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M Daniel Lane

Publications and source records attributed to M Daniel Lane.

36 records · Page 2Linked to original sources
PubMed2004

Sequential gene promoter interactions of C/EBPbeta, C/EBPalpha, and PPARgamma during adipogenesis.

Treatment of 3T3-L1 preadipocytes with differentiation inducers triggers a cascade in which C/EBPbeta is rapidly expressed, followed by C/EBPalpha and PPARgamma. C/EBPalpha and PPARgamma then activate the expression of adipocyte genes that produce the differentiated phenotype. Circumstantial evidence indicates that C/EBPbeta activates transcription of the C/EBPalpha and PPARgamma genes, both of which possess C/EBP regulatory elements in their proximal promoters. Although C/EBPbeta is expressed immediately upon induction of differentiation, acquisition of DNA binding activity is delayed for approximately 14h. Chromatin immunoprecipitation (ChIP) analysis conducted 24h after induction revealed that C/EBPbeta binds to C/EBP regulatory elements in the proximal promoters of the C/EBPalpha and PPARgamma genes. After an additional delay ChIP analysis showed that C/EBPalpha binds to its own promoter and to the promoters of the PPARgamma and 422/aP2 genes. These findings support the view that once expressed, C/EBPalpha is responsible for maintaining the expression of PPARgamma and C/EBPalpha, as well as adipocyte proteins (e.g., 422/aP2) in the terminally differentiated state. Together these findings provide compelling evidence that C/EBPbeta, C/EBPalpha, and PPARgamma participate in a cascade during adipogenesis.

3T3-L1 Cells↗
PubMed2004

Sequential gene promoter interactions by C/EBPbeta, C/EBPalpha, and PPARgamma during adipogenesis.

Treatment of 3T3-L1 preadipocytes with differentiation inducers triggers a cascade in which C/EBPbeta is rapidly expressed, followed by C/EBPalpha and PPARgamma. C/EBPalpha and PPARgamma then activate the expression of adipocyte genes that produce the differentiated phenotype. Circumstantial evidence indicates that C/EBPbeta activates transcription of the C/EBPalpha and PPARgamma genes, both of which possess C/EBP regulatory elements in their proximal promoters. Although C/EBPbeta is expressed immediately upon induction of differentiation, acquisition of DNA binding activity is delayed for approximately 14h. Chromatin immunoprecipitation (ChIP) analysis conducted 24h after induction revealed that C/EBPbeta binds to C/EBP regulatory elements in the proximal promoters of the C/EBPalpha and PPARgamma genes. ChIP analysis showed that after an additional delay C/EBPalpha binds to its own promoter and to the promoters of the PPARgamma and 422/aP2 genes. These findings support the view that once expressed, C/EBPalpha is responsible for maintaining the expression of PPARgamma, and C/EBPalpha, as well as adipocyte proteins (e.g., 422/aP2) in the terminally differentiated state. Together these findings provide compelling evidence that C/EBPbeta, C/EBPalpha, and PPARgamma participate in a cascade during adipogenesis.

3T3-L1 Cells↗
PubMed2004

Long-term effects of a fatty acid synthase inhibitor on obese mice: food intake, hypothalamic neuropeptides, and UCP3.

Short-term treatment of lean and obese mice with the fatty acid synthase (FAS) inhibitor, C75, alters expression of hypothalamic neuropeptides thereby reducing food intake, body weight, and body fat. Here we report the long-term effects of C75 on obese (Ob/Ob) mice. A low dose of C75 administered every third day for 30 days reduced food intake by 62% and body weight by 43% whereas body weight of ad lib-fed controls increased by 11%. Loss of body weight correlated with decreased adipose and liver tissue mass. Decreased food intake correlated with decreased expression of hypothalamic neuropeptide mRNAs for NPY, AgRP, and MCH and an increased expression of neuropeptide mRNAs for alphaMSH (i.e., POMC) and CART. Consistent with increased energy expenditure, C75 treatment caused greater weight loss than pair-fed controls and increased expression of skeletal muscle UCP-3 mRNA. Lowered blood glucose was due largely to restriction of food intake. C75 blocked the normal fasting-induced rise in blood free fatty acids and ketones due either to decreased adipose tissue lipolysis and hepatic ketogenesis or increased fatty acid and ketone utilization by peripheral tissues, notably skeletal muscle.

