PPARalpha governs glycerol metabolism

Area of Science:

• Metabolic regulation
• Molecular endocrinology
• Hepatology

Background:

• Glycerol is a key gluconeogenic substrate produced from lipolysis.
• Hepatic glycerol metabolism regulation remains poorly understood.
• Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors involved in lipid and glucose metabolism.

Purpose of the Study:

• To elucidate the role of PPARs in regulating hepatic glycerol metabolism.
• To identify direct PPAR target genes involved in glycerol processing.
• To investigate the functional consequences of PPAR-mediated glycerol metabolism regulation on glucose production.

Main Methods:

• Gene expression analysis in wild-type and PPARalpha-null mice under fasting and agonist treatment.
• PPAR agonist treatment in adipocytes.
• Biochemical assays including transactivation, gel shift, and chromatin immunoprecipitation.
• Measurement of plasma glycerol levels and hepatic glucose production in mice and humans.

Main Results:

• Fasting and PPARalpha agonists upregulate hepatic glycerol metabolism genes (GPDH, glycerol kinase, aquaporins) in a PPARalpha-dependent manner.
• Cytosolic GPDH is a direct PPAR target gene, regulated by PPARgamma and PPARbeta/delta in adipocytes.
• PPARalpha activation reduces plasma glycerol levels in mice and humans.
• PPARalpha deficiency impairs hepatic glucose production during fasting and agonist treatment.

Conclusions:

• PPARalpha directly controls hepatic glycerol metabolism and influences glucose production.
• PPARgamma regulates glycerol metabolism in adipose tissue.
• PPARs represent key regulators of glycerol homeostasis and gluconeogenesis.