Sequence, tissue distribution, and differential expression of mRNA for a putative insulin-responsive glucose transporter in mouse 3T3-L1 adipocytes

The cDNAs for two putative glucose transporters from mouse 3T3-L1 adipocytes were isolated and sequenced. One of these cDNAs encodes the murine homolog of the human hepG2/erythrocyte glucose transporter, termed GT1. GT1 mRNA is most abundant in mouse brain and is expressed in both 3T3-L1 preadipocytes and adipocytes. The other cDNA encodes a glucose transporter-like protein, termed GT2, that has a unique amino acid sequence and tissue distribution. GT2 cDNA encodes a protein with 63% amino acid sequence identity and a similar structural organization to GT1. GT2 mRNA is found at high levels in mouse skeletal muscle, heart, and adipose tissue, all of which exhibit insulin-stimulated glucose uptake. GT2 mRNA is absent from 3T3-L1 preadipocytes but is induced dramatically during differentiation into adipocytes. This increase in mRNA content correlates closely with the acquisition of insulin-stimulated glucose uptake. We propose that GT2 is an insulin-regulated glucose transporter.

Insulin regulates transcription of the CCAAT/enhancer binding protein (C/EBP) alpha, beta, and delta genes in fully-differentiated 3T3-L1 adipocytes

The effect of insulin on expression of CCAAT/enhancer binding protein (C/EBP) alpha, beta, and delta was investigated in fully-differentiated 3T3-L1 adipocytes. Treatment of adipocytes with insulin stimulated rapid dephosphorylation of C/EBP alpha, and repressed the expression of C/EBP alpha within 2-4 h, with > 90% suppression occurring at 24 h. While insulin induced expression of C/EBP beta and C/EBP delta within 1 h and caused a > 20-fold increase by 4 h, expression returned to nearly pretreatment levels by 24 h. The insulin concentration dependence of these effects was consistent with involvement of the insulin receptor. Gel shift analysis revealed that 6 h of insulin treatment decreased the binding of nuclear C/EBP alpha while increasing binding of nuclear C/EBP beta and C/EBP delta. The reciprocal effects of insulin on the steady-state levels of C/EBP transcription factors can be accounted for kinetically and quantitatively by changes in their mRNA levels, which can be accounted for by effects on gene transcription. The effects of insulin on adipocyte gene transcription (e.g. GLUT4) may be mediated, at least in part, by down-regulation of C/EBP alpha and/or its dephosphorylation.

Reconstruction of orbital wall defects: critical review of 72 patients

Between January 1996 and December 2001, 72 out of 354 patients were included in a retrospective study analysing the outcome of repaired orbital wall defects. Selection was dependent on the availability of pre and postoperative CT scans and on ophthalmologic examination. In particular, orthoptical assessment was performed up to 1 year after operation. In 72 patients, 83 orbital wall defects were analysed and allocated to one of five categories. Accuracy and type of reconstruction were assessed in unilateral orbital wall defects (n=61) and compared with functional outcome. Reconstruction was performed by using PDS membrane (39%), calvarian bone (13%), titanium mesh (7%) or a combination of these materials (37%). Postoperatively, 91% of the patients had normal vision without double images within 20 degrees at every gaze. Accuracy of reconstruction correlated with severity of orbital injury and functional outcome. Functional outcome between category II and III fractures showed no significant difference. The medial margin of the lateral infraorbital fissure being preserved (category II fracture) facilitates reconstruction technically. Accuracy of orbital reconstruction is one important factor to obtain best functional outcome, but other determinants like displacement and/or atrophy of intramuscular cone fat should be considered.

Regulation of lipoprotein lipase mRNA content in 3T3-L1 cells by tumour necrosis factor

Tumour necrosis factor (TNF) was previously shown to suppress lipoprotein lipase (LPL) synthesis and activity in 3T3-L1 adipocytes. The present study examined the effect of TNF on amounts of mRNA for LPL in 3T3-L1 cells. Northern-blot analysis of polyadenylated RNA using a cDNA probe to guinea-pig LPL identified two predominant species of LPL message, 3.7 and 3.9 kilobases in size. The steady-state amounts of these mRNAs increased 10-fold upon expression of the adipocyte phenotype. A single dose of 1.5 nM-TNF decreased LPL mRNA by approx. 60% in 17 h with a corresponding decrease in LPL activity, an effect that was reversed 48 h after exposure to TNF. The results demonstrate that TNF reversibly down-regulates LPL mRNA in fully differentiated 3T3-L1 adipocytes. Cells induced to differentiate in the presence of 1.5 nM-TNF exhibited a delayed time course for development of the adipocyte phenotype, as judged by attenuation of the normal increase in LPL mRNA that occurs with differentiation.

