Dietary moderately oxidized oil induces expression of fibroblast growth factor 21 in the liver of pigs

BACKGROUND: Fibroblast growth factor 21 (FGF21), whose expression is induced by peroxisome proliferator-activated receptor alpha (PPARalpha), has been recently identified as a novel metabolic regulator which plays a crucial role in glucose homeostasis, lipid metabolism, insulin sensitivity and obesity. Previous studies have shown that administration of oxidized fats leads to an activation of PPARalpha in the liver. Therefore, the present study investigated the hypothesis that feeding of oxidized fats causes an induction of FGF21 in the liver. METHODS: Twenty four crossbred pigs were allocated to two groups of 12 pigs each and fed nutritionally adequate diets with either fresh rapeseed oil or oxidized rapeseed oil prepared by heating at a temperature of 175 degrees C for 72 h. RESULTS: In pigs fed the oxidized fat mRNA abundance and protein concentrations of FGF21 in liver were significantly increased (P < 0.05), and the protein concentrations of FGF21 in plasma tended to be increased (P < 0.1) in comparison to control pigs. Moreover, pigs fed the oxidized fat had increased transcript levels of the PPARalpha target genes acyl-CoA oxidase, carnitine palmitoyltransferase-1 and novel organic cation transporter 2 in the liver (P < 0.05), indicative of PPARalpha activation. CONCLUSION: The present study shows for the first time that administration of an oxidized fat induces the expression of FGF21 in the liver, probably mediated by activation of PPARalpha. Induction of FGF21 could be involved in several effects observed in animals administered an oxidized fat

Ferromagnetism in the Kondo-lattice

We discuss the ferromagnetic phase of the planar Kondo lattice model using the bond fermion technique. For sufficiently small Kondo exchange we find a weakly ferromagnetic phase already for the weakly doped Kondo insulator. We present the phase diagram of the model and its quasiparticle band structure in the different phases

Hubbard model versus t-J model: The one-particle spectrum

The origin of the apparent discrepancies between the one-particle spectra of the Hubbard and t-J models is revealed: Wavefunction corrections, in addition to the three-site terms, should supplement the bare t-J. In this way a quantitative agreement between the two models is obtained, even for the intermediate-$U$ values appropriate for the high-Tc cuprate superconductors. Numerical results for clusters of up to 20 sites are presented. The momentum dependence of the observed intensities in the photoemission spectra of Sr2CuO2Cl2 are well described by this complete strong-coupling approach.Comment: 4 two-column RevTeX pages, including 4 Postscript figures. Uses epsf. Accepted for publication in Physical Review B, Rapid Communicatio

Optical conductivity due to orbital polarons in systems with orbital degeneracy

We consider the impact of orbital polarons in doped orbitally ordered systems on optical conductivity using the simplest generic model capturing the directional nature of either $t_{2g}$ (or $e_g$) orbital states in certain transition metal oxides, or $p$ orbital states of cold atoms in optical lattices. The origin of the optical transitions is analyzed in detail and we demonstrate that the optical spectra: (i) are determined by the string picture, i.e., flipped orbitals along the hole hopping path, and (ii) consist of three narrow peaks which stem from distinct excitations. They occur within the Mott-Hubbard gap similar to the superconducting cuprates but indicate hole confinement, in contrast to the spin t-J model. Finally, we point out how to use the point group symmetry to classify the optical transitions.Comment: 9 pages, 5 figures; final published versio

Ein Beitrag zur Entwicklung neuartiger keramischer Wärmeübertrager für Rekuperatorbrenner: Ein Beitrag zur Entwicklung neuartiger keramischer Wärmeübertrager für Rekuperatorbrenner

