Korinna Huber

University of Veterinary Medicine Hannover, Hanover, Lower Saxony, Germany

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Publications (65)127.78 Total impact

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    ABSTRACT: We recently showed that the mRNA expression of genes encoding for specific nutrient sensing receptors, namely the free fatty acid receptors (FFAR) 1, 2, 3, and the hydroxycarboxylic acid receptor (HCAR) 2, undergo characteristic changes during the transition from late pregnancy to lactation in certain adipose tissues (AT) of dairy cows. We hypothesised that divergent energy intake achieved by feeding diets with either high or low portions of concentrate (60% v. 30% concentrate on a dry matter basis) will alter the mRNA expression of FFAR 1, 2, 3, as well as HCAR2 in subcutaneous (SCAT) and retroperitoneal AT (RPAT) of dairy cows in the first 3 weeks postpartum (p.p.). For this purpose, 20 multiparous German Holstein cows were allocated to either the high concentrate ration (HC, n=10) or the low concentrate ration (LC, n=10) from day 1 to 21 p.p. Serum samples and biopsies of SCAT (tail head) and RPAT (above the peritoneum) were obtained at day -21, 1 and 21 relative to parturition. The mRNA abundances were measured by quantitative PCR. The concentrations of short-chain fatty acid (SCFA) in serum were measured by gas chromatography-flame ionisation detector. The FFAR1 and FFAR2 mRNA abundance in RPAT was higher at day -21 compared to day 1. At day 21 p.p. the FFAR2 mRNA abundance was 2.5-fold higher in RPAT of the LC animals compared to the HC cows. The FFAR3 mRNA abundance tended to lower values in SCAT of the LC group at day 21. The HCAR2 mRNA abundance was neither affected by time nor by feeding in both AT. On day 21 p.p. the HC group had 1.7-fold greater serum concentrations of propionic acid and lower concentrations of acetic acid (trend: 1.2-fold lower) compared with the LC group. Positive correlations between the mRNA abundance of HCAR2 and peroxisome proliferator-activated receptor γ-2 (PPARG2) indicate a link between HCAR2 and PPARG2 in both AT. We observed an inverse regulation of FFAR2 and FFAR3 expression over time and both receptors also showed an inverse mRNA abundance as induced by different portions of concentrate. Thus, indicating divergent nutrient sensing of both receptors in AT during the transition period. We propose that the different manifestation of negative EB in both groups at day 21 after parturition affect at least FFAR2 expression in RPAT.
    animal 11/2015; DOI:10.1017/S175173111500227X · 1.84 Impact Factor
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    ABSTRACT: The periparturient period is critical according to health, productivity and profitability. As this period is fundamental for the success of the lactation period, the interest in improving periparturient health by dietary supplements increased in recent years. The present study investigated the effects of feeding nicotinic acid (NA) combined with varying dietary energy densities on immunological, hematological and biochemical parameters of periparturient cows differing in parity. Thirty-six multiparous and 20 primiparous dairy cows were enrolled in the study 42 days before expected parturition date until 100 days postpartum with the half of the cows being supplemented with 24 g of NA/d. After parturition a diet with 30% concentrate was fed to all cows which was followed by different concentrate escalation strategies. Dietary NA supplementation was ceased on day 24 postpartum. Dietary NA increased (P = 0.010) serum nicotinamide concentrations (mean of 3.35 ± 1.65 µg/mL), whereas NA could not be detected. Present data emphasize that periparturient cows are faced with major physiological challenges and that both parity-groups have different prerequisites to adapt to those changes irrespective of NA supplementation. The overfeeding of energy to cows which were similar in body condition score had only minor effects on periparturient immune system function and the metabolism of those cows.
