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Lawrence Chan - One of the best experts on this subject based on the ideXlab platform.
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deficiency of Adipose differentiation related Protein impairs foam cell formation and protects against atherosclerosis
Circulation Research, 2008Co-Authors: Antoni Paul, Benny Hungjunn Chang, Vijay Yechoor, Lawrence ChanAbstract:Foam cells are a hallmark of atherosclerosis. However, it is unclear whether foam cell formation per se protects against atherosclerosis or fuels it. In this study, we investigated the role of Adipose Differentiation-Related Protein (ADFP), a major lipid droplet Protein (LDP), in the regulation of foam cell formation and atherosclerosis. We show that ADFP expression facilitates foam cell formation induced by modified lipoProteins in mouse macrophages in vitro. We show further that Adfp gene inactivation in apolipoProtein E-deficient (ApoE(-/-)) mice reduces the number of lipid droplets in foam cells in atherosclerotic lesions and protects the mice against atherosclerosis. Moreover, transplantation of ADFP-null bone marrow-derived cells effectively attenuated atherosclerosis in ApoE(-/-) mice. Deficiency of ADFP did not cause a detectable compensatory increase in the other PAT domain Proteins in macrophages in vitro or in vivo. Mechanistically, ADFP enables the macrophage to maintain its lipid content by hindering lipid efflux. We detected no significant difference in lesion composition or in multiple parameters of inflammation in macrophages or in their phagocytic activity between mice with and without ADFP. In conclusion, Adfp inactivation in ApoE(-/-) background protects against atherosclerosis and appears to be a relatively pure model of impaired foam cell formation.
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protection against fatty liver but normal adipogenesis in mice lacking Adipose differentiation related Protein
Molecular and Cellular Biology, 2006Co-Authors: Benny Hungjunn Chang, Susumu Taniguchi, Antoni Paul, Vijayalakshmi Nannegari, William C Heird, Lawrence ChanAbstract:Adipose Differentiation-Related Protein (ADFP; also known as ADRP or adipophilin), is a lipid droplet (LD) Protein found in most cells and tissues. ADFP expression is strongly induced in cells with increased lipid load. We have inactivated the Adfp gene in mice to better understand its role in lipid accumulation. The Adfp-deficient mice have unaltered Adipose differentiation or lipolysis in vitro or in vivo. Importantly, they display a 60% reduction in hepatic triglyceride (TG) and are resistant to diet-induced fatty liver. To determine the mechanism for the reduced hepatic TG content, we measured hepatic lipogenesis, very-low-density lipoProtein (VLDL) secretion, and lipid uptake and utilization, all of which parameters were shown to be similar between mutant and wild-type mice. The finding of similar VLDL output in the presence of a reduction in total TG in the Adfp-deficient liver is explained by the retention of TG in the microsomes where VLDL is assembled. Given that lipid droplets are thought to form from the outer leaflet of the microsomal membrane, the reduction of TG in the cytosol with concomitant accumulation of TG in the microsome of Adfp-/- cells suggests that ADFP may facilitate the formation of new LDs. In the absence of ADFP, impairment of LD formation is associated with the accumulation of microsomal TG but a reduction in TG in other subcellular compartments.
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protection against fatty liver but normal adipogenesis in mice lacking Adipose differentiation related Protein
Molecular and Cellular Biology, 2006Co-Authors: Benny Hungjunn Chang, Susumu Taniguchi, Antoni Paul, Vijayalakshmi Nannegari, William C Heird, Lan Li, Lawrence ChanAbstract:Adipose Differentiation-Related Protein (ADFP) was first isolated by differential hybridization screening of 1246 cells during their differentiation to adipocytes (29). Its mRNA is induced 100 fold during the process. Using 3T3L1 cells, Brasaemle et al. (3) showed that Adfp gene expression is induced early, at day 1 of adipocyte differentiation, and that mRNA levels are maintained throughout differentiation. In contrast, ADFP Protein levels, initially upregulated, gradually go down after day 4 (3), suggesting that these levels are subject to significant translational or posttranslational regulation. At the same time, upregulation of perilipin (PLIN), another lipid droplet (LD) Protein, is observed at day 4 of differentiation; it has been postulated that perilipin and ADFP might compete for LD localization during the differentiation of 3T3L1 cells (3, 36). ADFP Protein is localized to the surface of the LD, though it also has been detected in the LD core by freeze fracture electron microscopy (49, 50). ADFP shares sequence homology with other LD Proteins including perilipin and Tip47, collectively known as PAT domain-containing Proteins (36, 43), as well as with another LD Protein, S3-12 (53). S3-12 shares a 11-amino-acid repeat motif with ADFP, in addition to another region of homology