Autophagy in non-alcoholic fatty liver disease and alcoholic liver disease

Autophagy in Disease Onset and Progression

Autophagy is a biological phenomenon whereby components of cells can self-degrade using autophagosomes. During this process, cells can clear dysfunctional organelles or unwanted elements. Autophagy can recycle unnecessary biomolecules into new components or sometimes, even destroy the cells themselves. This cellular process was first observed in 1962 by Keith R. Porter et al. Since then, autophagy has been studied for over 60 years, and much has been learned on the topic. Nevertheless, the process is still not fully understood. It has been proven, for example, that autophagy can be a positive force for maintaining good health by removing older or damaged cells. By contrast, autophagy is also involved in the onset and progression of various conditions caused by pathogenic infections. These diseases generally involve several important organs in the human body, including the liver, kidney, heart, and central nervous system. The regulation of the defects of autophagy defects may potentially be used to treat some diseases. This review comprehensively discusses recent research frontiers and topics of interest regarding autophagy-related diseases.

Hepatoprotective effect of dietary pterostilbene against high-fat-diet-induced lipid accumulation exacerbated by chronic jet lag via SIRT1 and SIRT3 activation

Hepatic lipid metabolism is modulated by the circadian rhythm; therefore, circadian disruption may promote obesity and hepatic lipid accumulation. This study aims to investigate dietary pterostilbene (PSB) 's protective effect against high-fat-diet (HFD)-induced lipid accumulation exacerbated by chronic jet lag and the potential role of gut microbiota therein. Mice were treated with a HFD and chronic jet lag for 14 weeks. The experimental group was supplemented with 0.25% (w/w) PSB in its diet to evaluate whether PSB had a beneficial effect. Our study found that chronic jet lag exacerbates HFD-induced obesity and hepatic lipid accumulation, but these adverse effects were significantly mitigated by PSB supplementation. Specifically, PSB promoted hepatic lipolysis and β-oxidation by upregulating SIRT1 expression, which indirectly reduced oxidative stress caused by lipid accumulation. Additionally, the PSB-induced elevation of SIRT1 and SIRT3 expression helped prevent excessive autophagy and mitochondrial fission by activating Nrf2-mediated antioxidant enzymes. The result was evidenced by the use of SIRT1 and SIRT3 inhibitors in in vitro studies, which demonstrated that activation of SIRT1 and SIRT3 by PSB is crucial for the translocation of PGC-1α and Nrf2, respectively. Moreover, the analysis of gut microbiota suggested that PSB's beneficial effects were partly due to its positive modulation of gut microbial composition and functionality. The findings of this study suggest the potential of dietary PSB as a candidate to improve hepatic lipid metabolism via several mechanisms. It may be developed as a treatment adjuvant in the future.

Sesamin alleviates lipid accumulation induced by oleic acid via PINK1/Parkin-mediated mitophagy in HepG2 cells

Sesamin, a special compound present in sesame and sesame oil, has been reported a role in regulating lipid metabolism, while the underlying mechanisms remain unclear. Autophagy has been reported associated with lipid metabolism and regarded as a key modulator in liver steatosis. The present work aimed to investigate whether sesamin could exert its protective effects against lipid accumulation via modulating autophagy in HepG2 cells stimulated with oleic acid (OA). Cell viability was evaluated using the CCK-8 method, and triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein, cholesterol (LDL-C), alanine aminotransferase (ALT), along with aspartate aminotransferase (AST) were assessed by oil red O staining, transmission electron microscopy (TEM), and biochemical kits to investigate the lipid-lowering effects of sesamin. Differentially expressed genes were screened by RNA sequencing and validated using real-time quantitative PCR and Western blot. Autophagy and mitophagy related molecules were analyzed employing TEM, Western blot, and immunofluorescence. The data shows that in HepG2 cells stimulated by OA, sesamin reduces levels of TG, TC, LDL-C, ALT, and AST while elevating HDL-C, alleviates the lipid accumulation and improves fatty acid metabolism through modulating the levels of fat metabolism related genes including PCSK9, FABP1, CD36, and SOX4. Sesamin restores the suppressed autophagy in HepG2 cells caused by OA, which could be blocked by autophagy inhibitors. This indicates that sesamin improves fatty acid metabolism by enhancing autophagy levels, thereby mitigating the intracellular lipid accumulation. Furthermore, sesamin significantly enhances the mitophagy and improves mitochondrial homeostasis via activating the PINK/Parkin pathway. These data suggest that sesamin alleviates the excessive lipid accumulation in HepG2 caused by OA by restoring the impaired mitophagy via the PINK1/Parkin pathway, probably playing a preventive or therapeutic role in hepatic steatosis.

White adipose tissue in metabolic associated fatty liver disease

BACKGROUND

Metabolic associated fatty liver disease (MAFLD) is a prevalent chronic liver condition globally, currently lacking universally recognized therapeutic drugs, thereby increasing the risk of cirrhosis and hepatocellular carcinoma. Research has reported an association between white adipose tissue and MAFLD.

SCOPE OF REVIEW

White adipose tissue (WAT) is involved in lipid metabolism and can contribute to the progression of MAFLD by mediating insulin resistance, inflammation, exosomes, autophagy, and other processes. This review aims to elucidate the mechanisms through which WAT plays a role in the development of MAFLD.

MAJOR CONCLUSIONS

WAT participates in the occurrence and progression of MAFLD by mediating insulin resistance, inflammation, autophagy, and exosome secretion. Fibrosis and restricted expansion of adipose tissue can lead to the release of more free fatty acids (FFA), exacerbating the progression of MAFLD. WAT-secreted TNF-α and IL-1β, through the promotion of JNK/JKK/p38MAPK expression, interfere with insulin receptor serine and tyrosine phosphorylation, worsening insulin resistance. Adiponectin, by inhibiting the TLR-4-NF-κB pathway and suppressing M2 to M1 transformation, further inhibits the secretion of IL-6, IL-1β, and TNF-α, improving insulin resistance in MAFLD patients. Various gene expressions within WAT, such as MBPAT7, Nrf2, and Ube4A, can ameliorate insulin resistance in MAFLD patients. Autophagy-related gene Atg7 promotes the expression of fibrosis-related genes, worsening MAFLD. Non-pharmacological treatments, including diabetes-related medications and exercise, can improve MAFLD.

Vitamin D and Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD): Novel Mechanistic Insights

Metabolic dysfunction-associated steatotic liver disease (MASLD) is an increasingly prevalent condition characterized by abnormal fat accumulation in the liver, often associated with metabolic disorders. Emerging evidence suggests a potential link between vitamin D deficiency and the development and progression of MASLD. The current review provides a concise overview of recent studies uncovering novel mechanistic insights into the interplay between vitamin D and MASLD. Several epidemiological studies have highlighted a significant association between low vitamin D levels and an increased risk of MASLD. Vitamin D, traditionally known for its role in bone health, has now been recognized as a key player in various physiological processes, including immune regulation and inflammation. Experimental studies using animal models have demonstrated that vitamin D deficiency exacerbates liver steatosis and inflammation, suggesting a potential protective role against MASLD. Mechanistically, vitamin D appears to modulate MASLD through multiple pathways. Firstly, the vitamin D receptor (VDR) is abundantly expressed in liver cells, indicating a direct regulatory role in hepatic function. Activation of the VDR has been shown to suppress hepatic lipid accumulation and inflammation, providing a mechanistic basis for the observed protective effects. Additionally, vitamin D influences insulin sensitivity, a critical factor in MASLD pathogenesis. Improved insulin sensitivity may mitigate the excessive accumulation of fat in the liver, thus attenuating MASLD progression. In parallel, vitamin D exhibits anti-inflammatory properties by inhibiting pro-inflammatory cytokines implicated in MASLD pathophysiology. Experimental evidence suggests that the immunomodulatory effects of vitamin D extend to the liver, reducing inflammation and oxidative stress, key drivers of MASLD, and the likelihood of hepatocyte injury and fibrosis. Understanding the complex interplay between vitamin D and MASLD provides a basis for exploring targeted therapeutic strategies and preventive interventions. As vitamin D deficiency is a modifiable risk factor, addressing this nutritional concern may prove beneficial in mitigating the burden of MASLD and associated metabolic disorders.

Short-chain fatty acids in nonalcoholic fatty liver disease: New prospects for short-chain fatty acids as therapeutic targets

Nonalcoholic fatty liver disease (NAFLD) is a stress-induced liver injury related to heredity, environmental exposure and the gut microbiome metabolism. Short-chain fatty acids (SCFAs), the metabolites of gut microbiota (GM), participate in the regulation of hepatic steatosis and inflammation through the gut-liver axis, which play an important role in the alleviation of NAFLD. However, little progress has been made in systematically elucidating the mechanism of how SCFAs improve NAFLD, especially the epigenetic mechanisms and the potential therapeutic application as clinical treatment for NAFLD. Herein, we adopted PubMed and Medline to search relevant keywords such as 'SCFAs', 'NAFLD', 'gut microbiota', 'Epigenetic', 'diet', and 'prebiotic effect' to review the latest research on SCFAs in NAFLD up to November 2023. In this review, firstly, we specifically discussed the production and function of SCFAs, as well as their crosstalk coordination in the gut liver axis. Secondly, we provided an updated summary and intensive discussion of how SCFAs affect hepatic steatosis to alleviate NAFLD from the perspective of genetic and epigenetic. Thirdly, we paid attention to the pharmacological and physiological characteristics of SCFAs, and proposed a promising future direction to adopt SCFAs alone or in combination with prebiotics and related clinical drugs to prevent and treat NAFLD. Together, this review aimed to elucidate the function of SCFAs and provide new insights to the prospects of SCFAs as a therapeutic target for NAFLD.

