Rapamycin attenuates palmitate-induced lipid aggregation by up-regulating sirt-1 signaling in AML12 hepatocytes

Area of Science:

• Cellular biology
• Metabolism research
• Pharmacology

Background:

• Rapamycin (Rap) inhibits mTOR signaling and impacts lipid metabolism.
• Sirt-1, an NAD+-dependent deacetylase, regulates cellular processes including lipid metabolism.
• The interplay between rapamycin and Sirt-1 in lipid metabolism remains unclear.

Purpose of the Study:

• To investigate the association between rapamycin's lipid-lowering effects and Sirt-1 signaling.
• To explore the mechanism by which rapamycin influences lipid metabolism in a cellular steatosis model.

Main Methods:

• A cellular steatosis model using AML12 hepatocytes stimulated with palmitate.
• Treatment with rapamycin and/or siRNA-mediated knockdown of Sirt-1.
• Oil red O staining to visualize lipid droplets and quantification of intracellular lipid content.
• Measurement of Sirt-1 and AMPK expression levels and Sirt-1 deacetylase activity.

Main Results:

• Low-dose rapamycin significantly reduced lipid aggregation in steatotic AML12 cells.
• Knockdown of Sirt-1 abrogated the lipid-ameliorating effect of rapamycin.
• Rapamycin increased Sirt-1 and AMPK expression and enhanced Sirt-1 deacetylase activity.

Conclusions:

• Rapamycin ameliorates lipid accumulation in hepatocytes by upregulating Sirt-1 signaling.
• This study demonstrates a novel mechanism for rapamycin's metabolic effects.
• Rapamycin may positively influence Sirt-1 signaling to maintain metabolic homeostasis.