4-Butyrolactone↗
PubMed2003

Dominant-negative C/EBP disrupts mitotic clonal expansion and differentiation of 3T3-L1 preadipocytes.

Hormonal induction of growth-arrested 3T3-L1 preadipocytes rapidly activates expression of CCAAT/enhancer-binding protein (C/EBP) beta. Acquisition of DNA-binding activity by C/EBPbeta, however, is delayed until the cells synchronously enter the S phase of mitotic clonal expansion (MCE). After MCE, C/EBPbeta activates expression of C/EBPalpha and peroxisome proliferator-activated receptor gamma, which then transcriptionally activate genes that give rise to the adipocyte phenotype. A-C/EBP, which possesses a leucine zipper but lacks functional DNA-binding and transactivation domains, forms stable inactive heterodimers with C/EBPbeta in vitro. Infection of 3T3-L1 preadipocytes with an adenovirus A-C/EBP expression vector interferes with C/EBPbeta function after induction of differentiation. A-C/EBP inhibited events associated with hormone-induced entry of S-phase of the cell cycle, including the turnover of p27/Kip1, a key cyclin-dependent kinase inhibitor, expression of cyclin A and cyclin-dependent kinase 2, DNA replication, MCE, and, subsequently, adipogenesis. Although A-C/EBP blocked cell proliferation associated with MCE, it did not inhibit normal proliferation of 3T3-L1 preadipocytes. Immunofluorescent staining of C/EBPbeta revealed that A-C/EBP prevented the normal punctate nuclear staining of centromeres, an indicator of C/EBPbeta binding to C/EBP regulatory elements in centromeric satellite DNA. The inhibitory effects of A-C/EBP appear to be due primarily to interference with nuclear import of C/EBPbeta caused by obscuring its nuclear localization signal. These findings show that both MCE and adipogenesis are dependent on C/EBPbeta.

3T3-L1 Cells↗
PubMed2003

Regulatory sequence elements of mouse GLUT4 gene expression in adipose tissues.

Ablation of GLUT4 in adipose tissues results in whole body insulin resistance and high-fat feeding down-regulates GLUT4 mRNA in white adipose tissues. Previous studies demonstrated that adipose tissue specific element(s) (ASE) of the murine GLUT4 gene is located between -551 and -442 relative to transcription start site and that high-fat responsive element(s) (HFRE) for down-regulation of the GLUT4 gene is located between bases -1001 and -442. To further characterize these regulatory elements, the regulation of GLUT4 minigenes containing -701, -551, and -506 bp of 5(')-flanking region was studied in transgenic mice. GLUT4 minigene mRNA from -506 transgenic mice did not express in adipose tissues, indicating that ASE located within 45 bp is located between bases -551 and -506. An 80-kDa of nuclear DNA binding protein was found to bind to a -TCCTCGTGGGAAGCG- element located between bases -551 and -537. High-fat diet feeding down-regulated GLUT4 minigene mRNA in -701 transgenic mice, but not in -551 transgenic mice, indicating that HFRE is located within 150 bp between bases -701 and -551 of the GLUT4 gene and is distinct from ASE.

Adipose Tissue↗
PubMed2003

Role of CREB in transcriptional regulation of CCAAT/enhancer-binding protein beta gene during adipogenesis.