Role of autophagy in betaine-promoted hepatoprotection against non-alcoholic fatty liver disease in mice

Betaine, a compound found in plants and sea foods, is known to be beneficial against non-alcoholic fatty liver disease (NAFLD), but its hepatoprotective and anti-steatogenic mechanisms have been not fully understood. In the present study, we investigated the mechanisms underlying betaine-mediated alleviation of NAFLD induced by a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) in mice, with special focus on the contribution of betaine-stimulated autophagy to NAFLD prevention. Male ICR mice were fed a CDAHFD with or without betaine (0.2-1% in drinking water) for 1 week. Betaine ameliorated the CDAHFD-induced fatty liver by restoring sulfur amino acid (SAA)-related metabolites, such as S-adenosylmethionine and homocysteine, and the phosphorylation of AMPK and ACC. In addition, it reduced the CDAHFD-induced ER stress (BiP, ATF6, and CHOP) and apoptosis (Bax, cleaved caspase-3, and cleaved PARP); however, it induced autophagy (LC3II/I and p62) which was downregulated by CDAHFD. To determine the role of autophagy in the improvement of NAFLD, chloroquine (CQ), an autophagy inhibitor, was injected into the mice fed a CDAHFD and betaine (0.5 % in drinking water). CQ did not affect SAA metabolism but reduced the beneficial effects of betaine as shown by the increases of hepatic lipids, ER stress, and apoptosis. Notably, the betaine-induced improvements in lipid metabolism determined by protein levels of p-AMPK, p-ACC, PPARα, and ACS1, were reversed by CQ. Thus, the results of this study suggest that the activation of autophagy is an important upstream mechanism for the inhibition of steatosis, ER stress, and apoptosis by betaine in NAFLD.

Trehalose-Bearing Carriers to Target Impaired Autophagy and Protein Aggregation Diseases

In recent years, trehalose, a natural disaccharide, has attracted growing attention because of the discovery of its potential to induce autophagy. Trehalose has also been demonstrated to preserve the protein's structural integrity and to limit the aggregation of pathologically misfolded proteins. Both of these properties have made trehalose a promising therapeutic candidate to target autophagy-related disorders and protein aggregation diseases. Unfortunately, trehalose has poor bioavailability due to its hydrophilic nature and susceptibility to enzymatic degradation. Recently, trehalose-bearing carriers, in which trehalose is incorporated either by chemical conjugation or physical entrapment, have emerged as an alternative option to free trehalose to improve its efficacy, particularly for the treatment of neurodegenerative diseases, atherosclerosis, nonalcoholic fatty liver disease (NAFLD), and cancers. In the current Perspective, we discuss all existing literature in this emerging field and try to identify key challenges for researchers intending to develop trehalose-bearing carriers to stimulate autophagy or inhibit protein aggregation.

Methylsulfonylmethane ameliorates metabolic-associated fatty liver disease by restoring autophagy flux via AMPK/mTOR/ULK1 signaling pathway

Introduction: Metabolism-associated fatty liver disease (MAFLD) is a global health concern because of its association with obesity, insulin resistance, and other metabolic abnormalities. Methylsulfonylmethane (MSM), an organic sulfur compound found in various plants and animals, exerts antioxidant and anti-inflammatory effects. Here, we aimed to assess the anti-obesity activity and autophagy-related mechanisms of Methylsulfonylmethane. Method: Human hepatoma (HepG2) cells treated with palmitic acid (PA) were used to examine the effects of MSM on autophagic clearance. To evaluate the anti-obesity effect of MSM, male C57/BL6 mice were fed a high-fat diet (HFD; 60% calories) and administered an oral dose of MSM (200 or 400 mg/kg/day). Moreover, we investigated the AMP-activated protein kinase (AMPK)/mechanistic target of rapamycin complex 1 (mTORC1)/UNC-51-like autophagy-activating kinase 1 (ULK1) signaling pathway to further determine the underlying action mechanism of MSM. Results: Methylsulfonylmethane treatment significantly mitigated PA-induced protein aggregation in human hepatoma HepG2 cells. Additionally, Methylsulfonylmethane treatment reversed the PA-induced impairment of autophagic flux. Methylsulfonylmethane also enhanced the insulin sensitivity and significantly suppressed the HFD-induced obesity and hepatic steatosis in mice. Western blotting revealed that Methylsulfonylmethane improved ubiquitinated protein clearance in HFD-induced fatty liver. Remarkably, Methylsulfonylmethane promoted the activation of AMPK and ULK1 and inhibited mTOR activity. Conclusion: Our study suggests that MSM ameliorates hepatic steatosis by enhancing the autophagic flux via an AMPK/mTOR/ULK1-dependent signaling pathway. These findings highlight the therapeutic potential of MSM for obesity-related MAFLD treatment.

Involvement of Lipophagy and Chaperone-Mediated Autophagy in the Pathogenesis of Non-Alcoholic Fatty Liver Disease by Regulation of Lipid Droplets

Non-alcoholic fatty liver disease (NAFLD) is defined as the accumulation of lipids in the form of lipid droplets in more than 5% of hepatocytes. It is regarded as a range of diverse pathologies, including simple steatosis and steatohepatitis. The structural characteristics of lipid droplets, along with their protein composition, mainly including perilipins, have been implicated in the etiology of the disease. These proteins have garnered increasing attention as a pivotal regulator since their levels and distinct expression appear to be associated with the progression from simple steatosis to steatohepatitis. Perilipins are target proteins of chaperone-mediated autophagy, and their degradation is a prerequisite for lipolysis and lipophagy to access the lipid core. Both lipophagy and chaperone-mediated autophagy have significant implications on the development of the disease, as evidenced by their upregulation during the initial phases of simple steatosis and their subsequent downregulation once steatosis is established. On the contrary, during steatohepatitis, the process of chaperone-mediated autophagy is enhanced, although lipophagy remains suppressed. Evidently, the reduced levels of autophagic pathways observed in simple steatosis serve as a defensive mechanism against lipotoxicity. Conversely, in steatohepatitis, chaperone-mediated autophagy fails to compensate for the continuous generation of small lipid droplets and thus cannot protect hepatocytes from lipotoxicity.

The Impact of Intermittent Fasting on Non-Alcoholic Fatty Liver Disease in Older Adults: A Review of Clinicaltrials.gov Registry

Background

Non-alcoholic fatty liver disease (NAFLD) is a predominant health condition across the world due to its rising prevalence and association with various metabolic disorders. Intermittent fasting (IF) has attracted increasing attention as a dietary approach to addressing weight management and enhancing metabolic well-being, and its potential effects on NAFLD have been a topic of growing research interest.

Aim

This review aims to critically evaluate the current evidence on IF's impact on NAFLD, including the mechanisms underlying the observed effects in older adults (65+).

Methods

A comprehensive search of Clinicaltrials.gov was conducted to identify relevant studies that investigated the effects of IF on NAFLD in older adults (65+). Data on study design, sample size, intervention details, and outcomes related to NAFLD were extracted and analyzed.

Results

As of April 12th, 2023, there were 1304 clinical trials on NAFLD. Most of these were interventional studies. The investigation focused on completed studies and found that limited clinical trials were identified with limited interventional measures. Only five out of the 1304 studies on NAFLD involved IF. Basic and advanced outcome measures were examined.

Conclusion

Although some studies suggest that IF may have potential benefits for NAFLD, the evidence is still limited and inconclusive.

Circulating MicroRNA-30a, Beclin1 and Their Association with Different Variables in Females with Metabolically Healthy /Unhealthy Obesity

Background

Obesity is associated with metabolic and cardiovascular co-morbidities. It is important to determine the factors associated with metabolic derangement in obesity. Autophagy plays a major role in the pathogenesis of metabolic syndrome. MicroRNA-30a targets beclin1, the main regulator of autophagy.

Purpose

We assess circulating microRNA-30a and serum beclin1 in women with metabolically unhealthy obesity (MUO), women with metabolically healthy obesity (MHO) and non-obese healthy control and determine their relationship with different clinical and metabolic variables in women with obesity.

Patients and Methods

This cross-sectional study included 34 women with MHO, 34 with MUO, and 20 healthy non-obese women. Blood pressure, body mass index (BMI), and waist circumference were recorded. Glycemic and lipid indices, urinary albumin-to-creatinine ratio, ALT, AST, microRNA-30a expression in serum were measured using real-time polymerase chain reaction and beclin1 by enzyme-linked immunosorbent assay were measured.

Results

The expression of microRNA-30a was significantly higher, and beclin1 level was significantly lower in women with MUO compared to those in women with MHO (P<0.001; for both). People with MUO were significantly older (P<0.001) and had higher TSH (P=0.006), HbA1c (P<0.001), triglyceride (P<0.001), and ALT (P<0.001) compared to women with MHO. However, there was no significant difference between the two groups in any anthropometric measurements, HDL-C or LDL-C. In univariate analyses, age, ALT, TSH, microRNA-30a, and beclin1 were significantly correlated with the MUO phenotype (P<0.001; for all). Significance was confirmed in the multivariate analysis for microRNA-30a (95% CI 1.317-28.252; P=0.021).

