Department of Clinical Sciences, Section for Comparative Physiology and Medicine, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, SE-750 07, Uppsala, Sweden.
Acta Vet Scand. 2011 Mar 24;53(1):20. doi: 10.1186/1751-0147-53-20.
AMP-activated protein kinase (AMPK) plays an important role in the regulation of glucose and lipid metabolism in skeletal muscle. Many pigs of Hampshire origin have a naturally occurring dominant mutation in the AMPK γ3 subunit. Pigs carrying this PRKAG3 (R225Q) mutation have, compared to non-carriers, higher muscle glycogen levels and increased oxidative capacity in m. longissimus dorsi, containing mainly type II glycolytic fibres. These metabolic changes resemble those seen when muscles adapt to an increased physical activity level. The aim was to stimulate AMPK by exercise training and study the influence of the PRKAG3 mutation on metabolic and fibre characteristics not only in m. longissimus dorsi, but also in other muscles with different functions.
Eight pigs, with the PRKAG3 mutation, and eight pigs without the mutation were exercise trained on a treadmill. One week after the training period muscle samples were obtained after euthanisation from m. biceps femoris, m. longissimus dorsi, m. masseter and m. semitendinosus. Glycogen content was analysed in all these muscles. Enzyme activities were analysed on m. biceps femoris, m. longissimus dorsi, and m. semitendinosus to evaluate the capacity for phosphorylation of glucose and the oxidative and glycolytic capacity. Fibre types were identified with the myosin ATPase method and in m. biceps femoris and m. longissimus dorsi, immunohistochemical methods were also used.
The carriers of the PRKAG3 mutation had compared to the non-carriers higher muscle glycogen content, increased capacity for phosphorylation of glucose, increased oxidative and decreased glycolytic capacity in m. longissimus dorsi and increased phosphorylase activity in m. biceps femoris and m. longissimus dorsi. No differences between genotypes were seen when fibre type composition was evaluated with the myosin ATPase method. Immunohistochemical methods showed that the carriers compared to the non-carriers had a higher percentage of type II fibres stained with the antibody identifying type IIA and IIX fibres in m. longissimus dorsi and a lower percentage of type IIB fibres in both m. biceps femoris and m. longissimus dorsi. In these muscles the relative area of type IIB fibres was lower in carriers than in non-carriers.
In exercise-trained pigs, the PRKAG3 mutation influences muscle characteristics and promotes an oxidative phenotype to a varying degree among muscles with different functions.
AMP 激活的蛋白激酶（AMPK）在骨骼肌中葡萄糖和脂质代谢的调节中发挥重要作用。许多汉普夏起源的猪在 AMPKγ3 亚基中存在一种天然存在的显性突变。与非携带者相比，携带这种 PRKAG3（R225Q）突变的猪具有更高的肌肉糖原水平和背最长肌中氧化能力的增加，该肌肉主要包含 II 型糖酵解纤维。这些代谢变化类似于肌肉适应更高的体力活动水平时所发生的变化。目的是通过运动训练刺激 AMPK，并研究 PRKAG3 突变对代谢和纤维特征的影响，不仅在背最长肌中，而且在具有不同功能的其他肌肉中。
8 头携带 PRKAG3 突变的猪和 8 头不携带突变的猪在跑步机上进行运动训练。训练期结束后一周，通过安乐死从比目鱼肌、背最长肌、咬肌和半腱肌中获得肌肉样本。分析所有这些肌肉中的糖原含量。分析比目鱼肌、背最长肌和半腱肌中的酶活性，以评估葡萄糖磷酸化和氧化及糖酵解能力。用肌球蛋白 ATP 酶法鉴定纤维类型，并用免疫组织化学方法鉴定比目鱼肌和背最长肌中的纤维类型。
与非携带者相比，携带 PRKAG3 突变的猪的肌肉糖原含量更高，背最长肌的葡萄糖磷酸化能力增加，氧化能力增加，糖酵解能力降低，比目鱼肌和背最长肌的磷酸化酶活性增加。用肌球蛋白 ATP 酶法评估纤维类型组成时，未观察到基因型之间的差异。免疫组织化学方法显示，与非携带者相比，携带 PRKAG3 突变的猪的背最长肌中，用识别 IIA 和 IIX 纤维的抗体标记的 II 型纤维的百分比更高，而在比目鱼肌和背最长肌中 IIB 型纤维的百分比更低。在这些肌肉中，携带 PRKAG3 突变的猪的 IIB 型纤维相对面积低于非携带者。
在运动训练的猪中，PRKAG3 突变以不同程度影响具有不同功能的肌肉的肌肉特征，并促进氧化表型。
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