    Animals 09/2015; 5(3):910-933. DOI:10.3390/ani5030391
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    ABSTRACT: It is well observed that feeding energy-dense diets in dairy cows during the dry period can cause metabolic imbalances after parturition. Especially dairy cows with high body condition score (BCS) and fed an energy-dense diet were prone to develop production diseases due to metabolic disturbances postpartum. An experiment was conducted to determine the effects of an energy-dense diet and nicotinic acid (NA) on production and metabolic variables of primiparous and multiparous cows in late pregnancy and early lactation which were not pre-selected for high BCS. Thirty-six multiparous and 20 primiparous German Holstein cows with equal body conditions were fed with energy-dense (60% concentrate/40% roughage mixture; HC group) or adequate (30% concentrate/70% roughage mixture; LC group) diets prepartum. After parturition, concentrate proportion was dropped to 30% for all HC and LC groups and was increased to 50% within 16 days for LC and within 24 days for HC cows. In addition, half of the cows per group received 24 g NA supplement per day and cow aimed to attenuate the lipid mobilisation postpartum. Feeding energy-dense diets to late-pregnant dairy cows elevated the dry matter (p < 0.001) and energy intake (p < 0.001) as well as the energy balance (p < 0.001) without affecting the BCS (p = 0.265) during this period. However, this did not result in any metabolic deviation postpartum as the effects of prepartum concentrate feeding were not carried over into postpartum period. Multiparous cows responded more profoundly to energy-dense feeding prepartum compared with primiparous cows, and parity-related differences in the transition from late pregnancy to lactation were obvious pre- and postpartum. The supplementation with 24 g NA did not reveal any effect on energy metabolism. This study clearly showed that energy-dense feeding prepartum did not result in metabolic imbalances postpartum in multiparous and primiparous cows not selected for high BCS. A genetic predisposition for an anabolic metabolic status as indicated by high BCS may be crucial for developing production diseases at the onset of lactation.
    Archives of animal nutrition 09/2015; 69(5):319-339. DOI:10.1080/1745039X.2015.1073002 · 1.00 Impact Factor
  • Á Kenéz · R Tienken · L Locher · U Meyer · A Rizk · J Rehage · S Dänicke · K Huber ·
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    ABSTRACT: Dairy cattle will mobilize large amounts of body fat during early lactation as an effect of decreased lipogenesis and increased lipolysis. Regulation of lipid metabolism involves fatty acid synthesis from acetate and β-adrenergic-stimulated phosphorylation of hormone-sensitive lipase (HSL) and perilipin in adipocytes. Although basic mechanisms of mobilizing fat storage in transition cows are understood, we lack a sufficiently detailed understanding to declare the exact regulatory network of these in a broad range of dairy cattle. The objective of the present study was to quantify 1) protein abundance of fatty acid synthase (FAS), 2) extent of phosphorylation of HSL and perilipin in vivo, and 3) β-adrenergic stimulated lipolytic response of adipose tissues in vitro at different stages of the periparturient period. We fed 20 German Holstein cows an energy-dense or an energetically adequate diet prepartum and 0 or 24 g/d nicotinic acid (NA) supplementation. Biopsy samples of subcutaneous and retroperitoneal adipose tissue were obtained at d 42 prepartum (d -42) and at d 1, 21, and 100 postpartum (d +1, d +21, d +100, respectively). To assess β-adrenergic response, tissue samples were incubated with 1 μ isoproterenol for 90 min at 37°C. The NEFA and glycerol release, as well as HSL and perilipin phosphorylation, was measured as indicators of in vitro stimulated lipolysis. In addition, protein expression of FAS and extent of HSL and perilipin phosphorylation were measured in fresh, nonincubated samples. There was no effect of dietary energy density or NA on the observed variables. The extent of HSL and perilipin phosphorylation under isoproterenol stimulation was strongly correlated with the release of NEFA and glycerol, consistent with the functional link between β-adrenergic-stimulated protein phosphorylation and lipolysis. In the nonincubated samples, FAS protein expression was decreased at d +1 and d +21, whereas HSL and perilipin phosphorylation increased from d -42 to d +1 and remained at an increased level throughout the first 100 d of lactation. In vitro lipolytic response was significant in prepartum samples at times when in vivo lipolysis was only minimally activated by phosphorylation. These data extend our understanding of the complex nature of control of lipolysis and lipogenesis in dairy cows and could be useful to the ongoing development of systems biology models of metabolism to help improve our quantitative knowledge of the cow.
    Journal of Animal Science 07/2015; 94:4012. DOI:10.2527/jas2014-8833 · 2.11 Impact Factor
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    ABSTRACT: Dairy cows mobilize large amounts of body fat during early lactation to overcome negative energy balance which typically arises in this period. As an adaptation process, adipose tissues of cows undergo extensive remodeling during late pregnancy and early lactation. The objective of the present study was to characterize this remodeling to get a better understanding of adaptation processes in adipose tissues, affected by changing metabolic conditions including lipid mobilization and refilling as a function of energy status. This was done by determining adipocyte size in histological sections of subcutaneous and retroperitoneal adipose tissue biopsy samples collected from German Holstein cows at 42 days prepartum, and 1, 21, and 100 days postpartum. Characterization of cell size changes was extended by the analysis of DNA, triacylglycerol, and protein content per gram tissue, and β-actin protein expression in the same samples. In both adipose tissue depots cell size was becoming smaller during the course of the study, suggesting a decrease in cellular triacylglycerol content. Results of DNA, triacylglycerol, and protein content, and β-actin protein expression could only partially explain the observed differences in cell size. The retroperitoneal adipose tissue exhibited a greater extent of time-related differences in cell size, DNA, and protein content, suggesting greater dynamics and metabolic flexibility for this abdominal depot compared to the investigated subcutaneous depot.