to both ADFP and Tip47 at its carboxyl terminus (6, 24, 36). With the exception of perilipin, which is expressed only in fat and steroidogenic tissues, the other LD Proteins are detected in a variety of cells and tissues (22). Perilipin is phosphorylated by Protein kinase A during lipolysis, resulting in an altered conformation to allow hormone-sensitive lipase (10, 58, 61) and other lipases (73) to act on the LD. Consistent with this finding, perilipin-deficient mice exhibit elevated basal lipolysis, reduced fat mass, and resistance to diet-induced and genetic obesity (40, 62). In contrast, ADFP appears not to be phosphorylated (15) but is acylated (23), which may contribute to its association with LDs. Although the function of ADFP is not fully understood, some studies have suggested that it plays a role in fatty acid (FA) transport. Gao and colleagues transfected Adfp to COS-7 cells, which do not normally express Adfp, and observed that induced ADFP expression stimulated long-chain FA uptake (16, 17). Similarly, Imamura et al. showed that adenovirus-mediated overexpression of ADFP induced lipid accumulation in murine fibroblasts without changes in the level of expression of lipogenic genes (26). Serrero's group found that ADFP was associated with the plasma membrane of COS-7 cells (16, 17), a physical location consistent with its putative role in fatty acid transport, whereas others have observed an intracellular instead of a plasma membrane location of ADFP (26, 42). On the other hand, freeze fracture electron microscopy, combined with immunogold labeling, has demonstrated that ADFP and other PAT family Proteins are an integral part of the plasma membrane (49) and the LD core in cells that are cultured under high-lipid conditions. Adfp expression is induced during differentiation of adipocytes and other specialized cells such as keratinocytes and trophoblasts (1, 55), upon lipid loading, or under pathological conditions in other tissues and cells (5, 11, 13, 22, 54, 60, 66). Adfp expression is upregulated in 1246 cells by long-chain but not short-chain FAs (17). Since FAs have been implicated as ligands for members of the nuclear receptor transcription factor family, the induction of the Adfp gene may be mediated through one or more of these pathways. Indeed, all three peroxisome proliferator-activated receptor (PPAR) subtypes (alpha, delta, and gamma) have been reported to increase murine and human Adfp expression (1, 9, 31, 63, 65). To study the function of the Adfp gene in adipocyte differentiation, fatty acid transport, and LD formation, we have created ADFP-deficient mice by gene targeting. We found that absence of ADFP reduces the amount of triglyceride (TG) in the liver without affecting plasma lipid profile. It also protects against diet-induced fatty liver. Significantly, however, it does not affect adipocyte differentiation, fat mass, or body weight.
Constantine Londos - One of the best experts on this subject based on the ideXlab platform.
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Unique Regulation of Adipose Triglyceride Lipase (ATGL) by Perilipin 5, a Lipid Droplet-associated Protein
The Journal of biological chemistry, 2011Co-Authors: Hong Wang, Knut Tomas Dalen, Constantine Londos, Tomohiro Yamaguchi, Mark A Rizzo, Jun Liu, Ming Bell, Urmilla Sreenevasan, Rosalind A. ColemanAbstract:Lipolysis is a critical metabolic pathway contributing to energy homeostasis through degradation of triacylglycerides stored in lipid droplets (LDs), releasing fatty acids. Neutral lipid lipases act at the oil/water interface. In mammalian cells, LD surfaces are coated with one or more members of the perilipin Protein family, which serve important functions in regulating lipolysis. We investigated mechanisms by which three perilipin Proteins control lipolysis by adipocyte triglyceride lipase (ATGL), a key lipase in adipocytes and non-Adipose cells. Using a cell culture model, we examined interactions of ATGL and its co-lipase CGI-58 with perilipin 1 (perilipin A), perilipin 2 (Adipose Differentiation-Related Protein), and perilipin 5 (LSDP5) using multiple techniques as follows: anisotropy Forster resonance energy transfer, co-immunoprecipitation, [32P]orthophosphate radiolabeling, and measurement of lipolysis. The results show that ATGL interacts with CGI-58 and perilipin 5; the latter is selectively expressed in oxidative tissues. Both Proteins independently recruited ATGL to the LD surface, but with opposite effects; interaction of ATGL with CGI-58 increased lipolysis, whereas interaction of ATGL with perilipin 5 decreased lipolysis. In contrast, neither perilipin 1 nor 2 interacted directly with ATGL. Activation of Protein kinase A (PKA) increased [32P]orthophosphate incorporation into perilipin 5 by 2-fold, whereas neither ATGL nor CGI-58 was labeled under the incubation conditions. Cells expressing both ectopic perilipin 5 and ATGL showed a 3-fold increase in lipolysis following activation of PKA. Our studies establish perilipin 5 as a novel ATGL partner and provide evidence that the Protein composition of perilipins at the LD surface regulates lipolytic activity of ATGL.