Conclusion

MicroRNA-30a, beclin1, age, and ALT and TSH levels were significantly associated with the MUO phenotype, among which microRNA-30a was the best indicator of metabolic syndrome in women with obesity.

Therapeutic implications of targeting autophagy and TGF-β crosstalk for the treatment of liver fibrosis

Liver fibrosis is characterized by the excessive deposition and accumulation of extracellular matrix components, mainly collagens, and occurs in response to a broad spectrum of triggers with different etiologies. Under stress conditions, autophagy serves as a highly conserved homeostatic system for cell survival and is importantly involved in various biological processes. Transforming growth factor-β1 (TGF-β1) has emerged as a central cytokine in hepatic stellate cell (HSC) activation and is the main mediator of liver fibrosis. A growing body of evidence from preclinical and clinical studies suggests that TGF-β1 regulates autophagy, a process that affects various essential (patho)physiological aspects related to liver fibrosis. This review comprehensively highlights recent advances in our understanding of cellular and molecular mechanisms of autophagy, its regulation by TGF-β, and the implication of autophagy in the pathogenesis of progressive liver disorders. Moreover, we evaluated crosstalk between autophagy and TGF-β1 signalling and discussed whether simultaneous inhibition of these pathways could represent a novel approach to improve the efficacy of anti-fibrotic therapy in the treatment of liver fibrosis.

Glyphosate-induced autophagy inhibition results in hepatic steatosis via mediating epigenetic reprogramming of PPARα in roosters

Glyphosate (Gly) is the most widely used herbicide with well-defined hepatotoxic effects, but the underlying mechanisms of Gly-induced hepatic steatosis remain largely unknown. In this study, a rooster model combined with primary chicken embryo hepatocytes was established to dissect the progresses and mechanisms of Gly-induced hepatic steatosis. Data showed that Gly exposure caused liver injury with disrupted lipid metabolism in roosters, manifested by significant serum lipid profile disorder and hepatic lipid accumulation. Transcriptomic analysis revealed that PPARα and autophagy-related pathways played important roles in Gly-induced hepatic lipid metabolism disorders. Further experimental results suggested that autophagy inhibition was involved in Gly-induced hepatic lipid accumulation, which was confirmed by the effect of classic autophagy inducer rapamycin (Rapa). Moreover, data substantiated that Gly-mediated autophagy inhibition caused nuclear increase of HDAC3, which altered epigenetic modification of PPARα, leading to fatty acid oxidation (FAO) inhibition and subsequently lipid accumulation in the hepatocytes. In summary, this study provides novel evidence that Gly-induced autophagy inhibition evokes the inactivation of PPARα-mediated FAO and concomitant hepatic steatosis in roosters by mediating epigenetic reprogramming of PPARα.

Thymoquinone attenuates hepatic lipid accumulation by inducing autophagy via AMPK/mTOR/ULK1-dependent pathway in nonalcoholic fatty liver disease

Thymoquinone (TQ) has been proved to exert wide-ranging pharmacological activities, with anti-inflammatory, antioxidant, anticonvulsant, antimicrobial, anti-tumor, and antidiabetic properties. In this study, we investigated the beneficial effects of TQ on a high-fat diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD) in C57BL/6 N mice in vivo and free fatty acid (FFA)-induced human hepatocellular carcinoma HepG2 cells in vitro. Further, the underlying mechanisms of TQ to promote hepatic autophagy were also discovered. Data showed that TQ caused (p < 0.01) body weight reduction, improved glucose homeostasis, alleviated hepatosteatosis, and decreased hepatic lipid accumulation related to the induction of autophagy in HFD-fed mice. In vitro, TQ obviously increased (p < 0.01) autophagic flux in FFA-induced HepG2 cells and consequently reduced the lipid accumulation in combination with activation of AMPK/mTOR/ULK1 signaling pathways. Moreover, pharmacological inhibition of the AMPK pathway by addition with AMPK inhibitor Compound C (CC) or silence of ULK1 by transfection with siRNA(ULK1) into HepG2 cells reversed these beneficial effects of TQ on triggering hepatic autophagy and reducing lipid accumulation (p < 0.01). Taken together, these results suggested that TQ alleviated hepatic lipid accumulation by triggering autophagy through the AMPK/mTOR/ULK1-dependent signaling pathway. Our study supports a potential role for TQ in ameliorating NAFLD.

Selenium-Enriched Probiotic Alleviates Western Diet-Induced Non-alcoholic Fatty Liver Disease in Rats via Modulation of Autophagy Through AMPK/SIRT-1 Pathway

Current study was aimed to investigate the ability of L.acidophilus SNZ 86 to biotransform inorganic selenium to a more active organic form, resulting in trace element enrichment. Selenium-enriched L. acidophilus SNZ 86 has been shown to be effective in the treatment of a variety of gastrointestinal illnesses, indicating the need for additional research to determine the full potential of this therapeutic strategy in the treatment of metabolic disorders. Herein, we employed the western style diet-induced model of non-alcoholic fatty liver disease (NAFLD) to explore the therapeutic effect of selenium-enriched probiotic (SP). Male Sprague Dawley rats (160-180 g) were fed a high-fat (58% Kcal of fat) and high-fructose (30% w/v) diet for 12 weeks to develop an animal model mimicking NAFLD. High-fat and High-fructose diet-fed rats exhibited hyperglycemia, hyperlipidemia, insulin resistance, abnormal liver function test, increased hepatic oxidative stress, and steatosis. SP was then administered orally (L acidophilus 1 × 10⁹ CFU/ml containing 0.4 g Se/day; p.o.) for 8 weeks. The selenium enrichment within L. acidophilus SNZ 86 was validated by TEM, which allowed for visualisation of the selenium deposition and size distribution in the probiotic. In NAFLD control rats, the expression of autophagy proteins (LC-3 A/B and Beclin), AMPK, and SIRT-1 was significantly reduced indicating downregulation of autophagy. However, supplementation of SP ameliorates hepatic steatosis as evidenced by improved biochemical markers and autophagic activation via upregulation of the AMPK and SIRT-1 pathway showing the relevance of autophagy in the disease aetiology. Collectively, these findings provide us with a better understanding of the role of SP in the treatment of hepatic steatosis and establish a therapeutic basis for potential clinical application of SP in the prevention of NAFLD and associated pathological conditions.

Impaired hepatic autophagy exacerbates hepatotoxin induced liver injury

Hepatotoxins activate the hepatic survival pathway, but it is unclear whether impaired survival pathways contribute to liver injury caused by hepatotoxins. We investigated the role of hepatic autophagy, a cellular survival pathway, in cholestatic liver injury driven by a hepatotoxin. Here we demonstrate that hepatotoxin contained DDC diet impaired autophagic flux, resulting in the accumulation of p62-Ub-intrahyaline bodies (IHBs) but not the Mallory Denk-Bodies (MDBs). An impaired autophagic flux was associated with a deregulated hepatic protein-chaperonin system and significant decline in Rab family proteins. Additionally, p62-Ub-IHB accumulation activated the NRF2 pathway rather than the proteostasis-related ER stress signaling pathway and suppressed the FXR nuclear receptor. Moreover, we demonstrate that heterozygous deletion of Atg7, a key autophagy gene, aggravated the IHB accumulation and cholestatic liver injury. Conclusion: Impaired autophagy exacerbates hepatotoxin-induced cholestatic liver injury. The promotion of autophagy may represent a new therapeutic approach for hepatotoxin-induced liver damage.

Verapamil-loaded supramolecular hydrogel patch attenuates metabolic dysfunction-associated fatty liver disease via restoration of autophagic clearance of aggregated proteins and inhibition of NLRP3

BACKGROUND

Obesity, a serious threat to public health, is linked to chronic metabolic complications including insulin resistance, type-2 diabetes, and metabolic dysfunction-associated fatty liver disease (MAFLD). Current obesity medications are challenged by poor effectiveness, poor patient compliance, and potential side effects. Verapamil is an inhibitor of L-type calcium channels, FDA-approved for the treatment of hypertension. We previously investigated the effect of verapamil on modulating autophagy to treat obesity-associated lipotoxicity. This study aims to develop a verapamil transdermal patch and to evaluate its anti-obesity effects.

METHODS

Verapamil is loaded in biomimetic vascular bundle-like carboxymethyl pullulan-based supramolecular hydrogel patches cross-linked with citric acid and glycerol linkages (CLCMP). The investigation was then carried out to determine the therapeutic effect of verapamil-loaded CLCMP (Vera@CLCMP) on diet-induced obese mice.

RESULTS

Vera@CLCMP hydrogel patches with hierarchically organized and anisotropic pore structures not only improved verapamil bioavailability without modifying its chemical structure but also enhanced verapamil release through the stratum corneum barrier. Vera@CLCMP patches exhibit low toxicity and high effectiveness at delivering verapamil into the systemic circulation through the dermis in a sustained manner. Specifically, transdermal administration of this patch into diet-induced obese mice drastically improved glucose tolerance and insulin sensitivity and alleviated metabolic derangements associated with MAFLD. Furthermore, we uncovered a distinct molecular mechanism underlying the anti-obesity effects associated with the hepatic NLR family pyrin domain-containing 3 (NLRP3) inflammasome and autophagic clearance by the vera@CLCMP hydrogel patches.

