Effect of a negative energy balance induced by feed restriction in lactating sows on hepatic lipid metabolism,milk production and development of litters

In rodents, forced activation of hepatic peroxisome proliferator-activated receptor α (PPARα) by administration of exogenous PPARα activators during lactation leads to a reduction of milk triacylglycerol (TAG) production. Herein, we investigated whether a negative energy balance (NEB) induced by feed restriction (about 18% lower feed and energy intake) during lactation by increasing the release of fatty acids, which act as PPARα agonists, causes a disruption of hepatic lipid metabolism and thereby impairs milk TAG production in sows. Nutrient and energy content of the milk on day 20 of lactation and gains of litters during the first 14 d and the whole 21 d suckling period did not differ between Control and feed-restricted sows. The mRNA concentrations of several sterol regulatory element-binding protein target genes involved in lipid synthesis in the liver and the plasma concentration of TAG were reduced in the feed-restricted sows, whereas the mRNA concentrations of PPARα target genes involved in fatty acid oxidation in liver and skeletal muscle were not different between groups. In conclusion, it was shown that an NEB during lactation does not adversely affect milk composition and gains of litters, despite inhibiting hepatic expression of genes involved in lipid synthesis and reducing plasma TAG concentration. The finding that PPARα target genes involved in fatty acid utilisation in liver and muscle of sows are not induced by the NEB during lactation may explain that fatty acid availability in the mammary gland is sufficient to maintain milk TAG production and to allow normal litter gain.     

Protein-tyrosine phosphatase (PTP) wedge domain peptides: a novel approach for inhibition of PTP function and augmentation of protein-tyrosine kinase function

Inhibition of protein-tyrosine phosphatases (PTPs) counterbalancing protein-tyrosine kinases (PTKs) offers a strategy for augmenting PTK actions. Conservation of PTP catalytic sites limits development of specific PTP inhibitors. A number of receptor PTPs, including the leukocyte common antigen-related (LAR) receptor and PTPmu, contain a wedge-shaped helix-loop-helix located near the first catalytic domain. Helix-loop-helix domains in other proteins demonstrate homophilic binding and inhibit function; therefore, we tested the hypothesis that LAR wedge domain peptides would exhibit homophilic binding, bind to LAR, and inhibit LAR function. Fluorescent beads coated with LAR or PTPmu wedge peptides demonstrated PTP-specific homophilic binding, and LAR wedge peptide-coated beads precipitated LAR protein. Administration of LAR wedge Tat peptide to PC12 cells resulted in increased proliferation, decreased cell death, increased neurite outgrowth, and augmented Trk PTK-mediated responses to nerve growth factor (NGF), a phenotype matching that found in PC12 cells with reduced LAR levels. PTPmu wedge Tat peptide had no effect on PC12 cells but blocked the PTPmu-dependent phenotype of neurite outgrowth of retinal ganglion neurons on a PTPmu substrate, whereas LAR wedge peptide had no effect. The survival- and neurite-promoting effect of the LAR wedge peptide was blocked by the Trk inhibitor K252a, and reciprocal co-immunoprecipitation demonstrated LAR/TrkA association. The addition of LAR wedge peptide inhibited LAR co-immunoprecipitation with TrkA, augmented NGF-induced activation of TrkA, ERK, and AKT, and in the absence of exogenous NGF, induced activation of TrkA, ERK, and AKT. PTP wedge domain peptides provide a unique PTP inhibition strategy and offer a novel approach for augmenting PTK function.     

