ABCA1
Phospholipid-transporting ATPase ABCA1 (EC 7.6.2.1) (ATP-binding cassette sub-family A member 1) (ATP-binding cassette transporter 1) (ABC-1) (ATP-binding cassette 1) (Cholesterol efflux regulatory protein) [ABC1] [CERP]
Publications[править]
We have previously shown that blockade of ATP-binding cassette transporter A1 (ABCA1) with cyclosporine A (CsA) stimulates the epithelial sodium channel (ENaC) in cultured distal nephron cells. Here we show that CsA elevated systolic blood pressure in both wild-type and apolipoprotein E (ApoE) knockout (KO) mice to a similar level. The elevated systolic blood pressure was completely reversed by inhibition of cholesterol (Cho) synthesis with lovastatin. Inside-out patch-clamp data show that intracellular Cho stimulated ENaC in cultured distal nephron cells by interacting with phosphatidylinositol‑4,5‑bisphosphate (PIP ), an ENaC activator. Confocal microscopy data show that both α‑ENaC and PIP were localized in microvilli via a Cho-dependent mechanism. Deletion of membrane Cho reduced the levels of γ‑ENaC in the apical membrane. Reduced ABCA1 expression and elevated intracellular Cho were observed in old mice, compared to young mice. In parallel, cell-attached patch-clamp data from the split-open cortical collecting ducts (CCD) show that ENaC activity was significantly increased in old mice. These data suggest that elevation of intracellular Cho due to blockade of ABCA1 stimulates ENaC, which may contribute to CsA-induced hypertension. This study also implies that reduced ABCA1 expression may mediate age-related hypertension by increasing ENaC activity via elevation of intracellular Cho.
MeSH Terms
- ATP Binding Cassette Transporter 1
- Animals
- Blood Pressure
- Cell Line
- Cholesterol
- Cyclosporine
- Enzyme Inhibitors
- Epithelial Sodium Channels
- Hypertension
- Mice
- Mice, Inbred C57BL
- Phosphatidylinositol Phosphates
- Xenopus
Keywords
- ABCA1
- Aging
- Cyclosporine A
- ENaC
- PIP(2)
Photoreceptors have high intrinsic metabolic demand and are exquisitely sensitive to metabolic perturbation. In addition, they shed a large portion of their outer segment lipid membranes in a circadian manner, increasing the metabolic burden on the outer retina associated with the resynthesis of cell membranes and disposal of the cellular cargo. Here, we demonstrate that deletion of both ABCA1 and ABCG1 in rod photoreceptors leads to age-related accumulation of cholesterol metabolites in the outer retina, photoreceptor dysfunction, degeneration of rod outer segments, and ultimately blindness. A high-fat diet significantly accelerates rod neurodegeneration and vision loss, further highlighting the role of lipid homeostasis in regulating photoreceptor neurodegeneration and vision.
MeSH Terms
- ATP Binding Cassette Transporter 1
- ATP Binding Cassette Transporter, Subfamily G, Member 1
- Aging
- Animals
- Cholesterol
- Gene Deletion
- Mice
- Retinal Cone Photoreceptor Cells
- Retinal Rod Photoreceptor Cells
- Vision, Ocular
Keywords
- ATP binding cassette transporter G1
- aging
- cholesterol/dietary
- cholesterol/efflux
- eye/retina
- neurons
Reverse cholesterol transport (RCT), which is intimately linked to high-density lipoproteins (HDLs), plays a key role in cholesterol homeostasis and the prevention of atherosclerosis. The goal of the present study was to investigate the effect of aging and advanced glycation end products (AGEs) on RCT as well as on other factors that may affect the antiatherogenic property of HDLs. The transfer of macrophage-derived cholesterol to the plasma and liver and then to the feces for elimination was significantly lower in aged mice than in young mice. Chronic injection of d -galactose (D-gal) or AGEs also significantly reduced RCT (65.3% reduction in [ H]cholesterol levels in the plasma of D-gal-treated mice after 48 h compared with control mice, P < 0.01). The injection of both D-gal and aminoguanidine hydrochloride increased [ H]cholesterol levels in the plasma, although the levels were lower than those of control mice. The in vitro incubation of HDLs with dicarbonyl compounds increased the carbonyl and conjugated diene content of HDLs and significantly reduced PON1 paraoxonase activity (87.4% lower than control HDLs, P < 0.0001). Treating J774A.1 macrophages with glycated fetal bovine serum increased carbonyl formation (39.5% increase, P < 0.003) and reduced ABCA1 protein expression and the capacity of macrophages to liberate cholesterol (69.1% decrease, P < 0.0001). Our results showed, for the first time, that RCT is altered with aging and that AGEs contribute significantly to this alteration.
