Biomedical subjects

P J Buttery

Publications and source records attributed to P J Buttery.

At least 19 recordsLinked to original sources

PubMed2006

Fat and protein metabolism in growing steers fed either grass silage or dried grass.

Cattle fed grass silage diets have been reported to have high carcass fat:protein ratios. The effect of grass silage and dried grass diets, fed at different levels of intake to ensure a range of equivalent metabolisable energy intakes (MEI) from 1 .1 x metabolisable energy requirement for maintenance to ad libitum, on fat and protein metabolism in twenty-four Hereford x Friesian steers was investigated. After about 84 d of dietary treatment rates of whole-body fat and protein metabolism were measured, as were rates of lipogenesis in omental, perirenal and subcutaneous adipose tissue. Carcass composition was determined. Animals fed silage had greater (P<0 .001) carcass fat:protein ratios than animals fed dried grass at equivalent levels of MEI. Animals fed silage had lower (P<0 .001) rates of protein gain. Rates of leucine entry and oxidation were lower (P<0 .001) in animals fed silage, but there was no dietary difference in the rate of whole-body protein synthesis. There was no dietary difference in the rate of carcass fat gain, but rates of lipogenesis in perirenal adipose tissue were significantly (P=0 .007) higher in animals fed silage. There was no dietary difference in the rate of palmitate and glycerol entry or palmitate oxidation. There were no interactions between MEI and diet, indicating that increments of energy were utilised with the same efficiency from both diets. It was concluded that the high carcass fat:protein ratios of young growing steers was due to limited rates of protein accretion and not to elevated rates of carcass fat accretion.

Acetates↗

PubMed2006

Effect of anabolic agents on calpastatin promoters in porcine skeletal muscle and their responsiveness to cyclic adenosine monophosphate- and calcium-related stimuli.

The calpain proteinases and their specific inhibitor calpastatin have been proposed to influence both the rates of myofibrillar protein turnover in vivo and meat tenderization postmortem. Elevated calpastatin concentrations in particular are associated with certain forms of hypertrophic growth and meat toughness. In the 5'region of the porcine calpastatin gene, there are 3 calpastatin promoters upstream of exons 1xa, 1xb, and 1u, respectively, each of which contain transcription factor-binding motifs, suggesting sensitivity to a variety of growth-promoting stimuli. This study examined the effect of the beta-adrenergic agonist clenbuterol and porcine ST (pST) treatment on calpastatin promoter usage in porcine LM in vivo using real-time PCR and also the responsiveness of transfected calpastatin promoter sequences to cyclic adenosine monophosphate (cAMP) and calcium (Ca2+)-related stimuli in reporter gene systems in cell studies. The effect of clenbuterol and pST on potential signaling pathways in vivo was also assessed by monitoring protein phosphatase 2B (calcineurin), NFATc3, calpain 3, IkappaB alpha, and NFkappaB by quantitative immunoblotting. Total calpastatin mRNA was increased by 52% (P < 0.05) after treatment with clenbuterol for 1 d and reduced by 35% (P < 0.01) after pST treatment for 7 d. Whereas clenbuterol had no significant differential effects on individual mRNA transcripts (types 1 to 3) derived from the 3 upstream promoters, pST significantly reduced all of these by 51, 39, and 40% (P < 0.001, 0.05, and 0.05), respectively. Promoter activity was increased in rat L6G8 cells transfected with a construct derived from exon 1u after treatment with dibutyryl cAMP (68%, P < 0.05) or forskolin (43%, P < 0.05), whereas 1xa activity was reduced by both of these agents (47 and 33%, respectively, P < 0.05). Treatment of cells with the calcium ionophore calcimycin reduced the activity of the 1u promoter by 40% (P < 0.01), with no effect on the other promoter constructs. Cyclosporin A had no effect on any promoter construct. The only signaling pathway component to be significantly altered by the in vivo treatments was calcineurin, which was decreased by 24% (P < 0.05) in clenbuterol-treated animals. In conclusion, 2 types of growth promoter in pigs had contrasting effects on calpastatin expression in LM. Transfected calpastatin promoters were differentially sensitive to cAMP- and Ca2+-related stimuli, in agreement with the proposed mode of action of the 2 growth promoters.

