Secreted MUP1 that reduced under ER stress attenuates ER stress induced insulin resistance through suppressing protein synthesis in hepatocytes

Disruption of HSD17B12 in mouse hepatocytes leads to reduced body weight and defect in the lipid droplet expansion associated with microvesicular steatosis

The function of hydroxysteroid dehydrogenase 12 (HSD17B12) in lipid metabolism is poorly understood. To study this further, we created mice with hepatocyte-specific knockout of HSD17B12 (LiB12cKO). From 2 months on, these mice showed significant fat accumulation in their liver. As they aged, they also had a reduced whole-body fat percentage. Interestingly, the liver fat accumulation did not result in the typical formation of large lipid droplets (LD); instead, small droplets were more prevalent. Thus, LiB12KO liver did not show increased macrovesicular steatosis with the increasing fat content, while microvesicular steatosis was the predominant feature in the liver. This indicates a failure in the LD expansion. This was associated with liver damage, presumably due to lipotoxicity. Notably, the lipidomics data did not support an essential role of HSD17B12 in fatty acid (FA) elongation. However, we did observe a decrease in the quantity of specific lipid species that contain FAs with carbon chain lengths of 18 and 20 atoms, including oleic acid. Of these, phosphatidylcholine and phosphatidylethanolamine have been shown to play a key role in LD formation, and a limited amount of these lipids could be part of the mechanism leading to the dysfunction in LD expansion. The increase in the Cidec expression further supported the deficiency in LD expansion in the LiB12cKO liver. This protein is crucial for the fusion and growth of LDs, along with the downregulation of several members of the major urinary protein family of proteins, which have recently been shown to be altered during endoplasmic reticulum stress.

Piperlongumine, a natural alkaloid from Piper longum L. ameliorates metabolic-associated fatty liver disease by antagonizing the thromboxane A2 receptor

Metabolic dysfunction-associated fatty liver disease (MAFLD) encompasses a broad spectrum of hepatic disorders, including hyperglycemia, hepatic steatosis, and insulin resistance. Piperlongumine (PL), a natural amide alkaloid extracted from the fruits of Piper longum L., exhibited hepatoprotective effects in zebrafish and liver injury mice. This study aimed to investigate the therapeutic potential of PL on MAFLD and its underlying mechanisms. The findings demonstrate that PL effectively combats MAFLD induced by a high-fat diet (HFD) and improves metabolic characteristics in mice. Additionally, our results suggest that the anti-MAFLD effect of PL is attributed to the suppression of excessive hepatic gluconeogenesis, inhibition of de novo lipogenesis, and alleviation of insulin resistance. Importantly, the results indicate that, on the one hand, the hypoglycemic effect of PL is closely associated with CREB-regulated transcriptional coactivators (CRTC2)-dependent cyclic AMP response element binding protein (CREB) phosphorylation; on the other hand, the lipid-lowering effect of PL is attributed to reducing the nuclear localization of sterol regulatory element-binding proteins 1c (Srebp-1c). Mechanistically, PL could alleviate insulin resistance induced by endoplasmic reticulum stress by antagonizing the thromboxane A2 receptor (TP)/Ca2+ signaling, and the TP receptor serves as the potential target for PL in the treatment of MAFLD. Therefore, our results suggested PL effectively improved the major hallmarks of MAFLD induced by HFD, highlighting a potential therapeutic strategy for MAFLD.

Integration of network pharmacology and proteomics analysis to identify key target pathways of Ginsenoside Re for myocardial ischemia

BACKGROUND

Clinically, various diseases cause myocardial ischemia (MI), which further induces severe cardiac injury and leads to high mortality in patients. Ginsenoside Re, one of the major ginsenosides in ginseng, can regulate the level of oxidative stress in the injured myocardium. Thus, it may attenuate MI injury, but the related mechanism has not been comprehensively studied.

PURPOSE

This study aimed to investigate the anti-MI effect and comprehensively mechanisms of Ginsenoside Re.

STUDY DESIGN/METHODS

Oxygen-glucose deprivation (OGD), oxidative-induced cardiomyocyte injury, and isoproterenol-induced MI mice were used to explore their protective effect of Ginsenoside Re. An integrated approach of network pharmacology, molecular docking, and tandem mass tag proteomics was applied to determine the corresponding common potential targets of Ginsenoside Re against MI, such as target proteins and related pathways. The major anti-MI target proteins and related pathways were validated by immunofluorescence (IF) assay and Western blotting (WB).

