Human-induced pluripotent stem cell-based hepatic modeling of lipid metabolism-associated TM6SF2-E167K variant.

Background and aims: TM6SF2 rs58542926 (E167K) is related to an increased prevalence of metabolic dysfunction-associated steatotic liver disease. Conflicting mouse study results highlight the need for a human model to understand this mutation's impact. This study aims to create and characterize a reliable human in vitro model to mimic the effects of the TM6SF2-E167K mutation for future studies.

Approach and results: We used gene editing on human-induced pluripotent stem cells from a healthy individual to create cells with the TM6SF2-E167K mutation. After hepatocyte-directed differentiation, we observed decreased TM6SF2 protein expression, increased intracellular lipid droplets, and total cholesterol, in addition to reduced VLDL secretion. Transcriptomics revealed the upregulation of genes involved in lipid, fatty acid, and cholesterol transport, flux, and oxidation. Global lipidomics showed increased lipid classes associated with endoplasmic reticulum (ER) stress, mitochondrial dysfunction, apoptosis, and lipid metabolism. In addition, the TM6SF2-E167K mutation conferred a proinflammatory phenotype with signs of mitochondria and ER stress. Importantly, by facilitating protein folding within the ER of hepatocytes carrying TM6SF2-E167K mutation, VLDL secretion and ER stress markers improved.

Conclusions: Our findings indicate that induced hepatocytes generated from human-induced pluripotent stem cells carrying the TM6SF2-E167K recapitulate the effects observed in human hepatocytes from individuals with the TM6SF2 mutation. This study characterizes an in vitro model that can be used as a platform to identify potential clinical targets and highlights the therapeutic potential of targeting protein misfolding to alleviate ER stress and mitigate the detrimental effects of the TM6SF2-E167K mutation on hepatic lipid metabolism.