Lipophagy Dysfunction Links to Mitochondrial Stress in Fatty Liver [May. 27, 2026]

Hepatic lipid droplets require lysosomal turnover to limit lipid storage under nutrient stress, and lipophagy plays a central role in lipid droplet clearance in fatty liver disease. Two recent studies have examined the molecular mechanisms underlying this process. One study demonstrated that TMEM55B deficiency impairs lysosomal lipid degradation and mitochondrial quality control, linking these defects to MASLD/MASH progression. Another showed that Rubicon silencing restores autophagosome-lysosome fusion and lipophagy, offering a potential avenue for therapeutic intervention.

Loss of TMEM55B modulates lipid metabolism through dysregulated lipophagy and mitochondrial function (Cell Death & Disease, 2026)
Summary: 
Lipophagy and mitophagy protect hepatocytes from lipid overload. TMEM55B is a key regulator of lysosome positioning and mobility, but its role in hepatic lipid metabolism remains unclear. The authors addressed this gap using TMEM55B-deficient mouse and hepatocyte models, demonstrating that impaired lysosomal lipid degradation and defective mitochondrial quality control drive mitochondrial dysfunction, oxidative stress, lipid accumulation, and MASLD/MASH progression.  

Highlighted technique: 
To examine whether lysosomal lipid degradation failure causes mitochondrial stress, the authors visualized lipid accumulation in lysosomes using fluorescence-labeled fatty acids. They then assessed mitochondrial respiration by OCR analysis, membrane potential by TMRE staining, morphology by imaging, and oxidative stress by mitochondrial ROS staining.

There is an OCR plate-assay kit that requires fewer cells and offers lower running costs. It can also be used for preliminary evaluation prior to Seahorse analysis.
Together, pH-resistant Lysosomal staining, membrane potential and mitochondrial ROS measurements enable organelle-specific assessment of lysosomes and mitochondria.

Dual-targeted siRubicon delivery strategy triggers hepatocellular lipophagy for mitigating liver steatosis (Nature communications, 2025)
Summary: 
The authors focused on Rubicon, an autophagy brake elevated in fatty hepatocytes and MASH. They demonstrated that silencing Rubicon restores autophagosome–lysosome fusion and lipophagy, leading to lipid droplet clearance and reduced hepatic lipid accumulation.

Highlighted technique: 
To assess lipophagy rescue, the authors evaluated the colocalization of lipid droplets with lysosomes and the association of lipid droplets with autophagosomes.They also applied mCherry-GFP-LC3B to track autophagic flux and LC3/LAMP1 co-staining to examine autophagosome–lysosome fusion.

Visualize lipid droplet dynamics with bright, multicolor probes for live- and fixed-cell imaging. For lysosomal analysis, pH-independent probes assess lysosomal quantity, while pH-sensitive probes detect changes in lysosomal pH. 
Without the need for gene transfection, Autophagic flux assay kits enable monitoring of the entire autophagic process, from autophagosome formation to autolysosome maturation.