Die Effektivität keramischer Wärmeübertrager kann durch eine feinere Strukturierung der Oberflächen gesteigert werden. Dies kann durch die Integration textiler Urformen anstatt der konventionell im Schlickguss hergestellten gröberen Geometrien erfolgen. Für Strukturierungen in Form von wandgebundenen Halbbögen werden die Ergebnisse umfangreicher experimenteller und numerischer Untersuchungen zu den wärmetechnischen und strömungsmechanischen Eigenschaften vorgestellt. Basierend auf den Erkenntnissen der mittels numerischer Simulation durchgeführten Parameterstudie werden verschiedene Empfehlungen für eine optimierte Anordnung der Halbbögen gegeben, um das Verhältnis von Wärmeübergang zur Druckverlust zu verbessern. Die experimentellen Ergebnisse belegen die Richtigkeit der gewählten Randbedingungen und Vereinfachungen im numerischen Modell. Des Weiteren wurden die Strömungsstrukturen mit laserdiagnostischen Messmethoden umfangreich charakterisiert.:0 Verwendete Symbole und Formelzeichen IV 1 Einleitung 1 1.1 Motivation 1 1.2 Lösungsansatz 2 1.3 Zielstellung und Struktur der Arbeit 4 2 Stand der Technik 5 2.1 Vorwort 5 2.2 Kennzahlen zur Charakterisierung von Rekuperatoren und Wärmeüber-trageroberflächen 6 2.3 Strömungszustände und Strömungsprofile 13 2.3.1 Grenzschichten von Strömungen 13 2.3.2 Laminare Strömung zwischen zwei parallelen Platten und im Rechteckkanal 14 2.3.3 Turbulente Strömung zwischen zwei parallelen Platten 15 2.3.4 Kenngrößen, Längen- und Zeitmaße von turbulenten Strömungen 16 2.4 Umströmung von Zylindern und Wärmeübergang an Zylindern 19 2.4.1 Quer angeströmter Zylinder, Wirbelablösung und Kármánsche Wirbelstraße 19 2.4.2 Hufeisenwirbel um einen wandgebundenen Zylinder 25 2.4.3 Zylinder in Wechselwirkung miteinander und Zylinder in Tandempaarung 27 2.4.4 Quer angeströmter Zylinder parallel zu einer Wand 28 2.5 Weitere den Wärmeübergang steigernde Strukturen 29 2.5.1 Rohrbündel 30 2.5.2 Stabrippen – „pin fins“ 31 2.5.3 Zweidimensionale Rippengeometrien 33 2.5.4 Gedrehte Bleche und andere Einbauten in Rohrquerschnitten 36 2.5.5 Turbulatoren 38 2.5.6 Poröse Körper 39 2.5.7 Drähte als wärmeübergangsteigernde Struktur 40 2.6 Wärmeübertrager für Industriegasbrenner 41 3 Numerische und experimentelle Untersuchungen der neuentwickelten Wärmeübertragerstruktur 45 4 Numerische Untersuchungen bezüglich des Strömungsfelds um die Bogenstrukturen 49 4.1 Randbedingungen und Vernetzung der numerischen Simulation 49 4.2 Bemerkungen zum Turbulenzmodell 54 4.3 Validierung des numerischen Modells am leeren Kanal 59 4.4 Ergebnisse für die Grundgeometrie 63 4.5 Parameterstudie zur Anordnung und Anzahl der Bögen 70 4.5.1 Variation der Bogendichte 70 4.5.2 Variation der Anordnung der Bögen zueinander bei konstanter Bogendichte 75 4.5.3 Variation der Kanalhöhe bei konstanten Randbedingungen 78 4.5.4 Variation der Kanalhöhe bei umgekehrten Randbedingungen 80 4.5.5 Variation des Bogendurchmessers D 82 4.5.6 Bemerkung zum Anstellwinkel 83 5 Experimentelle Untersuchungen zum Wärmeübergangskoeffizienten 85 5.1 Versuchsaufbau 85 5.2 Versuchsdurchführung und Auswertung 88 5.3 Vergleich des Versuchsstandes mit Untersuchungen für Spaltströmungen 90 5.4 Referenzmessungen mit metallischen Wärmeübertragerstrukturen 93 5.4.1 Ergebnisse für die Grundgeometrie 93 5.4.2 Variation der Kanalhöhe 96 5.4.3 Variation der Kanalhöhe bei umgekehrten Randbedingungen 97 5.5 Messung mit keramischen Strukturen 98 6 Experimentelle Untersuchungen zum Strömungsverhalten 101 6.1 Versuchsaufbau 101 6.2 PIV-Messungen 104 6.2.1 Allgemeines zum Messprinzip 104 6.2.2 Messaufbau 105 6.2.3 Versuchsergebnisse 106 6.3 LDA-Messungen 111 6.3.1 Allgemeines zum Messprinzip und zur Versuchsdurchführung 111 6.3.2 Validierung des Versuchsstandes 114 6.3.3 Strömungsprofile aus der LDA-Messung 117 6.3.4 Wirbelablösung im Bogennachlauf 130 6.3.5 Skalen der Strömung 144 7 Anwendungsbeispiel: Rekuperatorbrenner 151 7.1 Brennerprototyp und Versuchsdurchführung 151 7.2 Versuchsergebnisse und Auswertung 153 8 Zusammenfassung und Ausblick 157 9 Literaturverzeichnis 161 10 Anhang 173 10.1 Messtechnik des Windkanals 173 10.2 PIV-Messtechnik 175 10.3 LDA-Messtechnik 176 10.4 Versuche mit dem Rekuperatorprototypen 17

Pharmacological doses of niacin stimulate the expression of genes involved in carnitine uptake and biosynthesis and improve the carnitine status of obese Zucker rats

