Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease around the world estimated to affect up to one-third of the adult population and is expected to continue ...rising in the coming years. Nonalcoholic fatty liver disease is considered as the hepatic manifestation of the metabolic syndrome because it is strongly associated with obesity, insulin resistance, type 2 diabetes mellitus, and cardiovascular complications. Despite its high prevalence, factors leading to NAFLD progression from simple steatosis to nonalcoholic steatohepatitis, cirrhosis, and, ultimately hepatocellular carcinoma remain poorly understood. To date, no treatment has proven efficacy, and also no reliable method is currently available for diagnosis or staging of NAFLD beyond the highly invasive liver biopsy. Recently, extracellular vesicles (EVs) have emerged as potential candidate biomarkers for the diagnosis of NAFLD. Extracellular vesicles are circulating, cell-derived vesicles containing proteins and nucleic acids, among other components, that interact with and trigger a plethora of responses in neighbor or distant target cells. Several mechanisms implicated in NAFLD progression, such as inflammation, fibrosis, and angiogenesis, all related to metabolic syndrome–associated lipotoxicity, trigger EV production and release by liver cells. As hepatocytes represent ~80% of the liver volume, in this review we will focus on hepatocyte-derived EVs as drivers of the interactome between different liver cell types in NAFLD pathogenesis, as well as in their role as noninvasive biomarkers for NAFLD diagnosis and progression. Based on that, we will highlight the research that is currently available on EVs in this topic, the current limitations, and future directions for implementation in a clinical setting as biomarkers or targets of liver disease.
Olanzapine (OLA), a widely used second-generation antipsychotic (SGA), causes weight gain and metabolic alterations when administered orally to patients. Recently, we demonstrated that, contrarily to ...the oral treatment which induces weight gain, OLA administered via intraperitoneal (i.p.) in male mice resulted in body weight loss. This protection was due to an increase in energy expenditure (EE) through a mechanism involving the modulation of hypothalamic AMPK activation by higher OLA levels reaching this brain region compared to those of the oral treatment. Since clinical studies have shown hepatic steatosis upon chronic treatment with OLA, herein we further investigated the role of the hypothalamus-liver interactome upon OLA administration in wild-type (WT) and protein tyrosine phosphatase 1B knockout (PTP1B–KO) mice, a preclinical model protected against metabolic syndrome. WT and PTP1B–KO male mice were fed an OLA-supplemented diet or treated via i.p. Mechanistically, we found that OLA i.p. treatment induces mild oxidative stress and inflammation in the hypothalamus in a JNK1-independent and dependent manner, respectively, without features of cell dead. Hypothalamic JNK activation up-regulated lipogenic gene expression in the liver though the vagus nerve. This effect concurred with an unexpected metabolic rewiring in the liver in which ATP depletion resulted in increased AMPK/ACC phosphorylation. This starvation-like signature prevented steatosis. By contrast, intrahepatic lipid accumulation was observed in WT mice treated orally with OLA; this effect being absent in PTP1B–KO mice. We also demonstrated an additional benefit of PTP1B inhibition against hypothalamic JNK activation, oxidative stress and inflammation induced by chronic OLA i.p. treatment, thereby preventing hepatic lipogenesis. The protection conferred by PTP1B deficiency against hepatic steatosis in the oral OLA treatment or against oxidative stress and neuroinflammation in the i.p. treatment strongly suggests that targeting PTP1B might be also a therapeutic strategy to prevent metabolic comorbidities in patients under OLA treatment in a personalized manner.
Display omitted
•Oral OLA treatment induced hepatic steatosis in WT, but not in PTP1B–KO male mice.•OLA ip treatment in male WT mice activates hypothalamic JNK and upregulates hepatic FAS without inducing steatosis.•Hypothalamic JNK1-driven metabolic rewiring avoids steatosis in OLA ip treatment.•Reduced hypothalamic inflammation/oxidative stress in OLA ip treated PTP1B–KO mice.
Lipotoxicity triggers non-alcoholic fatty liver disease (NAFLD) progression owing to the accumulation of toxic lipids in hepatocytes including saturated fatty acids (SFAs), which activate ...pro-inflammatory pathways. We investigated the impact of hepatocyte- or circulating-derived small extracellular vesicles (sEV) secreted under NAFLD conditions on liver inflammation and hepatocyte insulin signalling.
sEV released by primary mouse hepatocytes, characterised and analysed by lipidomics, were added to mouse macrophages/Kupffer cells (KC) to monitor internalisation and inflammatory responses. Insulin signalling was analysed in hepatocytes exposed to conditioned media from sEV-loaded macrophages/KC. Mice were i.v. injected sEV to study liver inflammation and insulin signalling. Circulating sEV from mice and humans with NAFLD were used to evaluate macrophage–hepatocyte crosstalk.