    PLoS ONE 05/2015; 10(5):e0127208. DOI:10.1371/journal.pone.0127208 · 3.23 Impact Factor
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    Korinna Huber · Ellen Zeller · Markus Rodehutscord ·
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    ABSTRACT: Dietary phosphorus (P) is known as a main modulator of phosphate (Pi) transporter expression. The effect of supplemented mineral P with or without phytase on protein expression of two sodium-dependent Pi (NaPi) transporters and a calcium channel was studied in the small intestine of broilers. Thirty-six broilers were randomly assigned to six different diets at 15 days of age. Two levels of total P (tP, adjusted by monocalcium phosphate (MCP) supplementation), 0.39% (BD-) and 0.47% (BD+) were fed until day 25; and at each tP level, three levels of phytase were used with 0, 500, and 12,500 FTU/kg of an E.coli phytase. Mucosa samples from jejunum and ileum were taken and apical membranes were isolated by MgCl2 precipitation. Protein expression of NaPi IIb, NaPi type III (PiT1) and the calcium channel TRPV6 were semiquantitatively measured by Western blotting and jejunal mucosal phytase activity by measurement of Pi release. The jejunal NaPi IIb transporter was expressed with two distinct bands, which were modulated differently by diet. NaPi IIb Band1 increased (P < 0.05) and Band2 decreased (P < 0.05) with phytase supplementation but was not affected by MCP supplementation. This inverse modulation of Band1 and Band2 was significantly related to the amount of net absorbed P with higher expression of Band1 at higher amounts of net absorbed P. In addition, a second Pi transporter, PiT1, was detected in which ileal expression decreased (P < 0.05) in response to higher phytase supplementation. The expression of the calcium channel TRPV6 was increased in BD+ groups. A trend for an interaction between MCP and phytase supplementation on mucosal phytase activity was observed (P = 0.079) with a decrease in activity when BD+ with 12,500 FTU/kg phytase was fed. Chicken intestinal epithelial cells responded to dietary supplemented phytase and MCP by changing the Pi transporter expression in apical membranes. In conclusion, availability of Pi is most likely the key modulator of transporter protein expression. However, a contribution of lower inositol phosphates generated by phytases and other phosphatases may also be relevant. © 2015 Poultry Science Association Inc.
    Poultry Science 03/2015; 94(5). DOI:10.3382/ps/pev065 · 1.67 Impact Factor
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    ABSTRACT: In response to negative energy balance, overconditioned cows mobilize more body fat than thin cows and subsequently are prone to develop metabolic disorders. Changes in adipose tissue (AT) metabolism are barely investigated in overconditioned cows. Therefore, the objective was to investigate the effect of increasing body condition on key regulator proteins of fat metabolism in subcutaneous AT and circulation of dairy cows. Nonlactating, nonpregnant dairy cows (n = 8) investigated in the current study served as a model to elucidate the changes in the course of overcondition independent from physiological changes related to gestation, parturition, and lactation. Cows were fed diets with increasing portions of concentrate during the first 6 wk of the experiment until 60% were reached, which was maintained for 9 wk. Biopsy samples from AT of the subcutaneous tailhead region were collected every 8 wk, whereas blood was sampled monthly. Within the experimental period cows had an average BW gain of 243 ± 33.3 kg. Leptin and insulin concentrations were increased until wk 12. Based on serum concentrations of glucose, insulin, and nonesterified fatty acids, the surrogate indices for insulin sensitivity were calculated. High-concentrate feeding led to decreased quantitative insulin sensitivity check index and homeostasis model assessment due to high insulin and glucose concentrations indicating decreased insulin sensitivity. Adiponectin, an adipokine-promoting insulin sensitivity, decreased in subcutaneous AT, but remained unchanged in the circulation. The high-concentrate diet affected key enzymes reflecting AT metabolism such as AMP-activated protein kinase and hormone-sensitive lipase, both represented as the proportion of the phosphorylated protein to total protein, as well as fatty acid synthase. The extent of phosphorylation of AMP-activated protein kinase and the protein expression of fatty acid synthase were inversely regulated throughout the experimental period, whereas the extent of phosphorylation of hormone-sensitive lipase was consistently decreasing by the high-concentrate diet. Overcondition in nonpregnant, nonlactating dairy cows changed the expression of key regulator proteins of AT metabolism and circulation accompanied by impaired insulin sensitivity, which might increase the risk for metabolic disorders. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
