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Effects of exercise on muscle glycogen synthesis signalling and enzyme activities in pigs carrying the PRKAG3 mutation
Author(s) -
Granlund Anna,
Kotova Olga,
Benziane Boubacar,
Galuska Dana,
JensenWaern Marianne,
Chibalin Alexander V.,
EssénGustavsson Birgitta
Publication year - 2010
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2009.051326
Subject(s) - glycogen , mutation , enzyme , signalling , endocrinology , biology , medicine , microbiology and biotechnology , biochemistry , genetics , chemistry , gene
The dominant RN − mutation in pigs results in excessive glycogen storage in skeletal muscle. The mutation is situated in the PRKAG3 gene, which encodes a muscle‐specific isoform of the AMP‐activated protein kinase (AMPK) γ3 subunit. AMPK is an important regulator of carbohydrate and fat metabolism in mammalian cells. The aim of the present study was to examine the effect of exercise on glycogen synthesis signalling pathways in muscle and to study enzyme activities of importance in carbohydrate metabolism in pigs with or without the PRKAG3 mutation. Glycogen content, metabolic enzyme activities and expression or phosphorylation of signalling proteins were analysed in skeletal muscle specimens obtained at rest, after a single treadmill exercise bout and after 3 h recovery. The PRKAG3 mutation carriers had higher glycogen content, a tendency for lower expression of AMPK ( P < 0.07) and higher hexokinase and phosphorylase activities, whereas citrate synthase, 3‐hydroxyacyl‐CoA dehydrogenase and glycogen synthase activities did not differ between genotypes. Carriers and non‐carriers of the RN − mutation showed a similar degradation of glycogen after exercise, whereas the rate of resynthesis was faster in the carriers. Acute exercise stimulated Akt phosphorylation on Ser 473 in both genotypes, and the effect was greater in the carriers than in the non‐carriers. Acute exercise also stimulated phosphorylation of Akt substrate of 160 kDA and Glycogen synthase kinase 3 in the carriers and GSK3α in the non‐carriers. In conclusion, the increased rate of glycogen synthesis following exercise in pigs carrying the PRKAG3 mutation correlates with an increased signalling response of Akt and its substrate, AS160, and a higher activity of hexokinase, indicating an increased glucose influx and phosphorylation of glucose, directed towards glycogen synthesis.