of LINC317.5 significantly decreased the protein expression of ACADM and CPT1A, whereas increased the protein expression of FAS and ACC1. TKFC partly reduced the triglyceride (TG) accumulation of LINC317.5. In conclusion, we suggested LINC317.5-TKFC as a key for TG accumulation in the HepG2-insulin resistant (IR). These might provide information of non-invasive biomarkers for the HTG with abnormal glucose.

Impaired lysosomal acidity maintenance in acid lipase-deficient cells leads to defective autophagy

The lysosome is an acid organelle that contains a variety of hydrolytic enzymes and plays a significant role in intracellular degradation to maintain cellular homeostasis. Genetic variants in lysosome-related genes can lead to severe congenital diseases, such as lysosomal storage diseases. In the present study, we investigated the impact of depleting lysosomal acid lipase A (LIPA), a lysosomal esterase that metabolizes esterified cholesterol or triglyceride, on lysosomal function. Under nutrient-rich conditions, LIPA gene KO (LIPAKO) cells exhibited impaired autophagy, whereas, under starved conditions, they showed normal autophagy. The cause underlying the differential autophagic activity was increased sensitivity of LIPAKO cells to ammonia, which was produced from l-glutamine in the medium. Further investigation revealed that ammonia did not affect upstream signals involved in autophagy induction, autophagosome-lysosome fusion, and hydrolytic enzyme activities in LIPAKO cells. On the other hand, LIPAKO cells showed defective lysosomal acidity upon ammonia loading. Microscopic analyses revealed that lysosomes of LIPAKO cells enlarged, whereas the amount of lysosomal proton pump V-ATPase did not proportionally increase. Since the enlargement of lysosomes in LIPAKO cells was not normalized under starved conditions, this is the primary change that occurred in the LIPAKO cells, and autophagy was affected by impaired lysosomal function under the specific conditions. These findings expand our comprehension of the pathogenesis of Wolman's disease, which is caused by a defect in the LIPA gene, and suggest that conditions, such as hyperlipidemia, may easily disrupt lysosomal functions.

Is lysosomal acid lipase activity associated with the presence and severity of coronary artery disease?

BACKGROUND

Lipid metabolism is considerably complex and there can be many critical steps in atherogenesis. The association between lysosomal acid lipase (LAL) activity and coronary artery disease (CAD) has not been elucidated in detail. We aimed to evaluate the association between LAL activity with the presence and severity of CAD in patients who are seen in daily clinical practice.

METHODS

Patients who underwent coronary angiography were divided into groups according to the angiography results. Syntax scores and Gensini scores were calculated. The LAL activity was measured from dried blood spots.

RESULTS

Median LAL activity values were similar in all study groups (normal coronary arteries: 0.40 nmol/punch/h; non-obstructive CAD: 0.44 nmol/punch/h; obstructive chronic CAD: 0.40 nmol/punch/h; obstructive acute coronary syndrome: 0.48 nmol/punch/h) and there was no correlation between coronary atherosclerotic burden and LAL activity (correlation coefficients Syntax score and LAL: -0.032; Gensini score and LAL: -0.030). In addition, no relationship between serum lipid levels and LAL activity was detected.

CONCLUSION

The presence of CAD and its severity is not associated with the LAL activity in patients encountered in daily clinical practice.

Role of Mn-LIPA in Sex Hormone Regulation and Gonadal Development in the Oriental River Prawn, Macrobrachium nipponense

This study investigates the role of lysosomal acid lipase (LIPA) in sex hormone regulation and gonadal development in Macrobrachium nipponense. The full-length Mn-LIPA cDNA was cloned, and its expression patterns were analyzed using quantitative real-time PCR (qPCR) in various tissues and developmental stages. Higher expression levels were observed in the hepatopancreas, cerebral ganglion, and testes, indicating the potential involvement of Mn-LIPA in sex differentiation and gonadal development. In situ hybridization experiments revealed strong Mn-LIPA signaling in the spermatheca and hepatopancreas, suggesting their potential role in steroid synthesis (such as cholesterol, fatty acids, cholesteryl ester, and triglycerides) and sperm maturation. Increased expression levels of male-specific genes, such as insulin-like androgenic gland hormone (IAG), sperm gelatinase (SG), and mab-3-related transcription factor (Dmrt11E), were observed after dsMn-LIPA (double-stranded LIPA) injection, and significant inhibition of sperm development and maturation was observed histologically. Additionally, the relationship between Mn-LIPA and sex-related genes (IAG, SG, and Dmrt11E) and hormones (17β-estradiol and 17α-methyltestosterone) was explored by administering sex hormones to male prawns, indicating that Mn-LIPA does not directly control the production of sex hormones but rather utilizes the property of hydrolyzing triglycerides and cholesterol to provide energy while influencing the synthesis and secretion of self-sex hormones. These findings provide valuable insights into the function of Mn-LIPA in M. nipponense and its potential implications for understanding sex differentiation and gonadal development in crustaceans. It provides an important theoretical basis for the realization of a monosex culture of M. nipponense.

Loss of lysosomal acid lipase results in mitochondrial dysfunction and fiber switch in skeletal muscles of mice

OBJECTIVE

Lysosomal acid lipase (LAL) is the only enzyme known to hydrolyze cholesteryl esters (CE) and triacylglycerols in lysosomes at an acidic pH. Despite the importance of lysosomal hydrolysis in skeletal muscle (SM), research in this area is limited. We hypothesized that LAL may play an important role in SM development, function, and metabolism as a result of lipid and/or carbohydrate metabolism disruptions.

RESULTS

Mice with systemic LAL deficiency (Lal-/-) had markedly lower SM mass, cross-sectional area, and Feret diameter despite unchanged proteolysis or protein synthesis markers in all SM examined. In addition, Lal-/- SM showed increased total cholesterol and CE concentrations, especially during fasting and maturation. Regardless of increased glucose uptake, expression of the slow oxidative fiber marker MYH7 was markedly increased in Lal-/-SM, indicating a fiber switch from glycolytic, fast-twitch fibers to oxidative, slow-twitch fibers. Proteomic analysis of the oxidative and glycolytic parts of the SM confirmed the transition between fast- and slow-twitch fibers, consistent with the decreased Lal-/- muscle size due to the "fiber paradox". Decreased oxidative capacity and ATP concentration were associated with reduced mitochondrial function of Lal-/- SM, particularly affecting oxidative phosphorylation, despite unchanged structure and number of mitochondria. Impairment in muscle function was reflected by increased exhaustion in the treadmill peak effort test in vivo.

CONCLUSION

We conclude that whole-body loss of LAL is associated with a profound remodeling of the muscular phenotype, manifested by fiber type switch and a decline in muscle mass, most likely due to dysfunctional mitochondria and impaired energy metabolism, at least in mice.

Shenlian extract protected ox-LDL-loaded macrophages against ER stress by promoting LAL-LXRα mediated cholesterol flux

ETHNOPHARMACOLOGICAL RELEVANCE

Shenlian (SL) extract is consisted of extracts from Salvia miltiorrhiza Bunge and Andrographis paniculata (Burm.f.) Nees, two herbs commonly used in Chinese clinical formula to treat atherosclerosis by removing blood stasis and clearing away heat. Pharmacologically, the anti-atherosclerotic effects of these two herbs are related to unresolved inflammation and the macrophage anergy or apoptosis in lesions led by the lipid flux blockage and ER stress. However, the deeper understanding of SL extract in protecting macrophage in plaques remains unknown.