    Journal of Dairy Science 12/2014; 98(2). DOI:10.3168/jds.2014-8710 · 2.57 Impact Factor
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    ABSTRACT: Background A number of different pathways to obesity with different metabolic outcomes are recognised. Prenatal undernutrition in rats leads to increased fat deposition in adulthood. However, the form of obesity is metabolically distinct from obesity induced through other pathways (e.g. diet-induced obesity). Previous rat studies have shown that maternal undernutrition during pregnancy led to insulin hyper-secretion and obesity in offspring, but not to systemic insulin resistance. Increased muscle and liver glycogen stores indicated that glucose is taken up efficiently, reflecting an active physiological function of these energy storage tissues. It is increasingly recognised that adipose tissue plays a central role in the regulation of metabolism and pathophysiology of obesity development. The present study investigated the cell size and endocrine responsiveness of subcutaneous and visceral adipose tissue from prenatally undernourished rats. We aimed to identify whether these adipose tissue depots contribute to the altered energy metabolism observed in these offspring. Methods Adipocyte size was measured in both subcutaneous (ScAT) and retroperitoneal adipose tissue (RpAT) in male prenatally ad libitum fed (AD) or prenatally undernourished (UN) rat offspring. Metabolic responses were investigated in adipose tissue explants stimulated by insulin and beta3 receptor agonists ex vivo. Expression of markers of insulin signalling was determined by Western blot analyses. Data were analysed by unpaired t-test or Two Way ANOVA followed by Fisher’s PLSD post-hoc test, where appropriate. Results Adipocytes in offspring of undernourished mothers were larger, even at a lower body weight, in both RpAT and ScAT. The insulin response of adipose tissue was reduced in ScAT, and statistically absent in RpAT of UN rats compared with control. This lack of RpAT insulin response was associated with reduced expression of insulin signalling pathway proteins. Adrenergic receptor-driven lipolysis was observed in both adipose depots; however insulin failed to express its anti-lipolytic effect in RpAT in both, AD and UN offspring. Conclusions Metabolic dysregulation in offspring of undernourished mothers is mediated by increased adipocyte size and reduced insulin responsiveness in both ScAT and especially in RpAT. These functional and morphological changes in adipocytes were accompanied by impaired activity of the insulin signalling cascade highlighting the important role of different adipose tissue depots in the pathogenesis of metabolic disorders.
    Nutrition & Metabolism 10/2014; 11(1):50. DOI:10.1186/1743-7075-11-50 · 3.26 Impact Factor
  • K. Tappenbeck · S. Hoppe · F. Geburek · K. Feige · K. Huber ·
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    ABSTRACT: By blocking the enteric nervous system (ENS) using tetrodotoxin (TTX), previous studies have documented the contractility-enhancing (CE) effects of lidocaine in equine intestinal smooth muscle (SM) at the level of SM cells and/or interstitial cells of Cajal (ICC). The present study examined the impact of ENS deactivation on CE lidocaine effects, and investigated the effects of lidocaine on ENS activity. TTX application did not affect the CE effects of lidocaine, indicating that these were not mediated by TTX-sensitive sodium channels. Application of TTX or ≥100 mg/L lidocaine reduced ENS activity. Although such concentrations of lidocaine exceed therapeutic blood concentrations, tissue concentrations may be higher with the potential to reduce ENS activity and impair intestinal motility in vivo. Improved understanding of underlying mechanisms is relevant for therapeutic use of lidocaine in horses with postoperative ileus.
