Biology

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14 pages, 3227 KiB

Open AccessArticle

Exploring Interactions between Primary Hepatocytes and Non-Parenchymal Cells on Physiological and Pathological Liver Stiffness

by Vaishaali Natarajan, Youra Moeun and Srivatsan Kidambi

Biology 2021, 10(5), 408; https://doi.org/10.3390/biology10050408 - 5 May 2021

Cited by 12 | Viewed by 3181

Abstract

Chronic liver disease is characterized by progressive hepatic fibrosis leading to the formation of cirrhosis irrespective of the etiology with no effective treatment currently available. Liver stiffness (LS) is currently the best clinical predictor of this fibrosis progression irrespective of the etiology. LS [...] Read more.

Chronic liver disease is characterized by progressive hepatic fibrosis leading to the formation of cirrhosis irrespective of the etiology with no effective treatment currently available. Liver stiffness (LS) is currently the best clinical predictor of this fibrosis progression irrespective of the etiology. LS and hepatocytes-nonparenchymal cells (NPC) interactions are two variables known to be important in regulating hepatic function during liver fibrosis, but little is known about the interplay of these cues. Here, we use polydimethyl siloxane (PDMS) based substrates with tunable mechanical properties to study how cell–cell interaction and stiffness regulates hepatocytes function. Specifically, primary rat hepatocytes were cocultured with NIH-3T3 fibroblasts on soft (2 kPa) and stiff substrates that recreates physiologic (2 kPa) and cirrhotic liver stiffness (55 kPa). Urea synthesis by primary hepatocytes depended on the presence of fibroblast and was independent of the substrate stiffness. However, albumin synthesis and Cytochrome P450 enzyme activity increased in hepatocytes on soft substrates and when in coculture with a fibroblast. Western blot analysis of hepatic markers, E-cadherin, confirmed that hepatocytes on soft substrates in coculture promoted better maintenance of the hepatic phenotype. These findings indicate the role of stiffness in regulating the hepatocytes interactions with NPCs necessary for maintenance of hepatocytes function. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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8 pages, 403 KiB

Open AccessArticle

PNPLA3 Single Nucleotide Polymorphism Prevalence and Association with Liver Disease in a Diverse Cohort of Persons Living with HIV

by Kenneth E. Sherman, Susan D. Rouster, Heidi Meeds, Javier Tamargo, Jun Chen, Richard Ehman and Marianna Baum

Biology 2021, 10(3), 242; https://doi.org/10.3390/biology10030242 - 21 Mar 2021

Cited by 3 | Viewed by 2712

Abstract

In persons living with HIV (PLWH), there are multiple sources of liver injury. Gene polymorphisms of PNPLA3 (patatin-like phospholipase domain-containing protein 3) have been identified as an important cofactor for increased disease severity in both alcoholic and non-alcoholic steatohepatitis (NASH). We utilized a [...] Read more.

In persons living with HIV (PLWH), there are multiple sources of liver injury. Gene polymorphisms of PNPLA3 (patatin-like phospholipase domain-containing protein 3) have been identified as an important cofactor for increased disease severity in both alcoholic and non-alcoholic steatohepatitis (NASH). We utilized a well-characterized cohort of ethnically and racially diverse patients with HIV to define the prevalence of PNPLA3 SNPs (single nucleotide polymorphism) (rs738409), and to determine the relationship to hepatic steatosis and liver fibrosis. Steatosis was determined using MRI-PDFF (magnetic resonance imaging-determined proton density fat fraction) and fibrosis was estimated using MR Elastography (MRE). From the Miami Area HIV Study (MASH) cohort, 100 HIV positive participants and 40 controls (HCV/HIV = 20; HCV and HIV negative = 20) were evaluated. Nearly 40% of all participants carried the variant G allele associated with increased liver disease severity and 5% were homozygotic GG. The variant SNP occurred most frequently in those self-identified as Hispanic compared to white or Black participants. Hepatic steatosis (>5% fat) was present significantly more often in those without HIV vs. those with (p < 0.001). Putative NAFLD/NASH was found to be present in 6% of tested subjects, who were HIV monoinfected. BMI was lower in those that carried the G allele for PNPLA3. This finding suggests that PNPLA3 may be an independent component to NAFLD (non-alcoholic fatty liver disease)/NASH development and longitudinal follow-up of the cohort is warranted. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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11 pages, 1771 KiB

