TY - JOUR
AU - Berri, C.
AB - ABSTRACT The present study was aimed at evaluating the molecular mechanisms associated with the differences in muscle glycogen content and breast meat quality between 2 experimental lines of chicken divergently selected on abdominal fatness. The glycogen at death (estimated through the glycolytic potential) of the pectoralis major muscle and the quality of the resulting meat were estimated in the 2 lines. The fat chickens exhibited greater glycolytic potential, and in turn lower ultimate pH than the lean chickens. Consequently, the breast meat of fat birds was paler and less colored (i.e., less red and yellow), and exhibited greater drip loss compared with that of lean birds. In relation to these variations, transcription and activation levels of adenosine monophosphate-activated protein kinase (AMPK) were investigated. The main difference observed between lines was a 3-fold greater level of AMPK activation, evaluated through phosphorylation of AMPKα-(Thr172), in the muscle of lean birds. At the transcriptional level, data indicated concomitant down- and upregulation for the γ1 and γ2 AMPK subunit isoforms, respectively, in the muscle of lean chickens. Transcriptional levels of enzymes directly involved in glycogen turnover were also investigated. Data showed greater gene expression for glycogen synthase, glycogen phosphorylase, and the γ subunit of phosphorylase kinase in lean birds. Together, these data indicate that selection on body fatness in chicken alters the muscle glycogen turnover and content and consequently the quality traits of the resulting meat. Alterations of AMPK activity could play a key role in these changes. INTRODUCTION With changes similar to those that occurred in the swine industry, the poultry market is now characterized by an increasing diversity of further processed products (Mead, 2004), and the improvement of meat processing ability has become a prevalent concern for meat companies. In both species, postmortem pH appears to be a key factor controlling poultry meat quality. In chickens as in pigs, stress and behavioral activity before slaughter are largely involved in the variations of pH in the early stages of rigor (Debut et al., 2003). The final pH of meat depends on the muscle glycogen content at the time of slaughter (Berri et al., 2005, 2007). Several studies highlighted the major role of the adenosine monophosphate (AMP)-activated protein kinase (AMPK) in regulating the level of muscle glycogen (Carling and Hardie, 1989; Jørgensen et al., 2004; Figure 1) and postmortem metabolism (Scheffler and Gerrard, 2007). Figure 1. View largeDownload slide Function of studied enzymes in the regulation of muscle glycogen metabolism. AMPK = adenosine monophosphate-activated protein kinase; GSK3 = glycogen synthase kinase; PHK = phosphorylase kinase; GYS = glycogen synthase; PYG = glycogen phosphorylase. Figure 1. View largeDownload slide Function of studied enzymes in the regulation of muscle glycogen metabolism. AMPK = adenosine monophosphate-activated protein kinase; GSK3 = glycogen synthase kinase; PHK = phosphorylase kinase; GYS = glycogen synthase; PYG = glycogen phosphorylase. In the present study, we compared the muscle glycogen content and breast meat quality traits from 2 experimental chicken lines divergently selected for abdominal fatness (i.e., fat and lean lines; Leclercq et al., 1980). To evaluate the possible role of AMPK to explain variations in pectoralis major (P. major) muscle glycogen content observed between the fat and lean lines, we characterized the mRNA expression of the PRKA genes (coding for the catalytic α, regulatory β and γ AMPK subunits) by quantitative reverse transcription PCR. In addition, we evaluated the level of AMPK activation by performing immunoblotting with a phospho-specific antibody. We also determined the gene expression of several enzymes directly involved in glycogen synthesis and degradation (Figure 1); that is, glycogen synthase (GYS), glycogen phosphorylase (PYG), and their upstream kinases glycogen synthase kinase 3 (GSK3) and phosphorylase kinase (PHK; composed of one catalytic subunit γ and 3 regulatory subunits α, β, and δ that inhibit the phosphotransferase activity of the γ subunit). MATERIALS AND METHODS All animal procedures and care were performed with due regard to legislation governing ethical treatments of animals. Principal investigators were certified by the French government to experiment on live animals. Birds The chickens originated from 2 experimental lines divergently selected for high abdominal fatness (fat line) or low abdominal fatness (lean line) at 9 wk of age (Leclercq et al., 1980). They were reared under similar conditions in a conventional poultry house at the INRA experimental poultry unit (UE1295, Nouzilly, France). They were given ad libitum access to standard diets throughout the growth period. At 9 wk of age, the birds were individually weighed 1 d before slaughter. After 7 h of feed withdrawal, 60 male birds in each line were slaughtered at the experimental processing plant (UE1295, Nouzilly, France). Before killing by ventral neck cutting, the birds were stunned in a waterbath (125 Hz AC, 80 mA/bird, 5 s). After evisceration, whole carcasses were air chilled (airflow of 7 m3) and stored at 2°C until the next day. Glycolytic potential (GP) and lipid content of P. major were determined on 12 birds per line selected at random. Tissue for RNA extraction and protein solubilization were collected 15 min postmortem from 9 chickens per line (issued from the 12 individuals assayed for GP and lipid measurements) and immediately frozen in liquid nitrogen. Muscle and Meat Characteristics Muscle glycogen, glucose-6-phosphate, free glucose, and lactate were measured in P. major from 12 individuals per line according to Dalrymple and Hamm (1973), from 1 g of frozen tissue. Glycolytic potential takes into account the main intermediates of glycogen degradation in live and postmortem muscle and therefore represents an estimate of the resting glycogen content (Monin and Sellier, 1985); it was calculated as follows:  \begin{eqnarray*}&&GP\ =\ 2[(glycogen)\ +\ (glucose)\\&&+\ (glucose-6-phosphate)]\ +\ (lactate),\end{eqnarray*} and was expressed as micromoles of lactate equivalent per gram of fresh tissue. On the same individuals, the P. major total lipids were extracted quantitatively by homogenizing a sample of minced tissue in chloroform/methanol 2:1 (vol/vol) and then quantified gravimetrically (Folch et al., 1957). All carcasses were processed 1 d after slaughter. Abdominal fat and pectoral muscles (P. major and P. minor) were removed and weighed. Abdominal fat and breast yields were calculated and expressed as percentage of BW. The ultimate pH (pHu) of the P. major muscle of all carcasses was measured at 24 h postmortem by direct insertion of an electrode (pH meter Model 506, Crison Instruments, Barcelona, Spain) into the muscle. At the same time, breast color was measured on the rostral, ventral side of the P. major muscle by using a Miniscan Spectrocolorimeter (Hunter Lab, Reston, VA). Color was measured by the CIELAB trichromatic system as lightness (L*), redness (a*), and yellowness (b*) values. The water-holding capacity of meat was estimated by measuring drip loss of the raw meat after storage. The breast P. major muscle was weighed 24 h postmortem and immediately placed in a plastic bag, hung from a hook, and stored at 2°C for 48 h. After hanging, the sample was wiped with absorbent paper and weighed again. The difference in weight corresponded to the drip loss and was expressed as the percentage of the initial muscle weight. RNA Isolation and Reverse Transcription PCR Total RNA was extracted using a commercial kit (RNA Now, Ozyme, Saint Quentin Yvelynes, France) according to Chomczynski and Sacchi (1987). Concentrations of RNA were measured by spectrophotometry (optical density at 260 nm) using a NanoDrop ND-1000 (NanoDrop Technologies LLC, Wilmington, DE) and their integrity was checked by electrophoresis. After DNase treatment (using Ambion's DNA-Free 1906 kit obtained from Clinisciences, Montrouge, France), total RNA (5 μg) was reverse transcribed using RNase H− MMLV reverse transcriptase (Superscript II, Invitrogen, Illkirch, France) and random primers (Promega, Charbonnières les Bains, France). Determination of mRNA Levels by Real-Time Reverse Transcription PCR After reverse transcription, the cDNA of PRKA subunits (α1, α2, β1, β2, γ1, γ2, and γ3), GYS, PYG, GSK3, and PHK subunits (α, β, δ, and γ) were amplified in real-time using an ABI PRISM 7000 apparatus (Applied Biosystems, Courtaboeuf, France) with the SYBR Green I qPCR Master Mix Plus (Eurogentec, Angers, France). The 18S ribosomal RNA (18S rRNA) chosen as a reference was determined with the TaqMan Universal qPCR Master Mix Kit and a predeveloped Taqman assay reagent (Applied Biosystems). For each gene, specific primers were designed from the corresponding chicken sequence to be intron-spanning to avoid coamplification of genomic DNA (Table 1) and were obtained from Eurogentec. The cycling conditions consisted of a denaturation step at 95°C for 10 min, followed by a 2-step amplification program (15 s at 95°C, followed by 1 min at 62°C or 64°C for PRKA β2 and γ 1) repeated 40 times. At the end, a dissociation program consisting of 15 s at 95°C, 20 s at 62°C or 64°C, and 15 s at 95°C was performed. The amplification products for all cDNA were checked by electrophoresis and exhibited the expected size (Table 1). Their sequences were also checked. For each individual sample (n = 9 per line), the cDNA of genes under study were amplified in triplicate in the same run. Each PCR run included a no-template control and triplicates of control; that is, a pool of all cDNA and unknown samples. To confirm the precision and the reproducibility of real-time PCR, intraassay variations were evaluated and found to be between 0.08 and 1.18% (CV) according to the gene. The calculation of absolute mRNA levels was based on the PCR efficiency and the threshold cycle deviation of an unknown cDNA vs. the control cDNA according to the equation proposed by Pfaffl (2001) and as described in Guernec et al. (2003). Absolute mRNA levels were corrected for 18S rRNA to give relative levels. Table 1. Oligonucleotide primer sequences1 Primer2    Sequence  Accession number  Product size, bp  PRKA α1  Sense  5′ CGG CAG ATA AAC AGA AGC ACG AG 3′  NM_001039603  148    Antisense  5′ CGA TTC AGG ATC TTC ACT GCA AC 3′      PRKA α2  Sense  5′ CAT GGA CGT GTT GAA GAG GCA G 3′  NM_001039605  110    Antisense  5′ TTC TCT GGT TTC AGG TCC CTG TGG 3′      PRKA β1  Sense  5′ TAA AAC CCC CAC TCA AGC TCG ACC 3′  NM_001039912  187    Antisense  5′ CCA CTG CCC ATC CAC AAA GAA C 3′      PRKA β2  Sense  5′ CAC GTC ATG CTC AAT CAC CTC TAC 3′  NM_001044662  168    Antisense  5′ CAG ACA AAG TGG TGT TTC GTG TCC 3′      PRKA γ1  Sense  5′ AGA AGG CTT TCT TTG CAC TGG TC 3′  NM_001034827  186    Antisense  5′ CGT CTC GAT TTT GTG CTC CTC C 3′      PRKA γ2  Sense  5′ ATC ACG GTG ACA CAA GCC CTA C 3′  NM_001030965  147    Antisense  5′ GCT ATC TGC TTC ATT CAC TAC CAC C 3′      PRKA γ3  Sense  5′ CCG ACA ACA ATT TCC AGA GCC 3′  NM_001031258  192    Antisense  5′ TCT GCA TCT TGC TGT CCC ACA G 3′      GYS  Sense  5′ GCC TCA ACG TCC GCA AGT T 3′  AB090806  148    Antisense  5′ CCC GCG ATG AAG AAG AAG AG 3′      PYG  Sense  5′ GAA GCA GGC AGT TGA CCA GAT 3′  NM_204392  101    Antisense  5′ TAA ACC GGT CGT GAT GGA AGA 3′      GSK3  Sense  5′ AGC TGT TCC GGA GTT TAG CCT AT 3′  NC_006088  151    Antisense  5′ ACG TTA GGT TCT CCA CGA ACC A 3′      PHK α  Sense  5′ GGC ACT CGA CAG CAA GAT GAT TG 3′  NC_006091  154    Antisense  5′ CTA TTC TCC CAC AGA GGA AGT TGG 3′      PHK β  Sense  5′ GCT TAA CCG ACG ACA AAT AGA TGG 3′  NM_001007831  148    Antisense  5′ CGT CAT ATC CGA TAA GGT TGG TTG 3′      PHK δ  Sense  5′ CCC CAC AGA AGC AGA ATT ACA GG 3′  NM_001110364  161    Antisense  5′ CAT CCT TGT CAA ACA CAC GGA AC 3′      PHK γ  Sense  5′ ATT GGC ACA CCC CTT CTT CCA G 3′  NM_001006217  124    Antisense  5′ GCG GTA CTG GTA GTA AAT GCG G 3′      Primer2    Sequence  Accession number  Product size, bp  PRKA α1  Sense  5′ CGG CAG ATA AAC AGA AGC ACG AG 3′  NM_001039603  148    Antisense  5′ CGA TTC AGG ATC TTC ACT GCA AC 3′      PRKA α2  Sense  5′ CAT GGA CGT GTT GAA GAG GCA G 3′  NM_001039605  110    Antisense  5′ TTC TCT GGT TTC AGG TCC CTG TGG 3′      PRKA β1  Sense  5′ TAA AAC CCC CAC TCA AGC TCG ACC 3′  NM_001039912  187    Antisense  5′ CCA CTG CCC ATC CAC AAA GAA C 3′      PRKA β2  Sense  5′ CAC GTC ATG CTC AAT CAC CTC TAC 3′  NM_001044662  168    Antisense  5′ CAG ACA AAG TGG TGT TTC GTG TCC 3′      PRKA γ1  Sense  5′ AGA AGG CTT TCT TTG CAC TGG TC 3′  NM_001034827  186    Antisense  5′ CGT CTC GAT TTT GTG CTC CTC C 3′      PRKA γ2  Sense  5′ ATC ACG GTG ACA CAA GCC CTA C 3′  NM_001030965  147    Antisense  5′ GCT ATC TGC TTC ATT CAC TAC CAC C 3′      PRKA γ3  Sense  5′ CCG ACA ACA ATT TCC AGA GCC 3′  NM_001031258  192    Antisense  5′ TCT GCA TCT TGC TGT CCC ACA G 3′      GYS  Sense  5′ GCC TCA ACG TCC GCA AGT T 3′  AB090806  148    Antisense  5′ CCC GCG ATG AAG AAG AAG AG 3′      PYG  Sense  5′ GAA GCA GGC AGT TGA CCA GAT 3′  NM_204392  101    Antisense  5′ TAA ACC GGT CGT GAT GGA AGA 3′      GSK3  Sense  5′ AGC TGT TCC GGA GTT TAG CCT AT 3′  NC_006088  151    Antisense  5′ ACG TTA GGT TCT CCA CGA ACC A 3′      PHK α  Sense  5′ GGC ACT CGA CAG CAA GAT GAT TG 3′  NC_006091  154    Antisense  5′ CTA TTC TCC CAC AGA GGA AGT TGG 3′      PHK β  Sense  5′ GCT TAA CCG ACG ACA AAT AGA TGG 3′  NM_001007831  148    Antisense  5′ CGT CAT ATC CGA TAA GGT TGG TTG 3′      PHK δ  Sense  5′ CCC CAC AGA AGC AGA ATT ACA GG 3′  NM_001110364  161    Antisense  5′ CAT CCT TGT CAA ACA CAC GGA AC 3′      PHK γ  Sense  5′ ATT GGC ACA CCC CTT CTT CCA G 3′  NM_001006217  124    Antisense  5′ GCG GTA CTG GTA GTA AAT GCG G 3′      1 All primers were designed from chicken sequences using the software MacVector 4.1.3 (http://www.macvector.com/). 