Numbers of sEV released by hepatocytes increased under NAFLD conditions. Lipotoxic sEV were internalised by macrophages through the endosomal pathway and induced pro-inflammatory responses that were ameliorated by pharmacological inhibition or deletion of Toll-like receptor-4 (TLR4). Hepatocyte insulin signalling was impaired upon treatment with conditioned media from macrophages/KC loaded with lipotoxic sEV. Both hepatocyte-released lipotoxic sEV and the recipient macrophages/KC were enriched in palmitic (C16:0) and stearic (C18:0) SFAs, well-known TLR4 activators. Upon injection, lipotoxic sEV rapidly reached KC, triggering a pro-inflammatory response in the liver monitored by Jun N-terminal kinase (JNK) phosphorylation, NF-κB nuclear translocation, pro-inflammatory cytokine expression, and infiltration of immune cells into the liver parenchyma. sEV-mediated liver inflammation was attenuated by pharmacological inhibition or deletion of TLR4 in myeloid cells. Macrophage inflammation and subsequent hepatocyte insulin resistance were also induced by circulating sEV from mice and humans with NAFLD.
We identified hepatocyte-derived sEV as SFA transporters targeting macrophages/KC and activating a TLR4-mediated pro-inflammatory response enough to induce hepatocyte insulin resistance.
Small extracellular vesicles (sEV) released by the hepatocytes under non-alcoholic fatty liver disease (NAFLD) conditions cause liver inflammation and insulin resistance in hepatocytes via paracrine hepatocyte–macrophage–hepatocyte crosstalk. We identified sEV as transporters of saturated fatty acids (SFAs) and potent lipotoxic inducers of liver inflammation. TLR4 deficiency or its pharmacological inhibition ameliorated liver inflammation induced by hepatocyte-derived lipotoxic sEV. Evidence of this macrophage–hepatocyte interactome was also found in patients with NAFLD, pointing to the relevance of sEV in SFA-mediated lipotoxicity in NAFLD.
Display omitted
•SFA-enriched sEV induce macrophage/Kupffer cells inflammation via TLR4.•Lipotoxic sEV impair hepatocyte insulin signalling via macrophages/Kupffer cells.•Lipotoxic sEV target Kupffer cells and induce liver inflammation in vivo.•Pharmacological inhibition or deletion of TLR4 ameliorates liver inflammation induced by lipotoxic sEV.•Lipotoxic sEV-mediated macrophage–hepatocyte crosstalk was found in patients with NAFLD.
Non-alcoholic steatohepatitis (NASH) is characterized by a robust pro-inflammatory component at both hepatic and systemic levels together with a disease-specific gut microbiome signature. Protein ...tyrosine phosphatase 1 B (PTP1B) plays distinct roles in non-immune and immune cells, in the latter inhibiting pro-inflammatory signaling cascades. In this study, we have explored the role of PTP1B in the composition of gut microbiota and gut barrier dynamics in methionine and choline-deficient (MCD) diet-induced NASH in mice.
Gut features and barrier permeability were characterized in wild-type (PTP1B WT) and PTP1B-deficient knockout (PTP1B KO) mice fed a chow or methionine/choline-deficient (MCD) diet for 4 weeks. The impact of inflammation was studied in intestinal epithelial and enteroendocrine cells. The secretion of GLP-1 was evaluated in primary colonic cultures and plasma of mice.
We found that a shift in the gut microbiota shape, disruption of gut barrier function, higher levels of serum bile acids, and decreased circulating glucagon-like peptide (GLP)-1 are features during NASH. Surprisingly, despite the pro-inflammatory phenotype of global PTP1B-deficient mice, they were partly protected against the alterations in gut microbiota composition during NASH and presented better gut barrier integrity and less permeability under this pathological condition. These effects concurred with higher colonic mucosal inflammation, decreased serum bile acids, and protection against the decrease in circulating GLP-1 levels during NASH compared with their WT counterparts together with increased expression of GLP-2-sensitive genes in the gut. At the molecular level, stimulation of enteroendocrine STC-1 cells with a pro-inflammatory conditioned medium (CM) from lipopolysaccharide (LPS)-stimulated macrophages triggered pro-inflammatory signaling cascades that were further exacerbated by a PTP1B inhibitor. Likewise, the pro-inflammatory CM induced GLP-1 secretion in primary colonic cultures, an effect augmented by PTP1B inhibition.
Altogether our results have unraveled a potential role of PTP1B in the gut–liver axis during NASH, likely mediated by increased sensitivity to GLPs, with potential therapeutic value.
Display omitted
•MCD diet induces a different shift of gut microbiota in PTP1BWT and PTP1B KO mice.•PTP1B KO mice present higher colonic mucosal inflammation under NASH conditions.•Gut barrier permeability was decreased in PTP1B KO mice with NASH.•PTP1B inhibition increases GLP-1 secretion in colonic cultures exposed to inflammatory stimulus.