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activation of hormone sensitive lipase requires two steps Protein phosphorylation and binding to the pat 1 domain of lipid droplet coat Proteins
Journal of Biological Chemistry, 2009Co-Authors: Hong Wang, Amy Marcinkiewicz, Knut Tomas Dalen, Heidi Dorward, Deanna L Russell, Dawei Gong, Constantine Londos, Tomohiro Yamaguchi, Cecilia Holm, Mark A RizzoAbstract:Lipolysis is an important metabolic pathway controlling energy homeostasis through degradation of triglycerides stored in lipid droplets and release of fatty acids. Lipid droplets of mammalian cells are coated with one or more members of the PAT Protein family, which serve important functions in regulating lipolysis. In this study, we investigate the mechanisms by which PAT family members, perilipin A, Adipose Differentiation-Related Protein (ADFP), and LSDP5, control lipolysis catalyzed by hormone-sensitive lipase (HSL), a major lipase in adipocytes and several non-Adipose cells. We applied fluorescence microscopic tools to analyze Proteins in situ in cultured Chinese hamster ovary cells using fluorescence recovery after photobleaching and anisotropy Forster resonance energy transfer. Fluorescence recovery after photobleaching data show that ADFP and LSDP5 exchange between lipid droplet and cytoplasmic pools, whereas perilipin A does not. Differences in Protein mobility do not correlate with PAT Protein-mediated control of lipolysis catalyzed by HSL or endogenous lipases. Forster resonance energy transfer and co-immunoprecipitation experiments reveal that each of the three PAT Proteins bind HSL through interaction of the lipase with amino acids within the highly conserved amino-terminal PAT-1 domain. ADFP and LSDP5 bind HSL under basal conditions, whereas phosphorylation of serine residues within three amino-terminal Protein kinase A consensus sequences of perilipin A is required for HSL binding and maximal lipolysis. Finally, Protein kinase A-mediated phosphorylation of HSL increases lipolysis in cells expressing ADFP or LSDP5; in contrast, phosphorylation of perilipin A exerts the major control over HSL-mediated lipolysis when perilipin is the main lipid droplet Protein.
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consequences of lipid droplet coat Protein downregulation in liver cells abnormal lipid droplet metabolism and induction of insulin resistance
Diabetes, 2008Co-Authors: Ming Bell, Hong Wang, Dawei Gong, Constantine Londos, Hui Chen, Michael J Quon, John C Mclenithan, Rong Zee Yang, Susan K Fried, Carole SztalrydAbstract:OBJECTIVE— Accumulation of intracellular lipid droplets (LDs) in non-Adipose tissues is recognized as a strong prognostic factor for the development of insulin resistance in obesity. LDs are coated with perilipin, Adipose differentiation–related Protein, tail interacting Protein of 47 kd (PAT) Proteins that are thought to regulate LD turnover by modulating lipolysis. Our hypothesis is that PAT Proteins modulate LD metabolism and therefore insulin resistance. RESEARCH DESIGN AND METHODS— We used a cell culture model (murine AML12 loaded with oleic acid) and small interfering RNA to directly assess the impact of PAT Proteins on LD accumulation, lipid metabolism, and insulin action. PAT Proteins associated with excess fat deposited in livers of diet-induced obese (DIO) mice were also measured. RESULTS— Cells lacking PAT Proteins exhibited a dramatic increase in LD size and a decrease in LD number. Further, the lipolytic rate increased by ∼2- to 2.5-fold in association with increased Adipose triglyceride lipase (ATGL) at the LD surface. Downregulation of PAT Proteins also produced insulin resistance, as indicated by decreased insulin stimulation of Akt phosphorylation ( P < 0.001). Phosphoinositide-dependent kinase-1 and phosphoinositide 3-kinase decreased, and insulin receptor substrate-1 307 phosphorylation increased. Increased lipids in DIO mice livers were accompanied by changes in PAT composition but also increased ATGL, suggesting a relative PAT deficiency. CONCLUSIONS— These data establish an important role for PAT Proteins as surfactant at the LD surface, packaging lipids in smaller units and restricting access of lipases and thus preventing insulin resistance. We suggest that a deficiency of PAT Proteins relative to the quantity of ectopic fat could contribute to cellular dysfunction in obesity and type 2 diabetes.
