Wenjun Shen - Academia.edu (original) (raw)
Papers by Wenjun Shen
Molecular and cellular endocrinology, Jan 28, 2016
Steroidogenesis is a complex process through which cholesterol traffics to mitochondria and is co... more Steroidogenesis is a complex process through which cholesterol traffics to mitochondria and is converted via a series of enzymatic steps to steroid hormones. Although the rate-limiting step in this process is the movement of cholesterol from the outer to the inner mitochondrial membrane via the actions of StAR, a continuous supply of cholesterol must be delivered to the outer mitochondrial membrane during active steroidogenesis and this is derived from multiple sources, including lipoprotein uptake, endogenous cholesterol synthesis and release from stores within cytoplasmic lipid droplets. A number of mechanisms have been suggested to contribute to cholesterol trafficking to mitochondria; however, there is no definitive consensus and this is particularly so in regards to trafficking from cytoplasmic lipid droplets. In this paper we review experiments in which we have surveyed the expression of SNARE proteins in steroidogenic tissue and cells and examined the role of SNAREs in mediat...
American Journal of Physiology-Endocrinology and Metabolism, 2006
Steroid hormones are synthesized using cholesterol as precursor. To determine the functional impo... more Steroid hormones are synthesized using cholesterol as precursor. To determine the functional importance of the low density lipoprotein (LDL) receptor and hormone-sensitive lipase (HSL) in adrenal steroidogenesis, adrenal cells were isolated from control, HSL−/−, LDLR−/−, and double LDLR/HSL−/−mice. The endocytic and selective uptake of apolipoprotein E-free human high density lipoprotein (HDL)-derived cholesteryl esters did not differ among the mice, with selective uptake accounting for >97% of uptake. In contrast, endocytic uptake of either human LDL- or rat HDL-derived cholesteryl esters was reduced 80–85% in LDLR−/−and double- LDLR/HSL−/−mice. There were no differences in the selective uptake of either human LDL- or rat HDL-derived cholesteryl esters among the mice. Maximum corticosterone production induced by ACTH or dibutyryl cyclic AMP and lipoproteins was not altered in LDLR−/−mice but was reduced 80–90% in HSL−/−mice. Maximum corticosterone production was identical in HSL...
Annual review of physiology, Jan 9, 2017
The scavenger receptor, class B type 1 (SR-B1), is a multiligand membrane receptor protein that f... more The scavenger receptor, class B type 1 (SR-B1), is a multiligand membrane receptor protein that functions as a physiologically relevant high-density lipoprotein (HDL) receptor whose primary role is to mediate selective uptake or influx of HDL-derived cholesteryl esters into cells and tissues. SR-B1 also facilitates the efflux of cholesterol from peripheral tissues, including macrophages, back to liver. As a regulator of plasma membrane cholesterol content, SR-B1 promotes the uptake of lipid soluble vitamins as well as viral entry into host cells. These collective functions of SR-B1 ultimately affect programmed cell death, female fertility, platelet function, vasculature inflammation, and diet-induced atherosclerosis and myocardial infarction. SR-B1 has also been identified as a potential marker for cancer diagnosis and prognosis. Finally, the SR-B1-linked selective HDL-cholesteryl ester uptake pathway is now being evaluated as a gateway for the delivery of therapeutic and diagnostic...
Endocrinology, 2019
ACSL4 is a member of the ACSL family that catalyzes the conversion of long-chain fatty acids to a... more ACSL4 is a member of the ACSL family that catalyzes the conversion of long-chain fatty acids to acyl-coenzyme As, which are essential for fatty-acid incorporation and utilization in diverse metabolic pathways, including cholesteryl ester synthesis. Steroidogenic tissues such as the adrenal gland are particularly enriched in cholesteryl esters of long-chain polyunsaturated fatty acids, which constitute an important pool supplying cholesterol for steroid synthesis. The current studies addressed whether ACSL4 is required for normal steroidogenesis. CYP11A1 promoter‒mediated Cre was used to generate steroid tissue‒specific ACSL4 knockout (KO) mice. Results demonstrated that ACSL4 plays an important role in adrenal cholesteryl ester formation, as well as in determining the fatty acyl composition of adrenal cholesteryl esters, with ACSL4 deficiency leading to reductions in cholesteryl ester storage and alterations in cholesteryl ester composition. Statistically significant reductions in c...
Endocrinology, 2019
ACSL4 is a member of the ACSL family that catalyzes the conversion of long-chain fatty acids to a... more ACSL4 is a member of the ACSL family that catalyzes the conversion of long-chain fatty acids to acyl-coenzyme As, which are essential for fatty-acid incorporation and utilization in diverse metabolic pathways, including cholesteryl ester synthesis. Steroidogenic tissues such as the adrenal gland are particularly enriched in cholesteryl esters of long-chain polyunsaturated fatty acids, which constitute an important pool supplying cholesterol for steroid synthesis. The current studies addressed whether ACSL4 is required for normal steroidogenesis. CYP11A1 promoter‒mediated Cre was used to generate steroid tissue‒specific ACSL4 knockout (KO) mice. Results demonstrated that ACSL4 plays an important role in adrenal cholesteryl ester formation, as well as in determining the fatty acyl composition of adrenal cholesteryl esters, with ACSL4 deficiency leading to reductions in cholesteryl ester storage and alterations in cholesteryl ester composition. Statistically significant reductions in c...
which permits unrestricted use, distribution, and reproduction in any medium, provided the origin... more which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. All treatments for obesity, including dietary restriction of carbohydrates, have a goal of reducing the storage of fat in adipocytes. The chief enzyme responsible for the mobilization of FFA from adipose tissue, i.e., lipolysis, is thought to be hormone-sensitive lipase (HSL). Studies of HSL knockouts have provided important insights into the functional significance of HSL and into adipose metabolism in general. Studies have provided evidence that HSL, though possessing triacylglycerol lipase activity, appears to be the rate-limiting enzyme for cholesteryl ester and diacylglycerol hydrolysis in adipose tissue and is essential for complete hormone stimulated lipolysis, but other triacylglycerol lipases are important in mediating triacylglycerol hydrolysis in lipolysis. HSL knockouts are resistant to both high fat diet-induced and genetic obesity, displaying redu...