MeSH Terms
- ATP Binding Cassette Transporter 1
- Animals
- Cell Line
- Cholesterol
- Gene Expression Regulation
- Glycation End Products, Advanced
- Lipoproteins, HDL
- Macrophages
- Male
- Mice
- Mice, Inbred C57BL
Keywords
- HDL
- advanced glycation end products
- aging
- produit finaux de glycation avancée
- reverse cholesterol transport
- transport inverse du cholestérol
- vieillissement
Poultry meat quality is associated with breed, age, tissue and other factors. Many previous studies have focused on distinct breeds; however, little is known regarding the epigenetic regulatory mechanisms in different age stages, such as DNA methylation. Here, we compared the global DNA methylation profiles between juvenile (20 weeks old) and later laying-period (55 weeks old) hens and identified candidate genes related to the development and meat quality of breast muscle using whole-genome bisulfite sequencing. The results showed that the later laying-period hens, which had a higher intramuscular fat (IMF) deposition capacity and water holding capacity (WHC) and less tenderness, exhibited higher global DNA methylation levels than the juvenile hens. A total of 2,714 differentially methylated regions were identified in the present study, which corresponded to 378 differentially methylated genes, mainly affecting muscle development, lipid metabolism, and the ageing process. Hypermethylation of the promoters of the genes ABCA1, COL6A1 and GSTT1L and the resulting transcriptional down-regulation in the later laying-period hens may be the reason for the significant difference in the meat quality between the juvenile and later laying-period hens. These findings contribute to a better understanding of epigenetic regulation in the skeletal muscle development and meat quality of chicken.
MeSH Terms
- Aging
- Animals
- Chickens
- DNA Methylation
- Epigenesis, Genetic
- Food Quality
- Lipid Metabolism
- Meat
- Muscle, Skeletal
- Whole Genome Sequencing
Development of atherosclerosis is a chronic pathological process. ApoE deficient (apoE(-/-)) mice spontaneously develop atherosclerotic lesions. However, the impact of age and sex on lesions and expression of the related genes have not been fully elucidated. In this study, we collected blood and tissue samples from normal chow fed male and female apoE(-/-) mice at different ages, and determined serum lipids, PCSK9 levels, en face aortic lesions and expression of some pro- or anti-atherogenic genes. We determined that lesion development was clearly associated with age, and more lesions in males than females (12.6 ± 1.7% vs. 8.9 ± 1.1% at 8 months old, P < 0.05). Associated with age, serum total, LDL- and HDL-cholesterol and PCSK9 levels increased with more PCSK9 in females than males (313 ± 31 ng/mL vs. 239 ± 28 ng/mL at 8 months old, P < 0.05); expression of liver LDLR and ABCA1 decreased while of SR-BI increased; expression of macrophage ABCA1 and SR-BI decreased but of CD36 increased. Estrogen and tamoxifen induced ABCA1 and SR-BI expression, respectively, in macrophages isolated from female mice at the different age. Taken together, our study suggests that aging facilitates lesion development in apoE(-/-) mice with greater effect on male mice. The lesion development is also related to expression of pro- or anti-atherogenic genes in tissues, particularly in macrophages.
MeSH Terms
- ATP Binding Cassette Transporter 1
- Aging
- Animals
- Apolipoproteins E
- Atherosclerosis
- CD36 Antigens
- Female
- Lipids
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Sex Characteristics
Keywords
- ABCA1
- Age
- Atherosclerosis
- CD36
- Sex
Cerebral hypoperfusion or aging often results into the disturbances of cholesterol and lipoprotein, which have been tightly associated with numerous neurological and psychiatric diseases, such as vascular dementia. The pathway of liver X receptor-β (LXR-β)/retinoic X receptor-α (RXR-α)/ABCA1 plays a vital role in lipoprotein metabolism. However, there were no reports about the relationship between the signal molecules of the pathway and lipoprotein homeostasis in cerebral hypoperfusion models. Therefore, we aimed to detect the expression of the pathway molecules in the aging rat models of chronic cerebral hypoperfusion and to explore its underlying mechanism. The model with cerebral hypoperfusion was established by ligating of the bilateral common carotid arteries (2VO). The temporal blood flow in the model rats was significantly decreased 14 d, 21 d and 28 d after 2VO compared with the control. The serum levels of high-density lipoprotein (HDL) and total cholesterol (TC) were reached a peak at 14 d, then, they were gradually decreased. The changes of LXR-β, RXR-α, ABCA1 and apolipoprotein A1 (apo A1) of the pathway were consistent with the changes of HDL and TC. We conclude that LXR-β/RXR-α/ABCA1 and downstream genes apo A1 undergo dynamic changes during the process of cerebral hypoperfusion. The LXR-β/RXR-α/ABCA1 mediated apo A1 cholesterol may play a protective effect, and the effect only exists in a certain period of time.
MeSH Terms
- ATP Binding Cassette Transporter 1
- Aging
- Animals
- Apolipoprotein A-I
- Blotting, Western
- Brain
- Cholesterol, HDL
- Dementia, Vascular
- Disease Models, Animal
- Fluorescent Antibody Technique
- Liver X Receptors
- Male
- Orphan Nuclear Receptors
- Rats
- Rats, Sprague-Dawley
- Retinoid X Receptors
- Reverse Transcriptase Polymerase Chain Reaction
- Signal Transduction
Keywords
- 2 vessel occlusion
- 2VO
- ABCA1
- AD
- ATP-binding cassette transporter A1
- Alzheimer's disease
- Apolipoprotein A1
- BBB
- HDL
- LXR
- Liver X receptor-β
- RXR
- Retinoic X receptor-α
- VD
- Vascular dementia
- blood–brain barrier
- high-density lipoprotein
- liver X receptor
- retinoid X receptor
- vascular dementia
Increased systemic level of inflammatory cytokines leads to numerous age-related diseases. In senescent macrophages, elevated prostaglandin E2 (PGE2) production contributes to the suppression of T cell function with aging, which increases the susceptibility to infections. However, the regulation of these inflammatory cytokines and PGE2 with aging still remains unclear. We have verified that cyclooxygenase (COX)-2 expression and PGE2 production are higher in LPS-stimulated macrophages from old mice than that from young mice. Downregulation of RXRα, a nuclear receptor that can suppress NF-κB activity, mediates the elevation of COX2 expression and PGE2 production in senescent macrophages. We also have found less induction of ABCA1 and ABCG1 by RXRα agonist in senescent macrophages, which partially accounts for high risk of atherosclerosis in aged population. Systemic treatment with RXRα antagonist HX531 in young mice increases COX2, TNF-α, and IL-6 expression in splenocytes. Our study not only has outlined a mechanism of elevated NF-κB activity and PGE2 production in senescent macrophages, but also provides RXRα as a potential therapeutic target for treating the age-related diseases.
