The essential effect of mTORC1-dependent lipophagy in non-alcoholic fatty liver disease

Loss of hepatic autophagy induces α-cell proliferation through impaired glutamine-dependent gluconeogenesis

Autophagy, the highly conserved process of protein and organelle degradation, is suppressed in the liver by obesity and metabolic dysfunction-associated fatty liver disease and associated with the development of insulin resistance. We generated adult liver-inducible ATG3 knockout mice (Atg3iLKO) to characterize pathways linking hepatic autophagy with metabolic homeostasis. Genetic loss of hepatic autophagy leads to a reduction in 16-h fasted glucose levels, a decrease in endogenous glucose production rates, and an increase in serum amino acids across the fed and fasted states. These changes collectively reflect a loss of hepatic gluconeogenic enzyme activity and not a general inability to degrade amino acids in the liver. Increased circulating glutamine levels resulting from this are associated with an induction of α-cell hyperplasia, leading to constitutively elevated glucagon levels. However, the loss of hepatic gluconeogenesis renders these animals highly glucagon resistant. Collectively, our data demonstrate that loss of hepatic autophagy is sufficient to activate the hepatic α-islet cell axis, leading to hyperglucagonemia with impaired glucose production.

Exploring the Effects of Pterocarpus Soyauxii Against Menopause-Related NAFLD Based on Network Pharmacology, Molecular Docking, and Experimental Validation

Pterocarpus soyauxii (P. soyauxii) is a Fabaceae family traditionally used to treat menopausal disorders. This study aims to investigate the effect of P. soyauxii on menopause-related non-alcoholic fatty liver disease (NAFLD) and to determine its mechanisms of action and signaling pathways. The pharmacokinetic and dynamic properties and the toxicological profile of P. soyauxii compounds were assessed using the SwissADME and Protox III databases. A pharmacology network was constructed to identify active compound targets and corresponding genes. Compound target and protein-protein interaction networks were created using Cytoscape software. Molecular docking studies were conducted to assess the binding affinity of P. soyauxii compounds with specific proteins. In vitro experiments evaluated the antioxidant properties of P. soyauxii. In vivo studies using ovariectomized (Ovx) rat models underlined pathways and effects of P. soyauxii on biochemical and histological features linked with NAFLD. Findings suggest that P. soyauxii compounds are readily absorbed through the intestine and exhibit a relatively low level of toxicity. Protein-protein interaction, compound-target networks, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed several pathways and target proteins of P. soyauxii compounds. Indeed, they target specific proteins such as estrogen receptor alpha/beta ERα/β, nicotinamide adenine dinucleotide phosphate oxidase (NADPH-O), epidermal growth factor receptor (EGFR), MAPK1, peroxisome proliferator-activated receptors alpha/gamma (PPARα/G), and HMG-CoA reductase. Molecular docking revealed that P. soyauxii compounds demonstrate high binding affinity to various proteins. In vitro, P. soyauxii inhibits the oxidative power of OH, H2O2, and NO. In vivo, P. soyauxii significantly (p < 0.01, p < 0.001, and p < 0.01, respectively) reduces ALAT (25.14%), hepatic cholesterol (15.27%), and malondialdehyde (MDA) (26.78%) levels at 200 mg/kg and prevents steatosis in the liver. These findings suggest that P. soyauxii may have a protective role against menopause-related NAFLD.

Cav3.2 deletion attenuates nonalcoholic fatty liver disease in mice

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and represents the main cause of liver cirrhosis and hepatocellular carcinoma. Cav3.2 is a T-type calcium channel that is widely present in tissues throughout the body and plays a vital role in energy and metabolic balance. However, the effects of Cav3.2 on the NFALD remain unclear. Here, we investigated the role of Cav3.2 channel in the development and progression of NAFLD. After 16 weeks on a high-fat diets (HFD), Cav3.2 knockout (Cav3.2 KO) improved hepatic steatosis, liver injury and metabolic syndrome in an NAFLD mouse model. We provided evidence that Cav3.2 KO inhibited HFD-induced hepatic oxidative stress, inflammation and hepatocyte apoptosis. In addition, Cav3.2 KO also attenuated hepatic lipid accumulation, oxidative stress, inflammation and hepatocyte apoptosis in palmitic acid/oleic acid (PAOA)-treated primary hepatocytes. These results suggest that therapeutic approaches targeting Cav3.2 provide effective approaches for treating NAFLD.