American Journal of Physiology-Endocrinology and Metabolism, 2001
Hormone-sensitive lipase (HSL) hydrolyzes triglyceride (TG) in adipose tissue. HSL is also expres... more Hormone-sensitive lipase (HSL) hydrolyzes triglyceride (TG) in adipose tissue. HSL is also expressed in heart. To explore the actions of cardiac HSL, heart-specific, tetracycline (Tc)-controlled HSL-overexpressing mice were generated. Tc-responsive element-HSL transgenic (Tg) mice were generated and crossed with myosin heavy chain (MHC)α-tTA Tg mice, which express the Tc-responsive transactivator (tTA) in the heart. The double-Tg mice (MHC-HSL) were maintained with doxycycline (Dox) to suppress Tg HSL. Upon removal of Dox, cardiac HSL activity and protein increased 12- and 8-fold, respectively, and the expression was heart specific. Although cardiac TG content increased twofold in control mice after an overnight fast, it did not increase in HSL-induced mice. Electron microscopy showed numerous lipid droplets in the myocardium of fasted control mice, whereas fasted HSL-induced mice showed virtually no droplets. Microarray analysis showed altered expression of cardiac genes for fatty ...
Journal of lipid research, 2018
Cholesterol is required for maintenance of plasma membrane fluidity and integrity and for many ce... more Cholesterol is required for maintenance of plasma membrane fluidity and integrity and for many cellular functions. Cellular cholesterol can be obtained from lipoproteins in a selective pathway of HDL-cholesteryl ester (CE) uptake without parallel apolipoprotein uptake. Scavenger receptor B type 1 (SR-B1) is a cell surface HDL receptor that mediates HDL-CE uptake. It is most abundantly expressed in liver, where it provides cholesterol for bile acid synthesis, and in steroidogenic tissues, where it delivers cholesterol needed for storage or steroidogenesis in rodents. SR-B1 transcription is regulated by trophic hormones in the adrenal gland, ovary, and testis; in the liver and elsewhere, SR-B1 is subject to posttranscriptional and posttranslational regulation. SR-B1 operates in several metabolic processes and contributes to pathogenesis of atherosclerosis, inflammation, hepatitis C virus infection, and other conditions. Here, we summarize characteristics of the selective uptake pathwa...
Future cardiology, May 1, 2017
The PPARs are a subfamily of three ligand-inducible transcription factors, which belong to the su... more The PPARs are a subfamily of three ligand-inducible transcription factors, which belong to the superfamily of nuclear hormone receptors. In mammals, the PPAR subfamily consists of three members: PPAR-α, PPAR-β/δ and PPAR-γ. PPARs control the expression of a large number of genes involved in metabolic homeostasis, lipid, glucose and energy metabolism, adipogenesis and inflammation. PPARs regulate a large number of metabolic pathways that are implicated in the pathogenesis of metabolic diseases such as metabolic syndrome, Type 2 diabetes mellitus, nonalcoholic fatty liver disease and cardiovascular disease. The aim of this review is to provide up-to-date information about the biochemical and metabolic actions of PPAR-β/δ and PPAR-γ, the therapeutic potential of their agonists currently under clinical development and the cardiovascular disease outcome of clinical trials of PPAR-γ agonists, pioglitazone and rosiglitazone.
Experimental Cell Research, 2016
Journal of lipid research, Jan 3, 2015
Insulin resistance underlies metabolic disease. Visceral, but not subcutaneous, white adipose tis... more Insulin resistance underlies metabolic disease. Visceral, but not subcutaneous, white adipose tissue (WAT) has been linked to the development of insulin resistance, potentially due to differences in regulatory protein abundance. Here we investigate how protein levels are changed in insulin resistance in different WAT depots by developing a targeted proteomics approach to quantitatively compare the abundance of 42 nuclear proteins in subcutaneous and visceral WAT from a commonly-used insulin resistant mouse model, Lepr(db/db), and from C57BL/6J control mice. The most differentially-expressed proteins were important in adipogenesis, as confirmed by siRNA-mediated depletion experiments, suggesting a defect in adipogenesis in visceral, but not subcutaneous, insulin-resistant WAT. Furthermore, differentiation of visceral, but not subcutaneous, insulin-resistant stromal vascular cells (SVC) was impaired. In an in vitro approach to understand the cause of this impaired differentiation, we ...
American journal of physiology. Endocrinology and metabolism, 2002
Starvation induces many biochemical and histological changes in the heart; however, the molecular... more Starvation induces many biochemical and histological changes in the heart; however, the molecular events underlying these changes have not been fully elucidated. To explore the molecular response of the heart to starvation, microarray analysis was performed together with biochemical and histological investigations. Serum free fatty acids increased twofold in both 16- and 48-h-fasted mice, and cardiac triglyceride content increased threefold and sixfold in 16- and 48-h-fasted mice, respectively. Electron microscopy showed numerous lipid droplets in hearts of 48-h-fasted mice, whereas fewer numbers of droplets were seen in hearts from 16-h-fasted mice. Expression of 11,000 cardiac genes was screened by microarrays. More than 50 and 150 known genes were detected by differential expression analysis after 16- and 48-h-fasts, respectively. Genes for fatty acid oxidation and gluconeogenesis were increased, and genes for glycolysis were decreased. Many other genes for metabolism, signaling/...