Anabolic Agents↗

PubMed2006

Effect of feeding rumen-protected conjugated linoleic acid on carcass characteristics and fatty acid composition of sheep tissues.

Two experiments were conducted to determine the effectiveness of a rumen-protected CLA (pCLA) supplement and the impact of feeding this pCLA on carcass characteristics and tissue fatty acid composition of lambs. In Exp. 1, a CLA-80 preparation (80% pure CLA; contained similar proportions of cis-9, trans-11, and trans-10, cis-12 CLA), protected against rumen degradation, was fed to sheep, and the proportion of CLA reaching the duodenum was determined. A 3 x 3 Latin square design was used with 3 diets (1.4 kg of concentrate-based control diet, the same control diet plus 22 g of CLA-80, or the same control diet plus 110 g of pCLA/d), 3 feeding periods, and 3 rumen and duodenally cannulated sheep (Mule x Charolais males, 10 mo of age, BW 55.3 +/- 1.8 kg). After 7 d of feeding, sheep were ruminally infused with chromium EDTA and Yb acetate for 7 d, after which samples of duodenal digesta were collected every 6 h for 48 h to determine the quantity of CLA reaching the small intestine each day. The amounts of CLA cis-9, trans-11 and trans-10, cis-12, and combined isomers, flowing through the duodenum each day were greater (P = 0.01) in sheep fed pCLA. Approximately 65% of the pCLA avoided rumen biohydrogenation, with the ratio of the 2 main isomers remaining similar. In Exp. 2, 36 Mule x Charolais ewe lambs (approximately 13-wk old, average initial BW 29.3 kg) were fed 3 levels of the pCLA or Megalac, which were fed to provide an equivalent energy content at each pCLA level. Lambs were randomly assigned to 1 of 7 treatment groups, which were fed for 10 wk to achieve a growth rate of 180 g/d. Treatments included the basal diet and the basal diet plus 25, 50, or 100 g of pCLA/kg of diet or the equivalent amount of Megalac. In liver (P < 0.001) and all adipose tissue depots studied, the proportions of both CLA isomers increased (P = 0.02) with the amount of pCLA fed but were not altered with increasing of Megalac. Although there was no effect of treatment on cis-9, trans-11 CLA content, accumulation (P < 0.001) in the LM with increasing of pCLA supplementation was observed for the trans-10, cis-12 isomer. Although tissues had been enriched with CLA, there was no evidence of a reduction in adipose tissue or an increase in muscle mass in these sheep. However, an effect of pCLA on tissue fatty acid composition was consistent with an inhibition of stearoyl-CoA desaturase.

Acetyl-CoA Carboxylase↗

PubMed2005

Ontogeny of factors associated with proliferation and differentiation of muscle in the ovine fetus.

The number of muscle fibers within a muscle has been found to be of high importance for the growth potential of an animal, and this number is set during fetal development. The objective of this study was to identify the ontogeny of muscle cell differentiation and fiber formation by observing the changes in expression of factors known to influence myoblast proliferation and differentiation. Twenty-one Swaledale x Leicester Blue Face ewes carrying twins were allotted to this trial. From d 40 of gestation, three ewes were killed every 15 d until term. At each time point, the fetuses were located, removed, and total muscle from both hind limbs was dissected from each fetus and snap frozen in liquid N2. Ribonuclease protection assays were used to quantify transcripts for IGF-I, IGF-II, GH receptor (GHR), and myostatin genes in the muscle samples, whereas quantitative real-time PCR was used to quantify myogenin transcripts. Histological sections also were taken from the fetal muscle samples and observed for evidence of muscle differentiation resulting in fiber formation. The abundance of mRNA for ovine IGF-II and ovine myogenin peaked at d 85 of gestation (P < 0.001). The abundance of ovine IGF-I transcripts peaked at d 100 of gestation, whereas the abundance of ovine GHR mRNA increased throughout gestation (P < 0.05). No change (P = 0.87) in the abundance of myostatin mRNA was observed. The histological sections from the muscle samples demonstrated a clear change in the appearance of the muscle tissue at each time period. Major fiber formation was observed around d 85. The results obtained from the analysis of gene expression and the histological sections suggest that the majority of muscle differentiation and fiber formation takes place around d 85, with myoblast proliferation mainly occurring before this time. It may be possible to manipulate the number of muscle fibers formed by targeting treatments during this proliferation stage immediately before the period of major fiber formation.

