PPARα-ATGL pathway improves muscle mitochondrial metabolism: implication in aging

Area of Science:

• Mitochondrial metabolism
• Skeletal muscle physiology
• Aging research

Background:

• Adipose triglyceride lipase (ATGL) is thought to support mitochondrial function by producing ligands for peroxisome proliferator-activated receptor α (PPARα).
• PPARα, along with PPARγ coactivator-1α (PGC1α), regulates muscle mitochondrial biogenesis, but the interplay between ATGL and PPARα in skeletal muscle aging is unclear.

Purpose of the Study:

• To investigate the cross-talk between ATGL and PPARα in skeletal muscle mitochondrial metabolism.
• To determine the role of this pathway in chronological aging.

Main Methods:

• Gene manipulation (overexpression and depletion) of ATGL in cultured myotubes and murine skeletal muscle.
• Assessment of mitochondrial oxidative phosphorylation and fatty acid oxidation.
• Analysis of gene expression and protein levels.
• Studies in middle-aged rats and fenofibrate-treated rats.

Main Results:

• PPARα directly induces ATGL expression during myogenesis.
• ATGL overexpression enhanced mitochondrial oxidative phosphorylation and fatty acid oxidation; ATGL depletion attenuated these functions.
• ATGL's effects on oxidative function were independent of mitochondrial content and rendered PPARα and PGC1α redundant.
• ATGL did not affect PPARα-dependent lipid accumulation or insulin sensitivity.
• Middle-aged rats showed higher ATGL and PPARα expression, correlating with sustained fatty acid oxidation in soleus muscle.
• Fenofibrate treatment increased ATGL expression in the soleus muscle.

Conclusions:

• PPARα and ATGL form a regulatory pathway in skeletal muscle.
• This pathway plays a significant role in maintaining mitochondrial metabolic reserve, particularly during aging.