Open AccessArticle

Susceptibility of Asialoglycoprotein Receptor-Deficient Mice to LPS/Galactosamine Liver Injury and Protection by Betaine Administration

by Karuna Rasineni, Serene M. L. Lee, Benita L. McVicker, Natalia A. Osna, Carol A. Casey and Kusum K. Kharbanda

Biology 2021, 10(1), 19; https://doi.org/10.3390/biology10010019 - 31 Dec 2020

Cited by 9 | Viewed by 2626

Abstract

Background: Work from our laboratory has shown that the ethanol-induced increase in apoptotic hepatocellular death is closely related to the impairment in the ability of the asialoglycoprotein receptor (ASGP-R) to remove neighboring apoptotic cells. In this study, we assessed the role of ASGP-R [...] Read more.

Background: Work from our laboratory has shown that the ethanol-induced increase in apoptotic hepatocellular death is closely related to the impairment in the ability of the asialoglycoprotein receptor (ASGP-R) to remove neighboring apoptotic cells. In this study, we assessed the role of ASGP-R in fulminant liver failure and investigated whether prior treatment with betaine (a naturally occurring tertiary amine) is protective. Methods: Lipopolysaccharide (LPS; 50 μg/kg BW) and galactosamine (GalN; 350 mg/kg BW) were injected together to wild-type and ASGP-R-deficient mice that were treated for two weeks prior with or without 2% betaine in drinking water. The mice were sacrificed 1.5, 3, or 4.5 h post-injection, and tissue samples were collected. Results: LPS/GalN injection generate distinct molecular processes, which includes increased production of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), thus causing apoptosis as evident by increased caspase-3 activity. ASGP-R deficient animals showed increased liver caspase activities, serum TNF-α and IL-6 levels, as well as more pronounced liver damage compared with the wild-type control animals after intraperitoneal injection of LPS/GalN. In addition, prior administration of betaine was found to significantly attenuate the LPS/GalN-induced increases in liver injury parameters. Conclusion: Our work underscores the importance of normal functioning of ASGP-R in preventing severe liver damage and signifies a therapeutic role of betaine in prevention of liver injuries from toxin-induced fulminant liver failure. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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17 pages, 2446 KiB

Open AccessArticle

Lauric Acid versus Palmitic Acid: Effects on Adipose Tissue Inflammation, Insulin Resistance, and Non-Alcoholic Fatty Liver Disease in Obesity

by Viswanathan Saraswathi, Narendra Kumar, Thiyagarajan Gopal, Saumya Bhatt, Weilun Ai, Carmen Ma, Geoffrey A. Talmon and Cyrus Desouza

Biology 2020, 9(11), 346; https://doi.org/10.3390/biology9110346 - 22 Oct 2020

Cited by 50 | Viewed by 7754

Abstract

Coconut oil, rich in medium-chain saturated fatty acids (MCSFA), in particular, lauric acid (LA), is known to exert beneficial metabolic effects. Although LA is the most abundant saturated fatty acid in coconut oil, the specific role of LA in altering obesity-related metabolic disorders [...] Read more.