Animals↗

PubMed2005

The effect of maternal undernutrition before muscle differentiation on the muscle fiber development of the newborn lamb.

There is a need to improve the lean tissue content of ruminant animals destined for meat production. Muscle fiber number is set during fetal development. The effect of undernutrition of pregnant ewes on subsequent muscle fiber characteristics of their offspring was investigated. The trial involved 32 pregnant ewes carrying twins. The ewes were allocated randomly to one of four groups: three different treatment groups (n = 8) and a control group (n = 8). The diet of the treatment groups was dropped to 50% of their daily requirement to support the ewe and allow for conceptus growth for varying periods before being returned to 100% of their daily requirement until term. Group d 30-70 ewes were fed 100% of their daily requirement until d 30, the diet was then decreased to 50% until d 70; it was then returned to 100% of their daily requirement until term. Group d 55-95 ewes were similarly restricted from d 55 through 95, and Group d 85-115 ewes were restricted from d 85 through 115. The control group was fed 100% of their daily requirement to support the ewe and allow for conceptus growth throughout gestation. After parturition, the lactating ewes were fed a normal commercial diet. On d 14 (after parturition), the lambs were slaughtered and the LM, semitendinosus (ST), and vastus lateralis (VL) were dissected and snap frozen. The immunochemical determination of myosin heavy-chain slow (MHC-slow) and myosin heavy-chain fast (MHC-fast) proteins was measured by immunoprobing of Western blots. The number of fast and slow fibers and the diameter of these fibers also were measured in each muscle sample by histochemical techniques. Decreased maternal nutrition before fiber formation (d 30 through 70) was observed to change the muscle characteristics of the newborn lambs. These lambs had significantly fewer fast fibers (P < 0.001) and significantly more slow fibers (P < 0.001) in both the LM and VL compared with the other groups. Maternal nutrient restriction at the other periods had no effect on the number of muscle fibers in the newborn lambs; however, a decrease (LM, P < 0.05; VL, P < 0.01; ST, P = 0.08) in muscle weight was observed in the lambs born to the ewes restricted between d 85 and 115 of gestation compared with the other groups. This study has shown that decreased maternal diet before muscle fiber formation will alter the muscle fiber development in the fetus.

Animal Feed↗

PubMed2004

Insulin and dexamethasone regulate stearoyl-CoA desaturase mRNA levels and fatty acid synthesis in ovine adipose tissue explants.

Sheep adipose tissue explants were maintained in culture for 24 h in the presence of insulin, dexamethasone, or insulin and dexamethasone, and stearoyl-CoA desaturase (SCD) messenger RNA (mRNA) levels and fatty acid synthesis were measured. Insulin increased SCD mRNA levels (P = 0.008) and synthesis of both saturated (P = 0.07) and unsaturated (P < 0.001) fatty acids but had the greatest effect on unsaturated fatty acid synthesis, resulting in the overall production of a greater (P < 0.001) proportion of monounsaturated fat. Dexamethasone, alone, had the opposite effect but actually potentiated the effect of insulin in stimulating SCD expression and both saturated and monounsaturated fatty acid synthesis, without affecting the relative proportions of each. Across adipose tissue depots, the effect of hormones was similar, although the increase in SCD mRNA levels (P = 0.008) and monounsaturated fatty acid synthesis (P < 0.001) was greater in subcutaneous adipose tissue than in the internal (omental and perirenal) depots. These data clearly show that, in ovine adipose tissue, changes in SCD gene expression in response to insulin and dexamethasone are associated with changes in monounsaturated fatty acid synthesis and suggest that it may be possible to develop strategies to manipulate sheep tissues to produce a less-saturated fatty acid profile.

Adipose Tissue↗

PubMed2004

Differing effects of forage and concentrate diets on the oleic acid and conjugated linoleic acid content of sheep tissues: the role of stearoyl-CoA desaturase.