The proximal promoter of the C/EBPbeta gene possesses dual cis regulatory elements (TGA1 and TGA2), both of which contain core CREB binding sites. Comparison of the activities of C/EBPbeta promoter-reporter genes with 5'-truncations or site-directed mutations in the TGA elements showed that both are required for maximal promoter function. Electrophoretic mobility shift and chromatin immunoprecipitation (ChIP) analyses with antibodies specific to CREB and ATF1 showed that these CREB family members associate with the proximal promoter both in vitro and ex vivo. Immunoblotting and ChIP analysis revealed that other CREB family members, CREM and ATF1, are up-regulated and associate with the proximal C/EBPbeta promoter in mouse embryonic fibroblasts (MEFs) from CREB(-/-) mice. ChIP analysis of wild-type MEFs and 3T3-L1 preadipocytes revealed that interaction of phospho-CREB, the active form of CREB, with the C/EBPbeta gene promoter occurs only after induction of differentiation of 3T3-L1 preadipocytes and MEFs. Consistent with the interaction of CREB and ATF1 at the TGA regulatory elements, expression of constitutively active CREB strongly activated C/EBPbeta promoter-reporter genes, induced expression of endogenous C/EBPbeta, and caused adipogenesis in the absence of the hormonal inducers normally required. Conversely, expression of a dominant-negative CREB blocked promoter-reporter activity, expression of C/EBPbeta, and adipogenesis. When subjected to the standard adipocyte differentiation protocol, wild-type MEFs differentiate into adipocytes at high frequency, whereas CREB(-/-) MEFs exhibit greatly reduced expression of C/EBPbeta and differentiation. The low level of expression of C/EBPbeta and differentiation in CREB(-/-) MEFs appears to be due to up-regulation of other CREB protein family members, i.e. ATF1 and CREM.

3T3-L1 Cells↗
PubMed2003

Hypothalamic malonyl-CoA as a mediator of feeding behavior.

Previous studies showed that i.p. administration of C75, a potent inhibitor of fatty acid synthase (FAS), blocked fasting-induced up-regulation of orexigenic neuropeptides and down-regulation of anorexigenic neuropeptides in the hypothalami of mice. As a result, food intake and body weight were drastically reduced. Here we provide evidence supporting the hypothesis that hypothalamic malonyl-CoA, a substrate of FAS, is an indicator of global energy status and mediates the feeding behavior of mice. We use a sensitive recycling assay to quantify malonyl-CoA to show that the hypothalamic malonyl-CoA level is low in fasted mice and rapidly (< or = 2 h) increases (approximately 5-fold) on refeeding. Intracerebroventricular (i.c.v.) administration of C75 to fasted mice rapidly (< or = 2 h) increased (by 4-fold) hypothalamic malonyl-CoA and blocked feeding when the mice were presented with food. Moreover, prior i.c.v. administration of an acetyl-CoA carboxylase inhibitor, 5-(tetradecyloxy)-2-furoic acid, rapidly (although only partially) prevented the C75-induced rise of hypothalamic malonyl-CoA and prevented the C75-induced decrease of food intake. These effects correlated closely with the rapid (< or = 2 h) and reciprocal effects of i.c.v. C75 on the expression of hypothalamic orexigenic (NPY and AgRP) and anorexigenic (proopiomelanocortin) neuropeptide mRNAs. Previous results showing that C75 administered i.c.v. rapidly activates hypothalamic neurons of the arcuate and paraventricular nuclei are consistent with the results reported in this paper. Together these findings suggest that level of hypothalamic malonyl-CoA, which depends on the relative activities of acetyl-CoA carboxylase and FAS, is an indicator of energy status and mediates feeding behavior.

4-Butyrolactone↗
PubMed2003

Convergence of peroxisome proliferator-activated receptor gamma and Foxo1 signaling pathways.

The forkhead factor Foxo1 (or FKHR) was identified in a yeast two-hybrid screen as a peroxisome proliferator-activated receptor (PPAR) gamma-interacting protein. Foxo1 antagonized PPARgamma activity and vice versa indicating that these transcription factors functionally interact in a reciprocal antagonistic manner. One mechanism by which Foxo1 antagonizes PPARgamma activity is through disruption of DNA binding as Foxo1 inhibited the DNA binding activity of a PPARgamma/retinoid X receptor alpha heterodimeric complex. The Caenorhabditis elegans nuclear hormone receptor, DAF-12, interacted with the C. elegans forkhead factor, DAF-16, paralleling the interaction between PPARgamma and Foxo1. daf-12 and daf-16 have been implicated in C. elegans insulin-like signaling pathways, and PPARgamma and Foxo1 likewise have been linked to mammalian insulin signaling pathways. These results suggest a convergence of PPARgamma and Foxo1 signaling that may play a role in insulin action and the insulinomimetic properties of PPARgamma ligands. A more general convergence of nuclear hormone receptor and forkhead factor pathways may be important for multiple biological processes and this convergence may be evolutionarily conserved.