    The Veterinary Journal 09/2014; 201(3). DOI:10.1016/j.tvjl.2014.05.014 · 1.76 Impact Factor
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    ABSTRACT: The influence of butyrate on insulin signaling in chickens was studied because butyrate is produced during microbial fermentation in the large intestine of birds and butyrate is widely used as a feed additive in animal production. Ross 308 broiler chickens received a daily intra-ingluvial bolus of sodium butyrate (0.25 g/kg BW) on d 20-24 of life (n = 10). Plasma butyrate concentration increased after receiving oral butyrate treatment (P < 0.001). Oral butyrate application was associated with decreased protein expression of insulin receptor β subunit (IRβ) in liver (P = 0.008) and both abdominal (P = 0.003) and subcutaneous adipose tissue (P < 0.001), but with elevated IRβ expression in muscle (P = 0.045), assessed by Western blotting. The quantity of hepatic phosphatidyl-inositol-3-kinase (PI3K) was reduced in the butyrate-treated group (P = 0.007), further, mammalian target of rapamycin (mTOR) was down-regulated by butyrate in liver (P < 0.001) and subcutaneous adipose tissue (P = 0.038). Oral butyrate application provoked reduced systemic insulin sensitivity in chickens, indicated by elevated fasting blood glucose and subsequently, insulin level. However, responses of insulin signaling cascade to butyrate were tissue-specific suggesting that butyrate could act on glucose shifting among tissues by selectively increasing the glucose uptake of skeletal muscle via IRβ up-regulation.
    Domestic Animal Endocrinology 08/2014; 50. DOI:10.1016/j.domaniend.2014.07.004 · 2.17 Impact Factor
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    ABSTRACT: Abstract Text: Apelin, a 77 amino acid preproprotein, which is also known as an adipokine is suggested to play a physiological role in glucose metabolism. It stimulates glucose uptake by adipose tissue in humans and mice, whereas lipolysis in humans is not affected. This might lead to a decreasing lipolysis during the transition period in cattle and may prevent lipid-related disorders. Nicotinic acid (NA), a known antilipolytic agent, might decrease plasma NEFA concentrations and enhances the response to insulin. As plasma apelin concentrations are decreased by a hypochaloric diet, we hypothesized, that different levels of concentrate in the diet combined with NA supplementation would affect the serum apelin concentrations in dairy cows. Thus the objectives of the present study were to quantify apelin in bovine serum samples and to examine the impact of different levels of concentrate in combination with a NA supplementation on apelin serum concentrations. Serum samples were obtained from 20 pluriparous Holstein-Friesian cows at day (d) -42, -14, 1, 7, 14, 21, 42 and d 100 relative to calving. Until d -42 all cows were fed the same silage-based diet. Between d -42 and d -1 10 animals each were assigned to either a high-concentrate (HC, 60:40 concentrate:roughage) or a low concentrate group (LC, 30:70 concentrate:roughage). Both groups were further subdivided into a control and a niacin group (n=5), the latter receiving 24 g/d NA (Lonza, Basel, Switzerland) until d 24. Serum apelin concentrations were measured using a commercially available ELISA kit (Phoenix Pharmaceuticals, Burlingame, CA, USA) validated for bovine samples. Statistical analysis was done using Mixed-Model procedure followed by Bonferroni correction (SPSS 22); d -42 values were considered as covariate. The serum apelin concentrations were not affected by treatment and time (P > 0.05) and remained on a constant concentration (mean 1.21 ± 0.08 ng/ml). The results of this study indicate that serum apelin concentrations are independent of the prepartum feeding regimen as well as of the stage of lactation. Keywords: apelin, nicotinic acid, dairy cow
    2014 ADSA-ASAS-CSAS Joint Annual Meeting; 07/2014
  • John P. McNamara · Korinna Huber · Akos Kenez ·