AIM OF THE STUDY

This study aimed to investigate the underlying mechanism of SL extract in protecting ER-stressed macrophages from apoptosis in atherosclerosis.

METHODS

The ApoE-/- atherosclerotic mice model and ox-LDL loaded macrophages model were established to assess the effect of SL extract on ER stress in vivo and in vitro. Key markers related to ER stress in plaque were determined by immunohistochemical staining. Proteins involved in apoptosis and ER stress in macrophages loaded by ox-LDL were assessed by Western blot. ER morphology was observed by electron microscope. Lipid flux was temporally and quantitatively depicted by Oil red staining. The LAL and LXRα were blocked by lalistat and Gsk 2033 respectively to investigate whether SL extract protected the function of macrophages by the activation of LAL-LXRα axis.

RESULTS

Our study reported that, in ApoE-/- atherosclerotic mice, SL extract effectively relieved ER stress of carotid artery plaque. In lipid-overloaded macrophage models, SL extract significantly alleviated ER stress by promoting cholesterol degradation and efflux, which finally prevented apoptosis of foam cells induced by ox-LDL. Blockage of ER stress by 4-Phenylbutyric acid (4-PBA), an inhibitor of Endoplasmic Reticulum (ER) stress, largely attenuated the protective effects of SL extract on macrophage. By utilizing the selective antagonists against both LAL and LXRα, this study further revealed that the beneficial effects of SL extract in macrophages was dependent on the proper functionalization of LAL-LXRα axis.

CONCLUSIONS

By highlighting the therapeutic significance of macrophage protection in resolving atherosclerosis inflammation, our study pharmacologically provided convincing mechanistic evidence of SL extract in the activation LAL-LXRα axis and revealed its promising potential in the promotion of cholesterol turnover and prevention of ER stress induced apoptosis in lipid-loaded macrophages.

Triacylglycerol uptake and handling by macrophages: From fatty acids to lipoproteins

Macrophages are essential innate immune cells and form our first line of immune defense. Also known as professional phagocytes, macrophages interact and take up various particles, including lipids. Defective lipid handling can drive excessive lipid accumulation leading to foam cell formation, a key feature of various cardiometabolic conditions such as atherosclerosis, non-alcoholic fatty liver disease, and obesity. At the same time, intracellular lipid storage and foam cell formation can also be viewed as a protective and anti-lipotoxic mechanism against a lipid-rich environment and associated elevated lipid uptake. Traditionally, foam cell formation has primarily been linked to cholesterol uptake via native and modified low-density lipoproteins. However, other lipids, including non-esterified fatty acids and triacylglycerol (TAG)-rich lipoproteins (very low-density lipoproteins and chylomicrons), can also interact with macrophages. Recent studies have identified multiple pathways mediating TAG uptake and processing by macrophages, including endocytosis and receptor/transporter-mediated internalization and transport. This review will present the current knowledge of how macrophages take up different lipids and lipoprotein particles and address how TAG-rich lipoproteins are processed intracellularly. Understanding how macrophages take up and process different lipid species such as TAG is necessary to design future therapeutic interventions to correct excessive lipid accumulation and associated co-morbidities.

Neural stem cell metabolism revisited: a critical role for mitochondria

Metabolism has emerged as a key regulator of stem cell behavior. Mitochondria are crucial metabolic organelles that are important for differentiated cells, yet considered less so for stem cells. However, recent studies have shown that mitochondria influence stem cell maintenance and fate decisions, inviting a revised look at this topic. In this review, we cover the current literature addressing the role of mitochondrial metabolism in mouse and human neural stem cells (NSCs) in the embryonic and adult brain. We summarize how mitochondria are implicated in fate regulation and how substrate oxidation affects NSC quiescence. We further explore single-cell RNA sequencing (scRNA-seq) data for metabolic signatures of adult NSCs, highlight emerging technologies reporting on metabolic signatures, and discuss mitochondrial metabolism in other stem cells.

Apolipoprotein E ε4 triggers neurotoxicity via cholesterol accumulation, acetylcholine dyshomeostasis, and PKCε mislocalization in cholinergic neuronal cells

The Apolipoprotein E (ApoE) has been known to regulate cholesterol and β-amyloid (Aβ) production, redistribution, and elimination, in the central nervous system (CNS). The ApoE ε4 polymorphic variant leads to impaired brain cholesterol homeostasis and amyloidogenic pathway, thus representing the major risk factor for Alzheimer's Disease (AD). Currently, less is known about the molecular mechanisms connecting ApoE ε4-related cholesterol metabolism and cholinergic system degeneration, one of the main AD pathological features. Herein, in vitro cholinergic neuron models were developed in order to study ApoE neuronal expression and investigate the possible interplay between cholesterol metabolism and cholinergic pathway impairment prompted by ε4 isoform. Particularly, alterations specifically occurring in ApoE ε4-carrying neurons (i.e. increased intracellular ApoE, amyloid precursor protein (APP), and Aβ levels, elevated apoptosis, and reduced cell survival) were recapitulated. ApoE ε4 expression was found to increase intracellular cholesterol accumulation, by regulating the related gene expression, while reducing cholesterol precursor acetyl-CoA, which in turn fuels the acetylcholine (ACh) synthesis route. In parallel, although the ACh intracellular signalling was activated, as demonstrated by the boosted extracellular ACh as well as increased IP₃ and Ca²⁺, the PKCε activation via membrane translocation was surprisingly suppressed, probably explained by the cholesterol overload in ApoE ε4 neuron-like cells. Consequently, the PKC-dependent anti-apoptotic and neuroprotective roles results impaired, reliably adding to other causes of cell death prompted by ApoE ε4. Overall, the obtained data open the way to further critical considerations of ApoE ε4-dependent cholesterol metabolism dysregulation in the alteration of cholinergic pathway, neurotoxicity, and neuronal death.

Lipid droplet biogenesis and functions in health and disease

Ubiquitous yet unique, lipid droplets are intracellular organelles that are increasingly being recognized for their versatility beyond energy storage. Advances uncovering the intricacies of their biogenesis and the diversity of their physiological and pathological roles have yielded new insights into lipid droplet biology. Despite these insights, the mechanisms governing the biogenesis and functions of lipid droplets remain incompletely understood. Moreover, the causal relationship between the biogenesis and function of lipid droplets and human diseases is poorly resolved. Here, we provide an update on the current understanding of the biogenesis and functions of lipid droplets in health and disease, highlighting a key role for lipid droplet biogenesis in alleviating cellular stresses. We also discuss therapeutic strategies of targeting lipid droplet biogenesis, growth or degradation that could be applied in the future to common diseases, such as cancer, hepatic steatosis and viral infection.

