Persistent lipotoxicity overwhelms adaptive capacity in human hepatic cell line

Area of Science:

• Hepatology
• Metabolic Disease
• Cellular Biology

Background:

• Chronic elevation of fatty acids (FA) is a key driver of metabolic dysfunction-associated liver disease (MASLD).
• Hepatocytes possess adaptive mechanisms to buffer transient lipid overload, but the limits of this capacity under sustained stress are not well understood.

Purpose of the Study:

• To investigate the temporal dynamics of hepatocellular responses to sustained lipid excess.
• To characterize early, intermediate, and prolonged cellular adaptations and dysfunctions.

Main Methods:

• HuH7 hepatocytes were exposed to palmitic/oleic acid (PA/OA) for 1, 14, or 28 days.
• Assessed cell viability, lipid accumulation, stress pathways, insulin signaling, metabolic regulators, mitochondrial function, FA uptake, and extracellular metabolomics.
• Statistical analysis included two-way ANOVA and linear regression.

Main Results:

• Sustained FA exposure increased lipid droplet accumulation and cumulative cell death.
• Exo-metabolomics revealed peak lactate release at Day 14 and increasing acetate by Day 28.
• By Day 28, cells showed altered expression of key proteins involved in FA metabolism, stress response, and apoptosis, alongside increased mitochondrial respiratory complex abundance.

Conclusions:

• Sustained exposure to fatty acids induces a staged hepatocellular response: early adaptation, intermediate compensation, and late decompensation.
• Chronic lipotoxicity results from a progressive loss of regulatory coordination, despite ongoing metabolic adaptation.