BACKGROUND: Activation of peroxisome proliferator-activated receptor (PPAR)alpha and PPARdelta causes an elevation of tissue carnitine concentrations through induction of genes involved in carnitine uptake [novel organic cation transporter 2, (OCTN2)], and carnitine biosynthesis [gamma-butyrobetaine dioxygenase (BBD), 4-N-trimethyl-aminobutyraldehyde dehydrogenase (TMABA-DH)]. Recent studies showed that administration of the plasma lipid-lowering drug niacin causes activation of PPARalpha and/or PPARdelta in tissues of obese Zucker rats, which have a compromised carnitine status and an impaired fatty acid oxidation capacity. Thus, we hypothesized that niacin administration to obese Zucker rats is also able to improve the diminished carnitine status of obese Zucker rats through PPAR-mediated stimulation of genes involved in carnitine uptake and biosynthesis. METHODS: To test this hypothesis, we used plasma, muscle and liver samples from a recent experiment with obese Zucker rats, which were fed either a niacin-adequate diet (30mg niacin/kg diet) or a diet with a pharmacological niacin dose (780mg niacin/kg diet), and determined concentrations of carnitine in tissues and mRNA and protein levels of genes critical for carnitine homeostasis (OCTN2, BBD, TMABA-DH). Statistical data analysis of all data was done by one-way ANOVA, and Fisher´s multiple range test. RESULTS: Rats of the obese niacin group had higher concentrations of total carnitine in plasma, skeletal muscle and liver, higher mRNA and protein levels of OCTN2, BBD, and TMABA-DH in the liver and higher mRNA and protein levels of OCTN2 in skeletal muscle than those of the obese control group (P<0.05), whereas rats of the obese control group had lower concentrations of total carnitine in plasma and skeletal muscle than lean rats (P<0.05). CONCLUSION: The results show for the first time that niacin administration stimulates the expression of genes involved in carnitine uptake and biosynthesis and improves the diminished carnitine status of obese Zucker rats. We assume that the induction of genes involved in carnitine uptake and biosynthesis by niacin administration is mediated by PPAR-activation

Carnitine transporter OCTN2 and carnitine uptake in bovine kidney cells is regulated by peroxisome proliferator-activated receptor beta/delta

BACKGROUND: Peroxisome proliferator-activated receptor alpha (PPARalpha), a central regulator of fatty acid catabolism, has recently been shown to be a transcriptional regulator of the gene encoding the carnitine transporter novel organic cation transporter 2 (OCTN2) in cattle. Whether PPARbeta/delta, another PPAR subtype, which has partially overlapping functions as PPARalpha and is known to share a large set of common target genes with PPARalpha, also regulates OCTN2 and carnitine transport in cattle is currently unknown. To close this gap of knowledge, we studied the effect of the PPARbeta/delta activator GW0742 on mRNA and protein levels of OCTN2 and carnitine uptake in the presence and absence of the PPARbeta/delta antagonist GSK3787 in the bovine Madin-Darby bovine kidney (MDBK) cell line. FINDINGS: Treatment of MDBK cells with GW0742 caused a strong increase in the mRNA level of the known bovine PPARbeta/delta target gene CPT1A in MDBK cells indicating activation of PPARbeta/delta. The mRNA and protein level of OCTN2 was clearly elevated in MDBK cells treated with GW0742, but the stimulatory effect of GW0742 on mRNA and protein level of OCTN2 was completely blocked by GSK3787. In addition, GW0742 increased Na+-dependent carnitine uptake, which is mediated by OCTN2, into MDBK cells, whereas treatment of cells with the PPARbeta/delta antagonist completely abolished the stimulatory effect of GW0742 on carnitine uptake. CONCLUSIONS: The present study shows for the first time that gene expression of the carnitine transporter OCTN2 and carnitine transport are regulated by PPARbeta/delta in bovine cells. These novel findings extend the knowledge about the molecular regulation of the OCTN2 gene and carnitine transport in cattle and indicate that regulation of OCTN2 gene expression and carnitine transport is not restricted to the PPARalpha subtype

Multiband Superconductivity in KFe2As2: Evidence for one Isotropic and several Liliputian Energy Gaps

We report a detailed low-temperature thermodynamic investigation (heat capacity and magnetization) of the superconducting state of KFe2As2 for H || c axis. Our measurements reveal that the properties of KFe2As2 are dominated by a relatively large nodeless energy gap (Delta?0 = 1.9 kBTc) which excludes dx2-y2 symmetry. We prove the existence of several additional extremely small gaps (?Delta0 < 1.0 kBTc) that have a profound impact on the low-temperature and low-field behavior, similar to MgB2, CeCoIn5 and PrOs4Sb12. The zero-field heat capacity is analyzed in a realistic self-consistent 4-band BCS model which qualitatively reproduces the recent laser ARPES results of Okazaki et al. (Science 337 (2012) 1314). Our results show that extremely low-temperature measurements, i.e. T < 0.1 K, will be required in order to resolve the question of the existence of line nodes in this compound.Comment: 7 pages, 6 figure