MeSH Terms
- Aging
- Animals
- Cell Line
- Cellular Senescence
- Cyclooxygenase 2
- Dinoprostone
- Down-Regulation
- Lipopolysaccharides
- Macrophages
- Mice
- Mice, Inbred C57BL
- NF-kappa B
- Retinoid X Receptor alpha
- Up-Regulation
Keywords
- 9-cis-retinoid acid
- 9cRA
- ABCA1
- ABCG1
- ATP-binding cassette transporter A1
- ATP-binding cassette transporter G1
- Aging
- COX2
- Macrophage
- NF-κB
- PGE2
- RXR
- RXRα
- TLR
- cyclooxygenase 2
- prostaglandin E2
- retinoid X receptor alpha
- toll-like receptor
To investigate genetic determinants of macular pigment optical density in women from the Carotenoids in Age-Related Eye Disease Study (CAREDS), an ancillary study of the Women's Health Initiative Observational Study. 1585 of 2005 CAREDS participants had macular pigment optical density (MPOD) measured noninvasively using customized heterochromatic flicker photometry and blood samples genotyped for 440 single nucleotide polymorphisms (SNPs) in 26 candidate genes related to absorption, transport, binding, and cleavage of carotenoids directly, or via lipid transport. SNPs were individually tested for associations with MPOD using least-squares linear regression. Twenty-one SNPs from 11 genes were associated with MPOD (P ≤ 0.05) after adjusting for dietary intake of lutein and zeaxanthin. This includes variants in or near genes related to zeaxanthin binding in the macula (GSTP1), carotenoid cleavage (BCMO1), cholesterol transport or uptake (SCARB1, ABCA1, ABCG5, and LIPC), long-chain omega-3 fatty acid status (ELOVL2, FADS1, and FADS2), and various maculopathies (ALDH3A2 and RPE65). The strongest association was for rs11645428 near BCMO1 (βA = 0.029, P = 2.2 × 10(-4)). Conditional modeling within genes and further adjustment for other predictors of MPOD, including waist circumference, diabetes, and dietary intake of fiber, resulted in 13 SNPs from 10 genes maintaining independent association with MPOD. Variation in these single gene polymorphisms accounted for 5% of the variability in MPOD (P = 3.5 × 10(-11)). Our results support that MPOD is a multi-factorial phenotype associated with variation in genes related to carotenoid transport, uptake, and metabolism, independent of known dietary and health influences on MPOD.
MeSH Terms
- Aged
- Aged, 80 and over
- Aging
- Carotenoids
- Cross-Sectional Studies
- Female
- Humans
- Macular Degeneration
- Phenotype
- Polymorphism, Single Nucleotide
- Postmenopause
- Retinal Pigments
- Scavenger Receptors, Class B
- beta-Carotene 15,15'-Monooxygenase
The accumulation of epigenetic changes was proposed to contribute to the age-related increase in the risk of most common diseases. In this study on 230 monozygotic twin pairs (MZ pairs), aged 18-89 years, we investigated the occurrence of epigenetic changes over the adult lifespan. Using mass spectrometry, we investigated variation in global (LINE1) DNA methylation and in DNA methylation at INS, KCNQ1OT1, IGF2, GNASAS, ABCA1, LEP, and CRH, candidate loci for common diseases. Except for KCNQ1OT1, interindividual variation in locus-specific DNA methylation was larger in old individuals than in young individuals, ranging from 1.2-fold larger at ABCA1 (P = 0.010) to 1.6-fold larger at INS (P = 3.7 × 10(-07) ). Similarly, there was more within-MZ-pair discordance in old as compared with young MZ pairs, except for GNASAS, ranging from an 8% increase in discordance each decade at CRH (P = 8.9 × 10(-06) ) to a 16% increase each decade at LEP (P = 2.0 × 10(-08) ). Still, old MZ pairs with strikingly similar DNA methylation were also observed at these loci. After 10-year follow-up in elderly twins, the variation in DNA methylation showed a similar pattern of change as observed cross-sectionally. The age-related increase in methylation variation was generally attributable to unique environmental factors, except for CRH, for which familial factors may play a more important role. In conclusion, sustained epigenetic differences arise from early adulthood to old age and contribute to an increasing discordance of MZ twins during aging.