CONCLUSION

The current study provides promising drug delivery platforms for long-term family treatment of chronic diseases, including obesity and metabolic dysfunctions.

Hepatic Steatosis Alleviated by a Novel Metformin and Quercetin Combination Activating Autophagy Through the cAMP/AMPK/SIRT1 Pathway

Non-alcoholic fatty liver disease (NAFLD) incidence and prevalence are rapidly increasing globally. The combined effects of metformin and quercetin (Que) have yet to be investigated. However, both have demonstrated the potential to reduce triglyceride (TG) levels and treat NAFLD by promoting autophagy. The objective of the present study was to elucidate the mechanism of action and assess the role of autophagy in the lipid-lowering effects of Que, both individually and in combination with metformin, in a HepG2 cell model of hepatic steatosis. Triglyceride levels and lipogenic gene expression were reduced in HepG2 cells exposed to palmitic acid (PA) when treated with Que-metformin, as evidenced by triglyceride measurements and real-time PCR. The LDH release assay also showed that this combination induced autophagy to protect HepG2 cells from PA-induced cell death. According to the Western blot analysis outcomes, Que-metformin increased LC3-I and LC3-II protein levels while decreasing p62 expression to induce autophagy. In HepG2 cells, the co-administration of Que-metformin elevated cAMP, phosphorylated AMP-activated protein kinase (p-AMPK), and Beclin-1 levels. Additionally, the inhibition of SIRT1 reversed the autophagy induced by Que-metformin. The findings of this study demonstrated for the first time that Que-metformin reduced hepatosteatosis by stimulating autophagy through the cAMP/AMPK/SIRT1 signaling pathway and diminishing inflammatory cytokines.

Salidroside in the Treatment of NAFLD/NASH

Non-alcoholic fatty liver disease (NAFLD) is the commonest reason for chronic liver diseases in the world and is commonly related to the hepatic manifestation of the metabolic syndrome. Non-alcoholic steatohepatitis (NASH) is a deteriorating form of NAFLD, which can eventually develop into fibrosis, cirrhosis, and liver cancer. The reason for NAFLD/NASH development is complicated, such as liver lipid metabolism, oxidative stress, inflammatory response, apoptosis and autophagy, liver fibrosis and gut microbiota. Apart from bariatric surgery and lifestyle changes, officially approved drug therapy for NAFLD/NASH treatment is lacking. Salidroside (SDS) is a phenolic compound extensively distributed in the tubers of Rhodiola plants, which possesses many significant biological activities. This review summarized the related targets regulated by SDS in treating NAFLD/NASH. It is indicated that SDS could improve the status of NAFLD/NASH by ameliorating abnormal lipid metabolism, inhibiting oxidative stress, regulating apoptosis and autophagy, reducing inflammatory response, alleviating fibrosis and regulating gut microbiota. In conclusion, although the multiple bioactivities of SDS have been confirmed, the clinical data are inadequate and need to become the focus of attention in the later study.

Alternate-day fasting prevents non-alcoholic fatty liver disease and working memory impairment in diet-induced obese mice

Alternate-day fasting (ADF) regimen has been reported to alleviate obesity and insulin resistance. However, the effects of ADF on preventing diet-induced non-alcoholic fatty liver disease (NAFLD) and related cognitive deficits are still elusive. In the present study, a high-fat diet (HFD)-induced obese (DIO) C57BL/6 mouse model was established. Mice were treated with a 4-week long ADF regimen and/or switching the diet to a standard diet. ADF reduced lipid accumulation, activated AMPK/ULK1 signaling, and suppressed the phosphorylation of mTOR. Also, ADF inhibited lipid accumulation and inflammatory responses in the white adipose tissue and down-regulated expressions of PPAR-γ and cytokines. Moreover, ADF improved the working memory and synaptic structure in the DIO mice and upregulated PSD-95 and BDNF in the hippocampus. ADF reduced oxidative stress and microglial over-activation in the CNS. These results suggest that ADF attenuates NAFLD development in the liver of DIO mice, which is related to the mediating effects of ADF on autophagy and energy metabolism. ADF also enhanced cognitive function, which could be partly explained by the down-regulated peripheral inflammatory responses. This study indicates that ADF could be a promising intervention for alleviating NAFLD development and cognitive decline.

Mitochondrial protease ClpP supplementation ameliorates diet-induced NASH in mice

BACKGROUND & AIMS

Mitochondrial dysfunction is considered a pathogenic linker in the development of non-alcoholic steatohepatitis (NASH). Inappropriate mitochondrial protein-quality control, possibly induced by insufficiency of the mitochondrial matrix caseinolytic protease P (ClpP), can potentially cause mitochondrial dysfunction. Herein, we aimed to investigate hepatic ClpP levels in a diet-induced model of NASH and determine whether supplementation of ClpP can ameliorate diet-induced NASH.

METHODS

NASH was induced by a high-fat/high-fructose (HF/HFr) diet in C57BL/6J mice. Stress/inflammatory signals were induced in mouse primary hepatocytes (MPHs) by treatment with palmitate/oleate (PA/OA). ClpP levels in hepatocytes were reduced using the RNAi-mediated gene knockdown technique but increased through the viral transduction of ClpP. ClpP activation was induced by administering a chemical activator of ClpP.

RESULTS

Hepatic ClpP protein levels in C57BL/6J mice fed a HF/HFr diet were lower than the levels in those fed a normal chow diet. PA/OA treatment also decreased the ClpP protein levels in MPHs. Overexpression or activation of ClpP reversed PA/OA-induced mitochondrial dysfunction and stress/inflammatory signal activation in MPHs, whereas ClpP knockdown induced mitochondrial dysfunction and stress/inflammatory signals in these cells. On the other hand, ClpP overexpression or activation improved HF/HFr-induced NASH characteristics such as hepatic steatosis, inflammation, fibrosis, and injury in the C57BL/6J mice, whereas ClpP knockdown further augmented steatohepatitis in mice fed a HF/HFr diet.

CONCLUSIONS

Reduced ClpP expression and subsequent mitochondrial dysfunction are key to the development of diet-induced NASH. ClpP supplementation through viral transduction or chemical activation represents a potential therapeutic strategy to prevent diet-induced NASH.

LAY SUMMARY

Western diets, containing high fat and high fructose, often induce non-alcoholic steatohepatitis (NASH). Mitochondrial dysfunction is considered pathogenically linked to diet-induced NASH. We observed that the mitochondrial protease ClpP decreased in the livers of mice fed a western diet and supplementation of ClpP ameliorated western diet-induced NASH.

Hepatic interleukin-1 receptor type 1 signalling regulates insulin sensitivity in the early phases of nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is associated with hepatic as well as systemic insulin resistance even in the absence of type 2 diabetes. The extent and pathways through which hepatic inflammation modulates insulin sensitivity in NAFLD are only partially understood. We explored the contribution of hepatic interleukin (IL)-1 signalling in a novel conditional knockout mouse model and expand the knowledge on this signalling pathway with regard to its liver-specific functions.

METHODS

A high-fat, high-carbohydrate diet (HFD) over 12 weeks was used in male hepatocyte-specific IL-1 receptor type 1 (IL-1R1) knockout mice (Il1r1Hep-/- ) and wild-type (WT) littermates.

RESULTS

Both genotypes developed an obese phenotype and accompanying macrovesicular hepatic steatosis. In contrast to WT mice, microvesicular steatosis and ballooning injury was less pronounced in HFD-fed Il1r1Hep-/- mice, and alanine aminotransferase remained in the normal range. This was paralleled by the suppression of injurious and proinflammatory hepatic c-Jun N-terminal kinases and extracellular signal-regulated kinases signalling, stable peroxisome proliferator activated receptor gamma coactivator-1alpha and farnesoid X receptor-alpha expression and preservation of mitochondrial function. Strikingly, despite HFD-feeding Il1r1Hep-/- mice remained highly insulin sensitive as indicated by lower insulin levels, homeostatic model assessment for insulin resistance, higher glucose tolerance, more stable hepatic insulin signalling cascade, and less adipose tissue inflammation compared to the WT.

CONCLUSIONS

The current data highlights that hepatocyte IL-1R1 contributes to hepatic and extrahepatic insulin resistance. Future liver-directed therapies in NAFLD could have effects on insulin sensitivity when improving hepatic inflammation and IL-1R1 signalling.