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post translational regulation of Adipose differentiation related Protein by the ubiquitin proteasome pathway
Journal of Biological Chemistry, 2005Co-Authors: Guoheng Xu, John T Tansey, Alan R Kimmel, Heidi Dorward, Carole Sztalryd, Xinyue Lu, Constantine LondosAbstract:Adipose Differentiation-Related Protein (ADRP) is localized to lipid droplets in most mammalian cells. ADRP, proposed to regulate fatty acid mobilization and lipid droplet formation, is linked to lipid accumulation in foam cells of human atherosclerotic lesions. In this report, we show that ADRP Protein accumulates in Chinese hamster ovary fibroblastic cells cultured in the presence of oleic acid but is destabilized when fatty acid sources are removed from culture serum. The latter effect was blocked by the proteasome inhibitor MG132, whereas inhibitors of other proteolytic processes were ineffective. Pulse-chase experiments confirmed that ADRP degradation is inhibited by MG132. Conditions that stimulate ADRP degradation also promoted the covalent modification of ADRP by ubiquitin, whereas the addition of oleic acid to culture media, which promotes triacylglycerol deposition, blunted the appearance of ubiquitinated-ADRP. Treatment with MG132 increased the levels of ADRP associated with lipid droplets, as well as throughout the cytosol. Finally, we demonstrate that the disappearance of ADRP Protein after the onset of perilipin expression during adipocyte differentiation is due to degradation by proteasomes Thus, proteolytic degradation of ADRP mediated through the ubiquitin/proteasome pathway appears to be a major mode for the post-translational regulation of ADRP.
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functional studies on native and mutated forms of perilipins a role in Protein kinase a mediated lipolysis of triacylglycerols in chinese hamster ovary cells
Journal of Biological Chemistry, 2003Co-Authors: John T Tansey, Alan R Kimmel, Dawn L Brasaemle, Anne M Huml, Rainbow Vogt, Kathryn Davis, Jennifer M Jones, Kathryn A Fraser, Constantine LondosAbstract:Abstract Perilipin A coats the lipid storage droplets in adipocytes and is polyphosphorylated by Protein kinase A (PKA); the fact that PKA activates lipolysis in adipocytes suggests a role for perilipins in this process. To assess whether perilipins participate directly in PKA-mediated lipolysis, we have expressed constructs coding for native and mutated forms of the two major splice variants of the perilipin gene, perilipins A and B, in Chinese hamster ovary fibroblasts. Perilipins localize to lipid droplet surfaces and displace the Adipose Differentiation-Related Protein that normally coats the droplets in these cells. Perilipin A inhibits triacylglycerol hydrolysis by 87% when PKA is quiescent, but activation of PKA and phosphorylation of perilipin A engenders a 7-fold lipolytic activation. Mutation of PKA sites within the N-terminal region of perilipin abrogates the PKA-mediated lipolytic response. In contrast, perilipin B exerts only minimal protection against lipolysis and is unresponsive to PKA activation. Since Chinese hamster ovary cells contain no PKA-activated lipase, we conclude that the expression of perilipin A alone is sufficient to confer PKA-mediated lipolysis in these cells. Moreover, the data indicate that the unique C-terminal portion of perilipin A is responsible for its protection against lipolysis and that phosphorylation at the N-terminal PKA sites attenuates this protective effect.
Benny Hungjunn Chang - One of the best experts on this subject based on the ideXlab platform.
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deficiency of Adipose differentiation related Protein impairs foam cell formation and protects against atherosclerosis
Circulation Research, 2008Co-Authors: Antoni Paul, Benny Hungjunn Chang, Vijay Yechoor, Lawrence ChanAbstract:Foam cells are a hallmark of atherosclerosis. However, it is unclear whether foam cell formation per se protects against atherosclerosis or fuels it. In this study, we investigated the role of Adipose Differentiation-Related Protein (ADFP), a major lipid droplet Protein (LDP), in the regulation of foam cell formation and atherosclerosis. We show that ADFP expression facilitates foam cell formation induced by modified lipoProteins in mouse macrophages in vitro. We show further that Adfp gene inactivation in apolipoProtein E-deficient (ApoE(-/-)) mice reduces the number of lipid droplets in foam cells in atherosclerotic lesions and protects the mice against atherosclerosis. Moreover, transplantation of ADFP-null bone marrow-derived cells effectively attenuated atherosclerosis in ApoE(-/-) mice. Deficiency of ADFP did not cause a detectable compensatory increase in the other PAT domain Proteins in macrophages in vitro or in vivo. Mechanistically, ADFP enables the macrophage to maintain its lipid content by hindering lipid efflux. We detected no significant difference in lesion composition or in multiple parameters of inflammation in macrophages or in their phagocytic activity between mice with and without ADFP. In conclusion, Adfp inactivation in ApoE(-/-) background protects against atherosclerosis and appears to be a relatively pure model of impaired foam cell formation.
