Research ArticleARRB1 inhibits non-alcoholic steatohepatitis progression by promoting GDF15 maturation
Graphical abstract
Introduction
Metabolic disorders, including obesity, insulin resistance, and non-alcoholic fatty liver disease (NAFLD), have become a public health issue worldwide as a result of dramatic changes to human lifestyles and dietary choices.1,2 Excessive nutritional intake and decreased energy expenditure appear to be crucial in the pathogenesis of NAFLD. This disease comprises a spectrum of liver diseases, ranging from simple fatty liver to non-alcoholic steatohepatitis (NASH), which can progress to cirrhosis and liver cancer.3,4 NASH is associated with reprogrammed hepatic metabolic profiles that lead to excessive lipid accumulation in the liver and imbalances in lipid metabolism and lipid catabolism.5,6 More advanced NASH is associated with impaired lipid metabolism, leading to the accumulation of triglycerides and other lipids in hepatocytes.7 Lipotoxicity in the liver is the primary insult that initiates and propagates damage leading to hepatocyte injury and resulting inflammation.8 Hepatic lipid homeostasis is fine-tuned by a complex machinery comprising hormones, signaling and/or transcriptional pathways, and downstream genes associated with lipogenesis and lipolysis.9 Although many molecular regulatory networks have been described, the underlying mechanisms initiating the metabolic rearrangement and inflammatory response underlying NASH remain incompletely elucidated.
β-Arrestin1 (ARRB1), originally identified as a negative regulator of G-protein-coupled receptor (GPCR) signaling, has been demonstrated to function as molecular scaffold that regulates cellular function by interacting with other partner proteins, and is involved in multiple physiological process, including immune response, tumorigenesis, and inflammation.[10], [11], [12], [13] ARRB1 has also been found to regulate the NF-κB pathway in multiple inflammatory disease models.14,15 In addition, previous research showed that ARRB1 is involved in regulating hepatocellular carcinoma aggressiveness by mediating the desensitization and internalization of CD97.16 Moreover, ARRB1 partially represses diet-induced obesity and improves glucose tolerance by interacting with peroxisome proliferator-activated receptor (PPAR)-γ in preadipocytes.17 However, the regulatory roles of ARRB1 in hepatic inflammation and lipid metabolism disorder during the progression of NASH remain unknown.
The regulation of energy balance in the liver and other peripheral tissues is influenced by humoral factors that impact various metabolic activities, such as lipolysis and lipogenesis. The dysregulation of hormones or cytokines, including leptin, adiponectin, and insulin, contributes to metabolic disorders and hepatic lipid accumulation. Thus, more comprehensive elucidation of the causal mechanism underlying abnormal expression of these hormones or cytokines could enable the development of new therapeutic approaches for NASH. Growth Differentiation Factor 15 (GDF15; also known as Macrophage Inhibitor 1), is predominantly expressed in the liver and is a member of the Transforming Growth Factor (TGF)-beta superfamily.18 GDF15 is initially translated to GDF15 precursor (pro-GDF15) in dimeric form and is subsequently cleaved and secreted as mature GFD15 dimers.19,20 Recent studies showed that GDF15 activates AKT, ERK1/2, and PLCγ by binding GDNF-Family Receptor-α-Like (GFRAL) and through a GFRAL-RET complex present in cells, thus, reducing food intake, driving weight loss, and enhancing glucose homeostasis.18,[21], [22], [23] In addition, GDF15 alleviates fatty acid metabolic dysfunction in the liver, indicating that the liver is the direct target organ of GDF15.24 However, the post-translational regulation of GDF15, such as the maturation of pro-GDF15, and the downstream molecular mechanisms of GDF15 in hepatocytes, remain to be investigated.