Effects of L-triiodothyronine and the thyromimetic L-94901 on serum lipoprotein levels and hepatic low-density lipoprotein receptor, 3-hydroxy-3-methylglutaryl coenzyme A reductase, and apo A-I gene expression

The mechanisms by which thyroid hormone (triiodothyronine (T3)) and a thyromimetic, 2-amino-3-(3,5-dibromo-4-[4-hydroxy-3-(6-oxo-1,6-dihydro-pyridazin -3-ylmethyl)-phenoxyl]-phenyl)propionic acid (L-94901), lower plasma low density lipoprotein (LDL) cholesterol and raise plasma high density lipoprotein (HDL) cholesterol levels was investigated in thyroidectomized and sham-operated rats. Thyroidectomy resulted in a 77% increase in plasma LDL cholesterol, a 60% decrease in plasma triglycerides, and a modest reduction in HDL cholesterol. Daily oral dosing with T3 (10-170 nmol/kg) or L94901 (100-1000 nmol/kg) for 7 days decreased plasma LDL cholesterol in thyroidectomized rats by 60-80%, respectively. This reduction in LDL cholesterol was accompanied by a dose-dependent increase in HDL cholesterol levels of up to 60%. Thus, the ratio of LDL to HDL was decreased from 1.01 to 0.12 after treatment with L-94901 and to 0.25 after dosing with T3. In sham-operated animals, T3 and L-94901 lowered LDL cholesterol by 61 and 46%, respectively, and increased HDL cholesterol by 25 and 53%, respectively. Immunoblotting analysis of liver membranes prepared from thyroidectomized or sham-operated rats demonstrated that LDL receptor protein levels were increased by up to eight-fold. Northern blotting analysis revealed similar large increases in hepatic LDL receptor mRNA levels that accounted for the increases in LDL receptor protein levels. Hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase mRNA, protein, and activity were increased 2- to 3-fold. The T3- and L-94901-mediated increases in serum HDL levels were associated with 2- to 3-fold increases in apo A-I mRNA levels. In contrast with most other hypocholesterolemic agents, T3 and L-94901 significantly increase HDL cholesterol levels in addition to decreasing LDL cholesterol levels due to induction of hepatic apo A-I and LDL receptor gene expression.

The regulation and activation of ciliary neurotrophic factor signaling proteins in adipocytes

Ciliary neurotrophic factor (CNTF) is primarily known for its roles as a lesion factor released by the ruptured glial cells that prevent neuronal degeneration. However, CNTF has also been shown to cause weight loss in a variety of rodent models of obesity/type II diabetes, whereas a modified form also causes weight loss in humans. CNTF administration can correct or improve hyperinsulinemia, hyperphagia, and hyperlipidemia associated with these models of obesity. In order to investigate the effects of CNTF on fat cells, we examined the expression of CNTF receptor complex proteins (LIFR, gp130, and CNTFRalpha) during adipocyte differentiation and the effects of CNTF on STAT, Akt, and MAPK activation. We also examined the ability of CNTF to regulate the expression of adipocyte transcription factors and other adipogenic proteins. Our studies clearly demonstrate that the expression of two of the three CNTF receptor complex components, CNTFRalpha and LIFR, decreases during adipocyte differentiation. In contrast, gp130 expression is relatively unaffected by differentiation. In addition, preadipocytes are more sensitive to CNTF treatment than adipocytes, as judged by both STAT 3 and Akt activation. Despite decreased levels of CNTFRalpha expression in fully differentiated 3T3-L1 adipocytes, CNTF treatment of these cells resulted in a time-dependent activation of STAT 3. Chronic treatment of adipocytes resulted in a substantial decrease in fatty-acid synthase and a notable decline in SREBP-1 levels but had no effect on the expression of peroxisome proliferator-activated receptor gamma, acrp30, adipocyte-expressed STAT proteins, or C/EBPalpha. However, CNTF resulted in a significant increase in IRS-1 expression. CNTFRalpha receptor expression was substantially induced in the fat pads of four rodent models of obesity/type II diabetes as compared with lean littermates. Moreover, we demonstrated that CNTF can activate STAT 3 in adipose tissue and skeletal muscle in vivo. In summary, CNTF affects adipocyte gene expression, and the specific receptor for this cytokine is induced in rodent models of obesity/type II diabetes.