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protection against fatty liver but normal adipogenesis in mice lacking Adipose differentiation related Protein
Molecular and Cellular Biology, 2006Co-Authors: Benny Hungjunn Chang, Susumu Taniguchi, Antoni Paul, Vijayalakshmi Nannegari, William C Heird, Lawrence ChanAbstract:Adipose Differentiation-Related Protein (ADFP; also known as ADRP or adipophilin), is a lipid droplet (LD) Protein found in most cells and tissues. ADFP expression is strongly induced in cells with increased lipid load. We have inactivated the Adfp gene in mice to better understand its role in lipid accumulation. The Adfp-deficient mice have unaltered Adipose differentiation or lipolysis in vitro or in vivo. Importantly, they display a 60% reduction in hepatic triglyceride (TG) and are resistant to diet-induced fatty liver. To determine the mechanism for the reduced hepatic TG content, we measured hepatic lipogenesis, very-low-density lipoProtein (VLDL) secretion, and lipid uptake and utilization, all of which parameters were shown to be similar between mutant and wild-type mice. The finding of similar VLDL output in the presence of a reduction in total TG in the Adfp-deficient liver is explained by the retention of TG in the microsomes where VLDL is assembled. Given that lipid droplets are thought to form from the outer leaflet of the microsomal membrane, the reduction of TG in the cytosol with concomitant accumulation of TG in the microsome of Adfp-/- cells suggests that ADFP may facilitate the formation of new LDs. In the absence of ADFP, impairment of LD formation is associated with the accumulation of microsomal TG but a reduction in TG in other subcellular compartments.
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protection against fatty liver but normal adipogenesis in mice lacking Adipose differentiation related Protein
Molecular and Cellular Biology, 2006Co-Authors: Benny Hungjunn Chang, Susumu Taniguchi, Antoni Paul, Vijayalakshmi Nannegari, William C Heird, Lan Li, Lawrence ChanAbstract:Adipose Differentiation-Related Protein (ADFP) was first isolated by differential hybridization screening of 1246 cells during their differentiation to adipocytes (29). Its mRNA is induced 100 fold during the process. Using 3T3L1 cells, Brasaemle et al. (3) showed that Adfp gene expression is induced early, at day 1 of adipocyte differentiation, and that mRNA levels are maintained throughout differentiation. In contrast, ADFP Protein levels, initially upregulated, gradually go down after day 4 (3), suggesting that these levels are subject to significant translational or posttranslational regulation. At the same time, upregulation of perilipin (PLIN), another lipid droplet (LD) Protein, is observed at day 4 of differentiation; it has been postulated that perilipin and ADFP might compete for LD localization during the differentiation of 3T3L1 cells (3, 36). ADFP Protein is localized to the surface of the LD, though it also has been detected in the LD core by freeze fracture electron microscopy (49, 50). ADFP shares sequence homology with other LD Proteins including perilipin and Tip47, collectively known as PAT domain-containing Proteins (36, 43), as well as with another LD Protein, S3-12 (53). S3-12 shares a 11-amino-acid repeat motif with ADFP, in addition to another region of homology to both ADFP and Tip47 at its carboxyl terminus (6, 24, 36). With the exception of perilipin, which is expressed only in fat and steroidogenic tissues, the other LD Proteins are detected in a variety of cells and tissues (22). Perilipin is phosphorylated by Protein kinase A during lipolysis, resulting in an altered conformation to allow hormone-sensitive lipase (10, 58, 61) and other lipases (73) to act on the LD. Consistent with this finding, perilipin-deficient mice exhibit elevated basal lipolysis, reduced fat mass, and resistance to diet-induced and genetic obesity (40, 62). In contrast, ADFP appears not to be phosphorylated (15) but is acylated (23), which may contribute to its association with LDs. Although the function of ADFP is not fully understood, some studies have suggested that it plays a role in fatty acid (FA) transport. Gao and colleagues transfected Adfp to COS-7 cells, which do not normally express Adfp, and observed that induced ADFP expression stimulated long-chain FA uptake (16, 17). Similarly, Imamura et al. showed that adenovirus-mediated overexpression of ADFP induced lipid accumulation in murine fibroblasts without changes in the level of expression of lipogenic genes (26). Serrero's group found that ADFP was associated with the plasma membrane of COS-7 cells (16, 17), a physical location consistent with its putative role in fatty acid transport, whereas others have observed an intracellular instead of a plasma membrane location of ADFP (26, 42). On the other hand, freeze fracture electron microscopy, combined with immunogold labeling, has demonstrated that ADFP and other PAT family Proteins are an integral part of the plasma membrane (49) and the LD core in cells that are cultured under high-lipid conditions. Adfp expression is induced during differentiation of adipocytes and other specialized cells such as keratinocytes and trophoblasts (1, 55), upon lipid loading, or under pathological conditions in other tissues and cells (5, 11, 13, 22, 54, 60, 66). Adfp expression is upregulated in 1246 cells by long-chain but not short-chain FAs (17). Since FAs have been implicated as ligands for members of the nuclear receptor transcription factor family, the induction of the Adfp gene may be mediated through one or more of these pathways. Indeed, all three peroxisome proliferator-activated receptor (PPAR) subtypes (alpha, delta, and gamma) have been reported to increase murine and human Adfp expression (1, 9, 31, 63, 65). To study the function of the Adfp gene in adipocyte differentiation, fatty acid transport, and LD formation, we have created ADFP-deficient mice by gene targeting. We found that absence of ADFP reduces the amount of triglyceride (TG) in the liver without affecting plasma lipid profile. It also protects against diet-induced fatty liver. Significantly, however, it does not affect adipocyte differentiation, fat mass, or body weight.