The results from the current study demonstrate that ARRB1 expression is diminished in liver samples from patients with NASH and in murine NASH models. Arrb1 deficiency accelerates the development of steatohepatitis in mice fed either a high-fat diet (HFD) or methionine/choline-deficient diet (MCDD) and upregulates lipogenic genes and downregulates β-oxidative genes. Functionally, ARRB1 interacts with GDF15 and facilitates the transportation of pro-GDF15 to the Golgi apparatus for cleavage and maturation, thereby promoting fatty acid β-oxidation and inhibiting de novo lipogenesis. Thus, our results collectively indicate that ARRB1 is a crucial regulator linking GDF15 maturation to the development of NASH.
Section snippets
Human liver samples
Liver samples with NASH were obtained from patients with NAFLD who were undergoing bariatric surgery (n = 40). Three experienced pathologists, blinded to clinical data, evaluated independently all the liver specimens according to the NAFLD activity score (NAS), defined as the sum of steatosis, inflammation, and hepatocyte ballooning. Patients with a NAS score ≥5 were considered likely to have NASH. The exclusion criteria were the presence of other causes of liver disease, including alcohol
Patients with NASH and mouse models of NASH have low hepatic levels of ARRB1
To investigate the involvement of ARRB1 in NASH, we first analyzed the expression of ARRB1 in liver samples from 40 patients without NASH and 40 patients pathologically diagnosed with NASH. Both hepatic ARRB1 mRNA and protein levels were significantly lower in patients with NASH than in those without NASH (Fig. 1A–C). Moreover, Arrb1 expression was lower at both the mRNA and protein levels in the liver of WT mice fed an HFD compared with those fed a LFD for 26 weeks, or in the liver of mice fed
Discussion
This study demonstrates that ARRB1 has an important role in the pathogenesis of NASH. The expression of ARRB1 was diminished in livers from patients or mice with NASH. Moreover, deletion of Arrb1 significantly exacerbated hepatic steatosis, fibrosis, and inflammation in both HFD- and MCDD-fed mouse models. Mechanistically, ARRB1 interacts with pro-GDF15 and promotes its localization to the Golgi apparatus where it undergoes cleavage and/or maturation.
ARRB1 was originally identified and
Financial support
This work was supported by grants from the National Key Research and Development Program of China (Grant number 2016YFC0905900 to B.S.), State Key Program of the National Natural Science Foundation (Grant numbers 81430062 and 81930086 to B.S.), National Natural Science Youth Foundation (Grant number 81600487 to W.T.), and Innovative Research Groups of the National Natural Science Foundation (Grant number 81521004 to B.S.). B.S. is Distinguished Professor Yangtze River Scholar.
Authors’ contributions
Z.Z., X.X., W.T., and R.J. drafted the manuscript; Z.Z., X.X., R.J., Y.L., Q.S., R.F., Q.H., J.W., Y.L., and H.Y. conducted the experiments; Z.Z., X.X., R.J., W.T., and B.S. participated in research design; W.T. and B.S. contributed to the writing of the manuscript, discussed data, and supervised the study; all authors performed data analysis and interpretation, and read and approved the final manuscript.
Conflict of interest
The authors declare no conflict of interest that pertains to this work. Please refer to the accompanying ICMJE disclosure forms for further details.
References (48)
- et al.
Modeling NAFLD disease burden in China, France, Germany, Italy, Japan, Spain, United Kingdom, and United States for the period 2016-2030
J Hepatol
(2018) - et al.
Obesity and cancer: the oil that feeds the flame
Cell Metab
(2016) - et al.
Genetics and epigenetics of NAFLD and NASH: clinical impact
J Hepatol
(2018) - et al.
Pathogenesis of nonalcoholic steatohepatitis
Gastroenterology
(2016) - et al.
The beta-arrestins: multifunctional regulators of G protein-coupled receptors
J Biol Chem
(2016) - et al.
beta-Arrestin-1 protects against endoplasmic reticulum stress/p53-upregulated modulator of apoptosis-mediated apoptosis via repressing p-p65/inducible nitric oxide synthase in portal hypertensive gastropathy
Free Radic Biol Med
(2015) - et al.
Beta-arrestin-1 protein represses adipogenesis and inflammatory responses through its interaction with peroxisome proliferator-activated receptor-gamma (PPARgamma)
J Biol Chem
(2011) - et al.