Proceedings of the National Academy of Sciences, 1999
Hormone-sensitive lipase (HSL) is a cytosolic neutral lipase that functions as the rate-limiting ... more Hormone-sensitive lipase (HSL) is a cytosolic neutral lipase that functions as the rate-limiting enzyme for the mobilization of free fatty acids in adipose tissue. By using the yeast two-hybrid system to examine the potential interaction of HSL with other cellular proteins, evidence is provided to demonstrate a direct interaction of HSL with adipocyte lipid-binding protein (ALBP), a member of the family of intracellular lipid-binding proteins that binds fatty acids, retinoids, and other hydrophobic ligands. The interaction was demonstrated in vitro by the binding of ALBP to HSL translated in vitro , to HSL in extracts of HSL overexpressing Chinese hamster ovary (CHO) cells, and to HSL in extracts of rat adipose tissue. Finally, the presence of ALBP was documented in immune complexes from rat adipose tissue immunoprecipitated with anti-HSL antibodies. The HSL–ALBP interaction was mapped to an N-terminal 300-aa region of HSL that is distinct from the C-terminal catalytic domain. These...
PLoS ONE, 2013
This study aimed to characterize and compare the effects of obesity on gene expression profiles i... more This study aimed to characterize and compare the effects of obesity on gene expression profiles in two distinct adipose depots, epididymal and bone marrow, at two different ages in mice. Alterations in gene expression were analyzed in adipocytes isolated from diet-induced obese (DIO) C57BL/6J male mice at 6 and 14 months of age and from leptin deficient mice (ob/ob) at 6 months of age using microarrays. DIO affected gene expression in both depots at 6 and 14 months, but more genes were altered in epididymal than bone marrow adipocytes at each age and younger mice displayed more changes than older animals. In epididymal adipocytes a total of 2789 (9.6%) genes were differentially expressed at 6-months with DIO, whereas 952 (3.3%) were affected at 14-months. In bone marrow adipocytes, 347 (1.2%) genes were differentially expressed at 6-months with DIO, whereas only 189 (0.66%) were changed at 14-months. 133 genes were altered by DIO in both fat depots at 6-months, and 37 genes at 14-months. Only four genes were altered in both depots at both ages with DIO. Bone marrow adipocytes are less responsive to DIO than epididymal adipocytes and the response of both depots to DIO declines with age. This loss of responsiveness with age is likely due to age-associated changes in expression of genes related to adipogenesis, inflammation and mitochondrial function that are similar to and obscure the changes commonly associated with DIO. Patterns of gene expression were generally similar in epididymal adipocytes from ob/ob and DIO mice; however, several genes were differentially expressed in bone marrow adipocytes from ob/ob and DIO mice, perhaps reflecting the importance of leptin signaling for bone metabolism. In conclusion, obesity affects age-associated alterations in gene expression in both epididymal and bone marrow adipocytes regardless of diet or genetic background.
Nutrition & Metabolism, 2010
Steroid hormones regulate diverse physiological functions such as reproduction, blood salt balanc... more Steroid hormones regulate diverse physiological functions such as reproduction, blood salt balance, maintenance of secondary sexual characteristics, response to stress, neuronal function and various metabolic processes. They are synthesized from cholesterol mainly in the adrenal gland and gonads in response to tissue-specific tropic hormones. These steroidogenic tissues are unique in that they require cholesterol not only for membrane biogenesis, maintenance of membrane fluidity and cell signaling, but also as the starting material for the biosynthesis of steroid hormones. It is not surprising, then, that cells of steroidogenic tissues have evolved with multiple pathways to assure the constant supply of cholesterol needed to maintain optimum steroid synthesis. The cholesterol utilized for steroidogenesis is derived from a combination of sources: 1) de novo synthesis in the endoplasmic reticulum (ER); 2) the mobilization of cholesteryl esters (CEs) stored in lipid droplets through ch...
Molecular and Cellular Endocrinology, 2013
Intracellular lipid droplets (LDs) are dynamic organelles that contain a number of associated pro... more Intracellular lipid droplets (LDs) are dynamic organelles that contain a number of associated proteins including perilipin (Plin) and vimentin. Cholesteryl ester (CE)-rich LDs normally accumulate in steroidogenic cells and their mobilization is the preferred initial source of cholesterol for steroidogenesis. Plin1a, 1b and 5 were found to preferentially associate with triacylglycerol-rich LDs and Plin1c and 4 to associate with CE-rich LDs, but the biological significance of this remains unanswered. Vimentin null mice were found to have decreased ACTH-stimulated corticosterone levels, and decreased progesterone levels in females, but normal hCG-stimulated testosterone levels in males. Smaller LDs were seen in null cells. Lipoprotein cholesterol delivery to adrenals and ovary was normal, as was the expression of steroidogenic genes; however, the movement of cholesterol to mitochondria was reduced in vimentin null mice. These results suggest that vimentin is important in the maintenance of CE-rich LDs and in the movement of cholesterol for steroidogenesis.