Feeding sheep concentrate-based diets increases the oleic acid content of their tissues, whereas the cis-9, trans-11 conjugated linoleic acid (CLA) content is increased by feeding forage diets. Both these metabolic transformations could be attributable to increased activity of stearoyl-CoA desaturase (SCD). Therefore, the effect of forage or concentrate feeding regimens on the fatty acid composition of sheep tissues were investigated to determine whether any changes are related to an alteration of SCD mRNA levels. Twenty-four ewe lambs were randomly allotted to one of three dietary treatment groups: 1) dehydrated grass pellets, 2) concentrate diet fed to achieve a growth rate similar to that of the dehydrated grass pellets, and 3) the same concentrate diet approaching ad libitum intake. As expected, animals fed ad libitum concentrates grew at a greater (P = 0.001) rate (280 g/d) than those fed either of the other two diets (180 g/d), which were similar. In samples of liver and the three adipose tissue depots studied, the concentration of oleic acid from sheep fed either level of the concentrate diet was greater (P < 0.001) than from animals fed forage. This was associated with an increase (P < 0.05) in the ratio of SCD to acetyl-CoA carboxylase mRNA in adipose tissue and liver. Compared with concentrate-fed, the forage-fed lambs had increased (P < 0.05) levels of the cis-9, trans-11 isomer of CLA and C18:1, trans-11 in all their tissues, although the levels of SCD mRNA were lower. It therefore seems that the increased oleic acid content of sheep tissues in response to concentrate-rich diets is associated with an increase in SCD gene expression. By contrast, the increased concentration of CLA in animals fed forage-based diets is associated with an increase in substrate (C18:1 trans-11) availability.

Abomasum↗

PubMed2001

Calpastatin expression in porcine cardiac and skeletal muscle and partial gene structure.

The expression in porcine skeletal and cardiac muscle of calpastatin, the specific endogenous inhibitor of the calpain proteolytic system, was examined 16 h after a single dose of a specific beta(2)-agonist. Immunoblotting of extracts indicated that treatment increased skeletal calpastatin 135-kDa band intensity (P < 0.01), while in cardiac combined 145- and 135-kDa band intensity decreased (P < 0.05). Treatment increased skeletal (P < 0.01) but not cardiac calpastatin mRNA steady-state levels. Three types of cardiac calpastatin mRNA transcripts were identified by 5'-RACE. Types I and II encoded a putative XL region that originated either from exon 1x(A) or exon 1x(B), arranged in tandem. Type III predominated in skeletal muscle and originated from exon 1u, which was located 40-50 kb 3' to exons 1x(A) and 1x(B). The region 5' to exon 1u may act as an independent promoter regulated by a cAMP-dependent mechanisms, thereby explaining the differential response of calpastatin to adrenergic stimulation in cardiac and skeletal muscle.

5' Flanking Region↗

PubMed2001

Effects of EGF receptor ligands on fetal ovine myoblasts.

Epidermal growth factor (EGF) receptors are widely distributed in mammalian tissues, including muscle. One ligand of these receptors, heparin-binding epidermal growth factor-like growth factor (HB-EGF) is also strongly expressed in adult muscle. However, in vitro studies of EGF action in cultured muscle cells of different species have yielded conflicting results. The purpose of this study was to investigate the potential role of EGF and related factors in the growth and development of fetal ovine muscle. High affinity EGF receptors were detected on clonally purified ovine fetal myoblasts, using [(125)I] human EGF as a ligand (K(d) values of 47 and 54 pM in separate experiments). Competitive binding studies in mixed secondary cultures showed that EGF had the highest affinity for the fetal ovine receptor, followed by HB-EGF and transforming growth factor alpha (TGF-alpha). These ligands all stimulated DNA synthesis in clonally purified ovine myoblasts, with their relative potencies at 0.1 nM reflecting their receptor binding affinities. Maximal effects were seen at 1-10 nM. EGF (10 nM) did not significantly inhibit the differentiation of clonally purified fetal ovine myoblasts, although there was increased proliferation of nondifferentiating cells. Hence a variety of EGF receptor ligands have the potential to influence the proliferation ovine muscle cell precursors in utero, but it is unlikely that they promote differentiation.