Coconut oil, rich in medium-chain saturated fatty acids (MCSFA), in particular, lauric acid (LA), is known to exert beneficial metabolic effects. Although LA is the most abundant saturated fatty acid in coconut oil, the specific role of LA in altering obesity-related metabolic disorders remains unknown. Here, we examined the effects of supplementing a high fat (HF) diet with purified LA on obesity-associated metabolic derangements in comparison with palmitic acid (PA), a long-chain saturated fatty acid. Male C57BL/6 mice were fed a control chow diet (CD) or an HF diet supplemented with 3% LA (HF + LA) or PA (HF + PA) for 12 wk. Markers of adipose tissue (AT) inflammation, systemic insulin resistance (IR), and hepatic steatosis, were assessed. The body weight and total fat mass were significantly higher in both HF + LA and HF + PA diet-fed groups compared to CD controls. However, the visceral adipose tissue (VAT) mass was significantly higher (p < 0.001) in HF + LA-fed mice compared to both CD as well as HF + PA-fed mice. Interestingly, markers of AT inflammation were promoted to a lesser extent in HF + LA-fed mice compared to HF + PA-fed mice. Thus, immunohistochemical analysis of VAT showed an increase in MCP-1 and IL-6 staining in HF + PA-fed mice but not in HF + LA-fed mice compared to CD controls. Further, the mRNA levels of macrophage and inflammatory markers were significantly higher in HF + PA-fed mice (p < 0.001) whereas these markers were increased to a lesser extent in HF + LA-fed group. Of note, the insulin tolerance test revealed that IR was significantly increased only in HF + PA-fed mice but not in HF + LA-fed group compared to CD controls. While liver triglycerides were increased significantly in both HF + PA and HF + LA-fed mice, liver weight and plasma markers of liver injury such as alanine aminotransferase and aspartate aminotransferase were increased significantly only in HF + PA-fed mice but not in HF + LA-fed mice. Taken together, our data suggest that although both LA and PA increased AT inflammation, systemic IR, and liver injury, the extent of metabolic derangements caused by LA was less compared to PA in the setting of high fat feeding. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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9 pages, 3517 KiB

Open AccessArticle

A Selective PPARγ Modulator Reduces Hepatic Fibrosis

by Benita L. McVicker, Frederick G. Hamel, Ronda L. Simpson and Robert G. Bennett

Biology 2020, 9(7), 151; https://doi.org/10.3390/biology9070151 - 2 Jul 2020

Cited by 6 | Viewed by 2825

Abstract

Hepatic fibrosis is the accumulation of excess collagen as a result of chronic liver injury. If left unabated, hepatic fibrosis can lead to the disruption of the liver architecture, portal hypertension, and increased risk of progression to cirrhosis and hepatocellular carcinoma. The thiazolidinedione [...] Read more.

Hepatic fibrosis is the accumulation of excess collagen as a result of chronic liver injury. If left unabated, hepatic fibrosis can lead to the disruption of the liver architecture, portal hypertension, and increased risk of progression to cirrhosis and hepatocellular carcinoma. The thiazolidinedione class of antidiabetic drugs, through their target peroxisome proliferator-activated receptor γ (PPARγ), have protective effects against liver fibrosis, and can inhibit the profibrotic activity of hepatic stellate cells, the major collagen-producing liver cells. However, these drugs have been ineffective in the treatment of established fibrosis, possibly due to side effects such as increased weight and adiposity. Recently, selective PPARγ modulators that lack these side effects have been identified, but their role in treating fibrosis has not been studied. In this study, we tested the effectiveness of one of these selective modulators, SR1664, in the mouse carbon tetrachloride model of established hepatic fibrosis. Treatment with SR1664 reduced the total and type 1 collagen content without increasing body weight. The abundance of activated hepatic stellate cells was also significantly decreased. Finally, SR1664 inhibited the profibrotic phenotype of hepatic stellate cells. In summary, a selective PPARγ modulator was effective in the reduction of established hepatic fibrosis and the activated phenotype of hepatic stellate cells. This may represent a new treatment approach for hepatic fibrosis. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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9 pages, 1488 KiB

Open AccessArticle

Hydralazine Sensitizes to the Antifibrotic Effect of 5-Aza-2′-deoxycytidine in Hepatic Stellate Cells

by Kiyoshi Asada, Kosuke Kaji, Shinya Sato, Kenichiro Seki, Naotaka Shimozato, Hideto Kawaratani, Hiroaki Takaya, Yasuhiko Sawada, Keisuke Nakanishi, Masanori Furukawa, Mitsuteru Kitade, Kei Moriya, Tadashi Namisaki, Ryuichi Noguchi, Takemi Akahane and Hitoshi Yoshiji

Biology 2020, 9(6), 117; https://doi.org/10.3390/biology9060117 - 3 Jun 2020

Cited by 1 | Viewed by 2681

Abstract

Background: Hepatic stellate cell (HSC) activation is essential for the development of liver fibrosis. Epigenetic machinery, such as DNA methylation, is largely involved in the regulation of gene expression during HSC activation. Although the pharmacological DNA demethylation of HSC using 5-aza-2′-deoxycytidine (5-aza-dC) yielded [...] Read more.