Journal of Proteome Research, 2010
Lipolysis involves a number of components including signaling pathways, droplet-associated protei... more Lipolysis involves a number of components including signaling pathways, droplet-associated proteins and lipases such as hormone-sensitive lipase (HSL). We used Surface Enhanced Laser Desorption/Ionization time-of-flight mass spectroscopy to identify cellular proteins that might interact with HSL and potentially influence lipolysis. Using recombinant HSL as bait on protein chips, clusters of proteins of 14.7 to 18.9 kDa, 25.8-26.8 kDa, 36.1 kDa, 44.3-49.1 kDa, and one at 53.7 kDa were identified that interact with HSL, particularly when lysates were examined from βagonist treated mouse adipocytes. The ability to detect these interacting proteins was markedly diminished when the adipocytes were treated with insulin. A very similar pattern of proteins was identified when anti-HSL IgG was used as the bait. Following immunocapture, the identification of the prominent 53.7 kDa protein was carried out by tryptic digestion and MS analysis, and determined to be vimentin. The interaction of HSL with vimentin, and its hormonal dependence, was confirmed by co-immunoprecipitation. β-agonist stimulated lipolysis and the rate of HSL translocation were impaired in vimentin null adipocytes, even though normal amounts of lipases and droplet-associated proteins are expressed. The current studies provide evidence that vimentin participates in lipolysis through direct, hormonally regulated interactions with HSL.
Journal of Lipid Research, 2002
Hormone-sensitive lipase (HSL) is an intracellular neutral lipase that is capable of hydrolyzing ... more Hormone-sensitive lipase (HSL) is an intracellular neutral lipase that is capable of hydrolyzing triacylglycerols, diacylglycerols, monoacylglycerols, and cholesteryl esters, as well as other lipid and water soluble substrates. HSL activity is regulated post-translationally by phosphorylation and also by pretranslational mechanisms. The enzyme is highly expressed in adipose tissue and steroidogenic tissues, with lower amounts expressed in cardiac and skeletal muscle, macrophages, and islets. Studies of the structure of HSL have identified several amino acids and regions of the molecule that are critical for enzymatic activity and regulation of HSL. This has led to important insights into its function, including the interaction of HSL with other intracellular proteins, such as adipocyte lipid binding protein. Accumulating evidence has defined important functions for HSL in normal physiology, affecting adipocyte lipolysis, steroidogenesis, spermatogenesis, and perhaps insulin secretion and insulin action; however, direct links between abnormal expression or genetic variations of HSL and human disorders, such as obesity, insulin resistance, type 2 diabetes, and hyperlipidemia, await further clarification. The published reports examining the regulation, and function of HSL in normal physiology and disease are reviewed in this paper.-Kraemer, F. B., and W-J. Shen. Hormone-sensitive lipase: control of intracellular tri-(di-)acylglycerol and cholesteryl ester hydrolysis.
Journal of Lipid Research, 2012
Lipid droplets (LDs) are organelles found in many types of eukaryotic cells and are composed of a... more Lipid droplets (LDs) are organelles found in many types of eukaryotic cells and are composed of a core of neutral lipids, such as triacylglycerol (TAG), covered by a monolayer of phospholipids, free cholesterol, and specifi c proteins (1). Proteomic studies have identifi ed LD-associated proteins involved in lipid metabolism and transport, intracellular traffi cking, signaling, and cytoskeletal organization (1). The major LD-associated proteins belong to the perilipin-adipophilin-TIP47 (PAT) family and are characterized by sequence similarity (2). Fat-specifi c protein 27 (FSP27), also known as Cidec for the human homolog, was discovered to be up-regulated during adipogenesis and is highly expressed in white adipose tissue (WAT) and brown adipose tissue (BAT) in mice (3-6) but only in WAT in humans (7). The LD localization of FSP27 and perilipin A (Plin1) in 3T3-L1 adipocytes is similar, and they share some conserved regions at the amino acid level (8), but there is no similarity within the PAT domains, which are regions highly conserved in PAT family proteins and which are not present in FSP27. Overexpression of FSP27 induces the accumulation of LDs and enhances LD size not only in adipocytes but also in many nonlipogenic cells (9, 10). Conversely, knockdown of FSP27 decreases LD size and increases LD number in 3T3-L1 adipocytes (6, 11). Thus, FSP27, like PAT proteins, appears to have an important role in the regulation of LDs but does not appear to function as effectively as Plin1 as a barrier to LD breakdown by cytosolic lipases. Two groups independently reported the phenotypes of FSP27-defi cient Abstract Fat-specifi c protein 27 (FSP27), a member of the cell death-inducing DNA fragmentation factor ␣-like effector (Cide) family, is highly expressed in adipose tissues and is a lipid droplet (LD)-associated protein that induces the accumulation of LDs. Using a yeast two-hybrid system to examine potential interactions of FSP27 with other proteins, a direct interaction with the N-terminal region of nuclear factor of activated T cells 5 (NFAT5) was identifi ed. NFAT5 is a transcription factor that induces osmoprotective and infl ammatory genes after its translocation to the nucleus. The interaction between FSP27 and NFAT5 was confi rmed by bimolecular fl uorescence complementation and coimmunoprecipitation. Using immunocytochemistry, NFAT5 is detected in the cytoplasm and in the nucleus under isotonic conditions; however, overexpression of FSP27 inhibited the hypertonic-induced nuclear translocation of NFAT5. Consistent with the suppression of NFAT5 nuclear translocation, in cells transfected with a reporter construct containing the NFAT5 response element from the monocyte chemoattractant protein 1 (MCP1) promoter, FSP27 overexpression repressed hypertonic-induced luciferase activity and the expression of NFAT5 target genes. Knockdown of FSP27 in differentiated 3T3-L1 adipocytes increased the NFAT5mediated rise in MCP1. These results suggest that FSP27 not only modulates LD homeostasis but also modulates the response to osmotic stress via a physical interaction with NFAT5 at the LD surface.-Ueno, M.