MeSH Terms
- Adolescent
- Adult
- Aged
- Aged, 80 and over
- Aging
- Cross-Sectional Studies
- DNA Methylation
- Denmark
- Epigenesis, Genetic
- Female
- Genetic Variation
- Humans
- Long Interspersed Nucleotide Elements
- Longitudinal Studies
- Male
- Middle Aged
- Netherlands
- Registries
- Twins, Monozygotic
- Young Adult
The incidence of nonalcoholic fatty liver disease is steadily increasing among the elderly population. Lipid metabolism is transcriptionally controlled by the nuclear receptors retinoid acid receptor alpha, liver-X-receptor alpha, and peroxisome proliferator-activated receptor alpha and their target genes ABCA1, sterol regulatory element-binding protein-1c, and fatty acid synthase. Using senescence-accelerated prone mice (SAMP8), we addressed the question as to whether age-related increase of oxidative stress affects nuclear receptor gene expression. In contrast to SAMR1 control mice, young SAMP8 mice exhibit hepatic steatosis with increased hepatic cholesterol content, plasma triglyceride, and aspartate aminotransferase levels. This is accompanied by an increase of liver-X-receptor alpha and retinoid acid receptor alpha expression, whereas peroxisome proliferator-activated receptor alpha expression is found diminished. SAMP8 mice further reveal a lower expression of ABCA1 as well as of sterol regulatory element-binding protein-1c and higher expression of fatty acid synthase. The dysbalance between the nuclear receptors and their target genes most probably mediates hepatic steatosis and underlines the pathological relevance of nuclear receptor shift toward lipogenesis in fat metabolism of the elderly patient.
MeSH Terms
- Aging
- Animals
- Blotting, Western
- Disease Models, Animal
- Fatty Liver
- Female
- Immunohistochemistry
- Lipogenesis
- Liver
- Mice
- Non-alcoholic Fatty Liver Disease
- Oxidative Stress
- Real-Time Polymerase Chain Reaction
- Receptors, Cytoplasmic and Nuclear
- Receptors, Retinoic Acid
High-density lipoproteins (HDL) are considered atheroprotective in contrast to low-density lipoproteins (LDL), which are atherogenic in their oxidized form. A growing body of evidence suggests that HDL exert part of their antiatherogenic effect by counteracting LDL oxidation as well as their proinflammatory effect. However, a number of studies, carried over the past 30 years, have shown that cholesterol efflux plays a major role in the atheroprotective effects of HDL and cholesterol homeostasis. These studies have further identified the scavenger receptor type B-I (SR-BI), the adenosine triphosphate (ATP)-binding cassette transporters ATP-binding cassette subfamily A1 (ABCA1), ATP-binding cassette subfamily G1 (ABCG1) and ABCG4, the liver X receptor/retinoid X receptor (LXR/RXR) and peroxisome proliferator-activated receptorgamma(PPAR gamma) transcription factors, the HDL components apolipoprotein A-I (apoA-I), lecithin-cholesterol acyltransferase (LCAT), and phospholipids as additional mediators of cholesterol transport. Cholesterol efflux occurs via three independent pathways: (1) aqueous diffusion, (2) nonspecific efflux via SR-BI receptors, and (3) specific efflux via cholesterol-responsive members of the ABC superfamily. Whereas aqueous diffusion and scavenger receptor class B, type I (SR-BI)-mediated efflux transport free cholesterol to a wide variety of cholesterol acceptors (particles containing phospholipids, HDL, and lipidated apo-lipoproteins; LDL, etc), the ABCA1 pathway mediates the transport of cholesterol in a unidirectional manner, mainly to lipid-poor apoA-I. In contrast, the ABCG1 pathway is responsible for the transport of cholesterol to all the subfamily members of HDL. Although HDL-mediated cholesterol efflux is apoA-I-dependent, recent studies have suggested an involvement of the enzyme paraoxonase 1 (PON1). Cholesterol efflux is carried on by a number of factors such as genetic mutations, smoking, stress, and high-fat diets. It is attenuated with aging due to changes in the composition and structure of HDL, especially the phosphatidylcholine/sphingomyelin ratio, the fluidity of the phospholipidic layer, the concentration of apoA-I, and the activity of PON1. This review summarizes the findings that cholesterol homeostasis is disrupted with aging as a consequence of dysfunctional cholesterol efflux and the impairment of physiological functions.
MeSH Terms
- ATP-Binding Cassette Transporters
- Aging
- Animals
- Biological Transport
- Cardiovascular Diseases
- Cholesterol
- Humans
- Lipoproteins, HDL
Despite the physiological importance of alpha-tocopherol (AT), the molecular mechanisms involved in maintaining cellular and tissue tocopherol levels remain to be fully characterized. Scavenger receptor B1 (SRB1), one of a large family of scavenger receptors, has been shown to facilitate AT transfer from HDL to peripheral tissues via apo A-1-mediated processes and to be important in the delivery of AT to the lung cells. In the present studies the effects of age and two environmental oxidants ozone (O(3)) (0.25 ppm 6 h/day) and cigarette smoke (CS) (60 mg/m(3) 6 h/day) for 4 days on selected aspects of AT transport in murine lung tissues were assessed. While AT levels were 25% higher (p<0.05) and 15% lower (p<0.05) in plasma and lung tissue, respectively, in aged versus young mice, acute environmental exposure to O(3) or CS at the doses used had no effect. Gene expression levels, determined by RT-PCR of AT transport protein (ATTP), SRB1, CD36, ATP binding cassette 3 (ABCA3) and ABCA1 and protein levels, determined by Western blots for SRB1, ATTP and ABCA1 were assessed. Aged mouse lung showed a lower levels of ATTP, ABCA3 and SRB1 and a higher level CD36 and ABCA1. Acute exposure to either O(3) or CS induced declines in ATTP and SRB1 in both aged and young mice lung. CD36 increased in both young and aged mice lung upon exposure to O(3) and CS. These findings suggest that both age and environmental oxidant exposure affect pathways related to lung AT homeostasis and do so in a way that favors declines in lung AT. However, given the approach taken, the effects cannot be traced to changes in these pathways or AT content in any specific lung associated cell type and thus highlight the need for further follow-up studies looking at specific lung associated cell types.
