Bisphenol A Induces Fatty Liver by an Endocannabinoid-Mediated Positive Feedback Loop

Area of Science:

• Environmental Science
• Toxicology
• Endocrinology

Background:

• Bisphenol A (BPA) is a pervasive xenoestrogen and plasticizer found in various ecosystems.
• BPA is recognized as a metabolic disruptor, but its precise mechanism in liver function remains unclear.
• Previous studies indicate BPA can trigger triglyceride accumulation in the liver.

Purpose of the Study:

• To investigate the mechanism by which BPA induces hepatosteatosis (fatty liver disease).
• To explore the role of the endocannabinoid system in BPA-induced liver effects.
• To determine if BPA's effects on liver fat accumulation are conserved between zebrafish and human hepatocytes.

Main Methods:

• Adult zebrafish (Danio rerio) were exposed to BPA to assess liver changes.
• Endocannabinoid levels (2-arachidonoylglycerol, anandamide, palmitoylethanolamide) and gene expression of related enzymes were analyzed.
• In vitro studies using HHL-5 cells (human hepatocytes) treated with BPA were conducted to examine anandamide levels, fatty acid amide hydrolase activity, and triglyceride accumulation.

Main Results:

• BPA exposure in zebrafish led to hepatosteatosis, increased levels of 2-arachidonoylglycerol and anandamide, and decreased palmitoylethanolamide.
• Changes in endocannabinoid enzyme expression and increased expression of the CB1 receptor (cnr1) were observed.
• In vitro, BPA increased anandamide levels, reduced fatty acid amide hydrolase activity, and promoted triglyceride accumulation in HHL-5 cells in a CB1-dependent manner.

Conclusions:

• Bisphenol A induces hepatosteatosis in both zebrafish and human hepatocytes.
• BPA exerts its liver-damaging effects by up-regulating the endocannabinoid system.
• The findings reveal a novel mechanism of BPA toxicity involving endocannabinoid signaling.