Molecular and cellular endocrinology, Jan 28, 2016
Steroidogenesis is a complex process through which cholesterol traffics to mitochondria and is co... more Steroidogenesis is a complex process through which cholesterol traffics to mitochondria and is converted via a series of enzymatic steps to steroid hormones. Although the rate-limiting step in this process is the movement of cholesterol from the outer to the inner mitochondrial membrane via the actions of StAR, a continuous supply of cholesterol must be delivered to the outer mitochondrial membrane during active steroidogenesis and this is derived from multiple sources, including lipoprotein uptake, endogenous cholesterol synthesis and release from stores within cytoplasmic lipid droplets. A number of mechanisms have been suggested to contribute to cholesterol trafficking to mitochondria; however, there is no definitive consensus and this is particularly so in regards to trafficking from cytoplasmic lipid droplets. In this paper we review experiments in which we have surveyed the expression of SNARE proteins in steroidogenic tissue and cells and examined the role of SNAREs in mediat...
American Journal of Physiology-Endocrinology and Metabolism, 2006
Steroid hormones are synthesized using cholesterol as precursor. To determine the functional impo... more Steroid hormones are synthesized using cholesterol as precursor. To determine the functional importance of the low density lipoprotein (LDL) receptor and hormone-sensitive lipase (HSL) in adrenal steroidogenesis, adrenal cells were isolated from control, HSL−/−, LDLR−/−, and double LDLR/HSL−/−mice. The endocytic and selective uptake of apolipoprotein E-free human high density lipoprotein (HDL)-derived cholesteryl esters did not differ among the mice, with selective uptake accounting for >97% of uptake. In contrast, endocytic uptake of either human LDL- or rat HDL-derived cholesteryl esters was reduced 80–85% in LDLR−/−and double- LDLR/HSL−/−mice. There were no differences in the selective uptake of either human LDL- or rat HDL-derived cholesteryl esters among the mice. Maximum corticosterone production induced by ACTH or dibutyryl cyclic AMP and lipoproteins was not altered in LDLR−/−mice but was reduced 80–90% in HSL−/−mice. Maximum corticosterone production was identical in HSL...
Annual review of physiology, Jan 9, 2017
The scavenger receptor, class B type 1 (SR-B1), is a multiligand membrane receptor protein that f... more The scavenger receptor, class B type 1 (SR-B1), is a multiligand membrane receptor protein that functions as a physiologically relevant high-density lipoprotein (HDL) receptor whose primary role is to mediate selective uptake or influx of HDL-derived cholesteryl esters into cells and tissues. SR-B1 also facilitates the efflux of cholesterol from peripheral tissues, including macrophages, back to liver. As a regulator of plasma membrane cholesterol content, SR-B1 promotes the uptake of lipid soluble vitamins as well as viral entry into host cells. These collective functions of SR-B1 ultimately affect programmed cell death, female fertility, platelet function, vasculature inflammation, and diet-induced atherosclerosis and myocardial infarction. SR-B1 has also been identified as a potential marker for cancer diagnosis and prognosis. Finally, the SR-B1-linked selective HDL-cholesteryl ester uptake pathway is now being evaluated as a gateway for the delivery of therapeutic and diagnostic...
Endocrinology, 2019
ACSL4 is a member of the ACSL family that catalyzes the conversion of long-chain fatty acids to a... more ACSL4 is a member of the ACSL family that catalyzes the conversion of long-chain fatty acids to acyl-coenzyme As, which are essential for fatty-acid incorporation and utilization in diverse metabolic pathways, including cholesteryl ester synthesis. Steroidogenic tissues such as the adrenal gland are particularly enriched in cholesteryl esters of long-chain polyunsaturated fatty acids, which constitute an important pool supplying cholesterol for steroid synthesis. The current studies addressed whether ACSL4 is required for normal steroidogenesis. CYP11A1 promoter‒mediated Cre was used to generate steroid tissue‒specific ACSL4 knockout (KO) mice. Results demonstrated that ACSL4 plays an important role in adrenal cholesteryl ester formation, as well as in determining the fatty acyl composition of adrenal cholesteryl esters, with ACSL4 deficiency leading to reductions in cholesteryl ester storage and alterations in cholesteryl ester composition. Statistically significant reductions in c...
Endocrinology, 2019
ACSL4 is a member of the ACSL family that catalyzes the conversion of long-chain fatty acids to a... more ACSL4 is a member of the ACSL family that catalyzes the conversion of long-chain fatty acids to acyl-coenzyme As, which are essential for fatty-acid incorporation and utilization in diverse metabolic pathways, including cholesteryl ester synthesis. Steroidogenic tissues such as the adrenal gland are particularly enriched in cholesteryl esters of long-chain polyunsaturated fatty acids, which constitute an important pool supplying cholesterol for steroid synthesis. The current studies addressed whether ACSL4 is required for normal steroidogenesis. CYP11A1 promoter‒mediated Cre was used to generate steroid tissue‒specific ACSL4 knockout (KO) mice. Results demonstrated that ACSL4 plays an important role in adrenal cholesteryl ester formation, as well as in determining the fatty acyl composition of adrenal cholesteryl esters, with ACSL4 deficiency leading to reductions in cholesteryl ester storage and alterations in cholesteryl ester composition. Statistically significant reductions in c...
which permits unrestricted use, distribution, and reproduction in any medium, provided the origin... more which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. All treatments for obesity, including dietary restriction of carbohydrates, have a goal of reducing the storage of fat in adipocytes. The chief enzyme responsible for the mobilization of FFA from adipose tissue, i.e., lipolysis, is thought to be hormone-sensitive lipase (HSL). Studies of HSL knockouts have provided important insights into the functional significance of HSL and into adipose metabolism in general. Studies have provided evidence that HSL, though possessing triacylglycerol lipase activity, appears to be the rate-limiting enzyme for cholesteryl ester and diacylglycerol hydrolysis in adipose tissue and is essential for complete hormone stimulated lipolysis, but other triacylglycerol lipases are important in mediating triacylglycerol hydrolysis in lipolysis. HSL knockouts are resistant to both high fat diet-induced and genetic obesity, displaying redu...