Probing lipid rafts with proximity imaging: actions of proatherogenic stimuli

Glycosylphosphatidylinositol (GPI)-anchored proteins have been shown to cluster in microdomains enriched in glycosphingolipids and cholesterol and represent a relatively selective marker of lipid rafts. In recent years, several attempts have been made to use fluorescent probes to nondisruptively label these domains in living cells. Here, we have transfected endothelial cells with a GPI-anchored thermotolerant green fluorescent protein (ttGFP) to show colocalization of this fluoroprobe with another marker of lipid rafts, urokinase-type plasminogen activator receptor-1. ttGFP was used to quantify the cell surface area occupied by lipid rafts and to examine the effect of various proatherogenic signals on lipid rafts. Exposure of endothelial cells to asymmetric dimethylarginine and oxidized LDL (oxLDL), as well as oxidant stress, reduced the cell surface area occupied by lipid rafts. Next, the property of ttGFP to undergo a shift in absorbance depending on the clustering of these molecules was utilized to perform proximity imaging (PRIM). PRIM showed that nitric oxide (NO) increased the distance between GPI-anchored ttGFP molecules clustered in lipid-rich microdomains. This "unclustering" of GPI-anchored ttGFP was not reproduced by prooxidant signals and was due to reduction in membrane-cytoskeletal constraints on the lipid rafts. These findings suggested that two fundamentally different mechanisms modulate lipid rafts: 1) substance regulation of lipid rafts involving modification of cholesterol and sphingolipids and 2) structural regulation of lipid rafts through disruption of membrane-cytoskeletal interactions, switching off the spatial confinement of lipid rafts.     

Novel Leb-like Helicobacter pylori-binding glycosphingolipid created by the expression of human alpha-1,3/4-fucosyltransferase in FVB/N mouse stomach

The "Le(b) mouse" was established as a model for investigations of the molecular events following Le(b)-mediated adhesion of Helicobacter pylori to the gastric epithelium. By the expression of a human alpha-1,3/4-fucosyltransferase in the gastric pit cell lineage of FVB/N transgenic mice, a production of Le(b) glycoproteins in gastric pit and surface mucous cells was obtained in this "Le(b) mouse," as demonstrated by binding of monoclonal anti-Le(b) antibodies. To explore the effects of the human alpha-1,3/4-fucosyltransferase on glycosphingolipid structures, neutral glycosphingolipids were isolated from stomachs of transgenic alpha-1,3/4-fucosyltransferase-expressing mice. A glycosphingolipid recognized by BabA-expressing H. pylori was isolated and characterized by mass spectrometry and proton NMR as Fuc alpha 2Gal beta 3(Fuc alpha 4)GalNAc beta 4 Gal beta 4 Glc beta 1Cer, i.e., a novel Le(b)-like glycosphingolipid on a ganglio core. In addition, two other novel glycosphingolipids were isolated from the mouse stomach epithelium that were found to be nonbinding with regard to H. pylori. The first was a pentaglycosylceramide, GalNAc beta 3 Gal alpha 3(Fuc alpha 2)Gal beta 4 Glc beta 1Cer, in which the isoglobotetrasaccharide has been combined with Fuc alpha 2 to yield an isoglobotetraosylceramide with an internal blood group B determinant. The second one was an elongated fucosyl-gangliotetraosylceramide, GalNAc beta 3(Fuc alpha 2)Gal beta 3GalNAc beta 4Gal beta 4 Glc beta 1Cer.     

Carbohydrate binding specificities and crystal structure of the cholera toxin-like B-subunit from Citrobacter freundii

Enterotoxigenic Escherichia coli and Vibrio cholerae are well known causative agents of severe diarrheal diseases. Both pathogens produce AB₅ toxins, with one enzymatically active A-subunit and a pentamer of receptor-binding B-subunits. The primary receptor for both B-subunits is the GM1 ganglioside (Galβ3GalNAcβ4(NeuAcα3)Galβ4GlcβCer), but the B-subunits from porcine isolates of E. coli also bind neolacto-(Galβ4GlcNAcβ-)terminated glycoconjugates and the B-subunits from human isolates of E. coli (hLTB) have affinity for blood group A type 2-(GalNAcα3(Fucα2)Galβ4GlcNAcβ-)terminated glycoconjugates.     