MeSH Terms
- ATP Binding Cassette Transporter 1
- ATP-Binding Cassette Transporters
- Aging
- Animals
- Biological Transport
- Blotting, Western
- CD36 Antigens
- Female
- Gene Expression Profiling
- Lipoproteins
- Lung
- Mice
- Mice, Hairless
- Oxidants, Photochemical
- Ozone
- RNA, Messenger
- Reverse Transcriptase Polymerase Chain Reaction
- Scavenger Receptors, Class B
- Smoke
- Tobacco
- Vitamin E
Our aim in this study was to investigate the effect of aging on the capacity of HDLs to promote reverse cholesterol transport. HDLs were isolated from plasma of young (Y-HDL) and elderly (E-HDL) subjects. HDL-mediated cholesterol efflux was studied using THP-1 and J774 macrophages. Our results show that E-HDLs present a lower capacity to promote cholesterol efflux than Y-HDLs (41.7 /- 1.4% vs. 49.0 /- 2.2%, respectively; P = 0.013). Reduction in the HDL-mediated cholesterol efflux capacity with aging was more significant with HDL(3) than HDL(2) (Y-HDL(3), 57.3 /- 1% vs. E-HDL(3), 50.9 /- 2%; P = 0.012). Moreover, our results show that ABCA1-mediated cholesterol efflux is the more affected pathway in terms of cholesterol-removing capacity. Interestingly, the composition and structure of HDL revealed a reduction in the phosphatidylcholine-sphingomyelin ratio (E-HDL, 32.7 /- 2.7 vs. Y-HDL, 40.0 /- 1.9; P = 0.029) and in the phospholipidic layer membrane fluidity in E-HDL compared with Y-HDL as well as an alteration in the apolipoprotein A-I structure and charge. In conclusion, our results shown that E-HDLs present a reduced capacity to promote cholesterol efflux, principally through the ABCA1 pathway, and this may explain the increase of the incidence of cardiovascular diseases observed during aging.
MeSH Terms
- ATP Binding Cassette Transporter 1
- ATP-Binding Cassette Transporters
- Adult
- Aged
- Aging
- Biological Transport
- Cholesterol
- Electrophoresis, Polyacrylamide Gel
- Female
- Humans
- Lipoproteins, HDL
- Male
Dietary sphingomyelin (SM) is hydrolyzed by intestinal alkaline sphingomyelinase and neutral ceramidase to sphingosine, which is absorbed and converted to palmitic acid and acylated into chylomicron triglycerides (TGs). SM digestion is slow and is affected by luminal factors such as bile salt, cholesterol, and other lipids. In the gut, SM and its metabolites may influence TG hydrolysis, cholesterol absorption, lipoprotein formation, and mucosal growth. SM accounts for approximately 20% of the phospholipids in human plasma lipoproteins, of which two-thirds are in LDL and VLDL. It is secreted in chylomicrons and VLDL and transferred into HDL via the ABCA1 transporter. Plasma SM increases after periods of large lipid loads, during suckling, and in type II hypercholesterolemia, cholesterol-fed animals, and apolipoprotein E-deficient mice. SM is thus an important amphiphilic component when plasma lipoprotein pools expand in response to large lipid loads or metabolic abnormalities. It inhibits lipoprotein lipase and LCAT as well as the interaction of lipoproteins with receptors and counteracts LDL oxidation. The turnover of plasma SM is greater than can be accounted for by the turnover of LDL and HDL particles. Some SM must be degraded via receptor-mediated catabolism of chylomicron and VLDL remnants and by scavenger receptor class B type I receptor-mediated transfer into cells.
MeSH Terms
- Aging
- Amidohydrolases
- Animals
- Animals, Newborn
- Apolipoproteins E
- Biological Transport, Active
- Cell Differentiation
- Cell Proliferation
- Ceramidases
- Cholesterol, Dietary
- Chylomicrons
- Dietary Fats
- Humans
- In Vitro Techniques
- Infant, Newborn
- Intestinal Absorption
- Lipoproteins
- Models, Biological
- Neutral Ceramidase
- Sphingomyelin Phosphodiesterase
- Sphingomyelins
- Triglycerides
Using in situ hybridization for the mouse brain, we analyzed developmental changes in gene expression for the ATP-binding cassette (ABC) transporter subfamilies ABCA1-4 and 7, and ABCG1, 2, 4, 5 and 8. In the embryonic brains, ABCA1 and A7 were highly expressed in the ventricular (or germinal) zone, whereas ABCA2, A3 and G4 were enriched in the mantle (or differentiating) zone. At the postnatal stages, ABCA1 was detected in both the gray and white matter and in the choroid plexus. On the other hand, ABCA2, A3 and A7 were distributed in the gray matter. In addition, marked up-regulation of ABCA2 occurred in the white matter at 14 days-of-age when various myelin protein genes are known to be up-regulated. In marked contrast, ABCA4 was selective to the choroid plexus throughout development. ABCG1 was expressed in both the gray and white matters, whereas ABCG4 was confined to the gray matter. ABCG2 was diffusely and weakly detected throughout the brain at all stages examined. Immunohistochemistry of ABCG2 showed its preferential expression on the luminal membrane of brain capillaries. Expression signals for ABCG5 and G8 were barely detected at any stages. The distinct spatio-temporal expressions of individual ABCA and G transporters may reflect their distinct cellular expressions in the developing and adult brains, presumably, to regulate and maintain lipid homeostasis in the brain.
