n/a
Article Publish Status: FREE
Abstract Title:

Fiber type-specific hypertrophy and increased capillarization in skeletal muscle following testosterone administration in young women.

Abstract Source:

J Appl Physiol (1985). 2020 May 1 ;128(5):1240-1250. Epub 2020 Mar 19. PMID: 32191598

Abstract Author(s):

Oscar Horwath, William Apró, Marcus Moberg, Manne Godhe, Torbjörn Helge, Maria Ekblom, Angelica Lindén Hirschberg, Björn Ekblom

Article Affiliation:

Oscar Horwath

Abstract:

It is well established that testosterone administration induces muscle fiber hypertrophy and myonuclear addition in men; however, it remains to be determined whether similar morphological adaptations can be achieved in women. The aim of the present study was therefore to investigate whether exogenously administered testosterone alters muscle fiber morphology in skeletal muscle of young healthy, physically active women. Thirty-five young (20-35 yr), recreationally trained women were randomly assigned to either 10-wk testosterone administration (10 mg daily) or placebo. Before and after the intervention, hormone concentrations and body composition were assessed, and muscle biopsies were obtained from the vastus lateralis. Fiber type composition, fiber size, satellite cell and myonuclei content, as well as muscle capillarization were assessed in a fiber type-specific manner by immunohistochemistry. After the intervention, testosterone administration elevated serum testosterone concentration (5.1-fold increase,= 0.001) and induced significant accretion of total lean mass (+1.9%,= 0.002) and leg lean mass (+2.4%,= 0.001). On the muscle fiber level, testosterone increased mixed-fiber cross-sectional area (+8.2%,= 0.001), an effect primarily driven by increases in type II fiber size (9.2%,= 0.006). Whereas myonuclei content remained unchanged, a numerical increase (+30.8%) was found for satellite cells associated with type II fibers in the Testosterone group. In parallel with fiber hypertrophy, testosterone significantly increased capillary contacts (+7.5%,= 0.015) and capillary-to-fiber ratio (+9.2%,= 0.001) in type II muscle fibers. The present study provides novel insight into fiber type-specific adaptations present already after 10 wk of only moderately elevated testosterone levels in women.We have recently demonstrated performance-enhancing effects of moderately elevated testosterone concentrations in young women. Here we present novel evidence that testosterone alters muscle morphology in these women, resulting in type II fiber hypertrophy and improved capillarization. Our findings suggest that low doses of testosterone potently impact skeletal muscle after only 10 wk. These data provide unique insights into muscle adaptation and support the performance-enhancing role of testosterone in women on the muscle fiber level.

Study Type : Human Study

Print Options


Key Research Topics

This website is for information purposes only. By providing the information contained herein we are not diagnosing, treating, curing, mitigating, or preventing any type of disease or medical condition. Before beginning any type of natural, integrative or conventional treatment regimen, it is advisable to seek the advice of a licensed healthcare professional.

© Copyright 2008-2024 GreenMedInfo.com, Journal Articles copyright of original owners, MeSH copyright NLM.