2 PRKA = adenosine monophosphate-activated protein kinase (also called AMPK); GYS = glycogen synthase; PYG = glycogen phosphorylase; GSK3 = glycogen synthase kinase; PHK = phosphorylase kinase. View Large Table 1. Oligonucleotide primer sequences1 Primer2    Sequence  Accession number  Product size, bp  PRKA α1  Sense  5′ CGG CAG ATA AAC AGA AGC ACG AG 3′  NM_001039603  148    Antisense  5′ CGA TTC AGG ATC TTC ACT GCA AC 3′      PRKA α2  Sense  5′ CAT GGA CGT GTT GAA GAG GCA G 3′  NM_001039605  110    Antisense  5′ TTC TCT GGT TTC AGG TCC CTG TGG 3′      PRKA β1  Sense  5′ TAA AAC CCC CAC TCA AGC TCG ACC 3′  NM_001039912  187    Antisense  5′ CCA CTG CCC ATC CAC AAA GAA C 3′      PRKA β2  Sense  5′ CAC GTC ATG CTC AAT CAC CTC TAC 3′  NM_001044662  168    Antisense  5′ CAG ACA AAG TGG TGT TTC GTG TCC 3′      PRKA γ1  Sense  5′ AGA AGG CTT TCT TTG CAC TGG TC 3′  NM_001034827  186    Antisense  5′ CGT CTC GAT TTT GTG CTC CTC C 3′      PRKA γ2  Sense  5′ ATC ACG GTG ACA CAA GCC CTA C 3′  NM_001030965  147    Antisense  5′ GCT ATC TGC TTC ATT CAC TAC CAC C 3′      PRKA γ3  Sense  5′ CCG ACA ACA ATT TCC AGA GCC 3′  NM_001031258  192    Antisense  5′ TCT GCA TCT TGC TGT CCC ACA G 3′      GYS  Sense  5′ GCC TCA ACG TCC GCA AGT T 3′  AB090806  148    Antisense  5′ CCC GCG ATG AAG AAG AAG AG 3′      PYG  Sense  5′ GAA GCA GGC AGT TGA CCA GAT 3′  NM_204392  101    Antisense  5′ TAA ACC GGT CGT GAT GGA AGA 3′      GSK3  Sense  5′ AGC TGT TCC GGA GTT TAG CCT AT 3′  NC_006088  151    Antisense  5′ ACG TTA GGT TCT CCA CGA ACC A 3′      PHK α  Sense  5′ GGC ACT CGA CAG CAA GAT GAT TG 3′  NC_006091  154    Antisense  5′ CTA TTC TCC CAC AGA GGA AGT TGG 3′      PHK β  Sense  5′ GCT TAA CCG ACG ACA AAT AGA TGG 3′  NM_001007831  148    Antisense  5′ CGT CAT ATC CGA TAA GGT TGG TTG 3′      PHK δ  Sense  5′ CCC CAC AGA AGC AGA ATT ACA GG 3′  NM_001110364  161    Antisense  5′ CAT CCT TGT CAA ACA CAC GGA AC 3′      PHK γ  Sense  5′ ATT GGC ACA CCC CTT CTT CCA G 3′  NM_001006217  124    Antisense  5′ GCG GTA CTG GTA GTA AAT GCG G 3′      Primer2    Sequence  Accession number  Product size, bp  PRKA α1  Sense  5′ CGG CAG ATA AAC AGA AGC ACG AG 3′  NM_001039603  148    Antisense  5′ CGA TTC AGG ATC TTC ACT GCA AC 3′      PRKA α2  Sense  5′ CAT GGA CGT GTT GAA GAG GCA G 3′  NM_001039605  110    Antisense  5′ TTC TCT GGT TTC AGG TCC CTG TGG 3′      PRKA β1  Sense  5′ TAA AAC CCC CAC TCA AGC TCG ACC 3′  NM_001039912  187    Antisense  5′ CCA CTG CCC ATC CAC AAA GAA C 3′      PRKA β2  Sense  5′ CAC GTC ATG CTC AAT CAC CTC TAC 3′  NM_001044662  168    Antisense  5′ CAG ACA AAG TGG TGT TTC GTG TCC 3′      PRKA γ1  Sense  5′ AGA AGG CTT TCT TTG CAC TGG TC 3′  NM_001034827  186    Antisense  5′ CGT CTC GAT TTT GTG CTC CTC C 3′      PRKA γ2  Sense  5′ ATC ACG GTG ACA CAA GCC CTA C 3′  NM_001030965  147    Antisense  5′ GCT ATC TGC TTC ATT CAC TAC CAC C 3′      PRKA γ3  Sense  5′ CCG ACA ACA ATT TCC AGA GCC 3′  NM_001031258  192    Antisense  5′ TCT GCA TCT TGC TGT CCC ACA G 3′      GYS  Sense  5′ GCC TCA ACG TCC GCA AGT T 3′  AB090806  148    Antisense  5′ CCC GCG ATG AAG AAG AAG AG 3′      PYG  Sense  5′ GAA GCA GGC AGT TGA CCA GAT 3′  NM_204392  101    Antisense  5′ TAA ACC GGT CGT GAT GGA AGA 3′      GSK3  Sense  5′ AGC TGT TCC GGA GTT TAG CCT AT 3′  NC_006088  151    Antisense  5′ ACG TTA GGT TCT CCA CGA ACC A 3′      PHK α  Sense  5′ GGC ACT CGA CAG CAA GAT GAT TG 3′  NC_006091  154    Antisense  5′ CTA TTC TCC CAC AGA GGA AGT TGG 3′      PHK β  Sense  5′ GCT TAA CCG ACG ACA AAT AGA TGG 3′  NM_001007831  148    Antisense  5′ CGT CAT ATC CGA TAA GGT TGG TTG 3′      PHK δ  Sense  5′ CCC CAC AGA AGC AGA ATT ACA GG 3′  NM_001110364  161    Antisense  5′ CAT CCT TGT CAA ACA CAC GGA AC 3′      PHK γ  Sense  5′ ATT GGC ACA CCC CTT CTT CCA G 3′  NM_001006217  124    Antisense  5′ GCG GTA CTG GTA GTA AAT GCG G 3′      1 All primers were designed from chicken sequences using the software MacVector 4.1.3 (http://www.macvector.com/). 2 PRKA = adenosine monophosphate-activated protein kinase (also called AMPK); GYS = glycogen synthase; PYG = glycogen phosphorylase; GSK3 = glycogen synthase kinase; PHK = phosphorylase kinase. View Large Determination of AMPK Expression and Phosphorylation All chemicals were purchased from Sigma-Aldrich (Saint-Quentin-Fallavier, France) unless otherwise noted. Frozen tissues were ground in liquid nitrogen. Powdered muscles (300 mg) were homogenized on ice with a homogenizer (IKA T25 Ultra-Turrax, Fontenay-sous-Bois, France) in a buffer containing 150 mmol/L NaCl, 10 mmol/L Tris (hydroxymethyl) amino-methane (pH 7.4), 1 mmol/L EDTA, 1 mmol/L ethylene glycol-bis (β-aminoethyl ether)-N,N,N',N'-tetraacetic acid, 1% triton X-100, 0.5% NP-40, protease inhibitors (complete protease inhibitor cocktail, Roche, Meylan, France), and phosphatase inhibitors (100 mmol/L sodium fluoride, 10 mmol/L sodium phosphate, and 2 mmol/L sodium orthovanadate). Homogenates were centrifuged at 1,000 × g for 30 min at 4°C and supernatants were ultracentrifuged for 45 min at 150,000 × g. Supernatants were aliquoted and stored at −80°C. Protein concentrations were determined by the Bradford (1976) method using the Bio-Rad protein assay kit (Bio-Rad Laboratories, Marnes-la-Coquette, France). Muscle lysates (40 μg of protein) were subjected to 10% (wt/vol) SDS-PAGE under reducing conditions and electrotransferred as described previously (Duchêne et al., 2008). The membranes were then incubated overnight at 4°C with appropriate antibodies (see below) at a final dilution of 1:1,000 in Tris-buffered saline (2 mM Tris-HCl, pH 8, 15 mM NaCl, pH 7.6) containing 0.1% Tween-20 and 5% nonfat dry milk powder. Rabbit polyclonal antibodies to AMPKα1 and to phospho-AMPKα Thr172 were obtained from Upstate Biotechnology Inc. (Lake Placid, NY) and from New England Biolabs Inc. (Beverly, MA), respectively. Mouse monoclonal anti-human vinculin was purchased from Sigma-Aldrich (St. Louis, MO). After washing, the membranes were incubated with an Alexa Fluor secondary antibody (Molecular Probes, In-terchim, Montluçon, France). Bands were visualized by infrared fluorescence by the Odyssey Imaging System (Li-Cor Inc. Biotechnology, Lincoln, NE) and quantified by Odyssey infrared imaging system software (application software, version 1.2). Statistical Analysis All data were analyzed using SAS (SAS Inst. Inc., Cary, NC). The accepted type I error was 5%. The effects of line were analyzed by a 1-way ANOVA (GLM procedure). Comparisons of means for each significant effect were performed by Student-Newman-Keul's test using the SNK statement of the GLM procedure. To assess the relationships between muscle and meat traits, Pearson correlation coefficients were analyzed with the CORR procedure. RESULTS Characterization of Carcass, Muscle, and Meat Quality Traits in Lean and Fat Lines The carcass and P. major muscle trait means and corresponding SD for each line are presented in Table 2. At 9 wk of age, BW was greater (P ≤ 0.001) and breast yield less (P ≤ 0.001) in the fat than in the lean line. The abdominal fat weight and yield were, respectively, 2.9- and 2.8-fold greater (P ≤ 0.001) in fat birds than in lean birds. The lipid content of the P. major muscle