Background: Hepatic stellate cell (HSC) activation is essential for the development of liver fibrosis. Epigenetic machinery, such as DNA methylation, is largely involved in the regulation of gene expression during HSC activation. Although the pharmacological DNA demethylation of HSC using 5-aza-2′-deoxycytidine (5-aza-dC) yielded an antifibrotic effect, this drug has been reported to induce excessive cytotoxicity at a high dose. Hydralazine (HDZ), an antihypertensive agent, also exhibits non-nucleoside demethylating activity. However, the effect of HDZ on HSC activation remains unclear. In this study, we performed a combined treatment with 5-aza-dC and HDZ to obtain an enhanced antifibrotic effect with lower cytotoxicity. Methods: HSC-T6 cells were used as a rat HSC cell line in this study. The cells were cultivated together with 1 µM 5-Aza-dC and/or 10 µg/mL of HDZ, which were refreshed every 24 h until the 96 h treatment ended. Cell proliferation was measured using the WST-1 assay. The mRNA expression levels of peptidylprolyl isomerase A (Ppia), an internal control gene, collagen type I alpha 1 (Cola1), RAS protein activator like 1 (Rasal1), and phosphatase and tensin homolog deleted from chromosome 10 (Pten) were analyzed using quantitative reverse transcription polymerase chain reaction. Results: The percentage cell viability with 5-aza-dC, HDZ, and combined treatment vs. the vehicle-only control was 101.4 ± 2.5, 95.2 ± 5.7, and 79.2 ± 0.7 (p < 0.01 for 5-aza-dC and p < 0.01 for HDZ), respectively, in the 48 h treatment, and 52.4 ± 5.6, 65.9 ± 3.4, and 29.9 ± 1.3 (p < 0.01 for 5-aza-dC and p < 0.01 for HDZ), respectively, in the 96 h treatment. 5-Aza-dC and the combined treatment markedly decreased Cola1 mRNA levels. Accordingly, the expression levels of Rasal1 and Pten, which are antifibrotic genes, were increased by treatment after the 5-aza-dC and combined treatments. Moreover, single treatment with HDZ did not affect the expression levels of Cola1, Rasal1, or Pten. These results suggest that HDZ sensitizes to the antifibrotic effect of 5-aza-dC in HSC-T6 cells. The molecular mechanism underlying the sensitization to the antifibrotic effect of 5-aza-dC by HDZ remains to be elucidated. The expression levels of rat equilibrative nucleoside transporter genes (rEnt1, rEnt2, and rEnt3) were not affected by HDZ in this study. Conclusions: Further confirmation using primary HSCs and in vivo animal models is desirable, but combined treatment with 5-aza-dC and HDZ may be an effective therapy for liver fibrosis without severe adverse effects. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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11 pages, 742 KiB

Open AccessArticle

The Prevalence and Impact of Hepatic Steatosis on Response to Direct-Acting Antiviral Therapy in HIV–HCV Coinfection

by Leigh P. Johnson and Richard K. Sterling

Biology 2020, 9(4), 87; https://doi.org/10.3390/biology9040087 - 24 Apr 2020

Cited by 3 | Viewed by 2845

Abstract

(1) Background: Direct-acting antiviral therapy for chronic hepatitis C virus (HCV) infection is associated with high sustained virologic response (SVR) and overcomes negative predictive factors, including steatosis, in patients without human immunodeficiency virus (HIV) coinfection. The impact of steatosis on SVR in patients [...] Read more.