Identification of circular RNA biomarkers for Pien Tze Huang treatment of CCl4‑induced liver fibrosis using RNA‑sequencing

Pien Tze Huang (PZH), a common hepatoprotective Traditional Chinese Medicine that has been found to be an effective treatment for carbon tetrachloride-induced hepatic damage, including liver fibrosis. Circular RNAs (circRNAs) serve a crucial role in regulating gene expression levels via circRNA/micro (mi)RNA/mRNA networks in several human diseases and biological processes. However, whether circRNAs are involved in the underlying mechanism of the therapeutic effects of PZH on liver fibrosis remains unclear. Therefore, the aim of the present study was to investigate these effects using circRNA expression profiles from PZH-treated fibrotic livers in model mice. A case-control study on >59,476 circRNAs from CCl₄-induced (control group, n=6) and PZH-treated (case group, n=6) mice was performed using circRNA sequencing in liver tissues. PZH treatment resulted in the differential expression of 91 circRNAs, including 58 upregulated and 33 downregulated circRNAs. Furthermore, the construction of competing endogenous networks also indicated that differentially expressed circRNAs acted as miRNA sponges. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis of miRNA targets demonstrated that PZH-affected circRNAs were mainly involved in biological processes such as ‘positive regulation of fibroblast proliferation’, ‘cellular response to interleukin-1’ and ‘regulation of DNA-templated transcription in response to stress’ and in a number of important pathways, such as ‘TNF signaling pathway’, ‘PI3K-Akt signaling pathway’, ‘IL-17 signaling pathway’ and ‘MAPK signaling pathway’. To further validate the bioinformatics data, reverse transcription–quantitative PCR was performed on seven miRNA targets in a human hepatic stellate LX-2 cell model. The results suggested that seven of the miRNAs exhibited regulatory patterns that were consistent with those of the transcriptome sequencing results. Kaplan-Meier survival analysis demonstrated that the expression levels of dihydrodiol dehydrogenase and solute carrier family 7, member 11 gene were significantly associated with patient survival, 269 patients with liver hepatocellular carcinoma from The Cancer Genome Atlas database. To the best of our knowledge, this was the first study to provide evidence that PZH affects circRNA expression levels, which may serve important roles in PZH-treated fibrotic liver through the regulation of functional gene expression. In conclusion, the present study provided new insights into the mechanism underlying the pathogenesis of liver fibrosis and identified potential novel, efficient, therapeutic targets against liver injury.

Inhibition of autophagy with expression of NADPH oxidase subunit p22phox in preneoplastic lesions in a high-fat diet and streptozotocin-related hepatocarcinogenesis rat model

To study the effects of autophagy inducer carbamazepine (CBZ) in a high-fat diet (HFD)/streptozotocin (STZ)-related early hepatocarcinogenesis model, we determined autophagic flux by immunohistochemical analysis of autophagy marker expression in preneoplastic liver foci and compared that with the expression of the NADPH oxidase subunit. Male F344 rats were fed a basal diet or HFD and subjected to two-stage hepatocarcinogenesis; diabetes mellitus was induced via STZ administration. Several STZ-treated, HFD-fed rats were administered CBZ (a total of five doses every one or two days) at week 7 and 8. STZ-treated, HFD-fed rats decreased β cells in the islet of Langerhans and increased adipophilin-positive lipid droplets in the liver; moreover, they had a larger area of glutathione S-transferase placental form-immunopositive preneoplastic liver foci, which was associated with inhibition of autophagy and induction of the NADPH oxidase subunit, as demonstrated by increased immunohistochemical expression of an autophagosome receptor marker microtubule-associated protein light chain 3 (LC3)-binding protein p62, and of an NADPH oxidase subunit p22phox in the preneoplastic foci. An increased trend of an autophagy phagophore marker LC3 in preneoplastic foci was also detected. CBZ administration could induce autophagy and impair p22phox expression, as shown by altered expression of autophagy regulators (Atg5, Atg6, Lamp1, Lamp2, and Lc3), NADPH oxidase subunits (P22phox and P67phox), and antioxidant enzymes Gpx1 and Gpx2. These results suggest that inhibition of autophagy and induction of p22phox might contribute to HFD/STZ-related early hepatocarcinogenesis in rats; however, the effects of CBZ administration on the STZ/HFD-increased preneoplastic foci were marginal in this study.

Curcumin effect on Acanthamoeba triangularis encystation under nutrient starvation

Background

Curcumin is an active compound derived from turmeric, Curcuma longa, and is known for its benefits to human health. The amoebicidal activity of curcumin against Acanthamoeba triangularis was recently discovered. However, a physiological change of intracellular pathways related to A. triangularis encystation mechanism, including autophagy in the surviving amoeba after curcumin treatment, has never been reported. This study aims to investigate the effect of curcumin on the survival of A. triangularis under nutrient starvation and nutrient-rich condition, as well as to evaluate the A. triangularis encystation and a physiological change of Acanthamoeba autophagy at the mRNA level.

Methods

In this study, A. triangularis amoebas were treated with a sublethal dose of curcumin under nutrient starvation and nutrient-rich condition and the surviving amoebas was investigated. Cysts formation and vacuolization were examined by microscopy and transcriptional expression of autophagy-related genes and other encystation-related genes were evaluated by real-time PCR.

Results

A. triangularis cysts were formed under nutrient starvation. However, in the presence of the autophagy inhibitor, 3-methyladenine (3-MA), the percentage of cysts was significantly reduced. Interestingly, in the presence of curcumin, most of the parasites remained in the trophozoite stage in both the starvation and nutrient-rich condition. In vacuolization analysis, the percentage of amoebas with enlarged vacuole was increased upon starvation. However, the percentage was significantly declined in the presence of curcumin and 3-MA. Molecular analysis of A. triangularis autophagy-related (ATG) genes showed that the mRNA expression of the ATG genes, ATG3, ATG8b, ATG12, ATG16, under the starvation with curcumin was at a basal level along the treatment. The results were similar to those of the curcumin-treated amoebas under a nutrient-rich condition, except AcATG16 which increased later. On the other hand, mRNA expression of encystation-related genes, cellulose synthase and serine proteinase, remained unchanged during the first 18 h, but significantly increased at 24 h post treatment.

Conclusion

Curcumin inhibits cyst formation in surviving trophozoites, which may result from its effect on mRNA expression of key Acanthamoeba ATG-related genes. However, further investigation into the mechanism of curcumin in A. triangularis trophozoites arrest and its association with autophagy or other encystation-related pathways is needed to support the future use of curcumin.

Pathogenesis of Liver Fibrosis and Its TCM Therapeutic Perspectives

Liver fibrosis is a pathological process of abnormal tissue proliferation in the liver caused by various pathogenic factors, which will further develop into cirrhosis or even hepatocellular carcinoma if liver injury is not intervened in time. As a diffuse progressive liver disease, its clinical manifestations are mostly excessive deposition of collagen-rich extracellular matrix resulting in scar formation due to liver injury. Hepatic fibrosis can be caused by hepatitis B and C, fatty liver, alcohol, and rare diseases such as hemochromatosis. As the metabolic center of the body, the liver regulates various vital activities. During the development of fibrosis, it is influenced by many other factors in addition to the central event of hepatic stellate cell activation. Currently, with the increasing understanding of TCM, the advantages of TCM with multiple components, pathways, and targets have been demonstrated. In this review, we will describe the factors influencing liver fibrosis, focusing on the effects of cells, intestinal flora, iron death, signaling pathways, autophagy and angiogenesis on liver fibrosis, and the therapeutic effects of herbal medicine on liver fibrosis.

Hepatic lipid accumulation induced by a high-fat diet is regulated by Nrf2 through multiple pathways

Nuclear factor erythroid 2-related factor 2 (Nrf2) is reportedly involved in hepatic lipid metabolism, but the results are contradictory, and the underlying mechanism remains unclear. Here, we focused on elucidating the effects of Nrf2 on hepatic adipogenesis and on determining the possible underlying mechanism. We established a non-alcoholic fatty liver disease (NAFLD) model in a high-fat diet (HFD)-fed Nrf2 knockout (Nrf2 KO) mice; further, a cell model of lipid accumulation was established using mouse primary hepatocytes (MPHs) treated with free fatty acids (FAs). Using these models, we investigated the relationship between Nrf2 and autophagy and its role in the development of NAFLD. We observed that Nrf2 expression levels were upregulated in patients with NAFLD and diet-induced obese mice. Nrf2 deficiency led to hepatic lipid accumulation in vivo and in vitro, in addition to, promoting lipogenesis mainly by increasing SREBP-1c activity. Moreover, Nrf2 deficiency attenuated autophagic flux and inhibited the fusion of autophagosomes and lysosomes in vivo and in vitro. Decreased autophagy caused reduced lipolysis in the liver. Importantly, chromatin immunoprecipitation-qPCR (ChIP-qPCR) and dual-luciferase assay results proved that Nrf2 bound to the LAMP1 promoter and regulated its transcriptional activity. Accordingly, we report that Nrf2-LAMP1 interaction plays an indispensable role in Nrf2-regulated hepatosteatosis. Our data collectively confirm that Nrf2 deficiency promotes hepatosteatosis by enhancing SREBP-1c activity and attenuating autophagy. Our findings provide a novel multi-pathway effect of Nrf2 on lipid metabolism in the liver. We believe that multi-target intervention of Nrf2 is a novel strategy for the treatment of NAFLD.

Sitagliptin Is More Effective Than Gliclazide in Preventing &nbsp;Pro-Fibrotic and Pro-Inflammatory Changes in a Rodent Model of Diet-Induced Non-Alcoholic Fatty Liver Disease

A diet-induced non-alcoholic fatty liver disease (NAFLD) model causing obesity in rodents was used to examine whether sitagliptin and gliclazide therapies have similar protective effects on pathological liver change. Methods: Male mice were fed a high-fat diet (HFD) or standard chow (Chow) ad libitum for 25 weeks and randomly allocated to oral sitagliptin or gliclazide treatment for the final 10 weeks. Fasting blood glucose and circulating insulin were measured. Inflammatory and fibrotic liver markers were assessed by qPCR. The second messenger ERK and autophagy markers were examined by Western immunoblot. F4/80, collagens and CCN2 were assessed by immunohistochemistry (IHC). Results: At termination, HFD mice were obese, hyperinsulinemic and insulin-resistant but non-diabetic. The DPP4 inhibitor sitagliptin prevented intrahepatic induction of pro-fibrotic markers collagen-IV, collagen-VI, CCN2 and TGF-β1 and pro-inflammatory markers TNF-α and IL-1β more effectively than sulfonylurea gliclazide. By IHC, liver collagen-VI and CCN2 induction by HFD were inhibited only by sitagliptin. Sitagliptin had a greater ability than gliclazide to normalise ERK-protein liver dysregulation. Conclusion: These data indicate that sitagliptin, compared with gliclazide, exhibits greater inhibition of pro-fibrotic and pro-inflammatory changes in an HFD-induced NAFLD model. Sitagliptin therapy, even in the absence of diabetes, may have specific benefits in diet-induced NAFLD.