Animals↗

PubMed2001

In vivo measurement of lipogenesis in ruminants using [1-(14)C]acetate.

A method for the measurement of the rate of lipogenesis in ruminants using a continuous intravenous infusion of [1-(14)C]acetate and measuring the rate of [1-(14)C]acetate incorporation into adipose tissue lipid was evaluated. Subcutaneous adipose tissue samples obtained by biopsy over the course of a 6 h continuous intravenous infusion of [1-(14)C]acetate into a wether and a steer maintained in a 'metabolic steady state' demonstrated that the incorporation of [1-(14)C]acetate into subcutaneous adipose tissue lipid was linear for the duration of the infusion period. Subsequent measures of rates of [1-(14)C]acetate incorporation into adipose tissue lipid were made on adipose tissue samples taken at a single time point during the infusion period. The technique was used to measure rates of lipogenesis in the subcutaneous adipose tissue of fourteen Hereford x Friesian steers that had been fed a pelleted diet of dried grass at a range of metabolizable energy (ME) intakes from 1.1 x ME requirement for maintenance to ad libitum for 11 weeks. Rates of lipogenesis increased linearly with increasing ME intake. It was concluded that the method is an effective technique for measuring rates of lipogenesis in specific adipose tissue depots in vivo in ruminants.

Acetates↗

PubMed2000

Effects of epinephrine infusion on expression of calpastatin in porcine cardiac and skeletal muscle.

beta-Adrenergic agonists induce muscle hypertrophy in mammalian species and alter the extractable activity of calpain proteinase and its specific endogenous inhibitor calpastatin. The effects on skeletal and cardiac muscle calpastatin of continuously infusing a group of pigs for 7 days with the physiological agonist epinephrine (0.15 microg/kg/min) were examined and compared with a placebo group. Basal levels of extractable calpastatin activity were higher in cardiac than skeletal muscle and epinephrine infusion increased the extractable activity in both muscle types (P < 0.05). An anti-recombinant porcine calpastatin antiserum detected a 135-kDa band and a 145/135-kDa doublet on Western blots of skeletal and cardiac extracts, respectively. Epinephrine infusion increased the 135-kDa band in skeletal muscle (P < 0.05), while the ratio of 145/135 kDa in cardiac muscle was decreased (P < 0.05). From Northern blots, the patterns of calpastatin mRNA species were similar in the two muscle types, two major transcripts at 5.8 and 3. 2 kb in cardiac muscle, with equivalent bands in skeletal muscle of 5.4 and 2.8 kb. A faint 7.9-kb band was also detected in skeletal muscle. Epinephrine infusion had no effect on skeletal calpastatin mRNA but tended to increase the 5.8-kb mRNA in cardiac muscle (P = 0. 053). These data indicate a differential response of the two muscle types to mildly elevated plasma epinephrine concentration and the response to elevated epinephrine may be at the translational or posttranslational level. Therefore, this type of stimulus appears to be less effective at perturbing calpastatin gene transcription than certain orally administered synthetic beta-adrenergic agonists.

Animals↗

PubMed2000

Effects of gastric inhibitory polypeptide, somatostatin and epidermal growth factor on lipogenesis in ovine adipose explants.

Feeding raises the plasma concentrations of a number of gut-related hormones that may, in turn, influence the metabolism of peripheral tissues. This study investigated the effects of gut-related hormones on lipogenesis in explants from three differing adipose depots in lambs (aged 4-9 months). Incorporation of [14C]-acetate into lipid was measured over a 2-h period, following 24 h pre-incubation in the presence of hormone combinations. In perirenal fat explants, gastric inhibitory polypeptide (GIP) in the concentration range 0.01-10 nM stimulated lipogenesis. Maximal effects were seen at 1 nM (an average increase of 64% over basal values). In contrast, in the presence of insulin (0.1 nM), a dose-dependent decrease in lipogenesis was seen with increasing GIP concentration (P < 0.001 for the insulin x GIP interaction). Epidermal growth factor (EGF) and somatostatin in the same concentration range each inhibited lipogenesis. both in the presence and the absence of insulin (P < 0.001 in each case). Subcutaneous (back) fat and intermuscular (popliteal) fat responded similarly to each other, but significantly differently from the perirenal depot (P < 0.001). Here GIP, somatostatin or EGF (each at 1 nM) all separately stimulated lipogenesis.