RESULTS

Ginsenoside Re (1.32-168.93 µM) had low toxicity to normal cardiomyocytes, and increased the survival of oxidative stress-injured (OGD-induced injury or H2O2-induced injury) cardiomyocytes in this concentration range. It regulated the reactive oxygen species (ROS) level in OGD-injured cardiomyocytes; stabilized the nuclear morphology, mitochondrial membrane potential (MMP), and mitochondrial function; and reduced apoptosis. Meanwhile, Ginsenoside Re (5-20 mg/kg) alleviated cardiac injury in MI mice and maintained cardiac function. Through network pharmacology and proteomics, the relevant mechanisms revealed several key pathways of Ginsenoside Re anti-MI, including inhibition of MAPK pathway protein phosphorylation, downregulation of phosphorylated PDPK1, AKT, and STAT3, and upregulation of TGF-β3, ferroptosis pathway (upregulation of GPX4 and downregulation of phosphorylation level of MDM2) and AMPK pathway (regulating the synthesis of cholesterol in the myocardium by downregulation of HMGCR). The key proteins of these target pathways were validated by IF and/or WB.

CONCLUSION

Ginsenoside Re may target MAPK, AKT, ferroptosis pathways and AMPK pathway to prevent and/or treat MI injury and protect cardiomyocytes from oxidative damage.

Advances in Integrated Multi-omics Analysis for Drug-Target Identification

As an essential component of modern drug discovery, the role of drug-target identification is growing increasingly prominent. Additionally, single-omics technologies have been widely utilized in the process of discovering drug targets. However, it is difficult for any single-omics level to clearly expound the causal connection between drugs and how they give rise to the emergence of complex phenotypes. With the progress of large-scale sequencing and the development of high-throughput technologies, the tendency in drug-target identification has shifted towards integrated multi-omics techniques, gradually replacing traditional single-omics techniques. Herein, this review centers on the recent advancements in the domain of integrated multi-omics techniques for target identification, highlights the common multi-omics analysis strategies, briefly summarizes the selection of multi-omics analysis tools, and explores the challenges of existing multi-omics analyses, as well as the applications of multi-omics technology in drug-target identification.

Research status and hotspots in the field of endoplasmic reticulum stress and liver disease: A bibliometric study

Recently, the study of endoplasmic reticulum stress (ERS) and liver disease has attracted much attention, but bibliometric analysis on this field is scarce. Therefore, to address this gap, we conducted a bibliometric analysis to explore the research status, hotspots, and trends in this field. We searched the Web of Science Core Collection database for publications on ERS and liver disease from 2007 to 2022. Bibliometric online analysis platform, VOSviewer, and CiteSpace were used to perform bibliometric analysis. Two thousand seven hundred fifty-one publications were retrieved form the Web of Science Core Collection database. The USA was the most productive and influential country. Seoul National University, International Journal of Molecular Sciences, and Kaufman RJ were the most productive institution, journal, and author. "Endoplasmic reticulum stress," "nonalcoholic fatty liver disease," "inflammation," "oxidative stress" and "insulin resistance" were the high-frequency keywords, "necrosis factor alpha" was the keywords with the strongest citation bursts, and "nonalcoholic fatty liver," "fibrosis" and "lipid droplet" were the keywords that were still bursting in 2022. The number of publications on ERS and liver disease has increased over the past years. The USA was the most productive and influential country. China has become the country with the largest number of annual publications, but it still needs to work on the quality. ERS and nonalcoholic fatty liver disease, especially the insulin resistance and lipotoxicity in hepatocytes may be the research hotspots and trends in this field of ERS and liver disease.