3T3-L1 Cells↗
PubMed2003

Effect of the anorectic fatty acid synthase inhibitor C75 on neuronal activity in the hypothalamus and brainstem.

Intraperitoneal (i.p.) injection of C75, a fatty acid synthase inhibitor, causes a rapid (<or=2-h) and persistent (to at least 24-h) approximately 95% decrease in food intake. The persistent effect seems to be due to inhibition of the fasting-induced up-regulation of expression of hypothalamic orexigenic neuropeptides neuropeptide Y and agouti-related protein and down-regulation of expression of anorexigenic neuropeptides pro-opiomelanocortinalpha-melanocyte-stimulating hormone and cocaine-amphetamine-related transcript. The effect of C75 on neuronal activity in the hypothalamus and brainstem was assessed by c-Fos expression. Consistent with its effect on neuropeptide expression, C75 blocked fasting-induced c-Fos expression in the arcuate nucleus (Arc), lateral hypothalamic area (LHA), and paraventricular nucleus (PVN) 10-24 h after i.p. injection. However, i.p. C75 induced a rapid (<or=2-h) c-Fos expression in the nucleus of the solitary tract (NTS) and area postrema of the brainstem but not in the Arc or LHA. Intracerebroventricular administration of C75 rapidly induced c-Fos expression in the Arc, PVN, and NTS, supporting a central role of C75 in the regulation of food intake. Thus, suppression of food intake by C75 administered i.p. seems to be mediated in two phases, a rapid initial phase via the NTSarea postrema of the brainstem and a delayed phase via the Arc, LHA, and PVN of the hypothalamus. The delayed effect of C75 on the Arc, LHA, and PVN correlates well with its ability to interfere with the fasting-induced effects on the expression of key orexigenic (neuropeptide Y and agouti-related protein) and anorexigenic (pro-opiomelanocortinalpha-melanocyte-stimulating hormone and cocaine-amphetamine-related transcript) messages in the hypothalamus.

4-Butyrolactone↗
PubMed2003

CCAAT/enhancer-binding protein beta is required for mitotic clonal expansion during adipogenesis.

Hormonal induction of growth-arrested 3T3-L1 preadipocytes triggers a signaling cascade that culminates in adipogenesis. CCAATenhancer-binding protein (CEBP)beta is expressed immediately but gains DNA-binding activity only after a long lag as the cells synchronously begin mitotic clonal expansion (MCE). After MCE, a process required for adipogenesis, CEBPbeta activates expression of CEBPalpha and peroxisome proliferator-activated receptor gamma, which then transcriptionally activate genes that produce the adipocyte phenotype. When mouse embryo fibroblasts (MEFs) are subjected to the same differentiation protocol, a subset of the MEFs undergoes a similar program of events. Similar to 3T3-L1 preadipocytes, the MEFs reenter the cell cycle (as indicated by the synchronous expression of cyclin A) and undergo MCE as evidenced by the incorporation of BrdUrd into DNA and the formation of mitotic foci of cells that undergo adipogenesis. CEBPbeta is expressed immediately after induction but exhibits delayed acquisition of DNA-binding activity followed by expression of adipocyte markers and the accumulation of cytoplasmic triglyceride. MEFs from CEBPbeta(-/-) mice, however, neither undergo MCE nor differentiate into adipocytes. Forced expression of CEBPbeta (LAP) but not dominant-negative CEBPbeta (LIP) in CEBPbeta(-/-) MEFs restores MCE, expression of adipocyte markers, and the capacity to form mitotic foci of cells that undergo adipogenesis. These findings demonstrate that expression of CEBPbeta is a prerequisite for MCE in the adipocyte-differentiation program.