American Journal of Physiology-Endocrinology and Metabolism, 2001
Hormone-sensitive lipase (HSL) hydrolyzes triglyceride (TG) in adipose tissue. HSL is also expres... more Hormone-sensitive lipase (HSL) hydrolyzes triglyceride (TG) in adipose tissue. HSL is also expressed in heart. To explore the actions of cardiac HSL, heart-specific, tetracycline (Tc)-controlled HSL-overexpressing mice were generated. Tc-responsive element-HSL transgenic (Tg) mice were generated and crossed with myosin heavy chain (MHC)α-tTA Tg mice, which express the Tc-responsive transactivator (tTA) in the heart. The double-Tg mice (MHC-HSL) were maintained with doxycycline (Dox) to suppress Tg HSL. Upon removal of Dox, cardiac HSL activity and protein increased 12- and 8-fold, respectively, and the expression was heart specific. Although cardiac TG content increased twofold in control mice after an overnight fast, it did not increase in HSL-induced mice. Electron microscopy showed numerous lipid droplets in the myocardium of fasted control mice, whereas fasted HSL-induced mice showed virtually no droplets. Microarray analysis showed altered expression of cardiac genes for fatty ...
Journal of lipid research, 2018
Cholesterol is required for maintenance of plasma membrane fluidity and integrity and for many ce... more Cholesterol is required for maintenance of plasma membrane fluidity and integrity and for many cellular functions. Cellular cholesterol can be obtained from lipoproteins in a selective pathway of HDL-cholesteryl ester (CE) uptake without parallel apolipoprotein uptake. Scavenger receptor B type 1 (SR-B1) is a cell surface HDL receptor that mediates HDL-CE uptake. It is most abundantly expressed in liver, where it provides cholesterol for bile acid synthesis, and in steroidogenic tissues, where it delivers cholesterol needed for storage or steroidogenesis in rodents. SR-B1 transcription is regulated by trophic hormones in the adrenal gland, ovary, and testis; in the liver and elsewhere, SR-B1 is subject to posttranscriptional and posttranslational regulation. SR-B1 operates in several metabolic processes and contributes to pathogenesis of atherosclerosis, inflammation, hepatitis C virus infection, and other conditions. Here, we summarize characteristics of the selective uptake pathwa...
Future cardiology, May 1, 2017
The PPARs are a subfamily of three ligand-inducible transcription factors, which belong to the su... more The PPARs are a subfamily of three ligand-inducible transcription factors, which belong to the superfamily of nuclear hormone receptors. In mammals, the PPAR subfamily consists of three members: PPAR-α, PPAR-β/δ and PPAR-γ. PPARs control the expression of a large number of genes involved in metabolic homeostasis, lipid, glucose and energy metabolism, adipogenesis and inflammation. PPARs regulate a large number of metabolic pathways that are implicated in the pathogenesis of metabolic diseases such as metabolic syndrome, Type 2 diabetes mellitus, nonalcoholic fatty liver disease and cardiovascular disease. The aim of this review is to provide up-to-date information about the biochemical and metabolic actions of PPAR-β/δ and PPAR-γ, the therapeutic potential of their agonists currently under clinical development and the cardiovascular disease outcome of clinical trials of PPAR-γ agonists, pioglitazone and rosiglitazone.
Experimental Cell Research, 2016
Journal of lipid research, Jan 3, 2015
Insulin resistance underlies metabolic disease. Visceral, but not subcutaneous, white adipose tis... more Insulin resistance underlies metabolic disease. Visceral, but not subcutaneous, white adipose tissue (WAT) has been linked to the development of insulin resistance, potentially due to differences in regulatory protein abundance. Here we investigate how protein levels are changed in insulin resistance in different WAT depots by developing a targeted proteomics approach to quantitatively compare the abundance of 42 nuclear proteins in subcutaneous and visceral WAT from a commonly-used insulin resistant mouse model, Lepr(db/db), and from C57BL/6J control mice. The most differentially-expressed proteins were important in adipogenesis, as confirmed by siRNA-mediated depletion experiments, suggesting a defect in adipogenesis in visceral, but not subcutaneous, insulin-resistant WAT. Furthermore, differentiation of visceral, but not subcutaneous, insulin-resistant stromal vascular cells (SVC) was impaired. In an in vitro approach to understand the cause of this impaired differentiation, we ...
American journal of physiology. Endocrinology and metabolism, 2002
Starvation induces many biochemical and histological changes in the heart; however, the molecular... more Starvation induces many biochemical and histological changes in the heart; however, the molecular events underlying these changes have not been fully elucidated. To explore the molecular response of the heart to starvation, microarray analysis was performed together with biochemical and histological investigations. Serum free fatty acids increased twofold in both 16- and 48-h-fasted mice, and cardiac triglyceride content increased threefold and sixfold in 16- and 48-h-fasted mice, respectively. Electron microscopy showed numerous lipid droplets in hearts of 48-h-fasted mice, whereas fewer numbers of droplets were seen in hearts from 16-h-fasted mice. Expression of 11,000 cardiac genes was screened by microarrays. More than 50 and 150 known genes were detected by differential expression analysis after 16- and 48-h-fasts, respectively. Genes for fatty acid oxidation and gluconeogenesis were increased, and genes for glycolysis were decreased. Many other genes for metabolism, signaling/...
