Hormonal
In vivo administration of triiodothyronine (T3) to healthy men significantly up-regulates gene expression in skeletal muscle, specifically increasing mRNA levels for proteins involved in energy metabolism (mitochondrial respiratory chain, uncoupling proteins) and protein turnover (ubiquitin-proteasome pathway).
This study demonstrates that thyroid hormone (T3) directly reprograms skeletal muscle gene expression to increase energy expenditure and protein breakdown. For healthy individuals, this explains why hyperthyroidism leads to weight loss and muscle wasting. It does not suggest T3 supplementation as a safe or effective weight loss strategy for the general population due to the significant physiological side effects (increased heart rate, blood pressure, and protein catabolism) observed.
The 381 up-regulated genes were involved in a wide range of cellular functions including ... energy metabolism. ... Our data show a concomitant increase in mRNA expression of protein catabolism factors ... Most changes affected the ubiquitin/proteasome pathway.
Why this rating
Randomized, controlled, in vivo human study with rigorous statistical analysis (SAM) and validation via qRT-PCR, though sample size is small (n=5 for microarray).
Source
In Vivo Regulation of Human Skeletal Muscle Gene Expression by Thyroid Hormone
Karine Clément et al. · Genome Research · 2002
DOI 10.1101/gr.207702
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