The aryl hydrocarbon receptor is downregulated in MASLD while its activation attenuates steatosis in human...

Metabolic dysfunction-associated steatotic liver disease (MASLD) represents a growing global health concern; however, its multiple pathogenic mechanisms remain incompletely understood. The role of the aryl hydrocarbon receptor (AHR) in MASLD is controversial, as it has been described as either pro- or anti-steatotic depending on the experimental context. Through whole-genome expression profiling and RT-qPCR analysis of human liver biopsies from two independent MASLD patient cohorts, we demonstrate that AHR expression and its canonical activity-assessed by CYP1A1 mRNA levels-are inversely correlated with hepatic steatosis. The role of AHR was further investigated in cultured human Upcyte® hepatocytes from different donors treated with a 2:1 oleate:palmitate mixture (0.6 mM) to induce steatosis, in combination with the exogenous AHR agonist β-naphthoflavone (BN, 25 µM) or the endogenous agonist 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE, 25 µM). Activation of AHR resulted in a statistically significant reduction of intracellular lipid levels, as determined by triglyceride quantification and AdipoRed staining. Microarray analysis of AHR-activated human hepatocytes identified IGFBP1 as a robustly induced target gene. Consistently, IGFBP1 expression was diminished in the livers of both MASLD cohorts and positively correlated with AHR expression levels. Furthermore, treatment of human hepatocytes with recombinant IGFBP1, alone or in combination with IGF1, reduced lipid accumulation, supporting IGFBP1 as a potential downstream effector within the anti-steatotic AHR pathway. Collectively, these findings support a role for AHR and its target IGFBP1, as key negative regulators of hepatic lipid accumulation in human hepatocytes and suggest that activation of this pathway may be taken into account in the therapeutic approaches for MASLD.