Proceedings of the National Academy of Sciences, 1999
Hormone-sensitive lipase (HSL) is a cytosolic neutral lipase that functions as the rate-limiting ... more Hormone-sensitive lipase (HSL) is a cytosolic neutral lipase that functions as the rate-limiting enzyme for the mobilization of free fatty acids in adipose tissue. By using the yeast two-hybrid system to examine the potential interaction of HSL with other cellular proteins, evidence is provided to demonstrate a direct interaction of HSL with adipocyte lipid-binding protein (ALBP), a member of the family of intracellular lipid-binding proteins that binds fatty acids, retinoids, and other hydrophobic ligands. The interaction was demonstrated in vitro by the binding of ALBP to HSL translated in vitro , to HSL in extracts of HSL overexpressing Chinese hamster ovary (CHO) cells, and to HSL in extracts of rat adipose tissue. Finally, the presence of ALBP was documented in immune complexes from rat adipose tissue immunoprecipitated with anti-HSL antibodies. The HSL–ALBP interaction was mapped to an N-terminal 300-aa region of HSL that is distinct from the C-terminal catalytic domain. These...
PLoS ONE, 2013
This study aimed to characterize and compare the effects of obesity on gene expression profiles i... more This study aimed to characterize and compare the effects of obesity on gene expression profiles in two distinct adipose depots, epididymal and bone marrow, at two different ages in mice. Alterations in gene expression were analyzed in adipocytes isolated from diet-induced obese (DIO) C57BL/6J male mice at 6 and 14 months of age and from leptin deficient mice (ob/ob) at 6 months of age using microarrays. DIO affected gene expression in both depots at 6 and 14 months, but more genes were altered in epididymal than bone marrow adipocytes at each age and younger mice displayed more changes than older animals. In epididymal adipocytes a total of 2789 (9.6%) genes were differentially expressed at 6-months with DIO, whereas 952 (3.3%) were affected at 14-months. In bone marrow adipocytes, 347 (1.2%) genes were differentially expressed at 6-months with DIO, whereas only 189 (0.66%) were changed at 14-months. 133 genes were altered by DIO in both fat depots at 6-months, and 37 genes at 14-months. Only four genes were altered in both depots at both ages with DIO. Bone marrow adipocytes are less responsive to DIO than epididymal adipocytes and the response of both depots to DIO declines with age. This loss of responsiveness with age is likely due to age-associated changes in expression of genes related to adipogenesis, inflammation and mitochondrial function that are similar to and obscure the changes commonly associated with DIO. Patterns of gene expression were generally similar in epididymal adipocytes from ob/ob and DIO mice; however, several genes were differentially expressed in bone marrow adipocytes from ob/ob and DIO mice, perhaps reflecting the importance of leptin signaling for bone metabolism. In conclusion, obesity affects age-associated alterations in gene expression in both epididymal and bone marrow adipocytes regardless of diet or genetic background.
Nutrition & Metabolism, 2010
Steroid hormones regulate diverse physiological functions such as reproduction, blood salt balanc... more Steroid hormones regulate diverse physiological functions such as reproduction, blood salt balance, maintenance of secondary sexual characteristics, response to stress, neuronal function and various metabolic processes. They are synthesized from cholesterol mainly in the adrenal gland and gonads in response to tissue-specific tropic hormones. These steroidogenic tissues are unique in that they require cholesterol not only for membrane biogenesis, maintenance of membrane fluidity and cell signaling, but also as the starting material for the biosynthesis of steroid hormones. It is not surprising, then, that cells of steroidogenic tissues have evolved with multiple pathways to assure the constant supply of cholesterol needed to maintain optimum steroid synthesis. The cholesterol utilized for steroidogenesis is derived from a combination of sources: 1) de novo synthesis in the endoplasmic reticulum (ER); 2) the mobilization of cholesteryl esters (CEs) stored in lipid droplets through ch...
Molecular and Cellular Endocrinology, 2013
Intracellular lipid droplets (LDs) are dynamic organelles that contain a number of associated pro... more Intracellular lipid droplets (LDs) are dynamic organelles that contain a number of associated proteins including perilipin (Plin) and vimentin. Cholesteryl ester (CE)-rich LDs normally accumulate in steroidogenic cells and their mobilization is the preferred initial source of cholesterol for steroidogenesis. Plin1a, 1b and 5 were found to preferentially associate with triacylglycerol-rich LDs and Plin1c and 4 to associate with CE-rich LDs, but the biological significance of this remains unanswered. Vimentin null mice were found to have decreased ACTH-stimulated corticosterone levels, and decreased progesterone levels in females, but normal hCG-stimulated testosterone levels in males. Smaller LDs were seen in null cells. Lipoprotein cholesterol delivery to adrenals and ovary was normal, as was the expression of steroidogenic genes; however, the movement of cholesterol to mitochondria was reduced in vimentin null mice. These results suggest that vimentin is important in the maintenance of CE-rich LDs and in the movement of cholesterol for steroidogenesis.