Inflammation driven metabolic regulation and adaptation in macrophages

Macrophages are a diverse population of phagocytic immune cells involved in the host defense mechanisms and regulation of homeostasis. Usually, macrophages maintain healthy functioning at the cellular level, but external perturbation in their balanced functions can lead to acute and chronic disease conditions. By sensing the cues from the tissue microenvironment, these phagocytes adopt a plethora of phenotypes, such as inflammatory or M1 to anti-inflammatory (immunosuppressive) or M2 subtypes, to fulfill their spectral range of functions. The existing evidence in the literature supports that in macrophages, regulation of metabolic switches and metabolic adaptations are associated with their functional behaviors under various physiological and pathological conditions. Since these macrophages play a crucial role in many disorders, therefore it is necessary to understand their heterogeneity and metabolic reprogramming. Consequently, these macrophages have also emerged as a promising target for diseases in which their role is crucial in driving the disease pathology and outcome (e.g., Cancers). In this review, we discuss the recent findings that link many metabolites with macrophage functions and highlight how this metabolic reprogramming can improve our understanding of cellular malfunction in the macrophages during inflammatory disorders. A systematic analysis of the interconnecting crosstalk between metabolic pathways with macrophages should inform the selection of immunomodulatory therapies for inflammatory diseases.

Atherosclerosis: The Involvement of Immunity, Cytokines and Cells in Pathogenesis, and Potential Novel Therapeutics

As a leading contributor to coronary artery disease (CAD) and stroke, atherosclerosis has become one of the major cardiovascular diseases (CVD) negatively impacting patients worldwide. The endothelial injury is considered to be the initial step of the development of atherosclerosis, resulting in immune cell migration and activation as well as inflammatory factor secretion, which further leads to acute and chronic inflammation. In addition, the inflammation and lipid accumulation at the lesions stimulate specific responses from different types of cells, contributing to the pathological progression of atherosclerosis. As a result, recent studies have focused on using molecular biological approaches such as gene editing and nanotechnology to mediate cellular response during atherosclerotic development for therapeutic purposes. In this review, we systematically discuss inflammatory pathogenesis during the development of atherosclerosis from a cellular level with a focus on the blood cells, including all types of immune cells, together with crucial cells within the blood vessel, such as smooth muscle cells and endothelial cells. In addition, the latest progression of molecular-cellular based therapy for atherosclerosis is also discussed. We hope this review article could be beneficial for the clinical management of atherosclerosis.

VLDL-VLDLR axis facilitates brown fat thermogenesis through replenishment of lipid fuels and PPARβ/δ activation

In mammals, brown adipose tissue (BAT) is specialized to conduct non-shivering thermogenesis for survival under cold acclimation. Although emerging evidence suggests that lipid metabolites are essential for heat generation in cold-activated BAT, the underlying mechanisms of lipid uptake in BAT have not been thoroughly understood. Here, we show that very-low-density lipoprotein (VLDL) uptaken by VLDL receptor (VLDLR) plays important roles in thermogenic execution in BAT. Compared with wild-type mice, VLDLR knockout mice exhibit impaired thermogenic features. Mechanistically, VLDLR-mediated VLDL uptake provides energy sources for mitochondrial oxidation via lysosomal processing, subsequently enhancing thermogenic activity in brown adipocytes. Moreover, the VLDL-VLDLR axis potentiates peroxisome proliferator activated receptor (PPAR)β/δ activity with thermogenic gene expression in BAT. Accordingly, VLDL-induced thermogenic capacity is attenuated in brown-adipocyte-specific PPARβ/δ knockout mice. Collectively, these data suggest that the VLDL-VLDLR axis in brown adipocytes is a key factor for thermogenic execution during cold exposure.

Macrophage-, Dendritic-, Smooth Muscle-, Endothelium-, and Stem Cells-Derived Foam Cells in Atherosclerosis

Atherosclerosis is an inflammatory disease depending on the buildup, called plaque, of lipoproteins, cholesterol, extracellular matrix elements, and various types of immune and non-immune cells on the artery walls. Plaque development and growth lead to the narrowing of the blood vessel lumen, blocking blood flow, and eventually may lead to plaque burst and a blood clot. The prominent cellular components of atherosclerotic plaque are the foam cells, which, by trying to remove lipoprotein and cholesterol surplus, also participate in plaque development and rupture. Although the common knowledge is that the foam cells derive from macrophages, studies of the last decade clearly showed that macrophages are not the only cells able to form foam cells in atherosclerotic plaque. These findings give a new perspective on atherosclerotic plaque formation and composition and define new targets for anti-foam cell therapies for atherosclerosis prevention. This review gives a concise description of foam cells of different pedigrees and describes the main mechanisms participating in their formation and function.

Secretory autophagy: a turn key for understanding AMD pathology and developing new therapeutic targets?

INTRODUCTION

Age-related macular degeneration (AMD) is an eye disease leading to vision loss with poorly known pathogenesis and limited therapeutic options. Degradative autophagy (DA) is impaired in AMD, but emerging evidence points to secretary autophagy (SA) as a key element in AMD pathogenesis.

AREAS COVERED

SA may cause the release of proteins and protein aggregates, lipofuscin, beta amyloid, faulty mitochondria, pro-inflammatory and pro-angiogenic factors from the retinal pigment epithelium (RPE) that may contribute to drusen formation and choroidal neovascularization. SA may replace DA, when formation of autolysosome is impaired, and then a harmful cargo, instead of being degraded, is extruded from the RPE contributing to drusen and/or angiogenic environment. Therefore, the interplay between DA and SA may be critical for drusen formation and choroidal neovascularization, so it can be a turn key to understand AMD pathogenesis.

EXPERT OPINION

Although SA fulfills some beneficial functions, it is detrimental for the retina in many cases. Therefore, inhibiting SA may be a therapeutic strategy in AMD, but it is challenged by the development of selective SA inhibitors that would not affect DA. The TRIM16, SEC22B and RAB8A proteins, specific for secretory autophagosome, may be primary candidates as therapeutic targets, but their action is not limited to autophagy and therefore requires further studies.

Lipid metabolism and retinal diseases

PURPOSE

The retina has enormous lipids demands and must meet those needs. Retinal lipid homeostasis appears to be based on the symbiosis between neurons, Müller glial cells (MGC), and retinal pigment epithelium (RPE) cells, which can be impacted in several retinal diseases. The current research challenge is to better understand lipid-related mechanisms involved in retinal diseases, such as age-related macular degeneration (AMD) and glaucoma.

RESULTS

In a first axis, in vitro and focus on Müller glial cell, we aimed to characterize whether the 24S-hydroxycholesterol (24S-OHC), an overexpressed end-product of cholesterol elimination pathway in neural tissue and likely produced by suffering retinal ganglion cells in glaucoma, may modulate MGC membrane organization, such as lipid rafts, to trigger cellular signalling pathways related to retinal gliosis. We have found that lipid composition appears to be a key factor of membrane architecture, especially for lipid raft microdomain formation, in MGC. However, 24S-OHC did not appear to trigger retinal gliosis via the modulation of lipid or protein composition within lipid rafts microdomains. This study provided a better understanding of the complex mechanisms involved in the pathophysiology of glaucoma. On a second clinical ax, we focused on the lipid-related mechanisms involved in the dysfunction of aging RPE and the appearance of drusenoid deposits in AMD. Using the Montrachet population-based study, we intend to report the frequency of reticular pseudodrusen (RPD) and its ocular and systemic risk factors, particularly related to lipid metabolisms, such as plasma lipoprotein levels, carotenoids levels, and lipid-lowering drug intake. Our study showed that RPD was less common in subjects taking lipid-lowering drugs. Lipid-lowering drugs, such as statins, may reduce the risk of RPD through their effect on the production and function of lipoproteins. This observation highlights the potential role of retinal lipid trafficking via lipoproteins between photoreceptors and retinal pigment epithelium cells in RPD formation. Those findings have been complemented with preliminary results on the analysis of plasma fatty acid (FA) profile, a surrogate marker of short-term dietary lipid intake, according to the type of predominant drusenoid deposit, soft drusen or RPD, in age-related maculopathy.

