Influence of the three RN genotypes on chemical composition, enzyme activities, and myofiber characteristics of porcine skeletal muscle.

Abstract

An experiment was conducted to evaluate the effects of the RN genotype on skeletal muscle characteristics in pigs sharing otherwise the same polygenic background. Animals were genotyped for RN on the basis of RTN (Rendement Technologique Napole) records using segregation analysis methods. Samples of longissimus (L) and semispinalis capitis (S) muscles were taken from 39 rn+/rn+, 38 RN-/rn+ and 37 RN-/RN- pigs slaughtered at 108 +/- 8.6 kg live weight. Activities of lactate dehydrogenase (LDH), citrate synthase (CS), and beta-hydroxy-acyl-coenzyme A dehydrogenase (HAD) were measured on both muscles to assess glycolytic, oxidative, and lipid beta-oxidation capacities, respectively. Histological examinations and chemical analyses were performed on L muscle. The energetic metabolism of the white L muscle was more oxidative in RN-/RN- than in rn+/rn+ pigs, as shown by increased CS and HAD activities (P < .001), decreased LDH activity (P < .001), larger cross-sectional area of IIA (P < .05) and IIB-red (P < .05) fibers, higher relative area of IIA fibers ( P < .05), and lower relative area of IIB-white fibers (P < .001). No significant difference was found between heterozygous and homozygous carriers of the RN- allele, except for CS activity, which was lower in RN-/rn+ than in RN-/RN- pigs. In L muscle, the RN- allele led to a large increase in glycolytic potential (+3.5 phenotypic SD between homozygotes) and lightness (+.7 SD), and a decrease in ultimate pH, dry matter, and protein contents (-1.7 to -2 phenotypic SD for these three traits), with an almost completely dominant effect. No differences were found between genotypes for intramuscular fat and hydroxyproline contents. In the red S muscle, the presence of RN- had no influence on enzyme activities. These results indicate that the RN genotype greatly influences compositional and histochemical traits and metabolic enzyme activities in a muscle type-dependent manner, with a completely or incompletely dominant effect of the RN- allele.

Comparison of PRKAG3 and RYR1 gene effect on carcass traits and meat quality in Slovenian commercial pigs

“…Available studies of Lindahl et al (2004a,b) LD muscle pH 199V and 200Q), in agreement with our results. The effect of PRKAG3 gene on meat quality traits proved to be very important (Table 3) Considering the effect of the 200Q allele or the so called RN -phenotype it has indubitably been proved that its presence induces lower ultimate pH value and water holding capacity (Andersson and Hansson, 1996;Enfält et al, 1997b;Lundström et al, 1998;Lebret et al, 1999;Hamilton et al, 2000;Le Roy et al, 2000;Miller et al, 2000a;Josell et al, 2003b;Lindahl et al, 2004a,b), and our study only confirms these evidences. According to Ciobanu et al (2001), the RN -phenotype is considered to be a combined effect of haplotype 199V-200Q rather than a mere result of R200Q substitution.…”

Effects of two supplementation levels of linseed combined with CLA or tallow on meat quality traits and fatty acid profile of adipose and different muscle tissues in slaughter pigs

“…Enzyme activities were measured on LM samples as described previously (Lebret et al, 1999) and expressed as mmol of substrate degraded/min per g of fresh tissue.…”

Role of AMP-activated protein kinase in the coordinated expression of genes controlling glucose and lipid metabolism in mouse white skeletal muscle

“…The γ subunit includes γ1, γ2 and γ3 isoforms, with γ3 being the predominant isoform in glycolytic skeletal muscle [21], a fibre type that depends upon the anaerobic metabolism of glucose when there is a high demand for energy. In skeletal muscle from pigs carrying a naturally occurring mutation of γ3 (R225Q), glycogen content [22,23] and the activities of citrate synthase (CS) and hydroxyacyl-CoA dehydrogenase are increased [24,25], suggesting that the γ3 subunit can regulate metabolic properties of skeletal muscle.…”