Xenobiotic-Induced Aggravation of Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD), which is often linked to obesity, encompasses a large spectrum of hepatic lesions, including simple fatty liver, steatohepatitis, cirrhosis and hepatocellular carcinoma. Besides nutritional and genetic factors, different xenobiotics such as pharmaceuticals and environmental toxicants are suspected to aggravate MAFLD in obese individuals. More specifically, pre-existing fatty liver or steatohepatitis may worsen, or fatty liver may progress faster to steatohepatitis in treated patients, or exposed individuals. The mechanisms whereby xenobiotics can aggravate MAFLD are still poorly understood and are currently under deep investigations. Nevertheless, previous studies pointed to the role of different metabolic pathways and cellular events such as activation of de novo lipogenesis and mitochondrial dysfunction, mostly associated with reactive oxygen species overproduction. This review presents the available data gathered with some prototypic compounds with a focus on corticosteroids and rosiglitazone for pharmaceuticals as well as bisphenol A and perfluorooctanoic acid for endocrine disruptors. Although not typically considered as a xenobiotic, ethanol is also discussed because its abuse has dire consequences on obese liver.

Mechanism by which Eucommia ulmoides leaves Regulate Nonalcoholic fatty liver disease based on system pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Eucommia ulmoides (E. ulmoides) leaves are included in the Chinese Pharmacopoeia, and are traditionally used to treat hypertension, obesity, diabetes, and other diseases. Numerous pharmacological studies have shown that E. ulmoides has a good effect on lowering blood lipids and can improve obesity and nonalcoholic fatty liver.

AIM

To study the mechanism of E. ulmoides leaves in regulating nonalcoholic fatty liver disease by combining prediction and validation.

METHODS

Using network pharmacology, and molecular docking to predict E. ulmoides in regulating the action mechanism and potential active ingredients of nonalcoholic fatty liver, large hole adsorption resin enrichment active sites, in vitro experiments were performed to verify its fat-lowering effect and mechanism.

RESULTS

The major components of E. ulmoides leaves exhibited good combination with lipid metabolism-regulating core proteins, particularly flavonoids. EUL 50 significantly reduced lipid accumulation, and increased PPARγ. Compared with the control group, the autophagy level increased after the administration of EUL 50. PPARγ decreased significantly after the addition of chloroquine (CQ, autophagy inhibitor).

CONCLUSION

The active ingredients in E. ulmoides leaves regulating nonalcoholic fatty liver disease are mainly flavonoids and phenolics. EUL 50 may play a role in lowering lipids by regulating PPARγ expression through inducing autophagy.

Alleviation of CCCP-induced mitochondrial injury by augmenter of liver regeneration via the PINK1/Parkin pathway-dependent mitophagy

The occurrence of liver diseases is attributed to mitochondrial damage. Mitophagy selectively removes dysfunctional mitochondria, thereby preserving mitochondrial function. Augmenter of liver regeneration (ALR) protects the mitochondria from injury. However, whether ALR protection is associated with mitophagy remains unclear. In this study, mitochondrial damage was induced by carbonyl cyanide 3-chlorophenylhydrazone (CCCP), and long-form ALR (lfRNA)-mediated protection against this damage was investigated. Treatment of HepG2 cells with CCCP elevated the level of intracellular ROS, inhibited ATP production, and increased the mitochondrial membrane potential and cell apoptotic rate. However, in lfALR-transfected cells, CCCP-induced cell injury was clearly alleviated, the apoptosis and ROS levels clearly declined, and the ATP production was significantly enhanced as compared with that in vector-Tx cells. Furthermore, lfALR overexpression promoted autophagy and mitophagy via a PINK1/Parkin-dependent pathway, whereas knockdown of ALR suppressed mitophagy. In lfALR-transfected cells, the phosphorylation of AKT was decreased, thus, downregulating the phosphorylation of the transcription factor FOXO3a at Ser315. In contrast, the phosphorylation of AMPK was enhanced, thereby upregulating the phosphorylation of FOXO3a at Ser413. Consequently, FOXO3a's nuclear translocation and binding to the promoter region of PINK1 was enhanced, and the accumulation of PINK1/Parkin in mitochondria increased. Meanwhile, short-form ALR (sfALR) also increased PINK1 expression through FOXO3a with the similar pathway to lfALR. In conclusion, our data suggest a novel mechanism through which both lfALR and sfALR protect mitochondria by promoting PINK1/Parkin-dependent mitophagy through FOXO3a activation.

RORα Enhances Lysosomal Acidification and Autophagic Flux in the Hepatocytes

Lysosomes are intracellular acidic organelles with catabolic functions that contribute to the activation of autophagy. Although autophagy abnormality is associated with defects in lysosomal acidification during the progression of nonalcoholic fatty liver disease (NAFLD), the mechanisms of control of lysosomal acidification are not well understood at the molecular level. Thus, we aimed to elucidate the role of the orphan nuclear receptor retinoic acid-related orphan receptor α (RORα) in lysosomal acidification and autophagic flux, particularly in nutrition-enriched hepatocytes. First, lysosomal acidity was much lower in the hepatocytes obtained from hepatocyte-specific RORα-deleted (RORα-LKO) mice, whereas the infusion of an adenovirus encoding RORα in wild-type hepatocytes increased lysosomal acidity, as determined by LysoSensor. Second, the lysosomal translocation of the mechanistic target of rapamycin was increased and immature cathepsin D was accumulated in the liver of RORα-LKO mice. Third, the accumulation of LC3-II, p62/sequestosome 1 (SQSTM1), and neighbor of BRCA1 gene 1 (NBR1) was increased in the livers of RORα-LKO mice, indicating an impaired autophagic flux in the livers. Consistently, the number of autolysosomes containing mitochondria and lipid droplets was dramatically reduced in the RORα-deleted hepatocytes. Finally, we found that RORα induced the transcription of genes involved in lysosomal function, such as Atp6v1g1, a vacuolar H+ -ATPase (v-ATPase) subunit, which were largely down-regulated in the livers of mice with high-fat diet-induced NAFLD and patients with hepatitis. Conclusion: Targeting RORα may be a potential therapeutic strategy to restore lysosomal acidification, which inhibits the progression of NAFLD.

Fasting Ketonuria and the Risk of Incident Nonalcoholic Fatty Liver Disease With and Without Liver Fibrosis in Nondiabetic Adults

INTRODUCTION

Dietary carbohydrate restriction or ketogenic diets are known to be beneficial in preventing liver fat accumulation. However, the effect of ketonemia on the risk of nonalcoholic fatty liver disease (NAFLD) in nondiabetic population is largely unknown. We investigated the association between fasting ketonuria and the risk of incident NAFLD in healthy adults.

METHODS

A cohort of 153,076 nondiabetic Koreans with no hepatic steatosis and low probability of fibrosis at baseline was followed for a median of 4.1 years. The outcome was incident hepatic steatosis with or without liver fibrosis, and it was assessed by liver ultrasound and noninvasive fibrosis indices, including fibrosis-4 and the NAFLD fibrosis score (NFS). Parametric proportional hazard models were used to estimate hazard ratios (HRs) for outcome according to ketonuria status.

RESULTS

Within 677,702.1 person-years of follow-up, 31,079 subjects developed hepatic steatosis. Compared with no ketonuria (reference), fasting ketonuria was significantly associated with a decreased risk of incident hepatic steatosis, with multivariable-adjusted HRs (95% confidence interval) of 0.81 (0.78-0.84). The corresponding HRs for incident hepatic steatosis with intermediate-to-high NFS were 0.79 (0.69-0.90). Similar associations were observed replacing NFS with fibrosis-4. In addition, the presence of persistent ketonuria at both baseline and subsequent visit was associated with the greatest decrease in the adjusted HR for incident NAFLD.

DISCUSSION

Ketonuria was associated with a reduced risk of developing incident hepatic steatosis with and without intermediate-to-high probability of advanced fibrosis in a large cohort of nondiabetic healthy individuals. The role of hyperketonemia in the prevention of NAFLD requires further exploration.

Coffeeberry Activates the CaMKII/CREB/BDNF Pathway, Normalizes Autophagy and Apoptosis Signaling in Nonalcoholic Fatty Liver Rodent Model

Nonalcoholic fatty liver disease (NAFLD) shows extensive liver cell destruction with lipid accumulation, which is frequently accompanied by metabolic comorbidities and increases mortality. This study aimed to investigate the effects of coffeeberry (CB) on regulating the redox status, the CaMKII/CREB/BDNF pathway, autophagy, and apoptosis signaling by a NAFLD rodent model senescence-accelerated mice prone 8 (SAMP8). Three-month-old male SAMP8 mice were divided into a control group and three CB groups (50, 100, and 200 mg/kg BW), and fed for 12 weeks. The results show that CB reduced hepatic malondialdehyde and carbonyl protein levels. CB significantly enhanced Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and brain-derived neurotrophic factor (BDNF) and reduced the phospho-cAMP response element-binding protein (p-CREB)/CREB ratio. In addition, CB increased the silent information regulator T1 level, promoted Beclin 1 and microtubule-associated protein light chain 3 II expressions, and reduced phosphorylated mammalian target of rapamycin and its downstream p-p70s6k levels. CB also inhibited the expressions of apoptosis-related factors poly (ADP-ribose) polymerase-1 and the apoptosis-inducing factor. In conclusion, CB might protect the liver by reducing oxidative stress, activating the CaMKII/CREB/BDNF pathway, and improving autophagic and apoptotic expressions in a dose-dependent manner.