CONCLUSION

Further research on lipid metabolism in retinal diseases is warranted to better understand the pathophysiology of retinal diseases and develop new promising diagnostic, prognostic, and therapeutic tools for our patients.

A Modern Approach to Dyslipidemia

Lipid disorders involving derangements in serum cholesterol, triglycerides, or both are commonly encountered in clinical practice and often have implications for cardiovascular risk and overall health. Recent advances in knowledge, recommendations, and treatment options have necessitated an updated approach to these disorders. Older classification schemes have outlived their usefulness, yielding to an approach based on the primary lipid disturbance identified on a routine lipid panel as a practical starting point. Although monogenic dyslipidemias exist and are important to identify, most individuals with lipid disorders have polygenic predisposition, often in the context of secondary factors such as obesity and type 2 diabetes. With regard to cardiovascular disease, elevated low-density lipoprotein cholesterol is essentially causal, and clinical practice guidelines worldwide have recommended treatment thresholds and targets for this variable. Furthermore, recent studies have established elevated triglycerides as a cardiovascular risk factor, whereas depressed high-density lipoprotein cholesterol now appears less contributory than was previously believed. An updated approach to diagnosis and risk assessment may include measurement of secondary lipid variables such as apolipoprotein B and lipoprotein(a), together with selective use of genetic testing to diagnose rare monogenic dyslipidemias such as familial hypercholesterolemia or familial chylomicronemia syndrome. The ongoing development of new agents-especially antisense RNA and monoclonal antibodies-targeting dyslipidemias will provide additional management options, which in turn motivates discussion on how best to incorporate them into current treatment algorithms.

Stable Integration of Inducible SPLICS Reporters Enables Spatio-Temporal Analysis of Multiple Organelle Contact Sites upon Modulation of Cholesterol Traffic

The study of organelle contact sites has received a great impulse due to increased interest in the understanding of their involvement in many disease conditions. Split-GFP-based contact sites (SPLICS) reporters emerged as essential tools to easily detect changes in a wide range of organelle contact sites in cultured cells and in vivo, e.g., in zebrafish larvae. We report here on the generation of a new vector library of SPLICS cloned into a piggyBac system for stable and inducible expression of the reporters in a cell line of interest to overcome any potential weakness due to variable protein expression in transient transfection studies. Stable HeLa cell lines expressing SPLICS between the endoplasmic reticulum (ER) and mitochondria (MT), the ER and plasma membrane (PM), peroxisomes (PO) and ER, and PO and MT, were generated and tested for their ability to express the reporters upon treatment with doxycycline. Moreover, to take advantage of these cellular models, we decided to follow the behavior of different membrane contact sites upon modulating cholesterol traffic. Interestingly, we found that the acute pharmacological inhibition of the intracellular cholesterol transporter 1 (NPC1) differently affects membrane contact sites, highlighting the importance of different interfaces for cholesterol sensing and distribution within the cell.

Functional Characterization of Genetic Variant Effects on Expression

Thousands of common genetic variants in the human population have been associated with disease risk and phenotypic variation by genome-wide association studies (GWAS). However, the majority of GWAS variants fall into noncoding regions of the genome, complicating our understanding of their regulatory functions, and few molecular mechanisms of GWAS variant effects have been clearly elucidated. Here, we set out to review genetic variant effects, focusing on expression quantitative trait loci (eQTLs), including their utility in interpreting GWAS variant mechanisms. We discuss the interrelated challenges and opportunities for eQTL analysis, covering determining causal variants, elucidating molecular mechanisms of action, and understanding context variability. Addressing these questions can enable better functional characterization of disease-associated loci and provide insights into fundamental biological questions of the noncoding genetic regulatory code and its control of gene expression. Expected final online publication date for the Annual Review of Biomedical Data Science, Volume 5 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Lysosomal acid lipase deficiency – an underestimated cause of hypercholesterolemia in children

Lysosomal acid lipase deficiency (LAL-D) is a rare, progressive, autosomal recessive disease, which develops due to impaired degradation and subsequent intra-lysosomal accumulation of triglycerides and cholesterol esters causing dyslipidemia. The clinical manifestations of the disease presumably depend on the residual activity of the enzyme, lysosomal acid lipase. A profound deficiency of the enzyme known as Wolman’s disease has an onset in the first 6 months of life. The disease reveals itself by dyspeptic disorders in the form of vomiting and diarrhea, lack of weight gain, hepatosplenomegaly, and adrenal calcification. If the Wolman’s disease is not treated, children die within the first 6 months as a result of exhaustion caused by malabsorption syndrome combined with progressive deterioration of liver and adrenal glands. Partial deficiency of lysosomal acid lipase manifests itself at a later age and is called cholesterol ester storage disease. Its clinical presentations include hepatosplenomegaly, elevated transaminases, hypercholesterolemia, and, in some cases, hypertriglyceridemia. Liver failure is the main cause of death in the natural course of cholesterol ester storage disease. Delayed diagnosis of the disease leads to its progression causing irreversible liver damage. The implementation of mass screening programs with the determination of cholesterol levels in childhood is critical to identifying asymptomatic patients.The article presents a clinical case of a patient aged 3 years. The molecular genetic testing showed a mutation in exon 8 of the LIPA gene: NM_000235.3:c.894G>A synonymous variant in the homozygous state. It was also found that both parents of the girl had this type of mutation in the heterozygous state. The patient was prescribed sebelipase alfa in a dose of 1 mg/kg once every 14 days. The treatment was well tolerated. Due to the early verification of the diagnosis and timely pathogenetic therapy, the prognosis of the course of LAL-D, the duration and quality of life of the child were considered to be favourable.Raising the awareness of doctors along with the introduction of effective screening programs for the timely detection of dyslipidemia in children contributes to timely diagnosis and early initiation of pathogenetic therapy, which can increase the life expectancy of patients with lysosomal acid lipase deficiency and improve their quality of life.