MeSH Terms
- ATP-Binding Cassette Transporters
- Aging
- Animals
- Animals, Newborn
- Brain
- Embryo, Mammalian
- Immunohistochemistry
- In Situ Hybridization
- Mice
- Mice, Inbred C57BL
- Tissue Distribution
Liver X receptors (LXR) alpha and beta are nuclear oxysterol receptors with established roles in cholesterol, lipid, and carbohydrate metabolism. Although LXRs have been extensively studied in liver and macrophages, the importance for development and metabolism of other tissues and cell types is not as well characterized. We demonstrate here that although LXRalpha and LXRbeta are not required for adipocyte development per se, LXRbeta is required for the increase in adipocyte size that normally occurs with aging and diet-induced obesity. Similar food intake and oxygen consumption in LXRbeta-/- mice suggests that reduced storage of lipid in adipose tissue is not due to altered energy balance. Despite reduced amounts of adipose tissue, LXRbeta-/- mice on a chow diet have insulin sensitivity and levels of adipocyte hormones similar to wild type mice. However, these mice are glucose-intolerant due to impaired glucose-induced insulin secretion. Lipid droplets in pancreatic islets may result from accumulation of cholesterol esters as analysis of islet gene expression reveals that LXRbeta is required for expression of the cholesterol transporters, ABCA1 and ABCG1. Our data establish novel roles for LXRbeta in adipocyte growth, glucose homeostasis, and beta cell function.
MeSH Terms
- Adipocytes
- Adipose Tissue
- Aging
- Animals
- Body Composition
- Carbohydrate Metabolism
- Cholesterol
- DNA-Binding Proteins
- Diet
- Glucose
- Immunoassay
- Insulin
- Islets of Langerhans
- Lipid Metabolism
- Liver
- Liver X Receptors
- Macrophages
- Male
- Mice
- Mice, Transgenic
- Obesity
- Orphan Nuclear Receptors
- Oxygen
- Oxygen Consumption
- Pyruvic Acid
- Receptors, Cytoplasmic and Nuclear
- Reverse Transcriptase Polymerase Chain Reaction
- Time Factors
Age-related macular degeneration (AMD) is a genetically heterogeneous disease that leads to progressive and irreversible vision loss among the elderly. Inflammation, oxidative damage, cholesterol metabolism and/or impaired function of retinal pigment epithelium (RPE) have been implicated in AMD pathogenesis. We examined toll-like receptor 4 (TLR4) as a candidate gene for AMD susceptibility because: (i) the TLR4 gene is located on chromosome 9q32-33, a region exhibiting evidence of linkage to AMD in three independent reports; (ii) the TLR4-D299G variant is associated with reduced risk of atherosclerosis, a chronic inflammatory disease with subendothelial accumulation; (iii) the TLR4 is not only a key mediator of proinflammatory signaling pathways but also linked to regulation of cholesterol efflux and (iv) the TLR4 participates in phagocytosis of photoreceptor outer segments by the RPE. We examined D299G and T399I variants of TLR4 in a sample of 667 unrelated AMD patients and 439 unrelated controls, all of Caucasian ancestry. Multiple logistic regression demonstrated an increased risk of AMD in carriers of the G allele at TLR4 residue 299 (odds ratio=2.65, P=0.025), but lack of an independent effect by T399I variant. TLR4-D299G showed an additive effect on AMD risk (odds ratio=4.13, P=0.002) with allelic variants of apolipoprotein E (APOE) and ATP-binding cassette transporter-1 (ABCA1), two genes involved in cholesterol efflux. Interestingly, the effect of TLR4, APOE and ABCA1 variants on AMD susceptibility was opposite to that of association with atherosclerosis risk. Our data provide evidence of a link between multiple diverse mechanisms underlying AMD pathogenesis.
MeSH Terms
- Aged
- Aging
- Base Sequence
- Cohort Studies
- DNA Primers
- Genetic Predisposition to Disease
- Genetic Variation
- Humans
- Macular Degeneration
The liver X receptor/retinoid X receptor (LXR/RXR)-regulated gene ABCA1 effluxes cellular cholesterol and phospholipid to apolipoprotein A1 (apoA1), which is the rate-limiting step in high-density lipoprotein synthesis. The RXR pathway plays a critical role in testicular lipid trafficking, and RXRbeta-deficient male mice are sterile and accumulate lipids in Sertoli cells. Here, we demonstrate that ABCA1 mRNA and protein are abundant in Sertoli cells, whereas germ cells express little ABCA1. LXR/RXR agonists stimulate ABCA1 expression in cultured Sertoli MSC1 and Leydig TM3 cell lines. However, Sertoli TM4 cells lack ABCA1, and TM4 cells or primary Sertoli cells cultured from ABCA1(-/-) mice both fail to efflux cholesterol to apoA1. Expression of exogenous ABCA1 restores apoA1-dependent cholesterol efflux in Sertoli TM4 cells. In vivo, ABCA1-deficient mice exhibit lipid accumulation in Sertoli cells and depletion of normal lipid droplets from Leydig cells by 2 months of age. By 6 months of age, intratesticular testosterone levels and sperm counts are significantly reduced in ABCA1(-/-) mice compared with wild-type (WT) controls. Finally, a 21% decrease (P = 0.01) in fertility was observed between ABCA1(-/-) males compared with WT controls across their reproductive lifespans. These results show that ABCA1 plays an important role in lipid transport in Sertoli cells and influences male fertility.