Caveolin-1 attenuates acetaminophen aggravated lipid accumulation in alcoholic fatty liver by activating mitophagy via the Pink-1/Parkin pathway

Alcoholic fatty liver (AFL) is a disease characterized by the abnormal structure and dysfunction of hepatocytes caused by long-term, excessive drinking. Acetaminophen (APAP) is a commonly used painkiller, but it can aggravate lipid deposition in the liver and cause liver injury when used in fatty liver disease. Here, we investigated the effect of caveolin-1 (CAV-1), an intracellular stent protein, on the pathogenesis of APAP aggravated lipid deposition in AFL mice. This study shows that lipid accumulation was more severe in APAP groups than in alcohol-treated mice. The CAV-1 stent-like domain (CSD, 82-101 amino acids of caveolin-1), used to upregulate CAV-1 expression, could reduce lipid accumulation and activate autophagy in AFL mice treated with APAP. The levels of CAV-1 and autophagy-related proteins (LC3-II/I and Beclin-1) had decreased, whereas SREBP-1c had increased in A/O (alcohol and oleic acid) and APAP-co-treated L02 cells. CAV-1 small interfering RNA and CAV1-overexpressing plasmid were separately transfected into A/O and APAP co-treated L02 cells. When CAV-1 was downregulated, the levels of Pink-1, Parkin, and autophagy-related proteins (LC3-II/I and Beclin-1) were decreased, whereas SREBP-1c was increased. The opposite trend was observed when CAV-1 was overexpressed. The results show that CAV-1 reduced lipid accumulation in L02 cells and activated Pink-1/Parkin-related mitophagy. This study highlights the positive role of CAV-1 in APAP-increased lipid accumulation under the AFL status and provides a new understanding of the function of CAV-1 in the liver through mitophagy associated with the Pink-1/Parkin pathway.

H2O2-mediated autophagy during ethanol metabolism

BACKGROUND

Alcoholic liver disease (ALD) is the most common liver disease worldwide and its underlying molecular mechanisms are still poorly understood. Moreover, conflicting data have been reported on potentially protective autophagy, the exact role of ethanol-metabolizing enzymes and ROS.

METHODS

Expression of LC3B, CYP2E1, and NOX4 was studied in a mouse model of acute ethanol exposure by immunoblotting and immunohistochemistry. Autophagy was further studied in primary mouse hepatocytes and huh7 cells in response to ethanol and its major intermediator acetaldehyde. Experiments were carried out in cells overexpressing CYP2E1 and knock down of NOX4 using siRNA. The response to external H2O2 was studied by using the GOX/CAT system. Autophagic flux was monitored using the mRFP-GFP-LC3 plasmid, while rapamycin and chloroquine served as positive and negative controls.

RESULTS

Acute ethanol exposure of mice over 24 h significantly induced autophagy as measured by LC3B expression but also induced the ROS-generating CYP2E1 and NOX4 enzymes. Notably, ethanol but not its downstream metabolite acetaldehyde induced autophagy in primary mouse hepatocytes. In contrast, autophagy could only be induced in huh7 cells in the presence of overexpressed CYP2E1. In addition, overexpression of NOX4 also significantly increased autophagy, which could be blocked by siRNA mediated knock down. The antioxidant N-acetylcysteine (NAC) also efficiently blocked CYP2E1-and NOX4-mediated induction of autophagy. Finally, specific and non-toxic production of H2O2 by the GOX/CAT system as evidenced by elevated peroxiredoxin (Prx-2) also induced LC3B which was efficiently blocked by NAC. H2O2 strongly increased the autophagic flux as measured by mRFP-GFP-LC3 plasmid.

CONCLUSION

We here provide evidence that short-term ethanol exposure induces autophagy in hepatocytes both in vivo and in vitro through the generation of ROS. These data suggest that suppression of autophagy by ethanol is most likely due to longer alcohol exposure during chronic alcohol consumption with the accumulation of e.g. misfolded proteins.

Dihydromyricetin attenuates palmitic acid-induced oxidative stress by promoting autophagy via SIRT3-ATG4B signaling in hepatocytes

BACKGROUND

Oxidative stress in hepatocytes was important pathogenesis of nonalcoholic steatohepatitis (NASH). Autophagy was a cellular process that can remove damaged organelles under oxidative stress, and thus presented a potential therapeutic target against NASH. This work aimed to investigate whether autophagy was participated in the protective effects of dihydromyricetin (DHM) on palmitic acid (PA)-induced oxidative stress in hepatocytes and the underlying mechanism.

METHODS

HepG2 and HHL-5 cell lines were pretreated with DHM (20 μM) for 2 h, followed by PA (0.2 mM) treatment for 16 h. The oxidative stress was assessed by the quantification of intracellular reactive oxygen species (ROS), mitochondrial ROS (mtROS), mitochondrial membrane potential (MMP) and mitochondrial ultrastructural analyses. The protein expressions of SIRT3, LC3I/II, P62 and ATG4B, as well as the acetylation of AGT4B were determined by western blotting using HepG2 and HepG2/ATG4B^± cells with heterozygous knockout of ATG4B.

RESULTS

Exposure to PA resulted in increased intracellular ROS and mtROS, decreased MMP and aggravated mitochondrial injury in HepG2 cells, which were notably attenuated by DHM treatment. DHM-induced inhibition of oxidative stress was associated with the induction of autophagy, characterized by upregulated ATG4B and LC3 II as well as downregulated P62 levels. Furthermore, the inhibitory effects of DHM on PA-induced autophagy arrest and oxidative stress were eliminated when pretreated with a SIRT3 inhibitor 3-TYP or conducted in HepG2/ATG4B^± cells, suggesting that SIRT3 and ATG4B were involved in DHM-induced benefits. Moreover, DHM treatment increased the protein expression of SIRT3 and SIRT3-dependent deacetylation of ATG4B in HepG2 cells.

CONCLUSION

Our results demonstrated that DHM attenuated PA-induced oxidative stress in hepatocytes through induction of autophagy, which was mediated through the increased expression of SIRT3 and SIRT3-mediated ATG4B deacetylation following DHM treatment.

Peganum harmala Extract Has Antiamoebic Activity to Acanthamoeba triangularis Trophozoites and Changes Expression of Autophagy-Related Genes

Peganum harmala, a well-known medicinal plant, has been used for several therapeutic purposes as it contains numerous pharmacological active compounds. Our study reported an anti-parasitic activity of P. harmala seed extract against Acanthamoeba triangularis. The stress induced by the extract on the surviving trophozoites for Acanthamoeba encystation and vacuolization was examined by microscopy, and transcriptional expression of Acanthamoeba autophagy-related genes was investigated by quantitative PCR. Our results showed that the surviving trophozoites were not transformed into cysts, and the number of trophozoites with enlarged vacuoles were not significantly different from that of untreated control. Molecular analysis data demonstrated that the mRNA expression of tested AcATG genes, i.e., ATG3, ATG8b, and ATG16, was at a basal level along the treatment. However, upregulation of AcATG16 at 24 h post treatment was observed, which may indicate an autophagic activity of this protein in response to the stress. Altogether, these data revealed the anti-Acanthamoeba activity of P. harmala extract and indicated the association of autophagy mRNA expression and cyst formation under the extract stress, representing a promising plant for future drug development. However, further identification of an active compound and a study of autophagy at the protein level are needed.