Modified Lipoproteins Induce Arterial Wall Inflammation During Atherogenesis

Circulating apolipoprotein B-containing lipoproteins, notably the low-density lipoproteins, enter the inner layer of the arterial wall, the intima, where a fraction of them is retained and modified by proteases, lipases, and oxidizing agents and enzymes. The modified lipoproteins and various modification products, such as fatty acids, ceramides, lysophospholipids, and oxidized lipids induce inflammatory reactions in the macrophages and the covering endothelial cells, initiating an increased leukocyte diapedesis. Lipolysis of the lipoproteins also induces the formation of cholesterol crystals with strong proinflammatory properties. Modified and aggregated lipoproteins, cholesterol crystals, and lipoproteins isolated from human atherosclerotic lesions, all can activate macrophages and thereby induce the secretion of proinflammatory cytokines, chemokines, and enzymes. The extent of lipoprotein retention, modification, and aggregation have been shown to depend largely on differences in the composition of the circulating lipoprotein particles. These properties can be modified by pharmacological means, and thereby provide opportunities for clinical interventions regarding the prevention and treatment of atherosclerotic vascular diseases.

Lipophagy at a glance

Lipophagy is a central cellular process for providing the cell with a readily utilized, high energy source of neutral lipids. Since its discovery over a decade ago, we are just starting to understand the molecular components that drive lipophagy, how it is activated in response to nutrient availability, and its potential as a therapeutic target in disease. In this Cell Science at a Glance article and the accompanying poster, we first provide a brief overview of the different structural and enzymatic proteins that comprise the lipid droplet (LD) proteome and reside within the limiting phospholipid monolayer of this complex organelle. We then highlight key players in the catabolic breakdown of LDs during the functionally linked lipolysis and lipophagy processes. Finally, we discuss what is currently known about macro- and micro-lipophagy based on findings in yeast, mammalian and other model systems, and how impairment of these important functions can lead to disease states.

Autophagy Is Differentially Regulated in Leukocyte and Nonleukocyte Foam Cells During Atherosclerosis

RATIONALE

Atherosclerosis is characterized by an accumulation of foam cells within the arterial wall, resulting from excess cholesterol uptake and buildup of cytosolic lipid droplets (LDs). Autophagy promotes LD clearance by freeing stored cholesterol for efflux, a process that has been shown to be atheroprotective. While the role of autophagy in LD catabolism has been studied in macrophage-derived foam cells, this has remained unexplored in vascular smooth muscle cell (VSMC)-derived foam cells that constitute a large fraction of foam cells within atherosclerotic lesions.

OBJECTIVE

We performed a comparative analysis of autophagy flux in lipid-rich aortic intimal populations to determine whether VSMC-derived foam cells metabolize LDs similarly to their macrophage counterparts.

METHODS AND RESULTS

Atherosclerosis was induced in GFP-LC3 transgenic mice by PCSK9 (proprotein convertase subtilisin/kexin type 9)-adeno-associated viral injection and Western diet feeding. Using flow cytometry of aortic digests, we observed a significant increase in dysfunctional autophagy of VSMC-derived foam cells during atherogenesis relative to macrophage-derived foam cells. Using cell culture models of lipid-loaded VSMC and macrophage, we show that autophagy-mediated cholesterol efflux from VSMC foam cells was poor relative to macrophage foam cells, and largely occurs when HDL (high-density lipoprotein) is used as a cholesterol acceptor, as opposed to apoA-1 (apolipoproteinA-1). This was associated with the predominant expression of ABCG1 in VSMC foam cells. Using metformin, an autophagy activator, cholesterol efflux to HDL was significantly increased in VSMC, but not in macrophage, foam cells.

CONCLUSIONS

These data demonstrate that VSMC and macrophage foam cells perform cholesterol efflux by distinct mechanisms, and that autophagy flux is highly impaired in VSMC foam cells, but can be induced by pharmacological means. Further investigation is warranted into targeting autophagy specifically in VSMC foam cells, the predominant foam cell subtype of advanced atherosclerotic plaques, to promote reverse cholesterol transport and resolution of the atherosclerotic plaque.

Lipid scavenging macrophages and inflammation

Macrophages are professional phagocytes, indispensable for maintenance of tissue homeostasis and integrity. Depending on their resident tissue, macrophages are exposed to highly diverse metabolic environments. Adapted to their niche, they can contribute to local metabolic turnover through metabolite uptake, conversion, storage and release. Disturbances in tissue homeostasis caused by infection, inflammation or damage dramatically alter the local milieu, impacting macrophage activation status and metabolism. In the case of persisting stimuli, defective macrophage responses ensue, which can promote tissue damage and disease. Especially relevant herein are disbalances in lipid rich environments, where macrophages are crucially involved in lipid uptake and turnover, preventing lipotoxicity. Lipid uptake is to a large extent facilitated by macrophage expressed scavenger receptors that are dynamically regulated and important in many metabolic diseases. Here, we review the receptors mediating lipid uptake and summarize recent findings on their role in health and disease. We further highlight the underlying pathways driving macrophage lipid acquisition and their impact on myeloid metabolic remodelling.

Cadmium induces triglyceride levels via microsomal triglyceride transfer protein (MTTP) accumulation caused by lysosomal deacidification regulated by endoplasmic reticulum (ER) Ca2+ homeostasis

Cadmium (Cd) exposure induced lipid metabolic disorder with changes in lipid composition, as well as triglyceride (TG) levels. Liver is the main organ maintaining body TG level and previous studies suggested that Cd exposure might increase TG synthesis but reduce TG uptake in liver. However, the effects of Cd exposure on TG secretion from liver and underlying mechanism are still unclear. In the present study, the data revealed that Cd exposure increased TG levels in the HepG2 cells and the cultured medium by increasing the expression of microsomal triglyceride transfer protein (MTTP), which was abrogated by siRNA knockdown of MTTP. MTTP was synergistically accumulated after Cd exposure or treated with proteasome inhibitor MG132 and lysosome inhibitor chloroquine (CQ), which suggested the Cd increased MTTP protein stability by inhibiting both the proteasome and the lysosomal protein degradation pathways. In addition, our results demonstrated that Cd exposure inhibited the lysosomal acidic degradation pathway through disrupting endoplastic reticulum (ER) Ca2+ homeostasis. Cd-induced MTTP protein and TG levels were significantly reduced by pretreatments of BAPTA/AM chelation of intracellular Ca2+, 2-APB inhibition of ER Ca2+ release channel inositol 1,4,5-trisphosphate receptor (IP3R) and CDN1163 activation of ER Ca2+ reuptake pump sarcoplasmic reticulum Ca2+-ATPase (SERCA). These results suggest that Cd-induced ER Ca2+ release impaired the lysosomal acidity, which associated with MTTP protein accumulation and contributed to increased TG levels.