Cellular communication network factor 1 promotes retinal leakage in diabetic retinopathy via inducing neutrophil stasis and neutrophil extracellular traps extrusion

BACKGROUND

Diabetic retinopathy (DR) is a major cause of blindness and is characterized by dysfunction of the retinal microvasculature. Neutrophil stasis, resulting in retinal inflammation and the occlusion of retinal microvessels, is a key mechanism driving DR. These plugging neutrophils subsequently release neutrophil extracellular traps (NETs), which further disrupts the retinal vasculature. Nevertheless, the primary catalyst for NETs extrusion in the retinal microenvironment under diabetic conditions remains unidentified. In recent studies, cellular communication network factor 1 (CCN1) has emerged as a central molecule modulating inflammation in pathological settings. Additionally, our previous research has shed light on the pathogenic role of CCN1 in maintaining endothelial integrity. However, the precise role of CCN1 in microvascular occlusion and its potential interaction with neutrophils in diabetic retinopathy have not yet been investigated.

METHODS

We first examined the circulating level of CCN1 and NETs in our study cohort and analyzed related clinical parameters. To further evaluate the effects of CCN1 in vivo, we used recombinant CCN1 protein and CCN1 overexpression for gain-of-function, and CCN1 knockdown for loss-of-function by intravitreal injection in diabetic mice. The underlying mechanisms were further validated on human and mouse primary neutrophils and dHL60 cells.

RESULTS

We detected increases in CCN1 and neutrophil elastase in the plasma of DR patients and the retinas of diabetic mice. CCN1 gain-of-function in the retina resulted in neutrophil stasis, NETs extrusion, capillary degeneration, and retinal leakage. Pre-treatment with DNase I to reduce NETs effectively eliminated CCN1-induced retinal leakage. Notably, both CCN1 knockdown and DNase I treatment rescued the retinal leakage in the context of diabetes. In vitro, CCN1 promoted adherence, migration, and NETs extrusion of neutrophils.

CONCLUSION

In this study, we uncover that CCN1 contributed to retinal inflammation, vessel occlusion and leakage by recruiting neutrophils and triggering NETs extrusion under diabetic conditions. Notably, manipulating CCN1 was able to hold therapeutic promise for the treatment of diabetic retinopathy.

Structure, Functions, and Implications of Selected Lipocalins in Human Disease

The lipocalin proteins are a large family of small extracellular proteins that demonstrate significant heterogeneity in sequence similarity and have highly conserved crystal structures. They have a variety of functions, including acting as carrier proteins, transporting retinol, participating in olfaction, and synthesizing prostaglandins. Importantly, they also play a critical role in human diseases, including cancer. Additionally, they are involved in regulating cellular homeostasis and immune response and dispensing various compounds. This comprehensive review provides information on the lipocalin family, including their structure, functions, and implications in various diseases. It focuses on selective important human lipocalin proteins, such as lipocalin 2 (LCN2), retinol binding protein 4 (RBP4), prostaglandin D2 synthase (PTGDS), and α1-microglobulin (A1M).

Thromboxane A2/thromboxane A2 receptor axis facilitates hepatic insulin resistance and steatosis through endoplasmic reticulum stress in non-alcoholic fatty liver disease

BACKGROUND AND PURPOSE

Defective insulin signalling and dysfunction of the endoplasmic reticulum (ER), driven by excessive lipid accumulation in the liver, is a characteristic feature in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Thromboxane A2 (TXA2 ), an arachidonic acid metabolite, is significantly elevated in obesity and plays a crucial role in hepatic gluconeogenesis and adipose tissue macrophage polarization. However, the role of liver TXA2 /TP receptors in insulin resistance and lipid metabolism is largely unknown.

EXPERIMENTAL APPROACH

TP receptor knockout (TP-/- ) mice were generated and fed a high-fat diet for 16 weeks. Insulin sensitivity, ER stress responses and hepatic lipid accumulation were assessed. Furthermore, we used primary hepatocytes to dissect the mechanisms by which the TXA2 /TP receptor axis regulates insulin signalling and hepatocyte lipogenesis.

KEY RESULTS

TXA2 was increased in diet-induced obese mice, and depletion of TP receptors in adult mice improved systemic insulin resistance and hepatic steatosis. Mechanistically, we found that the TXA2 /TP receptor axis disrupts insulin signalling by activating the Ca2+ /calcium calmodulin-dependent kinase II γ (CaMKIIγ)-protein kinase RNA-like endoplasmic reticulum kinase (PERK)-C/EBP homologous protein (Chop)-tribbles-like protein 3 (TRB3) axis in hepatocytes. In addition, our results revealed that the TXA2 /TP receptor axis directly promoted lipogenesis in primary hepatocytes and contributed to Kupffer cell inflammation.