3T3 Cells↗
PubMed2003

Cell cycle arrest by Kaposi's sarcoma-associated herpesvirus replication-associated protein is mediated at both the transcriptional and posttranslational levels by binding to CCAAT/enhancer-binding protein alpha and p21(CIP-1).

Lytic-cycle replication of Kaposi's sarcoma-associated herpesvirus (KSHV) in PEL cells causes G(1) cell cycle arrest mediated by the virus-encoded replication-associated protein (RAP) (or K8 protein), which induces high-level expression of the cellular C/EBPalpha and p21 proteins. Here we have examined the mechanism of this induction at both the transcriptional and posttranslational levels. RAP proved to bind very efficiently to both C/EBPalpha and p21 and stabilized them by up to 10-fold from proteasome-mediated degradation in vitro. Cross-linking revealed that RAP itself forms stable dimers and tetramers in solution and forms higher-order complexes but not heterodimers with C/EBPalpha. Cotransfection of RAP with C/EBPalpha cooperatively stimulated both the C/EBPalpha and p21 promoters in luciferase reporter gene assays. Only the basic/leucine zipper region of RAP was needed for interaction with and stabilization of C/EBPalpha, but both the N-terminal and C-terminal domains were required for transcriptional augmentation. In vitro-translated RAP interfered with DNA binding by C/EBPalpha in electrophonetic mobility shift assay (EMSA) experiments but did not itself bind to the target C/EBPalpha sites or form supershifted bands. However, in endogenous chromatin immunoprecipitation (ChIP) assays with tetradecanoyl phorbol acetate-induced PEL cells, RAP proved to specifically associate with the C/EBPalpha promoter in vivo, but only in a C/EBPalpha-dependent manner, implying an in vivo piggyback interaction with DNA-bound C/EBPalpha. Expression of exogenous RAP (Ad-RAP) caused G(1)/S cell cycle arrest in human dermal microvascular endothelial cells and also induced both the C/EBPalpha and p21 proteins, which formed punctate nuclear patterns that colocalized with RAP in PML nuclear bodies. In the presence of RAP, C/EBPalpha was also efficiently recruited into viral DNA replication compartments in both infected and cotransfected cells. In support of a direct role for this interaction in viral DNA replication, three C/EBPalpha binding sites were identified by in vitro EMSA experiments within a 220-bp core segment of the duplicated KSHV Ori-Lyt region, and although RAP did not bind to Ori-Lyt DNA directly in vitro, both endogenous RAP and C/EBPalpha were found to be associated with the Ori-Lyt region by ChIP assays in lytically induced PEL cells. Finally, we found that the KSHV lytic cycle could not be triggered by either synchronizing KSHV latently infected PEL cells in G(1) phase or inducing p21 in a C/EBPalpha-independent process.

Base Sequence↗
PubMed2002

Mitotic clonal expansion: a synchronous process required for adipogenesis.

When induced to differentiate, growth-arrested 3T3-L1 preadipocytes synchronously reenter the cell cycle and undergo mitotic clonal expansion (MCE) followed by expression of genes that produce the adipocyte phenotype. The preadipocytes traverse the G(1)S checkpoint synchronously as evidenced by the expressionactivation of cdk2-cyclin-EA, turnover of p27kip1, hyperphosphorylation of Rb, translocation of cyclin D(1) from nuclei to cytoplasm and GSK-3beta from cytoplasm to nuclei, and incorporation of [(3)H]thymidine into DNA. As the cells cross the G(1)S checkpoint, CEBPbeta acquires DNA-binding activity, initiating a cascade of transcriptional activation that culminates in the expression of adipocyte proteins. The mitogen-activated protein kinaseextracellular signal-regulated kinase kinase (MEK) inhibitor PD98059 delays, but does not block, MCE and differentiation, the extent of the delay causing a comparable delay in the expression of cell-cycle markers, MCE, and adipogenesis. The more potent and specific MEK inhibitor UO126 and the cyclin-dependent kinase inhibitor roscovitine, which inhibit the cell cycle at different points, block MCE, expression of cell cycle and adipocyte markers, as well as adipogenesis. These results show that MCE is a prerequisite for differentiation of 3T3-L1 preadipocytes into adipocytes.