Hepatic lysosomal acid lipase drives the autophagy-lysosomal response and alleviates cholesterol metabolic disorder in ApoE deficient mice

Lysosomal acid lipase (LAL)-dependent lipolysis degrades cholesteryl ester (CE) and triglyceride in the lysosome. LAL deficiency in human and mice leads to hypercholesterolemia, hepatic CE deposition, and atherosclerosis. Despite its hepatocyte-specific deficiency leads to CE accumulation, the regulation of LAL in cholesterol metabolic disease remains elusive. For the in vitro study, the target gene Lipa was transfected with recombinant shRNA or lentiviral vector in Hepa1-6 cells. It was found that LAL silencing in cells affected lysosomal function by reducing LAL activity and proteolytic activity, and altered the expression of genes related to cholesterol metabolism and autophagy, leading to cholesterol accumulation; whereas LAL overexpression improved the above effects. To explore the impacts of hepatic LAL on cholesterol metabolic disease in vivo, apolipoprotein E deficient (ApoE^-/-) mice were intravenously injected with lentivirus to achieve hepatic LAL overexpression and fed a Western diet for 16 weeks. The results showed that hepatic LAL overexpression significantly reduced plasma lipid levels, alleviated inflammation and oxidative status in plasma and liver, and attenuated hepatic steatosis and fibrosis in ApoE^-/- mice. Mechanically, hepatic LAL promoted cholesterol transport and biliary excretion by increasing liver X receptor alpha (LXRα) and its downstream genes, and modulated the compliance of the autophagy-lysosomal pathway. Our data provide the original evidence of the validity of hepatic LAL in controlling cholesterol metabolism and liver homeostasis, suggesting that targeting hepatic LAL may provide a promising approach to rescue cholesterol metabolic disorders, such as hypercholesterolemia and liver disease.

Loss of function of lysosomal acid lipase (LAL) profoundly impacts osteoblastogenesis and increases fracture risk in humans

Lysosomal acid lipase (LAL) is essential for cholesteryl ester (CE) and triacylglycerol (TAG) hydrolysis in the lysosome. Clinically, an autosomal recessive LIPA mutation causes LAL deficiency (LALD), previously described as Wolman Disease or Cholesteryl Ester Storage Disease (CESD). LAL-D is associated with ectopic lipid accumulation in the liver, small intestine, spleen, adrenal glands, and blood. Considering the importance of unesterified cholesterol and fatty acids in bone metabolism, we hypothesized that LAL is essential for bone formation, and ultimately, skeletal health. To investigate the role of LAL in skeletal homeostasis, we used LAL-deficient (^-/-) mice, in vitro osteoblast cultures, and novel clinical data from LAL-D patients. Both male and female LAL^-/- mice demonstarted lower trabecular and cortical bone parameters , which translated to reduced biomechanical properties. Further histological analyses revealed that LAL^-/- mice had fewer osteoblasts, with no change in osteoclast or marrow adipocyte numbers. In studying the cell-autonomous role of LAL, we observed impaired differentiation of LAL^-/- calvarial osteoblasts and in bone marrow stromal cells treated with the LAL inhibitor lalistat. Consistent with LAL's role in other tissues, lalistat resulted in profound lipid puncta accumulation and an altered intracellular lipid profile. Finally, we analyzed a large de-identified national insurance database (i.e. 2016/2017 Optum Clinformatics®) which revealed that adults (≥18 years) with CESD (n = 3076) had a higher odds ratio (OR = 1.21; 95% CI = 1.03-1.41) of all-cause fracture at any location compared to adults without CESD (n = 13.7 M) after adjusting for demographic variables and osteoporosis. These data demonstrate that alterations in LAL have significant clinical implications related to fracture risk and that LAL's modulation of lipid metabolism is a critical for osteoblast function.

A Selective Look at Autophagy in Pancreatic β-Cells

Insulin-producing pancreatic β-cells are central to glucose homeostasis, and their failure is a principal driver of diabetes development. To preserve optimal health β-cells must withstand both intrinsic and extrinsic stressors, ranging from inflammation to increased peripheral insulin demand, in addition to maintaining insulin biosynthesis and secretory machinery. Autophagy is increasingly being appreciated as a critical β-cell quality control system vital for glycemic control. Here we focus on the underappreciated, yet crucial, roles for selective and organelle-specific forms of autophagy as mediators of β-cell health. We examine the unique molecular players underlying each distinct form of autophagy in β-cells, including selective autophagy of mitochondria, insulin granules, lipid, intracellular amyloid aggregates, endoplasmic reticulum, and peroxisomes. We also describe how defects in selective autophagy pathways contribute to the development of diabetes. As all forms of autophagy are not the same, a refined view of β-cell selective autophagy may inform new approaches to defend against the various insults leading to β-cell failure in diabetes.

Cholesterol-related gene variants are associated with diabetes in coronary artery disease patients

Coronary artery disease (CAD) which is a complex cardiovascular disease is the leading cause of death worldwide. The changing prevalence of the disease in different ethnic groups pointing out the genetic background of CAD. In this study, we aimed to evaluate the contribution of selected cholesterol metabolism-related gene polymorphisms to CAD presence. A total of 493 individuals who underwent coronary angiography were divided into 2 groups: normal coronary arteries (≤ 30% stenosis) and critical disease (≥ 50% stenosis). Individuals were genotyped for APOC1 (rs11568822), APOD (rs1568565), LIPA (rs13500), SORL1 (rs2282649), and LDLR (rs5930) polymorphisms using hydrolysis probes in Real-Time PCR. Blood samples were drawn before coronary angiography and biochemical analyses were done. The results were statistically evaluated. When the study group was stratified according to CAD, the minor allele of APOD polymorphism was found related to decreased risk for T2DM in the non-CAD group. In logistic regression analysis adjusted for several confounders, LDLR rs5930 polymorphism was found associated with T2DM presence in the male CAD group [OR = 0.502, 95%CI (0.259-0.974), p = 0.042]. Besides, APOD and LIPA polymorphisms were shown to affect serum lipid levels in non-CAD T2DM patients (p < 0.05). The minor allele of APOC1 was found associated with triglyceride levels in males independent of CAD status. Besides, LDLR minor allele carrier females had elevated HbA1c and glucose levels independent from CAD status in the whole group. The cholesterol metabolism-related gene polymorphisms were found associated with T2DM and biochemical parameters stratified to sex, CAD, and T2DM status.

Lysosomal acid lipase gene single nucleotide polymorphism and pulmonary tuberculosis susceptibility

BACKGROUND

The factors that predispose to pulmonary tuberculosis (PTB) are not fully understood, However. Gene polymorphisms have been associated with PTB development.

OBJECTIVES

In this study, we investigated the relationship between LIPA gene polymorphisms and a predisposition to pulmonary tuberculosis caused by Mycobacterium tuberculosis.

METHODS

A total of 202 cases of PTB and 218 healthy controls (HCS) were included in this study. Analyses were done under allelic, homozygous, and heterozygous, dominant, recessive models, and were used to calculate values, odds ratios (ORs), and 95% confidence intervals (CIs) for assessing the association between single nucleotide polymorphisms (SNPs) and disease risk. Genotyping was conducted using the real time polymerase chain reaction with high resolution melting curve analysis.