was the same in both lines. In contrast, correlated responses to divergent selection for abdominal fatness were observed on breast meat traits. The fat chickens exhibited greater P. major muscle glycogen content (P ≤ 0.05) and GP (P ≤ 0.01) than the lean chickens. Moreover, the GP of P. major muscle was highly positively correlated with abdominal fat yield and negatively with breast yield (Table 3). The GP was also negatively correlated to pHu (Table 3). Therefore, in relation to its greater glycogen reserve at the time of death, the P. major muscle of fat birds was characterized by a lower pHu. In the same way, because of the correlations between muscle pHu and meat quality traits (Table 3), the color of breast meat was lighter (greater L*, P ≤ 0.001) and less red (lower a*, P ≤ 0.001) in fat chickens, which also exhibited greater drip loss (P ≤ 0.05). In addition, breast meat of fat chickens was characterized by lower values of yellowness (b*) in meat color (P ≤ 0.001). No difference in muscle lactate content at 15 min postmortem was observed between the fat and lean birds processed for quality measurements (data not shown). However, we noticed that lactate tended to be greater in lean than in fat birds assayed for AMPK protein (65.8 ± 5.2 and 54.1 ± 7.9, respectively; P ≤ 0.09, n = 6). Table 2. Body weight, yields, and pectoralis major muscle and meat quality traits of the lean and fat lines at 9 wk of age1 Item2  No. of chickens  Lean line  Fat line  Level of significance  BW, g  60  2,522 ± 25  2,627 ± 21  ***  Breast yield, % of BW  60  12.76 ± 0.12  11.51 ± 0.12  ***  Abdominal fat weight, g  60  35.7 ± 1.74  103.5 ± 2.79  ***  Abdominal fat yield, % of BW  60  1.40 ± 0.06  3.93 ± 0.09  ***  Pectoralis major muscle traits      Lipid content, %  12  0.95 ± 0.04  0.83 ± 0.04  NS      Glycogen, μM/g  12  15.0 ± 3.0  26.4 ± 3.0  *      GP, μM/g  12  93.6 ± 5.1  111.6 ± 3.8  **      pHu  60  5.79 ± 0.01  5.66 ± 0.01  ***      L*  60  44.8 ± 0.3  47.4 ± 0.3  ***      a*  60  −0.28 ± 0.09  −1.01 ± 0.09  ***      b*  60  9.31 ± 0.13  8.29 ± 0.17  ***      Drip loss,3 %  60  1.12 ± 0.07  1.35 ± 0.08  *  Item2  No. of chickens  Lean line  Fat line  Level of significance  BW, g  60  2,522 ± 25  2,627 ± 21  ***  Breast yield, % of BW  60  12.76 ± 0.12  11.51 ± 0.12  ***  Abdominal fat weight, g  60  35.7 ± 1.74  103.5 ± 2.79  ***  Abdominal fat yield, % of BW  60  1.40 ± 0.06  3.93 ± 0.09  ***  Pectoralis major muscle traits      Lipid content, %  12  0.95 ± 0.04  0.83 ± 0.04  NS      Glycogen, μM/g  12  15.0 ± 3.0  26.4 ± 3.0  *      GP, μM/g  12  93.6 ± 5.1  111.6 ± 3.8  **      pHu  60  5.79 ± 0.01  5.66 ± 0.01  ***      L*  60  44.8 ± 0.3  47.4 ± 0.3  ***      a*  60  −0.28 ± 0.09  −1.01 ± 0.09  ***      b*  60  9.31 ± 0.13  8.29 ± 0.17  ***      Drip loss,3 %  60  1.12 ± 0.07  1.35 ± 0.08  *  1 Data presented as means ± SE. 2 GP = muscle glycolytic potential; pHu = muscle pH 24 h postmortem; L*, a*, and b* = lightness, redness, and yellowness, respectively, at 24 h postmortem. 3 Drip loss is expressed as a percentage of pectoralis major muscle weight at 24 h. NS = nonsignificant; *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001. View Large Table 2. Body weight, yields, and pectoralis major muscle and meat quality traits of the lean and fat lines at 9 wk of age1 Item2  No. of chickens  Lean line  Fat line  Level of significance  BW, g  60  2,522 ± 25  2,627 ± 21  ***  Breast yield, % of BW  60  12.76 ± 0.12  11.51 ± 0.12  ***  Abdominal fat weight, g  60  35.7 ± 1.74  103.5 ± 2.79  ***  Abdominal fat yield, % of BW  60  1.40 ± 0.06  3.93 ± 0.09  ***  Pectoralis major muscle traits      Lipid content, %  12  0.95 ± 0.04  0.83 ± 0.04  NS      Glycogen, μM/g  12  15.0 ± 3.0  26.4 ± 3.0  *      GP, μM/g  12  93.6 ± 5.1  111.6 ± 3.8  **      pHu  60  5.79 ± 0.01  5.66 ± 0.01  ***      L*  60  44.8 ± 0.3  47.4 ± 0.3  ***      a*  60  −0.28 ± 0.09  −1.01 ± 0.09  ***      b*  60  9.31 ± 0.13  8.29 ± 0.17  ***      Drip loss,3 %  60  1.12 ± 0.07  1.35 ± 0.08  *  Item2  No. of chickens  Lean line  Fat line  Level of significance  BW, g  60  2,522 ± 25  2,627 ± 21  ***  Breast yield, % of BW  60  12.76 ± 0.12  11.51 ± 0.12  ***  Abdominal fat weight, g  60  35.7 ± 1.74  103.5 ± 2.79  ***  Abdominal fat yield, % of BW  60  1.40 ± 0.06  3.93 ± 0.09  ***  Pectoralis major muscle traits      Lipid content, %  12  0.95 ± 0.04  0.83 ± 0.04  NS      Glycogen, μM/g  12  15.0 ± 3.0  26.4 ± 3.0  *      GP, μM/g  12  93.6 ± 5.1  111.6 ± 3.8  **      pHu  60  5.79 ± 0.01  5.66 ± 0.01  ***      L*  60  44.8 ± 0.3  47.4 ± 0.3  ***      a*  60  −0.28 ± 0.09  −1.01 ± 0.09  ***      b*  60  9.31 ± 0.13  8.29 ± 0.17  ***      Drip loss,3 %  60  1.12 ± 0.07  1.35 ± 0.08  *  1 Data presented as means ± SE. 2 GP = muscle glycolytic potential; pHu = muscle pH 24 h postmortem; L*, a*, and b* = lightness, redness, and yellowness, respectively, at 24 h postmortem. 3 Drip loss is expressed as a percentage of pectoralis major muscle weight at 24 h. NS = nonsignificant; *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001. View Large Table 3. Pearson correlations between pectoralis major muscle and breast meat quality measurements Variable1  No. of chickens  Pearson correlation coefficient  Abdominal fat yield and GP  24  0.45*  Breast yield and GP  24  −0.53**  GP and pHu  24  −0.73***  pHu and L*  120  −0.62***  pHu and a*  120  0.28***  pHu and b*  120  NS  pHu and drip loss  120  −0.43***  Variable1  No. of chickens  Pearson correlation coefficient  Abdominal fat yield and GP  24  0.45*  Breast yield and GP  24  −0.53**  GP and pHu  24  −0.73***  pHu and L*  120  −0.62***  pHu and a*  120  0.28***  pHu and b*  120  NS  pHu and drip loss  120  −0.43***  1 GP = muscle glycolytic potential; pHu = muscle pH 24 h postmortem; L*, a*, and b* = lightness, redness, and yellowness, respectively, at 24 h postmortem. NS = nonsignificant; *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001. View Large Table 3. Pearson correlations between pectoralis major muscle and breast meat quality measurements Variable1  No. of chickens  Pearson correlation coefficient  Abdominal fat yield and GP  24  0.45*  Breast yield and GP  24  −0.53**  GP and pHu  24  −0.73***  pHu and L*  120  −0.62***  pHu and a*  120  0.28***  pHu and b*  120  NS  pHu and drip loss  120  −0.43***  Variable1  No. of chickens  Pearson correlation coefficient  Abdominal fat yield and GP  24  0.45*  Breast yield and GP  24  −0.53**  GP and pHu  24  −0.73***  pHu and L*  120  −0.62***  pHu and a*  120  0.28***  pHu and b*  120  NS  pHu and drip loss  120  −0.43***  1 GP = muscle glycolytic potential; pHu = muscle pH 24 h postmortem; L*, a*, and b* = lightness, redness, and yellowness, respectively, at 24 h postmortem. NS = nonsignificant; *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001. View Large AMPK Characterization and Regulation in the P. major Muscle of Lean and Fat Lines All the PRKA genes coding for the different isoforms of the AMPK subunits α, β, and γ were expressed in the P. major muscle of both lines. However, differences