PPARγ contributes to PKM2 and HK2 expression in fatty liver

Area of Science:

• Cellular metabolism
• Molecular biology
• Oncology

Background:

• Rapidly proliferating cells utilize aerobic glycolysis for biosynthesis.
• Pyruvate kinase M2 (PKM2) and hexokinase 2 (HK2) are key glycolytic enzymes supporting cell growth.
• Factors regulating selective expression of PKM2 and HK2 are largely unknown.

Purpose of the Study:

• Investigate the role of peroxisome proliferator-activated receptor gamma (PPARγ) in regulating PKM2 and HK2 gene expression.
• Elucidate the mechanism by which PPARγ influences metabolic adaptation in PTEN-null fatty liver.
• Determine the impact of PPARγ activity on liver steatosis, proliferation, and tumorigenesis.

Main Methods:

• Analysis of gene expression in PTEN-null mouse livers.
• Chromatin immunoprecipitation assays to assess PPARγ binding to gene promoters.
• In vivo experiments to modulate PPARγ activity and observe effects on liver phenotype.

Main Results:

• PPARγ directly activates transcription of PKM2 and HK2 genes in PTEN-null fatty liver.
• Akt2 kinase controls PPARγ expression, liver steatosis, aerobic glycolysis, and tumorigenesis in this model.
• In vivo restoration of PPARγ activity leads to liver steatosis, hypertrophy, and hyperplasia.

Conclusions:

• PPARγ is a critical regulator of aerobic glycolysis and associated gene expression in PTEN-null fatty liver.
• Therapeutic strategies using PPARγ agonists (thiazolidinediones) may have differential effects on liver steatosis based on its origin.
• Understanding PPARγ's role offers insights into metabolic reprogramming in cancer and liver disease.