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INTRODUCTION: A physically active lifestyle during pregnancy improves maternal and offspring health but can be difficult to follow. In Denmark, less than 40% of pregnant women meet physical activity (PA) recommendations. The FitMum study aims to explore strategies to increase PA during pregnancy among women with low PA and assess the health effects of PA. This paper presents the FitMum protocol, which evaluates the effects of structured supervised exercise training or motivational counselling supported by health technology during pregnancy on PA level and health of mother and offspring.METHODS AND ANALYSIS: A single-site three-arm randomised controlled trial that aims to recruit 220 healthy, pregnant women with gestational age (GA) no later than week 15 and whose PA level does not exceed one hour/week. Participants are randomised to one of three groups: structured supervised exercise training consisting of three weekly exercise sessions, motivational counselling supported by health technology or a control group receiving standard care. The interventions take place from randomisation until delivery. The primary outcome is min/week of moderate-to-vigorous intensity PA (MVPA) as determined by a commercial activity tracker, collected from randomisation until GA of 28 weeks and 0-6 days, and the secondary outcome is gestational weight gain (GWG). Additional outcomes are complementary measures of PA; clinical and psychological health parameters in participant, partner and offspring; analyses of blood, placenta and breastmilk samples; process evaluation of interventions; and personal understandings of PA.ETHICS AND DISSEMINATION: The study is approved by the Danish National Committee on Health Research Ethics (# H-18011067) and the Danish Data Protection Agency (# P-2019-512). Findings will be disseminated via peer-reviewed publications, at conferences, and to health professionals via science theatre performances.TRIAL REGISTRATION NUMBER: NCT036791

INTRODUCTION: Interleukin (IL)-18 is involved in regulation of lipid and glucose metabolism. Mice lacking whole-body IL-18 signalling are prone to develop weight gain and insulin resistance, a phenotype which is associated with impaired fat oxidation and ectopic skeletal muscle lipid deposition. IL-18 mRNA is expressed in human skeletal muscle but a role for IL-18 in muscle has not been identified. Patients with HIV-infection and lipodystrophy (LD) are characterized by lipid and glucose disturbances and increased levels of circulating IL-18. We hypothesized that skeletal muscle IL-18 and IL-18 receptor (R) expression would be altered in patients with HIV-lipodystrophy.DESIGN AND METHODS: Twenty-three HIV-infected patients with LD and 15 age-matched healthy controls were included in a cross-sectional study. Biopsies from the vastus lateralis muscle were obtained and IL-18 and IL-18R mRNA expression were measured by real-time PCR and sphingolipids (ceramides, sphingosine, sphingosine-1-Phosphate, sphinganine) were measured by HPLC. Insulin resistance was assessed by HOMA and the insulin response during an OGTT.RESULTS: Patients with HIV-LD had a 60% and 54% lower level of muscular IL-18 and IL-18R mRNA expression, respectively, compared to age-matched healthy controls. Patients with HIV-LD had a trend towards increased levels of ceramide (18.3±4.7 versus 14.8±3.0,p = 0.06) and sphingosine (0.41±0.13 versus 0.32±0.07, and lower level of sphinganine (p = 0.06). Low levels of muscle IL-18 mRNA correlated to high levels of ceramides (r = -0.31, p = 0.038) and sphingosine-1P (r = -0.29, p = 0.046) in skeletal muscle, whereas such a correlation was not found in healthy controls. Low expression of IL-18 mRNA in skeletal muscle correlated to elevated concentration of circulating triglycerides (Rp = -0.73, p<0.0001). Neither muscle expression of IL-18 mRNA or ceramide correlated to parameters of insulin resistance.CONCLUSION: IL-18 (mRNA) in skeletal