Antoni Paul - One of the best experts on this subject based on the ideXlab platform.
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deficiency of Adipose differentiation related Protein impairs foam cell formation and protects against atherosclerosis
Circulation Research, 2008Co-Authors: Antoni Paul, Benny Hungjunn Chang, Vijay Yechoor, Lawrence ChanAbstract:Foam cells are a hallmark of atherosclerosis. However, it is unclear whether foam cell formation per se protects against atherosclerosis or fuels it. In this study, we investigated the role of Adipose Differentiation-Related Protein (ADFP), a major lipid droplet Protein (LDP), in the regulation of foam cell formation and atherosclerosis. We show that ADFP expression facilitates foam cell formation induced by modified lipoProteins in mouse macrophages in vitro. We show further that Adfp gene inactivation in apolipoProtein E-deficient (ApoE(-/-)) mice reduces the number of lipid droplets in foam cells in atherosclerotic lesions and protects the mice against atherosclerosis. Moreover, transplantation of ADFP-null bone marrow-derived cells effectively attenuated atherosclerosis in ApoE(-/-) mice. Deficiency of ADFP did not cause a detectable compensatory increase in the other PAT domain Proteins in macrophages in vitro or in vivo. Mechanistically, ADFP enables the macrophage to maintain its lipid content by hindering lipid efflux. We detected no significant difference in lesion composition or in multiple parameters of inflammation in macrophages or in their phagocytic activity between mice with and without ADFP. In conclusion, Adfp inactivation in ApoE(-/-) background protects against atherosclerosis and appears to be a relatively pure model of impaired foam cell formation.
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protection against fatty liver but normal adipogenesis in mice lacking Adipose differentiation related Protein
Molecular and Cellular Biology, 2006Co-Authors: Benny Hungjunn Chang, Susumu Taniguchi, Antoni Paul, Vijayalakshmi Nannegari, William C Heird, Lawrence ChanAbstract:Adipose Differentiation-Related Protein (ADFP; also known as ADRP or adipophilin), is a lipid droplet (LD) Protein found in most cells and tissues. ADFP expression is strongly induced in cells with increased lipid load. We have inactivated the Adfp gene in mice to better understand its role in lipid accumulation. The Adfp-deficient mice have unaltered Adipose differentiation or lipolysis in vitro or in vivo. Importantly, they display a 60% reduction in hepatic triglyceride (TG) and are resistant to diet-induced fatty liver. To determine the mechanism for the reduced hepatic TG content, we measured hepatic lipogenesis, very-low-density lipoProtein (VLDL) secretion, and lipid uptake and utilization, all of which parameters were shown to be similar between mutant and wild-type mice. The finding of similar VLDL output in the presence of a reduction in total TG in the Adfp-deficient liver is explained by the retention of TG in the microsomes where VLDL is assembled. Given that lipid droplets are thought to form from the outer leaflet of the microsomal membrane, the reduction of TG in the cytosol with concomitant accumulation of TG in the microsome of Adfp-/- cells suggests that ADFP may facilitate the formation of new LDs. In the absence of ADFP, impairment of LD formation is associated with the accumulation of microsomal TG but a reduction in TG in other subcellular compartments.