in expression levels existed among the PRKA genes. According to the cycle threshold at which the fluorescence reached a given value (0.02 in this study) for each gene, the α2, β2, and γ1 or γ3 subunit isoforms appeared preferentially expressed in the P. major compared with the α1, β1, and γ2 subunits, respectively (Table 4). For comparison of the lines, 18S rRNA was chosen as reference gene because it was not different between lines. Further results based on the ratios between PRKA mRNA and 18S rRNA in the P. major muscle are presented in Figure 2. Although the relative levels of mRNA expression for PRKA genes showed only limited variations, PRKA α2 and γ1 mRNA levels were significantly less (−25% for each; P ≤ 0.05), whereas PRKA β1 and γ2 mRNA levels were greater (+50% and +30%, respectively; P ≤ 0.05) in lean chickens than in fat chickens. Table 4. Mean value of the threshold cycle at which the fluorescence reached a given value (0.02 in this study)1 PRKA2 subunit isoform  No. of chickens  Threshold cycle  α1  18  26.70 ± 0.16  α2  18  23.17 ± 0.14  β1  18  27.31 ± 0.16  β2  18  23.37 ± 0.17  γ1  18  23.58 ± 0.12  γ2  18  27.40 ± 0.12  γ3  18  23.22 ± 0.15  PRKA2 subunit isoform  No. of chickens  Threshold cycle  α1  18  26.70 ± 0.16  α2  18  23.17 ± 0.14  β1  18  27.31 ± 0.16  β2  18  23.37 ± 0.17  γ1  18  23.58 ± 0.12  γ2  18  27.40 ± 0.12  γ3  18  23.22 ± 0.15  1 Data presented as means ± SE. 2 PRKA = gene coding for adenosine monophosphate-activated protein kinase (AMPK). View Large Table 4. Mean value of the threshold cycle at which the fluorescence reached a given value (0.02 in this study)1 PRKA2 subunit isoform  No. of chickens  Threshold cycle  α1  18  26.70 ± 0.16  α2  18  23.17 ± 0.14  β1  18  27.31 ± 0.16  β2  18  23.37 ± 0.17  γ1  18  23.58 ± 0.12  γ2  18  27.40 ± 0.12  γ3  18  23.22 ± 0.15  PRKA2 subunit isoform  No. of chickens  Threshold cycle  α1  18  26.70 ± 0.16  α2  18  23.17 ± 0.14  β1  18  27.31 ± 0.16  β2  18  23.37 ± 0.17  γ1  18  23.58 ± 0.12  γ2  18  27.40 ± 0.12  γ3  18  23.22 ± 0.15  1 Data presented as means ± SE. 2 PRKA = gene coding for adenosine monophosphate-activated protein kinase (AMPK). View Large Figure 2. View largeDownload slide Relative mRNA levels (lean/fat, %) for the catalytic (α1/α2) and regulatory (β1/β2, γ1/γ2/γ3) subunits (coded by the PRKA gene) of adenosine monophosphate-activated protein kinase (AMPK) in pectoralis major muscle. The relative expression of each gene (i.e., corrected for 18S ribosomal RNA) was determined by real-time reverse transcription PCR as described in the Materials and Methods section. The value for the fat line was fixed to 100 (dotted line). The data (means ± SE, n = 9) are expressed as lean/fat (%). NS = nonsignificant; *P ≤ 0.05, difference between lines Figure 2. View largeDownload slide Relative mRNA levels (lean/fat, %) for the catalytic (α1/α2) and regulatory (β1/β2, γ1/γ2/γ3) subunits (coded by the PRKA gene) of adenosine monophosphate-activated protein kinase (AMPK) in pectoralis major muscle. The relative expression of each gene (i.e., corrected for 18S ribosomal RNA) was determined by real-time reverse transcription PCR as described in the Materials and Methods section. The value for the fat line was fixed to 100 (dotted line). The data (means ± SE, n = 9) are expressed as lean/fat (%). NS = nonsignificant; *P ≤ 0.05, difference between lines By Western blot, the AMPKα1 (63 kDa) protein was shown to be present in the P. major muscle of both lines. A quantitative analysis revealed no significant difference in AMPKα1 protein content between the fat and lean lines (Figure 3). Conversely, the phosphorylation level of the α-subunit of AMPK on the Thr172 residue was 3-fold greater in the muscle of lean birds compared with that of fat birds (Figure 3). Figure 3. View largeDownload slide Characterization of adenosine monophosphate-activated protein kinase (AMPK) in the pectoralis major muscle of 2 experimental chicken lines divergently selected on abdominal fatness (fat and lean lines). Representative Western blots of the pAMPKα-(Thr172) and AMPKα1. Protein extracts were prepared and subjected to Western blotting using anti-phospho-AMPKα-(Thr172), anti-AMPKα1 antibodies. Vinculin was used as a loading control (n = 6). The results are expressed as means ± SE of the AMPKα1/vinculin and of the pAMPKα-(Thr172)/AMPKα1 ratios (n = 6). NS = nonsignificant; *P ≤ 0.05, difference between lines. Figure 3. View largeDownload slide Characterization of adenosine monophosphate-activated protein kinase (AMPK) in the pectoralis major muscle of 2 experimental chicken lines divergently selected on abdominal fatness (fat and lean lines). Representative Western blots of the pAMPKα-(Thr172) and AMPKα1. Protein extracts were prepared and subjected to Western blotting using anti-phospho-AMPKα-(Thr172), anti-AMPKα1 antibodies. Vinculin was used as a loading control (n = 6). The results are expressed as means ± SE of the AMPKα1/vinculin and of the pAMPKα-(Thr172)/AMPKα1 ratios (n = 6). NS = nonsignificant; *P ≤ 0.05, difference between lines. mRNA Expression of GYS, PYG, GSK3, and PHK in the P. major Muscle of Lean and Fat Lines Results on the mRNA levels of GYS, PYG, GSK3, and PHK genes in the P. major muscle are presented in Figures 4 and 5. The expression of GYS and PYG was upregulated (P ≤ 0.05) in the lean line (Figure 4). The expression of the GSK3 was not altered by line (Figure 5). Among the PHK subunits, the regulatory d subunit was upregulated (P ≤ 0.01) in the P. major muscle of the lean line. There was also a trend for the regulatory α and the catalytic γ subunits of the PHK to be upregulated (P ≤ 0.06) in lean birds. By contrast, the regulatory β subunit of the PHK mRNA levels was not affected by the line. Figure 4. View largeDownload slide Relative mRNA levels (lean/fat, %) for glycogen synthase (GYS) and glycogen phosphorylase (PYG) in pectoralis major muscle. The relative expression of each gene (i.e., corrected for 18S ribosomal RNA) was determined by real-time reverse transcription PCR as described in the Materials and Methods section. The value for the fat line was fixed to 100 (dotted line). The data (means ± SE, n = 9) are expressed as lean/fat (%). *P ≤ 0.05, difference between lines. Figure 4. View largeDownload slide Relative mRNA levels (lean/fat, %) for glycogen synthase (GYS) and glycogen phosphorylase (PYG) in pectoralis major muscle. The relative expression of each gene (i.e., corrected for 18S ribosomal RNA) was determined by real-time reverse transcription PCR as described in the Materials and Methods section. The value for the fat line was fixed to 100 (dotted line). The data (means ± SE, n = 9) are expressed as lean/fat (%). *P ≤ 0.05, difference between lines. Figure 5. View largeDownload slide Relative mRNA levels (lean/fat, %) for glycogen synthase kinase 3 (GSK3) and phosphorylase kinase (PHK) subunits (α, β, d, and γ) in pectoralis major muscle. The relative expression of each gene (i.e., corrected for 18S rRNA) was determined by real-time reverse transcription PCR as described in