Aims: Poor myometrial contractility has been demonstrated in women at term with diabetes and decreased muscular mitochondrial content and/or function has been extensively implicated in the progression of type 2 diabetes. Alterations of the uterine mitochondrial phenotype in pregnant women with diabetes have yet to be investigated as a causal link to decreased myometrial contractility. Methods: Observational study of 18 women with diabetes (type 2 and gestational) scheduled for an elective Caesarean section at term with matching controls. A uterine biopsy and fasting blood samples were taken on the day of delivery. Results: Respiration rates in isolated mitochondria and myometrial mRNA levels of genes related to mitochondrial biogenesis were unaffected by diabetes. Mitochondrial quantity examined by quantification of the complexes of the respiratory chain and histology did not indicate alterations in mitochondrial quantity. Citrate syntase activity was higher (0.31 ± 0.02 vs. 0.24 ± 0.02 U/mg protein, P = 0.008), whereas protein content was lower in women with diabetes compared with the control group (94.6 ± 6.9 vs. 118.6 ± 7.4 mg/g wet wt, P = 0.027). Histological examinations did not support any structural alterations in the myometrium or its mitochondria. Conclusion: No indication of decreased mitochondrial function, content, morphology, or localization in the myometrium at term in women with diabetes compared with controls was observed. The increase in citrate syntase activity in the myometrium could be explained by the lower protein content in the myometrium, which we suggest is due to alterations in tissue or cellular composition.

Taurine ameliorates changes occurring in newborn skeletal muscle as a result of gestational protein restriction in C57BL/6 mice, but taurine supplementation effects may be exaggerated in C57BL/6 mice due to their inherent excessive taurinuria.We examined if maternal taurine supplementation could ameliorate changes in gene expression levels, properties of mitochondria, myogenesis, and nutrient transport and sensing, in male newborn skeletal muscle caused by a maternal low protein (LP) diet in Wistar rats.LP diet resulted in an 11% non-significant decrease in birth weight, which was not rescued by taurine supplementation (LP-Tau). LP-Tau offspring had significantly lower birth weight compared to controls. Gene expression profiling revealed 895 significantly changed genes, mainly an LP-induced down-regulation of genes involved in protein translation. Taurine fully or partially rescued 32% of these changes, but with no distinct pattern as to which genes were rescued.Skeletal muscle taurine content in LP-Tau offspring was increased, but no changes in mRNA levels of the taurine synthesis pathway were observed. Taurine transporter mRNA levels, but not protein levels, were increased by LP diet.Nutrient sensing signaling pathways were largely unaffected in LP or LP-Tau groups, although taurine supplementation caused a decrease in total Akt and AMPK protein levels. PAT4 amino acid transporter mRNA was increased by LP, and normalized by taurine supplementation.In conclusion, gestational protein restriction in rats decreased genes involved in protein translation in newborn skeletal muscle and led to changes in nutrient transporters. Taurine partly rescued these changes, hence underscoring the importance of taurine in development.

It has recently come to our attention that our paper Effect of high-fat diet on rat myometrium during pregnancy-isolated myometrial mitochondria are not affected published in July 2015 in Pflügers Archiv - European Journal of Physiology volume 467 issue 7 page 1539–49 contains an error due to miscalculations from our side. It concerns Table 3 Biochemical analyses of the myometrium. The last line in the table with CS activity (units CS /mg protein) should instead be CH 0.64 ± 0.08, HC 0.67 ± 0.21 and HF 0.68 ± 0.11 (mean ± SEM). The weighted one-way ANOVA with a Tukey’s post hoc test still yields non-significant results, thus the error does not alter any conclusions in the paper. The corrected table should read.

In order to characterize mechanisms responsible for fat accumulation we used a selectively bred obesity-prone (OP) and obesity-resistant (OR) rat model, where the rats were fed a Western diet for 76 days. Body composition was assessed by MRI scans and as expected the OP rats developed a higher degree of fat accumulation compared to OR rats. Indirect calorimetry showed that the OP rats had higher respiratory exchange ratio (RER) compared to OR rats indicating an impaired ability to oxidize fat. The OP rats had lower expression of carnitine palmitoyltransferase 1b in intra-abdominal fat, and higher expression of stearoyl-CoA desaturase 1 in subcutaneous fat compared to OR rats, which could explain the higher fat accumulation and RER values. Basal metabolic parameters were also examined in juvenile OP and OR rats before and during the introduction of the Western diet. Juvenile OP rats likewise had higher RER values indicating that this trait may be a primary and contributing factor to their obese phenotype. When the adult obese rats were exposed to the orexigenic and adipogenic hormone ghrelin, we observed increased RER values in both OP and OR rats, while OR rats were more sensitive to ghrelin's orexigenic effects as well as ghrelin-induced attenuation of activity and energy expenditure. Thus, increased fat accumulation characterizing obesity may be caused by impaired oxidative capacity due to decreased carnitine palmitoyltransferase 1b levels in the white adipose tissue, while ghrelin sensitivity did not seem to be a contributing factor.