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    ABSTRACT: Abstract Text: Research in dairy cattle biology has resulted in a large body of knowledge on nutrition and metabolism supporting and underlying milk production and efficiency. The adipose tissues are an essential part of the overall efficiency of dairy cattle. Therefore we constructed a dynamic, mechanistic model of control of metabolism in the adipose tissues of dairy cattle. The model describes the biochemical interconversion of glucose, acetate, glycerol, fatty acids, and triacylglycerols. Data from our own research and published references were used to set equation forms and parameter values. Metabolites are absorbed from blood, and fatty acids are activated to the Acyl CoEnzymeA counterparts. Fatty acids are partitioned to palmitic, stearic, oleic and linoleic acids. Enzymatically catalyzed reactions are explicitly described with parameters including maximal velocity and substrate sensitivity. Energetic stoichiometry is maintained by the balance of ATP utilizing and generating reactions. Changes in gene transcription or post-translational modification of enzyme activity control nutrient metabolism, including control by insulin and norepinephrine. The model behavior to availability of nutrients and insulin or norepinephrine is in agreement with published data. For example, triacylglycerol synthesis when glucose is low (1 mM) is 17.82 + 1.9 X ln (Fatty Acyl CoA); when glucose is high (5 mM) it is 44.96 + 5.67 ln(Fatty Acyl CoA). Triacylglycerol lipolysis is -13.28 - 4.33 ln (Fatty Acyl CoA)) when norepinephrine is low, and is - 22.14 - 7.22 ln (Fatty Acyl CoA) when it is high (25 % more than basal). This model can form a basis for more sophisticated integration of existing knowledge and future studies on metabolic efficiency of dairy cattle. Keywords: adipose, metabolism, mechanistic model, lactation
    2014 ADSA-ASAS-CSAS Joint Annual Meeting; 07/2014
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    ABSTRACT: Lidocaine is the most commonly chosen prokinetic for treating postoperative ileus in horses, a motility disorder associated with ischaemia-reperfusion injury of intestinal tissues. Despite the frequent use of lidocaine, the mechanism underlying its prokinetic effects is still unclear. Previous studies suggested that lidocaine altered cell membrane characteristics of smooth muscle cells. Therefore, the present study aimed to elucidate effects of lidocaine administration on characteristics of detergent-resistant membranes in equine jejunal smooth muscle. Lidocaine administration caused significant redistribution of flotillin-2, a protein marker of detergent-resistant membranes, in fractions of sucrose-density-gradients obtained from ischaemia-reperfusion injured smooth muscle solubilised with Triton X-100. It was concluded that lidocaine induced disruption of detergent-resistant membranes which might affect ion channel activity and therefore enhance smooth muscle contractility.
    The Veterinary Journal 05/2014; 200(2). DOI:10.1016/j.tvjl.2014.03.002 · 1.76 Impact Factor
  • A Kenéz · L Locher · J Rehage · S Dänicke · K Huber ·
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    ABSTRACT: A balanced lipolytic regulation in adipose tissues based on fine-tuning of prolipolytic and antilipolytic pathways is of vital importance to maintain the metabolic health in dairy cows. Antilipolytic pathways, such as the G protein-coupled receptor 109A (GPR109A)-mediated pathway and the insulin signaling pathway in bovine adipose tissues may be involved in prohibiting excessive lipomobilization by reducing triglycerol hydrolysis. This study aimed to evaluate the in vitro antilipolytic potential of the mentioned pathways in bovine adipose tissue explants. Therefore, subcutaneous and retroperitoneal adipose tissue samples (approximately 100 mg) of German Holstein cows were treated for 90 min ex vivo with nicotinic acid (2, 8, or 32 μM), nicotinamide (2, 8, or 32 μM), β-hydroxybutyrate (0.2, 1, or 5 mM), or insulin (12 mU/L), with a concurrent lipolytic challenge provoked with 1 μM isoproterenol. Lipolytic and antilipolytic responses of the adipose tissues were assessed by measuring free glycerol and nonesterified fatty acid release. To identify molecular components of the investigated antilipolytic pathways, protein abundance of GPR109A and the extent of hormone-sensitive lipase (HSL) phosphorylation at serine residue 563 were detected by Western blotting. Treatment with nicotinic acid or β-hydroxybutyrate decreased the lipolytic response in adipose tissue explants and concurrently reduced the extent of HSL phosphorylation, but treatment with nicotinamide or insulin did not. Subcutaneous adipose tissue constitutively expressed more GPR109A protein, but no other depot-specific differences were observed. This study provides evidence that the GPR109A-mediated pathway is functionally existent in bovine adipose tissues, and confirms that HSL phosphorylation at serine residue 563 is also important in antilipolytic regulation in vitro. This antilipolytic pathway may be involved in a balanced lipid mobilization in the dairy cow.