Bibliometric analysis of lipophagy:2013 to 2023

Lipophagy is defined as the autophagic degradation of lipid droplets. It is a selective autophagy process that can continuously circulate and redistribute metabolites to maintain the body's energy balance. Over the last ten years, there has been a significant increase in the amount of literature on lipophagy, making it more challenging to track the field's advancement using conventional techniques. The data from the lipophagy literature published in the last ten years was converted into visual representations with the use of bibliometric tools. An increasing number of countries and institutions are delving further into lipophagy research with the support of visualization technologies. The five main illnesses of cancer, atherosclerosis, fatty liver, hyperlipidemia, and neurodegenerative diseases have become study opportunities, as have the mechanisms of macroautophagy, microautophagy, and chaperone-mediated autophagy.

Regulation of Benzo[a]pyrene-Induced Hepatic Lipid Accumulation through CYP1B1-Induced mTOR-Mediated Lipophagy

Metabolic dysfunction-associated steatotic liver disease (MASLD) is caused by lipid accumulation within the liver. The pathogenesis underlying its development is poorly understood. Benzo[a]pyrene (B[a]P) is a polycyclic aromatic hydrocarbon and a group 1 carcinogen. The aryl hydrocarbon receptor activation by B[a]P induces cytochrome P450 (CYP) enzymes, contributing to hepatic lipid accumulation. However, the molecular mechanism through which the B[a]P-mediated induction of CYP enzymes causes hepatic lipid accumulation is unknown. This research was conducted to elucidate the role of CYP1B1 in regulating B[a]P-induced lipid accumulation within hepatocytes. B[a]P increased hepatic lipid accumulation, which was mitigated by CYP1B1 knockdown. An increase in the mammalian target of rapamycin (mTOR) by B[a]P was specifically reduced by CYP1B1 knockdown. The reduction of mTOR increased the expression of autophagic flux-related genes and promoted phagolysosome formation. Both the expression and translocation of TFE3, a central regulator of lipophagy, were induced, along with the expression of lipophagy-related genes. Conversely, enhanced mTOR activity reduced TFE3 expression and translocation, which reduced the expression of lipophagy-related genes, diminished phagolysosome production, and increased lipid accumulation. Our results indicate that B[a]P-induced hepatic lipid accumulation is caused by CYP1B1-induced mTOR and the reduction of lipophagy, thereby introducing novel targets and mechanisms to provide insights for understanding B[a]P-induced MASLD.

Cell-type specific role of autophagy in the liver and its implications in non-alcoholic fatty liver disease

Autophagy, a cellular degradative process, has emerged as a key regulator of cellular energy production and stress mitigation. Dysregulated autophagy is a common phenomenon observed in several human diseases, and its restoration offers curative advantage. Non-alcoholic fatty liver disease (NAFLD), more recently renamed metabolic dysfunction-associated steatotic liver disease, is a major metabolic liver disease affecting almost 30% of the world population. Unfortunately, NAFLD has no pharmacological therapies available to date. Autophagy regulates several hepatic processes including lipid metabolism, inflammation, cellular integrity and cellular plasticity in both parenchymal (hepatocytes) and non-parenchymal cells (Kupffer cells, hepatic stellate cells and sinusoidal endothelial cells) with a profound impact on NAFLD progression. Understanding cell type-specific autophagy in the liver is essential in order to develop targeted treatments for liver diseases such as NAFLD. Modulating autophagy in specific cell types can have varying effects on liver function and pathology, making it a promising area of research for liver-related disorders. This review aims to summarize our present understanding of cell-type specific effects of autophagy and their implications in developing autophagy centric therapies for NAFLD.