Ten-year survival analysis for renal carcinoma patients treated with an autologous tumour lysate vaccine in an adjuvant setting

About 30% of renal cell carcinomas (RCC) will develop recurrence after surgery. Despite evidence for a significantly improved survival by autologous tumour cell vaccination therapy, the procedure has not become standard. Between August 1993 and December 1996, 1,267 RCC patients undergoing radical nephrectomy in 84 German hospitals were subsequently treated by autologous tumour cell vaccination therapy. The study group comprised 692 patients with complete follow-up (stages pT2-3, pNx-2, M0 based on the TNM classification, 4th edition). Subsequent propensity-score matching according to 7 defined criteria with 861 control patients undergoing nephrectomy alone without adjuvant treatment at the Carl-Thiem-Hospital Cottbus, resulted in 495 matched pairs. Overall and stage-specific survival rates were analysed after a median follow-up of 131 months. The 5- and 10-year overall survival (OS) rates were 80.6 and 68.9% in the vaccine group and 79.2 and 62.1% in the control group (p = 0.066). Patients with pT3 stage RCC revealed 5- and 10-year OS rates of 71.3 and 53.6% in the study group and 65.4 and 36.2% in the control group (p = 0.022). In multivariable analysis, patients in the vaccine group showed a significantly improved survival both in the whole study group (HR = 1.28, p = 0.030) and in the subgroup presenting with pT3 stage tumours (HR = 1.67, p = 0.011). Adjuvant treatment with autologous vaccination therapy resulted in a significantly improved overall survival in pT3 stage RCC patients, suggesting benefit especially in this subgroup. However, controlled clinical trials integrating the recent TNM classification and further risk constellations are required to define additional patient groups that may derive benefit from this treatment.     

MAPK signalling in cellular metabolism: stress or wellness?

Mitogen-activated protein kinase (MAPK) signalling occurs in response to almost any change in the extracellular or intracellular milieu that affects the metabolism of the cell, organ or the entire organism. MAPK-dependent signal transduction is required for physiological metabolic adaptation, but inappropriate MAPK signalling contributes to the development of several interdependent pathological traits, collectively known as metabolic syndrome. Metabolic syndrome leads to life-threatening clinical consequences, such as type 2 diabetes. This Review provides an overview of the MAPK-signalling mechanisms that underly basic cellular metabolism, discussing their link to disease.     

Obesity as an Obstetric Risk Factor: Does It Matter in a Perinatal Center?

Objectives: Obesity before and during pregnancy is associated with several obstetrics risk factors for both mother and fetus. The aim of this retrospective study was to analyze the influence of BMI before pregnancy on distinct perinatal parameters. Research Methods and Procedures: The study includes 5067 singleton pregnancies from 2001 to 2004 at the Department of Obstetrics and Gynecology, University of Leipzig. The study group was divided into BMI groups: <18.5, ≥18.5 to <25, ≥25 to <30, ≥30 to <35, ≥35 to <40, and ≥40 kg/m². Analysis of perinatal data included rate of intrauterine death, rate of cesarean section and shoulder dystocia, time of hospital stay for mother and newborn, and gestational age of delivery. Neonatal outcome variables included percentage of newborns weighing >4000 grams, rate of umbilical cord pH <7.10, and rate of 1‐, 5‐, and 10‐minute Apgar scores of <8. Results: There was no difference in the gestational age at delivery among the groups. In the group with BMI ≥30 kg/m², the cesarean section rate was significantly elevated to 25.1%, with a more dramatic increase up to 30.2% in the group with BMI ≥35 kg/m² and 43.1% in the group with BMI ≥40 kg/m², mainly because of a higher number of secondary cesarean sections. Although newborns of obese women showed worse initial neonatal adaptation, the 10‐minute Apgar values did not differ among the groups. The higher rate of operative deliveries and the trend to an increased rate of shoulder dystocia did not influence duration of the hospital stay for mothers and newborns or morbidity of both. Discussion: A high pre‐pregnancy BMI is clearly associated with a higher rate of cesarean section deliveries. However, under the compensating conditions of a tertiary perinatal center, overall morbidity of mothers and newborns seems not to be increased.     

The MID1/PP2A complex: a key to the pathogenesis of Opitz BBB/G syndrome

Opitz BBB/G syndrome is a monogenic disorder that is characterized by malformations of the ventral midline. Investigations into the underlying genetic defects and the pathobiochemistry of this syndrome have already shed light on the mechanisms of both the physiological and the pathological development of the ventral midline, a complicated multistep process. Moreover, these studies have revealed the ubiquitin-dependent regulation of microtubule-associated phosphatase 2A, a central mechanism in many cellular processes. In this review, we summarize recent findings and speculate upon their implications for both medical and general research.