RESULTS

When comparing PTB patients with healthy controls (HCS), significant associations with disease development were observed for both SNPs rs1051338 and rs7922269. Analysis was done based on models of genetic inheritance in man that is co-dominant, recessive and dominant models. Rs1051338, the heterozygous (AC vs. AA) P: 0.001, OR: 1.998, 95% CI: 1.312-3.042 and homozygous (CC vs. AA) P: < 0.001, OR: 4.078, 95% CI: 2.134-7.796 Co-dominant associated with increased risk for the disease. Under recessive (CC vs. AA + AC), P: 0.001, OR: 2.829: 95% CI: 1.543-5.185 and dominant model (AC + CC vs. AA) P: < 001, OR: 2.331, 95% CI: 1.564-3.474 the genotypes distribution increased the individual risk, plus its alleles distribution (P: < 0.001, OR: 2.004, 95% CI: 1.505-2.669). Considering SNP rs7922269 mutation significantly increased pulmonary tuberculosis risk as was observed in the homozygous GG vs. TT (P: 0.003, OR: 3.162, 95% CI: 1.431-6.989); heterozygous GT vs. TT (P: < 0.001, OR: 1.2.259, 95% CI: 1.503-3.394); dominant model (GT + GG vs. TT; P: < 0.001, OR: 2.061, 95% CI: 1.402-3.032) and the allele G (P: < 0.001, OR: 1.829, 95% CI:1.361-2.458), however no significant association was observed in the Recessive model (GG vs. TT + GT; P: 0.057, OR: 2.568, 95% CI: 0.965-4.432).

CONCLUSION

The findings of our study strengthen the hypothesis that LIPA rs1051338 and rs7922269 polymorphism associated with increased risk for pulmonary Tb in a sample of northern Chinese population.

Interactions of Lipid Droplets with the Intracellular Transport Machinery

Historically, studies of intracellular membrane trafficking have focused on the secretory and endocytic pathways and their major organelles. However, these pathways are also directly implicated in the biogenesis and function of other important intracellular organelles, the best studied of which are peroxisomes and lipid droplets. There is a large recent body of work on these organelles, which have resulted in the introduction of new paradigms regarding the roles of membrane trafficking organelles. In this review, we discuss the roles of membrane trafficking in the life cycle of lipid droplets. This includes the complementary roles of lipid phase separation and proteins in the biogenesis of lipid droplets from endoplasmic reticulum (ER) membranes, and the attachment of mature lipid droplets to membranes by lipidic bridges and by more conventional protein tethers. We also discuss the catabolism of neutral lipids, which in part results from the interaction of lipid droplets with cytosolic molecules, but with important roles for both macroautophagy and microautophagy. Finally, we address their eventual demise, which involves interactions with the autophagocytotic machinery. We pay particular attention to the roles of small GTPases, particularly Rab18, in these processes.

Novel insights: Dynamic foam cells derived from the macrophage in atherosclerosis

Atherosclerosis can be regarded as a chronic disease derived from the interaction between disordered lipoproteins and an unsuitable immune response. The evolution of foam cells is not only a significant pathological change in the early stage of atherosclerosis but also a key stage in the occurrence and development of atherosclerosis. The formation of foam cells is mainly caused by the imbalance among lipids uptake, lipids treatment, and reverse cholesterol transport. Although a large number of studies have summarized the source of foam cells and the mechanism of foam cells formation, we propose a new idea about foam cells in atherosclerosis. Rather than an isolated microenvironment, the macrophage multiple lipid uptake pathways, lipid internalization, lysosome, mitochondria, endoplasmic reticulum, neutral cholesterol ester hydrolase (NCEH), acyl-coenzyme A-cholesterol acyltransferase (ACAT), and reverse cholesterol transport are mutually influential, and form a dynamic process under multi-factor regulation. The macrophage takes on different uptake lipid statuses depending on multiple uptake pathways and intracellular lipids, lipid metabolites versus pro-inflammatory factors. Except for NCEH and ACAT, the lipid internalization of macrophages also depends on multicellular organelles including the lysosome, mitochondria, and endoplasmic reticulum, which are associated with each other. A dynamic balance between esterification and hydrolysis of cholesterol for macrophages is essential for physiology and pathology. Therefore, we propose that the foam cell in the process of atherosclerosis may be dynamic under multi-factor regulation, and collate this study to provide a holistic and dynamic idea of the foam cell.

The diversity and breadth of cancer cell fatty acid metabolism

Tumor cellular metabolism exhibits distinguishing features that collectively enhance biomass synthesis while maintaining redox balance and cellular homeostasis. These attributes reflect the complex interactions between cell-intrinsic factors such as genomic-transcriptomic regulation and cell-extrinsic influences, including growth factor and nutrient availability. Alongside glucose and amino acid metabolism, fatty acid metabolism supports tumorigenesis and disease progression through a range of processes including membrane biosynthesis, energy storage and production, and generation of signaling intermediates. Here, we highlight the complexity of cellular fatty acid metabolism in cancer, the various inputs and outputs of the intracellular free fatty acid pool, and the numerous ways that these pathways influence disease behavior.

Serum lipoprotein-derived fatty acids regulate hypoxia-inducible factor

Oxygen regulates hypoxia-inducible factor (HIF) transcription factors to control cell metabolism, erythrogenesis, and angiogenesis. Whereas much has been elucidated about how oxygen regulates HIF, whether lipids affect HIF activity is un-known. Here, using cultured cells and two animal models, we demonstrate that lipoprotein-derived fatty acids are an independent regulator of HIF. Decreasing extracellular lipid supply inhibited HIF prolyl hydroxylation, leading to accumulation of the HIFα subunit of these heterodimeric transcription factors comparable with hypoxia with activation of downstream target genes. The addition of fatty acids to culture medium suppressed this signal, which required an intact mitochondrial respiratory chain. Mechanistically, fatty acids and oxygen are distinct signals integrated to control HIF activity. Finally, we observed lipid signaling to HIF and changes in target gene expression in developing zebrafish and adult mice, and this pathway operates in cancer cells from a range of tissues. This study identifies fatty acids as a physiological modulator of HIF, defining a mechanism for lipoprotein regulation that functions in parallel to oxygen.

Mitochondria orchestrate macrophage effector functions in atherosclerosis

Macrophages are pivotal in the initiation and development of atherosclerotic cardiovascular diseases. Recent studies have reinforced the importance of mitochondria in metabolic and signaling pathways to maintain macrophage effector functions. In this review, we discuss the past and emerging roles of macrophage mitochondria metabolic diversity in atherosclerosis and the potential avenue as biomarker. Beyond metabolic functions, mitochondria are also a signaling platform integrating epigenetic, redox, efferocytic and apoptotic regulations, which are exquisitely linked to their dynamics. Indeed, mitochondria functions depend on their density and shape perpetually controlled by mitochondria fusion/fission and biogenesis/mitophagy balances. Mitochondria can also communicate with other organelles such as the endoplasmic reticulum through mitochondria-associated membrane (MAM) or be secreted for paracrine actions. All these functions are perturbed in macrophages from mouse or human atherosclerotic plaques. A better understanding and integration of how these metabolic and signaling processes are integrated and dictate macrophage effector functions in atherosclerosis may ultimately help the development of novel therapeutic approaches.