CONCLUSIONS AND IMPLICATIONS

The TXA2 /TP receptor axis facilitates insulin resistance through Ca2+ /CaMKIIγ to activate PERK-Chop-TRB3 signalling. Inhibition of hepatocyte TP receptors improved hepatic steatosis and inflammation. The TP receptor is a new therapeutic target for NAFLD and metabolic syndrome.

MUP1 mediates urolithin A alleviation of chronic alcohol-related liver disease via gut-microbiota-liver axis

Alcohol-related liver disease (ALD) is recognized as a global health crisis, contributing to approximately 20% of liver cancer-associated fatalities. Dysbiosis of the gut microbiome is associated with the development of ALD, with the gut microbial metabolite urolithin A (UA) exhibiting a potential for alleviating liver symptoms. However, the protective efficacy of UA against ALD and its underlying mechanism mediated by microbiota remain elusive. In this study, we provide evidence demonstrating that UA effectively ameliorates alcohol-induced metabolic disorders and hepatic endoplasmic reticulum (ER) stress through a specific gut-microbiota-liver axis mediated by major urinary protein 1 (MUP1). Moreover, UA exhibited the potential to restore alcohol-induced dysbiosis of the intestinal microbiota by enriching the abundance of Bacteroides sartorii (B. sartorii), Parabacteroides distasonis (P. distasonis), and Akkermansia muciniphila (A. muciniphila), along with their derived metabolite propionic acid. Partial attenuation of the hepatoprotective effects exerted by UA was observed upon depletion of gut microbiota using antibiotics. Subsequently, a fecal microbiota transplantation (FMT) experiment was conducted to evaluate the microbiota-dependent effects of UA in ALD. FMT derived from mice treated with UA exhibited comparable efficacy to direct UA treatment, as it effectively attenuated ER stress through modulation of MUP1. It was noteworthy that strong associations were observed among the hepatic MUP1, gut microbiome, and metabolome profiles affected by UA. Intriguingly, oral administration of UA-enriched B. sartorii, P. distasonis, and A. muciniphila can enhance propionic acid production to effectively suppress ER stress via MUP1, mimicking UA treatment. Collectively, these findings elucidate the causal mechanism that UA alleviated ALD through the gut-microbiota-liver axis. This unique mechanism sheds light on developing novel microbiome-targeted therapeutic strategies against ALD.

HRD1 reduction promotes cholesterol-induced vascular smooth muscle cell phenotypic change via endoplasmic reticulum stress

Phenotypic change of vascular smooth muscle cells (VSMCs) is the main contributor of vascular pathological remodeling in atherosclerosis. The endoplasmic reticulum (ER) is critical for maintaining VSMC function through elimination of misfolded proteins that impair VSMC cellular function. ER-associated degradation (ERAD) is an ER-mediated process that controls protein quality by clearing misfolded proteins. One of the critical regulators of ERAD is HRD1, which also plays a vital role in lipid metabolism. However, the function of HRD1 in VSMCs of atherosclerotic vessels remains poorly understood. The level of HRD1 expression was analyzed in aortic tissues of mice fed with a high-fat diet (HFD). The H&E and EVG (VERHOEFF'S VAN GIESON) staining were used to demonstrate pathological vascular changes. IF (immunofluorescence) and WB (western blot) were used to explore the signaling pathways in vivo and in vitro. The wound closure and transwell assays were also used to test the migration rate of VSMCs. CRISPR gene editing and transcriptomic analysis were applied in vitro to explore the cellular mechanism. Our data showed significant reduction of HRD1 in aortic tissues of mice under HFD feeding. VSMC phenotypic change and HRD1 downregulation were detected by cholesterol supplement. Transcriptomic and further analysis of HRD1-KO VSMCs showed that HRD1 deficiency induced the expression of genes related to ER stress response, proliferation and migration, but reduced the contractile-related genes in VSMCs. HRD1 deficiency also exacerbated the proliferation, migration and ROS production of VSMCs induced by cholesterol, which promoted the VSMC dedifferentiation. Our results showed that HRD1 played an essential role in the contractile homeostasis of VSMCs by negatively regulating ER stress response. Thus, HRD1 in VSMCs could serve as a potential therapeutic target in metabolic disorder-induced vascular remodeling.