(1) Background: Direct-acting antiviral therapy for chronic hepatitis C virus (HCV) infection is associated with high sustained virologic response (SVR) and overcomes negative predictive factors, including steatosis, in patients without human immunodeficiency virus (HIV) coinfection. The impact of steatosis on SVR in patients with HIV–HCV coinfection is unknown. (2) Methods: A retrospective analysis of patients treated with direct-acting antivirals was performed. Demographic, laboratory and direct-acting antiviral regimen data were prospectively collected. Metabolic syndrome and its components—diabetes mellitus, hypertension, dyslipidemia and obesity—were assessed. Hepatic steatosis (≥5%) was defined by liver biopsy or controlled attenuation parameter (CAP) measurement during vibration-controlled transient elastography (VCTE). (3) Results: A total of 151 HIV–HCV-coinfected patients on combined antiretroviral therapy and direct-acting antiviral therapy were included in this analysis. Prevalence of steatosis by liver biopsy (n = 34) or CAP (≥263 db/m) during VCTE (n = 92) was 27% and was independently associated with obesity (OR 3.11; 95% CI 1.43–6.82; p = 0.004) and the metabolic syndrome (OR 1.08; 95% CI 1.01–0.15; p = 0.01). The overall SVR rate (n = 148) was 95% and was not impacted by the presence of steatosis (p = 0.42). (4) Conclusions: Hepatic steatosis is common in HIV–HCV coinfection, correlates with obesity and the metabolic syndrome and does not impact SVR. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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15 pages, 463 KiB

Open AccessArticle

Polymorphisms in Interleukin 13 Signaling and Interacting Genes Predict Advanced Fibrosis and Hepatocellular Carcinoma Development in Non-Alcoholic Steatohepatitis

by Marwa O. El-Derany

Biology 2020, 9(4), 75; https://doi.org/10.3390/biology9040075 - 9 Apr 2020

Cited by 18 | Viewed by 3758

Abstract

Background: non-alcoholic steatohepatitis (NASH) recently headlined hepatocellular carcinoma (HCC) worldwide. This study aims to unveil the role of some unaddressed critical players that might aid in understanding, predicting, and targeting NASH and NASH-HCC. Methods: Serum interleukin 13 (IL-13) levels and single nucleotide polymorphisms [...] Read more.

Background: non-alcoholic steatohepatitis (NASH) recently headlined hepatocellular carcinoma (HCC) worldwide. This study aims to unveil the role of some unaddressed critical players that might aid in understanding, predicting, and targeting NASH and NASH-HCC. Methods: Serum interleukin 13 (IL-13) levels and single nucleotide polymorphisms (SNPs) within interleukin (IL)-13 rs20541, IL-13 receptors (IL-13R1) rs2248841, (IL-13R2) rs5946040, signal transducer activator of transcription 6 (STAT6) rs167769, yes-associated protein (YAP1) rs11225163, programmed death-ligand 1 (PD-L1) rs2282055, and programmed death-ligand 2 (PD-L2) rs7854413 genes were analyzed by qRT-PCR. Multiple stepwise regression analysis was performed on a cohort of 134 Egyptian male patients diagnosed with NASH and NASH-HCC. RESULTS: higher serum alpha-fetoprotein (AFP) and higher serum IL-13 levels were directly associated with HCC development in NASH (odds ratio (OR) 19.6 and 1.9 p < 0.01). Reversibly, the presence of the C/C genotype in STAT6 rs167769 and the C allele carrier YAP1 rs11225163 were inversely associated with HCC in NASH patients (OR 0.015 and 0.047 p < 0.01). A predictive model was formulated with 97.5% specificity, 90.9% sensitivity, and 94.8% accuracy. Moreover, higher serum IL-13 levels and the presence of PD-L2 rs7854413 C allele carriers were associated with advanced fibrosis progression in NASH patients (OR 1.432 and 3.797 p < 0.01). Serum levels of IL-13 and C/C genotype in STAT6 rs167769 significantly increased the predictive capacity of serum AFP to predict HCC in F1–F2 and in F3–F4 fibrosis grades NASH patients. Conclusion: association between serum IL-13 and PD-L2 rs7854413 polymorphism successfully predict advanced fibrosis in NASH. However, HCC development in NASH is associated with higher serum AFP, IL-13 levels, and STAT6 rs167769, YAP1 rs11225163 polymorphisms. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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Review

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24 pages, 950 KiB

Open AccessReview

Beneficial Effects of Betaine: A Comprehensive Review

by Madan Kumar Arumugam, Matthew C. Paal, Terrence M. Donohue, Jr., Murali Ganesan, Natalia A. Osna and Kusum K. Kharbanda

Biology 2021, 10(6), 456; https://doi.org/10.3390/biology10060456 - 22 May 2021

Cited by 134 | Viewed by 19803

Abstract

Medicinal herbs and many food ingredients possess favorable biological properties that contribute to their therapeutic activities. One such natural product is betaine, a stable, nontoxic natural substance that is present in animals, plants, and microorganisms. Betaine is also endogenously synthesized through the metabolism [...] Read more.