Taurine is often referred to as a semi-essential amino acid as newborn mammals have a limited ability to synthesize taurine and have to rely on dietary supply. Taurine is not thought to be incorporated into proteins as no aminoacyl tRNA synthetase has yet been identified and is not oxidized in mammalian cells. However, taurine contributes significantly to the cellular pool of organic osmolytes and has accordingly been acknowledged for its role in cell volume restoration following osmotic perturbation. This review describes taurine homeostasis in cells and organelles with emphasis on taurine biophysics/membrane dynamics, regulation of transport proteins involved in active taurine uptake and passive taurine release as well as physiological processes, for example, development, lung function, mitochondrial function, antioxidative defence and apoptosis which seem to be affected by a shift in the expression of the taurine transporters and/or the cellular taurine content.

Laboring women with elevated body mass index (BMI) have an increased risk of inefficient uterine labor contractions, and despite the significance of mitochondria in the production of energy to drive uterine contractions, mitochondrial function in the myometrium with reference to the BMI has not been explored. The objective of this study was to determine whether obesity prior to and during gestation affects oxidative capacity and/or morphology of mitochondria in the myometrium at term in an animal model. Rat dams were fed for 47 days prior to impregnation and during gestation with either (1) a regular chow diet, (2) a low-fat high-carbohydrate diet, or (3) a high-fat low-carbohydrate diet (n = 10 in each group). On day 20 of gestation, corresponding to term pregnancy, total hysterectomy was performed with subsequent examination of the function and morphology of myometrial mitochondria. Body composition was regularly assessed by quantitative magnetic resonance imaging, and blood sampling was done prior to diet assignment, impregnation, and hysterectomy. Dams on the high-fat low-carbohydrate diet achieved higher fat percentage compared to rats on the regular chow diet (p < 0.05). Maximal oxygen consumption, phosphate/oxygen ratio, or the amount of mitochondria per gram of myometrium did not differ between the three feeding groups. Electron microscopic examinations did not reveal any morphological differences in mitochondria between groups; however, a previously undescribed subsarcolemmal localization of the mitochondria in the myocyte was identified. We did not find evidence of altered myometrial mitochondrial function or morphology in this animal model of obesity prior to and during pregnancy.

Calprotectin comprises more than 45% of the cytosolic content of neutrophil granulocytes. Because pathogenesis, disease activity and disease progression in COPD are believed to be partly dependent of neutrophil driven inflammation we decided to investigate whether plasma level of calprotectin (p-calprotectin) was associated with all-cause mortality in patients with COPD. We measured p-calprotectin in blood samples from 460 patients with moderate to very severe COPD in stable phase. Patients were stratified into three groups according to p-calprotectin level. Outcome measure was all-cause mortality. Analyses were adjusted for factors known to influence mortality using a Cox regression analysis. We found a time dependent correlation between p-calprotectin levels and mortality during the first 5 years of follow-up. Increasing levels of p-calprotectin were associated with concomitant increases in mortality from HR 1.56 (CI 95%: 1.03 -2.38) at calprotectin between 100 -200 ng/ml to HR 2.02 (CI 95%: 1.27-3.19) at calprotectin >200 ng/ml. P-calprotectin could be a useful marker of all-cause mortality in patients suffering from moderate to very severe COPD.