the Materials and Methods section. The value for the fat line was fixed to 100 (dotted line). The data (means ± SE, n = 9) are expressed as lean/fat (%). NS = nonsignificant; †P ≤ 0.06; **P ≤ 0.01, difference between lines. Figure 5. View largeDownload slide Relative mRNA levels (lean/fat, %) for glycogen synthase kinase 3 (GSK3) and phosphorylase kinase (PHK) subunits (α, β, d, and γ) in pectoralis major muscle. The relative expression of each gene (i.e., corrected for 18S rRNA) was determined by real-time reverse transcription PCR as described in the Materials and Methods section. The value for the fat line was fixed to 100 (dotted line). The data (means ± SE, n = 9) are expressed as lean/fat (%). NS = nonsignificant; †P ≤ 0.06; **P ≤ 0.01, difference between lines. DISCUSSION The fat and lean lines were obtained by divergent selection within a population originally derived from meat-type lines (Leclercq et al., 1980). At 9 wk of age, birds from the fat line exhibited almost 3 times greater abdominal fatness than birds from the lean line. The fat line was also characterized by decreased breast yield than the lean line but similar intramuscular fat content. A previous study carried out on the same 2 lines (Ricard et al., 1983) showed that the different fat deposits responded differently to selection for abdominal fat content. Although intermuscular and subcutaneous fat diverged, no differences in fat content of thigh muscles were observed between the 2 lines. Despite this lack of differences between P. major fat content, the present study highlighted differences in glycogen content of the P. major muscle between fat and lean birds. The P. major muscle from the fat birds was characterized by a greater amount of glycogen at the time of death. Moreover, the muscle glycogen content appeared positively correlated to abdominal fatness and negatively correlated to breast yield. Plasma glucose concentrations have been shown to be less in fat than in lean birds (Leclercq et al., 1988). Moreover, high negative phenotypic correlations have been reported between plasma glucose concentrations and abdominal fat content (Lefebvre et al., 1988). Together these observations suggest a greater glucose uptake that could lead to greater muscle glycogen content in fat than in lean birds. A relationship between muscle glycogen content and carcass fatness was already suggested in meat-type chicken by a strong genetic negative correlation (−0.54) reported between abdominal fatness and breast meat pHu (Le Bihan-Duval et al., 2001). On the other hand, a negative genetic correlation (−0.52) was reported between muscle fiber diameter and glycogen content at death in chicken breast muscle (Berri et al., 2007). Therefore, in this species, selection for meat yield and leanness would have led to decreased muscle glycogen content and greater pHu, whereas in pigs, muscle glycogen content is positively correlated with lean meat content and negatively to backfat thickness (Larzul et al., 1999). Variations in muscle glycogen content affect breast meat quality traits through their effect on pHu. Because of its lower pHu, the breast meat from fat birds was paler, less red, and more exudative than the meat from lean birds. Therefore, in relation to the greater amount of glycogen in muscle at death, the breast meat from fat birds would likely be less adapted to further processing than meat from lean birds. The present results are consistent with several studies that suggested that genetic selection for body composition could have changed several chicken characteristics including muscle biochemistry and ultimately meat characteristics. Indeed, selection for increased breast meat yield and reduced carcass fatness was associated with slower rate of postmortem muscle acidification, greater ultimate pH, and breast meat that was lighter in color and exhibited a lower drip loss (Le Bihan-Duval et al., 1999; Berri et al., 2001). Chicken lines diverging on growth rate also exhibit large differences in meat quality traits, with the heavier and fattier birds being characterized by a greater rate of postmortem acidification, lower ultimate pH, and lighter breast meat color than the smaller and leaner birds (Nadaf et al., 2007). To identify the molecular mechanisms underlying the variations in muscle and meat characteristics evidenced by the present study, we first focused on the determination of the AMPK at both the gene and protein levels. As already reported in chicken skeletal muscle (Proszkowiec-Weglarz et al., 2006), the gene expression of all 7 isoforms of the 3 subunits of AMPK were detected in the chicken P. major muscle. The α2, β2, γ1, and γ3 isoforms were expressed at greater levels than the α1, β1, and γ2 isoforms. In the present study, the γ1 and γ3 isoforms were expressed at similar levels, whereas a greater expression of γ3 compared with γ1 was reported earlier (Proszkowiec-Weglarz et al., 2006). Difference in type and age of chickens and in PCR techniques used in the 2 studies could explain the discrepancies between results. In both human and rodent white skeletal muscles, γ3 has been shown to be the most abundant γ isoform, suggesting a key role for this isoform in this particular type of muscle (Mahlapuu et al., 2004). According to our results, the high abundance of both γ1 and γ3 at the transcriptional level could suggest an important role for both in chicken white glycolytic muscle. Selection for or against fatness affected the mRNA levels of the catalytic α2 and the 2 regulatory β1 and γ1 AMPK subunits, which, respectively, serve a scaffolding and a AMP-binding function (Wong and Lodish, 2006). The AMP-dependence of the AMPK complex is markedly affected by the identity of the γ isoform present, with γ2-containing complexes having a greater AMP-related response than those containing γ1 or γ3 (Cheung et al., 2000). The downregulation of γ1 mRNA level in the muscle of lean chickens would lead to a greater proportion of γ2, likely implying a greater response of the kinase complex to AMP, which is coherent with the greater AMPK activation observed in this genotype. However, because we have not yet investigated protein levels of the different AMPK subunits, it seems premature to relate differences in transcriptional level to those observed for muscle glycogen content between chicken lines. Regarding the γ1 AMPK subunit, whose gene expression differed between the fat and lean line, it is worthy to note that in pork the gene encoding for it (PRKAG1) is mapped close to a region containing a QTL influencing fatness traits, suggesting possible involvement in the determination of body composition in this species (Demeure et al., 2004). The expression of several genes coding for enzymes involved in the synthesis and degradation of glycogen (Figure 1) were assessed. The upregulation of both GYS and PYG expression in the muscle of the lean birds would suggest a faster glycogen turnover in this line. Although no difference in gene expression of the GSK3 was observed in the present study, there was a general trend for the