MeSH Terms
- ATP Binding Cassette Transporter 1
- ATP-Binding Cassette Transporters
- Aging
- Animals
- Cell Line
- Fertility
- Genetic Predisposition to Disease
- Germ Cells
- Humans
- Lipid Metabolism
- Male
- Mice
- Mice, Knockout
- RNA, Messenger
- Sertoli Cells
- Testis
Adenosine triphosphate (ATP)-binding cassette transporter A1 (ABCA1) mediates the efflux of cholesterol to apolipoprotein A1, a process necessary for high-density lipoprotein (HDL) formation and reverse cholesterol transport. In patients with Tangier disease, mutations in ABCA1 result in low circulating HDL-cholesterol and predisposition to coronary heart disease (CHD). ABCA1 gene expression is decreased in diabetic mice. In humans, glycated hemoglobin (HbA(1c)) predicted future CHD events, even within the normal range. We hypothesised that leukocyte ABCA1 gene expression would be inversely associated with indices of glycemia in normoglycemic men. Fasting blood samples were taken from 32 healthy, nonsmoking, normoglycemic men (age 23 to 46 years). ABCA1, peroxisome proliferator-activated receptor gamma (PPARgamma), and liver X receptor alpha (LXRalpha) gene expressions in circulating leukocytes were measured using TaqMan technology. Significant inverse associations between ABCA1 gene expression and both fasting glucose concentration (r = -0.49, P =.008) and age (r = -0.39, P =.043) were found. There was no association with HbA(1c) (r = -0.23, P =.238) or HDL-cholesterol concentration (r = 0.02, P =.904). In a multiple regression model, fasting glucose remained a significant independent predictor (P =.037), whereas age did not (P =.226). Mechanisms underlying the association were explored; there were no significant associations between fasting glucose concentration and leukocyte PPARgamma gene expression, or between fasting glucose concentration and leukocyte LXRalpha gene expression. This is the first demonstration of an association between ABCA1 gene expression and fasting glucose concentration in vivo.
MeSH Terms
- ATP Binding Cassette Transporter 1
- ATP-Binding Cassette Transporters
- Adult
- Aging
- Blood Glucose
- Cholesterol, HDL
- DNA-Binding Proteins
- Fasting
- Gene Expression
- Glycated Hemoglobin A
- Humans
- Leukocytes
- Linear Models
- Liver
- Liver X Receptors
- Male
- Middle Aged
- Orphan Nuclear Receptors
- Receptors, Cytoplasmic and Nuclear
- Transcription Factors
Mutations in adenosine triphosphate (ATP)-binding cassette transporter 1 (ABCA1) gene have been established as the molecular defect in Tangier disease and familial hypoalphalipoproteinemia, uncommon genetic disorders characterized by deficient or depressed high-density lipoprotein (HDL) cholesterol and increased triglycerides. However, information regarding the frequency of common variants, including Arg219Lys (R219K) within the coding region of the ABCA1 gene and their effect on these phenotypes in the general population is limited. This study examined the frequency and phenotypic effect of R219K variant in a community-based sample of 887 white and 390 black young adults aged 20 to 38 years. The frequency of the variant allele (K219) was higher in blacks than in whites (0.595 v 0.262, P<.001), with carriers (KK RK) representing 83.8% of blacks versus 44.2% of whites. After adjusting for age, body mass index (BMI), and sex, the genotype effect on HDL cholesterol and natural logarithm of triglycerides was not apparent in whites or blacks. However, significant interaction effects of genotype and age on HDL cholesterol (P<.001) and genotype and BMI on triglycerides (P=.029) were found in whites. Carriers (KK RK), unlike noncarriers (RR) showed a positive relationship between age and HDL cholesterol (regression coefficient beta=0.28, P=.029 for carriers v beta=-0.18, P=.112 for noncarriers). In addition, the variant allele attenuated the adverse positive relationship between BMI and triglycerides (beta=0.032, P<.001 for carriers v beta=0.046, P<.001 for noncarriers). These results indicate that the K219 allele frequency differs markedly between blacks and whites, and that the variant-allele modulates the association between age and HDL cholesterol, as well as body fatness and triglycerides in a beneficial manner only in whites.
