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

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.

High-Throughput Muscle Fiber Typing From RNA Sequencing Data

BACKGROUND: Skeletal muscle fiber type distribution has implications for human health, muscle function and performance. This knowledge has been gathered using labor-intensive and costly methodology that limited these studies. Here we present a method based on muscle tissue RNA sequencing data (totRNAseq) to estimate the distribution of skeletal muscle fiber types from frozen human samples, allowing for a larger number of individuals to be tested.METHODS: By using single-nuclei RNA sequencing (snRNAseq) data as a reference, cluster expression signatures were produced by averaging gene expression of cluster gene markers and then applying these to totRNAseq data and inferring muscle fiber nuclei type via linear matrix decomposition. This estimate was then compared with fiber type distribution measured by ATPase staining or myosin heavy chain protein isoform distribution of 62 muscle samples in two independent cohorts (n = 39 and 22).RESULTS: The correlation between the sequencing-based method and the other two were rATPas = 0.65 [0.46 – 0.84], [95% CI] and rmyosin = 0.80 [0.71 – 0.89], with p = 7.96 x 10-6 and 8.06 x 10-6 respectively. The deconvolution inference of fiber type composition was accurate even for very low totRNAseq sequencing depths, i.e., down to an average of ~5.000 paired-end reads.CONCLUSIONS: This new method (https://github.com/OlaHanssonLab/PredictFiberType) consequently allows for measurement of fiber type distribution of a larger number of samples using totRNAseq in a cost and labor-efficient way. For the first time, it is now feasible to study the association between fiber type distribution and e.g. health outcomes in large well-powered studies.

Garcinol Promotes the Formation of Slow-Twitch Muscle Fibers by Inhibiting p300-Dependent Acetylation of PGC-1α

Background The conversion of skeletal muscle fiber from fast twitch to slow-twitch is crucial for sustained contractile and stretchable events, energy homeostasis, and anti-fatigue ability. The purpose of our study was to explore the mechanism and effects of garcinol on the regulation of skeletal muscle fiber type transformation. Methods Forty 21-day-old male C57/BL6J mice (n = 10/diet) were fed a control diet or a control diet plus garcinol at 100 mg/kg (Low Gar), 300 mg/kg (Mid Gar), or 500 mg/kg (High Gar) for 12 weeks. The tibialis anterior (TA) and soleus muscles were collected for protein and immunoprecipitation analyses. Results Dietary garcinol significantly downregulated (P<0.05) fast MyHC expression and upregulated (P<0.05) slow MyHC expression in the TA and soleus muscles. Garcinol significantly increased (P<0.05) the activity of PGC-1α and markedly decreased (P<0.05) the acetylation of PGC-1α. In vitro and in vivo experiments showed that garcinol decreased (P<0.05) lactate dehydrogenase activity and increased (P<0.05) the activities of malate dehydrogenase and succinic dehydrogenase. In addition, the results of immunostaining C2C12 myotubes showed that garcinol treatment increased (P<0.05) the transformation of glycolytic muscle fiber to oxidative muscle fiber by 45.9%. Garcinol treatment and p300 interference reduced (P<0.05) the expression of fast MyHC but increased (P<0.05) the expression of slow MyHC in vitro. Moreover, the acetylation of PGC-1α was significantly decreased (P<0.05). Conclusion Garcinol promotes the transformation of skeletal muscle fibers from the fast-glycolytic type to the slow-oxidative type through the p300/PGC-1α signaling pathway in C2C12 myotubes.

Cardiopulmonary exercise testing in clinical practice

The review is dedicated to the use of the cardiopulmonary exercise testing (CPET) in clinical practice. Main modes of CPET, most popular protocols and testing methods are discussed in details. Ample space is dedicated to main parameters measuring during CPET, their physiological values and changes in different pathological states. Main indications for CPET are presented and special attention is given to the use of CPET in chronic heart failure, apnea, lung diseases, skeletal muscle fiber and mitochondrial myopathy, rehabilitation. Emerging applications of CPET like congenital heart disease, pulmonary resection and several other are also discussed.