Medicinal herbs and many food ingredients possess favorable biological properties that contribute to their therapeutic activities. One such natural product is betaine, a stable, nontoxic natural substance that is present in animals, plants, and microorganisms. Betaine is also endogenously synthesized through the metabolism of choline or exogenously consumed through dietary intake. Betaine mainly functions as (i) an osmolyte and (ii) a methyl-group donor. This review describes the major physiological effects of betaine in whole-body health and its ability to protect against both liver- as well as non-liver-related diseases and conditions. Betaine’s role in preventing/attenuating both alcohol-induced and metabolic-associated liver diseases has been well studied and is extensively reviewed here. Several studies show that betaine protects against the development of alcohol-induced hepatic steatosis, apoptosis, and accumulation of damaged proteins. Additionally, it can significantly prevent/attenuate progressive liver injury by preserving gut integrity and adipose function. The protective effects are primarily associated with the regulation of methionine metabolism through removing homocysteine and maintaining cellular SAM:SAH ratios. Similarly, betaine prevents metabolic-associated fatty liver disease and its progression. In addition, betaine has a neuroprotective role, preserves myocardial function, and prevents pancreatic steatosis. Betaine also attenuates oxidant stress, endoplasmic reticulum stress, inflammation, and cancer development. To conclude, betaine exerts significant therapeutic and biological effects that are potentially beneficial for alleviating a diverse number of human diseases and conditions. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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14 pages, 1715 KiB

Open AccessReview

Treating the Metabolic Syndrome by Fecal Transplantation—Current Status

by Stephen D. H. Malnick, David Fisher, Marina Somin and Manuela G. Neuman

Biology 2021, 10(5), 447; https://doi.org/10.3390/biology10050447 - 20 May 2021

Cited by 12 | Viewed by 4118

Abstract

The intestinal microbiome (IM) is important for normal gastrointestinal (GI) and other organ systems’ functioning. An alteration in the normal IM, dysbiosis, and changes in intestinal motility result in microorganisms’ overgrowth and an alteration in intestinal permeability. The gut–brain axis is also of [...] Read more.

The intestinal microbiome (IM) is important for normal gastrointestinal (GI) and other organ systems’ functioning. An alteration in the normal IM, dysbiosis, and changes in intestinal motility result in microorganisms’ overgrowth and an alteration in intestinal permeability. The gut–brain axis is also of importance in the irritable bowel syndrome (IBS) and associated bowel overgrowth. Secondary to the epidemic of obesity, the metabolic syndrome has become a major health problem. Disturbances in the fecal microbiome are associated with the metabolic syndrome. Metabolic-associated fatty liver disease (MAFLD) is now the current terminology for non-alcoholic fatty liver disease. IM alteration by fecal transplantation is an approved treatment method for recurrent Clostridioides difficile infection. Initially performed by either duodenal infusion or colonoscopy, it is now easily performed by the administration of capsules containing stools. We discuss the intestinal microbiome—its composition, as well as the qualitative changes of microbiome composition leading to inflammation. In addition, we discuss the evidence of the effect of fecal transplantation on the metabolic syndrome and MAFLD, as well as its clinical indications. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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17 pages, 1657 KiB

Open AccessReview

Organismal Fructose Metabolism in Health and Non-Alcoholic Fatty Liver Disease

by Shea Skenderian, Grace Park and Cholsoon Jang

Biology 2020, 9(11), 405; https://doi.org/10.3390/biology9110405 - 18 Nov 2020

Cited by 12 | Viewed by 5726

Abstract

NAFLD has alarmingly increased, yet FDA-approved drugs are still lacking. An excessive intake of fructose, especially in liquid form, is a dietary risk factor of NAFLD. While fructose metabolism has been studied for decades, it is still controversial how fructose intake can cause [...] Read more.