Discovery of a novel series of 6-azauracil-based thyroid hormone receptor ligands: potent, TR beta subtype-selective thyromimetics

In this communication, we wish to describe the discovery of a novel series of 6-azauracil-based thyromimetics that possess up to 100-fold selectivities for binding and functional activation of the beta(1)-isoform of the thyroid receptor family. Structure-activity relationship studies on the 3,5- and 3'-positions provided compounds with enhanced TR beta affinity and selectivity. Key binding interactions between the 6-azauracil moiety and the receptor have been determined through of X-ray crystallographic analysis.

Cell-free transcription directed by the 422 adipose P2 gene promoter: activation by the CCAAT/enhancer binding protein

Previous investigations have shown that CCAAT/enhancer binding protein (C/EBP) can function as a trans-activator of the promoters of several adipocyte-specific genes--i.e., the 422 adipose P2 (422/aP2), stearoyl-CoA desaturase 1 (SCD1), and glucose transporter 4 (GLUT4) genes, in 3T3-L1 mouse preadipocytes. We now describe a cell-free system prepared from nuclei of 3T3-L1 cells that carries out transcription directed by these promoters. To measure transcript formation, we employed a polymerase chain reaction-assisted analysis. Nuclear extract from 3T3-L1 adipocytes that express C/EBP supports a higher rate of transcription of chimeric 422(aP2) promoter-chloramphenicol acetyltransferase (CAT) reporter gene constructs than nuclear extract from preadipocytes that lack C/EBP. A competitor oligonucleotide containing the C/EBP binding site sequence and antibodies raised against C/EBP inhibit transcription directed by the 422(aP2) promoter. The factor limiting transcription by nuclear extract from preadipocytes appears to be C/EBP, since recombinant C/EBP (rC/EBP) markedly activates transcription of the 422(aP2) promoter-CAT gene with preadipocyte extract but not with adipocyte extract. rC/EBP also activates cell-free transcription of SCD1 promoter-CAT and GLUT4 promoter-CAT chimeric genes. Point mutations within the C/EBP binding site in the 422(aP2) promoter markedly decrease transcription activated by rC/EBP. Consistent with activation by cAMP of the 422(aP2) promoter in intact preadipocytes, cAMP-dependent protein kinase activates transcription through this promoter with the cell-free system, this effect being independent of C/EBP. Thus, regulation of transcription directed by the 422(aP2) promoter in the cell-free system resembles that which occurs in intact 3T3-L1 cells.

Intranasal diamorphine for paediatric analgesia: assessment of safety and efficacy

OBJECTIVE

To evaluate the safety and efficacy of intranasal diamorphine as an analgesic for use in children in accident and emergency (A&E).

METHODS

A prospective, randomised clinical trial with consecutive recruitment of patients aged between 3 and 16 years with clinically suspected limb fractures. One group received 0.1 mg/kg intranasal diamorphine, and the other group received 0.2 mg/kg intramuscular morphine. At 0, 5, 10, 20, and 30 minutes pain scores, Glasgow coma score, and peripheral oxygen saturations were recorded; parental acceptability was assessed at 30 minutes.

RESULTS

58 children were recruited, with complete data collection in 51 (88%); the median summed decrease in pain score was better for intranasal diamorphine than intramuscular morphine (9 v 8), though this was not significant (P = 0.4, Mann-Whitney U test). The episode was recorded as "acceptable" in all parents whose child received intranasal diamorphine, compared with only 55% of parents in the intramuscular morphine group (P < 0.0001, Fisher's exact test). There was no incidence of decreased peripheral oxygen saturation or depression in the level of consciousness in any patient.

CONCLUSIONS

Intranasal diamorphine is an effective, safe, and acceptable method of analgesia for children requiring opiates in the A & E department.

Extensive bone marrow necrosis in patients with cancer and tumor necrosis factor activity in plasma

Tumor necrosis factor (TNF), a macrophage secretory protein produced by peripheral blood monocytes from patients with cancer, has been shown to possess cytotoxicity toward tumor cells in vitro. TNF in the blood of individuals with cancer is usually not detectable except with extremely sensitive radioimmunoassay or enzyme-linked immunosorbent assay (ELISA) methods. We have encountered two patients with the rare syndrome of extensive bone marrow necrosis in association with cancer. The first patient presented with marrow failure secondary to necrosis and was found to have adenocarcinoma in thoracic lymph nodes, lung, and marrow lymphatics at autopsy. Plasma tested at two dilutions (1:200 and 1:2,000) contained TNF at a concentration of 8.3 ng/ml, or 80 U/ml by a cytotoxicity assay using LM cells. The presence of TNF was confirmed with immunoblotting. The second patient had a poorly differentiated lymphoid tumor involving bone marrow, pancytopenia, and marrow necrosis. The plasma cytotoxicity assay indicated the presence of 0.7 ng/ml or 7 U/ml TNF. TNF was not detectable in plasma from six other patients with untreated cancer involving bone or bone marrow using either of our methods. The levels of TNF in the two patients with marrow necrosis were greater than those previously measured by others in patients with cancer but were comparable to those noted in patients with lethal sepsis. Since large doses of TNF have been shown to cause organ necrosis in animals, the data presented here are consistent with TNF involvement in mediating the observed marrow necrosis in our patients.