Journal of Proteome Research, 2010
Lipolysis involves a number of components including signaling pathways, droplet-associated protei... more Lipolysis involves a number of components including signaling pathways, droplet-associated proteins and lipases such as hormone-sensitive lipase (HSL). We used Surface Enhanced Laser Desorption/Ionization time-of-flight mass spectroscopy to identify cellular proteins that might interact with HSL and potentially influence lipolysis. Using recombinant HSL as bait on protein chips, clusters of proteins of 14.7 to 18.9 kDa, 25.8-26.8 kDa, 36.1 kDa, 44.3-49.1 kDa, and one at 53.7 kDa were identified that interact with HSL, particularly when lysates were examined from βagonist treated mouse adipocytes. The ability to detect these interacting proteins was markedly diminished when the adipocytes were treated with insulin. A very similar pattern of proteins was identified when anti-HSL IgG was used as the bait. Following immunocapture, the identification of the prominent 53.7 kDa protein was carried out by tryptic digestion and MS analysis, and determined to be vimentin. The interaction of HSL with vimentin, and its hormonal dependence, was confirmed by co-immunoprecipitation. β-agonist stimulated lipolysis and the rate of HSL translocation were impaired in vimentin null adipocytes, even though normal amounts of lipases and droplet-associated proteins are expressed. The current studies provide evidence that vimentin participates in lipolysis through direct, hormonally regulated interactions with HSL.
Journal of Lipid Research, 2002
Hormone-sensitive lipase (HSL) is an intracellular neutral lipase that is capable of hydrolyzing ... more Hormone-sensitive lipase (HSL) is an intracellular neutral lipase that is capable of hydrolyzing triacylglycerols, diacylglycerols, monoacylglycerols, and cholesteryl esters, as well as other lipid and water soluble substrates. HSL activity is regulated post-translationally by phosphorylation and also by pretranslational mechanisms. The enzyme is highly expressed in adipose tissue and steroidogenic tissues, with lower amounts expressed in cardiac and skeletal muscle, macrophages, and islets. Studies of the structure of HSL have identified several amino acids and regions of the molecule that are critical for enzymatic activity and regulation of HSL. This has led to important insights into its function, including the interaction of HSL with other intracellular proteins, such as adipocyte lipid binding protein. Accumulating evidence has defined important functions for HSL in normal physiology, affecting adipocyte lipolysis, steroidogenesis, spermatogenesis, and perhaps insulin secretion and insulin action; however, direct links between abnormal expression or genetic variations of HSL and human disorders, such as obesity, insulin resistance, type 2 diabetes, and hyperlipidemia, await further clarification. The published reports examining the regulation, and function of HSL in normal physiology and disease are reviewed in this paper.-Kraemer, F. B., and W-J. Shen. Hormone-sensitive lipase: control of intracellular tri-(di-)acylglycerol and cholesteryl ester hydrolysis.
Journal of Lipid Research, 2012
Lipid droplets (LDs) are organelles found in many types of eukaryotic cells and are composed of a... more Lipid droplets (LDs) are organelles found in many types of eukaryotic cells and are composed of a core of neutral lipids, such as triacylglycerol (TAG), covered by a monolayer of phospholipids, free cholesterol, and specifi c proteins (1). Proteomic studies have identifi ed LD-associated proteins involved in lipid metabolism and transport, intracellular traffi cking, signaling, and cytoskeletal organization (1). The major LD-associated proteins belong to the perilipin-adipophilin-TIP47 (PAT) family and are characterized by sequence similarity (2). Fat-specifi c protein 27 (FSP27), also known as Cidec for the human homolog, was discovered to be up-regulated during adipogenesis and is highly expressed in white adipose tissue (WAT) and brown adipose tissue (BAT) in mice (3-6) but only in WAT in humans (7). The LD localization of FSP27 and perilipin A (Plin1) in 3T3-L1 adipocytes is similar, and they share some conserved regions at the amino acid level (8), but there is no similarity within the PAT domains, which are regions highly conserved in PAT family proteins and which are not present in FSP27. Overexpression of FSP27 induces the accumulation of LDs and enhances LD size not only in adipocytes but also in many nonlipogenic cells (9, 10). Conversely, knockdown of FSP27 decreases LD size and increases LD number in 3T3-L1 adipocytes (6, 11). Thus, FSP27, like PAT proteins, appears to have an important role in the regulation of LDs but does not appear to function as effectively as Plin1 as a barrier to LD breakdown by cytosolic lipases. Two groups independently reported the phenotypes of FSP27-defi cient Abstract Fat-specifi c protein 27 (FSP27), a member of the cell death-inducing DNA fragmentation factor ␣-like effector (Cide) family, is highly expressed in adipose tissues and is a lipid droplet (LD)-associated protein that induces the accumulation of LDs. Using a yeast two-hybrid system to examine potential interactions of FSP27 with other proteins, a direct interaction with the N-terminal region of nuclear factor of activated T cells 5 (NFAT5) was identifi ed. NFAT5 is a transcription factor that induces osmoprotective and infl ammatory genes after its translocation to the nucleus. The interaction between FSP27 and NFAT5 was confi rmed by bimolecular fl uorescence complementation and coimmunoprecipitation. Using immunocytochemistry, NFAT5 is detected in the cytoplasm and in the nucleus under isotonic conditions; however, overexpression of FSP27 inhibited the hypertonic-induced nuclear translocation of NFAT5. Consistent with the suppression of NFAT5 nuclear translocation, in cells transfected with a reporter construct containing the NFAT5 response element from the monocyte chemoattractant protein 1 (MCP1) promoter, FSP27 overexpression repressed hypertonic-induced luciferase activity and the expression of NFAT5 target genes. Knockdown of FSP27 in differentiated 3T3-L1 adipocytes increased the NFAT5mediated rise in MCP1. These results suggest that FSP27 not only modulates LD homeostasis but also modulates the response to osmotic stress via a physical interaction with NFAT5 at the LD surface.-Ueno, M.