US adults take between approximately 2,000 and approximately 12,000 steps per day, a wide range of ambulatory activity that at the low range could increase risk for developing chronic metabolic diseases. Dramatic reductions in physical activity induce insulin resistance; however, it is uncertain if and how low ambulatory activity would influence peripheral insulin sensitivity. We aimed to explore if healthy, nonexercising subjects who went from a normal to a low level of ambulatory activity for 2 wk would display metabolic alterations including reduced peripheral insulin sensitivity. To do this, ten healthy young men decreased their daily activity level from a mean of 10,501+/-808 to 1,344+/-33 steps/day for 2 wk. Hyperinsulinemic-euglycemic clamps with stable isotopes and muscle biopsies, maximal oxygen consumption (VO2 max) tests, and blood samples were performed pre- and postintervention. A reduced number of daily steps induced a significant reduction of 17% in the glucose infusion rate (GIR) during the clamp. This reduction was due to a decline in peripheral insulin sensitivity with no effect on hepatic endogenous glucose production. The insulin-stimulated ratio of pAktthr308/total Akt decreased after step reduction, with a post hoc analysis revealing the most pronounced effect after 4 h of insulin infusion. In addition, the 2-wk period induced a 7% decline in VO2 max (ml/min; cardiovascular fitness). Lean mass of legs, but not arms and trunk, decreased concurrently. Taken together, one possible biological cause for the public health problem of Type 2 diabetes has been identified. Reduced ambulatory activity for 2 wk in healthy, nonexercising young men significantly reduced peripheral insulin sensitivity, cardiovascular fitness, and lean leg mass.

Low birth weight is associated with an increased risk of developing impaired glucose tolerance, and eventually type 2 diabetes in adult life. Gestational protein restriction in rodents gives rise to a low birth weight phenotype in the offspring.

Udgivelsesdato: 2010-Jan, We examined gene expression changes in liver and skeletal muscle of newborn mice subjected to a maternal low protein (LP) or normal protein (NP) diet during pregnancy, with or without taurine supplementation in the drinking water. LP offspring had a 40% lower birthweight than NP offspring, whereas it was reduced by only 20% with taurine supplementation. Microarray gene expression analysis revealed significant changes in 2012 genes in liver and 967 genes in skeletal muscle of LP offspring. By unknown mechanisms, taurine partially or fully prevented 30 and 46% of these expression changes, respectively. Mitochondrial genes, in particular genes associated with oxidative phosphorylation, were more abundantly changed in LP offspring, with primarily up-regulation in liver but down-regulation in skeletal muscle. In both tissues, citrate synthase activity remained unchanged. Taurine preferentially rescued changes in genes concerned with fatty acid metabolism in liver and with oxidative phoshorylation and tri carboxylic acid (TCA) cycle in skeletal muscle. Conclusion: Gestational protein restriction resulted in lower birthweight associated with significant gene expression changes, which was different in liver and muscle of offspring. However, a major part of the birthweight decrease and the expression changes were prevented by maternal taurine supplementation, implying taurine is a key component in metabolic fetal programming. ABBREVIATIONS

Udgivelsesdato: 2009-Mar, AIM: It was recently reported that serum retinol-binding protein (RBP), also known as retinol-binding protein 4 (RBP4), was positively associated with systemic insulin resistance. We hypothesized that an imbalance between RBP and retinol might be the underlying cause for this association. METHODS: We studied the ratio between RBP and retinol in 233 humans divided into groups depending on normal glucose tolerance (NGT), impaired glucose tolerance (IGT), type 2 diabetes (T2DM) and presence or absence of obesity. RESULTS: Plasma RBP and retinol levels were lower in patients with T2DM than in individuals with NGT (p < 0.05 and p < 0.0001 respectively). In contrast, RBP-to-retinol ratio was higher in individuals with T2DM (p < 0.0001) and IGT (p < 0.05). Following multivariate adjustment, RBP and retinol correlated positively with low-density lipoprotein (LDL) and triglycerides (p < 0.0001, except retinol and LDL: p < 0.001). RBP-to-retinol ratio correlated positively with glucose 2 h after an oral glucose tolerance test (p < 0.0001) and with C-reactive protein (p < 0.001). Retinol, RBP and adipose tissue RBP messenger RNA (mRNA) levels shared an inverse relationship with plasma interleukin-6, and adipose tissue RBP mRNA levels correlated positively with plasma tumour necrosis factor-alpha (TNF-alpha) and skeletal muscle TNF-alpha mRNA levels. CONCLUSIONS: Our results suggest that the excess of RBP relative to retinol, assessed as the RBP-to-retinol ratio, is more indicative of T2DM than RBP itself. Hence, the previously reported insulin resistance in mice induced by overexpression or injection of RBP could be because of higher levels of RBP relative to retinol rather than higher total levels of RBP. Moreover, TNF-alpha may have a role in RBP-mediated adipose to muscle crosstalk.