subunits of PHK to be overexpressed in the muscle of the lean line, although differences between lines were only significant for the regulatory d subunit. Whether or not the greater expression of PHK is consistent with the decreased muscle glycogen content of the lean line remains to be answered. In the present study, AMPK activation (assessed through phosphorylation level on Thr172 residue) was markedly greater in the P. major of lean birds than in that of fat birds. There is evidence that AMPK activation results in decreased glycogen stores by activating glycogen phosphorylase and inhibiting glycogen synthase (Carling and Hardie, 1989; Longnus et al., 2003; Jørgensen et al., 2004; Miyamoto et al., 2007). Therefore, the greater AMPK activation observed in lean birds is consistent with their decreased muscle glycogen content and suggests a potential role for AMPK in modulating chicken postmortem muscle metabolism. Moreover, data on lactate measured 15 min postmortem suggest a faster glycolysis after death in birds that exhibited a greater AMPK activation. The control of postmortem glycolysis by AMPK was first evidenced in pig muscle through the discovery of a mutation of the AMPKγ3 subunit responsible for a 70% increase in muscle glycogen and the production of meat characterized by low ultimate pH, reduced water-holding capacity, and poor processing ability (Milan et al., 2000; Andersson, 2003). The involvement of AMPK in modulating postmortem muscle metabolism was recently confirmed in several studies on mouse (Shen and Du, 2005; Shen et al., 2005, 2008) and pig (Shen et al., 2006a,b, 2007). These studies demonstrated that AMPK activation by diet, exercise, drugs, or stress can affect both the early rate and the extent of postmortem pH decrease, and is therefore a potential molecular target for the control of meat quality. Our observation confirms, in chickens, that AMPK can be a target to control muscle postmortem metabolism and meat quality. Therefore, one can consider modulating AMPK activation through nutrition or other breeding practices while taking into account general animal metabolism such as protein synthesis, which may be inhibited upon AMPK activation through mammalian target of rapamycin signaling (Rolfe and Brown, 1997; Hayashi and Proud, 2007). In conclusion, the mRNA encoding for the 2 enzymes regulating glycogen synthesis (GYS) and degradation (PYG) are both upregulated in the lean genotype showing the low muscle glycogen content. Although this remains to be directly measured, the greater activity of the AMPK complex in the lean genotype (as evidenced by pAMPKα) could trigger a greater rate of glycogen degradation by activating PYG activity and a decreased rate of synthesis by inactivating GYS activity. The modest overexpression of PHK α, β, and d, if confirmed at the protein level, could further enhance this mechanism. LITERATURE CITED Andersson, L. 2003. Identification and characterization of AMPK γ3 mutations in the pig. Biochem. Soc. Trans.  31: 232– 235. Google Scholar CrossRef Search ADS PubMed  Berri, C., M. Debut, V. Santé-Lhoutellier, C. Arnould, B. Boutten, N. Sellier, E. Baéza, N. Jehl, Y. Jégo, M. J. Duclos, and E. Le Bihan-Duval 2005. Variations in chicken breast meat quality: Implications of struggle and muscle glycogen content at death. Br. Poult. Sci.  46: 572– 579. Google Scholar CrossRef Search ADS PubMed  Berri, C., E. Le Bihan-Duval, M. Debut, V. Santé-Lhoutellier, E. Baéza, V. Gigaud, Y. Jégo, and M. J. Duclos 2007. Consequence of muscle hypertrophy on characteristics of Pectoralis major muscle and breast meat quality of broiler chickens. J. Anim. Sci.  85: 2005– 2011. Google Scholar CrossRef Search ADS PubMed  Berri, C., N. Wacrenier, N. Millet, and E. Le Bihan-Duval 2001. Effect of selection for improved body composition on muscle and meat characteristics of broilers from experimental and commercial lines. Poult. Sci.  80: 833– 838. Google Scholar CrossRef Search ADS PubMed  Bradford, M. M. 1976. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal. Biochem.  72: 248– 254. Google Scholar CrossRef Search ADS PubMed  Carling, D., and D. G. Hardie 1989. The substrate and sequence specificity of the AMP-activated protein kinase. Phosphorylation of glycogen synthase and phosphorylase kinase. Biochim. Biophys. Acta  1012: 81– 86. Google Scholar CrossRef Search ADS PubMed  Cheung, P. C., I. P. Salt, S. P. Davies, D. G. Hardie, and D. Carling 2000. Characterization of AMP-activated protein kinase gamma-subunit isoforms and their role in AMP binding. Biochem. J.  346: 659– 669. Google Scholar CrossRef Search ADS PubMed  Chomczynski, P., and N. Sacchi 1987. Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction. Anal. Biochem.  162: 156– 159. Google Scholar CrossRef Search ADS PubMed  Dalrymple, R. H., and R. Hamm 1973. A method for extraction of glycogen and metabolites from a single muscle sample. J. Food Technol.  8: 439– 444. Google Scholar CrossRef Search ADS   Debut, M., C. Berri, E. Baéza, N. Sellier, C. Arnould, D. Guémené, N. Jehl, B. Boutten, Y. Jégo, C. Beaumont, and E. Le Bihan-Duval 2003. Variation of chicken technological meat quality in relation to genotype and preslaughter stress conditions. Poult. Sci.  82: 1829– 1838. Google Scholar CrossRef Search ADS PubMed  Demeure, O., L. Liaubet, J. Riquet, and D. Milan 2004. Determination of PRKAG1 coding sequence and mapping of PRKAG1 and PRKAG2 relatively to porcine back fat thickness QTL. Anim. Genet.  35: 123– 125. Google Scholar CrossRef Search ADS PubMed  Duchêne, S., S. Métayer, E. Audouin, K. Bigot, J. Dupont, and S. Tesseraud 2008. Refeeding and insulin activate the AKT/p70S6 kinase pathway without affecting IRS1 tyrosine phosphorylation in chicken muscle. Domest. Anim. Endocrinol.  34: 1– 13. Google Scholar CrossRef Search ADS PubMed  Folch, J., M. Lees, and G. H. Sloane Stanley 1957. A simple method for the isolation and purification of total lipids from animal tissues. J. Biol. Chem.  226: 497– 509. Google Scholar PubMed  Guernec, A., C. Berri, B. Chevalier, N. Wacrenier-Ceré, E. Le Bihan-Duval, and M. J. Duclos 2003. Muscle development, insulin-like growth factor-I and myostatin mRNA levels in chickens selected for increased breast muscle yield. Growth Horm. IGF Res.  13: 8– 18. Google Scholar CrossRef Search ADS PubMed  Hayashi, A. A., and C. G. Proud 2007. The rapid activation of protein synthesis by growth hormone requires signaling through mTOR. Am. J. Physiol. Endocrinol. Metab.  