Guanidinoacetic Acid Supplementation Promotes Skeletal Muscle Fiber Type Transformation from Fast-to-Slow-Twitch via Increasing the PPARGC1A Based Mitochondrial Function and CaN/NFAT Pathway in Finishing Pigs

Jingzheng Li,Lin Zhang,Jiaolong Li,Tong Xing,Yun Jiang,Feng Gao

doi:10.3390/agriculture12010087

Abstract

Guanidinoacetic acid can improve pork quality. Previous studies have demonstrated that pork quality is closely linked to the muscle fiber type mediated by PPARGC1A. Therefore, this study aimed to evaluate the influence of dietary GAA supplementation on the skeletal muscle fiber type transformation. A total of 180 healthy Duroc × Landrace × Meishan cross castrated male pigs with a similar average weight (90 ± 1.5 kg) were randomly divided into three treatments with five replicates per treatment and 12 pigs per replicate, including a GAA-free basal diet and basal diet with 0.05% or 0.10% GAA for 15 days. Our results showed that 0.10% GAA supplementation increased the contents of Ca2+ in sarcoplasm (p < 0.05). Compared with the control group, both GAA supplementation groups upregulated the expression of Troponin I-ss (p < 0.05), and 0.10% GAA supplementation downregulated the expression of Troponin T3 (p < 0.05). GAA supplementation increased the expression of peroxisome proliferator activated receptor-γ coactivator-1alpha (PPARGC1A) (p < 0.05), and further upregulated the mitochondrial transcription factor A (TFAM), increased the level of membrane potential, and the activities of mitochondrial respiratory chain complex I, III (p < 0.05). The 0.10% GAA supplementation upregulated the protein expression of calcineurin catalytic subunit α (CnAα) and nuclear factor of activated T cells (NFATc1) (p < 0.05). Overall, dietary GAA supplementation promotes skeletal muscle fiber types transformation from fast-to-slow-twitch via increasing the PPARGC1A based mitochondrial function and the activation of CaN/NFAT pathway in finishing pigs.

Highlights

In mammals, different fiber types, which are the basis of muscle plasticity in response to a variety of functional demands, can be distinguished in skeletal muscle
Compared with the control group, the Guanidinoacetic acid (GAA) addition downregulated the expression of troponin IIb fast skeletal type (Troponin T3) in semitendinosus muscle (p < 0.05)
The present study indicated that GAA treatment increased the concentration of Ca2+ in longissimus thoracis muscle

Summary

Introduction

Different fiber types, which are the basis of muscle plasticity in response to a variety of functional demands, can be distinguished in skeletal muscle. The muscle fiber characteristics are the major factors for the evaluation of meat quality, especially the fiber type composition [1]. Fast-twitch type fibers include IIa, IIx, and IIb muscle fibers [3]. The excessive accumulation of postmortem lactic acid could further lead to a decline in pH and meat quality. It is important to promote the transformation of skeletal muscle fibers from fast-twitch to slow-twitch. Skeletal muscle fiber transformation can be caused by some factors, such as heredity, exercise, and nutrition [4]. Previous studies showed that skeletal muscle can be changed via decreasing the proportion of fast fibers and increasing slow fibers through some nutritional modulation strategies [6,7]

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Results