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protection against fatty liver but normal adipogenesis in mice lacking Adipose differentiation related Protein
Molecular and Cellular Biology, 2006Co-Authors: Benny Hungjunn Chang, Susumu Taniguchi, Antoni Paul, Vijayalakshmi Nannegari, William C Heird, Lan Li, Lawrence ChanAbstract:Adipose Differentiation-Related Protein (ADFP) was first isolated by differential hybridization screening of 1246 cells during their differentiation to adipocytes (29). Its mRNA is induced 100 fold during the process. Using 3T3L1 cells, Brasaemle et al. (3) showed that Adfp gene expression is induced early, at day 1 of adipocyte differentiation, and that mRNA levels are maintained throughout differentiation. In contrast, ADFP Protein levels, initially upregulated, gradually go down after day 4 (3), suggesting that these levels are subject to significant translational or posttranslational regulation. At the same time, upregulation of perilipin (PLIN), another lipid droplet (LD) Protein, is observed at day 4 of differentiation; it has been postulated that perilipin and ADFP might compete for LD localization during the differentiation of 3T3L1 cells (3, 36). ADFP Protein is localized to the surface of the LD, though it also has been detected in the LD core by freeze fracture electron microscopy (49, 50). ADFP shares sequence homology with other LD Proteins including perilipin and Tip47, collectively known as PAT domain-containing Proteins (36, 43), as well as with another LD Protein, S3-12 (53). S3-12 shares a 11-amino-acid repeat motif with ADFP, in addition to another region of homology to both ADFP and Tip47 at its carboxyl terminus (6, 24, 36). With the exception of perilipin, which is expressed only in fat and steroidogenic tissues, the other LD Proteins are detected in a variety of cells and tissues (22). Perilipin is phosphorylated by Protein kinase A during lipolysis, resulting in an altered conformation to allow hormone-sensitive lipase (10, 58, 61) and other lipases (73) to act on the LD. Consistent with this finding, perilipin-deficient mice exhibit elevated basal lipolysis, reduced fat mass, and resistance to diet-induced and genetic obesity (40, 62). In contrast, ADFP appears not to be phosphorylated (15) but is acylated (23), which may contribute to its association with LDs. Although the function of ADFP is not fully understood, some studies have suggested that it plays a role in fatty acid (FA) transport. Gao and colleagues transfected Adfp to COS-7 cells, which do not normally express Adfp, and observed that induced ADFP expression stimulated long-chain FA uptake (16, 17). Similarly, Imamura et al. showed that adenovirus-mediated overexpression of ADFP induced lipid accumulation in murine fibroblasts without changes in the level of expression of lipogenic genes (26). Serrero's group found that ADFP was associated with the plasma membrane of COS-7 cells (16, 17), a physical location consistent with its putative role in fatty acid transport, whereas others have observed an intracellular instead of a plasma membrane location of ADFP (26, 42). On the other hand, freeze fracture electron microscopy, combined with immunogold labeling, has demonstrated that ADFP and other PAT family Proteins are an integral part of the plasma membrane (49) and the LD core in cells that are cultured under high-lipid conditions. Adfp expression is induced during differentiation of adipocytes and other specialized cells such as keratinocytes and trophoblasts (1, 55), upon lipid loading, or under pathological conditions in other tissues and cells (5, 11, 13, 22, 54, 60, 66). Adfp expression is upregulated in 1246 cells by long-chain but not short-chain FAs (17). Since FAs have been implicated as ligands for members of the nuclear receptor transcription factor family, the induction of the Adfp gene may be mediated through one or more of these pathways. Indeed, all three peroxisome proliferator-activated receptor (PPAR) subtypes (alpha, delta, and gamma) have been reported to increase murine and human Adfp expression (1, 9, 31, 63, 65). To study the function of the Adfp gene in adipocyte differentiation, fatty acid transport, and LD formation, we have created ADFP-deficient mice by gene targeting. We found that absence of ADFP reduces the amount of triglyceride (TG) in the liver without affecting plasma lipid profile. It also protects against diet-induced fatty liver. Significantly, however, it does not affect adipocyte differentiation, fat mass, or body weight.
Susumu Taniguchi - One of the best experts on this subject based on the ideXlab platform.
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protection against fatty liver but normal adipogenesis in mice lacking Adipose differentiation related Protein
Molecular and Cellular Biology, 2006Co-Authors: Benny Hungjunn Chang, Susumu Taniguchi, Antoni Paul, Vijayalakshmi Nannegari, William C Heird, Lan Li, Lawrence ChanAbstract:Adipose Differentiation-Related Protein (ADFP) was first isolated by differential hybridization screening of 1246 cells during their differentiation to adipocytes (29). Its mRNA is induced 100 fold during the process. Using 3T3L1 cells, Brasaemle et al. (3) showed that Adfp gene expression is induced early, at day 1 of adipocyte differentiation, and that mRNA levels are maintained throughout differentiation. In contrast, ADFP Protein levels, initially upregulated, gradually go down after day 4 (3), suggesting that these levels are subject to significant translational or posttranslational regulation. At the same time, upregulation of perilipin (PLIN), another lipid droplet (LD) Protein, is observed at day 4 of differentiation; it has been postulated