Background
Previously, we demonstrated that Spp1−/− mice exhibit a greater susceptibility to alcohol‐induced liver injury than wild‐type (WT) mice. Notably, alcohol triggers the expression of ...osteopontin (encoded by SPP1) in hepatocytes. However, the specific role of hepatocyte‐derived SPP1 in either mitigating or exacerbating alcohol‐associated liver disease (AALD) has yet to be elucidated. We hypothesized that hepatocyte‐derived SPP1 plays a role in AALD by modulating the regulation of steatosis.
Methods
We analyzed hepatic SPP1 expression using four publicly available datasets from patients with alcoholic hepatitis (AH). Additionally, we examined SPP1 expression in the livers of WT mice subjected to either a control or ethanol Lieber‐DeCarli (LDC) diet for 6 weeks. We compared the relationship between SPP1 expression and significantly dysregulated genes in AH with controls using correlation and enrichment analyses. To investigate the specific impact of hepatocyte‐derived SPP1, we generated hepatocyte‐specific Spp1 knock‐out (Spp1ΔHep) mice and subjected them to either a control or ethanol Lieber‐DeCarli diet for 6 weeks.
Results
Alcohol induced hepatic SPP1 expression in both humans and mice. Our analysis, focusing on genes correlated with SPP1, revealed an enrichment of fatty acid oxidation (FAO) in three datasets, and peroxisome proliferator‐activated receptor signaling in one dataset. Notably, FAO genes correlating with SPP1 were downregulated in patients with AH. Ethanol‐fed WT mice exhibited higher serum‐free fatty acids (FFAs), adipose tissue lipolysis, and hepatic fatty acid (FA) transporters. In contrast, ethanol‐fed Spp1ΔHep mice displayed lower liver triglycerides, FFAs, and serum alanine transaminase and greater FAO gene expression than WT mice, indicating a protective effect against AALD. Primary hepatocytes from Spp1∆Hep mice exhibited heightened expression of genes encoding proteins involved in FAO.
Conclusions
Alcohol induces the expression of SPP1 in hepatocytes, leading to impaired FAO and contributing to the development of AALD.
Alcohol consumption induces steatosis, acting as a promoting factor for alcohol‐associated liver disease (AALD). Previous studies conducted by our team demonstrated a significant increase in the expression of osteopontin, encoded by SPP1, in hepatocytes in a mouse model of AALD. Our current study reveals elevated hepatic expression of SPP1 in patients with alcoholic hepatitis (AH). Moreover, heightened hepatic SPP1 levels under alcohol stress influence lipid metabolism by inhibiting fatty acid oxidation in hepatocytes. This, in turn, contributes to alcohol‐induced steatosis, further facilitating the progression of AALD.
Second-generation antipsychotics (SGAs), in particular, olanzapine and clozapine, have been associated with the development of type 2 diabetes mellitus (T2D) and metabolic syndrome in individuals ...with schizophrenia. In this context, beta cell dysfunction is a plausible mechanism by which SGAs cause T2D. Herein, we analyzed the direct effects of olanzapine, a commonly prescribed SGA with diabetogenic properties, on the INS-1 (821/13) beta cell line and isolated pancreatic islets. Treatment of INS-1 beta cells with non-toxic concentrations of olanzapine (3-6 μM) during 4 h activated endoplasmic reticulum (ER) stress-mediated signaling by increasing PERK/eIF2α phosphorylation, IRE-1 phosphorylation and XBP-1 splicing. Moreover, glucose-stimulated insulin secretion (GSIS) was inhibited when olanzapine was present for 16 h. The insulin secretory function of INS-1 cells was restored by inhibiting olanzapine-induced ER stress with tauroursodeoxycholic acid (TUDCA). Similar effects of olanzapine with or without TUDCA on ER-stress-mediated signaling and GSIS were found in pancreatic islets from female mice. Our results indicate that early activation of ER stress in pancreatic beta cells is a potential mechanism behind the alterations in glucose homeostasis induced by olanzapine.
The liver exhibits a variety of functions that are well-preserved during aging. However, the cellular hallmarks of aging increase the risk of hepatic alterations and development of chronic liver ...diseases. Acetaminophen (APAP) is a first choice for relieving mild-to-moderate pain. Most of the knowledge about APAP-mediated hepatotoxicity arises from acute overdose studies due to massive oxidative stress and inflammation, but little is known about its effect in age-related liver inflammation after chronic exposure. Our results show that chronic treatment of wild-type mice on the B6D2JRcc/Hsd genetic background with APAP at an infratherapeutic dose reduces liver alterations during aging without affecting body weight. This intervention attenuates age-induced mild oxidative stress by increasing HO-1, MnSOD and NQO1 protein levels and reducing ERK1/2 and p38 MAPK phosphorylation. More importantly, APAP treatment counteracts the increase in Cd8
and the reduction in Cd4
T lymphocytes observed in the liver with age. This response was also found in peripheral blood mononuclear cells. In conclusion, chronic infratherapeutic APAP treatment protects mice from age-related liver alterations by attenuating oxidative stress and inflammation.
PDF
