Myogenic Precursor Cells Show Faster Activation and Enhanced Differentiation in a Male Mouse Model Selected for Advanced Endurance Exercise Performance

Metabolic Pathway Modeling in Muscle of Male Marathon Mice (DUhTP) and Controls (DUC)-A Possible Role of Lactate Dehydrogenase in Metabolic Flexibility

In contracting muscles, carbohydrates and fatty acids serve as energy substrates; the predominant utilization depends on the workload. Here, we investigated the contribution of non-mitochondrial and mitochondrial metabolic pathways in response to repeated training in a polygenic, paternally selected marathon mouse model (DUhTP), characterized by exceptional running performance and an unselected control (DUC), with both lines descended from the same genetic background. Both lines underwent three weeks of high-speed treadmill training or were sedentary. Both lines' muscles and plasma were analyzed. Muscle RNA was sequenced, and KEGG pathway analysis was performed. Analyses of muscle revealed no significant selection-related differences in muscle structure. However, in response to physical exercise, glucose and fatty acid oxidation were stimulated, lactate dehydrogenase activity was reduced, and lactate formation was inhibited in the marathon mice compared with trained control mice. The lack of lactate formation in response to exercise appears to be associated with increased lipid mobilization from peripheral adipose tissue in DUhTP mice, suggesting a specific benefit of lactate avoidance. Thus, results from the analysis of muscle metabolism in born marathon mice, shaped by 35 years (140 generations) of phenotype selection for superior running performance, suggest increased metabolic flexibility in male marathon mice toward lipid catabolism regulated by lactate dehydrogenase.

PAX7 and MyoD Proteins Expression in Response to Eccentric and Concentric Resistance Exercise in Active Young Men

OBJECTIVE

Satellite cells play an important role in muscle regeneration, which this process can be affected by different genes including PAX7 and MyoD. Exercise training known as an important strategy for mediating the satellite cell's function. Therefore, the main purpose of the present study is to investigate the changes in PAX7 and MyoD protein expression in response to eccentric and concentric resistance exercise in healthy young men.

MATERIALS AND METHODS

In this semi-experimental and cross-sectional study, 10 healthy men (age range 18-30 years old) participated. They were randomly divided into two equal groups (n=5) to perform one of two high-intensity eccentric or concentric knee extensions muscle contraction protocols. The contractions included a maximum of 12 sets of 10 repetitions, with a 30 second rest time interval between sets. PAX7 and MyoD protein expression was assessed using Immunohistochemistry analysis from the Vastus Lateralis muscle needle biopsy samples that have been taken 24 hours before and 3 to 4 hours after the end of the exercise protocol.

RESULTS

We observed that the PAX7 protein expression level increased significantly after eccentric (47.75%) and concentric (39.21%) (P=0.01) intervention. While, the MyoD protein expression level reduced (38.14%) significantly following acute eccentric resistance exercise (P=0.01).

CONCLUSION

It seems that eccentric or concentric muscular contraction modulates the expression of PAX7 and MyoD protein expression in the skeletal muscle, with further effects observed in eccentric resistance exercise.

Skeletal Muscle Stem Cells in Aging: Asymmetric/Symmetric Division Switching

In aged muscle, satellite cells’ symmetric and asymmetric divisions are impaired, and intrinsic and extrinsic complex mechanisms govern these processes. This review presents many updated aspects regarding muscle stem cells’ fate in normal and aging conditions. The balance between self-renewal and commitment divisions contributes to muscle regeneration, muscle homeostasis, aging, and disease. Stimulating muscle regeneration in aging could be a therapeutic target, but there is still a need to understand the many mechanisms that influence each other in satellite cells and their niche. We highlight here the general outlines regarding satellite cell divisions, the primary markers present in muscle stem cells, the aging aspects concerning signaling pathways involved in symmetric/asymmetric divisions, the regenerative capacity of satellite cells and their niche alteration in senescent muscle, genetics and epigenetics mechanisms implied in satellite cells aging and exercise effect on muscle regeneration in the elderly.

Fundamental and Applied Advances in Stem Cell Therapeutic Research

We are pleased to present this Special Issue of Cells, entitled 'Feature Papers in Stem Cells' [...].