that perilipin and ADFP might compete for LD localization during the differentiation of 3T3L1 cells (3, 36). ADFP Protein is localized to the surface of the LD, though it also has been detected in the LD core by freeze fracture electron microscopy (49, 50). ADFP shares sequence homology with other LD Proteins including perilipin and Tip47, collectively known as PAT domain-containing Proteins (36, 43), as well as with another LD Protein, S3-12 (53). S3-12 shares a 11-amino-acid repeat motif with ADFP, in addition to another region of homology to both ADFP and Tip47 at its carboxyl terminus (6, 24, 36). With the exception of perilipin, which is expressed only in fat and steroidogenic tissues, the other LD Proteins are detected in a variety of cells and tissues (22). Perilipin is phosphorylated by Protein kinase A during lipolysis, resulting in an altered conformation to allow hormone-sensitive lipase (10, 58, 61) and other lipases (73) to act on the LD. Consistent with this finding, perilipin-deficient mice exhibit elevated basal lipolysis, reduced fat mass, and resistance to diet-induced and genetic obesity (40, 62). In contrast, ADFP appears not to be phosphorylated (15) but is acylated (23), which may contribute to its association with LDs. Although the function of ADFP is not fully understood, some studies have suggested that it plays a role in fatty acid (FA) transport. Gao and colleagues transfected Adfp to COS-7 cells, which do not normally express Adfp, and observed that induced ADFP expression stimulated long-chain FA uptake (16, 17). Similarly, Imamura et al. showed that adenovirus-mediated overexpression of ADFP induced lipid accumulation in murine fibroblasts without changes in the level of expression of lipogenic genes (26). Serrero's group found that ADFP was associated with the plasma membrane of COS-7 cells (16, 17), a physical location consistent with its putative role in fatty acid transport, whereas others have observed an intracellular instead of a plasma membrane location of ADFP (26, 42). On the other hand, freeze fracture electron microscopy, combined with immunogold labeling, has demonstrated that ADFP and other PAT family Proteins are an integral part of the plasma membrane (49) and the LD core in cells that are cultured under high-lipid conditions. Adfp expression is induced during differentiation of adipocytes and other specialized cells such as keratinocytes and trophoblasts (1, 55), upon lipid loading, or under pathological conditions in other tissues and cells (5, 11, 13, 22, 54, 60, 66). Adfp expression is upregulated in 1246 cells by long-chain but not short-chain FAs (17). Since FAs have been implicated as ligands for members of the nuclear receptor transcription factor family, the induction of the Adfp gene may be mediated through one or more of these pathways. Indeed, all three peroxisome proliferator-activated receptor (PPAR) subtypes (alpha, delta, and gamma) have been reported to increase murine and human Adfp expression (1, 9, 31, 63, 65). To study the function of the Adfp gene in adipocyte differentiation, fatty acid transport, and LD formation, we have created ADFP-deficient mice by gene targeting. We found that absence of ADFP reduces the amount of triglyceride (TG) in the liver without affecting plasma lipid profile. It also protects against diet-induced fatty liver. Significantly, however, it does not affect adipocyte differentiation, fat mass, or body weight.
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protection against fatty liver but normal adipogenesis in mice lacking Adipose differentiation related Protein
Molecular and Cellular Biology, 2006Co-Authors: Benny Hungjunn Chang, Susumu Taniguchi, Antoni Paul, Vijayalakshmi Nannegari, William C Heird, Lawrence ChanAbstract:Adipose Differentiation-Related Protein (ADFP; also known as ADRP or adipophilin), is a lipid droplet (LD) Protein found in most cells and tissues. ADFP expression is strongly induced in cells with increased lipid load. We have inactivated the Adfp gene in mice to better understand its role in lipid accumulation. The Adfp-deficient mice have unaltered Adipose differentiation or lipolysis in vitro or in vivo. Importantly, they display a 60% reduction in hepatic triglyceride (TG) and are resistant to diet-induced fatty liver. To determine the mechanism for the reduced hepatic TG content, we measured hepatic lipogenesis, very-low-density lipoProtein (VLDL) secretion, and lipid uptake and utilization, all of which parameters were shown to be similar between mutant and wild-type mice. The finding of similar VLDL output in the presence of a reduction in total TG in the Adfp-deficient liver is explained by the retention of TG in the microsomes where VLDL is assembled. Given that lipid droplets are thought to form from the outer leaflet of the microsomal membrane, the reduction of TG in the cytosol with concomitant accumulation of TG in the microsome of Adfp-/- cells suggests that ADFP may facilitate the formation of new LDs. In the absence of ADFP, impairment of LD formation is associated with the accumulation of microsomal TG but a reduction in TG in other subcellular compartments.
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adrp stimulates lipid accumulation and lipid droplet formation in murine fibroblasts
American Journal of Physiology-endocrinology and Metabolism, 2002Co-Authors: Minako Imamura, Toyoshi Inoguchi, Shoichiro Ikuyama, Susumu Taniguchi, Kunihisa Kobayashi, Naoki Nakashima, Hajime NawataAbstract:Adipose Differentiation-Related Protein (ADRP) is a lipid droplet-associated Protein that is expressed early during Adipose differentiation. The present study was undertaken to reveal the role of A...