Udgivelsesdato: 2009-null, BACKGROUND: The two inflammatory molecules, S100A8 and S100A9, form a heterodimer, calprotectin. Plasma calprotectin levels are elevated in various inflammatory disorders. We hypothesized that plasma calprotectin levels would be increased in subjects with low-grade systemic inflammation i.e. either obese subjects or subjects with type 2 diabetes. METHODOLOGY/PRINCIPAL FINDINGS: Plasma calprotectin and skeletal muscle S100A8 mRNA levels were measured in a cohort consisting of 199 subjects divided into four groups depending on presence or absence of type 2 diabetes (T2D), and presence or absence of obesity. There was a significant interaction between obesity and T2D (p = 0.012). Plasma calprotectin was increased in obese relative to non-obese controls (p<0.0001), whereas it did not differ between obese and non-obese patients with T2D (p = 0.62). S100A8 mRNA levels in skeletal muscle were not influenced by obesity or T2D. Multivariate regression analysis (adjusting for age, sex, smoking and HOMA2-IR) showed plasma calprotectin to be strongly associated with BMI, even when further adjusted for fitness, CRP, TNF-alpha or neutrophil number. CONCLUSIONS/SIGNIFICANCE: Plasma calprotectin is a marker of obesity in individuals without type 2 diabetes.

Udgivelsesdato: 2009-Dec-31, US adults take between ~2,000 to ~12,000 steps per day, a wide range of ambulatory activity, that at the low range could increase risk for developing chronic metabolic diseases. Dramatic reductions in physical activity induce insulin resistance; however it is uncertain if and how low ambulatory activity would influence peripheral insulin sensitivity. We aimed to explore if healthy, non-exercising subjects who went from a normal to a low level of ambulatory activity for two weeks would display metabolic alterations including reduced peripheral insulin sensitivity. -To do this, ten healthy young men decreased their daily activity level from a mean of 10,501 (+/- 808) to 1,344 (+/- 33) steps/day for 2 weeks. Hyperinsulinemic-euglycemic clamps with stable isotopes and muscle biopsies, maximal oxygen consumption (VO2max) tests, and blood samples were performed pre and post intervention.A reduced number of daily steps induced a significant reduction of 17% in the glucose infusion rate (GIR) during the clamp. This reduction was due to a decline in peripheral insulin sensitivity with no effect on hepatic endogenous glucose production. The insulin-stimulated ratio of pAkt(thr308)/total Akt decreased after step reduction, with a post hoc analysis revealing the most pronounced effect after 4 h of insulin infusion. In addition, the two-week period induced a 7% decline in VO2max (ml/min; cardiovascular fitness). Lean mass of legs, but not arms and truck, decreased concurrently. Taken together, one possible biological cause for the public health problem of type 2 diabetes has been identified. Reduced ambulatory activity for two weeks in healthy, non-exercising young men significantly reduced peripheral insulin sensitivity, cardiovascular fitness, and lean leg mass. Key words: Inactivity, Insulin resistance, Clamp, Insulin signalling.