Adipose Tissue↗

PubMed2000

Maternal nutrition alters the expression of insulin-like growth factors in fetal sheep liver and skeletal muscle.

We investigated the influence of maternal dietary restriction between days 28 and 80 of gestation followed by re-feeding to the intake of well-fed ewes up to 140 days of gestation (term is 147 days) in sheep, on expression of mRNA for insulin-like growth factor (IGF)-I, IGF-II and growth hormone receptor (GHR) in fetal liver and skeletal muscle. Singleton bearing ewes either consumed 3.2-3.8 MJ/day of metabolisable energy (ME) (i.e. nutrient restricted - approximately 60% of ME requirements, taking into account requirements for both ewe maintenance and growth of the conceptus) or 8.7-9.9 MJ/day (i.e. well fed - approximately 150% of ME requirements) between days 28 and 80 of gestation. All ewes were then well fed (150% of ME requirements) up to day 140 of gestation and consumed 8-10.9 MJ/day. At days 80 and 140 of gestation, five ewes were sampled from each group and fetal tissues taken. There was no difference in fetal body weight or liver weights between groups at either sampling date, or skeletal muscle (quadriceps) weight at 140 days. IGF-I mRNA abundance was lower in livers of nutrient-restricted fetuses at day 80 of gestation (nutrient restricted 2.35; well fed 3.70 arbitrary units), but was higher than well-fed fetuses at day 140 of gestation, after 60 days of re-feeding (restricted/re-fed 4.27; well fed 2.83;s.e.d. 0.98 arbitrary units, P=0.061 for dietxage interaction). IGF-II mRNA abundance was consistently higher in livers of nutrient-restricted fetuses (80 days: nutrient restricted 7.78; well fed 5.91; 140 days: restricted/re-fed 7.23; well fed 6.01;s.e.d. 1.09 arbitrary units, P=0.061 for diet). Nutrient restriction had no effect on hepatic GHR mRNA abundance, but re-feeding of previously nutrient-restricted fetuses increased GHR mRNA compared with continuously well-fed fetuses (80 days: nutrient restricted 70.6; well fed 75.1; 140 days: restricted/re-fed 115.7; well fed 89.4;s.e.d. 10.13 arbitrary units, P=0.047 for dietxage interaction). In fetal skeletal muscle, IGF-I mRNA abundance was not influenced by maternal nutrition and decreased with gestation age (P<0.01). IGF-II mRNA abundance was higher in skeletal muscle of nutrient-restricted fetuses compared with well-fed fetuses at day 80 of gestation (nutrient restricted 16.72; well fed 10.53 arbitrary units), but was lower than well-fed fetuses after 60 days of re-feeding (restricted/re-fed 7.77; well fed 13.72;s.e.d. 1.98 arbitrary units, P<0.001 for dietxage interaction). There was no effect of maternal nutrition or gestation age on fetal skeletal muscle GHR expression. In conclusion, maternal nutrient restriction in early to mid gestation with re-feeding thereafter results in alterations in hepatic and skeletal muscle expression of IGF-I, IGF-II and/or GHR in the fetus which may subsequently relate to altered organ and tissue function.

Analysis of Variance↗

PubMed2000

Ovine adipose tissue monounsaturated fat content is correlated to depot-specific expression of the stearoyl-CoA desaturase gene.