Dysregulation of autophagy acts as a pathogenic mechanism of non-alcoholic fatty liver disease (NAFLD) induced by common environmental pollutants

Non-alcoholic fatty liver disease (NAFLD) has been the most common chronic liver disease in the world, including the developing countries. NAFLD is metabolic disease with significant lipid deposition in the hepatocytes of the liver, which is usually associated with oxidative stress, inflammation and fibrogenesis, and insulin resistance. Progressive NAFLD can develop into non-alcoholic steatohepatitis (NASH) or hepatocellular carcinoma. The current evidence proposes that environmental pollutants promote development and progression of NAFLD, and autophagy plays a vital role but is multifactorial affected in NAFLD. In this review, we analyzed on the regulations of common environmental pollutants on autophagy in NAFLD. To clarify the involved roles of autophagy, we discussed the dysregulation of autophagy by environmental pollutants in adipose tissue and gut, and their interactions with liver, as well as epigenetic regulation on autophagy by environmental pollutants. Furthermore, protective roles of potential therapeutic treatments on the multiple-hits of autophagy in NAFLD were descripted.

alpha-Tocopherol supplementation reduces inflammation and apoptosis in high cholesterol mediated nonalcoholic steatohepatitis

Inflammation and apoptosis signaling are crucial steps in the progression from nonalcoholic fatty liver disease (NAFLD) to nonalcoholic steatohepatitis (NASH). Alpha-tocopherol, the most active form of vitamin E, is an important modulator of signaling mechanisms, but its involvement to cholesterol-induced NASH pathogenesis remains poorly defined. Herein we have reported a novel effect of α-tocopherol in the transition from hepatic steatosis to NASH. High cholesterol diet alone (without α-tocopherol) in rabbits elevated NASH development as indicated by increased inflammatory response, apoptotic activity and liver fibrosis. Such elevation results from induction of signaling mechanisms since the expressions of IL1β, phospho c-Jun/c-Jun ratio, JNK, caspase 9, CHOP and Bax were increased, and recruitment of macrophage, α-smooth muscle actin (α-SMA) and COL1A1 into the liver tissue were induced. Alpha-tocopherol supplementation inhibited inflammatory response, apoptosis and fibrosis development without affecting lipid accumulation in high cholesterol-induced NASH. Specifically, α-tocopherol lowered the inflammatory level as observed by reduced macrophage infiltration and JNK/c-Jun signaling. Lower inflammatory status co-occurred with the reduction of CHOP and Bax expressions as well as fibrosis-related COL1A1 and α-SMA levels. Taken together, α-tocopherol supplementation inhibits cholesterol-induced NASH development by lowering JNK/c-Jun/inflammation axis in addition to JNK/CHOP/apoptosis signaling, which might contribute to resistance against NAFLD/NASH transition.

Emerging Roles of Impaired Autophagy in Fatty Liver Disease and Hepatocellular Carcinoma

Autophagy is a conserved catabolic process that eliminates dysfunctional cytosolic biomolecules through vacuole-mediated sequestration and lysosomal degradation. Although the molecular mechanisms that regulate autophagy are not fully understood, recent work indicates that dysfunctional/impaired autophagic functions are associated with the development and progression of nonalcoholic fatty liver disease (NAFLD), alcoholic fatty liver disease (AFLD), and hepatocellular carcinoma (HCC). Autophagy prevents NAFLD and AFLD progression through enhanced lipid catabolism and decreasing hepatic steatosis, which is characterized by the accumulation of triglycerides and increased inflammation. However, as both diseases progress, autophagy can become impaired leading to exacerbation of both pathological conditions and progression into HCC. Due to the significance of impaired autophagy in these diseases, there is increased interest in studying pathways and targets involved in maintaining efficient autophagic functions as potential therapeutic targets. In this review, we summarize how impaired autophagy affects liver function and contributes to NAFLD, AFLD, and HCC progression. We will also explore how recent discoveries could provide novel therapeutic opportunities to effectively treat these diseases.

Long-term androgen excess induces insulin resistance and non-alcoholic fatty liver disease in PCOS-like rats

OBJECTIVE

Women with polycystic ovary syndrome (PCOS) are at higher risk for metabolic disorders compared to healthy women, and about 51 % of women with PCOS suffer from non-alcoholic fatty liver disease (NAFLD). Investigation into the pathological mechanism behind this association will provide insights for the prevention and treatment of this complication.

METHODS

Dihydrotestosterone (DHT), a nonaromatic androgen, was used to mimic the pathological conditions of hyperandrogenism and insulin resistance. Hematoxylin and eosin staining, Oil Red O staining, immunofluorescent staining, Western blots, and qRT-PCR were used to verify the hepatic steatosis and inflammation, and the latter two methods were also used for energy and mitochondrion-related assays. ELISA was used to measure the level of reactive oxygen species.

RESULTS

Twelve weeks of DHT exposure led to obesity and insulin resistance as well as hepatic steatosis, lipid deposition, and different degrees of inflammation. The expression of molecules involved in respiratory chain and aerobic respiration processes, such as electron transfer complex II, pyruvate dehydrogenase, and succinate dehydrogenase complex subunit A, was inhibited. In addition, molecules associated with apoptosis and autophagy were also abnormally expressed, such as increased Bak mRNA, an increased activated caspase-3 to caspase-3 ratio, and increased Atg12 protein expression. All of these changes are associated with the mitochondria and lead to lipid deposition and inflammation in the liver.

CONCLUSIONS

Long-term androgen excess contributes to insulin resistance and hepatic steatosis by affecting mitochondrial function and causing an imbalance in apoptosis and autophagy, thus suggesting the pathogenesis of NAFLD in women with PCOS.

Hepatic autophagy and mitophagy status in dairy cows with subclinical and clinical ketosis

Severe negative energy balance around parturition is an important contributor to ketosis, a metabolic disorder that occurs most frequently in the peripartal period. Autophagy and mitophagy are important processes responsible for breaking down useless or toxic cellular material, and in particular damaged mitochondria. However, the role of autophagy and mitophagy during the occurrence and development of ketosis is unclear. The objective of this study was to investigate autophagy and mitophagy in the livers of cows with subclinical ketosis (SCK) and clinical ketosis (CK). We assessed autophagy by measuring the protein abundance of microtubule-associated protein 1 light chain 3-II (LC3-II; encoded by MAP1LC3) and sequestosome-1 (p62, encoded by SQSTM1), as well as the mRNA abundance of autophagy-related genes 5 (ATG5), 7 (ATG7), and 12 (ATG12), beclin1 (BECN1), and phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3). Mitophagy was evaluated by measuring the protein abundance of the mitophagy upstream regulators PTEN-induced putative kinase 1 (PINK1) and Parkin. Liver and blood samples were collected from healthy cows [n = 15; blood β-hydroxybutyrate (BHB) concentration <1.2 mM], cows with SCK (n = 15; blood BHB concentration 1.2 to 3.0 mM) and cows with CK (n = 15; blood BHB concentration >3.0 mM with clinical signs) with similar lactation numbers (median = 3, range = 2 to 4) and days in milk (median = 6, range = 3 to 9). The serum activity of aspartate aminotransferase and alanine aminotransferase was greater in cows with CK than in healthy cows. Levels of oxidative stress biomarkers malondialdehyde and hydrogen peroxide were also higher in liver tissue from ketotic cows (SCK and CK) than from healthy cows. Compared with cows with CK and healthy cows, the hepatic mRNA abundance of MAP1LC3, SQSTM1, ATG5, ATG7, ATG12, and PIK3C3 was upregulated in cows with SCK. Compared with healthy cows, cows with SCK had a lower abundance of p62 and a greater abundance of LC3-II, but levels of both were higher in cows with CK. The mRNA abundance of ATG12 was lower in cows with CK than in healthy cows. Furthermore, the hepatic protein abundance of PINK1 and Parkin was greater in cows with SCK and slightly lower in cows with CK than in healthy cows. These data demonstrated differences in the hepatic activities of autophagy and mitophagy in cows with SCK compared with cows with CK. Although the precise mechanisms for these differences could not be discerned, autophagy and mitophagy seem to be involved in ketosis.

Autophagy in liver diseases

Autophagy is the liver cell energy recycling system regulating a variety of homeostatic mechanisms. Damaged organelles, lipids and proteins are degraded in the lysosomes and their elements are re-used by the cell. Investigations on autophagy have led to the award of two Nobel Prizes and a health of important reports. In this review we describe the fundamental functions of autophagy in the liver including new data on the regulation of autophagy. Moreover we emphasize the fact that autophagy acts like a two edge sword in many occasions with the most prominent paradigm being its involvement in the initiation and progress of hepatocellular carcinoma. We also focused to the implication of autophagy and its specialized forms of lipophagy and mitophagy in the pathogenesis of various liver diseases. We analyzed autophagy not only in well studied diseases, like alcoholic and nonalcoholic fatty liver and liver fibrosis but also in viral hepatitis, biliary diseases, autoimmune hepatitis and rare diseases including inherited metabolic diseases and also acetaminophene hepatotoxicity. We also stressed the different consequences that activation or impairment of autophagy may have in hepatocytes as opposed to Kupffer cells, sinusoidal endothelial cells or hepatic stellate cells. Finally, we analyzed the limited clinical data compared to the extensive experimental evidence and the possible future therapeutic interventions based on autophagy manipulation.

Function of the endolysosomal network in cholesterol homeostasis and metabolic-associated fatty liver disease (MAFLD)

Background

Metabolic-associated fatty liver disease (MAFLD), also known as non-alcoholic fatty liver disease, has become the leading cause of chronic liver disease worldwide. In addition to hepatic accumulation of triglycerides, dysregulated cholesterol metabolism is an important contributor to the pathogenesis of MAFLD. Maintenance of cholesterol homeostasis is highly dependent on cellular cholesterol uptake and, subsequently, cholesterol transport to other membrane compartments, such as the endoplasmic reticulum (ER).

Scope of review

The endolysosomal network is key for regulating cellular homeostasis and adaptation, and emerging evidence has shown that the endolysosomal network is crucial to maintain metabolic homeostasis. In this review, we will summarize our current understanding of the role of the endolysosomal network in cholesterol homeostasis and its implications in MAFLD pathogenesis.

Major conclusions

Although multiple endolysosomal proteins have been identified in the regulation of cholesterol uptake, intracellular transport, and degradation, their physiological role is incompletely understood. Further research should elucidate their role in controlling metabolic homeostasis and development of fatty liver disease.

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The intracellular cholesterol transport is tightly regulated by the endocytic and lysosomal network.

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Dysfunction of the endolysosomal network affects hepatic lipid homeostasis.

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The endosomal sorting of lipoprotein receptors is precisely regulated and is not a bulk process.