Influence of intramuscular steroid receptor content and fiber capillarization on skeletal muscle hypertrophy

[MR. BMJ]

Influence of intramuscular steroid receptor content and fiber capillarization on skeletal muscle hypertrophy - PubMed

Multiple intramuscular variables have been proposed to explain the high variability in resistance training induced muscle hypertrophy across humans. This study investigated if muscular androgen receptor (AR), estrogen receptor α (ERα) and β (ERβ) content and fiber capillarization are associated...

pubmed.ncbi.nlm.nih.gov

Scand J Med Sci Sports

2024 Jun;34(6):e14668.
doi: 10.1111/sms.14668.

Influence of intramuscular steroid receptor content and fiber capillarization on skeletal muscle hypertrophy​

Kim Van Vossel 1, Julie Hardeel 1, Thibaux Van der Stede 1 2, Anneleen Weyns 1, Jan Boone 1, Silvia Salinas Blemker 3 4, Wim Derave 1, Eline Lievens 1
Affiliations expand

• PMID: 38802727
• DOI: 10.1111/sms.14668

Abstract​

Multiple intramuscular variables have been proposed to explain the high variability in resistance training induced muscle hypertrophy across humans. This study investigated if muscular androgen receptor (AR), estrogen receptor α (ERα) and β (ERβ) content and fiber capillarization are associated with fiber and whole-muscle hypertrophy after chronic resistance training. Male (n = 11) and female (n = 10) resistance training novices (22.1 ± 2.2 years) trained their knee extensors 3×/week for 10 weeks. Vastus lateralis biopsies were taken at baseline and post the training period to determine changes in fiber type specific cross-sectional area (CSA) and fiber capillarization by immunohistochemistry and, intramuscular AR, ERα and ERβ content by Western blotting. Vastus lateralis volume was quantified by MRI-based 3D segmentation. Vastus lateralis muscle volume significantly increased over the training period (+7.22%; range: -1.82 to +18.8%, p < 0.0001) but no changes occurred in all fiber (+1.64%; range: -21 to +34%, p = 0.869), type I fiber (+1.33%; range: -24 to +41%, p = 0.952) and type II fiber CSA (+2.19%; range: -23 to +29%, p = 0.838). However, wide inter-individual ranges were found. Resistance training increased the protein expression of ERα but not ERβ and AR, and the increase in ERα content was positively related to changes in fiber CSA. Only for the type II fibers, the baseline capillary-to-fiber-perimeter index was positively related to type II fiber hypertrophy but not to whole muscle responsiveness. In conclusion, an upregulation of ERα content and an adequate initial fiber capillarization may be contributing factors implicated in muscle fiber hypertrophy responsiveness after chronic resistance training.

@Stewie @homonunculus @Type-IIx

Any thoughts on this study that is worthwhile?

 

[Stewie]

Well, I'm not sure what to conclude other than this.

Nuclear-localized androgen receptor content following resistance exercise training is associated with hypertrophy in males but not females

https://faseb.onlinelibrary.wiley.com/doi/abs/10.1096/fj.202301291RR

 

[Stewie]

This may give *some* explanation to the hypertrophic stimulus from ERa.

Estrogen Receptor α Rapidly Activates the IGF-1 Receptor Pathway

https://www.jbc.org/article/S0021-9258(19)83205-2/fulltext