NAFLD has alarmingly increased, yet FDA-approved drugs are still lacking. An excessive intake of fructose, especially in liquid form, is a dietary risk factor of NAFLD. While fructose metabolism has been studied for decades, it is still controversial how fructose intake can cause NAFLD. It has long been believed that fructose metabolism solely happens in the liver and accordingly, numerous studies have investigated liver fructose metabolism using primary hepatocytes or liver cell lines in culture. While cultured cells are useful for studying detailed signaling pathways and metabolism in a cell-autonomous manner, it is equally important to understand fructose metabolism at the whole-body level in live organisms. In this regard, recent in vivo studies using genetically modified mice and stable isotope tracing have tremendously expanded our understanding of the complex interaction between fructose-catabolizing organs and gut microbiota. Here, we discuss how the aberrant distribution of fructose metabolism between organs and gut microbiota can contribute to NAFLD. We also address potential therapeutic interventions of fructose-elicited NAFLD. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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19 pages, 1875 KiB

Open AccessReview

Emerging Roles of Liver Sinusoidal Endothelial Cells in Nonalcoholic Steatohepatitis

by Kunimaro Furuta, Qianqian Guo, Petra Hirsova and Samar H. Ibrahim

Biology 2020, 9(11), 395; https://doi.org/10.3390/biology9110395 - 12 Nov 2020

Cited by 30 | Viewed by 5155

Abstract

Nonalcoholic steatohepatitis (NASH) has become a growing public health problem worldwide, yet its pathophysiology remains unclear. Liver sinusoidal endothelial cells (LSEC) have unique morphology and function, and play a critical role in liver homeostasis. Emerging literature implicates LSEC in many pathological processes in [...] Read more.

Nonalcoholic steatohepatitis (NASH) has become a growing public health problem worldwide, yet its pathophysiology remains unclear. Liver sinusoidal endothelial cells (LSEC) have unique morphology and function, and play a critical role in liver homeostasis. Emerging literature implicates LSEC in many pathological processes in the liver, including metabolic dysregulation, inflammation, angiogenesis, and carcinogenesis. In this review, we highlight the current knowledge of the role of LSEC in each of the progressive phases of NASH pathophysiology (steatosis, inflammation, fibrosis, and the development of hepatocellular carcinoma). We discuss processes that have important roles in NASH progression including the detrimental transformation of LSEC called “capillarization”, production of inflammatory and profibrogenic mediators by LSEC as well as LSEC-mediated angiogenesis. The current review has a special emphasis on LSEC adhesion molecules, and their key role in the inflammatory response in NASH. Moreover, we discuss the pathogenic role of extracellular vesicles and their bioactive cargos in liver intercellular communication, inflammation, and fibrosis. Finally, we highlight LSEC-adhesion molecules and derived bioactive product as potential therapeutic targets for human NASH. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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21 pages, 2059 KiB

Open AccessReview

The Nuclear Envelope in Lipid Metabolism and Pathogenesis of NAFLD

by Cecilia Östlund, Antonio Hernandez-Ono and Ji-Yeon Shin

Biology 2020, 9(10), 338; https://doi.org/10.3390/biology9100338 - 15 Oct 2020

Cited by 13 | Viewed by 4963

Abstract

Nonalcoholic fatty liver disease (NAFLD) is a burgeoning public health problem worldwide. Despite its tremendous significance for public health, we lack a comprehensive understanding of the pathogenic mechanisms of NAFLD and its more advanced stage, nonalcoholic steatohepatitis (NASH). Identification of novel pathways or [...] Read more.

Nonalcoholic fatty liver disease (NAFLD) is a burgeoning public health problem worldwide. Despite its tremendous significance for public health, we lack a comprehensive understanding of the pathogenic mechanisms of NAFLD and its more advanced stage, nonalcoholic steatohepatitis (NASH). Identification of novel pathways or cellular mechanisms that regulate liver lipid metabolism has profound implications for the understanding of the pathology of NAFLD and NASH. The nuclear envelope is topologically connected to the ER, where protein synthesis and lipid synthesis occurs. Emerging evidence points toward that the nuclear lamins and nuclear membrane-associated proteins are involved in lipid metabolism and homeostasis. We review published reports that link these nuclear envelope proteins to lipid metabolism. In particular, we focus on the recent work demonstrating the essential roles for the nuclear envelope-localized torsinA/lamina-associated polypeptide (LAP1) complex in hepatic steatosis, lipid secretion, and NASH development. We also discuss plausible pathogenic mechanisms by which the loss of either protein in hepatocytes leads to hepatic dyslipidemia and NASH development. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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17 pages, 1416 KiB