    Journal of Dairy Science 04/2014; 97(6). DOI:10.3168/jds.2013-7662 · 2.57 Impact Factor
  • K. Huber · A. Kenez · J. P. McNamara · S. L. Shields ·
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    ABSTRACT: In order to assess the patterns of metabolism that affect efficiency, an existing mechanistic metabolic model of dairy cows (Molly) was expanded to include transcriptional control of metabolism in adipose tissue and reproductive processes. Our objective was to test the effects of changes in gene transcription in adipose tissue on patterns of metabolism, reproductive processes and efficiency. The model describes the substrate sensitivity and maximum velocity for lipogenesis, esterification and lipolysis. Data were collected from first and second parity cows from various studies, and included nutrient intake, milk component output, changes in adipose tissue lipid, visceral and body protein and lipid, and metabolism rates in adipose tissue and gene transcription. The lipogenic pathways were primarily controlled by transcriptional changes, whereas lipolysis varied primarily by post-translational control. We used the difference in transcriptional and post-translational metabolic control to alter Vmax and Ks
    Animal Production Science 01/2014; 54(9-9):1224-1227. DOI:10.1071/AN14209 · 1.29 Impact Factor
  • K. Huber · A. Kenez · J. P. McNamara · S. L. Shields ·
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    ABSTRACT: Our knowledge of genetics, nutrient metabolism and reproductive physiology demands an integrated systems approach to both research and on-farm application. Existing mechanistic, dynamic and biochemical models exist which describe (1) nutrient metabolism and control of nutritional processes and (2) estrous cyclicity in lactating dairy cows. The metabolic model contains a simple aggregated model of lipogenesis, esterification and lipolysis; however, it is not sufficiently detailed to provide a research framework for future research. The estrous model describes the cyclicity of follicular development as well as several key reproductive hormones, but it does not contain any nutritional control as we understand it. Therefore, we developed a more detailed model of metabolism in adipose tissue, including uptake of glucose and fatty acids, fatty acid activation to the AcylCoA form, lipogenesis from acetate and butyrate, esterification of glycerol and fatty acids, and lipolysis and release of fatty acids and gl
    Animal Production Science 01/2014; DOI:10.1071/AN14515 · 1.29 Impact Factor
  • S Starke · K Huber ·
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    ABSTRACT: In a previous study, in goats, we showed that apart from variations in dietary calcium (Ca) and phosphorus intake, also low dietary nitrogen (N) intake altered plasma concentrations of hormones, which regulate Ca and phosphate (Pi ) homeostasis. These hormonal responses in goats were in accordance with findings in monogastric animals and humans with low protein intake. In the aforementioned studies, alterations of electrolyte transport in the kidneys were also observed. However, whether renal electrolyte transport in goats is also involved in the adaptation of Ca and Pi homeostasis to low N intake remains unknown. Thus, the aim of the present study was to investigate whether in addition to the hormonal changes, as observed in our former study, renal Ca transport and renal Pi transport were also altered by low N intake in goats. Therefore, in kidney samples from the goats used in our former study, the protein expression of Ca and Pi transporters and of related regulatory proteins was examined. Furthermore, the uptake of Pi into isolated brush border membrane vesicles (BBMV) was detected. The results showed that the protein amount of the renal sodium-dependent Pi transporter NaPi IIa was elevated, and concomitantly, protein expression of its upstream regulators, the parathyroid hormone receptor and the extracellular signal-regulated kinases 1 and 2 was decreased. However, Pi uptake into renal BBMV was not enhanced. Furthermore, protein expression of the renal Ca channel, the transient receptor potential cation channel subfamily V member 5 (TRPV5) and of the vitamin D receptor was not influenced by dietary N reduction. We conclude that regulation of renal Pi transporter expression in goats is involved in the adaptation of electrolyte homeostasis to low N intake.
    J Anim Physiol a Anim Nutr 11/2013; 98(5). DOI:10.1111/jpn.12144 · 1.41 Impact Factor
  • S Starke · C Cox · K-H Südekum · K Huber ·
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    ABSTRACT: In our former studies low crude protein (LCP) intake influenced N homeostasis and electrolyte handling in goats. We hypothesised that due to rumino-hepatic nitrogen (N) recycling adaptation of N homeostasis and adjustment of electrolyte handling to LCP intake differs between goats and monogastric animals. Therefore, an experiment similar to that with goats was conducted with rats. Two feeding groups received a diet either containing 20 or 8 % crude protein (as fed basis) for 5 weeks and intake and excretion of N, calcium (Ca) and phosphorus (P) were determined. To detect systemic and endocrine adaptation to LCP intake plasma concentrations of urea, Ca, phosphate (Pi), insulin-like growth factor 1 (IGF-1), 1,25-dihydroxyvitamin D3 (calcitriol), parathyroid hormone (PTH) and cross-linked telopeptide of type I collagen (CTX) were measured. Adjustment of renal electrolyte transport was assessed by detecting protein expression of key proteins of renal Pi transport. All data were compared with the data of the goat experiment. LCP intake decreased plasma urea concentration stronger in goats than in rats. In both species urinary N excretion declined, but faecal N excretion decreased in goats only. Furthermore, in goats urinary Ca excretion decreased, but in rats urinary Ca concentration increased. Decreased plasma IGF-1 and calcitriol concentrations were found in goats only. Thus, renal Ca excretion appears to be a common target in adaptation of electrolyte homeostasis in both species, but is regulated differently.