Udgivelsesdato: 2009-null, INTRODUCTION: Glutamine supplementation has beneficial effects on morbidity and mortality in critically ill patients, possibly in part through an attenuation of the proinflammatory cytokine response and a stimulation of heat shock protein (HSP)70. We infused either alanine-glutamine or saline during endotoxin challenge and measured plasma cytokines and HSP70 protein expression. METHODS: This crossover study, conducted in eight healthy young men, was double-blind, randomized and placebo-controlled. It was performed on 2 trial days, separated by a 4-week washout period. The volunteers received an infusion of alanine-glutamine at a rate of 0.025 g/(kg body weight x hour) or saline for 10 hours. After 2 hours, an intravenous bolus of Escherichia coli endotoxin (0.3 ng/kg) was administered. Blood samples were collected hourly for the following 8 hours. HSP70 protein content in isolated blood mononuclear cells (BMNCs) was measured by Western blotting. RESULTS: Plasma glutamine increased during alanine-glutamine infusion. Endotoxin reduced plasma glutamine during both trials, but plasma glutamine levels remained above baseline with alanine-glutamine supplementation. Endotoxin injection was associated with alterations in white blood cell and differential counts, tumour necrosis factor-alpha, IL-6, temperature and heart rate, but glutamine affected neither the endotoxin-induced change in these variables nor the expression of HSP70 in BMNCs. CONCLUSIONS: Endotoxin reduced plasma glutamine independently of alanine-glutamine infusion, but supplementation allows plasma levels to be maintained above baseline. Glutamine alters neither endotoxin-induced systemic inflammation nor early expression of HSP70 in BMNCs. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT 00780520.

In a sheep model, we investigated diet effects on skeletal muscle mitochondria to look for fetal programming. During pregnancy, ewes were fed normally (N) or were 50% food restricted (L) during the last trimester, and lambs born to these ewes received a normal (N) or a high-fat diet (H) for the first 6 mo of life. We examined mitochondrial function in permeabilized muscle fibers from the lambs at 6 mo of age (adolescence) and after 24 mo of age (adulthood). The postpartum H diet for the lambs induced an approximately 30% increase (P < 0.05) of mitochondrial VO(2max) and an approximately 50% increase (P < 0.05) of the respiratory coupling ratio (RCR) combined with lower levels of UCP3 and PGC-1alpha mRNA levels (P < 0.05). These effects proved to be reversible by a normal diet from 6 to 24 mo of age. However, at 24 mo, a long-term effect of the maternal gestational diet restriction (fetal programming) became evident as a lower VO(2max) (approximately 40%, P < 0.05), a lower state 4 respiration (approximately 40%, P < 0.05), and lower RCR ( approximately 15%, P < 0.05). Both PGC-1alpha and UCP3 mRNA levels were increased (P < 0.05). Two analyzed muscles were affected differently, and muscle rich in type I fibers was more susceptible to fetal programming. We conclude that fetal programming, seen as a reduced VO(2max) in adulthood, results from gestational undernutrition. Postnatal high-fat diet results in a pronounced RCR and VO(2max) increase in adolescence. However, these effects are reversible by diet correction and are not maintained in adulthood.

Udgivelsesdato: 2008/7/19

Udgivelsesdato: 2007-Nov, We hypothesized that the peroxisome proliferator-activated receptor-gamma coactivator-1 (PGC-1) family of transcriptional coactivators (PGC-1alpha, PGC-1beta, and PRC) is differentially regulated by training once daily vs. training twice daily every second day and that this difference might be observed in the acute response to endurance exercise. Furthermore, we hypothesized that expression levels of the PGC-1 family differ with muscular fiber-type composition. Thus, before and after 10 wk of knee extensor endurance training, training one leg once daily and the other leg twice daily every second day, keeping the total amount of training for the legs equal, skeletal muscle mRNA expression levels of PGC-1alpha, PGC-1beta, and PRC were determined in young healthy men (n = 7) in response to 3 h of acute exercise. No significant difference was found between the two legs, suggesting that regulation of the PGC-1 family is independent of training protocol. Training decreased PGC-1beta in both legs, whereas PGC-1alpha was increased, but not significantly, in the leg training once daily. PRC did not change with training. Both PGC-1alpha and PRC were increased by acute exercise both before and after endurance training, whereas PGC-1beta did not change. The mRNA levels of the PGC-1 family were examined in different types of human skeletal muscle (triceps, soleus, and vastus lateralis; n = 7). Only the expression level of PGC-1beta differed and correlated inversely with percentage of type I fibers. In conclusion, there was no difference between training protocols on the acute exercise and training response of the PGC-1 family. However, training caused a decrease in PGC-1beta mRNA levels.