Fasting exacerbates hepatic growth differentiation factor 15 to promote fatty acid beta-oxidation and ketogenesis via activating XBP1 signaling in liver
Redox Biol
(2018) - et al.
The MIC-1/GDF15-GFRAL pathway in energy homeostasis: implications for obesity, cachexia, and other associated diseases
Cell Metab
(2018) - et al.
Beta-arrestin-1 protein represses diet-induced obesity
J Biol Chem
(2011)
miR-374a-5p promotes tumor progression by targeting ARRB1 in triple negative breast cancer
Cancer Lett
CXC chemokine receptor 3 promotes steatohepatitis in mice through mediating inflammatory cytokines, macrophages and autophagy
J Hepatol
Nonsteroidal anti-inflammatory drug-activated gene-1 over expression in transgenic mice suppresses intestinal neoplasia
Gastroenterology
Global burden of NAFLD and NASH: trends, predictions, risk factors and prevention
Nat Rev Gastroenterol Hepatol
Mechanisms of NAFLD development and therapeutic strategies
Nat Med
Gene expression in human NAFLD
Am J Physiol Gastrointest Liver Physiol
Hepatic triglyceride synthesis and nonalcoholic fatty liver disease
Curr Opin Lipidol
Nonalcoholic fatty liver disease: pathogenesis and disease spectrum
Annu Rev Pathol
Beta-arrestins and cell signaling
Annu Rev Physiol
Critical regulation of CD4+ T cell survival and autoimmunity by beta-arrestin 1
Nat Immunol
beta-Arrestin1 enhances hepatocellular carcinogenesis through inflammation-mediated Akt signalling
Nat Commun
beta-Arrestin1 alleviates acute pancreatitis via repression of NF-kappaBp65 activation
J Gastroenterol Hepatol
CD97 promotes tumor aggressiveness through the traditional G protein-coupled receptor-Mediated signaling in hepatocellular carcinoma
Hepatology
Non-homeostatic body weight regulation through a brainstem-restricted receptor for GDF15
Nature
Cited by (36)
GDF15 activates AMPK and inhibits gluconeogenesis and fibrosis in the liver by attenuating the TGF-β1/SMAD3 pathway
2024, Metabolism: Clinical and ExperimentalRole of XBP1 in regulating the progression of non-alcoholic steatohepatitis
2022, Journal of HepatologyOverexpression of NAG-1/GDF15 prevents hepatic steatosis through inhibiting oxidative stress-mediated dsDNA release and AIM2 inflammasome activation
2022, Redox BiologyCitation Excerpt :Liver-specific deletion of NAG-1/GDF15 via adenovirus injection has been reported to increase hepatic lipid and TG accumulation, and to inhibit fatty acid β-oxidation in the liver of fasting mice, accompanied by reduced gene expression of PPARa, ACOX1, and CPT1a [35]. A recent study reported that overexpression of NAG-1/GDF15 through adenovirus transfection in mice or using recombinant protein in hepatic cells inhibited lipid accumulation and the progression of NASH [36]. Together with our study, the current evidence suggests that NAG-1/GDF15 could be a promising target for the prevention or treatment of steatosis and NAFLD-related metabolic deterioration via regulating fatty acids metabolism.
GDF15, an emerging key player in human aging
2022, Ageing Research ReviewsCitation Excerpt :Moreover, very recently it has been observed that also β-arrestin 1 (ARRB1) plays a fundamental role in the maturation of GDF15 (Zhang et al., 2020; Wang et al., 2021). In particular, in hepatocytes ARRB1 binds the pro-GDF15 and facilitates its transport to the Golgi apparatus to promote the subsequent GDF15 cleavage and maturation through PCSK enzymes (Zhang et al., 2020; Wang et al., 2021). However, to date it is not yet clear what kind of stimuli (physiological or pathological) activate PCSK enzymes to regulate the maturation of GDF15 and their specific biological function in the aging process.
Author names in bold designate shared co-first authorship
- †
These authors contributed equally as joint first co-authors.