The basis for the variation in fatty acid composition in different ovine adipose tissue depots was investigated. The proportion of stearic (C18:0) and oleic (C18:1) acids vary in a site-specific fashion; abdominal depots (omental and perirenal) contain relatively more C18:0 than C18:1, and carcass depots, especially sternum, have a markedly higher proportion of C18:1. Additionally, expression of a number of lipogenic enzyme genes (stearoyl-CoA desaturase [SCD], acetyl-CoA carboxylase-alpha [ACC-alpha], lipoprotein lipase [LPL]) and the cytoskeletal protein gene alpha-tubulin vary among depots, although the pattern of variation differs for each mRNA. When these expression data were related to the mean cell volume of adipocytes pooled from all depots, a significant pattern emerged: expression of the ACC-alpha, LPL, and alpha-tubulin genes was highly correlated with the size of adipocytes. In contrast, when the expression of SCD mRNA was assessed as a function of mean cell volume, two populations of adipocytes emerged: no significant correlation was found between the expression of SCD mRNA per adipocyte and mean cell volume for the abdominal depots, although a highly significant correlation was observed between SCD gene expression and mean cell volume for the carcass and epicardial depots. Similarly, a highly significant correlation was found for the amount of C18:1 per adipocyte and the abundance of SCD mRNA per adipocyte for the carcass and epicardial depots, whereas no significant correlation was observed for these traits for the omental and perirenal depots. Thus, the SCD gene seems to be regulated in a depot-specific fashion and in a manner distinct from that of the ACC and LPL genes.

Acetyl-CoA Carboxylase↗

PubMed1999

Effect of gastric inhibitory polypeptide on bovine fat metabolism.

Gastric inhibitory polypeptide (GIP), a hormone secreted by the gastrointestinal tract in response to nutrient absorption, exerts anabolic effects on adipose tissue in some species. Cattle fed on grass silage diets tend to deposit more fat than animals fed on dried forages. We investigated the effect of diet on blood GIP concentrations in cattle. Plasma concentrations tended to be higher in cattle fed grass silage alone or supplemented with fishmeal (0.61 ng/ml) compared with animals fed dried grass/barley (0.43 ng/ml, P > 0.1) and were inversely correlated with plasma insulin concentrations (r = -0.727, P < 0.01). The effects of increasing concentrations (0, 0.1, 1.0, 10.0 nM) of GIP and glucagon-like peptide-1 (GLP-1) on basal and insulin-stimulated lipogenesis in bovine adipose tissue in vitro were investigated after 4 and 24 h of incubation. No conclusive effects were obtained with either peptide. Subsequently, the effect of exogenous administration of GIP (10 or 50 ng/kg liveweight per min) on whole-body fat metabolism was investigated in two steers in vivo. Plasma concentration and flux rate of palmitate was increased by GIP only at the higher infusion level suggesting lipolysis and possibly fatty acid re-esterification was stimulated at high concentration. We conclude that although gut peptides may regulate nutrient utilisation, it is unlikely that they play a major role in promoting fat accretion in cattle. However, the small number of animals used in these studies indicates the need for caution and further studies are warranted.

Adipose Tissue↗

PubMed1999

Fibre type-specific expression of p94, a skeletal muscle-specific calpain.

Members of the calpain proteinase family are present in all mammalian cells, although a novel calpain 94 kDa isoform is found almost exclusively in skeletal muscle. p94 is difficult to purify from muscle and recombinant p94 autolyses rapidly when expressed in COS cells. However, in vivo the enzyme may be stabilised by interaction with titin, which has two well-characterised binding sites for p94 at the N2- and M-lines. Both these titin subdomains are subject to muscle-specific alternative splicing, which could be related to p94 expression level or stability in muscles of different fibre type. In this study, porcine longissimus dorsi (LD), trapezius (TZ) and adductor longus (AL) were characterised as fast, intermediate and slow using commercially available specific anti-human fast- and slow-myosin heavy chain mAbs and also by conventional histochemistry. p94 was quantified both in whole muscle preparations and single fibres by western blotting using an anti-p94 antiserum generated by expressing a recombinant p94 sequence as a GST fusion protein antigen. SDS PAGE and immunoblotting revealed a single band of approximately 94 kDa with identical mobility in all muscle and fibre preparations. The intensity of the 94 kDa band was greater in LD (22 +/- 1.7 densitometric units mean +/- SEM, n = 3) than TZ and AL (10 +/- 2.3 and 6 +/- 0.9 units, respectively). Expressed as a ratio relative to actin immunoreactivity, p94 is present in all types of single fibres isolated from TZ, but at a significantly lower level (P < 0.01) in slow type I (0.08 +/- 0.01, n = 9), compared to fast IIA/IIB fibres (0.22 +/- 0.02, n = 26). No evidence was seen for rapid or variable rate of p94 degradation in either type of fibre. These data suggest a positive correlation between p94 expression level and fast glycolytic characteristics in porcine muscle.

