Overexpression of IGF-1 in muscle attenuates disease in a mouse model of spinal and bulbar muscular atrophy.
IGF-1 overexpression in a mouse model of SBMA showed promising effects on reducing AR aggregation and improving lifespan, but results may not directly apply to humans.
Where it sits
this study against the rest of the goserelin corpusSummary and findings
The study investigated the effects of insulin-like growth factor 1 (IGF-1) on spinal and bulbar muscular atrophy (SBMA) in a mouse model. Mice overexpressing a muscle-specific isoform of IGF-1 showed increased Akt activation and reduced androgen receptor (AR) aggregation. The findings suggest potential benefits in behavioral and histopathological outcomes, as well as lifespan extension.
Abstract
Expansion of a polyglutamine tract in the androgen receptor (AR) causes spinal and bulbar muscular atrophy (SBMA). We previously showed that Akt-mediated phosphorylation of AR reduces ligand binding and attenuates the mutant AR toxicity. Here, we show that in culture insulin-like growth factor 1 (IGF-1) reduces AR aggregation and increases AR clearance via the ubiquitin-proteasome system through phosphorylation of AR by Akt. In vivo, SBMA transgenic mice overexpressing a muscle-specific isoform of IGF-1 selectively in skeletal muscle show evidence of increased Akt activation and AR phosphorylation and decreased AR aggregation. Augmentation of IGF-1/Akt signaling rescues behavioral and histopathological abnormalities, extends the life span, and reduces both muscle and spinal cord pathology of SBMA mice. This study establishes IGF-1/Akt-mediated inactivation of mutant AR as a strategy to counteract disease in vivo and demonstrates that skeletal muscle is a viable target tissue for therapeutic intervention in SBMA.
Background
This paper addresses the role of insulin-like growth factor 1 (IGF-1) in the context of spinal and bulbar muscular atrophy (SBMA), a neurodegenerative disease caused by mutations in the androgen receptor (AR). Previous research indicated that Akt-mediated phosphorylation of AR could mitigate its toxicity. Understanding the mechanisms by which IGF-1 influences AR aggregation and clearance is crucial for exploring potential therapeutic strategies.
Methods
The study utilized SBMA transgenic mice overexpressing a muscle-specific isoform of IGF-1. The primary outcomes included Akt activation, AR phosphorylation, and AR aggregation. Behavioral and histopathological assessments were also conducted to evaluate the effects of IGF-1 overexpression.
Results
The study reported that SBMA transgenic mice overexpressing IGF-1 exhibited increased Akt activation and reduced AR aggregation. Specific numeric findings regarding the extent of these changes were not reported in the abstract.
Interpretation
The findings suggest that IGF-1/Akt signaling may provide a mechanism to counteract the effects of mutant AR in SBMA. However, the significance of the observed effects in terms of clinical relevance remains uncertain, especially given that the study was conducted in a mouse model. The limitations of translating these results to human patients must be considered.
Key findings
- In vivo, SBMA transgenic mice overexpressing IGF-1 showed increased Akt activation.
- Augmentation of IGF-1/Akt signaling reduced AR aggregation.
- Behavioral and histopathological abnormalities were rescued in SBMA mice.
- Lifespan was extended in SBMA mice with IGF-1 overexpression.
Limitations
- Based on a mouse model, which may not fully translate to human conditions.
- No specific numeric findings reported in the abstract.
- Potential confounding factors not addressed in the abstract.