MeSH Terms
- ATP Binding Cassette Transporter 1
- ATP-Binding Cassette Transporters
- Adipose Tissue
- Adult
- African Continental Ancestry Group
- Aging
- Alleles
- Body Composition
- Body Mass Index
- Cholesterol, HDL
- European Continental Ancestry Group
- Gene Frequency
- Genotype
- Humans
- Louisiana
- Polymorphism, Genetic
- Triglycerides
The family of adenosine triphosphate (ATP)-binding cassette (ABC) transporters is the largest gene family known. While some ABC transporters translocate single substances across membranes with high specificity, others transport a wide variety of different lipophilic compounds. They are responsible for many physiological processes and are also implicated in a number of diseases. The present review focuses on ABC transporter genes which are involved in ageing and age-related diseases. Expression of ABCB1 (MDR1, P-glycoprotein) increases with age in CD4( ) and CD8( ) T-lymphocytes indicating that P-glycoprotein may be involved in the secretion of cytokines, growth factors, and cytotoxic molecules. As T cells in aged individuals are hyporesponsive leading to a reduced immunodefence capability, a role of ABCB1 in age-related immunological processes is presumed. The ABCA1 (ABC1) gene product translocates intracellular cholesterol and phospholipids out of macrophages. Genetic aberrations in ABCA1 cause perturbations in lipoprotein metabolism and contribute to atherosclerosis. ABCA4 (ABCR) represents a retina-specific ABC transporter expressed in rod photoreceptor cells. The ABCA4 gene product translocates retinyl-derivatives. Mutations in the ABCA4 gene contribute to age-related macular degeneration. Polymorphisms in the sulfonylurea receptor gene (ABCC8, SUR1) are associated with non-insulin-dependent diabetes mellitus (NIDDM). Sulfonylureas inhibit potassium conductance and are used to treat NIDDM by stimulation of insulin secretion across ATP-sensitive potassium channels in pancreatic beta-cell membranes. Possible diagnostic and therapeutic implications of ABC transporters for age-related diseases are discussed.
MeSH Terms
- ATP-Binding Cassette Transporters
- Aging
- Animals
- Arteriosclerosis
- Diabetes Mellitus, Type 2
- Gene Expression Regulation
- Humans
- Macular Degeneration
Decreased concentrations of HDL cholesterol are associated with increased cardiovascular risk. These concentrations are directly related to cholesterol efflux from cells-the first step and a key process in reverse cholesterol transport. Cholesterol efflux is mediated by the ATP-binding cassette A1 transporter (ABCA1), the rate-limiting step in the production of HDL. We aimed to assess the relation between cholesterol efflux, HDL concentrations, and arterial-wall changes in individuals with impaired ABCA1 function. We investigated 30 individuals from families with ABCA1 mutations, and 110 controls matched for age, sex, and ethnic origin. We measured concentrations of HDL cholesterol in plasma and intima-media thickness of the carotid arteries by B-mode ultrasonography in all participants. We also measured cholesterol efflux from skin fibroblasts in nine individuals with ABCA1 mutations and in ten controls. Individuals with ABCA1 mutations had lower amounts of cholesterol efflux, lower HDL cholesterol concentrations, and greater intima-media thicknesses than controls. An intima-media thickness at the upper limit of normal (0.80 mm) was reached by age 55 years in the ABCA1 heterozygotes, and at age 80 years in unaffected controls (p<0.0001). Additionally, strong positive correlations were seen between HDL cholesterol concentrations and cholesterol efflux (r=0.90, p=0.001), and negative correlations between apolipoprotein-AI-mediated (r=-0.61, p=0.030) and HDL-particle-mediated (r=-0.60, p=0.018) efflux and intima-media thickness in the ABCA1 mutation carriers. These results show a direct relation between ABCA1-mediated cellular cholesterol efflux and arterial-wall thickness, and therefore suggest that increasing efflux could inhibit atherosclerosis progression before the manifestation of symptomatic cardiovascular disease.
MeSH Terms
- ATP Binding Cassette Transporter 1
- ATP-Binding Cassette Transporters
- Adult
- Aging
- Arteriosclerosis
- Carotid Arteries
- Case-Control Studies
- Cholesterol, HDL
- Female
- Humans
- Male
- Smoking
- Ultrasonography
Mutations in ABCA1, a member of the ATP-binding cassette family, have been shown to underlie Tangier disease (TD) and familial hypoalphalipoproteinemia (FHA), which are genetic disorders that are characterized by depressed concentrations of plasma high density lipoprotein (HDL) cholesterol. An important question is whether common variants within the coding sequence of ABCA1 can affect plasma HDL cholesterol in the general population. To address this issue, we developed a screening strategy to find common ABCA1 variants. This strategy involved long-range amplification of genomic DNA by using coding sequences only, followed by deep sequencing into the introns. This method helped us to characterize a new set of amplification primers, which permitted amplification of virtually all of the coding sequence of ABCA1 and its intron-exon boundaries with a single DNA amplification program. With these new sequencing primers, we found 3 novel ABCA1 mutations: a frameshift mutation (4570insA, A1484S-->X1492), a missense mutation (A986D) in a TD family, and a missense mutation (R170C) in aboriginal subjects with FHA. We also used these sequencing primers to characterize 4 novel common amino acid variants in ABCA1, in addition to 5 novel common silent variants. We tested for association of the ABCA1 I/M823 variant with plasma HDL cholesterol in Canadian Inuit and found that M823/M823 homozygotes had significantly higher plasma HDL cholesterol compared with subjects with the other genotypes. The results provide proof of principle of the effectiveness of this approach to identify both rare and common ABCA1 genomic variants and also suggest that common amino acid variation in ABCA1 is a determinant of plasma HDL cholesterol in the general population.
MeSH Terms
- ATP Binding Cassette Transporter 1
- ATP-Binding Cassette Transporters
- Adult
- Aged
- Aging
- Body Mass Index
- Child
- Cholesterol, HDL
- Exons
- Female
- Frameshift Mutation
- Genotype
- Humans
- Hypolipoproteinemias
- Introns
- Male
- Middle Aged
- Mutation
- Mutation, Missense
- Pedigree
- Sequence Analysis, DNA
- Smoking
- Tangier Disease