Animals↗

PubMed1999

Glucose and amino acids interact with hormones to control expression of insulin-like growth factor-I and growth hormone receptor mRNA in cultured pig hepatocytes.

Nutrients and hormones are major determinants of animal growth, but the mechanisms of how nutrients influence the growth process are still unclear. A primary pig hepatocyte culture system was used to investigate possible direct effects of glucose and individual amino acids on the expression of growth hormone receptor (GHR) and insulin-like growth factor-I (IGF-I) mRNA. The removal of glucose from the culture medium for 40 h resulted in significant reductions (to 45% of control, P = 0.013) in the expression of GHR in the presence of growth hormone (GH), dexamethasone (DEX) and tri-iodothyronine (T3). The decrease in GHR expression with removal of glucose from the culture medium resulted in a decreased response in class 1 (22% of control, P = 0.011) and 2 (5% of control P = 0. 068) transcripts of IGF-I to any GH added. The effects of glucose on GHR and IGF-I expression were dose-dependent, appearing to plateau at approximately 1-2 g/L (P = 0.031, for quadratic trend). Removal of arginine, proline, threonine, tryptophan or valine inhibited the stimulation of IGF-I expression that was induced by the combination of T3, DEX and GH (to 15, 6, 11, 16 and 16% of control, respectively, P < 0.05), with significant decreases in GHR expression also observed in some cases. The stimulatory effect of some of these amino acids (arginine, proline, threonine and tryptophan) was dose-dependent for expression of class 1 transcripts of IGF-I (P = 0. 041, 0.022, 0.016 and 0.097, respectively, for linear trends), but there was no effect on GHR or class 2 transcripts of IGF-I. Whether the observed effects of nutrients on mRNA levels are due to direct effects on gene transcription or differences in mRNA stability remains to be established. Energy, in the form of glucose, appears to control GHR expression, interacting with the effects of glucocorticoids and thyroid hormones, whereas protein, in the form of certain individual amino acids, appears to control GH-stimulated IGF-I expression.

Amino Acids↗

PubMed1999

Altered calpain levels in longissimus muscle from normal pigs and heterozygotes with the ryanodine receptor mutation.

The calpain proteolytic system was examined in the longissimus muscle (LD) of heterozygote pigs carrying a single copy of a mutation in the skeletal muscle ryanodine receptor gene (RyR1) that is associated with porcine stress syndrome and reduced meat quality. Conventional British White-type pigs (n = 30) were selected from a commercial line on the basis of slaughter weight, backfat depth, and pH at 45 min postmortem > 6.0; based on DNA analysis, 11 were heterozygous RyR1 mutants (Nn), and 19 were normal genotype (NN). The LD samples were taken from carcasses at 2, 4, and 24 h postmortem for calpain analysis with enzyme assay and immunoblotting, using specific antisera raised against recombinant polypeptides derived from calpain large subunits and calpastatin. Shear force (SF) was measured after conditioning for 8 d at 2 degrees C and did not differ between Nn and NN groups. The extractable activity of mu-calpain decreased over 24 h postmortem (P < .001), with no significant difference in activity between NN and Nn animals at any time. The activity of m-calpain also decreased with time (P < .001), but it was lower at all times in Nn than in normal genotypes (P < .001). After Western blotting, the immunoreactivity of mu- and m-calpain large subunit bands declined over 24 h postmortem (P < .001); values for mu-calpain were higher (P < .05) and for m-calpain were lower (P < .001) in heterozygotes than in normal animals at each sampling time. The calpastatin antibody detected a major band of 135 kDa that declined with time postmortem but did not differ between Nn and NN genotypes at any sampling time. These data indicate that the levels of extractable mu- and m-calpain, but not calpastatin, may be different in pigs that carry the RyR1 mutation.

Animals↗