Objective::Rubicon is an inhibitory interacting protein of the autophagy-related protein Uvrag. We previously showed that n Rubicon deficiency promotes autophagic flux n in vivo and that autophagy can degrade lipid droplets. This study aimed to investigate the effects of Rubicon deficiency on fasting-induced hepatic steatosis.n Methods::Two-month-old wild-type (WT) and n Rubicon-deficient mice were subjected to feeding or fasting for 24 hours to induce hepatic steatosis. The distribution of liver lipid droplets was revealed by oil red O staining. Hepatic and plasma triglyceride, non-esterified fatty acid (NEFA), and cholesterol levels were detected using commercially available kits. Real-time reverse transcriptasepolymerase chain reaction was performed to analyze the mRNA expression of genes related to lipid metabolism in the liver. Western blot was conducted to assess autophagy-related protein levels in the liver. The animal experiments were approved by the Institutional Animal Care and Use Committee at Shanghai Jiao Tong University, China.n Results::We showed that under fasting conditions, n Rubicon-deficient mice had more lipid droplets in the liver than WT controls. Consistent with these results, the hepatic triglyceride, NEFA, and cholesterol levels in fasted n Rubicon-deficient mice were significantly higher than those of fasted WT controls. The levels of n SREBP-1, a key regulator of lipid synthesis, were significantly lower in livers from fasted WT mice than those of fed WT mice. However, the decrease in n SREBP-1 in fasted mice was attenuated by n Rubicon deficiency. Western blot analysis demonstrated that the fasting-induced increase in autophagic flux was amplified by n Rubicon deficiency. Finally, we showed that n Rubicon deficiency in mice led to elevated plasma triglyceride and NEFA acid levels under fasting conditions.n Conclusion::Rubicon deficiency exacerbates fasting-induced hepatic steatosis in mice.n “,”Objective::Rubicon is an inhibitory interacting protein of the autophagy-related protein Uvrag. We previously showed that n Rubicon deficiency promotes autophagic flux n in vivo and that autophagy can degrade lipid droplets. This study aimed to investigate the effects of Rubicon deficiency on fasting-induced hepatic steatosis.n Methods::Two-month-old wild-type (WT) and n Rubicon-deficient mice were subjected to feeding or fasting for 24 hours to induce hepatic steatosis. The distribution of liver lipid droplets was revealed by oil red O staining. Hepatic and plasma triglyceride, non-esterified fatty acid (NEFA), and cholesterol levels were detected using commercially available kits. Real-time reverse transcriptasepolymerase chain reaction was performed to analyze the mRNA expression of genes related to lipid metabolism in the liver. Western blot was conducted to assess autophagy-related protein levels in the liver. The animal experiments were approved by the Institutional Animal Care and Use Committee at Shanghai Jiao Tong University, China.n Results::We showed that under fasting conditions, n Rubicon-deficient mice had more lipid droplets in the liver than WT controls. Consistent with these results, the hepatic triglyceride, NEFA, and cholesterol levels in fasted n Rubicon-deficient mice were significantly higher than those of fasted WT controls. The levels of n SREBP-1, a key regulator of lipid synthesis, were significantly lower in livers from fasted WT mice than those of fed WT mice. However, the decrease in n SREBP-1 in fasted mice was attenuated by n Rubicon deficiency. Western blot analysis demonstrated that the fasting-induced increase in autophagic flux was amplified by n Rubicon deficiency. Finally, we showed that n Rubicon deficiency in mice led to elevated plasma triglyceride and NEFA acid levels under fasting conditions.n Conclusion::Rubicon deficiency exacerbates fasting-induced hepatic steatosis in mice.n