Open AccessReview

Soluble Epoxide Hydrolase Inhibition in Liver Diseases: A Review of Current Research and Knowledge Gaps

by Jeffrey Warner, Josiah Hardesty, Kara Zirnheld, Craig McClain, Dennis Warner and Irina Kirpich

Biology 2020, 9(6), 124; https://doi.org/10.3390/biology9060124 - 12 Jun 2020

Cited by 16 | Viewed by 4820

Abstract

Emerging evidence suggests that soluble epoxide hydrolase (sEH) inhibition is a valuable therapeutic strategy for the treatment of numerous diseases, including those of the liver. sEH rapidly degrades cytochrome P450-produced epoxygenated lipids (epoxy-fatty acids), which are synthesized from omega-3 and omega-6 polyunsaturated fatty [...] Read more.

Emerging evidence suggests that soluble epoxide hydrolase (sEH) inhibition is a valuable therapeutic strategy for the treatment of numerous diseases, including those of the liver. sEH rapidly degrades cytochrome P450-produced epoxygenated lipids (epoxy-fatty acids), which are synthesized from omega-3 and omega-6 polyunsaturated fatty acids, that generally exert beneficial effects on several cellular processes. sEH hydrolysis of epoxy-fatty acids produces dihydroxy-fatty acids which are typically less biologically active than their parent epoxide. Efforts to develop sEH inhibitors have made available numerous compounds that show therapeutic efficacy and a wide margin of safety in a variety of different diseases, including non-alcoholic fatty liver disease, liver fibrosis, portal hypertension, and others. This review summarizes research efforts which characterize the applications, underlying effects, and molecular mechanisms of sEH inhibitors in these liver diseases and identifies gaps in knowledge for future research. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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8 pages, 599 KiB

Open AccessCommentary

Why Hepatic CYP2E1-Elevation by Itself Is Insufficient for Inciting NAFLD/NASH: Inferences from Two Genetic Knockout Mouse Models

by Maria Almira Correia and Doyoung Kwon

Biology 2020, 9(12), 419; https://doi.org/10.3390/biology9120419 - 26 Nov 2020

Cited by 14 | Viewed by 3000

Abstract

Hepatic cytochrome P450 CYP2E1 is an enzyme engaged in the metabolic biotransformation of various xenobiotics and endobiotics, resulting in both detoxification and/or metabolic activation of its substrates to more therapeutic or toxic products. Elevated hepatic CYP2E1 content is implicated in various metabolic diseases [...] Read more.

Hepatic cytochrome P450 CYP2E1 is an enzyme engaged in the metabolic biotransformation of various xenobiotics and endobiotics, resulting in both detoxification and/or metabolic activation of its substrates to more therapeutic or toxic products. Elevated hepatic CYP2E1 content is implicated in various metabolic diseases including alcoholic liver disease, nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH), diabetes and obesity. While hepatic CYP2E1 elevation is considered essential to the pathogenesis of these liver diseases, our findings in two mouse models of E3 ubiquitin ligase genetic ablation fed a regular lab chow diet, argue that it is not sufficient for triggering NAFLD/NASH. Thus, albeit comparable hepatic CYP2E1 elevation and functional stabilization in these two models upon E3 ubiquitin ligase genetic ablation and consequent disruption of its ubiquitin-dependent proteasomal degradation, NAFLD/NASH was only observed in the mouse livers that exhibited concurrent SREBP1c-transcriptional upregulation of hepatic lipogenesis. These findings reinforce the critical complicity of an associated prolipogenic scenario induced by either an inherently upregulated hepatic lipogenesis or a high fat/high carbohydrate diet in CYP2E1-mediated NAFLD/NASH. Full article

(This article belongs to the Special Issue Non-alcoholic Liver Injury)

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