Adenosine monophosphate-activated protein kinase involved in variations of muscle glycogen and breast meat quality between lean and fat chickens1

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 AMPKalpha-(Thr(172)), in the muscle of lean birds. At the transcriptional level, data indicated concomitant down- and upregulation for the gamma1 and gamma2 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 gamma 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.

The ability of genetically lean or fat slow-growing chickens to synthesize and store lipids is not altered by the dietary energy source

“…The better feed efficiency of lean chickens might be partly explained by the improved digestibility of dietary energy and lipids in that line compared with the fat line. As previously described (Sibut et al, 2008), lean chickens also displayed lower glycogen stores in the PM muscle, and the situation was similar for SART muscle in the present study. Interestingly, lactate content in the PM muscle was higher in lean than in fat chickens, suggesting a higher use of glycogen to produce energy by the anaerobic pathway.…”

An Expression QTL of Closely Linked Candidate Genes Affects pH of Meat in Chickens

“…Total RNA was extracted from P. major muscle of 12 qq and 11 QQ individuals (the same as those used for microarray analysis; one bird lacked sufficient material for this assay) and real-time RT-PCR was performed using cDNA synthesized as previously described (Sibut et al 2008). Primers were designed for each gene so that the amplicon contains the probe spotted on microarray (Table S2) and purchased from Eurogentec (Angers, France).…”

Chicken lines divergent for low or high abdominal fat deposition: a relevant model to study the regulation of energy metabolism

“…Moreover, the glycogen content of breast muscle in LL chickens was inversely related to abdominal fatness. The activation level of adenosine monophosphate-activated protein kinase (AMPK) was investigated in relation to these variations (Sibut et al, 2008). The main difference observed between lines was a threefold greater level of AMPK activation, evaluated by phosphorylation of AMPKa-(Thr 172 ) in the muscle of LL birds.…”

“…Their findings suggest that fatty acid utilization by mitochondria might be higher in both muscle and liver in FL chickens than in LL chickens, particularly when fed a high-fat and low-protein diet. Sibut et al (2008) investigated the transcriptional levels of enzymes involved in glycogen turnover in breast muscle. Their findings demonstrated downregulation and upregulation of the g1 and g2 AMPK subunit isoforms, respectively, in the muscle of LL chickens compared with FL chickens.…”