3T3 Cells↗
PubMed2002

Lytic replication-associated protein (RAP) encoded by Kaposi sarcoma-associated herpesvirus causes p21CIP-1-mediated G1 cell cycle arrest through CCAAT/enhancer-binding protein-alpha.

Kaposi sarcoma-associated herpesvirus (KSHV) is an oncogenic DNA virus that causes Kaposi sarcoma and AIDS-related primary effusion lymphoma (PEL). Here we show that KSHV lytic cycle replication in PEL cells induces G(1) cell cycle arrest, presumably to facilitate the progression of viral DNA replication. Expression of a KSHV-encoded early lytic protein referred to as RAP or K8 is induced within 12-24 h after the onset of lytic cycle induction in host PEL cells, and coincides with increased levels of both the endogenous C/EBPalpha and p21(CIP-1) proteins in the nucleus of the same cells. The KSHV RAP protein binds to C/EBPalpha in vitro and stimulates C/EBPalpha-induced expression from both the C/EBPalpha and p21 promoters in cotransfected cells. A recombinant adenovirus expressing the RAP protein induced the expression of both the C/EBPalpha and p21 proteins in primary human fibroblasts, and flow cytometric analysis revealed a dramatic inhibition of G(1) to S cell cycle progression in the same cells. All of these effects were abolished in cells that lack C/EBPalpha or by deletion of the basic/leucine zipper region in RAP that interacts with C/EBPalpha. Therefore, C/EBPalpha is essential for the p21-mediated inhibition of G(1) to S-phase progression by RAP in KSHV-infected host cells.

3T3 Cells↗
PubMed2002

Elevated nucleocytoplasmic glycosylation by O-GlcNAc results in insulin resistance associated with defects in Akt activation in 3T3-L1 adipocytes.

Increased flux of glucose through the hexosamine biosynthetic pathway (HSP) is believed to mediate hyperglycemia-induced insulin resistance in diabetes. The end product of the HSP, UDP beta-N-acetylglucosamine (GlcNAc), is a donor sugar nucleotide for complex glycosylation in the secretory pathway and for O-linked GlcNAc (O-GlcNAc) addition to nucleocytoplasmic proteins. Cycling of the O-GlcNAc posttranslational modification was blocked by pharmacological inhibition of O-GlcNAcase, the enzyme that catalyzes O-GlcNAc removal from proteins, with O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc). PUGNAc treatment increased levels of O-GlcNAc and caused insulin resistance in 3T3-L1 adipocytes. Insulin resistance induced through the HSP by glucosamine and chronic insulin treatment correlated with increased O-GlcNAc levels on nucleocytoplasmic proteins. Whereas insulin receptor autophosphorylation and insulin receptor substrate 2 tyrosine phosphorylation were not affected by PUGNAc inhibition of O-GlcNAcase, downstream phosphorylation of Akt at Thr-308 and glycogen synthase kinase 3 beta at Ser-9 was inhibited. PUGNAc-induced insulin resistance was associated with increased O-GlcNAc modification of several proteins including insulin receptor substrate 1 and beta-catenin, two important effectors of insulin signaling. These results suggest that elevation of O-GlcNAc levels attenuate insulin signaling and contribute to the mechanism by which increased flux through the HSP leads to insulin resistance in adipocytes.

3T3 Cells↗
PubMed2002

Differential effects of a centrally acting fatty acid synthase inhibitor in lean and obese mice.