292: E1647– E1655. Google Scholar CrossRef Search ADS PubMed  Jørgensen, S. B., J. N. Nielsen, J. B. Birk, G. S. Olsen, B. Viollet, F. Andreelli, P. Schjerling, S. Vaulont, D. G. Hardie, B. F. Hansen, E. A. Richter, and J. F. Wojtaszewski 2004. The alpha2–5′AMP-activated protein kinase is a site 2 glycogen synthase kinase in skeletal muscle and is responsive to glucose loading. Diabetes  53: 3074– 3081. Google Scholar CrossRef Search ADS PubMed  Larzul, C., P. Le Roy, J. Gogué, A. Talmant, G. Monin, and P. Sellier 1999. Selection for reduced muscle glycolytic potential in Large White pigs. III. Correlated responses in growth rate, carcass composition and reproductive traits. Genet. Sel. Evol.  31: 149– 161. Google Scholar CrossRef Search ADS   Le Bihan-Duval, E., C. Berri, E. Baéza, N. Millet, and C. Beaumont 2001. Estimation of the genetic parameters of meat characteristics and of their genetic correlations with growth and body composition in an experimental broiler line. Poult. Sci.  80: 839– 843. Google Scholar CrossRef Search ADS PubMed  Le Bihan-Duval, E., N. Millet, and H. Rémignon 1999. Broiler meat quality: Effect of selection for increased carcass quality and estimates of genetic parameters. Poult. Sci.  78: 822– 826. Google Scholar CrossRef Search ADS PubMed  Leclercq, B., J. C. Blum, and J. P. Boyer 1980. Selecting broilers for low and high abdominal fat: Initial observations. Br. Poult. Sci.  21: 107– 113. Google Scholar CrossRef Search ADS   Leclercq, B., J. Simon, and H. Karmann 1988. Glucagon-insulin balance in genetically lean or fat chickens. Diabete Metab.  14: 641– 645. Google Scholar PubMed  Lefebvre, F. L., S. P. Touchburn, J. F. Hayes, and C. W. Chan 1988. Correlations between plasma glucose and adiposity in genetically fat and lean chickens. Pages 327–328 in Leanness in Domestic Birds.  B. Leclercq, C. C. Whitehead ed. Butterworths, London, UK. Google Scholar CrossRef Search ADS   Longnus, S. L., R. B. Wambolt, H. L. Parsons, R. W. Brownsey, and M. F. Allard 2003. 5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside (AICAR) stimulates myocardial glycogenolysis by allosteric mechanisms. Am. J. Physiol. Regul. Integr. Comp. Physiol.  284: R936– R944. Google Scholar CrossRef Search ADS PubMed  Mahlapuu, M., C. Johansson, K. Lindgren, G. Hjälm, B. R. Barnes, A. Krook, J. R. Zierath, L. Andersson, and S. Marklund 2004. Expression profiling of the gamma-subunit isoforms of AMP-activated protein kinase suggests a major role for gamma3 in white skeletal muscle. Am. J. Physiol. Endocrinol. Metab.  286: E194– E200. Google Scholar CrossRef Search ADS PubMed  Mead, G. C. 2004. Meat quality and consumer requirements. Pages 1–18 in Poultry Meat Processing and Quality.  G. C. Mead ed. CRC Press, Boca Raton, FL; Woodhead Publishing Ltd., Cambridge, UK. Google Scholar CrossRef Search ADS   Milan, D., J. T. Jeon, C. Looft, V. Amarger, A. Robic, M. Thelander, C. Rogel-Gaillard, S. Paul, N. Iannuccelli, L. Rask, H. Ronne, K. Lundström, N. Reinsch, J. Gellin, E. Kalm, P. Le Roy, P. Chardon, and L. Andersson 2000. A mutation in PRKAG3 associated with excess glycogen content in pig skeletal muscle. Science  288: 1248– 1251. Google Scholar CrossRef Search ADS PubMed  Miyamoto, L., T. Toyoda, T. Hayashi, S. Yonemitsu, M. Nakano, S. Tanaka, K. Ebihara, H. Masuzaki, K. Hosoda, Y. Ogawa, G. Inoue, T. Fushiki, and K. Nakao 2007. Effect of acute activation of 5′-AMP-activated protein kinase on glycogen regulation in isolated rat skeletal muscle. J. Appl. Physiol.  102: 1007– 1013. Google Scholar CrossRef Search ADS PubMed  Monin, G., and P. Sellier 1985. Pork of low technological quality with a normal rate of pH fall in the intermediate post mortem period: The case of the Hampshire breed. Meat Sci.  13: 49– 63. Google Scholar CrossRef Search ADS PubMed  Nadaf, J., H. Gilbert, F. Pitel, C. M. Berri, K. Feve, C. Beaumont, M. J. Duclos, A. Vignal, T. E. Porter, J. Simon, S. E. Aggrey, L. A. Cogburn, and E. Le Bihan-Duval 2007. Identification of QTL controlling meat quality traits in an F2 cross between two chicken lines selected for either low or high growth rate. BMC Genomics  http://www.biomedcentral.com/1471-2164/8/155. Pfaffl, M. W. 2001. A new mathematical model for relative quantification in real-time RT-PCR. Nucleic Acids Res.  29: 2002– 2007. Google Scholar CrossRef Search ADS   Proszkowiec-Weglarz, M., M. P. Richards, R. Ramachandran, and J. P. McMurtry 2006. Characterization of the AMP-activated protein kinase pathway in chickens. Comp. Biochem. Physiol. B Biochem. Mol. Biol.  143: 92– 106. Google Scholar CrossRef Search ADS PubMed  Ricard, F. H., B. Leclercq, and C. Touraille 1983. Selecting broilers for low and high abdominal fat, distribution of carcass fat and quality of meat. Br. Poult. Sci.  24: 511– 516. Google Scholar CrossRef Search ADS   Rolfe, D. F., and G. C. Brown 1997. Cellular energy utilization and molecular origin of standard metabolic rate in mammals. Physiol. Rev.  77: 731– 758. Google Scholar CrossRef Search ADS PubMed  Scheffler, T. L., and D. E. Gerrard 2007. Mechanisms controlling pork quality development: The biochemistry controlling postmortem energy metabolism. Meat Sci.  77: 7– 16. Google Scholar CrossRef Search ADS PubMed  Shen, Q. W., and M. Du 2005. Role of AMP-activated protein kinase in the glycolysis of postmortem muscle. J. Sci. Food Agric.  85: 2401– 2406. Google Scholar CrossRef Search ADS   Shen, Q. W., D. E. Gerrard, and M. Du 2008. Compound C, an inhibitor of AMP-activated protein kinase, inhibits glycolysis in mouse longissimus dorsi post-mortem. Meat Sci.  78: 323– 330. Google Scholar CrossRef Search ADS PubMed  Shen, Q. W., C. S. Jones, N. Kalchayanand, M. J. Zhu, and M. Du 2005. Effect of dietary alpha-lipoic acid on growth, body composition, muscle pH, and AMP-activated protein kinase phosphorylation in mice. J. Anim. Sci.  83: 2611– 2617. Google Scholar CrossRef Search ADS PubMed  Shen, Q. W., W. J. Means, S. A. Thompson, K. R. Underwood, M. J. Zhu, R. J. McCormick, S. P. Ford, and M. Du 2006a. Pre-slaughter transport, AMP-activated protein kinase, glycolysis, and quality of pork loin. Meat Sci.  74: 388– 395. Google Scholar CrossRef Search ADS   Shen, Q. W., W. J. Means, K. R. Underwood, S. A. Thompson, M. J. Zhu, R. J. McCormick, S. P. Ford, M. Ellis, and M. Du 2006b. Early post-mortem AMP-activated protein kinase (AMPK) activation leads to phosphofructokinase-2 and -1 (PFK-2 and PFK-1) phosphorylation and the development of pale, soft, and exudative (PSE) conditions in porcine longissimus muscle. J. Agric. Food Chem.  54: 5583– 5589. Google Scholar CrossRef Search ADS   Shen, Q. W., K. R. Underwood, W. J. Means, R. J. McCormick, and M. Du 2007. The halothane gene, energy metabolism, adenosine monophosphate-activated protein kinase, and glycolysis in postmortem pig longissimus dorsi muscle. J. Anim. Sci.  85: 1054– 1061. Google Scholar CrossRef Search ADS PubMed  Wong, K. A., and H. F. Lodish 2006. A revised model for AMP-activated protein kinase structure: The alpha-subunit binds to both the beta- and gamma-subunits although there is no direct binding between the beta- and gamma-subunits. J. Biol. Chem.  281: 36434– 36442. Google Scholar CrossRef Search ADS PubMed  Copyright 2008 Journal of Animal Science
TI - Adenosine monophosphate-activated protein kinase involved in variations of muscle glycogen and breast meat quality between lean and fat chickens
JF - Journal of Animal Science
DO - 10.2527/jas.2008-1062
DA - 2008-11-01
UR - https://www.deepdyve.com/lp/oxford-university-press/adenosine-monophosphate-activated-protein-kinase-involved-in-0Prh94eM3y
SP - 2888
EP - 2896
VL - 86
IS - 11
DP - DeepDyve
ER -