Lysosomal quality control of cell fate: a novel therapeutic target for human diseases

In eukaryotic cells, lysosomes are digestive centers where biological macromolecules are degraded by phagocytosis and autophagy, thereby maintaining cellular self-renewal capacity and energy supply. Lysosomes also serve as signaling hubs to monitor the intracellular levels of nutrients and energy by acting as platforms for the assembly of multiple signaling pathways, such as mammalian target of rapamycin complex 1 (mTORC1) and adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK). The structural integrity and functional balance of lysosomes are essential for cell function and viability. In fact, lysosomal damage not only disrupts intracellular clearance but also results in the leakage of multiple contents, which pose great threats to the cell by triggering cell death pathways, including apoptosis, necroptosis, pyroptosis, and ferroptosis. The collapse of lysosomal homeostasis is reportedly critical for the pathogenesis and development of various diseases, such as tumors, neurodegenerative diseases, cardiovascular diseases, and inflammatory diseases. Lysosomal quality control (LQC), comprising lysosomal repair, lysophagy, and lysosomal regeneration, is rapidly initiated in response to lysosomal damage to maintain lysosomal structural integrity and functional homeostasis. LQC may be a novel but pivotal target for disease treatment because of its indispensable role in maintaining intracellular homeostasis and cell fate.

Metformin reduces saturated fatty acid-induced lipid accumulation and inflammatory response by restoration of autophagic flux in endothelial cells

Autophagy, an integral part of the waste recycling process, plays an important role in cellular physiology and pathophysiology. Impaired autophagic flux causes ectopic lipid deposition, which is defined as the accumulation of lipids in non-adipose tissue. Ectopic lipid accumulation is observed in patients with cardiometabolic syndrome, including obesity, diabetes, insulin resistance, and cardiovascular complications. Metformin is the first line of treatment for type 2 diabetes, and one of the underlying mechanisms for the anti-diabetic effect of metformin is mediated by the stimulation of AMP-activated protein kinase (AMPK). Because the activation of AMPK is crucial for the initiation of autophagy, we hypothesize that metformin reduces the accumulation of lipid droplets by increasing autophagic flux in vascular endothelial cells. Incubation of vascular endothelial cells with saturated fatty acid (SFA) increased the accumulation of lipid droplets and impaired autophagic flux. We observed that the accumulation of lipid droplets was reduced, and the autophagic flux was enhanced by treatment with metformin. The knock-down of AMPKα by using siRNA blunted the effect of metformin. Furthermore, treatment with SFA or inhibition of autophagy increased leukocyte adhesion, whereas treatment with metformin decreased the SFA-induced leukocyte adhesion. The results suggest a novel mechanism by which metformin protects vascular endothelium from SFA-induced ectopic lipid accumulation and pro-inflammatory responses. In conclusion, improving autophagic flux may be a therapeutic strategy to protect endothelial function from dyslipidemia and diabetic complications.

Serum protein profile analysis in lysosomal storage disorders patients

INTRODUCTION

Serum protein electrophoresis (SPE) is a well-established technique to identify alterations in plasma protein profiles, caused by diseases as multiple myeloma (MM). In addition, it could be a cost-effective technique to discover new plasma biomarkers. Relation between MM and lysosomal storage diseases (LSDs) as Gaucher disease has been set out but, it has not been evaluated on other LSDs nor the utility of the SPE as first step on LSDs biomarkers discovery projects.

MATERIALS AND METHODS

Stored plasma samples at diagnosis from several LSDs patients underwent analysis. Quality control was checked prior to the SPE was analyzed by capillary electrophoresis. The analysis for monoclonal spikes and the differences between each fraction on patients' samples vs the control data previously published, were evaluated. Furthermore, immunoprotein quantification and free light chains ratio were done by nephelometry and turbidimetry.

RESULTS

Seventy-five samples of LSD patients at diagnosis, were assessed. The frequency of the MGUS on LSDs patients was not higher than in general population whereas one lysosomal acid lipase deficiency infant showed increased IgA and kappa deviation. Regarding to the usefulness of SPE in biomarkers discovery, statistically significant differences were observed on SPE fractions between LSDs and healthy population.

DISCUSSION

The evaluation of SPE fractions can be a useful tool to understand pathophysiologic aspects in LDSs and, to simplify new marker discovery projects. In some of them, the MGUS appearance is a risk factor for the MM development despite its frequency is not increased on the studied LSDs at diagnosis.

Lipid Metabolism in Macrophages: Focus on Atherosclerosis

Mechanisms of lipid homeostasis and its impairment are of crucial importance for atherogenesis, and their understanding is necessary for successful development of new therapeutic approaches. In the arterial wall, macrophages play a prominent role in intracellular lipid accumulation, giving rise to foam cells that populate growing atherosclerotic plaques. Under normal conditions, macrophages are able to process substantial amounts of lipids and cholesterol without critical overload of the catabolic processes. However, in atherosclerosis, these pathways become inefficient, leading to imbalance in cholesterol and lipid metabolism and disruption of cellular functions. In this review, we summarize the existing knowledge on the involvement of macrophage lipid metabolism in atherosclerosis development, including both the results of recent studies and classical concepts, and provide a detailed description of these processes from the moment of lipid uptake with lipoproteins to cholesterol efflux.

Immunometabolic function of cholesterol in cardiovascular disease and beyond

Inflammation represents the driving feature of many diseases, including atherosclerosis, cancer, autoimmunity and infections. It is now established that metabolic processes shape a proper immune response and within this context the alteration in cellular cholesterol homeostasis has emerged as a culprit of many metabolic abnormalities observed in chronic inflammatory diseases. Cholesterol accumulation supports the inflammatory response of myeloid cells (i.e. augmentation of toll-like receptor signalling, inflammasome activation, and production of monocytes and neutrophils) which is beneficial in the response to infections, but worsens diseases associated with chronic metabolic inflammation including atherosclerosis. In addition to the innate immune system, cells of adaptive immunity, upon activation, have also been shown to undergo a reprogramming of cellular cholesterol metabolism, which results in the amplification of inflammatory responses. Aim of this review is to discuss (i) the molecular mechanisms linking cellular cholesterol metabolism to specific immune functions; (ii) how cellular cholesterol accumulation sustains chronic inflammatory diseases such as atherosclerosis; (iii) the immunometabolic profile of patients with defects of genes affecting cholesterol metabolism including familial hypercholesterolaemia, cholesteryl ester storage disease, Niemann-Pick type C, and immunoglobulin D syndrome/mevalonate kinase deficiency. Available data indicate that cholesterol immunometabolism plays a key role in directing immune cells function and set the stage for investigating the repurposing of existing 'metabolic' drugs to modulate the immune response.

Lipid efflux mechanisms, relation to disease and potential therapeutic aspects

Lipids are hydrophobic and amphiphilic molecules involved in diverse functions such as membrane structure, energy metabolism, immunity, and signaling. However, altered intra-cellular lipid levels or composition can lead to metabolic and inflammatory dysfunction, as well as lipotoxicity. Thus, intra-cellular lipid homeostasis is tightly regulated by multiple mechanisms. Since most peripheral cells do not catabolize cholesterol, efflux (extra-cellular transport) of cholesterol is vital for lipid homeostasis. Defective efflux contributes to atherosclerotic plaque development, impaired β-cell insulin secretion, and neuropathology. Of these, defective lipid efflux in macrophages in the arterial walls leading to foam cell and atherosclerotic plaque formation has been the most well studied, likely because a leading global cause of death is cardiovascular disease. Circulating high density lipoprotein particles play critical roles as acceptors of effluxed cellular lipids, suggesting their importance in disease etiology. We review here mechanisms and pathways that modulate lipid efflux, the role of lipid efflux in disease etiology, and therapeutic options aimed at modulating this critical process.