C75 is a potent inhibitor of fatty acid synthase that acts centrally to reduce food intake and body weight in mice; a single dose causes a rapid (>90%) decrease of food intake. These effects are associated with inhibition of fasting-induced up-regulation and down-regulation, respectively, of the expression of orexigenic (NPY and AgRP) and anorexigenic (POMC and CART) neuropeptide messages in the hypothalamus. Repeated administration of C75 at a submaximal level, however, differentially affected food intake of lean and obese mice. With lean mice, C75 suppressed food intake by approximately 50% and, with obese mice (ob/ob and dietary-induced obesity), by 85-95% during the first day of treatment. Lean mice, however, became tolerant/resistant to C75 over the next 2-5 days of treatment, with food intake returning to near normal and rebound hyperphagia occurring on cessation of treatment. In contrast, ob/ob obese mice responded to C75 with a >90% suppression of food intake throughout the same period with incipient tolerance becoming evident only after substantial weight loss had occurred. Dietary-induced obese mice exhibited intermediate behavior. In all cases, a substantial loss of body weight resulted. Pair-fed controls lost 24-50% less body weight than C75-treated mice, indicating that, in addition to suppressing food intake, C75 may increase energy expenditure. The decrease in body weight by ob/ob mice was due primarily to loss of body fat. In contrast to the short-term effects of C75 on "fasting-induced" changes of hypothalamic orexigenic and anorexigenic neuropeptide mRNAs, repeated administration of C75 either had the inverse or no effect as tolerance developed.

4-Butyrolactone↗
PubMed2001

Effect of a fatty acid synthase inhibitor on food intake and expression of hypothalamic neuropeptides.

The fatty acid synthase inhibitor, C75, acts centrally to reduce food intake and body weight in mice. Here we report the effects of C75 on the expression of key orexigenic [neuropeptide Y (NPY), agouti-related protein (AgRP), and melanin-concentrating hormone] and anorexigenic [pro-opiomelanocortin (POMC) and cocaine-amphetamine-related transcript (CART)] neuropeptide messages in the hypothalami of lean and obese (ob/ob) mice. In lean mice, C75 rapidly and almost completely blocked food intake and prevented fasting-induced up-regulation of hypothalamic AgRP and NPY mRNAs, as well as down-regulation of CART and POMC mRNAs. Thus, in lean mice C75 seems to interrupt the fasting-induced signals that activate expression of NPY and AgRP and suppression of POMC and CART. In obese mice, C75 rapidly suppressed food intake, reduced body weight, and normalized obesity-associated hyperglycemia and hyperinsulinemia. Like its effect in lean mice, C75 prevented the fasting-induced increase of hypothalamic NPY and AgRP mRNAs in obese mice, but had no effect on the expression of POMC and CART mRNAs. The suppressive effect of C75 on food intake in lean mice seems to be mediated both by NPY/AgRP and POMC/CART neurons, whereas in obese mice the effect seems to be mediated primarily by NPY/AgRP neurons. In both lean and obese mice, C75 markedly increased expression of melanin-concentrating hormone and its receptor in the hypothalamus.

4-Butyrolactone↗
PubMedDate not supplied

Adipose development: from stem cell to adipocyte.

Cell culture models have been developed to study commitment and subsequent differentiation of preadipocytes into adipocytes. Bone morphogenetic protein 4 commits mesenchymal stem cells to the adipose lineage. Other factors, including Wnt signaling, cell density, and cell shape, play a role in lineage commitment. Following commitment to the adipose lineage, growth-arrested preadipocytes can differentiate to adipocytes by treatment with insulin-like growth factor 1, glucocorticoid and an agent that increases cAMP level. This process is characterized by a rapid and transient increase in CCAAT/enhancer binding protein (C/EBP) beta and synchronous re-entry into the cell cycle. Acquisition of DNA-binding by C/EBPbeta occurs after the transcription factor becomes phosphorylated. The cells enter a growth-arrested state and begin terminal differentiation. C/EBPalpha, peroxisome proliferator-activated receptor gamma, and adipocyte determination, and differentiation-dependent factor 1 coordinate the expression of genes that create and maintain the adipocyte phenotype.

Adipocytes↗