Udgivelsesdato: 2007-May-15, Previously we have demonstrated that glucagon receptor mRNA expression in cultured rat hepatocytes and pancreatic islets can be regulated by various factors, including cAMP; however, the regulation of the human glucagon receptor gene has not been well-defined. Here we have characterized the promoter regions of the human glucagon receptor gene. Primer extension studies yielded multiple products in both liver and pancreas, corresponding to transcription start sites situated at -166 and -477 relative to the start of translation, indicating two putative promoters. Both transcription start sites were found to be active, when sequence immediately upstream of the start sites were cloned into luciferase reporter constructs. The transcriptional activity of the proximal promoter, but not the distal promoter, could be inhibited approximately 50% by cAMP, indicating that the previously observed inhibitory effects of cAMP on glucagon receptor mRNA expression is mediated at the level of gene transcription. The cAMP-mediated downregulation of the proximal promoter was examined by deletion analysis in the human hepatoma cell line HepG2 and the cAMP responsiveness was found to be located in a region between 1051 and 1016 base pairs upstream of the transcription start site, which contains several putative cAMP responsive elements. Expression of peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha), known to be upregulated in the liver by fasting, was found to abolish the cAMP-dependent downregulation of glucagon receptor mRNA expression in vitro, whereas overexpression of PGC-1beta had no effect.

Udgivelsesdato: 2001-Nov

Udgivelsesdato: 2001-Oct-15, Shedding of the extracellular domain of the ErbB2 tyrosine kinase receptor and expression of the remaining NH(2)-terminally truncated ErbB2 correlates with lymph node metastases and adverse outcome in human breast cancer. To study the possible signaling from such a truncated receptor, MCF-7 human breast cancer cells expressing NH(2)-terminally truncated ErbB2 (DeltaNErbB2) were compared with cells overexpressing wild-type ErbB2. Expression of DeltaNErbB2 in MCF-7 cells resulted in sustained activation of extracellular signal-regulated kinases (ERK) 1/2, extensive loss of the epithelial morphology, appearance of vesicles and long protrusions as well as pronounced scattering of the cells. Similar alterations were observed upon ErbB2 overexpression but at much lower levels. Employing cell clones with inducible expression of DeltaNErbB2, it was revealed that the morphological changes were fully reversible and depended on continuous expression of DeltaNErbB2 but not on the activation of the ERK1/2 pathway. Interestingly, the expression of DeltaNErbB2 resulted also in the increased expression and phosphorylation of ErbB1 as well as in the prolonged ligand-induced activation of the ErbB1 signaling pathway. In conclusion, constitutive signaling upon expression of the truncated ErbB2 receptor in human breast cancer cells promotes morphological changes indicative of a more motile and aggressive phenotype.

Udgivelsesdato: 2001-Feb-16, The activation of ErbB tyrosine kinase receptors (ErbB1, -2, -3, and -4) by ligand-induced homo- or heterodimerization regulates cell growth, death, and differentiation. AG1478 and PD153035 (also know as AG1517) have been adopted as specific ErbB1 inhibitors based on their high specificity for ErbB1 as compared to ErbB2 in in vitro kinase assays. We compared their ability to inhibit ErbB receptor signaling in intact cells to that of a novel ErbB receptor kinase inhibitor, BIBX1382BS. Neither AG1478 nor PD153035 displayed any specificity for ErbB1-mediated signaling induced by transforming growth factor alpha (TGF-alpha) as compared to signaling initiated through the other ErbB kinases. In contrast, BIBX1382BS was more potent at inhibiting signaling induced by TGF-alpha than that induced by neuregulin1-beta1 or anti-ErbB2 agonist antibodies. Interestingly, this compound blocked antibody-induced ErbB4 homodimer activation at even lower concentrations than ErbB1-triggered signaling. Thus, BIBX1382BS, but not AG1478 and PD153035, can be employed to differentiate between the ErbB kinases in intact cells when used at appropriate concentrations.