Activation of the G-protein-coupled receptor 119: a conformation-based hypothesis for understanding agonist response

The synthesis and properties of the bridged piperidine (oxaazabicyclo) compounds 8, 9, and 11 are described. A conformational analysis of these structures is compared with the representative GPR119 ligand 1. These results and the differences in agonist pharmacology are used to formulate a conformation-based hypothesis to understand activation of the GPR119 receptor. We also show for these structures that the agonist pharmacology in rat masks the important differences in human pharmacology.

Regulation of glucose transport as well as glucose transporter and immediate early gene expression in 3T3-L1 preadipocytes by 8-bromo-cAMP

In the present study we have examined the ability of 8-bromoadenosine cyclic 3',5'-phosphate (8-bromo-cAMP; the membrane permeant analog of cAMP which can activate protein kinase A) to mimic hormone action and stimulate glucose transport and glucose transporter (GLUT-1) gene expression as well as the expression of several growth-related protooncogenes in quiescent 3T3-L1 fibroblasts. 8-Bromo-cAMP induced a rapid and prolonged increase in the rate of hexose transport. Early activation of hexose transport (within 30 min) was associated with increased plasma membrane immunoreactive glucose transporters, which corresponded to a doubling in the number of D-glucose-displaceable, plasma membrane cytochalasin B binding sites. The time course for 8-bromo-cAMP-induced hexose transport preceded the accumulation of GLUT-1 mRNA, which peaked between 4 and 8 h after exposure to the agent, and subsequently declined to approach basal (control) levels. Expression of the immediate-early genes c-fos and jun-B was induced by 8-bromo-cAMP on a rapid, but sustained time course, whereas induction of c-jun expression was delayed. Alterations in specific mRNAs following exposure to 8-bromo-cAMP were due to increased gene transcription (as judged by nuclear transcription run-on assays), although with respect to GLUT-1, an increase in mRNA stability was also observed. Treatment of the cells with forskolin resulted in the induction of GLUT-1 expression as well as expression of the immediate early genes. Exposure of quiescent 3T3-L1 fibroblasts to 8-bromo-cAMP resulted in a substantial increase in rates of total protein and RNA synthesis, but had little effect on DNA synthesis. The results demonstrate that 8-bromo-cAMP initiated a G0/G1 transition, but did not permit progression into S-phase. The results further suggest that increased cytosolic cAMP results in the stimulation of glucose transport by three distinct mechanisms to include translocation of pre-existing transporters, increased transcription of the GLUT-1 gene and increased stability of GLUT-1 mRNA.

Monokine regulation of glucose transporter mRNA in L6 myotubes

Endotoxin-induced macrophage secretory proteins (monokines) have been shown to stimulate hexose uptake in L6 myotubes (1). In those studies a doubling of the Vmax for hexose uptake was observed which correlated with elevated numbers of glucose transporters (GT) in both plasma and microsomal membranes. To determine if these changes in transporter populations were due to increased GT mRNA, we performed Northern blot analysis using L6 cell RNA and a cDNA to the HepG2 glucose transporter. The L6 myotubes contained a single 2.8 kb species of GT mRNA that increased 2.5-fold after an 8h exposure to the monokine preparation. beta-Actin mRNA levels were unaltered by the treatment, indicating specificity of monokine action. Glucose transporter mRNA content appeared to reach a maximum 8 h after exposure to the monokine. Over the next 16 h the levels of this mRNA gradually decreased, approaching control levels. Data obtained from nuclear transcription run-on assays suggest that increased levels of CT mRNA are due to an increased rate of gene transcription. A second transporter, the insulin-sensitive glucose transporter, was also observed to be expressed in the L6 cells. Monokine treatment resulted in a 60% suppression of the mRNA coding for this protein.