    Journal of Comparative Physiology B 10/2013; 184(1). DOI:10.1007/s00360-013-0785-9 · 2.62 Impact Factor
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    ABSTRACT: The purpose of the study was to compare the contractility-enhancing effects of lidocaine in equine jejunal circular (CSM) and longitudinal smooth muscle (LSM) in vitro. In previous studies, more pronounced effects of lidocaine were observed in ischaemia-reperfusion (IR) injured smooth muscle. Therefore in this study, effects were examined in both non-injured control tissues and tissues challenged by a defined, artificial IR injury. Isometric contractile performance of CSM and LSM, assessed by frequency (F), amplitude (A) and mean active force (MAF) of contractions, was defined as contractility. LSM featured lower basic contractility compared to CSM. Lidocaine provoked contractility-enhancing effects in both smooth muscle layers, but except for F at high lidocaine concentrations, contractility of LSM remained lower throughout the trial. Additionally, higher lidocaine concentrations were required to cause significant effects in LSM. No differences were observed in contractility of control and IR injured smooth muscle, but higher lidocaine concentrations were needed to provoke effects in IR injured smooth muscle. In contrast to CSM, contractility of LSM did not decrease at comparably high lidocaine concentrations. Differences in basic contractility of CSM and LSM might be explained by physiologically lower activity of LSM per se or by a thinner LSM layer with fewer smooth muscle cells taking part in contractions. The smaller thickness of the LSM layer may also contribute to persisting discrepancies in contractility following lidocaine application. Additionally, variations in lidocaine concentrations necessary for inducing significant effects could result from differences in the molecular structure of CSM and LSM cells.
    The Veterinary Journal 08/2013; 198(1). DOI:10.1016/j.tvjl.2013.07.027 · 1.76 Impact Factor
  • S. Starke · C. Cox · K.-H. Südekum · K. Huber ·
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    ABSTRACT: In a previous study it was shown that low crude protein (LCP) intake affected the systemic and renal electrolyte handling (EH) in growing goats. The present study aimed to evaluate the consequences of these changes on the electrolyte excretion and its in vivo regulation by functional studies. Growing male Saanen-type goats were fed diets high or low in crude protein content, and nitrogen (N), phosphorus (P) and calcium (Ca) balance trials were performed to investigate electrolyte excretion. Additionally, plasma urea, Ca, phosphate (Pi) and endocrine regulators of electrolyte homeostasis including insulin-like growth factor-1 (IGF-1), calcitriol, cross-linked N-telopeptide of type I collagen and parathyroid hormone (PTH) concentrations were determined. Renal adaptation to LCP intake was investigated by determining the protein expression of the sodium-dependent Pi transporter types IIa and IIc (NaPi IIa and IIc) and the PTH receptor (PTHR) by Western blotting. To demonstrate associations between the measured variables and thereby to identify the possible pathways of electrolyte handling in goats, linear regression analyses were performed. While N metabolism was adapted to LCP intake, the plasma IGF-1 and, by trend, calcitriol concentration decreased and also the renal PTHR protein expression declined. However, Ca and P excretion and retention remained unaffected. Linear regression analyses showed that calcitriol and IGF-1 concentrations were associated with further key factors of systemic and renal EH. In summary, LCP intake in growing goats led to an adaptation of the systemic and renal EH, and IGF-1 and calcitriol appeared to play significant roles. However, these adaptations seemed to be counterbalanced by the whole systemic network regulating the electrolyte handling and therefore did not have any impact on the functional electrolyte excretion. (c) 2013 Elsevier B.V. All rights reserved.
    Small Ruminant Research 08/2013; 114(1):90-96. DOI:10.1016/j.smallrumres.2013.06.008 · 1.13 Impact Factor

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425 Citations
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  • 2002-2015
    • University of Veterinary Medicine Hannover
      • Institute of Physiology
      Hanover, Lower Saxony, Germany
  • 2013
    • Massey University
      • Institute of Food, Nutrition and Human Health
      Palmerston North City, Manawatu-Wanganui, New Zealand
  • 2008
    • University of Auckland
      • Faculty of Science
      Окленд, Auckland, New Zealand
  • 2007
    • Hannover Medical School
      Hanover, Lower Saxony, Germany
  • 2006
    • Martin Luther University Halle-Wittenberg
      Halle-on-the-Saale, Saxony-Anhalt, Germany
  • 1998
    • Justus-Liebig-Universität Gießen
      • Institute for Veterinary Physiology
      Gieben, Hesse, Germany