Characterization of the tumour necrosis factor receptor in human placenta

A specific receptor for tumour necrosis factor present in a purified plasma membrane preparation from the villous tissue of human placenta has been characterized. The data fit a one-class-of-sites model exhibiting a KD = 28.4 (+/- 0.002) nM, with 8.1 (+/- 0.05) X 10(11) receptors mg-1 membrane protein. These data provide evidence for the existence of a specific receptor for a major endotoxin-induced cytokine in the placenta.

Identification of potent, selective, CNS-targeted inverse agonists of the ghrelin receptor

The optimization for selectivity and central receptor occupancy for a series of spirocyclic azetidine-piperidine inverse agonists of the ghrelin receptor is described. Decreased mAChR muscarinic M2 binding was achieved by use of a chiral indane in place of a substituted benzylic group. Compounds with desirable balance of human in vitro clearance and ex vivo central receptor occupancy were discovered by incorporation of heterocycles. Specifically, heteroaryl rings with nitrogen(s) vicinal to the indane linkage provided the most attractive overall properties.

The first 22 base pairs of the proximal promoter of the rat class I alcohol dehydrogenase gene is bipartite and interacts with multiple DNA-binding proteins

The rat class I alcohol dehydrogenase (ADH) gene is primarily expressed in the liver. We previously showed that the liver-enriched transcription factor, the CCAAT/enhancer binding protein (C/EBP), binds to the proximal promoter of the rat class I ADH gene between positions -11 and -22 relative to the start site of transcription. We now demonstrate that another transcription factor, the liver activator protein (LAP), also interacts with the same region of the promoter based on the following observations: (1) LAP synthesized by in vitro transcription and translation of cloned cDNA sequence forms complexes with an oligonucleotide containing the C/EBP-binding sequence within the ADH promoter as determined by the electrophoretic mobility shift assay (EMSA), (2) purified LAP interacts with the proximal ADH promoter when analyzed by the DNase I protection assay, and (3) an ADH promoter-reporter gene construct containing the C/EBP-binding site is transactivated by an eukaryotic expression vector containing the LAP sequence. EMSA of an oligonucleotide containing the first 22 base pairs (between positions -1 and -22) of the ADH promoter with rat liver nuclear extracts (RLNE) resulted in the formation of two major complexes. Complex 1 was competed away by a heterologous oligonucleotide containing a C/EBP-binding site within the promoter of the adipocyte 422 (aP2) gene, while complex 2 was not. Additional competition experiments with the ADH or 422 (aP2) oligonucleotide using either RLNE or extracts from 3T3-L1 adipocytes demonstrated that complex 1 contains either C/EBP or LAP, while complex 2 contains a DNA-binding protein that binds to a novel sequence 5'-TGGCCCAGTT-3' between positions -1 and -10 of the ADH promoter. Ultraviolet cross-linking between RLNE and a labeled oligonucleotide containing the above sequence indicates that this protein, designated EDBP (for enhancer-site downstream binding protein), has an estimated molecular weight of 47 kDa, which is larger than that reported for either C/EBP (42 kDa) or LAP (36 kDa).

Design and synthesis of orally-active and selective azaindane 5HT2c agonist for the treatment of obesity

Based on our original pyrazine hit, CP-0809101, novel conformationally-restricted 5HT2c receptor agonists with 2-piperazin-azaindane scaffold were designed. Synthesis and structure-activity relationship (SAR) studies are described with emphasis on optimization of the selectivity against 5HT2a and 5HT2b receptors with excellent 2c potency. Orally-active and selective compounds were identified with dose-responsive in vivo efficacy in our pre-clinical food intake model.

Regulation of glucose transport by tumor necrosis factor-alpha in cultured murine 3T3-L1 fibroblasts

We have examined the ability of tumor necrosis factor-alpha (TNF) to stimulate hexose transport in 3T3-L1 fibroblasts. Activation of transport occurred in a dose- and time-dependent manner, with maximal stimulation (fourfold) occurring approximately 15 hours after exposure to 2.5 nM TNF. The protein synthesis inhibitor, cycloheximide, blunted TNF-induced 2-deoxyglucose uptake, suggesting that new synthesis was in part responsible for the observed increase. Increased hexose transport occurred concomitant with a 50% increase in general protein synthesis which preceded a fivefold stimulation of thymidine incorporation into DNA. Elevated hexose transport preceded an accumulation of glucose transporter (GLUT-1) mRNA. We have further demonstrated that the early accumulation of GLUT-1 mRNA is accompanied by accumulation of mRNA for both the prootooncogene c-fos as well as that for beta-actin. We suggest that these events represent the pleiotrophic growth factor-like properties of TNF-alpha.